1000 resultados para Redução de turbidez
Resumo:
O presente trabalho objetiva apresentar e discutir um caso clnico em que o fio de Kirschner foi empregado para fixao do osso zigomtico fraturado, no sendo removido aps quatro semanas, como recomendado pela literatura, comportando-se como corpo estranho, e sendo ento removido.
Resumo:
OBJETIVO: Determinar, por simulao Monte Carlo, os espectros de feixes de cobaltoterapia em profundidade na gua e fatores de correo para doses absorvidas em dosmetros termoluminescentes de fluoreto de ltio. MATERIAIS E MTODOS: As simulaes dos espectros secundrios da fonte clnica de cobalto-60 foram realizadas com o cdigo Monte Carlo PENELOPE, em diversas profundidades na gua. Medidas experimentais de dose profunda foram obtidas com dosmetros termoluminescentes e cmara de ionizao em condies de referncia em radioterapia. Os fatores de correo para os dosmetros termoluminescentes foram obtidos atravs da razo entre as absores relativas ao espectro de baixa energia e ao espectro total. RESULTADOS: A anlise espectral em profundidade revelou a existncia de espectros secundrios de baixa energia responsveis por uma parcela significativa da deposio de dose. Foram observadas discrepncias de 3,2% nas doses medidas experimentalmente com a cmara de ionizao e com os dosmetros termoluminescentes. O uso dos fatores de correo nessas medidas permitiu diminuir a discrepncia entre as doses absorvidas para, no mximo, 0,3%. CONCLUSO: Os espectros simulados permitem o clculo de fatores de correo para as leituras de dosmetros termoluminescentes utilizados em medidas de dose profunda, contribuindo para a redução das incertezas associadas ao controle de qualidade de feixes clnicos em radioterapia.
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OBJETIVO: Avaliar a relao entre o uso de vestimenta de proteo radiolgica e a diminuio da dose absorvida de radiao ionizante, reforando a eficcia do seu uso tanto para pacientes quanto para indivduos ocupacionalmente expostos. MATERIAIS E MTODOS: O estudo foi desenvolvido utilizando-se o mtodo de reviso integrativa de literatura, e teve como materiais: 21 artigos, 2 livros, 1 tese, 1 trabalho de concluso de curso, 1 programa de computador, 4 pesquisas em base de dados (Instituto Brasileiro de Geografia e Estatstica e Departamento de Informtica do Sistema nico de Sade) e 2 diretrizes de proteo radiolgica. RESULTADOS: A utilizao da vestimenta de proteo radiolgica, teoricamente, reduz 86% a 99% a dose absorvida. Na prtica, a redução nos pacientes pode ser de 88% na radiologia convencional e chegar a 95% no exame tomogrfico. Nos indivduos ocupacionalmente expostos, a redução durante um cateterismo cardaco em torno de 90% e durante uma cirurgia ortopdica de 75%. CONCLUSO: Conforme demonstrado em vrias pesquisas, o uso de vestimenta de proteo radiolgica eficaz e de baixo custo e reduz a dose desnecessria nos pacientes e nos indivduos ocupacionalmente expostos. Logo, sua utilizao necessria para a implementao de um efetivo programa de proteo radiolgica em um servio de radiodiagnstico.
Resumo:
Objetivo:Diversos estudos foram publicados quanto ao uso de blindagens de bismuto para proteo de mamas em exames de tomografia computadorizada (TC), e at a redao deste artigo encontrou-se apenas uma publicao sobre blindagens de brio. O objetivo deste estudo foi caracterizar, pela primeira vez, uma manta plumbfera para proteo de mamas.Materiais e Mtodos:Foram avaliadas a redução percentual da dose e a influncia desta blindagem em parmetros quantitativos da imagem. Medidas de dose foram feitas em um equipamento de TC com auxlio de fantomas especficos e detectores de radiao. Um software de processamento auxiliou na anlise qualitativa, que consistiu em avaliar a variao no nmero mdio de TC e do rudo nas imagens.Resultados:Uma redução de dose na entrada em at 30% e do CTDIvol em at 17% foi encontrada. Como previsto na literatura, a presena do algodo como objeto espaador reduziu significativamente os artefatos presentes na imagem. Em todas as medidas realizadas foi constatado aumento do nmero mdio de TC e do rudo das imagens na presena da manta.Concluso:Como esperado, os dados encontrados para a blindagem com chumbo foram da mesma ordem daqueles encontrados na literatura para blindagem com bismuto.
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In this paper some studies concerning the electroreduction of Mo(VI) in sulphuric acid solutions are described. We have shown that at suitable experimental conditions very stable molybdenum oxide films can be electrochemically deposited at glassy carbon electrodes, the reduction of bromate occurring at less negative potentials on the modified surface. Coulometric experiments have shown that bromide is not the only product of the catalytic bromate reduction by the molybdenum film and species like BrO2 may have part in this process. Based on chronoamperometric curves recorded at -0.60 V, analytical curves have been obtained for the reduction of bromate in the 0.1 - 0.8 mM range, a limit of detection of 20 M for bromate being determined.
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The strong reducing action of L-ascorbic acid (Vitamin C) are of fundamental interest in biochemical and related process. The oxidation of ascorbic acid by molecular oxygen and others oxidants are of fundamental importance, involving the intervention of transition metal ions as catalysts and the formation transition metal complexes of ascorbic acid as intermediates. The present article is intended to cover some aspects of the reactions of ascorbic acid and related compounds involving some transition metal ions.
