Transport properties in microcrystalline silicon solar cells under AM1.5 illumination analysed by two-dimensional numerical simulation

Microcrystalline silicon is a two-phase material. Its composition can be interpreted as a series of grains of crystalline silicon imbedded in an amorphous silicon tissue, with a high concentration of dangling bonds in the transition regions. In this paper, results for the transport properties of a mu c-Si:H p-i-n junction obtained by means of two-dimensional numerical simulation are reported. The role played by the boundary regions between the crystalline grains and the amorphous matrix is taken into account and these regions are treated similar to a heterojunction interface. The device is analysed under AM1.5 illumination and the paper outlines the influence of the local electric field at the grain boundary transition regions on the internal electric configuration of the device and on the transport mechanism within the mu c-Si:H intrinsic layer.

Alteração de resposta de suscetibilidade de Aedes aegypti a inseticidas organofosforados em municípios do Estado de São Paulo, Brasil

Foi detectada, por meio de bioensaios, alteração dos níveis de suscetibilidade do Aedes aegypti a organofosforados em municípios do Estado de São Paulo

Depreciações de activos fixos tangíveis: o impacto da alteração dos métodos de depreciação nos resultados das entidades

Dissertação para obtenção do Grau de Mestre em Contabilidade e Finanças Orientadora: Mestre Helena Maria Santos de Oliveira

Cyclic deformation of bidisperse two-dimensional foams

In-plane deformation of foams was studied experimentally by subjecting bidisperse foams to cycles of traction and compression at a prescribed rate. Each foam contained bubbles of two sizes with given area ratio and one of three initial arrangements: sorted perpendicular to the axis of deformation (iso-strain), sorted parallel to the axis of deformation (iso-stress), or randomly mixed. Image analysis was used to measure the characteristics of the foams, including the number of edges separating small from large bubbles N-sl, the perimeter (surface energy), the distribution of the number of sides of the bubbles, and the topological disorder mu(2)(N). Foams that were initially mixed were found to remain mixed after the deformation. The response of sorted foams, however, depended on the initial geometry, including the area fraction of small bubbles and the total number of bubbles. For a given experiment we found that (i) the perimeter of a sorted foam varied little; (ii) each foam tended towards a mixed state, measured through the saturation of N-sl; and (iii) the topological disorder mu(2)(N) increased up to an "equilibrium" value. The results of different experiments showed that (i) the change in disorder, Delta mu(2)(N), decreased with the area fraction of small bubbles under iso-strain, but was independent of it under iso-stress; and (ii) Delta mu(2)(N) increased with Delta N-sl under iso-strain, but was again independent of it under iso-stress. We offer explanations for these effects in terms of elementary topological processes induced by the deformations that occur at the bubble scale.

Effect of the number of shells on the pressure and energy of two-dimensional free bubble clusters

We have performed Surface Evolver simulations of two-dimensional hexagonal bubble clusters consisting of a central bubble of area lambda surrounded by s shells or layers of bubbles of unit area. Clusters of up to twenty layers have been simulated, with lambda varying between 0.01 and 100. In monodisperse clusters (i.e., for lambda = 1) [M.A. Fortes, F Morgan, M. Fatima Vaz, Philos. Mag. Lett. 87 (2007) 561] both the average pressure of the entire Cluster and the pressure in the central bubble are decreasing functions of s and approach 0.9306 for very large s, which is the pressure in a bubble of an infinite monodisperse honeycomb foam. Here we address the effect of changing the central bubble area lambda. For small lambda the pressure in the central bubble and the average pressure were both found to decrease with s, as in monodisperse clusters. However, for large,, the pressure in the central bubble and the average pressure increase with s. The average pressure of large clusters was found to be independent of lambda and to approach 0.9306 asymptotically. We have also determined the cluster surface energies given by the equation of equilibrium for the total energy in terms of the area and the pressure in each bubble. When the pressures in the bubbles are not available, an approximate equation derived by Vaz et al. [M. Fatima Vaz, M.A. Fortes, F. Graner, Philos. Mag. Lett. 82 (2002) 575] was shown to provide good estimations for the cluster energy provided the bubble area distribution is narrow. This approach does not take cluster topology into account. Using this approximate equation, we find a good correlation between Surface Evolver Simulations and the estimated Values of energies and pressures. (C) 2008 Elsevier B.V. All rights reserved.

Positive Solutions of the Dirichlet Problem for the One-dimensional Minkowski-Curvature Equation

We discuss existence and multiplicity of positive solutions of the Dirichlet problem for the quasilinear ordinary differential equation-(u' / root 1 - u'(2))' = f(t, u). Depending on the behaviour of f = f(t, s) near s = 0, we prove the existence of either one, or two, or three, or infinitely many positive solutions. In general, the positivity of f is not required. All results are obtained by reduction to an equivalent non-singular problem to which variational or topological methods apply in a classical fashion.

