Ascorbate enhances iron uptake into intestinal cells through formation of a FeCl3–ascorbate complex

It has been well documented that ascorbate enhances iron uptake, with a proposed mechanism based on reduction to the more absorbable ferrous form. We have performed a study on the effects of ascorbate on ferric iron uptake in the human epithelial Caco-2 cell-line. Ascorbate increased uptake in a concentration-dependent manner with a significant difference between iron uptake and reduction. Uptake kinetics are characteristic of a non-essential activator and the formation of an Fe³⁺–ascorbate complex. This investigation provides evidence that ascorbate enhances the apical uptake of ferric iron into Caco-2 cells through the formation of a Fe³⁺–ascorbate complex.     

Ein Konzept zur Dauerfestigkeitssteigerung autofrettierter Bauteile unter Innendruck

A Design Concept for Autofretted Parts under Pulsating Internal Pressure Autofrettage improves the endurance limit of pressurisized parts. The endurance limit is determined by crack arrest. The design concept first estimates the mean endurance limit, i. e. at a failure probability of 50 percent. This first step is explained in detail by the aid of a cross bore and validated by experimental results of this typical design feature. In a second step the allowable pressure range is predicted for defined low failure probability, typical for series production parts.     

Erhöhung der Ermüdungsfestigkeit von geschweißten höherfesten Baustählen durch Anwendung von Nachbehandlungsverfahren

Enhancement of the fatigue strength of welded high strength steels by application of post‐weld treatment methods. According to the present state of the art welded high strength steels have the same fatigue strength as welded standard steels. For an effective application of high strength steels in constructions subjected to fatigue are therefore additional efforts necessary in order to improve the fatigue strength, for example by the application of post‐weld treatment methods. However up to the present it is not possible to apply the positive effects of these methods in the fatigue design of steel structures. This paper shows first results of a research project, that examines the effectiveness of the post‐weld treatment method TIG‐dressing and the relatively new method “Ultrasonic Impact Treatment” (UIT) for the improvement of fatigue strength of welded high strength steels.     

Metabolomic profiling can differentiate between bactericidal effects of free and polymer bound halogen

The effects of two halogenated compounds (sodium hypochlorite and N‐halamine polymers) on the Escherichia coli metabolome were investigated. Changes in the intracellular metabolite pools of bacterial cells treated with different formulations of these compounds were analysed using FTIR (Fourier Transform Infra Red) spectroscopy and LC‐MS (Liquid Chromatography‐Mass Spectroscopy). Principal component analysis was used to generate metabolic profiles of the intracellular metabolites to investigate the effect of sublethal concentrations on the metabolome of treated cells. The effect of treatment with sodium hypochlorite was quantitatively dependent on the exposure time. The resulting metabolic profiles supported our previous hypothesis that the mode of action of some halogenated compounds, such as N‐halamine polymers, can be initiated by release of halogen ions into the aqueous environment, in addition to direct contact between the solid polymer material and the bacterial cells. Moreover, the metabolic profiles were able to differentiate between the effect of free and polymer‐bound halogen. Our metabolomic approach was used for hypothesis generation to distinguish apparently different bactericidal effects of free and polymer‐bound halogen. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Influence of the grid parameters during under voltage ride through (UVRT) testing

Under-voltage ride through (UVRT) tests can be carried out on system test benches, most of them are equipped with a converter based grid simulator. This paper describes the control of the artificial grid impedance at the 4 MW test bench at CWD. Validation measurements with the commercial wind turbine E‑115 E2 show that the virtual impedance specification is sufficient to perform UVRT tests with different grid parameters. Comparative measurements between the voltage divider based FRT Container and the grid simulator with deliberately different grid parameters show a different behavior of the research wind turbine FVA nacelle. Therefore, it is recommended to perform UVRT tests on the test bench with predefined grid parameters.

