Multi index model - uma abordagem para aplicação ao mercado accionista em Portugal

O mercado accionista, de uma forma global, tem-se revelado nos últimos tempos uma das principais fontes de incentivo ao mercado de valores mobiliários. O seu impacto junto do público em geral é enorme e a sua importância para as empresas é vital. Interessa, então, perceber como é que a teoria financeira tem obordado a avaliação e a compreensão do processo de formação de uma cotação. Desde os anos 50 até aos dias de hoje, interessa perceber como é que os diferentes autores têm tratado esta abordagem e quais os resultados deste confronto. Interessa sobretudo perceber o abordogem de Stephen Ross e a teoria do arbitragem. Na sequência desta obordagem e com o aparecimento do Multi Index Model, passou a ser possível extimar com maior precisão a evolução da cotação, na medida em que esta estaria dependente de um vasto conjunto de variavéis, que abragem uma vasta área de influência. O contributo de Ross é por isso decisivo. No final interessa reter a melhor técnica e teoria, que defende os interesses do investidor. Face o isto resta, então, saber qual a melhor técnica estatística para proceder a estes estudos empíricos.

Power law analysis of financial index dynamics

Power law PL and fractional calculus are two faces of phenomena with long memory behavior. This paper applies PL description to analyze different periods of the business cycle. With such purpose the evolution of ten important stock market indices DAX, Dow Jones, NASDAQ, Nikkei, NYSE, S&P500, SSEC, HSI, TWII, and BSE over time is studied. An evolutionary algorithm is used for the fitting of the PL parameters. It is observed that the PL curve fitting constitutes a good tool for revealing the signal main characteristics leading to the emergence of the global financial dynamic evolution.

Amygdala activation in response to 2D and 3D emotion-inducing stimuli

Studying changes in brain activation according to the valence of emotion-inducing stimuli is essential in the research on emotions. Due to the ecological potential of virtual reality, it is also important to examine whether brain activation in response to emotional stimuli can be modulated by the three-dimensional (3D) properties of the images. This study uses functional Magnetic Resonance Imaging to compare differences between 3D and standard (2D) visual stimuli in the activation of emotion-related brain areas. The stimuli were organized in three virtual-reality scenarios, each with a different emotional valence (pleasant, unpleasant and neutral). The scenarios were presented in a pseudo-randomized order in the two visualization modes to twelve healthy males. Data were analyzed through a GLM-based fixed effects procedure. Unpleasant and neutral stimuli activated the right amygdala more strongly when presented in 3D than in 2D. These results suggest that 3D stimuli, when used as “building blocks” for virtual environments, can induce increased emotional loading, as shown here through neuroimaging.

Milk intake is inversely related to body mass index and body fat in girls

Dairy foods comprise a range of products with varying nutritional content. The intake of dairy products (DPs) has been shown to have beneficial effects on body weight and body fat. This study aimed to examine the independent association between DP intake, body mass index (BMI), and percentage body fat (%BF) in adolescents. A cross-sectional, school-based study was conducted with 1,001 adolescents (418 boys), ages 15–18 years, from the Azorean Archipelago, Portugal. Anthropometric measurements were recorded (weight and height), and %BF was assessed using bioelectric impedance analysis. Adolescent food intake was measured using a self-administered, semiquantitative food frequency questionnaire. Data were analyzed separately for girls and boys, and separate multiple linear regression analysis was used to estimate the association between total DP, milk, yogurt, and cheese intake, BMI, and %BF, adjusting for potential confounders. For boys and girls, respectively, total DP consumption was 2.6 ± 1.9 and 2.9 ± 2.5 servings/day (P = 0.004), while milk consumption was 1.7 ± 1.4 and 2.0 ± 1.7 servings/day (P = 0.001), yogurt consumption was 0.5 ± 0.6 and 0.4 ± 0.7 servings/day (P = 0.247), and cheese consumption was 0.4 ± 0.6 and 0.5 ± 0.8 servings/day (P = 0.081). After adjusting for age, birth weight, energy intake, protein, total fat, sugar, dietary fiber, total calcium intake, low-energy reporters, parental education, pubertal stage, and physical activity, only milk intake was negatively associated with BMI and %BF in girls (respectively, girls: β = −0.167, P = 0.013; boys: β = −0.019, P = 0.824 and girls: β = −0.143, P = 0.030; boys: β = −0.051, P = 0.548). Conclusion: We found an inverse association between milk intake and both BMI and %BF only in girls.

