306 research outputs found
Landau damping in thin films irradiated by a strong laser field
The rate of linear collisionless damping (Landau damping) in a classical
electron gas confined to a heated ionized thin film is calculated. The general
expression for the imaginary part of the dielectric tensor in terms of the
parameters of the single-particle self-consistent electron potential is
obtained. For the case of a deep rectangular well, it is explicitly calculated
as a function of the electron temperature in the two limiting cases of specular
and diffuse reflection of the electrons from the boundary of the
self-consistent potential. For realistic experimental parameters, the
contribution of Landau damping to the heating of the electron subsystem is
estimated. It is shown that for films with a thickness below about 100 nm and
for moderate laser intensities it may be comparable with or even dominate over
electron-ion collisions and inner ionization.Comment: 15 pages, 2 figure
New insight into the low-energy He spectrum
The spectrum of He was studied by means of the He(,)He
reaction at a lab energy of 25 MeV/n and small center of mass (c.m.) angles.
Energy and angular correlations were obtained for the He decay products by
complete kinematical reconstruction. The data do not show narrow states at
1.3 and 2.4 MeV reported before for He. The lowest resonant
state of He is found at about 2 MeV with a width of 2 MeV and is
identified as . The observed angular correlation pattern is uniquely
explained by the interference of the resonance with a virtual state
(limit on the scattering length is obtained as fm), and with
the resonance at energy MeV.Comment: 5 pages, 4 figures, 2 table
10He low-lying states structure uncovered by correlations
The 0+ ground state of the 10He nucleus produced in the 3H(8He,p)10He
reaction was found at about MeV (\Gamma ~ 2 MeV) above the
three-body 8He+n+n breakup threshold. Angular correlations observed for 10He
decay products show prominent interference patterns allowing to draw
conclusions about the structure of low-energy excited states. We interpret the
observed correlations as a coherent superposition of the broad 1- state having
a maximum at energy 4-6 MeV and the 2+ state above 6 MeV, setting both on top
of the 0+ state "tail". This anomalous level ordering indicates that the
breakdown of the N=8 shell known in 12Be thus extends also to the 10He system.Comment: 5 pages, 5 figure
Three-body correlations in direct reactions: Example of Be populated in reaction
The Be continuum states were populated in the charge-exchange reaction
H(Li,Be) collecting very high statistics data ( events) on the three-body ++ correlations. The
Be excitation energy region below MeV is considered, where the
data are dominated by contributions from the and states. It is
demonstrated how the high-statistics few-body correlation data can be used to
extract detailed information on the reaction mechanism. Such a derivation is
based on the fact that highly spin-aligned states are typically populated in
the direct reactions.Comment: submitted to Physical Review
High magnetic fields thermodynamics of heavy fermion metal YbRh2Si2
We perform comprehensive theoretical analysis of high magnetic field behavior
of the heavy-fermion (HF) compound YbRh2Si2. At low magnetic fields B, YbRh2Si2
has a quantum critical point related to the suppression of antiferromagnetic
ordering at a critical magnetic field. Our calculations of the thermodynamic
properties of YbRh2Si2 in wide magnetic field range allow us to straddle a
possible metamagnetic transition region and probe the properties of both
low-field HF liquid and high-field fully polarized one. Namely, high magnetic
fields B\sim B^*\sim 10 T fully polarize corresponding quasiparticle band
generating Landau Fermi liquid (LFL) state and suppressing HF (actually NFL)
one, while at elevating temperatures both HF state and corresponding NFL
properties are restored. Our calculations are in good agreement with
experimental facts and show that the fermion condensation quantum phase
transition is indeed responsible for the observed NFL behavior and
quasiparticles survive both high temperatures and high magnetic fields.Comment: 6 pages, 7 figure
Violent solar events of October-November 2003 as recorded by IZMIRAN radio observations
The extreme solar activity of October-November 2003 was recorded at IZMIRAN with digital radiospectrographs at 25-270 MHz and fixed-frequency radiometers at 169, 204 and 3000 MHz. An outstanding metre-wavelength noise storm took place during the fist passage of the grandiose evolving active complex across the disc which testifies to permanent electron acceleration over the complex with energy of up to tens of kiloelectronvolts. Against this background, intense metric and microwave radio bursts were recorded in association with several outstanding flare and huge coronal mass ejection (CME) events. The dynamic spectra of these events display multiband and sometimes fine-structure type II bursts, initiated by coronal shocks, and various continuum emissions. In some cases, a corresponding microwave burst at 3000 MHz includes not only an impulsive component coinciding with a flare maximum but also a predominating delayed long-duration component with a smooth time profile. The latter component is thought to be linked with a post-eruptive energy release and particle acceleration when the magnetic field, strongly disturbed by a CME, relaxes to a new quasi-equilibrium configuration via reconnection in high coronal levels
\b{eta}-delayed three-proton decay of 31Ar
The beta decay of 31Ar, produced by fragmentation of a 36Ar beam at 880
MeV/nucleon, was investigated. Identified ions of 31Ar were stopped in a
gaseous time projection chamber with optical readout allowing to record decay
events with emission of protons. In addition to \b{eta}-delayed emission of one
and two protons we have clearly observed the beta-delayed three-proton branch.
