We aimed to evaluate the magnesium content in human cirrhotic liver and its correlation with serum AST levels, expression of hepatocellular injury, and MELDNa prognostic score. In liver biopsies obtained at liver transplantation we measured the magnesium content in liver tissue in 27 cirrhotic patients (CIRs) and 16 deceased donors with healthy liver (CTRLs) by atomic absorption spectrometry and within hepatocytes in 15 CIRs using synchrotron-based X-ray Fluorescence Microscopy. In 31 CIRs and 10 CTRLs we evaluated the immunohistochemical expression in hepatocytes of the transient receptor potential melastatin 7 (TRPM7), a magnesium influx chanzyme also involved in inflammation. CIRs showed a lower hepatic magnesium content [117.2 (IQR 110.5-132.9) vs 162.8 (IQR 155.9-169.8) μg/g; p<0.001] and a higher percentage of TRPM7 positive hepatocytes [53.0 (IQR 36.8-62.0) vs 20.7 (10.7-32.8) %; p<0.001) than CTRLs. In CIRs, MELDNa and serum AST at transplant correlated: a) inversely with the magnesium content both in liver tissue and hepatocytes; b) directly with the percentage of hepatocytes stained intensely for TRPM7. The latter also directly correlated with worsening of MELDNa at transplant compared to waitlisting. Magnesium depletion and overexpression of its influx chanzyme TRPM7 in hepatocytes are associated with severity of hepatocyte injury and prognosis in cirrhosis. These data represent the pathophysiological basis for a possible beneficial effect of magnesium supplementation in cirrhotic patients.
Oxide-ion conductors are of high interest in electrochemical devices such as solid-oxide fuel cells, oxygen sensors, and separation membranes. In this paper, high oxide-ion conductivity and associated ion conduction mechanism in perovskite-type oxides Na0.5Bi0.5–xTi1–yMgyO3–1.5x–y (for x = 0.0 and y = 0.0, x = 0.01 and y = 0.02, x = 0.01 and y = 0.04) are investigated systematically. Na0.5Bi0.5TiO3 ceramic is a poor conductor, whereas Na0.5Bi0.49Ti0.98Mg0.02O2.965 and Na0.5Bi0.49Ti0.96Mg0.04O2.945 ceramics are excellent oxide-ion conductors at 500 °C. While the Rietveld refinements of powder X-ray diffraction data using the monoclinic Cc space group and the rhombohedral R3c space group showed reasonably similar quality of fits, extended X-ray absorption fine structure (EXAFS) data could be fitted only with the monoclinic Cc structure at room temperature for all three ceramics. Extensive EXAFS investigations have also been used to probe the local environments of Bi and Ti atoms directly and reveal the ordering of Bi3+/Na+, displacements of the cations, oxygen-vacancy generation, and their migration pathways. Our EXAFS results demonstrate Bi- and Na-rich planes formation due to short-range ordering of Bi3+/Na+ in the perovskite units. Oxygen vacancies were found to be located in the Bi-rich planes. 23Na magic-angle spinning NMR experiments indicate that the local environments of Na atoms are disordered. The present work also provides an insight into the dramatically improved conducting behavior of Na0.5Bi0.49Ti0.98Mg0.02O2.965 and Na0.5Bi0.49Ti0.96Mg0.04O2.945 ceramics in terms of the local, long-range, and microstructure, which can be exploited to develop design principles for the syntheses of related oxides with even improved properties.
The contrast images of the different states of charge of manganese in a manganese hexacyanoferrate (MnHCF) cathode material are achieved with the synchrotron-based two-dimensional (2D) X-ray fluorescence (XRF) technique. XRF, otherwise known to be unable to differentiate between the various oxidation states of the elements, in this case becomes sensitive through the modification of the initial excitation energy due to the advantage of the particularly large energy gap between the K-edge energies of manganese species in the different oxidation states of MnHCF.
Here we explore the structural, magnetic, and dielectric properties of ${\mathrm{Na}}_{5}{\mathrm{Co}}_{15.5}{\mathrm{Te}}_{6}{\mathrm{O}}_{36}$, which reveal development of a short-range magnetic correlation and a dielectric anomaly in the system above N\`eel temperature (${T}_{N}$=) of 50 K. Low-temperature neutron powder diffraction (NPD) without any external magnetic field clearly indicates that the canted spin structure is responsible for the antiferromagnetic transition, and this canted spin structure brings several short-range ferromagnetic and antiferromagnetic correlations, and partially occupied Co form short-range magnetic correlation with other Co. Interestingly, a structural change in terms of changes in the lattice parameters and consequent development of dielectric anomaly around similar temperature is also recorded in the system. Additionally, the isothermal remanent magnetization and electron-spin resonance measurements reveal the presence of short-range magnetic correlations which coincide with an anomaly in the dielectric constant vs temperature curve. Further, a sharp jump in the magnetic-field-dependent magnetization clearly indicates the presence of metamagnetic transition, and magnetic-field-dependent NPD confirms that rotations of Co spins with applied magnetic field are responsible for this metamagnetic phase transition. Consequently, a magnetocaloric effect is developed in the system, which is suitable for the application in low-temperature refrigeration.
The surface region of austenitic stainless steel (SS) is investigated by synchrotron X‐ray powder diffraction (XRPD) and X‐ray absorption near edge structure (XANES) measurements, because its composition and structure are crucial for the corrosion resistance of SS. Grazing incidence XRPD of a polished AISI 304 bulk steel sample shows that the near‐surface structure is modified. The concentration of the ferrite phase of Fe, a typical minority phase in AISI 304, increases gradually from 10% to 30% when approaching the surface from 150 nm depth. XANES Fe K‐edge investigations of ultrathin, sputter‐deposited films also reveal much larger ferrite fractions than expected from the austenitic steel composition of the films. Reasons for the increased ferrite fraction in the surface region of bulk steel and thin films are discussed. However, right at the surface, the trend reverses. Analysis of XANES data for an ultrathin, 4 nm SS film shows that 80% of Fe is oxidized and 20% of metallic Fe is present only in austenite structure, suggesting that ferritic iron is preferentially subject to oxidation. The austenitic Fe is located at more than 2–3 nm below the surface where the Ni concentration is >10%.
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