Hopping Conductivity and Negative Magnetoresistance of the Bulk Nanograined Bi2Te3 Material

The bulk nanograined Bi2Te3 material was prepared by the microwave assisted solvothermal method and cold isostatic pressure method. It was found that above T* ≈ 190 K the temperature dependence of the specific electrical resistivity of material is of metallic type, while below this temperature a semiconductor conductivity takes place. Within the temperature ΔT ≈ 90 K-35 K interval the electrical conductivity of material can be described by the variable-range hopping conductivity mechanism. Negative magnetoresistance was observed at the same temperature interval

Linear Positive Magnetoresistivity of the Bi1.9Lu0.1Te3 Alloy with Inhomogeneous Micrograined Structure

Positive nonsaturating transverse magnetoresistivity (MR) has been observed below room temperature in the Bi1.9Lu0.1Te3 alloy with inhomogeneous micrograined structure. A crossover from parabolic MR ~ B2 dependence in low magnetic fields to linear MR ~ B dependence in high fields was found in the magnetoresistivity curves. The crossover field is shifted to lower magnetic fields as temperature decreases. Within the temperature range of “metal” type of conductivity, the temperature dependences of the specific electrical resistivity and MR magnitude are determined by the temperature dependence of the carrier mobility due to acoustic phonon scattering. Linear MR can be associated with microstructural inhomogeneity leading to strong electrical disorder of the Bi1.9Lu0.1Te3

Electromagnetic form factors of charged and neutral kaons in an extended vector-meson-dominance model

A model is developed for electromagnetic form factors of the charged and neutral K-mesons. The formalism is based on ChPT Lagrangians with vector mesons. The form factors, calculated without fitting parameters, are in a good agreement with experiment for space-like and time-like photon momenta. Contribution of the two-kaon channels to the muon anomalous magnetic moment a_\mu is calculated.Comment: 23 pages, 11 figures, accepted for publication in Eur. Phys. J.

Trapped Particle Stability for the Kinetic Stabilizer

A kinetically stabilized axially symmetric tandem mirror (KSTM) uses the momentum flux of low-energy, unconfined particles that sample only the outer end-regions of the mirror plugs, where large favorable field-line curvature exists. The window of operation is determined for achieving MHD stability with tolerable energy drain from the kinetic stabilizer. Then MHD stable systems are analyzed for stability of the trapped particle mode. This mode is characterized by the detachment of the central-cell plasma from the kinetic stabilizer region without inducing field-line bending. Stability of the trapped particle mode is sensitive to the electron connection between the stabilizer and the end plug. It is found that the stability condition for the trapped particle mode is more constraining than the stability condition for the MHD mode, and it is challenging to satisfy the required power constraint. Furthermore a severe power drain may arise from the necessary connection of low-energy electrons in the kinetic stabilizer to the central region

Chiral symmetry breaking in confining theories and asymptotic limits of operator product expansion

The pattern of spontaneous chiral symmetry breaking (CSB) in confining background fields is analyzed. It is explicitly demonstrated how to get the inverse square root large proper time asymptotic of the operator product expansion which is needed for CSB.Comment: LaTeX, 20 pages; minor revision

Insm1 cooperates with Neurod1 and Foxa2 to maintain mature pancreatic β-cell function

Key transcription factors control the gene expression program in mature pancreatic {beta}-cells, but their integration into regulatory networks is little understood. Here, we show that Insm1, Neurod1 and Foxa2 directly interact and together bind regulatory sequences in the genome of mature pancreatic {beta}-cells. We used Insm1 ablation in mature {beta}-cells in mice and found pronounced deficits in insulin secretion and gene expression. Insm1-dependent genes identified previously in developing {beta}-cells markedly differ from the ones identified in the adult. In particular, adult mutant {beta}-cells resemble immature {beta}-cells of newborn mice in gene expression and functional properties. We defined Insm1, Neurod1 and Foxa2 binding sites associated with genes deregulated in Insm1 mutant {beta}-cells. Remarkably, combinatorial binding of Insm1, Neurod1 and Foxa2 but not binding of Insm1 alone explained a significant fraction of gene expression changes. Human genomic sequences corresponding to the murine sites occupied by Insm1/Neurod1/Foxa2 were enriched in single nucleotide polymorphisms associated with glycolytic traits. Thus, our data explain part of the mechanisms by which {beta}-cells maintain maturity: Combinatorial Insm1/Neurod1/Foxa2 binding identifies regulatory sequences that maintain the mature gene expression program in {beta}-cells, and disruption of this network results in functional failure

Russia and the Arab Spring: supporting the counter-revolution

Russia’s response to the Arab Spring ranged from apprehension to deep anxiety and diverged significantly from the US and the EU responses. While initially welcoming the popular demands for political reform in North Africa, the Russian reaction rapidly became more critical as a result of Western military intervention into Libya and the threat of the spread of Islamist extremism. It was these twin fears which prompted the Russian leadership to adopt an uncompromizing stance towards Syria. While geopolitical factors certainly played a role in driving Russian strategy, domestic political factors were also more significant. As the Russian leadership felt internally threatened by the growing opposition within the country, conflict in the Middle East highlighted the perceived flaws of the imposition of Western liberal democracy and the virtues of Russia’s own model of state-managed political order. There was, as such, a significant ideational and ideological dimension to the Russian response to the Arab Spring

Electromagnetic Decays of Heavy Baryons

The electromagnetic decays of the ground state baryon multiplets with one heavy quark are calculated using Heavy Hadron Chiral Perturbation Theory. The M1 and E2 amplitudes for S^{*}--> S gamma, S^{*} --> T gamma and S --> T gamma are separately computed. All M1 transitions are calculated up to O(1/Lambda_chi^2). The E2 amplitudes contribute at the same order for S^{*}--> S gamma, while for S^{*} --> T gamma they first appear at O(1/(m_Q \Lambda_\chi^2)) and for S --> T gamma are completely negligible. The renormalization of the chiral loops is discussed and relations among different decay amplitudes are derived. We find that chiral loops involving electromagnetic interactions of the light pseudoscalar mesons provide a sizable enhancement of these decay widths. Furthermore, we obtain an absolute prediction for the widths of Xi^{0'(*)}_c--> Xi^{0}_c gamma and Xi^{-'(*)}_b--> Xi^{-}_b gamma. Our results are compared to other estimates existing in the literature.Comment: 17 pages, 3 figures, submitted to Phys. Rev.

New experimental data for the decays ϕ→μ+μ−\phi\to\mu^+\mu^- and ϕ→π+π−\phi\to\pi^+\pi^- from SND detector

The processes $e^+e^-\to\mu^+\mu^-$ and $e^+e^-\to\pi^+\pi^-$ have been studied with SND detector at VEPP-2M $e^+e^-$ collider in the vicinity of $\phi(1020)$ resonance. The branching ratios $B(\phi\to\mu^+\mu^-)=(3.30\pm 0.45\pm 0.32)\times 10^{-4}$ and $B(\phi\to\pi^+\pi^-)=(0.71\pm 0.11\pm 0.09)\times 10^{-4}$ were obtained.Comment: 5 pages, 4 figures, talk given at 8th International Conference on Hadron Spectroscopy (HADRON 99), Beijing, China, 24-28 Aug 199