115 research outputs found
Investigation of X-radiation of the moon by means of the lunar satellite ''Luna-10''
Lunik-10 observations of lunar X ray
Calculation of the Raman G peak intensity in monolayer graphene: role of Ward identities
The absolute integrated intensity of the single-phonon Raman peak at 1580
cm^{-1} is calculated for a clean graphene monolayer. The resulting intensity
is determined by the trigonal warping of the electronic bands and the
anisotropy of the electron-phonon coupling, and is proportional to the second
power of the excitation frequency. The main contribution to the process comes
from the intermediate electron-hole states with typical energies of the order
of the excitation frequency, contrary to what has been reported earlier. This
occurs because of strong cancellations between different terms of the
perturbation theory, analogous to Ward identities in quantum electrodynamics
X-radiation of the moon and Roentgen cosmic background according to data of AMS ''Luna-12''
Satellite measurements of lunar soft X radiation, and Roentgen cosmic backgroun
Image and Spectrum of the Sun in the Region 9.5-200 Angstrom
Short wave ultraviolet image and spectrum of sun obtained during course of X-ray flar
Study of the soft corpuscular radiation on the AMS ''Luna-10''
Lunar-10 measurements of soft corpuscular radiatio
Formation of the internal structure of solids under severe action
On the example of a particular problem, the theory of vacancies, a new form
of kinetic equations symmetrically incorporation the internal and free energies
has been derived. The dynamical nature of irreversible phenomena at formation
and motion of defects (dislocations) has been analyzed by a computer
experiment. The obtained particular results are extended into a thermodynamic
identity involving the law of conservation of energy at interaction with an
environment (the 1st law of thermodynamics) and the law of energy
transformation into internal degree of freedom (relaxation). The identity is
compared with the analogous Jarzynski identity. The approach is illustrated by
simulation of processes during severe plastic deformation, the Rybin kinetic
equation for this case has been derived.Comment: 9 pages, 5 figure
Dispersion of Ripplons in Superfluid 4he
A detailed study of the dispersion law of surface excitations in liquid \hef
at zero temperature is presented, with special emphasis to the short wave
length region. The hybridization mechanism between surface and bulk modes is
discussed on a general basis, investigating the scattering of slow rotons from
the surface. An accurate density functional, accounting for backflow effects,
is then used to determine the dispersion of both bulk and surface excitations.
The numerical results are close to the experimental data obtained on thick
films and explicitly reveal the occurrence of important hybridization effects
between ripplons and rotons.Comment: 23 pages, REVTEX 3.0, 11 figures upon request, UTF-326/9
Transport coefficients of O(N) scalar field theories close to the critical point
We investigate the critical dynamics of O(N)-symmetric scalar field theories
to determine the critical exponents of transport coefficients as a second-order
phase transition is approached from the symmetric phase. A set of stochastic
equations of motion for the slow modes is formulated, and the long wavelength
dynamics is examined for an arbitrary number of field components, , in the
framework of the dynamical renormalization group within the
expansion. We find that for a single component scalar field theory, N=1, the
system reduces to the model C of critical dynamics, whereas for the model
G is effectively restored owing to dominance of O(N)-symmetric charge
fluctuations. In both cases, the shear viscosity remains finite in the critical
region. On the other hand, we find that the bulk viscosity diverges as the
correlation length squared, for N=1, while it remains finite for .Comment: revised for publication in PR
North-Westward Expansion of the Invasive Range of Emerald Ash Borer, Agrilus planipennis Fairmaire (Coleoptera: Buprestidae) towards the EU: From Moscow to Saint Petersburg
Agrilus planipennis is a devastating invasive pest of ash trees in European Russia, Ukraine, and North America. To monitor the north-western limit of its European invasive range, in June 2018 we established 10 study plots along the federal highway M10 (Russia) that runs between Moscow and Saint Petersburg through Tver' City (approx. 180 km from Moscow), and lined with ash trees. On each plot, 2-4 Fraxinus pennsylvanica trees with heights ranging 6.1-17.0 m and diameters ranging 7.0-18.0 cm were girdled, i.e., 50 cm of their bark were removed. The study plots were visited and girdled trees were examined in September and November, 2018, and in October, 2019. Observations revealed that the current continuous north-western limit of A. planipennis range in European Russia coincides with the north-western border of Tver' City and this range limit has not distinctly shifted north-westward during 2015-2019. In spite of the rich food supply (due to abundant F. pennsylvanica and F. excelsior plantings) in Tver' City and along roads going to and from, the population density of A. planipennis in the area is currently low. Recent (September 2020) sudden detection of a spatially isolated A. planipennis outbreak approx. 520 km far north-westward from Tver' (in Saint Petersburg) suggested that A. planipennis most likely had arrived at Saint Petersburg not by gradual stepwise (flying tree-to-tree) expansion of its continuous invasive range in Tver' City, but as a result of its accidental introduction by means of, e.g., "insect-hitchhiked" vehicles, transported plants for planting, and/or other commodities. The proximity of the reported A. planipennis outbreak to the borders of the EU (approx. 130 km to Estonia and Finland) requires urgent measures for its containment and control, and constant monitoring
Theory of resonant multiphonon Raman scattering in graphene
We present a detailed calculation of intensities of two-phonon and
four-phonon Raman peaks in graphene. Writing the low-energy hamiltonian of the
interaction of electrons with the crystal vibrations and the electromagnetic
field from pure symmetry considerations, we describe the system in terms of
just a few independent coupling constants, considered to be parameters of the
theory. The electron scattering rate is introduced phenomenologically as
another parameter. The results of the calculation are used to extract
information about these parameters from the experimentally measured Raman peak
intensities.Comment: 49 pages, 25 figure
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