6,338 research outputs found

    Method and apparatus for optically monitoring the angular position of a rotating mirror

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    An optical system monitors the angular position of a rotating scanning mirror to indicate the effective start and end of each scan. At a certain angular position, a ray of energy transmitted to the mirror is reflected a plurality of times between the reflectors associated with the optical system and the line on the mirror parallel to the axis, and then to a detector to sense that angular position. A single optical system may be arranged to sense a plurality of different angular positions for each revolution of the mirror

    No new limit on the size distribution of gamma-ray bursts

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    The results of a study (Carter et. al.) of gamma ray bursts using long duration balloon exposure are analyzed. Arguments are presented against the conclusion that the size spectrum extrapolates to a power law with index from -1.0 to -0.5, and that therefore the gamma ray bursts are of galactic origin. It is claimed that the data are consistent with an upper limit over 100 times that proposed, and that therefore no conclusion can be drawn from the measurements regarding the nature or origin of gamma ray bursts. The resulting upper limit to the rate of occurrence of small bursts lies above the -1.5 index power law extrapolation of the size spectrum of known events, i.e., greater than the rate expected from an infinitely extended source region

    Bayesian inference of nanoparticle-broadened x-ray line profiles

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    A single and self-contained method for determining the crystallite-size distribution and shape from experimental x-ray line profile data is presented. We have shown that the crystallite-size distribution can be determined without assuming a functional form for the size distribution, determining instead the size distribution with the least assumptions by applying the Bayesian/MaxEnt method. The Bayesian/MaxEnt method is tested using both simulated and experimental CeO2_{2} data. The results demonstrate that the proposed method can determine size distributions, while making the least number of assumptions. The comparison of the Bayesian/MaxEnt results from experimental CeO2_2 with TEM results is favorableComment: 43 pages, 13 Figures, 5 Table

    Global water outlook to 2025

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    "... Based on a global model of supply and demand for food and water, this report shows that if current water policies continue, farmers will indeed find it difficult to meet the world's food needs. Hardest hit will be the world's poorest people. The results from the model used in this report also show the consequences of changing the course of water policy. Further inattention to water-related investments and policies will produce a severe water crisis, which will lead in turn to a food crisis. A commitment to sustainable use of water, through appropriate policies and investments, however, will lead to a more water- and food-secure world. Water may be a scarce resource, but humans have developed many ways of using it more efficiently — that is, getting more from each unit of water. But water-saving policies, practices, and technologies are of no help if they are not used. Inappropriate incentives and institutions often hinder effective use of water. This report spells out the future results of our current choices." Authors' Introduction

    Water and food to 2025

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    The world's farmers will likely need to produce enough food to feed 8 billion people by 2025, and to do so they must have enough water to raise their crops. Yet farmers are already competing with industry, domestic water users, and the environment for access to the world's finite supply of water. Will available freshwater meet the rapidly growing demands for household, industrial, and environmental needs and still provide enough water to produce food for a burgeoning population? New research from IFPRI shows what steps policymakers and water users can take now to help ensure that water scarcity will not result in worsening hunger for the world's poorest people.

    After All This Time: An Analysis of the Recent Trend to Extend Truth-in-Lending-Style Disclosures to Commercial-Financing Transactions

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    The Truth in Lending Act of 1968 (TILA) was designed to protect consumers by implementing uniform disclosures for consumer financing transactions and by creating substantive consumer protections. While TILA has been amended over the past fifty years to reflect modern needs, it has always remained a consumer financing law. Over the past few years, however, states have challenged that notion by passing laws which require TILA-inspired disclosures for certain commercial-financing trans-actions. And at the federal level, a bill was introduced in the United States House of Representatives (House Bill) that would expand TILA to commercial-financing transactions falling below a certain threshold. This Article contends that extending consumer-financing protections to small businesses will likely have unintended negative effects, and that although neither state nor federal expansion is advisable, of the two, a uniform fed-eral approach would be less harmful. After reviewing the commer-cial-financing disclosure requirements in the House Bill and in the three key states of California, New York, and North Carolina, the Article con-siders the effects on small businesses and consumers of an expansion of TILA and Regulation Z. The Article concludes by suggesting several revi-sions to ameliorate the negative impact of importing a consumer-financing disclosure regime into small-business commercial financing

