Anwendung elektrischer Hochspannungsimpulse als Vorbehandlungsverfahren zur Beeinflussung der Trocknungscharakteristika und Rehydratationseigenschaften von Kartoffelwürfeln

High intensity electric field pulses as pretreatment for affecting dehydration characteristics and rehydration properties of potato cubes. High intensity electric field pulse (HELP) treatment was evaluated as pretreatment to possibly affect dehydration and rehydration characteristics of potato cubes (1 × 1 × 1 cm). Effects of electric field strength E = 0.35-3.0 kV · cm^?1 and number of pulses n = 1-70 on the degree of permeabilization of potato cells was evaluated using a centrifugal method. Optimization of E and n regarding maximum permeabilization of cells was performed. Energy requirements were found to be low (6.4-16.2 kJ · kg^?1) resulting in an increase in temperature in the treated product of _ΔT = 1.8-4.5°C. The HELP treatment enabled a maximum degree of permeabilization and resulted in a cell liquid release from potato cubes after centrifugation (700 × g) to up to 27-29% (untreated control 0%) as related to total water content. Treatment with optimum parameters (E = 0.9-2.0 kV · cm^?1, n = 15-30) resulted in improved mass transfer within the product and drying time during fluidized bed drying (T_tr = 55°C, 70°C, air velocity 2 m · s^?1) of potato cubes could be reduced to up to 20-25%. Rehydration properties and quality characteristics of the products after cooking were not affected by the high intensity electric field pulse pretreatment.     

A 5-Gb/s OEIC with voltage-up-converter

In this paper (based on our previous paper at ESSCIRC 2004, "A 2.4 GHz-Bandwidth OEIC with Voltage-Up-Converter," but new results for 4 Gb/s and 5 Gb/s have been added), an optoelectronic integrated circuit (OEIC) with an integrated voltage-up-converter (VUC) to enhance the frequency response of an integrated pin photodiode is presented. With the VUC a voltage of 11 V is generated on the chip without any additional external components. Thus, for a single-supply environment of 5 V the bandwidth of the OEIC is increased from 1.5 to 2.4 GHz. For data rates of 1, 3, 4, and 5 Gb/s at a bit error rate of 10/sup -9/, sensitivities of -29.3, -24.3, -22.9, and -20.5 dBm, respectively, were measured at a wavelength of 660 nm. For the implementation of the OEIC a modified 0.6-/spl mu/m silicon BiCMOS technology with f/sub T/=25 GHz is used.     

Neue Entwicklungen in der Flüssigmembranpermeation mit gestützten Membranen

In a time of rising raw material prices und raw material shortage topics like recycling of heavy metal ions from aqueous solutions get in the focus of the public. Aim of the presented work is the development of a new apparatus design for liquid membrane permeation with support layers. The investigations are carried out in view of heavy metal recycling.     

Nanofiltration of river water — fouling, cleaning and micropollutant rejection

Four nanofiltration and low pressure reverse osmosis membranes were investigated concerning their retention and fouling behavior during filtration of a surface water (River Alb) spiked with four polar micropollutants. Filtration and cleaning experiments were also conducted in deionized water spiked with the model contaminants in order to evaluate the influence of the water matrix on retention. Steric and electrostatic effects were found to be the most important factors influencing retention of the organic substances. In the presented experiments, fouling had little influence on retention. In case of the DI water experiments, treatment of the membranes with NaOH solution considerably lowered the retention of the investigated micropollutants, whereas in the experiments with river water the effect of alkaline treatment on the rejection of the trace organic substances decreased to an insignificant amount already 1 h after membrane cleaning.     

Probing enzyme promiscuity of SGNH hydrolases

Several hydrolases of the SGNH superfamily, including the lipase SrLip from Streptomyces rimosus (Q93MW7), the acyl-CoA thioesterase I TesA from Pseudomonas aeruginosa (Q9HZY8) and the two lipolytic enzymes EstA (from P. aeruginosa, O33407) and EstP (from Pseudomonas putida, Q88QS0), were examined for promiscuity. These enzymes were tested against four chemically different classes of a total of 34 substrates known to be hydrolysed by esterases, thioesterases, lipases, phospholipases, Tweenases and proteases. Furthermore, they were also analysed with respect to their amino acid sequences and structural homology, and their phylogenetic relationship was determined. The Pseudomonas esterases EstA and EstP each have an N-terminal domain with catalytic activity together with a C-terminal autotransporter domain, and so the hybrid enzymes EstA(N)-EstP(C) and EstP(N)-EstA(C) were constructed by swapping the corresponding N- and C-terminal domains, and their hydrolytic activities were compared. Interestingly, substrate specificity and kinetic measurements indicated a significant influence of the autotransporter domains on the catalytic activities of these enzymes in solution. TesA, EstA and EstP were shown to function as esterases with different affinities and catalytic efficacies towards p-nitrophenyl butyrate. Of all the enzymes tested, only SrLip revealed lipase, phospholipase, esterase, thioesterase and Tweenase activities.     

