Biochemical and histochemical studies have indicated that there is specific cellular activity in the region of the calcification front of articular cartilage implying that a regulation process takes place there. Using scanning and transmission electron microscopy and light microscopy to examine tissue sections of both undecalcified and decalcified articular cartilage in the region of the calcification front, we have looked at its morphology with particular reference to its cellular control. Our observations show that physiological calcification is an active process under cellular control and is related to the presence of extracellular 72

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Hydrogen supplies constitute a significant cost for refineries. Thus, managing hydrogen flows and consumption in an integrated and cost-effective manner is critical. This work presents a systematic framework for modeling key units in a refinery hydrogen network. It proposes an improved superstructure and a simpler mixed-integer nonlinear programming model for synthesizing such a network with minimum total annualized cost. In contrast to the existing literature, it allows dedicated compressors, realistic cost correlations, temperature effects, stream-dependent properties, fuel gas specifications, heating, cooling, and valve expansions. Furthermore, it avoids the many bilinear and posynomial terms present in the existing models; thus it is easier to solve. Our tests with several literature examples confirm that our model gives better and more realistic solutions than the previous models, and it is also suitable for retrofit synthesis.

Aims: The predicted survival of Bacillus subtilis 168 spores from a polynomial regression equation was validated in milk. Methods and Results: Bias factor suggested as an index of model performance was used to validate the polynomial model predictions in ultrahigh temperature (UHT) treated and sterilized whole and skim milk. Model predictions were fail safe, predicting higher D-values (decimal reduction times) in buffer than actually noted in milk. Conclusions: The D-values for spores were lower in milk as compared with those predicted in potassium phosphate buffer contrary to the popular expectation of better spore survival in complex food systems. The Bias factor, a quantitative measure of the model performance, indicated that on average the model predictions exceed the observations by 40% in the case of whole milk and by 60% in the case of skim milk. Significance and Impact of the Study: The present work is an attempt to ascertain the extent of reliability that one can safely place in polynomial model predictions, without compromising on the safety or palatability of foods where it is eventually intended to be applied. The work has also highlighted the differences in the thermal inactivation pattern of spores in buffer and in milk with a possible influence of the various constituents of milk. The work will assist the dairy industry to better design thermal processes to ensure longer shelf life of dairy foods.

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