BENEFITS OF SERIAL LAYER MICROFILTRATION

Many filtration applications are of necessity being driven toward finer and finer particulate removal and improved permeate quality. Finer particle removal requires filters with smaller pore sizes and absolute pore size guarantees, and the finer the pores in the membrane filter, the sooner it will clog slowing its throughput rate and reducing its useful life. Engineers will frequently design processes involving several separate filtration and clarification steps to allow the process to run larger batches or for extended periods of operation without, system shutdown for filter changes. Membrane manufacturers who produce the final filters used at the end of the filtration train have resorted to a familiar technique in many liquid filtration and purification applications to achieve the desired final fluid quality level at reasonable filtration rates and final filter life by designing and producing filter elements with two membrane layers.

It is the objective of this paper to illustrate simple techniques used by a microporous nylon membrane manufacturer to select and optimize the prefilter membranes to be used in a dual-layered membrane pleated cartridge filter element. The membranes are thin polymeric sheets of nylon supported internally with a nonwoven polyester cloth that is coated with the nylon polymer in such a way that fluid passing through the filter contacts only the nylon and does not contact the polyester.     

Application of an extended Lee-Kesler corresponding-states technique to prediction of vapor-liquid equilibria in multicomponent mixtures containing polar components

Mixing rules for an extended Lee-Kesler (ELK) corresponding-states method for prediction of thermodynamic properties are presented. The mixing rules, which do not contain adjustable parameters, permit calculation of vapor-liquid equilibria in mixtures containing one or more polar components. While a single heat-of-mixing datum may be included for strongly associating components, generally only pure component properties are used in the calculations. A comparison of calculated bubble-point pressures and equilibrium vaporization ratios to experimental values is made for 26 ternary mixtures (791 points) and 5 quaternary mixtures (175 points). Bubble-point pressures are predicted quite well with ELK (9.1 % AAD for ternaries and 7.9% for quaternaries). Composition predictions are difficult to compare in multicomponent systems, but ELK predictions appear to be acceptable on both a system-by-system and an overall AAD basis.Paper presented at the Tenth Symposium on Thermophysical properties, June 20–23, 1988, Gaithersburg, Maryland, U.S.A.     

The extraction of natural cashew nut-shell liquid from the cashew nut (Anacardium occidentale)

In the two-stage recovery of natural cashew nut-shell liquid (CNSL) by solvent extraction, the overall yields from half-shells obtained by mechanical cutting and from chilled fragmented shells (to solidify the phenols) by manual processing are identical, indicating that no physical loss of phenolic material occurs in the mechanical process. At the first stage, prior to comminution, the yield from intact half-shells of mechanical origin is considerably less than that from manually processed shells due to extensive internal fracturing of the shell structure and greater solvent penetration in the latter case. Static solvent extraction of macerated shells gave the same yield as Soxhlet extraction, but the filtration stage was difficult and large volumes of solvent were required. Soxhlet solvent extraction or ultrasound/solvent extraction of manually processed shells at ambient temperature gave similar yields and economy in solvent usage. Both were much superior to mechanical agitation. By catalyzed decarboxylation of the recovered natural CNSL an almost theoretical yield (25%) of phenolic lipid rich in cardanol was obtained, which is considerably higher than that (10%) in the traditional recovery of technical CNSL by the hot oil bath industrial method. Natural CNSL contains a predominant amount of anacardic acid and represents a novel phenolic lipid source. Chemical reduction with air/aqueous hydrazine gave saturated natural CNSL. Polymerization of natural CNSL was effected in alkaline solution with paraformaldehyde. Part 27. Part 26, ref. 1.     

Low-energy electron-enhanced etching of HgCdTe

Low-energy electron-enhanced etching (LE4) is applied to HgCdTe to eliminate ion-induced surface damage. First, LE4 results for patterned samples are illustrated. The LE4 mechanism is understood from a mechanistic study in terms of three etch variables: direct current (DC) bias, gas composition, and sample temperature. For this paper, the effects of DC bias (electron energy) and gas composition (CH₄ concentration) are summarized qualitatively, followed by quantitative evidence. Etch rate, the amount of polymer, surface stoichiometry, and surface roughness have specific relations with each etch variable under competition between pure LE4 and polymer deposition.     

