Extreme Electron-Phonon Coupling in Boron-based Layered Superconductors

The phonon-mode decomposition of the electron-phonon coupling in the MgB2-like system Li_{1-x}BC is explored using first principles calculations. It is found that the high temperature superconductivity of such systems results from extremely strong coupling to only ~2% of the phonon modes. Novel characteristics of E_2g branches include (1) ``mode lambda'' values of 25 and greater compared to a mean of $\sim 0.4$ for other modes, (2) a precipitous Kohn anomaly, and (3) E_2g phonon linewidths within a factor of ~2 of the frequency itself, indicating impending breakdown of linear electron-phonon theory. This behavior in borne out by recent inelastic x-ray scattering studies of MgB2 by Shukla et al.Comment: 4 two-column pages, 4 figures. Equations simplified. Figure 4 changed. Comparison with new data include

Gaussian Tunneling Model of c-Axis Twist Josephson Junctions

We calculate the critical current density $J^J_c$ for c-axis Josephson tunneling between identical high temperature superconductors twisted an angle $\phi_0$ about the c-axis. We model the tunneling matrix element squared as a Gaussian in the change of wavevector q parallel to the junction, $<|t({\bf q})|^2>\propto\exp(-{\bf q}^2a^2/2\pi^2\sigma^2)$. The $J^J_c(\phi_0)/J^J_c(0)$ obtained for the s- and extended-s-wave order parameters (OP's) are consistent with the Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$ data of Li {\it et al.}, but only for strongly incoherent tunneling, $\sigma^2\ge0.25$. A $d_{x^2-y^2}$-wave OP is always inconsistent with the data. In addition, we show that the apparent conventional sum rule violation observed by Basov et al. might be understandable in terms of incoherent c-axis tunneling, provided that the OP is not $d_{x^2-y^2}$-wave.Comment: 6 pages, 6 figure

Correction of the immune status of cows by using aminoseleton during the dry period for prevention of antenatal calf hypotrophy

The article describes the indicators of secondary immune deficiency in pregnant cows during the cow drying off. Morphological, biochemical, and immunological blood parameters are displayed. Clinical manifestation of calf hypotrophy syndrome during the neonatal period is studied. The experience of using Aminoseleton for pregnant cows during the drying off is describes. Evaluation of the biological effect on the organism of cows of a new tissue biostimulator was carried out on 22 cows with secondary immunodeficiency 30-45 days before calving, formed on the principle of paired analogues in two groups. Aminoseleton was used subcutaneously five times every 72 hours at a dose of 40 ml. The positive effect of immunomodulator Aminoseleton on metabolic status and the overall non-specific resistance indicators during the cow drying off was revealed. According to the results hypotrophic calves were born with a deficiency of body weight and a non-proportional physique. Tendency to centralize circulation, hypovolemia, hyperdynamic reaction with infarction, pulmonary hypertension with, spastic condition precapillary arterioles, disturbance of microcirculation in microvessels in newborn hypotrophic calves was observed. In perinatal hypotrophy in calves, inhibition of cellular immunity was noted predominantly against the background of an increased activity of oxidative metabolism in neutrophils. The results of our research indicate a violation of the structure and links of non-specific cellular and humoral resistance in calves with perinatal hypotrophy. As a result, a direct correlation between the level of non-specific resistance of the mother’s organism, and the state of health condition of the newborns is established. © 2019 Popova et al

An ab initio study of PuO 2±0.25 , UO 2±0.25 , and U 0.5 Pu 0.5 O2±0.25

Hybrid density functional theory has been used to systematically study the electronic, geometric, and magnetic properties of strongly correlated materials PuO2±x, UO2±x, and U0.5Pu0.5O2±x with x = 0.25. The calculations have been performed using the all-electron full- potential linearized augmented plane wave plus local orbitals basis (FP-L/APW+lo) method. Each compound has been studied at the ferromagnetic (FM) and anti-ferromagnetic (AFM) configurations with and without spin-orbit coupling (SOC) and full geometry optimizations. The optimized lattice constants, bulk moduli, and band gaps are reported. Total energy calculations indicate that the ground states are AFM for all compounds studied here and the band gaps are typically higher than 1.0 eV, characteristic of semiconductors. The total energy is lowered significantly and the band gaps increase with the inclusion of SOC. The chemical bonds between the actinide metals and oxygen atoms are primarily ionic in character