Influência do sistema de produção sobre a formação de osteodermos no couro em jacaré do Pantanal (Caiman yacare, Daudin).

Com o objetivo de identificar a influência do sistema de criação na acumulação de cálcio no interior do couro de jacaré do Pantanal, foram obtidos dez animais de cada um dos criatórios situados em Cáceres, MT: Coocrijapan, Jacarepan e Aguacerito. Após o abate e a esfola, as peles foram conservadas por salmouragem e salga, embaladas em sacos de polipropileno e armazenadas em refrigerador a zero grau Celcius. O curtimento foi realizado após o alvejamento e abrandamento dos osteodermos. Foram retiradas amostras do centro da região dorsal dos couros e preparadas para análise em microscopia eletrônica de varredura. As eletromicrografias indicaram remanescentes de estruturas ósseas atacadas por produtos químicos descalcificantes, apresentando vários espaços vazios. Tais estruturas encontram-se envoltas por rede de feixes de fibras de colágeno, formando a derme superior e inferior, e ocupam, aproximadamente, metade da espessura total do couro. Os osteodermos das peles dos animais do criatório Coocrijapan foram mais facilmente atacados quimicamente e resultaram em couros mais macios quando comparados com os couros dos animais dos criatórios Jacarepan e Aguacerito. O sistema de criação adotado pelos criatórios comerciais interfere na formação de cálcio no interior das peles, resultando em peles com osteodermos mais ou menos suscetíveis ao ataque químico e, conseqüentemente, couros com diferentes graus de maciez

Chlorine evolution during the fusion of chlorofluoroindate glasses

Samples with a composition of 40InF 3-20ZnF 2-5MCl- xBaF 2-ySrF 2, where M=Na, Li and x+y=35 mol%, were prepared. The thermal properties related to the Ba/Sr ratio and to the remaining chlorine content in the glasses were studied. Thermal stability is improved with the addition of chlorine. However, chlorine concentration is regulated by the sublimation of indium fluorides which takes place at about 600°C. Indium fluorides arc formed during glass fusion. The mechanisms of chlorine sublimation were studied. © 2005 Akadémiai Kiadó, Budapest

Nucleation and crystallization in fluoroindate glasses

Devitrification of fluoride glasses of ZBSI and ZBCdSI composition has been studied by non isothermal differential thermal analysis. For all compositions the Avrami exponent n varies between 3 and 4 suggesting a tridimensional interface controlled growth process with a decreasing nucleation rate. For ZBSI glasses, he curves of activation energy and stability parameters versus InF3 concentration show an anomaly for x=35% InF3. No anomaly has been observed for ZBCdSI glasses composition. Mechanisms of nucleation and crystal growth are discussed

Influence of water on the physical properties of fluoride glass

Several physical properties of ZBLAN glass, including their characteristic transformation temperatures, density, refractive index and ultrasonic velocity, were studied as a function of their residual water content. A series of samples with OH concentrations up to ∼ 0.0043 mol dm-3 was prepared. The OH content was determined for the partially hydrated glasses from FTIR measurements, using a known molar extinction coefficient value for the 2.9 μm band, assigned to fundamental OH stretching vibrations in Zr{single bond}OH species. Molecular H2O was not found at the present levels of water concentration. The preliminary results obtained indicate that an increase in the OH concentration causes a decrease of the density and refractive index values, similar to what has been observed in v-SiO2, as opposed to the case of silicate glasses. This behavior was not expected, since ZBLAN glass has a complex structure closer to that of modified silicates than to v-SiO2. The effect of the OH concentration on the other physical properties was generally found to coincide with known trends for silicate glasses. © 1992 Elsevier Science Publishers B.V. All rights reserved

Bioactive glass prepared by sol-gel emulsion

Bioactive glass (BG) particles with nominal composition 60SiO2-36CaO-4P2O5 (mol%) were prepared by the sol-gel emulsion method. The thermal parameters, morphology, and phase composition were characterized by means of thermal analysis, scanning electron microscopy, X-ray diffraction, and FT-IR absorption spectroscopy. The in vitro bioactivity of the samples was determined by immersing the samples in simulated body fluid. The findings indicated that the sol–gel emulsion method may be useful to prepare BG samples free of crystallization.CNPqFUNDECTInstituto Nacional de Ciência e Tecnologia dos Materiais em Nanotecnologia (INCTMN)Instituto Nacional de Ciência e Tecnologia de Óptica e Fotônica (INCT - INOF

Influence of water on the physical properties of fluoride glass

Several physical properties of ZBLAN glass, including their characteristic transformation temperatures, density, refractive index and ultrasonic velocity, were studied as a function of their residual water content. A series of samples with OH concentrations up to ∼ 0.0043 mol dm-3 was prepared. The OH content was determined for the partially hydrated glasses from FTIR measurements, using a known molar extinction coefficient value for the 2.9 μm band, assigned to fundamental OH stretching vibrations in Zr{single bond}OH species. Molecular H2O was not found at the present levels of water concentration. The preliminary results obtained indicate that an increase in the OH concentration causes a decrease of the density and refractive index values, similar to what has been observed in v-SiO2, as opposed to the case of silicate glasses. This behavior was not expected, since ZBLAN glass has a complex structure closer to that of modified silicates than to v-SiO2. The effect of the OH concentration on the other physical properties was generally found to coincide with known trends for silicate glasses. © 1992 Elsevier Science Publishers B.V. All rights reserved

Mechanical properties of ZBLAN glasses

Elastic moduli (E, G, K, v) of various ZBLAN glass compositions have been determined using pulse echo ultrasonic technique. Vickers microhardness, Hv, was measured under 100 g load and also determined systematically as a function of the load (30-125 g) for a ZBLAN11.6 composition submitted to different surface treatments such as storage in dry and wet atmosphere and optical polishing. In all cases, Hv increases with load until reaching an almost constant value Hv ≅ 200 kg/mm2 for load > 100 g. The hardness variation with load is similar for as-prepared glasses stored in dry or wet atmosphere but is more pronounced for samples with a polished surface. The results are explained by a model which assumes that Hv is determined by the weighted average of plastically deformed volumes in a surface layer and in the bulk. The model allows one to estimate their microhardness and the thickness of the surface layer. © 1993