2,791 research outputs found

    Certificação e selos de qualidade asseguram requisitos na produção.

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    Em 2011, o Committee on Fisheries (Cofi) da Food and Agriculture Organization (FAO) comitê de pesca da FAO, órgão da Organização das Nações Unidas (ONU) aprovou o documento que contém as Diretrizes Técnicas para Certificação da Aquicultura, visando ao desenvolvimento, à organização e à implementação de regimes confiáveis de certificação de aquicultura. Os países signatários deverão internalizá-lo e usá-lo como base para adaptar ou criar as normas relacionadas ao tema. O documento abrange questões de saúde e bem-estar animal, segurança alimentar, integridade ambiental e aspectos socioeconômicos

    A model for the onset of transport in systems with distributed thresholds for conduction

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    We present a model supported by simulation to explain the effect of temperature on the conduction threshold in disordered systems. Arrays with randomly distributed local thresholds for conduction occur in systems ranging from superconductors to metal nanocrystal arrays. Thermal fluctuations provide the energy to overcome some of the local thresholds, effectively erasing them as far as the global conduction threshold for the array is concerned. We augment this thermal energy reasoning with percolation theory to predict the temperature at which the global threshold reaches zero. We also study the effect of capacitive nearest-neighbor interactions on the effective charging energy. Finally, we present results from Monte Carlo simulations that find the lowest-cost path across an array as a function of temperature. The main result of the paper is the linear decrease of conduction threshold with increasing temperature: Vt(T)=Vt(0)(14.8kBTP(0)/pc)V_t(T) = V_t(0) (1 - 4.8 k_BT P(0)/ p_c) , where 1/P(0)1/P(0) is an effective charging energy that depends on the particle radius and interparticle distance, and pcp_c is the percolation threshold of the underlying lattice. The predictions of this theory compare well to experiments in one- and two-dimensional systems.Comment: 14 pages, 10 figures, submitted to PR
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