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Mecanismos reacionais e os processos de carga e descarga no caso de eletrodos planos de Pb em ácido sulfúrico e formação de eletrodos planos de PbO2 partindo de eletrodos de Pb
(Universidade Federal de São Carlos, 2007-10-04) Pratta, Patrícia Maria Patrizi; D'Alkaine, Carlos Ventura; https://lattes.cnpq.br/8699821828310072; https://lattes.cnpq.br/8073226929054180
Two systems that form the basis of the lead-acid batteries were studied. The first system was the lead/sulfuric acid (Pb/H2SO4) interface. This interface is equivalent to negative electrode of lead acid batteries. The second system was the lead oxide/sulfuric acid (PbO2/H2SO4) interface. This interface is equivalente to the positive electrode of lead acid batteries. Of these two interfaces the PbO2/H2SO4 interface is the more complex. In order to devise a reproducible method of synthesizing this complexelectrode (and guaranteeing the production of only PbO2), various test were performed probing the electrooxidation of Pb in many different media, including alkaline solution. For both the Pb and PbO2 interfaces, mechanisms of reaction were studied via electrochemical and spectro-electrochemical methods including Fourier Transform Infrared Spectroscopy (FTIR). The behavior of the Pb/H2SO4 system was reproducible and independentof whether the electrode was pure Pb or an alloy of Pb/Ca/Sn/Ag. The reproducibility of measurements in the Pb/H2SO4 system depended on a method developed to remove disrupted filme on the electrode surface. In fact nucleation phenomena were only observed after complete removal of disrupted films from the electrode surface. The formation of reproducible PbO2 films was the main obstacle to obtaining reliable measurements in the PbO2/H2SO4 system. Measurements were sensitive to the planarity of the film and to the presence of excess acid in the solution in which the film was grown.
Composição florística e estrutura fitossociológica de uma floresta estacional semidecidual em Araras, SP
(Universidade Federal de São Carlos, 2007-10-04) Soares, Marcelo Steinmetz; Soares, João Juares; https://lattes.cnpq.br/6093800182799882; https://lattes.cnpq.br/1377239701436382
The purpose of this study was to analyze the specific composition of tree, arboreal structure, infestation by climbers, canopy layer and compare the results with other forest fragments and, from these, to form a data bank for monitoring. The forest studied is located in the geographical coordinates S 22º 17 and W 47º 24 . The soil is red-dark Latosoil type and its topography is irregular. The floristic analysis was made by expeditions and phytosociology by quadrats of 10x10m in three blocks. The canopy analysis was made by digital image and the climbers infest by coverage index. It was found 114 species belonging to 40 families and 74 genres. It was sampled 728 alive plants. The species with greater importance value were Trichilia clausenii, Galesia integrifolia, Trichilia catigua, Metrodora nigra e Cariniana estrelensis. The sample canopy coverture presented 70% of the samples with 70% of coverture e only 14% with minor than 50%. 83% of the trees presented any infestation by climber and 60% with indice 4 e 5, that was considered elevated. The greatest infestation occurred at the tree of the canopy layer. The population of pioneer species, in the sucessional classification, presented little number of young plants and the secondary and shade tolerant great number and a complete series of diametric classes.