An application of radon inversion to diffraction tomography

Basic equations of linear computer tomography are considered; a connection of the mathermatical formulation of problems of computer tomography with problems of integral geometry is indicated; the properties of the Radon transform for even- and odd-dimensional spaces are analyzed, and applications of Radon inversion to problems of diffraction tomography are presented. Bibliography: 5 titles. Translated fromZapiski Nauchnykh Seminarov POMI, Vol. 230, 1995, pp. 264–277. Translated by V. N. Troyan.     

Cyclic deformation of aluminium and its alloys

The formation of slip bands is the main mechanism of cyclic deformation in pure Al. Their density, orientation and heights in polycrystalline Al were investigated during cycling. Types, sizes and densities of precipitates are responsible for the mode of cyclic deformation in AlCu4 pure alloy. In technical Al alloys intermetallic phases have detrimental effects on deformation homogeneity and largely govern the fatigue mechanism of the material and especially microcrack initiation.     

含氧光敏引发体系的研究——Ⅵ.二苯酮/三乙胺体系引发光聚合过程中的再次引发效应

过去,作者曾发表了多种光敏引发体系引发烯类单体光聚合的工作,在研究2,2-二甲氧基苯乙酮在氧存在下引发甲基丙烯酸甲酯光聚合时,结合在聚合物链端的引发剂碎片具有光化学活性,在光聚合反应中产生高分子自由基,发生再次聚合,出现高分子量     

Adsorption of Gaseous Hydrocarbons on the Surface of Modified Petroleum-Polymeric Resins

The kinetics of adsorption of model hydrocarbons (benzene, toluene, ethyl benzene, isopropyl benzene, cyclohexane) from the gas phase on the surface of ozonized and maleized petroleum-polymeric resins was studied. The dependences of the dynamic equilibrium capacity of the petroleum-polymeric resins and of the adsorption kinetic parameters on the composition of the adsorbent-adsorbate system were elucidated.__________Translated from Zhurnal Prikladnoi Khimii, Vol. 78, No. 2, 2005, pp. 245–248.Original Russian Text Copyright © 2005 by Bondaletov, Troyan, Chernov, Bannikova, Dmitrieva.     

Electrical breakdown in ZnS:Mn films grown by rf-magnetron sputtering

We have studied the electrical breakdown field strength E_br of ZnS films doped with Mn(ZnS:Mn), produced by rf magnetron sputtering, as a function of film thickness d in the system Al-ZnS:Mn-Al. Electron-microscope studies have shown that breakdown is initiated under inhomogeneous field conditions imposed both by the roughness of the aluminum electrode and by the polycrystallinity of the ZnS:Mn film. An observed increase in E_br as d is reduced below 0.7 µm, with no polarity effect in breakdown under dc field conditions, is explained in terms of an electron-thermal breakdown model.Institute for Automation and Radio Electronics, Tomsk. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 3, pp. 41–44, March, 1993.     

Structural and electronic transitions in gadolinium iron borate GdFe<Superscript>3</Superscript>(BO<Superscript>3</Superscript>)<Superscript>4</Superscript> at high pressures

The optical properties and structure of gadolinium iron borate GdFe₃(BO₃)₄ crystals are studied at high pressures produced in diamond-anvil cells. X-ray diffraction data obtained at a pressure of 25.6 GPa reveal a firstorder phase transition retaining the trigonal symmetry and increasing the unit cell volume by 8%. The equation of state is obtained and the compressibility of the crystal is estimated before and after the phase transition. The optical spectra reveal two electronic transitions at pressures ～26 GPa and ～43 GPa. Upon the first transition, the optical gap decreases jumpwise from 3.1 to ～2.25 eV. Upon the second transition at P=43 GPa, the optical gap deceases down to ～0.7 eV, demonstrating a dielectric-semiconductor transition. By using the theoretical model developed for a FeBO₃ crystal and taking into account some structural analogs of these materials, the anomalies of the high-pressure optical spectra are explained.     

Resonant Raman scattering in superconducting Ba<Subscript>1−<Emphasis Type="Italic">x</Emphasis></Subscript>K<Subscript>x</Subscript>BiO<Subscript>3</Subscript>

The effect of the photon energy of the exciting laser radiation on the Raman spectra of Ba_1?xK_xBiO₃ with x=0.25, 0.40, and 0.50 is studied. An increase in the laser wavelength from 488 to 750 nm scarcely affects the amplitudes and frequencies of the spectral lines in the Raman spectra of the nonsuperconducting compound with x=0.25. For the optimally doped (x=0.40) and overdoped (x=0.50) superconducting compounds, a substantial increase in the line intensity and a considerable shift of the characteristic frequencies are observed. This result suggests that, in the whole range of superconducting compositions 0.37≤x≤0.50, the local symmetry of the Ba_1?xK_xBiO₃ crystal lattice differs from the perfect cubic symmetry, which should take place according to the literature data. The fact that resonance phenomena are observed when the laser photon energy is shifted toward the optical gap testifies to the presence of local electron pairs in the whole range of superconducting compositions 0.37≤x≤0.50 and is evidence in favor of the superconductivity mechanism proposed for Ba_1?xK_xBiO₃ on the basis of the X-ray absorption studies in our previous paper.     

脉冲激光沉积的金属原子团簇的电子状态及生长的研究

 介绍了采用X射线光电子谱(XPS)等技术研究脉冲激光沉积在Ni、Mo、C、NaCl(100)表面的Cu、Au原子团簇的电子状态;结合Cu₂p_3/2 X射线光电子谱峰和Cu L₃M_4,5M_4,5俄歇跃迁分离了电子结合能的初态和终态贡献,得出了它们随Cu表面浓度变化的关系,并对之作出了解释。使用XPS、RBS、TEM三项技术研究了Au在NaCl(100)表面的生长过程,通过计算得出了在不同表面浓度下Au原子团簇的平均高度和表面覆盖率。     

Seeking and investigating isospin-two narrow dibaryon resonances in neutron-proton interactions at P n =5.20±0.13 Gev/c

The results are presented that are obtained from searches for and an investigation of isospin-two narrow resonances in the effective-mass spectrum of ppπ⁺ combinations originating from the reaction np → ppπ⁺π^?π^? induced by P _n =5.20±0.13 GeV/c neutrons. Data subjected to our analysis come from the 1-m hydrogen bubble chamber installed at the Laboratory for High Energies, Joint Institute for Nuclear Research (Dubna), and exposed to a beam of quasimonochromatic neutrons. Narrow structures in the effective-mass spectrum of ppπ⁺ combinations are found at 2175, 2221, 2321, 2398, 2471, 2525, 2596, and 2709 MeV/c ². The experimental widths of the resonances are determined primarily by the instrumental resolution. The branching fractions for various channels through which the 2596-MeV/c ² resonance decays are determined to be (83±23)% for the Δ ₃₃ ⁺⁺ p channel, (10±3)% for the (BB) ₂₀₉₅ ⁺⁺ π⁺ channel, and (7 _?7 ⁺¹⁵ for the ppπ⁺ channel; here, (BB) ₂₀₉₅ ⁺⁺ is a dibaryon in the two-proton system with a mass around 2095 MeV/c ². A qualitative analysis of the spins of the 2596-and 2709-MeV/c ² resonances is performed.