932 resultados para 430000 History and Archaeology


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In this paper we determine the extent to which host-mediated mutations and a known sampling bias affect evolutionary studies of human influenza A. Previous phylogenetic reconstruction of influenza A (H3N2) evolution using the hemagglutinin gene revealed an excess of nonsilent substitutions assigned to the terminal branches of the tree. We investigate two hypotheses to explain this observation. The first hypothesis is that the excess reflects mutations that were either not present or were at low frequency in the viral sample isolated from its human host, and that these mutations increased in frequency during passage of the virus in embryonated eggs. A set of 22 codons known to undergo such “host-mediated” mutations showed a significant excess of mutations assigned to branches attaching sequences from egg-cultured (as opposed to cell-cultured) isolates to the tree. Our second hypothesis is that the remaining excess results from sampling bias. Influenza surveillance is purposefully biased toward sequencing antigenically dissimilar strains in an effort to identify new variants that may signal the need to update the vaccine. This bias produces an excess of mutations assigned to terminal branches simply because an isolate with no close relatives is by definition attached to the tree by a relatively long branch. Simulations show that the magnitude of excess mutations we observed in the hemagglutinin tree is consistent with expectations based on our sampling protocol. Sampling bias does not affect inferences about evolution drawn from phylogenetic analyses. However, if possible, the excess caused by host-mediated mutations should be removed from studies of the evolution of influenza viruses as they replicate in their human hosts.

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Exposure to intimate partner violence (IPV) puts women at risk for severe and chronic physical and mental health consequences, including elevations in IPV-related psychopathology and increased risk for future victimization. Previous research has examined attention as one of the key information processing mechanisms associated with elevated psychopathology and risk for victimization; however, the nature of attentional processing in response to IPV-related information in women exposed to IPV is poorly understood. Therefore, the current study aimed to further understanding of associations between attentional processing, IPV exposure, and related distress using measures of eye movement and subjective interpretations of IPV-related information. A sample of women exposed to IPV (n = 57) viewed sets of negative, positive, and neutral relationship images for 15 s each while having their eye movements monitored and later provided subjective ratings and interpretations of levels of risk and safety in those images. We examined associations of outcome measures with proximal victimization experiences and IPV-related psychopathology (i.e., depression, posttraumatic stress disorder (PTSD), anxiety, and dissociation). Results indicated a bias to attend to negative relationship images relative to positive and neutral images, though this attention bias fluctuated over time and varied as a function of symptomatology such that depression corresponded with increases in attention to negative images over time and PTSD corresponded with decreases in attention to negative images. The general attention bias for negative images appeared to be explained by rumination on and/or difficulty disengaging from negative images, which was related to general elevations in psychopathology as well as exposure to revictimization by different perpetrators. Subjective interpretations and perception of danger cues were related to victimization history and level and type of IPV-related distress. We replicated these procedures with a sample of undergraduate students without IPV histories or related symptomatology (n = 33) and found that the overall attention bias for negative images was not replicated, despite general similarities in patterns of attention over time. Results therefore indicated associations between attentional processing and IPV exposure and related symptomatology. Implications for models of IPV-related psychopathology and attentional processing as well as directions for future study and interventions are discussed.

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This article examines past and present systems requiring that a person receive permission before buying or borrowing a firearm. The article covers laws from the eighteenth century to the present. Such laws have traditionally been rare in the United States. The major exceptions are antebellum laws of the slaves states, and of those same states immediately after the Civil War, which forbade gun ownership by people of color, unless the individual had been granted government permission. Today “universal background checks” are based on a system created by former New York City Mayor Michael Bloomberg and his “Everytown” lobby. Such laws have been enacted in several states, and also proposed as federal legislation. Besides covering the private sale of firearms, they also cover most loans of firearms and the return of loaned firearms. By requiring that almost all loans and returns may only be processed by a gun store, these laws dangerously constrict responsible firearms activities, such as safety training and safe storage. Massachusetts, Connecticut, and California are among the jurisdictions which have enacted less restrictive, more effective legislation which create controls on private firearms sales, without inflicting so much harm on firearms safety.

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This thesis uses models of firm-heterogeneity to complete empirical analyses in economic history and agricultural economics. In Chapter 2, a theoretical model of firm heterogeneity is used to derive a statistic that summarizes the welfare gains from the introduction of a new technology. The empirical application considers the use of mechanical steam power in the Canadian manufacturing sector during the late nineteenth century. I exploit exogenous variation in geography to estimate several parameters of the model. My results indicate that the use of steam power resulted in a 15.1 percent increase in firm-level productivity and a 3.0-5.2 percent increase in aggregate welfare. Chapter 3 considers various policy alternatives to price ceiling legislation in the market for production quotas in the dairy farming sector in Quebec. I develop a dynamic model of the demand for quotas with farmers that are heterogeneous in their marginal cost of milk production. The econometric analysis uses farm-level data and estimates a parameter of the theoretical model that is required for the counterfactual experiments. The results indicate that the price of quotas could be reduced to the ceiling price through a 4.16 percent expansion of the aggregate supply of quotas, or through moderate trade liberalization of Canadian dairy products. In Chapter 4, I study the relationship between farm-level productivity and participation in the Commercial Export Milk (CEM) program. I use a difference-in-difference research design with inverse propensity weights to test for causality between participation in the CEM program and total factor productivity (TFP). I find a positive correlation between participation in the CEM program and TFP, however I find no statistically significant evidence that the CEM program affected TFP.

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From Introduction. Regional economic disequilibria was viewed as both an obstacle to and result of integration (European Commission 1965; European Commission 1962; European Commission 1969). Even within the Treaty of Rome, the Community tried to establish mechanisms to alleviate regional inequality. However, it was not until 1975 that the main mechanism of regional policy was established as a result of British and Irish enlargement: the European Regional Development Fund (ERDF). Since then, cohesion policy has become a significant EU expenditure accounting for €347bn, or 35.7% of the total EU budget for 2007-13(European Commission Regional Policy-Info Regio 2012). It has also become a key policy linked to enlargement. The underlying principle of cohesion policy assumes that the market alone cannot solve development problems and therefore government intervention is needed. This notion is in direct contrast to the underlying principle of EU competition policy, which asserts that the free market can solve economic development problems (Meadows, interview by author, 2003). The logic underlying cohesion policy is not only counter to EU competition policy, but also regulatory policies. Unlike other EU policies, cohesion policy is not a sectoral policy, but rather territorial in nature (Leonardi, 2006). Thus at times EU regulatory policy has also unintentionally worked counter to the goals of regional policy, sometimes disadvantaging poorer regions (Dudek, 2005). As the Community has sought to ameliorate regional disparities, it meant that all levels of government: local, regional, national and supranational would need to be involved, however, member states have different territorial governance and European regional development programs have to varying degrees impacted the relationship and policy responsibility of different levels of government (Leonardi, 2006; Bachtler and Michie 1993; Marks, 1993). The very nature of regional development policy has provoked a re-examination of subsidiarity, or which level of government is the lowest and most appropriate level. The discussion of policy formulation and implementation at the lowest level possible also addresses the issue of the democratic deficit. Some argue that the closer government is to the people the more responsive and representative it is. Democracy, however, also implies that public funds are used in a transparent way and for public rather than private good. Yet, as we examine the history and current situation of EU regional funds we find that corruption and misuse still abound. Thus, to understand the history of regional policy it is imperative to look at the major transformations of the policy, how regional policy has impacted subsidiarity and the quality of democracy, become an important instrument of enlargement and contradicted or conflicted with other EU policies.