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Determinação simultanêa de pesticidas utilizando métodos eletroanalíticos e quimiométricos
(Universidade Federal de São Carlos, 2011-03-17) Silva, Zilene Alves da; Souza, Ernesto Chaves Pereira de; https://lattes.cnpq.br/1505400360366643; https://lattes.cnpq.br/5700463114669811
This paper describes the simultaneous determination of the pesticides paraquat and diquat using electroanalytical techniques coupled with chemometric methods. Although these two pesticides can be easily determined in trace levels, the same does not apply to mix due to a large overlap of the voltammetric peaks. For this reason it became necessary to treat the data obtained by square wave voltammetry with chemometric methods that used no current peaks, but all points of the voltammogram. In a first stage of work, the parameters were optimized voltammetric technique, the frequency of the pulse, amplitude and increased potential for using the design of experiments. In this step, for each analyte were used as a response to peak current, ip, and the first principal component, PC1. Both analysis procedures showed that the frequency of the pulse amplitude and the cross effect of these variables has a significant effect on the response of the system (ip or PC1). In a second step, the effect of the most significant variables were studied by response surface, which employed a planning CCD (central composite design of English) was optimized. It was then built an empirical model that correlates the response (ip or PCs) with the variables studied. The optimum values to obtain the best voltammetric response was frequency 170 s-1, amplitude 40 mV and scan increment of 2 mV. Finally, in a third stage of labor was performed to analyze the mixture of paraquat and diquat, applying the optimized parameters and transforming the voltammograms for the space of principal components. The quantification of the mixture of pesticides was performed using the Partial Least Squares Regression, PLS. The XII models developed had a RMSEP, 1,39 and 2,22 for paraquat and diquat for the correlation coefficients greater than 0.99, which demonstrates the efficiency of the methodology used.
Perovskitas baseadas no PZT e PLZT sintetizadas usando o método dos complexos oxidantes de peróxido (OPM)
(Universidade Federal de São Carlos, 2011-03-17) Gonçalves, Mayra Dancini; Camargo, Emerson Rodrigues de; https://lattes.cnpq.br/7720754304065239; https://lattes.cnpq.br/9207706266657791
Were synthesized by the OPM, the solid solutions of Pb(Zr1-xTix)O3 with x = 0.8, 0.48 and 0.2, and also the lanthanum modified lead zirconate titanate compositions (Pb0.95La0.05) (Zr1-xTix)O3 with x = 0.8 and 0.2. This paper reports the first synthesis of PLZT by means of the OPM route. The techniques for X-ray diffraction and Raman spectroscopy at room temperature showed that the PZT and PLZT compositions Ti-rich have essentially tetragonal structure and the compositions Zr-rich are rhombohedral. Since the composition with x = 0.48 known as the morphotropic phase boundary (MPB) shows a mixture of both structures. Analysis by BET isotherms showed that the powders have high surface area even when thermally treated at 700 ° C, confirming its higher reactivity compared to powders obtained by other synthetic methods. At this temperature, images from scanning electron microscopy reveal the formation of aggregates of nanometric spherical particles already in the process of sintering due to diffusion of matter and formation of necks between them. Since these materials have great technological importance, the powders were conformed to the shape of discs and sintered in two types of ovens, conventional and microwave ones, for evaluation and comparison of morphological, structural and dielectric properties. The composition of PZT in the MPB showed dielectric constant higher than the values reported in the literature, both for the samples sintered in a conventional oven (12330) as for the sintered using microwave energy (17900). However, the Curie temperature also showed anomalous values of 460 and 465 ° C, respectively. It can be attributed to the influence of the absence or lower content of oxygen vacancies in the powders synthesized by means of the OPM route.
Percepção e memória em Bergson: um questionamento acerca das críticas sartrianas à Matéria e memória
(Universidade Federal de São Carlos, 2011-03-17) Bitterbier, Solange; Marques, Silene Torres; https://lattes.cnpq.br/4822141288006918; https://lattes.cnpq.br/2409795523544490
Important philosopher and researcher of the twentieth century, Henri Bergson has gained prominence not only for his detailed analysis of consciousness and for the new meaning given to already established philosophical terms, but also for his addressing of the notion of duration, which is present in his major works and is the basis many for many of his conceptions. Bergson's philosophical writings have earned him much admiration and, at the same time, many critcisms, which, as they raise questions concerning fundamental points of the bergsonian philosophy, allow discussions that result in several studies. Among the most prominent criticisms, some are concentrated in the text of the philosopher Jean-Paul Sartre, entitled The Imagination, which addresses important aspects of the work Matter and memory. However, Sartre s criticisms seem to address Bergson s arguments in an one-sided way. Given this, our objective is to analyze the bergsonian reflections presented in Matter and memory trying to show that Sartre's positions regarding to Bergson were taken in a superficial way, which leads us to assert that Bergson's philosophy has not, as claimed by the author of The imagination, failed in his conceptions. For that, we will emphasize two fundamental notions present in Matter and memory, which were widely criticized by Sartre, namely the notions of perception and consciousness, as well as the conclusions presented in the finalization of the work about the dualism of body and spirit.