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Sample records for ruthenium dimer catalysis

  1. Blue Ruthenium Dimer Catalysis for Hydrogen Generation | Advanced...

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    to APS Science Highlights rss feed Blue Ruthenium Dimer Catalysis for Hydrogen Generation APRIL 15, 2013 Bookmark and Share Key intermediates in the water oxidation catalytic...

  2. Structure and Electronic Configurations of the Intermediates of Water Oxidation in Blue Ruthenium Dimer Catalysis

    SciTech Connect (OSTI)

    Moonshiram, Dooshaye; Jurss, Jonah W.; Concepcion, Javier J.; Zakharova, Taisiya; Alperovich, Igor; Meyer, Thomas J.; Pushkar, Yulia

    2013-04-08

    Catalytic O{sub 2} evolution with cis,cis-[(bpy){sub 2}(H{sub 2}O)Ru{sup III}ORu{sup III}(OH{sub 2})(bpy){sub 2}]{sup 4+} (bpy is 2,2-bipyridine), the so-called blue dimer, the first designed water oxidation catalyst, was monitored by UV-vis, EPR, and X-ray absorption spectroscopy (XAS) with ms time resolution. Two processes were identified, one of which occurs on a time scale of 100 ms to a few seconds and results in oxidation of the catalyst with the formation of an intermediate, here termed [3,4]'. A slower process occurring on the time scale of minutes results in the decay of this intermediate and O{sub 2} evolution. Spectroscopic data suggest that within the fast process there is a short-lived transient intermediate, which is a precursor of [3,4]'. When excess oxidant was used, a highly oxidized form of the blue dimer [4,5] was spectroscopically resolved within the time frame of the fast process. Its structure and electronic state were confirmed by EPR and XAS. As reported earlier, the [3,4]' intermediate likely results from reaction of [4,5] with water. While it is generated under strongly oxidizing conditions, it does not display oxidation of the Ru centers past [3,4] according to EPR and XAS. EXAFS analysis demonstrates a considerably modified ligand environment in [3,4]'. Raman measurements confirmed the presence of the O-O fragment by detecting a new vibration band in [3,4]' that undergoes a 46 cm{sup -1} shift to lower energy upon {sup 16}O/{sup 18}O exchange. Under the conditions of the experiment at pH 1, the [3,4]' intermediate is the catalytic steady state form of the blue dimer catalyst, suggesting that its oxidation is the rate-limiting step.

  3. Sensitivity of the Properties of Ruthenium “Blue Dimer” to Method, Basis Set, and Continuum Model

    SciTech Connect (OSTI)

    Ozkanlar, Abdullah; Clark, Aurora E.

    2012-05-23

    The ruthenium “blue dimer” [(bpy)2RuIIIOH2]2O4+ is best known as the first well-defined molecular catalyst for water oxidation. It has been subject to numerous computational studies primarily employing density functional theory. However, those studies have been limited in the functionals, basis sets, and continuum models employed. The controversy in the calculated electronic structure and the reaction energetics of this catalyst highlights the necessity of benchmark calculations that explore the role of density functionals, basis sets, and continuum models upon the essential features of blue-dimer reactivity. In this paper, we report Kohn-Sham complete basis set (KS-CBS) limit extrapolations of the electronic structure of “blue dimer” using GGA (BPW91 and BP86), hybrid-GGA (B3LYP), and meta-GGA (M06-L) density functionals. The dependence of solvation free energy corrections on the different cavity types (UFF, UA0, UAHF, UAKS, Bondi, and Pauling) within polarizable and conductor-like polarizable continuum model has also been investigated. The most common basis sets of double-zeta quality are shown to yield results close to the KS-CBS limit; however, large variations are observed in the reaction energetics as a function of density functional and continuum cavity model employed.

  4. Butadiene Complexes of Titanium(II) and Titanium(0): Synthesis, Butadiene Dimerization Catalysis, and Crystal

    E-Print Network [OSTI]

    Girolami, Gregory S.

    Butadiene Complexes of Titanium(II) and Titanium(0): Synthesis, Butadiene Dimerization Catalysis, where dmpe is 1,2-bis(dimethylphosphino)- ethane, reacts with 1,3-butadiene and trans,trans-1,4-diphenyl-1,3-butadiene at -20 °C to produce the titanium(II) butadiene complexes TiMe2(4-C4H4R2)(dmpe), where

  5. INSTITUTE FOR INTEGRATED CATALYSIS Catalysis Research for

    E-Print Network [OSTI]

    . This work includes catalysis for upgrading biomass feedstocks; for chemical energy storage, retrieval

  6. Dendrimer-Encapsulated Ruthenium Nanoparticles as Catalysts for Lithium-O2 Batteries

    SciTech Connect (OSTI)

    Bhattacharya, Priyanka; Nasybulin, Eduard N.; Engelhard, Mark H.; Kovarik, Libor; Bowden, Mark E.; Li, Shari; Gaspar, Daniel J.; Xu, Wu; Zhang, Jiguang

    2014-12-01

    Dendrimer-encapsulated ruthenium nanoparticles (DEN-Ru) have been used as catalysts in lithium-O2 batteries for the first time. Results obtained from UV-vis spectroscopy, electron microscopy and X-ray photoelectron spectroscopy show that the nanoparticles synthesized by the dendrimer template method are ruthenium oxide instead of metallic ruthenium reported earlier by other groups. The DEN-Ru significantly improve the cycling stability of lithium (Li)-O2 batteries with carbon black electrodes and decrease the charging potential even at low catalyst loading. The monodispersity, porosity and large number of surface functionalities of the dendrimer template prevent the aggregation of the ruthenium nanoparticles making their entire surface area available for catalysis. The potential of using DEN-Ru as stand-alone cathode materials for Li-O2 batteries is also explored.

  7. Structure of a Loose Dimer: an Intermediate in Nitric Oxide Synthase Assembly

    SciTech Connect (OSTI)

    Pant,K.; Crane, B.

    2005-01-01

    Cooperativity among ligand binding, subunit association, and protein folding has implications for enzyme regulation as well as protein aggregation events associated with disease. The binding of substrate l-arginine or cofactor tetrahydrobiopterin converts nitric oxide synthases (NOSs) from a 'loose dimer', with an exposed active center and higher sensitivity to proteolysis, to a 'tight dimer' competent for catalysis. The crystallographic structure of the Bacillus subtilis NOS loose dimer shows an altered association state with severely destabilized subdomains. Ligand binding or heme reduction converts loose dimers to tight dimers in solution and crystals. Mutations at key positions in the dimer interface that distinguish prokaryotic from eukaryotic NOSs affect the propensity to form loose dimers. The loose dimer structure indicates that non-native interactions can mediate subunit association in NOS.

  8. Selective deposition of nanostructured ruthenium oxide using...

    Office of Scientific and Technical Information (OSTI)

    Selective deposition of nanostructured ruthenium oxide using Tobacco mosaic virus for micro-supercapacitors in solid Nafion electrolyte Citation Details In-Document Search Title:...

  9. Magnetic Catalysis in Graphene

    E-Print Network [OSTI]

    Christopher Winterowd; Carleton DeTar; Savvas Zafeiropoulos

    2015-09-22

    One of the most important developments in condensed matter physics in recent years has been the discovery and characterization of graphene. A two-dimensional layer of Carbon arranged in a hexagonal lattice, graphene exhibits many interesting electronic properties, most notably that the low energy excitations behave as massless Dirac fermions. These excitations interact strongly via the Coulomb interaction and thus non-perturbative methods are necessary. Using methods borrowed from lattice QCD, we study the graphene effective theory in the presence of an external magnetic field. Graphene, along with other $(2+1)$-dimensional field theories, has been predicted to undergo spontaneous breaking of flavor symmetry including the formation of a gap as a result of the external magnetic field. This phenomenon is known as magnetic catalysis. Our study investigates magnetic catalysis using a fully non-perturbative approach.

  10. Magnetic Catalysis in Graphene

    E-Print Network [OSTI]

    Winterowd, Christopher; Zafeiropoulos, Savvas

    2015-01-01

    One of the most important developments in condensed matter physics in recent years has been the discovery and characterization of graphene. A two-dimensional layer of Carbon arranged in a hexagonal lattice, graphene exhibits many interesting electronic properties, most notably that the low energy excitations behave as massless Dirac fermions. These excitations interact strongly via the Coulomb interaction and thus non-perturbative methods are necessary. Using methods borrowed from lattice QCD, we study the graphene effective theory in the presence of an external magnetic field. Graphene, along with other $(2+1)$-dimensional field theories, has been predicted to undergo spontaneous breaking of flavor symmetry including the formation of a gap as a result of the external magnetic field. This phenomenon is known as magnetic catalysis. Our study investigates magnetic catalysis using a fully non-perturbative approach.

  11. Electron Microscopy Catalysis Projects: Success Stories from...

    Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site

    Catalysis Projects: Success Stories from the High Temperature Materials Laboratory (HTML) User Program Electron Microscopy Catalysis Projects: Success Stories from the High...

  12. Catalysis Research for Energy Independence

    E-Print Network [OSTI]

    -conversions to significantly reduce the carbon footprint of the global energy system. We provide a fundamental understandingCatalysis Research for Energy Independence Chemical transformations are at the heart of energy production and use, and catalysis lies at the core of efficiently and effectively using our current energy

  13. Zeolite catalysis: technology

    SciTech Connect (OSTI)

    Heinemann, H.

    1980-07-01

    Zeolites have been used as catalysts in industry since the early nineteen sixties. The great majority of commercial applications employ one of three zeolite types: zeolite Y; Mordenite; ZSM-5. By far the largest use of zeolites is in catalytic cracking, and to a lesser extent in hydrocracking. This paper reviews the rapid development of zeolite catalysis and its application in industries such as: the production of gasoline by catalytic cracking of petroleum; isomerization of C/sub 5/ and C/sub 6/ paraffin hydrocarbons; alkylation of aromatics with olefins; xylene isomerization; and conversion of methanol to gasoline.

  14. Platinum-ruthenium-palladium fuel cell electrocatalyst

    DOE Patents [OSTI]

    Gorer, Alexander

    2006-02-07

    A catalyst suitable for use in a fuel cell, especially as an anode catalyst, that contains platinum at a concentration that is between about 20 and about 60 atomic percent, ruthenium at a concentration that is between about 20 and about 60 atomic percent, palladium at a concentration that is between about 5 and about 45 atomic percent, and having an atomic ratio of platinum to ruthenium that is between about 0.7 and about 1.2. Alternatively, the catalyst may contain platinum at a concentration that is between about 25 and about 50 atomic percent, ruthenium at a concentration that is between about 25 and about 55 atomic percent, palladium at a concentration that is between about 5 and about 45 atomic percent, and having a difference between the concentrations of ruthenium and platinum that is no greater than about 20 atomic percent.

  15. Low-Temperature Hydrocarbon/CO Oxidation Catalysis in Support...

    Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site

    Catalysis in Support of HCCI Emission Control Low-Temperature HydrocarbonCO Oxidation Catalysis in Support of HCCI Emission Control Lean NOx Catalysis Research and Development...

  16. Enhanced Micellar Catalysis LDRD.

    SciTech Connect (OSTI)

    Betty, Rita G.; Tucker, Mark David; Taggart, Gretchen; Kinnan, Mark K.; Glen, Crystal Chanea; Rivera, Danielle; Sanchez, Andres; Alam, Todd Michael

    2012-12-01

    The primary goals of the Enhanced Micellar Catalysis project were to gain an understanding of the micellar environment of DF-200, or similar liquid CBW surfactant-based decontaminants, as well as characterize the aerosolized DF-200 droplet distribution and droplet chemistry under baseline ITW rotary atomization conditions. Micellar characterization of limited surfactant solutions was performed externally through the collection and measurement of Small Angle X-Ray Scattering (SAXS) images and Cryo-Transmission Electron Microscopy (cryo-TEM) images. Micellar characterization was performed externally at the University of Minnesota's Characterization Facility Center, and at the Argonne National Laboratory Advanced Photon Source facility. A micellar diffusion study was conducted internally at Sandia to measure diffusion constants of surfactants over a concentration range, to estimate the effective micelle diameter, to determine the impact of individual components to the micellar environment in solution, and the impact of combined components to surfactant phase behavior. Aerosolized DF-200 sprays were characterized for particle size and distribution and limited chemical composition. Evaporation rates of aerosolized DF-200 sprays were estimated under a set of baseline ITW nozzle test system parameters.

  17. Catalysis Working Group Meeting: January 2015

    Broader source: Energy.gov [DOE]

    Agenda and presentations from the Catalysis Working Group meeting held January 21, 2015, in Los Alamos, New Mexico.

  18. Catalysis Working Group Meeting: June 2015

    Broader source: Energy.gov [DOE]

    Agenda and presentations from the Catalysis Working Group meeting held on June 8, 2015, in Arlington, Virginia.

  19. Fuel Synthesis Catalysis Laboratory (Fact Sheet)

    SciTech Connect (OSTI)

    Not Available

    2013-07-01

    This fact sheet provides information about Fuel Synthesis Catalysis Laboratory capabilities and applications at NREL's National Bioenergy Center.

  20. A method for activation analysis of ruthenium in sea water 

    E-Print Network [OSTI]

    Dixon, Bryan William

    1965-01-01

    of Ruthenium in the Gulf of Mexico . 8 Solubility of Ruthenium in Sea Water C H A P T E R I INTRODUCTION Ruthenium, the rarest of the platinum metals, was discovered in 1845 by Klaus. Sidgewick (1950) and Goldschmidt (1954) state an abundance of about 0... of allow ing for the detection of the contributing physical and chemical forms to the total present. It is thought that the method is applicable to marine biota and sediments as well as water samples. The concentrations of soluble ruthenium found...

  1. Cationic Ruthenium Catalysts for Olefin Hydrovinylation 

    E-Print Network [OSTI]

    Sanchez, Richard P., Jr

    2010-01-14

    of the Hydrovinylation Reaction ................................. 1 1.2 Mechanism of the Hydrovinylation Reaction........................... 4 1.3 Nickel and Palladium Catalyzed Reactions.............................. 6 1.4 Ruthenium Catalyzed Reactions... to form followed by isomerization to give the observed product. Ph Ph Me Ph Me Me RhCl3?3H2O 1000 atm ethylene MeOH, 50 ?C (6) Few catalysts had been used in early studies, but typically nickel and palladium catalysts were used due to their higher...

  2. Reaction Selectivity in Heterogeneous Catalysis

    SciTech Connect (OSTI)

    Somorjai, Gabor A.; Kliewer, Christopher J.

    2009-02-02

    The understanding of selectivity in heterogeneous catalysis is of paramount importance to our society today. In this review we outline the current state of the art in research on selectivity in heterogeneous catalysis. Current in-situ surface science techniques have revealed several important features of catalytic selectivity. Sum frequency generation vibrational spectroscopy has shown us the importance of understanding the reaction intermediates and mechanism of a heterogeneous reaction, and can readily yield information as to the effect of temperature, pressure, catalyst geometry, surface promoters, and catalyst composition on the reaction mechanism. DFT calculations are quickly approaching the ability to assist in the interpretation of observed surface spectra, thereby making surface spectroscopy an even more powerful tool. HP-STM has revealed three vitally important parameters in heterogeneous selectivity: adsorbate mobility, catalyst mobility, and selective site-blocking. The development of size controlled nanoparticles from 0.8 to 10 nm, of controlled shape, and of controlled bimetallic composition has revealed several important variables for catalytic selectivity. Lastly, DFT calculations may be paving the way to guiding the composition choice for multi-metallic heterogeneous catalysis for the intelligent design of catalysts incorporating the many factors of selectivity we have learned.

  3. Fischer-Tropsch synthesis process employing a moderated ruthenium catalyst

    DOE Patents [OSTI]

    Abrevaya, H.

    1990-07-31

    A Fischer-Tropsch type process produces hydrocarbons from carbon monoxide and hydrogen using a novel catalyst comprising moderated ruthenium on an inorganic oxide support. The preferred moderator is silicon. Preferably the moderator is effectively positioned in relationship to ruthenium particles through simultaneous placement on the support using reverse micelle impregnation. 1 fig.

  4. Workshop: Synchrotron Applications in Chemical Catalysis | Stanford...

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    Applications in Chemical Catalysis Tuesday, October 25, 2011 - 8:00am 2011 SSRLLCLS Annual Users Conference This workshop, part of the 2011 SSRLLCLS Annual Users...

  5. Basic Research Needs: Catalysis for Energy

    SciTech Connect (OSTI)

    Bell, Alexis T.; Gates, Bruce C.; Ray, Douglas; Thompson, Michael R.

    2008-03-11

    The report presents results of a workshop held August 6-8, 2007, by DOE SC Basic Energy Sciences to determine the basic research needs for catalysis research.

  6. Low-Temperature Hydrocarbon/CO Oxidation Catalysis in Support...

    Energy Savers [EERE]

    HydrocarbonCO Oxidation Catalysis in Support of HCCI Emission Control Low-Temperature HydrocarbonCO Oxidation Catalysis in Support of HCCI Emission Control Presentation from the...

  7. Plasma Assisted Catalysis System for NOx Reduction | Department...

    Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site

    Plasma Assisted Catalysis System for NOx Reduction Plasma Assisted Catalysis System for NOx Reduction 2002 DEER Conference Presentation: Noxtech, Inc. 2002deerslone.pdf More...

  8. Thermochemical Conversion: Using Heat and Catalysis to Make Biofuels...

    Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site

    Catalysis to Make Biofuels and Bioproducts The Bioenergy Technologies Office works with industry to develop pathways that use heat, pressure, and catalysis to convert domestic,...

  9. Shining Light on Catalysis | Stanford Synchrotron Radiation Lightsourc...

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    A. van Bokhoven, Professor for Heterogeneous Catalysis Institute for Chemical and Bioengineering ETH Zurich Head of Laboratory for Catalysis and Sustainable Chemistry (LSK) Swiss...

  10. The CRAC channel consists of a tetramer formed by Stim-induced dimerization of Orai dimers

    E-Print Network [OSTI]

    Parker, Ian

    LETTERS The CRAC channel consists of a tetramer formed by Stim-induced dimerization of Orai dimers terminus of Stim thus induces Orai dimers to dimerize, forming tetramers that constitute the Ca21-treated cells14 , whereas functional measurements of expressed tandem Orai multimers indicate a tetramer

  11. Height fluctuations in interacting dimers

    E-Print Network [OSTI]

    Alessandro Giuliani; Vieri Mastropietro; Fabio Lucio Toninelli

    2015-05-05

    We consider a non-integrable model for interacting dimers on the two-dimensional square lattice. Configurations are perfect matchings of $\\mathbb Z^2$, i.e. subsets of edges such that each vertex is covered exactly once ("close-packing" condition). Dimer configurations are in bijection with discrete height functions, defined on faces $\\boldsymbol{\\xi}$ of $\\mathbb Z^2$. The non-interacting model is "integrable" and solvable via Kasteleyn theory; it is known that all the moments of the height difference $h_{\\boldsymbol{\\xi}}-h_{\\boldsymbol{\\eta}}$ converge to those of the massless Gaussian Free Field (GFF), asymptotically as $|{\\boldsymbol{\\xi}}-{\\boldsymbol{\\eta}}|\\to \\infty$. We prove that the same holds for small non-zero interactions, as was conjectured in the theoretical physics literature. Remarkably, dimer-dimer correlation functions are instead not universal and decay with a critical exponent that depends on the interaction strength. Our proof is based on an exact representation of the model in terms of lattice interacting fermions, which are studied by constructive field theory methods. In the fermionic language, the height difference $h_{\\boldsymbol{\\xi}}-h_{\\boldsymbol{\\eta}}$ takes the form of a non-local operator, consisting of a sum of monomials along an {\\it arbitrary} path connecting $\\boldsymbol{\\xi}$ and $\\boldsymbol{\\eta}$. As in the non-interacting case, this path-independence plays a crucial role in the proof.

  12. DOE Laboratory Catalysis Research Symposium - Abstracts

    SciTech Connect (OSTI)

    Dunham, T.

    1999-02-01

    The conference consisted of two sessions with the following subtopics: (1) Heterogeneous Session: Novel Catalytic Materials; Photocatalysis; Novel Processing Conditions; Metals and Sulfides; Nuclear Magnetic Resonance; Metal Oxides and Partial Oxidation; Electrocatalysis; and Automotive Catalysis. (2) Homogeneous Catalysis: H-Transfer and Alkane Functionalization; Biocatalysis; Oxidation and Photocatalysis; and Novel Medical, Methods, and Catalyzed Reactions.

  13. Ruthenium / aerogel nanocomposits via Atomic Layer Deposition

    SciTech Connect (OSTI)

    Biener, J; Baumann, T F; Wang, Y; Nelson, E J; Kucheyev, S O; Hamza, A V; Kemell, M; Ritala, M; Leskela, M

    2006-08-28

    We present a general approach to prepare metal/aerogel nanocomposites via template directed atomic layer deposition (ALD). In particular, we used a Ru ALD process consisting of alternating exposures to bis(cyclopentadienyl)ruthenium (RuCp{sub 2}) and air at 350 C to deposit metallic Ru nanoparticles on the internal surfaces of carbon and silica aerogels. The process does not affect the morphology of the aerogel template and offers excellent control over metal loading by simply adjusting the number of ALD cycles. We also discuss the limitations of our ALD approach, and suggest ways to overcome these.

  14. Fiber optic D dimer biosensor

    DOE Patents [OSTI]

    Glass, R.S.; Grant, S.A.

    1999-08-17

    A fiber optic sensor for D dimer (a fibrinolytic product) can be used in vivo (e.g., in catheter-based procedures) for the diagnosis and treatment of stroke-related conditions in humans. Stroke is the third leading cause of death in the United States. It has been estimated that strokes and stroke-related disorders cost Americans between $15-30 billion annually. Relatively recently, new medical procedures have been developed for the treatment of stroke. These endovascular procedures rely upon the use of microcatheters. These procedures could be facilitated with this sensor for D dimer integrated with a microcatheter for the diagnosis of clot type, and as an indicator of the effectiveness, or end-point of thrombolytic therapy. 4 figs.

  15. Nanocrystal assembly for tandem catalysis

    DOE Patents [OSTI]

    Yang, Peidong; Somorjai, Gabor; Yamada, Yusuke; Tsung, Chia-Kuang; Huang, Wenyu

    2014-10-14

    The present invention provides a nanocrystal tandem catalyst comprising at least two metal-metal oxide interfaces for the catalysis of sequential reactions. One embodiment utilizes a nanocrystal bilayer structure formed by assembling sub-10 nm platinum and cerium oxide nanocube monolayers on a silica substrate. The two distinct metal-metal oxide interfaces, CeO.sub.2--Pt and Pt--SiO.sub.2, can be used to catalyze two distinct sequential reactions. The CeO.sub.2--Pt interface catalyzed methanol decomposition to produce CO and H.sub.2, which were then subsequently used for ethylene hydroformylation catalyzed by the nearby Pt--SiO.sub.2 interface. Consequently, propanal was selectively produced on this nanocrystal bilayer tandem catalyst.

  16. A BRIEF HISTORY OF INDUSTRIAL CATALYSIS

    E-Print Network [OSTI]

    Heinemann, Heinz

    2013-01-01

    A. Ethylene and its industrial derivatives. Ernst Bern,1974, 8(159). and its industrial Ernst Bern, 1973. u.s.A BRIEF HISTORY OF INDUSTRIAL CATALYSIS Heinz Heinemann TWO-

  17. Study of catalysis of coal gasification at elevated pressures...

    Office of Scientific and Technical Information (OSTI)

    Study of catalysis of coal gasification at elevated pressures. Evaluation of 20 compounds at 850sup 0C Citation Details In-Document Search Title: Study of catalysis of coal...

  18. Electronic transitions of palladium dimer

    SciTech Connect (OSTI)

    Qian, Yue; Ng, Y. W.; Chen, Zhihua; Cheung, A. S.-C., E-mail: hrsccsc@hku.hk [Department of Chemistry, The University of Hong Kong, Pokfulam Road (Hong Kong)

    2013-11-21

    The laser induced fluorescence spectrum of palladium dimer (Pd{sub 2}) in the visible region between 480 and 700 nm has been observed and analyzed. The gas-phase Pd{sub 2} molecule was produced by laser ablation of palladium metal rod. Eleven vibrational bands were observed and assigned to the [17.1] {sup 3}II{sub g} - X{sup 3}?{sub u}{sup +} transition system. The bond length (r{sub o}) and vibrational frequency (?G{sub 1/2}) of the ground X{sup 3}?{sub u}{sup +} state were determined to be 2.47(4) Å and 211.4(5) cm{sup ?1}, respectively. A molecular orbital energy level diagram was used to understand the observed ground and excited electronic states. This is the first gas-phase experimental investigation of the electronic transitions of Pd{sub 2}.

  19. The geometry of dimer models

    E-Print Network [OSTI]

    David Cimasoni

    2014-09-16

    This is an expanded version of a three-hour minicourse given at the winterschool Winterbraids IV held in Dijon in February 2014. The aim of these lectures was to present some aspects of the dimer model to a geometrically minded audience. We spoke neither of braids nor of knots, but tried to show how several geometrical tools that we know and love (e.g. (co)homology, spin structures, real algebraic curves) can be applied to very natural problems in combinatorics and statistical physics. These lecture notes do not contain any new results, but give a (relatively original) account of the works of Kasteleyn, Cimasoni-Reshetikhin and Kenyon-Okounkov-Sheffield.

  20. Geometrically induced magnetic catalysis and critical dimensions

    E-Print Network [OSTI]

    Antonino Flachi; Kenji Fukushima; Vincenzo Vitagliano

    2015-04-27

    We discuss the combined effect of magnetic fields and geometry in interacting fermionic systems. At leading order in the heat-kernel expansion, the infrared singularity (that in flat space leads to the magnetic catalysis) is regulated by the chiral gap effect, and the catalysis is deactivated by the effect of the scalar curvature. We discover that an infrared singularity is found in higher-order terms that mix the magnetic field with curvature, and these lead to a novel form of geometrically induced magnetic catalysis. The dynamical mass squared is then modified not only due to the chiral gap effect by an amount proportional to the curvature, but also by a magnetic shift $\\propto (4-D)eB$, where $D$ represents the number of space-time dimensions. We argue that $D=4$ is a critical dimension across which the behavior of the magnetic shift changes qualitatively.

  1. Benzene Dimer DOI: 10.1002/anie.201300653

    E-Print Network [OSTI]

    Benzene Dimer DOI: 10.1002/anie.201300653 Structure of the Benzene Dimer--Governed by Dynamics van der Avoird* The benzene dimer is a prototypical system for studying noncovalent interactions in the structure and dynamic behavior of proteins and DNA. The first (1975) experimental study of the benzene dimer

  2. Reversible Dimerization of (+)-Myrmicarin 215B

    E-Print Network [OSTI]

    Movassaghi, Mohammad

    Brønsted acid promoted reversible dimerization of myrmicarin 215B leads to formation of a new heptacyclic product, isomyrmicarin 430B, that possesses a C1,C2-trans,C2,C3-trans-substituted cyclopentane ring. Mechanistic ...

  3. Discovery of Yttrium, Zirconium, Niobium, Technetium, and Ruthenium Isotopes

    E-Print Network [OSTI]

    A. Nystrom; M. Thoennessen

    2011-02-11

    Currently, thirty-four yttrium, thirty-five zirconium, thirty-four niobium, thirty-five technetium, and thirty-eight ruthenium isotopes have been observed and the discovery of these isotopes is discussed here. For each isotope a brief synopsis of the first refereed publication, including the production and identification method, is presented.

  4. Discovery of Yttrium, Zirconium, Niobium, Technetium, and Ruthenium Isotopes

    E-Print Network [OSTI]

    Nystrom, A

    2011-01-01

    Currently, thirty-four yttrium, thirty-five zirconium, thirty-four niobium, thirty-five technetium, and thirty-eight ruthenium isotopes have been observed and the discovery of these isotopes is discussed here. For each isotope a brief synopsis of the first refereed publication, including the production and identification method, is presented.

  5. Platinum-ruthenium-nickel alloy for use as a fuel cell catalyst

    DOE Patents [OSTI]

    Gorer, Alexander (Sunnyvale, CA)

    2003-01-01

    An improved noble metal alloy composition for a fuel cell catalyst, the alloy containing platinum, ruthenium, and nickel. The alloy shows methanol oxidation activity.

  6. Platinum-ruthenium-nickel alloy for use as a fuel cell catalyst

    DOE Patents [OSTI]

    Gorer, Alexander

    2004-04-20

    An improved noble metal alloy composition for a fuel cell catalyst, the alloy containing platinum, ruthenium, and nickel. The alloy shows methanol oxidation activity.

  7. USD Catalysis Group for Alternative Energy

    SciTech Connect (OSTI)

    Hoefelmeyer, James D.; Koodali, Ranjit; Sereda, Grigoriy; Engebretson, Dan; Fong, Hao; Puszynski, Jan; Shende, Rajesh; Ahrenkiel, Phil

    2012-03-13

    The South Dakota Catalysis Group (SDCG) is a collaborative project with mission to develop advanced catalysts for energy conversion with two primary goals: (1) develop photocatalytic systems in which polyfunctionalized TiO2 are the basis for hydrogen/oxygen synthesis from water and sunlight (solar fuels group), (2) develop new materials for hydrogen utilization in fuel cells (fuel cell group). In tandem, these technologies complete a closed chemical cycle with zero emissions.

  8. Nanoscale Advances in Catalysis and Energy Applications

    SciTech Connect (OSTI)

    Li, Yimin; Somorjai, Gabor A.

    2010-05-12

    In this perspective, we present an overview of nanoscience applications in catalysis, energy conversion, and energy conservation technologies. We discuss how novel physical and chemical properties of nanomaterials can be applied and engineered to meet the advanced material requirements in the new generation of chemical and energy conversion devices. We highlight some of the latest advances in these nanotechnologies and provide an outlook at the major challenges for further developments.

  9. Low-Temperature Hydrocarbon/CO Oxidation Catalysis in Support...

    Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site

    of Energy Low-Temperature HydrocarbonCO Oxidation Catalysis in Support of HCCI Emission Control Ken Rapp, Liyu Li, Jonathan Male, Dave King Pacific Northwest National...

  10. Low-Temperature Hydrocarbon/CO Oxidation Catalysis in Support...

    Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site

    (OFCVT). deer07rappe.pdf More Documents & Publications Low-Temperature HydrocarbonCO Oxidation Catalysis in Support of HCCI Emission Control Selectlive Catalytic Reducution of...

  11. Lean NOx Catalysis Research and Development | Department of Energy

    Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site

    Documents & Publications Lean-NOx Catalyst Development for Diesel Engine Applications Plasma-Activated Lean NOx Catalysis for Heavy-Duty Diesel Emissions Control Fuel Effects on...

  12. Catalysis by Design: Bridging the Gap between Theory and Experiments...

    Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site

    between Theory and Experiments Catalysis by Design: Bridging the Gap between Theory and Experiments Poster presentation at the 2007 Diesel Engine-Efficiency & Emissions Research...

  13. Catalysis by Design: Bridging the Gap Between Theory and Experiments...

    Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site

    Between Theory and Experiments at Nanoscale Level Catalysis by Design: Bridging the Gap Between Theory and Experiments at Nanoscale Level Studies on a simple platinum-alumina...

  14. Theoretical/Computational Tools for Energy-Relevant Catalysis...

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    TheoreticalComputational Tools for Energy-Relevant Catalysis FWPProject Description: Project Leader(s): James Evans, Mark Gordon Principal Investigators: James Evans, Mark Gordon...

  15. Neutrons for Catalysis: A Workshop on Neutron Scattering Techniques for Studies in Catalysis

    SciTech Connect (OSTI)

    Overbury, Steven {Steve} H; Coates, Leighton; Herwig, Kenneth W; Kidder, Michelle

    2011-10-01

    This report summarizes the Workshop on Neutron Scattering Techniques for Studies in Catalysis, held at the Spallation Neutron Source (SNS) at Oak Ridge National Laboratory (ORNL) on September 16 and 17, 2010. The goal of the Workshop was to bring experts in heterogeneous catalysis and biocatalysis together with neutron scattering experimenters to identify ways to attack new problems, especially Grand Challenge problems in catalysis, using neutron scattering. The Workshop locale was motivated by the neutron capabilities at ORNL, including the High Flux Isotope Reactor (HFIR) and the new and developing instrumentation at the SNS. Approximately 90 researchers met for 1 1/2 days with oral presentations and breakout sessions. Oral presentations were divided into five topical sessions aimed at a discussion of Grand Challenge problems in catalysis, dynamics studies, structure characterization, biocatalysis, and computational methods. Eleven internationally known invited experts spoke in these sessions. The Workshop was intended both to educate catalyst experts about the methods and possibilities of neutron methods and to educate the neutron community about the methods and scientific challenges in catalysis. Above all, it was intended to inspire new research ideas among the attendees. All attendees were asked to participate in one or more of three breakout sessions to share ideas and propose new experiments that could be performed using the ORNL neutron facilities. The Workshop was expected to lead to proposals for beam time at either the HFIR or the SNS; therefore, it was expected that each breakout session would identify a few experiments or proof-of-principle experiments and a leader who would pursue a proposal after the Workshop. Also, a refereed review article will be submitted to a prominent journal to present research and ideas illustrating the benefits and possibilities of neutron methods for catalysis research.

  16. ISHHC XIII International Symposium on the Relations between Homogeneous and Heterogeneous Catalysis

    E-Print Network [OSTI]

    Somorjai Ed., G.A.

    2007-01-01

    Key Laboratory of Catalysis, Dalian Institute of ChemicalAcademy of Sciences, Dalian 116023, P. R. China CarbonApplied Catalysis Laboratory, Dalian Institute of Chemical

  17. Complex of transferrin with ruthenium for medical applications

    DOE Patents [OSTI]

    Richards, Powell (Bayport, NY); Srivastava, Suresh C. (Setauket, NY); Meinken, George E. (Middle Island, NY)

    1984-05-15

    A novel Ruthenium-transferrin complex, prepared by reacting iron-free human transferrin dissolved in a sodium acetate solution at pH 7 with ruthenium by heating at about 40.degree. C. for about 2 hours, and purifying said complex by means of gel chromotography with pH 7 sodium acetate as eluent. The mono- or di-metal complex produced can be used in nuclear medicine in the diagnosis and/or treatment of tumors and abscesses. Comparative results with Ga-67-citrate, which is the most widely used tumor-localizing agent in nuclear medicine, indicate increased sensitivity of detection and greater tumor uptake with the Ru-transferrin complex.

  18. Universal bosonic tetramers of dimer-atom-atom structure

    E-Print Network [OSTI]

    A. Deltuva

    2012-03-28

    Unstable four-boson states having an approximate dimer-atom-atom structure are studied using momentum-space integral equations for the four-particle transition operators. For a given Efimov trimer the universal properties of the lowest associated tetramer are determined. The impact of this tetramer on the atom-trimer and dimer-dimer collisions is analyzed. The reliability of the three-body dimer-atom-atom model is studied.

  19. Universal bosonic tetramers of dimer-atom-atom structure

    E-Print Network [OSTI]

    Deltuva, A

    2012-01-01

    Unstable four-boson states having an approximate dimer-atom-atom structure are studied using momentum-space integral equations for the four-particle transition operators. For a given Efimov trimer the universal properties of the lowest associated tetramer are determined. The impact of this tetramer on the atom-trimer and dimer-dimer collisions is analyzed. The reliability of the three-body dimer-atom-atom model is studied.

  20. On the asymptotics of dimers on tori

    E-Print Network [OSTI]

    Richard W. Kenyon; Nike Sun; David B. Wilson

    2015-11-09

    We study asymptotics of the dimer model on large toric graphs. Let $\\mathbb L$ be a weighted $\\mathbb{Z}^2$-periodic planar graph, and let $\\mathbb{Z}^2 E$ be a large-index sublattice of $\\mathbb{Z}^2$. For $\\mathbb L$ bipartite we show that the dimer partition function on the quotient $\\mathbb{L}/(\\mathbb{Z}^2 E)$ has the asymptotic expansion $\\exp[A f_0 + \\text{fsc} + o(1)]$, where $A$ is the area of $\\mathbb{L}/(\\mathbb{Z}^2 E)$, $f_0$ is the free energy density in the bulk, and $\\text{fsc}$ is a finite-size correction term depending only on the conformal shape of the domain together with some parity-type information. Assuming a conjectural condition on the zero locus of the dimer characteristic polynomial, we show that an analogous expansion holds for $\\mathbb{L}$ non-bipartite. The functional form of the finite-size correction differs between the two classes, but is universal within each class. Our calculations yield new information concerning the distribution of the number of loops winding around the torus in the associated double-dimer models.

  1. Neutrons for Catalysis: A Workshop on Neutron Scattering Techniques for Studies in Catalysis

    E-Print Network [OSTI]

    Pennycook, Steve

    -EM Fischer Tropsch Catalysis on Fe- or Co-catalysts, ,,CTL" Coal to Liquids ­ ,a rough (?) analogy #12;Peter Albers, AQ-EM Carbonaceous Deposits on Catalysts #12;Peter Albers, AQ-EM IINS on Coked Catalysts from Industrial Plants High-temperature and low-temperature cokes deposited on catalysts during

  2. Lithium Diisopropylamide-Mediated Enolization: Catalysis by Hemilabile Ligands

    E-Print Network [OSTI]

    Collum, David B.

    Lithium Diisopropylamide-Mediated Enolization: Catalysis by Hemilabile Ligands Antonio Ramirez of a lithium diisopropylamide (LDA)-mediated ester enolization. Hemilabile amino ether MeOCH2CH2NMe2, binding-based catalysis are thwarted by the occlusion of the catalyst on the lithium salt products and byproducts (eq 1

  3. Dynamic control of catalysis within biological cells

    E-Print Network [OSTI]

    Biman Jana; Biman Bagchi

    2011-05-26

    We develop a theory of enzyme catalysis within biological cells where the substrate concentration [S](t) is time dependent, in contrast to the Michaelis-Menten theory that assumes a steady state. We find that the time varying concentration can combine, in a non-linear way, with the ruggedness of the free energy landscape of enzymes (discovered both in single molecule studies and in simulations) to provide a highly efficient switch (or, bifurcation) between two catalytically active states, at a critical substrate concentration. This allows a dynamic control of product synthesis in cell.

  4. Catalysis and Synthesis | Argonne National Laboratory

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative Fuels Data Center Homesum_a_epg0_fpd_mmcf_m.xls" ,"Available from WebQuantity ofkandz-cm11 OutreachProductswsicloudwsiclouddenDVA N C E D B LReports fromSheetsCascadia AnalysisCatalysis and Synthesis

  5. Opportunities in Catalysis Research Using Synchrotron Radiation

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative Fuels Data Center Homesum_a_epg0_fpd_mmcf_m.xls" ,"Available from WebQuantityBonneville Power Administration wouldMass mapSpeeding access toOctober 1996Technologies /JuneOperatingBusinessin Catalysis

  6. Fibrillar dimer formation of islet amyloid polypeptides

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Chiu, Chi -cheng; de Pablo, Juan J.

    2015-05-08

    Amyloid deposits of human islet amyloid polypeptide (hIAPP), a 37-residue hormone co-produced with insulin, have been implicated in the development of type 2 diabetes. Residues 20 – 29 of hIAPP have been proposed to constitute the amyloidogenic core for the aggregation process, yet the segment is mostly unstructured in the mature fibril, according to solid-state NMR data. Here we use molecular simulations combined with bias-exchange metadynamics to characterize the conformational free energies of hIAPP fibrillar dimer and its derivative, pramlintide. We show that residues 20 – 29 are involved in an intermediate that exhibits transient ?-sheets, consistent with recent experimentalmore »and simulation results. By comparing the aggregation of hIAPP and pramlintide, we illustrate the effects of proline residues on inhibition of the dimerization of IAPP. The mechanistic insights presented here could be useful for development of therapeutic inhibitors of hIAPP amyloid formation.« less

  7. Dimerization specificities of leucine zipper mutants 

    E-Print Network [OSTI]

    Rieker, Jennifer Dawn

    2013-02-22

    -1 DIMEItIZA TION SPECIFICITIES OF LEUCINE ZIPPER MUTAIV TS A Senior Thesis By Jennifer Dawn Rieker 1997-98 University Undergraduate Research Fellow Texas ARM University Group: Biochemistry/Chemistry DIMERIZATION SPECIFICITIES OF LEUCINE ZIPPER... MUTANTS by Jennifer Dawn Rieker Submitted to the Office of Honors Programs and Academic Scholarships, Texas AkM University in partial fulfillment of the requirements for 1997-98 UNVERSITY UNDERGRADUATE RESEARCH FELLOWS PROGRAM April 16, 1998...

  8. Hydrodesulfurization of dibenzothiophene catalyzed by alumina-supported ruthenium carbonyl complexes in a pressurized flow system

    SciTech Connect (OSTI)

    NONE

    1994-11-01

    Ruthenium sulfide has been found to be most active for hydrodesulfurization (HDS) of thiophenes as well as hydrogenation and hydrodenitrogenation among transition metal sulfides. When ruthenium sulfide is supported on alumina, silica, or zeolite with high surface area, highly dispersed ruthenium sulfide formed on the supports would increase the catalytic activity per a ruthenium atom. Several researchers have already reported HDS using supported ruthenium sulfides. In these works [Ru(NH{sub 3}){sub 6}]{sup +}, Ru{sub 3}(CO){sub 12}, RuCl{sub 3}, and Ru(III) acetate supported on alumina, zeoliate, carbon, etc., were used as catalyst precursors in HDS of thiophene, benzothiophene, or dibenzothiophene. Although these HDS reactions were performed under an atmospheric pressure, the activity of the catalysts derived from supported ruthenium in a pressurized flow system have not yet been understood. In the present study, HDS of DBT catalyzed by ruthenium catalysts is investigated in a pressurized flow reactor. 17 refs., 2 figs., 2 tabs.

  9. Ruthenium Behavior at Phase Separation of Borosilicate Glass-12259

    SciTech Connect (OSTI)

    Enokida, Youichi [Graduate School of Engineering, Nagoya University, Nagoya, 463-8603 (Japan); Sawada, Kayo [EcoTopia Science Institute, Nagoya University, Nagoya, 463-8603 (Japan)

    2012-07-01

    The Rokkasho reprocessing plant (RRP) located in Aomori, Japan, vitrifies high level waste (HLW) into a borosilicate glass. The HLW is generated from the reprocessing of spent fuel and contains ruthenium (Ru) and other platinum group metals (PGMs). Based on the recent consequences after a huge earthquake that occurred in Japan, a hypothetical blackout was postulated for the RRP to address additional safety analysis requirements. During a prolonged blackout, the borosilicate glass could phase separate due to cooling of the glass in the melter. The Ru present in the glass matrix could migrate into separate phases and impact the durability of the borosilicate glass. The durability of the glass is important for quality assurance and performance assessment of the vitrified HLW. A fundamental study was performed at an independent university to understand the impact of a prolonged blackout. Simulated HLW glasses were prepared for the RRP, and the Ru behavior in phase separated glasses was studied. The simulated HLW glasses contained nonradioactive elements and PGMs. The glass compositions were then altered to enhance the formation of the phase-separated glasses when subjected to thermal treatment at 700 deg. C for 24 hours. The synthesized simulated glasses contained 1.1 % Ru by weight as ruthenium dioxide (RuO{sub 2}). A portion of the RuO{sub 2} formed needle-shaped crystals in the glass specimens. After the thermal treatment, the glass specimen had separated into two phases. One of the two phases was a B{sub 2}O{sub 3} rich phase, and the other phase was a SiO{sub 2} rich phase. The majority of the chemical species in the B{sub 2}O{sub 3} rich phase was leached away with the Material Characterization Center-3 (MCC-3) protocol standardized by the Pacific Northwest National Laboratory using an aqueous low-concentrated nitric acid solution, but the leaching of the Ru fraction was very limited; less than 1% of the original Ru content. The Ru leaching was much less than those of the other elements, and the needle-shaped crystals of RuO{sub 2} were observed in the B{sub 2}O{sub 3} rich phase in the specimen after the leaching test. Another experiment was performed using another glass specimen which had been prepared with the same frits, but used reagent RuO{sub 2} of granular shape at lower content (0.0073% by weight as RuO{sub 2}). The leached fractions of elements for the latter specimen increased to almost the same fraction (more than 10% of the original Ru content) as observed for boron and sodium, when the phase separated glass was leached using the MMC-3 protocol with non-acidic de-ionized water. Based on the results of this study, it was concluded that needle-shaped RuO{sub 2} crystals are contained in the B{sub 2}O{sub 3}-rich phase after phase separation of the borosilicate glass after a hypothetical blackout. The leaching fraction for the needle-shaped RuO{sub 2} present in the phase separated glass is much lower than those for boron or sodium. Ruthenium behavior has been studied for a hypothetical loss of cooling in the liquid fed ceramic melter for high level waste by taking into account the phase separation of borosilicate glass. The needle-shaped crystal of ruthenium dioxide after bi-nodal-type phase separation of the borosilicate glass at 700 deg. C migrated into the B{sub 2}O{sub 3} rich phase, but remained without dissolution by an acidic aqueous solution. Additionally, granular ruthenium dioxide can be a morphological form of ruthenium after bimodal-type phase separation of the vitrified high level waste with borosilicate glass media. After the phase separation of the borosilicate glass, the crystal shape of the ruthenium dioxide is either needle-shaped or granular, and the leachable fraction of ruthenium is relatively much lower than those of major components (boron and sodium) in the vitrified borosilicate glass. The fraction of leached ruthenium increased to almost the same fraction as observed for boron and sodium when the phase-separated glass was leached with ultrapure water. (authors)

  10. Frontiers in Catalysis Science and Engineering Seminar Series

    E-Print Network [OSTI]

    Engineering School of Chemistry and Biochemistry J. Carl & Sheila Pirkle Faculty Fellow Abstract Metal salenFrontiers in Catalysis Science and Engineering Seminar Series Heterogenized M-Salen Catalysts

  11. Materials and interfaces for catalysis, separation, storage, and environmental applications

    E-Print Network [OSTI]

    Nair, Sankar

    the next generation of catalysts, separation processes, gas and liquid storage technologiesMaterials and interfaces for catalysis, separation, storage, and environmental applications Advanced materials and interfaces (including surfaces, thin films, and membranes) are a key to developing

  12. Catalysis Working Group Kick-Off Meeting Agenda

    Broader source: Energy.gov [DOE]

    Agenda for the kick-off meeting of the U.S. Department of Energy Fuel Cell Technologies Program's Catalysis Working Group, held May 14, 2012, in Arlington, Virginia.

