389 resultados para Tyler, Imogen
Resumo:
Research on endocrine disruption in fish has been dominated by studies on estrogen-active compounds which act as mimics of the natural estrogen, 17β-estradiol (E2), and generally exert their biological actions by binding to and activation of estrogen receptors (ERs). Estrogens play central roles in reproductive physiology and regulate (female) sexual differentiation. In line with this, most adverse effects reported for fish exposed to environmental estrogens relate to sexual differentiation and reproduction. E2, however, utilizes a variety of signaling mechanisms, has multifaceted functions and targets, and therefore the toxicological and ecological effects of environmental estrogens in fish will extend beyond those associated with the reproduction. This review first describes the diversity of estrogen receptor signaling in fish, including both genomic and non-genomic mechanisms, and receptor crosstalk. It then considers the range of non-reproductive physiological processes in fish that are known to be responsive to estrogens, including sensory systems, the brain, the immune system, growth, specifically through the growth hormone/insulin-like growth factor system, and osmoregulation. The diversity in estrogen responses between fish species is then addressed, framed within evolutionary and ecological contexts, and we make assessments on their relevance for toxicological sensitivity as well as ecological vulnerability. The diversity of estrogen actions raises questions whether current risk assessment strategies, which focus on reproductive endpoints, and a few model fish species only, are protective of the wider potential health effects of estrogens. Available - although limited - evidence nevertheless suggests that quantitative environmental threshold concentrations for environmental protection derived from reproductive tests with model fish species are protective for non-reproductive effects as well. The diversity of actions of estrogens across divergent physiological systems, however, may lead to and underestimation of impacts on fish populations as their effects are generally considered on one functional process only and this may underrepresent the impact on the different physiological processes collectively.
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The greater Himalayan region demarcates two of the most prominent linguistic phyla in Asia: Tibeto-Burman and Indo-European. Previous genetic surveys, mainly using Y-chromosome polymorphisms and/or mitochondrial DNA polymorphisms suggested a substantially reduced geneflow between populations belonging to these two phyla. These studies, however, have mainly focussed on populations residing far to the north and/or south of this mountain range, and have not been able to study geneflow patterns within the greater Himalayan region itself. We now report a detailed, linguistically informed, genetic survey of Tibeto-Burman and Indo-European speakers from the Himalayan countries Nepal and Bhutan based on autosomal microsatellite markers and compare these populations with surrounding regions. The genetic differentiation between populations within the Himalayas seems to be much higher than between populations in the neighbouring countries. We also observe a remarkable genetic differentiation between the Tibeto-Burman speaking populations on the one hand and Indo-European speaking populations on the other, suggesting that language and geography have played an equally large role in defining the genetic composition of present-day populations within the Himalayas.
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This survey provides a self-contained account of M-estimation of multivariate scatter. In particular, we present new proofs for existence of the underlying M-functionals and discuss their weak continuity and differentiability. This is done in a rather general framework with matrix-valued random variables. By doing so we reveal a connection between Tyler's (1987) M-functional of scatter and the estimation of proportional covariance matrices. Moreover, this general framework allows us to treat a new class of scatter estimators, based on symmetrizations of arbitrary order. Finally these results are applied to M-estimation of multivariate location and scatter via multivariate t-distributions.
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In order to explore the diversity and selective signatures of duplication and deletion human copy number variants (CNVs), we sequenced 236 individuals from 125 distinct human populations. We observed that duplications exhibit fundamentally different population genetic and selective signatures than deletions and are more likely to be stratified between human populations. Through reconstruction of the ancestral human genome, we identify megabases of DNA lost in different human lineages and pinpoint large duplications that introgressed from the extinct Denisova lineage now found at high frequency exclusively in Oceanic populations. We find that the proportion of CNV base pairs to single nucleotide variant base pairs is greater among non-Africans than it is among African populations, but we conclude that this difference is likely due to unique aspects of non-African population history as opposed to differences in CNV load.
Resumo:
For probability distributions on ℝq, a detailed study of the breakdown properties of some multivariate M-functionals related to Tyler's [Ann. Statist. 15 (1987) 234] ‘distribution-free’ M-functional of scatter is given. These include a symmetrized version of Tyler's M-functional of scatter, and the multivariate t M-functionals of location and scatter. It is shown that for ‘smooth’ distributions, the (contamination) breakdown point of Tyler's M-functional of scatter and of its symmetrized version are 1/q and inline image, respectively. For the multivariate t M-functional which arises from the maximum likelihood estimate for the parameters of an elliptical t distribution on ν ≥ 1 degrees of freedom the breakdown point at smooth distributions is 1/(q + ν). Breakdown points are also obtained for general distributions, including empirical distributions. Finally, the sources of breakdown are investigated. It turns out that breakdown can only be caused by contaminating distributions that are concentrated near low-dimensional subspaces.
