Faculty of Physics
M.V.Lomonosov Moscow State University
Theoretical and mathematical physics

## Ionization of a two-dimensional quantum dot by the field of an electromagnetic wave

### P.A. Eminov$^{1,2}$, S.V. Gordeeva

Moscow University Physics Bulletin 2013. 68. N 4. P. 267

The process of ionization of a two-dimensional quantum dot by the field of a linearly polarized electromagnetic wave is studied. For the first time, analytic expressions for the ionization rate and partial probabilities of the process per unit time are obtained. The dependence of the probability of the process on the parameters of the confining potential and the Keldysh parameter are studied. The results of the work are compared with the earlier results on one- and three-dimensional nanostructures with a short-range potential.

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## The Aharonov-Bohm effect in a 3-D Gross-Neveu model with compactification at finite temperature

### V.Ch. Zhukovsky, P.B. Kolmakov

Moscow University Physics Bulletin 2013. 68. N 4. P. 272

Gross-Neveu model in (2+1)-dimensional space-time with one compactified spatial dimension (cylinder) is investigated under the influence of nontrivial boundary conditions. The Aharonov-Bohm effect induced by a magnetic flux contained within the cylinder is considered. Possible applications of the results obtained to the description of polymeric tubes are discussed.

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Physics of nuclei and elementary particles

## The mass distribution of $^{238}$U photofission fragments

### B.S. Ishkhanov$^1$, A.A. Kuznetsov$^2$

Moscow University Physics Bulletin 2013. 68. N 4. P. 279

The mass distribution of the $^{238}$U photofission fragments formed under γ-quanta action is analyzed in the range of excitation energies of a fissile nucleus from 5 to 20 MeV. The influence on the ratio of asymmetric and symmetric photofission of the $^{238}$U structure and excitation energy of a fissile nucleus is discussed. A combined analysis and the comparison of the behavior of the asymmetric and symmetric modes of photofission were conducted for the first time. The results we obtained are compared with the prediction of the multimode model of the dependence of fission modes on the nuclear excitation energy.

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Condensed matter physics

## Specific features of magnetic field penetration into granular superconductors and possible sensitivity of magnetic sensors based on them

### S.V. Chernykh

Moscow University Physics Bulletin 2013. 68. N 4. P. 288

The results of experimental and theoretical studies of the magnetic properties of a superconducting ceramic with the composition YBa$_2$Cu$_3$O$_{7-x}$ are presented. The limiting sensitivity of magnetic field sensors on the basis of a high-temperature superconducting ceramic is discussed.

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Chemical physics, physical kinetics, and plasma physics

## External combustion of high-speed multicomponent hydrocarbon-air flow under conditions of low-temperature plasma

### A.Yu. Baurov, L.V. Shibkova, V.M. Shibkov, P.V. Kopyl, O.S. Surkont

Moscow University Physics Bulletin 2013. 68. N 4. P. 293

The stabilization of external combustion (at the plate surface) of high-speed multicomponent (air, alcohol, and propane) flows is realized experimentally. It is shown that heat fluxes during alcohol combustion rise by a factor of about 7 and during propane combustion by a factor of 15, in comparison with the heat flux from a discharge in a high-speed air flow. The electron concentration measured at a distance of 10 cm down-stream from the electrode ends is approximately 10$^9$ cm$^{−3}$ in the case of the discharge in an air flow, whereas during alcohol combustion it attains 2×10$^{11}$ cm$^{−3}$ and during propane combustion it is 3×10$^{11}$ cm$^{−3}$. The flame temperature in the area of the discharge existence varies from 2000 up to 2500 K and outside the discharge at the distance of z=20 cm from electrodes is 1800 K, gradually decreasing downstream. It is shown that the combined discharge in the subsonic flow allows for complete combustion of liquid and gaseous hydrocarbons. The completeness of combustion in supersonic flows attains 95%, depending on the flow velocity.

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Biophysics and medical physics

## Self-organization of a system of dipole particles according to the keesom model

### V.N. Blinov$^1$, V.N. Buravtsev$^2$, T.I. Makarova$^3$, A.I. Poletaev$^4$

Moscow University Physics Bulletin 2013. 68. N 4. P. 299

Self-organization of dipolar hard spherical particles at low temperatures was studied using the Monte Carlo method. Configurations of the principal stable structures formed by the particles upon the destabilization of homogeneous distribution were described. The possibility of the formation of structural domains of different symmetries and sizes commensurate with the volume of the system under certain circumstances was demonstrated. The dipole moment of the domains thus formed is considerably higher than that of the entire system. The existence of dipole interactions in the model apparently leads to the appearance of layered structures. The results we obtained can be used in the development of biotechnologies involving the use of synthetic magnetic particles for targeted delivery of chemotherapeutics into an affected organ, as contrast agents in magnetic resonance imaging, and for the studies of magnitotaxis mechanisms.