  13. Theoretical investigation of solar energy conversion and water oxidation catalysis

    E-Print Network [OSTI]

    Wang, Lee-Ping

    2011-01-01

    Solar energy conversion and water oxidation catalysis are two great scientific and engineering challenges that will play pivotal roles in a future sustainable energy economy. In this work, I apply electronic structure ...

  14. Quantum Phase Transition in Dimerized Spin-1/2 Chains

    E-Print Network [OSTI]

    Aparajita Das; Sreeparna Bhadra; Sonali Saha

    2015-03-30

    Quantum phase transition in dimerized antiferromagnetic Heisenberg spin chain has been studied. A staircase structure in the variation of concurrence within strongly coupled pairs with that of external magnetic field has been observed indicating multiple critical points. Emergence of entanglement due to external magnetic field or magnetic entanglement is observed for weakly coupled spin pairs in the same dimer chain. Though closed dimerized isotropic XXX Heisenberg chains with different dimer strengths were mainly explored, analogous studies on open chains as well as closed anisotropic (XX interaction) chains with tilted external magnetic field have also been studied.

  15. Dedicated Beamline Facilities for Catalytic Research. Synchrotron Catalysis Consortium (SCC)

    SciTech Connect (OSTI)

    Chen, Jingguang; Frenkel, Anatoly; Rodriguez, Jose; Adzic, Radoslav; Bare, Simon R.; Hulbert, Steve L.; Karim, Ayman; Mullins, David R.; Overbury, Steve

    2015-03-04

    Synchrotron spectroscopies offer unique advantages over conventional techniques, including higher detection sensitivity and molecular specificity, faster detection rate, and more in-depth information regarding the structural, electronic and catalytic properties under in-situ reaction conditions. Despite these advantages, synchrotron techniques are often underutilized or unexplored by the catalysis community due to various perceived and real barriers, which will be addressed in the current proposal. Since its establishment in 2005, the Synchrotron Catalysis Consortium (SCC) has coordinated significant efforts to promote the utilization of cutting-edge catalytic research under in-situ conditions. The purpose of the current renewal proposal is aimed to provide assistance, and to develop new sciences/techniques, for the catalysis community through the following concerted efforts: Coordinating the implementation of a suite of beamlines for catalysis studies at the new NSLS-II synchrotron source; Providing assistance and coordination for catalysis users at an SSRL catalysis beamline during the initial period of NSLS to NSLS II transition; Designing in-situ reactors for a variety of catalytic and electrocatalytic studies; Assisting experimental set-up and data analysis by a dedicated research scientist; Offering training courses and help sessions by the PIs and co-PIs.

  16. Characterization of Palladium and Ruthenium after Reaction with Tetraphenylborate and Mercury

    SciTech Connect (OSTI)

    Duff, M.C.

    2001-09-11

    This report documents a second series of X-ray fine structure and chemical analyses to examine the form that Pd - and, to a lesser extent, ruthenium (Ru) - takes in simulated high-level slurries containing TPB salts.

  17. Platinum-ruthenium-palladium alloys for use as a fuel cell catalyst

    DOE Patents [OSTI]

    Gorer, Alexander (Sunnyvale, CA)

    2002-01-01

    A noble metal alloy composition for a fuel cell catalyst, a ternary alloy composition containing platinum, ruthenium and palladium. The alloy shows increased activity as compared to well-known catalysts.

  18. Novel Ruthenium complexes and their application in dye sensitised solar cells 

    E-Print Network [OSTI]

    McCall, Keri Laura

    2009-01-01

    This work focuses on the design, synthesis and characterisation of novel ruthenium bipyridyl complexes and their use in dye sensitised solar cells (DSSCs). Four series of dyes have been synthesised with the general formula ...

  19. Ruthenium or osmium complexes and their uses as catalysts for water oxidation

    SciTech Connect (OSTI)

    Concepcion Corbea, Javier Jesus; Chen, Zuofeng; Jurss, Jonah Wesley; Templeton, Joseph L; Hoertz, Paul; Meyer, Thomas J

    2014-10-28

    The present invention provides ruthenium or osmium complexes and their uses as a catalyst for catalytic water oxidation. Another aspect of the invention provides an electrode and photo-electrochemical cells for electrolysis of water molecules.

  20. Ruthenium or osmium complexes and their uses as catalysts for water oxidation

    DOE Patents [OSTI]

    Corbea, Javier Jesus Concepcion; Chen, Zuofeng; Jurss, Jonah Wesley; Templeton, Joseph L.; Hoertz, Paul; Meyer, Thomas J.

    2013-09-03

    The present invention provides ruthenium or osmium complexes and their uses as a catalyst for catalytic water oxidation. Another aspect of the invention provides an electrode and photo-electrochemical cells for electrolysis of water molecules.

  1. Volume$3, number 3 CHEMICAL. PHYSICS LETTERS 1 Februrf 1978 INTERACTION OF METHANOL WITH RUTHENIUM

    E-Print Network [OSTI]

    Goodman, Wayne

    Volume$3, number 3 CHEMICAL. PHYSICS LETTERS 1 Februrf 1978 INTERACTION OF METHANOL WITH RUTHENIUM of methanol with a clean methods. Methanol dissociates upon adsorption at 300 K and yields Ha(g) and chemisorbed CO as the domiwt

  2. Equivalence between XY and dimerized models

    SciTech Connect (OSTI)

    Campos Venuti, Lorenzo; Roncaglia, Marco

    2010-06-15

    The spin-1/2 chain with XY anisotropic coupling in the plane and the XX isotropic dimerized chain are shown to be equivalent in the bulk. For finite systems, we prove that the equivalence is exact in given parity sectors, after taking care of the precise boundary conditions. The proof is given constructively by finding unitary transformations that map the models onto each other. Moreover, we considerably generalized our mapping and showed that even in the case of fully site-dependent couplings the XY chain can be mapped onto an XX model. This result has potential application in the study of disordered systems.

  3. Ruthenium on rutile catalyst, catalytic system, and method for aqueous phase hydrogenations

    DOE Patents [OSTI]

    Elliot, Douglas C. (Richland, WA); Werpy, Todd A. (West Richland, WA); Wang, Yong (Richland, WA); Frye, Jr., John G. (Richland, WA)

    2001-01-01

    An essentially nickel- and rhenium-free catalyst is described comprising ruthenium on a titania support where the titania is greater than 75% rutile. A catalytic system containing a nickel-free catalyst comprising ruthenium on a titania support where the titania is greater than 75% rutile, and a method using this catalyst in the hydrogenation of an organic compound in the aqueous phase is also described.

  4. Solvation and Acid Strength Effects on Catalysis by Faujasite Zeolites

    SciTech Connect (OSTI)

    Gounder, Rajamani P.; Jones, Andrew J.; Carr, Robert T.; Iglesia, Enrique

    2012-02-01

    Kinetic, spectroscopic, and chemical titration data indicate that differences in monomolecular isobutane cracking and dehydrogenation and methanol dehydration turnover rates (per H+) among FAU zeolites treated thermally with steam (H-USY) and then chemically with ammonium hexafluorosilicate (CDHUSY) predominantly reflect differences in the size and solvating properties of their supercage voids rather than differences in acid strength. The number of protons on a given sample was measured consistently by titrations with Na+, with CH3 groups via reactions of dimethyl ether, and with 2,6-di-tert-butylpyridine during methanol dehydration catalysis; these titration values were also supported by commensurate changes in acidic OH infrared band areas upon exposure to titrant molecules. The number of protons, taken as the average of the three titration methods, was significantly smaller than the number of framework Al atoms (Alf) obtained from X-ray diffraction and 27Al magic angle spinning nuclear magnetic resonance spectroscopy on H-USY (0.35 H+/Alf) and CD-HUSY (0.69 H+/Alf). These data demonstrate that the ubiquitous use of Alf sites as structural proxies for active H+ sites in zeolites can be imprecise, apparently because distorted Al structures that are not associated with acidic protons are sometimes detected as Alf sites. Monomolecular isobutane cracking and dehydrogenation rate constants, normalized non-rigorously by the number of Alf species, decreased with increasing Na+ content on both H-USY and CD-HUSY samples and became undetectable at sub-stoichiometric exchange levels (0.32 and 0.72 Na+/Alf ratios, respectively), an unexpected finding attributed incorrectly in previous studies to the presence of minority ‘‘super-acidic’’ sites. These rate constants, when normalized rigorously by the number of residual H+ sites were independent of Na+ content on both H-USY and CD-HUSY samples, reflecting the stoichiometric replacement of protons that are uniform in reactivity by Na+ cations. Monomolecular isobutane cracking and dehydrogenation rate constants (per H+; 763 K), however, were higher on H-USY than CD-HUSY (by a factor of 1.4). Equilibrium constants for the formation of protonated methanol dimers via adsorption of gaseous methanol onto adsorbed methanol monomers, determined from kinetic studies of methanol dehydration to dimethyl ether (433 K), were also higher on H-USY than CD-HUSY (by a factor of 2.1). These larger constants predominantly reflect stronger dispersive interactions in H-USY, consistent with its smaller supercage voids that result from the occlusion of void space by extraframework Al (Alex) residues. These findings appear to clarify enduring controversies about the mechanistic interpretation of the effects of Na+ and Alex species on the catalytic reactivity of FAU zeolites. They also illustrate the need to normalize rates by the number of active sites instead of more convenient but less accurate structural proxies for such sites.

  5. New and Future Developments in Catalysis. Activation of Carbon Dioxide, 1st edition Supporting Information to Chapter 17

    E-Print Network [OSTI]

    Glaser, Rainer

    New and Future Developments in Catalysis. Activation of Carbon Dioxide, 1st Developments in Catalysis. Activation of Carbon Dioxide, 1st edition S2 Cartesian

  6. Size Effect of Ruthenium Nanoparticles in Catalytic Carbon Monoxide Oxidation

    SciTech Connect (OSTI)

    Joo, Sang Hoon; Park, Jeong Y.; Renzas, J. Russell; Butcher, Derek R.; Huang, Wenyu; Somorjai, Gabor A.

    2010-04-04

    Carbon monoxide oxidation over ruthenium catalysts has shown an unusual catalytic behavior. Here we report a particle size effect on CO oxidation over Ru nanoparticle (NP) catalysts. Uniform Ru NPs with a tunable particle size from 2 to 6 nm were synthesized by a polyol reduction of Ru(acac){sub 3} precursor in the presence of poly(vinylpyrrolidone) stabilizer. The measurement of catalytic activity of CO oxidation over two-dimensional Ru NPs arrays under oxidizing reaction conditions (40 Torr CO and 100 Torr O{sub 2}) showed an activity dependence on the Ru NP size. The CO oxidation activity increases with NP size, and the 6 nm Ru NP catalyst shows 8-fold higher activity than the 2 nm catalysts. The results gained from this study will provide the scientific basis for future design of Ru-based oxidation catalysts.

  7. Platinum adlayered ruthenium nanoparticles, method for preparing, and uses thereof

    DOE Patents [OSTI]

    Tong, YuYe; Du, Bingchen

    2015-08-11

    A superior, industrially scalable one-pot ethylene glycol-based wet chemistry method to prepare platinum-adlayered ruthenium nanoparticles has been developed that offers an exquisite control of the platinum packing density of the adlayers and effectively prevents sintering of the nanoparticles during the deposition process. The wet chemistry based method for the controlled deposition of submonolayer platinum is advantageous in terms of processing and maximizing the use of platinum and can, in principle, be scaled up straightforwardly to an industrial level. The reactivity of the Pt(31)-Ru sample was about 150% higher than that of the industrial benchmark PtRu (1:1) alloy sample but with 3.5 times less platinum loading. Using the Pt(31)-Ru nanoparticles would lower the electrode material cost compared to using the industrial benchmark alloy nanoparticles for direct methanol fuel cell applications.

  8. Mechanisms and Design in Homogeneous Catalysis

    SciTech Connect (OSTI)

    Clark R. Landis

    2010-05-26

    The major goal of this research is the determination of structure-activity relationships with respect to the elementary reactions that constitute catalytic alkene polymerization. Three classes of structure-activity relationships pertain to this work: (1) The influence of the nature of the propagating alkyl (secondary, primary, ?-substituted) and alkene monomer on the rates and selectivity of propagation, termination, isomerization, hydrogenolysis, etc. Such analyses are possible by direct observation methods (2) Influence of Cp-ligand substituents on fundamental reaction steps by application of direct observation and quenched-flow methods (3) Influence of counterion and solvent polarity on rates and selectivities of elementary steps during polymerization. At this point our rate of progress is limited by a combination of inefficiencies in some data collection modes (particularly quenched-flow studies) and by a relatively narrow range of accessible rates (especially for the NMR methods). Therefore, the bulk of our work concerns the development NMR, mass spectrometric, and chromatographic methods for probing catalytic reactions in a high throughput mode. Although these methods will be applied in the context of alkene polymerization, the NMR and mass spectrometric methods are completely general and will benefit research in all areas of catalysis.

  9. Some General Themes in Catalysis at LANL

    SciTech Connect (OSTI)

    Gordon, John C.

    2012-07-19

    Some general themes in catalysis at LANL are: (1) Storage and release of energy within chemical bonds (e.g. H{sub 2} storage in and release from covalent bonds, N{sub 2} functionalization, CO{sub 2} functionalization, H{sub 2} oxidation/evolution, O{sub 2} reduction/evolution); (2) Can we control the chemistry of reactive substrates to effect energy relevant transformations in non-traditional media (e.g. can we promote C-C couplings, dehydrations, or hydrogenations in water under relatively mild conditions)? (3) Can we supplant precious metal or rare earth catalysts to effect these transformations, by using earth abundant metals/elements instead? Can we use organocatalysis and circumvent the use of metals completely? (4) Can we improve upon existing rare earth catalyst systems (e.g. in rare earth oxides pertinent to fluid cracking or polymerization) and reduce amounts required for catalytic efficacy? Carbohydrates can be accessed from non-food based biomass sources such as woody residues and switchgrass. After extracted from the plant source, our goal is to upgrade these classes of molecules into useful fuels.

  10. Geek-Up[3.11.2011]: Energy Efficiency, Catalysis and Open Source...

    Energy Savers [EERE]

    Geek-Up3.11.2011: Energy Efficiency, Catalysis and Open Source Tools Geek-Up3.11.2011: Energy Efficiency, Catalysis and Open Source Tools March 11, 2011 - 4:37pm Addthis L....

  11. ISHHC XIII International Symposium on the Relations between Homogeneous and Heterogeneous Catalysis

    E-Print Network [OSTI]

    Somorjai Ed., G.A.

    2007-01-01

    K. Lee Semiconductor Photocatalysis in Advanced Oxidationthermal) catalysis or photocatalysis on nanoporous supportswith Heterogeneous Photocatalysis using Nanostructured

  12. Development of a stable cobalt-ruthenium Fisher-Tropsch catalyst. Final report

    SciTech Connect (OSTI)

    Frame, R.R.; Gala, H.B.

    1995-02-01

    The reverse micelle catalyst preparation method has been used to prepare catalysts on four supports: magnesium oxide, carbon, alumina- titania and steamed Y zeolite. These catalysts were not as active as a reference catalyst prepared during previous contracts to Union Carbide Corp. This catalyst was supported on steamed Y zerolite support and was impregnated by a pore-filling method using a nonaqueous solvent. Additional catalysts were prepared via pore- filling impregnation of steamed Y zeolites. These catalysts had levels of cobalt two to three and a half times as high as the original Union Carbide catalyst. On a catalyst volume basis they were much more active than the previous catalyst; on an atom by atom basis the cobalt was about of the same activity, i.e., the high cobalt catalysts` cobalt atoms were not extensively covered over and deactivated by other cobalt atoms. The new, high activity, Y zerolite catalysts were not as stable as the earlier Union Carbide catalyst. However, stability enhancement of these catalysts should be possible, for instance, through adjustment of the quantity and/or type of trace metals present. A primary objective of this work was determination whether small amounts of ruthenium could enhance the activity of the cobalt F-T catalyst. The reverse micelle catalysts were not activated by ruthenium, indeed scanning transmission electronic microscopy (STEM) analysis provided some evidence that ruthenium was not present in the cobalt crystallites. Ruthenium did not seem to activate the high cobalt Y zeolite catalyst either, but additional experiments with Y zeolite-supported catalysts are required. Should ruthenium prove not to be an effective promoter under the simple catalyst activation procedure used in this work, more complex activation procedures have been reported which are claimed to enhance the cobalt/ruthenium interaction and result in activity promotion by ruthenium.

  13. Final technical report, Symposium on New Theoretical Concepts and Directions in Catalysis

    SciTech Connect (OSTI)

    Metiu, Horia

    2014-08-22

    We organized in August 2013 a “Symposium on New Theoretical Concepts and Directions in Catalysis” with the participation of 20 invited distinguished quantum chemists and other researchers who use computations to study catalysis. Symposium website; http://catalysis.cnsi.ucsb.edu/

  14. Seventh BES (Basic Energy Sciences) catalysis and surface chemistry research conference

    SciTech Connect (OSTI)

    Not Available

    1990-03-01

    Research programs on catalysis and surface chemistry are presented. A total of fifty-seven topics are included. Areas of research include heterogeneous catalysis; catalysis in hydrogenation, desulfurization, gasification, and redox reactions; studies of surface properties and surface active sites; catalyst supports; chemical activation, deactivation; selectivity, chemical preparation; molecular structure studies; sorption and dissociation. Individual projects are processed separately for the data bases. (CBS)

  15. Exhaust aftertreatment using plasma-assisted catalysis

    SciTech Connect (OSTI)

    Penetrante, B

    2000-01-20

    In the field of catalysis, one application that has been classified as a breakthrough technology is the catalytic reduction of NO{sub x} in oxygen-rich environments using hydrocarbons. This breakthrough will require dramatic improvements in both catalyst and engine technology, but the benefits will be substantial for energy efficiency and a cleaner environment. Engine and automobile companies are placing greater emphasis on the diesel engine because of its potential for saving fuel resources and reducing CO{sub 2} emissions. The modern direct-injection diesel engine offers demonstrated fuel economy advantages unmatched by any other commercially-viable engine. The main drawback of diesel engines is exhaust emissions. A modification of existing oxidation catalyst/engine technology is being used to address the CO, hydrocarbon and particulates. However, no satisfactory solution currently exists for NO{sub x}. Diesel engines operate under net oxidizing conditions, thus rendering conventional three-way catalytic converters ineffective for the controlling the NO{sub x} emission. NO{sub x} reduction catalysts, using ammonia as a reductant, do exist for oxygen-rich exhausts; however, for transportation applications, the use of on-board hydrocarbon fuels is a more feasible, cost-effective, and environmentally-sound approach. Selective catalytic reduction (SCR) by hydrocarbons is one of the leading catalytic aftertreatment technologies for the reduction of NO{sub x} in lean-burn engine exhaust (often referred to as lean-NO{sub x}). The objective is to chemically reduce the pollutant molecules of NO{sub x} to benign molecules such as N{sub 2}. Aftertreatment schemes have focused a great deal on the reduction of NO because the NO{sub x} in engine exhaust is composed primarily of NO. Recent studies, however, have shown that the oxidation of NO to NO{sub 2} serves an important role in enhancing the efficiency for reduction of NO{sub x} to N{sub 2}. It has become apparent that preconverting NO to NO{sub 2} could improve both the efficiency and durability of lean-NO{sub x} catalysts. A non-thermal plasma is an efficient means for selective partial oxidation of NO to NO{sub 2}. The use of a non-thermal plasma in combination with a lean-NO{sub x} catalyst opens the opportunity for catalysts that are more efficient and more durable compared to conventional catalysts. In the absence of hydrocarbons, the O radicals will oxidize NO to NO{sub 2}, and the OH radicals will further oxidize NO{sub 2} to nitric acid. In plasma-assisted catalysis it is important that the plasma oxidize NO to NO{sub 2} without further producing acids.

  16. Center for Catalysis at Iowa State University

    SciTech Connect (OSTI)

    Kraus, George A.

    2006-10-17

    The overall objective of this proposal is to enable Iowa State University to establish a Center that enjoys world-class stature and eventually enhances the economy through the transfer of innovation from the laboratory to the marketplace. The funds have been used to support experimental proposals from interdisciplinary research teams in areas related to catalysis and green chemistry. Specific focus areas included: • Catalytic conversion of renewable natural resources to industrial materials • Development of new catalysts for the oxidation or reduction of commodity chemicals • Use of enzymes and microorganisms in biocatalysis • Development of new, environmentally friendly reactions of industrial importance These focus areas intersect with barriers from the MYTP draft document. Specifically, section 2.4.3.1 Processing and Conversion has a list of bulleted items under Improved Chemical Conversions that includes new hydrogenation catalysts, milder oxidation catalysts, new catalysts for dehydration and selective bond cleavage catalysts. Specifically, the four sections are: 1. Catalyst development (7.4.12.A) 2. Conversion of glycerol (7.4.12.B) 3. Conversion of biodiesel (7.4.12.C) 4. Glucose from starch (7.4.12.D) All funded projects are part of a soybean or corn biorefinery. Two funded projects that have made significant progress toward goals of the MYTP draft document are: Catalysts to convert feedstocks with high fatty acid content to biodiesel (Kraus, Lin, Verkade) and Conversion of Glycerol into 1,3-Propanediol (Lin, Kraus). Currently, biodiesel is prepared using homogeneous base catalysis. However, as producers look for feedstocks other than soybean oil, such as waste restaurant oils and rendered animal fats, they have observed a large amount of free fatty acids contained in the feedstocks. Free fatty acids cannot be converted into biodiesel using homogeneous base-mediated processes. The CCAT catalyst system offers an integrated and cooperative catalytic system that performs both esterification (of free fatty acids) and transesterification (of soybean oil) in a one-pot fashion. This will allow the biodiesel producers to use the aforementioned cheap feedstocks without any pretreatment. In addition, the catalyst system is heterogeneous and is highly recyclable and reusable. Although markets currently exist for glycerin, concern is mounting that the price of glycerin may plummet to $.05 - $.10 per pound if future production exceeds demand. Developing a system to make high value chemicals such as 1,3-propanediol from the glycerin stream will add value for biodiesel producers who implement the new technology. Given the fact that both DuPont and Shell chemicals have announced the commercialization of two new PDO-based polymers, a rapid increase of market demand for a cheaper PDO source is very likely. 4. Comparison of actual accomplishments with goals and objectives From our progress reports, the four areas are: 1. Catalyst development (7.4.12.A) 2. Conversion of glycerol (7.4.12.B) 3. Conversion of biodiesel (7.4.12.C) 4. Glucose from starch (7.4.12.D)

  17. Adsorption of silver dimer on graphene - A DFT study

    SciTech Connect (OSTI)

    Kaur, Gagandeep, E-mail: gaganj1981@yahoo.com [Department of Physics and Centre of Advanced Studies in Physics, Panjab University, Chandigarh-160014, India and Chandigarh Engineering College, Landran, Mohali-140307, Punjab (India); Gupta, Shuchi [Department of Physics and Centre of Advanced Studies in Physics, Panjab University, Chandigarh-160014, India and University Institute of Engineering and Technology, Panjab University, Chandigarh -160014 (India); Rani, Pooja; Dharamvir, Keya [Department of Physics and Centre of Advanced Studies in Physics, Panjab University, Chandigarh-160014 (India)

    2014-04-24

    We performed a systematic density functional theory (DFT) study of the adsorption of silver dimer (Ag{sub 2}) on graphene using SIESTA (Spanish Initiative for Electronic Simulations with Thousands of Atoms) package, in the generalized gradient approximation (GGA). The adsorption energy, geometry, and charge transfer of Ag2-graphene system are calculated. The minimum energy configuration for a silver dimer is parallel to the graphene sheet with its two atoms directly above the centre of carbon-carbon bond. The negligible charge transfer between the dimer and the surface is also indicative of a weak bond. The methodology demonstrated in this paper may be applied to larger silver clusters on graphene sheet.

  18. A quantum dimer model for the pseudogap metal

    E-Print Network [OSTI]

    Matthias Punk; Andrea Allais; Subir Sachdev

    2015-07-05

    We propose a quantum dimer model for the metallic state of the hole-doped cuprates at low hole density, $p$. The Hilbert space is spanned by spinless, neutral, bosonic dimers and spin $S=1/2$, charge $+e$ fermionic dimers. The model realizes a `fractionalized Fermi liquid' with no symmetry-breaking and small hole pocket Fermi surfaces enclosing a total area determined by $p$. Exact diagonalization, on lattices of sizes up to $8 \\times 8$, shows anisotropic quasiparticle residue around the pocket Fermi surfaces. We discuss the relationship to experiments.

  19. Development of carbon-metal oxide supercapacitors from sol-gel derived carbon-ruthenium xerogels

    SciTech Connect (OSTI)

    Lin, C.; Ritter, J.A.; Popov, B.N.

    1999-09-01

    There has been increasing interest in electrochemical capacitors as energy storage systems because of their high power density and long cycle life, compared to battery devices. According to the mechanism of energy storage, there are two types of electrochemical capacitors. One type is based on double layer (dl) formation due to charge separation, and the other type is based on a faradaic process due to redox reactions. Sol-gel derived high surface area carbon-ruthenium xerogels were prepared from carbonized resorcinol-formaldehyde resins containing an electrochemically active form of ruthenium oxide. The electrochemical capacitance of these materials increased with an increase in the ruthenium content indicating the presence of pseudocapacitance associated with the ruthenium oxide undergoing reversible faradaic redox reactions. A specific capacitance of 256 F/g (single electrode) was obtained from a carbon xerogel containing 14 wt% Ru, which corresponded to more than 50% utilization of the ruthenium. The double layer accounted for 40% of this capacitance. This material was also electrochemically stable, showing no change in a cyclic voltammogram for over 2,000 cycles.

  20. A structural investigation of the chemokine dimer interface 

    E-Print Network [OSTI]

    Hayes, Garret Lance

    2013-02-22

    Macrophage Inflammatory Protein (MIP)-1b is a dimeric protein of the CC chemokine subfamily. Interest in both the structure and function of MIP-1b has increased rapidly over the past several years, resulting primarily from ...

  1. Glassy Dislocation Dynamics in 2-D Colloidal Dimer Crystals

    E-Print Network [OSTI]

    Sharon J. Gerbode; Umang Agarwal; Desmond C. Ong; Chekesha M. Liddell; Fernando Escobedo; Itai Cohen

    2010-08-11

    Although glassy relaxation is typically associated with disorder, here we report on a new type of glassy dynamics relating to dislocations within 2-D crystals of colloidal dimers. Previous studies have demonstrated that dislocation motion in dimer crystals is restricted by certain particle orientations. Here, we drag an optically trapped particle through such dimer crystals, creating dislocations. We find a two-stage relaxation response where initially dislocations glide until encountering particles that cage their motion. Subsequent relaxation occurs logarithmically slowly through a second process where dislocations hop between caged configurations. Finally, in simulations of sheared dimer crystals, the dislocation mean squared displacement displays a caging plateau typical of glassy dynamics. Together, these results reveal a novel glassy system within a colloidal crystal.

  2. Mathematical and experimental approaches to the dimer catastrophe theory

    E-Print Network [OSTI]

    Field, Christopher Martyn

    2011-02-08

    to the Dimer Catastrophe Theory Christopher Martyn Field Gonville & Caius College Department of Genetics University of Cambridge A dissertation submitted for the degree of Doctor of Philosophy November 12, 2010 Title Mathematical and Experimental Approaches... to the Dimer Catastrophe Theory Abstract Multicopy plasmids rely on random distribution for stable inheritance by daughter cells at division. Threats to plasmid copy number increase the probability of plasmid loss, which can be detrimental to both plasmid...

  3. Frontiers in Catalysis Science and Engineering Seminar Series

    E-Print Network [OSTI]

    Frontiers in Catalysis Science and Engineering Seminar Series H· Transfer from Transition-Metal Hydrides. Applications to Radical Polymerizations and Cyclizations Presented by... Jack R. Norton(II) metalloradical, but both the metalloradical and the hydride are present during the operation of newer (Cr

  4. Homogeneous Catalysis Selective Oxidation of Methane to Methanol

    E-Print Network [OSTI]

    Goddard III, William A.

    Homogeneous Catalysis Selective Oxidation of Methane to Methanol Catalyzed, with CÀH Activation (generated by dissolution[6] of Au2O3) react with methane at 1808C to selectively generate methanol (as a mixture of the ester and methanol) in high yield (Table 1, entries 1 and 2). As expected, the irreversible

  5. Frontiers in Catalysis Science and Engineering Seminar Series

    E-Print Network [OSTI]

    of 5-HMF and derivatives Presented by... Prof. Z Conrad Zhang · Industrial Catalysis · Dalian Institute of Chemical Physics · Dalian, China Abstract One of the most notable advances toward biorefinery in recent. This talk covers the recent progress in three areas of research in my laboratory at the Dalian Institute

  6. JOURNAL OF CATALYSIS 177, 343351 (1998) ARTICLE NO. CA982143

    E-Print Network [OSTI]

    Iglesia, Enrique

    1998-01-01

    - modynamically favorable at high temperatures, but often leads to high yields of coke and smaller hydrocarbons, but it requires a selective catalyst in order to avoid complete oxidation to CO and CO2. A number of recentJOURNAL OF CATALYSIS 177, 343­351 (1998) ARTICLE NO. CA982143 Structure and Properties of Vanadium

  7. Lithium Diisopropylamide-Mediated Ortholithiations: Lithium Chloride Catalysis

    E-Print Network [OSTI]

    Collum, David B.

    Lithium Diisopropylamide-Mediated Ortholithiations: Lithium Chloride Catalysis Lekha Gupta, 2008 Ortholithiations of a range of arenes mediated by lithium diisopropylamide (LDA) in THF at -78 °C protocols with unpurified commercial samples of n-butyl- lithium to prepare LDA or commercially available

  8. SouthWest Catalysis Society 2011 Spring Symposium

    E-Print Network [OSTI]

    Natelson, Douglas

    , TX 77478 scott.mitchell@sabicusa.com Lin Luo The Dow Chemical Co. 2301 Brazosport Blvd. Freeport, TX of Texas A&M University to co-sponsor a symposium honoring Prof. Jack Lunsford for his accomplishments Award for Excellence in Applied Catalysis later in the day. On-site registration will begin at 7:30 AM

  9. Simulating Ru L3-Edge X-ray Absorption Spectroscopy with Time-Dependent Density Functional Theory: Model Complexes and Electron Localization in Mixed-Valence Metal Dimers

    SciTech Connect (OSTI)

    Kuiken, Benjamin E. Van; Valiev, Marat; Daifuku, Stephanie L.; Bannan, Caitlin; Strader, Matthew L.; Cho, Hana; Huse, Nils; Schoenlein, Robert W.; Govind, Niranjan; Khalil, Munira

    2013-04-26

    Ruthenium L3-edge X-ray absorption (XA) spectroscopy probes unoccupied 4d orbitals of the metal atom and is increasingly being used to investigate the local electronic structure in ground and excited electronic states of Ru complexes. The simultaneous development of computational tools for simulating Ru L3-edge spectra is crucial for interpreting the spectral features at a molecular level. This study demonstrates that time-dependent density functional theory (TDDFT) is a viable and predictive tool for simulating ruthenium L3-edge XA spectroscopy. We systematically investigate the effects of exchange correlation functional and implicit and explicit solvent interactions on a series of RuII and RuIII complexes in their ground and electronic excited states. The TDDFT simulations reproduce all of the experimentally observed features in Ru L3-edge XA spectra within the experimental resolution (0.4 eV). Our simulations identify ligand-specific charge transfer features in complicated Ru L3-edge spectra of [Ru(CN)6]4- and RuII polypyridyl complexes illustrating the advantage of using TDDFT in complex systems. We conclude that the B3LYP functional most accurately predicts the transition energies of charge transfer features in these systems. We use our TDDFT approach to simulate experimental Ru L3-edge XA spectra of transition metal mixed-valence dimers of the form [(NC)5MII-CN-RuIII(NH3)5] (where M = Fe or Ru) dissolved in water. Our study determines the spectral signatures of electron delocalization in Ru L3-edge XA spectra. We find that the inclusion of explicit solvent molecules is necessary for reproducing the spectral features and the experimentally determined valencies in these mixed-valence complexes. This study validates the use of TDDFT for simulating Ru 2p excitations using popular quantum chemistry codes and providing a powerful interpretive tool for equilibrium and ultrafast Ru L3-edge XA spectroscopy.

  10. Synergism of Catalysis and Reaction Center Rehybridization. A Novel Mode of Catalysis in the Hydrolysis of Carbon Dioxide

    E-Print Network [OSTI]

    Lewis, Michael

    in the Hydrolysis of Carbon Dioxide Michael Lewis and Rainer Glaser* Contribution from the Department of Chemistry dioxide in carbonic anhydrase has long been an active area of research due to its fundamental importance-known that the hydrolysis of carbon dioxide in solution proceeds with catalysis from the solvent;3 however the structure

  11. This issue of Topics in Catalysis is devoted to ``Nanotechnology in Catalysis'' and covers some of the

    E-Print Network [OSTI]

    Resasco, Daniel

    silica, catalyst supports and catalytic membranes. Nanosized hollow spheres (silica or carbon) have been that generates the possibility of creating controlled porosity and molecular sieving effects. Gold nanoparticles attention by many catalysis research groups because of their very high carbon monoxide oxidation catalytic

  12. Molecular-Level Design of Heterogeneous Chiral Catalysis

    SciTech Connect (OSTI)

    Francisco Zaera

    2012-03-21

    The following is a proposal to continue our multi-institutional research on heterogeneous chiral catalysis. Our team combines the use of surface-sensitive analytical techniques for the characterization of model systems with quantum and statistical mechanical calculations to interpret experimental data and guide the design of future research. Our investigation focuses on the interrelation among the three main mechanisms by which enantioselectivity can be bestowed to heterogeneous catalysts, namely: (1) by templating chirality via the adsorption of chiral supramolecular assemblies, (2) by using chiral modifiers capable of forming chiral complexes with the reactant and force enantioselective surface reactions, and (3) by forming naturally chiral surfaces using imprinting chiral agents. Individually, the members of our team are leaders in these various aspects of chiral catalysis, but the present program provides the vehicle to generate and exploit the synergies necessary to address the problem in a comprehensive manner. Our initial work has advanced the methodology needed for these studies, including an enantioselective titration procedure to identify surface chiral sites, infrared spectroscopy in situ at the interface between gases or liquids and solids to mimic realistic catalytic conditions, and DFT and Monte Carlo algorithms to simulate and understand chirality on surfaces. The next step, to be funded by the monies requested in this proposal, is to apply those methods to specific problems in chiral catalysis, including the identification of the requirements for the formation of supramolecular surface structures with enantioselective behavior, the search for better molecules to probe the chiral nature of the modified surfaces, the exploration of the transition from supramolecular to one-to-one chiral modification, the correlation of the adsorption characteristics of one-to-one chiral modifiers with their physical properties, in particular with their configuration, and the development of ways to imprint chiral centers on achiral solid surfaces. Chiral catalysis is not only a problem of great importance in its own right, but also the ultimate test of how to control selectivity in catalysis. The time is ripe for fundamental work in heterogeneous chiral catalysis to provide the U.S. with a leadership role in developing the next generation of catalytic processes for medicinal and agrochemical manufacturing. Our team provides the required expertise for a synergistic and comprehensive integration of physical and chemical experimentation with solid state and molecular reactivity theories to solve this problem.

  13. Highly stable tetrathiafulvalene radical dimers in [3]catenanes

    SciTech Connect (OSTI)

    Spruell, Jason M.; Coskun, Ali; Friedman, Douglas C.; Forgan, Ross S.; Sarjeant, Amy A.; Trabolsi, Ali; Fahrenbach, Albert C.; Barin, Gokhan; Paxton, Walter F.; Dey, Sanjeev K.; Olson, Mark A.; Benítez, Diego; Tkatchouk, Ekaterina; Colvin, Michael T.; Carmielli, Raanan; Caldwell, Stuart T.; Rosair, Georgina M.; Hewage, Shanika Gunatilaka; Duclairoir, Florence; Seymour, Jennifer L.; Slawin, Alexandra M.Z.; Goddard, III, William A.; Wasielewski, Michael R.; Cooke, Graeme; Stoddart, J. Fraser

    2010-12-03

    Two [3]catenane 'molecular flasks' have been designed to create stabilized, redox-controlled tetrathiafulvalene (TTF) dimers, enabling their spectrophotometric and structural properties to be probed in detail. The mechanically interlocked framework of the [3]catenanes creates the ideal arrangement and ultrahigh local concentration for the encircled TTF units to form stable dimers associated with their discrete oxidation states. These dimerization events represent an affinity umpolung, wherein the inversion in electronic affinity replaces the traditional TTF-bipyridinium interaction, which is over-ridden by stabilizing mixed-valence (TTF){sub 2}{sup {sm_bullet}+} and radical-cation (TTF{sup {sm_bullet}+}){sub 2} states inside the 'molecular flasks.' The experimental data, collected in the solid state as well as in solution under ambient conditions, together with supporting quantum mechanical calculations, are consistent with the formation of stabilized paramagnetic mixed-valence dimers, and then diamagnetic radical-cation dimers following subsequent one-electron oxidations of the [3]catenanes.

  14. Synthesis, Characterization and Reactivity of Electrophilic Organometallic Compounds of Ruthenium, Tantalum and Silicon 

    E-Print Network [OSTI]

    Ramirez, Rodrigo

    2014-12-11

    symmetry and charge distribution. The synthesis of a family of d^6 ML5 and d^6 ML6 ruthenium triflate complexes of the pincer (P2C=)Ru(X) (X = Cl, H, OAc, acac) architecture by ligand exchange using Me3SiOTf will be presented. It was speculated...

  15. The Reactivity Limit for Methanol Oxidation on Platinum/Ruthenium Catalysts

    E-Print Network [OSTI]

    The Reactivity Limit for Methanol Oxidation on Platinum/Ruthenium Catalysts A. Wieckowski 0.5 1.0 1.5 2.0 2.5 3.0 Pt/Ru Decorated (UIUC) PtRu Alloy (JM) E = 0.4 V Oxidation in 0.5 M Methanol

  16. Investigation of ruthenium dioxide formation mechanisms in containment glass synthesized by liquid feed

    SciTech Connect (OSTI)

    Sawada, K.; Shimada, T.; Sako, N.; Enokida, Y. [Graduate School of Engineering, Nagoya University (Japan); Schuller, S.; Angeli, F. [CEA-DEN-DTCD-LCV-SECM, 30207 Bagnols-sur-Ceze (France); Charpentier, T. [CEA-Saclay, DSM-IRAMIS-SIS2M, 91191 Gif-sur-Yvette (France)

    2013-07-01

    The presenting paper focuses on the structural configuration of ruthenium in vitreous matrices with the objective of obtaining more insight into ruthenium incorporation and solubilization mechanisms in borosilicate glasses. To determine the structural effect of an increasing RuO{sub 2} in a borosilicate glass, a series of glass samples were selected from a benchmark composition. {sup 11}B NMR shows that the borate network is influenced by the presence of RuO{sub 2} in the glass: the addition of 2% RuO{sub 2} in a borosilicate glass led to a significant rise of BO{sub 4}. RuO{sub 2} precipitated in the glass does not seem to be the cause of this modification because when RuO{sub 2} increase there is no further change of BO{sub 4} fraction. This effect can be therefore attributed to RuO{sub 2} dissolved in the glass. RuO{sub 2} is known to have a very low solubility in borosilicate glasses (50 to 2000 ppm depending on the temperature, sodium concentration and conditions of synthesis). The link between the ruthenium and the borated network is not yet clearly identified, however, assumptions can be made such as the formation of Ru-O-B when a sufficient quantity of Ru is add (> 400 ppm). Ruthenium could play the role of silicon in increasing the possibility of bridging bond formation with boron coordination number IV.

  17. Method for producing electricity using a platinum-ruthenium-palladium catalyst in a fuel cell

    DOE Patents [OSTI]

    Gorer, Alexander

    2004-01-27

    A method for producing electricity using a fuel cell that utilizes a ternary alloy composition as a fuel cell catalyst, the ternary alloy composition containing platinum, ruthenium and palladium. The alloy shows increased activity as compared to well-known catalysts.

  18. Recent advances of lanthanum-based perovskite oxides for catalysis

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Zhu, Huiyuan; Zhang, Pengfei; Dai, Sheng

    2015-09-21

    There is a need to reduce the use of noble metal elements especially in the field of catalysis, where noble metals are ubiquitously applied. To this end, perovskite oxides, an important class of mixed oxide, have been attracting increasing attention for decades as potential replacements. Benefiting from the extraordinary tunability of their compositions and structures, perovskite oxides can be rationally tailored and equipped with targeted physical and chemical properties e.g. redox behavior, oxygen mobility, and ion conductivity for enhanced catalysis. Recently, the development of highly efficient perovskite oxide catalysts has been extensively studied. This review article summarizes the recent developmentmore »of lanthanum-based perovskite oxides as advanced catalysts for both energy conversion applications and traditional heterogeneous reactions.« less

  19. Palladium- and Ruthenium-Catalyzed Decarboxylative Allylations and Michael Addition-Allylation Reactions. Applications in Nitrogen Heterocycle Synthesis

    E-Print Network [OSTI]

    Wang, Chao

    2008-08-21

    Our group has a long-standing interest in Pd or Ru-catalyzed decarboxylative coupling reactions. It has been shown that allyl ?-ketoesters, upon treatment with palladium or ruthenium, generate freely diffusing enolates and ?-allyl electrophiles...

  20. PHYSICAL REVIEW B 84, 214110 (2011) Ordered phases in ruthenium binary alloys from high-throughput first-principles calculations

    E-Print Network [OSTI]

    Hart, Gus

    2011-01-01

    properties, as a pure element and as an alloy component. Ruthenium's practical importance as a catalytic-oxidation, CO electro-oxidation, and methane steam reforming).7 Experimental examples of this potential

  1. Plasma-Activated Lean NOx Catalysis for Heavy-Duty Diesel Emissions...

    Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site

    Heavy-Duty NOx Emissions Control: Reformer-Assisted vs. Plasma-Facilitated Lean NOx Catalysis Selective reduction of NOx in oxygen rich environments with plasma-assisted...

  2. Support for U.S. Participants at the 15th International Congress on Catalysis

    SciTech Connect (OSTI)

    Wachs, Israel E.

    2013-08-05

    The grant was used to partially assist the travel expenses of U.S. academic scientists to attend the 15th International Congress on Catalysis. The conference was held in Munich, Germany from July 1-6, 2012. The importance of the International Congress was to bring together the international community of faculty members who participate in catalysis research, and to share information that would lead to further developments and directions in the field of study. Graduate students and Post Docs were invited to apply for travel assistance based on criteria established by the North American Catalysis Society (NACS) and the local Catalysis Clubs.

  3. KINETICS, CATALYSIS, AND REACTION ENGINEERING Staged O2 Introduction and Selective H2 Combustion during

    E-Print Network [OSTI]

    Iglesia, Enrique

    KINETICS, CATALYSIS, AND REACTION ENGINEERING Staged O2 Introduction and Selective H2 Combustion2 increased the selectivity of propane conversion to aromatics o

  4. Selective catalytic reduction system and process for treating NOx emissions using a palladium and rhodium or ruthenium catalyst

    DOE Patents [OSTI]

    Sobolevskiy, Anatoly (Orlando, FL); Rossin, Joseph A. (Columbus, OH); Knapke, Michael J. (Columbus, OH)

    2011-07-12

    A process for the catalytic reduction of nitrogen oxides (NOx) in a gas stream (29) in the presence of H.sub.2 is provided. The process comprises contacting the gas stream with a catalyst system (38) comprising zirconia-silica washcoat particles (41), a pre-sulfated zirconia binder (44), and a catalyst combination (40) comprising palladium and at least one of rhodium, ruthenium, or a mixture of ruthenium and rhodium.

  5. Transition Metal Dimer Internuclear Distances from Measured Force Constants Joseph L. Jules and John R. Lombardi*

    E-Print Network [OSTI]

    Lombardi, John R.

    Transition Metal Dimer Internuclear Distances from Measured Force Constants Joseph L. Jules distances, have been extended to the transition metal dimers to test which one gives the most accurate fit's and Guggenheimer's for the transition metal dimers. Although Pauling's rule gives the best results, the remarkable

  6. Complex of transferrin with ruthenium for medical applications. [Ru 97, Ru 103

    DOE Patents [OSTI]

    Richards, P.; Srivastava, S.C.; Meinken, G.E.

    1980-11-03

    A novel Ruthenium-transferrin complex, prepared by reacting iron-free human transferrin dissolved in a sodium acetate solution at pH 7 with ruthenium by heating at about 40/sup 0/C for about 2 hours, and purifying said complex by means of gel chromatography with pH 7 sodium acetate as eluent. The mono- or di-metal complex produced can be used in nuclear medicine in the diagnosis and/or treatment of tumors and abscesses. Comparitive results with Ga-67-citrate, which is the most widely used tumor-localizing agent in nuclear medicine, indicate increased sensitivity of detection and greater tumor uptake with the Ru-transferrin complex.

  7. Hydrogen catalysis and scavenging action of Pd-POSS nanoparticles

    SciTech Connect (OSTI)

    Maiti, A; Gee, R H; Maxwell, R; Saab, A

    2007-02-01

    Prompted by the need for a self-supported, chemically stable, and functionally flexible catalytic nanoparticle system, we explore a system involving Pd clusters coated with a monolayer of polyhedral oligomeric silsesquioxane (POSS) cages. With an initial theoretical focus on hydrogen catalysis and sequestration in the Pd-POSS system, we report Density Functional Theory (DFT) results on POSS binding energies to the Pd(110) surface, hydrogen storing ability of POSS, and possible pathways of hydrogen radicals from the catalyst surface to unsaturated bonds away from the surface.

  8. Inorganic Chemistry in Hydrogen Storage and Biomass Catalysis

    SciTech Connect (OSTI)

    Thorn, David [Los Alamos National Laboratory

    2012-06-13

    Making or breaking C-H, B-H, C-C bonds has been at the core of catalysis for many years. Making or breaking these bonds to store or recover energy presents us with fresh challenges, including how to catalyze these transformations in molecular systems that are 'tuned' to minimize energy loss and in molecular and material systems present in biomass. This talk will discuss some challenging transformations in chemical hydrogen storage, and some aspects of the inorganic chemistry we are studying in the development of catalysts for biomass utilization.

