Observation of exchange Coulomb interactions in the quantum Hall state at nu=3

Coulomb exchange interactions of electrons in the nu=3 quantum Hall state are determined from two inter-Landau level spin-flip excitations measured by resonant inelastic light scattering. The two coupled collective excitations are linked to inter-Landau level spin-flip transitions arising from the N=0 and N=1 Landau levels. The strong repulsion between the two spin-flip modes in the long-wave limit is clearly manifested in spectra displaying Coulomb exchange contributions that are comparable to the exchange energy for the quantum Hall state at nu=1. Theoretical calculations within the Hartree-Fock approximation are in a good agreement with measured energies of spin-flip collective excitations.Comment: 5 pages, 3 figures, to appear in PRB Rapid Communication

X-ray Diffraction Study of Superstructure in GdBaCo2O5.5

A single crystal of GdBaCo2O5.47(2) has been studied by means of X-ray diffraction. Appearance of superstructure reflections at T = 341.5(7) K gives an evidence of continuous transition to the phase with unit cell doubled along the shortest edge a1. Critical exponent for the order parameter is found to be beta=0.33(1). The superstructure reflections are about 2-4 orders of magnitude weaker than the basic ones. Their systematic extinction indicates the crystal symmetry change from Pmmm to Pmma. The integrated intensities allow to calculate displacements of atoms from the positions in the high-temperature phase. The cobalt-ligand distances in the ordered phase are discussed in terms of the spin-state/orbital ordering of Co3+ ions.Comment: 4 page

Development of High Granulated Straw Chambers of Large Sizes

We have developed the baseline design for the straw drift tube tracking detectors for high rate environment application. The low-mass inner straw elements and the technology of the multianode straws assembly was devised and checked. The prototype chamber was constructed and studied the granularity of similar chambers can be reduced to one cm2. Submitted to Physics of Elementary Particles and Atomic Nuclei, LettersComment: 6 pages, 10 figure

Inhibition of Horse Liver Alcohol Dehydrogenase by Methyltin Compounds

The study of inorganic tin (SnCl2, SnCl4) and methyltin compounds (MeSnCl3, Me2SnCI2, Me3SnCl) effects on the enzymatic activity of alcohol dehydrogenase (ADH) in the reaction of ethanol oxidation has been carried out. The experimental results of the study show that inorganic tin and methyltin substances induce slight inhibition of the catalytic activity of horse liver alcohol dehydrogenase (HLADH), unable to be improved during pre-incubation with the enzyme. The conditions for carrying out the kinetic investigation of the mentioned phenomenon were optimized and as it turned out the mechanism of methyltin trichloride action, as the most effective methyltin inhibitor, is more complex than the proposed interaction of the metal atom with SH-groups of the enzyme protein. It was demonstrated that the tin compounds act in the same manner as methylmercury compounds and might serve as oxidative agents towards the co-enzyme NADH. Kinetic data on MeSnCl3 were calculated. Data acquired on NAD-dependent ADH from horse liver and those regarding NAD-dependent LDH from sturgeon liver were compared

Innovative approaches in assessing social and economic damage from road accidents

The article is devoted to the review of approaches and analysis of methods for assessing the cost of social and economic damage from road accidents. The urgency of the problem is determined by the high rates of accidents and deaths. Social and economic consequences of non-underestimation of human life in the country can negatively affect the individual quality of life of Russians, and state level in the form of damage from losses of the economically active population and the state's compensation for damages to the families of victims. Therefore, the development of new theoretical approaches to assess social and economic damage from accidents, which meet modern conditions, has become of particular relevance in Russia. The article considers methodological peculiarities of accounting and assessment of the consequences of road accidents both within the framework of international experience and within the framework of the Russian Federation, which has allowed developing scientifically grounded approach to assessing damage from road accidents in our country, this in its turn contributes to reducing mortality rates through development and financial support of road safety programs. Based on the author's research, an innovative approach to assessing social and economic losses from road accidents in the Russian Federation has been formed, which focuses on damage resulting from death and injury of people, taking into account age and gender structure of the deceased, wounded people and regional characteristics, damage as a result of damage to vehicles and goods, damage as a result of damage to roads and road structures, as well as moral damage.peer-reviewe

Observation of Spin Relaxation Anisotropy in Semiconductor Quantum Wells

Spin relaxation of two-dimensional electrons in asymmetrical (001) AlGaAs quantum wells are measured by means of Hanle effect. Three different spin relaxation times for spins oriented along [110], [1-10] and [001] crystallographic directions are extracted demonstrating anisotropy of D'yakonov-Perel' spin relaxation mechanism. The relative strengths of Rashba and Dresselhaus terms describing the spin-orbit coupling in semiconductor quantum well structures. It is shown that the Rashba spin-orbit splitting is about four times stronger than the Dresselhaus splitting in the studied structure.Comment: 4 pages, 3 figure

Radioactivity and Electron Acceleration in Supernova Remnants

We argue that the decays of radioactive nuclei related to $^{44}$Ti and $^{56}$Ni ejected during supernova explosions can provide a vast pool of mildly relativistic positrons and electrons which are further accelerated to ultrarelativistic energies by reverse and forward shocks. This interesting link between two independent processes - the radioactivity and the particle acceleration - can be a clue for solution of the well known theoretical problem of electron injection in supernova remnants. In the case of the brightest radio source Cas A, we demonstrate that the radioactivity can supply adequate number of energetic electrons and positrons for interpretation of observational data provided that they are stochastically pre-accelerated in the upstream regions of the forward and reverse shocks.Comment: 6 pages, 1 figure, revised version accepted to Phys.Rev.

Rashba coupling in quantum dots: exact solution

We present an analytic solution to the problem of the Rashba spin-orbit coupling in semiconductor quantum dots. We calculate the exact energy spectrum, wave-functions, and spin--flip relaxation times. We discuss various effects inaccessible via perturbation theory. In particular, we find that the effective gyromagnetic ratio is strongly suppressed by the spin-orbit coupling. The spin-flip relaxation rate has a maximum as a function of the spin-orbit coupling and is therefore suppressed in both the weak- and strong coupling limits.Comment: 5 pages, 4 figs, reference adde

Slowing down of spin relaxation in two dimensional systems by quantum interference effects

The effect of weak localization on spin relaxation in a two-dimensional system with a spin-split spectrum is considered. It is shown that the spin relaxation slows down due to the interference of electron waves moving along closed paths in opposite directions. As a result, the averaged electron spin decays at large times as $1/t$. It is found that the spin dynamics can be described by a Boltzmann-type equation, in which the weak localization effects are taken into account as nonlocal-in-time corrections to the collision integral. The corrections are expressed via a spin-dependent return probability. The physical nature of the phenomenon is discussed and it is shown that the "nonbackscattering" contribution to the weak localization plays an essential role. It is also demonstrated that the magnetic field, both transversal and longitudinal, suppresses the power tail in the spin polarization.Comment: 12 pages, 2 figure

Triplet pairing due to spin-orbit-assisted electron-phonon coupling

We propose a microscopic mechanism for triplet pairing due to spin-orbit-assisted electron interaction with optical phonons in a crystal with a complex unit cell. Using two examples of electrons with symmetric Fermi surfaces in crystals with either a cubic or a layered square lattice, we show that spin-orbit-assisted electron-phonon coupling can, indeed, generate triplet pairing and that, in each case, it predetermines the tensor structure of a p-wave order parameter