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Column Height (column + height)

Distribution by Scientific Domains

Chemistry	40%

Selected Abstracts

Internal heat integration , the key to an energy-conserving distillation column,

JOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 2-3 2003
Z Olujic
Abstract This paper illustrates the thermal energy conservation potential of the so-called heat integrated distillation column (HIDiC), which combines advantages of direct vapour recompression and diabatic operation at half of the normal column height. In a typical close boiling mixture separation, compared with a column utilising the usual vapour recompression scheme, HIDiC halved the consumption of exergy at approximately the same capital cost, indicating a strikingly short pay-off time. The complexities of integrating the heat transfer equipment in the stripping section with proven gas/liquid contacting devices, which may work adversely to practical implementation of HIDiC concept, are also addressed. © 2003 Society of Chemical Industry [source]

DOSE-DEPENDENT EFFECT OF LUMINAL BUTYRATE ON EPITHELIAL PROLIFERATION IN THE DISTAL COLON OF RATS

JOURNAL OF GASTROENTEROLOGY AND HEPATOLOGY, Issue 2001
S Sengupta
Butyrate, a major product of bacterial fermentation of dietary fibre, is trophic to the colonic epithelium, when deprived of dietary fibre or faecal stream. However, the dose,response relationship of butyrate to this trophic effect is not known. The mechanism of this effect is still debated and how it relates to the antitumorigenic action of butyrate is unclear. Aim, To characterise the dose,response relationship of the effect of butyrate delivered topically to the distal colon on fibre-deprived atrophic colonic epithelium in rats. Methods, Sixty-four male Sprague,Dawley rats were maintained on a fibre-free AIN 93G diet for 3 weeks to induce mucosal atrophy in the colon. The rats then underwent laparotomy for colonic intubation, in which a polyethylene tube was positioned at the proximal end of the distal colon via a caecotomy. After recovering from surgery, they were randomly divided into five groups, which were given for 4 days twice daily infusions of 0.5 mL butyrate at doses of 0, 10, 20, 40 or 80 mm (at which complete reversal of atrophy has been previously observed). Prior to sacrifice, the rats were injected intraperitoneally with vincristine to induce mitotic arrest. Crypt column heights and mitotic arrests were quantified by light microscopy. Results, All treatment groups were healthy and stress-free. The mucosa of vehicle-infused rats was atrophic (mean 38 cells/crypt). Effects of twice daily infusions of butyrate were first observed on cell proliferation (number of mitotic arrests per crypt column) at 10 mm, and increased linearly to 80 mm. Crypt column height increased linearly from 20 mm to 80 mm, at which a mean of 45 cells/crypt were observed (the number usually observed in chow-fed healthy rats). The mitotic index (number of mitotic arrests per 100 crypt cells) also increased linearly from 10 mm. Conclusions, Butyrate's trophic effect showed a linear dose,dependent relationship. Although a maximal effect was not convincingly demonstrated, the results indicate that very small amounts of butyrate are required to affect epithelial proliferation. Since much higher luminal delivery is required to suppress tumorigenesis in this model, the mechanism by which butyrate exerts its trophic and antitumorigenic effects are likely to be different. [source]

Dietary fibre on cell proliferation in large bowel mucosal crypts near or away from lymphoid nodules and on mineral bioavailability

CELL PROLIFERATION, Issue 6 2000
I. L. Cameron
The effect of consumption for 24 weeks of different amounts (0%, 5% or 10% w/w) of fermentable (pectin and guar gum) or nonfermentable (cellulose and lignin) dietary fibres on cell proliferation and other parameters in large bowel mucosal crypts was studied in rats. In all 12 dietary groups, the crypts located over the distal aggregate of lymphoid nodules (ALN) had more colchicine arrested metaphase figures per midaxial crypt section (MC) and a longer crypt column height than crypts located three to four cm away from this ALN. These differences are attributed to the tropic influence of nodular cells in the ALN. Consumption of fermentable fibre decreased pH in the lumen of the caecum, and glucose, Zn and Cu in serum but increased Ca and Mg in serum. The decrease in caecal pH and serum glucose was significantly correlated with a decrease in MC. Increased intake of the nonfermentable fibre types increased faecal bulk but had no significant correlation with the other measured crypt parameters. Multiple regression analyses was used to model the relationships between the mucosal crypt criterion variables and the two measured predictor variables, caecal pH and serum glucose. Relationships between dietary fibre, ALN, MC, bioavailability of dietary minerals and risk of colorectal cancer are discussed. [source]

Numerical Simulation of the Hydrodynamics of Gas/Solid Two-Phase Flow in a Circulating Fluidized Bed with Different Inlet Configurations

CHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 6 2009
Y. Li
Abstract The gas/solid flow characteristics in a circulating fluidized bed with two different inlet configurations were investigated by numerical simulation based on an Eulerian approach. In order to describe the interaction between the gas phase and the solid phase and the influence of the solid phase on the gas turbulence, a source term formulation with a more reasonable physical meaning was introduced. The simulation results were validated by the experimental data; then, the model was employed to examine the effect of the inlet configuration on the gas and solid feeding. The simulation results showed that, using the side feeding system, the distributions of solid flow and concentration were highly variable both over the column cross-section and along the column height. However, such variations can be improved by using the elbow inlet system where the gas and solid are fed from the bottom. [source]