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This paper describes the evaluation of different refractory compounds – SiO2, ZrO2 and Y2O3 –as face coats of investment casting shells for c-TiAl. The effect of the different refractories on the metal–mould interaction is studied in different aspects. Experimental results include characterisation of the constituents present at the metal/ mould interface, the segregation profiles of residual elements, namely oxygen, from the interface to the inner part of the samples, the extension and microhardness of the samples external hard case and the samples surface finishing.

In this study, it will be investigated the diffusion of critical elements, namely, carbon (C) and iron (Fe), into a steel substrate (Impax Supreme) during the diamond chemical vapour deposition (CVD) process. The substrate temperature was varied from 700 to 850oC by plasma power manipulations to enable the correlation of substrate temperature with diffusion length and depth of the above mentioned critical elements into steel during film growth conditions. Methane concentration is also a parameter which has been considered during the parametric analysis. The crystalline compounds formed during the diamond growth process are studied using XRD analysis. In addition, SIMS technique is used with depth profiling to monitor the diffusion of elements during the process. The results obtained enabled to improve traditional understanding about the mechanisms relating to diamond deposition on steel substrates using CVD processes.

Denitrification, or dissimilative nitrate reduction, is an anaerobic process used by some bacteria for energy generation. This process is important in many aspects, but its environmental implications have been given particular relevance. Nitrate accumulation and release of nitrous oxide in the atmosphere due to excess use of fertilizers in agriculture are examples of two environmental problems where denitrification plays a central role. The reduction of nitrate to nitrogen gas is accomplished by four different types of metalloenzymes in four simple steps: nitrate is reduced to nitrite, then to nitric oxide, followed by the reduction to nitrous oxide and by a final reduction to dinitrogen. In this manuscript we present a concise updated review of the bioinorganic aspects of denitrification. (c) 2006 Elsevier Inc. All rights reserved.

Induced defects in silver polycrystalline samples irradiated with 4 keV Ar+ were characterised with slow positron implantation spectroscopy. The implanted gas was found to interact with ion irradiation defects. The evolution of the defects and gas-defect interactions were followed through a multi-step isochronal annealing treatment. Two different defected regions were detected. A region near to the surface, due to a distribution of vacancy-like defects produced by irradiation, and a deeper one due to coalescence of Ar. The deeper defects evolve with thermal treatments and probably produce cavities which are not easily recovered.

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GaN films were deposited by cyclic pulsed laser deposition (cyclic-PLD) at different substrate temperatures between 400 and 600◦C. Alignment of the films along the c-axis, grain size, roughness and conductivity increased with temperature. Surface elemental ratio N/Ga was determined by X-ray photoelectron spectroscopy (XPS) and was smaller for films deposited at higher temperature. A decrease of the resistivity of the films agreed with higher metallic (Ga) surface concentration. Bulk elemental ratio N/Ga, determined by Rutherford backscattering spectroscopy (RBS), was higher than the XPS ratio and showed a very small tendency to decrease with deposition temperature. At 600 ◦C, there was evidence of contamination of the films by oxygen probably resulting from diffusion from the sapphire (Al2O3) substrate. These results suggest that adjustments in the deposition conditions are needed in order to have high crystal alignment, large grain size and good N/Ga ratio.

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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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During the last decades titanium alloys were found to be valuable engineering materials for many different applications. Formerly used in critical applications like aerospace, aeronautic and military equipment, where the factor cost is not relevant, titanium alloys are finding now new and different markets. However, the development of such new markets will depend on an effective cost reduction of titanium parts, in order to achieve a selling cost suitable with its application in consumer goods. A possible solution to decrease production costs might be the use of traditional casting techniques to produce near net shape functional parts. During the last years, the authors have developed extensive research work on this field, and a new technique both for melting and moulding, using ceramic multi-layered crucibles and investment casting shells was developed. This paper presents some of the results obtained during that research work: Ti-48Al alloy were melted and cooled inside CaO, MgO and Y O stabilized ZrO crucibles with inside layer of Y O . The chemical composition, hardness and microstructure at the metal-crucible interface, studied by secondary ion mass spectrometry, SEM/EDS and XRS are presented. On a second step, the same alloy was melted on the same crucibles, and poured into graphite moulds, and the crucibles wall was characterized by SEM/EDS and XRS.

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{Superoxide reductases are a class of non-haem iron enzymes which catalyse the monovalent reduction of the superoxide anion O2- into hydrogen peroxide and water. Treponema pallidum (Tp), the syphilis spirochete, expresses the gene for a superoxide reductase called neelaredoxin, having the iron protein rubredoxin as the putative electron donor necessary to complete the catalytic cycle. In this work, we present the first cloning, overexpression in Escherichia coli and purification of the Tp rubredoxin. Spectroscopic characterization of this 6 kDa protein allowed us to calculate the molar absorption coefficient of the 490 nm feature of ferric iron