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The “tragedy of the commons” is the familiar problem that open access to a common property resource leads to overexploitation and to zero profits. A commons model is applied to an example of state sponsored private violence, the practice of privateering or licensed piracy. It is predicted that the presence of uncertainty about the value of the prey will reduce the amount of exploitation effort, and that industry profits may be positive due to both uncertainty and heterogeneous exploiters. Using data from England's wars with France and Spain between 1625 and 1630, the model suggests that the commons, represented by enemy merchant shipping, was not overexploited and that privateering profits were positive. The dynamic paths of privateering effort, ships seized, and individual firm profits were, however, consistent with the normal expectation that commons exploitation will peak and fall, as competition drives down returns through entry. “England was never richer than when at war with Spain.” Sir Edward Coke   相似文献   
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A report is given of two young people who died after intake of dextromethorphan, one by suicide and the other for uncertain reasons. To our knowledge this is the first reported fatal intoxications with this drug.  相似文献   
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Appraisals about the implications of stressful events that are evaluated as involving a threat to self (negative self-evaluation, negative evaluation from others, rejection by others) have been shown to place youth at risk for the development of mental health problems. This longitudinal study tested a protective-stabilizing interactive model, in which high maternal acceptance was predicted to mitigate the prospective relation between threat to self appraisals and change in adolescents’ mental health problems six months later. Participants were 89 adolescents from divorced families ages 10–12 and residential mothers. Adolescents reported on threat to self appraisals from the most stressful event experienced in the past month. Mothers and youth reported on maternal acceptance and mental health problems. Multiple regression analyses provided support for the protective effects of maternal acceptance on adolescents’ mental health problems. Intervention implications are discussed. Ana Brown is a pre-doctoral fellow in prevention research (NIMH 2 T32 MH18387–19) and doctoral student in the Department of Psychology at Arizona State University, Tempe, AZ. Research interests include the study of children’s appraisals and responses to stressful events in the prevention of mental health problems. Sharlene Wolchik is a clinical psychologist and professor in the Department of Psychology at Arizona State University, Tempe, AZ. Her research focuses on identifying risk and protective factors for children whose parents have divorced. She also has designed and evaluated the efficacy of preventive interventions for children from divorced families and children who have experienced parental bereavement. Jenn-Yun Tein is a research associate professor and Co-Director of the Research Methodology Core of the Prevention Research Center at Arizona State University, Tempe, AZ. Her research interests include analyses of mediation and moderation of preventive interventions as well as applications of methodology and statistics in prevention research. Irwin Sandler is a Regents’ Professor in the Department of Psychology and Director of the Prevention Research Center at Arizona State University, Tempe, AZ. His research interests focus on understanding resilience for children exposed to stress and on the development, evaluation and dissemination of programs to promote resilience and prevent mental health problems for children in stress.  相似文献   
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We examine whether nations, faced with the threat of terrorism, will be motivated to engage in the efficient amount of retaliation against terrorists. We demonstrate that the problem confronting the efforts of nations to achieve an optimal retaliation against terrorists is understated by the traditional free-rider analysis. In particular, nations have the option of actually selling or reducing the public good of retaliation, provided through the efforts of others, by offering safe havens to terrorists in return for the terrorists' pledge to attack elsewhere. This paid-rider behavior is also shown to apply to other public good scenarios.The authors gratefully acknowledge the helpful comments of Gordon Tullock on an earlier draft. Sole responsibility for the paper's content rests with the authors. Todd Sandler's research was supported by a Science and Humanities Research Institute Summer Grant at Iowa State University.  相似文献   
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发展了一种基于高阶迎风格式和嵌套网格捕捉直升机悬停旋翼涡尾迹的方法.无粘通量采用Roe Reimann求解器,使用改进的5阶加权基本无振荡(WENO)格式对交界面左右状态进行高阶插值,并与MUSCL插值进行比较.为便于捕捉尾迹和实施周期性边界条件,计算采用结构嵌套网格,其中高质量的旋翼网格完全嵌套于背景网格中.当解达到近似收敛后在桨尖涡分布区域对背景网格进行加密,如此经过3次得到优化的背景网格.考虑到WENO格式插值的特点,提出了搜索3层洞边界和人工外边界的方法以便插值的直接进行.用该方法对一跨音速和一亚音速悬停旋翼粘性流场进行了数值计算.数值结果表明:所发展方法对涡尾迹具有很高的捕捉能力;与MUSCL格式相比,WENO格式具有较低的数值耗散.  相似文献   
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This paper investigates the role that International Criminal Police Organization (INTERPOL) surveillance—the Mobile INTERPOL Network Database (MIND) and the Fixed INTERPOL Network Database (FIND)—played in the War on Terror since its inception in 2005. MIND/FIND surveillance allows countries to screen people and documents systematically at border crossings against INTERPOL databases on terrorists, fugitives, and stolen and lost travel documents. Such documents have been used in the past by terrorists to transit borders. By applying methods developed in the treatment‐effects literature, this paper establishes that countries adopting MIND/FIND experienced fewer transnational terrorist attacks than they would have had they not adopted MIND/FIND. Our estimates indicate that, on average, from 2008 to 2011, adopting and using MIND/FIND results in 0.5 fewer transnational terrorist incidents each year per 100 million people. Thus, a country like France with a population just above 64 million people in 2008 would have 0.32 fewer transnational terrorist incidents per year owing to its use of INTERPOL surveillance. This amounts to a sizeable average proportional reduction of about 30 percent.  相似文献   
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Using campaign contributions to legislators as an indicator of member influence, we explore the impact of term limits on the distribution of power within state legislatures. Specifically, we perform a cross‐state comparison of the relative influence of party caucus leaders, committee chairs, and rank‐and‐file legislators before and after term limits. The results indicate that term limits diffuse power in state legislatures, both by decreasing average contributions to incumbents and by reducing the power of party caucus leaders relative to other members. The change in contribution levels across legislators in different chambers implies a shift in power to the upper chamber in states with term limits. Thus, the impact of term limits may be attenuated in a bicameral system.  相似文献   
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