"Technical Physics Letters"

Krekov, G. M.;Lisenko, A. A.;Matvienko, G. G.;Sosnin, É. V.

doi: 10.1134/S1063785009110017pmid: N/A

Abstract We present the results of real and numerical experiments devoted to investigation of the spatial gradient of the intensity of chlorophyll fluorescence in the volume of a plant leaf. It is demonstrated for the first time that potential effective sources capable of exciting spontaneous fluorescence from the photosystem of a leaf are the exciplex lamps (exilamps) that generate continuous UV radiation. Estimations using the Monte Carlo method show that the main factor responsible for a transformation of the fluorescence spectrum during the passage of radiation through the volume of the leaf is the reabsorption process.

Kyutt, R. N.;Dinaev, Yu. A.

doi: 10.1134/S1063785009110029pmid: N/A

Abstract The structure perfection in two samples of the InN-GaN bilayer heterosystem, grown by molecular beam epitaxy (MBE) and metalorganic vapor phase epitaxy (MOVPE) on (0001)-oriented sapphire substrates, has been studied by the X-Ray diffraction techniques. Components of the microdistortion tensor were determined from an analysis of the broadening of diffraction peaks measured in various geometries. These data were used to evaluate the densities of various dislocation families in each layer of the heterosystem and to trace a change in the dislocated structure from the lower (GaN) to upper (InN) layer. A difference in the behavior of dislocations in the two samples grown by different methods (MBE versus MOVPE) suggests that different mechanisms of relaxation of the elastic stresses between InN and GaN layers are operative in these cases.

Kaminskiĭ, V. V.;Didik, V. A.;Kazanin, M. M.;Romanova, M. V.;Solov’ev, S. M.

doi: 10.1134/S1063785009110030pmid: N/A

Abstract A thermovoltaic effect has been observed for the first time in a polycrystalline sample of samarium sulfide (SmS) with artificially created concentration gradient of excess (overstoichiometric) samarium ions, in which an electric voltage of 12–22.5 mV was generated in a temperature interval of 370–485 K. It is shown that the specific voltage generation in SmS due to the thermovoltaic effect can be observed in a temperature range of 100–1800 K.

Kolesnikova, A. L.;Romanov, A. E.

doi: 10.1134/S1063785009110042pmid: N/A

Abstract A solution of the boundary-value problem in the isotropic theory of elasticity for a twist disclination loop (TDL) in a spherical body (spheroid) has been obtained for the first time using the method of virtual defects. The virtual defects are represented by TDLs with elastic fields, which are expanded into series with respect to Legendre polynomials. The elastic fields and energy of a TDL are determined depending on its position in the spheroid.

Volkov, N. V.;Eremin, E. V.;Tsikalov, V. S.;Patrin, G. S.;Kim, P. D.;Yu, Seong-Cho;Kim, Dong-Hyun;Chau, Nguyen

doi: 10.1134/S1063785009110054pmid: N/A

Abstract We have experimentally studied the transport properties of a planar La0.7Sr0.3MnO3 (LSMO)/Mn-depleted LSMO/MnSi tunneling structure, in which the Mn-depleted LSMO layer plays the role of a potential barrier between the conducting layers of LSMO and MnSi. The measurements were performed in geometry with the current direction parallel to the planes of interfaces in the tunneling structure. It is established that the structure exhibits a nonlinear current-voltage characteristic and possesses a positive magnetoresistance, the value of which depends on the tunneling current. It is suggested that specific features of the transport properties of this structure are related to the phenomenon of current channel switching between the conducting layers. The switching mechanism is based on the dependence of the resistance of the tunneling junction between the conducting layers on the bias voltage and the applied magnetic field.

Sadykov, N. R.;Skorkin, N. A.

doi: 10.1134/S1063785009110066pmid: N/A

Abstract It is shown that a mechanism of microwave radiation enhancement and self-focusing can be operative in a wave channel and spatial cavity filled with air containing elongated (dumbbell-shaped) nanoparticles at a volume fraction of c 0 ∼ 10−3. This nonlinear medium can be pumped using a quasi-stationary electric field. At an oscillation frequency of Ω ∼ 1010−1011s−1, the radiation enhancement and self-focusing in a wave channel is possible over a length of Δz ∼ 50−200 m, while that in a spatial cavity can take place within a period of time Δt ∼ (2−7) × 10−7 s.

Davydov, S. Yu.

doi: 10.1134/S1063785009110078pmid: N/A

Abstract Changes in the charge of adatoms and the substrate work function have been calculated for the adsorption layers of sodium and cesium on graphite using the Anderson-Newns model. The results of calculations are in good agreement with the available experimental data. It is established that there is electron transfer from Na and Cs adatoms to the graphite substrate, which leads to a decrease in the substrate work function.

Lipnitskii, Yu. M.;Panasenko, A. V.

doi: 10.1134/S106378500911008Xpmid: N/A

Abstract An important distinctive feature of gaseous media that possess relaxation properties is a delay in the heat transfer, which must be taken into account in the description of processes in these media. Numerical solution of the Navier-Stokes equations shows that the classical distribution of parameters in a shock wave described by the well-known analytical solution of Becker [1] can be unacceptable if the medium possesses relaxation properties manifested on a nanosecond time scale.

Bityurin, V. A.;Velikodnyi, V. Yu.;Samuolis, I. A.

doi: 10.1134/S1063785009110091pmid: N/A

Abstract Erosive discharge in the flow of a gas-dispersion mixture (air with dispersed microscopic drops of an electrolyte) has been experimentally studied. The products of erosion were obtained by coating the electrodes with a wax (this method was originally used by N. Tesla). Two phenomena were observed behind the discharge gap, i.e., (i) a linear breakdown in the form of a bead lightning (within 0.5–1 m behind the interelectrode gap) and (ii) the appearance of long-lived plasma formations (plasmoids). Cotton-like wax deposits formed on glass slides were examined in optical microscopes at various magnifications. The propagation of long-lived plasmoids in an applied magnetic field was monitored by a high-speed TV camera. Waveforms of a current transferred by the gas-dispersion flow were measured using a conducting screen. Based on these data, a self-consistent physical model is formulated, which describes the generation, evolution, and decay of the long-lived plasmoids.

Matveev, D. G.;Popov, I. Yu.

doi: 10.1134/S1063785009110108pmid: N/A

Abstract It is shown that a bound electron state exists in a system of quantum waveguides laterally coupled via a small window and placed in a transverse electric field. A field-induced shift of the eigenvalue is estimated using a variational method.