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  1. Characterization of Fine Particulate Matter (PM) and Secondary PM Precursor Gases in the Mexico City Metropolitan Area

    This project was one of three collaborating grants funded by DOE/ASP to characterize the fine particulate matter (PM) and secondary PM precursors in the Mexico City Metropolitan Area (MCMA) during the MILAGRO Campaign. The overall effort of MCMA-2006, one of the four components, focused on i) examination of the primary emissions of fine particles and precursor gases leading to photochemical production of atmospheric oxidants and secondary aerosol particles; ii) measurement and analysis of secondary oxidants and secondary fine PM production, with particular emphasis on secondary organic aerosol (SOA), and iii) evaluation of the photochemical and meteorological processes characteristic of themore » Mexico City Basin. The collaborative teams pursued the goals through three main tasks: i) analyses of fine PM and secondary PM precursor gaseous species data taken during the MCMA-2002/2003 campaigns and preparation of publications; ii) planning of the MILAGRO Campaign and deployment of the instrument around the MCMA; and iii) analysis of MCMA-2006 data and publication preparation. The measurement phase of the MILAGRO Campaign was successfully completed in March 2006 with excellent participation from the international scientific community and outstanding cooperation from the Mexican government agencies and institutions. The project reported here was led by the Massachusetts Institute of Technology/Molina Center for Energy and the Environment (MIT/MCE2) team and coordinated with DOE/ASP-funded collaborators at Aerodyne Research Inc., University of Colorado at Boulder and Montana State University. Currently 24 papers documenting the findings from this project have been published. The results from the project have improved significantly our understanding of the meteorological and photochemical processes contributing to the formation of ozone, secondary aerosols and other pollutants. Key findings from the MCMA-2003 include a vastly improved speciated emissions inventory from on-road vehicles: the MCMA motor vehicles produce abundant amounts of primary PM, elemental carbon, particle-bound polycyclic aromatic hydrocarbons, carbon monoxide and a wide range of air toxics; the feasibility of using eddy covariance techniques to measure fluxes of volatile organic compounds in an urban core and a valuable tool for validating local emissions inventory; a much better understanding of the sources and atmospheric loadings of volatile organic compounds; the first spectroscopic detection of glyoxal in the atmosphere; a unique analysis of the high fraction of ambient formaldehyde from primary emission sources; characterization of ozone formation and its sensitivity to VOCs and NO x; a much more extensive knowledge of the composition, size distribution and atmospheric mass loadings of both primary and secondary fine PM, including the fact that the rate of MCMA SOA production greatly exceeded that predicted by current atmospheric models; evaluations of significant errors that can arise from standard air quality monitors for O 3 and NO 2; and the implementation of an innovative Markov Chain Monte Carlo method for inorganic aerosol modeling as a powerful tool to analyze aerosol data and predict gas phase concentrations where these are unavailable. During the MILAGRO Campaign the collaborative team utilized a combination of central fixed sites and a mobile laboratory deployed throughout the MCMA to representative urban and boundary sites to measure trace gases and fine particles. Analysis of the extensive 2006 data sets has confirmed the key findings from MCMA-2002/2003; additionally MCMA-2006 provided more detailed gas and aerosol chemistry and wider regional scale coverage. Key results include an updated 2006 emissions inventory; extension of the flux system to measure fluxes of fine particles; better understanding of the sources and apportionment of aerosols, including contribution from biomass burning and industrial sources; a comprehensive evaluation of metal containing particles in a complex urban environment; identification of a close correlation between the rate of production of SOA and “Odd Oxygen” (O 3 + NO 3) and primary organic PM with CO in the urban plume; a more sophisticated understanding of the relationship between ozone formation and ozone precursors: while ozone production in the urban area is VOC-limited, the response is mostly NOx-limited in the surrounding mountain. Comparison of the findings from 2003 and 2006 also confirm that the VOC levels have decreased during the three-year period, while NO x levels remain the same. The results from the 2002/2003 and 2006 have been presented at international conferences and communicated to Mexican government officials. In addition, a large number of graduate students and post-doctoral associates were involved in the project. All data sets and publications are available to the scientific community.« less
  2. Charting the Course for Elementary Particle Physics

    ''It was the best of times; it was the worst of times'' is the way Dickens begins the Tale of Two Cities. The line is appropriate to our time in particle physics. It is the best of times because we are in the midst of a revolution in understanding, the third to occur during my career. It is the worst of times because accelerator facilities are shutting down before new ones are opening, restricting the opportunity for experiments, and because of great uncertainty about future funding. My task today is to give you a view of the most important opportunitiesmore » for our field under a scenario that is constrained by a tight budget. It is a time when we cannot afford the merely good, but must give first priority to the really important. The defining theme of particle physics is to learn what the universe is made of and how it all works. This definition spans the full range of size from the largest things to the smallest things. This particle physics revolution has its origins in experiments that look at both.« less
  3. Laboratory Investigation of Organic Aerosol Formation from Aromatic Hydrocarbons