  9. USD Catalysis Group for Alternative Energy - Final report

    SciTech Connect (OSTI)

    Hoefelmeyer, James

    2014-10-03

    I. Project Summary Catalytic processes are a major technological underpinning of modern society, and are essential to the energy sector in the processing of chemical fuels from natural resources, fine chemicals synthesis, and energy conversion. Advances in catalyst technology are enormously valuable since these lead to reduced chemical waste, reduced energy loss, and reduced costs. New energy technologies, which are critical to future economic growth, are also heavily reliant on catalysts, including fuel cells and photo-electrochemical cells. Currently, the state of South Dakota is underdeveloped in terms of research infrastructure related to catalysis. If South Dakota intends to participate in significant economic growth opportunities that result from advances in catalyst technology, then this area of research needs to be made a high priority for investment. To this end, a focused research effort is proposed in which investigators from The University of South Dakota (USD) and The South Dakota School of Mines and Technology (SDSMT) will contribute to form the South Dakota Catalysis Group (SDCG). The multidisciplinary team of the (SDCG) include: (USD) Dan Engebretson, James Hoefelmeyer, Ranjit Koodali, and Grigoriy Sereda; (SDSMT) Phil Scott Ahrenkiel, Hao Fong, Jan Puszynski, Rajesh Shende, and Jacek Swiatkiewicz. The group is well suited to engage in a collaborative project due to the resources available within the existing programs. Activities within the SDCG will be monitored through an external committee consisting of three distinguished professors in chemistry. The committee will provide expert advice and recommendations to the SDCG. Advisory meetings in which committee members interact with South Dakota investigators will be accompanied by individual oral and poster presentations in a materials and catalysis symposium. The symposium will attract prominent scientists, and will enhance the visibility of research in the state of South Dakota. The SDCG requests funding through the Department of Energy (DoE) to establish this multidisciplinary research cluster in the area of catalysis. This long-term approach includes synthesis, characterization, catalyst evaluation, modeling, and scale-up. The project includes plans to acquire instrumentation critical to enabling competitive research. These acquisitions will complement existing resources in the state. The effect of implementation of the proposed efforts will be to significantly enhance state infrastructure in personnel and equipment, and lead to a nationally and internationally recognized research center.

  10. Quark Antiscreening at Strong Magnetic Field and Inverse Magnetic Catalysis

    E-Print Network [OSTI]

    E. J. Ferrer; V. de la Incera; X. J. Wen

    2015-02-17

    The dependence of the QCD coupling constant with a strong magnetic field and the implications for the critical temperature of the chiral phase transition are investigated. It is found that the coupling constant becomes anisotropic in a strong magnetic field and that the quarks, confined by the field to the lowest Landau level where they pair with antiquarks, produce an antiscreening effect. These results lead to inverse magnetic catalysis, providing a natural explanation for the behavior of the critical temperature in the strong-field region.

  11. 2012 Chinese Journal of Catalysis Vol. 33 No. 10 : 0253-9837(2012)10-1706-06 DOI: 10.3724/SP.J.1088.2012.20617 : 17061711

    E-Print Network [OSTI]

    Li, Weixue

    2012-01-01

    of Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, Liaoning, China

  12. UV resonance Raman analysis of trishomocubane and diamondoid dimers

    SciTech Connect (OSTI)

    Meinke, Reinhard Thomsen, Christian; Maultzsch, Janina; Richter, Robert; Merli, Andrea; Fokin, Andrey A.; Department of Organic Chemistry, Kiev Polytechnic Institute, pr. Pobedy 37, 03056 Kiev ; Koso, Tetyana V.; Schreiner, Peter R.; Rodionov, Vladimir N.

    2014-01-21

    We present resonance Raman measurements of crystalline trishomocubane and diamantane dimers containing a C=C double bond. Raman spectra were recorded with excitation energies between 2.33 eV and 5.42 eV. The strongest enhancement is observed for the C=C stretch vibration and a bending mode involving the two carbon atoms of the C=C bond, corresponding to the B{sub 2g} wagging mode of ethylene. This is associated with the localization of the ?-HOMO and LUMO and the elongation of the C=C bond length and a pyramidalization of the two sp{sup 2}-hybridized carbon atoms at the optical excitation. The observed Raman resonance energies of the trishomocubane and diamantane dimers are significantly lower than the HOMO-LUMO gaps of the corresponding unmodified diamondoids.

  13. Binding Energies in Benzene Dimers: Nonlocal Density Functional Calculations

    E-Print Network [OSTI]

    Aaron Puzder; Maxime Dion; David C. Langreth

    2005-09-15

    The interaction energy and minimum energy structure for different geometries of the benzene dimer has been calculated using the recently developed nonlocal correlation energy functional for calculating dispersion interactions. The comparison of this straightforward and relatively quick density functional based method with recent calculations can elucidate how the former, quicker method might be exploited in larger more complicated biological, organic, aromatic, and even infinite systems such as molecules physisorbed on surfaces, and van der Waals crystals.

  14. On the structure of the Nx phase of symmetric dimers

    E-Print Network [OSTI]

    Anke Hoffmann; Alexandros G. Vanakaras; Alexandra Kohlmeier; Georg H. Mehl; Demetri J. Photinos

    2014-07-07

    NMR measurements on a selectively deuteriated liquid crystal dimer CB-C9-CB exhibiting two nematic phases show that the molecules in the lower temperature nematic phase, Nx, experience a chiral environment and are ordered about a unique direction. The results are contrasted with previous reports that proposed a twist-bend spatial variation of the director. A structural model is proposed wherein the molecules show organization into highly correlated assemblies of opposite chirality.

  15. Mercury dimer spectroscopy and an Einstein-Podolsky-Rosen experiment 

    E-Print Network [OSTI]

    Qu, Xinmei

    2009-05-15

    SPECTROSCOPY AND AN EINSTEIN-PODOLSKY-ROSEN EXPERIMENT A Dissertation by XINMEI QU Submitted to the Office of Graduate Studies of Texas A&M University in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY... August 2008 Major Subject: Physics MERCURY DIMER SPECTROSCOPY AND AN EINSTEIN-PODOLSKY-ROSEN EXPERIMENT A Dissertation by XINMEI QU Submitted to the Office of Graduate Studies of Texas A&M University in partial...

  16. Dimer Models, Integrable Systems and Quantum Teichmuller Space

    E-Print Network [OSTI]

    Sebastian Franco

    2011-07-05

    We introduce a correspondence between dimer models (and hence superconformal quivers) and the quantum Teichmuller space of the Riemann surfaces associated to them by mirror symmetry. Via the untwisting map, every brane tiling gives rise to a tiling of the Riemann surface with faces surrounding punctures. We explain how to obtain an ideal triangulation by dualizing this tiling. In order to do so, tiling nodes of valence greater than 3 (equivalently superpotential terms of order greater than 3 in the corresponding quiver gauge theories) must be decomposed by the introduction of 2-valent nodes. From a quiver gauge theory perspective, this operation corresponds to integrating-in massive fields. Fock coordinates in Teichmuller space are in one-to-one correspondence with chiral fields in the quiver. We present multiple explicit examples, including infinite families of theories, illustrating how the right number of Fock coordinates is generated by this procedure. Finally, we explain how Chekhov and Fock commutation relations between coordinates give rise to the commutators associated to dimer models by Goncharov and Kenyon in the context of quantum integrable systems. For generic dimer models (i.e. those containing nodes that are not 3-valent), this matching requires the introduction of a natural generalization of Chekhov and Fock rules. We also explain how urban renewal in the original brane tiling (Seiberg duality for the quivers) is mapped to flips of the ideal triangulation.

  17. Benchmark calculations for elastic fermion-dimer scattering

    E-Print Network [OSTI]

    Shahin Bour; H. -W. Hammer; Dean Lee; Ulf-G. Meißner

    2012-06-08

    We present continuum and lattice calculations for elastic scattering between a fermion and a bound dimer in the shallow binding limit. For the continuum calculation we use the Skorniakov-Ter-Martirosian (STM) integral equation to determine the scattering length and effective range parameter to high precision. For the lattice calculation we use the finite-volume method of L\\"uscher. We take into account topological finite-volume corrections to the dimer binding energy which depend on the momentum of the dimer. After subtracting these effects, we find from the lattice calculation kappa a_fd = 1.174(9) and kappa r_fd = -0.029(13). These results agree well with the continuum values kappa a_fd = 1.17907(1) and kappa r_fd = -0.0383(3) obtained from the STM equation. We discuss applications to cold atomic Fermi gases, deuteron-neutron scattering in the spin-quartet channel, and lattice calculations of scattering for nuclei and hadronic molecules at finite volume.

  18. Polar Chemoreceptor Clustering by Coupled Trimers of Dimers

    E-Print Network [OSTI]

    Robert G. Endres

    2009-06-11

    Receptors of bacterial chemotaxis form clusters at the cell poles, where clusters act as "antennas" to amplify small changes in ligand concentration. Interestingly, chemoreceptors cluster at multiple length scales. At the smallest scale, receptors form dimers, which assemble into stable timers of dimers. At a large scale, trimers form large polar clusters composed of thousands of receptors. Although much is known about the signaling properties emerging from receptor clusters, it is unknown how receptors localize at the cell poles and what the cluster-size determining factors are. Here, we present a model of polar receptor clustering based on coupled trimers of dimers, where cluster size is determined as a minimum of the cluster-membrane free energy. This energy has contributions from the cluster-membrane elastic energy, penalizing large clusters due to their high intrinsic curvature, and receptor-receptor coupling favoring large clusters. We find that the reduced cluster-membrane curvature mismatch at the curved cell poles leads to large and robust polar clusters in line with experimental observation, while lateral clusters are efficiently suppressed.

  19. Calculation of the Dimer Equilibrium Constant of Heavy Water Saturated Vapor

    E-Print Network [OSTI]

    L. A. Bulavin; S. V. Khrapatiy; V. N. Makhlaichuk

    2015-03-13

    Water is the most common substance on Earth.The discovery of heavy water and its further study have shown that the change of hydrogen for deuterium leads to the significant differences in their properties.The triple point temperature of heavy water is higher,at the same time the critical temperature is lower.Experimental values of the second virial coefficient of the EOS for the vapor of normal and heavy water differ at all temperatures.This fact can influence the values of the dimerization constant for the heavy water vapor.The equilibrium properties of the dimerization process are described with the methods of chemical thermodynamics.The chemical potentials for monomers (m) and dimers (d)are the functions of their concentrations.The interactions of monomer-dimer and dimer-dimer types are taken into account within the solution of equation for chemical potentials.The obtained expression for the dimerization constant contains the contributions of these types.The averaged potentials are modeled by the Sutherland potential.Theoretical values of the dimerization constant for the heavy water vapor at different temperatures are compared to those for normal water.We see the exceeding of the values for the heavy water at all temperatures.This fact is in good agreement with all experimental data that is available.The excess is related to the differences in the character of the heat excitations of the dimers of normal and heavy water,their rotational constants and energy of their vibrational excitations.Significant role is also played by the monomer-dimer and dimer-dimer interactions.

  20. Catalysis of Electroweak Baryogenesis via Fermionic Higgs Portal Dark Matter

    E-Print Network [OSTI]

    Wei Chao; Michael J. Ramsey-Musolf

    2015-02-27

    We investigate catalysis of electroweak baryogenesis by fermionic Higgs portal dark matter using a two Higgs doublet model augmented by vector-like fermions. The lightest neutral fermion mass eigenstate provides a viable dark matter candidate in the presence of a stabilizing symmetry Z_2 or gauged U(1)_D symmetry. Allowing for a non-vanishing CP-violating phase in the lowest-dimension Higgs portal dark matter interactions allows generation of the observed dark matter relic density while evading direct detection bounds. The same phase provides a source for electroweak baryogenesis. We show that it is possible to obtain the observed abundances of visible and dark matter while satisfying present bounds from electric dipole moment (EDM) searches and direct detection experiments. Improving the present electron (neutron) EDM sensitivity by one (two) orders of magnitude would provide a conclusive test of this scenario.

  1. Highly efficient solid state catalysis by reconstructed (001) Ceria surface

    SciTech Connect (OSTI)

    Solovyov, VF; Ozaki, T; Atrei, A; Wu, LJ; Al-Mahboob, A; Sadowski, JT; Tong, X; Nykypanchuk, D; Li, Q

    2014-04-10

    Substrate engineering is a key factor in the synthesis of new complex materials. The substrate surface has to be conditioned in order to minimize the energy threshold for the formation of the desired phase or to enhance the catalytic activity of the substrate. The mechanism of the substrate activity, especially of technologically relevant oxide surfaces, is poorly understood. Here we design and synthesize several distinct and stable CeO2 (001) surface reconstructions which are used to grow epitaxial films of the high-temperature superconductor YBa2Cu3O7. The film grown on the substrate having the longest, fourfold period, reconstruction exhibits a twofold increase in performance over surfaces with shorter period reconstructions. This is explained by the crossover between the nucleation site dimensions and the period of the surface reconstruction. This result opens a new avenue for catalysis mediated solid state synthesis.

  2. Inverse magnetic catalysis in holographic models of QCD

    E-Print Network [OSTI]

    Kiminad A. Mamo

    2015-05-11

    We study the effect of magnetic field $B$ on the critical temperature $T_{c}$ of the confinement-deconfinement phase transition in hard-wall AdS/QCD, and holographic duals of flavored and unflavored $\\mathcal{N}=4$ super-Yang Mills theories on $\\mathbb{R}^3\\times \\rm S^1$. For all of the holographic models, we find that $T_{c}(B)$ decreases with increasing magnetic field $B\\ll T^2$, consistent with the inverse magnetic catalysis recently observed in lattice QCD for $B\\lesssim 1~GeV^2$. We also predict that, for large magnetic field $B\\gg T^2$, the critical temperature $T_{c}(B)$, eventually, starts to increase with increasing magnetic field $B\\gg T^2$ and asymptotes to a constant value.

  3. Radiation-induced tetramer-to-dimer transition of Escherichia coli lactose repressor

    SciTech Connect (OSTI)

    Goffinont, S. [Centre de Biophysique Moleculaire, CNRS, rue C. Sadron, 45071 Orleans (France)] [Centre de Biophysique Moleculaire, CNRS, rue C. Sadron, 45071 Orleans (France); Davidkova, M. [Department of Radiation Dosimetry, Nuclear Physics Institute AS CR, Na Truhlarce 39/64, 18086, Prague 8 (Czech Republic)] [Department of Radiation Dosimetry, Nuclear Physics Institute AS CR, Na Truhlarce 39/64, 18086, Prague 8 (Czech Republic); Spotheim-Maurizot, M., E-mail: spotheim@cnrs-orleans.fr [Centre de Biophysique Moleculaire, CNRS, rue C. Sadron, 45071 Orleans (France)

    2009-08-21

    The wild type lactose repressor of Escherichia coli is a tetrameric protein formed by two identical dimers. They are associated via a C-terminal 4-helix bundle (called tetramerization domain) whose stability is ensured by the interaction of leucine zipper motifs. Upon in vitro {gamma}-irradiation the repressor losses its ability to bind the operator DNA sequence due to damage of its DNA-binding domains. Using an engineered dimeric repressor for comparison, we show here that irradiation induces also the change of repressor oligomerisation state from tetramer to dimer. The splitting of the tetramer into dimers can result from the oxidation of the leucine residues of the tetramerization domain.

  4. Theoretical Investigation of Uranyl Dihydroxide: Oxo Ligand Exchange, Water Catalysis, and Vibrational Spectra

    E-Print Network [OSTI]

    Schlegel, H. Bernhard

    Theoretical Investigation of Uranyl Dihydroxide: Oxo Ligand Exchange, Water Catalysis is employed to investigate uranyl dihydroxide, UO2(OH)2, isomerization reaction energy barriers, including those occurring via proton shuttles. The ground-state structure of a uranyl dihydroxide complex

  5. Applied Catalysis A: General 243 (2003) 1524 On the potential role of hydroxyl groups in

    E-Print Network [OSTI]

    Marks, Laurence D.

    2003-01-01

    Applied Catalysis A: General 243 (2003) 15­24 On the potential role of hydroxyl groups in CO of metallic Au atoms and a cationic Au with a hydroxyl group. © 2002 Elsevier Science B.V. All rights reserved

  6. Transformation of Sorbitol to Biofuels by Heterogeneous Catalysis: Chemical and Industrial

    E-Print Network [OSTI]

    Boyer, Edmond

    Transformation of Sorbitol to Biofuels by Heterogeneous Catalysis: Chemical and Industrial ainsi que des exemples d'applications industrielles. Abstract -- Transformation of Sorbitol to Biofuels and biodiesel production led to first generation biofuels. Nowadays, research is focused on lignocellulosic

  7. Catalysis Today 215 (2013) 3642 Contents lists available at SciVerse ScienceDirect

    E-Print Network [OSTI]

    Li, Weixue

    2013-01-01

    , Wei-Xue Li State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China a r t i c l e i n f o Article history: Received 14 December 2012 Received

  8. Dendrimer-encapsulated metal nanoparticles: synthesis, characterization, and applications to catalysis 

    E-Print Network [OSTI]

    Niu, Yanhui

    2004-09-30

    The research in this dissertation examines the chemistry and applications of dendrimers in homogeneous catalysis. We examined interactions between dendrimers and charged probe molecules, prepared dendrimer-encapsulated metal nanoparticles...

  9. Synergism of Catalysis and Reaction Center Rehybridization. An ab Initio Study of the

    E-Print Network [OSTI]

    Lewis, Michael

    were also obtained for the hydrolysis of SO3.18 Obviously, the catalysis arises in all of these cases/mol, and this result can be rationalized just as in the case of the other heterocumulenes and SO3

  10. Molecular computations for reactions and phase transitions: applications to protein stabilization, hydrates and catalysis

    E-Print Network [OSTI]

    Anderson, Brian J.

    In this work we have made significant contributions in three different areas of interest: therapeutic protein stabilization, thermodynamics of natural gas clathrate-hydrates, and zeolite catalysis. In all three fields, ...

  11. Enhanced Dimer Relaxation in an Atomic/Molecular BEC

    E-Print Network [OSTI]

    Eric Braaten; H. -W. Hammer

    2004-08-02

    We derive a universal formula for the rate constant \\beta for relaxation of a shallow dimer into deeply-bound diatomic molecules in the case of atoms with a large scattering length a. We show that \\beta is determined by a and by two 3-body parameters that also determine the binding energies and widths of Efimov states. The rate constant \\beta scales like \\hbar a/m near the resonance, but the coefficient is a periodic function of ln(a) that may have resonant enhancement at values of a that differ by multiples of 22.7.

  12. Jamming probabilities for a vacancy in the dimer model

    E-Print Network [OSTI]

    V. S. Poghosyan; V. B. Priezzhev; P. Ruelle

    2008-01-28

    Following the recent proposal made by Bouttier et al [Phys. Rev. E 76, 041140 (2007)], we study analytically the mobility properties of a single vacancy in the close-packed dimer model on the square lattice. Using the spanning web representation, we find determinantal expressions for various observable quantities. In the limiting case of large lattices, they can be reduced to the calculation of Toeplitz determinants and minors thereof. The probability for the vacancy to be strictly jammed and other diffusion characteristics are computed exactly.

  13. Multiple-charge transfer and trapping in DNA dimers

    E-Print Network [OSTI]

    Tornow, Sabine; Anders, Frithjof B; Zwicknagl, Gertrud

    2010-01-01

    We investigate the charge transfer characteristics of one and two excess charges in a DNA base-pair dimer using a model Hamiltonian approach. The electron part comprises diagonal and off-diagonal Coulomb matrix elements such a correlated hopping and the bond-bond interaction, which were recently calculated by Starikov [E. B. Starikov, Phil. Mag. Lett. {\\bf 83}, 699 (2003)] for different DNA dimers. The electronic degrees of freedom are coupled to an ohmic or a super-ohmic bath serving as dissipative environment. We employ the numerical renormalization group method in the nuclear tunneling regime and compare the results to Marcus theory for the thermal activation regime. For realistic parameters, the rate that at least one charge is transferred from the donor to the acceptor in the subspace of two excess electrons significantly exceeds the rate in the single charge sector. Moreover, the dynamics is strongly influenced by the Coulomb matrix elements. We find sequential and pair transfer as well as a regime wher...

  14. Ionization satellites of the ArHe dimer

    SciTech Connect (OSTI)

    Miteva, Tsveta; Klaiman, Shachar; Gokhberg, Kirill [Theoretische Chemie, Physikalisch-Chemisches Institut, Universität Heidelberg, Im Neuenheimer Feld 229, D-69120 Heidelberg (Germany); Gromov, Evgeniy V., E-mail: Evgeniy.Gromov@pci.uni-heidelberg.de [Theoretische Chemie, Physikalisch-Chemisches Institut, Universität Heidelberg, Im Neuenheimer Feld 229, D-69120 Heidelberg (Germany); Laboratory of Quantum Chemistry, Computer Center, Irkutsk State University, K. Marks 1, 664003 Irkutsk (Russian Federation)

    2014-05-28

    Ionization satellites are key ingredients in the control of post ionization processes such as molecular dissociation and interatomic Coulombic decay. Here, using the high-level ab initio method of multi-reference configuration interaction up to triple excitations, we study the potential energy curves (PECs) of the ionization satellites of the ArHe dimer. With this model system, we demonstrate that the simple model used in alkaline earth metal and rare gas complexes to describe the satellites as a Rydberg electron moving on top of a dicationic core does not fully hold for the rare gas clusters. The more complex valence structure in the rare gas atom leads to the mixing of different electronic configurations of the dimer. This prevents one from assigning a single dicationic parent state to some of the ionization satellites. We further analyze the structure of the different PECs, demonstrating how the density of the Rydberg electron is reflected in the structure of the PEC wherever the simple model is applicable.

  15. Structures and Properties of Zirconia-Supported Ruthenium Oxide Catalysts for the Selective Oxidation of Methanol to Methyl Formate

    E-Print Network [OSTI]

    Iglesia, Enrique

    Structures and Properties of Zirconia-Supported Ruthenium Oxide Catalysts for the Selective Species, College of Chemistry and Molecular Engineering, Green Chemistry Center, Peking UniVersity, Beijing 100871, China, and Department of Chemical Engineering, UniVersity of California at Berkeley

  16. Proton transfer in adsorbed water dimers Xiao Liang Hu, Jir i Klimes and Angelos Michaelides*

    E-Print Network [OSTI]

    Alavi, Ali

    Proton transfer in adsorbed water dimers Xiao Liang Hu, Jir i´ Klimes and Angelos Michaelides) reveal rapid proton transfer within clusters of just two water molecules. Facile dissociation and recombination of the molecules within the dimers along with a concerted surface-mediated exchange of protons

  17. Protonated Water Dimer on Benzene: Standing Eigen or Crouching Huan Wang and Noam Agmon*

    E-Print Network [OSTI]

    Agmon, Noam

    Protonated Water Dimer on Benzene: Standing Eigen or Crouching Zundel? Huan Wang and Noam Agmon to a neutral benzene molecule are a reductionist model for protons at hydrophobic surfaces, which water dimer ("Zundel ion") on benzene, whose gas-phase messenger IR spectrum has been previously

  18. Giant Helium Dimers Produced by Photoassociation of Ultracold Metastable Atoms J. Leonard,* M. Walhout,

    E-Print Network [OSTI]

    Cohen-Tannoudj, Claude

    Giant Helium Dimers Produced by Photoassociation of Ultracold Metastable Atoms J. Le´onard,* M long-range helium dimers by photoassociation of metastable helium atoms in a magnetically trapped ion production rates, which are usually high for He , we measure the tempera- ture increase

  19. Intramolecular Energy Transfer within Butadiyne-Linked Chlorophyll and Porphyrin Dimer-Faced, Self-Assembled

    E-Print Network [OSTI]

    photosynthesis and solar cell applications. Introduction Photofunctional materials for use in organic-Northwestern Solar Energy Research (ANSER) Center, Northwestern UniVersity, EVanston, Illinois 60208-3113, Chemistry axes of the dimers. These transitions greatly increase the ability of these dimers to absorb the solar

  20. Curved EFC/F-BAR-Domain Dimers Are Joined End to End into a Filament for

    E-Print Network [OSTI]

    Zhijie, Liu

    Curved EFC/F-BAR-Domain Dimers Are Joined End to End into a Filament for Membrane Invagination a gently curved helical-bundle dimer of $220 A° in length, which forms filaments through end that impaired filament formation also impaired membrane tubulation and cell membrane invagination. Furthermore

  1. Getting in Sync with Dimeric Eg5 INITIATION AND REGULATION OF THE PROCESSIVE RUN*S

    E-Print Network [OSTI]

    Grabe, Michael

    Getting in Sync with Dimeric Eg5 INITIATION AND REGULATION OF THE PROCESSIVE RUN*S Received the Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania 15260 Eg5/KSP assembly and dynamics. Recent work using a dimeric form of Eg5 has found it to be a processive motor

  2. Chemical equilibrium in supercritical fluids: Solvent effects on the dimerization equilibrium constant

    E-Print Network [OSTI]

    Rabani, Eran

    supercritical sol- vents CO2 , CHF3 , CClF3 , Ar, and Xe across the whole solvent density range, from gasChemical equilibrium in supercritical fluids: Solvent effects on the dimerization equilibrium; accepted 27 February 2002 We study dimerization equilibrium between two dilute solutes in a supercritical

  3. Higher Energy States in the CO Dimer: Millimeter-Wave Spectra and Rovibrational Calculations

    E-Print Network [OSTI]

    Higher Energy States in the CO Dimer: Millimeter-Wave Spectra and Rovibrational Calculations Leonid millimeter-wave data yielded the precise location of 33 new energy levels of A+ symmetry and 20 levels of A extensive millimeter-wave measurements of the 12C16O dimer have been made, and more than 300 new spectral

  4. Coherent low-frequency motions of hydrogen bonded acetic acid dimers in the liquid phase

    E-Print Network [OSTI]

    Mukamel, Shaul

    of 1­2 ps. Calculations of the vibrational potential energy surface based on density functional theoryCoherent low-frequency motions of hydrogen bonded acetic acid dimers in the liquid phase Karsten; accepted 22 April 2004 Ultrafast vibrational dynamics of cyclic hydrogen bonded dimers and the underlying

  5. Effects of Ar plasma treatment for deposition of ruthenium film by remote plasma atomic layer deposition

    SciTech Connect (OSTI)

    Park, Taeyong; Lee, Jaesang; Park, Jingyu; Jeon, Heeyoung; Jeon, Hyeongtag; Lee, Ki-Hoon; Cho, Byung-Chul; Kim, Moo-Sung; Ahn, Heui-Bok

    2012-01-15

    Ruthenium thin films were deposited on argon plasma-treated SiO{sub 2} and untreated SiO{sub 2} substrates by remote plasma atomic layer deposition using bis(ethylcyclopentadienyl)ruthenium [Ru(EtCp){sub 2}] as a Ru precursor and ammonia plasma as a reactant. The results of in situ Auger electron spectroscopy (AES) analysis indicate that the initial transient region of Ru deposition was decreased by Ar plasma treatment at 400 deg. C, but did not change significantly at 300 deg. C The deposition rate exhibited linearity after continuous film formation and the deposition rates were about 1.7 A/cycle and 0.4 A/cycle at 400 deg. C and 300 deg. C, respectively. Changes of surface energy and polar and dispersive components were measured by the sessile drop test. The quantity of surface amine groups was measured from the surface nitrogen concentration with AES. Furthermore, the Ar plasma-treated SiO{sub 2} contained more amine groups and less hydroxyl groups on the surface than on untreated SiO{sub 2}. Auger spectra exhibited chemical shifts by Ru-O bonding, and larger shifts were observed on untreated substrates due to the strong adhesion of Ru films.

  6. Exploring ruthenium dye synthesis and TiO2-dye-I-/I3- electron transfer reactions in a dye-sensitised solar cell. 

    E-Print Network [OSTI]

    Chadwick, Nina

    2013-11-28

    Octahedral, six co-ordinate ruthenium complexes containing acid substituted polypyridyl ligands have proved particularly successful as dyes for Dye-Sensitised Solar Cells (DSSCs); thus there have been hundreds, if not ...

  7. Charge localization and JahnTeller distortions in the benzene dimer cation Piotr A. Pieniazek, Stephen E. Bradforth,a

    E-Print Network [OSTI]

    Krylov, Anna I.

    Charge localization and Jahn­Teller distortions in the benzene dimer cation Piotr A. Pieniazek August 2008 Jahn­Teller JT distortions and charge localization in the benzene dimer cation are analyzed.1063/1.2969107 I. INTRODUCTION The benzene dimer cation is an important model system for radiation

  8. Application of solid ash based catalysts in heterogeneous catalysis

    SciTech Connect (OSTI)

    Shaobin Wang

    2008-10-01

    Solid wastes, fly ash, and bottom ash are generated from coal and biomass combustion. Fly ash is mainly composed of various metal oxides and possesses higher thermal stability. Utilization of fly ash for other industrial applications provides a cost-effective and environmentally friendly way of recycling this solid waste, significantly reducing its environmental effects. On the one hand, due to the higher stability of its major component, aluminosilicates, fly ash could be employed as catalyst support by impregnation of other active components for various reactions. On the other hand, other chemical compounds in fly ash such as Fe{sub 2}O{sub 3} could also provide an active component making fly ash a catalyst for some reactions. In this paper, physicochemical properties of fly ash and its applications for heterogeneous catalysis as a catalyst support or catalyst in a variety of catalytic reactions were reviewed. Fly-ash-supported catalysts have shown good catalytic activities for H{sub 2} production, deSOx, deNOx, hydrocarbon oxidation, and hydrocracking, which are comparable to commercially used catalysts. As a catalyst itself, fly ash can also be effective for gas-phase oxidation of volatile organic compounds, aqueous-phase oxidation of organics, solid plastic pyrolysis, and solvent-free organic synthesis. 107 refs., 4 figs., 2 tabs.

  9. Nonlocal fluctuations and control of dimer entanglement dynamics

    SciTech Connect (OSTI)

    Susa, Cristian E.; Reina, John H.

    2010-10-15

    We report on the dissipative dynamics of an entangled, bipartite interacting system. We show how to induce and control the so-called early-stage disentanglement (and 'delayed' entanglement generation) dynamics by means of a driving laser field. We demonstrate that some of the features currently associated with pure non-Markovian effects in such entanglement behavior can actually take place in Markovian environments if background-noise quantum electrodynamics fluctuations are considered. We illustrate this for the case of a dimer interacting molecular system for which emission rates, interaction strength, and radiative corrections have been previously measured. We also show that even in the absence of collective decay mechanisms and qubit-qubit interactions, the entanglement still exhibits collapse-revival behavior. Our results indicate that zero-point energy fluctuations should be taken into account when formulating precise entanglement dynamics statements.

  10. Restricted Dislocation Motion in Crystals of Colloidal Dimer Particles

    E-Print Network [OSTI]

    Sharon J. Gerbode; Stephanie H. Lee; Chekesha M. Liddell; Itai Cohen

    2008-11-07

    At high area fractions, monolayers of colloidal dimer particles form a degenerate crystal (DC) structure in which the particle lobes occupy triangular lattice sites while the particles are oriented randomly along any of the three lattice directions. We report that dislocation glide in DCs is blocked by certain particle orientations. The mean number of lattice constants between such obstacles is 4.6 +/- 0.2 in experimentally observed DC grains and 6.18 +/- 0.01 in simulated monocrystalline DCs. Dislocation propagation beyond these obstacles is observed to proceed through dislocation reactions. We estimate that the energetic cost of dislocation pair separation via such reactions in an otherwise defect free DC grows linearly with final separation, hinting that the material properties of DCs may be dramatically different from those of 2-D crystals of spheres.

  11. Calculation of the Dimer Equilibrium Constant of Heavy Water Saturated Vapor

    E-Print Network [OSTI]

    Bulavin, L A; Makhlaichuk, V N

    2015-01-01

    Water is the most common substance on Earth.The discovery of heavy water and its further study have shown that the change of hydrogen for deuterium leads to the significant differences in their properties.The triple point temperature of heavy water is higher,at the same time the critical temperature is lower.Experimental values of the second virial coefficient of the EOS for the vapor of normal and heavy water differ at all temperatures.This fact can influence the values of the dimerization constant for the heavy water vapor.The equilibrium properties of the dimerization process are described with the methods of chemical thermodynamics.The chemical potentials for monomers (m) and dimers (d)are the functions of their concentrations.The interactions of monomer-dimer and dimer-dimer types are taken into account within the solution of equation for chemical potentials.The obtained expression for the dimerization constant contains the contributions of these types.The averaged potentials are modeled by the Sutherlan...

  12. Lean NOx Trap Catalysis for Lean Natural Gas Engine Applications

    SciTech Connect (OSTI)

    Parks, II, James E; Storey, John Morse; Theiss, Timothy J; Ponnusamy, Senthil; Ferguson, Harley Douglas; Williams, Aaron M; Tassitano, James B

    2007-09-01

    Distributed energy is an approach for meeting energy needs that has several advantages. Distributed energy improves energy security during natural disasters or terrorist actions, improves transmission grid reliability by reducing grid load, and enhances power quality through voltage support and reactive power. In addition, distributed energy can be efficient since transmission losses are minimized. One prime mover for distributed energy is the natural gas reciprocating engine generator set. Natural gas reciprocating engines are flexible and scalable solutions for many distributed energy needs. The engines can be run continuously or occasionally as peak demand requires, and their operation and maintenance is straightforward. Furthermore, system efficiencies can be maximized when natural gas reciprocating engines are combined with thermal energy recovery for cooling, heating, and power applications. Expansion of natural gas reciprocating engines for distributed energy is dependent on several factors, but two prominent factors are efficiency and emissions. Efficiencies must be high enough to enable low operating costs, and emissions must be low enough to permit significant operation hours, especially in non-attainment areas where emissions are stringently regulated. To address these issues the U.S. Department of Energy and the California Energy Commission launched research and development programs called Advanced Reciprocating Engine Systems (ARES) and Advanced Reciprocating Internal Combustion Engines (ARICE), respectively. Fuel efficiency and low emissions are two primary goals of these programs. The work presented here was funded by the ARES program and, thus, addresses the ARES 2010 goals of 50% thermal efficiency (fuel efficiency) and <0.1 g/bhp-hr emissions of oxides of nitrogen (NOx). A summary of the goals for the ARES program is given in Table 1-1. ARICE 2007 goals are 45% thermal efficiency and <0.015 g/bhp-hr NOx. Several approaches for improving the efficiency and emissions of natural gas reciprocating engines are being pursued. Approaches include: stoichiometric engine operation with exhaust gas recirculation and three-way catalysis, advanced combustion modes such as homogeneous charge compression ignition, and extension of the lean combustion limit with advanced ignition concepts and/or hydrogen mixing. The research presented here addresses the technical approach of combining efficient lean spark-ignited natural gas combustion with low emissions obtained from a lean NOx trap catalyst aftertreatment system. This approach can be applied to current lean engine technology or advanced lean engines that may result from related efforts in lean limit extension. Furthermore, the lean NOx trap technology has synergy with hydrogen-assisted lean limit extension since hydrogen is produced from natural gas during the lean NOx trap catalyst system process. The approach is also applicable to other lean engines such as diesel engines, natural gas turbines, and lean gasoline engines; other research activities have focused on those applications. Some commercialization of the technology has occurred for automotive applications (both diesel and lean gasoline engine vehicles) and natural gas turbines for stationary power. The research here specifically addresses barriers to commercialization of the technology for large lean natural gas reciprocating engines for stationary power. The report presented here is a comprehensive collection of research conducted by Oak Ridge National Laboratory (ORNL) on lean NOx trap catalysis for lean natural gas reciprocating engines. The research was performed in the Department of Energy's ARES program from 2003 to 2007 and covers several aspects of the technology. All studies were conducted at ORNL on a Cummins C8.3G+ natural gas engine chosen based on industry input to simulate large lean natural gas engines. Specific technical areas addressed by the research include: NOx reduction efficiency, partial oxidation and reforming chemistry, and the effects of sulfur poisons on the partial oxidation

  13. Photochemical dimerization and functionalization of alkanes, ethers, primary and secondary alcohols, phosphine oxides and silanes

    DOE Patents [OSTI]

    Crabtree, R.H.; Brown, S.H.

    1989-10-17

    The space-time yield and/or the selectivity of the photochemical dimerization of alkanes, ethers, primary and secondary alcohols, phosphine oxides and primary, secondary and tertiary silanes with Hg and U.V. light is enhanced by refluxing the substrate in the irradiated reaction zone at a temperature at which the dimer product condenses and remains condensed promptly upon its formation. Cross-dimerization of the alkanes, ethers and silanes with primary alcohols is disclosed, as is the functionalization to aldehydes of the alkanes with carbon monoxide.

  14. Ruthenium ion-catalyzed oxidation of Shenfu coal and its residues

    SciTech Connect (OSTI)

    Yao-Guo Huang; Zhi-Min Zong; Zi-Shuo Yao; Yu-Xuan Zheng; Jie Mou; Guang-Feng Liu; Jin-Pei Cao; Ming-Jie Ding; Ke-Ying Cai; Feng Wang; Wei Zhao; Zhi-Lin Xia; Lin Wu; Xian-Yong Wei

    2008-05-15

    Shenfu coal (SFC), its liquefaction residue (RL), and carbon disulfide (CS{sub 2})/tetrahydrofuran (THF)-inextractable matter (RE) were subject to ruthenium ion-catalyzed oxidation to understand the differences in structural features among the above three samples. The results suggest that SFC is rich in long-chain arylalkanes and {alpha}. {omega}-diarylalkanes (DAAs) with carbon number of methylene linkage from 2 to 4 and that long-chain arylalkanes and DAAs are reactive toward hydroliquefaction and soluble in a CS{sub 2}/THF mixed solvent, whereas highly condensed aromatic species in SFC show poor solubility in the CS{sub 2}/THF mixed solvent. 29 refs., 6 figs., 4 tabs.

  15. 2010 CATALYSIS GORDON RESEARCH CONFERENCE, JUNE 27 - JULY 2, 2010, NEW LONDON, NEW HAMPSHIRE

    SciTech Connect (OSTI)

    Abhaya Datye

    2010-07-02

    Catalysis is a key technology for improving the quality of life while simultaneously reducing the adverse impact of human activities on the environment. The discovery of new catalytic processes and the improvement of existing ones are also critically important for securing the nation's energy supply. The GRC on Catalysis is considered one the most prestigious conference for catalysis research, bringing together leading researchers from both academia, industry and national labs to discuss the latest, most exciting research in catalysis and the future directions for the field. The 2010 GRC on Catalysis will follow time-honored traditions and feature invited talks from the world's leading experts in the fundamentals and applications of catalytic science and technology. We plan to have increased participation from industry. The extended discussions in the company of outstanding thinkers will stimulate and foster new science. The conference will include talks in the following areas: Alternative feedstocks for chemicals and fuels, Imaging and spectroscopy, Design of novel catalysts, Catalyst preparation fundamentals, Molecular insights through theory, Surface Science, Catalyst stability and dynamics. In 2010, the Catalysis conference will move to a larger conference room with a new poster session area that will allow 40 posters per session. The dorm rooms provide single and double accommodations, free WiFi and the registration fee includes all meals and the famous lobster dinner on Thursday night. Afternoons are open to enjoy the New England ambiance with opportunities for hiking, sailing, golf and tennis to create an outstanding conference that will help you network with colleagues, and make long lasting connections.

  16. Growth mechanism of graphene on platinum: Surface catalysis and carbon segregation

    SciTech Connect (OSTI)

    Sun, Jie Lindvall, Niclas; Yurgens, August; Nam, Youngwoo; Cole, Matthew T.; Teo, Kenneth B. K.; Woo Park, Yung

    2014-04-14

    A model of the graphene growth mechanism of chemical vapor deposition on platinum is proposed and verified by experiments. Surface catalysis and carbon segregation occur, respectively, at high and low temperatures in the process, representing the so-called balance and segregation regimes. Catalysis leads to self-limiting formation of large area monolayer graphene, whereas segregation results in multilayers, which evidently “grow from below.” By controlling kinetic factors, dominantly monolayer graphene whose high quality has been confirmed by quantum Hall measurement can be deposited on platinum with hydrogen-rich environment, quench cooling, tiny but continuous methane flow and about 1000?°C growth temperature.

  17. On the ro-vibrational energies for the lithium dimer; maximum-possible rotational levels

    E-Print Network [OSTI]

    Omar Mustafa

    2015-03-02

    The Deng-Fan potential is used to discuss the reliability of the improved Greene-Aldrich approximation and the factorization recipe of Badawi et al.'s [17] for the central attractive/repulsive core. The factorization recipe is shown to be a more reliable approximation and is used to obtain the ro-vibrational energies for the lithium dimer. For each vibrational state only a limited number of the rotational levels are found to be supported by the lithium dimer.

  18. Structure of a Rabbit Muscle Fructose-1,6-Bisphosphate Aldolase A Dimer Variant

    SciTech Connect (OSTI)

    Sherawat,M.; Tolan, D.; Allen, K.

    2008-01-01

    Fructose-1,6-bisphosphate aldolase (aldolase) is an essential enzyme in glycolysis and gluconeogenesis. In addition to this primary function, aldolase is also known to bind to a variety of other proteins, a property that may allow it to perform 'moonlighting' roles in the cell. Although monomeric and dimeric aldolases possess full catalytic activity, the enzyme occurs as an unusually stable tetramer, suggesting a possible link between the oligomeric state and these noncatalytic cellular roles. Here, the first high-resolution X-ray crystal structure of rabbit muscle D128V aldolase, a dimeric form of aldolase mimicking the clinically important D128G mutation in humans associated with hemolytic anemia, is presented. The structure of the dimer was determined to 1.7 Angstroms resolution with the product DHAP bound in the active site. The turnover of substrate to produce the product ligand demonstrates the retention of catalytic activity by the dimeric aldolase. The D128V mutation causes aldolase to lose intermolecular contacts with the neighboring subunit at one of the two interfaces of the tetramer. The tertiary structure of the dimer does not significantly differ from the structure of half of the tetramer. Analytical ultracentrifugation confirms the occurrence of the enzyme as a dimer in solution. The highly stable structure of aldolase with an independent active site is consistent with a model in which aldolase has evolved as a multimeric scaffold to perform other noncatalytic functions.

  19. Shear-response of the spectrin dimer-tetramer equilibrium in the red blood cell membrane

    SciTech Connect (OSTI)

    An, Xiuli; Lecomte, M. Christine; Chasis, Joel Anne; Mohandas, Narla; Gratzer, Walter

    2003-06-18

    The red cell membrane derives its elasticity and resistance to mechanical stresses from the membrane skeleton, a network composed of spectrin tetramers. These are formed by the head-to-head association of pairs of heterodimers attached at their ends to junctional complexes of several proteins. Here we examine the dynamics of the spectrin dimer-dimer association in the intact membrane. We show that univalent fragments of spectrin, containing the dimer self-association site, will bind to spectrin on the membrane and thereby disrupt the continuity of the protein network. This results in impairment of the mechanical stability of the membrane. When, moreover, the cells are subjected to a continuous low level of shear, even at room temperature, the incorporation of the fragments and the consequent destabilization of the membrane are greatly accentuated. It follows that a modest shearing force, well below that experienced by the red cell in the circulation, is sufficient to sever dimer-dimer links in the network. Our results imply (1) that the membrane accommodates the enormous distortions imposed on it during the passage of the cell through the micro vasculature by means of local dissociation of spectrin tetramers to dimers, (2) that the network in situ is in a dynamic state and under goes a ''breathing'' action of tetramer dissociation and re-formation.

  20. Ras-GTP dimers activate the mitogen-activated protein kinase (MAPK) pathway

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Nan, Xiaolin; Tamgüney, Tanja M.; Collisson, Eric A.; Lin, Li -Jung; Pitt, Cameron; Galeas, Jacqueline; Lewis, Sophia; Gray, Joe W.; McCormick, Frank; Chu, Steven

    2015-06-16

    Rat sarcoma (Ras) GTPases regulate cell proliferation and survival through effector pathways including Raf-MAPK, and are the most frequently mutated genes in human cancer. Although it is well established that Ras activity requires binding to both GTP and the membrane, details of how Ras operates on the cell membrane to activate its effectors remain elusive. Efforts to target mutant Ras in human cancers to therapeutic benefit have also been largely unsuccessful. Here we show that Ras-GTP forms dimers to activate MAPK. We used quantitative photoactivated localization microscopy (PALM) to analyze the nanoscale spatial organization of PAmCherry1-tagged KRas 4B (hereafter referredmore »to KRas) on the cell membrane under various signaling conditions. We found that at endogenous expression levels KRas forms dimers, and KRasG12D, a mutant that constitutively binds GTP, activates MAPK. Overexpression of KRas leads to formation of higher order Ras nanoclusters. Conversely, at lower expression levels, KRasG12D is monomeric and activates MAPK only when artificially dimerized. Moreover, dimerization and signaling of KRas are both dependent on an intact CAAX (C, cysteine; A, aliphatic; X, any amino acid) motif that is also known to mediate membrane localization. These results reveal a new, dimerization-dependent signaling mechanism of Ras, and suggest Ras dimers as a potential therapeutic target in mutant Ras-driven tumors.« less

  1. Photoexcited energy transfer in a weakly coupled dimer

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Hernandez, Laura Alfonso; Nelson, Tammie; Tretiak, Sergei; Fernandez-Alberti, Sebastian

    2015-01-08

    Nonadiabatic excited-state molecular dynamics (NA-ESMD) simulations have been performed in order to study the time-dependent exciton localization during energy transfer between two chromophore units of the weakly coupled anthracene dimer dithia-anthracenophane (DTA). Simulations are done at both low temperature (10 K) and room temperature (300 K). The initial photoexcitation creates an exciton which is primarily localized on a single monomer unit. Subsequently, the exciton experiences an ultrafast energy transfer becoming localized on either one monomer unit or the other, whereas delocalization between both monomers never occurs. In half of the trajectories, the electronic transition density becomes completely localized on themore »same monomer as the initial excitation, while in the other half, it becomes completely localized on the opposite monomer. In this article, we present an analysis of the energy transfer dynamics and the effect of thermally induced geometry distortions on the exciton localization. Finally, simulated fluorescence anisotropy decay curves for both DTA and the monomer unit dimethyl anthracene (DMA) are compared. As a result, our analysis reveals that changes in the transition density localization caused by energy transfer between two monomers in DTA is not the only source of depolarization and exciton relaxation within a single DTA monomer unit can also cause reorientation of the transition dipole.« less

  2. Journal of Catalysis 237 (2006) 111117 www.elsevier.com/locate/jcat

    E-Print Network [OSTI]

    Bell, Alexis T.