Korrosionsbeständigkeit eines nichtrostenden Chromstahls in karbonatisiertem Normal‐, Leicht‐ und Recyclingbeton

Um der Forderung nach Nachhaltigkeit nachzukommen, wird in den nächsten Jahren der Einsatz von Betonen mit rezyklierten Gesteinskörnungen (Beton‐ und Mischabbruch) zunehmen. Wegen den wärmedämmenden Eigenschaften wird auch der Bedarf an Betonen mit Leichtzuschlägen (z. B. Blähglas) steigen. Als wesentliches Element dieser Entwicklung werden für die Zementund Betonproduktion zunehmend Zemente mit reduziertem Portlandzementklinkergehalt sowie Zusatzstoffe wie Flugasche und Hüttensand verwendet. Damit nimmt der Karbonatisierungswiderstand der Betone tendenziell ab und das Risiko für Korrosionsschäden zu. Die nachfolgend vorgestellten Untersuchungen hatten zum Ziel, die Korrosionsbeständigkeit eines nichtrostenden Chromstahls (Top12, Zusammensetzung entspricht ungefähr dem Stahl mit der Werkstoffnummer 1.4003) in karbonatisiertem Beton mit unterschiedlicher Zusammensetzung zu evaluieren, mit normalem Betonstahl zu vergleichen und zu beurteilen. Die Ergebnisse lassen den Schluss zu, dass der Top12, im Gegensatz zum normalen Betonstahl, in allen untersuchten Betonen und damit auch in stark karbonatisierten Recyclingbetonen beständig ist. Corrosion Resistance of a Stainless Chromium‐Steel in Carbonated Ordinary, Light‐Weight and Recycling Concrete In order to achieve the goals for a sustainable development, concrete with recycled aggregates (concrete and mixtures from concrete and masonry, e.g. clay bricks and calcium silicate blocks etc.) is going to be used more and more in the future. Due to its thermal insulating properties, the demand for concrete with light‐weight aggregates (e.g. foam glass) will also increase. As an essential element of this development, an increasing amount of cements with a reduced clinker factor as well as of mineral additions such as fly ash and ground granulated blast furnace slag is used for concrete production. Therefore, as a general tendency, the carbonation resistance of concrete mixes decreases while the risk of corrosion damages increases. The goal of the investigations described in this paper was to evaluate and to assess the corrosion resistance of a stainless rebar (Top12, composition corresponds approx. to steel grade 1.4003) in various carbonated concrete mixes and to compare the results with common rebars. The results lead to the conclusion that, in contrast to common rebars, Top12 is durable in all investigated concrete mixes, including strongly carbonated recycling concretes.     

Electrical conductivity: a new tool for the determination of high hydrostatic pressure-induced starch gelatinisation

The degree of gelatinisation and electrical conductivity of wheat starch and tapioca starch suspensions (5% w/w) were determined after a pressure treatment of up to 530 MPa. With increasing pressure at a constant treatment time the degree of gelatinisation increased resulting in a gelatinisation curve similar to that of thermal gelatinisation. A pressure increase also caused an increase in electrical conductivity. A good linear relationship between the degree of gelatinisation and the electrical conductivity for both starches investigated was found. Since electrical conductivity correlates well with the degree of gelatinisation of starches after pressure treatment it is applicable for the quick and simple determination of pressure-induced starch gelatinisation.     

Functionalization of Scanning Force Microscopy Cantilevers via Galvanic Displacement Technique

A galvanic displacement technique is used to coat silicon scanning force microscopy cantilevers with copper. The copper coating is characterized using X-ray photoelectron spectroscopy, scanning force microscopy, contact angle measurements, scanning electron microscopy and energy-dispersive X-ray spectroscopy. This coating technique results in uniform, reflective and conformal films and hence, no stress-induced bending of the cantilever is observed. To demonstrate the effectiveness of this approach for tribological studies, the coated cantilevers are chemically modified with alkanethiol monolayers in order to functionalize the cantilevers. The effect of changed surface energy are detected with adhesion measurements in water and ethanol.