1,380 research outputs found

    Aerospace management techniques: Commercial and governmental applications

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    A guidebook for managers and administrators is presented as a source of useful information on new management methods in business, industry, and government. The major topics discussed include: actual and potential applications of aerospace management techniques to commercial and governmental organizations; aerospace management techniques and their use within the aerospace sector; and the aerospace sector's application of innovative management techniques

    Missing salts on early Mars

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    Our understanding of the role of water on Mars has been profoundly influenced over the past several years by the detection of widespread aqueous alteration minerals. Clay minerals are found throughout ancient Noachian terrains and sulfate salts are abundant in younger Hesperian terrains, but these phases are rarely found together in the early Martian rock record. Full alteration assemblages are generally not recognized at local scales, hindering our ability to close mass balance in the ancient crust. Here we demonstrate the dissolution of basalt and subsequent formation of smectite results in an excess of cations that should reside with anions such as OH^−, Cl^−, SO^(2-)_3 SO^(2-)_4, SO^(2-)_4, or CO^(2-)_3 in a significant reservoir of complementary salts. Such salts are largely absent from Noachian terrains, yet the composition and/or fate of these ‘missing salts’ is critical to understanding the oxidation state and primary atmospheric volatile involved in crustal weathering on early Mars

    A methodology for boost-glide transport technology planning

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    A systematic procedure is presented by which the relative economic value of technology factors affecting design, configuration, and operation of boost-glide transport can be evaluated. Use of the methodology results in identification of first-order economic gains potentially achievable by projected advances in each of the definable, hypersonic technologies. Starting with a baseline vehicle, the formulas, procedures and forms which are integral parts of this methodology are developed. A demonstration of the methodology is presented for one specific boost-glide system

    Searches for New Quarks and Leptons Produced in Z-Boson Decay

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    We have searched for events with new-particle topologies in 390 hadronic Z decays with the Mark II detector at the SLAC Linear Collider. We place 95%-confidence-level lower limits of 40.7 GeV/c^2 for the top-quark mass, 42.0 GeV/c^2 for the mass of a fourth-generation charge - 1/3 quark, and 41.3 GeV/c^2 for the mass of an unstable Dirac neutral lepton

    Measurement of Z Decays into Lepton Pairs

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    We present measurements by the Mark II experiment of the ratios of the leptonic partial widths of the Z boson to the hadronic partial width. The results are Γ_(ee)/Γ_(had)=0.037_(-0.012^()+0.016),Γ_(µµ)/Γ_(had)=0.053-_(0.015)^(+0.020), and Γ_(ττ)/Γ_(had)=0.066_(-0.017)^(+0.021), in good agreement with the standard-model prediction of 0.048. From the average leptonic width result, Γ_(ll)/Γ_(had)=0.053_(-0.009)^(+0.010), we derive Γ_(had)=1.56_(-0.24)^(+0.28) GeV. We find for the vector coupling constants of the tau and muon v_τ^2=0.31±0.31_(-0.30)^(+0.43) and v_μ^2=0.05±0.30_(-0.23)^(+0.34)

    Effects of packaging on bone marrow discoloration in beef arm, rib, shoulder blade, and thoracic vertebra bones

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    Meat retailers have reported bone marrow discoloration to be a problem, especially in modified-atmosphere packages (MAP). To evaluate causes of bone marrow discoloration in different beef bones and packaging systems, 36 beef arm bones, ribs, shoulder blades, and thoracic vertebrae from USDA Select and Choice carcasses were obtained from a commercial abattoir, cut into 1-inch-thick sections at 4 days postmortem, and packaged into 1) polyvinyl chloride film (PVC) overwrap; 2) high-oxygen (80% O2, 20% CO2) MAP; or 3) ultra-low-oxygen (70% N2, 30% CO2) MAP. Packages were displayed under continuous fluorescent lighting for 4 days at 35.6°F. Ribs, shoulder blades, and thoracic vertebrae packaged in PVC and high-oxygen MAP developed undesirable gray or black discoloration during display. In ultra-low-oxygen MAP, mean visual-color scores were acceptable throughout display. The a* values (larger values equate to redder color) for ribs, shoulder blades, and thoracic vertebrae decreased (P<0.05) over time. Arm-bone marrow had less oxidation and dramatically less total iron and hemoglobin than did marrow from ribs and thoracic vertebrae. The much larger amounts of iron and hemoglobin in ribs and thoracic vertebrae likely correspond to marrow discoloration. In summary, bone marrow discoloration occurs in ribs, shoulder blades, and thoracic vertebrae packaged in PVC or high-oxygen MAP. Bones packaged in ultralow- oxygen MAP or arm bones packaged in PVC or high-oxygen MAP had minimal oxidation and discoloration

    Paleoclimate of Mars as captured by the stratigraphic record in Gale Crater

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    A kilometers-thick sedimentary sequence in Gale Crater exhibits stratigraphic changes in lithology that are consistent with transitions in aqueous and climatic conditions purported to be global in scale. The sequence is divided into two formations, where the Lower formation exhibits a net transition in mineralogy from clay/sulfate to sulfate/oxide assemblages and is separated from the overlying Upper formation by an erosional unconformity. Superposition and crater counts suggest strata in the Lower formation lie along the Noachian-Hesperian time-stratigraphic boundary, whereas beds in the Upper formation, which lack signatures indicative of clay minerals or sulfates, are thinner, more regularly spaced, and clearly younger. The observed stratigraphic trends are consistent with the rocks at Gale Crater recording a global transition from a climate favorable to clay mineral formation to one more favorable to forming sulfates and other salts

    Bed thickness distributions on Mars: An orbital perspective

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    Studies on Earth show that sedimentary bed thickness and bed thickness distributions record information about the processes controlling sediment deposition. High-resolution digital terrain models (DTMs) such as those derived from the High Resolution Imaging Science Experiment (HiRISE) now provide the opportunity to quantify bed thickness properties on Mars over several orders of magnitude, down to the submeter scale. This study uses HiRISE DTMs and visible images to measure bed thickness distributions at 10 deposits on Mars, with the aim of determining whether statistical techniques can provide useful criteria for distinguishing sedimentary depositional processes. Basic statistics, including mean thickness and range, are examined, as are histograms, cumulative frequency plots, and log-log plots. Statistical tests interrogate these deposits for thinning or thickening upward trends and the presence of normal, lognormal, and exponential distributions. Although there are challenges associated with these methods, the statistical analysis of bed thickness, coupled with morphological and mineralogical interpretations, has the potential to be a powerful tool for characterizing and classifying sedimentary rocks on Mars. In particular, bed thickness statistics are particularly well suited for examining changes in sediment supply and accommodation within Martian sedimentary sequences
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