938 resultados para Geiger-M©·uller counters.
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In this study, the length-weight relationship and the condition factor of Brycon opalinus were analyzed in three rivers within the Santa Virgínia Unit, at Serra do Mar State Park, in São Paulo State. The different conditions in these three environments were evidenced, such as the seasonality, reproductive period, and the differences between females and males according to the parameters which evidenced the best physiological condition of the fish. In this species, the condition factor varied along the seasons at all three collection sites. The length of the first gonadal maturation and the reproductive period were long, with the highest intensity in the spring and summer.
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The aim of this work was to assess and compare the diversity of the ichthyofauna in three headwater rivers of Paraíba-do-Sul basin in the Serra do Mar State Park, Núcleo Santa Virgínia. A total of 1,774 specimens of 16 species of fishes belonging to 6 families were caught. Characiforms were the most abundant fish at all three sites, followed by Cyprinodontiformes, Siluriformes, and Perciformes. The Shannon index (H′), evenness (E), and the Jaccard and Morisita-Horn similarity indexes were low, indicating both low diversity and low similarity of species among the three streams. The values of these indexes should be evaluated according to the biotic and abiotic conditions in each environment. It is clear that in mountain streams of the Atlantic Forest, these low values occur because of the presence of a few abundant and many rare species.
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The length-weight relationship and condition factor of Salminus hilarii were analyzed in a section of the lower part of the Sorocaba river basin, São Paulo State. By studying male, female and immature individuals separately, different length-weight patterns were found for each. The same happened when distinct seasonal variations of the relationships were compared, related to feeding alterations and to the reproductive period of the species.
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The length-weight relationship and condition factor for Cichla kelberi introduced in an artificial lake in southeastern Brazil were analyzed. By studying separately the male, female and immature individuals, different length-weight patterns were found to happen among them. The same happened when distinct seasonal variations were compared. They are related to feeding alterations and me reproductive periods. The length-weight relationship and condition factor for these fishes vary in accordance with the time of introduction, population size, the characteristics of the ecosystem, sexual maturity, as well as the intra- and interspecific interactions.
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The aim of this study was to discuss aspects of the diet of Serrasalmus maculatus. Fish were collected using gill nets, whose lengths measured 100 m and mesh diameters varied from 3 to 8 cm. A total of 107 individuals were collected. Their length varied from 62 to 210 mm. They were mainly represented by female and immature individuals. No individual was caught in temperatures below 21°C. Four feeding item categories were observed: fish muscle pieces, parts of fish fins, plant fragments, and insects. Comparisons made among individual length classes revealed some significant differences within stomach consumed contents. Individuals whose length exceeded 165 mm consumed only parts of fish muscles and plants. The food availability in the environment and the class lengths amplitude may, however, have influenced the results, in which ontogenetic differences should not be precisely observed.
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Incluye Bibliografía
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We report the combination of recent measurements of the helicity of the W boson from top quark decay by the CDF and D0 collaborations, based on data samples corresponding to integrated luminosities of 2.7-5.4fb -1 of pp̄ collisions collected during Run II of the Fermilab Tevatron collider. Combining measurements that simultaneously determine the fractions of W bosons with longitudinal (f 0) and right-handed (f +) helicities, we find f 0=0.722±0.081[±0.062(stat)±0.052(syst)] and f +=-0.033±0.046[±0.034(stat)±0.031(syst)]. Combining measurements where one of the helicity fractions is fixed to the value expected in the standard model, we find f 0=0.682±0. 057[±0.035(stat)±0.046(syst)] for fixed f + and f +=-0.015±0.035[±0.018(stat)±0.030(syst)] for fixed f 0. The results are consistent with standard model expectations. © 2012 American Physical Society.
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The top quark is the heaviest known elementary particle, with a mass about 40 times larger than the mass of its isospin partner, the bottom quark. It decays almost 100% of the time to a W boson and a bottom quark. Using top-antitop pairs at the Tevatron proton-antiproton collider, the CDF and D0 Collaborations have measured the top quark's mass in different final states for integrated luminosities of up to 5.8fb -1. This paper reports on a combination of these measurements that results in a more precise value of the mass than any individual decay channel can provide. It describes the treatment of the systematic uncertainties and their correlations. The mass value determined is 173.18±0.56(stat)±0.75(syst)GeV or 173.18±0.94GeV, which has a precision of ±0.54%, making this the most precise determination of the top-quark mass. © 2012 American Physical Society.
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
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Incluye Bibliografía
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We describe an experimental procedure to probe the validity of Newton's second law. The experimental arrangement allows us to accelerate a glider on an air track by means of forces that are both steady and known. We also show how to determine acceleration from average speeds calculated for successive time intervals of the motion measured by using several electronic counters connected to a single-crystal oscillator circuit. Within experimental errors, the experiments clearly show the proportionality between acceleration and force for a fixed mass and between acceleration and inverse of mass for a fixed force. © by the Sociedade Brasileira de Física.
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Pós-graduação em Ciência Animal - FMVA
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Pós-graduação em Medicina Veterinária - FMVZ
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)