957 research outputs found
Kohn anomalies in momentum dependence of magnetic susceptibility of some three-dimensional systems
We study a question of presence of Kohn points, yielding at low temperatures
non-analytic momentum dependence of magnetic susceptibility near its maximum,
in electronic spectum of some three-dimensional systems. In particular, we
consider one-band model on face centered cubic lattice with hopping between
nearest and next-nearest neighbors, which models some aspects of the dispersion
of ZrZn, and the two-band model on body centered cubic lattice, modeling
the dispersion of chromium. For the former model it is shown that Kohn points
yielding maxima of susceptibility exist in a certain (sufficiently wide) region
of electronic concentrations; the dependence of the wave vectors, corresponding
to the maxima, on the chemical potential is investigated. For the two-band
model we show existence of the lines of Kohn points, yielding maximum of the
susceptibility, which position agrees with the results of band structure
calculations and experimental data on the wave vector of antiferromagnetism of
chromium.Comment: 13 pages, 9 figures. JETP, in press (2017
Foster care in Russia: problems and prospects
This paper discusses the process of development and functioning of foster families, one of the priority interventions for children without parental care in Russia. The author analyzes the main barriers to the development of foster care in Russia on the basis of national surveys; identifies obstacles to the development of foster care in the country and the necessity of its active implementation in domestic social practice
Hybridization and spin-orbit coupling effects in quasi-one-dimensional spin-1/2 magnet Ba3Cu3Sc4O12
We study electronic and magnetic properties of the quasi-one-dimensional
spin-1/2 magnet Ba3Cu3Sc4O12 with a distinct orthogonal connectivity of CuO4
plaquettes. An effective low-energy model taking into account spin-orbit
coupling was constructed by means of first-principles calculations. On this
basis a complete microscopic magnetic model of Ba3Cu3Sc4O12, including
symmetric and antisymmetric anisotropic exchange interactions, is derived. The
anisotropic exchanges are obtained from a distinct first-principles numerical
scheme combining, on one hand, the local density approximation taking into
account spin-orbit coupling, and, on the other hand, projection procedure along
with the microscopic theory by Toru Moriya. The resulting tensors of the
symmetric anisotropy favor collinear magnetic order along the structural chains
with the leading ferromagnetic coupling J1 = -9.88 meV. The interchain
interactions J8 = 0.21 meV and J5 = 0.093 meV are antiferromagnetic. Quantum
Monte Carlo simulations demonstrated that the proposed model reproduces the
experimental Neel temperature, magnetization and magnetic susceptibility data.
The modeling of neutron diffraction data reveals an important role of the
covalent Cu-O bonding in Ba3Cu3Sc4O12.Comment: 11 pages, 12 figure
Physics Reach of High-Energy and High-Statistics IceCube Atmospheric Neutrino Data
This paper investigates the physics reach of the IceCube neutrino detector
when it will have collected a data set of order one million atmospheric
neutrinos with energies in the 0.1 \sim 10^4 TeV range. The paper consists of
three parts. We first demonstrate how to simulate the detector performance
using relatively simple analytic methods. Because of the high energies of the
neutrinos, their oscillations, propagation in the Earth and regeneration due to
\tau decay must be treated in a coherent way. We set up the formalism to do
this and discuss the implications. In a final section we apply the methods
developed to evaluate the potential of IceCube to study new physics beyond
neutrino oscillations. Not surprisingly, because of the increased energy and
statistics over present experiments, existing bounds on violations of the
equivalence principle and of Lorentz invariance can be improved by over two
orders of magnitude. The methods developed can be readily applied to other
non-conventional physics associated with neutrinos.Comment: 21 pages, 7 figures, Revtex
Highly mobile carriers in orthorhombic phases of iron-based superconductors FeSeS
The field and temperature dependencies of the longitudinal and Hall
resistivity have been measured for FeSeS (x=0.04, 0.09 and
0.19) single crystals. The sample FeSeS does not show a
transition to an orthorhombic phase and exhibits at low temperatures the
transport properties quite different from those of orthorhombic samples. The
behavior of FeSeS is well described by the simple two
band model with comparable values of hole and electron mobility. In particular,
at low temperatures the transverse resistance shows a linear field dependence,
the magnetoresistance follow a quadratic field dependence and obeys to Kohler's
rule. In contrast, Kohler's rule is strongly violated for samples having an
orthorhombic low temperature structure. However, the transport properties of
the orthorhombic samples can be satisfactory described by the three band model
with the pair of almost equivalent to the tetragonal sample hole and electron
bands, supplemented with the highly mobile electron band which has two order
smaller carrier number. Therefore, the peculiarity of the low temperature
transport properties of the orthorhombic Fe(SeS) samples, as probably of many
other orthorhombic iron superconductors, is due to the presence of a small
number of highly mobile carriers which originate from the local regions of the
Fermi surface, presumably, nearby the Van Hove singularity points
Dynamical lattice instability versus spin liquid state in a frustrated spin chain system
The low-dimensional s=1/2 compound (NO)[Cu(NO3)3] has recently been suggested
to follow the Nersesyan-Tsvelik model of coupled spin chains. Such a system
shows unbound spinon excitations and a resonating valence bond ground state due
spin frustration. Our Raman scattering study demonstrates phonon anomalies as
well as the suppression of a broad magnetic scattering continuum for
temperatures below a characteristic temperature, T<T*=100K. We interpret these
effects as evidence for a dynamical interplay of spin and lattice degrees of
freedom that might lead to a further transition into a dimerized or
structurally distorted phase at lower temperatures.Comment: 5 pages, 6 figure
Preclinical manifestations of students’ eating disorders as an impact of the information and communication university environment
Students’ eating disorders include conditions and diseases characterized by irregular foods intake accomplished by stable anxiety effect regarding the mass and shape of their bodies. Information and communicative university environment is able to create a motivation for eating disorders, which damages individual’s health and well-being. The most typical forms of students’ eating disorders affected both girls and boys, are nervous bulimia and anorexia nervos
The incarnation of the Nersesyan-Tsvelik model in (NO)[Cu(NO3)3]
The topology of the magnetic interactions of the copper spins in the
nitrosonium nitratocuprate (NO)[Cu(NO3)3] suggests that it could be a
realization of the Nersesyan-Tsvelik model, whose ground state was argued to be
either a resonating valence bond (RVB) state or a valence bond crystal (VBC).
The measurement of thermodynamic and resonant properties reveals a behavior
inherent to low dimensional spin S = 1/2 systems and provides indeed no
evidence for the formation of long-range magnetic order down to 1.8 K.Comment: 12 pages, 6 figure
Social interaction as a factor of elderly and disabled peoples activity in receiving cardiovascular health services in Russia
The article presents the results of studying the peculiarities of the social interaction and its influence on the social activity of the elderly and disabled people in receiving cardiovascular health services in the Russian Federation. In order to study the level of knowledge about cardiovascular health and the prevention of cardiovascular diseases in February – June, 2018 the sociological research was conducted in Belgorod region (Russia) among elderly and disabled (n=240) by Laboratory of social projects of the Belgorod National Research University. The main research methods were qualitative (content analysis of individual social rehabilitation maps of the elderly and disabled) and quantitative methods (questionnaires
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