An Investigation of Evaporation of Liquid Alloys of Iron with Copper

The Knudsen method of mass-spectrometry and the integral option of the Knudsen effusion method realized under conditions of ultrahigh oilless vacuum are used in the overall temperature range from 1440 to 1916 K to investigate the evaporation of pure iron and copper and of a dilute liquid Fe–Cu solution with the copper content ranging from 0.17 to 10.1 at. %. The obtained data are used to calculate the values of standard sublimation enthalpy for Fe and Cu, as well as the partial and integral thermodynamic characteristics of liquid alloys of iron with copper. Significant positive deviations from Raoult's law are observed.     

The DNA binding properties of Saccharomyces cerevisiae Rad51 protein

Saccharomyces cerevisiae Rad51 protein is the paradigm for eukaryotic ATP-dependent DNA strand exchange proteins. To explain some of the unique characteristics of DNA strand exchange promoted by Rad51 protein, when compared with its prokaryotic homologue the Escherichia coli RecA protein, we analyzed the DNA binding properties of the Rad51 protein. Rad51 protein binds both single-stranded DNA (ssDNA) and double-stranded DNA (dsDNA) in an ATP- and Mg2+-dependent manner, over a wide range of pH, with an apparent binding stoichiometry of approximately 1 protein monomer per 4 (+/-1) nucleotides or base pairs, respectively. Only dATP and adenosine 5'-gamma-(thiotriphosphate) (ATPgammaS) can substitute for ATP, but binding in the presence of ATPgammaS requires more than a 5-fold stoichiometric excess of protein. Without nucleotide cofactor, Rad51 protein binds both ssDNA and dsDNA but only at pH values lower than 6.8; in this case, the apparent binding stoichiometry covers the range of 1 protein monomer per 6-9 nucleotides or base pairs. Therefore, Rad51 protein displays two distinct modes of DNA binding. These binding modes are not inter-convertible; however, their initial selection is governed by ATP binding. On the basis of these DNA binding properties, we conclude that the main reason for the low efficiency of the DNA strand exchange promoted by Rad51 protein in vitro is its enhanced dsDNA-binding ability, which inhibits both the presynaptic and synaptic phases of the DNA strand exchange reaction as follows: during presynapsis, Rad51 protein interacts with and stabilizes secondary structures in ssDNA thereby inhibiting formation of a contiguous nucleoprotein filament; during synapsis, Rad51 protein inactivates the homologous dsDNA partner by directly binding to it.     

Investigation of the influence of the geometric parameter and the mixing chamber length of an ejector on the origination of the critical mode

Results are presented of experimental investigations to determine the dependence of the pressure drop at which the critical mode sets in in an ejector, on the geometric parameter and the mixing chamber length.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 59, No. 1, pp. 119–122, July, 1990.     

Replacement of Electrofilters in an External Cyclone System for Dust Removal from Regeneration Stack Gases on the 1A/1M Unit

Replacement of electrofilters in a external cyclone system for dust removal from regeneration gases on the 1A/1M unit allowed significantly reducing operating costs while maintaining emission of catalyst dust into the atmosphere at the previous level.     

An automated system for PAA control and adjustment

The paper presents a classification of contemporary methods for measurement of PAA characteristics, potentialities of their development and hardware implementation. The emphasis is made on diagnostic of PAA technical state, on determination of amplitude-phase distribution (APD) over the aperture, and on PAA adjustment procedures. The paper considers technical characteristics of automated measurement systems (AMS) and of the relevant equipment. Examples of AMS application for PAA parameter determination are included.     

Novel nonlinear-modulation acoustic technique for crack detection

Novel nonlinear-modulation methods for crack detection are discussed. The approach is based on the so-called cross-modulation effect consisting of the modulation transfer from an intensive, initially slowly amplitude-modulated stronger (pump) excitation to the probe signal. Advantage of this technique is a very flexible choice of the operation frequencies, since their ratio for both carriers and the modulation may be rather arbitrary. This in its turn allows one to effectively use the sample resonances in order to achieve the necessary level of the pump excitation and to ameliorate conditions for detection of the modulation sidelobes for the probe wave. Unlike higher harmonic-generation methods the initial nonlinear distortions of the pump and probe excitations (e.g. due to nonlinearities in the electronics) are not critical for this technique. In the paper we summarise results of recent test experiments that indicated high sensitivity of the new technique.     

Study of the Effect of Process Parameters in Steel Production on the Content of Corrosion-Active Nonmetallic Inclusions in Corrosion-Resistant Pipes

The main reason for the accelerated local corrosion of tubes is contamination of the steel by corrosion-active nonmetallic inclusions (CANI), which determine the metallurgical properties of tube steel in terms of their corrosion resistance. Studies have shown that there are two main types of corrosion-active nonmetallic inclusions: CANI₁ — inclusions based on calcium aluminates; CANI₂ — complex inclusions that contain calcium sulfide. In order to master to production of tubes of steel 20-PKS at the Volga Pipe Plant (VTZ), a study was made of the effect of the parameters of out-of-furnace treatments on the contamination of steel by CANI. 1. The mechanisms and main sources of formation of CANI in tube steels made by the VTZ were determined. The main reasons for the formation of CANI₁ in furnace slag containing thermodynamically active CaO are mixing of the metallic and slag phases during the argon blow and the simultaneous introduction of additions to correct the chemical composition of the steel. Inclusions of the CANI₂ type may be formed by deoxidation operations carried out with suboptimal proportions of added aluminum and calcium (lime). 2. The following measures are recommended to ensure that steel 20-PKS made by the VTZ is clean with respect to both types of CANI: • optimize the composition of the ladle slag (increase the average content of Al₂O₃, increase the average content of SiO₂ as much as possible, and in any case decrease the average concentration of CaO); • keep the mass ratio of added CaO to added Al within the range 1.5–2; • continue the argon blow done after addition of the last batch of ferroalloys for at least 15–20 min; • ensure that the intensity of the blow is at least 0.5–1.5 m³/min. 3. Vacuum-degassing steel in the ladle after treatment on a ladle-furnace unit makes it possible to distribute the CANI more uniformly over the volume of the steel. __________ Translated from Metallurg, No. 7, pp. 38–42, July, 2005.