Nanostructured Silicon Matrix for Materials Engineering

Tin-containing layers with different degrees of oxidation are uniformly distributed along the length of silicon nanowires formed by a top-down method by applying metalorganic chemical vapor deposition. The electronic and atomic structure of the obtained layers is investigated by applying nondestructive surface-sensitive X-ray absorption near edge spectroscopy using synchrotron radiation. The results demonstrated, for the first time, a distribution effect of the tin-containing phases in the nanostructured silicon matrix compared to the results obtained for planar structures at the same deposition temperatures. The amount and distribution of tin-containing phases can be effectively varied and controlled by adjusting the geometric parameters (pore diameter and length) of the initial matrix of nanostructured silicon. Due to the occurrence of intense interactions between precursor molecules and decomposition by-products in the nanocapillary, as a consequence of random thermal motion of molecules in the nanocapillary, which leads to additional kinetic energy and formation of reducing agents, resulting in effective reduction of tin-based compounds to a metallic tin state for molecules with the highest penetration depth in the nanostructured silicon matrix. This effect will enable clear control of the phase distributions of functional materials in 3D matrices for a wide range of applications.     

Influence of Heat Treatment Parameters on the Carbide Morphology of PM High-Speed Steel HS 6-5-3-8

The influence of heat treatment parameters on the carbide morphology of the powder metallurgic high-speed steel HS 6-5-3-8 is examined. To that end, diverse heat treatment parameters are selected and applied by quenching dilatometry. In particular, different austenitizing temperatures, as well as an isothermal holding stage during quenching in the temperature regime of the transformation gap at temperatures between 450 and 600 °C, are produced. Extensive computer-aided image analysis is performed to investigate the carbide morphology. It is found that the circularity of the tungsten-rich M₆C carbides increases significantly after short holding times at a temperature of 550 °C due to the carbide precipitation from metastable and supersaturated austenite onto pre-existing carbides. Longer holding times lead to further growth of the carbides, while the circularity of the carbides does not change. It is further shown that the hardness of the isothermally treated material is increased, all other parameters being equal. Increased carbide circularity might be helpful for increasing the toughness while reaching the same hardness and wear resistance as the conventional heat-treated material. Moreover, it might be possible to enhance the austenitizing temperature with regain of positive carbide morphology properties during the isothermal holding stage. Thus, improved material properties could be achieved.     

Feinstaubemissionen trockenlaufender Friktionssysteme in Fahrzeugen

Forschung im Ingenieurwesen - Nicht nur der Verbrennungsmotor eines Fahrzeuges emittiert Feinstaub, auch durch das Bremsen und Abrollen des Reifens entstehen solche gesundheitsschädlichen...     

Biodegradable Cationic and Ionizable Cationic Lipids: A Roadmap for Safer Pharmaceutical Excipients

Cationic and ionizable cationic lipids are broadly applied as auxiliary agents, but their use is associated with adverse effects. If these excipients are rapidly degraded to endogenously occurring metabolites such as amino acids and fatty acids, their toxic potential can be minimized. So far, synthesized and evaluated biodegradable cationic and ionizable cationic lipids already showed promising results in terms of functionality and safety. Within this review, an overview about the different types of such biodegradable lipids, the available building blocks, their synthesis and cleavage by endogenous enzymes is provided. Moreover, the relationship between the structure of the lipids and their toxicity is described. Their application in drug delivery systems is critically discussed and placed in context with the lead compounds used in mRNA vaccines. Moreover, their use as preservatives is reviewed, guidance for their design is provided, and an outlook on future developments is given.     

Lipase-mediated plant oil hydrolysis—Toward a quantitative glycerol recovery for the synthesis of pure allyl alcohol and acrylonitrile

Plant based triacylglycerides are a sustainable feedstock for the chemical, bioenergy, food and cosmetic sector. While fatty acids conversion has been intensively studied, processes for glycerol valorization have been scarce. In contrast to chemical hydrolysis of plant triacylglycerides enzymatic hydrolysis methods provide a cleaner glycerol stream. This study focuses on the selection of a commercial lipase capable of quantitative hydrolysis of rapeseed- and high oleic sunflower oils. Enzymatic process using only water as the reaction medium allows simplified recovery of pure glycerol. Among the six commercial lipase preparations tested, Candida rugosa lipase was identified as the most effective biocatalyst. Catalytic behavior in buffer and pure water was equivalent. Glycerol generated using a washed lipase was recovered by just three purification steps. The FTIR spectrum of the recovered glycerol was equivalent to pure glycerol standard. Over the entire recovery process, 82%–88% of the theoretical glycerol yield could be obtained. Purified glycerol was further didehydroxylated to allyl alcohol by a formic acid mediated open distillation process. The enriched allyl alcohol had a quality, which allows to use it for the synthesis of bio-based acrylonitrile.     

Numerische Untersuchung des Abkühlverhaltens von eingetafelten Schokoladenprodukten

In addition to taste and melting behavior, the gloss is an important quality criterion of chocolate products. Differences considering the gloss on products can be attributed to different causes in the production process. The chocolate that has been pre-crystallized by shearing and supercooling is further cooled, crystallized and transported as a solid chocolate out of the cooling process. The cooling of the chocolate is largely unexplored in a paternoster refrigerator and therefore the resulting streaming profile and temperature profile are numerically studied in this work.     

DNA-Methyltransferasen und AdoMet-Analoga als Werkzeuge für die Molekularbiologie und Biotechnologie

For a long time, DNA methyltransferases were of particular interest for basic molecular biology research since they regulate important processes in both prokaryotes and eukaryotes. Since the development of synthetic analogs of the cofactor S-adenosyl-L-methionine, it has been possible to transfer not only methyl groups but also numerous functional groups to DNA in a sequence-specific manner. Due to their structure, some DNA methyltransferases exhibit remarkable promiscuity with respect to the cofactor, so that DNA labeling can succeed with good efficiency. In this review article, we summarize the important developments in this field and discuss interesting current and potential applications in molecular biology and biotechnology.