Comparação entre análises para permanência no rebanho de vacas Nelore utilizando modelo linear e modelo de limiar

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

Atributos físicos de um Latossolo Vermelho correlacionados linear e espacialmente com a consorciação de guandu com milheto

O sistema cultivo mínimo, por possibilitar pouca movimentação de solo, menor número de operações agrícolas sem incorporação dos resíduos vegetais, apresenta vantagens em razão do menor custo de preparo e da redução das perdas de solo e água. No ano agrícola de 2006/2007, na Fazenda de Ensino e Pesquisa da Faculdade de Engenharia de Ilha Solteira, SP, Brasil - FEIS/UNESP, situada nas condições do Cerrado Brasileiro, objetivou-se analisar a produtividade de massa de matéria seca da consorciação de forragem (guandu+milheto) (MSF), em função de atributos físicos do solo, tais como resistência à penetração (RP), umidade gravimétrica (UG), umidade volumétrica (UV) e densidade do solo (DS) nas profundidades de 0,0-0,10 m; 0,10-0,20 m e 0,20-0,30 m. Para tanto, foi instalado um ensaio, contendo 117 pontos amostrais, em um Latossolo Vermelho distroférrico, sob pivô central, numa área experimental de 1600 m² sob cultivo mínimo. A análise estatística constou de análise descritiva inicial dos atributos e análise das correlações lineares simples entre eles, e, finalmente, de análise geoestatística. do ponto de vista da correlação espacial, o atributo que mais bem explica a produtividade de massa de matéria seca da consorciação é a densidade do solo na camada de 0,20-0,30 m, com uma correlação inversa, indicando que as espécies se desenvolvem bem em solos adensados.

Non-linear growth models for bullfrog tadpoles

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

Iterated deferred correction for linear two-point boundary value problems

An analysis of iterated deferred correction based on various classes of implicit Runge-Kutta formulae is given. Out of different possibilities considered, it is shown that those based purely on Lobatto formulae have the best stability. The enhanced stability of Lobatto schemes is very important for the efficient integration of excessively stiff boundary value problems and this is demonstrated by means of some numerical results.

Use of a carbon paste electrode modified with spinel-type manganese oxide as a potentiometric sensor for lithium ions in flow injection analysis

A potentiometric sensor constructed from a mixture of 25% (m/m) spinel-type manganese oxide (lambda-MnO2), 50% (m/m) graphite powder and 25% (m/m) mineral oil is used for the determination of lithium ions in a flow injection analysis system. Experimental parameters, such as pH of the carrier solution, flow rate, injection sample volume, and selectivity for Li+ against other alkali and alkaline-earth ions and the response time of this sensor were investigated. The sensor response to lithium ions was linear in the concentration range 8.6 x 10(-5) - 1.0 x 10(-2) mol L-1 with a slope 78.9 +/- 0.3 mV dec(-1) over a wide pH range 7 - 10 (Tris buffer), without interference of other alkali and alkaline-earth metals. For a flow rate of 5.0 mL min(-1) and a injection sample volume of 408.6 muL, the relative standard deviation for repeated injections of a 5.0 x 10(-4) mol L-1 lithium ions was 0.3%.

Design and management optimization of trickle irrigation systems using non-linear programming

A non-linear model is presented which optimizes the lay-out, as well as the design and management of trickle irrigation systems, to achieve maximum net benefit. The model consists of an objective function that maximizes profit at the farm level, subject to appropriate geometric and hydraulic constraints. It can be applied to rectangular shaped fields, with uniform or zero slope. The software used is the Gams-Minos package. The basic inputs are the crop-water-production function, the cost function and cost of system components, and design variables. The main outputs are the annual net benefit and pipe diameters and lengths. To illustrate the capability of the model, a sensitivity analysis of the annual net benefit for a citrus field is evaluated with respect to irrigated area, ground slope, micro-sprinkler discharge and shape of the field. The sensitivity analysis suggests that the greatest benefit is obtained with the smallest microsprinkler discharge, the greatest area, a square field and zero ground slope. The costs of the investment and energy are the components of the objective function that had the greatest effect in the 120 situations evaluated. (C) 1996 Academic Press Limited

Application of voltammetric technique to the analysis of indanthrene dye in alkaline solution

The Indanthrene Olive Green B (C.I. Vat Green 3; C.I. 69500), VG3 dye, a vat dye bearing an anthraquinonoid group and a ketonic group, can be detected by differential pulse voltammetry in alkaline solution using glassy carbon electrode. on the adsorbed form the dyes are reduced into three cathodic steps at -0.54 V, -0.65 V and -0.93 V vs Ag/AgCl. The leuco form generated after previous electrolysis at controlled potential of -1 V can be detected by voltammetry due to its reoxidation peak at -0.08 V. An analytical method is proposed for determining the vat dye using modified glassy carbon electrode by electrochemical activation in alkaline medium. Linear relationship was observed between l(Pu) vs concentration from I X 10(-5) mol L-1 to 6.0 X 10(-4) mol L-1. The detection limit was calculated to be 9.3 X 10(-6) mol L-1. (c) 2005 Elsevier Ltd. All rights reserved.

