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Frequency-temperature characteristics of dielectric permittivity and loss factor of Bi 12 SiO 20 crystals doped by Cr and Mn ions have been carried out in audio frequency range in temperature interval 290 to 800 K. Dielectric anomalies of relaxation (Bi 12 SiO 20 :Cr) and resonance (Bi 12 SiO 20 :Mn) types and Cole-Cole dependences close to linear ones have been observed. The results are discussed on the basis of "screened hopping" model.

Abstract: A study is reported of the temperature and frequency dependences of the permittivity and losses in Cr-doped Bi12SiO20 crystals at sonic frequencies and in the range 300–800 K. A number of dielectric anomalies and a close-to-linear Cole-Cole diagram have been observed. The results are discussed by invoking the concepts of electron hopping and screening of the induced polarization through the relaxation of local lattice distortions.

Abstract: The thermally stimulated depolarization currents and the temperature dependences of optical absorption are investigated. Interaction processes between defects are observed. A model consisting of association-dissociation of quasidipoles in the form of donor-acceptor pairs with a distribution of activation energies and relaxation times is proposed.

The structures of magnetoabrasive powders from iron-carbon melts alloyed with carbideforming elements constitute disperse systems which can arbitrarily be divided into two groups: 1) structures characterized by the presence of two distinct types of components — a monocarbide (TiC, Nb4,C3, ZrC, or VC), which possesses abrasive qualities, and a ferromagnetic (Fe-Si) matrix, which ensures the necessary magnetic properties, and 2) structures characterized by the fact that abrasive functions are performed by all their structural constituents — a double carbide formed by iron together with an alloying element (Si, Mo, W, or Cr) and a martensitic (bainitic) matrix. The particles of an atomized magnetoabrasive powder from any given alloyed melt have structures differing in macromorphology, which is a result of differences in conditions of solidification of metal drops during melt disintegration. In the presence of carbide-forming elements silicon in an iron-carbon melt dissolves mainly in ferrite, without significantly affecting the morphology of structure of the atomized particles. The effectiveness of magnetoabrasive machining (polishing) depends to a large extent on the choice of abrasive and work materials.

Catalysts with nonuniform distribution of the catalytically active component (Pt) over their porous support (Al2O3) have been studied. A nonuniform activity distribution changes not only the reaction rate but also the kinetics can be different on these catalysts.

Germanium, tin or lead additives decrease the activity of supported nickel by several orders of magnitude in the hydrogenation of benzene and hydrogenolysis of propane and n-hexane. n-Hexane is transformed to aromatization products, whereas non-modified Ni is known as a hydrogenolysis catalyst. These catalytic effects are due to changes in the electronic and chemisorption properties of nickel alloyed with inactive metals of the additives.

Abstract: The reaction of 5-phenyl-2,3-dihydrofuran-2,3-dione with 6,7-dimethoxy-3,4-dihydroisoquinoline gave 1-benzoyl-2-hydroxy-8,9-dimethoxy-3,5,6,10b-tetrahydropyrrolo[2,1-a]isoquinolin-3-one and its oxidation product,viz., 1-benzoyl-8,9-dimethoxy-2,3,5,6-tetrahydropyrrolo[2,1-a]isoquinoline-2,3-dione. The last-mentioned compound was studied by X-ray structural analysis.

The method of thermally stimulated depolarization currents was used to investigate electrically active defects in Bi12SiO20 doped with Mn and Cr-ions. The activation energy and the charge localized at these defects during the polarization processes were determined.

Abstract: The influence of doping of Bi12SiO20 (BSO) with chromium and manganese ions on the thermal depolarization currents (TDCs) is investigated. Measurements are performed in the temperature interval 300–800 K as the preliminary polarization temperature is varied in the range T p=300–523 K. It is shown that doping significantly alters the structure of the TDC spectra. The Cr and Mn ions produce a set of new peaks over the entire investigated temperature range. The thermal activation energies are 0.85–1.98 eV (BSO:Cr) and 0.58–1.72 eV (BSO:Mn). Another consequence of doping is an increase in the amplitudes of the peaks and the charge accumulated during preliminary polarization.

In the polishing of steels the best results are obtained with a magnetoabrasive powder whose particles constitute disperse systems (metallic alloys) composed of ferromagnetic matrices and abrasive phases. A difference in magnetic properties between different steels affects the quality of polishing with a cast MAP less than it does with a composite powder. The character of the relationship between the amount of material removed and the hardness of a steel being polished is determined to a large extent by the latter's magnetic properties. Compared with a composite powder, a cast MAP enables a higher dimensional accuracy of parts to be preserved, attained in an operation preceding polishing.

A device below and from the side, the removal and collection of excretions of dogs in an isolated chamber in extended experiments. This device is made from rubber-impregnated stockinet and is placed on the animal. Excretions are collected into a special reservior. This device functioned well without traumatizing the animal, providing freedom of movement for 20 experimental days.

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