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A series of hydrogenated amorphous silicon carbide (a-Si 1- xC x:H) films were prepared by plasma-enhanced chemical vapour deposition (PECVD) using a gas mixture of silane, methane, and hydrogen as the reactive source. The previous results show that a high excitation frequency, together with a high hydrogen dilution ratio of the reactive gases, allow an easier incorporation of the carbon atoms into the silicon-rich a-Si 1-xC x:H film, widen the valence controllability. The data show that films with optical gaps ranging from about 1.9 to 3.6 eV could be produced. In this work the influence of the hydrogen dilution ratio of the reactive gases on the a-Si 1-xC x:H film properties was investigated. The microstuctural and photoelectronic properties of the silicon carbide films were characterized by Rutherford backscattering spectrometry (RBS), elastic recoil detection analysis (ERDA), and FT-IR spectrometry. The results show that a higher hydrogen dilution ratio enhances the incorporation of silicon atoms in the amorphous carbon matrix for carbon-rich a-Si 1-xC x:H films. One pin structure was prepared by using the a-Si 1-xC x:H film as the intrinsic layer. The light spectral response shows that this structure fits the requirement for the top junction of colour sensor. © 2004 Elsevier B.V. All rights reserved.

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An understanding of space charge build-up in the polymeric insulation of power cables is important in determining how aging occurs and progresses and, also in predicting cable lifetime. In this investigation electric-field induced space charge in peelings from XLPE (cross-linked polyethylene) cables was measured using two different methods: the pulsed electro-acoustic technique (PEA) and the combined procedure of isothermal and non-isothermal charging/discharging currents (FTSDC). These two methods allow the study of space charge in highly insulating materials. Also, since electric fields of different orders of magnitude are applied to the sample in the two methods, it is possible to analyze different characteristics of the space charge traps. Prior to the measurements the samples were subjected to conditioning to remove volatiles. Cable peelings from various brands aged under different conditions (including field aged and thermally aged samples) were studied as received from the manufacturers. Some of the samples have undergone further ageing in AC electric field (50Hz) for 1000h to see the influence of further ageing on space charge build-up. The results for the different types of samples are compared in an attempt to correlate different ageing parameters.

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The thermal decompositions of methyl azidoformate (N3COOMe), ethyl azidoformate (N3COOEt) and 2-azido-N,N-dimethylacetamide (N3CH2CONMe2) have been studied by matrix isolation infrared spectroscopy and real-time ultraviolet photoelectron spectroscopy. N2 appears as an initial pyrolysis product in all systems, and the principal interest lies in the fate of the accompanying organic fragment. For methyl azidoformate, four accompanying products were observed: HNCO, H2CO, CH2NH and CO2, and these are believed to arise as a result of two competing decomposition routes of a four-membered cyclic intermediate. Ethyl azidoformate pyrolysis yields four corresponding products: HNCO, MeCHO, MeCHNH and CO2, together with the five-membered-ring compound 2-oxazolidone. In contrast, the initial pyrolysis of 2-azido-N,N-dimethyl acetamide, yields the novel imine intermediate Me2NCOCHNH, which subsequently decomposes into dimethyl formamide (HCONMe2), CO, Me2NH and HCN. This intermediate was detected by matrix isolation IR spectroscopy, and its identity confirmed both by a molecular orbital calculation of its IR spectrum, and by the temperature dependence and distribution of products in the PES and IR studies. Mechanisms are proposed for the formation and decomposition of all the products observed in these three systems, based on the experimental evidence and the results of supporting molecular orbital calculations.

The thermal decompositions of methyl azidoformate (N3COOMe), ethyl azidoformate (N3COOEt) and 2-azido-N,N-dimethylacetamide (N3CH2CONMe2) have been studied by matrix isolation infrared spectroscopy and real-time ultraviolet photoelectron spectroscopy. N2 appears as an initial pyrolysis product in all systems, and the principal interest lies in the fate of the accompanying organic fragment. For methyl azidoformate, four accompanying products were observed: HNCO, H2CO, CH2NH and CO2, and these are believed to arise as a result of two competing decomposition routes of a four-membered cyclic intermediate. Ethyl azidoformate pyrolysis yields four corresponding products: HNCO, MeCHO, MeCHNH and CO2, together with the five-membered-ring compound 2-oxazolidone. In contrast, the initial pyrolysis of 2-azido-N,N-dimethyl acetamide, yields the novel imine intermediate Me2NCOCHNH, which subsequently decomposes into dimethyl formamide (HCONMe2), CO, Me2NH and HCN. This intermediate was detected by matrix isolation IR spectroscopy, and its identity confirmed both by a molecular orbital calculation of its IR spectrum, and by the temperature dependence and distribution of products in the PES and IR studies. Mechanisms are proposed for the formation and decomposition of all the products observed in these three systems, based on the experimental evidence and the results of supporting molecular orbital calculations.

Pseudoazurin binds at a single site on cytochrome c peroxidase from Paracoccus pantotrophus with a K-d of 16.4 muM at 25 degreesC, pH 6.0, in an endothermic reaction that is driven by a large entropy change. Sedimentation velocity experiments confirmed the presence of a single site, although results at higher pseudoazurin concentrations are complicated by the dimerization of the protein. Microcalorimetry, ultracentrifugation, and H-1 NMR spectroscopy studies in which cytochrome c550, pseudoazurin, and cytochrome c peroxidase were all present could be modeled using a competitive binding algorithm. Molecular docking simulation of the binding of pseudoazurin to the peroxidase in combination with the chemical shift perturbation pattern for pseudoazurin in the presence of the peroxidase revealed a group of solutions that were situated close to the electron-transferring heme with Cu-Fe distances of about 14 Angstrom. This is consistent with the results of H-1 NMR spectroscopy, which showed that pseudoazurin binds closely enough to the electron - transferring heme of the peroxidase to perturb its set of heme methyl resonances. We conclude that cytochrome c550 and pseudoazurin bind at the same site on the cytochrome c peroxidase and that the pair of electrons required to restore the enzyme to its active state after turnover are delivered one-by-one to the electron-transferring heme.

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The main aim of the Valomat project was the development of new materials for quarry back-filling and underground constructions, based on the reuse of bottom ashes from MSWI. Bottom ashes were collected in six incineration plants of Europe. Some of them were selected for the development of new materials.
One task of this project comprised the study of the long-term behavior of new materials, under simulated conditions of environmental exposure. Three different scenarios were studied. For each scenario, a pilot plant was constructed and the new materials were studied under laboratory conditions or natural weather. The long-term behavior of these materials was assessed through the characterization of chemical and ecotoxicological properties of the leachates.
The chemical contamination and the ecotoxicological levels of the leachates were relatively low, although different levels had been determined for the three different scenarios. The immersion in dechlorinated tap water (scenario S1) had shown the highest emission levels of chlorides, sulphates, DOC, and Al, especially for the materials B2/1 and B2/2. The lowest ecotoxicological and chemical levels were determined in the scenario in which the materials were buried in a sieved soil.

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