Mikrowellen‐Plasmabrenner bei Atmosphärendruck

Microwave Plasma Torch at Atmospheric Pressure The development of the microwave plasma torch shows that a combination of two resonators is targeting for a reliable ignition under atmospheric pressure and stable continuous operation at high power conditions. An adapted gas management with jacket flow and good mixing can be produced by the coaxial design. The spectroscopic investigation of the torch gives information about the spatial temperature distribution in the plasma. The distribution of the OH‐rotation‐vibration band is observed in the line of sight with a high spectroscopic resolution. In an air plasma a constant core gas temperature of 3600 K is determined. It is independent of the outside parameters, like microwave power or gas flow. Only the plasma volume adapts, in order to keep the energy content constant.     

Pliocene palaeoceanography of the Arctic Ocean and subarctic seas

The Pliocene is important in the geological evolution of the high northern latitudes. It marks the transition from restricted local- to extensive regional-scale glaciations on the circum-Arctic continents between 3.6 and 2.4Ma. Since the Arctic Ocean is an almost land-locked basin, tectonic activity and sea-level fluctuations controlled the geometry of ocean gateways and continental drainage systems, and exerted a major influence on the formation of continental ice sheets, the distribution of river run-off, and the circulation and water mass characteristics in the Arctic Ocean. The effect of a water mass exchange restricted to the Bering and Fram Straits on the oceanography is unknown, but modelling experiments suggest that this must have influenced the Atlantic meridional overturning circulation. Cold conditions associated with perennial sea-ice cover might have prevailed in the central Arctic Ocean throughout the Pliocene, whereas colder periods alternated with warmer seasonally ice-free periods in the marginal areas. The most pronounced oceanographic change occurred in the Mid-Pliocene when the circulation through the Bering Strait reversed and low-salinity waters increasingly flowed from the North Pacific into the Arctic Ocean. The excess freshwater supply might have facilitated sea-ice formation and contributed to a decrease in the Atlantic overturning circulation.     

Biofunctionalized poly(ethylene glycol)-<Emphasis Type="Italic">block</Emphasis>-poly(ε-caprolactone) nanofibers for tissue engineering

Electrospun fibers with contrasting cell adhesion properties provided non-woven substrates with enhanced in vitro acceptance and controllable cell interactions. Poly(ethylene glycol)-block-poly(ε-caprolactone) (PEG-b-PCL) block copolymers with varying segment lengths were synthesized in two steps and characterized by NMR and GPC. A cell adhesive peptide sequence, GRGDS, was covalently coupled to the PEG segment of the copolymer in an additional step. The suitability of polymers with molecular weights ranging from 10 to 30 kDa for electrospinning and the influences of molecular weight, solvent, and concentration on the resulting morphologies were investigated. Generally, electrospun fibers were obtained by electrospinning polymers with molecular weight larger than 25 kDa and concentrations of 10 wt%. Methanol/chloroform (25/75, v/v) mixtures proved to be good solvent systems for electrospinning the PEG-b-PCL and resulted in hydrophilic, non-woven fiber meshes (contact angle 30°). The mesh without cell adhesive GRGDS ligands showed no attachment of human dermal fibroblasts after 24 h cell culture demonstrating that the particular combination of the material and electrospinnig conditions yielded protein and cell repellent properties. The GRGDS immobilized mesh showed excellent cellular attachment with fibroblasts viable after 24 h with spread morphology. Electrospun nanofibers based on block copolymers have been produced which are capable of specifically targeting cell receptor binding and are a promising material for tissue engineering and controlling cell material interactions.     

Schubtragfähigkeit von Mauerwerk aus Wärmedämmziegeln

Der Beitrag berichtet über zentrische und exzentrische Schubversuche an Mauerwerk aus Wärmedämmziegeln. Die Ergebnisse werden mit den aktuell gültigen Bemessungsansätzen in DIN 1053‐1 verglichen. Es wird gezeigt, dass die Versuchsergebnisse immer eine ausreichende Sicherheit gegenüber den Bemessungswerten nach DIN 1053‐1 aufweisen. Auch für Mauerwerk aus Wärmedämmziegeln mit allgemeiner bauaufsichtlicher Zulassung können somit die vereinfachten Bemessungsregeln der DIN 4149 ohne Abminderungen angewendet werden. In plane shear resistance of thermal insulating vertically perforated clay brick masonry. In plane shear tests on thermal insulating vertically perforated clay brick masonry are presented. The results are compared with the design rules from DIN 1053‐1. The test results exceeded the design predictions of DIN 1053‐1 by a significant safety margin. The simplified design rules from the German earthquake standard DIN 4149 can be applied to thermal insulating clay unit masonry with technical approvals without any reduction.     

Development of a candidate reference method for the simultaneous quantitation of the boar taint compounds androstenone, 3α-androstenol, 3β-androstenol, skatole, and indole in pig fat by means of stable isotope dilution analysis-headspace solid-phase microextraction-gas chromatography/mass spectrometry

