Rail strengthening in prolonged operation

In rail operation (with traffic corresponding to passed tonnage of gross loads of 500 and 1000 million t), the surface layer of the steel is significantly strengthened. Electron-microscope data permit quantitative analysis of the contribution of different mechanisms to rail strengthening in prolonged operation, at different distances from the contact surface. The strengthening is multifactorial: it involves substructural strengthening associated with nanofragment formation; dispersional strengthening by carbide particles; the formation of atmospheres at dislocations; and polar stress due to interphase and intraphase boundaries. The significant increase in the surface strength of rail steel after prolonged operation (passed tonnage of gross loads of 1000 million t) is due to the presence of long-range internal stress fields and to the fragmentation of material with the formation of nanostructure.     

Oxidation of magnetite

The oxidation of large octahedral single crystals of magnetite extracted from chlorite shale at Shabrovsk talc mine (Middle Urals) is experimentally studied. Differential heating curves show that the processes occurring in the oxidative roasting of magnetite (Fe₃O₄) are highly reproducible. The mechanism of martensite oxidation is considered, as well as the temperature ranges corresponding to exothermal and endothermal reactions. The thermal effect of martensite oxidation is determined from that of a standard (CaCO₃) and the areas under the differential heating curves on the corresponding thermograms. Those areas are proportional to the thermal effect. The results obtained are of considerable interest: knowing the temperature range of martensite oxidation, the heat sources in the various technological zones of the conveyer roasting machines may be taken into account in establishing the roasting conditions, thereby optimizing the thermal conditions and reducing the fuel consumption.     

N-glycosylation of recombinant human interferon-gamma produced in different animal expression systems

Recombinant human interferon-gamma (IFN-gamma) was expressed in Chinese hamster ovary cells, baculovirus-infected Sf9 insect cells and the mammary gland of transgenic mice. The N-linked carbohydrate populations associated with both Asn25 and Asn97 glycosylation sites were characterized by matrix-assisted laser desorption/ionization-mass spectrometry (MALDI-MS) in combination with exoglycosidase array sequencing. A site-specific analysis of dual (2N) and single (1N) site-occupancy variants of IFN-gamma derived from Chinese hamster ovary cells showed that N-glycans were predominantly of the complex bi- and triantennary type. Although Asn25-linked glycans were substituted with a core fucose residue, Asn97 N-glycans were predominantly non-fucosylated, and truncated complex and high-mannose oligosaccharide chains were also evident. Transgenic mouse derived IFN-gamma exhibited considerable site-specific variation in N-glycan structures. Asn25-linked carbohydrates were of the complex, core fucosylated type, Asn97-linked carbohydrates were mainly of the oligomannose type, with smaller proportions of hybrid and complex N-glycans. Carbohydrates associated with both glycosylation sites of IFN-gamma from Sf9 insect cells were mainly tri-mannosyl core structures, with fucosylation confined to the Asn25 site. These data demonstrate the profound influence of host cell type and protein structure on the N-glycosylation of recombinant proteins.     

The computational procedure of the power and kinematic parameters of the deformation center upon rolling the multilayer systems with a dispersed layer

A model of rolling the multilayer system in which some layers can be powered is proposed. A computational procedure for the distribution of energy consumption over the deformation center in the presence of the powdered layer in the system is developed.     

Quality of bulk-quenched rail after double tempering

Repeated tempering of bulk-quenched rail reduces the residual stress without significant change in the mechanical properties and hardness of the metal. Double tempering with optimal cold straightening is suitable for the manufacture of rail that is resistant to corrosion-fatigue cracks.     

Magnetohydrodynamic processes in the electromagnetic mixing of liquid phase in the ingot on continuous bar- and bloom-casting machines

The influence of electromagnetic mixing of liquid metal in the continuous-casting machine on the quality of continuous-cast bar and bloom depends on the mixing rate. In world practice, the mixing rate is characterized by the maximum linear velocity of the liquid metal in the flow. Physical and mathematical simulation reveals the relations between all the relevant parameters of the mixing stator that affect the mixing rate.     

Improved method for measuring the γ-ray absorbed dose rate in models of iron shielding of a thermonuclear reactor

An improved method of measuring the absorbed γ-ray dose rate usingCaSO ₄ andSrSO ₄ type thermoluminescent detectors in models of iron shielding of a thermonuclear reactor is described. The reactionT(d, n)⁴ He served as a neutron source. The method obtained makes it possible to determine the absorbed γ-ray dose rate in shielding without using computed information and relying only on experimental data on the rates of nuclear reactions in threshold detectors. 7 figures, 1 table, 9 references. Moscow Engineering-Physics Institute. Translated from Atomnaya énergiya, Vol. 86, No. 3, pp. 219–225, March, 1999.     

Optical Properties of AlGaAs/GaAs Resonant Bragg Structure at the Second Quantum State

Photoluminescence, optical reflectance and electro-reflectance spectroscopies were employed to study an AlGaAs/GaAs multiple-quantum-well based resonant Bragg structure, which was designed to match optical Bragg resonance with the exciton-polariton resonance at the second quantum state in the GaAs quantum wells. The structure with 60 periods of AlGaAs/GaAs quantum wells was grown on a semi-insulating substrate by molecular beam epitaxy. Broad and enhanced optical and electro-reflectance features were observed when the Bragg resonance was tuned to the second quantum state of the GaAs quantum well excitons manifesting an enhancement of the light-matter interaction under double-resonance conditions. By applying an alternating electric field, we revealed electro-reflectance features related to the x(e2-hh2) and x(e2-hh1) excitons. The excitonic transition x(e2-hh1), which is prohibited at zero electric field, was allowed by a DC bias due to brake of symmetry and increased overlap of the electron and hole wave functions caused by electric field.