New aspects of unsaturated polyester resin synthesis. Part 2. Reactant sequence distribution and its effect on cure kinetics

The distribution of unsaturations in the prepolymer of a typical unsaturated polyester (UP) resin (maleic anhydride, phthalic anhydride and 1,2‐propylene glycol) has been shown to influence the kinetics of the cure process with styrene monomer. Segments containing double bonds in close proximity appear to lower the reactivity of the resin due to steric hindrance, as indicated by the fact that the rate of cure and the final degree of cure, measured by differential scanning calorimetry (DSC), increase as the average sequence length (SL) of maleic units decreases. This implies that the reactivity of UP resins may be improved by synthesis of prepolymers with certain reactant sequence‐length distributions. The copolymer formed by the melt condensation process of maleic anhydride, phthalic anhydride and 1,2‐propylene glycol in the absence of a transesterification catalyst has a non‐random structure with a tendency towards blockiness. This was established using ¹H NMR analysis in tandem with deterministic and Monte Carlo modelling techniques. Copyright © 2003 Society of Chemical Industry     

STZ transport and cytotoxicity. Specific enhancement in GLUT2-expressing cells

The glucose analog streptozotocin (STZ) has long been used as a tool for creating experimental diabetes because of its relatively specific beta-cell cytotoxic effect, but the mechanism by which systemic injection of STZ causes beta-cell destruction is not well understood. In the current study, we have used insulinoma (RIN) and AtT-20ins cell lines engineered for overexpression of GLUT2 or GLUT1 to investigate the role of glucose transporter isoforms in mediating STZ cytotoxicity. The in vivo effects of STZ were evaluated by implantation of RIN cells expressing or lacking GLUT2 into athymic nude rats. The drug had a potent cytotoxic effect on RIN cells expressing GLUT2, but had no effect on cells lacking GLUT2 expression, as indicated by histological analysis and measurement of the blood glucose levels of treated animals. The preferential cytotoxic effect of STZ on GLUT2-expressing cell lines was confirmed by in vitro analysis of GLUT2-expressing and untransfected RIN cells, as well as GLUT2- and GLUT1-overexpressing AtT-20ins cells. Consistent with these data, only GLUT2-expressing RIN or AtT-20ins cells transported STZ efficiently. We conclude that expression of GLUT2 is required for efficient killing of neuroendocrine cells by STZ, and this effect is related to specific recognition of the drug as a transported substrate by GLUT2 but not GLUT1.     

The plastic bending of clamped polygonal plates with an application to radial buckling in milk bottle tops

Solutions for the plastic bending of clamped polygonal plates are investigated. For an isosceles triangular plate, and for a truncated isosceles triangular plate, minima exist for plastic work of formation with respect to angles of the triangle, and location of the apex of the deformed pyramid shape. A characteristic number of radial buckles is formed when the foil circular top of British one-pint milk bottles is pushed in and material drawn over the rim of the bottle on opening. The plastic bending analysis provides an approximate means of predicting the number of buckles.     

Effect of nitrogen dioxide and other combustion products on asthmatic subjects in a home-like environment

Nitrogen dioxide (NO2) is one of a number of nitrogen compounds that are by-products of combustion and occur in domestic environments following the use of gas or other fuels for heating and cooking. In this study, we examined the effect of two levels of NO2 on symptoms, lung function and airway hyperresponsiveness (AHR) in asthmatic adults and children. In addition, in the same subjects, we examined the effects of the same levels of NO2 mixed with combustion by-products from a gas space heater. The subjects were nine adults, aged 19-65 yrs, and 11 children, aged 7-15 yrs, with diagnosed asthma which was severe enough to require daily medication. All subjects had demonstrable AHR to histamine. Exposures were for 1 h on five separate occasions, 1 week apart, to: 1) ambient air, drawn from outside the building; 2) 0.3 parts per million (ppm) NO2 in ambient air; 3) 0.6 ppm NO2 in ambient air; 4) ambient air+combustion by-products+NO2 to give a total of 0.3 ppm; and 5) ambient air+combustion by-products+NO2 to give a total of 0.6 ppm. Effects were measured as changes in lung function and symptoms during and 1 h after exposure, in AHR 1 h and 1 week after exposure, and in lung function and symptoms during the week following exposure. Exposure to NO2 either in ambient air or mixed with combustion by-products from a gas heater, had no significant effect on symptoms or lung function in adults or in children. There was a small, but statistically significant, increase in AHR after exposure to 0.6 ppm NO2 in ambient air. However, there was no effect of 0.6 ppm NO2 on AHR when the combustion by-products were included in the test atmosphere nor of 0.3 ppm NO2 under either exposure condition. We conclude that a 1 h exposure to 0.3 or 0.6 ppm NO2 has no clinically important effect on the airways of asthmatic adults or children, but that 0.6 ppm may cause a slight increase in airway hyperresponsiveness.