    Our work for this DOE funded project includes: (1) measurements of the kinetics and mechanism of the gas-phase oxidation reactions of the aromatic hydrocarbons initiated by OH; (2) measurements of aerosol formation from the aromatic hydrocarbons; and (3) theoretical studies to elucidate the OH-toluene reaction mechanism using quantum-chemical and rate theories.
  4. The Supernova Legacy Survey: Measurement of Omega_M, Omega_Lambda,and w from the First Year Data Set

    We present distance measurements to 71 high redshift type Ia supernovae discovered during the first year of the 5-year Supernova Legacy Survey (SNLS). These events were detected and their multi-color light-curves measured using the MegaPrime/MegaCam instrument at the Canada-France-Hawaii Telescope (CFHT), by repeatedly imaging four one-square degree fields in four bands. Follow-up spectroscopy was performed at the VLT, Gemini and Keck telescopes to confirm the nature of the supernovae and to measure their redshift. With this data set, we have built a Hubble diagram extending to z = 1, with all distance measurements involving at least two bands. Systematic uncertaintiesmore » are evaluated making use of the multiband photometry obtained at CFHT. Cosmological fits to this first year SNLS Hubble diagram give the following results: {Omega}{sub M} = 0.263 {+-} 0.042 (stat) {+-} 0.032 (sys) for a flat {Lambda}CDM model; and w = -1.023 {+-} 0.090 (stat) {+-} 0.054 (sys) for a flat cosmology with constant equation of state w when combined with the constraint from the recent Sloan Digital Sky Survey measurement of baryon acoustic oscillations.« less
  5. Infrared Absorption Spectroscopy and Chemical Kinetics of Free Radicals

    This research was directed at the detection, monitoring, and study of the chemical kinetic behavior by infrared absorption spectroscopy of small free radical species thought to be important intermediates in combustion. Work on the reaction of OH with acetaldehyde has been completed and published and work on the reaction of O({sup 1}D) with CH{sub 4} has been completed and submitted for publication. In the course of our investigation of branching ratios of the reactions of O({sup 1}D) with acetaldehyde and methane, we discovered that hot atom chemistry effects are not negligible at the gas pressures (13 Torr) initially used. Branchingmore » ratios of the reaction of O({sup 1}D) with CH{sub 4} have been measured at a tenfold higher He flow and fivefold higher pressure.« less
  6. THE DISCOVERY OF THE TAU LEPTON AND THE CHANGES IN ELEMENTARY PARTICLE PHYSICS IN 40 YEARS

    This is a history of my discovery of the tau lepton in the 1970s for which I was awarded the Nobel Prize in Physics. I have previously described some aspects of the discovery. In 1996 in my collection of papers entitled, ''Reflections on Experimental Science,'' I gave a straightforward account of the experimental method and the physics involved in the discovery as an introduction to the collection. In a 2002 paper written with Mary A. Meyer published in the journal ''Theoria et Historia Scientiarum'' I used the story of the discovery to outline my thoughts on the practice of experimentalmore » science. That 2002 paper was written primarily for young women and men who are beginning their lives in science and it was based on a lecture given at Los Alamos National Laboratory. Some of the historical material in this paper has appeared in those two earlier papers.« less
  7. The ASTRAL Compendium in 2004

    The ASTRAL compendium provides several databases and tools to aid in the analysis of protein structures, particularly through the use of their sequences. Partially derived from the SCOP database of protein structure domains, it includes sequences for each domain and other resources useful for studying these sequences and domain structures. The current release of ASTRAL contains 54,745 domains, more than three times as many as the initial release four years ago. ASTRAL has undergone major transformations in the past two years. In addition to several complete updates each year, ASTRAL is now updated on a weekly basis with preliminary classificationsmore » of domains from newly released PDB structures. These classifications are available as a stand-alone database, as well as available integrated into other ASTRAL databases such as representative subsets. To enhance the utility of ASTRAL to structural biologists, all SCOP domains are now made available as PDB-style coordinate files as well as sequences. In addition to sequences and representative subsets based on SCOP domains, sequences and subsets based on PDB chains are newly included in ASTRAL. Several search tools have been added to ASTRAL to facilitate retrieval of data by individual users and automated methods. ASTRAL may be accessed at http://astral.stanford.edu/.« less
  8. The distant type Ia supernova rate

