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931.
The energy spectrum of low-frequency vibrational modes in amorphous polyisobutylene doped with chromophore tetra-tert-butylterrylene molecules has been measured. The technique for measuring the spectra of vibrational modes in solid amorphous media by single-molecule spectroscopy is described. The measured spectrum is compared with the data on the density of vibrational states (bosonic peak) in pure polyisobutylene, which were obtained by inelastic neutron scattering. It is shown that incorporation of small amounts of tetra-tert-butylterrylene into polyisobutylene did not significantly change the low-temperature vibrational dynamics of the matrix. 相似文献
932.
I. B. Krynetskiĭ B. A. Gizhevskiĭ S. V. Naumov E. A. Kozlov 《Physics of the Solid State》2008,50(4):756-758
The temperature dependence of the thermal expansion ΔL/L of samples of high-density nanostructural CuO ceramics with a crystallite size of 20, 70, and 90 nm was measured. The nanoceramics were obtained from coarse-grained CuO powders under converging spherical shock waves. It is found that, at temperatures T > 50 K, the thermal expansion coefficient α(T) of the nanoceramic samples increases with decreasing crystallite sizes and exceeds the value of α(T) of the CuO single crystal by a factor of 3.5 to 4.5. At temperatures T < 50 K, regions with zero and negative values of α(T) were revealed. The possible reasons for the increase in the thermal expansion coefficient of nanoceramics based on 3d-metal oxides are discussed. 相似文献
933.
The effect of structural defects in cobalt and oxygen sublattices with the constant average oxidation level 3+ of all cobalt ions on the magnetic properties of the EuBaCo1.90O5.36 single crystal has been studied. The magnetic properties of the single crystal and the polycrystalline sample of the corresponding composition are compared in the range T = 200–650 K. The results show that the cobalt-deficient EuBaCo2–xO5.5–δ samples demonstrate a three-dimensional XY ferromagnetic ordering of magnetic sublattices. The values of the effective magnetic moment at T > 480 K indicate the existence of the IS and HS states of Co3+ ions. The large difference of values of μeff of the EuBaCo1.90O5.36 single crystal and polycrystal can be due to that the magnetic ion spins lie in plane ab. The magnetic field directed along plane ab substantially influences the magnetic ordering at T < 300 K. 相似文献
934.
Dr. Durga Prasad Karothu Zainab Alhaddad Dr. Christian R. Göb Dr. Christian J. Schürmann Dr. Robert Bücker Prof. Panče Naumov 《Angewandte Chemie (International ed. in English)》2023,62(26):e202303761
Levocetirizine is an orally administrated, second-generation antihistaminic active pharmaceutical ingredient that has been used to treat symptoms of allergy and long-term hives for over 25 years. Despite the wide use of this compound, its crystal structure has remained unknown. Here we report the application of 3D electron diffraction (3D ED)/Micro-crystal electron diffraction (MicroED) to determine the crystal structure of Levocetirizine dihydrochloride directly from crystalline powders that were extracted from commercially available tablets containing the compound. We also showcase the utility of dynamical refinement to unambiguously assign absolute configuration. The results highlight the immense potential of 3D ED/MicroED for structure elucidation of components of microcrystalline mixtures that obviates the need to grow large-size single crystals and the use of complementary analytical techniques, which could be important for identification as well as for primary structural characterization. 相似文献
935.
A. S. Ionkin S. N. Ignat'Eva I. A. Litvinov V. A. Naumov B. A. Arbuzov 《Heteroatom Chemistry》1992,3(4):459-461
A dimer of thioxo-N-t-butylimino(trimethylsiloxy)-phosphorane 5 has been prepared by reaction of tris(trimethylsilyl) phosphine with N-sulfinyl-N-tert-butylamine. The structure of 5 has been confimed by X-ray analysis data. 1-Aza-2-thia-3-phosphaallene 1 , thiaphosphaziridine 3 , iminophosphine P-sulfide 4 are postulated as intermediates of the reaction studied. 相似文献
936.
Ryabov D. S. Chechin G. M. Naumov E. K. Bebikhov Yu. V. Korznikova E. A. Dmitriev S. V. 《Nonlinear dynamics》2023,111(9):8135-8153
Nonlinear Dynamics - All possible one-component delocalized nonlinear vibrational modes (DNVMs) in a square lattice are analyzed. DNVMs are obtained taking into account exclusively the symmetry of... 相似文献