Square-wave voltammetry applied to the analysis of the dye marker, solvent blue 14, in kerosene and fuel alcohol

The purpose of this paper is to develop an electroanalytical method based on square-wave voltammetry (SWV) for the determination of the solvent blue 14 (SB-14) in fuel samples. The electrochemical reduction of SB-14 at glassy carbon electrode in a mixture of Britton-Robinson buffer with N,N-dimethyiformamide (1:1, v/v) presented a well-defined peak at-0.40 V vs. Ag/AgCl. All parameters of the SWV technique were optimized and the electroanalytical method presented a linear response from 1.0 x 10(-6) to 6.0 x 10(-6) mol L-1 (r = 0.998) with a detection limit of 2.90 x 10(-7) mol L-1. The developed method was successfully utilized in the quantification of the dye SB-14 in kerosene and alcohol samples with average recovery from 93.00 to 98.10%.

A new three-phase transformer modeling for three-phase harmonic analysis in distribution systems

This work presents a new three-phase transformer modeling suitable for simulations in Pspice environment, which until now represents the electrical characteristics of a real transformer. It is proposed the model comparison to a three-phase transformer modeling present in EMTP - ATP program, which includes the electrical and magnetic characteristics. In addition, a set including non-linear loads and a real three-phase transformer was prepared in order to compare and validate the results of this new proposed model. The three-phase Pspice transformer modeling, different from the conventional one using inductance coupling, is remarkable for its simplicity and ease in simulation process, since it uses available voltage and current sources present in Pspice program, enabling simulations of three-phase network system including the most common configuration, three wires in the primary side and four wires in the secondary side (three-phases and neutral). Finally, the proposed modeling becomes a powerful tool for three-phase network simulations due to its simplicity and accuracy, able to simulate and analyze harmonic flow in three-phase systems under balanced and unbalanced conditions.

Assessment of the application of cathodic stripping voltammetry to the analysis of diazo reactive dyes and their hydrolysis products

Two reactive dyes, C.I. Reactive Red 120 (RR120) and C.I. Reactive Green 19 (RG19), each bearing two azo groups as the chromophoric moiety and two monochloro-s-triazine groups as reactive groups, can be detected at nanomolar levels using cathodic stripping voltammetry. Linear calibration graphs were obtained for both reactive dyes, from 0.015 to 0.14 mu mol l(-1) for RR120 in pH 4 buffer and from 0.012 to 0.26 mu mol l(-1) for RG19 in pH 3 buffer, using a preconcentration at 0 V during 180 and 240 s on the mercury electrode, respectively. (C) 2001 Elsevier B.V. Ltd. All rights reserved.

Structure characterization of molecular complexes for non-linear optical materials. II. 1 : 1 complexes of 4-methyl-morpholine-N-oxide (1) and 3-picoline-N-oxide (2) with 2,4,6-trinitrophenol, studied by X-ray, AM1 and DFT calculations

(1) C6H2N3O7- center dot C5H12NO2+, Mr = 346.26, P2(1)/c, a = 7.2356(6), b = 10.5765(9), c = 19.593(2) angstrom, 3 beta=95.101(6)degrees, V = 1493.5(2) angstrom(3), Z = 4, R-1 = 0.0414; (2) C6H2N3O7- center dot C6H8NO+, Mr = 38.24, P2(1)/n, a = 7.8713(5), b = 6.1979(7), c = 28.697(3) angstrom, beta = 90.028(7)degrees, V = 1400.0(2) angstrom(3), Z = 4, R-1 = 0.0416. The packing units in both compounds consist of hydrogen bonded cation-anion pairs. The (hyper)polarizabilities have been calculated for the crystallographic and optimized molecules, by AM1 and at the DFT/B3LYP(6-31G**) level.

The asynchronous motor one-dimensional analysis

An application of the linear machine one-dimensional analysis method to the modeling of a conventional asynchronous induction motor, considered as a particular case of linear and sectorial machines, is described. A mathematical model for the calculation of the propulsive force developed by this motor, taking into account the transversal edge effect, is derived from the application of the one-dimensional theory and presented in this paper. As an application example, an induction motor is analyzed by means of the one-dimensional theory.

On a regular convex solver potential for an elastic-damage constitutive model: a theoretical analysis

This work is related with the proposition of a so-called regular or convex solver potential to be used in numerical simulations involving a certain class of constitutive elastic-damage models. All the mathematical aspects involved are based on convex analysis, which is employed aiming a consistent variational formulation of the potential and its conjugate one. It is shown that the constitutive relations for the class of damage models here considered can be derived from the solver potentials by means of sub-differentials sets. The optimality conditions of the resulting minimisation problem represent in particular a linear complementarity problem. Finally, a simple example is present in order to illustrate the possible integration errors that can be generated when finite step analysis is performed. (C) 2003 Elsevier Ltd. All rights reserved.