The steroidal pig pheromones androstenone (5α-androst-16-en-3-one), 3α-androstenol (5α-androst-16-en-3α-ol), and 3β-androstenol (5α-androst-16-en-3β-ol) as well as the heterocyclic aromatic amines skatole and indole, originating from microbial degradation of tryptophan in the intestine of pigs, are frequently recognized as the major compounds responsible for boar taint. A new procedure, applying stable isotope dilution analysis (SIDA) and headspace solid-phase microextraction-gas chromatography/mass spectrometry (HS-SPME-GC/MS) for the simultaneous quantitation of these boar taint compounds in pig fat was developed and validated. The deuterated compounds androstenone-d(3), 3β-androstenol-d(3), skatole-d(3), and indole-d(6) were synthesized and successfully employed as internal standards for SIDA. The new procedure is characterized by a fast, simple, and economic sample preparation: methanolic extraction of the melted fat followed by a freezing and an evaporation step allows for extraction and enrichment of all five analytes. Additional time-consuming cleanup steps were not necessary, as HS-SPME sampling overcomes fat-associated injector and column contamination. The method has been validated by determining intra- and interday precision and accuracy as well as the limit of detection (LOD) and limit of quantitation (LOQ). Additionally, a cross-validation for androstenone, skatole, and indole was carried out comparing the results of 25 back fat samples obtained simultaneously by the new SIDA-HS-SPME-GC/MS procedure with those obtained in separate GC/MS and high-performance liquid chromatography fluorescence detection (HPLC-FD) measurements. The cross-validation revealed comparable results and confirms the feasibility of the new SIDA-HS-SPME-GC/MS procedure.     

Influence of different ECM mimetic peptide sequences embedded in a nonfouling environment on the specific adhesion of human-skin keratinocytes and fibroblasts on deformable substrates

Mechanical stress is a decisive factor for the differentiation, proliferation, and general behavior of cells. However, the specific signaling of mechanotransduction is not fully understood. One basic problem is the clear distinction between the different extracellular matrix (ECM) constituents that participate in cellular adhesion and their corresponding signaling pathways. Here, a system is proposed that enables mechanical stimulation of human-skin-derived keratinocytes and human dermal fibroblasts that specifically interact with peptide sequences immobilized on a non-interacting but deformable substrate. The peptide sequences mimic fibronectin, laminin, and collagen type IV, three major components of the ECM. To achieve this, PDMS is activated using ammonia plasma and coated with star-shaped isocyanate-terminated poly(ethylene glycol)-based prepolymers, which results in a functional coating that prevents unspecific cell adhesion. Specific cell adhesion is achieved by functionalization of the layers with the peptide sequences in different combinations. Moreover, a method that enables the decoration of deformable substrates with cell-adhesion peptides in extremely defined nanostructures is presented. The distance and clustering of cell adhesion molecules below 100 nm has been demonstrated to be of utmost importance for cell adhesion. Thus we present a new toolbox that allows for the detailed analysis of the adhesion of human-skin-derived cells on structurally and biochemically decorated deformable substrates.     

Characterization of Steel Thixoforming Tool Materials by High Temperature Compression Tests

The experimental set‐up and the results of high temperature compression tests for the characterization of tool materials for steel thixoforming are presented. The scope of this test is to reproduce the load profile of steel thixoforming processes consisting of mechanical, thermal, tribological, and chemical components on the forming mould. Tool materials were chosen following a concept within the Collaborative Research Center ‐ SFB 289 ‐ “Forming of metals in the semi‐solid state and their properties”. Three materials groups are distinguished: thin film deposited by physical vapor deposition (PVD) and plasma assisted chemical vapour deposition (PACVD), thick coatings (thermal spraying), and bulk ceramic materials. Samples were characterized using scanning electron microscopy (SEM), electron‐dispersive spectroscopy (EDS) and X‐Ray diffraction analysis (XRD). The results show varying resistance of the tool materials concerning the load profile. In order to provide an appropriate tool solution for the thixoforming of steels, different load profiles within the forming moulds are identified and the corresponding tool part is made from that material with the best performance.     

SOI-based optical board technology

A SOI-based optical board technology is presented. Hybrid integration combines the strength of silicon and InP. The SOI board provides passive optical components and acts as the mounting platform. Adapted active III/V devices are integrated using Au/Sn solder technology and passive alignment. Precise mounting of lasers on the board is necessary to ensure low coupling losses.     

Properties of high-temperature PEFC Celtec-P 1000 MEAs in start/stop operation mode

This paper aims at the comparison of two differently operated Celtec^®-P 1000 MEAs: one MEA is operated in a start/stop cycling mode (12 h operation at 160 °C followed by 12 h shutdown), the other MEA is continuously operated at 160 °C. We demonstrate more than 6000 h total operation time with more than 240 start/stop cycles, while the test is still ongoing. The degradation rate is 0.2 mV cycle⁻¹ or 11 μV h⁻¹ on a time basis. The continuously operated MEA is operated more than 6000 h with a degradation rate of approximately 5 μV h⁻¹. Through separation of the individual cathodic loss terms, a detailed insight into the doubled time-based degradation rate under start/stop cycling conditions could be given. Both Ohmic resistances and oxygen reduction overpotentials are basically identical in MEAs under continuous and start/stop cycling operation. In the start/stop cycled MEA, however, significantly increased cathodic mass transport overpotentials are observed as a result of enhanced corrosion of the cathode catalyst support, which confirms the generally discussed reverse-current mechanism under start/stop cycling conditions. Results from a newly developed MEA demonstrate that this mechanism can successfully be mitigated through improvement of the materials used in the MEA.     

The promotional impacts of green power products on renewable energy sources: direct and indirect eco-effects

Green power products may be seen as a means of fostering renewable energy sources because they create and channel consumer demand for environmentally sound power generation. They can therefore be evaluated on a par with other support instruments regarding their effectiveness to connect new capacity to the grid. Apart from this direct effect however, green power products confer a much more active role for customers and utilities. Thus, learning processes, which foster eco-oriented decisions beyond the construction of new renewable generation capacity, may be induced.