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Spatial variation in soil inorganic nitrogen across an arid urban ecosystem   总被引:4,自引:1,他引:3  
We explored variations in inorganic soil nitrogen (N) concentrations across metropolitan Phoenix, Arizona, and the surrounding desert using a probability-based synoptic survey. Data were examined using spatial statistics on the entire region, as well as for the desert and urban sites separately. Concentrations of both NO3-N and NH4-N were markedly higher and more heterogeneous amongst urban compared to desert soils. Regional variation in soil NO3-N concentration was best explained by latitude, land use history, population density, along with percent cover of impervious surfaces and lawn, whereas soil NH4-N concentrations were related to only latitude and population density. Within the urban area, patterns in both soil NO3-N and NH4-N were best predicted by elevation, population density and type of irrigation in the surrounding neighborhood. Spatial autocorrelation of soil NO3-N concentrations explained 49% of variation among desert sites but was absent between urban sites. We suggest that inorganic soil N concentrations are controlled by a number of ‘local’ or ‘neighborhood’ human-related drivers in the city, rather than factors related to an urban-rural gradient.  相似文献   
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Most North American cities no longer display strong ethnic differentiation of speech within the European‐origin population. This is not true in the English‐speaking community of Montreal, Canada, where English is a minority language. Differences in the phonetic realization of vowels by Montrealers of Irish, Italian, and Jewish ethnic origin are investigated by means of acoustic analysis. A statistical analysis of ethnic differences in formant frequencies shows that ethnicity has a significant effect on several variables, particularly the phonetic position of /u:/ and /ou/ and the allophonic conditioning of /æ/ and /au/ before nasal consonants. The unusual tenacity of ethnophonetic variation in Montreal English is explained in light of the minority status of English, and the social and residential segregation of ethnic groups in distinct neighborhoods, which limits their exposure to speakers of Standard Canadian English who might otherwise serve as models for assimilation.  相似文献   
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Abstract Nonmetropolitan (nonmetro) inequality patterns are contrasted with those of metropolitan (metro) areas to assess the utility of neoclassical and restructuring theoretical frameworks. Inequality measures are constructed from March Current Population Surveys for the years 1968–1991. Results indicate that inequality is greater in nonmetro areas than in metro areas. Results of decomposition procedures suggest that the observed inequality is due to a mix of neoclassical and restructuring factors that account for more inequality in metro than nonmetro areas. National policies must take account of metro/nonmetro differences in patterns and sources of inequality.  相似文献   
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Definitions of child abuse are culturally driven. Hong Kong, with a predominantly Chinese population, has managed to eradicate much of the societal abuse that children suffer elsewhere in Asia. Professional and government attention has now shifted to child abuse and neglect within the family. The paper, based on interviews with key professionals. analysis of policy documents and practice records examines traditional Chinese parent-child relationships. the status of parental authority and corporal punishment and changes in contemporary Hong Kong family life. It goes on to outline the development of responses to child abuse in Hong Kong, some of the dilemmas that professionals face in defining abuse and areas for future research.  相似文献   
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Summary.  When evaluating potential interventions for cancer prevention, it is necessary to compare benefits and harms. With new study designs, new statistical approaches may be needed to facilitate this comparison. A case in point arose in a proposed genetic substudy of a randomized trial of tamoxifen versus placebo in asymptomatic women who were at high risk for breast cancer. Although the randomized trial showed that tamoxifen substantially reduced the risk of breast cancer, the harms from tamoxifen were serious and some were life threaten-ing. In hopes of finding a subset of women with inherited risk genes who derive greater bene-fits from tamoxifen, we proposed a nested case–control study to test some trial subjects for various genes and new statistical methods to extrapolate benefits and harms to the general population. An important design question is whether or not the study should target common low penetrance genes. Our calculations show that useful results are only likely with rare high penetrance genes.  相似文献   
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