Browsing by Author "Stathopoulos, Nikos A."

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    Influence of temperature on biofilm processes
    (1981) Stathopoulos, Nikos A.; Characklis, William G.; Tomson, Mason B.; Papoutsakis, T.
    Biofilm development on surfaces exposed to aqueous environments usually causes an increase in fluid frictional resistance, heat transfer resistance, and corrosion which are of major concern to the water supply and power industries. The objective of this study was to investigate the effect of temperature, an important environmental factor, on the biofilm processes. A tubular fouling reactor system was used for this experimental study. Trypticase Soy Broth was added to the reactors providing the necessary growth requirements for a mixed culture of four bacterial species. A model with the appropriate material balances was developed for the experimental system. Six different temperatures (15-5°C) were tested and their effects on the rate coefficients are reported. An optimum temperature range for biomass growth and for the microbial process occurring within the biofilm was found.
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    Shear stress effects on epithelium cell cultures in vitro
    (1983) Stathopoulos, Nikos A.; Hellums, Jesse D.; Armeniades, C. D.; McIntire, Larry V.
    This study aims to determine the influence of shear stress on cell cultures under carefully controlled conditions. Human embryonic kidney cells grow^as an attached, confluent monolayer on a flat substrate were subjected to steady, uniform laminar flow in a specially designed flow chamber, in which shear stress was precisely defined and controlled. Experiments performed for shear stresses ranging from .2 to 6. N/m, with a varied shear stress exposure time from 2 to 24 hours. The influence of the shear field was slight at low shear stress (.26 N/m) but it had a dramatic effect on cell morphology at higher shear stresses (above 2.6 N/m ) and long exposure times (24 hours). It was also found that shear stress and time stimulated the release of urokinase enzyme. The significance of such flow studies is presented in relation to their possible use for biosynthesis of urokinase enzyme by kidney epithelial cells/