Effect of the sample geometry on the second magnetization peak in single crystalline Ba0.63_{0.63}K0.37_{0.37}BiO3_3 thick film

Magnetization hysteresis loop $M(H)$ measurements performed on a single crystalline Ba$_{0.63}$K$_{0.37}$BiO$_3$ superconducting thick film reveal pronounced sample geometry dependence of the "second magnetization peak" (SMP), i.e. a maximum in the width of $M(H)$ occurring at the field $H_{\rm SMP}(T)$. In particular, it is found that the SMP vanishes decreasing the film dimension. We argue that the observed sample geometry dependence of the SMP cannot be accounted for by models which assume a vortex pinning enhancement as the origin of the SMP. Our results can be understood considering the thermomagnetic instability effect and/or non-uniform current distribution at $H < H_{\rm SMP}$ in large enough samples.Comment: 8 pages 3 figure

Relativistic Description of Exclusive Semileptonic Decays of Heavy Mesons

Using quasipotential approach, we have studied exclusive semileptonic decays of heavy mesons with the account of relativistic effects. Due to more complete relativistic description of the $s$ quark more precise expressions for semileptonic form factors are obtained. Various differential distributions in exclusive semileptonic decays of heavy mesons are calculated. It is argued that consistent account of relativistic effects and HQET motivated choice of the parameters of quark-antiquark potential allow to get reliable value for the ratio $A_2(0)/A_1(0)$ in the $D\to K^*l\nu_l$ decay as well as the ratio~$\Gamma(D\to K^*l\nu_l)/\Gamma(D\to Kl\nu_l)$. All calculated branching ratios are in accord with available experimental data.Comment: 18 pages, LATEX, 2 figures inclosed + 4 Postscript figure

Decay constants of the heavy-light mesons from the field correlator method

Meson Green's functions and decay constants $f_{\Gamma}$ in different channels $\Gamma$ are calculated using the Field Correlator Method. Both, spectrum and $f_\Gamma$, appear to be expressed only through universal constants: the string tension $\sigma$, $\alpha_s$, and the pole quark masses. For the $S$-wave states the calculated masses agree with the experimental numbers within $\pm 5$ MeV. For the $D$ and $D_s$ mesons the values of $f_{\rm P} (1S)$ are equal to 210(10) and 260(10) MeV, respectively, and their ratio $f_{D_s}/f_D$=1.24(3) agrees with recent CLEO experiment. The values $f_{\rm P}(1S)=182, 216, 438$ MeV are obtained for the $B$, $B_s$, and $B_c$ mesons with the ratio $f_{B_s}/f_B$=1.19(2) and $f_D/f_B$=1.14(2). The decay constants $f_{\rm P}(2S)$ for the first radial excitations as well as the decay constants $f_{\rm V}(1S)$ in the vector channel are also calculated. The difference of about 20% between $f_{D_s}$ and $f_D$, $f_{B_s}$ and $f_B$ directly follows from our analytical formulas.Comment: 37 pages, 10 tables, RevTeX

Quark-antiquark potential with retardation and radiative contributions and the heavy quarkonium mass spectra

The charmonium and bottomonium mass spectra are calculated with the systematic account of all relativistic corrections of order v^2/c^2 and the one-loop radiative corrections. Special attention is paid to the contribution of the retardation effects to the spin-independent part of the quark-antiquark potential, and a general approach to accounting for retardation effects in the long-range (confining) part of the potential is presented. A good fit to available experimental data on the mass spectra is obtained.Comment: 20 pages, revtex, 2 Postscript figure

Prospects for Establishment of Technological Complexes in Machine Building Industry on The Basis of Electromechatronic Propulsion Systems

The authors consider prospects for technological complex establishment in machine building industry on the basis of electromechatronic propulsion systems for production of innovative products with different novelty levels: world, state, brunch, region, etc

Spin interference in silicon three-terminal one-dimensional rings

We present the first findings of the spin transistor effect in the Rashba gate-controlled ring embedded in the p-type self-assembled silicon quantum well that is prepared on the n-type Si (100) surface. The coherence and phase sensitivity of the spin-dependent transport of holes are studied by varying the value of the external magnetic field and the bias voltage that are applied perpendicularly to the plane of the double-slit ring. Firstly, the amplitude and phase sensitivity of the 0.7(2e^2/h) feature of the hole quantum conductance staircase revealed by the quantum point contact inserted in the one of the arms of the double-slit ring are found to result from the interplay of the spontaneous spin polarization and the Rashba spin-orbit interaction. Secondly, the quantum scatterers connected to two one-dimensional leads and the quantum point contact inserted are shown to define the amplitude and the phase of the Aharonov-Bohm and the Aharonov-Casher conductance oscillations.Comment: 8 pages, 5 figure

