Desempenho produtivo de tilápias-do-nilo alimentadas com rações contendo parte aérea de mandioca.

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Parede celular de levedura em rações para alevinos de Tilápia do Nilo.

Este estudo avaliou a suplementação de diferentes níveis de parede celular de levedura spray dried (0,0%; 0,1%; 0,2% e 0,4%), em rações para alevinos de tilápia do Nilo. Foram utilizados 120 alevinos revertidos sexualmente para macho, com peso médio inicial de 2,48 ± 0,07 g, distribuídos aleatoriamente em 20 aquários circulares com volume de 60 L (seis peixes por aquário), dotados de sistema de recirculação de água com biofiltro e aquecimento controlado. O delineamento experimental foi inteiramente casualizado, com quatro tratamentos e cinco repetições. Não houve diferença significativa para conversão alimentar, taxa de crescimento específico e taxa de eficiência protéica. Para o ganho de peso houve efeito quadrático (p<0,05), com nível ótimo estimado em 0,22% de parede celular. Pode-se concluir que a inclusão de 0,22% de parede celular de levedura proporciona melhores resultados de desempenho produtivo para alevinos de tilápia do Nilo. Termos para indexação: Saccharomyces sp., glucano, manano,bitstream/item/38744/1/BP200847.pdfDocumento on-line

ultrasonic vibration turning to increase the deposition efficiency of a silica based sol gel coating

Abstract Magnesium alloys are attracting more and more attention for producing temporary prosthetic devices thanks to their bioresorbable characteristics in human environment. However, they present a reduced corrosion resistance to body fluids, which still limits their applications to a great extent. One possible way to increase the corrosion performances is to coat the device with a suitable coating that provides a barrier to the body fluids corrosion. In this work, Ultrasonic Vibration Turning (UVT) is used to create a surface texture to the AZ31 magnesium alloy with the aim of improving the surface wettability and therefore helping the subsequent coating deposition. The obtained results showed that the surface texture induced by UVT contributed to increase the surface wettability of approximately 17% compared to the conventional turning case, regardless of the adopted cutting parameters. The UVT texture proved to improve the efficiency of the coating deposition since the thickness of the deposited sol-gel coating was increased when applied to UVT surfaces, especially at the lowest depth of cut and highest cutting speed that contributed to generate deeper dimples

large strain extrusion machining of magnesium alloys for biomedical applications

Abstract Recently, magnesium alloys are attracting more and more attention as degradable materials for manufacturing temporary biomedical devices, although their rapid degradation in physiological environment limits their clinical applications to a great extent. Different Severe Plastic Deformation (SPD) processes have been recently applied to magnesium alloys in order to improve the surface integrity, which is directly correlated to their corrosion resistance. The current study investigates the possibility of exploiting Large Strain Extrusion Machining (LSEM) as a processing route to increase corrosion resistance of magnesium alloys for biomedical applications. Different cooling conditions and cutting speeds were adopted during LSEM and their effects on the surface integrity and corrosion resistance on both the machined workpiece and obtained chips were studied. For the first time, liquid nitrogen was used as cooling medium in LSEM and its effect was properly investigated. Results showed that LSEM, regardless of the adopted cutting parameters, is an effective method to obtain a workpiece with improved functional performances. Similar results pertain to the chips, but a careful choice of process parameters is even more mandatory than in the case of the workpiece

the effect of cooling strategies and machining feed rate on the corrosion behavior and wettability of az31 alloy for biomedical applications

Abstract In this work, the corrosion rate of the AZ31 magnesium alloy in physiological environment was improved by optimized machining process parameters. Cryogenic turning was exploited to obtain a featureless layer in the machined sub-surface, while the feed rate was modified to reduce the aspect ratio of the feed marks characteristic of the turning operation, achieving a decrease of the alloy wettability. The obtained results showed that the aforementioned combined aspects acted as an efficient strategy to enhance the AZ31 poor corrosion behavior, which represents the major obstacle of its effective application in the biomedical field

Composição bromatológica e digestibilidade aparente da parte aérea seca da mandioca na alimentação de tilápia-do-nilo.

O objetivo deste trabalho foi avaliar o efeito da secagem da parte aérea da mandioca, ao sol e à sombra, sobre a composição bromatológica e o coeficiente de digestibilidade aparente (CDA) de nutrientes, energia e aminoácidos para tilápia-do-nilo (Oreochromis niloticus). Não houve diferença entre os métodos de secagem para a composição bromatológica. O CDA da proteína bruta apresentou maior digestibilidade para a parte aérea seca à sombra. A secagem da parte aérea da mandioca à sombra permite maior conservação do conteúdo proteico e melhor digestibilidade aparente da fração proteica e aminoacídica para a tilápia-do-nilo

Effect of cold rolling on pitting resistance in duplex stainless steels

Duplex Stainless Steels (DSS) are biphasic austeno-ferritic steels in which the best combination of mechanicaland corrosion-resistance properties is achieved for almost equal volume fractions of the phases. These steelsare classifi ed according to their pitting corrosion resistance, assessed by the PREN index (Pitting ResistanceEquivalent Number) which, although qualitatively, is widely employed as comparison. The present work isaimed to study the pitting resistance of four DSS grades (SAF 2101, 2304, 2205 and 2507) in the as-receivedconditions and after cold rolling at various thickness reductions (from 15% to 85%), to highlight the effects ofcold working on the corrosion behaviour. The materials were potentiodynamically tested in artifi cial seawater(pH 7) and the corresponding Critical Pitting Temperatures (CPT) were determined. Cold deformation mainlyaffected the Lean DSS grades, whereas the high-alloyed DSS were stable, even after heavy deformations.These differences can be attributed not only to composition but also to the onset of diffusionless phasetransformations induced by cold working, which make the materials more prone to corrosive attacks