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Search Results: 1 - 10 of 133712 matches for " V. V. Bel'kov "
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Magneto-gyrotropic effects in semiconductor quantum wells (review)
V. V. Bel'kov,S. D. Ganichev
Physics , 2008, DOI: 10.1088/0268-1242/23/11/114003
Abstract: Magneto-gyrotropic photogalvanic effects in quantum wells are reviewed. We discuss experimental data, results of phenomenological analysis and microscopic models of these effects. The current flow is driven by spin-dependent scattering in low-dimensional structures gyrotropic media resulted in asymmetry of photoexcitation and relaxation processes. Several applications of the effects are also considered.
Photoproduction of neutral pion pairs in the Coulomb field of the nucleus
A. A. Bel'kov,M. Dillig,A. V. Lanyov
Physics , 1995, DOI: 10.1088/0954-3899/23/7/007
Abstract: The total cross section for Coulomb photoproduction of neutral pion pairs in the reaction gamma A --> pi0 pi0 A is estimated within the effective chiral lagrangian approach. The amplitude of gamma gamma* --> pi0 pi0 with one off-shell photon is calculated at O(p^6) in the momentum expansion; in addition, nuclear absorption is taken into account. Besides its experimental feasibility, the results of the calculation demonstrate that the reaction gamma A --> pi0 pi0 A is a powerful source of information on the process gamma gamma --> pi0 pi0 close to threshold.
$γγ\toπ^0π^0$ and $η\toπ^0γγ$ at $O(p^6)$ in the NJL model
A. A. Bel'kov,A. V. Lanyov,S. Scherer
Physics , 1995, DOI: 10.1088/0954-3899/22/10/004
Abstract: We discuss the processes $\gamma\gamma\to\pi^0\pi^0$ and $\eta\to\pi^0 \gamma\gamma$ at $O(p^6)$ in the momentum expansion. The calculation involves tree--level, one--loop and two--loop diagrams of a chiral effective lagrangian which is obtained by a bosonization of the NJL model. The importance of integrating out meson resonances (reduction) is pointed out. Our final results for the total cross section of $\gamma\gamma\to\pi^0\pi^0$ are in good agreement with the experimental data of the Crystal Ball Collaboration. For the width of the $\eta\to\pi^0\gamma\gamma$ decay we obtain the value $0.11$ eV which has to be compared with the experimental value of $(0.84 \pm 0.18)$ eV. Alternatively, taking empirical parameters from a vector--meson--dominance model the prediction for the decay width is $0.35$ eV. We present a prediction for the differential decay probability as a function of $m_{\gamma\gamma}^2/m_\eta^2$.
Calculation of Heat-Kernel Coefficients and Usage of Computer Algebra
A. A. Bel'kov,A. V. Lanyov,A. Schaale
Physics , 1995, DOI: 10.1016/0010-4655(96)00031-8
Abstract: The calculation of heat-kernel coefficients with the classical DeWitt algorithm has been discussed. We present the explicit form of the coefficients up to $h_5$ in the general case and up to $h_7^{min}$ for the minimal parts. The results are compared with the expressions in other papers. A method to optimize the usage of memory for working with large expressions on universal computer algebra systems has been proposed.
Reduction of Vector and Axial--Vector Fields in a Bosonized Nambu--Jona--Lasinio Model
A. A. Bel'kov,A. V. Lanyov,A. Schaale
Physics , 1993,
Abstract: We derive the effective action for pseudoscalar mesons by integrating out vector and axial--vector collective fields in the generating functional of the bosonized NJL--model. The corresponding modifications of the nonlinear effective Lagrangian and the bosonized currents, arising at $O(p^4)$, are discussed.
Radiative Kaon Decays and $CP$ Violation
A. A. Bel'kov,A. V. Lanyov,A. Schaale
Physics , 1993,
Abstract: The amplitudes of $K \rightarrow \pi \gamma^* \rightarrow \pi e^+e^-$ and $K \rightarrow \pi \pi \gamma$ decays have been calculated within chiral Lagrangian approach including higher-order derivative terms and meson loops. The selfconsistency of the simultaneous description of the experimental data on the nonleptonic and radiative kaon decays have been demonstrated. We estimate the effects of ``indirect'' and ``direct'' $CP$-violation in $K^0_L \rightarrow \pi^0 e^+e^-$ decays and discuss $CP$-violating charge asymmetries in $K^{\pm} \rightarrow \pi^{\pm} \pi^0 \gamma$ decays.
