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Mary K. Gilles

Bio: Mary K. Gilles is an academic researcher from Lawrence Berkeley National Laboratory. The author has contributed to research in topics: Aerosol & Particle. The author has an hindex of 44, co-authored 105 publications receiving 6974 citations. Previous affiliations of Mary K. Gilles include University of California, San Diego & Cooperative Institute for Research in Environmental Sciences.


Papers
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Journal ArticleDOI
15 Dec 2006-Science
TL;DR: The Stardust spacecraft collected thousands of particles from comet 81P/Wild 2 and returned them to Earth for laboratory study, and preliminary examination shows that the nonvolatile portion of the comet is an unequilibrated assortment of materials that have both presolar and solar system origin.
Abstract: The Stardust spacecraft collected thousands of particles from comet 81P/Wild 2 and returned them to Earth for laboratory study. The preliminary examination of these samples shows that the nonvolatile portion of the comet is an unequilibrated assortment of materials that have both presolar and solar system origin. The comet contains an abundance of silicate grains that are much larger than predictions of interstellar grain models, and many of these are high-temperature minerals that appear to have formed in the inner regions of the solar nebula. Their presence in a comet proves that the formation of the solar system included mixing on the grandest scales.

886 citations

Journal ArticleDOI
15 Dec 2006-Science
TL;DR: The presence of deuterium and nitrogen-15 excesses suggest that some organics have an interstellar/protostellar heritage and a diverse suite of organic compounds is present and identifiable within the returned samples.
Abstract: Organics found in comet 81P/Wild 2 samples show a heterogeneous and unequilibrated distribution in abundance and composition. Some organics are similar, but not identical, to those in interplanetary dust particles and carbonaceous meteorites. A class of aromatic-poor organic material is also present. The organics are rich in oxygen and nitrogen compared with meteoritic organics. Aromatic compounds are present, but the samples tend to be relatively poorer in aromatics than are meteorites and interplanetary dust particles. The presence of deuterium and nitrogen-15 excesses suggest that some organics have an interstellar/protostellar heritage. Although the variable extent of modification of these materials by impact capture is not yet fully constrained, a diverse suite of organic compounds is present and identifiable within the returned samples.

547 citations

Journal ArticleDOI
TL;DR: Negative ion photoelectron spectroscopy and gas-phase proton transfer kinetics were employed to determine the CH bond dissociation energies of acetylene, ethylene, and vinyl radical.
Abstract: Negative ion photoelectron spectroscopy and gas-phase proton transfer kinetics were employed to determine the CH bond dissociation energies of acetylene, ethylene, and vinyl radical: Do(HCC-H) = 131.3 f 0.7 kcal mol-', Do(CH2CH-H) = 109.7 f 0.8 kcal mol-', and Do(CH2C-H) = 81.0 f 3.5 kcal mol-'. The strengths of each of the other CH and CC bonds in acetylene and ethylene and their fragments were derived. The energy required to isomerize acetylene to vinylidene was also determined: HCWH - H2C=C: AHbo = 47.4 f 4.0 kcal mol-'. As part of this study, proton transfer kinetics in a flowing afterglow/selected-ion flow tube apparatus were used to refine the acidities of ethylene, acetylene, and vinyl. The gas-phase acidity of acetylene was tied to the precisely known values for hydrogen fluoride, AGsdd298(HF) = 365.6 f 0.2 kcal mol-', and water, AG-(H20) = 383.9 f 0.3 kcal mor', yielding AG-(HCC-H) = 369.8 f 0.6 kcal mol-'. The gas-phase acidity equilibria of acetylene with isopropyl alcohol and terr-butyl alcohol were also measured. Combined with relative acidities from the literature, these measurements yielded improved acidities for the alcohols, AGad,298( (CH3)2CHO-H) = 370.1 f 0.6 kcal mol-', AGaa298((CH3)3CO-H) = 369.3 f 0.6 kcal mol-', hGadd,298(C2HSO-H) = 372.0 f 0.6 kcal mol-', and AGacid.298(CH30-H) = 375.1 f 0.6 kcal mol-'. The gas-phase acidity of ethylene was measured relative to ammonia, AGacid.298(NH3) = 396.5 f 0.4 kcal mol-', giving AGadJ98(C2H1) = 401.0 f 0.5 kcal mol-'. The gas-phase acidity of vinyl radical was bracketed, 375.1 f 0.6 kcal mol-' I AGaaB8(CH2C-H) I 380.4 f 0.3 kcal mol-'. The electron affinities of ethynyl, vinyl, and vinylidene radicals were determined by photoelectron spectroscopy: EA(HCC) = 2.969 f 0.010 eV, EA(CH2CH) = 0.667 f 0.024 eV, and EA(CH2C) = 0.490 f 0.006 eV.