    2006-01-01

    , and the carboxylation of methane has been demonstrated in both water and strong acids using soluble V-based catalysts [4Journal of Catalysis 237 (2006) 111­117 www.elsevier.com/locate/jcat Methane oxidation to acetic Department of Chemical Engineering, University of California, Berkeley, CA 94720-1462, USA Received 13

  3. Catalysis by Confinement: Enthalpic Stabilization of NO Oxidation Transition States by Micropororous and Mesoporous Siliceous

    E-Print Network [OSTI]

    Iglesia, Enrique

    . INTRODUCTION The homogeneous oxidation of nitric oxide (NO) to nitrogen dioxide (NO2) with O2 as the oxidant transformation in selective catalytic NOx reduction (SCR) by NH3 on metal- exchanged zeolites7-11 and in NOxCatalysis by Confinement: Enthalpic Stabilization of NO Oxidation Transition States

  4. Applied Catalysis B: Environmental 37 (2002) 2735 NOx reduction by urea under lean conditions over

    E-Print Network [OSTI]

    Gulari, Erdogan

    2002-01-01

    Applied Catalysis B: Environmental 37 (2002) 27­35 NOx reduction by urea under lean conditions over using a single step sol­gel process (designated as 2% Pt-SG) and tested its activity for NOx reduction and hydrothermally stable in the range of 150­500 C in the reduction of NOx by hy- drocarbons or oxygenated

  5. ISHHC XIII International Symposium on the Relations betweenHomogeneous and Heterogeneous Catalysis

    SciTech Connect (OSTI)

    Somorjai , G.A.

    2007-06-11

    The International Symposium on Relations between Homogeneous and Heterogeneous Catalysis (ISHHC) has a long and distinguished history. Since 1974, in Brussels, this event has been held in Lyon, France (1977), Groeningen, The Netherlands (1981); Asilomar, California (1983); Novosibirsk, Russia (1986); Pisa, Italy (1989); Tokyo, Japan (1992); Balatonfuered, Hungary (1995); Southampton, United Kingdom (1999); Lyon, France (2001); Evanston, Illinois (2001) and Florence, Italy (2005). The aim of this international conference in Berkeley is to bring together practitioners in the three fields of catalysis, heterogeneous, homogeneous and enzyme, which utilize mostly nanosize particles. Recent advances in instrumentation, synthesis and reaction studies permit the nanoscale characterization of the catalyst systems, often for the same reaction, under similar experimental conditions. It is hoped that this circumstance will permit the development of correlations of these three different fields of catalysis on the molecular level. To further this goal we aim to uncover and focus on common concepts that emerge from nanoscale studies of structures and dynamics of the three types of catalysts. Another area of focus that will be addressed is the impact on and correlation of nanosciences with catalysis. There is information on the electronic and atomic structures of nanoparticles and their dynamics that should have importance in catalyst design and catalytic activity and selectivity.

  6. A general approach to the enantioselective a-oxidation of aldehydes via synergistic catalysis

    E-Print Network [OSTI]

    MacMillan, David W. C.

    with Zhong, we reported the first catalytic enantioselective a-oxidation of aldehydes, utilizing nitroA general approach to the enantioselective a-oxidation of aldehydes via synergistic catalysis Scott 6th September 2011 DOI: 10.1039/c1sc00556a A new enantioselective a-oxidation of aldehydes has been

  7. Laboratory Evolution of Escherichia coli Thioredoxin for Enhanced Catalysis of Protein Oxidation in the Periplasm

    E-Print Network [OSTI]

    Bardwell, James

    catalytic activity in the oxidation of alkaline phosphatase but was unable to oxidize FlgI and restore cellLaboratory Evolution of Escherichia coli Thioredoxin for Enhanced Catalysis of Protein Oxidation, Michigan 48109 Thioredoxin exported into the Escherichia coli periplasm cat- alyzes the oxidation

  8. Asymmetric Catalysis at the Mesoscale: Gold Nanoclusters Embedded in Chiral Self-Assembled Monolayer as Heterogeneous

    E-Print Network [OSTI]

    Asymmetric Catalysis at the Mesoscale: Gold Nanoclusters Embedded in Chiral Self of the catalytically active metallic sites and the surrounding chiral SAM for the formation of a mesoscale the catalytically active site from the nanoscale to the mesoscale, which implies a principle of operating systems

  9. High surface area crystalline titanium dioxide: potential and limits in electrochemical energy storage and catalysis

    E-Print Network [OSTI]

    Pfeifer, Holger

    and it is widely applied, for example in photocatalysis, electrochemical energy storage, in white pigmentsHigh surface area crystalline titanium dioxide: potential and limits in electrochemical energy storage and catalysis T. Fröschl1 , U. Hörmann2 , P. Kubiak3 , G. Kucerova2 , M. Pfanzelt3 , C.K. Weiss4

  10. Challenges for the application of quantum chemical calculations to problems in catalysis

    E-Print Network [OSTI]

    Bell, Alexis T.

    2004) A long-standing goal of researchers in the field of catalysis is to develop first-principles of a catalysed reaction occurring in a reactor given knowledge only of reactor configuration, catalyst accurate determinations of reactor performance given a set of rate parameters describing catalyst

  11. Catalysis Today 165 (2011) 8995 Contents lists available at ScienceDirect

    E-Print Network [OSTI]

    Li, Weixue

    2011-01-01

    of Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China b Center for Computational and Theoretical Chemistry, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China a r t i c l e i n f o Article history: Received 31 August 2010 Received in revised

  12. JOURNAL OF CATALYSIS 92, 127-135 (1985) Oxidative Dehydrogenation of Methanol to Formaldehyde'

    E-Print Network [OSTI]

    Goddard III, William A.

    1985-01-01

    JOURNAL OF CATALYSIS 92, 127-135 (1985) Oxidative Dehydrogenation of Methanol to Formaldehyde/mol at 275°C (I). Because of the extreme industrial impor- tance of formaldehyde for plastics, dyes, etc con- cepts are generally accepted regarding the oxidation of methanol to formaldehyde over Mo03: (a

  13. Catalysis Winter School 2012 Oxford University / Imperial College London / University College London

    E-Print Network [OSTI]

    Wallace, Mark

    . Simon Jones (Ox): Modified Palladium Nanoparticles for Hydrogen production from Formic acid 8. Thomas-borane (H3B.NMe2H) dehydrocoupling 2. Ed Emmett (Ox): Sulfonyl group incorporation using palladium catalysis and DABSO 3. Adam Healy (Ox): New insights into bio-catalytic hydrogen oxidation using electrochemistry

  14. Structure of a rabbit muscle fructose-1, 6-bisphosphate aldolase A dimer variant

    SciTech Connect (OSTI)

    Sherawat, Manashi [Department of Physiology and Biophysics, Boston University School of Medicine, 715 Albany Street, Boston, MA 02118-2394 (United States); Tolan, Dean R., E-mail: tolan@bu.edu [Department of Biology, Boston University, 5 Cummington Street, Boston, MA 02215 (United States); Allen, Karen N., E-mail: tolan@bu.edu [Department of Physiology and Biophysics, Boston University School of Medicine, 715 Albany Street, Boston, MA 02118-2394 (United States)

    2008-05-01

    The X-ray crystallographic structure of a dimer variant of fructose-1, 6-bisphosphate aldolase demonstrates a stable oligomer that mirrors half of the native tetramer. The presence of product demonstrates that this is an active form. Fructose-1, 6-bisphosphate aldolase (aldolase) is an essential enzyme in glycolysis and gluconeogenesis. In addition to this primary function, aldolase is also known to bind to a variety of other proteins, a property that may allow it to perform ‘moonlighting’ roles in the cell. Although monomeric and dimeric aldolases possess full catalytic activity, the enzyme occurs as an unusually stable tetramer, suggesting a possible link between the oligomeric state and these noncatalytic cellular roles. Here, the first high-resolution X-ray crystal structure of rabbit muscle D128V aldolase, a dimeric form of aldolase mimicking the clinically important D128G mutation in humans associated with hemolytic anemia, is presented. The structure of the dimer was determined to 1.7 Å resolution with the product DHAP bound in the active site. The turnover of substrate to produce the product ligand demonstrates the retention of catalytic activity by the dimeric aldolase. The D128V mutation causes aldolase to lose intermolecular contacts with the neighboring subunit at one of the two interfaces of the tetramer. The tertiary structure of the dimer does not significantly differ from the structure of half of the tetramer. Analytical ultracentrifugation confirms the occurrence of the enzyme as a dimer in solution. The highly stable structure of aldolase with an independent active site is consistent with a model in which aldolase has evolved as a multimeric scaffold to perform other noncatalytic functions.

  15. MERCURY-NITRITE-RHODIUM-RUTHENIUM INTERACTIONS IN NOBLE METAL CATALYZED HYDROGEN GENERATION FROM FORMIC ACID DURING NUCLEAR WASTE PROCESSING AT THE SAVANNAH RIVER SITE - 136C

    SciTech Connect (OSTI)

    Koopman, D.; Pickenheim, B.; Lambert, D.; Newell, J; Stone, M.

    2009-09-02

    Chemical pre-treatment of radioactive waste at the Savannah River Site is performed to prepare the waste for vitrification into a stable waste glass form. During pre-treatment, compounds in the waste become catalytically active. Mercury, rhodium, and palladium become active for nitrite destruction by formic acid, while rhodium and ruthenium become active for catalytic conversion of formic acid into hydrogen and carbon dioxide. Nitrite ion is present during the maximum activity of rhodium, but is consumed prior to the activation of ruthenium. Catalytic hydrogen generation during pre-treatment can exceed radiolytic hydrogen generation by several orders of magnitude. Palladium and mercury impact the maximum catalytic hydrogen generation rates of rhodium and ruthenium by altering the kinetics of nitrite ion decomposition. New data are presented that illustrate the interactions of these various species.

  16. The roles of redox active cofactors in catalysis : structural studies of iron sulfur cluster and flavin dependent enzymes

    E-Print Network [OSTI]

    Goldman, Peter John

    2013-01-01

    Cofactors are highly prevalent in biological systems and have evolved to take on many functions in enzyme catalysis. Two cofactors, flavin adenine dinucleotide (FAD) and [4Fe-4S] clusters, were originally determined to aid ...

  17. Hydrous ruthenium oxide nanoparticles anchored to graphene and carbon nanotube hybrid foam for supercapacitors

    SciTech Connect (OSTI)

    Wang, Wei; Guo, S.; Lee, I.; Ahmed, K.; Zhong, J.; Favors, Z.; Zaera, F.; Ozkan, M.; Ozkan, C. S

    2014-03-25

    In real life applications, supercapacitors (SCs) often can only be used as part of a hybrid system together with other high energy storage devices due to their relatively lower energy density in comparison to other types of energy storage devices such as batteries and fuel cells. Increasing the energy density of SCs will have a huge impact on the development of future energy storage devices by broadening the area of application for SCs. Here, we report a simple and scalable way of preparing a three-dimensional (3D) sub-5 nm hydrous ruthenium oxide (RuO?) anchored graphene and CNT hybrid foam (RGM) architecture for high-performance supercapacitor electrodes. This RGM architecture demonstrates a novel graphene foam conformally covered with hybrid networks of RuO? nanoparticles and anchored CNTs. SCs based on RGM show superior gravimetric and per-area capacitive performance (specific capacitance: 502.78 F g?¹, areal capacitance: 1.11 F cm?²) which leads to an exceptionally high energy density of 39.28 Wh kg?¹ and power density of 128.01 kW kg?¹. The electrochemical stability, excellent capacitive performance, and the ease of preparation suggest this RGM system is promising for future energy storage applications.

  18. Rhodium mediated bond activation: from synthesis to catalysis

    SciTech Connect (OSTI)

    Ho, Hung-An

    2012-03-06

    Recently, our lab has developed monoanionic tridentate ligand, To{sup R}, showing the corresponding coordination chemistry and catalyst reactivity of magnesium, zirconium, zinc and iridium complexes. This thesis details synthetic chemistry, structural study and catalytic reactivity of the To{sup R}-supported rhodium compounds. Tl[To{sup R}] has been proved to be a superior ligand transfer agent for synthesizing rhodium complexes. The salt metathesis route of Tl[To{sup M}] with [Rh({mu}-Cl)(CO)]{sub 2} and [Rh({mu}- Cl)(COE)]{sub 2} gives To{sup M}Rh(CO){sub 2} (2.2) and To{sup M}RhH({eta}{sup 3}-C{sub 8}H{sub 13}) (3.1) respectively while Tl[To{sup P}] with [Rh({mu}-Cl)(CO)]{sub 2} affords To{sup P}Rh(CO){sub 2} (2.3). 2.2 reacts with both strong and weak electrophiles, resulting in the oxazoline N-attacked and the metal center-attacked compounds correspondingly. Using one of the metal center-attacked electrophiles, 2.3 was demonstrated to give high diastereoselectivity. Parallel to COE allylic C-H activation complex 3.1, the propene and allylbenzene allylic C-H activation products have also been synthesized. The subsequent functionalization attempts have been examined by treating with Brønsted acids, Lewis acids, electrophiles, nucleophiles, 1,3-dipolar reagents and reagents containing multiple bonds able to be inserted. Various related complexes have been obtained under these conditions, in which one of the azide insertion compounds reductively eliminates to give an allylic functionalization product stoichiometrically. 3.1 reacts with various primary alcohols to give the decarbonylation dihydride complex To{sup M}Rh(H){sub 2}CO (4.1). 4.1 shows catalytic reactivity for primary alcohol decarbonylation under a photolytic condition. Meanwhile, 2.2 has been found to be more reactive than 4.1 for catalytic alcohol decarbonylation under the same condition. Various complexes and primary alcohols have been investigated as well. The proposed mechanism is based on the stochiometric reactions of the possible metal and organic intermediates. Primary amines, hypothesized to undergo a similar reaction pathway, have been verified to give dehydrogenative coupling product, imines. In the end, the well-developed neutral tridentate Tpm coordinates to the rhodium bis(ethylene) dimer in the presence of TlPF{sub 6} to give the cationic complex, [TpmRh(C{sub 2}H{sub 4}){sub 2}][PF{sub 6}] (5.1). 5.1 serves as the first example of explicit determination of the solid state hapticity, evidenced by X-ray structure, among all the cationic Tpm{sup R}M(C{sub 2}H{sub 4}){sub 2}{sup +} (Tpm{sup R} = Tpm, Tpm*, M = Rh, Ir) derivatives. The substitution chemistry of this compound has been studied by treating with soft and hard donors. The trimethylphosphine-sbustituted complex activates molecular hydrogen to give the dihydride compound.

  19. Charge Transfer and Support Effects in Heterogeneous Catalysis

    SciTech Connect (OSTI)

    Hervier, Antoine

    2011-12-21

    The kinetic, electronic and spectroscopic properties of two?dimensional oxide?supported catalysts were investigated in order to understand the role of charge transfer in catalysis. Pt/TiO{sub 2} nanodiodes were fabricated and used as catalysts for hydrogen oxidation. During the reaction, the current through the diode, as well as its I?V curve, were monitored, while gas chromatography was used to measure the reaction rate. The current and the turnover rate were found to have the same temperature dependence, indicating that hydrogen oxidation leads to the non?adiabatic excitation of electrons in Pt. A fraction of these electrons have enough energy to ballistically transport through Pt and overcome the Schottky barrier at the interface with TiO{sub 2}. The yield for this phenomenon is on the order of 10{sup ?4} electrons per product molecule formed, similar to what has been observed for CO oxidation and for the adsorption of many different molecules. The same Pt/TiO{sub 2} system was used to compare currents in hydrogen oxidation and deuterium oxidation. The current through the diode under deuterium oxidation was found to be greater than under hydrogen oxidation by a factor of three. Weighted by the difference in turnover frequencies for the two isotopes, this would imply a chemicurrent yield 5 times greater for D{sub 2} compared to H{sub 2}, contrary to what is expected given the higher mass of D{sub 2}. Reversible changes in the rectification factor of the diode are observed when switching between D{sub 2} and H{sub 2}. These changes are a likely cause for the differences in current between the two isotopes. In the nanodiode experiments, surface chemistry leads to charge flow, suggesting the possibility of creating charge flow to tune surface chemistry. This was done first by exposing a Pt/Si diode to visible light while using it as a catalyst for H{sub 2} oxidation. Absorption of the light in the Si, combined with the band bending at the interface, gives rise to a steady?state flow of hot holes to the surface. This leads to a decrease in turnover on the surface, an effect which is enhanced when a reverse bias is applied to the diode. Similar experiments were carried out for CO oxidation. On Pt/Si diodes, the reaction rate was found to increase when a forward bias was applied. When the diode was exposed to visible light and a reverse bias was applied, the rate was instead decreased. This implies that a flow of negative charges to the surface increases turnover, while positive charges decrease it. Charge flow in an oxide supported metal catalyst can be modified even without designing the catalyst as a solid state electronic device. This was done by doping stoichiometric and nonstoichiometric TiO{sub 2} films with F, and using the resulting oxides as supports for Pt films. In the case of stoichiometric TiO{sub 2}, F was found to act as an n?type dopant, creating a population of filled electronic states just below the conduction band, and dramatically increasing the conductivity of the oxide film. The electrons in those states can transfer to surface O, activating it for reaction with CO, and leading to increased turnover for CO oxidation. This reinforces the hypothesis that CO oxidation is activated by a flow of negative charges to the surface. The same set of catalysts was used for methanol oxidation. The electronic properties of the TiO{sub 2} films again correlated with the turnover rates, but also with selectivity. With stoichiometric TiO{sub 2} as the support, F?doping caused an increase in selectivity toward the formation of partial oxidation products, formaldehyde and methyl formate, versus the total oxidation product, CO{sub 2}. With non?stoichiometric TiO{sub 2}, F?doping had the reverse effect. Ambient Pressure X?Ray Photoelectron Spectroscopy was used to investigate this F?doping effect in reaction conditions. In O2 alone, and in CO oxidation conditions, the O1s spectrum showed a high binding energy peak that correlated in intensity with the activity of the different films: for stoichiomet

  20. Van der Waals interactions in rare-gas dimers: The role of interparticle interactions

    E-Print Network [OSTI]

    Chen, Yu-Ting; Chai, Jeng-Da

    2015-01-01

    We investigate the potential energy curves of rare-gas dimers with various ranges and strengths of interparticle interactions (nuclear-electron, electron-electron, and nuclear-nuclear interactions). Our investigation is based on the highly accurate coupled-cluster theory associated with those interparticle interactions. For comparison, the performance of the corresponding Hartree-Fock theory, second-order Moller-Plesset perturbation theory, and density functional theory is also investigated. Our results reveal that when the interparticle interactions retain the long-range Coulomb tails, the nature of van der Waals interactions in the rare-gas dimers remains similar. By contrast, when the interparticle interactions are sufficiently short-range, the conventional van der Waals interactions in the rare-gas dimers completely disappear, yielding purely repulsive potential energy curves.

  1. Dimerization Induced Deprotonation of Water on RuO2(110)

    SciTech Connect (OSTI)

    Mu, Rentao; Cantu Cantu, David; Lin, Xiao; Glezakou, Vassiliki Alexandra; Wang, Zhitao; Lyubinetsky, Igor; Rousseau, Roger J.; Dohnalek, Zdenek

    2014-10-02

    RuO2 has proven to be indispensable as a co-catalyst in numerous systems designed for photocatalytic water splitting. In this study we have carried out a detailed mechanistic study of water behavior on the most stable RuO2 face, RuO2(110), by employing variable temperature scanning tunneling microscopy and density functional theory calculations. We show that water monomers adsorb molecularly on Ru sites, become mobile above 238 K, diffuse along the Ru rows and form water dimers. The onset for dimer diffusion is observed at ~277 K indicating significantly higher diffusion barrier than that for monomers. More importantly, we find that water dimers deprotonate readily to form Ru-bound H3O2 and bridging OH species. The observed behavior is compared and contrasted with that observed for water on isostructural rutile TiO2(110).

  2. On (no) inverse magnetic catalysis in the QCD hard and soft wall models

    E-Print Network [OSTI]

    Dudal, D; Mertens, T G

    2015-01-01

    In this paper, we study the influence of an external magnetic field in holographic QCD models where the backreaction is modeled in via an appropriate choice of the background metric. We add a phenomenological soft wall dilaton to incorporate better IR behavior (confinement). Elaborating on previous studies conducted by [JHEP 1505 (2015) 121], we first discuss the Hawking-Page transition, the dual of the deconfinement transition, as a function of the magnetic field. We confirm that the critical deconfinement temperature can drop with the magnetic field. Secondly, we study the quark condensate holographically as a function of the applied magnetic field and demonstrate that this model does not exhibit inverse magnetic catalysis at the level of the chiral transition. The quest for a holographic QCD model that qualitatively describes the inverse magnetic catalysis at finite temperature is thus still open. Throughout this work, we pay special attention to the different holographic parameters and we attempt to fix t...

  3. Kokes Awards for the 23rd North American Catalysis Society Meeting

    SciTech Connect (OSTI)

    Jacobs, Gary

    2014-01-31

    The Tri-State Catalysis Society awarded 107 Kokes Travel Awards. The program was very successful and to date this was the most Kokes Travel Awards ever awarded at a North American Catalysis Society Meeting. It provided students who merited an award the opportunity to attend the meeting, present a paper in the form of either an oral presentation or a poster presentation, and to serve the North American Catalysis Society by participating in the organization of the meeting. Students worked very hard during the week of the meeting to make it a success. Financial support for the Kokes awards was provided by DOE, NSF, NACS, as well as the Tri-State Catalysis Society, the latter through fund raising activities, and other donations. AT the meeting, each student received over $1050 in kind to offset the costs of registration fees ($260), hotel accommodations ($295.7), transportation ($400 travel allowance), as well as T-shirts ($20), and banquet tickets ($95 provided by donations from society members). In addition, for the first time, students received certificates that were signed by the President of NACS, Professor Enrique Iglesia, and by the Kokes Awards Chair, Gary Jacobs (see last page). A list of meeting co-chairs (i.e., Uschi M. Graham, Umit S. Ozkan, and Madan Bhassin) and the honorary chair (Burtron H. Davis) was also included on the certificate, along with the name of the recipient. The awardees were chosen on a merit-based guideline which also included the requirements of having a presentation accepted at the meeting and being a student at a North American University. The Richard J. Kokes Student Travel Award Committee (Gary Jacobs, Rodney Andrews, and Peter Smirniotis) with help from the Organizing Committee were able to secure money from four sources as detailed in Table 1. As detailed by our Treasurer, Dr. Helge Toufar of Clariant, the total amount spent was $105,000.

  4. Kokes Awards for the 22nd North American Catalysis Society Meeting, June 5-10, 2011

    SciTech Connect (OSTI)

    Fabio H. Ribeiro

    2011-06-05

    The biennial North American Catalysis Society (NACS) Meetings are the premiere conferences in the area of catalysis, surface science, and reaction engineering. The 22nd meeting will be held the week of June 5-10, 2011 in Detroit, Michigan. The objective of the Meetings is to bring together leading researchers for intensive scientific exchange and interactions. Financial support that offsets some of the associated costs (specifically, registration fee, airline tickets, and hotel accommodations) would encourage graduate students, and for the first time undergraduate students, to attend and participate meaningfully in this conference. The funds sought in this proposal will help support the Richard J. Kokes Travel Award program. Graduate students eligible for these merit-based Awards are those who study at a North American university and who will present at the Meeting. We have currently 209 applications and we expect to be able to fund about half of them. The NACS has traditionally sought to encourage graduate student, and this year for the first time undergraduate studies, participation at the National Meetings and providing financial support is the most effective means to do so. Their attendance would contribute significantly to their scientific training and communication and presentation skills. They would be exposed to the leading researchers from the US and abroad; they would meet their peers from other universities; they would learn about cutting-edge results that could benefit their research projects; and they may become interested in becoming active participants in the catalysis community. These young investigators represent the next generation of scientists and engineers, and their proper training will lead to future scientific breakthroughs and technological innovations that benefit the US economy. Advances in catalysis can come in the form of more energy-efficient and environmentally-friendly chemical processes, improved fuel cell performance, efficient hydrogen production, and a cleaner environment.

  5. Resonant dimer relaxation in cold atoms with a large scattering length

    SciTech Connect (OSTI)

    Braaten, Eric; Hammer, H.-W.

    2007-05-15

    Efimov physics refers to universal phenomena associated with a discrete scaling symmetry in the three-body problem with a large scattering length. The first experimental evidence for Efimov physics was the recent observation of a resonant peak in the three-body recombination rate for {sup 133}Cs atoms with large negative scattering length. There can also be resonant peaks in the atom-dimer relaxation rate for large positive scattering length. We calculate the atom-dimer relaxation rate as a function of temperature and show how measurements of the relaxation rate can be used to determine accurately the parameters that govern Efimov physics.

  6. Resonant Dimer Relaxation in Cold Atoms with a Large Scattering Length

    E-Print Network [OSTI]

    Eric Braaten; H. -W. Hammer

    2009-03-13

    Efimov physics refers to universal phenomena associated with a discrete scaling symmetry in the 3-body problem with a large scattering length. The first experimental evidence for Efimov physics was the recent observation of a resonant peak in the 3-body recombination rate for 133Cs atoms with large negative scattering length. There can also be resonant peaks in the atom-dimer relaxation rate for large positive scattering length. We calculate the atom-dimer relaxation rate as a function of temperature and show how measurements of the relaxation rate can be used to determine accurately the parameters that govern Efimov physics.

  7. Coupled cluster benchmarks of water monomers and dimers extracted from density-functional theory liquid water: The importance of monomer

    E-Print Network [OSTI]

    Alavi, Ali

    Coupled cluster benchmarks of water monomers and dimers extracted from density-functional theory functionals in simulations of liquid water, water monomers and dimers were extracted from a PBE simulation liquid water: The importance of monomer deformations Biswajit Santra,1 Angelos Michaelides,1,2,a

  8. Parallel Dimers and Anti-parallel Tetramers Formed by Epidermal Growth Factor Receptor Pathway Substrate Clone 15 (EPS15)*

    E-Print Network [OSTI]

    Kirchhausen, Tomas

    Parallel Dimers and Anti-parallel Tetramers Formed by Epidermal Growth Factor Receptor Pathway- dependent endocytic traffic. We report here that Eps15 forms dimers and tetramers of distinct shape. The Eps tetramer has a "dumbbell" shape, 31 nm in length; it is formed by the anti-parallel association of two Eps

  9. Electronic structure of the benzene dimer cation Piotr A. Pieniazek, Anna I. Krylov, and Stephen E. Bradforth

    E-Print Network [OSTI]

    Krylov, Anna I.

    Electronic structure of the benzene dimer cation Piotr A. Pieniazek, Anna I. Krylov, and Stephen E-0482 Received 20 March 2007; accepted 22 May 2007; published online 31 July 2007 The benzene and benzene dimer benzene. Both sandwich and t-shaped structures feature intense charge resonance bands, whose location

  10. NMR Computational Studies of Solid Acidity/Fundamental Studies of Catalysis by Solid Acids

    SciTech Connect (OSTI)

    James F. Haw

    2008-06-28

    This project focused on catalysis by zeolites and the synergy of spectroscopic characterization and theoretical modeling. In collaboration with the Waroquier group in Belgium we used state-of-the-art quantum chemical simulations on a supramolecular model of both the HZSM-5 zeolite and the co-catalytic hydrocarbon pool species and calculated a full catalytic cycle (including all rate constants) for methanol-to-olefin (MTO) catalysis involving a hydrocarbon pool species. This work not only represents the most robust computational analysis of a successful MTO route to date, but it also succeeds in tying together the many experimental clues. That work was featured on the cover of Angewandte Chemie. More recently we elucidated several unsuspected roles for formaldehyde in methanol to olefin catalysis. Formaldehyde proves to be a key species responsible for both the growth of the catalytically active hydrocarbon pool and its inevitable aging into deactivated polycyclic aromatic species. The apparent inevitability of formaldehyde formation at high temperatures, in particular in contact with active metal or metal oxide surfaces, may put some fundamental limitations on the economic potential of conversion of methanol to olefins.

  11. Engineering of a novel Ca{sup 2+}-regulated kinesin molecular motor using a calmodulin dimer linker

    SciTech Connect (OSTI)

    Shishido, Hideki; Maruta, Shinsaku

    2012-06-29

    Highlights: Black-Right-Pointing-Pointer Engineered kinesin-M13 and calmodulin involving single cysteine were prepared. Black-Right-Pointing-Pointer CaM mutant was cross-linked to dimer by bifunctional thiol reactive reagent. Black-Right-Pointing-Pointer Kinesin-M13 was dimerized via CaM dimer in the presence of calcium. Black-Right-Pointing-Pointer Function of the engineered kinesin was regulated by a Ca{sup 2+}-calmodulin dimer linker. -- Abstract: The kinesin-microtubule system holds great promise as a molecular shuttle device within biochips. However, one current barrier is that such shuttles do not have 'on-off' control of their movement. Here we report the development of a novel molecular motor powered by an accelerator and brake system, using a kinesin monomer and a calmodulin (CaM) dimer. The kinesin monomer, K355, was fused with a CaM target peptide (M13 peptide) at the C-terminal part of the neck region (K355-M13). We also prepared CaM dimers using CaM mutants (Q3C), (R86C), or (A147C) and crosslinkers that react with cysteine residues. Following induction of K355-M13 dimerization with CaM dimers, we measured K355-M13 motility and found that it can be reversibly regulated in a Ca{sup 2+}-dependent manner. We also found that velocities of K355-M13 varied depending on the type and crosslink position of the CaM dimer used; crosslink length also had a moderate effect on motility. These results suggest Ca{sup 2+}-dependent dimerization of K355-M13 could be used as a novel molecular shuttle, equipped with an accelerator and brake system, for biochip applications.

  12. Dimer Dissociation and Unfolding Mechanism of Coagulation Factor XI Apple 4 Domain: Spectroscopic

    E-Print Network [OSTI]

    Roder, Heinrich

    Dimer Dissociation and Unfolding Mechanism of Coagulation Factor XI Apple 4 Domain: Spectroscopic of disulfide- linked chains each containing four apple domains and a catalytic domain. The apple 4 domain (A4; A4, apple 4 domain of factor XI; DLS, dynamic light scattering; FXI, factor XI; FXIa, factor FXIa

  13. Receptor expression is essential for proliferation induced by dimerized Jak kinases

    SciTech Connect (OSTI)

    Fujii, Hodaka

    2008-06-13

    Two members of Jak kinases, Jak1 and Jak3, are associated with the cytoplasmic domains of the interleukin-2 (IL-2) receptor (IL-2R) {beta} chain (IL-2R{beta}) and the common cytokine receptor {gamma} chain ({gamma}c), respectively, and accumulating evidence indicates their functional importance in IL-2 signaling. Here, I showed that coumermycin-induced chemical heterodimerization of Jak1 and Jak3 but not homodimerization of Jak1 or Jak3 induces cell proliferation of an IL-2R-reconstituted cell line. In this regard, expression of IL-2R{beta} was essential for cell proliferation by chemical heterodimerization of Jak1 and Jak3, indicating that dimerized Jak1 and Jak3 induce heterodimerization of IL-2R{beta} and {gamma}c, which may activate receptor-bound signaling molecules. Previous reports using chemical dimerization suggest that dimerization of Jak kinases is sufficient to induce cell proliferation. The present study indicates that re-evaluation of this conclusion is necessary and that interpretation of functional analysis of signaling molecules using chemical dimerizers needs more careful assessment.

  14. A new model for myosin dimeric motors incorporating Brownian ratchet and powerstroke mechanisms

    E-Print Network [OSTI]

    Kawai, Ryoichi

    A new model for myosin dimeric motors incorporating Brownian ratchet and powerstroke mechanisms motor proteins in general. A single motor domain is modeled using our previous work on hybrid motors that exhibit elements of both a powerstroke and a Brownian motor mechanism. The different behavior observed

  15. Selfdiffusion of adatoms, dimers, and vacancies on Cu(100) Ghyslain Boisvert ? and Laurent J. Lewis y

    E-Print Network [OSTI]

    Lewis, Laurent J.

    (GCM), Universit'e de Montr'eal, Case Postale 6128, Succursale Centre­Ville, Montr'eal, Qu'ebec, Canada of the diffusion of adatoms, dimers, and vacancies on Cu(100). It is found that the dynamical energy barriers is a ``prefactor'', kB the Boltzmann constant, T the absolute temperature, and EA the activation energy or barrier

  16. Dimerization of 1,3-Butadiene on Highly Characterized Hydroxylated Surfaces of Ultrathin

    E-Print Network [OSTI]

    Dimerization of 1,3-Butadiene on Highly Characterized Hydroxylated Surfaces of Ultrathin Films-cyclohexene on highly ordered hydroxylated ultrathin films of -Al2O3. High surface area, powdered -Al2O3 is widely used to prepare not only highly characterized surfaces of -Al2O3, but also to prepare hydroxylated -Al2O3

  17. ERK Nuclear Translocation Is Dimerization-independent but Controlled by the Rate of Phosphorylation*S

    E-Print Network [OSTI]

    Rieger, Bernd

    ERK Nuclear Translocation Is Dimerization-independent but Controlled by the Rate of Phosphorylation, Universite´ de Nice, Centre A. Lacassagne, 06189 Nice, France Upon activation, ERKs translocate from the molecular mechanisms that regulate ERK nuclear translocation are not fully understood. We have used a mouse

  18. Barrierless proton transfer across weak CH?O hydrogen bonds in dimethyl ether dimer

    SciTech Connect (OSTI)

    Yoder, Bruce L. West, Adam H. C.; Signorell, Ruth; Bravaya, Ksenia B.; Bodi, Andras; Sztáray, Bálint

    2015-03-21

    We present a combined computational and threshold photoelectron photoion coincidence study of two isotopologues of dimethyl ether, (DME ? h{sub 6}){sub n} and (DME ? d{sub 6}){sub n}n = 1 and 2, in the 9–14 eV photon energy range. Multiple isomers of neutral dimethyl ether dimer were considered, all of which may be present, and exhibited varying C–H?O interactions. Results from electronic structure calculations predict that all of them undergo barrierless proton transfer upon photoionization to the ground electronic state of the cation. In fact, all neutral isomers were found to relax to the same radical cation structure. The lowest energy dissociative photoionization channel of the dimer leads to CH{sub 3}OHCH{sub 3}{sup +} by the loss of CH{sub 2}OCH{sub 3} with a 0 K appearance energy of 9.71 ± 0.03 eV and 9.73 ± 0.03 eV for (DME ? h{sub 6}){sub 2} and deuterated (DME ? d{sub 6}){sub 2}, respectively. The ground state threshold photoelectron spectrum band of the dimethyl ether dimer is broad and exhibits no vibrational structure. Dimerization results in a 350 meV decrease of the valence band appearance energy, a 140 meV decrease of the band maximum, thus an almost twofold increase in the ground state band width, compared with DME ? d{sub 6} monomer.

  19. Chemical reaction equilibrium in nanoporous materials: NO dimerization reaction in carbon slit nanopores

    E-Print Network [OSTI]

    Lisal, Martin

    Chemical reaction equilibrium in nanoporous materials: NO dimerization reaction in carbon slit of confinement on chemical reaction equilibrium in nanoporous materials. We use the reaction ensemble Monte Carlo of confinement on chemical properties, particularly on chemical reaction equilibria. A chemical reaction

  20. Density functional study of chemical reaction equilibrium for dimerization reactions in slit and cylindrical nanopores

    E-Print Network [OSTI]

    Lisal, Martin

    Density functional study of chemical reaction equilibrium for dimerization reactions in slit a theoretical study of the effects of confinement on chemical reaction equilibrium in slit and cylindrical equilibrium, for which much less is known. The behavior of chemical reactions in confinement spans a wide

  1. Spectrum and vibrational predissociation of the HF dimer. II. Photodissociation cross sections and product state distributions

    E-Print Network [OSTI]

    and dimer geared-bending modes. We find that dissociation is sufficiently slow for the Fermi golden rule approximate them as bound states. This was the approach taken in the preceding paper1 hereafter called Paper I­DF complex using a time- dependent golden rule approach. In this paper we present the results of full

  2. A concerted, alternating sites mechanism of ubiquinol oxidation by the dimeric cytochrome bc1 complex

    E-Print Network [OSTI]

    Trumpower, Bernard L.

    A concerted, alternating sites mechanism of ubiquinol oxidation by the dimeric cytochrome bc1 A refinement of the protonmotive Q cycle mechanism is proposed in which oxidation of ubiquinol is a concerted reaction and occurs by an alternating, half-of-the-sites mechanism. A concerted mechanism of ubiquinol

  3. Dimeric Drug Polymeric Nanoparticles with Exceptionally High Drug Loading and Quantitative Loading Efficiency

    E-Print Network [OSTI]

    Cheng, Jianjun

    Dimeric Drug Polymeric Nanoparticles with Exceptionally High Drug Loading and Quantitative LoadingChampaign, Urbana, Illinois 61801, United States Key Laboratory of Smart Drug Delivery, Ministry of Education-molecule drugs in hydrophobic polymers or amphiphilic copolymers has been extensively used for preparing

  4. Microwave and tunable far-infrared laser spectroscopy of the ammonia-water dimer

    E-Print Network [OSTI]

    Blake, Geoffrey

    Microwave and tunable far-infrared laser spectroscopy of the ammonia- water dimer Paul A. Stockman of Technology,170-25,Pasadena,CA 91125 (Received14August 1991;accepted5 November 1991) Microwave and far cosmochemically. In a gasof solar composition,the most stablecarbon,nitro- gen,and oxygencontaining speciesat

  5. Polarizable interaction potential for water from coupled cluster calculations. I. Analysis of dimer potential energy surface

    E-Print Network [OSTI]

    by nonadditive effects which make it impossible to sufficiently accurately represent the energy of water as a sumPolarizable interaction potential for water from coupled cluster calculations. I. Analysis of dimer potential energy surface Robert Bukowski,1 Krzysztof Szalewicz,1,a Gerrit C. Groenenboom,2 and Ad van der

  6. Probing the Role of Metal Ions in RNA Catalysis: Kinetic and Thermodynamic Characterization of a Metal Ion Interaction with the 2-Moiety of the Guanosine

    E-Print Network [OSTI]

    Herschlag, Dan

    Probing the Role of Metal Ions in RNA Catalysis: Kinetic and Thermodynamic Characterization of a Metal Ion Interaction with the 2-Moiety of the Guanosine Nucleophile in the Tetrahymena Group I Ribozyme: Deciphering the role of individual metal ions in RNA catalysis is a tremendous challenge, as numerous metal

  7. Catalysis Center for Energy Innovation (CCEI) | U.S. DOE Office of Science

    Office of Science (SC) Website

    AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative Fuels Data Center Homesum_a_epg0_fpd_mmcf_m.xls" ,"Available from WebQuantityBonneville Power AdministrationRobust,Field-effectWorkingLosThe 26thIWalter H. Zinn, 1969CALCD Energy(SC)(SC) Catalysis

  8. Concise Total Synthesis and Stereochemical Revision of (+)-Naseseazines A and B: Regioselective Arylative Dimerization of Diketopiperazine Alkaloids

    E-Print Network [OSTI]

    Kim, Justin

    Concise and enantioselective total syntheses of (+)-naseseazines A and B are described. Our regioselective and directed dimerization of diketopiperazines provides their critical C3–C[2 over sp] linkages, an assembly with ...

  9. Elastic properties of the degenerate f.c.c. crystal of polydisperse soft dimers at zero temperature

    E-Print Network [OSTI]

    Narojczyk, J W

    2015-01-01

    Elastic properties of soft, three-dimensional dimers, interacting through site-site n-inverse-power potential, are determined by computer simulations at zero temperature. The degenerate crystal of dimers exhibiting (Gaussian) size distribution of atomic diameters - i.e. size polydispersity - is studied at the molecular number density $1/\\sqrt{2}$; the distance between centers of atoms forming dimers is considered as a length unit. It is shown that, at the fixed number density of the dimers, increasing polydispersity causes, typically, an increase of pressure, elastic constants and Poisson's ratio; the latter is positive in most direction. A direction is found, however, in which the size polydispersity causes substantial decrease of Poisson's ratio, down to negative values for large $n$. Thus, the system is partially auxetic for large polydispersity and large n.

  10. Elastic properties of the degenerate f.c.c. crystal of polydisperse soft dimers at zero temperature

    E-Print Network [OSTI]

    J. W. Narojczyk; K. W. Wojciechowski

    2015-04-12

    Elastic properties of soft, three-dimensional dimers, interacting through site-site n-inverse-power potential, are determined by computer simulations at zero temperature. The degenerate crystal of dimers exhibiting (Gaussian) size distribution of atomic diameters - i.e. size polydispersity - is studied at the molecular number density $1/\\sqrt{2}$; the distance between centers of atoms forming dimers is considered as a length unit. It is shown that, at the fixed number density of the dimers, increasing polydispersity causes, typically, an increase of pressure, elastic constants and Poisson's ratio; the latter is positive in most direction. A direction is found, however, in which the size polydispersity causes substantial decrease of Poisson's ratio, down to negative values for large $n$. Thus, the system is partially auxetic for large polydispersity and large n.

  11. A Concise and Versatile Double-Cyclization Strategy for the Highly Stereoselective Synthesis and Arylative Dimerization of Aspidosperma Alkaloids

    E-Print Network [OSTI]

    Medley, Jonathan William

    Building cycles: A strategy for the concise, stereoselective synthesis of aspidosperma alkaloids and related structures via a common putative diiminium ion intermediate is reported. The approach enables the dimerization ...

  12. Morphological variations as nonstandard test parameters for the response to pollutant gas concentration: An application to Ruthenium Phthalocyanine sensing films

    SciTech Connect (OSTI)

    Generosi, A.; Paci, B.; Albertini, V. Rossi; Perfetti, P.; Paoletti, A.M.; Pennesi, G.; Rossi, G.; Caminiti, R.

    2006-03-06

    A systematic time-resolved energy dispersive x-ray reflectometry study was performed in situ on Ruthenium Phthalocyanine thin fims to estimate the morphological detection limits of this material as NO{sub 2} transducer and the influence of the gas concentration on the gas-film interaction mechanisms. The work validates the use of this unconventional method--based on the observation of the morphological parameters change--for evaluating the response of novel sensing materials in alternative to more standard procedures. Indeed, the morphological monitoring is shown to be sensitive to the gas concentration in a range comparable to the usual electroresistive measurements. Moreover, while the latter is only able to give the information on whether the gas is interacting with the sensor, the former is also able to discriminate among interaction processes of a different nature (in the present case the interaction limited to the film surface and the one involving the material bulk)

  13. Modeling theta-theta Interactions with the Effective Fragment Potential Method: The Benzene Dimer and Substituents

    SciTech Connect (OSTI)

    Toni Smithl; Lyudmila V. Slipchenko; Mark S. Gordon

    2008-02-27

    This study compares the results of the general effective fragment potential (EFP2) method to the results of a previous combined coupled cluster with single, double, and perturbative triple excitations [CCSD(T)] and symmetry-adapted perturbation theory (SAPT) study [Sinnokrot and Sherrill, J. Am. Chem. Soc., 2004, 126, 7690] on substituent effects in {pi}-{pi} interactions. EFP2 is found to accurately model the binding energies of the benzene-benzene, benzene-phenol, benzene-toluene, benzene-fluorobenzene, and benzene-benzonitrile dimers, as compared with high-level methods [Sinnokrot and Sherrill, J. Am. Chem. Soc., 2004, 126, 7690], but at a fraction of the computational cost of CCSD(T). In addition, an EFP-based Monte Carlo/simulated annealing study was undertaken to examine the potential energy surface of the substituted dimers.

  14. Photo-induced strengthening of weak bonding in noble gas dimers

    SciTech Connect (OSTI)

    Miyamoto, Yoshiyuki; Miyazaki, Takehide; Rubio, Angel

    2014-05-19

    We demonstrate through extensive first-principles time-dependent density functional calculations that attractive van der Waals interaction between closed-shell atoms can be enhanced by light with constant spatial intensity. We illustrate this general phenomenon for a He dimer as a prototypical case of complex van der Waals interactions and show that when excited by light with a frequency close to the 1s ? 2p He-atomic transition, an attractive force larger than 7 pN is produced. This force gain is manifested as a larger acceleration of He-He contraction under an optical field. The concerted dynamical motions of the He atoms together with polarity switching of the charge-induced dipole cause the contraction of the dimer. These findings are relevant for the photo-induced control of weakly bonded molecular species, either in gas phase or in solution.

  15. A mean-field monomer-dimer model with attractive interaction: Exact solution and rigorous results

    SciTech Connect (OSTI)

    Alberici, D. Contucci, P. Mingione, E.

    2014-06-15

    A mean-field monomer-dimer model which includes an attractive interaction among both monomers and dimers is introduced and its exact solution rigorously derived. The Heilmann-Lieb method for the pure hard-core interacting case is used to compute upper and lower bounds for the pressure. The bounds are shown to coincide in the thermodynamic limit for a suitable choice of the monomer density m. The computation of the monomer density is achieved by solving a consistency equation in the phase space (h, J), where h tunes the monomer potential and J the attractive potential. The critical point and exponents are computed and show that the model is in the mean-field ferromagnetic universality class.

  16. Interaction energies of monosubstituted benzene dimers via nonlocal density functional theory

    E-Print Network [OSTI]

    T. Thonhauser; Aaron Puzder; David C. Langreth

    2005-09-15

    We present density-functional calculations for the interaction energy of monosubstituted benzene dimers. Our approach utilizes a recently developed fully nonlocal correlation energy functional, which has been applied to the pure benzene dimer and several other systems with promising results. The interaction energy as a function of monomer distance was calculated for four different substituents in a sandwich and two T-shaped configurations. In addition, we considered two methods for dealing with exchange, namely using the revPBE generalized gradient functional as well as full Hartree-Fock. Our results are compared with other methods, such as Moller-Plesset and coupled-cluster calculations, thereby establishing the usefulness of our approach. Since our density-functional based method is considerably faster than other standard methods, it provides a computational inexpensive alternative, which is of particular interest for larger systems where standard calculations are too expensive or infeasible.

  17. The HPr Proteins from the Thermophile Bacillus stearothermophilus Can Form Domain-swapped Dimers

    SciTech Connect (OSTI)

    Sridharan, Sudharsan; Razvi, Abbas; Scholtz, J. Martin; Sacchettini, James C. (TAM)

    2010-07-20

    The study of proteins from extremophilic organisms continues to generate interest in the field of protein folding because paradigms explaining the enhanced stability of these proteins still elude us and such studies have the potential to further our knowledge of the forces stabilizing proteins. We have undertaken such a study with our model protein HPr from a mesophile, Bacillus subtilis, and a thermophile, Bacillus stearothermophilus. We report here the high-resolution structures of the wild-type HPr protein from the thermophile and a variant, F29W. The variant proved to crystallize in two forms: a monomeric form with a structure very similar to the wild-type protein as well as a domain-swapped dimer. Interestingly, the structure of the domain-swapped dimer for HPr is very different from that observed for a homologous protein, Crh, from B. subtilis. The existence of a domain-swapped dimer has implications for amyloid formation and is consistent with recent results showing that the HPr proteins can form amyloid fibrils. We also characterized the conformational stability of the thermophilic HPr proteins using thermal and solvent denaturation methods and have used the high-resolution structures in an attempt to explain the differences in stability between the different HPr proteins. Finally, we present a detailed analysis of the solution properties of the HPr proteins using a variety of biochemical and biophysical methods.

