931 resultados para State And Transition Models


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Cattle resistance to ticks is measured by the number of ticks infesting the animal. The model used for the genetic analysis of cattle resistance to ticks frequently requires logarithmic transformation of the observations. The objective of this study was to evaluate the predictive ability and goodness of fit of different models for the analysis of this trait in cross-bred Hereford x Nellore cattle. Three models were tested: a linear model using logarithmic transformation of the observations (MLOG); a linear model without transformation of the observations (MLIN); and a generalized linear Poisson model with residual term (MPOI). All models included the classificatory effects of contemporary group and genetic group and the covariates age of animal at the time of recording and individual heterozygosis, as well as additive genetic effects as random effects. Heritability estimates were 0.08 ± 0.02, 0.10 ± 0.02 and 0.14 ± 0.04 for MLIN, MLOG and MPOI models, respectively. The model fit quality, verified by deviance information criterion (DIC) and residual mean square, indicated fit superiority of MPOI model. The predictive ability of the models was compared by validation test in independent sample. The MPOI model was slightly superior in terms of goodness of fit and predictive ability, whereas the correlations between observed and predicted tick counts were practically the same for all models. A higher rank correlation between breeding values was observed between models MLOG and MPOI. Poisson model can be used for the selection of tick-resistant animals. © 2013 Blackwell Verlag GmbH.

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Searches are reported for Higgs bosons in the context of either the standard model extended to include a fourth generation of fermions (SM4) with masses of up to 600 GeV or fermiophobic models. For the former, results from three decay modes (ττ, WW, and ZZ) are combined, whilst for the latter the diphoton decay is exploited. The analysed proton-proton collision data correspond to integrated luminosities of up to 5.1 fb-1 at 7 TeV and up to 5.3 fb-1 at 8 TeV. The observed results exclude the SM4 Higgs boson in the mass range 110-600 GeV at 99% confidence level (CL), and in the mass range 110-560 GeV at 99.9% CL. A fermiophobic Higgs boson is excluded in the mass range 110-147 GeV at 95% CL, and in the range 110-133 GeV at 99% CL. The recently observed boson with a mass near 125 GeV is not consistent with either an SM4 or a fermiophobic Higgs boson. © 2013 CERN.

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

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Sectoral policies make explicit and implicit assumptions about the behaviour and capabilities of the agents (such as dynamic responses to market signals, demand-led assistance, collaborative efforts, participation in financing); which we consider to be rather unrealistic. Because of this lack of realism, policies that aim to be neutral often turn out to be highly exclusive. They fail to give sufficient importance to the special features of the sector -with its high climatic, biological and commercial risks and its slow adaptation- or to the fact that those who take decisions in agriculture are now mostly in an inferior position because of their incomes below the poverty line, their inadequate training, their traditions based on centuries of living in precarious conditions, and their geographical location in marginal areas, far from infrastructure and with only a minimum of services and sources of information. These people have only scanty and imperfect access to the markets which, according to the prevailing model, should govern decisions and the (re);distribution of the factors of production. In our opinion, this explains the patchy and lower-than-expected growth registered by the sector after the reforms to promote the liberalization of markets and external openness in the region. In view of the results of the application of the new model, it may be wondered whether Latin America can afford a form of development which excludes over half of its agricultural producers; what the alternatives are; and what costs and benefits each of them offers in terms of production and monetary, social, spatial and other aspects. The article outlines the changes in policies and their results at the aggregate level, summarizes the arguments usually put forward to explain agricultural performance in the region, and proposes a second set of explanations based on a description of the agents and the responses that may be expected from them, contrasting the latter with the supposedly neutral nature of the policies.

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