373 citations

Journal ArticleDOI
13 Nov 2008-Nature
TL;DR: Scanning transmission X-ray microscopy can be used at atmospheric pressure and up to 350 °C to monitor in situ phase changes in a complex iron-based Fisher–Tropsch catalyst and the nature and location of carbon species produced.
Abstract: The modern chemical industry uses heterogeneous catalysts in almost every production process. They commonly consist of nanometre-size active components (typically metals or metal oxides) dispersed on a high-surface-area solid support, with performance depending on the catalysts' nanometre-size features and on interactions involving the active components, the support and the reactant and product molecules. To gain insight into the mechanisms of heterogeneous catalysts, which could guide the design of improved or novel catalysts, it is thus necessary to have a detailed characterization of the physicochemical composition of heterogeneous catalysts in their working state at the nanometre scale. Scanning probe microscopy methods have been used to study inorganic catalyst phases at subnanometre resolution, but detailed chemical information of the materials in their working state is often difficult to obtain. By contrast, optical microspectroscopic approaches offer much flexibility for in situ chemical characterization; however, this comes at the expense of limited spatial resolution. A recent development promising high spatial resolution and chemical characterization capabilities is scanning transmission X-ray microscopy, which has been used in a proof-of-principle study to characterize a solid catalyst. Here we show that when adapting a nanoreactor specially designed for high-resolution electron microscopy, scanning transmission X-ray microscopy can be used at atmospheric pressure and up to 350 degrees C to monitor in situ phase changes in a complex iron-based Fisher-Tropsch catalyst and the nature and location of carbon species produced. We expect that our system, which is capable of operating up to 500 degrees C, will open new opportunities for nanometre-resolution imaging of a range of important chemical processes taking place on solids in gaseous or liquid environments.

364 citations


Cited by
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[...]

08 Dec 2001-BMJ
TL;DR: There is, I think, something ethereal about i —the square root of minus one, which seems an odd beast at that time—an intruder hovering on the edge of reality.
Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

33,785 citations

Journal ArticleDOI
TL;DR: In this paper, the authors provided an assessment of black-carbon climate forcing that is comprehensive in its inclusion of all known and relevant processes and that is quantitative in providing best estimates and uncertainties of the main forcing terms: direct solar absorption; influence on liquid, mixed phase, and ice clouds; and deposition on snow and ice.
Abstract: Black carbon aerosol plays a unique and important role in Earth's climate system. Black carbon is a type of carbonaceous material with a unique combination of physical properties. This assessment provides an evaluation of black-carbon climate forcing that is comprehensive in its inclusion of all known and relevant processes and that is quantitative in providing best estimates and uncertainties of the main forcing terms: direct solar absorption; influence on liquid, mixed phase, and ice clouds; and deposition on snow and ice. These effects are calculated with climate models, but when possible, they are evaluated with both microphysical measurements and field observations. Predominant sources are combustion related, namely, fossil fuels for transportation, solid fuels for industrial and residential uses, and open burning of biomass. Total global emissions of black carbon using bottom-up inventory methods are 7500 Gg yr−1 in the year 2000 with an uncertainty range of 2000 to 29000. However, global atmospheric absorption attributable to black carbon is too low in many models and should be increased by a factor of almost 3. After this scaling, the best estimate for the industrial-era (1750 to 2005) direct radiative forcing of atmospheric black carbon is +0.71 W m−2 with 90% uncertainty bounds of (+0.08, +1.27) W m−2. Total direct forcing by all black carbon sources, without subtracting the preindustrial background, is estimated as +0.88 (+0.17, +1.48) W m−2. Direct radiative forcing alone does not capture important rapid adjustment mechanisms. A framework is described and used for quantifying climate forcings, including rapid adjustments. The best estimate of industrial-era climate forcing of black carbon through all forcing mechanisms, including clouds and cryosphere forcing, is +1.1 W m−2 with 90% uncertainty bounds of +0.17 to +2.1 W m−2. Thus, there is a very high probability that black carbon emissions, independent of co-emitted species, have a positive forcing and warm the climate. We estimate that black carbon, with a total climate forcing of +1.1 W m−2, is the second most important human emission in terms of its climate forcing in the present-day atmosphere; only carbon dioxide is estimated to have a greater forcing. Sources that emit black carbon also emit other short-lived species that may either cool or warm climate. Climate forcings from co-emitted species are estimated and used in the framework described herein. When the principal effects of short-lived co-emissions, including cooling agents such as sulfur dioxide, are included in net forcing, energy-related sources (fossil fuel and biofuel) have an industrial-era climate forcing of +0.22 (−0.50 to +1.08) W m−2 during the first year after emission. For a few of these sources, such as diesel engines and possibly residential biofuels, warming is strong enough that eliminating all short-lived emissions from these sources would reduce net climate forcing (i.e., produce cooling). When open burning emissions, which emit high levels of organic matter, are included in the total, the best estimate of net industrial-era climate forcing by all short-lived species from black-carbon-rich sources becomes slightly negative (−0.06 W m−2 with 90% uncertainty bounds of −1.45 to +1.29 W m−2). The uncertainties in net climate forcing from black-carbon-rich sources are substantial, largely due to lack of knowledge about cloud interactions with both black carbon and co-emitted organic carbon. In prioritizing potential black-carbon mitigation actions, non-science factors, such as technical feasibility, costs, policy design, and implementation feasibility play important roles. The major sources of black carbon are presently in different stages with regard to the feasibility for near-term mitigation. This assessment, by evaluating the large number and complexity of the associated physical and radiative processes in black-carbon climate forcing, sets a baseline from which to improve future climate forcing estimates.