  18. The Structure of the Poxvirus A33 Protein Reveals a Dimer of Unique C-Type Lectin-Like Domains

    SciTech Connect (OSTI)

    Su, Hua-Poo; Singh, Kavita; Gittis, Apostolos G.; Garboczi, David N. (NIH)

    2010-11-03

    The current vaccine against smallpox is an infectious form of vaccinia virus that has significant side effects. Alternative vaccine approaches using recombinant viral proteins are being developed. A target of subunit vaccine strategies is the poxvirus protein A33, a conserved protein in the Chordopoxvirinae subfamily of Poxviridae that is expressed on the outer viral envelope. Here we have determined the structure of the A33 ectodomain of vaccinia virus. The structure revealed C-type lectin-like domains (CTLDs) that occur as dimers in A33 crystals with five different crystal lattices. Comparison of the A33 dimer models shows that the A33 monomers have a degree of flexibility in position within the dimer. Structural comparisons show that the A33 monomer is a close match to the Link module class of CTLDs but that the A33 dimer is most similar to the natural killer (NK)-cell receptor class of CTLDs. Structural data on Link modules and NK-cell receptor-ligand complexes suggest a surface of A33 that could interact with viral or host ligands. The dimer interface is well conserved in all known A33 sequences, indicating an important role for the A33 dimer. The structure indicates how previously described A33 mutations disrupt protein folding and locates the positions of N-linked glycosylations and the epitope of a protective antibody.

  19. Design of a new reactor-like high temperature near ambient pressure scanning tunneling microscope for catalysis studies

    E-Print Network [OSTI]

    Tao, Franklin Feng; Nguyen, Luan; Zhang, Shiran

    2013-01-01

    Here, we present the design of a new reactor-like high-temperature near ambient pressure scanning tunneling microscope (HT-NAP-STM) for catalysis studies. This HT-NAP-STM was designed for exploration of structures of catalyst surfaces at atomic...

  20. Chloroyttrium 2(1-(Arylimino)alkyl)quinolin-8-olate Complexes: Synthesis, Characterization, and Catalysis of the Ring-Opening

    E-Print Network [OSTI]

    Glaser, Rainer

    the polymerization in the BnOH-free process. Most polymers generated by BnOH-assisted catalysis possess Mn values materials" because they are biocompatible, readily biodegradable, and easily recyclable. Because showed low catalytic activity and resulted in polymers with relatively low molecular weights.5 In sharp

  1. Structure of Human Epoxide Hydrolase Reveals Mechanistic Inferences on Bifunctional Catalysis in Epoxide and Phosphate Ester Hydrolysis,

    E-Print Network [OSTI]

    Hammock, Bruce D.

    is unclear. Recent experiments demonstrate that the N-terminal domain of human sEH catalyzes the metalStructure of Human Epoxide Hydrolase Reveals Mechanistic Inferences on Bifunctional Catalysis ReceiVed February 4, 2004 ABSTRACT: The X-ray crystal structure of human soluble epoxide hydrolase (s

  2. Channeling of Fusion Alpha-Particle Power Using Minority Ion Catalysis A. I. Zhmoginov and N. J. Fisch

    E-Print Network [OSTI]

    , with electrons kept cold, so that the effective fusion reactivity can be increased [9­11]. The meansChanneling of Fusion Alpha-Particle Power Using Minority Ion Catalysis A. I. Zhmoginov and N. J greatly facilitate controlled nuclear fusion. The parameter range for achieving this temperature disparity

  3. Reaction Kinetics and Catalysis Letters, Vol. 1, No. 2/1974/209-213 STOCHASTIC SIMULATION OF CHEMICAL REACTIONS BY

    E-Print Network [OSTI]

    Tóth, János

    OF CHEMICAL REACTIONS BY DIGITAL COMPUTER, H. APPLICATIONS T. Sipos1, J.TSth 2 and P. ~.rdi1 1. Danube Oil chemical reactions (especially those of biological interest, e.g. reactions exhibiting oscillationReaction Kinetics and Catalysis Letters, Vol. 1, No. 2/1974/209-213 STOCHASTIC SIMULATION

  4. Decarboxylative Arylation of Amino Acids via Photoredox Catalysis: A One-Step Conversion of Biomass to Drug

    E-Print Network [OSTI]

    MacMillan, David W. C.

    Decarboxylative Arylation of Amino Acids via Photoredox Catalysis: A One-Step Conversion of Biomass. This method offers rapid entry to prevalent benzylic amine architectures from an abundant biomass the worldwide abundance of biomass6 that incorporates carboxylate functionality (e.g., amino acids, -hydroxy

  5. Catalysis Workshop

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative Fuels Data Center Homesum_a_epg0_fpd_mmcf_m.xls" ,"Available from WebQuantity ofkandz-cm11 OutreachProductswsicloudwsiclouddenDVA N C E D B LReports fromSheetsCascadia Analysis

  6. Is It Homogeneous or Heterogeneous Catalysis Derived from [RhCp*Cl2]2? In Operando-XAFS, Kinetic and Crucial Kinetic Poisoning Evidence for Subnanometer Rh4 Cluster-Based Benzene Hydrogenation Catalysis

    SciTech Connect (OSTI)

    Bayram, Ercan; Linehan, John C.; Fulton, John L.; Roberts, John A.; Szymczak, Nathaniel; Smurthwaite, Tricia D.; Ozkar, Saim; Balasubramanian, Mahalingam; Finke, Richard G.

    2011-11-23

    Determining the true, kinetically dominant catalytically active species, in the classic benzene hydrogenation system pioneered by Maitlis and co-workers 34 years ago starting with [RhCp*Cl2]2 (Cp* = [{eta}5-C5(CH3)5]), has proven to be one of the most challenging case studies in the quest to distinguish single-metal-based 'homogeneous' from polymetallic, 'heterogeneous' catalysis. The reason, this study will show, is the previous failure to use the proper combination of (i) operando spectroscopy to determine the dominant form(s) of the precatalyst's mass under catalysis (i.e., operating) conditions, plus then and crucially also (ii) the previous lack of the necessary kinetic studies, catalysis being a 'wholly kinetic phenomenon' as J. Halpern long ago noted. An important contribution from this study will be to reveal the power of quantitiative kinetic poisoning experiments for distinguishing single-metal, or in this case subnanometer Rh4 cluster-based catalysis from larger, polymetallic Rh(0)n nanoparticle catalysis, at least under favorable conditions. The combined operando-XAFS (X-ray absorption fine structure) spectroscopy and kinetic evidences provide a compelling case for Rh4-based, with average stoichiometry 'Rh4Cp*2.4Cl4Hc', benzene hydrogenation catalysis in 2-propanol with added Et3N and at 100 C and 50 atm initial H2 pressure. The results also reveal, however, that if even ca. 1.4% of the total soluble Rh(0)n had formed nanoparticles, then those Rh(0)n nanoparticles would have been able to account for all the observed benzene hydrogenation catalytic rate (using commercial, ca. 2 nm, polyethyleneglycol-dodecylether hydrosol stabilized Rh(0)n nanoparticles as a model system). The results 'especially the poisoning methodology developed and employed' are of significant, broader interest since determining the nature of the true catalyst continues to be a central, often vexing issue in any and all catalytic reactions. The results are also of fundamental interest in that they add to a growing body of evidence indicating that certain, appropriately ligated, coordinatively unsaturated, subnanometer M4 transition-metal clusters can be relatively robust catalysts. Also demonstrated herein is that Rh4 clusters are poisoned by Hg(0), demonstrating for the first time that the classic Hg(0) poisoning test of 'homogeneous' vs 'heterogeneous'catalysts cannot distinguish Rh4-based subnanometer catalysts from Rh(0)n nanoparticle catalysts, at least for the present examples of these two specific, Rh-based catalysts.

  7. The Design and Investigation of the Self-Assembly of Dimers with two Nematic Phases

    E-Print Network [OSTI]

    Z. Ahmed; C. Welch; G. H. Mehl

    2015-09-06

    A series of non-symmetric dimers were synthesised containing either cyanobiphenyl or difluoroterphenyl moieties on one side and a range of long, short, bent, polar or apolar mesogens on the other side of the molecules. The dielectric anisotropy of the mesogens was varied systematically. The systems were characterised by differential scanning calorimetry (DSC), optical polarizing microscopy (OPM) and detailed X-ray diffraction (XRD) studies, both in the nematic and the Nx phase. The results are compared and structure properties relationships are discussed. A model for the assembly in the Nx phase is developed discussing Ntb structures, coaxial helices, swiss roll structures and chiral domain formation.

  8. Directed transport in equilibrium : analysis of the dimer model with inertial terms

    E-Print Network [OSTI]

    A. Bhattacharyay

    2011-08-15

    We have previously shown an analysis of our dimer model in the over-damped regime to show directed transport in equilibrium. Here we analyze the full model with inertial terms present to establish the same result. First we derive the Fokker-Planck equation for the system following a Galilean transformation to show that a uniformly translating equilibrium distribution is possible. Then, we find out the velocity selection for the centre of mass motion using that distribution on our model. We suggest generalization of our calculations for soft collision potentials and indicate to interesting situation with possibility of oscillatory non-equilibrium state within equilibrium.

  9. Enhanced dimer relaxation in an atomic and molecular Bose-Einstein condensate

    SciTech Connect (OSTI)

    Braaten, Eric; Hammer, H.-W.

    2004-10-01

    We derive a universal formula for the rate constant {beta} for relaxation of a shallow dimer into deeply-bound diatomic molecules in the case of atoms with a large scattering length a. We show that {beta} is determined by a and by 2 three-body parameters that also determine the binding energies and widths of Efimov states. The rate constant {beta} scales like ({Dirac_h}/2{pi})a/m near the resonance, but the coefficient is a periodic function of ln(a) that may have resonant enhancement at values of a that differ by multiples of 22.7.

  10. Spectroscopic accuracy directly from quantum chemistry: application to ground and excited states of beryllium dimer

    E-Print Network [OSTI]

    Sharma, Sandeep; Booth, George H; Umrigar, C J; Chan, Garnet Kin-Lic

    2014-01-01

    We combine explicit correlation via the canonical transcorrelation approach with the density matrix renormalization group and initiator full configuration interaction quantum Monte Carlo methods to compute a near-exact beryllium dimer curve, {\\it without} the use of composite methods. In particular, our direct density matrix renormalization group calculations produce a well-depth of $D_e$=931.2 cm$^{-1}$ which agrees very well with recent experimentally derived estimates $D_e$=929.7$\\pm 2$~cm$^{-1}$ [Science, 324, 1548 (2009)] and $D_e$=934.6~cm$^{-1}$ [Science, 326, 1382 (2009)

  11. Covalent features in the hydrogen bond of a water dimer: molecular orbital analysis

    E-Print Network [OSTI]

    Wang, Bo; Dai, Xing; Gao, Yang; Wang, Zhigang; Zhang, Rui-Qin

    2015-01-01

    The covalent-like characteristics of hydrogen bonds offer a new perspective on intermolecular interactions. Here, using density functional theory and post-Hartree-Fock methods, we reveal that there are two bonding molecular orbitals (MOs) crossing the O and H atoms of the hydrogen-bond in water dimer. Energy decomposition analysis also shows a non-negligible contribution of the induction term. These results illustrate the covalent-like character of the hydrogen bond between water molecules, which contributes to the essential understanding of ice, liquid water, related materials, and life sciences.

  12. Magnetic coupling in neutral and charged Cr{sub 2}, Mn{sub 2}, and CrMn dimers

    SciTech Connect (OSTI)

    Desmarais, N. [Institut de Physique Experimentale, Ecole Polytechnique Federale de Lausanne, PHB-Ecublens, CH-1015 Lausanne, (Switzerland)] [Institut de Physique Experimentale, Ecole Polytechnique Federale de Lausanne, PHB-Ecublens, CH-1015 Lausanne, (Switzerland); Reuse, F. A. [Institut de Physique Experimentale, Ecole Polytechnique Federale de Lausanne, PHB-Ecublens, CH-1015 Lausanne, (Switzerland)] [Institut de Physique Experimentale, Ecole Polytechnique Federale de Lausanne, PHB-Ecublens, CH-1015 Lausanne, (Switzerland); Khanna, S. N. [Department of Physics, Virginia Commonwealth University, Richmond, Virginia 23284-2000 (United States)] [Department of Physics, Virginia Commonwealth University, Richmond, Virginia 23284-2000 (United States)

    2000-04-01

    Theoretical ab initio studies of neutral, cationic and anionic Cr{sub 2}, Mn{sub 2}, and CrMn dimers have been carried out to explore the progression of magnetic coupling with the number of electrons. It is shown that while Cr{sub 2} and Cr{sub 2}{sup -} have antiferromagnetically coupled atomic spins, Cr{sub 2}{sup +} has a ferromagnetic ground state closely followed by an antiferromagnetic state. On the other hand, all Mn{sub 2} dimers are ferromagnetic, irrespective of the charge. The neutral CrMn is ferrimagnetic while the charged CrMn are antiferromagnetic. In all cases, the charged dimers are found to be more stable than the neutral ones. The results are compared with available calculations and experiments and the difficulties associated with theoretical description and the experimental interpretations are discussed. (c) 2000 American Institute of Physics.

  13. Adsorption of Ruthenium, Rhodium and Palladium from Simulated High-Level Liquid Waste by Highly Functional Xerogel - 13286

    SciTech Connect (OSTI)

    Onishi, Takashi [Fukushima Fuels and Materials Department O-arai Research and Development Center Japan Atomic Energy Agency, Narita-cho 4002, O-arai-machi, Ibaraki, 311-1393 (Japan)] [Fukushima Fuels and Materials Department O-arai Research and Development Center Japan Atomic Energy Agency, Narita-cho 4002, O-arai-machi, Ibaraki, 311-1393 (Japan); Koyama, Shin-ichi [Fukushima Fuels and Materials Department O-arai Research and Development Center Japan Atomic Energy Agency, Narita-cho 4002, O-arai-machi, Ibaraki, 311-1393 (Japan)] [Fukushima Fuels and Materials Department O-arai Research and Development Center Japan Atomic Energy Agency, Narita-cho 4002, O-arai-machi, Ibaraki, 311-1393 (Japan); Mimura, Hitoshi [Dept. of Quantum Science and Energy Engineering, Graduate School of Engineering, Tohoku University Aramaki-Aza-Aoba 6-6-01-2,Aoba-ku, Sendai-shi, Miyagi-ken, 980-8579 (Japan)] [Dept. of Quantum Science and Energy Engineering, Graduate School of Engineering, Tohoku University Aramaki-Aza-Aoba 6-6-01-2,Aoba-ku, Sendai-shi, Miyagi-ken, 980-8579 (Japan)

    2013-07-01

    Fission products are generated by fission reactions in nuclear fuel. Platinum group (Pt-G) elements, such as palladium (Pd), rhodium (Rh) and ruthenium (Ru), are also produced. Generally, Pt-G elements play important roles in chemical and electrical industries. Highly functional xerogels have been developed for recovery of these useful Pt-G elements from high - level radioactive liquid waste (HLLW). An adsorption experiment from simulated HLLW was done by the column method to study the selective adsorption of Pt-G elements, and it was found that not only Pd, Rh and Ru, but also nickel, zirconium and tellurium were adsorbed. All other elements were not adsorbed. Adsorbed Pd was recovered by washing the xerogel-packed column with thiourea solution and thiourea - nitric acid mixed solution in an elution experiment. Thiourea can be a poison for automotive exhaust emission system catalysts, so it is necessary to consider its removal. Thermal decomposition and an acid digestion treatment were conducted to remove sulfur in the recovered Pd fraction. The relative content of sulfur to Pd was decreased from 858 to 0.02 after the treatment. These results will contribute to design of the Pt-G element separation system. (authors)

  14. Vapor Synthesis and Thermal Modification of Supportless Platinum-Ruthenium Nanotubes and Application as Methanol Electrooxidation Catalysts

    SciTech Connect (OSTI)

    Atkinson III, Robert [University of Tennessee (UT); Unocic, Raymond R [ORNL; Unocic, Kinga A [ORNL; Veith, Gabriel M [ORNL; Papandrew, Alexander B [ORNL; Zawodzinski, Thomas A [ORNL

    2015-01-01

    Metallic, mixed-phase, and alloyed bimetallic Pt-Ru nanotubes were synthesized by a novel route based on the sublimation of metal acetylacetonate precursors and their subsequent vapor deposition within anodic alumina templates. Nanotube architectures were tuned by thermal annealing treatments. As-synthesized nanotubes are composed of nanoparticulate, metallic platinum and hydrous ruthenium oxide whose respective thicknesses depend on the sample chemical composition. The Pt-decorated, hydrous Ru oxide nanotubes may be thermally annealed to promote a series of chemical and physical changes to the nanotube structures including alloy formation, crystallite growth and morphological evolution. Annealed Pt-Ru alloy nanotubes and their as-synthesized analogs demonstrate relatively high specific activities for the oxidation of methanol. As-synthesized, mixed-phase Pt-Ru nanotubes (0.39 mA/cm2) and metallic alloyed Pt64Ru36NTs (0.33 mA/cm2) have considerably higher area-normalized activities than PtRu black (0.22 mA/cm2) at 0.65 V vs. RHE.

  15. Surface-Defects and Core Excitons at the (2x1) Asymmetric-Dimer (100) Surface of Si 

    E-Print Network [OSTI]

    BOWEN, MA; Allen, Roland E.; DOW, JD.

    1984-01-01

    VOLUME 30, NUMBER 8 15 OCTOBER 1984 Surface defects and core excitons at the (2X 1) asymmetric-dimer (100) surface of Si Marshall A. Bowen Department ofPhysics, Western Illinois University, Macomb, Illinois 61455 Roland E. Allen Department of... with 28 sp3- bonded substitutional defects, and (ii) energies of Hjalmarson-Frenkel core excitons 'at the (100) sur- face of Si, reconstructed according to Chadi s (2& 1) asymmetric-dimer model. The predictions sug- gest that P at. this surface should...

  16. Excitonic splitting and coherent electronic energy transfer in the gas-phase benzoic acid dimer

    SciTech Connect (OSTI)

    Ottiger, Philipp; Leutwyler, Samuel

    2012-11-28

    The benzoic acid dimer, (BZA){sub 2}, is a paradigmatic symmetric hydrogen bonded dimer with two strong antiparallel hydrogen bonds. The excitonic S{sub 1}/S{sub 2} state splitting and coherent electronic energy transfer within supersonically cooled (BZA){sub 2} and its {sup 13}C-, d{sub 1}-, d{sub 2}-, and {sup 13}C/d{sub 1}- isotopomers have been investigated by mass-resolved two-color resonant two-photon ionization spectroscopy. The (BZA){sub 2}-(h-h) and (BZA){sub 2}-(d-d) dimers are C{sub 2h} symmetric, hence only the S{sub 2} Leftwards-Arrow S{sub 0} transition can be observed, the S{sub 1} Leftwards-Arrow S{sub 0} transition being strictly electric-dipole forbidden. A single {sup 12}C/{sup 13}C or H/D isotopic substitution reduces the symmetry of the dimer to C{sub s}, so that the isotopic heterodimers (BZA){sub 2}-{sup 13}C, (BZA){sub 2}-(h-d), (BZA){sub 2}-(h{sup 13}C-d), and (BZA){sub 2}-(h-d{sup 13}C) show both S{sub 1} Leftwards-Arrow S{sub 0} and S{sub 2} Leftwards-Arrow S{sub 0} bands. The S{sub 1}/S{sub 2} exciton splitting inferred is {Delta}{sub exc}= 0.94 {+-} 0.1 cm{sup -1}. This is the smallest splitting observed so far for any H-bonded gas-phase dimer. Additional isotope-dependent contributions to the splittings, {Delta}{sub iso}, arise from the change of the zero-point vibrational energy upon electronic excitation and range from {Delta}{sub iso}= 3.3 cm{sup -1} upon {sup 12}C/{sup 13}C substitution to 14.8 cm{sup -1} for carboxy H/D substitution. The degree of excitonic localization/delocalization can be sensitively measured via the relative intensities of the S{sub 1} Leftwards-Arrow S{sub 0} and S{sub 2} Leftwards-Arrow S{sub 0} origin bands; near-complete localization is observed even for a single {sup 12}C/{sup 13}C substitution. The S{sub 1}/ S{sub 2} energy gap of (BZA){sub 2} is {Delta}{sub calc}{sup exc}=11 cm{sup -1} when calculated by the approximate second-order perturbation theory (CC2) method. Upon correction for vibronic quenching, this decreases to {Delta}{sub vibron}{sup exc}=2.1 cm{sup -1} [P. Ottiger et al., J. Chem. Phys. 136, 174308 (2012)], in good agreement with the observed {Delta}{sub exc}= 0.94 cm{sup -1}. The observed excitonic splittings can be converted to exciton hopping times {tau}{sub exc}. For the (BZA){sub 2}-(h-h) homodimer {tau}{sub exc}= 18 ps, which is nearly 40 times shorter than the double proton transfer time of (BZA){sub 2} in its excited state [Kalkman et al., ChemPhysChem 9, 1788 (2008)]. Thus, the electronic energy transfer is much faster than the proton-transfer in (BZA){sub 2}{sup *}.

  17. Probing the Impact of the EchinT C-Terminal Domain on Structure and Catalysis

    SciTech Connect (OSTI)

    S Bardaweel; J Pace; T Chou; V Cody; C Wagner

    2011-12-31

    Histidine triad nucleotide binding protein (Hint) is considered as the ancestor of the histidine triad protein superfamily and is highly conserved from bacteria to humans. Prokaryote genomes, including a wide array of both Gram-negative bacteria and Gram-positive bacteria, typically encode one Hint gene. The cellular function of Hint and the rationale for its evolutionary conservation in bacteria have remained a mystery. Despite its ubiquity and high sequence similarity to eukaryote Hint1 [Escherichia coli Hint (echinT) is 48% identical with human Hint1], prokaryote Hint has been reported in only a few studies. Here we report the first conformational information on the full-length N-terminal and C-terminal residues of Hint from the E. coli complex with GMP. Structural analysis of the echinT-GMP complex reveals that it crystallizes in the monoclinic space group P2{sub 1} with four homodimers in the asymmetric unit. Analysis of electron density for both the N-terminal residues and the C-terminal residues of the echinT-GMP complex indicates that the loops in some monomers can adopt more than one conformation. The observation of conformational flexibility in terminal loop regions could explain the presence of multiple homodimers in the asymmetric unit of this structure. To explore the impact of the echinT C-terminus on protein structure and catalysis, we conducted a series of catalytic radiolabeling and kinetic experiments on the C-terminal deletion mutants of echinT. In this study, we show that sequential deletion of the C-terminus likely has no effect on homodimerization and a modest effect on the secondary structure of echinT. However, we observed a significant impact on the folding structure, as reflected by a significant lowering of the T{sub m} value. Kinetic analysis reveals that the C-terminal deletion mutants are within an order of magnitude less efficient in catalysis compared to wild type, while the overall kinetic mechanism that proceeds through a fast step, followed by a rate-limiting hydrolysis step, was conserved. Nevertheless, the ability of the C-terminal deletion mutants to hydrolyze lysyl-AMP generated by LysU was greatly impaired. Taken together, our results highlight the emerging role of the C-terminus in governing the catalytic function of Hints.

  18. Two-photon induced fabrication of gold microstructures in polystyrene sulfonate thin films using a ruthenium(II) dye as photoinitiator

    SciTech Connect (OSTI)

    Vurth, Laeticia; Baldeck, Patrice; Stephan, Olivier [Laboratoire de Spectrometrie Physique, Universite Joseph Fourier, CNRS (UMR 5588), BP 87, 38402 Saint Martin d'heres Cedex (France); Vitrant, Guy [Institut Microelectronique Electromagnetisme et Photonique, ENSERG-INPG, CNRS (UMR 5130), BP 257, 38016 Grenoble Cedex 1 (France)

    2008-04-28

    Gold microstructures are produced with a femtosecond laser in thin films of a polystyrene sulfonate matrix containing gold ions. Two-photon induced metal reduction is obtained by addition of 0.1 wt % of ruthenium(II)tris(bipyridine) in the formulation. Laser power is reduced to 5 mW, thereby limiting thermal effects. Lines of typically 150 nm heights and 1 {mu}m widths are fabricated as well as freestanding bidimensional structures. An additional electroless plating step produces gold structures with conductivities only ten times smaller than the bulk metal.

  19. Relativistic ab initio treatment of the second-order spin-orbit splitting potential of rubidium and cesium dimers

    E-Print Network [OSTI]

    Kotochigova, Svetlana

    of rubidium and cesium dimers S. Kotochigova, E. Tiesinga, and P. S. Julienne National Institute of Standards. So far unacceptably large inelastic losses for cesium have prevented it from condensing 2 depolarization of room-temperature doubly polarized rubidium and cesium atoms 8 . In this pap

  20. Excitation Energy Transfer in Dimeric Light Harvesting Complex I: A Combined Streak-Camera/Fluorescence Upconversion Study

    E-Print Network [OSTI]

    van Stokkum, Ivo

    Excitation Energy Transfer in Dimeric Light Harvesting Complex I: A Combined Streak harvesting complex I, the peripheral light harvesting complex associated with photosystem I in green plants upconversion and synchroscan streak-camera measurements, revealed the energy transfer and decay of excitations

  1. A Fundamental Study on the [(?-Cl)3Mg2(THF)6]+ Dimer Electrolytes for Rechargeable Mg Batteries

    SciTech Connect (OSTI)

    Liu, Tianbiao L.; Cox, Jonathan T.; Hu, Dehong; Deng, Xuchu; Hu, Jian Z.; Hu, Mary Y.; Xiao, Jie; Shao, Yuyan; Tang, Keqi; Liu, Jun

    2015-01-01

    We present a fundamental study on [(?-Cl)3Mg2(THF)6]+dimer electrolytes using various physical methods including Subambient Pressure Ionization with Nanoelectrospray Mass spectrometry (SPIN-MS), Raman spectroscopy, 25Mg{1H} NMR, 27Al{1H} NMR and electrochemical analysis. For the first time, long time sought THF solvated [MgCl]+ species was experimentally characterized by SPIN mass spectrometry in the solution of the Mgdimer containing electrolyte, confirming the mono-Cl- abstraction reaction between MgCl2 and an Al Lewis acid. Solvated MgCl2 in the electrolyte was confirmed by Raman spectroscopy. The experimental results establish the previously proposed dimerization equilibrium of solvated [MgCl]+ and MgCl2 with [(?-Cl)3Mg2(THF)6]+. 25Mg{1H} NMR, 27Al{1H} NMR and electrochemical analysis on chloration reaction of [(?-Cl)3Mg2(THF)6]AlPh3Cl with external Cl- led to further insights on the coordination chemistry of the dimer electrolyte. Finally, a comprehensive mechanism is proposed for the reversible electrochemical Mg deposition and stripping and Mg2+ and Cl- ion transports of the Mg dimer electrolytes in rechargeable Mg batteries.

  2. Ultralow-power local laser control of the dimer density in alkali-metal vapors through photodesorption

    SciTech Connect (OSTI)

    Jha, Pankaj K.; Scully, Marlan O. [Texas A and M University, College Station, Texas 77843 (United States); Princeton University, Princeton, New Jersey 08544 (United States); Dorfman, Konstantin E. [Texas A and M University, College Station, Texas 77843 (United States); University of California, Irvine, Irvine, California 92697 (United States); Yi Zhenhuan; Yuan Luqi; Welch, George R. [Texas A and M University, College Station, Texas 77843 (United States); Sautenkov, Vladimir A. [Texas A and M University, College Station, Texas 77843 (United States); Joint Institute of High Temperature, RAS, Moscow 125412 (Russian Federation); Rostovtsev, Yuri V. [University of North Texas, Denton, Texas 76203 (United States); Zheltikov, Aleksei M. [Texas A and M University, College Station, Texas 77843 (United States); M.V. Lomonosov Moscow State University, Moscow 119992 (Russian Federation)

    2012-08-27

    Ultralow-power diode-laser radiation is employed to induce photodesorption of cesium from a partially transparent thin-film cesium adsorbate on a solid surface. Using resonant Raman spectroscopy, we demonstrate that this photodesorption process enables an accurate local optical control of the density of dimer molecules in alkali-metal vapors.

  3. Sulfation of metal-organic framework: Opportunities for acid catalysis and proton conductivity

    SciTech Connect (OSTI)

    Goesten, M.G.; Stavitski, E.; Juan-Alcaniz, J.; Ramos-Fernandez, E.V.; Sai Sankar Gupta, K.B.; van Bekkum, H.; Gascon, J. and Kapteijn, F.

    2011-05-24

    A new post-functionalization method for metal-organic frameworks (MOFs) has been developed to introduce acidity for catalysis. Upon treatment with a mixture of triflic anhydride and sulfuric acid, chemically stable MOF structures MIL-101(Cr) and MIL-53(Al) can be sulfated, resulting in a Broensted sulfoxy acid group attached to up to 50% of the aromatic terephthalate linkers of the structure. The sulfated samples have been extensively characterized by solid-state NMR, XANES, and FTIR spectroscopy. The functionalized acidic frameworks show catalytic activity similar to that of acidic polymers like Nafion{reg_sign} display in the esterification of n-butanol with acetic acid (TOF {approx} 1 min{sup -1} {at} 343 K). Water adsorbs strongly up to 4 molecules per sulfoxy acid group, and an additional 2 molecules are taken up at lower temperatures in the 1-D pore channels of S-MIL-53(Al). The high water content and Broensted acidity provide the structure S-MIL-53(Al) a high proton conductivity up to moderate temperatures.

  4. Molecular Insights into Substrate Recognition and Catalysis by Tryptophan 2,3-dioxygenase

    SciTech Connect (OSTI)

    Forouhar,F.; Ross Anderson, J.; Mowat, C.; Vorobiev, S.; Hussain, A.; Abashidze, M.; Bruckmann, C.; Thackray, S.; Seetharaman, J.; et al.

    2007-01-01

    Tryptophan 2,3-dioxygenase (TDO) and indoleamine 2,3-dioxygenase (IDO) constitute an important, yet relatively poorly understood, family of heme-containing enzymes. Here, we report extensive structural and biochemical studies of the Xanthomonas campestris TDO and a related protein SO4414 from Shewanella oneidensis, including the structure at 1.6-{angstrom} resolution of the catalytically active, ferrous form of TDO in a binary complex with the substrate l-Trp. The carboxylate and ammonium moieties of tryptophan are recognized by electrostatic and hydrogen-bonding interactions with the enzyme and a propionate group of the heme, thus defining the l-stereospecificity. A second, possibly allosteric, l-Trp-binding site is present at the tetramer interface. The sixth coordination site of the heme-iron is vacant, providing a dioxygen-binding site that would also involve interactions with the ammonium moiety of l-Trp and the amide nitrogen of a glycine residue. The indole ring is positioned correctly for oxygenation at the C2 and C3 atoms. The active site is fully formed only in the binary complex, and biochemical experiments confirm this induced-fit behavior of the enzyme. The active site is completely devoid of water during catalysis, which is supported by our electrochemical studies showing significant stabilization of the enzyme upon substrate binding.

  5. Quantum Non-Demolition Detection of Polar Molecule Complexes: Dimers, Trimers, Tetramers

    E-Print Network [OSTI]

    Mekhov, Igor B

    2011-01-01

    The optical nondestructive method for in situ detection of the bound states of ultracold polar molecules is developed. It promises a minimally destructive measurement scheme up to a physically exciting quantum non-demolition (QND) level. The detection of molecular complexes beyond simple pairs of quantum particles (dimers, known, e.g., from the BEC-BCS theory) is suggested, including three-body (trimers) and four-body (tertramers) complexes trapped by one-dimensional tubes. The intensity of scattered light is sensitive to the molecule number fluctuations beyond the mean-density approximation. Such fluctuations are very different for various complexes, which leads to radically different light scattering. This type of research extends "quantum optics of quantum gases" to the field of ultracold molecules. Merging the quantum optical and ultracold gas problems will advance the experimental efforts towards the study of the light-matter interaction at its ultimate quantum level, where the quantizations of both ligh...

  6. Semiclassical molecular dynamics simulations of excited state double-proton transfer in 7-azaindole dimers

    SciTech Connect (OSTI)

    Guallar, V.; Batista, V.S.; Miller, W.H. [Department of Chemistry, University of California, and Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States)] [Department of Chemistry, University of California, and Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States)

    1999-05-01

    An {ital ab initio} excited state potential energy surface is constructed for describing excited state double proton transfer in the tautomerization reaction of photo-excited 7-azaindole dimers, and the ultrafast dynamics is simulated using the semiclassical (SC) initial value representation (IVR). The potential energy surface, determined in a reduced dimensionality, is obtained at the CIS level of quantum chemistry, and an approximate version of the SC-IVR approach is introduced which scales {ital linearly} with the number of degrees of freedom of the molecular system. The accuracy of this approximate SC-IVR approach is verified by comparing our semiclassical results with full quantum mechanical calculations. We find that proton transfer usually occurs during the first intermonomer symmetric-stretch vibration, about 100 fs after photoexcitation of the system, and produces an initial 15 percent population decay of the reactant base-pair, which is significantly reduced by isotopic substitution. {copyright} {ital 1999 American Institute of Physics.} thinsp

  7. The retroviral RNA dimer linkage: different structures may reflect different roles

    E-Print Network [OSTI]

    Greatorex, Jane S.

    2004-08-18

    G G G C C CA C G C G U A C G G C A G C U G C A GA U G C G U A C G G C A C ..CCCGGG.. ..GGGCCC.. ..GACGUC.. ..CUGCAG.. VL30 ..UGUCUUGUC.. Human foamy virus ..UCCCUAGGGA.. Moloney murine leukaemia virus G A C G G C G C G U C G U A U A C G G U A A G A C... :5598-5604. 27. Lanchy JM, Lodmell JS: Alternate usage of two dimerization ini- tiation sites in HIV-2 viral RNA in vitro. J Mol Biol 2002, 319:637-648. 28. Griffin SD, Allen JF, Lever AM: The major human immunodefi- ciency virus type 2 (HIV-2) packaging signal...

  8. Spin-lattice relaxation within a dimerized Ising chain in a magnetic field

    SciTech Connect (OSTI)

    Erdem, R?za E-mail: rerdem29@hotmail.com; Gülp?nar, Gül; Yalç?n, Orhan; Pawlak, Andrzej

    2014-07-21

    A qualitative study of the spin-lattice relaxation within a dimerized Ising chain in a magnetic field is presented. We have first determined the time dependence of the deviation of the lattice distortion parameter ?? from the equilibrium state within framework of a technique combining the statistical equilibrium theory based on the transfer matrix method and the linear theory of irreversible thermodynamics. We have shown that the time dependence of the lattice distortion parameter is characterized by a single time constant (?) which diverges around the critical point in both dimerized (??0) and uniform (?=0) phase regions. When the temperature and magnetic field are fixed to certain values, the time ? depends only on exchange coupling between the spins. It is a characteristic time associated with the long wavelength fluctuations of distortion. We have also taken into account the effects of spatial fluctuations on the relaxation time using the full Landau-Ginzburg free energy functional. We have found an explicit expression for the relaxation time as a function of temperature, coupling constant and wave vector (q) and shown that the critical mode corresponds to the case q=0. Finally, our results are found to be in good qualitative agreement with the results obtained in recent experimental study on synchrotron x-ray scattering and muon spin relaxation in diluted material Cu{sub 1?y}Mg{sub y}GeO{sub 3} where the composition y is very close to 0.0209. These results can be considered as natural extensions of some previous works on static aspects of the problem.

  9. Dimer Structure of an Interfacially Impaired Phosphatidylinositol-Specific Pholpholipase C

    SciTech Connect (OSTI)

    Shao,C.; Shi, X.; Wehbi, H.; Zambonelli, C.; Head, J.; Seaton, B.; Roberts, M,.

    2007-01-01

    The crystal structure of the W47A/W242A mutant of phosphatidylinositol-specific phospholipase C (PI-PLC) from Bacillus thuringiensis has been solved to 1.8{angstrom} resolution. The W47A/W242A mutant is an interfacially challenged enzyme, and it has been proposed that one or both tryptophan side chains serve as membrane interfacial anchors (Feng, J., Wehbi, H., and Roberts, M. F. (2002) J. Biol. Chem. 277, 19867-19875). The crystal structure supports this hypothesis. Relative to the crystal structure of the closely related (97% identity) wild-type PI-PLC from Bacillus cereus, significant conformational differences occur at the membrane-binding interfacial region rather than the active site. The Trp {yields} Ala mutations not only remove the membrane-partitioning aromatic side chains but also perturb the conformations of the so-called helix B and rim loop regions, both of which are implicated in interfacial binding. The crystal structure also reveals a homodimer, the first such observation for a bacterial PI-PLC, with pseudo-2-fold symmetry. The symmetric dimer interface is stabilized by hydrophobic and hydrogen-bonding interactions, contributed primarily by a central swath of aromatic residues arranged in a quasiherringbone pattern. Evidence that interfacially active wild-type PI-PLC enzymes may dimerize in the presence of phosphatidylcholine vesicles is provided by fluorescence quenching of PI-PLC mutants with pyrene-labeled cysteine residues. The combined data suggest that wild-type PI-PLC can form similar homodimers, anchored to the interface by the tryptophan and neighboring membrane-partitioning residues.

  10. Structure of a Longitudinal Actin Dimer Assembled by Tandem W Domains: Implications for Actin Filament Nucleation

    SciTech Connect (OSTI)

    Rebowski, Grzegorz; Namgoong, Suk; Boczkowska, Malgorzata; Leavis, Paul C.; Navaza, Jorge; Dominguez, Roberto

    2013-11-20

    Actin filament nucleators initiate polymerization in cells in a regulated manner. A common architecture among these molecules consists of tandem WASP homology 2 domains (W domains) that recruit three to four actin subunits to form a polymerization nucleus. We describe a low-resolution crystal structure of an actin dimer assembled by tandem W domains, where the first W domain is cross-linked to Cys374 of the actin subunit bound to it, whereas the last W domain is followed by the C-terminal pointed end-capping helix of thymosin {beta}4. While the arrangement of actin subunits in the dimer resembles that of a long-pitch helix of the actin filament, important differences are observed. These differences result from steric hindrance of the W domain with intersubunit contacts in the actin filament. We also determined the structure of the first W domain of Vibrio parahaemolyticus VopL cross-linked to actin Cys374 and show it to be nearly identical with non-cross-linked W-Actin structures. This result validates the use of cross-linking as a tool for the study of actin nucleation complexes, whose natural tendency to polymerize interferes with most structural methods. Combined with a biochemical analysis of nucleation, the structures may explain why nucleators based on tandem W domains with short inter-W linkers have relatively weak activity, cannot stay bound to filaments after nucleation, and are unlikely to influence filament elongation. The findings may also explain why nucleation-promoting factors of the Arp2/3 complex, which are related to tandem-W-domain nucleators, are ejected from branch junctions after nucleation. We finally show that the simple addition of the C-terminal pointed end-capping helix of thymosin {beta}4 to tandem W domains can change their activity from actin filament nucleation to monomer sequestration.

  11. MOLYBDENUM, RUTHENIUM, AND THE HEAVY r-PROCESS ELEMENTS IN MODERATELY METAL-POOR MAIN-SEQUENCE TURNOFF STARS

    SciTech Connect (OSTI)

    Peterson, Ruth C. [Astrophysical Advances, 607 Marion Place, Palo Alto, CA 94301 (United States)

    2013-05-01

    The ratios of elemental abundances observed in metal-poor stars of the Galactic halo provide a unique present-day record of the nucleosynthesis products of its earliest stars. While the heaviest elements were synthesized by the r- and s-processes, dominant production mechanisms of light trans-ironic elements were obscure until recently. This work investigates further our 2011 conclusion that the low-entropy regime of a high-entropy wind (HEW) produced molybdenum and ruthenium in two moderately metal-poor turnoff stars that showed extreme overabundances of those elements with respect to iron. Only a few, rare nucleosynthesis events may have been involved. Here we determine abundances for Mo, Ru, and other trans-Fe elements for 28 similar stars by matching spectral calculations to well-exposed near-UV Keck HIRES spectra obtained for beryllium abundances. In each of the 26 turnoff stars with Mo or Ru line detections and no evidence for s-process production (therefore old), we find Mo and Ru to be three to six times overabundant. In contrast, the maximum overabundance is reduced to factors of three and two for the neighboring elements zirconium and palladium. Since the overproduction peaks sharply at Mo and Ru, a low-entropy HEW is confirmed as its origin. The overabundance level of the heavy r-process elements varies significantly, from none to a factor of four, but is uncorrelated with Mo and Ru overabundances. Despite their moderate metallicity, stars in this group trace the products of different nucleosynthetic events: possibly very few events, possibly events whose output depended on environment, metallicity, or time.

  12. Transverse spin freezing in Ruthenium-doped a Fe 90 Zr 10 Physics Department and Centre for the Physics of Materials, McGill University, 3600 University Street, Montreal, Quebec

    E-Print Network [OSTI]

    Ryan, Dominic

    Transverse spin freezing in Ruthenium-doped a Fe 90 Zr 10 D.H. Ryan Physics Department and Centre , followed by transverse spin freezing at Txy . Comparison with earlier Mossbauer data shows that the break in B hf (T) is indeed due to transverse spin freezing, and that both Mossbauer spectroscopy and #22;SR

  13. Transverse spin freezing in ruthenium-doped a-Fe90Zr10 Physics Department and Centre for the Physics of Materials, McGill University, 3600 University Street,

    E-Print Network [OSTI]

    Ryan, Dominic

    Transverse spin freezing in ruthenium-doped a-Fe90Zr10 D. H. Ryan Physics Department and Centre at Tc , followed by transverse spin freezing at Txy . Comparison with earlier Mo¨ssbauer data shows that the break in Bhf(T) is indeed due to transverse spin freezing, and that both Mo¨ssbauer spectroscopy and SR

  14. Exploring the Potential of Fulvalene Dimetals as Platforms for Molecular Solar Thermal Energy Storage: Computations, Syntheses, Structures, Kinetics, and Catalysis

    SciTech Connect (OSTI)

    Borjesson, K; Coso, D; Gray, V; Grossman, JC; Guan, JQ; Harris, CB; Hertkorn, N; Hou, ZR; Kanai, Y; Lee, D; Lomont, JP; Majumdar, A; Meier, SK; Moth-Poulsen, K; Myrabo, RL; Nguyen, SC; Segalman, RA; Srinivasan, V; Tolman, WB; Vinokurov, N; Vollhardt, KPC; Weidman, TW

    2014-10-03

    A study of the scope and limitations of varying the ligand framework around the dinuclear core of FvRu(2) in its function as a molecular solar thermal energy storage framework is presented. It includes DFT calculations probing the effect of substituents, other metals, and CO exchange for other ligands on Delta H-storage. Experimentally, the system is shown to be robust in as much as it tolerates a number of variations, except for the identity of the metal and certain substitution patterns. Failures include 1,1',3,3'-tetra-tert-butyl (4), 1,2,2',3'-tetraphenyl (9), diiron (28), diosmium (24), mixed iron-ruthenium (27), dimolybdenum (29), and di-tungsten (30) derivatives. An extensive screen of potential catalysts for the thermal reversal identified AgNO3-SiO2 as a good candidate, although catalyst decomposition remains a challenge.

  15. Electrochemical Oxidation of H? Catalyzed by Ruthenium Hydride Complexes Bearing P?N? Ligands With Pendant Amines as Proton Relays

    SciTech Connect (OSTI)

    Liu, Tianbiao L.; Rakowski DuBois, Mary; DuBois, Daniel L.; Bullock, R. Morris

    2014-01-01

    Two Ru hydride complexes (Cp*Ru(PPh?NBn?)H, (1-H) and Cp*Ru(PtBu?NBn?)H, (2-H) supported by cyclic PR?NR'? ligands (Cp* = n?-C?Me?; 1,5-diaza-3,7-diphosphacyclooctane, where R = Ph or tBu and R' = Bn) have been synthesized and fully characterized. Both complexes are demonstrated to be electrocatalysts for oxidation of H? (1 atm, 22 °C) in the presence of external base, DBU (1,8-diazabicyclo[5.4.0]undec-7-ene). The turnover frequency of 2-H is 1.2 s-1, with an overpotential at Ecat/2 of 0.45 V, while catalysis by 1-H has a turnover frequency of 0.6 s-1 and an overpotential of 0.6 V at Ecat/2. Addition of H?O facilitates oxidation of H? by 2-H and increases its turnover frequency to 1.9 s-1 while , H?O slows down the catalysis by 1-H. The different effects of H?O for 1-H and 2-H are ascribed to different binding affinities of H?O to the Ru center of the corresponding unsaturated species, [Cp*Ru(PPh?NBn?)]+ and [Cp*Ru(PPh?NBn?)]+. In addition, studies of Cp*Ru(dmpm)H (where dmpm = bis(dimethylphosphino)methane), a control complex lacking pendent amines in its diphosphine ligand, confirms the critical roles of the pendent amines of P?N? ligands for oxidation of H?. We thank the U.S. Department of Energy, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences and Biosciences, for supporting initial parts of the work. Current work is supported by the Center for Molecular Electrocatalysis, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences. Pacific Northwest National Laboratory is operated by Battelle for the U.S. Department of Energy.

  16. Support for Speakers and Attendees at 2008 GRC Conference Catalysis (to be held at Colby Sawyer College, New London, New Hampshire on June 22-27, 2008)

    SciTech Connect (OSTI)

    Stuart L. Soled and Nancy Ryan Gray

    2009-01-01

    The GRC on Catalysis is one of the most prestigious catalysis conferences as it brings together leading researchers from around the world to discuss their latest, most exciting work in catalysis. The 2008 conference will continue this tradition. The conference will cover a variety of themes including new catalytic materials, theoretical and experimental approaches to improve understanding of kinetics and transport phenomena, and state of the art nanoscale characterization probes to monitor active sites. The conference promotes interactions among established researchers and young scientists. It provides a venue for students to meet, talk to and learn from some of the world leading researchers in the area. It also gives them a platform for displaying their own work during the poster sessions. The informal nature of the meeting, excellent quality of the presentations and posters, and ability to meet many outstanding colleagues makes this an excellent conference.

  17. Opportunities for Catalysis in The 21st Century. A report from the Basic Energy Sciences Advisory Committee

    SciTech Connect (OSTI)

    White, J. M.; Bercaw, J.