An efficient numerical scheme for solving multi-dimensional fractional optimal control problems with a quadratic performance index

The shifted Legendre orthogonal polynomials are used for the numerical solution of a new formulation for the multi-dimensional fractional optimal control problem (M-DFOCP) with a quadratic performance index. The fractional derivatives are described in the Caputo sense. The Lagrange multiplier method for the constrained extremum and the operational matrix of fractional integrals are used together with the help of the properties of the shifted Legendre orthonormal polynomials. The method reduces the M-DFOCP to a simpler problem that consists of solving a system of algebraic equations. For confirming the efficiency and accuracy of the proposed scheme, some test problems are implemented with their approximate solutions.

Sertraline accumulation and effects in the estuarine decapod Carcinusmaenas: Importance of the history of exposure to chemical stress

Sertraline is widely prescribed worldwide and frequently detected in aquatic systems. There is, however, a remarkable gap of information on its potential impact on estuarine and coastal invertebrates. This study investigated sertraline accumulation and effects in Carcinus maenas. Crabs from a moderately contaminated (Lima) and a low-impacted (Minho) estuary were exposed to environmental and high levels of sertraline (0.05, 5, 500 μg L−1). A battery of biomarkers related to sertraline mode of action was employed to assess neurotransmission, energy metabolism, biotransformation and oxidative stress pathways. After a seven-day exposure, sertraline accumulation in crabs’ soft tissues was found in Lima (5 μg L−1: 15.3 ng L−1 ww; 500 μg L−1: 1010 ng L−1 ww) and Minho (500 μg L−1: 605 ng L−1 ww) animals. Lima crabs were also more sensitive to sertraline than those from Minho, exhibiting decreased acetylcholinesterase activity, indicative of ventilatory and locomotory dysfunction, inhibition of anti-oxidant enzymes and increased oxidative damage at ≥0.05 μg L−1. The Integrated Biomarker Response (IBR) index indicated their low health status. In addition, Minho crabs showed non-monotonic responses of acetylcholinesterase suggestive of hormesis. The results pointed an influence of the exposure history on differential sensitivity to sertraline and the need to perform evaluations with site-specific ecological receptors to increase relevance of risk estimations when extrapolating from laboratory to field conditions.

Proposta de modelo para obtenção do Work Index das rochas

Este trabalho pretende estabelecer uma relação entre o Work Index e algumas propriedades das rochas. Através da pesquisa bibliográfica foram identificadas varias propriedades com possível influência no valor do Work Index, das quais foram seleccionadas a massa volúmica aparente, a resistência à carga pontual, a composição química, a composição mineralógica e a abrasividade. Adicionalmente a porosidade aberta e resistência à compressão também foram analisadas. Assim foram analisadas 10 amostras de rocha, quatro de granitos, uma de quartzodiorito, uma de ardósia, uma de serpentinito, uma de calcário, uma de mármore e uma de sienito nefelínico, sobre as quais já eram conhecidos os valores de cinco das propriedades referidas previamente, tendo sido determinados os valores das ainda desconhecidas, resistência à carga pontual e a abrasividade que está representada através do resultado do ensaio capon. Devido à dificuldade de execução do ensaio de determinação do Work Index de Bond foram recolhidos dados bibliográficos de valores do Work Index para as amostras de rocha seleccionadas e adoptado o valor médio para cada uma. Os dados obtidos foram tratados estatisticamente através do método de análise de componentes principais assim como através de regressões lineares simples e múltiplas. A análise de componentes principais permitiu identificar várias propriedades da rocha com possível influência sobre o Work Index de entre as analisadas. Foi possível estabelecer uma relação entre o Work Index e quatro das propriedades seleccionadas, designadamente a porosidade aberta, a resistência à compressão, a resistência à carga pontual e a abrasividade.