4,215 research outputs found

    CONDOR: Long endurance high altitude vehicle, volume 5

    Get PDF
    The results of a design study resulting in the proposed CONDOR aircraft are presented. The basic requirements are for the aircraft to maintain continuous altitude at or above 45,000 feet for at least a 3-day mission, be able to comfortably support a two-man crew during this period with their field of vision not obstructed to a significant degree, carry a payload of 200 pounds, and provide a power supply to the payload of 2000 watts. The take-off and landing distances must be below 5000. feet, and time to reach cruise altitude must not exceed 3 hours. The subjects discussed are configuration selection, structural analysis, stability and control, crew and payload accomodations, and economic estimates

    Flow-injection sandwich ELISA for bioprocess monitoring

    Get PDF
    A fully automated flow-injection immunoassay based on sandwich enzyme-linked immunosorbent assay (ELISA) is described for the model system: protein G-sepharose, rabbit IgG and horseradish peroxidase (HRP)-labelled protein A. After injecting rabbit IgG and HRP-labelled protein A into a cartridge containing protein G-sepharose sequentially, a mixture of hydrogen peroxide and the redox indicator, 2.2'-azino-bis(3-ethylbenzthiazoline-6-sulphonic acid) (ABTS) is passed through the cartridge. The HRP-labelled protein A bound in the cartridge is directly proportional to the concentration of rabbit IgG. The colour variation of ABTS caused during the reaction between HRP and H2O2 in the cartridge is detected photometrically. The whole assay procedure is controlled and evaluated by a computer. Rabbit Ige and HRP-labelled protein A are also detected by a fluorometer, which is introduced into the flow system. In the flow-injection sandwich ELISA, the slope of the calibration curve is 0.4491 in the range of 0 and 300 mu g ml(-1) rabbit IgG, while it is 0.1274 in the heterogeneous immunoassay. So the flow-injection sandwich ELISA system is found to be more sensitive than a heterogeneous immunoassay for the monitoring of the model protein

    Rank-width and Well-quasi-ordering of Skew-Symmetric or Symmetric Matrices

    Get PDF
    We prove that every infinite sequence of skew-symmetric or symmetric matrices M_1, M_2, ... over a fixed finite field must have a pair M_i, M_j (i<j) such that M_i is isomorphic to a principal submatrix of the Schur complement of a nonsingular principal submatrix in M_j, if those matrices have bounded rank-width. This generalizes three theorems on well-quasi-ordering of graphs or matroids admitting good tree-like decompositions; (1) Robertson and Seymour's theorem for graphs of bounded tree-width, (2) Geelen, Gerards, and Whittle's theorem for matroids representable over a fixed finite field having bounded branch-width, and (3) Oum's theorem for graphs of bounded rank-width with respect to pivot-minors.Comment: 43 page

    A Physics-Based Parameterization of Air–Sea Momentum Flux at High Wind Speeds and Its Impact on Hurricane Intensity Predictions

    Get PDF
    A new bulk parameterization of the air–sea momentum flux at high wind speeds is proposed based on coupled wave–wind model simulations for 10 tropical cyclones that occurred in the Atlantic Ocean during 1998–2003. The new parameterization describes how the roughness length increases linearly with wind speed and the neutral drag coefficient tends to level off at high wind speeds. The proposed parameterization is then tested on real hurricanes using the operational Geophysical Fluid Dynamics Laboratory (GFDL) coupled hurricane–ocean prediction model. The impact of the new parameterization on the hurricane prediction is mainly found in increased maximum surface wind speeds, while it does not appreciably affect the hurricane central pressure prediction. This helps to improve the GFDL model–predicted wind–pressure relationship in strong hurricanes. Attempts are made to provide physical explanations as to why the reduced drag coefficient affects surface wind speeds but not the central pressure in hurricanes

    Pulmonary giant cells and their significance for the diagnosis of asphyxiation

    Get PDF
    This study was performed to prove whether the detection of polynuclear giant cells in lungs is useful for the diagnosis of asphyxiation due to throttling or strangulation. Therefore, lung specimens of 54 individuals with different natural and unnatural causes of death were investigated. In most lungs examined numerous alveolar macrophages with 1-2 nuclei were found. Polynuclear giant cells, which were arbitrarily defined as alveolar macrophages containing 3 or more nuclei, were observed in all groups investigated except in the cases of hypoxia due to covering the head with plastic bags. Apparent differences between the other groups in particular an increased number in cases of throttling or strangulation, could not be observed. Immunohistochemical investigations confirmed the hypothesis that the observed polynuclear giant cells were derived from alveolar macrophages. The immunohistochemical analysis of the proliferation marker antigen Ki 67 revealed no positive reaction in the nuclei of polynuclear giant cells indicating that these cells had not developed shortly before death by endomitosis as an adaptative change following reduction in oxygen supply. The results provide evidence that the detection of pulmonary polynuclear giant cells cannot be used as a practical indicator for death by asphyxiation due to throttling or strangulation