On designing linear tunable high-Q OTA-C filters with low sensitivity

This paper discusses a design approach for a high-Q low-sensitivity OTA-C biquad bandpass section. An optimal relationship is established between transconductances defining the differencebeta - gamma in the Q-factor denominator, setting the Q-sensitivity to tuning voltages around unity. A 30-MHz filter was designed based on a 0.35 mum CMOS process and V-DD=3.3 V. A range of circuit simulation supports the theoretical analysis. Q-factor spans from 20.5 to 60, while ensuring filter stability along the tuning range. Although a triode-operating OTA is used, the procedure can be extended to other types of transconductor.

Stability analysis of the attitude of artificial satellites subject to gravity gradient torque

Using a canonical formulation, the stability of the rotational motion of artificial satellites is analyzed considering perturbations due to the gravity gradient torque. Here Andoyer's variables are used to describe the rotational motion. One of the approaches that allow the analysis of the stability of Hamiltonian systems needs the reduction of the Hamiltonian to a normal form. Firstly equilibrium points are found. Using generalized coordinates, the Hamiltonian is expanded in the neighborhood of the linearly stable equilibrium points. In a next step a canonical linear transformation is used to diagonalize the matrix associated to the linear part of the system. The quadratic part of the Hamiltonian is normalized. Based in a Lie-Hori algorithm a semi-analytic process for normalization is applied and the Hamiltonian is normalized up to the fourth order. Once the Hamiltonian is normalized up to order four, the analysis of stability of the equilibrium point is performed using the theorem of Kovalev and Savichenko. This semi-analytical approach was applied considering some data sets of hypothetical satellites. For the considered satellites it was observed few cases of stable motion. This work contributes for space missions where the maintenance of spacecraft attitude stability is required.

A Chloro-Bridged Linear Chain Imine-Copper(II) Complex and Its Application as an Enzyme-Free Amperometric Biosensor for Hydrogen Peroxide

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Non-stationary frequency analysis of extreme daily rainfall in São Paulo, Brazil

This work is an assessment of frequency of extreme values (EVs) of daily rainfall in the city of São Paulo. Brazil, over the period 1933-2005, based on the peaks-over-threshold (POT) and Generalized Pareto Distribution (GPD) approach. Usually. a GPD model is fitted to a sample of POT Values Selected With a constant threshold. However. in this work we use time-dependent thresholds, composed of relatively large p quantities (for example p of 0.97) of daily rainfall amounts computed from all available data. Samples of POT values were extracted with several Values of p. Four different GPD models (GPD-1, GPD-2, GPD-3. and GDP-4) were fitted to each one of these samples by the maximum likelihood (ML) method. The shape parameter was assumed constant for the four models, but time-varying covariates were incorporated into scale parameter of GPD-2. GPD-3, and GPD-4, describing annual cycle in GPD-2. linear trend in GPD-3, and both annual cycle and linear trend in GPD-4. The GPD-1 with constant scale and shape parameters is the simplest model. For identification of the best model among the four models WC used rescaled Akaike Information Criterion (AIC) with second-order bias correction. This criterion isolates GPD-3 as the best model, i.e. the one with positive linear trend in the scale parameter. The slope of this trend is significant compared to the null hypothesis of no trend, for about 98% confidence level. The non-parametric Mann-Kendall test also showed presence of positive trend in the annual frequency of excess over high thresholds. with p-value being virtually zero. Therefore. there is strong evidence that high quantiles of daily rainfall in the city of São Paulo have been increasing in magnitude and frequency over time. For example. 0.99 quantiles of daily rainfall amount have increased by about 40 mm between 1933 and 2005. Copyright (C) 2008 Royal Meteorological Society

Bayesian outlier analysis in binary regression

We propose alternative approaches to analyze residuals in binary regression models based on random effect components. Our preferred model does not depend upon any tuning parameter, being completely automatic. Although the focus is mainly on accommodation of outliers, the proposed methodology is also able to detect them. Our approach consists of evaluating the posterior distribution of random effects included in the linear predictor. The evaluation of the posterior distributions of interest involves cumbersome integration, which is easily dealt with through stochastic simulation methods. We also discuss different specifications of prior distributions for the random effects. The potential of these strategies is compared in a real data set. The main finding is that the inclusion of extra variability accommodates the outliers, improving the adjustment of the model substantially, besides correctly indicating the possible outliers.

Assessment of luteal function in goats by ultrasonographic image attribute analysis

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Fibre analysis and fibre digestibility in pet foods - a comparison of total dietary fibre, neutral and acid detergent fibre and crude fibre

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Analysis of bone microarchitecture related to anthropometry in climateric women

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Impact of breed and sex on porcine endocrine transcriptome: a bayesian biometrical analysis

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)