Avaliação da postura corporal em estudantes do ensino superior

A Era moderna trouxe ao Homem meios que facilitam muitas das suas tarefas diárias, diminuindo a actividade física e condicionando a postura corporal. Actualmente a população jovem, e sobretudo os estudantes, encontra-se exposta a uma grande quantidade de riscos de alterações posturais. Todavia, a postura assumida por parte desta classe não tem sido muito investigada. Sendo assim, este estudo tem como objectivo geral a avaliação bi-dimensional da postura corporal, na posição de pé e de sentado, de estudantes do 1º ano do Curso de Terapia Ocupacional, do Instituto Politécnico de Leiria. Os objectivos específicos centram-se na verificação das relações entre as alterações posturais desse grupo de estudantes e os sintomas de lesões músculo-esqueléticas nos últimos 12 meses, os factores sócio-demográficos e os factores considerados de risco de alterações posturais em estudantes. Para tal, utilizaram-se o Software para Avaliação Postural e a Versão adaptada do Questionário Nórdico Músculoesquelético. Constataram-se elevadas percentagens de posturas inadequadas. Na posição de pé todos os indivíduos apresentam alterações posturais num ou mais segmentos analisados, sendo que a flexão do tronco é a mais frequente. Já na posição sentada a alteração postural mais frequente é a inclinação da cabeça para o lado direito. Verificou-se ainda que algumas das alterações posturais apresentam uma relação positiva e significativa com os sintomas de lesões músculo-esqueléticas, com alguns factores de risco e sócio-demográficos. A partir dos resultados obtidos, torna-se evidente a necessidade de estabelecer programas de consciencialização para esta problemática, assim como programas de prevenção de desvios posturais.

Fabrication of Three-Dimensional Dendritic Ni-Co Films By Electrodeposition on Stainless Steel Substrates

Co-deposition of nickel and cobalt was carried out on austenitic stainless steel (AISI 304) substrates by imposing a square waveform current in the cathodic region. The innovative procedure applied in this work allows creating a stable, fully developed, and open porous three-dimensional (3D) dendritic structure, which can be used as electrode for redox supercapacitors. This study investigates in detail the influence of the applied current density on the morphology, mass, and chemical composition of the deposited Ni-Co films and the resulting 3D porous network dendritic structure. The morphology and the physicochemical composition were studied by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (W). The electrochemical behavior of the materials was evaluated by cyclic voltammetry (CV). The results highlight the mechanism involved in the coelectrodeposition process and how the lower limit current density tailors the film composition and morphology, as well as its electrochemical activity.

Multi-dimensional scaling applied to histogram-based DNA analysis

This paper aims to study the relationships between chromosomal DNA sequences of twenty species. We propose a methodology combining DNA-based word frequency histograms, correlation methods, and an MDS technique to visualize structural information underlying chromosomes (CRs) and species. Four statistical measures are tested (Minkowski, Cosine, Pearson product-moment, and Kendall τ rank correlations) to analyze the information content of 421 nuclear CRs from twenty species. The proposed methodology is built on mathematical tools and allows the analysis and visualization of very large amounts of stream data, like DNA sequences, with almost no assumptions other than the predefined DNA “word length.” This methodology is able to produce comprehensible three-dimensional visualizations of CR clustering and related spatial and structural patterns. The results of the four test correlation scenarios show that the high-level information clusterings produced by the MDS tool are qualitatively similar, with small variations due to each correlation method characteristics, and that the clusterings are a consequence of the input data and not method’s artifacts.

Alteração de enzimas hepáticas em trabalhadores de refinaria de petróleo

OBJETIVO: A exposição ocupacional típica de uma refinaria de petróleo pode alterar a função hepática de seus trabalhadores. Assim, o objetivo do estudo foi identificar fatores de risco de alterações em enzimas hepáticas em trabalhadores de uma refinaria de petróleo. MÉTODOS: Os trabalhadores de uma refinaria de petróleo, localizada em São Francisco do Conde, Estado da Bahia, eram submetidos a exames periódicos anuais de 1982 a1998. O estudo caso-controle investigou todos os 150 casos de indivíduos com alteração simultânea de gama-glutamil transferase e de alanino amino transferase, de pelo menos 10% acima do valor de referência. Como controles, foram selecionados 150 indivíduos sem quaisquer alterações de enzimas hepáticas ou de bilirrubinas, desde a sua admissão. Foram calculadas as razões de chance e respectivos intervalos de confiança de 95% a partir de modelos de regressão logística. RESULTADOS: Em todos os setores de produção, o risco de alteração de enzimas hepáticas foi significantemente mais elevado do que no setor administrativo (RC=5,7; IC 95%: 1,7-18,4), estando controlados os efeitos do álcool, obesidade e antecedentes médicos de hepatite. No período 1992-1994 foram registrados 89 casos, 88 deles provieram dos diversos setores da produção. CONCLUSÕES: A exposição ocupacional desempenha papel importante na determinação de alterações de enzimas hepáticas em trabalhadores do refino de petróleo, além dos fatores de risco eminentemente biológicos e/ou comportamentais como obesidade e o consumo de álcool.

