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Reduced Pressure (reduced + pressure)
Selected AbstractsLipase-Catalyzed Enantioselective Reaction of Amines with Carboxylic Acids under Reduced Pressure in Non-Solvent System and in Ionic Liquids.CHEMINFORM, Issue 17 2004Roxana Irimescu No abstract is available for this article. [source] Tubular reabsorption and diabetes-induced glomerular hyperfiltrationACTA PHYSIOLOGICA, Issue 1 2010P. Persson Abstract Elevated glomerular filtration rate (GFR) is a common observation in early diabetes mellitus and closely correlates with the progression of diabetic nephropathy. Hyperfiltration has been explained to be the result of a reduced load of sodium and chloride passing macula densa, secondarily to an increased proximal reabsorption of glucose and sodium by the sodium-glucose co-transporters. This results in an inactivation of the tubuloglomerular feedback (TGF), leading to a reduced afferent arteriolar vasoconstriction and subsequently an increase in GFR. This hypothesis has recently been questioned due to the observation that adenosine A1 -receptor knockout mice, previously shown to lack a functional TGF mechanism, still display a pronounced hyperfiltration when diabetes is induced. Leyssac demonstrated in the 1960s (Acta Physiol Scand58, 1963:236) that GFR and proximal reabsorption can work independently of each other. Furthermore, by the use of micropuncture technique a reduced hydrostatic pressure in Bowman's space or in the proximal tubule of diabetic rats has been observed. A reduced pressure in Bowman's space will increase the pressure gradient over the filtration barrier and can contribute to the development of diabetic hyperfiltration. When inhibiting proximal reabsorption with a carbonic anhydrase inhibitor, GFR decreases and proximal tubular pressure increases. Measuring intratubular pressure allows a sufficient time resolution to reveal that net filtration pressure decreases before TGF is activated which highlights the importance of intratubular pressure as a regulator of GFR. Taken together, these results imply that the reduced intratubular pressure observed in diabetes might be crucial for the development of glomerular hyperfiltration. [source] A comparison between the experimental and estimated evaporation paths from emulsionsFLAVOUR AND FRAGRANCE JOURNAL, Issue 4 2009Abeer Al-Bawab Abstract The evaporation paths in linalool emulsions were experimentally determined using a rotary evaporator coupled to a vacuum pump and calculated from vapour pressures for a series of emulsions with varied oil/water (O/W) ratios. The evaporation paths were comparable to an acceptable degree, suggesting that determination of the evaporation path under reduced pressure, combined with a straightforward calculation using vapour pressures, can be used to estimate the evaporation under different relative humilities. Copyright © 2009 John Wiley & Sons, Ltd. [source] Effects of reduced pressure and vibration on haz-mat packages for liquidsPACKAGING TECHNOLOGY AND SCIENCE, Issue 6 2006S. Paul Singh Abstract Eleven different bottle/closure systems used to package dangerous goods for transportation by air were tested for leakage. The bottles were filled with water and subjected to the combined effects of random vibration and external pressure equivalent to an altitude of 14000ft (4267m) for up to an hour. The bottles were placed in the vertical, horizontal and inverted orientations and observed for leaks. The differences in bottle weights before and after the tests were used to quantify leakage. The results show that of the 11 package types tested, six leaked when subjected to simulation of the air transport environment. Those systems utilizing ,stretch tape' around the closure did not leak. Copyright © 2006 John Wiley & Sons, Ltd. [source] Effect of poly(ethylene glycol) on the solid-state polymerization of poly(ethylene terephthalate)POLYMER INTERNATIONAL, Issue 3 2006E Bhoje Gowd Abstract Poly(ethylene glycol) (PEG) and end-capped poly(ethylene glycol) (poly(ethylene glycol) dimethyl ether (PEGDME)) of number average molecular weight 1000 g mol,1 was melt blended with poly(ethylene terephthalate) (PET) oligomer. NMR, DSC and WAXS techniques characterized the structure and morphology of the blends. Both these samples show reduction in Tg and similar crystallization behavior. Solid-state polymerization (SSP) was performed on these blend samples using Sb2O3 as catalyst under reduced pressure at temperatures below the melting point of the samples. Inherent viscosity data indicate that for the blend sample with PEG there is enhancement of SSP rate, while for the sample with PEGDME the SSP rate is suppressed. NMR data showed that PEG is incorporated into the PET chain, while PEGDME does not react with PET. Copyright © 2005 Society of Chemical Industry [source] Sample preparation effects in matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry of partially depolymerised carboxymethyl celluloseRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 11 2003Dane Momcilovic Sample preparation effects in matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOFMS) of partially depolymerised carboxymethyl cellulose (CMC) have been investigated. The depolymerisation was either enzymatic or acidic. Fractions of enzymatically depolymerised CMC were collected from size-exclusion chromatography (SEC) and further investigated by MALDI-TOFMS. 