777 research outputs found

    Airborne Wind Energy: Implementation and Design for the U.S. Air Force

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    Excitement among researchers about Airborne Wind Energy (AWE) technology matches DoD aims to advance and employ renewable energy. AWE seeks to cost-effectively tap the vast supply of wind energy available at altitudes high above the reach of conventional, ground-based wind turbines (e.g. 500-12,000m). This paper explores viability and implementation of AWE technology for fulfilling USAF energy needs. Characteristics, potential, and developmental status of the AWE resource are presented. A design tool for a rotor-based AWE system is developed, facilitating the analysis of blade performance to simplify design and provide the best efficiencies for a range of conditions. USAF bases are evaluated upon energy needs, design requirements, and other factors to determine which bases could benefit most from AWE. Bases most viable for an AWE project, with 75% potential savings on energy costs/base (up to $40M annually for larger bases), are: Tinker, Vance, Wright-Patt, Arnold, Ellsworth, and Grand Forks. Key results reveal it is possible to achieve notable benefits for the USAF using AWE technology

    Mapping Ethnophysiographies: An Investigation of Toponyms and Land Cover of Missoula County, Montana

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    This thesis investigates the ethnophysiography of Missoula County, Montana via place names. Toponyms and landscape have been observed to have a relationship that can be studied through many lenses. Ethnophysiography, the study of how language and landscape relate to each other via human conceptualization, is a lens that was applied to this thesis because it recognizes the embodied information that toponyms carry and investigates landscape accordingly. Thus, the following research seeks to understand if ethnophysiographic diversity exists between toponyms in the Salish and English languages of Missoula County, Montana by analyzing place names and land cover in GIS and analyzing the data for a Zipfian distribution. I research, collect, and analyze the secondary information available on Missoula County names and land covers in order to empirically examine this ethnophysiographic relationship

    Atom detection in a two-mode optical cavity with intermediate coupling: Autocorrelation studies

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    We use an optical cavity in the regime of intermediate coupling between atom and cavity mode to detect single moving atoms. Degenerate polarization modes allow excitation of the atoms in one mode and collection of spontaneous emission in the other, while keeping separate the two sources of light; we obtain a higher confidence and efficiency of detection by adding cavity-enhanced Faraday rotation. Both methods greatly benefit from coincidence detection of photons, attaining fidelities in excess of 99% in less than 1 microsecond. Detailed studies of the second-order intensity autocorrelation function of light from the signal mode reveal evidence of antibunched photon emissions and the dynamics of single-atom transits.Comment: 10 pages, 10 figures, to be published in Phys. Rev.

    How should we use the coronary artery calcium score to predict cardiovascular risk?

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    The coronary artery calcium (CAC) score--an independent predictor of cardiovascular events (strength of recommendation [SOR]: C, systematic review of disease-oriented outcomes)--can be used, in addition to traditional risk factor assessment, to further stratify the risk of coronary heart disease (CHD) in asymptomatic patients (SOR: C, multiple large observational studies with disease-oriented outcomes). Although a high CAC score is associated with a greater risk of cardiovascular disease, no studies have evaluated cardiovascular outcomes of CAC-guided treatment, so its value remains theoretical

    A thraustochytrid diacylglycerol acyltransferase 2 with broad substrate specificity strongly increases oleic acid content in engineered \u3ci\u3eArabidopsis thaliana\u3c/i\u3e seeds

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    Diacylglycerol acyltransferase (DGAT) catalyses the last step in acyl-CoA-dependent triacylglycerol (TAG) biosynthesis and is an important determinant of cellular oil content and quality. In this study, a gene, designated TaDGAT2, encoding a type 2 DGAT (DGAT2)-related enzyme was identified from the oleaginous marine protist Thraustochytrium aureum. The deduced TaDGAT2 sequence contains a ~460 amino acid domain most closely related to DGAT2s from Dictyostelium sp. (45–50% identity). Recombinant TaDGAT2 restored TAG biosynthesis to the Saccharomyces cerevisiae H1246 TAG-deficient mutant, and microsomes from the complemented mutant displayed DGAT activity with C16 and C18 saturated and unsaturated fatty acyl-CoA and diacylglycerol substrates. To examine its biotechnological potential, TaDGAT2 was expressed under control of a strong seed-specific promoter in wild-type Arabidopsis thaliana and the high linoleic acid fad3fae1 mutant. In both backgrounds, little change was detected in seed oil content, but a striking increase in oleic acid content of seeds was observed. This increase was greatest in fad3fae1 seeds, where relative amounts of oleic acid increased nearly 2-fold to \u3e50% of total fatty acids. In addition, \u3e2-fold increase in oleic acid levels was detected in the triacylglycerol sn-2 position and in the major seed phospholipid phosphatidylcholine. These results suggest that increased seed oleic acid content mediated by TaDGAT2 is influenced in part by the fatty acid composition of host cells and occurs not by enhancing oleic acid content at the TAG sn-3 position directly but by increasing total oleic acid levels in seeds, presumably by limiting flux through phosphatidylcholine-based desaturation reactions. Includes supplementary information

