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A new technique allowing the Q-method to be used surely for both the spectral classification of young O–A0 stars and older spectral subclasses A1–M5 is described. Characteristics of interstellar light absorption dependence on distance in the given direction of the sky is used as a main criterion for excluding possible multiplicity of star spectral estimates at some constant values of QUBV. Information on open cluster membership probabilities is also useful as additional criterion of the spectral classification. The method was tested on stars up to $V=14$mag in directions of young open clusters NGC 2244 and NGC 2264. The spectral study based on UBVphotometry was extended to faint stars of NGC 2264 in the Vmagnitude range 17-22 mag.

Conclusion Analysis of the state-of-the-art of the scientific and engineering aspects of the development and application of nuclear membranes shows that rapid progress has been made in the quantitative and qualitative respects. Fields where the use of nuclear membranes is particularly effective have now been determined. Nuclear membranes with pores measuring 0.5–1 µm in size are used extensively for analytical purposes in physicochemical studies and in biological and medical experiments. Membranes with pores of diameter 0.1–0.2 µm are used to make filters for fine purification of technological materials in the fabrication of semiconductor devices. Structures with the smallest pores (<0.1 µm) are used in the technique of thorough gas treatment and in the microbiological industry. The demand for nuclear membranes will rise rapidly. In view of this, it is important to develop and build customized accelerators for the mass production of high-quality filtration material.

Nitrogen-containing heterocyclic analogs of anthracene, viz., benzo[g]isoquinolines and benzo[g]quinolines, were obtained by dehydrocyclization on a K-16 catalyst of mixtures of methyl-substituted 2- and 4-benzylpyridines with methyl groups in various positions of the pyridine and benzyl rings, which are formed by benzylation of ß-picoline, as well as pyridine, by the Ladenburg method. The spectral characteristics of the synthesized compounds are presented.

⁵⁷Fe Mössbauer spectroscopy data obtained between 4.2 and 298 K, TEM, and magnetic measurements were used to study details of the real structure of cobalt oxides, CoO and Co₃O₄. In Co₃O₄ samples synthesized at low temperatures the tracer is nonuniformly distributed. It exists in the form of α-Fe₂O₃ inclusions generating stacking faults as well as in the form of Fe³⁺ ions in octahedral positions of the spinel matrix. An excess of oxygen in Co₃O₄ was found to generate cation vacancies in the octahedra. The two-phase CoO-Co₃O₄ system displays a dislocation network broadening the resonance lines and increasing the quadrupole splitting. For monophasic CoO an excess of oxygen leads to the formation of microclusters of Co₃O₄. A periodic array of shear type extended defects found in modified CoO was proposed to be generated by ordering of Fe impurities in some planes of the cubic structure. Copyright 1993, 1999 Academic Press

An x-ray crystallographic investigation was made of 6-methyl-2,7-diphenyl-1,3-diformylindolizine, obtained by the formylation of 6-methyl-2,7-diphenylindolizine. The effect of various carbonyl-containing substituents at positions 1 and 3 on the geometry of the indolizine ring in the structually investigated indolizine derivatives is discussed.

The mass-spectral behavior of 15 compounds from the 6-methyl-2-aryl-7-benzylindolizine series was investigated, and it was shown that the peculiarities of their dissociative ionization are due to the formation of stable resonance-stabilized ions that contain a quaternized nitrogen atom in the heteroring.

A study has been made of the relationship f′(T) (T=77–300°K) for platinum-group metal complexes containing Sn(II)-X (X=F, Cl, Br); these data have been used to determine the mean-square amplitudes of vibrations of the Sn atom in the anions and together with the anion, and their temperature dependences have been found. The observed relationships at f′(T) depend to a considerable degree on the vibrations of the first type, i.e., on the rigidity of the bonds between the Sn and the immediate enrivonment. The different Sn-X ligands have their own characteristic relationships f′(T), so that they can be used for identification of types of Sn(II)-containing complexes. The normal vibrations of the different complexes have been calculated, and it has been established that the observed changes in their f′(T) in the series of halides can be explained by the increase in the number of low-frequency vibrations in the series Br>Cl>F and by their effective inclusion in the absorption of the recoil energy given up by the Sn atom. Within the framework of the analysis, an explanation has been found for the increase in f′ of the complexes when they are supported on the surface of substances containing acidic OH groups.

Radiation-induced accumulation and annealing processes of radiation defects with level Ec-0,22 eV in silicon of various perfection are analysed and it is concluded that they consist of oxygen and two vacancies (oxygen-divacancy complex).

A change in the concentration and charge-carrier lifetime in n-Si when irradiating by high-energy γ-rays was studied and parameters of radiation defect clusters produced by them were determined.

The annealing mechanism of divacancies involved in radiation defect clusters is suggested in accordance with which the interaction of interstitial carbon atoms and intrinsic diinterstitials, mobile at T≳ 100°C, with divacancies results in their smooth annealing in a wide temperature range.

The peculiarities of the radiation defects accumulation processes during irradiation by60Co γ-quanta and rearrangement of these defects at further isochronal annealing are studied for n-type silicon epitaxial layers of 1.2 and 5 μm thickness and ρ = lΩ.cm. The experimental results are based an analysis of the Hall coefficient temperature dependencies obtained at various stages of irradiation or annealing. It is established that, as compared to bulk crystals, the epitaxial silicon layers demonstrate a number of salient features during radiation defect formation and annealing. Among them are the lower rate of vacancy defects introduction, lower annealing temperature for certain defects etc. It is demonstrated that these features are caused by interaction of irradiation-generated mobile-at-annealing defects with the surface and atoms of impurities. The vacancies generated by γ-quanta efficiently migrate to the surface. This process decreases the rate of vacancy defects formation in thin layers. The layers are characterized by non-uniform profile of technological impurities such as oxygen and carbon which capture irradiation-generated Frenkel pairs with formation of electrically active defect complexes (Ci;Cs, A-centers); a gradient in the distribution of the complexes is thus created. TheCiCs complexes are mainly formed near the surface and theA-centers are created near thep-n layer-substrate junction.

