84,676 research outputs found

    Mission analysis of solar powered aircraft

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    The effect of a real mission scenario on a solar powered airplane configuration which had been developed in previous work were assessed. The mission used was surveillance of crop conditions over a route from Phoenix to Tucson to Tombstone, Arizona. Appendices are attached which address the applicability of existing platforms and payloads to do this mission

    Does Micro-CT scanning damage DNA in museum specimens?

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    X-ray micro-computed tomography and DNA sequencing are useful and increasingly common tools in taxonomy and collections research. Whilst the benefits of each method are continually evaluated and debated individually, how the methods impact each other requires more attention. We compared DNA fragment length and the barcode sequence CO1 in samples throughout a CT-scanning protocol, for a range of X-ray exposures and energies. We found no evidence of DNA damage, but advise caution when using precious or archival material, highlighting the need for further investigations and considering potential areas for research.NatSCA supports open access publication as part of its mission is to promote and support natural science collections. NatSCA uses the Creative Commons Attribution License (CCAL) http://creativecommons.org/licenses/by/2.5/ for all works we publish. Under CCAL authors retain ownership of the copyright for their article, but authors allow anyone to download, reuse, reprint, modify, distribute, and/or copy articles in NatSCA publications, so long as the original authors and source are cited. The attached file is the published version of the article

    Overbilling and Informed Financial Consent — A Contractual Solution

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    U.S. hospitals and physicians regularly charge uninsured patients and patients receiving care outside their health-plan networks far more what most health insurers pay and far more than their actual costs. Such practices have triggered over 100 lawsuits and prompted calls for pricing transparency in Congress and price regulation in several states. This Perspective argues that the theory of implied contracts, a foundation in most first-year courses in contract law, offers a useful legal and ethical mechanism for handling these troubling problems in health care billing

    A Survival Analysis of Australian Equity Mutual Funds

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    Determining which types of mutual (or managed) investment funds are good financial investments is complicated by potential surbivorship biases. This project adds to a small recent international literature on the patterns and determinants of mutual fund survivorship. We use statistical techniques for survival data that are rarely applied in finance. Of specific interest is the hazard rate of fund closure, which gives the variation over time in the conditional probability of fund closure given fund survival to date. For a sample of 251 retail investment funds in Australia from 1980 to 1999 we identify a hump-shaped hazard function that reaches its maximum after about five or six years, a pattern similar to the UK findings of Lunde, Timmermann and Blake (1999). We also consider the impact of monthly and annual fund performance (gross and relative to a market benchmark). Returns relative to the benckmark are much more important than gross returns, with hgiher relative returns associated with lower hazard of fund closure. There appears to be an asymmetric response to performance, with positive shocks having a larger impact on the hazard rate than negative shocks.mutual funds; survivorship bias; duration analysis; cox regression

    Development of EM-CCD-based X-ray detector for synchrotron applications

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    A high speed, low noise camera system for crystallography and X-ray imaging applications is developed and successfully demonstrated. By coupling an electron-multiplying (EM)-CCD to a 3:1 fibre-optic taper and a CsI(Tl) scintillator, it was possible to detect hard X-rays. This novel approach to hard X-ray imaging takes advantage of sub-electron equivalent readout noise performance at high pixel readout frequencies of EM-CCD detectors with the increase in the imaging area that is offered through the use of a fibre-optic taper. Compared with the industry state of the art, based on CCD camera systems, a high frame rate for a full-frame readout (50 ms) and a lower readout noise (<1 electron root mean square) across a range of X-ray energies (6–18 keV) were achieved

    Evaluation of the micro-carburetor

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    A prototype sonic, variable-venturi automotive carburetor was evaluated for its effects on vehicle performance, fuel economy, and exhaust emissions. A 350 CID Chevrolet Impala vehicle was tested on a chassis dynamometer over the 1975 Federal Test Procedure, urban driving cycle. The Micro-carburetor was tested and compared with stock and modified-stock engine configurations. Subsequently, the test vehicle's performance characteristics were examined with the stock carburetor and again with the Micro-carburetor in a series of on-road driveability tests. The test engine was then removed from the vehicle and installed on an engine dynamometer. Engine tests were conducted to compare the fuel economy, thermal efficiency, and cylinder-to-cylinder mixture distribution of the Micro-carburetor to that of the stock configuration. Test results show increases in thermal efficiency and improvements in fuel economy at all test conditions. Improve fuel/air mixture preparation is implied from the information presented. Further improvements in fuel economy and exhaust emissions are possible through a detailed recalibration of the Micro-carburetor
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