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31.
Silphids in urban forests: Diversity and function 总被引:2,自引:0,他引:2
Many ecologists have examined the process of how urbanization reduces biological diversity but rarely have its ecological consequences been assessed. We studied forest-dwelling burying beetles (Coleoptera: Silphidae)—a guild of insects that requires carrion to complete their life cycles—along an urban-rural gradient of land use in Maryland. Our objective was to determine how forest fragmentation associated with urbanization affects (1) beetle community diversity and structure and (2) the ecological function provided by these insects, that is, decomposition of vertebrate carcasses. Forest fragmentation strongly reduced burying beetle diversity and abundance, and did so far more pervasively than urbanization of the surrounding landscape. The likelihood that beetles interred experimental baits was a direct, positive function of burying beetle diversity. We conclude that loss of burying beetle diversity resulting from forest fragmentation could have important ecological consequences in urban forests. 相似文献
32.
We examine how attention to animacy information may contribute to children's developing knowledge of language. This research extends beyond prior research in that children were shown dynamic events with novel entities, and were asked not only to comprehend sentences but to use sentence structure to infer the meaning of a new word. In a 4 × 3 design, animacy status (e.g., animate agent, inanimate patient) and labeling syntax (agent, patient, nonlabel control) were varied. Across most events, 2 1/2‐year‐old participants responded as if they expected animate entities to be named. However, in a prototypical (animate agent‐inanimate patient) event condition, children responded differentially across different syntactic structures. Thus, the clearest evidence for attention to syntactic cues was found in the prototypical event condition. These results suggest that young children attend to the animacy status of unfamiliar entities, that they have expectations about animacy relations in events, and that these expectations support emerging syntactic knowledge. 相似文献
33.
Donald B. Rubin 《Scandinavian Journal of Statistics》2004,31(2):161-170
Abstract. The use of the concept of ‘direct’ versus ‘indirect’ causal effects is common, not only in statistics but also in many areas of social and economic sciences. The related terms of ‘biomarkers’ and ‘surrogates’ are common in pharmacological and biomedical sciences. Sometimes this concept is represented by graphical displays of various kinds. The view here is that there is a great deal of imprecise discussion surrounding this topic and, moreover, that the most straightforward way to clarify the situation is by using potential outcomes to define causal effects. In particular, I suggest that the use of principal stratification is key to understanding the meaning of direct and indirect causal effects. A current study of anthrax vaccine will be used to illustrate ideas. 相似文献
34.
Abstract Using data from a national survey in Bolivia and from a regional sample of poor communities in two regions of Bolivia, we model the effects of community conditions, household characteristics, and social relations on child health as measured by child mortality and stunted growth. Based on national data, children in rural areas are twice as likely to die before the age of two than are children in large cities, and about one‐third of the children in rural areas are stunted. Including measures of community, household, and maternal characteristics accounts for at least two‐thirds of the urban/rural difference in child health. We conclude that expansion of health services, improvements in household and community sanitation, and socioeco‐nomic development are all needed to overcome the rural disadvantage in child health. 相似文献
35.
1. Most diagnosed cases of tardive dyskinesia (TD) are mildly inconvenient to the patient, but some can be severe or life-threatening. The primary goal of intervention should be early identification of abnormal movements related to TD and the prescribing of an appropriate medication regimen. 2. Unless specific training occurs and a specific monitoring system is in place, TD movements may be missed. However, not all movements are necessarily related to TD. 3. Although screening and monitoring are valuable, nothing is more important than prevention. New medications must be developed that do not carry the risk of TD, and other approaches to treat TD must be developed. 相似文献
36.
