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Multivariate receptor models aim to identify the pollution sources based on multivariate air pollution data. This article is concerned with estimation of the source profiles (pollution recipes) and their contributions (amounts of pollution). The estimation procedures are based on constrained nonlinear least squares methods with the constraints given by nonnegativity and identifiability conditions of the model parameters. We investigate several identifiability conditions that are appropriate in the context of receptor models, and also present new sets of identifiability conditions, which are often reasonable in practice when the other traditional identifiability conditions fail. The resulting estimators are consistent under appropriate identifiability conditions, and standard errors for the estimators are also provided. Simulation and application to real air pollution data illustrate the results. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   
73.
Gross scoliosis of the fetal thoracic spine was diagnosed at 18 weeks gestation. The pregnancy was terminated and the fetus found to have webbing of the neck and an imperforate anus in addition to vertebral defects.  相似文献   
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The efficiency and sustainability of climate change adaptation projects depend on appropriate models and tools to take climate‐smart practices to scale. This paper presents the “Building assets and agency” approach taken by the Accelerating Adoption of Agroforestry project whose objective is to scale the adoption of context‐specific adaptation and mitigation options. Through the approach, communities are encouraged to identify, mobilise, and use their existing assets to define community plans that are responsive to their identities, interests, and preferences. This innovative approach combines conscious selection of project staff and partners, group capacity and agency training, cocreation of skills in self‐selected agricultural practices with an emphasis on business skills, and tools for sustainable scaling through farmer‐to‐farmer extension. The paper addresses challenges and solutions, and case study data justifying proof of concept. While developed in a climate change context, and being sensitive to a number of factors, the approach can support effective, efficient, and socially appropriate action in any sector.  相似文献   
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Carson HS  Cook GS  López-Duarte PC  Levin LA 《Ecology》2011,92(10):1972-1984
Recently researchers have gone to great lengths to measure marine metapopulation connectivity via tagging, genetic, and trace-elemental fingerprinting studies. These empirical estimates of larval dispersal are key to assessing the significance of metapopulation connectivity within a demographic context, but the life-history data required to do this are rarely available. To evaluate the demographic consequences of connectivity we constructed seasonal, size-structured metapopulation matrix models for two species of mytilid mussel in San Diego County, California, USA. The self-recruitment and larval exchange terms were produced from a time series of realized connectivities derived from trace-elemental fingerprinting of larval shells during spring and fall from 2003 to 2008. Both species exhibited a strong seasonal pattern of southward movement of recruits in spring and northward movement in fall. Growth and mortality terms were estimated using mark-recapture data from representative sites for each species and subpopulation, and literature estimates of juvenile mortality. Fecundity terms were estimated using county-wide settlement data from 2006-2008; these data reveal peak reproduction and recruitment in fall for Mytilus californianus, and spring for M. galloprovincialis. Elasticity and life-stage simulation analyses were employed to identify the season- and subpopulation-specific vital rates and connectivity terms to which the metapopulation growth rate (lambda) was most sensitive. For both species, metapopulation growth was most sensitive to proportional changes in adult fecundity, survival and growth of juvenile stages, and population connectivity, in order of importance, but relatively insensitive to adult growth or survival. The metapopulation concept was deemed appropriate for both Mytilus species as exchange between the subpopulations was necessary for subpopulation persistence. However, highest metapopulation growth occurred in years when a greater proportion of recruits was retained within the predominant source subpopulation. Despite differences in habitat and planktonic duration, both species exhibited similar overall metapopulation dynamics with respect to key life stages and processes. However, different peak reproductive periods in an environment of seasonal current reversals led to different regional (subpopulation) contributions to metapopulation maintenance; this result emphasizes the importance of connectivity analysis for spatial management of coastal resources.  相似文献   
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环境表现对金融利害攸关者的价值   总被引:1,自引:0,他引:1  
公司财务表现与环境表现之间的联系日益明显.各公司可以通过促进后者而力求获得资助优势.公司环境表现对金融利害攸关者的价值随资助类型而异,同样也随环境改善的程度和具体细节而异.争取资助的公司,以及政府和非政府组织,应当熟悉不同的金融服务业及其具体需要和问题.  相似文献   
79.
Chemical fingerprinting techniques recently have been used to track larval dispersal of estuarine species that bear calcified structures, but the applicability of this important approach may be limited on the open coast where chemical signatures may be less distinctive and for the many species that do not retain calcified structures throughout development. Externally brooded embryos of the porcelain crab, Petrolisthes cinctipes, and inductively coupled plasma mass spectrometry were used to determine whether fine-scale variation in trace-elemental composition occurred along an open coast. Embryos were collected from 16 sites from 37.8° to 39.5° north latitude along the Pacific Coast of California, USA during late January and early February 2003. Discriminant function analysis revealed that collection sites, many separated by only a few kilometers along an open coast, could be differentiated with an overall accuracy of 73%, and combining the sites into three regions increased the accuracy to 88%. Thus, distinctive elemental signatures can be detected in open coast species even at a fine scale raising the possibility that larval tags can be developed for many more species than previously thought possible.  相似文献   
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