D.M. da Silva

Scales for measuring subjective distance in children and adults in a large open field.

Summary Five age levels (6, 8, 10, 12 years, and adults, N = 127) estimated distance in a large open field by the fractionation method. Scales for subjective distance were derived for each group. It was found that (a) the adults differed from all the other groups, (b) the 12-year-olds differed from the six-year-olds, (c) all the exponents were smaller than 1, (d) perceived distance in a large open field was characterized by underconstancy, and (e) underconstancy was greater for the younger subjects.

A new technique based on genetic algorithms for tracking of power system harmonics

Voltage and current waveforms of a distribution or a transmission system are not pure sinusoids. There are distortions in these waveforms that consist of a combination of the fundamental frequency, harmonics and high frequency transients. This work presents an approach of a harmonic identification method for distorted waveforms in electric power systems. The proposed method is based on the genetic algorithm, which is a technique for optimization inspired by genetics and natural evolution. The proposed algorithm was tested with simulated data. The effect of the size of the initial population, the crossover rate and the mutation rate were studied. The results demonstrate that the method presented is precise when compared with the traditional Fourier transform.

Toxicity assessment of 2,4-D and MCPA herbicides in primary culture of fish hepatic cells

In this study, we used primary cultures of fish hepatic cells as a tool for evaluating the effects of environmental contamination. Primary hepatic cell cultures derived from the subtropical fish Metynnis roosevelti were exposed to different concentrations (0.275, 2.75 and 27.5 μg L−1) of the herbicides 2,4-dichlorophenoxyacetic acid (2,4-D) and 4-chloro-2-methylphenoxyacetic acid (MCPA). Cellular respiratory activity was evaluated by polarography using three substrates: 0.5 M glucose, 0.5 M succinate and 0.5 M α-ketoglutarate. Significant changes were observed in cellular oxygen consumption with 0.5 M α-ketoglutarate. Even at low concentrations, 2,4-D and MCPA were potent uncouplers of oxidative phosphorylation. Primary cultures of M. roosevelti liver cells may provide a useful tool for the evaluation of environmental contaminant effects. A review of regulations regarding permitted concentrations of these herbicides is needed.

MRS data deconvolution through KBDM with multiple signal truncation and clustering: circumventing noise effects

This work describes an unsupervised Lorentzian model function-based deconvolution method for MRS applications through Krylov Basis Diagionalization Method (KBDM) using a strategy to circumvent noise effects sensibility of the direct application of the original algorithm. We simulate a brain MRS signal with known peaks parameters (amplitude, phase, frequency and transversal relaxation time) with SNR similar to the obtained in clinical settings and applied our method. The resulting peak list and the residual between the original signal and the estimated revealed the potential of the proposed method using multiple signal truncation in combination with clustering strategies. Further studies are needed in order to extend the applicability of this promising method, which will be crucial to demonstrate the potential value of the KBDM as a clinical MRS data processing tool.

Study of the effects of heat treatments in the paramagnetic centers of alkaline feldspars and their implications in the luminescence properties

The present work shows a detailed study of the effects of preheating in ESR signals of four alkaline feldspar samples. ESR results showed Fe3+, Al-O−Al, Ti3+ and [Pb-Pb]3+ centers, When the samples were gamma-irradiated, the concentration of the Fe3+ centers deceased in all the samples, but the Al-O -Al center concentration increased after about 50 Gy while that of the Ti3+ and [Pb-Pb]3+ centres became almost constant. The effects of preheating were observed in samples previously irradiated with doses of 0.2 and 3 kGy after heating at 100, 200, 300 and 400 oC, respectively for 10 minutes. In the orthoclase sample FELW, the Fe3+ signal remained almost constant up to 300 oC and increased at 400 oC, while that of the Al center decreased slowly between 100 and 300 oC, but increased at 400 oC. In the microcline sample FELG an increase of the Al coupled with [TiO4] centres was observed up to 300 oC, while a decrease occurred for higher temperatures. Fe3+ center concentration increased up to 200 oC and became nearly constant for higher temperatures. According to our results, even preheating at temperatures as low as 200 oC can change the concentration of Fe, Al and Ti centers in the sample; this fact can modify the luminescence response of the samples with the dose, because all these centers are associated with one or more emission spectra bands.

Fabrication and Characterization of GeO2-PbO Optical Waveguides

Departamento de Engenharia de Sistemas Eletronicos Escola Politecnica Universidade de Sao Paulo, Sao Paulo, SP