921 resultados para FIBRAS DE VIDRIO


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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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Patients with chronic heart failure (CHF) show metabolic, hemodynamic and skeletal muscle alterations, which decrease the life expectancy. These alterations are attributed to several factors. The focus of this review was to approach the questions related to physiological, metabolic, morphological and molecular alterations which affect the muscular system of these patients. Later, it was discussed the benefits of physical exercise to this syndrome as well as the pharmacological interventions, which are in investigation aiming the treatment of the same. Some muscle alterations are already described on the literature. For example, the more predominance of type II fibers, lower oxidative enzymatic activity, muscle atrophy and elevated concentration of cytokines that affect the muscle integrity. Thus, further studies involving cellular and molecular mechanisms of skeletal muscle in order to create strategies for prevention and treatment for patients with CHF are required

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Tin oxide has wakened up great scientific and technological interest for its potential use in varistors production and as gas sensor. In order to improve the microstructural and electrical properties in SnO2 varistor ceramics, the influence of differents dopants used, like TiO2 and Al2O3, is under research. The effect of TiO2 and Al2O3 on the properties of Sn-Co-Nb varistor systems obtained by the Pechini method has been investigated in this work. Characterization of synthesized raw material was performed by X-Ray Diffraction (XRD) and Scanning Electronic Microscopy (SEM). The microstructural and electrical characterization of sintered samples show that the TiO2 favors the grain growth and the Al2O3 contributes to the decrease it, effect that is manifested in the Sn-Co-Nb varistor systems. Breakdown field increase up to 6300V/cm with increasing Al2O3 content and non-linear coefficients with alpha=22 were obtained.

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Lithium niobate (LiNbO3) thin films with 1/1 stoichiometry were prepared by a spin-coating from polymeric precursor method. The films deposited on silicon (100) substrates, were thermally treated from 400° to 600°C for 3 hours in order to study the influence of thermal treatment on the crystallinity, microstructure, grain size and roughness. X-ray diffraction (XRD) results showed that LiNbO3 phase crystallizes at low temperature (400°C). It was observed by scanning electron microscopy (SEM) that it is possible to obtain dense thin films at temperatures around 500°C. The atomic force microscopy (AFM) results showed that the grain size and roughness are strongly influenced by the annealing temperature.

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Barium titanate is used extensively as a dielectric in ceramic capacitors, particularly due to its high dielectric constant and low dielectric loss characteristics. It can be made semiconducting by addition of certain dopants and by proper modification of grains and grain boundary properties obtaining very interesting characteristics for various applications. The synthesis method and sintering regime have a strong influence on properties of obtained barium titanate ceramics. Doped barium titanate was prepared with Nb+5 and Y+3 ions as donor dopants, and with Mn+2 ions as acceptor dopant by polymeric precursors method. By this procedure nanosized powders were obtained after calcination. Sintering was performed in the temperature range of 1290°C to 1380°C The microstructure of doped BaTiO3 was performed using scanning electron microscopy. The influence of dopants and sintering temperature on grain size was analysed.

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The work describes actions carried out in colaboration among the National Steel Company - (CSN)-Brazil and the Interdisciplinary Laboratory of Electrochemistry and Ceramic - LIEC of the Federal University of Sao Carlos Brazil (UFSCar-Brazil), in the area of I&D, for integral management and improvement of the quality and performance of the refractory linings in the sintering areas, blast furnace, hot air pipe lines transferency to the blast furnace, pig-iron ladles, running channels, blast furnaces hearths, torpedo car, etc., as well as, the economic impact generated by the installation of the adopted measures.