Effect of phase maldistribution on performance of two-phase catalytic monolith reactor and its comparison with trickle bed reactor

Monolith reactors are widely considered as an alternative to the conventional trickle bed reactor. For the commercial deployment of monolith reactors, comparative performance studies are required. Reliable comparative and performance studies require a detailed understanding of the effect of phase distribution/maldistribution on the performance studies. In this work, performance and comparative studies were carried out in a relatively large column that was 4.8 cm in diameter. Experiments were performed in the same conditions that were used in studies for which phase distribution data were available. Since the properties of the catalyst used were different in both the reactors, the apparent kinetics were studied to facilitate the comparison. The hydrogenation of alpha-methyl styrene (AMS) was used as a test reaction. From the performance studies, it was found that the effect of maldistribution on the performance was stronger than the catalyst availability. From the comparative studies, it was found that the monolith reactor with maldistributed flow conditions provides higher productivity than the trickle bed reactor.     

CFD modeling of multiphase flow distribution in catalytic packed bed reactors: scale down issues

Flow maldistribution in either a bench-scale or commercial scale packed bed is often responsible for the failure of the scale down unit to mimic the performance of the large reactor. The modeling of multiphase flow in a bench-scale unit is needed for proper interpretation of reaction rate data obtained in such units. Understanding the mechanism of flow maldistribution is the first step to avoiding it. In order to achieve this objective, computational fluid dynamic (CFD) simulations of multiphase flow under steady state and unsteady state conditions in bench-scale cylindrical and rectangular packed beds are presented for the first time. The porosity distribution in packed beds is implemented into CFD simulation by pseudo-randomly assigned cell porosity values within certain constraints. The flow simulation results provide valuable information on velocity, pressure, and phase holdup distribution.     

Significance of adrenal hormones in brain energy metabolism

Intensity of glycolysis was studied under conditions of immobilization stress and adrenalectomy as well as with administration of adrenaline and hydrocortisone. The processes of aerobic glycolysis, activity of enzymes of the tricarboxylic acid cycle and mitochondria respiratory chain, content of total, free and protein-bound glycogen, glucose-I-phosphate, glucose-6-phosphate, pyruvate, alpha-ketoglutarate, cytrate and macroergs in the brain are shown to depend on the level of adrenal hormones producing a multilateral effect on a series of energy metabolism links.     

Mercury levels in freshwater fish of the state of South Carolina

Samples of fish from freshwater sources of rivers, lakes and ponds all over the state of South Carolina were collected during the Summer of 1974 and 1975. The fish collected were Bass, Bluegill, Redbreast, Catfish, Shad, Carp, Crappie, Mudfish and Pike. Samples were analyzed using the flameless atomic absorption procedure outlined by Hatch and Ott, and Uthe et al as modified for use with Perkin-Elmer, Coleman MAS-50 mercury analyzer. Triplicate samples of fish tissue were analyzed by wet digestion method. The mean mercury levels in ppb were determined for baseline mercury levels. A significant finding of this report is that those species for which fish of widely differing weights were analyzed, larger fish had higher mercury levels. Mercury levels exceeding the U.S. Food and Drug Administration guideline of 500 ppb for fish tissues have been found in the Mudfish from Edisto River and Pike fish from Lake Murray. Higher levels of mercury occurred in the highly vascularized blood tissues of liver and kidney than in muscle. Carnivorous and bottom-feeding fishes are the most reliable indicators of mercury pollution.     

Adsorption of chitin derivatives onto liposomes: optimization of adsorption conditions

A 2(4) factorial design is used to optimize the adsorption conditions of the hydrophilic anionic polyelectrolytes. Carboxymethylchitin (CMC) and Carboxymethyl/Glycolchitin (CO) onto liposomes at physiological ionic strength (I) and pH using phosphate buffered saline (PBS, I = 154 mM, pH = 7.4). Positive ([+]) or high surface affinity liposomes (DSPC:CHOL:DMTAP, 5:4:1), and Neutral ([N]) or low surface affinity liposomes (DSPC:CHOL, 1:1) were used as adsorption surfaces. Results of the calculations of the main effects indicate that polymer molecular weight (mwt), Surface Affinity (S), Number of Adsorption Shots (Sh), Temperature (T), and the combinations mwt x S, mwt x Sh are the most important process parameters. Results of a study conducted at T = 37 degrees C show that no loss occurs from the positive surface at the highest particle concentration, Np = 4.043 x 10(11). Finally, the extent of polymer-induced particle aggregation is decreased when the diameter of the uncoated liposomes is doubled from 0.22 to 0.45 micron. These results are as expected, given the stiffness and the dimensions of the macromolecules.     

Engagement of ICAM-3 activates polymorphonuclear leukocytes: aggregation without degranulation or beta 2 integrin recruitment

ICAM-3 is a preferred counterreceptor for the leukocyte alpha(L)beta2 integrin. It activates T cells through outside-in signaling, but polymorphonuclear leukocytes (PMN) are reported to be refractory to ICAM-3 stimulation. We found that engagement of ICAM-3 by a mAb (CAL3.10), which binds in the region where alpha(L)beta2 integrin binds, activates PMN homotypic aggregation and adhesion to surfaces. These functional changes were due to ICAM-3 outside-in signaling because aggregation and adhesion were beta2 integrin-dependent, tyrosine kinase and protein kinase C activities were activated, and there was a reorganization of the cytoskeleton. This reorganization and kinase activity was required for ICAM-3-, but not FMLP-, induced aggregation. This is not an Fc-mediated event as an appropriate anti-ICAM-3 F(ab')2 fragment still induced aggregation. Another anti-ICAM-3 Ab (HP2/19), which activates T cells, did not activate PMN. Strikingly, anti-ICAM-3 did not induce degranulation or cause an increase in surface beta2 integrin expression, so adhesion and aggregation were due solely to the activation of the constitutively expressed beta2 integrins. Aggregation in response to ICAM-3, but not FMLP, was compromised at lower cell densities, showing that beta2 integrin recruitment enhances aggregation under suboptimal conditions. We conclude that engagement of ICAM-3 stimulates PMN as well as T cells, but that the appropriate epitope varies between these two cells. ICAM-3 outside-in signaling reorganizes the cytoskeleton without causing degranulation, induces serine and tyrosine kinase activation, and activates existing surface beta2 integrins to a proadhesive state.