Electric field dependence of thermal conductivity of a granular superconductor: Giant field-induced effects predicted

The temperature and electric field dependence of electronic contribution to the thermal conductivity (TC) of a granular superconductor is considered within a 3D model of inductive Josephson junction arrays. In addition to a low-temperature maximum of zero-field TC K(T,0) (controlled by mutual inductance L_0 and normal state resistivity R_n), the model predicts two major effects in applied electric field: (i) decrease of the linear TC, and (ii) giant enhancement of the nonlinear (i.e., grad T-dependent) TC with [K(T,E)-K(T,0)]/K(T,0) reaching 500% for parallel electric fields E=E_T (E_T=S_0|grad T| is an "intrinsic" thermoelectric field). A possiblity of experimental observation of the predicted effects in granular superconductors is discussed.Comment: 5 LaTeX pages (jetpl.sty included), 2 EPS figures. To be published in JETP Letter

Electrical conductivity and magnetic properties of La1-xCaxMn1-yFeyO3 Ceramic Samples (x= 0.67, y= 0, 0.05)

The temperature dependence of the electrical resistivity in the range of the charge-ordered phase conforms to the variable-range hopping model. The behavior of the electrical resistivity is governed by the complex structure of the density of localized states near the Fermi levelyesBelgorod State Universit

Changes in the superconducting properties of high-T(sub c) ceramics produced by applied electric fields

Effect of an electrostatic field in the electrode-insulator-superconductor system on the current-voltage characteristics of high-T(sub c) ceramics with various composition and different preparation technology has been studied at 77 K. Ceramics of Y-Ba-Cu-O (123) and Bi-Pb-Sr-Ca-Cu-O (2223) systems and also ones doped by Ag have been used. Electric field strength has been up to 140 MV/m. It has been shown that there are reversible changes in the critical current I(sub c) and in the conductivity in electric field at the currents somewhat more than I(sub c) at T is less than T(sub c), while at T is greater than T(sub c) the noticeable electric field effect has not been found. These effects are qualitatively similar in both ceramic systems. High negative and positive gate voltages result in an increase of the conductivity. The electric field effect is modified by magnetic field H. The field effect decreases with increasing magnetic field and disappears at H is greater than 30 Oe. In Y-Ba-Cu-O/Ag (10 wt. percent) ceramics the field effect is practically absent. It may be supposed that in the ceramics the field-induced effect is consistent with weak links at grain boundaries

Effect of Copper Doping on Charge Ordering in La 1/3 Ca 2/3 Mn 1 - y Cu y O 3 (0 ≤ y ≤ 0.07)

Electron microscope studies have shown that the presence of copper suppresses the formation of a regular superstructure, which is characteristic of the undoped starting compound, beginning already from low concentrations (y=0.01). Differential scanning calorimetry revealed a substantial decrease in the transition entropy at the onset of charge ordering in copper-doped samples as compared to the starting compound. Doping with copper destroys long-range charge-orbital ordering and retains apparently only short-range orderyesBelgorod State Universit

Analog of Magnetoelectric Effect in High-Tc Granular Superconductors

We propose the existence of an electric-field induced nonlinear magnetization in a weakly coupled granular superconductor due to time-parity violation. As the field increases the induced magnetization passes from para- to dia-magnetic behavior. We discuss conditions under which this effect could be experimentally measured in high-temperature superconductors.Comment: REVTEX (epsf style), 1 PS figure; to appear in Europhysics Letter

Thermal conductivity of Fe graphitized wood derived carbon

Graphitic porous carbon materials from pyrolysis of wood precursors were obtained by means of a nanosized Fe catalyst, and their microstructure and electrical and thermal transport properties investigated. Thermal and electrical conductivity of graphitized carbon materials increase with the pyrolysis temperature, indicating a relationship between the degree of graphitization and thus in crystallite size with transport properties in the resulting carbon scaffolds. Evaluation of the experimental results indicate that thermal conductivity is mainly through phonons and increases with the temperature in Fe-catalyzed carbons suggesting that the mean free path of phonons in the material is small and defect scattering dominates over phonon-phonon interactions in the range from room temperature to 800 °C.Junta de Andalucía PE2012-TEP862Ministerio de Economía y Competitividad MAT2013-41233-

