64,407 research outputs found

    Observations of Cygnus X-1 in the MeV band by the INTEGRAL imager

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    The spectrum of the MeV tail detected in the black-hole candidate Cygnus X-1 remains controversial as it appeared much harder when observed with the INTEGRAL Imager IBIS than with the INTEGRAL spectrometer SPI or CGRO. We present an independent analysis of the spectra of Cygnus X-1 observed by IBIS in the hard and soft states. We developed a new analysis software for the PICsIT detector layer and for the Compton mode data of the IBIS instrument and calibrated the idiosyncrasies of the PICsIT front-end electronics. The spectra of Cygnus X-1 obtained for the hard and soft states with the INTEGRAL imager IBIS are compatible with those obtained with the INTEGRAL spectrometer SPI, with CGRO, and with the models that attribute the MeV hard tail either to hybrid thermal/non-thermal Comptonisation or to synchrotron emission.Comment: 6 pages, 7 figure

    Approximating Stellar Orbits: Improving on Epicycle Theory

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    Already slightly eccentric orbits, such as those occupied by many old stars in the Galactic disk, are not well approximated by Lindblad's epicycle theory. Here, alternative approximations for flat orbits in axisymmetric stellar systems are derived and compared to results from numeric integrations. All of these approximations are more accurate than Lindblad's classical theory. I also present approximate, but canonical, maps from ordinary phase-space coordinates to a set of action-angle variables. Unfortunately, the most accurate orbit approximation leads to non-analytical R(t). However, from this approximation simple and yet very accurate estimates can be derived for the peri- and apo-centers, frequencies, and actions integrals of galactic orbits, even for high eccentricities. Moreover, further approximating this approximation allows for an analytical R(t) and still an accurate approximation to galactic orbits, even with high eccentricities.Comment: accepted for publication in AJ; 12 pages LaTeX, 9 figures (coloured only here, not in AJ) uses aas2pp4.st

    "Financing Long-Term Care, Replacing a Welfare: Model with an Insurance Model"

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    The nation is not prepared to deal with the jump in expenditures for long-term care that will come with the aging of the baby boom generation. Only a small part of that care is paid for privately (out-of-pocket or through private insurance). Most is financed through Medicaid, the program that is intended to ensure medical care for the indigent. This use of Medicaid comes at a high cost for individuals and society: the allotment of more than a third of the Medicaid budget to long-term care; a two-tier care system; and the commandeering of limited funds by middle- and high-income people through elaborate estate planning to circumvent eligibility requirements. These problems would be mitigated by replacing the welfare model with an insurance model--voluntary or compulsory private insurance, with subsidies through income-scaled tax credits to ensure affordability. An equitable and efficient system could be created with a blend of public money, private insurance, and other private saving, with a safety net for those in greatest need

    A Revised Parallax and its Implications for RX J185635-3754

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    New astrometric analysis of four WFPC2 images of the isolated neutron star RX J185635-3754 show that its distance is 117 +/- 12 pc, nearly double the originally published distance. At the revised distance, the star's age is 5 x 10^5 years, its space velocity is about 185 km/s, and its radiation radius inferred from thermal emission is approximately 15 km, in the range of many equations of state both with and without exotic matter. These measurements remove observational support for an extremely soft equation of state. The star's birthplace is still likely to be in the Upper Sco association, but a connection with zeta Oph is now unlikely.Comment: submitted to ApJ Letter

    "An Ethical Framework for Cost-Effective Medicine: Confronting the Risks in Managed Care"

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    This paper looks at the ethical problems posed by managed care (in particular, at its incentives to physicians to economize on care), and points to a regulatory framework to provide consumer protection. HMO medicine has been effective in controlling once runaway health care costs. But it sets up inevitable conflict between patient care and the financial well-being of the health plan and of its employee or contract physicians. The trend to capitated payments is especially problematic. It relieves the insurer from interfering in medical decision-making as a means of cost-control, but it pits the interests of physicians directly against the interest of patients. Policy makers, the finding is, should not try to micro-manage HMO medicine, which they have done by mandating, for example, minimal hospital stays after childbirth. The real need is for regulatory oversight of financial incentives and disclosure. Health plans ought to be required to disclose the incentives under which their physicians are paid; to provide subscribers with honest information on health care coverage; and to be prohibited from imposing "gag rules" on physicians. Moreover, ERISA ought to be re-cast to hold health plans accountable for errant care decisions, which they are not now in many cases. Purchasing cooperatives, the conclusion also is, would play an especially useful role if managed care continues to take hold as the institutional norm.

    "Prescription for Health Care Policy, The Case for Retargeting Tax Subsidies to Health Care"

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    With health care delivery increasingly shaped by market and budgetary discipline, the provision of health care for all seems an ever-more-distant goal.The high cost of American health care is the inevitable by-product of its method of financing. Cadette proposes shifting the tax subsidies to health care from the tax exclusion of employment-based health insurance to an income-scaled tax credit for the individual purchase of basic health insurance. This plan holds out promise of improving the operation of the health insurance market, making the labor market more efficient, reducing overall health care costs, and providing protection for the unemployed.

    Evaluating the Variability of Urban Land Surface Temperatures Using Drone Observations

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    Urbanization and climate change are driving increases in urban land surface temperatures that pose a threat to human and environmental health. To address this challenge, we must be able to observe land surface temperatures within spatially complex urban environments. However, many existing remote sensing studies are based upon satellite or aerial imagery that capture temperature at coarse resolutions that fail to capture the spatial complexities of urban land surfaces that can change at a sub-meter resolution. This study seeks to fill this gap by evaluating the spatial variability of land surface temperatures through drone thermal imagery captured at high-resolutions (13 cm). In this study, flights were conducted using a quadcopter drone and thermal camera at two case study locations in Milwaukee, Wisconsin and El Paso, Texas. Results indicate that land use types exhibit significant variability in their surface temperatures (3.9–15.8 °C) and that this variability is influenced by surface material properties, traffic, weather and urban geometry. Air temperature and solar radiation were statistically significant predictors of land surface temperature (R2 0.37–0.84) but the predictive power of the models was lower for land use types that were heavily impacted by pedestrian or vehicular traffic. The findings from this study ultimately elucidate factors that contribute to land surface temperature variability in the urban environment, which can be applied to develop better temperature mitigation practices to protect human and environmental health
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