TESTAMENTARY BEHAVIOR: 总被引:1,自引:0,他引:1
T.P. Schwartz 《The Sociological quarterly》1993,34(2):337-355
Content analysis and qualitative analysis of all 319 last wills that were filed in Providence Probate Court, 1985, revealed that about ten percent of the testators used testamentary material, disinheritance or altruism to express their individuality. About 42 percent of the wills were personalized directly in other ways. Forty-eight percent displayed indirect influences of family, friends and community. Less that ten percent displayed primary influences of attorneys, banks, nursing homes, governments, religions or other organizations. In the light of these findings, while none of the three major theoretical positions on testamentary behavior prevails, the individualist position is manifested more often than is the family-community position. Both of these positions are manifested much more often than is the legalist position.
These findings are related to the work of Emile Durkheim and to contemporary sociological theories of the family, community and law. 相似文献
These findings are related to the work of Emile Durkheim and to contemporary sociological theories of the family, community and law. 相似文献
37.
The authors investigated the prevalence of recurrent pain in a college student sample. Of the 1,564 students surveyed, 467 (29%) indicated that they had experienced recurrent pain at an intensity that was mostly in the mild-to-moderate range. Students who reported having recurrent pain were significantly older and more depressed than students who did not indicate they suffered from recurrent pain. Pain intensity was positively correlated (r = .14) with depression among the students who reported having recurrent pain. Implications of the findings for future research, treatment, and health promotion efforts are discussed. 相似文献
38.
This study investigated the gender-specific, self-reported sexual behaviors and attitudes of never-married college students attending a southeastern university in 1973 and 1988. Data were collected by means of a mailed questionnaire that remained essentially unchanged for both years. The authors found that both men and women reported an increase in heterosexual relationships that included sexual intercourse and a decrease in nonsexual relationships with the other gender. The majority of the students perceived themselves as adequately informed about sexuality and satisfied with their relationships, although the proportion of men who reported being satisfied with their relationships declined over the 15 years. The students indicated that sexuality education should focus primarily on information about AIDS and on preparation for marriage. 相似文献
39.
Charles W. Griffiths Chris Dockins Nicole Owens Nathalie B. Simon Daniel A. Axelrad 《Risk analysis》2002,22(4):679-688
To quantify the health benefits of environmental policies, economists generally require estimates of the reduced probability of illness or death. For policies that reduce exposure to carcinogenic substances, these estimates traditionally have been obtained through the linear extrapolation of experimental dose-response data to low-exposure scenarios as described in the U.S. Environmental Protection Agency's Guidelines for Carcinogen Risk Assessment (1986). In response to evolving scientific knowledge, EPA proposed revisions to the guidelines in 1996. Under the proposed revisions, dose-response relationships would not be estimated for carcinogens thought to exhibit nonlinear modes of action. Such a change in cancer-risk assessment methods and outputs will likely have serious consequences for how benefit-cost analyses of policies aimed at reducing cancer risks are conducted. Any tendency for reduced quantification of effects in environmental risk assessments, such as those contemplated in the revisions to EPA's cancer-risk assessment guidelines, impedes the ability of economic analysts to respond to increasing calls for benefit-cost analysis. This article examines the implications for benefit-cost analysis of carcinogenic exposures of the proposed changes to the 1986 Guidelines and proposes an approach for bounding dose-response relationships when no biologically based models are available. In spite of the more limited quantitative information provided in a carcinogen risk assessment under the proposed revisions to the guidelines, we argue that reasonable bounds on dose-response relationships can be estimated for low-level exposures to nonlinear carcinogens. This approach yields estimates of reduced illness for use in a benefit-cost analysis while incorporating evidence of nonlinearities in the dose-response relationship. As an illustration, the bounding approach is applied to the case of chloroform exposure. 相似文献
40.
樊宝敏 《北京林业大学学报(社会科学版)》2003,2(3):69-74
张钧成先生是我国著名的林业历史学家.该文从林业史学科建设、林业史研究概况、中国古代林业通史、中国古代林业思想和传统文化、林业科技史和经济史、近现代林业史等研究领域,概述了张先生的学术成就,并回顾了张先生高尚的人生哲学和宝贵的治学经验.张先生的研究成果和治学经验,为我国林史学科的发展奠定了基础. 相似文献