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121.
V. V. Gladkii V. A. Kirikov T. R. Volk D. V. Isakov E. S. Ivanova 《Physics of the Solid State》2003,45(11):2171-2177
The dielectric properties of strontium-barium niobate crystals with a strontium concentration of 0.75, which corresponds to the most smeared ferroelectric phase transition, were measured. The dielectric hysteresis loops and the polarization relaxation are shown to exhibit clearly pronounced features characteristic of crystals with structural disorder and a broad distribution of a random internal electric field. The measurements were performed in dc, slowly varying (quasi-static), and pulsed electric fields. The experimental data obtained are used to construct the distribution function for the coercive field in the crystal bulk. 相似文献
122.
We study a model of hard-core bosons with short-range repulsive interactions at half filling on the kagome lattice. Using quantum Monte Carlo numerics, we find that this model shows a continuous superfluid-insulator quantum phase transition, with exponents z=1 and nu approximately 0.67(5). The insulator, I*, exhibits short-ranged density and bond correlations, topological order, and exponentially decaying spatial vison correlations, all of which point to a Z2 fractionalized phase. We estimate the vison gap in I* from the temperature dependence of the energy. Our results, together with the equivalence between hard-core bosons and S=1/2 spins, provide compelling evidence for a spin-liquid phase in an easy-axis spin-1/2 model with no special conservation laws. 相似文献
123.
The paper deals with the problem of recovering the parameters (functions)
and
of the Maxwell dynamical system
(tan is the tangent component;
is a solution) by the response operator
(
is the normal). The parameters determine the velocity
, the c-metric
, and the time
. It is shown that for any fixed
, the operator
determines
and
in
uniquely. Bibliography: 15 titles. 相似文献
124.
I. V. Isakov A. I. Kalyukanov V. L. Volkov R. P. Ozerov L. E. Fykin 《Crystallography Reports》2011,56(3):420-424
The atomic structure of a single crystal of one of four Na0.69WO3 phases, which exist below 293 K, has been refined from neutron diffraction data (WWR-c reactor at the Karpov Institute of Physical Chemistry, Obninsk Branch; λ = 1.168 Å; λ/2 contribution < 0.8%; sinθ/λ ≤ 0.810; T = 288 K; crystal sphere ? = 4.4 mm; cubic unit cell with a = 7.672 Å, sp. gr. Im3, z = 8, μ = 1.9 mm?1). The Na0.69WO3 atomic structure has been refined (198 independent reflections) taking into account the anisotropy of thermal vibrations (R w = 4.0%). The stoichiometric coefficient Na(0.69) is also refined. A structural distortion is revealed, which is characterized by the displacement of oxygen atoms (0, 0.2609(2), 0.2391(2)) from the ideal perovskite positions (0, 1/4, 1/4); this displacement doubles the ideal perovskite lattice period. The oxygen displacements can be described as rotations of oxygen octahedra by 3.58° around the [111] direction. The structure remains cubic because the octahedra rotations with respect to all three perovskite cubic axes are identical. 相似文献
125.
M. I. Kusaikin S. P. Ermakova N. M. Shevchenko V. V. Isakov A. G. Gorshkov A. L. Vereshchagin M. A. Grachev T. N. Zvyagintseva 《Chemistry of Natural Compounds》2010,46(1):1-4
The 1→3;1→6-β-D-glucan chrysolaminaran with molecular weight 8.5 kDa and 3.6:1 ratio of 1→3:1→6 bonds was isolated from cultivated diatom
alga Synedra acus and characterized. It was shown that the isolated chrysolaminaran inhibited growth and colony formation of human colon tumor
cells. 相似文献
126.
127.
128.
G Fuchs K-H Müller J Freudenberger K Nenkov S-L Drechsler SV Shulga D Lipp A Gladun T Cichorek P Gegenwart 《Pramana》2002,58(5-6):791-797
The effect of substitutional disorder on the superconducting properties of YNi2B2C was studied by partially replacing yttrium and nickel by Lu and Pt, respectively. For the two series of (Y, Lu)Ni2B2C and Y(Ni, Pt)2B2C compounds, the upper critical field H
c2(T) and the specific heat c
p(T, H) in the superconducting mixed state have been investigated. Disorder is found to reduce several relevant quantities such
as T
c, the upper critical field H
c2(0) at T=0 and a characteristic positive curvature of H
c2(T) observed for these compounds near T
c. The H
c2(T) data point to the clean limit for (Y, Lu) substitutions and to a transition to the quasi-dirty limit for (Ni, Pt) substitutions.
The electronic specific heat contribution γ(H) exhibits significant deviations from the usual linear γ(H) law. These deviations reduce with growing substitutional disorder but remain even in the quasidirty limit which is reached
in the Y(Ni1−x
, Pt
x
)2B2C samples for x=0.1. 相似文献
129.
130.