    2002-05-16

    Chemical catalysis affects our lives in myriad ways. Catalysis provides a means of changing the rates at which chemical bonds are formed and broken and of controlling the yields of chemical reactions to increase the amounts of desirable products from these reactions and reduce the amounts of undesirable ones. Thus, it lies at the heart of our quality of life: The reduced emissions of modern cars, the abundance of fresh food at our stores, and the new pharmaceuticals that improve our health are made possible by chemical reactions controlled by catalysts. Catalysis is also essential to a healthy economy: The petroleum, chemical, and pharmaceutical industries, contributors of $500 billion to the gross national product of the United States, rely on catalysts to produce everything from fuels to ''wonder drugs'' to paints to cosmetics. Today, our Nation faces a variety of challenges in creating alternative fuels, reducing harmful by-products in manufacturing, cleaning up the environment and preventing future pollution, dealing with the causes of global warming, protecting citizens from the release of toxic substances and infectious agents, and creating safe pharmaceuticals. Catalysts are needed to meet these challenges, but their complexity and diversity demand a revolution in the way catalysts are designed and used. This revolution can become reality through the application of new methods for synthesizing and characterizing molecular and material systems. Opportunities to understand and predict how catalysts work at the atomic scale and the nanoscale are now appearing, made possible by breakthroughs in the last decade in computation, measurement techniques, and imaging and by new developments in catalyst design, synthesis, and evaluation.

  18. Heat capacity of the site-diluted spin dimer system Ba?(Mn1-xVx)?O?

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Samulon, E. C.; Shapiro, M. C.; Fisher, I. R.

    2011-08-01

    Heat-capacity and susceptibility measurements have been performed on the diluted spin dimer compound Ba?(Mn1-xVx)?O?. The parent compound Ba?Mn?O? is a spin dimer system based on pairs of antiferromagnetically coupled S=1, 3d² Mn?? ions such that the zero-field ground state is a product of singlets. Substitution of nonmagnetic S=0, 3d? V?? ions leads to an interacting network of unpaired Mn moments, the low-temperature properties of which are explored in the limit of small concentrations 0?x?0.05. The zero-field heat capacity of this diluted system reveals a progressive removal of magnetic entropy over an extended range of temperatures, with no evidence for a phase transition. The concentration dependence does not conform to expectations for a spin-glass state. Rather, the data suggest a low-temperature random singlet phase, reflecting the hierarchy of exchange energies found in this system.

  19. Frustrated smectic layer structures in bent-shaped dimer liquid crystals studied by x-ray microbeam diffraction

    SciTech Connect (OSTI)

    Takanishi, Yoichi; Toshimitsu, Megumi; Nakata, Michi; Takada, Naoki; Izumi, Tatsuya; Ishikawa, Ken; Takezoe, Hideo; Watanabe, Junji; Takahashi, Yumiko; Iida, Atsuo

    2006-11-15

    The layer structures in bent-shaped liquid crystal dimers mOAM5AMOm (m=6-16) have been investigated by x-ray microbeam diffraction. These liquid crystal molecules have two rodlike mesogens connected with an odd-numbered alkylene spacer and form a bent shape. In these compounds it is found that the structure changes from the single (m=6) to frustrated-layer structures (m=8, 10, and 12) and switchable frustrated-layer structures (m=14 and 16) with increasing terminal chain length. An anticlinic antiferroelectric structure is suggested in the compound with m=16, based on the different electric-field-induced reorientation behavior from those in the other dimers.

  20. Communication: Towards the binding energy and vibrational red shift of the simplest organic hydrogen bond: Harmonic constraints for methanol dimer

    SciTech Connect (OSTI)

    Heger, Matthias; Suhm, Martin A.; Mata, Ricardo A., E-mail: rmata@gwdg.de [Georg-August-Universität Göttingen, Institut für Physikalische Chemie, Tammannstr. 6, 37077 Göttingen (Germany)

    2014-09-14

    The discrepancy between experimental and harmonically predicted shifts of the OH stretching fundamental of methanol upon hydrogen bonding to a second methanol unit is too large to be blamed mostly on diagonal and off-diagonal anharmonicity corrections. It is shown that a decisive contribution comes from post-MP2 electron correlation effects, which appear not to be captured by any of the popular density functionals. We also identify that the major deficiency is in the description of the donor OH bond. Together with estimates for the electronic and harmonically zero-point corrected dimer binding energies, this work provides essential constraints for a quantitative description of this simple hydrogen bond. The spectroscopic dissociation energy is predicted to be larger than 18 kJ/mol and the harmonic OH-stretching fundamental shifts by about ?121 cm{sup ?1} upon dimerization, somewhat more than in the anharmonic experiment (?111 cm{sup ?1})

  1. Atomic geometry of mixed Ge-Si dimers in the initial-stage growth of Ge on Si,,001...2 1 X. Chen* and D. K. Saldin

    E-Print Network [OSTI]

    Saldin, Dilano

    Atomic geometry of mixed Ge-Si dimers in the initial-stage growth of Ge on Si,,001...2 1 X. Chen quantitatively the geometry of mixed Ge-Si dimers on a single domain Si 001 2 1 surface by azimuthal scanning core-level photoelectron diffraction. By analyzing Ge 3d diffraction patterns from Ge/Si 001 at 0.1 ML

  2. A Multinuclear Copper(I) Cluster Forms the Dimerization Interface in Copper-Loaded Human Copper Chaperone for Superoxide Dismutase

    SciTech Connect (OSTI)

    Stasser, J.P.; Siluvai, G.S.; Barry, A.N.; Blackburn, N.J.

    2009-06-04

    Copper binding and X-ray aborption spectroscopy studies are reported on untagged human CCS (hCCS; CCS = copper chaperone for superoxide dismutase) isolated using an intein self-cleaving vector and on single and double Cys to Ala mutants of the hCCS MTCQSC and CSC motifs of domains 1 (D1) and 3 (D3), respectively. The results on the wild-type protein confirmed earlier findings on the CCS-MBP (maltose binding protein) constructs, namely, that Cu(I) coordinates to the CXC motif, forming a cluster at the interface of two D3 polypeptides. In contrast to the single Cys to Ser mutations of the CCS-MBP protein (Stasser, J. P., Eisses, J. F., Barry, A. N., Kaplan, J. H., and Blackburn, N. J. (2005) Biochemistry 44, 3143-3152), single Cys to Ala mutations in D3 were sufficient to eliminate cluster formation and significantly reduce CCS activity. Analysis of the intensity of the Cu-Cu cluster interaction in C244A, C246A, and C244/246A variants suggested that the nuclearity of the cluster was greater than 2 and was most consistent with a Cu4S6 adamantane-type species. The relationship among cluster formation, oligomerization, and metal loading was evaluated. The results support a model in which Cu(I) binding converts the apo dimer with a D2-D2 interface to a new dimer connected by cluster formation at two D3 CSC motifs. The predominance of dimer over tetramer in the cluster-containing species strongly suggests that the D2 dimer interface remains open and available for sequestering an SOD1 monomer. This work implicates the copper cluster in the reactive form and adds detail to the cluster nuclearity and how copper loading affects the oligomerization states and reactivity of CCS for its partner SOD1.

  3. Quantum Non-Demolition Detection of Polar Molecule Complexes: Dimers, Trimers, Tetramers

    E-Print Network [OSTI]

    Igor B. Mekhov

    2011-11-16

    The optical nondestructive method for in situ detection of the bound states of ultracold polar molecules is developed. It promises a minimally destructive measurement scheme up to a physically exciting quantum non-demolition (QND) level. The detection of molecular complexes beyond simple pairs of quantum particles (dimers, known, e.g., from the BEC-BCS theory) is suggested, including three-body (trimers) and four-body (tertramers) complexes trapped by one-dimensional tubes. The intensity of scattered light is sensitive to the molecule number fluctuations beyond the mean-density approximation. Such fluctuations are very different for various complexes, which leads to radically different light scattering. This type of research extends "quantum optics of quantum gases" to the field of ultracold molecules. Merging the quantum optical and ultracold gas problems will advance the experimental efforts towards the study of the light-matter interaction at its ultimate quantum level, where the quantizations of both light and matter are equally important.

  4. Antiferromagnetic exchange in a bis(imido) uranium (V) dimeric complex

    SciTech Connect (OSTI)

    Spencer, Liam P [Los Alamos National Laboratory; Schelter, Eric J [Los Alamos National Laboratory; Boncella, James M [Los Alamos National Laboratory; Yang, Ping [Los Alamos National Laboratory; Gdula, Robyn L [NON LANL; Scott, Brian L [Los Alamos National Laboratory; Thompson, Joe D [Los Alamos National Laboratory; Kiplinger, Jacqueline L [Los Alamos National Laboratory; Batista, Enrique R [Los Alamos National Laboratory

    2008-01-01

    Magnetic coupling between two or more metal centers is an important facet of d- and f-block transition metal chemistry due to its implications in chemical bonding. With respect to actinide metals, magnetic coupling between polymetallic actinide centers is less well-known. Of the few documented examples, only one bimetallic uranium(V) complex, [(MeC{sub 5}H{sub 4}){sub 2}U]{sub 2}[{mu}-1,4-N{sub 2}C{sub 6}H{sub 4}] (1), has unequivocally demonstrated antiferromagnetic coupling. This complex employs a {pi}-conjugated 1,4-phenylenedimide ligand system which bridges the two f{sup 1}-metal centers and enables antiferromagentic coupling between unpaired f-e1ectrons residing in a {pi}-symmetry orbital. In this communication, we report the synthesis of a dimeric bis(imido) uranium(V) iodide complex and demonstrate with magnetic susceptibility measurements and density functional theory (DFT) calculations that the f{sup 1}-uranium centers display antiferromagnetic coupling at low temperatures.

  5. Unbiased charge oscillations in DNA monomer-polymers and dimer-polymers

    E-Print Network [OSTI]

    Lambropoulos, Konstantinos; Morphis, Andreas; Kaklamanis, Konstantinos; Theodorakou, Marina; Simserides, Constantinos

    2015-01-01

    We call {\\it monomer} a B-DNA base-pair and examine, analytically and numerically, electron or hole oscillations in monomer- and dimer-polymers, i.e., periodic sequences with repetition unit made of one or two monomers. We employ a tight-binding (TB) approach at the base-pair level to readily determine the spatiotemporal evolution of a single extra carrier along a $N$ base-pair polymer. We study HOMO and LUMO eigenspectra as well as the mean over time probabilities to find the carrier at a particular monomer. We use the pure mean transfer rate $k$ to evaluate the easiness of charge transfer. The inverse decay length $\\beta$ for exponential fits $k(d)$, where $d$ is the charge transfer distance, and the exponent $\\eta$ for power law fits $k(N)$ are computed; generally power law fits are better. We illustrate that increasing the number of different parameters involved in the TB description, the fall of $k(d)$ or $k(N)$ becomes steeper and show the range covered by $\\beta$ and $\\eta$. Finally, both for the time-...

  6. Improved Modeling of Transition Metals, Applications to Catalysis and Technetium Chemistry

    SciTech Connect (OSTI)

    Cundari, T. R.

    2004-03-05

    There is considerable impetus for identification of aqueous OM catalysts as water is the ultimate ''green'' solvent. In collaboration with researchers at Ames Lab, we investigated effective fragment and Monte Carlo techniques for aqueous-phase hydroformylation (HyF). The Rh of the HyF catalyst is weakly aquated, in contrast to the hydride of the Rh-H bond. As the insertion of the olefin C=C into Rh-H determines the linear-to-branched aldehyde ratio, it is reasonable to infer that solvent plays an important role in regiochemistry. Studies on aqueous-phase organometallic catalysis were complemented in studies of the gas-phase reaction. A Rh-carbonyl-phosphine catalyst was investigated. Two of the most important implications of this research include (a) pseudorotation among five-coordinate intermediates is significant in HyF, and (b) CO insertion is the rate-determining step. The latter is in contrast to experimental deductions, highlighting the need for more accurate modeling. To this end, we undertook studies of (a) experimentally relevant PR{sub 3} co-ligands (PMe{sub 3}, PPh{sub 3}, P(p-PhSO{sub 3{sup -}}){sub 3}, etc.), and (b) HyF of propene. For the propylene research, simulations indicated that the linear: branched aldehyde ratio (linear is more desirable) is determined by thermodynamic discrimination of two distinct pathways. Other projects include a theory-experiment study of C-H activation by early transition metal systems, which establishes that weakly-bound adducts play a key role in activity selectivity. By extension, more selective catalysts for functionalization of methane (major component of natural gas) will require better understanding of these adducts, which are greatly affected by steric interactions with the ligands. In the de novo design of Tc complexes, we constructed (and are now testing) a coupled quantum mechanics-molecular mechanics protocol. Initial research shows it to be capable of accurately predicting structure ''from scratch.'' Challenges include conformational, geometric, coordination, spin, and particularly linkage (e.g., Tc-SCN versus Tc-NCS) isomerism. In general, our protocol can rapidly (<1 day with desktop software/hardware) predict the structure of diverse Tc complexes with an accuracy commensurate to organics. Our de novo strategy is also being used to investigate tris-pyrazolyl borate (Tp) complexes. Data suggests a fundamental difference in methane activation between TpRe and related CpRe complexes. Furthermore, Tp is a more electronically ''flexible'' platform for catalysts modification than Cp.

  7. New Iron(II) and Manganese(II) Complexes of Two Ultra-Rigid, Cross-Bridged Tetraazamacrocycles for Catalysis and Biomimicry

    E-Print Network [OSTI]

    Hubin, Tim

    for Catalysis and Biomimicry Timothy J. Hubin, James M. McCormick, Simon R. Collinson, Maria Buchalova, Christopher M. Perkins,§ Nathaniel W. Alcock, Pawan K. Kahol, Ahasuya Raghunathan, and Daryle H. Busch. (2) (a) Jang, H. G.; Cox, D. D.; Que, L., Jr. J. Am. Chem. Soc. 1991, 113, 9200. (b) Han, S.; Eltis

  8. Applied Catalysis A: General 192 (2000) 227234 Hydrogen production via the direct cracking of methane over Ni/SiO2

    E-Print Network [OSTI]

    zur Loye, Hans-Conrad

    2000-01-01

    Applied Catalysis A: General 192 (2000) 227­234 Hydrogen production via the direct cracking is a potential route to the production of CO-free hydrogen and filamentous carbon. Eventually, however. ©2000 Elsevier Science B.V. All rights reserved. Keywords: Methane cracking; Hydrogen production

  9. Spectroscopic accuracy directly from quantum chemistry: Application to ground and excited states of beryllium dimer

    SciTech Connect (OSTI)

    Sharma, Sandeep; Booth, George H.; Chan, Garnet Kin-Lic, E-mail: gkc1000@gmail.com [Department of Chemistry, Frick Laboratory, Princeton University, New Jersey 08544 (United States); Yanai, Takeshi [Department of Theoretical and Computational Molecular Science, Institute for Molecular Science, Okazaki, Aichi 444-8585 (Japan)] [Department of Theoretical and Computational Molecular Science, Institute for Molecular Science, Okazaki, Aichi 444-8585 (Japan); Umrigar, C. J. [Laboratory of Atomic and Solid State Physics, Cornell University, New York 14853 (United States)] [Laboratory of Atomic and Solid State Physics, Cornell University, New York 14853 (United States)

    2014-03-14

    We combine explicit correlation via the canonical transcorrelation approach with the density matrix renormalization group and initiator full configuration interaction quantum Monte Carlo methods to compute a near-exact beryllium dimer curve, without the use of composite methods. In particular, our direct density matrix renormalization group calculations produce a well-depth of D{sub e} = 931.2 cm{sup ?1} which agrees very well with recent experimentally derived estimates D{sub e} = 929.7±2 cm{sup ?1} [J. M. Merritt, V. E. Bondybey, and M. C. Heaven, Science 324, 1548 (2009)] and D{sub e}= 934.6 cm{sup ?1} [K. Patkowski, V. Špirko, and K. Szalewicz, Science 326, 1382 (2009)], as well the best composite theoretical estimates, D{sub e} = 938±15 cm{sup ?1} [K. Patkowski, R. Podeszwa, and K. Szalewicz, J. Phys. Chem. A 111, 12822 (2007)] and D{sub e}=935.1±10 cm{sup ?1} [J. Koput, Phys. Chem. Chem. Phys. 13, 20311 (2011)]. Our results suggest possible inaccuracies in the functional form of the potential used at shorter bond lengths to fit the experimental data [J. M. Merritt, V. E. Bondybey, and M. C. Heaven, Science 324, 1548 (2009)]. With the density matrix renormalization group we also compute near-exact vertical excitation energies at the equilibrium geometry. These provide non-trivial benchmarks for quantum chemical methods for excited states, and illustrate the surprisingly large error that remains for 1 {sup 1}?{sub g}{sup ?} state with approximate multi-reference configuration interaction and equation-of-motion coupled cluster methods. Overall, we demonstrate that explicitly correlated density matrix renormalization group and initiator full configuration interaction quantum Monte Carlo methods allow us to fully converge to the basis set and correlation limit of the non-relativistic Schrödinger equation in small molecules.

  10. Methanol Synthesis over Cu/ZnO/Al2O3: The Active Site in Industrial Catalysis

    SciTech Connect (OSTI)

    Behrens, Malte

    2012-03-28

    Unlike homogeneous catalysts, heterogeneous catalysts that have been optimized through decades are typically so complex and hard to characterize that the nature of the catalytically active site is not known. This is one of the main stumbling blocks in developing rational catalyst design strategies in heterogeneous catalysis. We show here how to identify the crucial atomic structure motif for the industrial Cu/ZnO/Al{sub 2}O{sub 3} methanol synthesis catalyst. Using a combination of experimental evidence from bulk-, surface-sensitive and imaging methods collected on real high-performance catalytic systems in combination with DFT calculations. We show that the active site consists of Cu steps peppered with Zn atoms, all stabilized by a series of well defined bulk defects and surface species that need jointly to be present for the system to work.

  11. Operando X-ray absorption and EPR evidence for a single electron redox process in copper catalysis

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Lu, Qingquan; Zhang, Jian; Peng, Pan; Zhang, Guanghui; Huang, Zhiliang; Yi, Hong; Miller, Jeffrey T.; Lei, Aiwen

    2015-05-26

    An unprecedented single electron redox process in copper catalysis is confirmed using operando X-ray absorption and EPR spectroscopies. The oxidation state of the copper species in the interaction between Cu(II) and a sulfinic acid at room temperature, and the accurate characterization of the formed Cu(I) are clearly shown using operando X-ray absorption and EPR evidence. Further investigation of anion effects on Cu(II) discloses that bromine ions can dramatically increase the rate of the redox process. Moreover, it is proven that the sulfinic acids are converted into sulfonyl radicals, which can be trapped by 2-arylacrylic acids and various valuable ?-keto sulfonesmore »are synthesized with good to excellent yields under mild conditions.« less

  12. Preparation, catalysis, and characterization of highly dispersed molybdenum sulfide catalysts supported on a NaY zeolite

    SciTech Connect (OSTI)

    Okamoto, Yasuaki; Katsuyama, Hiromoto [Osaka Univ., Toyonaka, Osaka (Japan)] [Osaka Univ., Toyonaka, Osaka (Japan)

    1996-06-01

    The structure and dispersion of the molybdenum sulfides supported on a NaY zeolite were studied using XAFS techniques. It was found that molybdenum sulfide species prepared by sulfiding vapor deposited Mo(CO){sub 6} or by sulfiding molybdenum oxide dimer species encaged in the zeolite are highly dispersed and thermally stabilized against sintering or restructuring. These molybdenum species are formed via molybdenum sulfide dimer species as an intermediate. On the other hand, with the molybdenum sulfide catalysts prepared by an impregnation method, the sulfidation of molybdenum oxides was incomplete. The molybdenum oxide species are suggested to be mainly located in the zeolite cavities after calcination, forming isolated molybdenum oxides in tetrahedral configurations. The molybdenum sulfide species prepared from Mo(CO){sub 6} showed much higher catalytic activities for thiophene hydrodesulfurization and butadiene hydrogenation than the molybdenum sulfides prepared by the impregnation, in conformity with a higher dispersion and higher fraction of the molybdenum sulfide species. It is demonstrated that in combination with metal carbonyl techniques, zeolite supports are very suitable for the preparation of highly dispersed molybdenum sulfides at a high Mo loading.

  13. Rapid dimerization of quercetin through an oxidative mechanism in the presence of serum albumin decreases its ability to induce cytotoxicity in MDA-MB-231 cells

    SciTech Connect (OSTI)

    Pham, Anh; Bortolazzo, Anthony [Department of Biological Sciences, San Jose State University, San Jose, CA 95192-0100 (United States)] [Department of Biological Sciences, San Jose State University, San Jose, CA 95192-0100 (United States); White, J. Brandon, E-mail: Brandon.White@sjsu.edu [Department of Biological Sciences, San Jose State University, San Jose, CA 95192-0100 (United States)

    2012-10-19

    Highlights: Black-Right-Pointing-Pointer Quercetin cannot be detected intracellularly despite killing MDA-MB-231 cells. Black-Right-Pointing-Pointer Quercetin forms a heterodimer through oxidation in media with serum. Black-Right-Pointing-Pointer The quercetin heterodimer does not kill MDA-MB-231 cells. Black-Right-Pointing-Pointer Ascorbic acid stabilizes quercetin increasing cell death in quercetin treated cells. Black-Right-Pointing-Pointer Quercetin, and not a modified form, is responsible for apoptosis and cell death. -- Abstract: Quercetin is a member of the flavonoid family and has been previously shown to have a variety of anti-cancer activities. We and others have reported anti-proliferation, cell cycle arrest, and induction of apoptosis of cancer cells after treatment with quercetin. Quercetin has also been shown to undergo oxidation. However, it is unclear if quercetin or one of its oxidized forms is responsible for cell death. Here we report that quercetin rapidly oxidized in cell culture media to form a dimer. The quercetin dimer is identical to a dimer that is naturally produced by onions. The quercetin dimer and quercetin-3-O-glucopyranoside are unable to cross the cell membrane and do not kill MDA-MB-231 cells. Finally, supplementing the media with ascorbic acid increases quercetin's ability to induce cell death probably by reduction oxidative dimerization. Our results suggest that an unmodified quercetin is the compound that elicits cell death.

  14. Singlet-triplet dispersion reveals additional frustration in the triangular dimer compound Ba$_3$Mn$_2$O$_8$

    SciTech Connect (OSTI)

    Stone, Matthew B [ORNL; Lumsden, Mark D [ORNL; Chang, S. [Ames Laboratory; Samulon, Eric C [Stanford University; Batista, C. D. [Los Alamos National Laboratory (LANL); Fisher, Ian R [Stanford University

    2008-01-01

    We present single crystal inelastic neutron scattering measurements of the $S=1$ dimerized quasi-two-dimensional antiferromagnet Ba$_3$Mn$_2$O$_8$. The singlet-triplet dispersion reveals nearest-neighbor and next-nearest-neighbor ferromagnetic interactions between adjacent bilayers that compete against each other. Although the inter-bilayer exchange is comparable to the intra-bilayer exchange, this additional frustration reduces the effective coupling along the $c$-axis and leads to a quasi-two dimensional behavior. In addition, the obtained exchange values are able to reproduce the four critical fields in the phase diagram.

  15. Heat capacity of the site-diluted spin dimer system Ba?(Mn1-xVx)?O?

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Samulon, E. C.; Shapiro, M. C.; Fisher, I. R.

    2011-08-01

    Heat-capacity and susceptibility measurements have been performed on the diluted spin dimer compound Ba?(Mn1-xVx)?O?. The parent compound Ba?Mn?O? is a spin dimer system based on pairs of antiferromagnetically coupled S=1, 3d² Mn?? ions such that the zero-field ground state is a product of singlets. Substitution of nonmagnetic S=0, 3d? V?? ions leads to an interacting network of unpaired Mn moments, the low-temperature properties of which are explored in the limit of small concentrations 0?x?0.05. The zero-field heat capacity of this diluted system reveals a progressive removal of magnetic entropy over an extended range of temperatures, with no evidence for amore »phase transition. The concentration dependence does not conform to expectations for a spin-glass state. Rather, the data suggest a low-temperature random singlet phase, reflecting the hierarchy of exchange energies found in this system.« less

  16. Protonation effect on the electronic properties of 2-pyridone monomer, dimer and its water clusters: A theoretical study

    SciTech Connect (OSTI)

    Saed, Behnaz; Omidyan, Reza E-mail: reza.omidyan@u-psud.fr; Centre Laser de l’Université Paris Sud , Bât. 106, Univ. Paris-Sud 11, 91405 Orsay Cedex

    2014-01-14

    The CC2 (second order approximate coupled cluster method) has been applied to investigate protonation effect on electronic transition energies of 2-pyridone (2PY), 2-pyridone dimer, and micro-solvated 2-pyridone (0-2 water molecules). The PE profiles of protonated 2-pyridone (2PYH{sup +}) as well as monohydrated 2PYH{sup +} at the different electronic states have been investigated. The {sup 1}??* state in protonated species (2PYH{sup +}) is a barrier free and dissociative state along the O-H stretching coordinate. In this reaction coordinate, the lowest lying {sup 1}??* predissociates the bound S{sub 1}({sup 1}??*) state, connecting the latter to a conical intersection with the S{sub 0} state. These conical intersections lead the {sup 1}??* state to proceed as predissociative state and finally direct the excited system to the ground state. Furthermore, in presence of water molecule, the {sup 1}??* state still remains dissociative but the conical intersection between {sup 1}??* and ground state disappears. In addition, according to the CC2 calculation results, it has been predicted that protonation significantly blue shifts the S{sub 1}-S{sub 0} electronic transition of monomer, dimer, and microhydrated 2-pyridone.

  17. Crystal structure of dimeric cardiac L-type calcium channel regulatory domains bridged by Ca[superscript 2+]·calmodulins

    SciTech Connect (OSTI)

    Fallon, Jennifer L.; Baker, Mariah R.; Xiong, Liangwen; Loy, Ryan E.; Yang, Guojun; Dirksen, Robert T.; Hamilton, Susan L.; Quiocho, Florante A.; (Baylor); (Rochester-Med)

    2009-11-10

    Voltage-dependent calcium channels (Ca(V)) open in response to changes in membrane potential, but their activity is modulated by Ca(2+) binding to calmodulin (CaM). Structural studies of this family of channels have focused on CaM bound to the IQ motif; however, the minimal differences between structures cannot adequately describe CaM's role in the regulation of these channels. We report a unique crystal structure of a 77-residue fragment of the Ca(V)1.2 alpha(1) subunit carboxyl terminus, which includes a tandem of the pre-IQ and IQ domains, in complex with Ca(2+).CaM in 2 distinct binding modes. The structure of the Ca(V)1.2 fragment is an unusual dimer of 2 coiled-coiled pre-IQ regions bridged by 2 Ca(2+).CaMs interacting with the pre-IQ regions and a canonical Ca(V)1-IQ-Ca(2+).CaM complex. Native Ca(V)1.2 channels are shown to be a mixture of monomers/dimers and a point mutation in the pre-IQ region predicted to abolish the coiled-coil structure significantly reduces Ca(2+)-dependent inactivation of heterologously expressed Ca(V)1.2 channels.

  18. Benchmark Theoretical Study of the ?–? Binding Energy in the Benzene Dimer

    SciTech Connect (OSTI)

    Miliordos, Evangelos; Apra, Edoardo; Xantheas, Sotiris S.

    2014-09-04

    We establish a new estimate for the interaction energy between two benzene molecules in the parallel displaced (PD) conformation by systematically converging (i) the intra- and intermolecular geometry at the minimum geometry, (ii) the expansion of the orbital basis set and (iii) the level of electron correlation. The calculations were performed at the second order Møller - Plesset perturbation (MP2) and the Coupled Cluster including Singles, Doubles and a perturbative estimate of Triples replacements [CCSD(T)] levels of electronic structure theory. At both levels of theory, by including results corrected for Basis Set Superposition Error (BSSE), we have estimated the Complete Basis Set (CBS) limit by employing the family of Dunning’s correlation consistent polarized valence basis sets. The largest MP2 calculation was performed with the cc-pV6Z basis set (2,772 basis functions), whereas the largest CCSD(T) calculation with the cc-pV5Z basis set (1,752 basis functions). The cluster geometries were optimized with basis sets up to quadruple-? quality, observing that both its intra- and inter-molecular parts have practically converged with the triple-? quality sets. The use of converged geometries was found to play an important role for obtaining accurate estimates for the CBS limits. Our results demonstrate that the binding energies with the families of the plain (cc-pVnZ) and augmented (aug-cc-pVnZ) sets converge [to within < 0.01 kcal/mol for MP2 and < 0.15 kcal/mol for CCSD(T)] to the same CBS limit. In addition, the average of the uncorrected and BSSEcorrected binding energies was found to converge to the same CBS limit must faster than either of the two constituents (uncorrected or BSSE-corrected binding energies). Due to the fact that the family of augmented basis sets (especially for the larger sets) causes serious linear dependency problems, the plain basis sets (for which no linear dependencies were found) are deemed as a more efficient and straightforward path for obtaining an accurate CBS limit. We considered extrapolations of the uncorrected (?𝐸) and BSSE-corrected (?𝐸!") binding energies, their average value (?𝐸!"#) as well as the average of the latter over the plain and augmented sets (?𝐸!"#) with the cardinal number of the basis set n. Our best estimate of the CCSD(T)/CBS limit for the ?-? interaction energy in the PD benzene dimer is De = 2.65 ± 0.02 kcal/mol. The best CCSD(T)/cc-pV5Z calculated value is 2.62 kcal/mol, just 0.03 kcal/mol away from the CBS limit. For comparison, the MP2/CBS limit estimate is 5.00 ± 0.01 kcal/mol, demonstrating a 90% overbinding with respect to CCSD(T). The Spin-Component-Scaled (SCS) MP2 variant was found to closely reproduce the CCSD(T) results for each basis set, while Scaled-Opposite-Spin (SOS) yielded results that are too low when compared to CCSD(T).

  19. Charge transfer from an adsorbed ruthenium-based photosensitizer through an ultra-thin aluminium oxide layer and into a metallic substrate

    E-Print Network [OSTI]

    Gibson, Andrew J; Handrup, Karsten; Weston, Matthew; Mayor, Louise C; O'Shea, James N

    2014-01-01

    The interaction of the dye molecule N3 (cis-bis(isothiocyanato)bis(2,2-bipyridyl-4,4'-dicarboxylato)-ruthenium(II)) with the ultra-thin oxide layer on a AlNi(110) substrate, has been studied using synchrotron radiation based photoelectron spectroscopy, resonant photoemission spectroscopy (RPES) and near edge X-ray absorption fine structure spectroscopy (NEXAFS). Calibrated X-ray absorption and valence band spectra of the monolayer and multilayer coverages reveal that charge transfer is possible from the molecule to the AlNi(110) substrate via tunnelling through the ultra-thin oxide layer and into the conduction band edge of the substrate. This charge transfer mechanism is possible from the LUMO+2&3 in the excited state but not from the LUMO, therefore enabling core-hole clock analysis, which gives an upper limit of $6.0\\pm$2.5fs for the transfer time. This indicates that ultra-thin oxide layers are a viable material for use in dye-sensitized solar cells (DSSC), which may lead to reduced recombination effe...

  20. Chiral Attachment of Styrene Mediated by Surface Dimers on Ge(100) Yun Jeong Hwang, Ansoon Kim, Eunkyung Hwang, and Sehun Kim*

    E-Print Network [OSTI]

    Kim, Sehun

    Chiral Attachment of Styrene Mediated by Surface Dimers on Ge(100) Yun Jeong Hwang, Ansoon Kim + 2] cycloaddition forming di- bonds.5 We expect that styrene (C6H5-CHdCH2) molecules on Ge(100) may to the orientation of the phenyl ring of each styrene molecule: the diastereomeric (R,S) and the enantio- meric (R

  1. 'Escherichia Coli' MutS Tetramerization Domain Structure Reveals That Stable Dimers But Not Tetramers are Essential for DNA Mismatch Repair in Vivo

    SciTech Connect (OSTI)

    Mendillo, M.L.; Putnam, C.D.; Kolodner, R.D.; /UC, San Diego

    2007-07-10

    The E. coli mispair binding protein MutS forms dimers and tetramers in vitro, although the functional form in vivo is under debate. Here we demonstrate that the MutS tetramer is extended in solution using small angle x-ray scattering (SAXS) and the crystal structure of the C-terminal 34 amino acids of MutS containing the tetramer-forming domain fused to maltose binding protein (MBP). Wild-type C-terminal MBP fusions formed tetramers and could bind MutS and MutS-MutL-DNA complexes. In contrast, Asp835Arg and Arg840Glu mutations predicted to disrupt tetrameric interactions only allowed dimerization of MBP. A chromosomal MutS truncation mutation eliminating the dimerization/tetramerization domain eliminated mismatch repair, whereas the tetramer-disrupting MutS Asp835Arg and Arg840Glu mutations only modestly affected MutS function. These results demonstrate that dimerization but not tetramerization of the MutS C- terminus is essential for mismatch repair.

  2. The hyperfine energy levels of alkali metal dimers: ground-state polar molecules in electric and magnetic fields

    E-Print Network [OSTI]

    Aldegunde, J; Zuchowski, Piotr S \\; Hutson, Jeremy M

    2008-01-01

    We investigate the energy levels of heteronuclear alkali metal dimers in levels correlating with the lowest rotational level of the ground electronic state, which are important in efforts to produce ground-state ultracold molecules. We use density-functional theory to calculate nuclear quadrupole and magnetic coupling constants for RbK and RbCs and explore the hyperfine structure in the presence of electric and magnetic fields. For nonrotating states, the zero-field splittings are dominated by the electron-mediated part of the nuclear spin-spin coupling. They are a few kHz for RbK isotopologs and a few tens of kHz for RbCs isotopologs.

  3. X-ray Crystallographic Studies of Substrate Binding to Aristolochene Synthase Suggest a Metal Ion Binding Sequence for Catalysis

    SciTech Connect (OSTI)

    Shishova,E.; Yu, F.; Miller, D.; Faraldos, J.; Zhao, Y.; Coates, R.; Allemann, R.; Cane, D.; Christianson, D.

    2008-01-01

    The universal sesquiterpene precursor, farnesyl diphosphate (FPP), is cyclized in an Mg2+-dependent reaction catalyzed by the tetrameric aristolochene synthase from Aspergillus terreus to form the bicyclic hydrocarbon aristolochene and a pyrophosphate anion (PPi) coproduct. The 2.1- Angstroms resolution crystal structure determined from crystals soaked with FPP reveals the binding of intact FPP to monomers A-C, and the binding of PPi and Mg2+B to monomer D. The 1.89- Angstroms resolution structure of the complex with 2-fluorofarnesyl diphosphate (2F-FPP) reveals 2F-FPP binding to all subunits of the tetramer, with Mg2+Baccompanying the binding of this analogue only in monomer D. All monomers adopt open activesite conformations in these complexes, but slight structural changes in monomers C and D of each complex reflect the very initial stages of a conformational transition to the closed state. Finally, the 2.4- Angstroms resolution structure of the complex with 12,13-difluorofarnesyl diphosphate (DF-FPP) reveals the binding of intact DF-FPP to monomers A-C in the open conformation and the binding of PPi, Mg2+B, and Mg2+C to monomer D in a predominantly closed conformation. Taken together, these structures provide 12 independent 'snapshots' of substrate or product complexes that suggest a possible sequence for metal ion binding and conformational changes required for catalysis.

  4. Structure of acostatin, a dimeric disintegrin from Southern copperhead (Agkistrodon contortrix contortrix), at 1.7 Å resolution

    SciTech Connect (OSTI)

    Moiseeva, Natalia [National Synchrotron Light Source, Brookhaven National Laboratory, Building 725D, Upton, NY 11973 (United States); Bau, Robert, E-mail: bau@usc.edu [Chemistry Department, University of Southern California, Los Angeles, CA 90089 (United States); Swenson, Stephen D.; Markland, Francis S. Jr [Department of Biochemistry and Molecular Biology and Norris Comprehensive Cancer Center, Keck School of Medicine, University of Southern California, Los Angeles, CA 90033 (United States); Choe, Jun-Yong [Division of Chemistry and Chemical Engineering, Howard Hughes Medical Institute/California Institute of Technology, Pasadena, CA 91125 (United States); Liu, Zhi-Jie [Departments of Biochemistry and Molecular Biology and Chemistry, University of Georgia, Athens, GA 30602 (United States); Allaire, Marc, E-mail: bau@usc.edu [National Synchrotron Light Source, Brookhaven National Laboratory, Building 725D, Upton, NY 11973 (United States)

    2008-04-01

    Two acostatin heterodimers interact together to form an ???? tetramer. Disintegrins are a family of small (4–14 kDa) proteins that bind to another class of proteins, integrins. Therefore, as integrin inhibitors, they can be exploited as anticancer and antiplatelet agents. Acostatin, an ?? heterodimeric disintegrin, has been isolated from the venom of Southern copperhead (Agkistrodon contortrix contortrix). The three-dimensional structure of acostatin has been determined by macromolecular crystallography using the molecular-replacement method. The asymmetric unit of the acostatin crystals consists of two heterodimers. The structure has been refined to an R{sub work} and R{sub free} of 18.6% and 21.5%, respectively, using all data in the 20–1.7 Å resolution range. The structure of all subunits is similar and is well ordered into N-terminal and C-terminal clusters with four intramolecular disulfide bonds. The overall fold consists of short ?-sheets, each of which is formed by a pair of antiparallel ?-strands connected by ?-turns and flexible loops of different lengths. Conformational flexibility is found in the RGD loops and in the C-terminal segment. The interaction of two N-terminal clusters via two intermolecular disulfide bridges anchors the ?? chains of the acostatin dimers. The C-terminal clusters of the heterodimer project in opposite directions and form a larger angle between them in comparison with other dimeric disintegrins. Extensive interactions are observed between two heterodimers, revealing an ???? acostatin tetramer. Further experiments are required to identify whether the ???? acostatin complex plays a functional role in vivo.

  5. Structure of Acostatin, a Dimeric Disintegrin From Southern Copperhead (Agkistrodon Contortrix Contortrix), at 1.7 Angstrom Resolution

    SciTech Connect (OSTI)

    Moiseeva, N.; Bau, R.; Swenson, S.D.; Marklund, F.S.; Jr.; Choe, J.-Y.; Liu, Z.-J.; Allaire, M.

    2009-05-26

    Disintegrins are a family of small (4-14 kDa) proteins that bind to another class of proteins, integrins. Therefore, as integrin inhibitors, they can be exploited as anticancer and antiplatelet agents. Acostatin, an {alpha}{beta} heterodimeric disintegrin, has been isolated from the venom of Southern copperhead (Agkistrodon contortrix contortrix). The three-dimensional structure of acostatin has been determined by macromolecular crystallography using the molecular-replacement method. The asymmetric unit of the acostatin crystals consists of two heterodimers. The structure has been refined to an R{sub work} and R{sub free} of 18.6% and 21.5%, respectively, using all data in the 20-1.7 {angstrom} resolution range. The structure of all subunits is similar and is well ordered into N-terminal and C-terminal clusters with four intramolecular disulfide bonds. The overall fold consists of short {beta}-sheets, each of which is formed by a pair of antiparallel {beta}-strands connected by {beta}-turns and flexible loops of different lengths. Conformational flexibility is found in the RGD loops and in the C-terminal segment. The interaction of two N-terminal clusters via two intermolecular disulfide bridges anchors the {alpha}{beta}chains of the acostatin dimers. The C-terminal clusters of the heterodimer project in opposite directions and form a larger angle between them in comparison with other dimeric disintegrins. Extensive interactions are observed between two heterodimers, revealing an {alpha}{beta}{beta}{alpha} acostatin tetramer. Further experiments are required to identify whether the {alpha}{beta}{beta}{alpha} acostatin complex plays a functional role in vivo.

  6. Superacid catalysis of light hydrocarbon conversion. DOE PETC third quarterly report, February 25, 1994--May 24, 1994

    SciTech Connect (OSTI)

    Gates, B.C.

    1995-12-31

    Environmental concerns are leading to the replacement of aromatic hydrocarbons in gasoline by high-octane-number branched paraffins and oxygenated compounds such as methyl t-butyl ether. The ether is produced from methanol and isobutylene, and the latter can be formed from n-butane by isomerization followed by dehydrogenation. Paraffin isomerization reactions are catalyzed by very strong acids such as aluminum chloride supported on alumina. The aluminum chloride-containing catalysts are corrosive, and their disposal is expensive. Alternatively, hydroisomerization is catalyzed by zeolite-supported metals at high temperatures, but high temperatures do not favor branched products at equilibrium. Thus there is a need for improved catalysts and processes for the isomerization of n-butane and other straight-chain paraffins. Consequently, researchers have sought for solid acids that are noncorrosive and active enough to catalyze isomerization of paraffins at low temperatures. For example, sulfated zirconia catalyzes isomerization of n-butane at temperatures as low as 25{degrees}C. The addition of iron and manganese promoters has been reported to increase the activity of sulfated zirconia for n-butane isomerization by three orders of magnitude. Although the high activity of this catalyst is now established, the reaction network is not known, and the mechanism has not been investigated. The goal of this work is to investigate low-temperature reactions of light paraffins catalyzed by solid superacids of the sulfated zirconia type. The present report is concerned with catalysis of n-butane conversion catalyzed by the Fe- and Mn- promoted sulfated zirconia described in the previous report in this series.

  7. Structural Basis for Catalysis of a Tetrameric Class IIa Fructose 1,6-Bisphosphate Aldolase from Mycobacterium tuberculosis

    SciTech Connect (OSTI)

    Pegan, Scott D.; Ruskseree, Kamolchanok; Franzblau, Scott G.; Mesecar, Andrew D. ((NSTDC)); ((UIC))

    2009-03-04

    Mycobacterium tuberculosis, the causative agent of tuberculosis (TB), currently infects one-third of the world's population in its latent form. The emergence of multidrug-resistant and extensive drug-resistant strains has highlighted the need for new pharmacological targets within M. tuberculosis. The class IIa fructose 1,6-bisphosphate aldolase (FBA) enzyme from M. tuberculosis (MtFBA) has been proposed as one such target since it is upregulated in latent TB. Since the structure of MtFBA has not been determined and there is little information available on its reaction mechanism, we sought to determine the X-ray structure of MtFBA in complex with its substrates. By lowering the pH of the enzyme in the crystalline state, we were able to determine a series of high-resolution X-ray structures of MtFBA bound to dihydroxyacetone phosphate, glyceraldehyde 3-phosphate, and fructose 1,6-bisphosphate at 1.5, 2.1, and 1.3 {angstrom}, respectively. Through these structures, it was discovered that MtFBA belongs to a novel tetrameric class of type IIa FBAs. The molecular details at the interface of the tetramer revealed important information for better predictability of the quaternary structures among the FBAs based on their primary sequences. These X-ray structures also provide interesting and new details on the reaction mechanism of class II FBAs. Substrates and products were observed in geometries poised for catalysis; in addition, unexpectedly, the hydroxyl-enolate intermediate of dihydroxyacetone phosphate was also captured and resolved structurally. These concise new details offer a better understanding of the reaction mechanisms for FBAs in general and provide a structural basis for inhibitor design efforts aimed at this class of enzymes.

  8. Bioinspired design of redox-active ligands for multielectron catalysis: Effects of positioning pyrazine reservoirs on cobalt for electro- and photocatalytic generation of hydrogen from water

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Jurss, Jonah W.; Khnayzer, Rony S.; Panetier, Julien A.; El Roz, Karim A.; Nichols, Eva M.; Head-Gordon, Martin; Long, Jeffrey R.; Castellano, Felix N.; Chang, Christopher J.

    2015-06-09

    Mononuclear metalloenzymes in nature can function in cooperation with precisely positioned redox-active organic cofactors in order to carry out multielectron catalysis. Inspired by the finely tuned redox management of these bioinorganic systems, we present the design, synthesis, and experimental and theoretical characterization of a homologous series of cobalt complexes bearing redox-active pyrazines. These donor moieties are locked into key positions within a pentadentate ligand scaffold in order to evaluate the effects of positioning redox non-innocent ligands on hydrogen evolution catalysis. Both metal- and ligand-centered redox features are observed in organic as well as aqueous solutions over a range of pHmore »values, and comparison with analogs bearing redox-inactive zinc(II) allows for assignments of ligand-based redox events. Varying the geometric placement of redox non-innocent pyrazine donors on isostructural pentadentate ligand platforms results in marked effects on observed cobalt-catalyzed proton reduction activity. Electrocatalytic hydrogen evolution from weak acids in acetonitrile solution, under diffusion-limited conditions, reveals that the pyrazine donor of axial isomer 1-Co behaves as an unproductive electron sink, resulting in high overpotentials for proton reduction, whereas the equatorial pyrazine isomer complex 2-Co is significantly more active for hydrogen generation at lower voltages. Addition of a second equatorial pyrazine in complex 3-Co further minimizes overpotentials required for catalysis. The equatorial derivative 2-Co is also superior to its axial 1-Co congener for electrocatalytic and visible-light photocatalytic hydrogen generation in biologically relevant, neutral pH aqueous media. Density functional theory calculations (B3LYP-D2) indicate that the first reduction of catalyst isomers 1-Co, 2-Co, and 3-Co is largely metal-centered while the second reduction occurs at pyrazine. Taken together, the data establish that proper positioning of non-innocent pyrazine ligands on a single cobalt center is indeed critical for promoting efficient hydrogen catalysis in aqueous media, akin to optimally positioned redox-active cofactors in metalloenzymes. In a broader sense, these findings highlight the significance of electronic structure considerations in the design of effective electron–hole reservoirs for multielectron transformations.« less

  9. Kinetic Stability May Determine the Interaction Dynamics of the Bifunctional Protein DCoH1, the Dimerization Cofactor of the Transcription Factor HNF-1[alpha

    SciTech Connect (OSTI)

    Rho, H.; Jones, C.N.; Rose, R.B. (NCSU)

    2010-12-07

    The two disparate functions of DCoH1 (dimerization cofactor of HNF-1)/PCD (pterin-4a-carbinolamine dehydratase) are associated with a change in oligomeric state. DCoH dimers enhance the activity of the diabetes-associated transcription factor HNF-1{alpha} (hepatocyte nuclear factor-1{alpha}), while the PCD activity of DCoH1 homotetramers aids in aromatic amino acid metabolism. These complexes compete for the same interface of the DCoH dimer. Formation of the DCoH1/HNF-1{alpha} complex requires cofolding. The homotetramer of the DCoH1 paralogue, DCoH2, interacts with HNF-1{alpha} through simple mixing. To further investigate regulation of DCoH/HNF-1{alpha} complex formation, we measured the stability of the DCoH1 homotetramer through unfolding studies by intrinsic tryptophan fluorescence. DCoH2 unfolding is reversible. Surprisingly, the DCoH1 homotetramer is resistant to guanidine unfolding but refolds at a much lower guanidine concentration. We show that a point mutation at the DCoH1 tetramer interface, Thr 51 Ser, overcomes the dissociation barrier of the homotetramer and increases the interaction with HNF-1{alpha}. The 1.8 {angstrom} resolution crystal structure of DCoH1 T51S shows the presence of an ordered water molecule at the tetramer interface, as in DCoH2, which may destabilize the homotetramer. The equilibrium unfolding data were fit to a two-state model with no apparent intermediate. Folding intermediates were detectable by size exclusion chromatography. For wild-type DCoH1 the intermediates changed with time, suggesting a kinetic origin for the unfolding barrier of the homotetramer. We propose an unfolding pathway in which the tetramer unfolds slowly, but the dimer folds reversibly. Implications for regulation of DCoH1/HNF-1{alpha} complex formation are discussed.

