1,051 research outputs found

    The interaction of unidirectional winds with an isolated barchan sand dune

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    Velocity profile measurements are determined on and around a barchan dune model inserted in the roughness layer on the tunnel floor. A theoretical investigation is made into the factors influencing the rate of sand flow around the dune. Flow visualization techniques are employed in the mapping of streamlines of flow on the dune's surface. Maps of erosion and deposition of sand are constructed for the barchan model, utilizing both flow visualization techniques and friction velocities calculated from the measured velocity profiles. The sediment budget found experimentally for the model is compared to predicted and observed results reported. The comparison shows fairly good agreement between the experimentally determined and predicted sediment budgets

    Simulation model of erosion and deposition on a barchan dune

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    Erosion and deposition over a barchan dune near the Salton Sea, California, are modeled by bookkeeping the quantity of sand in saltation following streamlines of transport. Field observations of near surface wind velocity and direction plus supplemental measurements of the velocity distribution over a scale model of the dune are combined as input to Bagnold type sand transport formulas corrected for slope effects. A unidirectional wind is assumed. The resulting patterns of erosion and deposition compare closely with those observed in the field and those predicted by the assumption of equilibrium (downwind translation of the dune without change in size or geometry). Discrepancies between the simulated results and the observed or predicted erosional patterns appear to be largely due to natural fluctuations in the wind direction. The shape of barchan dunes is a function of grain size, velocity, degree of saturation of the oncoming flow, and the variability in the direction of the oncoming wind. The size of the barchans may be controlled by natural atmospheric scales, by the age of the dunes, or by the upwind roughness. The upwind roughness can be controlled by fixed elements or by sand in the saltation. In the latter case, dune scale is determined by grain size and wind velocity

    Physics Case for the ILC Project: Perspective from Beyond the Standard Model

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    The International Linear Collider (ILC) has recently proven its technical maturity with the publication of a Technical Design Report, and there is a strong interest in Japan to host such a machine. We summarize key aspects of the Beyond the Standard Model physics case for the ILC in this contribution to the US High Energy Physics strategy process. On top of the strong guaranteed physics case in the detailed exploration of the recently discovered Higgs boson, the top quark and electroweak precision measurements, the ILC will offer unique opportunities which are complementary to the LHC program of the next decade. Many of these opportunities have connections to the Cosmic and Intensity Frontiers, which we comment on in detail. We illustrate the general picture with examples of how our world could turn out to be and what the ILC would contribute in these cases, with an emphasis on value-added beyond the LHC. These comprise examples from Supersymmetry including light Higgsinos, a comprehensive bottom-up coverage of NLSP-LSP combinations for slepton, squark, chargino and neutralino NLSP, a stau-coannihilation dark matter scenario and bilinear R-parity violation as explanation for neutrino masses and mixing, as well as generic WIMP searches and Little Higgs models as non-SUSY examples.Comment: 20 pages, 10 figures. Contributed to Snowmass Community Summer Study 201

    Understanding the Role of Federal Procurement Policy in Federal Social Policy

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    Human sex trafficking is a significant issue in the modern world. The International Labor Organization has estimated that 4.5 million people are the victims of forced commercial sexual exploitation worldwide. The United States\u27 laws on human sex trafficking can be found in 22 U.S.C. -§7104 Prevention of Trafficking, and promulgate the strategy of prevention of trafficking, protection of trafficking victims, and punishment of traffickers. Under the terms of 22 U.S.C. -§7104, federal contractors can be penalized if any of their employees or subcontractor employees engage in a commercial sex act. The reliance on the private sector to curb sex trafficking through federal contracts is a nuance, and there is a gap in the literature regarding the Congressional rationale for creating a federal contract policy that places federal contractors in the position of being liable for the off-duty activities of their employees. This research question focused on understanding this shift in usage of federal contract policy to influence individual behavior expressed in this Act. A content analysis of documents was performed which relied on official U.S. government documentation, including transcripts of Congressional hearings. The findings indicate that the legislation was a tactical response to a pair of scandals involving U.S. personnel overseas, combined with a belief in money as a motivating force, international political factors, and moral certainty among elected officials that the Federal Government had to \u27do something.\u27 Positive social change was addressed in the process of this study by providing greater insight into the legislative thought process regarding federal procurement related statutes, and by providing future reformers with additional information regarding effective legislative strategies

