Confinamento de fónons ópticos em estruturas piezoelétricas periódicas e quasiperiódicas

We study the optical-phonon spectra in periodic and quasiperiodic (Fibonacci type) superlattices made up from III-V nitride materials (GaN and AlN) intercalated by a dielectric material (silica - SiO2). Due to the misalignments between the silica and the GaN, AlN layers that can lead to threading dislocation of densities as high as 1010 cm−1, and a significant lattice mismatch (_ 14%), the phonon dynamics is described by a coupled elastic and electromagnetic equations beyond the continuum dielectric model, stressing the importance of the piezoelectric polarization field in a strained condition. We use a transfer-matrix treatment to simplify the algebra, which would be otherwise quite complicated, allowing a neat analytical expressions for the phonon dispersion relation. Furthermore, a quantitative analysis of the localization and magnitude of the allowed band widths in the optical phonon s spectra, as well as their scale law are presented and discussed

Efeitos interfaciais em heteroestruturas quânticas nô-abruptas: GaAs/ALxGa1-xAs

Um minuncioso estudo das propriedades de confinamento em heterostructuras bidimensionais(poços quânticos) GaAs/AlxGa1_xAs, com interfaces graduais é realizado. Um modelo teórico que represente bem a variação da fração molar do alumínio nas interfaces, resultante do aparecimento de micro-rugosidades e ilhas durante os processos de crescimento e recozimento pós-crescimento da amostra, é elaborado. Vários perfis desta fração molar de alumínio nas interfaces são considerados. Soluções analíticas da equação de Schrodinger, na aproximação da massa efetiva constatne nas interfaces, resultando em equações transcendentais, que possibilitam a obtenção dos níveis de energia dos portadores, decorrentes do seu confinamento quântico, são apresentadas. Energias de ligação e de confinamento de excitons 2D, utilizando-se um método analítico e numerérico e a aproximação do potencial efetivo, são também calculadas. Resultados numéricos para os níveis de energia dos portadores e para as energias de ligação e de confinamento dos excitons 2D, em poços quânticos GaAs/Al0.35Ga0.65As não-abruptos, sem e com a presença de campo elétrico aplicado para vários perfis interfaciais da fração de molar, são mostrados. Para a obtenção desses resultados, faz-se uso do método dos degraus múltiplos e da técnica da matriz de transferência, e adota-se, como operador de energia cinética, o de Ben-Daniel e Duque para uma massa efetiva dependente da posição. Conclui-se que um modelo que leva em conta a existência de interfaces não-abruptas e seus diversos perfis é indispensável para uma melhor descrição das propriedades opto-eletrônicas de poços quânticos GaAs/AlxGa1-xAs, enquanto que a aproximação das interfaces abruptas apresenta-se bastante limitada

Espectro de Polariton de Plasmons e Ondas de Luz em Quasi-Cristais

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior

Excitações em cristais fotônicos unidimensionais

In this work, we present a theoretical study of the propagation of electromagnetic waves in multilayer structures called Photonic Crystals. For this purpose, we investigate the phonon-polariton band gaps in periodic and quasi-periodic (Fibonacci-type) multilayers made up of both positive and negative refractive index materials in the terahertz (THz) region. The behavior of the polaritonic band gaps as a function of the multilayer period is investigated systematically. We use a theoretical model based on the formalism of transfer matrix in order to simplify the algebra involved in obtaining the dispersion relation of phonon-polaritons (bulk and surface modes). We also present a quantitative analysis of the results, pointing out the distribution of the allowed polaritonic bandwidths for high Fibonacci generations, which gives good insight about their localization and power laws. We calculate the emittance spectrum of the electromagnetic radiation, in THZ frequency, normally and obliquely incident (s and p polarized modes) on a one-dimensional multilayer structure composed of positive and negative refractive index materials organized periodically and quasi-periodically. We model the negative refractive index material by a effective medium whose electric permittivity is characterized by a phonon-polariton frequency dependent dielectric function, while for the magnetic permeability we have a Drude like frequency-dependent function. Similarity to the one-dimensional photonic crystal, this layered effective medium, called polaritonic Crystals, allow us the control of the electromagnetic propagation, generating regions named polaritonic bandgap. The emittance spectra are determined by means of a well known theoretical model based on Kirchoff s second law, together with a transfer matrix formalism. Our results shows that the omnidirectional band gaps will appear in the THz regime, in a well defined interval, that are independent of polarization in periodic case as well as in quasiperiodic case

