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"The spread of HIV-1 in the United Kingdom is simulated by a model which integrates behavioural and epidemiological processes within a multi-regional population projection framework and represents the spatial heterogeneities in the distribution of HIV which have significant effects on transmission patterns. Analyses determine the significance of different parameters in contributing to prediction uncertainty and highlight the importance of behavioural change and international population movements." 相似文献
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A multidisciplinary programme of research on Islamic pottery has been focused on questions of the dating, provenance and technology of Islamic pottery. One particular question has been the development of stonepaste, a material made primarily of crushed quartz with added frit-glass and clay. The combination of the different approaches of this study has revealed early foundations for the technology in ninth-century AD Iraq, apparently originating in the clay ceramic rather than the ‘Egyptian faience’ tradition. Subsequent and final practice developed in tenth- and eleventh-century AD Egypt. This technology becomes the primary body for all fine Islamic ceramics. 相似文献
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Dimitrios S. Dendrinos 《Geographical analysis》1994,26(3):261-281
The purpose of this paper is first, to present some evidence indicative of a rough daily periodicity in traffic counts at a cross-section of an urban road accompanied by a considerable amount of seemingly random additional variation; and second, to attempt an accounting through Fast Fourier Transform and power spectrum density functions of this additional variation beyond the rough daily cycle. Reasons behind the macroscopic variable's dynamic behavior are provided. Relatively extensive traffic counts make them especially suited for investigating various dynamic behaviors, including possibly nonperiodic (chaotic) patterns. 相似文献
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An important line of research concerning historical fertility patterns in currently developed countries of Europe has concluded that, prior to the fertility transition, marital fertility was essentially constant over time, and deliberate fertility control was virtually unknown. It has been argued that variations over time in overall fertility were largely the consequence of variations in nuptiality. Other researchers have challenged these views and present evidence for the existence of a significant minority of fertility controllers in pretransition populations. In this article, we find support for this second view and argue that (1) there was significant, non-random variation in marital fertility over time, prior to the transition; (2) in many cases, this variation in marital fertility was large relative to contemporaneous variations in nuptiality; and (3) in a substantial minority of the cases, the variation over time in pretransition marital fertility was so large that it is suggestive of deliberate fertility control. Thus, our findings question the view of fertility transition as an innovation in deliberate marital fertility control. While most of our evidence is based on data from England and Wales, we find corroboration of our key results in other European data. 相似文献
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Blue glass trade beads from well-dated late seventeenth- to early twentieth-century sites and collections have been analysed non-destructively by instrumental neutron activation analysis. The beads display enough variations in their elemental contents to allow us to characterize the different chemistries. The implication of these results is that similar chemical analyses of blue beads from undated archaeological sites may be used to help date the sites, since each bead chemistry has a specific earliest period. 相似文献