Resumo:
by Constance de Rothschild [[Elektronische Ressource]] ; aus: The New Quarterly Magazine, Vol. 5. 1876
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Governance of food systems is a poorly understood determinant of food security. Much scholarship on food systems governance is non-empirical, while existing research is often case study-based and theoretically and methodologically incommensurable. This frustrates aggregation of evidence and generalisation. We undertook a systematic review of methods used in food systems governance research with a view to identifying a core set of indicators for future research. We gathered literature through a structured consultation and sampling from recent reviews. Indicators were identified and classified according to the levels and sectors they investigate. We found a concentration of indicators in food production at local to national levels and a sparseness in distribution and consumption. Unsurprisingly, many indicators of institutional structure were found, while agency-related indicators are moderately represented. We call for piloting and validation of these indicators and for methodological development to fill gaps identified. These efforts are expected to support a more consolidated future evidence base and eventual meta-analysis.
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Through the correct implementation of lean manufacturing methods, a company can greatly improve their business. Over a period of three months at TTM Technologies, I utilized my knowledge to fix existing problems ans streamline production. In addition, other trouble areas in their production process were discovered and proper lean methods were used to address them. TTM Technologies saw many changed in the right direction over this time period.
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This research examines the site and situation characteristics of community trails as landscapes promoting physical activity. Trail segment and neighborhood characteristics for six trails in urban, suburban, and exurban towns in northeastern Massachusetts were assessed from primary Global Positioning System (GPS) data and from secondary Census and land use data integrated in a geographic information system (GIS). Correlations between neighborhood street and housing density, land use mix, and sociodemographic characteristics and trail segment characteristics and amenities measure the degree to which trail segment attributes are associated with the surrounding neighborhood characteristics.
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This paper describes the procedures used to create a distributed collection of topographic maps of the Austro-Hungarian Empire, the Spezialkarte der Öesterriechisch-ungarnischen Monarchie, Masse. 1:75,000 der natur. This set of maps was published in Vienna over a period of years from 1877 to 1914. The part of the set used in this project includes 776 sheets; all sheets from all editions number over 3,665. The paper contains detailed information on how the maps were converted to digital images, how metadata were prepared, and how Web-browser access was created using ArcIMS Metadata Server. The project, funded by a 2004 National Leadership Grant from the Institute for Museums and Library Science (IMLS), was a joint project of the Homer Babbidge Library Map and Geographic Information Center at the University of Connecticut, the New York Public Library, and the American Geographical Society’s Map Library at the University of Wisconsin Milwaukee.
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124 Briefe zwischen Leo Löwenthal und Max Horkheimer; 2 Briefe von Leo Löwenthal an The Trustes of Hermann Weil Memorial Foundation (New York), 27.04.1955; 4 Briefe zwischen Leo Löwenthal und Chauncy D. Harris, 1954/1955; 1 Brief von L. R. Little an Leo Löwenthal, 09.06.1955; 2 Briefe zwischen Leo Löwenthal und Ralph Tyler, 1955; 1 Brief von Richard Hofstadter an Paul F. Lazarsfeld, 05.01.1955;
Resumo:
The biological safety profession has historically functioned within an environment based on recommended practices rather than regulations, so summary data on compliance or noncompliance with recommended practices is largely absent from the professional literature. The absence of safety performance outcome data is unfortunate since the concept of biosafety containment is based on a combination of facility based controls and workplace practices, and persistent failures in either type of controls could ultimately result in injury or death. In addition, the number of laboratories requiring biosafety containment is likely to grow significantly in the coming years in the wake of the terrorist events of 2001. In this study, the outcomes of 768 biosafety level 2 (BSL-2) safety surveys were analyzed for commonalities and trends. Items of non-compliance noted were classified as facility related or practice related. The most frequent item of noncompliance encountered was the failure to re-certify biosafety cabinetry. Not surprisingly, the preponderance of the other frequent items of non-compliance encountered were practice related, such as general housekeeping orderly, changes in compliance levels, as well as establish trends in the elements of items of non-compliance during the sequential survey period. The findings described in this study are significant because, for the first time, the outcomes of compliance with recommended biosafety practices can be characterized and thus used as the basis for focused interventions. Since biosafety is heavily reliant on adherence to specific safety practices, the ability to focus interventions on objectively identified practice-related items of non-compliance can assist in the reduction of worker risk in this area experiencing tremendous growth. The information described is also of heighten importance given the number of workplaces expected to involve potentially infectious agents in the coming years. ^
Resumo:
The purpose of this study is to descriptively analyze the current program at Ben Taub Pediatric Weight Management Program in Houston, Texas, a program designed to help overweight children ages three to eighteen to lose weight. In Texas, approximately one in every three children is overweight or obese. Obesity is seen at an even greater level within Ben Taub due to the hospital's high rate of service for underserved minority populations (Dehghan et al, 2005; Tyler and Horner, 2008; Hunt, 2009). The weight management program consists of nutritional, behavioral, physical activity, and medical counseling. Analysis will focus on changes in weight, BMI, cholesterol levels, and blood pressure from 2007–2010 for all participants who attended at least two weight management sessions. Recommendations will be given in response to the results of the data analysis.^