Compactability of Stabilized Zirconium Dioxide Powder

Features of compacting articles from stabilized zirconium dioxide powder synthesized by the sol-gel method, and also their structure and properties are studied. Compaction parameters are determined. It is shown that the relationship between compact density and extrusion pressure may be described by the Bal'shin equation. It is established that parameters of this equation depend linearly on the duration of zirconium dioxide synthesis.     

Influence of pressure on the effective thermal conductivity and electrical resistivity of coke

The influence of pressure on the effective thermal conductivity and electrical resistivity of coke is investigated. The scope of the investigation includes analysis of the relevant literature; measurement of the thermal conductivity and electrical resistivity of coke with different granulometric composition as a function of the temperature, at different pressures; and the derivation of regression equations for the experimental results. The temperature dependence of the coke’s thermal conductivity is measured by the standard coaxial-cylinder method. The electrical resistivity of coke is measured by a two-probe potentiometric method. Coke of the ≤2 mm and 6–8 mm classes is used in the thermal tests, with a temperature range of 200–1000°C, at pressures of 0–68 kPa. Coke of the 0–10 mm class is used in the electrical tests, with a temperature range of 30–800°C, at pressures of 1.5–40 kPa. A second-order polynomial for the temperature, mean particle size, and pressure is derived as the regression equation for the thermal conductivity. A polynomial formula is derived for the electrical resistivity of coke at pressures of 13–40 kPa.     

Chemical resistance of electrical insulating epoxyisocyanates compound

The chemical resistance of hardened epoxyisocyanate compound to alkalis, acids, sodium carbonate, and chloride solutions, as well as to hot water, is examined. According to the test results, the compound can be classified as a chemically resistant substance and recommended for application in the insulating systems of electrical machines that operate under conditions with increased chemical contamination, as well as for electrical machines used in seagoing ships.     

Experimental and theoretical studies of the influence of pulse pressure oscillations on the processes of microhemocirculation

The influence of pulse pressure oscillations on the processes of transcapillary exchange in the hemodynamics has been investigated by experimental and numerical methods. The active role of microvessel walls in the mass transfer has been confirmed. On the basis of the generalized nonstationary Starling scheme patterns of transcapillary exchange with alternation of the filtration and reabsorption processes have been determined. Flows in the interstitial space have been modeled numerically. It has been established that the presence of pulsations promotes enhancement of the transcapillary exchange.     

Barnase mutant Ser57Ala: preparation and properties

Barnase, an extracellular ribonuclease produced by Bacillus amyloliquefaciens, belongs to a family of small microbial ribonucleases with similar structure and properties. These enzymes hydrolyze phosphodiester bonds on the 3' side of guanosine nucleotides in RNA. The guanylic specificity of barnase is more pronounced in the hydrolysis of dinucleotides or cyclonucleotide phosphates as substrates than in the hydrolysis of RNA or polynucleotides. To have an insight into the molecular basis of this phenomenon, we mutated amino acid residue Ser-57 in the "base recognition loop" of RNase Ba. The mutant protein was expressed in Escherichia coli producing system and purified for the study of the kinetic properties in the cleavage polynucleotide reactions. It was shown that the mutation of amino acid residue Ser-57 for Ala in the "recognition loop" of RNase Ba does not significantly influence the kinetic parametres of hydrolysis of polynucleotide substrates.     

Properties of R6M5 steel powders of various particle sizes and the structure of the steel in the sintered condition

Conclusions An investigation was carried out into the effect of particle size of powders produced by comminution of R6M5 high-speed steel waste (swarf) on their compressibility and sinterability. It is shown that with decreasing mean particle size the compressibility of such powders deteriorates, but their sinterability improves. The finer the steel powder, the lower is the sintering temperature necessary for the attainment of a given density. Varying the powder particles size brings about marked changes in the microstructure of the steel in the sintered condition. The liquid phase (ledeburitic eutectic) appearing during the sintering of steel powders of different particle sizes varies in form and distribution. With coarse powders (d_m=100 m) the eutectic is similar to that in cast steel, but with powders of small particle size (d_m=22 m) it is finer and evenly distributed throughout the structure in the form of thin lamellae.A 0.85%C-6% W-5% Mo-4% Cr-2% V (nominal composition) high-speed steel — Translator.The authors wish to thank A. N. Nikolaev of the Gorkii Polytechnic Institute for helpful discussion in the experimental part of the work.Translated from Poroshkovaya Metallurgiya, No. 6(234), pp. 9–15, June, 1982.