Sicher zündende,langzeitstabile Kaltkathode

Long term stable cold cathode with reliable ignition Cold cathodes gauges have been used in various areas of vacuum technology for decades. Their unique properties make them the method of choice even despite the residual magnetic field, poor ignition characteristics in the UHV‐region and long term stability. In other applications they do not significantly shorten the maintenance intervals. However, especially in the UHV or XHV region these properties lead to an extinguishing of cold cathode discharge. Considering the underlying processes and their correlation in this contribution an improved cold cathode will be presented. The measured data show a residual magnetic field of 1 mT in close vicinity to the gauge and an extended operating pressure range down to the 10^?12 mbar region. Furthermore the ignition characteristics were improved to < 60 s at 1×10^?9 mbar.     

Durability test and degradation behavior of a 2.5 kW SOFC stack with internal reforming of LNG

Forschungszentrum Jülich has demonstrated SOFC stacks and systems ranging from 50 W to 20 kW. Previous studies have shown the reproducible stable long-term performance of the F10-design short stacks developed in Forschungszentrum Jülich. Within this work, a 2.5 kW F20-stack consisting of eighteen cells was assembled, and tested at a furnace temperature of 700 °C mainly with the simulated reformate gas, which corresponds to 10% pre-reforming of liquefied natural gas (LNG). The current density and fuel utilization were mostly kept at 0.5 A cm⁻² and 70%, respectively. The purpose was to investigate the behavior of the stack in the kW-range for at least 5000 h with internal reforming of LNG or methane at a fuel utilization of at least 60%. A voltage degradation rate of around 0.3%/1000 h was obtained during the operation with pre-reformed LNG. The stack performance under normal working conditions and an unplanned redox cycle, as well as the results from post mortem analysis are discussed.     

Atomic layer deposition process with TiF4 as a precursor for depositing metal fluoride thin films

A novel atomic layer deposition process for the preparation of fluoride thin films in a temperature range of 225 degrees C-400 degrees C is introduced. The crystallinity, morphology, composition, thicknesses, refractive indices, and transmittance of the films are analyzed. Low impurity levels are obtained at 350 degrees C-400 degrees C with good stoichiometry. Refractive indices of 1.34-1.42 for MgF(2), 1.43 for CaF(2), and 1.57-1.61 for LaF(3) films are obtained.     

Activity-based probes for the study of proteases: recent advances and developments

Proteases are important targets for the treatment of human disease. Several protease inhibitors have failed in clinical trials due to a lack of in vivo specificity, indicating the need for studies of protease function and inhibition in complex, disease-related models. The tight post-translational regulation of protease activity complicates protease analysis by traditional proteomics methods. Activity-based protein profiling is a powerful technique that can resolve this issue. It uses small-molecule tools-activity-based probes-to label and analyze active enzymes in lysates, cells, and whole animals. Over the last twelve years, a wide variety of protease activity-based probes have been developed. These synthetic efforts have enabled techniques ranging from real-time in vivo imaging of protease activity to high-throughput screening of uncharacterized proteases. This Review introduces the general principles of activity-based protein profiling and describes the recent advancements in probe design and analysis techniques, which have increased the knowledge of protease biology and will aid future protease drug discovery.     

Potent odorants causing the warmed-over flavour in boiled beef

Summary The flavour compounds showing higher odour units resulting from peroxidation of unsaturated fatty acids were analysed comparatively in freshly boiled beef and in a stored (48 h, 4° C) sample exhibiting warmed-over flavour. The results obtained by aroma extract dilution analysis revealed that this flavour was mainly caused by hexanal, 1-octen-3-one, (E)- and (Z)-2-octenal, (Z)-2-nonenal, (E, E)-2,4-nonadienal andtrans-4,5-epoiiy-(E)-2-decenal.

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Intensive Geruchsstoffe des Warmed-over Flavour (WOF) von gekochtem Rindfleisch

Zusammenfassung Die Aromastoffe mit hohen Aromawerten, die aus der Peroxidation ungesättigter Fettsäuren hervorgehen, wurden in frisch gekochtem Rindfleisch und in einer gelagerten (48 h, 4 °C) Probe mit WOF analysiert. Ein Vergleich der Ergebnisse von Aromaextraktverdünnungsanalysen ergab, daß der WOF hauptsächlich durch Hexanal, 1-Octen-3-on, (E)- und (Z)2-Octenal, (Z)-2-Nonenal, (E, E)-2,4-Nonadienal sowietrans-4,5-Epoxy-(E)-2-decenal verursacht wird.

     

Transformations of carbon adsorbates on graphene substrates under extreme heat

We describe new phenomena of structural reorganization of carbon adsorbates as revealed by in situ atomic-resolution transmission electron microscopy (TEM) performed on specimens at extreme temperatures. In our investigations, a graphene sheet serves as both a quasi-transparent substrate for TEM and as an in situ heater. The melting of gold nanoislands deposited on the substrate surface is used to evaluate the local temperature profile. At annealing temperatures around 1000 K, we observe the transformation of physisorbed hydrocarbon adsorbates into amorphous carbon monolayers and the initiation of crystallization. At temperatures exceeding 2000 K the transformation terminates in the formation of a completely polycrystalline graphene state. The resulting layers are bounded by free edges primarily in the armchair configuration.     

Core‐Brominated Tetraazaperopyrenes as n‐Channel Semiconductors for Organic Complementary Circuits on Flexible Substrates

Organic thin‐film transistors (TFTs) are prepared by vacuum deposition and solution shearing of 2,9‐bis(perfluoroalkyl)‐substituted tetraazaperopyrenes (TAPPs) with bromine substituents at the aromatic core. The TAPP derivatives are synthesized by reacting known unsubstituted TAPPs with bromine in fuming sulphuric acid, and their electrochemical properties are studied in detail by cyclic voltammetry and modelled with density functional theory (DFT) methods. Lowest unoccupied molecular orbital (LUMO) energies and electron affinities indicate that the core‐brominated TAPPs should exhibit n‐channel semiconducting properties. Current‐voltage characteristics of the TFTs established electron mobilities of up to μ_n = 0.032 cm² V^?1 s^?1 for a derivative which was subsequently processed in the fabrication of a complementary ring oscillator on a flexible plastic substrate (PEN).     

Logic circuits based on individual semiconducting and metallic carbon-nanotube devices

Nanoscale transistors employing an individual semiconducting carbon nanotube as the channel hold great potential for logic circuits with large integration densities that can be manufactured on glass or plastic substrates. Carbon nanotubes are usually produced as a mixture of semiconducting and metallic nanotubes. Since only semiconducting nanotubes yield transistors, the metallic nanotubes are typically not utilized. However, integrated circuits often require not only transistors, but also resistive load devices. Here we show that many of the metallic carbon nanotubes that are deposited on the substrate along with the semiconducting nanotubes can be conveniently utilized as load resistors with favorable characteristics for the design of integrated circuits. We also demonstrate the fabrication of arrays of transistors and resistors, each based on an individual semiconducting or metallic carbon nanotube, and their integration on glass substrates into logic circuits with switching frequencies of up to 500 kHz using a custom-designed metal interconnect layer.