PhotoLin: a program to identify and analyze linear structures in aerial photographs, satellite images and maps

A computer program, PhotoLin, written for an IBM-PC-compatible microcomputer is described which detects linear features in aerial photographs, satellite images and topographic maps. The program accepts images saved to PCX files as input and applies noise correction and smoothing filters and thinning routines. The output consists of a skeleton containing the median lines of linear features which can be represented on a map. The branches of the skeleton can be broken into sections of constant length for which the mean orientations are obtained for the preparation of rose diagrams. (C) 2001 Elsevier B.V. Ltd. All rights reserved.

Computer-assisted analysis of cell proliferation markers in oral lesions

Abnormalities in any component of the cell cycle regulatory machine may result in oral. cancer, and markers of cell proliferation have been used to determine the prognosis of tumor progression. The aim of this study was to determine whether silver-stained nucleolar organizer region (AgNOR) and Ki-67 measurements could improve the assessment of growth rates in oral lesions. Eighty-three oral biopsies were studied, 20 of which were classified as fibrous inflammatory hyperplasia (FIH), 40 as leukoplakia (LKP) and 23 as oral. squamous cell carcinoma (OSCC). Within the LKP group, 22 out of 29 biopsies were diagnosed as non-dysplastic leukoplakia (LK) and 18 as dysplastic teukoptakia (DLK), presenting discrete, moderate and severe dysplasia. Ki-67 immunotabeting of the lesions increased steadily in the following order: FIH, DLK, LK and OSCC, indicating that Ki-67 is a good marker for predicting the protiferative fraction among benign, premalignant and malignant oral lesions. The median values of AgNOR parameters indicate that the morphometric index gives better results regarding the proliferative rate than the numerical one. A series of linear regressions between AgNOR parameters and Ki-67 showed positive associations. We conclude that a combination of Ki-67 and morphometric AgNOR analyses could be used as an aid in the determination of the protiferative status of oral epithelial. cells in oral cancer. (C) 2007 Elsevier GmbH. All rights reserved.

On non-linear dynamics and a periodic control design applied to the potential of membrane action

The Fitzhugh-Nagumo (fn) mathematical model characterizes the action potential of the membrane. The dynamics of the Fitzhugh-Nagumo model have been extensively studied both with a view to their biological implications and as a test bed for numerical methods, which can be applied to more complex models. This paper deals with the dynamics in the (FH) model. Here, the dynamics are analyzed, qualitatively, through the stability diagrams to the action potential of the membrane. Furthermore, we also analyze quantitatively the problem through the evaluation of Floquet multipliers. Finally, the nonlinear periodic problem is controlled, based on the Chebyshev polynomial expansion, the Picard iterative method and on Lyapunov-Floquet transformation (L-F transformation).

Analysis of secondary phases segregated and precipitated in SnO2-based varistors

Transmission and scanning electron microscopy techniques were used to study the heterogeneities found in the microstructure of (SnO2Co3O4Nb2O5Fe2O3)-Co-.-Nb-.-Fe-. and (SnO2ZnONb2O5FC2O3)-Zn-.-Nb-.-F-. varistors. Second phases encountered both inside the grains and ingrain boundary regions were identified using energy dispersive spectrometry and electron diffraction patterns. Through the electrical characterisation, the presence of iron oxide among the additives was determined to highlight the non-linear properties of the specimens. A discussion on the influence of second phases on the non-linear features of these systems is also addressed. (C) 2004 Elsevier Ltd. All rights reserved.

