Navegando por Data de Publicação, começando com "2008-03-13"

Filtrar resultados por ano ou mês

Agora exibindo 1 - 4 de 4

Estudo dos processos de eletrodeposição de filmes finos de Se, ZnSe e PbS
(Universidade Federal de São Carlos, 2008-03-13) Fernandes, Valéria Cristina; Mascaro, Lucia Helena; https://lattes.cnpq.br/9130022476352844; https://lattes.cnpq.br/7987385835577071
This work describes studies on the underpotential deposition (UPD) of selenium, zinc, as well for Zn/Se systems deposited on polycrystalline Pt electrodes in acid solutions. The effects of Zn presence in the Se dissolution process were also investigated in the UPD and bulk potential range, 0.6 and 0.03 V respectively. The measurements were carried out using cyclic voltammetry and electrochemical quartz crystal microbalance (EQCM). Furthermore Lead sulfide (PbS) multilayers were grown on a single crystal Ag(111) substrate by Electrochemical Atomic Layer Epitaxy (ECALE) method. For Zn UPD in sulfuric acid, two different processes were observed, which are attributed to the dissolution of submonolayer of Znads and H-atoms adsorbed on the electrode surface. For Se UPD was observed that hydrogen desorption were completely inhibited indicating that Se film recovered the Pt surface. The deposition of UPD Se in perchloric acid solution showed the transference of 4 electrons with 1.4 and 1.12 active sites of Pt occupied by 1 Se ad-atom in the UPD and bulk potential range, respectively. In the evaluation of the Se monolayers dissolution process formed at 0.03 V during 2000 s a process not mentioned in the literature it was observed which was evaluated by the technique MECQ. The experimental results obtained by this technique allowed to end that the dissolution process occurred by two stages, and the first involved the participation of 6e-. The dissolution mechanism with 6e- happens with the participation of water in the dissolution process of Se, leading to the formation of an oxygenated selenium compound which in next step undergo slow oxidation and is dissolved as soluble Se(VI) species. Then the total dissolution process of Se occurs in a six-electron transfer reaction. For Se deposition in the Zn presence the dissolution charges associated with Se UPD increase, indicating that the presence of Zn favors the deposition of UPD Se. In the case of PbS multilayers on Ag (111) the voltammetric analysis of the first PbUPD and SUPD peaks indicates a mechanism of two-dimensional growth, which is consistent with epitaxial growth. Electrochemical stripping measurements indicate that the amount of Pb and S deposited in a given number of cycles is a function of the number of cycles employed, again suggesting a layer-by-layer growth. This result indicates that the amount of Pb and S in these films corresponds to the stoichiometric 1:1 ratio, indicating the formation of a compound.
Caracterização elétrica e magnética de Fe granular embebido em matriz de ZnSe
(Universidade Federal de São Carlos, 2008-03-13) Muniz, Pedro Schio de Noronha; Oliveira, Adilson Jesus Aparecido de; https://lattes.cnpq.br/4640148190073166; https://lattes.cnpq.br/4464937635959170
Electric and magnetic properties of nanoscopic clusters of iron immersed in Zinc Selenide were studied in this work. The system presents superparamagnetic behavior with a weak thermally activate ferromagnetic interaction. Small tunnel magnetoresistence was observed in room temperature (approximately 1% with fields of 30 kOe) and its behavior was observed as a function of temperature and bias. This work demonstrate that a despite of excellent macroscopic and microscopic properties of Fe/ZnSe/Fe epitaxial heterostructures the experimental observation shows small values of tunnel magnetoristance in room temperature. This results shows that the application of this materials in spintronics devices is limited.
Programação de ensino de leitura e escrita para crianças com deficiência mental
(Universidade Federal de São Carlos, 2008-03-13) Freitas, Maria Clara de; Rose, Julio Cesar Coelho de; https://lattes.cnpq.br/3386857761295187; https://lattes.cnpq.br/6993887072345221
The importance of reading and spelling for citizens is a significant issue. However, repeatedly the school system shows failures in teaching these repertoires. When children with mental retardation are inserted in the regular classroom, the problems increase. Teachers don t know how to teach them academic skills, therefore obscuring their potential and prejudicing their social inclusion. Moreover, studies in equivalence of stimulus have systematically demonstrated the applicability of procedures based on this paradigm for individuals with mental retardation, as well as the effectiveness of similar methodologies applied to the teaching of rudimentary reading and spelling skills to other populations, such as preschool students and children with developmental disorders. Therefore, the objectives of this study were: a. to investigate the necessary conditions for the teaching of children with mental deficiency using a procedure designed to of teaching reading and spelling, and b. to redesign the software that contains this procedure in order to achieve results for the children with mental retardation compatible with the ones obtained by the application of this same software to children with school failures. A multiple baseline design with a mobile criterion, has been used, focusing the analysis on the three participants performance when exposed to the modifications implemented by the three consecutive procedures. The results indicated small profits for Procedure 1, when only formal modifications in the software were made, such as exchange of stimuli (words and pictures) and exhibition of the font in capital letters. As the second procedure introduced more structural modifications, as blocked-trial trainings and auditory-visual trials with critical differences between the words, the results showed great success for all the reading and spelling skills tested. The last procedure made refinements in the program, and equally reached success with shorter trainings and bigger words. As a conclusion of the work, success was reached in the adaptation and application of the teaching program: the children with mental retardation showed results of reading and spelling compatible with the results the pupils with learning difficulties had shown in previous studies. Furthermore, it was also possible to say that the data obtained had contributed to understand a little more how and how much this students learn, and how this learning can be guaranteed and optimized using procedures based on matching to sample, constructed response matching to sample and exclusion.
Do conhecimento tradicional ao princípio ativo: dilemas sociais da atividade de pesquisa etnofarmacológica
(Universidade Federal de São Carlos, 2008-03-13) Almeida, Marcelo Fetz de; Vargas, Marcelo Coutinho; https://lattes.cnpq.br/3936124976880088
The Research and Development (R&D) in ethnopharmacology and etnobiology fields, guided by the therapeutic information obtained with local communities and indigenous people, holders of traditional knowledge, produces social conflicts and social disputes. Firstly, it is a paradoxical scientific activity since the modern scientific discovery in ethnopharmacology is produced by a non-scientific knowledge. This controversial research strategy intends to produce a socially legitimized knowledge through a process of epistemic standardization. Secondly, although the use of traditional knowledge is a typical activity, to access it and to use it requires the signature of a contract for the equitable sharing of benefits as well as the signature of a term of prior consent access. These two juridical requirements are at the same time a new ethical parameter in scientific research and a barrier to the autonomy of the scientific field. Therefore, through the politic action scientists and researches seeks new social strategies to recovery the autonomy of the scientific field in ethnopharmacology and ethnobiology areas. Thus, this sociological research analyzes the internal conflicts between scientists in the scientific field through the examination of the social controversies in the use of two distinct research models, the vertical and the horizontal research models, as well as the examination of the external social disputes of the scientific activity, specially the politic action of scientists concerning to the autonomy question. In this research, the question of access, use and equitable sharing of benefits in R&D processes emerges as an interesting strategy used by scientists to legitimate the appropriation of the traditional knowledge. As non-knowledge, the traditional knowledge is transformed by the modern commercial science in generic information without significance. At the same time, this traditional generic information would be liable to be manipulated and appropriated by pharmaceutical multinationals trough the application of intellectual property rights. Finally, the appropriation of the traditional communities claim intends to legitimate socially the controversial scientific activity of ethnopharmacologists, ethnobiologists and pharmaceutical industries.