Flavio Aristone

Electronic Levels of Quantum Dots: A Variational Approach

We introduce an efficient variational method to solve the three-dimensional Schrodinger equation for any arbitrary potential V ( x , y , z ). The method uses a basis set of localized functions which are build up as a product of three one-dimensional cubic β-splines. We have analysed the accuracy of such a method by studying some exact 3D potentials: the harmonic oscillator, the hydrogen atom and the quantum box. Finally, we have calculated energy levels of GaAs/AlGaAs cubic quantum dots and make a comparison with the ones resulting from two well known simplification schemes based in a decomposition of the full potential problem into three separated one-dimensional problems. We show that the scheme making a sequential decomposition gives eingenvalues in better agreement with exact values here obtained variationally.

Evaluation of Variations in Ground-Level Ozone (O3) Concentrations

ABSTRACT This article presents the results of measuring the concentrations of ground-level ozone (O3) in ambient air and meteorological parameters (atmospheric pressure, temperature, wind speed, and relative humidity during the year 2008. The measurements were performed at measuring station located near Campo Grande, away from local sources of O3. Fourier analysis, Principal Component Analysis (PCA) and Multiple Linear Regression (MLR) were used as tools for mathematical analysis of the indicated occurrence. The results of Fourier analysis indicate that not only the daily cycles but also the weekly and monthly cycles are visible in all periods as well as the 12-h cycles. The statistical analysis of the obtained data, based on PCA have shown that approximately 60% of the variance in the measured values can be described with two factors. The attempt of O3 distribution modeling, using MLRA, resulted in a linear model whose coefficient of determination was equal to R2 = 0.98. The results of the study indicate that all these methods are useful for understanding the impact of meteorological parameters on variations of ozone concentration over time.

IMPACTO DE FATORES METEOROLÓGICOS SOBRE AS CONCENTRAÇÕES DE OZÔNIO MODELADOS POR ANÁLISE DE SÉRIES TEMPORAIS E MÉTODOS ESTATÍSTICOS MULTIVARIADOS

O objetivo desta pesquisa foi de desenvolver um modelo para prever as concentracoes de ozonio em funcao das variaveis climaticas. As medidas de concentracao do ozonio foram realizadas na Universidade Federal de Mato Grosso do Sul, utilizando dados do periodo de janeiro a dezembro de 2014. As variaveis preditoras referentes ao clima (umidade relativa, velocidade do vento, chuva, aeerossois, indice de claridade, radiacao solar global e temperatura) foram cedidas pela CEMTEC-Campo Grande-MS. Foram realizadas analise de componentes principais (PCA) e analise de regressao linear multipla (MLR) aplicadas a estas series temporais. As principais relacoes observadas nestas analises foram entao usadas para obter uma equacao de regressao que liga as concentracoes de ozonio diurnas com parâmetros climaticos. O modelo desenvolvido e capaz de explicar 99% da variabilidade nas concentracoes de ozonio de superficie com um erro de 0,2%

Hospitalizações por infecção respiratória associada a fatores ambientais

Objective: To evaluate the relationship between the meteorological variables and respiratory diseases by age. Methods: This is an ecological time-series study, for the period comprised between 2008 and 2011. First, admissions were analyzed by age group and then related to climate information: temperature, precipitation, relative air humidity, and wind speed, through dynamic climatology and statistical parameters using multiple regression analysis, chi-square test and normal distribution. Results: The results showed 12,067 records of hospital admissions for respiratory diseases according to the age group. The highest average number of hospitalizations was found in the age range from 1 to 4 years, with a mean of 42.09% (5079), and over 60 years, with a mean of 27.14% (3274) for the study period. The highest prevalence was due to pneumonia, accounting for 81.0% (9,774) of admissions. The number of hospitalizations was lower in January and higher in June and July. Conclusion: Based on the investigations carried out, a significant correlation was observed between climate parameters and hospitalization for respiratory diseases. doi:10.5020/18061230.2014.p312

Two-subband electron transport in nonideal quantum wells

Electron transport in nonideal quantum wells (QWs) with large-scale variations of energy levels is studied when two subbands are occupied. Although the mean variations of these two levels are screened by the in-plane redistribution of electrons, the energies of both levels remain nonuniform over the plane. The effect of random inhomogeneities on the classical transport is studied within the framework of a local response approach for weak disorder. Both short-range and small-angle scattering mechanisms are considered. Magnetotransport characteristics and the modulation of the effective conductivity by transverse voltage are evaluated for different kinds of confinement potentials (hard-wall QW, parabolic QW, and stepped QW).