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Efeito da modulação da topologia do confinamento em sistemas quase zero-dimensionais induzida por campo elétrico
(Universidade Federal de São Carlos, 2015-04-01) Oliveira, Edson Rafael Cardozo de; Teodoro, Marcio Daldin; https://lattes.cnpq.br/5602634309535528; https://lattes.cnpq.br/3121276256053722
Quantum dots grown by epitaxial techniques for optical and transport studies are usually capped by a layer of the same material on which the QDs were grown. Recently, several studies have shown how the growth parameters and materials used in this layer significantly affect the morphological, optical and electrical properties of these nanostructures. In this work Indium Arsenide quantum dots capped with a layer of Gallium Arsenide and Antimony are studied. After the growth, a rapid thermal annealing was performed, which improved significantly the size distribution of the quantum dots, increasing the optical eficiency, and inducing a change in the band structure from a Type-I to Type-II. The investigations performed by magnetophotoluminescence have shown that the effects of the topology confinement on the band structure of these quasi zero-dimensional systems are strongly modulated by an external electric field applied parallel to the magnetic field orientation. Purely quantum effects such as Aharonov-Bohm interference and the inversion of the excitonic Landfie g-factor were observed at low temperatures and for specific values of electric fields, showing that the choice of the material and growth conditions of quantum dots capping layer leads to controlled experimental results which could not be achieved using conventional growth methods of semiconductor quantum dots.
Aversão ao contexto associado ao estresse de derrota social em camundongos : um estudo etológico
(Universidade Federal de São Carlos, 2015-04-01) Crestani, Ariela Maltarolo; Souza, Ricardo Luiz Nunes de; https://lattes.cnpq.br/2475842684688693; https://lattes.cnpq.br/9795258348421849
Aggressive interactions between conspecific animals have been used as an ethological source of social stress to study some aspects of social anxiety. Through this work we used a new experimental protocol in order to develop a new behavioural paradigm in the study of social anxiety. Mice were exposed to an apparatus adapted from rat exposure test (RET) and it consisted of three interconnected regions: home chamber, tunnel and surface area. Animals were exposed to the experimental apparatus for five consecutive days, being the first three days for habituation to the apparatus (habituation 1 , 2 and 3) and on the fourth day occurred the social interaction between conspecifics (not aggressive for animals from "non-defeated group" and aggressive for animals from "defeated group"). On the fifth and final experimental day the animals were re-exposed to the apparatus for 10 minutes and the following behaviors were assessed: frequency of entries and time spent in the three regions of the apparatus (home chamber/tunnel/surface area), frequency of the stretched attend posture (SAP) behaviour in the three regions, time spent on self-grooming in the three regions, frequency of rearing in the surface area and latency to reach the surface area once the animals were re-exposed to the experimental apparatus. Factor analysis was used in this study to trace the behavioural profile of socially defeated mice (n=90) when re-exposed to the apparatus where the aggressive interaction occurred; we also compared the behavioural profile of non-defeated (n=89) and defeated (n=90) mice when re-exposed to the context where social (non-aggressive or aggressive) interaction occurred, using Student’s t test. Final factor analysis yielded 4 factors that together represent 72.09% of total variance: factor 1 was loaded with time spent in the home chamber and in the surface area and self-grooming in the home chamber, while factor 2 loaded on time spent in the tunnel and total entries in the three compartments of the apparatus (home chamber, tunnel and surface area). Factor 3 was loaded with SAP frequency in the tunnel and in the surface area; and factor 4 was loaded only with latency to reach the surface area. Student’s t test showed that socially defeated mice spent more time to reach the surface area and performing self-grooming in the home chamber when compared to non-defeated mice. Together, these results suggest that the increase in the latency to reach the surface area and self-grooming in the home chamber were conditioned to a single social defeat, but there were no conditioning for classical measures such as: place aversion and risk assessment behaviour (SAP).
