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81.
O. V. Smetannikov E. A. Mushina M. S. Chinova V. M. Frolov Yu. Ya. Podol’skii G. N. Bondarenko B. F. Shklyaruk E. M. Antipov 《Polymer Science Series A》2006,48(8):793-797
The high activity of a titanium-magnesium catalyst in the polymerization of isoprene with formation of a unique thermoplastic material, synthetic gutta percha, was shown. It is established that a change in polymerization conditions over a wide range has no effect on the content of trans-1,4 units in the polymer. Unlike natural gutta percha with the crystalline phase containing a mixture of α-and β-crystalline modifications, the synthetic trans-1,4-polyisoprene crystallizes only in an α-monoclinic form, the melting temperature of which is close to 70°C. The melting followed by crystallization results in formation of a stable β-crystalline modification with a melting temperature approximating 50°C. 相似文献
82.
N.R. Khasanova G. Van TendelooO.I. Lebedev S. AmelinckxA.Yu. Grippa A.M. AbakumovS.Ya. Istomin O.G. D'yachenkoE.V. Antipov 《Journal of solid state chemistry》2002,164(2):345-353
The structure model for the Eu1.3Nb1.9S5 compound is determined based on high-resolution electron microscopy evidence. This compound crystallizes in a hexagonal unit cell with a=8.8732(8) Å and c=23.45(1) Å. Its structure is built up as an alternating sequence of trigonal-prismatic NbS2 layers of formula [Nb7S14] and [Nb(Eu3S4)2] slabs along the c-direction. In the [Nb(Eu3S4)2] block the stacking of two close-packed (Eu3S4) layers creates octahedral interstices formed by S atoms; these cavities are occupied by Nb cations. The model is compared with structures of other Eu-containing niobium sulfides, such as Eu0.167NbS2 and the misfit compound [(EuS)1.5]1.15NbS2. 相似文献
83.
Bulychev BM Shpanchenko RV Antipov EV Sheptyakov DV Bushmeleva SN Balagurov AM 《Inorganic chemistry》2004,43(20):6371-6376
Single-phase ternary deuteride Li(2)BeD(4) was synthesized by a high-pressure high-temperature technique from LiD and BeD(2). The crystal structure of Li(2)BeD(4) was solved from X-ray and neutron powder diffraction data. The compound crystallizes in the monoclinic space group P2(1)/c with lattice parameters a = 7.06228(9) A, b = 8.3378(1) A, c = 8.3465(1) A, beta =93.577(1) degrees, and Z = 8. Its structure contains isolated BeD(4) tetrahedra and Li atoms that are located in the structure interstices. Li(2)BeD(4) does not undergo any structural phase transitions at temperatures down to 8 K. 相似文献
84.
Roman V. Shpanchenko Rodion V. Panin Catherine Bougerol Evgeny V. Antipov 《Journal of solid state chemistry》2005,178(12):3715-3721
Lead vanadium phosphate Pb3V(PO4)3 was synthesized by solid state reaction and characterized by X-ray single crystal and powder diffraction, electron microscopy, and magnetic susceptibility measurements. The crystal structure model of Pb3V(PO4)3 was refined using X-ray single crystal data (a=10.127(1)Å, S.G. Z=4). The compound has an eulytite-like structure and its average structure model may be presented as a three-dimensional network formed by strongly distorted mixed (Pb/VIII) metal-oxygen octahedra connected by edge sharing and forming corrugated chains. The octahedra are additionally linked by tetrahedral phosphate groups via corner sharing. Lead and vanadium atoms randomly occupy two close positions in the octahedra. The electron microscopy study revealed the presence of a rhombohedral superstructure with and indicating ordering in the structure. The same type of superstructure was found by us for two another lead-containing eulytite Pb3Fe(PO4)3 where Fe+3 has an ionic radius close to that of V+3. Magnetic susceptibility measurements revealed Curie-Weiss behavior for the Pb3V(PO4)3 compound. 相似文献
85.
The novel compound Ca2Co1.6Ga0.4O5 with brownmillerite (BM) structure has been prepared from citrates at 950 °C. The crystal structure of Ca2Co1.6Ga0.4O5 was refined, from neutron powder diffraction (NPD) data, in space group Pnma, , , , χ2=1.798, , Rwp=0.0378 and Rp=0.0292. On the basis of the NPD refinement the compound was found to be a G-type antiferromagnet (space group Pn′m′a) at room temperature, with the magnetic moments of cobalt atoms directed along chains of tetrahedra in the BM structure. Electron diffraction and electron microscopy studies revealed disorder in the crystallites, which can be interpreted as the presence of slabs with BM-type structure of Pnma and I2mb symmetry. 相似文献
86.
87.
Comparative analysis of the temperature evolution of the structure of linear organoelement polyfluoroalkoxyphosphazenes and wholly aromatic main-chain copolyesters was carried out using X-ray analysis, differential scanning calorimetry and dynamic mechanical testing within a wide temperature range. Experimental observations show that flexible-chain polyfluoroalkoxyphosphazenes are inclined to formation of the columnar mesophase and condis crystalline structures, while rigid-chain random copolyesters mainly exhibit peculiar smectic and nematic liquid crystalline states. 相似文献
88.
Evgenij Zubko Yuriy Shkuratov Gorden Videen 《Journal of Quantitative Spectroscopy & Radiative Transfer》2006,100(1-3):483-488
We study the backscattered light of agglomerated debris particles using the discrete dipole approximation (DDA) in order to isolate specific physical components that contribute to negative polarization and the brightness opposition surge. We examine a few specific particle systems that display a prominent brightness surge and significant negative polarization over a range of near backscatter angles. In all cases, removal of the far-field interaction components results in the disappearance of the brightness surge and negative polarization branch; whereas, these phenomena remained if the near-field or radial components of the interaction fields are removed. This suggests that the mechanisms for these phenomena are embedded within the far-field interaction component. 相似文献
89.
Evgenij Zubko Yuriy Shkuratov Karri Muinonen Gorden Videen 《Journal of Quantitative Spectroscopy & Radiative Transfer》2006,100(1-3):489-495
We present an analysis of backscattered light by agglomerated debris particles whose size is comparable with the wavelength. We consider agglomerates that consist of one or two large central particles and a few relatively small fragments surrounding the particles. We find that for the particles we studied, the attachment of small fragments onto the particles leads to a decrease of the negative polarization branch (NPB) at small phase angles in comparison with the branch produced by the isolated particles. For relatively large agglomerates (with size parameters x about 25) the internal scatter in the agglomerates may produce a secondary minimum of the NPB. In this case the second order of scatter between constituents of aggregates plays the dominant role. 相似文献
90.
Evgenij Kritchevski 《Annales Henri Poincare》2008,9(4):685-709
We study the eigenvalue statistics for the hieracharchial Anderson model of Molchanov [21–23,27,28]. We prove Poisson fluctuations
at arbitrary disorder, when the the model has a spectral dimension d < 1. The proof is based on Minami’s technique [25] and
we give an elementary exposition of the probabilistic arguments.
Submitted: October 8, 2007. Accepted: December 17, 2007. 相似文献