    A thraustochytrid diacylglycerol acyltransferase 2 with broad substrate specificity strongly increases oleic acid content in engineered \u3ci\u3eArabidopsis thaliana\u3c/i\u3e seeds

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    Diacylglycerol acyltransferase (DGAT) catalyses the last step in acyl-CoA-dependent triacylglycerol (TAG) biosynthesis and is an important determinant of cellular oil content and quality. In this study, a gene, designated TaDGAT2, encoding a type 2 DGAT (DGAT2)-related enzyme was identified from the oleaginous marine protist Thraustochytrium aureum. The deduced TaDGAT2 sequence contains a ~460 amino acid domain most closely related to DGAT2s from Dictyostelium sp. (45–50% identity). Recombinant TaDGAT2 restored TAG biosynthesis to the Saccharomyces cerevisiae H1246 TAG-deficient mutant, and microsomes from the complemented mutant displayed DGAT activity with C16 and C18 saturated and unsaturated fatty acyl-CoA and diacylglycerol substrates. To examine its biotechnological potential, TaDGAT2 was expressed under control of a strong seed-specific promoter in wild-type Arabidopsis thaliana and the high linoleic acid fad3fae1 mutant. In both backgrounds, little change was detected in seed oil content, but a striking increase in oleic acid content of seeds was observed. This increase was greatest in fad3fae1 seeds, where relative amounts of oleic acid increased nearly 2-fold to \u3e50% of total fatty acids. In addition, \u3e2-fold increase in oleic acid levels was detected in the triacylglycerol sn-2 position and in the major seed phospholipid phosphatidylcholine. These results suggest that increased seed oleic acid content mediated by TaDGAT2 is influenced in part by the fatty acid composition of host cells and occurs not by enhancing oleic acid content at the TAG sn-3 position directly but by increasing total oleic acid levels in seeds, presumably by limiting flux through phosphatidylcholine-based desaturation reactions. Includes supplementary information

    The pursuit of isotopic and molecular fire tracers in the polar atmosphere and cryosphere

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    We present an overview of recent multidisciplinary, multi-institutional efforts to identify and date major sources of combustion aerosol in the current and paleoatmospheres. The work was stimulated, in part, by an atmospheric particle \u27sample of opportunity\u27 collected at Summit, Greenland in August 1994, that bore the 14C imprint of biomass burning. During the summer field seasons of 1995 and 1996, we collected air filter, surface snow and snowpit samples to investigate chemical and isotopic evidence of combustion particles that had been transported from distant fires. Among the chemical tracers employed for source identification are organic acids, potassium and ammonium ions, and elemental and organic components of carbonaceous particles. Ion chromatography, performed by members of the Climate Change Research Center (University of New Hampshire), has been especially valuable in indicating periods at Summit that were likely to have been affected by the long range transport of biomass burning aerosol. Univariate and multivariate patterns of the ion concentrations in the snow and ice pinpointed surface and snowpit samples for the direct analysis of particulate (soot) carbon and carbon isotopes. The research at NIST is focusing on graphitic and polycyclic aromatic carbon, which serve as almost certain indicators of fire, and measurements of carbon isotopes, especially 14C, to distinguish fossil and biomass combustion sources. Complementing the chemical and isotopic record, are direct \u27visual\u27 (satellite imagery) records and less direct backtrajectory records, to indicate geographic source regions and transport paths. In this paper we illustrate the unique way in which the synthesis of the chemical, isotopic, satellite and trajectory data enhances our ability to develop the recent history of the formation and transport of soot deposited in the polar snow and ice
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