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831.
Many proponents of disaster mitigation claim that it offers potential benefits in terms of saved lives and property far exceeding its costs. To provide evidence for this, and to justify the use of public funds, agencies involved in mitigation can use benefit–cost analysis (BCA). Such analysis, if well done, offers a testable, defensible means of evaluating and comparing projects, helps decision-makers choose between mitigation projects, and provides a means to assess the way we spend public funds. In this critical overview of the more contentious issues and latest developments in BCA, I emphasize the pragmatic choices that one can make in accordance with good practice in project evaluation.  相似文献   
832.
The effects of month of birth (MOB) on life expectancy of a German subpopulation was investigated. Data from people who died in North Rhine Westphalia in the years 1984 (n=188,515) and 1999 (n=188,850) were analyzed. For comparative purposes, all deaths that occurred at an age of <50 years were excluded (1984: 8.4%; 1999: 6.2%). In general, individuals born in May through July had the lowest age at death (1984: 75.27±0.09 years; 1999: 77.58±0.09 years), while those born between October and December had the highest (1984: 75.98±0.08 years; 1999: 78.35±0.09 years), supporting earlier findings. The observed amplitudes (differences between highest and lowest values) were more pronounced in men than in women. When comparing these data of MOB effects on life expectancy with earlier findings in Australia, Austria, Denmark, Ukraine, and the USA, it is evident that a negative correlation exists between the average age at death and the MOB amplitudes. Separate analyses by gender, possible for the data from Germany, the Ukraine, and the USA, revealed a significant negative correlation for men, but not for women. A new hypothesis is therefore presented describing an influence of life quality, as reflected by average life expectancy, on the extent of MOB effects; for example, seasonally variable sensitivities during pregnancy/early childhood.  相似文献   
833.
营区道路景观规划是营区景观规划中十分重要的组成部分,它直接影响到营区景观的整体规划效果。提出营区道路景观设计应重点考虑的几个问题,并加以剖析。  相似文献   
834.
分析了粉末烧结材料泊松比与屈服准则的关系 ,指出了泊松比Kuhn模型的等价假设 ,比较了几种泊松比模型的特点 ,提出了一种能反映致密过程中密度较大时泊松比增长率减缓的特点的箕舌线函数型泊松比模型。  相似文献   
835.
Light,timing of biological rhythms,and chronodisruption in man   总被引:3,自引:2,他引:3  
This paper reviews abundant evidence suggesting that causes and course of aging and cancers can be considered as being both light- and rhythm-related. We define chronodisruption as a relevant disturbance of orderly biological rhythms over days and seasons and years in man. Light is the primary external mediator and melatonin a primary internal intermediary of such disturbances, which can result in earlier deaths via premature aging and cancers. We conclude that experimental and epidemiological research can provide further insights into common denominators of these chronic processes and may offer novel and uniform targets for prevention.  相似文献   
836.
837.
838.
The cicada genus Platypleura has a wide distribution across Africa and southern Asia. We describe endothermic thermoregulation in four South African species that show crepuscular signaling behavior. This is the first evidence of thermoregulation in platypleurine cicadas. Field measurements of body temperature ( T b) show that these animals regulate T b through endogenous heat production. Maximum T b measured was 22.1°C above ambient temperature during calling activity at dusk. The mean T b during dusk activity did not differ from the mean T b during diurnal activity. A unique behavior for cicadas, a temperature-dependent telescoping pulsation of the abdomen, was observed in the laboratory during endogenous warm-up. This behavior is part of a unique method of heat generation in endothermic cicadas. Males generally call from trunks and branches within the canopy and appear to use endothermy even when the sun is available to elevate T b. Endothermy may provide the cicadas with the advantage of decreasing predation and acoustic competition by permitting calling from perches that most complement their cryptic coloration patterns and that ectotherms cannot use due to thermal constraints. In addition, endothermy may permit calling activity during crepuscular hours when atmospheric conditions are optimal for acoustic communication and predation risks are minimal.  相似文献   
839.
The study of the origin and early evolution of birds has never produced as much excitement and public attention as in the past decade. Well preserved and abundant new fossils of birds and dinosaurs have provided unprecedented new evidence on the dinosaurian origin of birds, the arboreal origin of avian flight, and the origin of feathers prior to flapping flight. The Mesozoic avian assemblage mainly comprises two major lineages: the prevalent extinct group Enantiornithes, and the Ornithurae, which gave rise to all modern birds, as well as several more basal taxa. Cretaceous birds radiated into various paleoecological niches that included fish- and seed-eating. Significant size and morphological differences and variation in flight capabilities, ranging from gliding to powerful flight among early birds, highlight the diversification of birds in the Early Cretaceous. There is little evidence, however, to support a Mesozoic origin of modern avian groups. Controversy and debate, nevertheless, surround many of these findings, and more details are needed to give a better appreciation of the significance of these new discoveries.  相似文献   
840.
The recently reported Jeholornis represents the only known bird with a complete long skeletal tail except for Archaeopteryx. Two newly discovered specimens referable to Jeholornis provide some important new information about its anatomy. The tail of Jeholornis is much longer than that of Archaeopteryx and comprises a maximum of 27 caudal vertebrae compared with only 23 in Archaeopteryx. More interestingly, the tail feathers are shaped more like those of dromaeosaurs than those of Archaeopteryx. We conclude that the common ancestor of birds must have a more primitive tail than that in Archaeopteryx, confirming the side branch position of Archaeopteryx in the early avian evolution. The synsacrum is composed of six sacrals, representing a transitional stage between Archaeopteryx and more advanced birds. The scapula of Jeholornis has a dorso-laterally exposed glenoid facet, and the coracoid has a supracoracoid foramen. The presence of a pair of fenestrae in the sternum of Jeholornis has further implications for the air-sac system in early birds. Electronic Supplementary Material  The online version of this article (doi: contains supplementary material, which is available to authorized users.  相似文献   
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