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At least 469 records · Page 26Linked to original sources
PubMed1994

Enhanced filtration using flat membranes and standing vortex waves.

The performance of membrane filters is limited by concentration polarisation and membrane fouling. High shear rates reduce these effects but can damage delicate cells and proteins in biological fluids. Secondary flows to promote fluid mixing, and hence enhance filtration, can be highly effective, but usually carry the penalty of complexity. Oscillatory flow over furrowed or dimpled membrane surfaces (vortex mixing) has been shown to be very efficient in the microfiltration and oxygenation of blood, but carries the added complexity of oscillatory flow and the need to thermoform the membranes. To allow the use of asymmetric or rigid membranes, a new form of vortex mixing has been studied, in which the membranes are flat and form parallel channels. Feed flow is oscillatory and passes back-and-forth across ladder-like flow deflectors to generate standing vortex waves. Flow visualisation studies and numerical calculations of standing vortex waves (SVW) were undertaken to help optimise flow parameters and flow deflector geometry. Flat plate membrane ultrafilters were built and evaluated for different geometries of flow deflector, using solutions of bovine serum albumin (BSA) as the test fluid. Very high filtration rates were measured with BSA concentrations ranging from 1 to 24%. A SVW ultrafilter was compared with a Millipore Pellicon ultrafilter using BSA as the test fluid. Filtration flux was similar at low concentrations of BSA, but was greater by a factor of 4.5 in the SVW device at high concentrations of BSA.

Chemical Engineering↗
PubMed1994

Materials science.

Explore the source record for details and available documents.

Chemical Engineering↗
PubMed1998

Cellulose as a (bio)affinity carrier: properties, design and applications.

This contribution presents a framework for the rational design of affinity sorbents based on cellulose materials as a support. A three-level evaluation procedure, utilizing the knowledge of physical, chemical and engineering theories, is discussed, which integrates the design of support, affinity sorbent and chromatographic contactor. The principal support properties, such as morphological, diffusional, hydrodynamic, mechanical or ligand-binding properties, are presented and literature data on them are surveyed.

Affinity Labels↗
PubMed2004

A reevaluation of the literature regarding the health assessment of diesel engine exhaust.

While the International Agency for Research on Cancer (IARC) classified diesel exhaust (DE) as a"probable"carcinogen in 1989 based primarily on"sufficient"animal data, other investigators have since concluded that the lung tumors found in the rat studies were a result of particle overloading. Subsequent health risk assessments of DE have not used the rat cancer data. The U.S. Environmental Protection Agency (EPA), in developing its 2002 Health Assessment Document (HAD) for DE, primarily considered the epidemiology studies of railroad workers and truck drivers to develop health risk assessments of DE. However, both sets of epidemiology studies have serious weaknesses that make them unsuitable for cancer risk assessment. Major shortcomings were the lack of contemporaneous measurements of exposures to DE, difficulties with exposure history reconstruction, and adequately accounting for other exposures such as gasoline exhaust and cigarette smoke. To compound these problems, there was not, and there is still not, a specific exposure marker for DE. Interestingly, in the underground mining industry, where diesel exposures are much higher than observed in railroad workers and truck drivers, there was no increase in lung cancer. These problems and concerns led the U.S. EPA to conclude that while DE was a"likely"carcinogen, a unit risk value or range of risk cannot be calculated from existing data and that the risk could be zero. In addition, the DE emissions have changed and continue to change with the implementation of new emission control technologies. The HAD recognized this fact and noted that further studies are needed to assess new diesel engine emissions. Recent chemical characterization studies on low-emitting diesel engines with catalyzed particulate filters have shown emissions rates for several chemicals of concern that are even lower than comparable compressed natural gas (CNG)-fueled engines. With lower emissions, better fire safety, and improved cost-effectiveness of new low-emitting diesels compared to CNG, current efforts to restrict use of low-emitting diesels seems misguided.

Air Pollutants↗
PubMed2000

Quality control of automotive engine oils with mass-sensitive chemical sensors--QCMs and molecularly imprinted polymers.

Molecularly imprinted polyurethanes were used as sensor materials for monitoring the degradation of automotive engine oils. Imprinting with characteristic oils permits the analysis of these complex mixtures without accurately knowing their composition. Mass-sensitive quartz crystal microbalances (QCMs) coated with such layers exhibit mass effects in addition to frequency shifts caused by viscosity, which can be compensated by an uncoated quartz or a non-imprint layer. Incorporation of degradation products into the imprinted coatings is a bulk phenomenon, which is proven by variation of the sensor layer height. Therefore, the resulting sensor effects are determined by the degradation products in the oil.

Journal Article↗