2,048 research outputs found

    hybridModels: An R Package for the Stochastic Simulation of Disease Spreading in Dynamic Networks

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    Disease spreading simulations are traditionally performed using coupled differential equations. However, in the setting of metapopulations, most of the solutions provided by this method do not account for the dynamic topography of subpopulations. Conversely, the alternative approach of individual-based modeling (IBM) may add computational cost and complexity. Hybrid models allow for the study of disease spreading because they combine both aforementioned approaches by separating them across different scales: a local scale that addresses subpopulation dynamics using coupled differential equations and a global scale that addresses the contact between these subpopulations using IBM. We present a simple way of simulating the spread of disease in dynamic networks using the high-level statistical computational language R and the hybridModels package. We built four examples using disease spread models at the local scale in several different networks: an animal movement network; a three-node network, whose model solution using a stochastic simulation algorithm is compared with the ordinary differential equations approach; the commuting of individuals between patches, which we compare with the permanent migration of individuals; and the commuting of individuals within the metropolitan area of São Paulo

    Toxicological Study Employing Repeated Doses of Garcinielliptone FC, a Polyisoprenylated-Benzophenone Isolated from Seed of Platonia Insignis Mart

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    The major constituent from the hexane extract of the seeds of P. insignis is GFC (garcinielliptone FC). Doses of 25, 50and 75 mg/kg of GFC were aseptically suspended in 0.05% Tween 80 dissolved in 0.9% saline (vehicle) and orally administered for30, 90 and 120 consecutive days to adult Swiss mice. In this work, the repeated oral administration, in animals of both sexes,demonstrates that this compound is not able to induce mortality and/or behavioral changes in adult mice. In addition, body weightgain, feed intake and disposal of excreta were not altered by the administration of this compound with repeated doses. Furthermore,no differences in weight and macroscopic structure of the brain, liver, kidney, lung, heart and spleen between groups of male andfemale adult mice were observed after treatment. During the periods of treatment, GFC produced no significant changes onhaematological and biochemical parameters in male and female mice treated with all doses used. The aim of this study was toinvestigate the toxicological potential of GFC through behavioral, hematological, biochemical and morphological parameters inanimals in order to ensure the safe use of Platonia insignis in folk medicine.Fil: Silva, Ana P.. Federal University of Piauí; BrasilFil: Filho, José Carlos C. L. S.. North Union of Parana; BrasilFil: da Costa Júnior, Joaquim S.. Federal Institute of Piauí; BrasilFil: Peláez, Walter José. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; ArgentinaFil: Faillace, Martín Sebastián. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; ArgentinaFil: Falcão Ferraz, Alexandre de B.. Lutheran University of Brazil; BrasilFil: David, Jorge M.. Institute Of Chemistry, Federal University Of Bahia; Brasil. Universidade Federal da Bahia; BrasilFil: Freitas, Rivelilson M.. Federal University of Bahia; Brasi

    Obtaining high purity silica from rice hulls

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    Many routes for extracting silica from rice hulls are based on direct calcining. These methods, though, often produce silica contaminated with inorganic impurities. This work presents the study of a strategy for obtaining silica from rice hulls with a purity level adequate for applications in electronics. The technique is based on two leaching steps, using respectively aqua regia and Piranha solutions, which extract the organic matrix and inorganic impurities. The material was characterized by Fourier-transform infrared spectroscopy (FTIR), powder x-ray diffraction (XRD), x-ray fluorescence (XRF), scanning electron microscopy (SEM), particle size analysis by laser diffraction (LPSA) and thermal analysis

    Influência da variação da produtividade das usinas hidroelétricas no cálculo da energia firme

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    In the present work, the problem associated to the firm energy evaluation is treated as a non linear optimization model, which allows the representation of the productivity variation of the hydro plants. The proposed model takes into account the individualized representation of the plants and the historical series of flows since the month of January of 1931. The proposed optimization problem will be solved using the Primal-Dual Interior Point Method. A case study will be presented including the Brazilian Interconnected National System. The results obtained show that the proposed methodology is promising, since it presents an energy market value more realistic when compared with existing methodologies.No presente trabalho, o problema associado ao cálculo da energia firme é tratado como um modelo não linear de otimização, o que permite a representação da variação da produtividade das usinas. No modelo proposto é considerada a representação individualizada das usinas bem como a série histórica de vazões desde o mês de janeiro de 1931. O problema de otimização proposto é resolvido através do método primal-dual de pontos interiores. Adicionalmente, é apresentado um estudo de caso abrangendo o Sistema Interligado Nacional Brasileiro. Os resultados obtidos mostram que a metodologia proposta é promissora, tendo em vista que apresenta um valor de mercado de energia mais realista quando comparado com outras metodologias

    Revisão do Conhecimento sobre os Mamíferos Aquáticos da Costa Norte do Brasil

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    The Brazilian north coast represents a new frontier in several fields of knowledge. The aquatic mammals of the Brazilian northern coast were poorly studied until recently. Recent efforts promoted by Projeto Piatam Oceano are changing the scenario. New research groups on aquatic mammals were formed and are conducting a large survey of this unique group of mammals. A total of 22 species of aquatic mammals were recorded along the Brazilian northern region. It should be emphasized the rediscovery of the Antillean manatee in several localities along the coasts of Amapá, Pará and Maranhão states. On the other hand, the estuarine dolphin is widely distributed along the Amazonian coast but is frequently by-caught in gill nets fisheries throughout the northern coast. The intense use of love charms has also a negative effect on these populations and should be better evaluated. An awareness program will be implemented as a first step for changing attitude towards the aquatic mammals of the northern coast.A costa norte do Brasil representa uma nova fronteira para o avanço do conhecimento sobre a fauna de mamíferos aquáticos. A ausência de dados pretéritos sobre os mamíferos aquáticos nessa região e a própria dificuldade logística de monitoramento resultou, até muito recentemente, numa lacuna de conhecimento. A fim de reverter este quadro, o Projeto Piatam Oceano vem incentivando a formação de grupos de pesquisa sobre mamíferos aquáticos da costa amazônica. Como resultado dos esforços recentes, foi reunido um conjunto relevante de informações inéditas ou complementares sobre as 22 espécies de mamíferos aquáticos registradas até o momento na região. Destacam-se as áreas de ocorrência do peixe-boi-marinho no litoral dos Estados do Maranhão, Pará e Amapá, as quais poderiam garantir a manutenção destas populações criticamente ameaçadas. Merece destaque ainda a ocorrência do boto-cinza em toda costa amazônica e sua problemática de interação com a pesca artesanal e o comércio de peças anatômicas. Sugere-se uma ampla campanha de conscientização e a promoção de campanhas educativas visando uma nova tomada de atitude em relação aos mamíferos aquáticos e seus hábitats, respeitando os valores tradicionais e o conhecimento etnoecológico das comunidades costeiras
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