Influence of Irradiation Temperature on Grafting of Styrene into Poly(tetrafluoroethylene‐co‐hexafluoropropylene) Films

This study concerns with the investigation of the effect of irradiation conditions on grafting of styrene into FEP films by the pre‐irradiation method. EPR spectroscopy was used to characterize the base polymer material regarding the trapped radical species and their concentration. Radiation‐induced changes in the chemical structure were studied by IR spectroscopy. Tensile strength and elongation at break as well as yield of grafting were found to be strongly influenced by irradiation temperature. Main‐chain scissions were identified to be the reason for the deterioration of the mechanical properties after radiation treatment at temperatures below glass transition temperature.

     

Increased in vitro Anti-HIV Activity of Caffeinium-Functionalized Polyoxometalates

Polyoxometalates (POMs), molecular metal oxide anions, are inorganic clusters with promising antiviral activity. Herein we report increased anti-HIV-1 activity of a POM when electrostatically combined with organic counter-cations. To this end, Keggin-type cerium tungstate POMs have been combined with organic methyl-caffeinium (Caf) cations, and their cytotoxicity, antiviral activity and mode of action have been studied. The novel compound, Caf₄K[β₂-CeSiW₁₁O₃₉]×H₂O, exhibits sub-nanomolar antiviral activity and inhibits HIV-1 infectivity by acting on an early step of the viral infection cycle. This work demonstrates that combination of POM anions and organic bioactive cations can be a powerful new strategy to increase antiviral activity of these inorganic compounds.     

Manufacturing of Composite Coatings by Atmospheric Plasma Spraying Using Different Feed-Stock Materials as YSZ and MoSi<Subscript>2</Subscript>

Yttria-stabilized zirconia (YSZ) is the state-of-the-art material for the top coat of thermal barrier coatings. To increase the efficiency and lifetime of gas turbines, the integration of MoSi₂ as a healing material was proposed. A new method of manufacture was explored in order to enable the spraying of a homogeneous mixed layer of YSZ and MoSi₂. As the chemical and physical properties of these powders are very different, they require contrasting process conditions. Due to the evaporation of Si from MoSi₂ at spraying conditions suitable for YSZ, more moderate conditions and a shorter time of flight are required for depositing MoSi₂. At the same time, the spraying conditions still need to be sufficient for melting the YSZ particles in order to produce a coating. To obtain a homogeneous mixture, both conditions can be matched using an injection system that allows powder injection at two different locations of the plasma jet. Two-color pyrometry during flight (DPV-2000, Tecnar) was used to monitor the actual particle temperature. By optimizing the injection point for the MoSi₂, a mixed coating was obtained without decomposition of the MoSi₂, which has been analyzed by means of XRD and SEM.     

Monitoring and Improving the Reliability of Plasma Spray Processes

Monitoring and improving of process reliability are prevalent issues in thermal spray technology. They are intended to accomplish specific quality characteristics by controlling the process. For this, implicit approaches are in demand to rapidly conclude on relevant coating properties, i.e., they are not directly measured, but it is assumed that the monitored variables are in fact suggestive for them. Such monitoring can be performed in situ (during the running process) instead of measuring coating characteristics explicitly (directly) and ex situ (after the process). Implicit approaches can be based on extrinsic variables (set from outside) as well as on intrinsic parameters (internal, not directly adjustable) having specific advantages and disadvantages, each. In this work, the effects of atmospheric plasma spray process variables are systemized in process schemes. On this basis, different approaches to contribute to improved process reliability are described and assessed paying particular attention to in-flight particle diagnostics. Finally, a new test applying spray bead analysis is introduced and first results are presented.     

Untersuchungen zum Kegelstirnplanfräsen und Stirnplanfräsen am Institut für Werkzeugmaschinen der Universität Stuttgart

Slab milling with a conical shaped milling tool and slab milling with a face milling tool are wood machining techniques which meet the current requirements of wood machining and processing (e.g. changing batch sizes, flexible machines and equipment). That is why the Institute for Machine Tools at University of Stuttgart has already conducted comprehensive basic research in this field (Heisel 1997). Research on slab milling with a face milling tool was especially promoted as an alternative to slab milling with a peripheral milling tool (also known as planing) due to its low noise emission and low energy consumption. Amongst others, slab milling with a face milling tool as pre-milling procedure when calibrating wood-based panel products was examined under technical and economic aspects. The results showed higher service life and continuously better surfaces when choosing the right geometry of the cutting tools as compared to conventional slab milling with a peripheral milling tool. Notwithstanding the high costs, diamond cutting edges are more cost-effective than carbide insert tips due to their longer service life (Heisel 2004).     

Assignment of raw material and authentication of spirits by gas chromatography, hydrogen- and carbon-isotope ratio measurements I. Analytical methods and results of a study of commercial products

Gas chromatography and the determination of natural isotope ratios are powerful analytical methods which can be used to check the authenticity of alcoholic beverages and to detect any adulteration. To check the origin and the authenticity of commercial fruit spirits, whiskies, etc., 197 samples were analysed by gas chromatography, ²H-NMR and ¹³C isotope mass spectrometry. The discrimination between different varieties was demonstrated by bivariate and multivariate discriminant analysis using different concentrations of volatile compounds such as methanol, butan-1-ol, 2- and 3-methyl-butanol, benzaldehyde and hexanol as well as isotopic data like (D/H)_I, (D/H)_II and ¹³C/¹²C isotopomers of ethanol. The results show that by using multivariate discriminant analysis it is possible to distinguish not only between different groups of spirits, e.g. those made of stone-fruit, malaceous fruit, grain and corn, but also between individual varieties, such as cherry, plum, mirabelle and apple. If the detection of highly rectified ethyl alcohol of agricultural origin and the identification of its raw materials are required, then natural isotope ratios are the only discriminant analytical parameters available.     

Experimental validation of the linear drive train for a total artificial heart system

In industrialized countries cardiovascular diseases are the major cause of death. Beside heart transplants, which are a limited option due to the limited number of available human donor hearts, Total Artificial Hearts (TAHs) are the only therapy available for some patients with terminal heart diseases. For various reasons a total implantable artificial heart is desirable, but also sets restrictions in terms of weight and dimensions due to the limited space in the human thorax. Therefore a precise requirement profile is needed for the drive design to provide sufficient force for the blood pump and to avoid oversizing of the drive and to prevent blood damage by overheating.