Ondas de spin em quasi-cristais magnônicos

In this paper we investigate the spectra of band structures and transmittance in magnonic quasicrystals that exhibit the so-called deterministic disorders, specifically, magnetic multilayer systems, which are built obeying to the generalized Fibonacci (only golden mean (GM), silver mean (SM), bronze mean (BM), copper mean (CM) and nickel mean (NM) cases) and k-component Fibonacci substitutional sequences. The theoretical model is based on the Heisenberg Hamiltonian in the exchange regime, together with the powerful transfer matrix method, and taking into account the RPA approximation. The magnetic materials considered are simple cubic ferromagnets. Our main interest in this study is to investigate the effects of quasiperiodicity on the physical properties of the systems mentioned by analyzing the behavior of spin wave propagation through the dispersion and transmission spectra of these structures. Among of these results we detach: (i) the fragmentation of the bulk bands, which in the limit of high generations, become a Cantor set, and the presence of the mig-gap frequency in the spin waves transmission, for generalized Fibonacci sequence, and (ii) the strong dependence of the magnonic band gap with respect to the parameters k, which determines the amount of different magnetic materials are present in quasicrystal, and n, which is the generation number of the sequence k-component Fibonacci. In this last case, we have verified that the system presents a magnonic band gap, whose width and frequency region can be controlled by varying k and n. In the exchange regime, the spin waves propagate with frequency of the order of a few tens of terahertz (THz). Therefore, from a experimental and technological point of view, the magnonic quasicrystals can be used as carriers or processors of informations, and the magnon (the quantum spin wave) is responsible for this transport and processing

Polaritons em materiais magnéticos nanoestruturados

In this work we present a theoretical study about the properties of magnetic polaritons in superlattices arranged in a periodic and quasiperiodic fashíons. In the periodic superlattice, in order to describe the behavior of the bulk and surface modes an effective medium approach, was used that simplify enormously the algebra involved. The quasi-periodic superlattice was described by a suitable theoretical model based on a transfer-matrix treatment, to derive the polariton's dispersion relation, using Maxwell's equations (including effect of retardation). Here, we find a fractal spectra characterized by a power law for the distribution of the energy bandwidths. The localization and scaling behavior of the quasiperiodic structure were studied for a geometry where the wave vector and the external applied magnetic field are in the same plane (Voigt geometry). Numerical results are presented for the ferromagnet Fe and for the metamagnets FeBr2 and FeCl2

Ssitema integrado de gestão pública: proposta de implantação de um sistema integrado de gestão, autuação e distribuição de termos circunstanciados e inquéritos policiais entre os juizados especiais criminais e delegacias de Natal

Universidade Federal do Rio Grande do Norte

Tradução e adaptação da escala de dependência de substâncias do Millon Clinical Multiaxial III para o Brasil

