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Title: Dependence of amine-accelerated silicate condensation on amine structure


Abstract not provided.

; ; ;
Publication Date:
Research Org.:
Sandia National Lab. (SNL-CA), Livermore, CA (United States)
Sponsoring Org.:
USDOE National Nuclear Security Administration (NNSA)
OSTI Identifier:
Report Number(s):
Journal ID: ISSN 0959-9428; JMACEP; 524298
DOE Contract Number:
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Materials Chemistry; Journal Volume: 17; Journal Issue: 20
Country of Publication:
United States

Citation Formats

Robinson, David B., Rognlien, Judith L., Bauer, Christina A., and Simmons, Blake A. Dependence of amine-accelerated silicate condensation on amine structure. United States: N. p., 2007. Web. doi:10.1039/B700514H.
Robinson, David B., Rognlien, Judith L., Bauer, Christina A., & Simmons, Blake A. Dependence of amine-accelerated silicate condensation on amine structure. United States. doi:10.1039/B700514H.
Robinson, David B., Rognlien, Judith L., Bauer, Christina A., and Simmons, Blake A. Mon . "Dependence of amine-accelerated silicate condensation on amine structure". United States. doi:10.1039/B700514H.
title = {Dependence of amine-accelerated silicate condensation on amine structure},
author = {Robinson, David B. and Rognlien, Judith L. and Bauer, Christina A. and Simmons, Blake A.},
abstractNote = {Abstract not provided.},
doi = {10.1039/B700514H},
journal = {Journal of Materials Chemistry},
number = 20,
volume = 17,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2007},
month = {Mon Jan 01 00:00:00 EST 2007}
  • No abstract prepared.
  • The source of the experimentally observed anomalous behavior of the first sharp diffraction peak (FSDP) in lithium silicate glasses was determined using classical molecular dynamics simulations. Partial structure factors obtained from simulations were used to investigate the sensitivity of the total structure factor to the scattering length of alkali ions. The result clearly establishes that the major difference of the FSDP between lithium and sodium disilicate glasses is due to the negative scattering length of lithium ions. Additionally, it was determined that the unusual intense FSDP in lithium silicate glass has little to do with differences of the medium-range structuremore » in these glasses.« less
  • Amorphous, astrophysically relevant silicates were prepared by laser ablation of siliceous targets and subsequent quenching of the evaporated atoms and clusters in a helium/oxygen gas atmosphere. The described gas-phase condensation method can be used to synthesize homogeneous and astrophysically relevant silicates with different compositions ranging from nonstoichiometric magnesium iron silicates to pyroxene- and olivine-type stoichiometry. Analytical tools have been used to characterize the morphology, composition, and spectral properties of the condensates. The nanometer-sized silicate condensates represent a new family of cosmic dust analogs that can generally be used for laboratory studies of cosmic processes related to condensation, processing, and destructionmore » of cosmic dust in different astrophysical environments. The well-characterized silicates comprising amorphous Mg{sub 2}SiO{sub 4} and Fe{sub 2}SiO{sub 4}, as well as the corresponding crystalline silicates forsterite and fayalite, produced by thermal annealing of the amorphous condensates, have been used as real grain surfaces for H{sub 2} formation experiments. A specifically developed ultra-high vacuum apparatus has been used for the investigation of molecule formation experiments. The results of these molecular formation experiments on differently structured Mg{sub 2}SiO{sub 4} and Fe{sub 2}SiO{sub 4} described in this paper will be the topic of the next paper of this series.« less
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  • The pH dependence of steady-state parameters for (1,1-1H2)- and (1,1-2H2)benzylamine oxidation and of tritium exchange from (2-/sup 3/H)dopamine has been measured in the bovine plasma amine oxidase reaction. Deuterium isotope effects on kcat/Km for benzylamine are observed to be constant, near the intrinsic value of 13.5, over the experimental pH range, indicating that C-H bond cleavage is fully rate limiting for this parameter. As a consequence, pKa values derived from kcat/Km profiles, 8.0 +/- 0.1 (pK1) and 9.0 +/- 0.16 (pKs), can be ascribed to microscopic pKa values for the ionization of an essential active site residue (EB1) and substrate,more » respectively. Profiles for kcat and Dkcat show that EB1 undergoes a perturbation from 8.0 to 5.6 +/- 0.3 (pK1') in the presence of substrate; additionally, a second ionization, pK2 = 7.25 +/- 0.25, is observed to mediate but not be essential for enzyme reoxidation. The pH dependence of the ratio of tritium exchange to product formation for dopamine also indicates base catalysis with a pKexch = 5.5 +/- 0.01, which is within experimental error of pK1'. We conclude that the data presented herein support a single residue catalyzing both substrate oxidation and exchange, consistent with recent stereochemical results that implicate a syn relationship between these processes (Farnum, M., and Klinman, J.P. (1985) Fed. Proc., Fed. Am. Soc. Exp. Biol. 44, 1055). This conclusion contrasts with earlier kinetic data in support of a large rate differential for the exchange of hydrogen from C-1 vs. C-2 of phenethylamine derivatives.« less