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Search Results: 1 - 10 of 401180 matches for " M. Jouravlev "
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Modelling of light driven CO2 concentration gradient and photosynthetic carbon assimilation flux distribution at the chloroplast level
M. Jouravlev
Quantitative Biology , 2012,
Abstract: The steady state of the two-substance model of light driven carbon turnover for the photosynthetic CO2 assimilation rate is presented. The model is based on the nonlinear diffusion equation for a single chloroplast in the elliptical geometry by assuming light driven Ribulose-1,5-bisphosphate (RuBP) regeneration and CO2 assimilation reaction of carboxilation coupled with the photosynthetic sink strength. The detailed analysis of 3 -dimensional CO2 concentration and flux on the chloroplast level is made. It is shown that under intense light irradiation there exists a boundary layer of chloroplasts with a high value of CO2 assimilation flux. The presented simplified model can be used for the calculations and experimental estimations of the CO2 assimilation rate for environmental applications.
Asymptotic estimations of power thresholds and anti-Stokes frequency of laser induced thermal scattering in microresonators
M. V. Jouravlev
Physics , 2007,
Abstract: A derivation of the asymptotic expressions for the threshold intensity of laser induced thermal scattering in silica microresonator when illuminated with a plane wave is present. The calculation of anti-Stokes thermal combination frequencies are made for the spherical high Q-factor microresonators. The three modes regime of nonlinear interaction is considered. One pump-driven, two signal modes, and one mode of temperature relaxation are taken into account, satisfying morphology-dependent input and output resonances. There are low power thresholds for laser induced thermal scattering at morphology dependent resonances.
Power thresholds of morphology dependent induced thermal scattering in silica microresonators
M. V. Jouravlev
Physics , 2007,
Abstract: Induced thermal scattering power thresholds have been calculated as a function of size and laser pump frequency. The thermal coupling coefficients of morphology dependent resonances were estimated by asymptotic methods. The resulting power threshold is comparable with experimental observations of thresholds of Raman lasing and thermal instability in spherical silica resonators. Applications may include the remote measurement of the temperature of aerosol droplets and the stabilization of microcavity lasers against thermal oscillations and temperature deviations on microcavity. A silica resonator can be used as an IR sensor, as well as an additional tool for precisely measuring the thermal conductivity and heat capacity of a target in a microsphere by calculating of the thermal shifts of eigenfrequencies in spectra of nonlinear scattering.
Nonstationary theory of magnetic field induced current for molecular spin nanojunction
M. Jouravlev,Kwang S. Kim
Physics , 2009,
Abstract: For the study of molecular spin junctions, we take into account two types of couplings between the molecule and the metal leads: (i) electron transfer that gives rise to net current in the biased junction and (ii) energy transfer between the molecule and the leads. Using a rotating wave approximation in the Heisenberg representation, we derive a set of differential equations for the expectation values of relevant variables: electron and phonon populations and molecular polarization. A magnetic field control method to enhance the charge transfer at spin nanojunctions, which characterizes the molecule feature, is discussed. An approximate analytical solution of the resulting dynamical equation is supported by numerical solution. The magnetic control by charge transfer is described by transient pseudo-fermions of electrons interacting with spins. The rapid adiabatic passage of the energy between the molecule and the leads is taken into account. The current for molecular spin nanojunctions is derived.
Theory of light-induced current in molecular-tunneling junctions excited with intense shaped pulses
B. D. Fainberg,M. Jouravlev,A. Nitzan
Physics , 2007, DOI: 10.1103/PhysRevB.76.245329
Abstract: A theory for light-induced current by strong optical pulses in molecular-tunneling junctions is described. We consider a molecular bridge represented by its highest occupied and lowest unoccupied levels, HOMO and LUMO, respectively. We take into account two types of couplings between the molecule and the metal leads: electron transfer that gives rise to net current in the biased junction and energy transfer between the molecule and electron-hole excitations in the leads. Using a Markovian approximation, we derive a closed system of equations for the expectation values of the relevant variables: populations and molecular polarization that are binary, and exciton populations that are tetradic in the annihilation and creation operators for electrons in the molecular states. We have proposed an optical control method using chirped pulses for enhancing charge transfer in unbiased junctions where the bridging molecule is characterized by a strong charge-transfer transition. An approximate analytical solution of the resulting dynamical equation is supported by a full numerical solution. When energy transfer between the molecule and electron-hole excitations in the leads is absent, the optical control problem for inducing charge transfer with linearly chirped pulse can be reduced to the Landau-Zener transition to a decaying level. When chirp is fast with respect to the rate of the electron transfer, the Landau theory is recovered. The proposed control mechanism is potentially useful for developing novel opto-electronic single-electron devices with optical gating based on molecular nanojunctions.
Enhanced Fullerene Yield in Plasma-Aerosol Reactor at Cryogenic Boundary Temperature
Mikhail Jouravlev
Physics , 2011,
Abstract: We demonstrate remarkably enhanced yield of C60 fullerenes in an aerosol discharge chamber due to the additional presence of a strong spatial temperature gradient. The role of the temperature gradients in the increased yield of C60 and fullerene-like structures is discussed. The reaction is not fully reversible and carbon soot matter is formed as a secondary product in the form of carbon aerosol particles. The increasing concentration of C60 was easily recognized from the characteristic UV-spectra. The result of this paper will be useful for improvement of fullerene synthesis technology and for application to constructing new types of aerosol-plasma reactors.
Statistics of Transmission Eigenvalues for a Disordered Quantum Point Contact
G. Campagnano,O. N. Jouravlev,Ya. M. Blanter,Yu. V. Nazarov
Physics , 2004, DOI: 10.1103/PhysRevB.69.235319
Abstract: We study the distribution of transmission eigenvalues of a quantum point contact with nearby impurities. In the semi-classical case (the chemical potential lies at the conductance plateau) we find that the transmission properties of this system are obtained from the ensemble of Gaussian random reflection matrices. The distribution only depends on the number of open transport channels and the average reflection eigenvalue and crosses over from the Poissonian for one open channel to the form predicted by the circuit theory in the limit of large number of open channels.
Electron Transport in Double Quantum Dot governed by Nuclear Magnetic Field
Oleg N. Jouravlev,Yuli V. Nazarov
Physics , 2005, DOI: 10.1103/PhysRevLett.96.176804
Abstract: We investigate theoretically electron transfer in a doble dot in a situation where it is governed by nuclear magnetic field: This has been recently achieved in experiment. We show how to partially compensate the nuclear magnetic field to restore Spin Blockade.
Coherent oscillations of current due to nuclear spins
Sigurdur I. Erlingsson,Oleg N. Jouravlev,Yuli V. Nazarov
Physics , 2003,
Abstract: We propose a mechanism for very slow coherent oscillations of current and nuclear spins in a quantum dot system, that may qualitatively explain some recent experimental observations. We concentrate on an experimentally relevant double dot setup where hyperfine interaction lifts the spin blockade. We study the dependence of the magnitude and period of the oscillations on magnetic field and anisotropy.
Efficient Magnetization Reversal with Noisy Currents
Wouter Wetzels,Gerrit E. W. Bauer,Oleg N. Jouravlev
Physics , 2005, DOI: 10.1103/PhysRevLett.96.127203
Abstract: We propose to accelerate reversal of the ferromagnetic order parameter in spin valves by electronic noise. By solving the stochastic equations of motion we show that the current-induced magnetization switching time is drastically reduced by a modest level of externally generated current (voltage) noise. This also leads to a significantly lower power consumption for the switching process.
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