Nodal-to-nodeless superconducting order parameter in LaFeAs1−x_{1-x}Px_xO synthesized under high pressure

Similar to chemical doping, pressure produces and stabilizes new phases of known materials, whose properties may differ greatly from those of their standard counterparts. Here, by considering a series of LaFeAs$_{1-x}$P$_x$O iron-pnictides synthesized under high-pressure high-temperature conditions, we investigate the simultaneous effects of pressure and isoelectronic doping in the 1111 family. Results of numerous macro- and microscopic technique measurements, unambiguously show a radically different phase diagram for the pressure-grown materials, characterized by the lack of magnetic order and the persistence of superconductivity across the whole $0.3 \leq x \leq 0.7$ doping range. This unexpected scenario is accompanied by a branching in the electronic properties across $x = 0.5$, involving both the normal and superconducting phases. Most notably, the superconducting order parameter evolves from nodal (for $x < 0.5$) to nodeless (for $x \geq 0.5$), in clear contrast to other 1111 and 122 iron-based materials grown under ambient-pressure conditions.Comment: 9 pages, 7 figures, Suppl. materia

Synthesis and Bulk Properties of Oxychloride Superconductor Ca2-xNaxCuO2Cl2

Polycrystalline samples and submillimeter size single crystals of Na-doped Ca2CuO2Cl2 have been synthesized under high pressure. A series of experiments showed that the Na content depends not only on the pressure during the synthesis but also on the synthesis temperature and time. From a comparison of the Na-CCOC data with those of structurally related La214 cuprate superconductors we concluded that chlorine at the apical site is less effective that oxygen in supplying charge carriers to the CuO2 plans. As a result, the coupling between the CuO2 planes is weakened, the transition temperature Tc is reduced and the anisotropic nature is enhanced.Comment: 7 pages, 7 figures, 1 table, presenthed at the Eucas 2007 conference. Accepted for "Journal of Physics: Conference Series (JPCS)" 2008 and European News Forum, Issue 3 (2008

Empagliflozin: a path from glycemic control to reduced cardiovascular mortality and heart failure-related hospitalizations

In the EMPA-REG OUTCOME, CANVAS and DECLARE-TIMI 58 studies, in patients with type 2 diabetes and established cardiovascular diseases or risk factors, a decrease in the risk of cardiovascular events and development or worsening of heart failure course without an increase in hypoglycemia incidence was revealed in those receiving sodium-glucose co-transporter-2 (SGLT2) inhibitors compared with placebo. To date, various mechanisms of action of SGLT2 inhibitors have been described, which are considered from the standpoint of their influence on the course and prognosis of heart failure. In the EMPEROR-Reduced study in the group of patients receiving empagliflozin, a significant reduction in the risk of cardiovascular death and hospitalizations for heart failure, regardless of the type 2 diabetes presence, was revealed

Study of the in-plane magnetic penetration depth in the cuprate superconductor Ca_2-xNa_xCuO_2Cl_2: role of the apical sites

A study of the in-plane magnetic penetration depth \lambda_ab in a series of the cuprate superconductors Ca_2-xNa_xCuO_2Cl_2 (Na-CCOC) with Na content x=0.11, 0.12, 0.15, 0.18, and 0.19 is reported. The zero temperature values of \lambda_ab(0) were obtained by means of the muon-spin rotation technique, as well as from measurements of the intrinsic susceptibility \chi^int(0) by using the procedure developed by Kanigel et al. [Phys.Rev.B 71, 224511 (2005)]. \lambda_ab at T=0K was found to increase with decreasing doping from \lambda_ab(0)=316(19)nm for the x=0.19 sample to \lambda_ab(0)=430(26)nm for the x=0.11 one. From a comparison of the present Na-CCOC data with those of Bi2201 and La214 cuprate superconductors it is concluded that substitution of the apical oxygen by chlorine decreases the coupling between the superconducting CuO_2 planes, leading to an enhancement of the two-dimensional properties of Na-CCOC.Comment: 8 pages, 7 figure

