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Eingeladener Vortrag
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In this study, bulked adhesives were examined regarding changes in properties for their use in the restoration of stained-glass windows. Two epoxy adhesives commonly used in the restoration of flat glass, Araldite® 2020 and Hxtal NYL-1™, were investigated. The adhesives were mixed with various silica-based micro- and nano-particles as fillers. Different tests were carried out on the adhesives with and without fillers in order to characterise their chemical and mechanical properties. The tests included colorimetry, dynamic-mechanical methods of analysis and tests on bending strength. No property changes could be ascertained in the bulked adhesives that would be negative for the restoration of delicate flat glass.
The maximum magnetisation (saturation magnetisation) obtainable for iron oxide nanoparticles can be increased by doping the nanocrystals with non-magnetic elements such as zinc. Herein, we closely study how only slightly different synthesis approaches towards such doped nanoparticles strongly influence the resulting sub-nano/atomic structure. We compare two co-precipitation approaches, where we only vary the base (NaOH versus NH3), and a thermal decomposition route. These methods are the most commonly applied ones for synthesising doped iron oxide nanoparticles. The measurable magnetisation change upon zinc doping is about the same for all systems. However, the sub-nano structure, which we studied with Mössbauer and X-ray absorption near edge spectroscopy, differs tremendously. We found evidence that a much more complex picture has to be drawn regarding what happens upon Zn doping compared to what textbooks tell us about the mechanism. Our work demonstrates that it is crucial to study the obtained structures very precisely when “playing” with the atomic order in iron oxide nanocrystals.
In dem IGF-Vorhaben IGF-Nr. 17978 N (P 1011) wurden unter gezielter definierter Schrumpfbehinderung Schweißexperimente an hochfesten Feinkornbaustählen durchgeführt, um den Einfluss der Wärmeführung sowie den Einsatz modifizierter Sprühlichtbogenprozesse verbunden mit schmaleren Nahtfugen auf die lokalen Eigenspannungen und die Gesamteigenbeanspruchungen an geschweißten Bauteilen zu analysieren. Diese Kurzdarstellung fasst die wesentlichen Zusammenhänge zu schweißbedingten Beanspruchungen an hochfesten Schweißverbindungen sowie einige der erarbeiteten Erkenntnisse und erreichten Ziele des Forschungsprojektes zusammen.
Observations on the biology of the wasp Baryscapus tineivorus (Hymenoptera: Eulophidae), a parasitoid of tineid moths. Laboratory studies were undertaken to determine the effectiveness of Baryscapus tineivorus, a gregarious parasitoid wasp with high potential to biologically control Tineola bisselliella, the webbing clothes moth and general pest on textiles. It was found that the sex ratio of B. tineivorus is often heavily female-biased (~6 females to one male). Parthenogenetic reproduction occurrs when males develop from unfertilized eggs. Baryscapus tineivorus is oligophagous, parasitising at least another tineid moth, the casemaking clothes moth Tinea pellionella. I investigated how B. tineivorous finds and selects hosts of various larval ages for egg deposition using two different approaches: (1) an acceptance test, for which only one defined larval stage of T. bisselliella or T. pellionella was offered for egg laying; and (2) a choice test, for which different larval stages or different species were offered. In the acceptance tests, B. tineivorus offspring developed within four to seven weeks old webbing clothes moths larvae and within six to seven weeks old casemaking clothes moth larvae. Dual-choice experiments with both tineid host species revealed that B. tineivorus is more attracted to T. bisselliella than to T. pellionella. Because B. tineivorus was reared on T. bisselliella, parasitoid conditioning (learning) could explain the host preference.
Bacterial infections are a global threat to human health1. Especially nosocomial infections with multidrug-resistant Gram-negative bacteria challenge public health systems and endanger successful treatment of patients in many modern medicine applications as e.g. organ transplant. In the last three decades classical approaches failed to find novel chemical scaffolds suitable for the development of antibiotics that reach the market and caused the modern antibiotics crisis1.
Insect microbiomes produce potent antibiotics with low toxicity to eukaryotic cells to defend their hosts against entomopathogenic microorganisms2. In order to exploit insect microbiomes efficiently and to identify novel antibiotics producing bacteria, we implemented an ultra-high throughput Microfluidics/FACS (fluorescence-associated cell sorting) cultivation and screening pipeline. Here we present the technical aspects of our pipeline including downstream processing of identified producer strains and its suitability for antibiotics discovery.
Fundamental understanding of crack healing in glassy crystalline materials is very important for many applications, especially for sealing solid oxide fuel cells (SOFC) since cracks caused by sealing or thermal cycling still remain a substantial bottleneck in developing durable SOFC.
Previous studies on soda lime silicate glass [Sin14] showed that crack healing is driven by viscous flow and that healing progress is proportional to time t and inverse viscosity η. This finding would allow to present healing data of a given glass for different temperatures in a master curve healing progress versus t/η. Such master curves would be a helpful tool in understanding crack healing kinetics.
Against this background, crack healing in non-crystallizing sodium calcium silicate (NCS) and sodium borosilicate glasses (NBS) have been studied. Moreover, to evaluate the influence of micros structure in crystallized glass on crack healing process, glass matrix composites (GMC) where prepared out of NCS and zirconia as inert ceramic filler material mimicking a partially crystalline micro structure. Cracks were generated by Vickers indention and healed isothermally at different temperatures. Crack healing progress was monitored by optical and electron microscopy. Results show that the above mentioned proportionality actually applies for the studied glasses for which such a master curve could be obtained. In comparison to a non-crystallized glass, the effective viscosity of GMC is increased by rigid filler content. This effect substantially retards crack broadening during later healing stages, which often ends up in large pores. On the other hand, local viscous crack healing is still possible in larger glassy regions. This behavior seems to be very interesting for crack healing optimized sealants.