VE-cadherin and claudin-5: it takes two to tango

Endothelial barrier function requires the adhesive activity of VE-cadherin and claudin-5, which are key components of adherens and tight endothelial junctions, respectively. Emerging evidence suggests that VE-cadherin controls claudin-5 expression by preventing the nuclear accumulation of FoxO1 and -catenin, which repress the claudin-5 promoter. This indicates that a crosstalk mechanism operates between these junctional structures

Biosensors Based on Micro-algae for Ecological Monitoring of the Aquatic Environment

This chapter is devoted to research possibilities of using micro-algae as sensor elements for biological sensors of aquatic pollutants. The characteristics of the fluorescence of micro-algae pigments caused by laser light, called laser-induced fluorescence (LIF), were used as informative parameters. It is shown that the functioning of biological sensors is determined by the consistency and concentration of micro-algal cells as well as their internal state, which depends on the temperature, illumination, and chemical composition of the water. The results indicate a significant dependence of the LIF intensities of micro-algae from exposure of heavy metal ions, temperature, and illumination. In text is demonstrated specificity of the reaction of various micro-algae, belonging to different phylum. This fact can be used for identify the phylum of micro-algae in situ, and for the creation the biosensors of ecological monitoring aquatic environment

Chemical composition of bird cherry fruits in the Northwestern region of Russia

Background. Among stone fruit plants, a special place belongs to bird cherry (Padus Mill.). As a food plant, it has found use in areas with harsh climate conditions. Since the breeding of bird cherry cultivars for food purposes continues to develop, there is a need to know the chemical composition of its fruits. The aim of this research was to study bird cherry in the environments of the Russian Northwest and isolate genotypes with an optimal biochemical composition for subsequent use.Materials and methods. Fruit composition in 21 accessions from the bird cherry collection was analyzed in 2009 and 2011–2013 at the Biochemistry and Molecular Biology Laboratory of the N.I. Vavilov All-Russian Institute of Plant Genetic Resources (VIR). Biochemical studies were performed using the methods adopted at VIR. Statistical processing of the data obtained was made using the Microsoft Excel software package.Results. The best genotypes were selected for each chemical component: for increased soluble solid content (SSC), accessions of Group I ‘Nevesta’ (29.63%), 1-1-8 (30.35), ‘Carpaty 5’ (30.87), ‘Chaika’ (33.9); for accumulation of sugars, ‘Granatovaya grozd’ (Group III; 12.13%), 1-1-8 (Gr. I; 12.5), ‘Pamyati Salamatova’ (Gr. IV; 12.8); for low acid content, ‘Sibirskaya krasavitsa’ (Gr. II; 1.03%), 1-1-8 (Gr. I; 1.14) ‘Granatovaya grozd’ (Gr. III; 1.17), ‘Zelenoplodnaya’ (Gr. I; 1.21), ‘Pozdnyaya radost’ (Gr. III; 1.25); for high content of ascorbic acid, 1-1-8 (Gr. I; 19.1 mg/100 g), ‘Sakhalinskaya chernaya’ (Gr. I; 19.35) ‘Rannyaya kruglaya’ (Gr. IV; 20.65), ‘Krasny shater’ (Gr. II; 21.23); for triterpene (ursolic, oleanolic) acids, ‘Cherny blesk’ (Gr. IV; 0.045%) and ‘Atica’ (Gr. I; 0.056).Conclusion. Significant differences were found in SSC between accessions of Groups I (P. avium) and II (P. avium × P. virginiana); and in the sugar/acid ratio (SAR), between I (P. avium) and IV (seedlings of cv. ‘Pamyati Salamatova’); II (P. avium × P. virginiana) and III (P. virginiana × P. avium); III (P. virginiana × P. avium) and IV (seedlings of cv. ‘Pamyati Sala matova’)