Interactions and Chemical Transformations of Coronene Inside and Outside Carbon Nanotubes

By exposing flat and curved carbon surfaces to coronene, a variety of van der Waals hybrid heterostructures are prepared, including coronene encapsulated in carbon nanotubes, and coronene and dicoronylene adsorbed on nanotubes or graphite via π–π interactions. The structure of the final product is determined by the temperature of the experiment and the curvature of the carbon surface. While at temperatures below and close to the sublimation point of coronene, nanotubes with suitable diameters are filled with single coronene molecules, at higher temperatures additional dimerization and oligomerization of coronene occurs on the surface of carbon nanotubes. The fact that dicoronylene and possible higher oligomers are formed at lower temperatures than expected for vapor‐phase polymerization indicates the active role of the carbon surface used primarily as template. Removal of adsorbed species from the nanotube surface is of utmost importance for reliable characterization of encapsulated molecules: it is demonstrated that the green fluorescence attributed previously to encapsulated coronene is instead caused by dicoronylene adsorbed on the surface which can be solubilized and removed using surfactants. After removing most of the adsorbed layer, a combination of Raman spectroscopy and transmission electron microscopy was employed to follow the transformation dynamics of coronene molecules inside nanotubes.     

The role of the concept of "history of safe use" in the safety assessment of novel foods and novel food ingredients. Opinion of the Senate Commission on Food Safety (SKLM) of the German Research Foundation (DFG)

The Council of the European Union has proposed a revision on the EU regulation on novel foods and novel food ingredients concerning safety assessment of traditional foods from non-EU countries and their introduction onto the EU market. The proposal stipulates that such foods may be placed on the EU market if their history of safe use in the country of origin is appropriately documented. The present statement of the SKLM gives an overview on current discussions on practical implementation of the "history of safe use" concept as well as examples of its application. The SKLM, in principle, agrees with these concepts, underscores, however, in connection with convincing evidence for a "history of safe use" the need for a range of additional information to achieve a comprehensive risk assessment. In the opinion of the SKLM such information must comprise compositional data as well as experience on adverse effects. A list of questions considered essential is presented. The following opinion was adopted on December 23rd 2010.     

Optimized battery-management system to improve storage lifetime in renewable energy systems

Lead-acid batteries are the main technology used in renewable energy systems (RESs) and autonomous power-supply systems due to their maturity and low cost, factors that will remain valid for the next few years. It is often stated, however, that batteries in RES applications exhibit shorter lifetimes than those expected by manufacturers’ data or those experienced in real traditional applications. Overall, in relation to all other components in RESs, the battery lifetime is quite short and has an intensive impact on the costs of the total system.     

Carbohydrate, peptide and lipid metabolism of lactic acid bacteria in sourdough

The metabolic pathways of lactic acid bacteria that influence bread quality are coupled to the central carbon flux by the availability of cofactors influencing the cellular and environmental redox potential. Homo- and heterofermentative metabolism differ fundamentally with respect to the requirement for regeneration of reduced cofactors, NADH or NADPH. The utilization of co-substrates such as oxygen or fructose as electron acceptors by obligate heterofermentative lactobacilli is coupled to an increased production of acetate in dough. Recently, several oxidoreductases involved in cofactor regeneration were characterized and glutathione and short-chain aldehydes derived from lipid oxidation were identified as substrates for cofactor regeneration by Lactobacillus sanfranciscensis. Based on the different metabolic requirements for cofactor regeneration, homo- and heterofermentative lactobacilli exert divergent effects on redox-reactions in sourdough that influence bread quality beyond the formation of acetate. Proteolysis, followed by peptide or amino acid metabolism by LAB is one of the key routes of flavour formation in bread flavour, and enables the strain-specific formation of antifungal metabolites. Peptide metabolism as well as the metabolism of cysteine, arginine, and phenylalanine in Lactobacillus plantarum, L. sanfranciscensis, and Lactobacillus pontis is increasingly understood and these insights provide new opportunities for the directed application of sourdough LAB for improved bread quality.     

Development and application of new nucleic acid-based technologies for microbial community analyses in foods

Several challenges still persist in the analysis of microorganisms in foods, particularly in studies of complex communities. Nucleic acid-based methods are promising tools in addressing new questions concerning microbial communities. We have developed several new methods in the field of nucleic acid-based microbial community analyses. These methods cover both sample preparation and detection approaches. The sample preparation method involves simplified DNA purification using paramagnetic beads. As an extension of this method, the same paramagnetic beads are used for both cell separation and DNA purification. This enables full automation. The separate detection of viable and dead bacteria is a major issue in nucleic acid-based diagnostics. We have applied a living/dead dye that binds covalently to DNA and inhibits the PCR from dead cells. In addition, a DNA array-based detection assay has been developed. The assay combines the specificity obtained by enzymatic labeling of DNA probes with the possibility of detecting several targets simultaneously by DNA array hybridization. In combination with 16S rDNA amplification, this is a promising tool for community analyses. Also, we have developed a novel approach for multiplex quantitative PCR. The multiplex PCR has been combined with our DNA array-based detection method. Finally, we are now in the process of adapting a system for monitoring microbial growth and death in real-time through the tagging of bacteria with green fluorescent protein (GFP) combined with fluorescence detection using a high-resolution confocal laser scanner.     

Induction of Gushing with Recombinant Class II Hydrophobin FcHyd5p from Fusarium culmorum and the Impact of Hop Compounds on its Gushing Potential

Malt‐induced gushing is a problem that has been known for many years. Mechanisms and inducing agents are still not fully understood and identified. Hydrophobins produced by various filamentous fungi are currently under discussion as biological gushing‐inducing compounds. In the current study the class II hydrophobin FcHyd5p, from the cereal pathogen Fusarium culmorum, was employed in beer and other carbonated beverages for gushing experiments and the influence of hop compounds on gushing potential was examined. It was demonstrated that this protein strongly induces gushing in various carbonated beverages, including beer. It was further demonstrated that the resulting gushing volume is susceptible to certain hop compounds and can be decreased significantly by the addition of these substances.     

Design criteria for liners of concrete vessels of future HTRs

The paper summarizes the work on design criteria for liners of Prestressed Concrete Reactor Vessels (PCRVs), which has been carried out by several German institutions from 1984 to 1988 within a future High Temperature Reactor (HTR) research project.The liner is discussed as part of the concept guaranteeing the integrity of the safe enclosure of the cooling medium. Its main function is leak-tightness during the whole lifetime of the power station. On the basis of the minor safety function of the composite liner compared to that of the prestressed concrete structure with its pressure bearing function and its integrity requirements the combined action and its effects between the liner and the concrete structure has been worked out. As it is shown the composite structure ‘steel liner + anchorage + concrete structure’ guarantees a high safety of the liner.The results deal with general and special requirements to the liner-anchor-system with regard to material, design details, analytical methods, fabrication and testing.     

Solid-state Reactions and Phase Relations in the Ti-Si-O System at 1373 K

Reactions between Ti and SiO₂ were studied at 1373 K (1100°C) under vacuum conditions using planar diffusion couples. A method to correct for the presence of surface oxide was developed which led to improved oxygen measurements with the electron probe microanalyzer. An isothermal section through the Ti-Si-O phase diagram at 1373 K was determined using measured diffusion paths and phase compositions in equilibrated alloys. The experimentally determined isothermal section was compared to isothermal sections calculated using thermodynamic data. In addition the sequence of reaction layers formed in the diffusion couples is discussed in terms of thermodynamic activity diagrams.