Andreev states and shot noise in bicrystal junctions of cuprate superconductors

Experimentally observed features of the electrical and noise characteristics of bicrystal junctions of cuprate superconductors, such as linearity of the critical current density versus square root of the junction transparency and increase in the spectral density of shot noise for small bias voltages (below the superconducting gap), indicate that the superconducting current in cuprate bicrystal junctions is determined by the passage of quasi-particles through a potential barrier at the superconductor boundaries. This process involves bound states appearing as a result of multiple Andreev reflections in superconductors with dominant wavefunction components of the d _x ² ? _y ² symmetry type. At the same time, interpretation of the experimental current-phase and current-magnetic field curves requires that the character of faceting at the bicrystal junctions would be also taken into account.     

Dipolar spirocyclic σ-complexes based on of 4,6-dinitrobenzofuroxan

The first dipolar spiro-σ-complexes with a superelectrophilic dinintrobenzofuroxan fragment and tropolone systems with diastereotopic substituents were synthesized. The kinetics of their enantiotopomerization, which occursvia cleavage-formation of the C_spiro-heteroatom bond, was studied by dynamic¹H NMR. The stereorigidity of dinitrobenzofuroxan spiro-complexes in this degenerated process increases in the series: tropolone<aminotropone<aminothiotropone≈aminotroponimine. The two last posses the highest kinetic stability compared to all known zwitterionic spiro-complexes. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1509–1512, August, 1997.     

The sectional curvature of the Sasaki metric of T1Mn

We study the tangent bundle of vectors of fixed length on a Riemannian manifold. We give sufficient conditions for the sectional curvature of the Sasaki metric on the tangent bundle of vectors of fixed length to be nonnegative.Translated from Ukrainskií Geometricheskií Sbornik, No. 30, 1987, pp. 10–17.     

Affine classification of points of multidimensional surfaces

Khar'kov. Translated from Sibirskii Matematicheskii Zhurnal, Vol. 31, No. 3, pp. 19–29, May–June, 1990.     

Particular features of the transmission of laser radiation with wavelength 0.438 µm and intensity (3–7)·1014 W/cm2 through an undercritical plasma from polymer aerogels

The velocities of energy transport in an undercritical plasma of polymer aerogel with and without copper nanoparticles were measured. Transmission of the laser light through targets of different thicknesses such as submicron three-dimensional polymer networks with densities below the critical value (0.13–0.52 N _cr) for a wavelength of 0.438 μm and intensity of (3–7)·10¹⁴ W/cm² at a half-height pulse duration of 0.32 ns was studied. The transfer of a heating laser radiation was registered on the rear side of the target. It ranged from a level of ∼0.5% for the thickness of a low-density layer of 400 μm and density of 9 mg/cm³ (mass per unit square of 0.36 mg/cm²) up to 50–60% for a thickness of 100 μm and density of 2.25 mg/cm³ (mass per unit square of 0.02 mg/cm²). The time dependences of the optical emission from the rear side of the targets were measured. They appear to be indicative of the plasma dynamics in two-layer targets (polymer foam on Al foil) and enable the estimation of the absorption depth for the laser light in an undercritical plasma. __________ Translated from Preprint No. 8 of the P. N. Lebedev Physical Institute, Moscow (2007).     

Modeling the atomic and electronic structure of diamond nanocrystals containing [NV]<Superscript>−</Superscript> centers by the density functional method

We have used the density functional method to model the atomic and electronic structure of diamond nanocrystals passivated by hydrogen atoms and either not containing defects or containing a single [NV]⁻ center. We have shown that in all cases, after relaxation the nanocrystals are formed as diamond-like structures. We have studied the features of the electronic structure of the nanocrystals. We have analyzed in detail the mechanism for the formation of energy levels in the bandgap due to [NV]⁻ centers. We have established that the optical absorption and fluorescence spectra for the [NV]⁻ centers are mainly associated with transitions of electrons between the highest occupied β orbitals (projection of the electron spin equal to +1/2) and lower unoccupied α orbitals (projection of the electron spin equal to −1/2). The results on the localization and energy position of the states in the bandgap match data obtained for the [NV]⁻ center in bulk diamond. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 1, pp. 86–92, January–February, 2007.