Linear relationship between potential and concentration in flow potentiometry

In potentiometric-flow systems, linear-potential responses for logarithmic concentrations can be attained for first-(or pseudo-first-) order reactions in which the monitored chemical species react with the analyte during a fixed time interval. To demonstrate this property, the determination of glycerol based on its oxidation by periodate and potentiometric monitoring of the remaining periodate was selected. Influence of reagent concentration and timing on the linearity of the analytical curve were investigated. A mathematical treatment was derived, and potentialities/limitations of the approach were outlined. The system was applied to analysis of soap and lixivia samples. The analytical curve within 200 and 2000 mg L-1 (r = 0.99975; n = 5) was described as E = 8.166 + 0.0478 (glycerol). The sample throughput was 100 h(-1), and a measurement repeatability within 0.5 mV was always observed. By applying a t-test, there was no statistical difference between the results obtained by the proposed procedure and by iodimetric titration at the 95% confidence level. (C) 2000 John Wiley & Sons, Inc. Lab Robotics and Automation 12:41-45, 2000.

Bayesian longitudinal data analysis with mixed models and thick-tailed distributions using MCMC

Linear mixed effects models are frequently used to analyse longitudinal data, due to their flexibility in modelling the covariance structure between and within observations. Further, it is easy to deal with unbalanced data, either with respect to the number of observations per subject or per time period, and with varying time intervals between observations. In most applications of mixed models to biological sciences, a normal distribution is assumed both for the random effects and for the residuals. This, however, makes inferences vulnerable to the presence of outliers. Here, linear mixed models employing thick-tailed distributions for robust inferences in longitudinal data analysis are described. Specific distributions discussed include the Student-t, the slash and the contaminated normal. A Bayesian framework is adopted, and the Gibbs sampler and the Metropolis-Hastings algorithms are used to carry out the posterior analyses. An example with data on orthodontic distance growth in children is discussed to illustrate the methodology. Analyses based on either the Student-t distribution or on the usual Gaussian assumption are contrasted. The thick-tailed distributions provide an appealing robust alternative to the Gaussian process for modelling distributions of the random effects and of residuals in linear mixed models, and the MCMC implementation allows the computations to be performed in a flexible manner.

Chronopotentiometric stripping analysis using gold electrodes, an efficient technique for mercury quantification in natural waters

This paper proposes a simple methodology for mercury quantification in natural water by stripping chronopotentiometry at constant current, using gold (film) electrodes constructed from recordable CDs in stationary cell. The proposed method allows the direct measurement of labile mercury in natural waters. To quantify total mercury, a robust and low cost UV irradiation system was developed for the degradation of organic constituents of water. The proposed system presents such advantages as excellent sensitivity, low cost, versatility, and smaller dimensions (portability for on-field applications) when compared with other techniques (ICP, GFAAS, fluorimetry) traditionally utilized for mercury quantification. A large linear region of responses was observed, situated over the range 0.02 - 200 μ g L-1. Various experimental parameters were optimized and the system allowed quantifications in natural samples, with detection limit of 8 ng L-1 and excellent reproducibility (RSD of 1.4% for 48 repetitive measurements using a 10 μ g L-1 mercury solution). Different metal ions were evaluated, including copper, as possible interferences on stripping mercury signals. Applications of the new method were demonstrated for the analysis of certified and groundwater samples spiked with a known amount of mercury and for the quantification of methylmercury in synthetic oceanic water, originally utilized for fishes contamination experiment.

Analysis of aromatic amines in surface waters receiving wastewater from a textile industry by liquid chromatographic with electrochemical detection

A high performance liquid chromatography ( HPLC) method with electrochemical detection (ED) was developed for the determination of benzidine, 3,3-dimethylbenzidine, o-toluidine and 3,3-dichlorobenzidine in the wastewater of the textile industry. The aromatic amines were eluted on a reversed phase column Shimadzu Shimpack C-18 using acetonitrile + ammonium acetate (1 x 10(-4) mol L-1) at a ratio 46: 54 v/v as mobile phase, pumped at a flow rate of 1.0 mL min(-1). The electrochemical oxidation of the aromatic amines exhibits well-defined peaks at a potential range of +0.45 to +0.78 V on a glassy carbon electrode. Optimum working potentials for amperometric detection were from 0.70 V to +1.0 V vs. Ag/AgCl. Analytical curves for all the aromatic amines studied using the best experimental conditions present linear relationship from 1 x 10(-8) mol L-1 to 1.5 x 10(-5) mol L-1, r = 0.99965, n = 15. Detection limits of 4.5 nM (benzidine), 1.94 nM (o-toluidine), 7.69 nM (3,3-dimethylbenzidine), and 5.15 nM (3,3-dichlorobenzidine) were achieved, respectively. The detection limits were around 10 times lower than that verified for HPLC with ultra violet detection. The applicability of the method was demonstrated by the determination of benzidine in wastewater from the textile industry dealing with an azo dye processing plant.