Environmental Assessment of Products over the Complete Life Cycle

Russian Engineering Research - The environmental impact of products is assessed over the complete life cycle. The proposed approach to impact assessment takes account of all the potential hazards...     

Identification of the Primary Factors Determining the Specificity of Human VKORC1 Recognition by Thioredoxin-Fold Proteins

Redox (reduction–oxidation) reactions control many important biological processes in all organisms, both prokaryotes and eukaryotes. This reaction is usually accomplished by canonical disulphide-based pathways involving a donor enzyme that reduces the oxidised cysteine residues of a target protein, resulting in the cleavage of its disulphide bonds. Focusing on human vitamin K epoxide reductase (hVKORC1) as a target and on four redoxins (protein disulphide isomerase (PDI), endoplasmic reticulum oxidoreductase (ERp18), thioredoxin-related transmembrane protein 1 (Tmx1) and thioredoxin-related transmembrane protein 4 (Tmx4)) as the most probable reducers of VKORC1, a comparative in-silico analysis that concentrates on the similarity and divergence of redoxins in their sequence, secondary and tertiary structure, dynamics, intraprotein interactions and composition of the surface exposed to the target is provided. Similarly, hVKORC1 is analysed in its native state, where two pairs of cysteine residues are covalently linked, forming two disulphide bridges, as a target for Trx-fold proteins. Such analysis is used to derive the putative recognition/binding sites on each isolated protein, and PDI is suggested as the most probable hVKORC1 partner. By probing the alternative orientation of PDI with respect to hVKORC1, the functionally related noncovalent complex formed by hVKORC1 and PDI was found, which is proposed to be a first precursor to probe thiol–disulphide exchange reactions between PDI and hVKORC1.     

Quantifying adherence of oxide scales on steels exposed to high temperature and pressure steam

Oxide scale exfoliation is a major concern in fossil fuel power generation because it can cause tube blockages and erode valves and steam turbine components downstream. There is still considerable scientific and commercial interest to improve the mechanistic understanding of oxide failures by developing models to predict exfoliation and the extent of tube blockage as a function of operating conditions and component geometries. Tensile testing inside a scanning electron microscope was conducted on ferritic–martensitic and austenitic steel specimens with the steam side (Fe,Cr)-rich oxides grown after exposures for up to 1000 h in steam with ~100 ppb O₂ at 276 bar and 550°C. Multiple oxide layer cracks and delamination events were observed and analyzed in detail during the tests. Results from the testing agreed well with earlier observations that had identified the failure location at the outer–inner oxide layer for all tested materials. Calculated adhesion energies identified the outer–inner oxide interface of alloy 347HFG as the weakest interface.     

Study on tribological properties of the DV–FV polyarylate system

Tribological properties of two fully compatible polyarylates having similar chemical structures and different kinetic chain flexibilities have been studied. During the processing and forming the polyarylates, a polymer mixture system containing the copolymer has been formed. It is shown that the formation of the DV?FV polymer system by mixing the “flexible” and “rigid” polyarylates leads to a sharp increase in the glass transition temperature and to a more complicated mechanism of friction characterized by a specific structure of the transfer products. It leads to the formation of metal-polymer system on the counterbody surface. This works provides the possibility to control the tribological properties of polymer mixtures.     

Determination of a vocal source by the spectral ratio method

The inverse problem with respect to functions proportional to a voice source and volume velocity of the air flow through the glottis is solved as follows: we compute the inverse Fourier transform of the regularized fraction of short-term speech-signal spectra at intervals with an opened (closed) glottis, minimizing the optimality criterion with respect to the regularization parameter and the glottis opening (closing) time. The optimality criterion for solutions includes the values of the volume velocity and its time derivative at the ends of the interval with an opened glottis and the total value of the negative volume velocity. To obtain an empirical error estimate for the solution, experiments using synthesized signals with various parameters, direct measurements of the glottis, and signals synchronously recorded through pairs of microphones of different types are performed. The most probable determination error for the volume velocity is less than 5% for synthetic sources; if the area of the glottis of the source is measured experimentally, then the said error is about 10%. The discrepancy of solutions for the same signal synchronously recorded through a pair of microphones of different types is less than 10%.     

Low-temperature properties of porous silicon-indium nanocomposite

A new nanocomposite material with stable properties has been obtained representing a metal (indium) incorporated into a semiconducting porous silicon (por-Si) matrix. Electrical properties of the por-Si-In nanocomposite have been studied for the first time. At low temperatures (T = 1.4?C4.2 K), the por-Si-In samples exhibit a positive magnetoresistance [??R/R(H = 0) ?? 600%], which is related to breakage of the superconducting state of In particles in the por-Si matrix.     

Interaction of thermosetting plastics with clinkering coal

The influence of phenol-formaldehyde resin on the clinkering properties of coal batch is studied by means of the dilatometric method proposed by the Institute of Mining and Dnepropetrovsk Metallurgical Institute. For comparison, its influence on the clinkering ability is studied by the Roga method. The results show that this organic additive has a similar influence in both cases.