New monoclonal antibodies to the Chlamydia trachomatis main outer membrane protein and their immunobiological properties

One of the methods that have been widely used in the diagnosis of urogenital chlamydia is an enzyme-linked immunosorbent assay (ELISA), the use of which allows for differential diagnosis. In order to increase the efficiency of ELISA test kits production, for the kits for the diagnosis of urogenital chlamydia, based on the principle of indirect modification, following synthetic positive controls (PCs) can be used: a conjugate of IgM (IgA) normal immunoglobulins and monoclonal antibodies (McAbs) to C. trachomatis major outer membrane protein (MOMP). The goal of this work was to obtain high active and affinity McAbs to the C. trachomatis MOMP as well as the study of its immunobiological properties which are important for future biochemical approaches. The study was conducted using: polyclonal antibodies (PcAbs) to C. trachomatis; recombinant major outer membrane protein (MOMP) (191-354 a.r.; W4-W5); epitope mapping based on phage display technology. The original set from 16 clones of hybridomas, producers of McAbs to the C. trachomatis MOMP has been obtained. More than half of the tested McAbs (8 out of 14) were characterized by a rather high titer (≥1:800), and three of them had a titer of ≥1:1600. In general, the McAbs titer was correlated with the value of the affinity constant: McAbs with higher titles were characterized by a high value of the affinity constant. For McAbs with a titer of <1:800, the average Ka is 5.2×109 M-1, while for McAbs with a titer ≥1:800 – Ka = 10.7×109 M-1. Antigenic determinants of two McAbs 293F4 and 291F8 that actively competed with PcAbs are represented by two linear sequences of 320-325 a.r. and 326-330 a.r., respectively. The epitope, which interacts with McAb 296G2, is represented by a linear sequence of 347-352 a.r. McAb 296G2 did not show active competition with serum PcAbs. The resulting set of data allows selecting McAbs for use in PCs of the ELISA kit for the detection of IgA or IgM antibodies to C. trachomatis

Electronic structure and optical properties of Ca2Si films grown on silicon different oriented substrates and calculated from first principles

The work considered the growth, optical properties and emerging interband transitions in Ca2Si films grown on silicon substrates with (111), (001), and (110) orientations at two temperatures (250 °C and 300 °C) using the sacrificial-template method. The optimum temperature for MBE single-phase growth of Ca2Si is 250 °C. Calculations of optical functions from the transmission and reflection spectra were carried out within the framework of a two-layer model and by the Kramers–Kronig method. It is shown that the main peaks in the experimental reflection spectra and the optical conductivity calculated according to Kramers–Kronig are in good agreement with each other. Comparison of ab initio calculations of the energy band structure and optical properties of a Ca2Si single crystal and two-dimensional Ca2Si layers with experimental data in the region of high-energy transitions showed good coincidence

Relativistic Description of Exclusive Heavy-to-Light Semileptonic Decays B→π(ρ)eνB\to\pi(\rho)e\nu

The method of calculating electroweak decay matrix elements between heavy-heavy and heavy-light meson states is developed in the framework of relativistic quark model based on the quasipotential approach in quantum field theory. This method is applied for the study of exclusive semileptonic $B\to\pi(\rho)$ decays. It is shown that the large value of the final $\pi(\rho)$ meson recoil momentum allows for the expansion in inverse powers of $b$-quark mass of the decay form factors at $q^2=0$, where $q^2$ is a momentum carried by the lepton pair. This $1/m_b$ expansion considerably simplifies the analysis of these decays and is carried out up to the second order. The $q^2$-dependence of the form factors is investigated. It is found that the $q^2$-behaviour of the axial form factor $A_1$ is different from the other form factors. It is argued that the ratios $\Gamma(B\to\rho e\nu)/\Gamma(B\to\pi e\nu)$ and $\Gamma_L/\Gamma_T$ are sensitive probes of the $A_1$ $q^2$-dependence, and thus their experimental measurement may discriminate between different approaches. We find $\Gamma(B\to\pi e\nu)=(3.0\pm0.6) \times|V_{ub}|^2\times10^{12}$s$^{-1}$ and $\Gamma(B\to\rho e\nu) =(5.4\pm 1.2)\times|V_{ub}|^2\times10^{12}$s$^{-1}$. The relation between semileptonic and rare radiative $B$-decays is discussed.Comment: 20 pages, two figures included, LATE