Multicomponent diffusion and energy characteristics of partially ionized plasma in the ionosphere of a planet

The problem of energy and multicomponent ambipolar diffusion of plasma in the lower ionosphere of a planet with a weak magnetic field is considered

Quantum interference effects in a system of two tunnel point-contacts in the presence of single scatterer: simulation of a double-tip STM experiment

The conductance of systems containing two tunnel point-contacts and a single subsurface scatterer is investigated theoretically. The problem is solved in the approximation of s-wave scattering giving analytical expressions for the wave functions and for the conductance of the system. Conductance oscillations resulting from the interference of electron waves passing through different contacts and their interference with the waves scattered by the defect are analyzed. The prospect for determining the depth of the impurity below the metal surface by using the dependence of the conductance as a function of the distance between the contacts is discussed. It is shown that the application of an external magnetic field results in Aharonov-Bohm type oscillations in the conductance, the period of which allows detection of the depth of the defect in a double tip STM experiment.Comment: 11 pages, 4 figures, to be published in Fiz. Nizk. Temp. (Low Temp. Phys.), V.37, No.1 (2011) corrected figure

Kinematic power corrections in off-forward hard reactions

We develop a general approach to the calculation of kinematic corrections ~t/Q^2, ~m^2/Q^2 in hard processes which involve momentum transfer from the initial to the final hadron state. As the principal result, the complete expression is derived for the time-ordered product of two electromagnetic currents that includes all kinematic corrections to twist-four accuracy. The results are immediately applicable e.g. to the studies of deeply-virtual Compton scattering.Comment: 4 page

Giant oscillations of the current in a dirty 2D electron system flowing perpendicular to a lateral barrier under magnetic field

The charge transport in a dirty 2-dimensional electron system biased in the presence of a lateral potential barrier under magnetic field is theoretically studied. The quantum tunneling across the barrier provides the quantum interference of the edge states localized on its both sides that results in giant oscillations of the charge current flowing perpendicular to the lateral junction. Our theoretical analysis is in a good agreement with the experimental observations presented in Ref.8. In particular, positions of the conductance maxima coincide with the Landau levels while the conductance itself is essentially suppressed even at the energies at which the resonant tunneling occurs and hence these puzzling observations can be resolved without taking into account the electron-electron interaction.Comment: 6 pages, 4 figure

Exotic hybrid mesons in hard electroproduction

We estimate the sizeable cross section for deep exclusive electroproduction of an exotic $J^{PC}=1^{-+}$ hybrid meson in the Bjorken regime. The production amplitude scales like the one for usual meson electroproduction, i.e. as $1/Q^2$. This is due to the non-vanishing leading twist distribution amplitude for the hybrid meson, which may be normalized thanks to its relation to the energy momentum tensor and to the QCD sum rules technique. The hard amplitude is considered up to next-to-leading order in $\alpha_{S}$ and we explore the consequences of fixing the renormalization scale ambiguity through the BLM procedure. We study the particular case where the hybrid meson decays through a $\pi\eta$ meson pair. We discuss the $\pi\eta$ generalized distribution amplitude and then calculate the production amplitude for this process. We propose a forward-backward asymmetry in the production of $\pi$ and $\eta$ mesons as a signal for the hybrid meson production. We briefly comment on hybrid electroproduction at very high energy, in the diffractive limit where a QCD Odderon exchange mechanism should dominate. The conclusion of our study is that hard electroproduction is a promissing way to study exotic hybrid mesons, in particular at JLAB, HERA (HERMES) or CERN (Compass)

Effect of carbamylated darbepoetin administration at different doses on the thymus and spleen structure of rats

In this article, the morphological features of the structure of the thymus and spleen under the influence of carbamylated darbepoetin in different doses were studied. The material for the study was 40 white male rats of the Wistar bree

Issues of the world economy’s assessment : the demographic factor

The article analyzes the impact of the demographic factor on the prospects for the development of the world economy. The basis of the methodology is an analysis of the dynamics of macro indicators of the world's 10 leading economies, whose contribution exceeds 61% of world GDP. In the article the dynamics of macroeconomic and demographic indicators were analyzed, and their interrelation was established. The study analyzes the dynamics of the world economy. In the course of the study, it was shown that globalization brings not only advantages, but notable threats. The economic growth within the last 21 years led to the accumulation of colossal debts, which in future will become a limitation of the development of the world economy. The article shows that attempts to overcome demographic problems in the last decades did not have any success, and consequently, in the future it will be a barrier to the sustainable development of the world economy.peer-reviewe

Effect of point-contact transparency on coherent mixing of Josephson and transport supercurrents

The influence of electron reflection on dc Josephson effect in a ballistic point contact with transport current in the banks is considered theoretically. The effect of finite transparency on the vortex-like currents near the contact and at the phase difference $\phi =\pi ,$ which has been predicted recently \cite{KOSh}, is investigated. We show that at low temperatures even a small reflection on the contact destroys the mentioned vortex-like current states, which can be restored by increasing of the temperature.Comment: 6 pages, 8 Figures, Latex Fil

On the Selfconsistent Theory of Josephson Effect in Ballistic Superconducting Microconstrictions

The microscopic theory of current carrying states in the ballistic superconducting microchannel is presented. The effects of the contact length L on the Josephson current are investigated. For the temperatures T close to the critical temperature T_c the problem is treated selfconsistently, with taking into account the distribution of the order parameter $\Delta (r)$ inside the contact. The closed integral equation for $\Delta$ in strongly inhomogeneous microcontact geometry ($L\lesssim \xi_{0}, \xi_{0}$ is the coherence length at T=0) replaces the differential Ginzburg-Landau equation. The critical current $I_{c}(L)$ is expressed in terms of solution of this integral equation. The limiting cases of $L\ll \xi_{0}$ and $L\gg \xi_{0}$ are considered. With increasing length L the critical current decreases, although the ballistic Sharvin resistance of the contact remains the same as at L=0. For ultra short channels with $L\lesssim a_{D}$ ($a_{D}\sim v_{F}/\omega_{D}, \omega_{D}$ is the Debye frequency) the corrections to the value of critical current I_c(L=0) are sensitive to the strong coupling effects.Comment: 15 pages LaTex, 3 jpg figure