The exchange bias of bilayer magnetic films consisting of ferromagnetic （FM） and antiferromagnetic （AFM） layers in an uncompensated case is studied by use of the many-body Green＇s function method of quantum stati...The exchange bias of bilayer magnetic films consisting of ferromagnetic （FM） and antiferromagnetic （AFM） layers in an uncompensated case is studied by use of the many-body Green＇s function method of quantum statistical theory. The effects of the layer thickness and temperature and the interracial coupling strength on the exchange bias HE are investigated. The dependence of the exchange bias HE on the FM layer thickness and temperature is qualitatively in agreement with experimental results. When temperature varies, both the coercivity HC and HE decrease with the temperature increasing. For each FM thickness, there exists a least AFM thickness in which the exchange bias occurs, which is called pinning thickness.展开更多
Since 1969 private, nonprofit hospitals have qualified for tax exemption as charitable institutions and in exchange for the preferential tax treatment were required to provide community benefits. However, in the absen...Since 1969 private, nonprofit hospitals have qualified for tax exemption as charitable institutions and in exchange for the preferential tax treatment were required to provide community benefits. However, in the absence of mandatory reporting of community benefits at the federal level and in the absence of a clear definition of community benefits, the previous literature provides but ambiguous evidence regarding hospitals’ supply of community benefits. Responding to policymakers’ concerns, the Internal Revenue Service (IRS) mandates all private, non-profit hospitals to report charity care at cost as well as unreimbursed Medicaid costs starting with the tax year 2008. Using data from hospitals in California before and after tax year 2008 (2009 filing), this study examines whether changes in the IRS 990 Schedule H had a significant effect on the supply of community benefits by non-profit hospitals relative to for-profit hospitals. Empirical results suggest that nonprofit hospitals do not supply more community benefits relative to for-profit hospitals for both definitions of community benefits reported in Schedule H. Although the supply of community benefits increased for all hospitals after 2008, the increase was not higher for nonprofits. Moreover, nonprofits supplied significantly less community benefits according to some definitions. Thus, minimum charity care standard is justified.展开更多
基金Project supported by the National Natural Science Foundation of China （Grant Nos 10574121, 90406024 and 10025420）, Chinese Education Ministry and Chinese Academy of Sciences.
文摘The exchange bias of bilayer magnetic films consisting of ferromagnetic （FM） and antiferromagnetic （AFM） layers in an uncompensated case is studied by use of the many-body Green＇s function method of quantum statistical theory. The effects of the layer thickness and temperature and the interracial coupling strength on the exchange bias HE are investigated. The dependence of the exchange bias HE on the FM layer thickness and temperature is qualitatively in agreement with experimental results. When temperature varies, both the coercivity HC and HE decrease with the temperature increasing. For each FM thickness, there exists a least AFM thickness in which the exchange bias occurs, which is called pinning thickness.
文摘Since 1969 private, nonprofit hospitals have qualified for tax exemption as charitable institutions and in exchange for the preferential tax treatment were required to provide community benefits. However, in the absence of mandatory reporting of community benefits at the federal level and in the absence of a clear definition of community benefits, the previous literature provides but ambiguous evidence regarding hospitals’ supply of community benefits. Responding to policymakers’ concerns, the Internal Revenue Service (IRS) mandates all private, non-profit hospitals to report charity care at cost as well as unreimbursed Medicaid costs starting with the tax year 2008. Using data from hospitals in California before and after tax year 2008 (2009 filing), this study examines whether changes in the IRS 990 Schedule H had a significant effect on the supply of community benefits by non-profit hospitals relative to for-profit hospitals. Empirical results suggest that nonprofit hospitals do not supply more community benefits relative to for-profit hospitals for both definitions of community benefits reported in Schedule H. Although the supply of community benefits increased for all hospitals after 2008, the increase was not higher for nonprofits. Moreover, nonprofits supplied significantly less community benefits according to some definitions. Thus, minimum charity care standard is justified.
