935 resultados para osmotic shrinkage


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COMBINED METHODS TO OBTAIN DRIED PAPAYA of FORMOSA CULTIVAR (Carica papaya) The aim of this work was to evaluate the influence of blanching in hot water, osmotic dehydration in sucrose solution and pectin coating on color and water activity of papaya slices after convective drying. on the first experiments, the influence of concentration and time of dehydration on color changes and water activity of fresh and blanched papaya slices was evaluated based on a factorial design. It was not verified significant color changes at the studied ranges. An expression for the water activity of osmotically dehydrated blanched samples was found. Then, the influences of blanching, osmotic dehydration, edible coating and combinations among these pre-treatments on color and water activity were evaluated after convective drying of papaya slices. Blanching was not an advantageous pre-treatment to maintain color and reduce water activity of dried fruits. Osmotically dehydrated fresh samples with or without coating presented the best results.

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A desidratação osmótica (DO) de fatias de carambola (Averrhoa carambola L.) em solução de sacarose foi estudada, com o objetivo de otimizar o processo. Num primeiro conjunto de experimentos, aplicou-se revestimento de coberturas comestíveis (pectina ou pectina+amido) sobre as fatias, seguido de do em solução aquosa de sacarose (50%, p/p, 27°C). Num segundo conjunto, foi realizada secagem parcial da cobertura, em estufa, antes da DO. Num terceiro conjunto de experimentos testou-se a adição de CaCl2 na solução osmótica. A aplicação dos revestimentos antes da do não melhorou a eficiência (máxima perda água/ganho soluto) devido à grande retenção de umidade e à fácil impregnação de sacarose nos mesmos, enquanto que o tecido vegetal sem revestimento restringiu mais o ganho de soluto e propiciou maior saída de água. A utilização de CaCl2 a 0,04M, na própria solução osmótica de sacarose, melhorou ligeiramente a eficiência do processo, em relação à solução sem o sal. A do em solução de sacarose, sem e com a adição de CaCl2, geraram resultados positivos na qualidade sensorial da carambola em fatias, desidratadas em secador (60 e 70°C), em comparação com a fruta não tratada, sendo que a melhor temperatura de secagem foi 60°C.

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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)

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The present work analyzed the tetrameric stability of the hemoglobins from the rattlesnake C. durissus terrificus using analytical gel filtration chromatography, SAXS and osmotic stress. We show that the dissociation mechanism proposed for L. miliaris hemoglobin does not apply for these hemoglobins, which constitute stable tetramers even at low concentrations.

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

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Objective. To determine the influence of cement thickness and ceramic/cement bonding on stresses and failure of CAD/CAM crowns, using both multi-physics finite element analysis and monotonic testing.Methods. Axially symmetric FEA models were created for stress analysis of a stylized monolithic crown having resin cement thicknesses from 50 to 500 mu m under occlusal loading. Ceramic-cement interface was modeled as bonded or not-bonded (cement-dentin as bonded). Cement polymerization shrinkage was simulated as a thermal contraction. Loads necessary to reach stresses for radial cracking from the intaglio surface were calculated by FEA. Experimentally, feldspathic CAD/CAM crowns based on the FEA model were machined having different occlusal cementation spaces, etched and cemented to dentin analogs. Non-bonding of etched ceramic was achieved using a thin layer of poly(dimethylsiloxane). Crowns were loaded to failure at 5 N/s, with radial cracks detected acoustically.Results. Failure loads depended on the bonding condition and the cement thickness for both FEA and physical testing. Average fracture loads for bonded crowns were: 673.5 N at 50 mu m cement and 300.6 N at 500 mu m. FEA stresses due to polymerization shrinkage increased with the cement thickness overwhelming the protective effect of bonding, as was also seen experimentally. At 50 mu m cement thickness, bonded crowns withstood at least twice the load before failure than non-bonded crowns.Significance. Occlusal "fit" can have structural implications for CAD/CAM crowns; pre-cementation spaces around 50-100 mu m being recommended from this study. Bonding benefits were lost at thickness approaching 450-500 mu m due to polymerization shrinkage stresses. (C) 2012 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

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

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

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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)

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The sintering behavior of SnO2-CuO system has been investigated for two preparation methods and as a function of antimony concentration. A chemical preparation (Pechini's method) resulted in powders with smaller particle sizes than for a conventional oxide mixture. This led to smaller grain sizes in Pechini's method ceramics. The microstructures were heterogeneous in both systems, showing grain coarsening. The densification was aided by liquid phase formation, due to copper, in both systems, but the temperature of maximum shrinkage rate was larger for the Pechini's method ceramic because copper had to diffuse to the grain surface. Independently of the preparation method, antimony did not aid densification, and increasing its concentration led to a higher densification temperature and lower shrinkage rate. (C) 2003 Kluwer Academic Publishers.

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Usually, the kinetic models used in the study of sintered ceramic are performed by means of indirect physical tests, such as, results obtained from data of linear shrinkage and mass loss. This fact is justified by the difficulty in the determinations of intrinsic parameters of ceramic materials along every sintering process. In this way, the technique of atomic force microscopy (AFM) was used in order to determine the importance and the evolution of the dihedral angle in the sintering of 0.5 mol% MnO2-doped tin dioxide obtained by the polymeric precursor method.

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)