High pressure magnetic state of MnP probed by means of muon-spin rotation

We report a detailed $\mu$SR study of the pressure evolution of the magnetic order in the manganese based pnictide MnP, which has been recently found to undergo a superconducting transition under pressure once the magnetic ground state is suppressed. Using the muon as a volume sensitive local magnetic probe, we identify a ferromagnetic state as well as two incommensurate helical states (with propagation vectors ${\bf Q}$ aligned along the crystallographic $c-$ and $b-$directions, respectively) which transform into each other through first order phase transitions as a function of pressure and temperature. Our data appear to support that the magnetic state from which superconductivity develops at higher pressures is an incommensurate helical phase.Comment: 11 pages, 9 figure

Pressure induced softening of YB_6: pressure effect on the Ginzburg-Landau parameter \kappa=\lambda/\xi

Measurements of the transition temperature T_c, the second critical filed H_{c2} and the magnetic penetration depth \lambda under hydrostatic pressure (up to 9.2 kbar) in the YB_6 superconductor were carried out. A pronounced and {\it negative} pressure effects (PE) on T_c and H_{c2} with dT_c/dp=-0.0547(4) K/kbar and \mu_0dH_{c2}(0)/dp =-4.84(20) mT/kbar, and zero PE on \lambda(0) were observed. The PE on the coherence length d\xi(0)/dp=0.28(2) nm/kbar was calculated from the measured pressure dependence of H_{c2}(0). Together with the zero PE on the magnetic penetration depth \lambda(0), our results imply that the Ginzburg-Landau parameter \kappa(0)=\xi(0)/\lambda(0) depends on pressure and that pressure "softens" YB_6, e.g. moves it to the type-I direction.Comment: 4 pages, 2 figure

Iron deficiency in patients with coronary artery disease

A number of studies have demonstrated the negative impact of iron deficiency (ID) on the prognosis and course of heart failure. The prevalence of patients with coronary artery disease (CAD) in these studies was 39,4-65%, while the proportion of patients who had myocardial infarction reached 60%. The effect of ID on CAD course requires further study. The aim of this review was to analyze the available data on the effect of ID on heart function, quality of life, and prognosis in patients with CAD. This literature review analyzed 359 publications and systematized information on ID prevalence in patients with CAD, pathophysiological effects of ID on the function and structure of cardiomyocytes, the impact of ID on the course, prognosis, and quality of life in patients with CAD. The influence of ID and its correction on cardiomyocytes and left ventricular systolic function were studied

Slow magnetic fluctuations and superconductivity in fluorine-doped NdFeAsO

Among the widely studied superconducting iron-pnictide compounds belonging to the Ln1111 family (with Ln a lanthanide), a systematic investigation of the crossover region between the superconducting and the antiferromagnetic phase for the Ln = Nd case has been missing. We fill this gap by focusing on the intermediate doping regime of NdFeAsO(1-x)F(x) by means of dc-magnetometry and muon-spin spectroscopy measurements. The long-range order we detect at low fluorine doping is replaced by short-range magnetic interactions at x = 0.08, where also superconductivity appears. In this case, longitudinal-field muon-spin spectroscopy experiments show clear evidence of slow magnetic fluctuations that disappear at low temperatures. This fluctuating component is ascribed to the glassy-like character of the magnetically ordered phase of NdFeAsO at intermediate fluorine doping

Carbonate postsedimentation processes studies by electron paramagnetic resonance

© SGEM2014. All Rights Reserved. The purpose of this study was to show possibilities of the electron paramagnetic resonance (EPR) method on the example of carbonate rocks Lodemskoy area Zimnebrezhnogo diamond district by separating inhomogeneities in them and identifying indicators going changes. In calcite ions Mn2+ replace Ca2+, and in dolomite occupy positions as Ca2+ as well as Mg2+ positions. Although the basic form of the iron presence in carbonates is Fe2+, but with an increase in the medium oxidation potential some part of the impurity iron as Fe3+ is included a Ca2+ position in calcite and position Mg2+ in dolomite. EPR spectrometer X-band PS 100X (ADANI, Minsk) for recording the spectra at room temperature was used with including Al2O3:Cr3+ crystal in the side hole of the cavity as internal standard lines. Postsedimentary processes carbonates may be explained by the fact that in this area developed ultrabasic rocks (kimberlitic), which is a hotbed for ions Cr, Mn, Fe, Mg which migrate as a true solution and diffuse into the structure of the carbonates, the cations occupying the position that resulted in neoplasm of calcite and dolomite