Millon describes the normal personality by means of adaptation styles that are effective in normal environments and personality disorders such as unadapted operating styles. To operacionalize his theoretical model, Millon has built several instruments, including the Millon Clinical Multiaxial Inventory III (MCMI-III), wich consists of a self report inventory composed by 175 true or false response items, containing four verification scales, and others scales wich evaluates 14 personality patterns and 10 clinical syndromes. The Substance Dependence scale (T) is placed along with Clinical Syndromes scales. This research is justified by the lack of a Brazilian instrument to assess personality psychopathological aspects, and aims to translate and semantically adapt the MCMI-III to the Brazilian context, checking validity elements of the Substance Dependence scale, and developing a computer application for assisting the evaluation of assessment results. To this intent, 2.588 individuals data was collected, male and female, aged between 18 and 85 years, characterized as belonging to a clinical or non-clinical group, who took part in the survey via the internet or in person. Respondents completed the MCMI-III, a socio-demographic questionnaire and a subgroup also answered to the Goldberg General Health Questionnaire (GHQ). Besides descriptive statistics, we performed the analysis using the Student t test, principal components analysis and internal consistency. Despite difficulties related to translating very specific English terms, the assessment by judges, experts on Millon´s theory, and the back translation, attested the adequacy of the Brazilian version. Factorial analysis indicated the grouping of translated T scale items into three factors (social activities prejudice, lack of impulse control, and oppositional behavior), by presenting a single item on a fourth factor (apparently related to seeking pleasurable stimuli). The Cronbach alpha for this set of items was 0,82, indicating an acceptable scale reliability. The data analysis resulted in distinction of scores between clinical and non-clinical groups and between men and women; the relationship between high scores on the scale T and the other scales; scores of drug users according to the declared used substance; and the relationship between high scores on T and the verification of disorder or risk on GHQ mental health factor, indicating the instrument´s adequate sensistivity in identifying psychopathologies and the relationship between the different disorders or psychopathological personality patterns. Although further studies are necessary to develop the scores transformation factors, the computerized correction tool was adequate.

Estudo das propriedades psicométricas da escala WHOQOLold em idosos da região Nordeste

The population aging process increases the number of elderly people worldwide. In Brazil, a country of continental size, this process began in the 40s and happens with specific features in each of the different region s realities. This way, this thesis aimed to evaluate the psychometric properties of a elderly s quality of life (QOL) scale, the WHOQOL-old, in a population of the Northeast of Brazil. We sought to investigate the congruence between the content covered by the scale and the ones deemed as relevant by the participants. It aimed also study the validity evidences of the instrument s internal structure. To achieve the research objectives we adopted the design of multiple methods. The research was organized in two studies. For data collection, both studies used a sociodemographic questionnaire to obtain a profile of the participants and the Mini Mental State Exam (MMSE), used as exclusion criterion. A number of 18 elderly residents of the cities of Natal-RN and Campina Grande-PB, mean age of 73.3 years (SD = 5.9) took part od the study, They were organized into three focal groups (FG) in witch they discussed about the concept of QOL, what enhance and what hinders QOL. For Study II, a quantitative approach, 335 elderly from Campina Grande responded scale WHOQOL-old. They are between 65 and 99 years (M = 74.17, SD = 6.5). The FG data were analyzed by categorical thematic content. For the data analysis of the WHOQOL-old scale were used exploratory factor analysis and calculation of the Akaike and Bayesian information criteria. The results of both studies were triangulated. According to the discussions in the FG, health and social participation have central roles in quality of life. Social participation is related to all the other QOL s influences raised. The participants indicated the relevance of religiosity and were divided about the importance of sexual activity. Exploratory factor analysis (EFA) extracted a model of six factors. Two items (OLD_3 and OLD_9), not loaded on any factor and were excluded. The other items had factor loadings > 0.3. The response categories were reduced from five to three. After the scale changes, the empirical model showed better fit (-2loglikelihood = 8993.90, BIC and AIC = 9183.90 = 9546.24) than the theoretical model (-2loglikelihood = 18390.88, AIC = 18678.88 and BIC = 19228.11). Despite the best information criterion values, the RMESA remained above the ideal (0.06). We conclude that the WHOQOL-old presents psychometric parameters below the ideal when used with the Northeast population, but the improvements made the scale s use acceptable. The WHOQOL-old uses observable variables that matches with the participants' perceptions on quality of life. However, new strategies must be tested for a better sacale refinement