  10. Calculation of two-centre two-electron integrals over Slater-type orbitals revisited. III. Case study of the beryllium dimer

    E-Print Network [OSTI]

    Micha? Lesiuk; Micha? Przybytek; Monika Musia?; Bogumi? Jeziorski; Robert Moszynski

    2015-01-20

    In this paper we present results of ab-initio calculations for the beryllium dimer with basis set of Slater-type orbitals (STOs). Nonrelativistic interaction energy of the system is determined using the frozen-core full configuration interaction calculations combined with high-level coupled cluster correction for inner-shell effects. Newly developed STOs basis sets, ranging in quality from double to sextuple zeta, are used in these computations. Principles of their construction are discussed and several atomic benchmarks are presented. Relativistic effects of order ${\\alpha}^2$ are calculated perturbatively by using the Breit-Pauli Hamiltonian and are found to be significant. We also estimate the leading-order QED effects. Influence of the adiabatic correction is found to be negligible. Finally, the interaction energy of the beryllium dimer is determined to be 929.0$\\,\\pm\\,$1.9 $cm^{-1}$, in a very good agreement with the recent experimental value. The results presented here appear to be the most accurate ab-initio calculations for the beryllium dimer available in the literature up to date and probably also one of the most accurate calculations for molecular systems containing more than four electrons.

  11. Superacid catalysis of light hydrocarbon conversion. DOE PETC seventh quarterly progress report, April 1, 1995--July 31, 1995

    SciTech Connect (OSTI)

    Gates, B.C.

    1996-02-01

    Iron- and manganese-promoted sulfated zirconia is a catalyst for the conversion of propane, but the rate of conversion of propane is much less than the rate of conversion of butane. Whereas this catalyst appears to be a good candidate for practical, industrial conversion of butane, it appears to lack sufficient activity for practical conversion of propane. The propane conversion data reported here provide excellent insights into the chemistry of the catalytic conversion. Solid and catalysts, namely, sulfated zirconia, iron- and manganese-promoted sulfated zirconia, and USY zeolite, were tested for conversion of propane at 1 atm, 200-450{degrees}C, and propane partial pressures in the range of 0.01-0.05 atm. Both promoted and unpromoted sulfated zirconia were found to be active for conversion of propane into butanes, pentanes, methane, ethane, ethylene, and propylene in the temperature range of 200-350{degrees}C, but catalyst deactivation was rapid. At the higher temperatures, only cracking and dehydrogenation products were observed. In contrast to the zirconia-supported catalysts, USY zeolite was observed to convert propane (into propylene, methane, and ethylene) only at temperatures {ge}400{degrees}C. The initial (5 min on stream) rates of propane conversion in the presence of iron- and manganese-promoted sulfated zirconia, sulfated zirconia, and USY zeolite at 450{degrees}C and 0.01 atm propane partial pressure were 3.3 x 10{sup -8}, 0.3 x 10{sup -8}, and 0.06 x 10{sup -8} mol/(s{center_dot}g), respectively. The product distributions in the temperature range 200-450{degrees}C are those of acid-base catalysis, being similar to what has been observed in superacid solution chemistry at temperatures <0{degrees}C. If propane conversion at 450{degrees}C can be considered as a probe of acid strength of the catalyst, the activity comparison suggests that the promoted sulfated zirconia is a stronger acid than sulfated zirconia, which is a stronger acid than USY zeolite.

  12. HETEROGENEOUS CATALYSIS RESEARCH MEETING

    E-Print Network [OSTI]

    Authors, Various

    2011-01-01

    synthesis gas by coal gasification is very expensive andin the cost of coal gasification would have a significantthe feed derived from coal gasi.fication. To establish the

  13. CATALYSIS, PERCEPTION, AND CONSCIOUSNESS

    E-Print Network [OSTI]

    CARPENTER, PATRICIA A.; DAVIA, CHRISTOPHER J.; VIMAL, RAM LAKHAN PANDEY

    2009-01-01

    Higher Cognitive Functions was provided by World Scientific.Access to World Scientific is possible through the

  14. HETEROGENEOUS CATALYSIS RESEARCH MEETING

    E-Print Network [OSTI]

    Authors, Various

    2011-01-01

    synthesis gas by coal gasification is very expensive andin the cost of coal gasification would have a significantas K co , to promote gasification would be beneficial s1nce

  15. Computational Catalysis and Electrocatalysis

    E-Print Network [OSTI]

    Bermúdez, José Luis

    ;Applications from our research · Fuel cell electrocatalysts · Controlled growth of carbon nanostructures · Hydrogen storage · Photocatalysis #12;Fuel cell electrocatalysts Parallelism between bimetallics-- Another fuel cell challenge #12;Predictions and challenges Using molecular dynamics simulations we showed

  16. HETEROGENEOUS CATALYSIS RESEARCH MEETING

    E-Print Network [OSTI]

    Authors, Various

    2011-01-01

    Coal Conversion Catalysts (Fred R. Brown) Solid State, Surface and Catalytic Propertiescoals. THE INFLUENCE f-ELECTRON CONFIGURATION ON CATALYTIC PROPERTIES

  17. HETEROGENEOUS CATALYSIS RESEARCH MEETING

    E-Print Network [OSTI]

    Authors, Various

    2011-01-01

    have been investigated: 1) catalytic oxidation of CO onPt and Pd1 2) catalytic oxidation of H2 on Pd; compet iveof the catalytic properties of oxides to specific oxidation

  18. ZEOLITE CATALYSIS - TECHNOLOGY

    E-Print Network [OSTI]

    Heinemann, Heinz

    2013-01-01

    in 1978 Catalytic Hydrocracking Catalyst Sales million lbs/to a lesser extent in hydrocracking. Table 1 presents somein hydrocrackring Hydrocracking is catalytic cracking in the

  19. Hydrocracking reactions and catalysis

    SciTech Connect (OSTI)

    Dolbear, G.E. [G.E. Dolbear and Associates, Diamond Bar, CA (United States)

    1995-12-31

    Hydrocracking processes convert aromatic gas oils into high quality gasoline, diesel, and turbine stocks. In doing this, they saturate aromatic rings, crack naphthenes and paraffins, and saturate olefins formed during cracking. The organic chemistry of these steps is well known. Catalysts for hydrocracking contain components for both the hydrogenation and cracking reactions. Hydrogenation activity is provided by Pd or promoted molybdenum or tungsten sulfides. Cracking takes place on strong acid sites in zeolites or amorphous silica aluminas. Specialty catalysts including narrow pore zeolites are used in dewaxing tube oil stocks. Basic nitrogen compounds such as quinoline can poison the acid sites. They are usually removed in a pretreating step, typically with a nickel/molybdenum sulfide catalyst that also removes sulfur.

  20. Metal Oxide Nanofiber Catalysis

    E-Print Network [OSTI]

    Noon, Daniel Patrick

    2015-01-01

    and Mechanism. Chemical Engineering Science, 1980. 35(6): p.Catalytic Combustor. Chemical Engineering Science, 1980. 35(Gas Shift Reaction. Chemical Engineering Science, 1981. 36(

  1. ZEOLITE CATALYSIS - TECHNOLOGY

    E-Print Network [OSTI]

    Heinemann, Heinz

    2013-01-01

    olefins and aromatics from coal derived methanol Again workCycloparaffins Aromatics XBL 805-1067 Fig. 8 Methanol

  2. Catalysis Without Precious Metals

    SciTech Connect (OSTI)

    Bullock, R. Morris

    2010-11-01

    Written for chemists in industry and academia, this ready reference and handbook summarizes recent progress in the development of new catalysts that do not require precious metals. The research thus presented points the way to how new catalysts may ultimately supplant the use of precious metals in some types of reactions, while highlighting the remaining challenges. This material is based upon work supported as part of the Center for Molecular Electrocatalysis, an Energy Frontier Research Center funded by the US Department of Energy, Office of Science, Office of Basic Energy Sciences.

  3. ZEOLITE CATALYSIS - TECHNOLOGY

    E-Print Network [OSTI]

    Heinemann, Heinz

    2013-01-01

    and after Hydrodewaxing with 2SH-5 Virgin heavy gas oil MMDWprocessed heavy gas oil Properties Gravity, API Pour point,

  4. HETEROGENEOUS CATALYSIS RESEARCH MEETING

    E-Print Network [OSTI]

    Authors, Various

    2011-01-01

    merits and disadvantages of LEED, Auger, photo- emissionelectron dif- fraction, (LEED), and the investigation of theof overlayer structures by LEED has concentrated on the

  5. ZEOLITE CATALYSIS - TECHNOLOGY

    E-Print Network [OSTI]

    Heinemann, Heinz

    2013-01-01

    palladium) tubular pore zeolite such as mordenite, while the Mobil process uses ZSM-5 zeolite. Hydrogen

  6. 2012 Catalysis Lectures

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative Fuels Data Center Homesum_a_epg0_fpd_mmcf_m.xls" ,"Available from WebQuantity ofkandz-cm11 Outreach Home RoomPreservationBio-InspiredAtmosphericdevicesPPONe β+-DecayUpgrade P.July 31, 2012201222

  7. Electron Transfer Catalyzed [2 + 2] Cycloreversion of Benzene G. Devi Reddy and Olaf Wiest*

    E-Print Network [OSTI]

    Hudlicky, Tomas

    Electron Transfer Catalyzed [2 + 2] Cycloreversion of Benzene Dimers G. Devi Reddy and Olaf Wiest, Florida 32611-7200 Received December 8, 1998 The catalysis of the [2 + 2] cycloreversion of the anti-o,o-benzene dimer 1 and the syn-o,o- naphthalene-benzene dimer 2 through thermal and photoinduced electron transfer

  8. CRM1-dependent nuclear export and dimerization with hMSH5 contribute to the regulation of hMSH4 subcellular localization

    SciTech Connect (OSTI)

    Neyton, Sophie; Lespinasse, Francoise; Lahaye, Francois [Equipe M3R, UMR 6543, Universite de Nice Sophia-Antipolis, CNRS, Faculte de Medecine, Avenue de Valombrose 06107, Nice Cedex 2 (France); Staccini, Pascal [Stic, Universite de Nice-Sophia Antipolis, Faculte de Medecine, Avenue de Valombrose 06107, Nice Cedex 2 (France); Paquis-Flucklinger, Veronique [Equipe M3R, UMR 6543, Universite de Nice Sophia-Antipolis, CNRS, Faculte de Medecine, Avenue de Valombrose 06107, Nice Cedex 2 (France); Santucci-Darmanin, Sabine [Equipe M3R, UMR 6543, Universite de Nice Sophia-Antipolis, CNRS, Faculte de Medecine, Avenue de Valombrose 06107, Nice Cedex 2 (France)], E-mail: santucci@hermes.unice.fr

    2007-10-15

    MSH4 and MSH5 are members of the MutS homolog family, a conserved group of proteins involved in DNA mismatch correction and homologous recombination. Although several studies have provided compelling evidences suggesting that MSH4 and MSH5 could act together in early and late stages of meiotic recombination, their precise roles are poorly understood and recent findings suggest that the human MSH4 protein may also exert a cytoplasmic function. Here we show that MSH4 is present in the cytoplasm and the nucleus of both testicular cells and transfected somatic cells. Confocal studies on transfected cells provide the first evidence that the subcellular localization of MSH4 is regulated, at least in part, by an active nuclear export pathway dependent on the exportin CRM1. We used deletion mapping and mutagenesis to define two functional nuclear export sequences within the C-terminal part of hMSH4 that mediate nuclear export through the CRM1 pathway. Our results suggest that CRM1 is also involved in MSH5 nuclear export. In addition, we demonstrate that dimerization of MSH4 and MSH5 facilitates their nuclear localization suggesting that dimerization may regulate the intracellular trafficking of these proteins. Our findings suggest that nucleocytoplasmic traffic may constitute a regulatory mechanism for MSH4 and MSH5 functions.

  9. Calculation of two-centre two-electron integrals over Slater-type orbitals revisited. III. Case study of the beryllium dimer

    E-Print Network [OSTI]

    Lesiuk, Micha?; Musia?, Monika; Jeziorski, Bogumi?; Moszynski, Robert

    2014-01-01

    In this paper we present results of ab-initio calculations for the beryllium dimer with basis set of Slater-type orbitals (STOs). Nonrelativistic interaction energy of the system is determined using the frozen-core full configuration interaction calculations combined with high-level coupled cluster correction for inner-shell effects. Newly developed STOs basis sets, ranging in quality from double to sextuple zeta, are used in these computations. Principles of their construction are discussed and several atomic benchmarks are presented. Relativistic effects of order ${\\alpha}^2$ are calculated perturbatively by using the Breit-Pauli Hamiltonian and are found to be significant. We also estimate the leading-order QED effects. Influence of the adiabatic correction is found to be negligible. Finally, the interaction energy of the beryllium dimer is determined to be 929.0$\\,\\pm\\,$1.9 $cm^{-1}$, in a very good agreement with the recent experimental value. The results presented here appear to be the most accurate ab-...

  10. VOLUME 76, NUMBER 26 P H Y S I C A L R E V I E W L E T T E R S 24 JUNE 1996 Dimer Shearing as a Novel Mechanism for Cluster Diffusion and Dissociation

    E-Print Network [OSTI]

    . This process provides the easiest pathway for diffusion of compact clusters of sizes 4, 6, and 8 of cluster dif- fusion and dissociation in metal (100) epitaxy have been based on the central assumption of a col- lective atomic process, shear motion of a dimer belonging to a compact cluster. This previously

  11. Finite-Volume Energy Spectrum, Fractionalized Strings, and Low-Energy Effective Field Theory for the Quantum Dimer Model on the Square Lattice

    E-Print Network [OSTI]

    Banerjee, D; Hofmann, C P; Jiang, F -J; Widmer, P; Wiese, U -J

    2015-01-01

    We present detailed analytic calculations of finite-volume energy spectra, mean field theory, as well as a systematic low-energy effective field theory for the square lattice quantum dimer model. The analytic considerations explain why a string connecting two external static charges in the confining columnar phase fractionalizes into eight distinct strands with electric flux $\\frac{1}{4}$. An emergent approximate spontaneously broken $SO(2)$ symmetry gives rise to a pseudo-Goldstone boson. Remarkably, this soft phonon-like excitation, which is massless at the Rokhsar-Kivelson (RK) point, exists far beyond this point. The Goldstone physics is captured by a systematic low-energy effective field theory. We determine its low-energy parameters by matching the analytic effective field theory with exact diagonalization results and Monte Carlo data. This confirms that the model exists in the columnar (and not in a plaquette or mixed) phase all the way to the RK point.

  12. UNC-45/CRO1/She4p (UCS) Protein Forms Elongated Dimer and Joins Two Myosin Heads Near Their Actin Binding Region

    SciTech Connect (OSTI)

    H Shi; G Blobel

    2011-12-31

    UNC-45/CRO1/She4p (UCS) proteins have variously been proposed to affect the folding, stability, and ATPase activity of myosins. They are the only proteins known to interact directly with the motor domain. To gain more insight into UCS function, we determined the atomic structure of the yeast UCS protein, She4p, at 2.9 {angstrom} resolution. We found that 16 helical repeats are organized into an L-shaped superhelix with an amphipathic N-terminal helix dangling off the short arm of the L-shaped molecule. In the crystal, She4p forms a 193-{angstrom}-long, zigzag-shaped dimer through three distinct and evolutionary conserved interfaces. We have identified She4p's C-terminal region as a ligand for a 27-residue-long epitope on the myosin motor domain. Remarkably, this region consists of two adjacent, but distinct, binding epitopes localized at the nucleotide-responsive cleft between the nucleotide- and actin-filament-binding sites. One epitope is situated inside the cleft, the other outside the cleft. After ATP hydrolysis and Pi ejection, the cleft narrows at its base from 20 to 12 {angstrom} thereby occluding the inside the cleft epitope, while leaving the adjacent, outside the cleft binding epitope accessible to UCS binding. Hence, one cycle of higher and lower binding affinity would accompany one ATP hydrolysis cycle and a single step in the walk on an actin filament rope. We propose that a UCS dimer links two myosins at their motor domains and thereby functions as one of the determinants for step size of myosin on actin filaments.

  13. Global Structure of a Three-Way Junction in a Phi29 Packaging RNA Dimer Determined Using Site-Directed Spin Labeling

    SciTech Connect (OSTI)

    Zhang, Xiaojun; Tung, Chang-Shung; Sowa, Glenna; Hatmal, Ma'mon M.; Haworth, Ian S.; Qin, Peter Z.

    2012-02-08

    The condensation of bacteriophage phi29 genomic DNA into its preformed procapsid requires the DNA packaging motor, which is the strongest known biological motor. The packaging motor is an intricate ring-shaped protein/RNA complex, and its function requires an RNA component called packaging RNA (pRNA). Current structural information on pRNA is limited, which hinders studies of motor function. Here, we used site-directed spin labeling to map the conformation of a pRNA three-way junction that bridges binding sites for the motor ATPase and the procapsid. The studies were carried out on a pRNA dimer, which is the simplest ring-shaped pRNA complex and serves as a functional intermediate during motor assembly. Using a nucleotide-independent labeling scheme, stable nitroxide radicals were attached to eight specific pRNA sites without perturbing RNA folding and dimer formation, and a total of 17 internitroxide distances spanning the three-way junction were measured using Double Electron-Electron Resonance spectroscopy. The measured distances, together with steric chemical constraints, were used to select 3662 viable three-way junction models from a pool of 65 billion. The results reveal a similar conformation among the viable models, with two of the helices (HT and HL) adopting an acute bend. This is in contrast to a recently reported pRNA tetramer crystal structure, in which HT and HL stack onto each other linearly. The studies establish a new method for mapping global structures of complex RNA molecules, and provide information on pRNA conformation that aids investigations of phi29 packaging motor and developments of pRNA-based nanomedicine and nanomaterial.

  14. Combining X-ray Absorption and X-ray Diffraction Techniques for in Situ Studies of Chemical Transformations in Heterogeneous Catalysis: Advantages and Limitations

    SciTech Connect (OSTI)

    Frenkel, A.I.; Hanson, J.; Wang, Q.; Marinkovic, N.; Chen, J.G.; Barrio, L.; Si, R.; Lopez Camara, A.; Estrella, A.M.; Rodriguez, J.A.

    2011-08-05

    Recent advances in catalysis instrumentations include synchrotron-based facilities where time-resolved X-ray scattering and absorption techniques are combined in the same in situ or operando experiment to study catalysts at work. To evaluate the advances and limitations of this method, we performed a series of experiments at the new XAFS/XRD instrument in the National Synchrotron Light Source. Nearly simultaneous X-ray diffraction (XRD) and X-ray absorption fine-structure (XAFS) measurements of structure and kinetics of several catalysts under reducing or oxidizing conditions have been performed and carefully analyzed. For CuFe{sub 2}O{sub 4} under reducing conditions, the combined use of the two techniques allowed us to obtain accurate data on kinetics of nucleation and growth of metallic Cu. For the inverse catalyst CuO/CeO{sub 2} that underwent isothermal reduction (with CO) and oxidation (with O{sub 2}), the XAFS data measured in the same experiment with XRD revealed strongly disordered Cu species that went undetected by diffraction. These and other examples emphasize the unique sensitivity of these two complementary methods to follow catalytic processes in the broad ranges of length and time scales.

  15. Combining X-ray Absorption and X-ray Diffraction Techniques for in Situ Studies of Chemical Transformations in Heterogeneous Catalysis:Advantages and Limitations

    SciTech Connect (OSTI)

    A Frenkel; Q Wang; N Marinkovic; J Chen; L Barrio; R Si; A Lopez Camara; A Estella; J Rodriquez; J Hanson

    2011-12-31

    Recent advances in catalysis instrumentations include synchrotron-based facilities where time-resolved X-ray scattering and absorption techniques are combined in the same in situ or operando experiment to study catalysts at work. To evaluate the advances and limitations of this method, we performed a series of experiments at the new XAFS/XRD instrument in the National Synchrotron Light Source. Nearly simultaneous X-ray diffraction (XRD) and X-ray absorption fine-structure (XAFS) measurements of structure and kinetics of several catalysts under reducing or oxidizing conditions have been performed and carefully analyzed. For CuFe{sub 2}O{sub 4} under reducing conditions, the combined use of the two techniques allowed us to obtain accurate data on kinetics of nucleation and growth of metallic Cu. For the inverse catalyst CuO/CeO{sub 2} that underwent isothermal reduction (with CO) and oxidation (with O{sub 2}), the XAFS data measured in the same experiment with XRD revealed strongly disordered Cu species that went undetected by diffraction. These and other examples emphasize the unique sensitivity of these two complementary methods to follow catalytic processes in the broad ranges of length and time scales.

  16. Visible-Light Photoredox Catalysis: Selective Reduction of Carbon Dioxide to Carbon Monoxide by a Nickel N-Heterocyclic Carbene-Isoquinoline Complex

    SciTech Connect (OSTI)

    Thoi, VanSara; Kornienko, Nick; Margarit, C; Yang, Peidong; Chang, Christopher

    2013-06-07

    The solar-driven reduction of carbon dioxide to value-added chemical fuels is a longstanding challenge in the fields of catalysis, energy science, and green chemistry. In order to develop effective CO2 fixation, several key considerations must be balanced, including (1) catalyst selectivity for promoting CO2 reduction over competing hydrogen generation from proton reduction, (2) visible-light harvesting that matches the solar spectrum, and (3) the use of cheap and earth-abundant catalytic components. In this report, we present the synthesis and characterization of a new family of earth-abundant nickel complexes supported by N-heterocyclic carbene amine ligands that exhibit high selectivity and activity for the electrocatalytic and photocatalytic conversion of CO2 to CO. Systematic changes in the carbene and amine donors of the ligand have been surveyed, and [Ni(Prbimiq1)]2+ (1c, where Prbimiq1 = bis(3-(imidazolyl)isoquinolinyl)propane) emerges as a catalyst for electrochemical reduction of CO2 with the lowest cathodic onset potential (Ecat = 1.2 V vs SCE). Using this earth-abundant catalyst with Ir(ppy)3 (where ppy = 2-phenylpyridine) and an electron donor, we have developed a visible-light photoredox system for the catalytic conversion of CO2 to CO that proceeds with high selectivity and activity and achieves turnover numbers and turnover frequencies reaching 98,000 and 3.9 s1, respectively. Further studies reveal that the overall efficiency of this solar-to-fuel cycle may be limited by the formation of the active Ni catalyst and/or the chemical reduction of CO2 to CO at the reduced nickel center and provide a starting point for improved photoredox systems for sustainable carbon-neutral energy conversion.

  17. Effects of {pi}-stacking interactions on the near carbon K-edge x-ray absorption fine structure: A theoretical study of the ethylene pentamer and the phthalocyanine dimer

    SciTech Connect (OSTI)

    Linares, Mathieu; Stafstroem, Sven; Norman, Patrick [Department of Physics, Chemistry and Biology, Linkoeping University, SE-581 83 Linkoeping (Sweden)

    2009-03-14

    X-ray absorption spectra have been determined for ethylene and free base phthalocyanine at the carbon K-edge with use of the complex polarization propagator method combined with Kohn-Sham density functional theory and the Coulomb attenuated method B3LYP exchange-correlation functional. Apart from isolated molecules, the study includes {pi}-stacked systems of the phthalocyanine dimer and the ethylene dimer, trimer, tetramer, and pentamer. For ethylene, {pi}-stacking involves a reduction in transition energy of the valence {pi}*-band by some 70 meV and large spectral changes (regarding also shape and intensity) of the Rydberg bands. For phthalocyanine, there are large spectral changes in the entire valence {pi}*-part of the spectrum.

  18. Photoionization of cold gas phase coronene and its clusters: Autoionization resonances in monomer, dimer, and trimer and electronic structure of monomer cation

    SciTech Connect (OSTI)

    Bréchignac, Philippe, E-mail: philippe.brechignac@u-psud.fr; Falvo, Cyril; Parneix, Pascal; Pino, Thomas; Pirali, Olivier [Institut des Sciences Moléculaires d’Orsay, CNRS UMR8214, Univ Paris-Sud, F-91405 Orsay (France); Garcia, Gustavo A.; Nahon, Laurent [Synchrotron SOLEIL, L’Orme des Merisiers, Saint-Aubin, B.P. 48, F-91192 Gif-sur-Yvette (France); Joblin, Christine; Kokkin, Damian; Bonnamy, Anthony [IRAP, Université de Toulouse 3 - CNRS, 9 Av. Colonel Roche, B.P. 44346, F-31028 Toulouse Cedex 4 (France); Mulas, Giacomo [INAF - Osservatorio Astronomico di Cagliari, via della scienza 5, I-09047 Selargius (Italy)

    2014-10-28

    Polycyclic aromatic hydrocarbons (PAHs) are key species encountered in a large variety of environments such as the Interstellar Medium (ISM) and in combustion media. Their UV spectroscopy and photodynamics in neutral and cationic forms are important to investigate in order to learn about their structure, formation mechanisms, and reactivity. Here, we report an experimental photoelectron-photoion coincidence study of a prototypical PAH molecule, coronene, and its small clusters, in a molecular beam using the vacuum ultraviolet (VUV) photons provided by the SOLEIL synchrotron facility. Mass-selected high resolution threshold photoelectron (TPES) and total ion yield spectra were obtained and analyzed in detail. Intense series of autoionizing resonances have been characterized as originating from the monomer, dimer, and trimer neutral species, which may be used as spectral fingerprints for their detection in the ISM by VUV absorption spectroscopy. Finally, a full description of the electronic structure of the monomer cation was made and discussed in detail in relation to previous spectroscopic optical absorption data. Tentative vibrational assignments in the near-threshold TPES spectrum of the monomer have been made with the support of a theoretical approach based on density functional theory.

  19. Characterization of fundamental catalytic properties of MoS2/WS2 nanotubes and nanoclusters for desulfurization catalysis - a surface temperature study

    SciTech Connect (OSTI)

    U. Burghaus

    2012-07-05

    The prior project consisted of two main project lines. First, characterization of novel nanomaterials for hydrodesulfurization (HDS) applications. Second, studying more traditional model systems for HDS such as vapor-deposited silica-supported Mo and MoSx clusters. In the first subproject, we studied WS2 and MoS2 fullerene-like nanoparticles as well as WS2 nanotubes. Thiophene (C4H4S) was used as the probe molecule. Interestingly, metallic and sulfur-like adsorption sites could be identified on the silica-supported fullerene-particles system. Similar structures are seen for the traditional system (vapor-deposited clusters). Thus, this may be a kinetics fingerprint feature of modern HDS model systems. In addition, kinetics data allowed characterization of the different adsorption sites for thiophene on and inside WS2 nanotube bundles. The latter is a unique feature of nanotubes that has not been reported before for any inorganic nanotube system; however, examples are known for carbon nanotubes, including prior work of the PI. Although HDS has been studied for decades, utilizing nanotubes as nanosized HDS reactors has never been tried before, as far as we know. This is of interest from a fundamental perspective. Unfortunately, the HDS activity of the nanocatalysts at ultra-high vacuum (UHV) conditions was close to the detection limit of our techniques. Therefore, we propose to run experiments at ambient pressure on related nanopowder samples as part of the renewal application utilizing a now-available GC (gas chromatograph) setup. In addition, Ni and Co doped nanocatalyts are proposed for study. These dopants will boost the catalytic activity. In the second subproject of the prior grant, we studied HDS-related chemistry on more traditional supported cluster catalysts. Mo clusters supported by physical vapor deposition (PVD) on silica have been characterized. Two reaction pathways are evident when adsorbing thiophene on Mo and MoSx clusters: molecular adsorption and dissociation. PVD Mo clusters turned out to be very reactive toward thiophene bond activation. Sulfur and carbon residuals form, which poison the catalyst and sulfide the Mo clusters. Sulfided silica-supported MoSx samples are not reactive toward thiophene bond activation. In addition to S and C deposits, H2, H2S, and small organic molecules were detected in the gas phase. Catalyst reactivation procedures, including O2 and atomic hydrogen treatments, have been tested. Cluster size effects have been seen: thiophene adsorbs molecularly with larger binding energies on smaller clusters. However, larger clusters have smaller activation energy for C4H4S bond activation than smaller clusters. The latter is consistent with early catalysis studies. Kinetics and dynamics parameters have been determined quantitatively. We spent a significant amount of time on upgrades of our equipment. A 2nd-hand refurbished X-ray photoelectron spectrometer (XPS) has been integrated into the existing molecular beam scattering system and is already operational (supported by the DoE supplemental grant available in October 2009). We also added a time of flight (TOF) system to the beam scattering apparatus and improved on the accessible impact energy range (new nozzle heater and gas mixing manifold) for the beam scattering experiments. In addition, a GC-based powder atmospheric flow reactor for studies on powder samples is now operational. Furthermore, a 2nd UHV kinetics system has been upgraded as well. In summary, mostly single crystal systems have so far been considered in basic science studies about HDS. Industrial catalysts, however, can be better approximated with the supported cluster systems that we studied in this project. Furthermore, an entirely new class of HDS systems, namely fullerene-like particles and inorganic nanotubes, has been included. Studying new materials and systems has the potential to impact science and technology. The systems investigated are closely related to energy and environmental-related surface science/catalysis. This prior project, conducted at NDSU by a sma

  20. "Nanocrystal bilayer for tandem catalysis"

    E-Print Network [OSTI]

    Yamada, Yusuke

    2012-01-01

    Part VI. Hydrogenolysis of Ethane, Propane, n-Butane andiso-Butane over Supported Platinum Catalysts. J. Catal. 176,

  1. Reaction Selectivity in Heterogeneous Catalysis

    E-Print Network [OSTI]

    Somorjai, Gabor A.

    2010-01-01

    G. A. Abstracts of Papers of the American Chemical SocietyG. A. Abstracts of Papers of the American Chemical Society

  2. "Nanocrystal bilayer for tandem catalysis"

    E-Print Network [OSTI]

    Yamada, Yusuke

    2012-01-01

    Part VI. Hydrogenolysis of Ethane, Propane, n-Butane andactivation energy for ethane hydrogenolysis over platinum-such as propanol or ethane was less than the detection

  3. "Nanocrystal bilayer for tandem catalysis"

    E-Print Network [OSTI]

    Yamada, Yusuke

    2012-01-01

    Hydrogenolysis of Ethane, Propane, n-Butane and iso-Butanethe Hydroformylation of Propane over Silica-supported Groupproduct and small amount of propane, which is likely to be

  4. Electrochemistry: Catalysis at the boundaries

    SciTech Connect (OSTI)

    Appel, Aaron M.

    2014-04-09

    Renewable energy provides an opportunity to power society without the potential impacts from the use of fossil fuels, but a major limitation of sources such as solar and wind is their intermittent availability. Efficient storage of energy from these renewable sources is critical in developing their widespread utilization. One approach to the storage of renewable energy is the production of fuels, such as ethanol, from water and carbon dioxide. Unlike traditional centralized fuel production, electrochemical systems can operate under mild pressures and temperatures in dispersed, small-scale reactors. Renewable sources of energy are inherently dispersed, and therefore are well matched with the production of fuels electrochemically. However, the development of efficient catalysts is essential for the intended chemical transformations.

  5. SOUTHWEST CATALYSIS 2015 SPRING SYMPOSIUM

    E-Print Network [OSTI]

    Natelson, Douglas

    Baton Rouge, LA 70817 jnovak@PIDC.com Lin Luo The Dow Chemical Company 2301 Brazosport Blvd., B-251 University Chair #12;3 3 2015 PROGRAM All talks & breaks will be held in Melcher Hall, Room 150 7:30 AM Registration ­ Victor Johnston, Treasurer (& helpers) 8:25 AM Welcoming Remarks ­ Dan Shantz, Chair 8:30 AM Bob

  6. SOUTHWEST CATALYSIS 2012 SPRING SYMPOSIUM

    E-Print Network [OSTI]

    Natelson, Douglas

    Daniel Shantz Chemical Engineering Texas A&M University College Station, TX 77843 979-845-3492 shantz.chandler@trinity.edu Lin Luo Dow Chemical Co. 2301 Brazosport Blvd. B-251 Freeport, TX 77541 979-238-3204 LLuo2@dow Chair #12;2012 PROGRAM 7:30 AM Registration ­ John Novak, Treasurer Duncan Hall All talks will be held

  7. SOUTHWEST CATALYSIS 2012 SPRING SYMPOSIUM

    E-Print Network [OSTI]

    Natelson, Douglas

    Daniel Shantz Chemical Engineering Texas A&M University College Station, TX 77843 979-845-3492 shantz.chandler@trinity.edu Lin Luo Dow Chemical Co. 2301 Brazosport Blvd. B-251 Freeport, TX 77541 979-238-3204 LLuo2@dow #12;2012 PROGRAM 7:30 AM Registration ­ John Novak, Treasurer Duncan Hall All talks will be held in Mc

  8. SOUTHWEST CATALYSIS 2010 SPRING SYMPOSIUM

    E-Print Network [OSTI]

    Natelson, Douglas

    :35 AM Prof. Kerry Dooley (LSU, Baton Rouge, LA) "Perspectives on Catalytic Oxidative Desulfurization" 9' Nanocatalysts for Electrochemical Energy Conversion: The Challenges for Synthesis and Characterization" 1:45 PM Hall ­ McMurtry Auditorium 4:00 PM Adjourn #12;Perspectives on Catalytic Oxidative Desulfurization

  9. Solution Structure of the 128 kDa Enzyme I Dimer from Escherichia coli and Its 146 kDa Complex with HPr Using Residual Dipolar Couplings and Small- and Wide-Angle X-ray Scattering

    SciTech Connect (OSTI)

    Schwieters, Charles D.; Suh, Jeong-Yong; Grishaev, Alexander; Ghirlando, Rodolfo; Takayama, Yuki; Clore, G. Marius (NIH)

    2010-09-17

    The solution structures of free Enzyme I (EI, {approx}128 kDa, 575 x 2 residues), the first enzyme in the bacterial phosphotransferase system, and its complex with HPr ({approx}146 kDa) have been solved using novel methodology that makes use of prior structural knowledge (namely, the structures of the dimeric EIC domain and the isolated EIN domain both free and complexed to HPr), combined with residual dipolar coupling (RDC), small- (SAXS) and wide- (WAXS) angle X-ray scattering and small-angle neutron scattering (SANS) data. The calculational strategy employs conjoined rigid body/torsion/Cartesian simulated annealing, and incorporates improvements in calculating and refining against SAXS/WAXS data that take into account complex molecular shapes in the description of the solvent layer resulting in a better representation of the SAXS/WAXS data. The RDC data orient the symmetrically related EIN domains relative to the C{sub 2} symmetry axis of the EIC dimer, while translational, shape, and size information is provided by SAXS/WAXS. The resulting structures are independently validated by SANS. Comparison of the structures of the free EI and the EI-HPr complex with that of the crystal structure of a trapped phosphorylated EI intermediate reveals large ({approx}70-90{sup o}) hinge body rotations of the two subdomains comprising the EIN domain, as well as of the EIN domain relative to the dimeric EIC domain. These large-scale interdomain motions shed light on the structural transitions that accompany the catalytic cycle of EI.

  10. Active-space completely-renormalized equation-of-motion coupled-cluster formalism: Excited-state studies of green fluorescent protein, free-base porphyrin, and oligoporphyrin dimer

    SciTech Connect (OSTI)

    Kowalski, Karol; Krishnamoorthy, Sriram; Villa, Oreste; Hammond, Jeffrey R.; Govind, Niranjan

    2010-04-21

    The development of efficient parallel implementations of electronic structure methods enables not only the study of excited states of large molecular systems but also a unique opportunity to assess the role of various correlation effects in describing excitation energies for systems composed of hundreds of electrons. In this article, we discuss the impact of triply excited configurations in Equation-of-Motion Coupled Cluster (EOMCC) formalism. As a benchmark system we chose the fused porphyrin dimer, which is described by the basis set composed of 942 functions and where 270 electrons were correlated in the EOMCC calculations.

  11. Investigations of the Dimerized Antiferromagnetic

    E-Print Network [OSTI]

    Petta, Jason

    ;Theoretical Spin Wave Energy Spectra #12;Theoretical One-magnon Energy Spectra #12;Conclusions · More going temperature superconductivity · Many future technological applications ­ Need to understand physics first

  12. Combined Use of Residual Dipolar Couplings and Solution X-ray Scattering To Rapidly Probe Rigid-Body Conformational Transitions in a Non-phosphorylatable Active-Site Mutant of the 128 kDa Enzyme I Dimer

    SciTech Connect (OSTI)

    Takayama, Yuki; Schwieters, Charles D.; Grishaev, Alexander; Ghirlando, Rodolfo; Clore, G. Marius (NIH)

    2012-10-23

    The first component of the bacterial phosphotransferase system, enzyme I (EI), is a multidomain 128 kDa dimer that undergoes large rigid-body conformational transitions during the course of its catalytic cycle. Here we investigate the solution structure of a non-phosphorylatable active-site mutant in which the active-site histidine is substituted by glutamine. We show that perturbations in the relative orientations and positions of the domains and subdomains can be rapidly and reliably determined by conjoined rigid-body/torsion angle/Cartesian simulated annealing calculations driven by orientational restraints from residual dipolar couplings and shape and translation information afforded by small- and wide-angle X-ray scattering. Although histidine and glutamine are isosteric, the conformational space available to a Gln side chain is larger than that for the imidazole ring of His. An additional hydrogen bond between the side chain of Gln189 located on the EIN{sup {alpha}/{beta}} subdomain and an aspartate (Asp129) on the EIN{sup {alpha}} subdomain results in a small ({approx}9{sup o}) reorientation of the EIN{sup {alpha}} and EIN{sup {alpha}/{beta}} subdomains that is in turn propagated to a larger reorientation ({approx}26{sup o}) of the EIN domain relative to the EIC dimerization domain, illustrating the positional sensitivity of the EIN domain and its constituent subdomains to small structural perturbations.

  13. Analytical Morse/long-Range model potential and predicted infrared and microwave spectra for a symmetric top-atom dimer: A case study of CH{sub 3}F–He

    SciTech Connect (OSTI)

    Ma, Yong-Tao; Li, Hui, E-mail: Prof-huili@jlu.edu.cn [Institute of Theoretical Chemistry, State Key Laboratory of Theoretical and Computational Chemistry, Jilin University, 2519 Jiefang Road, Changchun 130023 (China); Zeng, Tao [Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853 (United States)

    2014-06-07

    Four-dimensional ab initio intermolecular potential energy surfaces (PESs) for CH{sub 3}F–He that explicitly incorporates dependence on the Q{sub 3} stretching normal mode of the CH{sub 3}F molecule and are parametrically dependent on the other averaged intramolecular coordinates have been calculated. Analytical three-dimensional PESs for v{sub 3}(CH{sub 3}F) = 0 and 1 are obtained by least-squares fitting the vibrationally averaged potentials to the Morse/Long-Range potential function form. With the 3D PESs, we employ Lanczos algorithm to calculate rovibrational levels of the dimer system. Following some re-assignments, the predicted transition frequencies are in good agreement with experimental microwave data for ortho-CH{sub 3}F, with the root-mean-square deviation of 0.042 cm{sup ?1}. We then provide the first prediction of the infrared and microwave spectra for the para-CH{sub 3}F–He dimer. The calculated infrared band origin shifts associated with the ?{sub 3} fundamental of CH{sub 3}F are 0.039 and 0.069 cm{sup ?1} for para-CH{sub 3}F–He and ortho-CH{sub 3}F–He, respectively.

  14. Ruthenium Aluminides: Deformation Mechanisms and Substructure Development

    SciTech Connect (OSTI)

    Tresa M. Pollock

    2005-05-11

    Structural and functional materials that can operate in severe, high temperature environments are key to the operation of a wide range of energy generation systems. Because continued improvements in the energy efficiency of these systems is critical, the need for new materials with higher temperature capabilities is inevitable. Intermetallic compounds, with strong bonding and generally high melting points offer this possibility for a broad array of components such as coatings, electrode materials, actuators and/or structural elements. RuAl is a very unusual intermetallic compound among the large number of B2compounds that have been identified and investigated to date. This material has a very high melting temperature of 2050?C, low thermal expansion, high thermal conductivity and good corrosion resistance. Unlike most other high temperature B2 intermetallics, RuAl possesses good intrinsic deformability at low temperatures. In this program fundamental aspects of low and high temperature mechanical properties and deformation mechanisms in binary and higher order RuAl-based systems have been investigated. Alloying additions of interest included platinum, boron and niobium. Additionally, preliminary studies on high temperature oxidation behavior of these materials have been conducted.

  15. Model Catalysis of Ammonia Synthesis ad Iron-Water Interfaces - ASum Frequency Generation Vibrational Spectroscopic Study of Solid-GasInterfaces and Anion Photoelectron Spectroscopic Study of Selected Anionclusters

    SciTech Connect (OSTI)

    Ferguson, Michael James

    2005-12-15

    The ammonia synthesis reaction has been studied using single crystal model catalysis combined with sum frequency generation (SFG) vibrational spectroscopy. The adsorption of gases N{sub 2}, H{sub 2}, O{sub 2} and NH{sub 3} that play a role in ammonia synthesis have been studied on the Fe(111) crystal surface by sum frequency generation vibrational spectroscopy using an integrated Ultra-High Vacuum (UHV)/high-pressure system. SFG spectra are presented for the dissociation intermediates, NH{sub 2} ({approx}3325 cm{sup -1}) and NH ({approx}3235 cm{sup -1}) under high pressure of ammonia or equilibrium concentrations of reactants and products on Fe(111) surfaces. Special attention was paid to understand how potassium promotion of the iron catalyst affects the intermediates of ammonia synthesis. An Fe(111) surface promoted with 0.2 monolayers of potassium red shifts the vibrational frequencies of the reactive surface intermediates, NH and NH{sub 2}, providing evidence for weakened the nitrogen-hydrogen bonds relative to clean Fe(111). Spectral features of these surface intermediates persisted to higher temperatures for promoted iron surfaces than for clean Fe(111) surfaces implying that nitrogen-iron bonds are stronger for the promoted surface. The ratio of the NH to NH{sub 2} signal changed for promoted surfaces in the presence of equilibrium concentrations of reactants and products. The order of adding oxygen and potassium to promoted surfaces does not alter the spectra indicating that ammonia induces surface reconstruction of the catalyst to produce the same surface morphology. When oxygen is co-adsorbed with nitrogen, hydrogen, ammonia or potassium on Fe(111), a relative phase shift of the spectra occurs as compared to the presence of adsorbates on clean iron surfaces. Water adsorption on iron was also probed using SFG vibrational spectroscopy. For both H{sub 2}O and D{sub 2}O, the only spectral feature was in the range of the free OH or free OD. From the absence of SFG spectra of ice-like structure we conclude that surface hydroxides are formed and no liquid water is present on the surface. Other than model catalysis, gas phase anion photoelectron spectroscopy of the Cl + H{sub 2} van der Waals well, silicon clusters, germanium clusters, aluminum oxide clusters and indium phosphide clusters were studied. The spectra help to map out the neutral potential energy surfaces of the clusters. For aluminum oxide, the structures of the anions and neutrals were explored and for silicon, germanium and indium phosphide the electronic structure of larger clusters was mapped out.

  16. 2H2O O2 + 4H+ + 4e b H2O OH + H+

    E-Print Network [OSTI]

    Hendry, Andrew

    2 R2 R2 Ruthenium 'blue dimer' + Figure 1 | Catalytic water oxidation. Photosynthesis is fuelled by the conversion of water into oxygen and hydrogen. a, In the first part of this process, known as water oxidation, water is converted into oxygen, four protons (H+ ) and four electrons (e­ ). b, Oxidation by the removal

  17. A BRIEF HISTORY OF INDUSTRIAL CATALYSIS

    E-Print Network [OSTI]

    Heinemann, Heinz

    2013-01-01

    Gasification In coal gasification there are two worthwhiledemonstrated. Many coal gasification plants are in operationCatalytic Coal Liquefaction and Gasification a) Liquefaction

  18. Nanoscale Advances in Catalysis and Energy Applications

    E-Print Network [OSTI]

    Li, Yimin

    2011-01-01

    Gratzel,  M. ,   Solar  energy  conversion  by  dye-­8,  51]   Solar  Energy  Conversion   Solar  energy   for  solar  energy   conversion.   Journal  of  

  19. A BRIEF HISTORY OF INDUSTRIAL CATALYSIS

    E-Print Network [OSTI]

    Heinemann, Heinz

    2013-01-01

    Control XIII Cata XIV Fuel Cell XV The Profession of XVIanode and cathode of a fuel celL Hydrogen has been the mostindustrial applications Fuel cells were used in the Gemini

  20. A BRIEF HISTORY OF INDUSTRIAL CATALYSIS

    E-Print Network [OSTI]

    Heinemann, Heinz

    2013-01-01

    process technology is far greater in chemical and petrochemicalprocesses such as hydrotreating and hydrocrack.ing, and for petrochemical

  1. Method for producing catalysis from coal

    DOE Patents [OSTI]

    Farcasiu, Malvina (Pittsburgh, PA); Derbyshire, Frank (Lexington, KY); Kaufman, Phillip B. (Library, PA); Jagtoyen, Marit (Lexington, KY)

    1998-01-01

    A method for producing catalysts from coal is provided comprising mixing an aqueous alkali solution with the coal, heating the aqueous mixture to treat the coal, drying the now-heated aqueous mixture, reheating the mixture to form carbonized material, cooling the mixture, removing excess alkali from the carbonized material, and recovering the carbonized material, wherein the entire process is carried out in controlled atmospheres, and the carbonized material is a hydrocracking or hydrodehalogenation catalyst for liquid phase reactions. The invention also provides for a one-step method for producing catalysts from coal comprising mixing an aqueous alkali solution with the coal to create a mixture, heating the aqueous mixture from an ambient temperature to a predetermined temperature at a predetermined rate, cooling the mixture, and washing the mixture to remove excess alkali from the treated and carbonized material, wherein the entire process is carried out in a controlled atmosphere.