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In the selective reduction procedure proposed by Magos SnCl2 was used as reductant for inorganic mercury while total mercury was determined after reduction with a mixture of SnCl2 and CdCl2. The difference between total mercury and inorganic mercury determines the content of organic mercury. The procedure of the present work differs of Magos in that the mercury vapour is carried to the absorption cell after magnetic stirring of the solution in the reaction flask; in the Magos procedure, mercury vapour is carried by bubbling the gas in to the solution. In contrast to the Magos procedure this slight modification overcame the necessity of at calibration by analyte addition, saving time and gainning accuracy.
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The kinetic parameters for the CO oxidation reaction using copper/alumina-modified ceria as catalysts were determined. The catalysts with different concentrations of the metals were prepared using impregnation methods. In addition, the reduction-oxidation behaviour of the catalysts were investigated by temperature-programmed reduction. The activity results show that the mechanism for CO oxidation is bifunctional : oxygen is activated on the anionic vacancies of ceria surface, while carbon monoxide is adsorbed preferentially on the higher oxidation copper site. Therefore, the reaction occurs on the interfacial active centers. Temperatures-programmed Reduction patterns show a higher disperdion when cerium oxide is present.
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Despite the fact that boranes are frequently used in amide reductions, the reaction mechanisms of the involved are note well known. This work presents the results of a bibliographic search on probable amide reduction mechanisms and an analysis of the existing literature. Steric and electronic effects were considered in light of reactivity since it could be concluded that the formation of intermediates and products depends mainly on the substitution patterns of both the boron and nitrogen atoms. Otherwise, results described in the literature for the reactions of boranes, sodium borohydride, lithium aluminum hydride, alkylboranes or haloboranes with others functional groups such as carboxylic acids, esters, ketones and alkenes were analysed with the aim to obtain something about the N-substituted amide reactions employing boranes.
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New methodologies for protection of Saccharomyces cerevisiae (FP) cells when supported in montmorillonite K10 (K10), recovered or not with gelatin (G) and in the presence or absence of sucrose (S) are presented. These systems were used for the enantioselective reduction of ethyl acetoacetate and a-chloroacetophenone in hexane, under FP/K10/G/S and FP/S at 20C during 24 hours, affording S-(+)-ethyl-3-hydroxybutanoate in 100% conversion and 99% ee, and R-(-)-2-chloro-1-phenylethanol 79% and 78% ee at 20 and 30 C, respectivelly.
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The abatement of recalcitrant lignin macromolecules from effluents of pulp and paper industry was investigated by combined process. Flocculation and coagulation with aluminum sulfate and natural polyelectrolytes extracted from cactus Cereus peruvianus were used in the first step. After separation of solid residues by filtration, the photochemical methods using TiO2 as catalyst were employed for photocatalytic degradation of lignin compounds from solution. The abatement of lignin compounds after flocculation and coagulation was 46%, and after the overall process, the pollutants reduction observed were 66%. The remaining organic compounds may be removed by any biological treatment.
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The importance of chiral alcohols as starting materials for the production of fine chemicals and as useful chirons for the building of several interesting molecules or natural products is reported. The useful and common methods of asymmetric reduction such as the chemical (with organoboron or organoaluminum reagents) and the catalytic ones (with ruthenium or rhodium complexes) for preparation of chiral alcohols are described; even the newer and much more rare electrocatalytic methods are reported.
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A series of seven Schiff bases have been synthesized from 3,3-diphenylpropilamine and substituted benzaldehydes. These imines were treated with NaBH4 in ethanol affording the corresponding amines in 98-55% yields. A molecular modeling study was performed with the Schiff bases in order to compare the theoretical parameters with the experimental results. The theoretical parameters were obtained by AM1 and PM3 semi-empirical methods. The analysis of charge, electron densities and LUMO coefficients suggested that the most favorable interactions should occur with Schiff bases containing electron-donating groups, in accordance with experimental yields, showing that the higher reactivity is due to higher electrophilic character of imine carbons.
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The exhaust emissions of vehicles greatly contribute to environmental pollution. Diesel engines are extremely fuel-efficient. However, the exhaust compounds emitted by diesel engines are both a health hazard and a nuisance to the public. This paper gives an overview of the emission control of particulates from diesel exhaust compounds. The worldwide emission standards are summarized. Possible devices for reducing diesel pollutants are discussed. It is clear that after-treatment devices are necessary. Catalytic converters that collect particulates from diesel exhaust and promote the catalytic burn-off are examined. Finally, recent trends in diesel particulate emission control by novel catalysts are presented.
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This work discusses the electrocatalytic processes taking place in the polymer electrolyte fuel cell electrodes, specifically the hydrogen oxidation reaction (HOR) and the oxygen reduction reaction (ORR), because these are clear examples of electrochemical reactions favored by the use of electrocatalysts. Since the gaseous reactants are very little soluble in the electrolyte, the use of special electrodes, named gas diffusion electrodes, is required to promote easy and continuous access of reactant gases to the electrocatalytic sites. Besides this, other important aspects such as the use of spectroscopic techniques and of theoretical models to improve the knowledge of the electrocatalytic systems are shortly discussed.