    Local structures of polar wurtzites Zn_{1-x}Mg_{x}O studied by Raman and {67}Zn/{25}Mg NMR spectroscopies and by total neutron scattering

    Full text link
    Local compositions and structures of Zn_{1-x}Mg_{x}O alloys have been investigated by Raman and solid-state {67}Zn/{25}Mg nuclear magnetic resonance (NMR) spectroscopies, and by neutron pair-distribution-function (PDF) analyses. The E2(low) and E2(high) Raman modes of Zn_{1-x}Mg_{x}O display Gaussian- and Lorentzian-type profiles, respectively. At higher Mg substitutions, both modes become broader, while their peak positions shift in opposite directions. The evolution of Raman spectra from Zn_{1-x}Mg_{x}O solid solutions are discussed in terms of lattice deformation associated with the distinct coordination preferences of Zn and Mg. Solid-state magic-angle-spinning (MAS) NMR studies suggest that the local electronic environments of {67}Zn in ZnO are only weakly modified by the 15% substitution of Mg for Zn. {25}Mg MAS spectra of Zn_{0.85}Mg_{0.15}O show an unusual upfield shift, demonstrating the prominent shielding ability of Zn in the nearby oxidic coordination sphere. Neutron PDF analyses of Zn_{0.875}Mg_{0.125}O using a 2x2x1 supercell corresponding to Zn_{7}MgO_{8} suggest that the mean local geometry of MgO_{4} fragments concurs with previous density functional theory (DFT)-based structural relaxations of hexagonal wurtzite MgO. MgO_{4} tetrahedra are markedly compressed along their c-axes and are smaller in volume than ZnO_{4} units by ~6%. Mg atoms in Zn_{1-x}Mg_{x}O have a shorter bond to the cc-axial oxygen atom than to the three lateral oxygen atoms, which is distinct from the coordination of Zn. The precise structure, both local and average, of Zn_{0.875}Mg_{0.125}O obtained from time-of-flight total neutron scattering supports the view that Mg-substitution in ZnO results in increased total spontaneous polarization.Comment: 12 pages, 14 figures, 2 table

    How Cereal Grass Shoots Perceive And Respond To Gravity

    Full text link
    Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/141646/1/ajb208758.pd

    Simulation of a steel-aluminum composite material subjected to rolling contact fatigue

    Get PDF
    Rolling bearings are frequently used machine elements in mechanical assemblies to connect rotating parts. Resource efficiency and reliability enhancement are considered to be important factors of rolling bearing development. One of the ways to meet these requirements is the tailored forming (TF) technology, which enables the functionalization of several metal layer composites in a single component. The so-called hybrid machine elements can be produced by co-extrusion of aluminum and steel and subsequent die forging, heat treatment, and machining. The TF rolling bearings made by this process can provide optimized characteristics that use aluminum to reduce weight and steel for a highly loaded contact zone between a rolling element and a bearing raceway. To evaluate the applicability and the potential of this technology, theoretical investigations are presented in this paper. The stress distribution under fully flooded conditions, caused by an external load in the contact between a rolling element and the TF outer ring of an angular contact ball bearing, is analyzed statically with the finite element method. The fatigue life of the TF component can be calculated for different external axial loads and manufacturing parameters, such as steel-to-aluminum volume ratios and osculation. As a damage model, the Ioannides and Harris fatigue model and the Dang Van multiaxial fatigue criterion were used. The results show that the fatigue life has high sensitivity to the steel-to-aluminum volume ratio. For the hybrid component with a steel layer thickness of 3 mm, 90 percent of the fatigue life of pure 100Cr6 steel bearing bushings is reached. In this FE model, residual stresses due to machining processes can be regarded as an initial state, which can increase the fatigue life of this TF machine component. © 2019 by the authors

    Rank-width and Tree-width of H-minor-free Graphs

    Get PDF
    We prove that for any fixed r>=2, the tree-width of graphs not containing K_r as a topological minor (resp. as a subgraph) is bounded by a linear (resp. polynomial) function of their rank-width. We also present refinements of our bounds for other graph classes such as K_r-minor free graphs and graphs of bounded genus.Comment: 17 page
    • …
    corecore