390 resultados para Polarização


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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

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Once petroleum is na exhaustible source of energy, alternative fuels are having more prominence. A much discussed option for replacing fossil fuels is the use of biofuels derived from oils or fats, especially biodiesel. The biodiesel preparation is through a reaction named transesterification, a reaction of triglycerides with a short chain alcohol with a catalyst, producing a mixture of fatty acid esters and glycerol. According to ANP (National Petroleum Agency) specifications, biodiesel can have contaminants due to the catalyst or oil used on its synthesis, such as phosphorus, wich can damage the catalytic converter and cause significant increase in the particles emission. This project aims to develop na alternative method using chemically modified electrodes with iron nanoparticles for determination of phosphorus in biodiesel. For the formation of the iron nanoparticles film on the surface of a glassy carbon electrode, was used a iron sulfate solution. The film was formed after 10 successive cycles, with a scanning speed of 50 mV s-1 and a potential range of -0,9 to -1,25 V. To reduce possible oxides on the surface and activate the electrode, it has been subjected to a cathodic polarization with a potential of -1,25 V for 15 minutes in a sodium hydroxide solution. In cyclic voltammograms obtained in the study of the speed of scanning, there is an increase in the intensity of the anodic and cathodic current peaks. The cathodic peak current varied linearly with the square root of scan rate, showing that the electrode is controlled by diffusion. After successive additions of phosphate there is a linear variation in the current peak in the concentration range of 1,0 x 10-7 a 1,0 x 10-6 mol L-1. To determine if the concentration of phosphorus in real sample, the method of adding standard was used by adding aliquots of phosphate ions in the solution containing soy biodiesel extracted with ....

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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Pós-graduação em Ciência dos Materiais - FEIS

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Pós-graduação em Educação para a Ciência - FC

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Currently has few studies today concerning the behavior of the ethyl alcohol hydrated combustible in the geological environment, results of eventual spill or leaks in a wide transport chain and distribution. This work discusses the results of an experiment in laboratorial scale, that involves the monitoring of alterations in physical properties a simulate leak of alcohol in a tank with sand saturated in water, during 4920 hours. Are applied electrical resistivity, induced polarization and spontaneous potential geophysical methods. The electric resistivity is clearly correlating to the ethanol degradation pattern. The chargeability demonstrated sensibility to this pattern, while the natural electric potential revealed direct association with the oscillations of groundwater level. The variability of the physical parameters monitoring probable control for ethanol degradation process in environment study.

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The geophysical methods may be employed in aquifer system studies, as determination of groundwater level, soil/rock contact, beyond estimative of the aquifer thickness horizon. The geoeletric methods are particularly relevant in evaluations of the oilfields systems, due to directs relations between porosity and electrical resistivity, which allow inferences about oil and gas production. The indirect estimative of the productions in free aquifers system is something complex before of the diverse variables responsible for factors or physical phenomena, as clays minerals, which conditioned the physical parameters by electric geophysical methods. This paper present analyzed correlation among electrical resistivity, chargeability and direct measure flow in shallow wells, for determination of statistical relationships between parameters and evaluation of the geological constraints evolved. The study count with the 23 shallow wells located in free aquifer, constituted by alteration materials of the granites localized in Caçapava do Sul (RS). The geophysical data are acquired by vertical electric sounding in Schlumberger array. The correlations between electrical resistivity and flow, chargeability and flow, thickness of the soil/saprolite and flow indicated relationships between physical and hydrogeologic parameters, with variations conditioned by factors as porosity, permeability, besides intrinsic geological heterogeneities such soil variable thickness and rock fragments with several alteration degrees.

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Geophysical methods are widely used in mineral exploration for several types of mineral deposits. When combined with direct studies as geochemistry, a substantial increase in the probability of ore discovery is possible in mineral exploration activities. Electrical geophysical methods are particularly promising in studies related to the search of sulphides due to the contrast of physical properties electric resistivity and chargeability. This paper presents the results obtained from the application of Resistivity (DC) and Induced Polarization methods, through the electrical profiling technique, aiming at evaluating the potential mineral of a gabbro intruded in a metasedimentary sequence, in an area where several occurrences of gold and copper were described. This gabbro is ranked on the Basic-Ultrabasic stratiform bodies, which gather peridotites, gabbros, and layered anortosites. Three radial lines of electrical profiling were performed, spaced of 60° and crossing at the area center, with readings of electric resistivity and chargeability in Wenner-Schlumberger array. The association of low resistivity and high chargeability areas has allowed defining potentially mineralized zones related to structures that condition the drainage net in the gabbro domain. Grains of gold detected through geochemical prospection of alluvial sediments dowstream from the gabbro may have originated from leaching of ores deposited in fractures through the action of river waters within the gabbro domain, possibly consisting of sulphides and gold.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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Contexto e objetivo: A hanseníase caracteriza-se por ter diagnóstico eminentemente clínico, principalmente através da constatação de hipo ou anestesia das lesões, ou seja, sem necessariamente o uso de exames adicionais, como baciloscopia e biópsia, utilizados para classificação clínica da doença. Buscou-se definir se há tendência à desvalorização da avaliação clínica em favor do excesso de exames complementares, investigar a adequação do registro nos atendimentos da atenção básica e compará-los com o obtido em serviço de média complexidade. Desenho e local: Estudo transversal, de base populacional, utilizando registros de prontuários, realizado em dois âmbitos de atendimentos de saúde da cidade de Campinas (SP): os Centros de Saúde e a assistência dermatológica especializada de hospital de ensino. Métodos: Os registros foram investigados por meio da aplicação de checklist, contendo itens indispensáveis ao atendimento a hansenianos. Associações foram testadas pela prova de Goodman e ao nível de 5% de significância. Resultados: Foram avaliados 33 prontuários oriundos dos centros de saúde e 36 do hospital, observou-se polarização entre registros adequados e ausentes, evidenciando a presença de efeito tudo ou nada nos atendimentos; de 26 variáveis, apenas em 5 (19,23%) obteve-se predomínio da avaliação do hospital sobre os centros de saúde; evidenciou-se dependência de exames complementares, solicitados em 67 dos 69 atendimentos (97,10%), para diagnóstico da doença. Conclusão: Confirmou-se, neste estudo, déficit da avaliação médica e indicação inadequada de exames adicionais. Por associar-se com excesso de solicitação de exames, a observação clínica mostrou-se incompleta, comprometendo a capacidade diagnóstica dos atendimentos a hansenianos.

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)