Propriedades termo-eletrônicas da molécula do DNA

Conselho Nacional de Desenvolvimento Científico e Tecnológico

Excitações elementares em super-redes quasiperiódicas com simetria espelho

In this thesis, we investigated the magnonic and photonic structures that exhibit the so-called deterministic disorder. Speci cally, we studied the effects of the quasiperiodicity, associated with an internal structural symmetry, called mirror symmetry, on the spectra of photonics and magnonics multilayer. The quasiperiodicity is introduced when stacked layers following the so-called substitutional sequences. The three sequences used here were the Fibonacci sequence, Thue-Morse and double-period, all with mirror symmetry. Aiming to study the propagation of light waves in multilayer photonic, and spin waves propagation in multilayer magnonic, we use a theoretical model based on transfer matrix treatment. For the propagation of light waves, we present numerical results that show that the quasiperiodicity associated with a mirror symmetry greatly increases the intensity of transmission and the transmission spectra exhibit a pro le self-similar. The return map plotted for this system show that the presence of internal symmetry does not alter the pattern of Fibonacci maps when compared with the case without symmetry. But when comparing the maps of Thue-Morse and double-time sequences with their case without the symmetry mirror, is evident the change in the pro le of the maps. For magnetic multilayers, we work with two di erent systems, multilayer composed of a metamagnetic material and a non-magnetic material, and multilayers composed of two cubic Heisenberg ferromagnets. In the rst case, our calculations are carried out in the magnetostatic regime and calculate the dispersion relation of spin waves for the metamgnetic material considered FeBr2. We show the e ect of mirror symmetry in the spectra of spin waves, and made the analysis of the location of bulk bands and the scaling laws between the full width of the bands allowed and the number of layers of unit cell. Finally, we calculate the transmission spectra of spin waves in quasiperiodic multilayers consisting of Heisenberg ferromagnets. The transmission spectra exhibit self-similar patterns, with regions of scaling well-de ned in frequency and the return maps indicates only dependence of the particular sequence used in the construction of the multilayer

Propriedades estruturais e optoeletrônicas dos compostos SrSnO3, SrxBa1-xSnO3 e BaSnO3

In this work we present a study for the structural, electronic and optical properties, at ambient conditions of SrSnO3, SrxBa1

Contribuições de modelagem de equações estruturais na análise de dados em modelos comportamentais de destino turístico

A fragilidade brasileira quanto à competitividade turística é um fato observável nos dados da Organização Mundial do Turismo. O Brasil caiu em 2011, da 45ª para a 52ª posição, apesar de liderar no atributo recursos naturais e estar colocado na 23° em recursos culturais. Assim, grandes interesses e esforços têm sido direcionados para o estudo da competitividade dos produtos e destinos turísticos. O destino turístico é caracterizado por um conjunto complexo e articulado de fatores tangíveis e intangíveis, apresentando alta complexidade, dados de elevada dimensionalidade, não linearidade e comportamento dinâmico, tornando-se difícil a modelagem desses processos por meio de abordagens baseadas em técnicas estatísticas clássicas. Esta tese investigou modelos de equações estruturais e seus algoritmos, aplicados nesta área, analisando o ciclo completo de análise de dados, em um processo confirmatório no desenvolvimento e avaliação de um modelo holístico da satisfação do turista; na validação da estrutura do modelo de medida e do modelo estrutural, por meio de testes de invariância de múltiplos grupos; na análise comparativa dos métodos de estimação MLE, GLS e ULS para a modelagem da satisfação e na realização de segmentação de mercado no setor de destino turístico utilizando mapas auto-organizáveis de Kohonen e sua validação com modelagem de equações estruturais. Aplicações foram feitas em análises de dados no setor de turismo, principal indústria de serviços do Estado do Rio Grande do Norte, tendo sido, teoricamente desenvolvidos e testados empiricamente, modelos de equações estruturais em padrões comportamentais de destino turístico. Os resultados do estudo empírico se basearam em pesquisas com a técnica de amostragem aleatória sistemática, efetuadas em Natal-RN, entre Janeiro e Março de 2013 e forneceram evidências sustentáveis de que o modelo teórico proposto é satisfatório, com elevada capacidade explicativa e preditiva, sendo a satisfação o antecedente mais importante da lealdade no destino. Além disso, a satisfação é mediadora entre a geração da motivação da viagem e a lealdade do destino e que os turistas buscam primeiro à satisfação com a qualidade dos serviços de turismo e, posteriormente, com os aspectos que influenciam a lealdade. Contribuições acadêmicas e gerenciais são mostradas e sugestões de estudo são dadas para trabalhos futuros.