Three-dimensional patchy lattice model for empty fluids

The phase diagram of a simple model with two patches of type A and ten patches of type B (2A10B) on the face centred cubic lattice has been calculated by simulations and theory. Assuming that there is no interaction between the B patches the behavior of the system can be described in terms of the ratio of the AB and AA interactions, r. Our results show that, similarly to what happens for related off-lattice and two-dimensional lattice models, the liquid-vapor phase equilibria exhibit reentrant behavior for some values of the interaction parameters. However, for the model studied here the liquid-vapor phase equilibria occur for values of r lower than 1/3, a threshold value which was previously thought to be universal for 2AnB models. In addition, the theory predicts that below r = 1/3 (and above a new condensation threshold which is < 1/3) the reentrant liquid-vapor equilibria are so extreme that it exhibits a closed loop with a lower critical point, a very unusual behavior in single-component systems. An order-disorder transition is also observed at higher densities than the liquid-vapor equilibria, which shows that the liquid-vapor reentrancy occurs in an equilibrium region of the phase diagram. These findings may have implications in the understanding of the condensation of dipolar hard spheres given the analogy between that system and the 2AnB models considered here. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4771591]

Study of the one dimensional and transient bioheat transfer equation: Multi-layer solution development and applications

: In this work we derive an analytical solution given by Bessel series to the transient and one-dimensional (1D) bioheat transfer equation in a multi-layer region with spatially dependent heat sources. Each region represents an independent biological tissue characterized by temperature-invariant physiological parameters and a linearly temperature dependent metabolic heat generation. Moreover, 1D Cartesian, cylindrical or spherical coordinates are used to define the geometry and temperature boundary conditions of first, second and third kinds are assumed at the inner and outer surfaces. We present two examples of clinical applications for the developed solution. In the first one, we investigate two different heat source terms to simulate the heating in a tumor and its surrounding tissue, induced during a magnetic fluid hyperthermia technique used for cancer treatment. To obtain an accurate analytical solution, we determine the error associated with the truncated Bessel series that defines the transient solution. In the second application, we explore the potential of this model to study the effect of different environmental conditions in a multi-layered human head model (brain, bone and scalp). The convective heat transfer effect of a large blood vessel located inside the brain is also investigated. The results are further compared with a numerical solution obtained by the Finite Element Method and computed with COMSOL Multi-physics v4.1 (c). (c) 2013 Elsevier Ltd. All rights reserved.

Prevalência de alteração vocal em educadoras e sua relação com a auto-percepção

OBJETIVO: Verificar a prevalência de alteração vocal auto-referida em educadoras de creche e fatores associados. MÉTODOS: Estudo observacional transversal, realizado em 2001, em oito creches da cidade de São Paulo, nas quais estavam sendo desenvolvidas ações do Programa Creche. Esse Programa faz parte de um laboratório de investigação fonoaudiológica em promoção da saúde. A coleta de dados foi feita por meio de questionário, com 93 educadoras, sobre características sociodemográficas, aspectos da organização e do ambiente físico do trabalho, comportamento vocal, histórico de doenças, estilo de vida e percepção acerca de alterações vocais. Foi realizada análise perceptivo-auditiva da voz das participantes. Para análise estatística foram utilizadas proporções, medidas de tendência central, teste do qui-quadrado, com correção de Yates e análise de regressão logística múltipla. RESULTADOS: Registrou-se 80% das educadoras referindo presença de alteração vocal, sendo que 26% delas procuraram algum tratamento. Grande parte (39%) referiu que o problema está presente há quatro anos ou mais, intermitente (82%) e de grau leve ou moderado (74%). Acreditam que o uso da voz seja a principal causa da alteração vocal (82%) e a rouquidão, o principal sintoma vocal (54%). Alteração vocal auto-referida foi estatisticamente associada à presença de alteração vocal constatada por avaliação e com o fato de já terem tido alguma orientação sobre uso da voz. CONCLUSÕES: A adequada percepção das educadoras para seus problemas de voz pode vir a se tornar uma ferramenta importante em futuros trabalhos com esta população, com vistas a diminuir a alta prevalência de alteração vocal encontrada.

Bi-Dimensional Characterization of a Wimax Radio Channel at 3.5GHz

This paper presents the characterization of an indoor Wimax radio channel using the Finite-Difference Time-Domain (FDTD) [1] method complemented with the Convolutional Perfect Matched Layer (CPML) technique [2]. An indoor 2D scenario is simulated in the 3.5GHz band (IEEE 802.16d-2004 and IEEE 802.16e-2005 [3]). In this study, we used two complementary techniques in both analysis, technique A and B for fading based on delay spread and technique C and D for fading based on Doppler spread. Both techniques converge to the same result. Simulated results define the channel as flat, slow and without inter-symbolic interference (ISI), making the application of the spatial diversity the most appropriate scheme.