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671.
Because of the inherent complexity of biological systems, there is often a choice between a number of apparently equally applicable physiologically based models to describe uptake and metabolism processes in toxicology or risk assessment. These models may fit the particular data sets of interest equally well, but may give quite different parameter estimates or predictions under different (extrapolated) conditions. Such competing models can be discriminated by a number of methods, including potential refutation by means of strategic experiments, and their ability to suitably incorporate all relevant physiological processes. For illustration, three currently used models for steady-state hepatic elimination--the venous equilibration model, the parallel tube model, and the distributed sinusoidal perfusion model--are reviewed and compared with particular reference to their application in the area of risk assessment. The ability of each of the models to describe and incorporate such physiological processes as protein binding, precursor-metabolite relations and hepatic zones of elimination, capillary recruitment, capillary heterogeneity, and intrahepatic shunting is discussed. Differences between the models in hepatic parameter estimation, extrapolation to different conditions, and interspecies scaling are discussed, and criteria for choosing one model over the others are presented. In this case, the distributed model provides the most general framework for describing physiological processes taking place in the liver, and has so far not been experimentally refuted, as have the other two models. These simpler models may, however, provide useful bounds on parameter estimates and on extrapolations and risk assessments.  相似文献   
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674.
This paper deals with parents' perspectives and experiences of bringing up children with a variety of impairments in Iceland, and how they impact the young disabled adults' approach to the status of adulthood. The paper is based on a qualitative study that explored perspectives and experiences of 36 young disabled adults (16-24 years old), their parents, friends and teachers. The purpose of this paper is to share themes related to patterns of parents' reactions and choices when coming to terms with parenting a disabled child, the support they found from their social network and professionals, and their sons or daughters' subsequent views of themselves and their prospects as young adults. The paper includes different perspectives on adulthood and the extent to which the young disabled people expect to reach that status or remain as 'eternal youth' enmeshed in segregated services. Findings show that the type and nature of early support for parents of disabled children is critical for the young adults' approaching adulthood in regular society or expecting to remain in the limbo of 'eternal youth' within segregated settings. Early 'betrayals' may, however, be revisited at each subsequent transition point. Furthermore, parents and their disabled children who struggled for social inclusion could obtain full active membership in society, even against social and physical barriers, and medically defined disability labels.  相似文献   
675.
This paper presents a case study of the August 1994 Cuban balseros crisis, during which more than 35,000 fled the island and headed toward Florida in the span of a few weeks. It argues that Castro launched the crisis in an attempt to manipulate US fears of another Mariel, and in order to compel a shift in US policy, both on immigration and on a wider variety of issues. The paper further contends that from Castro’s perspective, this exercise in coercion proved a qualified success – his third such successful use of the Cuban people as an asymmetric political weapon against the US. In addition, the paper argues that Castro’s success was predicated on his ability to internationalize his own domestic crisis and transform it into an American domestic political and foreign policy crisis. Finally, it offers a novel explanation of how, why, and under what conditions, states and/or non–state actors may attempt to use refugees as coercive political weapons. Although dwarfed in size by the larger 1980 Mariel boatlift, the 1994 crisis is important for several reasons. First, despite its brevity, it had far reaching consequences for US–Cuban relations. Without warning or preamble, it catalyzed a shift in US policy vis–à–vis Cuban immigration that represented a radical departure from what it had been for the previous three decades. Second, it influenced US domestic politics on the national level, by expanding the scope and salience of the issue, and mobilizing not only Floridians, but also the larger public concerned about illegal immigration. Third, the crisis illustrated the potential potency of engineered migration as an asymmetric weapon of the weak. Finally, the brief, but significant, interactions of international and domestic actors in this case warrant examination because, although the 1994 crisis was limited, in its dynamics it resembles myriad other international refugee crises, large and small. Thus the case offers valuable lessons that may aid in dealing with future (real or threatened) crises.  相似文献   
676.
The authors examine the effect of premarital cohabitation on the division of household labor in 22 countries. First, women do more routine housework than men in all countries. Second, married couples that cohabited before marriage have a more equal division of housework. Third, national cohabitation rates have equalizing effects on couples regardless of their own cohabitation experience. However, the influence of cohabitation rates is only observed in countries with higher levels of overall gender equality. The authors conclude that the trend toward increasing cohabitation may be part of a broader social trend toward a more egalitarian division of housework.  相似文献   
677.
In this paper, with the use of linear regressions to investigate how relationship dissolution affects sexual attitudes and behaviors, the authors address the stereotype that newly single people seek multiple sexual partners. Although the newly single people surveyed did obtain new sexual partners, the rate at which they acquired new partners did not support the stereotype. Specifically, men with custody of their children seemed oriented toward finding a steady partner. Additionally, men and women with low incomes reported relatively high rates of partner acquisition after relationship dissolution. The high rates reported by disadvantaged groups may be more directly related to familial instability accompanying poverty than to cultural characteristics associated with income or race. We argue that a life stage model with categorical stages in a rigid, anachronistic progression provides insufficient means to gain an understanding of newly single people.  相似文献   
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679.
Abstract Although scholars cite the Tennessee Valley Authority as one of President Franklin Roosevelt's major reform programs, the valley authority model did not replace the limited‐purpose water programs of the Bureau of Reclamation and the Army Corps of Engineers. State‐centered theorists hold that reformers are most likely to succeed during periods such as the New Deal era, when they are supported by a democratized polity and when they dominate Congress and the administration. This paper shows that in river policy, the strength of opposing interest groups also mattered. The TVA bill was passed in 1933 because reformers skillfully coordinated action at potential choke points and weakened the already disorganized opposing lobbyists. In 1936, however, after regrouping, opposing river lobbyists and legislators took advantage of the New Dealers' spending mood by expanding the Corps' flood control program. They also helped defeat further valley authorities, the most promising of the New Deal water policy reforms.  相似文献   
680.
Extractive industries such as logging and mining are generally expected to bring significant economic benefits to rural regions, but a growing number of findings have now challenged that common expectation. Still, it is not clear whether the findings of less–than–desirable economic outcomes are isolated or representative. In this article, we assemble literally all of the relevant quantitative findings on mining that we have been able to identify in published and/or technical literature from the United States. In the interest of rigor, we limit the assessment to cases in which strictly nonmetropolitan mining regions are compared against other nonmetropolitan regions and/or against those regions’ own experiences over time. Overall, 301 findings meet the criteria for inclusion. Contrary to the long–established assumptions, but consistent with more recent critiques, roughly half of all published findings indicate negative economic outcomes in mining communities, with the remaining findings being split roughly evenly between favorable and neutral/indeterminate ones. Positive findings are more likely to be associated with incomes than with poverty or (especially) unemployment rates, and they are more likely to come from the western United States, where much of the mining involves relatively large, new coal strip mines. Over half of all positive findings come from the years prior to 1982. In virtually all other categories, the plurality or majority of findings have been negative. When the patterns of findings are subjected to one–sample means tests, the only way to produce a significantly positive outcome is by combining all neutral/indeterminate findings with the positive ones, while focusing exclusively on incomes; by contrast, in the case of poverty or unemployment rates—as well as for the overall body of findings—the results are consistently and significantly negative, whether the neutral/indeterminate findings are combined with negative ones or omitted from the equations altogether. Until or unless future studies produce dramatically different findings, there appears to be no scientific basis for accepting the widespread, “obvious” assumption that mining will lead to economic improvement.  相似文献   
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