A simple topological quantum field theory for manifolds with triangulated boundary
S. I. Bel'kov,I. G. Korepanov,E. V. Martyushev
Mathematics , 2009,
Abstract: We construct a simple finite-dimensional topological quantum field theory for compact 3-manifolds with triangulated boundary.
REGULATION OF ARABIDOPSIS GDH2 NUCLEAR GENE EXPRESSION DEPENDS ON FUNCTIONAL STATE OF MITOCHONDRIA AND CHLOROPLASTS
Garnik E.Yu.,V.I. Tarasenko,V.N. Shmakov,V.I. Bel'kov
Journal of Stress Physiology & Biochemistry , 2012,
Abstract: The results of recent studies indicate that expression of some plant nuclear genes depends on functional state of mitochondria and chloroplasts. We have demonstrated that expression of gdh2 gene encoding beta-subunit of mitochondrial glutamate dehydrogenase depends on a redox state of mitochondrial respiratory chain. Treatment of Arabidopsis thaliana cell culture with respiratory complex III inhibitor antimycin A or complex IV inhibitor KCN led to rapid increase of gdh2 transcript content. Complex I inhibition by rotenone had no influence on the transcript level. We suggest that gdh2 expression responds to changes of redox state of the respiratory chain segment located between complex I and complex III. We suppose that the revealed effect is not due to elevated generation of reactive oxygen species occurring upon the electron transport chain blockage, because cell treatment with hydrogen peroxide and paraquat did not lead to induction of gdh2 expression. Experiments with Arabidopsis green seedlings have demonstrated that gdh2 gene expression and GDH2 enzyme activity decrease strongly in the normal and high light conditions and increase in darkness. Resuming our experiments on different Arabidopsis organs and cell types we generalize that gdh2 expression is maximal when both respiratory and photosynthetic electron transport chains are inhibited, and minimal when both of the electron transport chains are highly active. There are a number of hypotheses which would explain such a regularity. The first one proposes an energetic deficit as a regulatory factor initiating gdh2 gene induction. We assume, however, that sugar starvation or ATP depletion cannot be the main factors in regulation of gdh2 expression, because oxidative phosphorylation uncoupling by FCCP did not mimic the effects of antimycin A or prolonged dark treatment on the gdh2 gene expression. The second hypothesis is developed for chloroplast-to-nucleus signaling and proposes that the regulatory signal can be initiated by redox state of plastoquinone pool and mediated by thylakoid membrane-bound protein kinases. We assume that similar mechanism would exist also in mitochondria-to-nucleus signaling, so that gdh2 expression would depend on redox state of both ubiquinone and plastoquinone pools. This is confirmed by our experiments, in which the involvement of serine/threonine protein kinases in the antimycin-related gdh2 induction was demonstrated as an ultimate step in transduction of the regulatory signal to the nucleus. Abscisic acid and/or pyridine nucleotides ratio changes can also participat
Spin-dependent tunnelling through a symmetric barrier
V. I. Perel',S. A. Tarasenko,I. N. Yassievich,S. D. Ganichev,V. V. Bel'kov,W. Prettl
Physics , 2003, DOI: 10.1103/PhysRevB.67.201304
Abstract: The problem of electron tunnelling through a symmetric semiconductor barrier based on zinc-blende-structure material is studied. The $k^3$ Dresselhaus terms in the effective Hamiltonian of bulk semiconductor of the barrier are shown to result in a dependence of the tunnelling transmission on the spin orientation. The difference of the transmission probabilities for opposite spin orientations can achieve several percents for the reasonable width of the barriers.
Tuning of structure inversion asymmetry by the $δ$-doping position in (001)-grown GaAs quantum wells
V. Lechner,L. E. Golub,P. Olbrich,S. Stachel,D. Schuh,W. Wegscheider,V. V. Bel'kov,S. D. Ganichev
Physics , 2009, DOI: 10.1063/1.3156027
Abstract: Structure and bulk inversion asymmetry in doped (001)-grown GaAs quantum wells is investigated by applying the magnetic field induced photogalvanic effect. We demonstrate that the structure inversion asymmetry (SIA) can be tailored by variation of the delta-doping layer position. Symmetrically-doped structures exhibit a substantial SIA due to impurity segregation during the growth process. Tuning the SIA by the delta-doping position we grow samples with almost equal degrees of structure and bulk inversion asymmetry.
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