    Nonabelian dark matter: models and constraints

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    Numerous experimental anomalies hint at the existence of a dark matter (DM) multiplet chi_i with small mass splittings. We survey the simplest such models which arise from DM in the low representations of a new SU(2) gauge symmetry, whose gauge bosons have a small mass mu < 1 GeV. We identify preferred parameters M_chi ~ 1 TeV, mu ~ 100 MeV, alpha_g ~ 0.04 and the chi chi -> 4e annihilation channel, for explaining PAMELA, Fermi, and INTEGRAL/SPI lepton excesses, while remaining consistent with constraints from relic density, diffuse gamma rays and the CMB. This consistency is strengthened if DM annihilations occur mainly in subhalos, while excitations (relevant to the excited DM proposal to explain the 511 keV excess) occur in the galactic center (GC), due to higher velocity dispersions in the GC, induced by baryons. We derive new constraints and predictions which are generic to these models. Notably, decays of excited DM states chi' -> chi gamma arise at one loop and could provide a new signal for INTEGRAL/SPI; big bang nucleosynthesis (BBN) constraints on the density of dark SU(2) gauge bosons imply a lower bound on the mixing parameter epsilon between the SU(2) gauge bosons and photon. These considerations rule out the possibility of the gauge bosons that decay into e^+e^- being long-lived. We study in detail models of doublet, triplet and quintuplet DM, showing that both normal and inverted mass hierarchies can occur, with mass splittings that can be parametrically smaller, e.g., O(100) keV, than the generic MeV scale of splittings. A systematic treatment of Z_2 symmetry which insures the stability of the intermediate DM state is given for cases with inverted mass hierarchy, of interest for boosting the 511 keV signal from the excited dark matter mechanism.Comment: 28 pages, 17 figures; v2. added brief comment, reference

    The Role of Ketamine in the Management of Chronic Pain

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    Chronic pain diagnoses are on the rise amongst people within the United States and thought to be an epidemic. It is estimated to affect millions of patients who have suffered trauma, injury, or complications from surgical procedures. The treatment of chronic pain, defined as pain lasting longer than 3 months, can be complicated. There are no definitive treatment options that have garnered a consensus among medical professionals. Treatment usually involves several medical specialties and pharmacological options. Reliance on the use of multiple pharmacological options can cause patients increased hospitalizations, and a reliance on opioids can potentially cause other illnesses due to the treatment side effects. The purpose of this literature review was to evaluate whether ketamine is a suitable option for the treatment of chronic pain. Articles published in the last 15 years that examined its’ use in the treatment of chronic pain were evaluated. Articles were eliminated if they involved animal studies or the involvement of pediatric (less than 18 years of age) and/or geriatric patients (over 65 years of age). The systematic review recommends ketamine as an option for patients in the treatment of chronic pain. Evidence suggests a substantial reduction in patients pain scores after the administration of low dose, subanesthetic ketamine. While side effects are common, they are usually mild, and can be easily managed by practitioners and patients. Further investigation is needed via doubleblinded placebo-based studies with a larger sample size to fully substantiate the benefits of ketamine in treating chronic pain

    The role of rainfed agriculture in the future of global food production:

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    This paper examines future prospects for rainfed cereal production, and its importance in the evolving global food system. First, the paper undertakes a critical synthesis of the literature to assess three primary ways to enhance rainfed cereal yields: increasing effective rainfall use through improved water management, particularly water harvesting; increasing crop yields in rainfed areas through agricultural research; and reforming policies and increasing investments in rainfed areas. Second, the IMPACT-WATER integrated water-food modeling framework is applied to assess the current situation and plausible future options of irrigation water supply and food security, primarily on a global scale. This model simulates the relationships among water availability and demand, food supply and demand, international food prices, and trade at regional and global levels. The results show that rainfed agriculture will maintain an important role in the growth of food production in the future, although appropriate investments and policy reforms will be required to enhance the contribution of rainfed agriculture.Agricultural policy., Rainfed farming Developing countries., Cereal crops. Agricultural policy., Rainfed farming Developing countries., Cereal crops., Food security., Water-supply., Food supply., Trade., Crop yields., Water use Management.,
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