The branching ratio for this channel in 31Ar is found to be 0.07(2)%.Comment: 5 pages, 3 figures, submitted to Physical Rev.
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Ozone climatology using interactive chemistry: results from the Canadian Middle Atmosphere Model
The climatology of ozone produced by the Canadian Middle Atmosphere Model (CMAM) is presented. This three-dimensional global model incorporates the radiative feedbacks of ozone and water vapor calculated on-line with a photochemical module. This module includes a comprehensive gas-phase reaction set and a limited set of heterogeneous reactions to account for processes occurring on background sulphate aerosols. While transport is global, photochemistry is solved from about 400 hPa to the top of the model at ∼95 km. This approach provides a complete and comprehensive representation of transport, emission, and photochemistry of various constituents from the surface to the mesopause region. A comparison of model results with observations indicates that the ozone distribution and variability are in agreement with observations throughout most of the model domain. Column ozone annual variation is represented to within 5–10% of the observations except in the Southern Hemisphere for springtime high latitudes. The vertical ozone distribution is generally well represented by the model up to the mesopause region. Nevertheless, in the upper stratosphere, the model generally underestimates the amount of ozone as well as the latitudinal tilting of ozone isopleths at high latitude. Ozone variability is analyzed and compared with measurements. The comparison shows that the phase and amplitude of the seasonal variation as well as shorter timescale variations are well represented by the model at various latitudes and heights. Finally, the impact of incorporating ozone radiative feedback on the model climatology is isolated. It is found that the incorporation of ozone radiative feedback results in a cooling of ∼8 K in the summer stratopause region, which corrects a warm bias that results when climatological ozone is used
Multiphoton detachment of electrons from negative ions
A simple analytical solution for the problem of multiphoton detachment from
negative ions by a linearly polarized laser field is found. It is valid in the
wide range of intensities and frequencies of the field, from the perturbation
theory to the tunneling regime, and is applicable to the excess-photon as well
as near-threshold detachment. Practically, the formulae are valid when the
number of photons is greater than two. They produce the total detachment rates,
relative intensities of the excess-photon peaks, and photoelectron angular
distributions for the hydrogen and halogen negative ions, in agreement with
those obtained in other, more numerically involved calculations in both
perturbative and non-perturbative regimes. Our approach explains the extreme
sensitivity of the multiphoton detachment probability to the asymptotic
behaviour of the bound-state wave function. Rapid oscillations in the angular
dependence of the -photon detachment probability are shown to arise due to
interference of the two classical trajectories which lead to the same final
state after the electron emerges at the opposite sides of the atom when the
field is close to maximal.Comment: 27 pages, Latex, and PostScript figures fig1.ps, fig2.ps, fig3.ps,
accepted for publication in Phys. Rev.
Problems of semiotics of diseases of the Achilles tendon in clinical and educational aspects
Achilles tendon disorders are represented by a big group of heterogenous in etiology and pathogenesis conditions, that are quite frequent in patients of various age groups. The diversity of this group of orthopedic disorders and the insufficient information provided on this topic in specialized literature leads to confusion in terminology, which, in turn, leads to misunderstanding the essence of patient’s problem and to mistakes in treatment of such patients.We carried out a content-analysis of contemporary Russian and foreign literature to summarize the existing knowledge and to create the universal nomenclature of the studied pathological conditions for further correct understanding of the problem and creation of classification of disorders and injuries of Achilles tendon
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