Hochselektive Stofftrennungen mit Carriermembranen — Stand der Entwicklung und Erwartungen

Membrane processes are able to separate liquid mixtures as well as mixtures of gases or vapours according to the sizes, solubilities, rates of diffusion or charges of the components. A separation is also possible using membranes in which the transport is coupled to a specific chemical reaction between the permeand and the membrane (facilitated or carrier mediated transport). This paper discusses aspects related to carrier‐mediated separation processes such as the transport mechanisms, the choice of appropriate carriers, the incorporation of carriers in the polymeric membrane material, the coating of porous support membranes with thin selective layers of the carrier‐polymer and, finally, the choice of appropriate parameters for the separation process. The separation of gas mixtures by carrier‐membranes appears very promising from a technical point of view. Experimental membrane samples often show excellent separation factors, but they have not met the permeability requirements for an economic use so far.     

Investigation of flow and material induced hemolysis with a Couette type high shear system

Damage of red blood cells (hemolysis) in miniaturized pump systems for heart support is induced by contact with artificial surfaces and high mechanical shear forces. In vitro experiments with porcine blood under well defined material and flow conditions with a new Couette model showed hemolysis not starting until shear stresses of 400 Pa and exposure times of 400 ms. Hemolysis in general was much lower than predicted in earlier investigations. Heparinized blood revealed a more sensitive behaviour as compared to citrated blood (CPDA‐1).     

Polarized FTIR photoacoustic spectroscopy on blends of thermoplastic poly(ether‐urethanes) with modified polypropylenes

Polarized Fourier transform infrared (FTIR) transmission and attenuated total reflection (ATR) spectroscopy are well‐known powerful tools to determine the orientation function of polymer materials. Both methods demand a special sample preparation. In our present studies, we used polarized FTIR photoacoustic spectroscopy (PAS) to determine the orientation function of real products from polymer processing without special preparation. We compare the results with those obtained with polarized FTIR transmission spectroscopy. It is demonstrated that polarized FTIR–PAS is useful to describe differences in the orientational behavior of hard and soft segments of thermoplastic poly(ether‐urethane) in different elongated blends with common polypropylene and polypropylene grafted with maleic anhydride. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 1194–1204, 2000     

Evidence of ionic components in vulcanization mixtures by means of electric current measurements: Investigations with natural rubber/sulfur/zinc bis(dimethyldithiocarbamate) and comparison mixtures

Continuous low‐level current (CLLC) measurements for detecting ionic species in the course of vulcanization reactions were applied to investigate the vulcanization of a mixture of natural rubber (NR), sulfur (S), and zinc bis(dimethyldithiocarbamate) (ZnDMTC). A dc voltage was applied to the reaction mixture in a special vulcanization mold and the current (e.g., in the range of 10⁻⁹ A) was measured. Temperature‐dependent current maxima were found after reaction times t_max. The simplest explanation is that transitory ionic species occur during vulcanization. An activation energy (E_a ) = 116.4 kJ/mol, similar to that obtained in previous chemical investigations, was determined from the decrease of t_max with increasing temperature. The maxima corresponded to reaction times where a strong increase of polymer crosslinking was observed, as measured using vulcametry. For comparison, dc measurements were carried out with the corresponding mixture without elemental sulfur (NR/ZnDMTC) and mixtures containing zinc stearate (ZnST) instead of zinc bis(dimethyldithiocarbamate) (NR/S/ZnST and NR/ZnST). © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 2206–2212, 2000     

Economic implications of Agro–Food biotechnology

Biotechnology has emerged as one of the key technologies of the 20th century but it has not had strong economic impacts in the Agro‐Food sector so far. Based on a Delphi survey in Germany, Greece, Italy, the Netherlands and Spain the implications of modern biotechnology on the food and non‐food markets as well as its employment effects are analysed in this paper. Using factor analysis the habituation of consumers to gene food, the emergence of specific biotechnology related market niches in the food and non‐food area, the regulation procedures and the price strategy could be empirically filtered out as main influential factors for future markets impacts of modern biotechnology. Only limited job growth is to be expected in the coming years in specialised biotech and food supplying companies, while traditional jobs in agriculture and the food industry will probably decrease in future partly due to the use of modern biotechnology. © 2000 Society of Chemical Industry     

Construction of robust class hierarchies

This article discusses the problem of constructing robust class libraries. Further design criteria include the flexibility of class libraries, the efficiency of the implementations, and their safe extensibility. We show that it is possible to design robust libraries to satisfy any two of the requirements at the same time. Although the solution may require an exponential growth in the number of classes compared to the original design, this apparent class explosion can be controlled by generating only the necessary additional classes automatically. As an application demonstrating both the theoretical problems and the power of our generator approach, the design of a library modelling data structures and algorithms for graphs is considered. Both the discussion and the results in this article generalize to other domains. Copyright © 2000 John Wiley & Sons, Ltd.