922 resultados para Analytical biochemistry


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Procymidone, a potentially carcinogenic and mutagenic pesticide, can contribute to environmental and human contamination when applied to apple crops. In this work, we propose a reliable and sensitive method to determine procymidone in Brazilian apples. The method involves differential pulse (DPV) and square-wave voltammetry (SWV) techniques on a glassy carbon electrode. In a supporting electrolyte solution of 0.5 mol L−1 NaOH, procymidone undergoes an irreversible one-electron oxidation at +1.42 V by cyclic voltammetric vs. Ag|AgCl, KCl 3 M reference electrode. The proposed DPV and SWV methods have a good linear response in the 8.00–20.0 mg L−1 range, with limits of detection (LOD) of 0.678 and 0.228 mg L−1, respectively, in the absence of the matrix. We obtained improved LOD (0.097 mg L−1) in the presence of apple matrix and the supporting electrolyte solution. We used three commercial apple samples to evaluate recovery, and we achieved recovery percentages ranging from 94.6 to 110 % for procymidone determinations. We also tested the proposed voltammetric method for reproducibility, repeatability, and potential interferents, and the results were satisfactory for electroanalytical purposes.

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Pós-graduação em Biotecnologia - IQ

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CONTEXTO E OBJETIVO:Há poucos estudos sobre os fatores de risco para os subgrupos de gagueira. O objetivo deste estudo foi caracterizar os fatores de risco para a gagueira desenvolvimental familial em meninos que gaguejam e que não gaguejam como tipologia das disfluências, fatores qualitativos e comunicativos associados, estresse físico e emocional, atitude familiar e reação pessoal.TIPO DE ESTUDO E LOCAL:Estudo transversal analítico com um grupo controle, realizado no Laboratório de Estudo da Fluência, que faz parte do Departamento de Fonoaudiologia de uma universidade pública.MÉTODOS:Pais de 40 meninos com e sem gagueira pareados por idade fizeram parte do estudo. Os participantes foram divididos em dois grupos: crianças com gagueira e crianças sem gagueira, com idades entre 6 anos 0 meses e 11 anos 11 meses Inicialmente todos os participantes foram submetidos a uma avaliação de fluência e depois os dados foram coletados por meio do Protocolo de Risco para a Gagueira do Desenvolvimento.RESULTADOS:Não foi observada diferença nos fatores de estresse físicos e reações pessoais entre os grupos. As atitudes inadequadas familiares foram apresentadas por 95% das crianças com gagueira e 30% das crianças sem gagueira. Quatro fatores de risco analisados não ocorreram nas crianças sem gagueira, a saber, disfluências gagas, fatores qualitativos, estresse físico e emocional.CONCLUSÕES:Os achados sugerem que a presença de disfluências gagas, fatores qualitativos e comunicativos associados, estresse emocional e atitude familiar inadequada são fatores de risco importantes para a gagueira desenvolvimental familial em meninos.

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The aim of this paper is to present an analytical solution for the spin motion equations of spin-stabilized satellite considering only the influence of solar radiation torque. The theory uses a cylindrical satellite on a circular orbit and considers that the satellite is always illuminated. The average components of this torque were determined over an orbital period. These components are substituted in the spin motion equations in order to get an analytical solution for the right ascension and declination of the satellite spin axis. The time evolution for the pointing deviation of the spin axis was also analyzed. These solutions were numerically implemented and compared with real data of the Brazilian Satellite of Data Collection - SCD1 an SCD2. The results show that the theory has consistency and can be applied to predict the spin motion of spin-stabilized artificial satellites.

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This study at aims performing the stability analysis of the rotational motion to artificial satellites using quaternions to describe the satellite attitude (orientation on the space). In the system of rotational motion equations, which is composed by four kinematic equations of the quaternions and by the three Euler equations in terms of the rotational spin components. The influence of the gravity gradient and the direct solar radiation pressure torques have been considered. Equilibrium points were obtained through numerical simulations using the softwares Matlab and Octave, which are then analyzed by the Routh-Hurwitz Stability Criterion.

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

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This study evaluated alternatives for producing erosion susceptibility maps, considering different weight combinations for an environment's attributes, according to four different points of views. The attributes considered were landform, steepness, soils, rocks and land occupation. Considered alternatives were: (1) equal weights, more traditional approach, (2) different weights, according to a previous study in the area, (3) different weights, based on other works in the literature, and (4) different weights based on the analytical hierarchical process. The area studied included the Prosa Basin located in Campo Grande-Mato Grosso do Sul State, Brazil. The results showed that the assessed alternatives can be used together or in different stages of studies aiming at urban planning and decision-making on the interventions to be applied.

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

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Convergence to a period one fixed point is investigated for both logistic and cubic maps. For the logistic map the relaxation to the fixed point is considered near a transcritical bifurcation while for the cubic map it is near a pitchfork bifurcation. We confirmed that the convergence to the fixed point in both logistic and cubic maps for a region close to the fixed point goes exponentially fast to the fixed point and with a relaxation time described by a power law of exponent -1. At the bifurcation point, the exponent is not universal and depends on the type of the bifurcation as well as on the nonlinearity of the map.

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

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)