     

Determination of local characteristics for the application of the Weakest‐Link Model

The Weakest‐Link model is based on defects that are statistically distributed within the material with local stress. The failure at least at one defect causes the failure of the total structure. Based on this model, the so‐called statistic size effect can be evaluated in the case of cyclic loading and in the case of static loading the failure behaviour of ferritic steel within the brittle fracture range is highlighted. The application of the Weakest‐Link model requires the allocation of the local characteristics ‐ surface and / or volume ‐ to the discrete points of the stress. By using the method “SPIEL” which is independent from the FE code used, the allocation of couples of values ‐surface and stress and / or volume and stress ‐ by a suitable choice of unit load cases is possible. In consequence of the method “SPIEL” particularities are to be taken into consideration. In the present paper these particularities will be described exemplarily for the FE programs ABAQUS¹ and ANSYS².     

Local limit loads in components with competing failure locations

The plastic limit load is an important feature of the S‐N curve. The classical way of plastic limit load calculation using elastic‐ideal plastic material behaviour is restricted to one location of the component. Complex components normally have several fatigue critical locations, for all of them the local plastic limit loads has to be determined. By the classical way the plastic limit load can be evaluated only for one of them. A new method is presented. The local plastic notch factor K_p and the corresponding plastic limit loads are calculated applying Neuber's rule to FE calculations with plastic hardening material. The new method is validated on the basis of six different notched specimens. The need and capability is exemplarily shown on a specimen with two competing failure locations.     

A prediction method for endurance of carburized components based on fatigue of corresponding material states with different carbon contents

Carburizing generates different material properties and residual stresses in the carburized layer. A material mechanics based model for endurance prediction of carburized steel components has been developed, in which thin walled tubes are used under cyclic internal and monotonic external pressures allow the determination of the material properties of the carburized layers. An unexpected independence of endurance and mean stress sensitivity from carbon content and hardness has been found, contrary to existing scientific knowledge. Component like specimens were tested to validate the endurance prediction model. The deviations of the predictions from the experiment are in the range of ±8 percent.     

Variable amplitude fatigue of autofrettaged diesel injection parts

Experimental and analytical investigations of constant and variable amplitude fatigue life of not autofrettaged and autofrettaged components have been performed. In variable amplitude loading the new standardised CO mmon‐ RA il‐ L oad sequence CORAL has been used as well as two‐level‐tests with small cycles at high mean stresses interrupted by large cycles for the evaluation of load sequence effects. The results of the two level tests show that small cycles with amplitudes far below the fatigue limit cause fatigue damage. Life calculations have been performed according to the nominal stress approach with S‐N‐curves and improved Miner’s Rule, linear‐elastic fracture mechanics with 3D‐weight functions, elastic‐plastic fracture mechanics applying an extended strip yield‐model, and explicit 3D‐FE‐simulation of fatigue crack growth with predefined crack fronts. All approaches are appropriate for predicting realistic variable amplitude lives. From a practical point of view the explicit 3D‐FE‐simulation of fatigue crack growth is too time‐consuming. However, such simulations show that the approaches based on linear‐elastic fracture mechanics and elastic‐plastic fracture mechanics with extended strip yield‐model capture the essential physics of fatigue crack growth in a realistic way.     

Activated carbon cloth as anode for sulfate removal in a microbial fuel cell

By employing the sulfate-reducing bacterium Desulfovibrio desulfuricans we demonstrate the possibility of electricity generation in a microbialfuel cell (MFC) with concomitant sulfate removal. This approach is based on an in situ anodic oxidative depletion of sulfide produced by D. desulfuricans. Three different electrode materials, graphite foil (GF), carbon fiber veil (CFV), and high surface area activated carbon cloth (ACC), were evaluated for sulfide electrochemical oxidation. In comparison to CFV and GF electrodes, ACC was a superior materialfor sulfide adsorption and oxidation and showed significant potential for harvesting energy from sulfate-rich solutions in the form of electricity. Sulfate (3.03 g dm(-3)) was removed from a bacterial suspension, which represented 99% removal. A maximum power density of 0.51 mW cm(-2) (normalized to geometric electrode area) was obtained with a one-chamber, air-breathing cathode and continuous flow MFC operated in batch mode at 22 degrees C.