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## Molecular association processes and fluorescent characteristics of nanomarkers of the fluorescein family in solutions of bovine serum albumin

### I.M. Vlasova$^1$, A.A. Kuleshova$^1$, A.A. Vlasov$^2$, A.M. Saletsky$^1$

Moscow University Physics Bulletin 2013. 68. N 4. P. 304

An analysis of the molecular association and fluorescent characteristics of nanomarkers of the fluorescein family, viz., fluorescein, erythrosine, eosine, and Rose Bengal, in BSA solutions was conducted. For all the markers a decreasing degree of molecular association was observed in the BSA solutions as compared with the solutions without protein. In the solutions with BSA, fluorescence quenching and red shifting of the fluorescence spectrum maximum occurred for the solutions with BAS compared with solutions without protein for the markers of the fluorescein family. The dependences of the degree of molecular association on pH differed for fluorescein and its halogen derivatives. The efficiency dependences of nanomarker binding with BSA on pH differed for fluorescein and its halogen derivatives.

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## Simulation of irradiation of thin layers of biological matter by low-energy photon radiation

### A.V. Belousov, A.S. Osipov

Moscow University Physics Bulletin 2013. 68. N 4. P. 311

Passage of 1–400 keV photons through thin layers (0.001–1.0 mm) of biological matter was simulated. Monte Carlo simulation was performed using the GEANT4.9 software package. The energy dependences of the absorbed dose and number of ionizing events and the number of ionizing events per unit absorbed dose were obtained. It was shown that the dependences in many respects are determined by the thickness of layers. Assuming that equal numbers of ionizing events in the layer cause equal biological effects, energy dependences of relative biological effectiveness of photons in the energy range studied have been estimated.

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Physics of Earth, atmosphere, and hydrosphere

## Computer simulation of vortex self-maintenance and amplification

### U. Yusupaliyev$^1$, N.P. Savenkova$^2$, S.A. Shuteyev$^1$, S.A. Skladchikov$^2$, A.K. Maslov$^1$, V.G. Yelensky$^2$

Moscow University Physics Bulletin 2013. 68. N 4. P. 317

We consider a mechanism of the self-maintenance and amplification of vortices (tropical cyclones and toroidal vortices of various nature) on the basis of their common relationships. The results of numerical simulations show that the heat energy in these vortices is partially transformed into vortex rotational energy due to buoyancy and Coriolis forces.

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## A braking drift current on the slopes of wind waves in an amplification zone

### O.N. Mel’nikova, K.V. Pokazeev, A.A. Rozhnovskaya

Moscow University Physics Bulletin 2013. 68. N 4. P. 320

A drift current was experimentally studied on the slopes of wind waves in an amplification zone. It was found that the drift decreases proportionally to the wave steepness at the front wave slope. We tested a hypothesis that relates the decrease in the drift velocity at the front wave slope with the formation of vortices in a viscous air layer. A physical model of the event and a method for the calculation of the drift decrease at the front wave slope in an amplification zone are suggested. The model calculations agree well with experimental data within the measurement error, which is less than 10% of the measured value.

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## The influence of wind on the development of a thermal bar and currents in a small reservoir during melting of its ice cover

### N.S. Blokhina

Moscow University Physics Bulletin 2013. 68. N 4. P. 324

The effect of wind on the development of a thermal bar and the accompanying currents in a reservoir during the melting of its ice cover are studied based on mathematical modeling. The thermohydrodynamic processes in a reservoir that is partially covered with ice in its central part are considered. The wind is shown to have a significant impact on the structure of currents. The behavior and lifetime of vortex structures in the reservoir, the location of the convergence zone, and the 4°C isotherm are determined by the velocity and direction of the wind. The interpretation of the thermal bar as an area of convergence of water masses near the isotherm of 4°C is shown to be incorrect, even at low wind velocities.

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## A probabilistic description of atmospheric turbulence

### V.P. Yushkov

Moscow University Physics Bulletin 2013. 68. N 4. P. 330

A way from the statistical description of homogeneous and isotropic turbulence to the anisotropic probability distribution is proposed. The role of adiabatic motions in the transfer of energy of turbulent fluctuations by spectrum is discussed. We justify the proposition that for large Reynolds numbers the distribution of the energy of adiabatic fluctuations at scales of homogeneous and isotropic turbulence has the form of a Planck curve.

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