2,5-Dihydroxybenzoic acid was used as matrix, dissolved in H2O due to the poor solubility of CMC in suitable organic solvents. The samples were dried by two methods, in ambient atmosphere and at reduced pressure. Under reduced pressure the sample spot homogeneity increased. This drying method, however, produced additional adduct peaks in the mass spectra originating from ion exchange on the CMC oligomers. Analysis of CMC could be performed in both negative and positive ion modes. Mass discrimination and variation in ionisation efficiency were demonstrated by comparing mass spectra with SEC data. Measurements of the degree of substitution (DS) were performed on three CMCs with different DS values, which were depolymerised in trifluoroacetic acid. The three CMCs were easily distinguished from one another, but the obtained DS values deviated from the values supplied by the manufacturer. Copyright © 2003 John Wiley & Sons, Ltd. [source] Downstream Processing of Enzymatically Produced Geranyl GlucosideBIOTECHNOLOGY PROGRESS, Issue 5 2001B. Mattheus de Roode Geraniol plays an important role in the fragrance and flavor industry. The corresponding glucoside has interesting properties as a "slow release" aroma compound. Therefore, the enzymatic production and downstream processing of geranyl glucoside were investigated. Geranyl glucoside was produced in a spray column reactor with an initial production rate of 0.58 mg U,1 h,1. A pretreated hydrophobic microfiltration membrane was used to prevent migration of the aqueous, enzyme-containing phase to the downstream process. No retention of the glucoside, which accumulated in the geraniol phase, was found. On the basis of examples from the literature, four downstream processes were tested on their viability for this system. Extraction with water and foaming were not suitable to recover geranyl glucoside from geraniol. In the first case, the glucoside selectivity for the geraniol phase was found to be high, which made extraction with water unsuccessful. In the second case it was possible to obtain a stable foam, but significant enrichment of the foam with glucoside did not occur. Adsorption on alumina and distillation under reduced pressure were applied successfully and tested in-line with the bioreactor. A maximum glucoside adsorption of 7.86 mg g,1 was achieved on alumina. After desorption and evaporation of the extractant the pure glucoside was obtained quantitatively. A pure product could not be obtained after distillation because a small amount of glucose was present in the permeate as well, which accumulated in the bottom fraction. It was shown that with this reactor system a production of 1 kg of geranyl glucoside in 2 days is possible using an initial amount of 50,000 units of enzyme. [source] Enhancement Boiling Heat Transfer Study of a Newly Compact In-line Bundle Evaporator under Reduced Pressure ConditionsCHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 3 2006Z.-H. Liu Abstract For common flooded-type evaporators, nucleate boiling heat transfer cannot occur on the heated tubes since heat fluxes and wall superheats of heated tubes are generally quite low. However, when the tube spacing is very small, nucleate boiling in restricted spaces can occur easily under low heat flux or low wall superheat conditions. The generation of nucleate boiling can effectively enhance the heat transfer performance of bundle evaporators. This study investigated experimentally the boiling heat transfer enhancement effects of the restricted space in compact in-line tube bundles with smooth tubes under various reduced pressures. The experimental results show that the compact in-line tube bundles have a significantly enhanced heat transfer compared to those of the common tube bundles, and there is an optimum tube spacing that provides the greatest heat transfer enhancement effect. The test pressures have a marked influence on the boiling heat transfer enhancement in the compact bundles. The heat transfer enhancement effect decreases with decreasing test pressure. In addition, the heat transfer enhancement effects of the in-line tube bundles are also compared with those of the staggered bundles. Under reduced pressure, there is no significant difference between the heat transfer enhancement effects for the two types of bundles. [source] | |||||||||||||