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891.
Use of Acute Toxicity to Estimate Carcinogenic Risk   总被引:1,自引:0,他引:1  
Data on the effects of human exposure to carcinogens are limited, so that estimation of the risks of carcinogens must be obtained indirectly. Current risk estimates are generally based on lifetime animal bioassays which are expensive and which take more than two years to complete. We here show how data on acute toxicity can be used to make a preliminary estimate of carcinogenic risk and give an idea of the uncertainty in that risk estimate. The estimates obtained are biased upwards, and so are useful for setting interim standards and determining whether further study is worthwhile. A general scheme which incorporates the use of such estimates is outlined, and it is shown by example how adoption of the procedures suggested could have prevented regulatory hiatus in the past.  相似文献   
892.
893.
Conclusion Obregón and Calles encountered intense but disunited resistance at home and abroad. They responded with land and labor reforms to coopt campesinos and urban workers, thereby undercutting popular opposition and enlisting the masses in the campaign against regionalist bosses, Porfirian oligarchs, and foreign investors. These populist alliances helped the Sonoran diarchy build more loyal and professional military and civilian bureaucracies, which in turn helped regulate local and metropolitan firms, increase and stabilize tax revenues, and develop the economy's infrastructure. Following Obregón assasination in 1928, Calles forestalled collapse by integrating many military and civilian bosses into a central party organization. Yet the state remained only partially consolidated. At the end of the Calles administration, regionalist cliques retained considerable political autonomy, and a major campesino rebellion challenged federal authority. Furthermore, dependence on foreign petroleum and mining companies limited government revenue and spending. In mid-1927, Calles inaugurated several years of conservative domestic policies and open collaboration with North Americans. But Calles did not purge all progressive elements from the state machinery. His quest for political stability led him to enroll in the official party many elites who depended on mass followings and who opposed the rightward shift of government policy. During the Great Depression, these elites formed a coalition with intellectuals, small business, and the lower classes that after electing Lázaro Cardenas president, ended Callista hegemony and undertook far-reaching reforms. Thus the Cardenistas completed what Obregón and Calles had begun: the Mexican state's transformation from the poorly centralized oligarchic structure of the Porfiriato to the highly centralized, mass-inclusionary structure of the postrevolutionary era. In the next decade, Mexico joined the ranks of the world's intermediate, semiperipheral economies thanks to import-substitution and metropolitan capital. Since then, Mexican governments have maintained political stability and spurred industrialization by steering a pragmatic course between reformism and conservatism, nationalism and collaborationism.In regard to future research, this essay suggests that we consider not only Mexico's relationship to North Atlantic powers in the 1920s but also its standing vis-à-vis the states and classes of other late-industrializing countries. One possibility is to study the interplay of metropolitan actions to control the raw materials and markets of the periphery with the politics of resistance and accommodation throughout the Caribbean basin: How did international and local conflicts affect the distribution of United States and Western European investments in the Caribbean basin? What impact did metropolitan investments have on the region's struggles over state power and pattern of economic change? How did the state-building struggles and economic changes of the 1920s influence the region's nationalist break-throughs and defeats during the Great Depression and World War II? What were the consequences of nationalist successes and failures for the subsequent paths of state making and economic development in the Caribbean basin, as well as for North Atlantic investors and governments after World War II?  相似文献   
894.
There is a current surge of writings on spirituality and related topics. For instance, Woodward (1997) has pointed out that since Thomas Moore's publication of Care of the Soul in 1994 there have been nearly 800books published with the word soul in the title. These run all the way from Chicken Soup for theWoman's Soul (Canfield et al., 1996) to A Guide to Liberating YourSoul (Barrett, 1995). Spirituality of work is a big part of this surge. Definitionsof spirituality of work seem to vary widely. Bowman (1998, p. 8) in his `reviewof the phenomenon of spirituality of work' found `Definitions of the term spirituality in the context of the Spirituality of Work troublesome and particularly subjective. Many writers do not even attempt definitions.' The purpose of this article is to review the concept of spirituality of work in its historical and current use and to propose a comprehensive definition.  相似文献   
895.
