Influence of Quantum Hall Effect on Linear and Nonlinear Conductivity in the FISDW States of the Organic Conductor (TMTSF)_2PF_6

We report a detailed characterization of quantum Hall effect (QHE) influence on the linear and non-linear resistivity tensor in FISDW phases of the organic conductor (TMTSF)2PF6. We show that the behavior at low electric fields, observed for nominally pure single crystals with different values of the resistivity ratio, is fully consistent with a theoretical model, which takes QHE nature of FISDW and residual quasi-particle density associated with different crystal imperfection levels into account. The non-linearity in longitudinal and diagonal resistivity tensor components observed at large electric fields reconciles preceding contradictory results. Our theoretical model offers a qualitatively good explanation of the observed features if a sliding of the density wave with the concomitant destruction of QHE, switched on above a finite electric field, is taken into account.Comment: 8 pages, 6 figures, submitted to EPJ

Coexistence of Superconductivity and Spin Density Wave orderings in the organic superconductor (TMTSF)_2PF_6

The phase diagram of the organic superconductor (TMTSF)_2PF_6 has been revisited using transport measurements with an improved control of the applied pressure. We have found a 0.8 kbar wide pressure domain below the critical point (9.43 kbar, 1.2 K) for the stabilisation of the superconducting ground state featuring a coexistence regime between spin density wave (SDW) and superconductivity (SC). The inhomogeneous character of the said pressure domain is supported by the analysis of the resistivity between T_SDW and T_SC and the superconducting critical current. The onset temperature T_SC is practically constant (1.20+-0.01 K) in this region where only the SC/SDW domain proportion below T_SC is increasing under pressure. An homogeneous superconducting state is recovered above the critical pressure with T_SC falling at increasing pressure. We propose a model comparing the free energy of a phase exhibiting a segregation between SDW and SC domains and the free energy of homogeneous phases which explains fairly well our experimental findings.Comment: 13 pages, 10 figures, revised v: fig.9 added, section 4.2 rewritten, accepted v: sections 4&5 improve

Two Intranasal Administration Techniques Give Two Different Pharmacokinetic Results

Minor changes in the administration technique used for intranasal instillation of clonazepam, have been  found to influence the results significantly. A simple study was performed, where rabbits received 0.5 mg  clonazepam intranasally. One group received the drug while fixed in a sitting position, where the other  group was fixed in a supine position. The results show that both techniques where able to provide a rapid  absorption with a tmax around 3-4 min. The Cmax and AUC, however, were very different. The Cmax was found  to be 40 ng/ml and 86 ng/ml, respectively, and the AUC was found to be 891 and 2249 (ng/ml/min), respectively,  for the sitting and the supine position. The relative bioavailability for sitting/supine was found to be  38%. These results show that the administration technique is very important and should not be underestimated.

Anomalous In-Plane Anisotropy of the Onset of Superconductivity in (TMTSF)2ClO4

We report the magnetic field-amplitude and field-angle dependence of the superconducting onset temperature Tc_onset of the organic superconductor (TMTSF)2ClO4 in magnetic fields H accurately aligned to the conductive ab' plane. We revealed that the rapid increase of the onset fields at low temperatures occurs both for H // b' and H // a, irrespective of the carrier confinement. Moreover, in the vicinity of the Pauli limiting field, we report a shift of a principal axis of the in-plane field-angle dependence of Tc_onset away from the b' axis. This feature may be related to an occurrence of Fulde-Ferrell-Larkin-Ovchinnikov phases.Comment: 4 pages, 4 figure

Self-organization of charge under pressure in the organic conductor (TMTSF)2ReO4

(TMTSF)2ReO4 presents a phase coexistence between two anion orderings defined by their wave vectors q_2=(1/2,1/2,1/2) and q_3=(0,1/2,1/2) in a wide range of pressure (8-11kbar) and temperature. From the determination of the anisotropy of the conductivity and the superconducting transitions in this regime we were able to extract the texture which results from a self-organization of the orientations of the ReO4 anions in the sample. At the lowest pressures, the metallic parts, related to the q_3 order, form droplets elongated along the a-axis embedded in the semiconducting matrix associated with the q_2 order. Above 10kbar, filaments along the a-axis extend from one end of the sample to the other nearly up to the end of the coexistence regime. A mapping of the system into an anisotropic Ising lattice is satisfactory to analyze the data. satisfactory to analyze the data.Comment: 7 pages, 3 figures, EPL forma

Kinetics of glucose oxidase catalyzed electron transfer mediated by sulfur and selenium compounds

AbstractUnusually high electron transfer rates in Aspergillus niger glucose oxidase catalyzed oxidation of glucose using 5,6:11,12-Bis(dithio)tetracene (TTT), 1,2-dimethyltetraselenafulvalene (DMTSF) and tetrathiafulvalene (TTF) were observed. At pH 7.0 oxidation rate constants (TN/Km) in the range from 1.0 · 107 to 8.7 · 107 M · s−1 were deduced from experimental data. One of the investigated mediators, DMTSF, has been used for electrocatalytical glucose oxidation on graphite at a potential of 0.3 V vs. a standard calomel electrode (SCE). The prepared bioelectrodes have a sensitivity of 1.3 μA/(cm2 · mM), a pH optimum at 6.5-7.0, and a linear range which covers the relevant range for monitoring physiological levels of glucose. The bioelectrodes are stable for more than one month

Temperature-Modulated Differential Scanning Calorimetry Analysis of High-Temperature Silicate Glasses

Differential scanning calorimetry (DSC) is one of the most versatile probes for silicate glasses, allowing determination of, e.g., transition temperatures (glass, crystallization, melting) and the temperature dependence of heat capacity. However, complications arise for glasses featuring overlapping transitions and low sensitivity, e.g., arising from SiO2-rich compositions with small change in heat capacity during glass transition or the low sensitivity of thermocouples at high temperature. These challenges might be overcome using temperature-modulated DSC (TM-DSC), which enables separation of overlapping signals and improved sensitivity at the expense of increased measurement duration

Upper critical field divergence induced by mesoscopic phase separation in the organic superconductor (TMTSF)2ReO4

Due to the competition of two anion orders, (TMTSF)2ReO4, presents a phase coexistence between semiconducting and metallic (superconducting) regions (filaments or droplets) in a wide range of pressure. In this regime, the superconducting upper critical field for H parallel to both c* and b' axes present a linear part at low fields followed by a divergence above a cross-over field. This cross-over corresponds to the 3D-2D decoupling transition expected in filamentary or granular superconductors. The sharpness of the transition also demonstrates that all filaments are of similar sizes and self organize in a very ordered way. The distance between the filaments and their cross-section are estimated.Comment: 4 pages, 4 figure