Rehydration and shrinkage behaviour of dried pineapple

The shrinking behavior, apparent densities and rehydration indexes of fresh and osmotically pre-treated pineapple slices during air-drying were obtained. The air drying velocity varied from 1.5 to 2.5 m/s and the air temperature from 40 to 70 degreesC. By means of automatic control, it was possible to obtain drying curves under conditions of constant product temperature. Volumetric shrinkage of fresh samples was temperature independent for drying at high air velocities but, at lower velocities, increased with decreasing drying temperature. Osmotically pre-treating the material resulted in reduced shrinkage, as well as drying with product temperature controlled, due to lower drying times needed that led to shorter high temperature exposition. Moisture dependence of apparent density was highly non-linear and could be fitted by an empirical model. Fresh sample rehydration indexes were higher than osmosed ones and increased with increasing temperature, except for pre-treated samples dried at 70 degreesC, probably due to superficial sugar caramelization, which reduced surface water permeability.

Evaluation of the thermal shrinkage of titanium and the setting and thermal expansion of phosphate-boded investments

Statement of problem. There are few studies on titanium casting shrinkage, and phosphate-bonded investments for titanium casting have not produced appropriate marginal fit.Purpose. The purpose of this study was to determine the thermal shrinkage of titanium and the setting and thermal expansion of 3 phosphate-bonded investments.Material and methods. The thermal shrinkage between the melting temperature and room temperature was calculated using a titanium thermal expansion coefficient. The thermal and setting expansion were measured for 3 phosphate bonded investments: Rematitan Plus (RP) specific for titanium, Rema Exakt (RE), and Castorit Super C (CA), using different special liquid concentrations (100%, 75%, and 50%). Setting expansion was measured for cylindrical specimens 50 mm long x 8 mm in diameter with a transducer. The heating and cooling curves were obtained with a dilatometer (DIL 402 PC). The total expansion curve was drawn using software, and temperatures to obtain expansion equivalent to titanium casting shrinkage were determined (n=5). In addition, the total expansion of the control group (RP at 430 degrees C) was measured, as well as the temperatures at which the other groups achieved equivalent total expansion (n=5). Data were analyzed by 1-way ANOVA and the Tukey HSD test (alpha=.05).Results. Titanium casting shrinkage was estimated as 1.55%. RP did not achieve this expansion. RE achieved expansion of 1.55% only with a special liquid concentration of 100% at 594 degrees C. CA with all special liquid concentrations attained this expansion (351 degrees C to 572 degrees C). Total expansion of the control group was 0.86%, and the other groups reached that expansion within the range of 70 degrees C to 360 degrees C.Conclusions. Only RE and CA demonstrated sufficient expansion to compensate for titanium casting shrinkage. All groups reached total expansion equivalent to that of the control group at significantly lower temperatures.

Interfacial integrity of low-shrinkage composite restorations related to the filling technique and consistency

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