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Aprendizado semi-supervisionado e não supervisionado para análise de dados de expressão gênica
(Universidade Federal de São Carlos, 2008-05-27) Assao, Fabiana Mari; Camargo, Heloisa de Arruda; https://lattes.cnpq.br/0487231065057783; https://lattes.cnpq.br/3998840368387781
Data clustering has been seen, in the last decades, as an important tool for gene expression data analysis. In recent years, due to the progress in gene annotation research, a growing interest has been noticed for the semi-supervised clustering techniques, which use knowledge previously available about some gene functions to discover functions of other genes by means of clustering. This work investigates non-supervised and semi-supervised clustering algorithms applied to gene expression data. The goal is to perform an inspection on strengths and weaknesses of the use of such clustering methods and, based on these findings, to provide ways of obtaining results significant to biology. Algorithms with different characteristics were implemented and tested, with the objective of verifying evidences of eventual gains with the partial labeling, as compared to the non-supervised techniques. The experiments considered data sets from the gene expression domain as well as more generic domains. The obtained results were evaluated with validation measures usually applied in similar contexts. The analysis developed, though, emphasize the important role of computational techniques in biological data analysis, by accelerating the process of deriving results and conclusions, to better understand gene functions and structures. The results of this stydy justify the large investiment in the research of behavior of semi-supervised techniques in gene expression data, as we shall see.
Estudo de propriedades de filmes de óxidos anódicos crescidos em diferentes eletrólitos ácidos sobre o biomaterial Ti-50Zr at.%
(Universidade Federal de São Carlos, 2008-05-27) Ferreira, Elivelton Alves; Rocha Filho, Romeu Cardozo; https://lattes.cnpq.br/5200717413563550; https://lattes.cnpq.br/9791486511562981
Studies on the influence of the nature of the growth electrolyte on the properties of oxide films grown on the Ti-50Zr at.% alloy were carried out. The results obtained through the different measurements done (chronoamperometry, open circuit potentials, and reconstruction rates) showed that phosphate incorporation into the matrix of oxide films grown in H3PO4 make them unstable, bringing a greater dissolution compared to the ones grown in CH3SO3H, H2SO4, and HNO3. The electrochemical impedance spectroscopy measurements showed that the phosphate incorporation into the oxide films grown on the Ti-50Zr at.% alloy by different methods and thickenesses lead to high values of electrical resistance when compared with the ones of films grown in CH3SO3H, H2SO4, and HNO3. The nature of the growth electrolyte was observed to also affect the semiconducting properties of the different oxide films grown on the alloy, leading to different voltammetric profiles of these films when illuminated with radiation of energy greater than that of the band gap. The studies on the effect of the exchange of the electrolyte solution in the galvanostatic growth of anodic films in two steps showed that the breakdown potentials are dependent on the nature of the electrolyte. On the other hand, these measurements also revealed that the initial electrical breakdown of the film or the nature of the electrolyte in which it was initially grown do not alter the film growth kinetics during the second step, carried out in another electrolyte.