4,591 citations

Journal Article
TL;DR: In this paper, a documento: "Cambiamenti climatici 2007: impatti, adattamento e vulnerabilita" voteato ad aprile 2007 dal secondo gruppo di lavoro del Comitato Intergovernativo sui Cambiamentsi Climatici (Intergovernmental Panel on Climate Change).
Abstract: Impatti, adattamento e vulnerabilita Le cause e le responsabilita dei cambiamenti climatici sono state trattate sul numero di ottobre della rivista Cda. Approfondiamo l’argomento presentando il documento: “Cambiamenti climatici 2007: impatti, adattamento e vulnerabilita” votato ad aprile 2007 dal secondo gruppo di lavoro del Comitato Intergovernativo sui Cambiamenti Climatici (Intergovernmental Panel on Climate Change). Si tratta del secondo di tre documenti che compongono il quarto rapporto sui cambiamenti climatici.

3,979 citations

Journal ArticleDOI
TL;DR: The Gaussian-2 theoretical procedure (G2 theory) as discussed by the authors was proposed to calculate molecular energies (atomization energies, ionization potentials, and electron affinities) of compounds containing first and second-row atoms.
Abstract: The Gaussian‐2 theoretical procedure (G2 theory), based on a b i n i t i o molecular orbital theory, for calculation of molecular energies (atomization energies, ionization potentials,electron affinities, and proton affinities) of compounds containing first‐ (Li–F) and second‐row atoms (Na–Cl) is presented. This new theoretical procedure adds three features to G1 theory [J. Chem. Phys. 9 0, 5622 (1989)] including a correction for nonadditivity of diffuse‐s p and 2d f basis set extensions, a basis set extension containing a third d function on nonhydrogen and a second p function on hydrogen atoms, and a modification of the higher level correction. G2 theory is a significant improvement over G1 theory because it eliminates a number of deficiencies present in G1 theory. Of particular importance is the improvement in atomization energies of ionic molecules such as LiF and hydrides such as C2H6, NH3, N2H4, H2O2, and CH3SH. The average absolute deviation from experiment of atomization energies of 39 first‐row compounds is reduced from 1.42 to 0.92 kcal/mol. In addition, G2 theory gives improved performance for hypervalent species and electron affinities of second‐row species (the average deviation from experiment of electron affinities of second‐row species is reduced from 1.94 to 1.08 kcal/mol). Finally, G2 atomization energies for another 43 molecules, not previously studied with G1 theory, many of which have uncertain experimental data, are presented and differences with experiment are assessed.

3,216 citations

Journal ArticleDOI
TL;DR: In this article, the authors reviewed existing knowledge with regard to organic aerosol (OA) of importance for global climate modelling and defined critical gaps needed to reduce the involved uncertainties, and synthesized the information to provide a continuous analysis of the flow from the emitted material to the atmosphere up to the point of the climate impact of the produced organic aerosols.
Abstract: The present paper reviews existing knowledge with regard to Organic Aerosol (OA) of importance for global climate modelling and defines critical gaps needed to reduce the involved uncertainties. All pieces required for the representation of OA in a global climate model are sketched out with special attention to Secondary Organic Aerosol (SOA): The emission estimates of primary carbonaceous particles and SOA precursor gases are summarized. The up-to-date understanding of the chemical formation and transformation of condensable organic material is outlined. Knowledge on the hygroscopicity of OA and measurements of optical properties of the organic aerosol constituents are summarized. The mechanisms of interactions of OA with clouds and dry and wet removal processes parameterisations in global models are outlined. This information is synthesized to provide a continuous analysis of the flow from the emitted material to the atmosphere up to the point of the climate impact of the produced organic aerosol. The sources of uncertainties at each step of this process are highlighted as areas that require further studies.

2,863 citations