论嗜杀物种     
包括黑猩猩在内的很多物种的动物都经常杀害同类。这些事实再次引起了关于进化过程中形成的生物特性是否影响着以及如何影响着人类好战的倾向等问题的讨论。要讨论这方面的问题,需要区分动物的两类暴力行为,即“猎杀”与“斗杀”。猎杀是猎食者对无助的动物的攻击。小群的黑猩猩或游动性的狩猎—采集者有时会杀死邻近社群的竞争对手。现有的资料表明,由这种群间攻击导致的死亡在总的死亡率中所占的比例与人类与黑猩猩这两个物种大致相同。这方面行为的普遍性说明这两个物种都存在进化过程中形成的致命的暴力行为,其认知能力也适应了成功地进行杀戮的需要。  相似文献   
896.
Many methods have been developed for the nonparametric estimation of a mean response function, but most of these methods do not lend themselves to simultaneous estimation of the mean response function and its derivatives. Recovering derivatives is important for analyzing human growth data, studying physical systems described by differential equations, and characterizing nanoparticles from scattering data. In this article the authors propose a new compound estimator that synthesizes information from numerous pointwise estimators indexed by a discrete set. Unlike spline and kernel smooths, the compound estimator is infinitely differentiable; unlike local regression smooths, the compound estimator is self‐consistent in that its derivatives estimate the derivatives of the mean response function. The authors show that the compound estimator and its derivatives can attain essentially optimal convergence rates in consistency. The authors also provide a filtration and extrapolation enhancement for finite samples, and the authors assess the empirical performance of the compound estimator and its derivatives via a simulation study and an application to real data. The Canadian Journal of Statistics 39: 280–299; 2011 © 2011 Statistical Society of Canada  相似文献   
897.
898.
Capture–recapture experiments are commonly used to estimate the size of a closed population. However, the associated estimators of the population size are well known to be highly sensitive to misspecification of the capture probabilities. To address this, we present a general semiparametric framework for the analysis of capture–recapture experiments when the capture probability depends on individual characteristics, time effects and behavioural response. This generalizes well‐known general parametric capture–recapture models and extends previous semiparametric models in which there is no time dependence or behavioural response. The method is evaluated in simulations and applied to two real data sets.  相似文献   
899.
The goal of this research was to investigate the origins of social networks by examining the formation of children's peer relationships in 11 preschool classes throughout the school year. We investigated whether several fundamental processes of relationship formation were evident at this age, including reciprocity, popularity, and triadic closure effects. We expected these mechanisms to change in importance over time as the network crystallizes, allowing more complex structures to evolve from simpler ones in a process we refer to as structural cascading. We analyzed intensive longitudinal observational data of children's interactions using the SIENA actor-based model. We found evidence that reciprocity, popularity, and triadic closure all shaped the formation of preschool children's networks. The influence of reciprocity remained consistent, whereas popularity and triadic closure became increasingly important over the course of the school year. Interactions between age and endogenous network effects were non-significant, suggesting that these network formation processes were not moderated by age in this sample of young children. We discuss the implications of our longitudinal network approach and findings for the study of early network developmental processes.  相似文献   
900.
The cultural diversity now evident in Greek society creates educational challenges and opportunities. Space to address these is provided by the multicultural awareness aspects of the discourse of the Cross‐Thematic Curriculum Framework (CTCF). For English language classes, multicultural direction is provided through the disciplinary discussion of new teaching paradigm possibilities. In particular, these discussions encourage us to explore the repositioning of English teaching in Greek state schooling from a foreign language orientation towards a multicultural one. In this article, having set the context, we present the Multicultural Awareness Through English (MATE) paradigm. We conclude by illustrating the MATE paradigm in action.

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