25 research outputs found

    Simulação de interação gravitacional de N corpos

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    Simulação de interação gravitacional de N corpos

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    Efeitos de subprodutos da fotodegradação da deltametrina na população de Tetranychus urticae Koch (Acari: Tetranychidae)

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    O objetivo deste trabalho foi avaliar os efeitos da aplicação em algodoeiros (Gossypium hirsutum L.), do ácido-fenoxibenzóico (principal subproduto da fotodegradação da deltametrina e de muitos outros piretróides) e de emulsões aquosas de Deltametrina (expostas à luz solar por dois, oito e 15 dias antes da pulverização) sobre a população do ácaro Tetranychus urticae Koch. Nas plantas pulverizadas com emulsões de Deltametrina expostas à luz solar e com ácido fenoxi-benzóico (nas maiores doses) as populações de T. urticae foram significativamente maiores que nas plantas testemunhas.The objective of this research was to study the populational behavior of Tetranychus urticae Koch, feeding on cotton plants (Gossypium hirsutum L.) submitted to the application of deltamethrin and the phenoxy-benzoic-acid, the main decomposition product of deltamethrin and several other pyretroyds. The insecticide was exposed to fotodecomposition for two, eight and 15 days, before sprayed on cotton plants. The reproduction rate of the T. urticae increased after cotton plants were sprayed with deltamethrin and phenoxi-benzoic-acid.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP

    Daily Forage Intake by Cattle on Natural Grassland: Response to Forage Allowance and Sward Structure

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    We investigated the hypothesis that not only forage allowance but also sward structure affects daily forage intake by beef heifers on natural grasslands of the Pampa Biome (southern Brazil). We used data from a long-term experiment, which has been managed by forage allowance levels since 1986. The objective was to investigate sward management targets that maximize daily forage intake. During January and December 2009, we evaluated the effect of forage allowance on forage mass, sward height and tussock frequency, and its consequences on dry matter intake (DMI). The experiment was arranged in a randomized complete block design with two replicates. Treatment was level of daily forage allowance (4, 8, 12, and 16 kg dry matter [DM] per 100 kg of animal body weight [BW]). Data were analyzed using regression, principal component analysis, and descriptive analyses from three-dimensional contour graphs with the data of sward structure, DMI, and DMI rate. Results demonstrated that DMI was positively correlated to forage allowance. However, higher levels of forage allowance can cause lower intake rates of forage and nutrients. We concluded that sward targets which promoted higher DMI and DMI rate were: daily forage allowance of ∼ 12 kg of dry matter per 100 kg of the animal's body weight, forage mass between 1 800 and 2 300 kg DM·ha-1, sward height between 11.5 and 13.4 cm, and tussock frequency lower than 30% of occurrence in the pastures. Within these targets, a high intake of nutrients was obtained, indicating the potential use of sward structure as a tool for managing natural grasslands in order to promote high intake of forage and nutrients by cattle. © 2016 Society for Range Management. Published by Elsevier Inc. All rights reserved.The Rangeland Ecology & Management archives are made available by the Society for Range Management and the University of Arizona Libraries. Contact [email protected] for further information
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