Contribuições ao estudo de modelagem de equações estruturais na avaliação da satisfação do cliente de serviços de comunicações móveis

No mercado de telecomunicações as transformações tecnológicas das últimas décadas aliaram-se a um cenário formado por empresas de alta tecnologia que caracterizam o setor de comunicações móveis pessoais em todo mundo. Neste contexto, as empresas deste setor preocupam-se cada vez mais com a competitividade, oferta de serviços, área de atendimento, demanda reprimida e a lealdade do cliente. Estudos de comportamento do consumidor pesquisam a satisfação e lealdade de clientes como fatores básicos para relações bem sucedidas e duradouras com as empresas. A complexidade das relações entre variáveis na avaliação da satisfação do cliente em comunicações móveis pode ser adequadamente pesquisada com a utilização de métodos estatísticos multivariados. Essa tese analisou as relações causais envolvendo os antecedentes e consequentes associados à satisfação do cliente, no segmento de comunicações móveis, bem como desenvolveu e validou um modelo comportamental do cliente no uso deste serviço, buscando explicar as relações entre os construtos envolvidos: satisfação, qualidade dos serviços, valor percebido, imagem da marca, lealdade e reclamação. Foi estabelecida uma ampla base teórica para avaliar a importância estratégica do modelo que relaciona a influência na satisfação do serviço com as percepções dos clientes e avaliada a precisão deste modelo, por meio de uma análise comparativa a utilização de três métodos de estimação dos seus parâmetros, MLE, GLS, e ULS, com o emprego de modelagem de equações estruturais. Foram feitas aplicações em análises de dados, sendo testada e avaliada empiricamente, a influência do gênero na satisfação do cliente deste setor, além de uma segmentação de mercado utilizando mapas auto-organizáveis e a correspondente validação deste processo, com modelagem de equações estruturais.Os resultados do estudo empírico produziram uma boa qualidade de ajustamento para o modelo teórico proposto, com evidências do estabelecimento de uma adequada capacidade explicativa e preditiva, destacando-se a relevância da relação causal entre a satisfação e lealdade, em consonância com diversos estudos realizados para os mercados de comunicações móveis.

Análise da problemática socioambiental de nascentes urbanas no município de Garanhuns-PE

Garanhuns City, in Pernambuco, undergoes a rapid, polluting and non-organized urban development affecting its freshwater springs around the urban environment. These sources are of great importance to the district as well as to the hydrographic basin of the Mundaú River. In this view, this paper aims at analyzing the socio-environmental problems resulting from the urban expansion surrounding the Garanhuns’ sources. The study considers the social and environmental dynamics and follows the theoretical contributions of socio-environmental geography proposed by Mendonça’s Urban Environmental System methodological and theoretical model (2004), as well as the conceptual values of Santos’ space theory (2002a). The data treatment included bibliographical and documental research, evaluation of environmental impact, and water analysis. It revealed that Garanhuns possesses many local environmental traits favoring the coming out of freshwater springs and that these sources have played an important role in the making and development of that village. The environmental impacts on freshwater springs, like Olho D’água, Bom Pastor, Vila Maria, Pau Amarelo and Pau Pombo have been evaluated through the environmental impact score IIAN. It put alight serious cases of socio-environmental impacts on the dynamics of the freshwater springs. In the period of April 2013 and April 2014, it monitored the superficial water quality expelled by the Pau Pombo, Pau Amarelo e Vila Maria water sources, and the analyses of the contents followed the determinations of the Environmental National Board, whose parameters are dissolved oxygen, biochemical demand of oxygen, nitrate, total coliforms, faecal coliforms, and electrical conductivity. The results recollected suggest the existence of organic pollution and deep alteration in the water coming out from the sources. In consequence, it seems important the putting out of measures destined to stop those impacts and guaranteeing protection and maintenance of the freshwater springs and their micro-basins.