Characterization of metal hydrides by in-situ XRD

In-situ synchrotron radiation powder X-ray diffraction (SR-PXD) technique is a powerful tool to gain a deeper understanding of reaction mechanisms in crystalline materials. In this paper, the implementation of a new in-situ SR-PXD cell for solid–gas reactions is described in detail. The cell allows performing measurements in a range of pressure which goes from light vacuum (10⁻² bar) up to 200 bar and temperatures from room temperature up to 550 °C. The high precision, with which pressure and temperature are measured, enables to estimate the thermodynamic properties of the observed changes in the crystal structure and phase transformations.     

Dioxins, dioxin-like PCBs and non-dioxin-like PCBs in dairy products on the German market and the temporal tendency in Schleswig-Holstein

Levels of polychlorinated dibenzodioxins and dibenzofurans, dioxin-like polychlorinated biphenyls (PCBs) and non-dioxin-like PCBs were measured in 140 dairy products collected in 2006 from different regions of Germany. The samples (a total of 66 cheese, 23 butter and 51 curd products) were taken from super markets and retail stores on the basis of production volumes in different states of the Federal Republic of Germany. The dioxin and total WHO-TEQ concentrations of all 140 samples were clearly below the EU limits of 3?pg WHO-polychlorinated dibenzo-p-dioxin (PCDD)/F-TEQ/g fat and 6?pg WHO-PCDD/F-PCB-TEQ/g fat, as laid down in the EU regulation No 199/2006. Dioxin concentrations ranged from low 0.07 to 0.53?pg WHO-PCDD/F-TEQ/g fat with a mean value of 0.19?pg WHO-PCDD/F-TEQ/g fat. The WHO-TEQ concentrations (PCDD/F?+?dl-PCBs TEQ) ranged from 0.21 and 2.1?pg WHO-TEQ/g fat with an average value of 0.76?pg WHO-TEQ/g fat. Significant differences of the WHO-TEQ contamination levels at regional level and between the different product groups could not be identified. The temporal tendency of dioxin concentrations in butter and cheese from Schleswig-Holstein was studied over the past 13?years that showed a decrease by more than 50?% from 0.43 to 0.19?pg WHO-PCDD/F-TEQ/g fat.     

Adsorptionshysterese von Phosphorsäure in Polybenzimidazol‐Hochtemperatur‐Polymerelektrolytmembran‐Brennstoffzellen

During thermal cycling investigations on polybenzimidazole high temperature polymer electrolyte membrane fuel cells a stationary hysteresis behavior of the cell current was observed. With the Tafel equation a correlation to the surface oxygen concentration on the platinum is given. Because no such hysteresis of oxygen adsorption on platinum is known a new theory is proposed. This theory is based on the thermal dependence of the surface coverage of phosphoric acid on platinum. The resulting adsorption hysteresis is confirmed as being the reason for the observed cell current hysteresis by the results of a Monte Carlo simulation. This is validated through a qualitative comparison with measured data from aged test cells.     

Ungewöhnliche Adsorptions‐ und Trenneigenschaften des Molekularsiebs ZIF‐8

Low‐temperature rectification represents the state‐of the‐art in olefin/paraffin separation. Adsorption on microporous coordination polymers could be a less energy and cost‐intensive alternative. Especially zeolitic imidazolate frameworks, such as ZIF‐8, exhibits an interesting adsorption behavior since alkanes are preferentially adsorbed in comparison with the corresponding olefins. The single‐component adsorption isotherms and mixed gas breakthrough experiments of C₂ to C₄ hydrocarbons show the potential of ZIF‐8 for olefin/paraffin separation.     

Renewable energy and employment in Germany

The positive impacts of an increasing share of renewable energy on the mitigation of climate change as well as on the decrease of the dependency of energy imports are indisputable. However, one persistent problem for the German economy has been its high level of unemployment in the recent past. Therefore, any policy strategy will be measured also by its net impact on the labor market. The paper describes the results of a study that models this impact and is novel within three respects: firstly, an Input–Output-Vector for the renewable energy sector was developed based on the results of more than 1000 interviews with an extensive questionnaire, secondly gross and net effect of two different policy scenarios for Germany until 2030 were calculated and thirdly the approach varies from earlier studies by its explicit modeling of export and foreign trade effects.     

Crosslinking poly(allylamine) fibers electrospun from basic and acidic solutions

Mechanically robust, non-toxic polymer fiber mats are promising materials for a range of biomedical applications; however, further research into enhancing polymer selection is needed. In this study, poly(allylamine) (PAH), an amine-containing polyelectrolyte, was successfully electrospun from aqueous solutions into continuous, cylindrical fibers with a mean diameter of 150 ± 41 nm. A one-step crosslinking method using glutaraldehyde provides insight into the chemical and morphological changes that result from altering the molar ratio of amine to aldehyde groups, whereas a two-step crosslinking method yielded chemically and mechanically robust mats. These results indicate PAH fibrous mats synthesized from aqueous solutions could potentially be applied in biomedical applications.