    Decoupling and the radiatively-corrected MSSM Higgs sector

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    In the decoupling limit of a non-minimal Higgs sector, the lightest CP-even Higgs boson (h) is indistinguishable from the Standard Model (SM) Higgs boson. In the two-Higgs-doublet sector of the MSSM, the approach to the decoupling limit (for m_A>>m_Z) persists, even in the presence of potentially large (tan(beta)-enhanced) radiative corrections to the hbb coupling. Radiative corrections can also generate an accidental cancellation between tree-level and one-loop terms, resulting in a SM-like Higgs boson for moderate m_A outside the decoupling regime.Comment: 6 pages, 1 figure, LaTeX with npb.sty, talk at RADCOR-2002 - Loops and Legs 2002, Kloster Banz, Germany, 8-13 September 200

    Intrepretation of surface features and surface processes on Mars

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    Eolian erosion and deposition on earth was studied in order to interpret the eolian land forms of Mars. Emphasis of the wind tunnel studies was on the flow field around models of eolian forms. Areas of the wind tunnel studies include: simulation of the atmospheric boundary layer; velocity profile measurements around different models in the desert boundary layer, and estimating shear stress distributions on the model surfaces; flow visualization techniques; streamline mapping using tuft photographs; and roughness contrasts

    Novel patient-centered approach to facilitate same-day discharge in patients undergoing elective percutaneous coronary intervention

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    Background Same‐day discharge ( SDD ) after elective percutaneous coronary intervention is safe, less costly, and preferred by patients, but it is usually performed in low‐risk patients, if at all. To increase the appropriate use of SDD in more complex patients, we implemented a “patient‐centered” protocol based on risk of complications at Barnes‐Jewish Hospital. Methods and Results Our objectives were as follows: (1) to evaluate time trends in SDD ; (2) to compare (a) mortality, bleeding, and acute kidney injury, (b) patient satisfaction, and (c) hospital costs by SDD versus no SDD ( NSDD ); and (3) to compare SDD eligibility by our patient‐centered approach versus Society for Cardiovascular Angiography and Interventions guidelines. Our patient‐centered approach was based on prospectively identifying personalized bleeding, mortality, and acute kidney injury risks, with a personalized safe contrast limit and mitigating those risks. We analyzed Barnes‐Jewish Hospital's National Cardiovascular Data Registry Cath PCI Registry data from July 1, 2009 to September 30, 2015 (N=1752). SDD increased rapidly from 0% to 77% ( P &lt;0.001), independent of radial access. Although SDD patients were comparable to NSDD patients, SDD was not associated with adverse outcomes (0% mortality, 0% bleeds, and 0.4% acute kidney injury). Patient satisfaction was high with SDD . Propensity score–adjusted costs were 7331 lower/ SDD patient ( P <0.001), saving an estimated 1.8 million annually. Only 16 patients (6.95%) met the eligibility for SDD by Society for Cardiovascular Angiography and Interventions guidelines, implying our patient‐centered approach markedly increased SDD eligibility. Conclusions With a patient‐centered approach, SDD rapidly increased and was safe in 75% of patients undergoing elective percutaneous coronary intervention, despite patient complexity. Patient satisfaction was high, and hospital costs were lower. Patient‐centered decision making to facilitate SDD is an important opportunity to improve the value of percutaneous coronary intervention. </jats:sec

    Engineering the Processive Run Length of the Kinesin Motor

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    Conventional kinesin is a highly processive molecular motor that takes several hundred steps per encounter with a microtubule. Processive motility is believed to result from the coordinated, hand-over-hand motion of the two heads of the kinesin dimer, but the specific factors that determine kinesin's run length (distance traveled per microtubule encounter) are not known. Here, we show that the neck coiled-coil, a structure adjacent to the motor domain, plays an important role in governing the run length. By adding positive charge to the neck coiled-coil, we have created ultra-processive kinesin mutants that have fourfold longer run lengths than the wild-type motor, but that have normal ATPase activity and motor velocity. Conversely, adding negative charge on the neck coiled-coil decreases the run length. The gain in processivity can be suppressed by either proteolytic cleavage of tubulin's negatively charged COOH terminus or by high salt concentrations. Therefore, modulation of processivity by the neck coiled-coil appears to involve an electrostatic tethering interaction with the COOH terminus of tubulin. The ability to readily increase kinesin processivity by mutation, taken together with the strong sequence conservation of the neck coiled-coil, suggests that evolutionary pressures may limit kinesin's run length to optimize its in vivo function
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