Duas involuções comutantes fixando certas variedades de Dold e certas uniões de espaços projetivos relativos a anéis diferentes
(Universidade Federal de São Carlos, 2015-04-01) Ura, Sérgio Tsuyoshi; Pergher, Pedro Luiz Queiroz; https://lattes.cnpq.br/3328545959112090
Let (M; _) be a smooth action of Z2 2 on a closed, smooth and m-dimensional manifold, with fixed point set F = m[ j=0 Fj , where Fj means the union of the components of F of dimension j. Given such a F, we can ask for the actions that have F as fixed point set, and in the positive case we have the question of the cobordism classification of such actions. In this work we obtain such classifications when F is a Dold manifold of the form P(1; 2n + 1), and when F is the disjoint union of two projectives spaces of the form KdP(m) [ KeP(2n + 1), with d; e 2 f1; 2; 4g and d < e. In particular, this last case is concerning questions leaved open in [2]. The crucial point concerning such classifications was an improvement refering to the Pergher s result ([22], Theorem 1), which established conditions on a collection of three vector bundles in such a way it can be realized as the fixed data of some Z2 2-action. Specifically, we become such conditions more efficient in computational terms, by removing one of the conditions, specifically the more complicated. This possibilited to detect certain exotic actions (see the definition 1.9.15) in the mentioned classifications.
Propriedades psicométricas de um instrumento para avaliar o envolvimento de idosos em atividades prazerosas
(Universidade Federal de São Carlos, 2015-04-01) Ferreira, Heloísa Gonçalves; Barham, Elizabeth Joan; https://lattes.cnpq.br/9868595523538592; https://lattes.cnpq.br/0481517225958265
Researchers have identified various factors that affect seniors’ well-being, including their engagement with life. As such, to help seniors with mental health problems, one strategy is to increase the frequency of their involvement in pleasant events. However, there are no instruments that Brazilian professionals can use, to identify activities that are pleasant for a specific older person. Thus, the aim of this doctoral research program was to investigate the psychometric properties of an instrument culturally adapted for use in Brazil, the COPPES-BR, which can be used to assess older people’s engagement in pleasant events. First, a literature review was conducted to describe the context in which the original instrument (the California Older Person’s Pleasant Events Schedule - COPPES) was developed, its theoretical underpinnings, and to define the construct this instrument measures. Next, in Manuscript 1, initial evidence of the validity of the COPPES-BR is presented. In total, 337 Brazilian, community-dwelling seniors (68,2% female), without cognitive impairments, between the ages of 60 and 93 (M = 69.7; sd = 7.31), living in neighborhoods with different levels of social vulnerability, responded to the following instruments, all adapted for use in Brazil: (a) the COPPES-BR, (b) the Beck Depression Inventory (BDI), (c) the Pfeffer Index, to evaluate functional dependency, and (d) sociodemographic questions. The internal consistency of the Frequency, Pleasure, and Obtained Pleasure scales was excellent (Cronbach’s alpha values of .96, .95 and .97, respectively). In addition, Frequency and Obtained Pleasure scores were negatively correlated with depressive symptoms. Thus, initial evidence of precision and external validity were found. However, the results of a confirmatory factor analysis, to compare the responses of American and Brazilian participants, indicate that the dimensions established for the original instrument do not explain the responses obtained with Brazilians. Thus, in Manuscript 2, the results of an exploratory factor analysis are presented, suggesting that Brazilians respond to the COPPES-BR on the basis of four domains: F1 – Social Activities and Competence (α = .94); F2 - Contemplative Activities (α = .83); F3 - Practical Activities (α = .72); and F4 - Intellectual Activities (α = .70). The factor solution explained 43.6% of the total variance. In Manuscript 3, additional evidence of the external validity of the COPPESBR is presented, examining relationships between respondents’ scores on the four factors of the Frequency scale and: (a) sociodemographic indicators, (b) functional dependence, and (c) depressive symptoms. The factor scores were negatively correlated with depressive symptoms and functional dependence scores, and positively correlated with purchasing power and educational level. The correlations with depressive symptoms add to the evidence of the external validity of the COPPES-BR. The other results suggest that the frequency of seniors’ involvement in pleasant events is also affected by functionality and sociodemographic factors. Thus, although there is already satisfactory evidence of the internal and external validity of the COPPES-BR, additional studies are needed, using more representative samples of Brazilian older people, to strengthen the evidence regarding the precision and validity of this instrument.