Navegando por Data de Publicação, começando com "2012-01-27"

Filtrar resultados por ano ou mês

Agora exibindo 1 - 3 de 3

Síntese eletroquímica e caracterização de filmes finos de CdZnTe
(Universidade Federal de São Carlos, 2012-01-27) Felício, Nathalie Honorio; Mascaro, Lucia Helena; https://lattes.cnpq.br/9130022476352844; https://lattes.cnpq.br/6472591049528112
Studies on the electrodeposition of semiconductor films has been developed primarily for the binary chalcogenides. However, there are several ternary systems that are poorly researched and have broad application spectrum, for example, the CdZnTe. In this sense, the objective of this work is to study the electrodeposition process of thin films of CdZnTe semiconductors and evaluate their optical properties, composition and morphology. In this work were used as substrates ITO and Pt electrodes, and CdSO4, ZnSO4, TeO2 solutions in the presence at different support electrolytes (C4H4O6KNa, acetate buffer (pH4) and (NH4)2SO4). The influence of supporting electrolyte in the electrodeposition process and films morphology was also evaluated. It was observed that the most suitable deposition media was sodium and potassium tartrate, because the films were more homogeneous. In this media was studied the influence of bath composition on the morphology, composition and band gap of the films. The films were grown at -1,2 V for 1h. Images obtained by FEG (field-emission scanning electron microscopy) revealed uniform films, and grain refinement was observed for coating deposited on ITO substrate. The films on ITO were analyzed by UV-vis to determine the band gap values, which varied from 1.5 to 1.7 eV, depending on the film composition. The deposition was also performed by multiple pulsed-potentials technique. The deposition potentials, based on the voltammograms, were -0.2, -0.9 and -1.2 V for Te, Cd and Zn, respectively. In these experiments the substrate was Pt and different deposition times were employee for each potential, maintaining a total time of 30 min. The morphology indicated Cd-rich clusters and Te-rich smooth regions, according to the EDX (Energy Dispersive X-ray) data. In order to promote a major change in the composition of ternary films, new deposition conditions were used, in which the elements quantities of the films were adjusted by changing the time on each applied potential and ions concentration. In this case the band gap values were around 1.8 eV, an intermediate value between the band gap of two binary semiconductors, CdTe and ZnTe. The analysis carried out by XRD (Diffraction X-rays) was also an indicative of ternary phase s presence, such as, cubic, tetrahedral and hexahedron. By the proposed methodology, was possible to obtain CdZnTe films with ternaries phases and control its grain size, optical properties and composition. Therefore, the main objective of this study was achieved, since it was possible to obtain films with different stoichiometry and thereby change its properties. The electrodeposits showed optical properties comparable with those of films obtained by physical techniques. Thus, the use of a technique relatively simple and low cost could easily be adjusted to produce these materials on a large scale and allow its use in photovoltaic systems, for example.
O papel dos receptores histaminérgicos H1 da amídala na modulação da ansiedade e evocação da memória emocional em camundongos reexpostos ao labirinto em cruz elevado
(Universidade Federal de São Carlos, 2012-01-27) Serafim, Kelly Regina; Mattioli, Rosana; https://lattes.cnpq.br/8930329663162350
This study investigated the role of H1 amygdala receptors in state-dependent memory deficits induced by L-histidine (LH).To address this question, we investigated the effects of H1 antagonist chlorpheniramine (CPA) microinjected into the amygdala on anxiety and emotional memory retrieval in mice submitted to the EPM. Experimental subjects were 117 adult male Swiss mice weighing 25-32g at testing. Tests using an elevated plus-maze (EPM) were performed on two consecutive days: Trial 1 (T1) and Trial 2 (T2). Before each trial, mice were intraperitoneally (IP) injected with LH (500mg/kg), a histaminergic precursor. Two hours later, they were microinjected with chlorpheniramine (CPA; 0.016, 0.052, or 0.16 nmol/ 0.1 μl), or saline (SAL) into the amygdala, and five minutes later reexposed to the EPM. For each CPA dose administered, the animals were randomly assigned to four groups based on drug treatment: control (i.p injection and i.a SAL), LH-SAL (i.p injection LH and i.a SAL), SAL-CPA (i.p injection SAL and i.a CPA) and LH-CPA (i.p injection of LH and i.a CPA). The data were analyzed using two-way analysis of variance (ANOVA) and Fisher LSD tests. IP injection of LH and microinjection of CPA into the amygdala did not induce significant T1 differences between groups for percentages of open arm entries (%OAE) or open arm time (%OAT) (ANOVA, p > 0.05), which indicated that the drugs did not affect anxiety. In T2, the control group and the groups that received IP injection of SAL and an 0.016- or 0.052-mnol infusion of CPA (SAL-CPA) demonstrated significant reductions in open arm exploration (%OAE and %OAT) (p < 0.05), suggesting a retrieval of aversive information concerning the open arms. Importantly, the LH groups that received an injection of SAL (LH-SAL) or CPA (LH-CPA) did not exhibit decreased open arm activity; no significant differences in %OAE and %OAT (p > 0.05) were observed between T1 and T2, suggesting that the LH-induced deficit in emotional memory retrieval was not reversed by CPA injection. Furthermore, animals that received IP injections of SAL and 0.16 nmol infusion of CPA (SAL-CPA) did not exhibit decreased open arm exploration in T2 compared to T1 (p > 0.05). No significant changes were observed in the number of enclosed arm entries (EAE), an EPM index of general exploratory activity. Taken together, these results suggest that the H1 receptors in the amygdala are not implicated in anxiety-like behaviors but are involved in emotional memory deficits induced by the T1/T2 EPM protocol in mice.
Comparação das distribuições α-estável, normal, t de student e Laplace assimétricas
(Universidade Federal de São Carlos, 2012-01-27) Macerau, Walkiria Maria de Oliveira; Milan, Luis Aparecido; https://lattes.cnpq.br/9334093984788993
Abstract The asymmetric distributions has experienced great development in recent times. They are used in modeling financial data, medical, genetics and other applications. Among these distributions, the Skew normal (Azzalini, 1985) has received more attention from researchers (Genton et al., (2001), Gupta et al., (2004) and Arellano-Valle et al., (2005)). We present a comparative study of _-stable distributions, Skew normal, Skew t de Student and Skew Laplace. The _-stable distribution is studied by Nolan (2009) and proposed by Gonzalez et al., (2009) in the context of genetic data. For some real datasets, in areas such as financial, genetics and commodities, we test which distribution best fits the data. We compare these distributions using the model selection criteria AIC and BIC.