Solving q-Virasoro constraints

Letters in Mathematical Physics - We show how q-Virasoro constraints can be derived for a large class of (q, t)-deformed eigenvalue matrix models by an elementary trick of inserting...     

Selenium Dihalides Click Chemistry: Highly Efficient Stereoselective Addition to Alkynes and Evaluation of Glutathione Peroxidase-Like Activity of Bis(E-2-halovinyl) Selenides

Highly efficient stereoselective syntheses of novel bis(E-2-chlorovinyl) selenides and bis(E-2-bromovinyl) selenides in quantitative yields by reactions of selenium dichloride and dibromide with alkynes were developed. The reactions proceeded at room temperature as anti-addition giving products exclusively with (E)-stereochemistry. The glutathione peroxidase-like activity of the obtained products was estimated and compounds with high activity were found. The influence of substituents in the products on their glutathione peroxidase-like activity was discussed.     

Exploration of the Crystal Structure and Thermal and Spectroscopic Properties of Monoclinic Praseodymium Sulfate Pr2(SO4)3

Praseodymium sulfate was obtained by the precipitation method and the crystal structure was determined by Rietveld analysis. Pr₂(SO₄)₃ is crystallized in the monoclinic structure, space group C2/c, with cell parameters a = 21.6052 (4), b = 6.7237 (1) and c = 6.9777 (1) Å, β = 107.9148 (7)°, Z = 4, V = 964.48 (3) ų (T = 150 °C). The thermal expansion of Pr₂(SO₄)₃ is strongly anisotropic. As was obtained by XRD measurements, all cell parameters are increased on heating. However, due to a strong increase of the monoclinic angle β, there is a direction of negative thermal expansion. In the argon atmosphere, Pr₂(SO₄)₃ is stable in the temperature range of T = 30–870 °C. The kinetics of the thermal decomposition process of praseodymium sulfate octahydrate Pr₂(SO₄)₃·8H₂O was studied as well. The vibrational properties of Pr₂(SO₄)₃ were examined by Raman and Fourier-transform infrared absorption spectroscopy methods. The band gap structure of Pr₂(SO₄)₃ was evaluated by ab initio calculations, and it was found that the valence band top is dominated by the p electrons of oxygen ions, while the conduction band bottom is formed by the d electrons of Pr³⁺ ions. The exact position of ZPL is determined via PL and PLE spectra at 77 K to be at 481 nm, and that enabled a correct assignment of luminescent bands. The maximum luminescent band in Pr₂(SO₄)₃ belongs to the ³P₀ → ³F₂ transition at 640 nm.     

Simulation of the current induced by 63Ni beta radiation

The current generated by radiation from a ⁶³Ni layer of variable thickness is simulated with the actual spectrum of emitted electrons and with their distribution over the angles for Si and SiC taken into account. The dependences of the generation rate for nonequilibrium charge carriers on the depth are obtained for the cases of several Ni film thicknesses for both materials. The results are compared with the simulation results for a monoenergetic electron beam that is perpendicular to a semiconductor detector. It is shown that, for both Si and SiC, it is possible to choose an energy value of the electron beam in a SEM such that the ratio of the currents induced by the SEM beam and beta radiation from ⁶³Ni is essentially independent of the diffusion length.     

Structural elements of collapses in shallow water flows with horizontally nonuniform density

The mechanisms and structural elements of instability whose evolution results in the occurrence of the collapse are studied in the scope of the rotating shallow water model with a horizontally nonuniform density. The diagram stability based on the integral collapse criterion is suggested to explain system behavior in the space of constants of motion. Analysis of the instability shows that two collapse scenarios are possible. One scenario implies anisotropic collapse during which the contact area of a collapsing drop-like fragment with the bottom contracts into a rotating segment. The other implies isotropic contraction of the area into a point.     

On the approximation of harmonic functions by harmonic polynomials

Siberian Mathematical Journal -     

On the origin of the shallow and “replica” bands in FeSe monolayer superconductors

We compare the electronic structures of single FeSe layer films on SrTiO₃ substrate (FeSe/STO) and K _x Fe_2-y Se₂ superconductors obtained from extensive LDA and LDA + DMFT calculations with the results of ARPES experiments. It is demonstrated that correlation effects on Fe-3d states are sufficient in principle to explain the formation of the shallow electron-like bands at the M(X)-point. However, in FeSe/STO these effects alone are apparently insufficient for the simultaneous elimination of the hole-like Fermi surface around the Γ-point which is not observed in ARPES experiments. Detailed comparison of ARPES detected and calculated quasiparticle bands shows reasonable agreement between theory and experiment. Analysis of the bands with respect to their origin and orbital composition shows, that for FeSe/STO system the experimentally observed “replica” quasiparticle band at the M-point (usually attributed to forward scattering interactions with optical phonons in SrTiO₃ substrate) can be reasonably understood just as the LDA calculated Fe-3d _xy band, renormalized by electronic correlations. The only manifestation of the substrate reduces to lifting the degeneracy between Fe-3d _xz and Fe-3d _yz bands near M-point. For the case of K _x Fe_2-y Se₂ most bands observed in ARPES can also be understood as correlation renormalized Fe-3d LDA calculated bands, with overall semi-quantitative agreement with LDA + DMFT calculations.     

Thin films of YBaCuO high-temperature superconductor grown in a simplified magnetron sputterer and their microwave application

The physicochemical properties of YBa₂Cu₃O_7?δ high-temperature superconductor exclude designing standard magnetron sputterers and adopting standard film growth conditions that would ensure good and highly reproducible results. A simple and flexible magnetron sputterer making it possible to grow high-quality films (with a critical temperature of 90 K, a critical current density of 4 MA/cm², and a surface resistance of ≤0.5 mΘ at a frequency of 10 GHz and 77 K) is described. The high quality of the films is proved by successfully applying them in a microwave circuit demonstrating an intrinsic Q factor of 58 000 at a frequency of 70 MHz and 77 K, which is higher than the results obtained by other teams of researchers.     

Solvability of boundary value problems in a half-space for differential equations with constant coefficients in the class of tempered distributions

We present sufficient conditions for existence of solutions to general boundary value problems in a half-space for homogeneous differential equations with constant coefficients and arbitrary boundary data in the space of tempered distributions.