    We present a measurement of the rate of distant Type Ia supernovae derived using 4 large subsets of data from the Supernova Cosmology Project. Within this fiducial sample,which surveyed about 12 square degrees, thirty-eight supernovae were detected at redshifts 0.25--0.85. In a spatially flat cosmological model consistent with the results obtained by the Supernova Cosmology Project, we derive a rest-frame Type Ia supernova rate at a mean red shift z {approx_equal} 0.55 of 1.53 {sub -0.25}{sub -0.31}{sup 0.28}{sup 0.32} x 10{sup -4} h{sup 3} Mpc{sup -3} yr{sup -1} or 0.58{sub -0.09}{sub -0.09}{sup +0.10}{sup +0.10} h{sup 2} SNu(1 SNu = 1more » supernova per century per 10{sup 10} L{sub B}sun), where the first uncertainty is statistical and the second includes systematic effects. The dependence of the rate on the assumed cosmological parameters is studied and the redshift dependence of the rate per unit comoving volume is contrasted with local estimates in the context of possible cosmic star formation histories and progenitor models.« less
  9. MAXIMA-1: A Measurement of the Cosmic Microwave BackgroundAnisotropy on angular scales of 10' to 5 degrees

    We present a map and an angular power spectrum of the anisotropy of the cosmic microwave background (CMB) from the first flight of MAXIMA. MAXIMA is a balloon-borne experiment with an array of 16 bolometric photometers operated at 100 mK. MAXIMA observed a 124 deg region of the sky with 10' resolution at frequencies of 150, 240 and 410 GHz. The data were calibrated using in-flight measurements of the CMB dipole anisotropy. A map of the CMB anisotropy was produced from three 150 and one 240 GHz photometer without need for foreground subtractions. Analysis of this CMB map yields amore » power spectrum for the CMB anisotropy over the range 36 {le} {ell} {le} 785. The spectrum shows a peak with an amplitude of 78 {+-} 6 {mu}K at {ell} {approx_equal} 220 and an amplitude varying between {approx} 40 {mu}K and {approx} 50 {mu}K for 400 {approx}< {ell} {approx}< 785.« less
  10. The Discovery of the Point-Like Structure of Matter

    The organizers of this workshop have invited me here to reminisce. The assigned subject is the proton and how it lost its identity as an elementary particle. In its youth, the proton was very much neglected. It was overweight and introverted, and all the attention went to its lighter and more gregarious companion, the electron. The electron was noticed first and was accepted as a constituent of all matter almost immediately. As a result, the chemical ''elements'' lost their elementary status. With Rutherford's discovery of the nuclear atom it became clear that there was something rather small inside the hydrogenmore » atom with nearly 2000 times the mass of the electron, and equal but opposite charge. That something was called the ''positive electron'' or ''H-particle'' until 1930 or so. The Standard Model in those days had only two elementary particles with mass (whether light quanta might also be a particle was a subject of debate) and the only known forces were electromagnetic and gravitational. In the early days it was assumed that there were some extra positive electrons (each paired with a negative electron) inside nuclei other than hydrogen, to account for the observation that the atomic weight is equal to or greater than twice the atomic number. In 1914, Rutherford's group at Manchester turned its attention to alpha-particle scattering experiments on light nuclei. The group was intrigued by a calculation predicting that forward-scattered H-particles would have a much greater range than the incoming alpha particles. An experiment, the very first on the proton, verified the prediction experimentally and Marsden and Lantsberry concluded that the Coulomb field of the H particle could account for their results (at distances of closest approach that approximated 10{sup -13} cms.) World War I stopped most of the research in Rutherford's laboratory when many of the young scientists left to serve in the armed forces. Rutherford himself continued to do some research in parallel with his war work and in his spare time he discovered the first nuclear reaction on a nitrogen target along with anomalies in the scattering of alpha particles from hydrogen. Much improved measurements on hydrogen came after the war when Chadwick and Bieler, (now with Rutherford at the Cavendish) redid the earlier experiments, finding that there were too many H particles at large angles when the distance of closest approach was less than 3.5 x 10{sup -13} cms. In their 1921 paper, Chadwick and Bieler stated that there must be ''forces of very great intensity'' acting at small distances. Great significance was attached to the fact that such distances are about the same as the classical electron radius. Compare the modest activity on the proton with the intense effort (both experimental and theoretical) on electrons after the war. Progress was swift and by 1929, the basics needed for understanding the atom were in place, although the nucleus was still not understood at all. Only the charge, mass and spin (but not the magnetic moment) of the proton were known. In 1920 Rutherford had suggested that combinations of positive and negative electrons in the nucleus formed a neutral entity where the ''ordinary properties of the electrons are suppressed''. By the end of the decade there was growing recognition of the problems inherent in assuming the presence of electrons in the nucleus though it still seemed obvious that they had to be in there somewhere.« less
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