Updating of equipment for thermochemical treatment of steel parts in a fluidized bed

Results of updating commercial equipment for thermochemical treatment (TCT) of steel parts in a fluidized bed are presented. The updating has led to the creation of an ecologically safe treatment area with mechanized equipment for carburizing and carbonitriding in a fluidized bed with the use of natural gas, ammonia, and compressed air instead of the equipment for pack cyaniding.     

Method of determining the single-domain property of magnetic powder particles

A method of determining the single-domain property of magnetic powder particles based on Mossbauer spectroscopy is proposed and checked experimentally. Pis’ma Zh. Tekh. Fiz. 23, 70–3 (December 26, 1997)     

Deoxyribonuclease treatment improves the homogeneity of single-stranded DNA preparations

The isolation of single-stranded (ss) phagemid DNA using standard protocols often results in impure preparations, which contain undesirable quantities of chromosomal and/or double-stranded (ds) phagemid DNA. Here we report a simple and efficient method for elimination of virtually all dsDNA by incubation of phagemid viral particles with deoxyribonuclease I. In addition to analyzing the ratio of linear-to-circular topological forms of ssDNA after deoxyribonuclease I treatment, we verified that no decrease in transformation efficiency occurred and demonstrated that ssDNA molecules covered by capsid proteins remained intact following such treatment.     

Convective mass exchange between flows in a valve-pulsatory apparatus with permeable partition

A mathematical model of convective mass exchange between flows in a valve-pulsatory apparatus with permeable partition is proposed. The mass exchange between flows of aqueous Na₂CO₃ solution and distilled water, or pearlite suspension in water and aqueous solution of NaCl was studied on a pilot apparatus.     

Specific heat and magnetocaloric effect of Pr1−x Ag x MnO3 manganites

This paper presents experimental results of the specific heat and magnetocaloric effect in Pr_1?x Ag _x MnO₃ (x = 0.05–0.25) manganites. A maximum value of magnetic entropy change for the sample with x = 0.15 was observed in magnetic field of 18 kOe at T _C = 125 K and was ΔS _max ≈ 2.96 J/kg K. In Pr_0.95Ag_0.05MnO₃ sample, a sign inversion of the magnetocaloric effect was observed at low temperatures (~80 K) in low magnetic fields of 750 Oe. The coexistence of ferromagnetic and canted antiferromagnetic phases with closely spaced critical temperatures was found to force the magnetocaloric effect into abrupt sign inversion.     

Energy spectrum of charge carriers in Sm<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>Pb<Subscript>1 − <Emphasis Type="Italic">x</Emphasis></Subscript>Te

The electrical conductivity (σ), Hall coefficient (R _H, and thermopower (α) of Sm _x Pb_{1 − x} Te have been measured at temperatures from 80 to 800 K. The results demonstrate that the Sm _x Pb_{1 − x} Te solid solutions with x ≤ 0.04 are p-type semiconductors. We have determined the electron effective mass at the conduction band bottom (m _n = (0.031 ± 0.001)m ₀) and Fermi level (m* = (0.06 ± 0.001)m ₀) and the hole effective mass (m _p = (0.34 ± 0.001)m ₀). The temperature-dependent σ, R _H, and α data are interpreted in terms of a model with two carrier types.     

On the thermal properties of Ag2Te and Ag2Se in the region of the phase transition

A setup is developed for measuring the thermal properties of Ag₂Te and Ag₂Se near the main phase transition and in the region of it in high vacuum. The samples are of stoichiometric composition with an excess of Ag, Te, and Se. Differential thermal analysis is performed and the temperature differences across and along the samples are measured by the pulsed light method. Using data on the thermal diffusivity a(T), the temperature dependence of the thermal conductivity K = apc is determined, where p is the density and c is the specific heat. The measurement technique used allows us to establish that the main phase transitions are accompanied by intense heat release. New phase transitions before and after the main structural phase transition with heat absorption are found. According to the DTA data, in the Ag₂Te sample with an excess of Ag (0.25 at.%, cn = 1.2 × 10¹⁹ cm^?3) the phase transition at 365 K is also accompanied by heat absorption. Thus, it is established that all of the phase transitions in Ag₂Te and Ag₂Se are first-order.     

Waste-free technology of deironization of acidic water

A new technology of deironization of natural and waste acid waters has been developed. Lime wastes of building material production are used as a reagent. The effect is achieved by introducing 3–4 g/dm³ of pulverized wastes (chippings) with a fraction ～0.1 mm to the water during its continuous stirring for 1–5 h (depending on the water composition and limestone) and initial aeration 10–20min. The technology is waste-free including a new method of dehydration of the sediment that forms and which may be employed, in particular, in nonferrous metallurgy or the production of facing plates.     

Statistical Description of the Coke Balance in a Reactor–Regenerator System Containing a Fine-Particle Catalyst

Using a statistical concept, a mathematical model is developed to describe the coke concentration in a fine-particle catalyst in a reactor–regenerator circulation system in terms of the coke concentration distribution of particles. The efficiencies of the proposed model and a perfect-mixing quasi-homogeneous model are compared.