High mobility GaAs-AlxGa1?xAs single period modulation-doped heterojunctions

Single period modulation-doped structures composed of an AlxGa1?xAs layer, part of which is doped with Si, on top of an undoped GaAs layer have been grown by molecular beam epitaxy. The films were characterised using Hall effect measurements carried out at temperatures between 10 and 300 K. With 50?75 ? thick undoped (Al, Ga)As layers near the interface, mobilities in excess of 115000 cm2/Vs at 10 K and 7450 cm2/Vs at 300 K have been achieved for an average doping concentration of ?5×1016 cm?3. These are some of the highest mobilities as yet obtained from modulation-doped structures, and represent an increase in mobility over equivalently doped GaAs by about a factor of 20 at 10 K and by a factor of 2 at 300 K.     

Regulation of protein tyrosine phosphatase 1C: opposing effects of the two src homology 2 domains

The regulatory roles of the two src homology 2 (SH2) domainsof protein tyrosine phosphatase 1C were investigated by comparingrecombinant full-length PTP1C with mutants in which either theN-terminal SH2 (N-SH2) domain (PTP1CANSH2), the C-terminal SH2(C-SH2) domain (PTP1CACSH2) or both SH2 domains were deleted(PTP1CANSH2ACSH2). This revealed that the SH2 domains have opposingand independent effects on activity: strong inhibition by N-SH2(42-fold) and weak activation by C-SH2 (2.1-fold). C-SH2 causedactivation across a wide pH range while N-SH2 inhibited mostat neutral and high pH through a shift of the basic limb ofthe pH profile of kmt/Km, apparently via perturbation of anactive-site pKa value. A phosphotyrosyl peptide derived fromthe erythro-poietin receptor caused an {small tilde}30-foldactivation of PTP1C and PTP1CACSH2 but had no effect on PTP1CANSH2or PTP1CANSH2ACSH2, indicating that binding of this peptideto N-SH2 abolished its inhibition. Since C-SH2 separates N-SH2from the catalytic domain in full-length PTP1C and activationis observed for PTP1CACSH2, it appears that the inhibitory effectof N-SH2 is independent of the position in the sequence andthat intermolecular interactions may also be possible     

Verfahrenstechnik der aeroben Abwasserreinigung. Entwicklungen und Trends

Chemical engineering of aerobic waste water treatment – developments and trends . The present article deals with chemical engineering problems encountered in biological waste water treatment, as seen in research reports published during the last 5 to 10 years. It is seen that important advances in our biological and engineering knowledge of the biological degradation of organic wastes, relating to residence time distribution, concentration of biomass, and the temperature in the activation process have not been given sufficiently consistent attention in practice. Controversial views and possible solutions are indicated. Immobilization (especially with activated charcoal as carrier) offers certain advantages for raising the concentration of biomass in the activation space, this also facilitating separation of the biomass from the purified water. Flotation could offer an alternative. Disposal of the excess activated sludge is nowadays accomplished largely by anaerobic fermentation (bioconversion); the engineering of this step was developed in the 1930's and should be updated at the earliest possible opportunity. This would enhance the appeal of the process because the energetic potential of the biomass could then be fully utilized.     

Auslegung und Dimensionierung eines mechanischen Schaumzerstörers

Design and dimensions of a mechanical defoamer. This paper presents a newly developed powerful mechanical defoamer which exploits centrifugal force and, thanks to circular channels, also Coriolis force for destruction of foam. It is incorporated into containers such that the expelled foam concentrate is deflected by the lid without producing fresh foam. Model experiments with three geometrically similar but different sized laboratory models led to dimensionaltheoretically formulated process-relations of the defoamer for various material systems (five chemical foamers, two biological substrates). Such process-relations represent a reliable basis for design and dimensions of the defoamer presented, on the one hand, and permit determination of an ?intermediate characteristic”?, having the dimensions of acceleration, which represents the mechanical degradability of the foam.     

Hidden logistic potentials of working systems

Nowadays, the companies operate in a turbulent environment caused by various effects of global market, quick expansion of new products and production processes, fastidious customers and increased competition.In these circumstances only those companies are successful which can respond to market changes as fast as possible—i.e. they have the shortest response time regarding fulfilment of customer requirements (short delivery time and reliable delivery in addition to price and quality).Consequently, a reduction of mean inventory, range and lead time of working systems in the company is an ever increasing strategy that ensures an increase of growth and profit of the company.The article shows how the tools for modelling the flow of orders through working systems can be used in order to discover the hidden logistic potentials of working systems in a company.Presented are the results of finding hidden logistic potentials of working systems in the tool-production department of "ETI d.d." company from Izlake, Slovenia.     

Modellübertragung in der Verfahrenstechnik

Model scale-up in chemical engineering . Similarity theory and the theory of models based thereon are working tools which permit reasonable planning of experiments, their execution with a minimum of effort, and their evaluation in such a way as to provide reliable information about the design and the operating conditions of the technical plant – provided these methods are used in good time and in the proper manner. A brief introduction to the problems involved and to the methodology of similarity theory is provided by the introductory section and the first example. Four more problems and their solutions according to similarity theory serve to answer questions concerning the size of the experimental scale, the choice of material system used in the experiment, and the problem of scale-up under conditions of partial similarity. Two of these examples clearly illustrate that an inadequate knowledge of the material parameters (e. g. for foams and slurries) necessitates model measurements on the technical system with a change of scale.     

Films from oat spelt arabinoxylan plasticized with glycerol and sorbitol

The development of packaging films based on renewable materials is an important and active area of research today. This is the first extensive study focusing on film‐forming properties of an agrobiomass byproduct, namely, oat spelt arabinoxylan. A plasticizer was needed for cohesive film formation, and glycerol and sorbitol were compared. The tensile properties of the films varied with the type and amount of the polyol. With a 10% (w/w) plasticizer content, the films containing glycerol had higher tensile strength than the films containing sorbitol, but with a 40% plasticizer content, the result was the opposite. Sorbitol‐plasticized films retained their tensile properties better than films with glycerol during 5 months of storage. The films were semicrystalline with similar crystallinity indices of 0.20–0.26. The largest crystallites (9.5 nm) were observed in the film with 40% glycerol. The softening of films with 40% (w/w) glycerol started at a significantly lower relative humidity (RH) than that of the corresponding sorbitol‐containing films. The films with sorbitol also had lower water vapor permeability (WVP) than the films with glycerol. The films plasticized with 10% (w/w) sorbitol had a WVP value of 1.1 g mm/(m²·d·kPa) at the RH gradient of 0/54%. The oxygen permeability of films containing 10% (w/w) glycerol or sorbitol was similar: 3 cm³·μm/(m²·d·kPa) at 50–75% RH. A higher plasticizer content resulted in more permeable films. Permeation of sunflower oil through the films was not detected. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009