  2. A BRIEF HISTORY OF INDUSTRIAL CATALYSIS

    E-Print Network [OSTI]

    Heinemann, Heinz

    2013-01-01

    Dealkylation Catalytic Coal Liquefaction and Gasification a)Liquefaction Gasification c) IX Methanation Heterogeneous~IQUEFACTION AND GASIFICATION a) Liquefaction Production of

  3. Catalysis using hydrous metal oxide ion exchangers

    DOE Patents [OSTI]

    Dosch, R.G.; Stephens, H.P.; Stohl, F.V.

    1983-07-21

    In a process which is catalyzed by a catalyst comprising an active metal on a carrier, said metal being active as a catalyst for the process, an improvement is provided wherein the catalyst is a hydrous, alkali metal or alkaline earth metal titanate, zirconate, niobate or tantalate wherein alkali or alkaline earth metal cations have been exchanged with a catalytically effective amount of cations of said metal.

  4. A BRIEF HISTORY OF INDUSTRIAL CATALYSIS

    E-Print Network [OSTI]

    Heinemann, Heinz

    2013-01-01

    there were supplies of n-butane which could be isomerized.as a catalytic liquid n~butane gas was passed; in the other,and ts: butadiene, 2) 1) butane lbenzene dehydro~~ genation

  5. Consequences of Confinement in Zeolite Acid Catalysis

    E-Print Network [OSTI]

    Gounder, Rajamani Pachayappan

    2011-01-01

    diameters of propane and n-butane. Scheme 3.5. MOR crystaldehydrogenation of propane, n-butane and isobutane. CHAPTERkJ mol -1 ] Propane n n-Butane n-P Pentane n-H Hexane Figure

  6. Two component-three dimensional catalysis

    DOE Patents [OSTI]

    Schwartz, Michael (Boulder, CO); White, James H. (Boulder, CO); Sammells, Anthony F. (Boulder, CO)

    2002-01-01

    This invention relates to catalytic reactor membranes having a gas-impermeable membrane for transport of oxygen anions. The membrane has an oxidation surface and a reduction surface. The membrane is coated on its oxidation surface with an adherent catalyst layer and is optionally coated on its reduction surface with a catalyst that promotes reduction of an oxygen-containing species (e.g., O.sub.2, NO.sub.2, SO.sub.2, etc.) to generate oxygen anions on the membrane. The reactor has an oxidation zone and a reduction zone separated by the membrane. A component of an oxygen containing gas in the reduction zone is reduced at the membrane and a reduced species in a reactant gas in the oxidation zone of the reactor is oxidized. The reactor optionally contains a three-dimensional catalyst in the oxidation zone. The adherent catalyst layer and the three-dimensional catalyst are selected to promote a desired oxidation reaction, particularly a partial oxidation of a hydrocarbon.

  7. Biochemical Conversion: Using Hydrolysis, Fermentation, and Catalysis...

    Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site

    hydrolyze the cellulose and hemicellulose in biomass to free the sugars for conversion. The program is working to identify the most productive, naturally occurring...

  8. A microreactor sample environment for catalysis research

    E-Print Network [OSTI]

    Crowther, Paul

    opportunity for industrial researchers to develop new, challenging materials for energy, chemistry materials. In many cases, exploring the relationship between the structure of a new material and its thereby aiding the development of new materials. For further information please contact the Diamond

  9. A BRIEF HISTORY OF INDUSTRIAL CATALYSIS

    E-Print Network [OSTI]

    Heinemann, Heinz

    2013-01-01

    Oil and Esso, are more severe; pressures range up to 2000 psig are as lowOil Phase Isomeration Process" (MVPI) and tn 1978 the "Mobil Low Pressure

  10. A BRIEF HISTORY OF INDUSTRIAL CATALYSIS

    E-Print Network [OSTI]

    Heinemann, Heinz

    2013-01-01

    b) Isomerization Hydrocracking v VI VII VIII Hydrogenationinto zeolite~cracking hydrocracking catalysts will besome paraffins and also hydrocracking some paraffins. The

  11. N-heterocyclic carbene catalysis: expansion of 

    E-Print Network [OSTI]

    Ogle, James William

    2009-05-15

    Scheme 1.3. Feringa?s total synthesis of Lardolure????????????? 8 Scheme 1.4. Synthesis of some 1,2-dialkyl fragments???????????? 9 Scheme 1.5. Asymmetric hydrogenation of ?-trocotrienyl acetate by Pfaltz???. 12 Scheme 2.1. Monoene... electrophiles, which tended to give the 1,4-syn product as the predominant stereoisomer (Diagram 1.2). Also, his development and use of lithium ammonium borate (LAB) as a reducing agent for amides to alcohols gave a protocol to generate either stereocenter...

  12. Consequences of Confinement in Zeolite Acid Catalysis

    E-Print Network [OSTI]

    Gounder, Rajamani Pachayappan

    2011-01-01

    of monomolecular propane cracking-to- dehydrogenation rate3.4. Kinetic diameters of propane and n-butane. Scheme 3.5.Intrinsic rate constant for propane cracking, k int on H-

  13. A BRIEF HISTORY OF INDUSTRIAL CATALYSIS

    E-Print Network [OSTI]

    Heinemann, Heinz

    2013-01-01

    of gasoline from a barrel of crude oil and results in theestimated that savings of crude oil alone by this improvedtheir yield-per-barrel of crude oil. In both cases, the pour

  14. Basic Research Needs: Catalysis for Energy

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    with heretofore unprecedented detail. Examples of new computational methods include optimization of structures determined experimentally by diffraction scattering based on...

  15. A BRIEF HISTORY OF INDUSTRIAL CATALYSIS

    E-Print Network [OSTI]

    Heinemann, Heinz

    2013-01-01

    R. H. , and Boyer, R. F. Styrene. Reinhold Publishing co. ,AMMOXIDATION) LO STYRENE { DEHYDROGENATION) HYDROGENATIONSlbenzene dehydro~~ genation to styrene monomero Butane

  16. Consequences of Confinement in Zeolite Acid Catalysis

    E-Print Network [OSTI]

    Gounder, Rajamani Pachayappan

    2011-01-01

    sta ate stabilizat tion energie es (E stab ) (S Scheme 3.1bmeasured activ vation energie s (E meas ) and e entropies (?Measured acti ivation energie es (E meas ) for monomolecular

  17. SOUTHWEST CATALYSIS SOCIETY 2008 SPRING SYMPOSIUM

    E-Print Network [OSTI]

    Natelson, Douglas

    for registration (membership due included). Group registration can be accommodated on-site; the group, Micromeritics) 10:05 AM Gary Gildert (Custom Catalytic Solution Inc., La Porte, TX) The Seven Steps

  18. Nanomaterials Engineering and Applications in Catalysis

    E-Print Network [OSTI]

    Zhang, Qiao

    2012-01-01

    75 Although direct photocatalysis utilizing such plasmoniclittle investigated. In photocatalysis research, anatase TiOthe perspective of photocatalysis, there are also several

  19. The impact of nanoscience on heterogeneous catalysis

    SciTech Connect (OSTI)

    Bell, Alexis T.

    2003-03-03

    Most catalysts consist of nanometer-sized particles dispersed on a high-surface area support. Advances in characterization methods have led to a molecular level understanding of the relationships between nanoparticle properties and catalytic performance. Together with novel approaches to nanoparticle synthesis, this knowledge is contributing to the design and development of new catalysts.

  20. SOUTHWEST CATALYSIS SOCIETY 2005 SPRING SYMPOSIUM

    E-Print Network [OSTI]

    Natelson, Douglas

    of Carbides and Nitrides" 9:35 AM Dr. Ed Sughrue, ConocoPhillips, Bartsville, OK "Chemistry-Aided Design of Future Clean Fuels" 10:05 AM Coffee Break (Micromeritics Inc., GA) 10:15 AM Professor Wayne Goodman

  1. BERKELEY CATALYSIS CENTER March 29, 2005

    E-Print Network [OSTI]

    Iglesia, Enrique

    /microchannel plates or microchannel cermets. For a given fuel (natural gas, isooctane, decane, gasoline) and a type), the composition of the active component and support properties are tuned. At operation temperatures in the range of 800-1100 oC and short contact times, catalysts ensure the equilibrium composition of reformate being

  2. A BRIEF HISTORY OF INDUSTRIAL CATALYSIS

    E-Print Network [OSTI]

    Heinemann, Heinz

    2013-01-01

    from methane, naphtha, heavy oil, and coal has achievedare suspended in a heavy oil. High-per-pass conversions (95%the catalytic cracking of heavy gas oils can be saturated,

  3. A BRIEF HISTORY OF INDUSTRIAL CATALYSIS

    E-Print Network [OSTI]

    Heinemann, Heinz

    2013-01-01

    this by ion exchanging rare earth metals for alkali meta lChlorides of rare earths and alkali metals often serve as

  4. BERKELEY CATALYSIS CENTER Distinguished Lecture Series

    E-Print Network [OSTI]

    Iglesia, Enrique

    to Commercialization and Back ABSTRACT: The November 2002 start-up of a 1.4-MW Kawasaki gas turbine with a Xonon-M1A-13X engine contains two foil monoliths coated with supported palladium oxide catalyst downstream exhibit many phenomena that are of academic interest and that represent practical engineering challenges

  5. A BRIEF HISTORY OF INDUSTRIAL CATALYSIS

    E-Print Network [OSTI]

    Heinemann, Heinz

    2013-01-01

    Aniline Cyclohexane BUTADIENE rr:ABLE C MAJOE AI:'PLICA!and acetylenes, such as butadiene, , and removed 'These mustto butenes and ts: butadiene, 2) 1) butane lbenzene dehydro~

  6. BERKELEY CATALYSIS CENTER November 11, 2005

    E-Print Network [OSTI]

    Iglesia, Enrique

    of carbon monoxide, hydrocarbons and nitric oxides emitted from the gasoline internal combustion engine has in fuel cells and hydrogen generation research. Most major automobile companies are demonstrating fuel

  7. BERKELEY CATALYSIS CENTER Distinguished Lecture Series

    E-Print Network [OSTI]

    Iglesia, Enrique

    is a subject of great practical importance in the chemical and petrochemical industry. Porous materials propane (CHA) and carbon dioxide from methane (DDR). These separations are of great practical importance

  8. SOUTHWEST CATALYSIS SOCIETY 2006 SPRING SYMPOSIUM

    E-Print Network [OSTI]

    Natelson, Douglas

    XIAO TOTAL PETROCHEMICALS USA, INC. RESEARCH & TECHNOLOGY CENTER Deer Park, TX 77536 (281) 884 in Methane Reactions Catalyzed by Supported Metal Clusters" 8:50 AM Dr. Jon G. McCarty, Catalytica Energy

  9. Workshop: Synchrotron Applications in Chemical Catalysis | Stanford

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative Fuels Data Center Homesum_a_epg0_fpd_mmcf_m.xls" ,"Available from WebQuantity ofkandz-cm11 Outreach Home RoomPreservationBio-Inspired SolarAbout /Two0PhotosPresentations Workshop

  10. Catalysis Working Group | Department of Energy

    Broader source: Energy.gov (indexed) [DOE]

    AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative Fuels Data Center Homesum_a_epg0_fpd_mmcf_m.xls" ,"Available from WebQuantity of Natural GasAdjustmentsShirleyEnergyTher i n c i p a lCarib Energy (USA)civilEnergy Watertimeplan proposes

  11. Pressure dependence of the exchange interaction in the dimeric single-molecule magnet [Mn{sub 4}O{sub 3}Cl{sub 4}(O{sub 2}CEt){sub 3}(py){sub 3}]{sub 2} from inelastic neutron scattering

    SciTech Connect (OSTI)

    Sieber, A.; Waldmann, O.; Ochsenbein, S. T.; Carver, G.; Guedel, H. U.; Foguet-Albiol, D.; Christou, G.; Mutka, H.; Fernandez-Alonso, F.; Mezouar, M.; Weber, H. P.

    2006-07-01

    The low-lying magnetic excitations in the dimers of single-molecule magnets [Mn{sub 4}O{sub 3}Cl{sub 4}(O{sub 2}CEt){sub 3}(py){sub 3}]{sub 2}, or (Mn{sub 4}){sub 2}, are studied by inelastic neutron scattering as a function of hydrostatic pressure. The anisotropy parameters D and B{sub 0}{sup 4}, which describe each Mn{sub 4} subunit, are essentially pressure independent, while the antiferromagnetic exchange coupling J between the two Mn{sub 4} subunits strongly depends on pressure, with an increase of 42% at 17 kbar. Additional pressure-dependent powder x-ray measurements allow a structural interpretation of the findings.

  12. Highly Efficient Acyclic Diene Metathesis Depolymerization Using a Ruthenium

    E-Print Network [OSTI]

    *, Departments of Chemistry and Polymer Science and Engineering, University of Massachusetts, Amherst, Amherst and recycling of these materials, is also demonstrated. The metathetical degradation of unsaturated poly- mers olefins to the investigation of linear polymer microstructure. For example, the distribution of 1,2 and 1

  13. Size Effect of Ruthenium Nanoparticles in Catalytic Carbon Monoxide Oxidation

    E-Print Network [OSTI]

    Joo, Sang Hoon

    2011-01-01

    sensitivity The catalytic oxidation of carbon monoxide (CO)stabilizer. The catalytic activity of CO oxidation overintriguing catalytic behavior for CO oxidation 5-15 ; while

  14. Selective Lability of Ruthenium(II) Arene Amino Acid Complexes

    E-Print Network [OSTI]

    Scrase, Tom G.; O’Neill, Michael J.; Peel, Andrew J.; Senior, Paul W.; Matthews, Peter D.; Shi, Heyao; Boss, Sally R.; Barker, Paul D.

    2015-02-16

    methionine molecule. Further, we believe that this result indicates that the car-boxylate residue (rather than an amine ligand) has been displaced from the metal. Displacement of an amine ligand would yield an ammonium group whose presence would be detected... the Spectrum software package. DFT calculations were performed using the Gaussian09 package. 20 After trialing several different methods (see SI), we settled on using the B3LYP hybrid functional and the LANL2DZ basis set for Ru and the 6-31G(d,p) basis set...

  15. PLATINUM-GROUP METALS (Platinum, palladium, rhodium, ruthenium, iridium, osmium)

    E-Print Network [OSTI]

    Africa, 59%; United Kingdom,14%; Russia, 9%; Germany, 5%; and other, 13%. Palladium: Russia, 48%; South the ore body, about 18,500 feet from the portal entrance, by the end of 1999. A second TBM also began

  16. Electrooxidation of Alcohols Catalyzed by Amino Alcohol Ligated Ruthenium Complexes

    E-Print Network [OSTI]

    Zare, Richard N.

    Alcohols are attractive chemical fuels for fuel cells due to their high energy densities, established, even the most highly optimized alcohol electrooxidation catalysts suffer from kinetic limitations

  17. Thermoelectric Properties of Rare-Earth-Ruthenium-Germanium Compounds |

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative Fuels Data Center Homesum_a_epg0_fpd_mmcf_m.xls" ,"Available from WebQuantity ofkandz-cm11 Outreach Home RoomPreservationBio-Inspired Solar FuelTechnologyTel: Name:Departmentand inreceiver survey

  18. Ruthenium on Carbon Nanostructures for Supercapacitor Electrodes - Energy

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative Fuels Data Center Homesum_a_epg0_fpd_mmcf_m.xls" ,"Available from WebQuantityBonneville Power AdministrationRobust, High-Throughput Analysis of Protein StructuresMaintenance / AP SpearRunningInnovation

  19. Selective deposition of nanostructured ruthenium oxide using Tobacco mosaic

    Office of Scientific and Technical Information (OSTI)

    AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative Fuels Data Center Homesum_a_epg0_fpd_mmcf_m.xls" ,"Available from WebQuantity of NaturalDukeWakefieldSulfateSciTechtail. (Conference) |Janka,Ferrara U./INFN,TaÅŸ,Superconductors (Conference) |Seeking

  20. Frontiers in Catalysis Science and Engineering Seminar Series

    E-Print Network [OSTI]

    (JCAP) Abstract JCAP's mission is to build fully integrated solar-fuels generators that utilize earth Manufacturable Solar-Fuels Generators Presented by... Carl A. Koval ·Joint Center for Artificial Photosynthesis operating conditions. JCAP's long-term goal is to develop a commercially viable, solar-generation technology

  1. Enantioselective nickel catalysis : exploiting activated C-H bonds

    E-Print Network [OSTI]

    Bencivenga, Nicholas Ernest

    2012-01-01

    A method for the nickel-catalyzed cross-coupling between benzoxazole and secondary halides was explored. This method was to make use of the activated C-H bond found in benzoxazole at the 2-position to generate the nucleophilic ...

  2. Thermochemical Conversion: Using Heat and Catalysis to Make Biofuels...

    Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site

    facilities, improving energy security and resilience. Integration in Traditional Refineries Successfully integrating biomass product streams for further processing in...

  3. Catalysis of 6? Electrocyclizations & Catalytic Disproportionation of Lignin Model Compounds

    E-Print Network [OSTI]

    Bishop, Lee

    2010-01-01

    of the thermal and catalyzed reactions gave activationfor the thermal reaction reveals activation parameters2. Activation parameters of the thermal and catalyzed (2

  4. From palladium to iron: towards more sustainable catalysis 

    E-Print Network [OSTI]

    Jones, Alison Sarah

    2015-06-30

    The construction of bonds in a controlled and selective manner and the development of operationally simple, general and reliable methods to achieve these aims remains a key goal of chemical synthesis and the countless ...

  5. Phase selectively soluble polymer supports to facilitate homogeneous catalysis 

    E-Print Network [OSTI]

    Ortiz-Acosta, Denisse

    2009-05-15

    and selectivity, and they often allow the use of mild reaction conditions. However, the metals used in the catalytic reactions most popular in organic synthesis like palladium, rhodium, and platinum are generally very expensive. The organic ligands...

  6. Temperature Transient Effects in Plasma-Catalysis | Department...

    Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site

    More Documents & Publications Dynamometer Evaluation of Plasma-Catalyst for Diesel NOx Reduction A Parametric Study of the Effect of Temperature and Hydrocarbon Species on...

  7. Pre-Competitive Catalysis Research: Fundamental Sulfation/Desulfation...

    Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site

    & Publications Emissions Control for Lean Gasoline Engines Functionality of Commercial NOx Storage-Reduction Catalysts and the Development of a Representative Model CLEERS...

  8. Frontiers in Catalysis Science and Engineering Seminar Series

    E-Print Network [OSTI]

    Catalysts for the Selective Catalytic Reduction of NOx Presented by... Prof. Raul F. Lobo University oxides (NOx) are a major atmospheric pollutant produced through the combustion of fossil fuels in internal combustion engines and power plants. Copper-exchanged promising as selective catalytic reduction

  9. Fundamental Studies in Catalysis Enabled the use of Efficient...

    Office of Environmental Management (EM)

    The same research program also advanced the foundational understanding of catalyst structures and reactions, leading among other things to a 2009 publication in Science. The...

  10. Enzyme Catalysis DOI: 10.1002/anie.200502903

    E-Print Network [OSTI]

    Zhao, Huimin

    one of only two known examples of aryl- amine oxidases or N-oxygenases involved in the formation and Biomolecular Engineering University of Illinois at Urbana-Champaign 600 S. Mathews Ave., Urbana, IL 61801 (USA

  11. Nanostructured transition metal oxides useful for water oxidation catalysis

    DOE Patents [OSTI]

    Frei, Heinz M; Jiao, Feng

    2013-12-24

    The present invention provides for a composition comprising a nanostructured transition metal oxide capable of oxidizing two H.sub.2O molecules to obtain four protons. In some embodiments of the invention, the composition further comprises a porous matrix wherein the nanocluster of the transition metal oxide is embedded on and/or in the porous matrix.

  12. ALS X-Rays Shine a New Light on Catalysis

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    times science has used high-brilliance x-rays to look so closely at these reactions. Lead author Dr. David Mueller at the ALS using x-rays to characterize working fuel cells....

  13. Catalysis of 6? Electrocyclizations & Catalytic Disproportionation of Lignin Model Compounds

    E-Print Network [OSTI]

    Bishop, Lee

    2010-01-01

    protodestannylated 1-phenyl-1,3-butadiene. Tin impurities1-phenyl-2- methyl-1,3-butadiene. As no conditions could be4-iodo-2-methyl-1-phenyl-1,3-butadiene (5.5). This material

  14. Biomimetic C-H Oxidation Catalysis in Aqueous Solution

    E-Print Network [OSTI]

    Djernes, Katherine Elizabeth

    2013-01-01

    Y. ; Breslow, R. "Catalytic Oxidations of Steroid Substratesapplicable catalytic methods for hydrocarbon oxidation haveof hydrocarbon oxidation catalysts 1.7 and 1.8 The catalytic

  15. Charge Transfer and Catalysis at the Metal-Support Interface

    E-Print Network [OSTI]

    Baker, Lawrence Robert

    2012-01-01

    Support for Platinum in the Catalytic Oxidation of Carboncertain instances, catalytic oxidation reactions proceed byenhances the rate of catalytic oxidation while a flux of

  16. Catalysis of 6? Electrocyclizations & Catalytic Disproportionation of Lignin Model Compounds

    E-Print Network [OSTI]

    Bishop, Lee

    2010-01-01

    catalytic reductions, and catalytic oxidations. 13 The high-processes for the catalytic oxidation of lignin has focusedand paper industry. Catalytic oxidation is of less interest

  17. Charge Transfer and Support Effects in Heterogeneous Catalysis

    E-Print Network [OSTI]

    Hervier, Antoine

    2012-01-01

    Support  for  Platinum in the Catalytic Oxidation of Carbon in  Hydrogen  and  Deuterium  Oxidation  on  Catalytic Platinum in  the Catalytic Oxidation of Carbon  Monoxide   

  18. Low-Temperature Hydrocarbon/CO Oxidation Catalysis in Support...

    Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site

    Annual Merit Review and Peer Evaluation Meeting, May 18-22, 2009 -- Washington D.C. acep03rappe.pdf More Documents & Publications Low-Temperature HydrocarbonCO Oxidation...

  19. Frontiers in Catalysis Science and Engineering Seminar Series

    E-Print Network [OSTI]

    Abstract The (CH2O)n stoichiometry of biomass implies that its conversion to energy carriers and other://research.cems.umn.edu/bhan/ Catalytic science will play a critical role in developing alternative energy sources and new conversion of this challenge by efficiently controlling hydrocarbon-based reaction pathways important in energy conversion

  20. Frontiers in Catalysis Science and Engineering Seminar Series

    E-Print Network [OSTI]

    Institute Department of Chemical Engineering Abstract The considerable interest in molecule-based models. Solution of this chemical reaction network, in the context of the chemical reactor, provides a prediction

  1. Synthesis of Donor Ligands and Their Applications in Catalysis

    E-Print Network [OSTI]

    DeHope, Alan

    2010-01-01

    R. ; Mertwoy, H. , E. Chemical Abstracts 1965, 63, 18147; b)American Chemical Society vi ABSTRACT OF THE DISSERTATION

  2. Hangman Catalysis for Photo- and Photoelectro- Chemical Activation of Water

    SciTech Connect (OSTI)

    Nocera, Daniel

    2014-04-15

    The focus of this DOE program is solar fuels – specifically the chemistry for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) from water and the oxygen reduction reaction (ORR) to water These three reactions are at the heart of renewable energy conversion. The bond-making and bond-breaking chemistry that underpins these transformations is not well understood. We are developing insight into such chemistry by creating a series of ligand constructs that poise an acid-base functionality over a redox active metal platform. These “hangman” ligands utilize the acid-base functionality to form a secondary coordination sphere that can assist proton movement and facilitate substrate assembly and activation within the molecular cleft. The grant period funding cycle focused on synthesis and reactivity of hangman porphyrins and corroles for HER, OER and ORR.

  3. Technology Development for Iron Fischer-Tropsch Catalysis.

    SciTech Connect (OSTI)

    Davis, B.H.

    1997-12-16

    The goal of the proposed work is the development of iron-based Fischer-Tropsch catalysts that combined high activity, selectivity and life with physical robustness for slurry phase reactors that will produce either low-alpha or high-alpha products. The catalyst that is developed will be suitable for testing at the Advanced Fuels Development Facility at LaPorte, Texas or similar sized plant. Previous work by the offeror has produced a catalyst formulation that is 1.5 times as active as the `standard-catalyst` developed by German workers for slurry phase synthesis. The proposed work will optimize the catalyst composition and pretreatment operation for this low-alpha catalyst. In parallel, work will be conducted to design a high-alpha iron catalyst that is suitable for slurry phase synthesis. Studies will be conducted to define the chemical phases present at various stages of the pretreatment and synthesis stages and to define the course of these changes. The oxidation/reduction cycles that are anticipated to occur in large, commercial reactors will be studied at the laboratory scale. Catalyst performance will be determined for catalysts synthesized in this program for activity, selectivity and aging characteristics.

  4. Theoretical Study on Catalysis by Protein Enzymes and Ribozyme

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    Publications P. D. Lyne and M. Karplus, "Determination of the pKa of the 2'-hydroxyl group at the active site of hammerhead ribozyme from ab initio calculations with...

  5. Thermochemical Conversion: Using Heat and Catalysis to Make Biofuels...

    Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site

    & Publications BETO Conversion Program Replacing the Whole BarrelTo Reduce U.S. Dependence on Oil Bioenergy Technologies Office R&D Pathways: Ex-Situ Catalytic Fast Pyrolysis...

  6. Role of adsorption in catalysis: applications of NMR relaxometry

    E-Print Network [OSTI]

    Arias Vecino, Pablo

    2015-06-09

    , the performance of the diesel oxidation Chapter 1 Introduction 9 catalyst (DOC) to reduce CO and hydrocarbon emissions is affected by the presence of NOx from the exhaust engine, due to competitive adsorption (Al-Harbi et al., 2012). 1.1.3.1 Volcano plots...

  7. Reduced ternary molybdenum and tungsten sulfides and hydroprocessing catalysis therewith

    DOE Patents [OSTI]

    Hilsenbeck, S.J.; McCarley, R.E.; Schrader, G.L.; Xie, X.B.

    1999-02-16

    New amorphous molybdenum/tungsten sulfides with the general formula M{sup n+}{sub 2x/n}(L{sub 6}S{sub 8})S{sub x}, where L is molybdenum or tungsten and M is a ternary metal, has been developed. Characterization of these amorphous materials by chemical and spectroscopic methods (IR, Raman, PES) shows that the (M{sub 6}S{sub 8}){sup 0} cluster units are present. Vacuum thermolysis of the amorphous Na{sub 2x}(Mo{sub 6}S{sub 8})S{sub x}{hor_ellipsis}yMeOH first produces poorly crystalline NaMo{sub 6}S{sub 8} by disproportionation at 800 C and well-crystallized NaMo{sub 6}S{sub 8} at {>=} 900 C. Ion-exchange of the sodium material in methanol with soluble M{sup 2+} and M{sup 3+} salts (M=Sn, Co, Ni, Pb, La, Ho) produces the M{sup n+}{sub 2x/n}(Mo{sub 6}S{sub 8})S{sub x}{hor_ellipsis}yMeOH compounds. Additionally, the new reduced ternary molybdenum sulfides with the general formula M{sup n+}{sub 2x/n}Mo{sub 6}S{sub 8+x}(MeOH){sub y}[MMOS] (M=Sn, Co, Ni) is an effective hydrodesulfurization (HDS) catalyst both as-prepared and after a variety of pretreatment conditions. Under specified pretreatment conditions with flowing hydrogen gas, the SnMoS type catalyst can be stabilized, and while still amorphous, can be considered as ``Chevrel phase-like`` in that both contain Mo{sub 6}S{sub 8} cluster units. Furthermore, the small cation NiMoS and CoMoS type pretreated catalyst is shown to be very active HDS catalysts with rates that exceeded the model unpromoted and cobalt-promoted MoS{sub 2} catalysts. 9 figs.

  8. FIRST BERKELEY CATALYSIS AND SURFACE SCIENCE CONFERENCE JULY 1980

    E-Print Network [OSTI]

    Authors, Various

    2013-01-01

    reduced the volume of crude oil that had to be refined tooil prices, a dwindling supply of indigenous petroleum crude, and

  9. Progress in transition metal-based enantioselective catalysis

    E-Print Network [OSTI]

    Arp, Forrest O

    2008-01-01

    In Chapter 1, the first enantioselective cross-coupling reactions of racemic secondary benzylic halides are described (eq 1). This method was applied to the syntheses of intermediates employed by other groups in the ...

  10. Materials with supramolecular chirality : liqid crystals and polymers for catalysis

    E-Print Network [OSTI]

    Martin, Karen Villazor

    2005-01-01

    Mesomorphic organizations provide a powerful and efficient method for the preorganization of molecules to create synthetic materials with controlled supramolecular architectures. Incorporation of polymerizable groups within ...

  11. JOURNAL OF CATALYSIS 179, 192202 (1998) ARTICLE NO. CA982177

    E-Print Network [OSTI]

    Iglesia, Enrique

    1998-01-01

    to form light alkanes. Many groups have examined the catalytic role of these Zn species during light were separated from the solution by filtering. The exchange procedure was repeated three times using 0.07 wt% by atomic absorption analysis. Catalyst samples were then dried in flowing air at 383 K

  12. Neutron Catalysis of Resonance Fusion in Stellar Matter

    E-Print Network [OSTI]

    Nurgali Takibayev

    2005-08-22

    Within the framework of resonance fusion study in stellar matter the features of system consisted of two alpha particles and one neutron have been investigated at astrophysical energies. Consideration of three body scattering has been carried out on base of well-known Faddeev's equations. It is found that under certain conditions the series of resonance states appear in this system at very low energies. The lifetimes of these three body resonances are close to the lifetime of unstable nucleus 8Be. The simple forms of two body repulsive potentials are taken into account to describe the parameters of the alpha, alpha resonance and to satisfy n, alpha scattering data at very low energies. The explanation of resonance phenomena in n, alpha, alpha system is offered on base of physical model. The effect results from resonance quantum phenomena in few body dynamics. In turn, the resonance fusion can give influence on many astrophysical phenomena. The possibility of catalyzing this new mode of fusion by free neutrons in alpha particle matter is considered too.

  13. Frontiers in Catalysis Science and Engineering Materials Science

    E-Print Network [OSTI]

    -controlled metal nanocrystals, and applied them to the systematic investigation of catalytic processes for steam reforming of alcohols and the oxidation of carbon monoxide on nanoscale facets. Aberration- corrected

  14. Microwaves and Chemistry: The Catalysis of an Exciting Marriage 

    E-Print Network [OSTI]

    Wan, J.

    1992-01-01

    hydrocarbon oxidations to environmental technology will be illustrated. BACKGROUND The concept of using microwaves as an energy source for chemical reactions has only recently been appreciated. Part of the reason for this has been the bias of chemists... our first major success in cracking methane to ethylene and hydrogen [1,2], lhe destruction of chlorinated hydrocarbons [3,4], the hydrodesulfurization of hydrocracked pitch [5], and the microwave treatment of some Alberta oil sands and bitumens...

  15. Method for producing high surface area chromia materials for catalysis

    DOE Patents [OSTI]

    Gash, Alexander E. (Brentwood, CA); Satcher, Joe (Patterson, CA); Tillotson, Thomas (Tracy, CA); Hrubesh, Lawrence (Pleasanton, CA); Simpson, Randall (Livermore, CA)

    2007-05-01

    Nanostructured chromium(III)-oxide-based materials using sol-gel processing and a synthetic route for producing such materials are disclosed herein. Monolithic aerogels and xerogels having surface areas between 150 m.sup.2/g and 520 m.sup.2/g have been produced. The synthetic method employs the use of stable and inexpensive hydrated-chromium(III) inorganic salts and common solvents such as water, ethanol, methanol, 1-propanol, t-butanol, 2-ethoxy ethanol, and ethylene glycol, DMSO, and dimethyl formamide. The synthesis involves the dissolution of the metal salt in a solvent followed by an addition of a proton scavenger, such as an epoxide, which induces gel formation in a timely manner. Both critical point (supercritical extraction) and atmospheric (low temperature evaporation) drying may be employed to produce monolithic aerogels and xerogels, respectively.

  16. ALS X-Rays Shine a New Light on Catalysis

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    ALS in a novel way to observe the behavior of electrons during technologically important chemical reactions in metal oxide electrocatalysts. What they learned has upended...

  17. Catalysis by Design: Bridging the Gap between Theory and Experiments

    Broader source: Energy.gov [DOE]

    Poster presentation at the 2007 Diesel Engine-Efficiency & Emissions Research Conference (DEER 2007). 13-16 August, 2007, Detroit, Michigan. Sponsored by the U.S. Department of Energy's (DOE) Office of FreedomCAR and Vehicle Technologies (OFCVT).

  18. Supporting information for: Asymmetric catalysis at the mesoscale: Gold nanoclusters

    E-Print Network [OSTI]

    . Immobilization of quinine 3 on MCF-17: 1. Propargylation of quinine: 250 mg of quinine were dissolved in 2.5 m

  19. ALS X-Rays Shine a New Light on Catalysis

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    were able to directly observe redox processes in thin-film iron and cobalt perovskite oxide electrocatalysts using surface-sensitive, x-ray absorption spectroscopy while...

  20. Conformational Entropy in PEPCK Catalysis: Dynamic Motions Critical to Function

    E-Print Network [OSTI]

    Johnson, Troy A.

    2011-12-31

    studies carried out on rodents. For this reason what is known in detail, about the expression and regulation, is limited to the cytosolic isoform of PEPCK (10). Cytosolic PEPCK is expressed in liver, the major organ for gluconeogenesis, but it has also..., triglyceride biosynthesis, and serine synthesis (Figure 1-1) (reviewed in (9)). PEPCK participates in glucose homeostasis by catalyzing the first committed step of the gluconeogenesis pathway. This role for PEPCK explains its presence in the liver and kidney...

  1. Synthesis of Donor Ligands and Their Applications in Catalysis

    E-Print Network [OSTI]

    DeHope, Alan

    2010-01-01

    and -0.525 e.Å-3 Table S2. Atomic coordinates ( x 104) andand -0.349 e.Å-3 Table 2. Atomic coordinates ( x 104) andand -0.541 e.Å-3 Table S2. Atomic coordinates ( x 104) and

  2. Computational Studies of Organic, Organometallic, and Enzyme Catalysis

    E-Print Network [OSTI]

    Noey, Elizabeth Lynn

    2015-01-01

    d,p) with CPCM water single point energies on TPSS/6-31G(d)14c TS14-15 15a water ?G ?H ?G ?H Energies are calculatedsingle point energies were calculated with CPCM water or ? =

  3. Asymmetric Catalysis DOI: 10.1002/anie.200601501

    E-Print Network [OSTI]

    Zhang, Xumu

    at the 3,3'-positions.[7] Inspired by the success of many hybrid C1- symmetric chelating ligands,[8] we of the methoxy methyl (MOM) groups of 2 in HCl/ MeOH, the desired product 1 was prepared by heating 3 of several standard a-aryl enamides. Initial studies on the [Rh/1a] system using the benchmark substrate 4a

  4. Technology development for iron fisher-tropsch catalysis

    SciTech Connect (OSTI)

    Davis, B.H.

    1997-07-15

    The goal of the proposed work is the development of iron-based Fischer-Tropsch catalysts that combined high activity, selectivity and life with physical robustness for slurry phase reactors that will produce either low-alpha or high-alpha products. the catalyst that is developed will be suitable for testing at the Advanced Fuels Development Facility at LaPorte, Texas or similar sized plant. Previous work by the offeror has produced a catalyst formulation that is 1.5 times as active as the standard-catalyst developed by German workers for slurry phase synthesis, The proposed work will optimize the catalyst composition and pretreatment operation for this low-alpha catalyst. In parallel, work will be conducted to design a high-alpha iron catalyst that is suitable for slurry phase synthesis. Studies will be conducted to define the chemical phases present at various stages of the pretreatment and synthesis stages and to define the course of these changes. the oxidation/reduction cycles that are anticipated to occur in large, commercial reactors will be studies at the laboratory scale. Catalyst performance will be determined for catalysts synthesized in this program for activity, selectivity, and aging characteristics.

  5. Transmural Catalysis - High Efficiency Catalyst Systems for NOx...

    Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site

    Systems for NOx Adsorbers and SCR Presentation given at DEER 2006, August 20-24, 2006, Detroit, Michigan. Sponsored by the U.S. DOE's EERE FreedomCar and Fuel Partnership and 21st...

  6. BERKELEY CATALYSIS CENTER Monday, October 10, 2005 4 pm

    E-Print Network [OSTI]

    Iglesia, Enrique

    synthesis of sophisticated mixed ceramic and noble metal composite nanoparticles. These materials seemed, Au or Ag) on ceramic (TiO2, SiO2 and Al2O3) nanoparticles will be shown. For example, the open-ray absorbing matrix. The structural identification at such small concentration turned out to be important since

  7. Catalysis of 6? Electrocyclizations & Catalytic Disproportionation of Lignin Model Compounds

    E-Print Network [OSTI]

    Bishop, Lee

    2010-01-01

    The initial reaction velocity and initial concentration ofTable 4. Table 4. Initial reaction velocity of the catalyzedof the initial reaction velocity versus the logarithm of the

  8. Hybrid Porous Materials for Controlled Release and Catalysis

    E-Print Network [OSTI]

    Liu, Rui

    2010-01-01

    Catalytic Preparation of Biodiesel ? 7.1. Introduction Duepossible resources, biodiesel, a nonpetroleum-based fuels,solid acid catalysts for biodiesel synthesis based on

  9. BERKELEY CATALYSIS CENTER Friday, October 7, 2005 2 pm

    E-Print Network [OSTI]

    Iglesia, Enrique

    ,2] directed attention towards sulfated zirconia as a low-temperature alkane isomerization catalyst zirconia [4], but this claim could not be substantiated. The nature of the active sites in these catalysts and UV-vis spectroscopies [5-9]: 1)Calcination 2)Interaction between promoters and zirconia 3

  10. Heterogeneous Catalysis DOI: 10.1002/anie.200503898

    E-Print Network [OSTI]

    Iglesia, Enrique

    , as in the reactions of isobutane on sulfated zirconia[14] and tert-butyl alcohol[5,7,8] on acidic ZSM5, MOR, BEA of Chemical Engineering University of California at Berkeley Berkeley, CA 94720 (USA) Fax: (+1)510-642-4778 E

  11. Polyisobutylene as a Polymer Support for Homogeneous Catalysis 

    E-Print Network [OSTI]

    Hongfa, Chayanant

    2010-01-14

    , a Hoveyda-Grubbs 2nd generation catalyst, and a N-heterocyclic carbene. The syntheses of these PIB-supported ligands and catalysts are simple and straightforward. The synthetic products and the intermediates in these syntheses can all be readily...

  12. Homogeneous Catalysis Selective Oxidation of Methane to Methanol

    E-Print Network [OSTI]

    Goddard III, William A.

    formed when SO3 or persulfate (K2S2O8) were added as possible oxidants of metallic gold (entries 5 and 6 oxidizing agent than SVI ions (Eo = 1.5 V SeO4 2À /H2SeO3, Eo = 0.17 V SO4 2À /H2SO3, respec- tively) and

  13. Frontiers in Catalysis Science and Engineering Seminar Series

    E-Print Network [OSTI]

    . Sterically encumbered Lewis acid and base combinations do not form "classical" Lewis acid-base adducts. Rather, the unquenched Lewis acidity and basicity of such sterically "frustrated Lewis pairs (FLPs

  14. Frontiers in Catalysis Science and Engineering Seminar Series

    E-Print Network [OSTI]

    -Chemisches Institut ·Germany Abstract Frustrated Lewis Pairs (FLPs) are comprised of pairs of Lewis acids and Lewis or by electronic means. The simultaneous presence of active Lewis acids and bases in solution provides

  15. JOURNAL OF CATALYSIS 178, 499510 (1998) ARTICLE NO. CA982161

    E-Print Network [OSTI]

    Iglesia, Enrique

    1998-01-01

    . The dehydrogenation of ethanol to acetaldehyde and the aldol condensation to n-butanol both in- volved the initial pair sites. Acetaldehyde condensation toward n-butanol is a bimolecular reaction between adjacent surface ethoxide formation on a Lewis acid­strong base pair. Pure MgO exhibited poor activity because

  16. Frontiers in Catalysis Science and Engineering Seminar Series

    E-Print Network [OSTI]

    the refining before condensation of the vapors occurs. Degradation by further reaction (oligomerization) occurs of short carbon fragments (C1-C3) into the aromatic ring of phenolic compounds; (c) deoxygenation

  17. The Interplay of Catalysis and Toxicity by Amyloid

    E-Print Network [OSTI]

    Miranker, Andrew

    Words IAPP, amylin, protein folding, -synuclein, A, mechanism Abstract The dynamics, energies, and structures governing protein folding are critical to biological function. Amyloidoses are a class of disease #12;Contents PROTEIN FOLDING DEFINED . . . 126 PROTEIN MISFOLDING AS A BASIS FOR DISEASE

  18. Catalysis of 6? Electrocyclizations & Catalytic Disproportionation of Lignin Model Compounds

    E-Print Network [OSTI]

    Bishop, Lee

    2010-01-01

    protodestannylated 1-phenyl-1,3-butadiene. Tin impurities1-phenyl-2- methyl-1,3-butadiene. As no conditions could be2-methyl-1-phenyl-1,3-butadiene (5.5). This material was

  19. Catalysis by Design - Theoretical and Experimental Studies of...

    Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site

    Detroit, Michigan. Sponsored by the U.S. DOE's EERE FreedomCar and Fuel Partnership and 21st Century Truck Programs. 2006deernarula.pdf More Documents & Publications Lean NOx...

  20. Role of acid catalysis in dimethyl ether conversion processes

    SciTech Connect (OSTI)

    Tartamella, T.L.; Lee, S.

    1996-12-31

    Acidity plays an important role in the conversion of methanol and dimethyl ether (DME) to hydrocarbons and oxygenates. In the conversion to hydrocarbons over zeolite catalyst, Broensted acidity is the main contributor to the first hydrocarbon formed. Here, acidity is also an important factor in determining olefin, paraffin, and aromatic content in the final product distribution. Catalyst life has also been found to be related to acidity content in zeolites. DME conversion to oxygenates is especially dependent on high acidity catalysts. Superacids like BF{sub 3}, HF-BF{sub 3}, and CF{sub 3}COOH have been used in the past for conversion of DME in carbonylation reactions to form methyl acetate and acetic acid at high pressures. Recently, heteropoly acids and their corresponding metal substituted salts have been used to convert DME to industrially important petrochemicals resulting in shorter reaction times and without the use of harsh operating conditions.

  1. Heterogeneous Catalysis DOI: 10.1002/anie.200900541

    E-Print Network [OSTI]

    Iglesia, Enrique

    ) is a valuable fuel additive with a research octane number of 112. It can be produced with high selectivity from methanol (or dimethyl ether (DME)) using solutions of Zn[1­4] or In[5,6] halides at approximately 473 K triptane molecule formed per ZnI2.[2] Acid-catalyzed homologation of meth- anol/DME also occurs on zeolites

  2. Control Heterogeneous Catalysis at Atomic and Electronic-level Using

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  3. ALS X-Rays Shine a New Light on Catalysis

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  4. ALS X-Rays Shine a New Light on Catalysis

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  5. ALS X-Rays Shine a New Light on Catalysis

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  6. ALS X-Rays Shine a New Light on Catalysis

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  7. Biomimetic Chalcogels for Solar Fuel Catalysis | ANSER Center |

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  8. University of Delaware | Catalysis Center for Energy Innovation | Aromatics

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  9. University of Delaware | Catalysis Center for Energy Innovation | Biomass

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  10. University of Delaware | Catalysis Center for Energy Innovation | Fuel

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  11. University of Delaware | Catalysis Center for Energy Innovation | Furans

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  12. University of Delaware | Catalysis Center for Energy Innovation | Materials

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  13. University of Delaware | Catalysis Center for Energy Innovation | Modeling

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  14. University of Delaware | Catalysis Center for Energy Innovation | Pyrolysis

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  15. ALS X-Rays Shine a New Light on Catalysis

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  16. ALS X-Rays Shine a New Light on Catalysis

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  18. Pre-Competitive Catalysis Research: Fundamental Sulfation/Desulfation

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  19. Catalysis Working Group Meeting: June 2014 | Department of Energy

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  20. Catalysis Working Group Meeting: May 2013 | Department of Energy

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  1. Biochemical Conversion: Using Hydrolysis, Fermentation, and Catalysis to

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  2. Rare-earth nanoparticles for catalysis | The Ames Laboratory

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  3. Catalysis Center for Energy Innovation KEY ACCOMPLISHMENTS AND CORE CAPABILITIES

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  4. Materials Design and Discovery: Catalysis and Energy Storage (Mira Early

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  6. Study of catalysis of coal gasification at elevated pressures. [Evaluation

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  7. Catalysis Center for Energy Innovation: University of Delaware

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  8. Catalysis Science | U.S. DOE Office of Science (SC)

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  9. Catalysis | U.S. DOE Office of Science (SC)

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  10. Integrated Mesoscale Architectures for Sustainable Catalysis (IMASC) | U.S.

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  11. Theoretical Study on Catalysis by Protein Enzymes and Ribozyme

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  12. Textured Metal Catalysts for Heterogeneous Catalysis - Energy Innovation

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  13. Electron Microscopy Catalysis Projects: Success Stories from the High

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  14. Thermochemical Conversion: Using Heat and Catalysis to Make Biofuels and

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  15. Iran Thomas Auditorium, 8600 Environmental Transmission Electron Microscopy for Catalysis

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  16. Iron Catalysis in Oxidations by Ozone - Energy Innovation Portal

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  17. Homogeneous and Interfacial Catalysis in 3D Controlled Environment | The

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  18. Fundamental Studies in Catalysis Enabled the use of Efficient

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  19. Shining Light on Catalysis | Stanford Synchrotron Radiation Lightsource

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  20. Anthraquinone-Imide-Based Dimers: Synthesis, Piezochromism, Liquid Crystalline,

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    Wan, Xin-hua

    -Infrared Electrochromic Properties Fengkun Chen, Jie Zhang, Xinhua Wan* Introduction Organic materials that respond-sensitive paints and shock detec- tors, for instance.[2] Since the early studies on piezochromic phenomena,[11­15] and poly(3-alkylthiophene),[16­21] inorganic metal complexes,[22,23] and some organic dyes.[24