979 resultados para Lecture à vue


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The high-temperature superconductors are complex oxides, generally containing two-dimensional CuO2 sheets. Various families of the cuprate superconductors are described, paying special attention to aspects related to oxygen stoichiometry, phase stability, synthesis and chemical manipulation of charge carriers. Other aspects discussed are chemical applications of cuprates, possibly as gas sensors and copper-free oxide superconductors. All but the substituted Nd and Pr cuprates are hole-superconductors. Several families of cuprates show a nearly constant n(h) at maximum T(c). Besides this universality, the cuprates exhibit a number of striking common features. Based on Cu(2p) photoemission studies, it is found that the Cu-O charge-transfer energy, DELTA, and the Cu(3d)-O(2p) hybridization strength, t(pd), are key factors in the superconductivity of cuprates. The relative intensity of the satellite in the Cu(2p) core-level spectra, the polarizability of the CuO2 sheets as well as the hole concentration are related to DELTA/t(pd). These chemical bonding factors have to be explicitly taken into account in any model for superconductivity of the cuprates.

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O presente trabalho tem o objetivo de estudar o ethos constituído nas redações argumentativas de vestibular, verificando, a partir das escolhas linguísticas dos estudantes, a representação discursiva que eles constroem de si para defender sua tese. O corpus se constitui de cem redações, que integraram a segunda fase dos vestibulares 2006 e 2007, da Universidade do Estado do Rio de Janeiro. Para alcançarmos essa imagem coletiva, utilizamos, prioritariamente, a noção de ethos discursivo proposta por Dominique Maingueneau. Optamos por realizar uma análise quantitativa e qualitativa do corpus. A primeira abordagem nos proporcionou uma visão panorâmica das redações ao passo que a segunda revelou os casos mais representativos de cada fenômeno observado. No decorrer da análise, verificamos nas redações práticas que incidiam no risco de configurar ethé indesejados e mesmo censuráveis, causando prejuízo à argumentação dos vestibulandos. Por essa razão, finalizamos a pesquisa com sugestões de atividades didáticas, que focam o aprimoramento das habilidades de escrita e leitura, na tentativa de apresentar uma contribuição ao processo de ensino-aprendizagem de Produção Textual

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Cynoglossus canariensis has a very rapid growth. The rate of the males is 0,36 and the female one is 0,32. The asymptotic size is 55,0cm for the females and 50,5cm for the males. Females and males younger than three years (40cm), which represent 90 per cent of the Côte d'Ivoire stock have a similar growth, so the average equation: Lt=53,5 (1-e -0,34(t+1)) will be used.

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The genesis and the early history of the Woods Hole Laboratory (WHL), to a lesser extent the Marine Biological Laboratory (MBL), and to some degree the Woods Hole Oceanographic Institution (WHOI), were elegantly covered by Paul S. Galtsoff (1962) in his BCF Circular "The Story of the Bureau of Commercial Fisheries Biological Laboratory, Woods Hole, Massachusetts." It covers the period from the beginning in 1871 to 1958. Galtsoffs more than 35-year career in the fishery service was spent almost entirely in Woods Hole. I will only briefly touch on that portion of the Laboratory's history covered by Galtsoff. Woods Hole, as a center of marine science, was conceived and implemented largely by one man, Spencer Fullerton Baird, at that time Assistant Secretary of the Smithsonian and who was also instrumental in the establishment of the National Museum and Permanent Secretary of the newly established American Association for the Advancement of Science. He was appointed by President Ulysses S. Grant in 1871 as the first U.S. Commissioner of Fisheries. Fisheries research began here as early as 1871, but a permanent station did not exist until 1885.