The fusion of 3,8-diphenyl-, 1,2-diphenyl-, and 6-methyl-2,7-diphenyl-indolizines with sulfur results in the formation of bis(indolizin-3-yl) disulfides with the respective substituents. Bis(2,8-diphenylindolizin-3-yl) disulfide is reduced to the original indolizine, and its treatment with nitric acid gives 2,8-diphenyl-1, 3-dinitroindolizine. Bis(dibenzo[b,g]indolizin-11-yl) disulfide is obtained from dibenzo[b,g]indolizine. The formation of the disulfides is apparently a general region of indolizines without substituents at C3 or C1 of the pyrrole ring. The structures of the disulfides obtained have been confirmed by data from x-ray diffraction analysis and NMR spectroscopy.

Aryl(6-methyl-2-phenyl-7-indolizinyl)methanes were obtained by quaternization of aryl(?-pyridyl)methanes with bromoacetophenone and subsequent cyclization of the quaternary salts with 40% potassium carbonate solution (the Chichibabin method). The stable 2, 5-dimethyl-4-(2,4-dimethylbenzyl)pyridinium benzoylmethylid, which was converted to an indolizine by the action of Al2O3, was isolated by the action of a 10% potassium carbonate solution on the corresponding quaternary salt. The ability of 3-unsubstituted indolizines to undergo protonation in both the 3 and 1 position was shown on the basis of the PMR spectra. The aryl(7-indolizinyl)methanes are selectively hydrogenated thoroughly over rhenium heptasulfide in the indolizine ring to give tetra or octahydro derivatives without involvement of the aryl groups. Data from the IR, PMR, and mass spectra are presented.

Methanol oxidation on mechanically treated amorphous catalysts has been shown to lead to their crystallization and the restoration of their primary properties except for the surface area, which remains decreased. It is suggested that the amorphous state is not responsible for the catalytic properties.

Mössbauer spectroscopic studies of the state of Pt−Sn catalyst for hydrocarbon conversion supported on prechlorinated γ-Al2O3 indicate that, unlike nonchlorinated Al2O3, this system is much more reduced and besides Pt3Sn−PtSn2, its surface contains sigfificant amounts of Sn(II) and Sn(IV) chlorides bonded to the surface.

Measurements have been made on the surface flow of hydrogen, nitrogen, krypton, and xenon in polyethylene terephthalate membranes having pore sizes less than 15 nm. The gas-selective behavior is considered and surface molecular migration coefficients are estimated.

The characteristic feature of the structure of electrolytic copper and nickel is the presence in the grains of subgranular dislocation boundaries and twinning of growth origin. The subgranular dislocation boundaries are mostly found in the form of planar networks of dislocations having almost screw orientation. Other types of boundaries were also noticed: edge boundaries, dipole configurations, volumetric dislocation nodes, and ragged boundaries. The presence of thermal and stress fields causes disintegration of unstable subgranular dislocation boundaries of growth origin. The disintegration of the boundaries is related to significant restructuring of the dislocation structure and is clearly demonstrated by various methods of physical analysis.

Comparative experiments on the formation and annealing of radiation defects in float-zone n-Si (ρ0≃200 ω cm) irradiated with 8600 MeV protons or 60Co γ-rays were carried out. From the analysis of the temperature dependences of the Hall coefficient the values of the activation energy δE of radiation defect ionization are determined. The annealing character and nature of radiation defects with close values of δE are found to be dependent on the kind of irradiation. The results obtained are discussed taking into account the radiation defect formation mechanism for the kinds of irradiation used and the influence of the potential barrier Ψ of proton-produced defect clusters on the value of δE for defects localized in clusters (δE= δE - Ψ, where δE is the radiation defect ionization energy). Proton-irradiation-produced radiation defects with δE=Ec - 012 eV (annealing temperature range 200-300°C) are concluded to represent planar tetravacancies (Si-A3 centres) whose ionization energy is δE≃Ec - 0.23 eV, localized in the central region (the core) of the defect cluster.

Radiation-induced accumulation and annealing processes of radiation defects with level Ec–0,22 eV in silicon of various perfection are analysed and it is concluded that they consist of oxygen and two vacancies (oxygen-divacancy complex). [ABSTRACT FROM PUBLISHER]

A model of water-saturated soil as an ideal liquid has already been proposed [1], Experimental investigations of shock waves [2] have shown that for small stresses in water-saturated soil features of a solid plastic body begin to manifest themselves. As regards its properties the soil approximates to the model proposed in [3].

Physical models of specific heat at constant volume and thermal conductivity of uranium dioxide are developed based on phonon spectrum data. It is explained an abnormal growth of thermal conductivity coefficient of oxide nuclear fuel in high temperature region. It is shown that the contribution from charge carrier's degrees of freedom into observed thermal conductivity coefficient of uranium dioxide can be neglected up to melting point. Developed models of thermophysical properties do not contain fitting parameters.

The case of one-sided heat transfer to a flat plate immersed in a flow of heated liquid is examined. Equations are obtained for the liquid temperature distribution in the boundary layer, and for the heat flux from the liquid to the wall.