Hydrogen location and diffusion in a two-dimensional metal: Proton magnetic resonance in metallic zirconium monohalide hydrides

Proton magnetic resonance has been studied in a new class of metal-hydrogen systems, ZrXH, based on the metallic double-layered monohalides of zirconium, ZrCl and ZrBr. The rigid lattice second moments of the proton resonance show that in the hemihydride phases hydrogen predominantly occupies alternate chains of tetrahedral sites within the double layer of close-packed Zr atoms. In the monohydrides all tetrahedral sites are occupied by hydrogen. Activation energies for hydrogen diffusion within the layers are derived from the temperature dependence of the resonance linewidth. A substantial anisotropy of the proton resonance shape is observed at high temperatures.     

Neuromodulation by soy diets or equol: Anti-depressive &; anti-obesity-like influences,age- &; hormone-dependent effects

Background  

Soy-derived isoflavones potentially protect against obesity and depression. In five different studies we examined the influence of soy-containing diets or equol injections on depression, serotonin levels, body weight gain (BW) and white adipose tissue (WAT) deposition in female Long-Evans rats at various stages of life [rats were intact, ovariectomized or experienced natural ovarian failure (NOF)].     

93Nb knight shift and quadrupole coupling parameters in the orthorhombic β phase hydride and deuteride of niobium

The Knight shift tensor components and quadrupole coupling parameters of the ⁹³Nb NMR have been measured for the first time in the orthorhombic β phase hydride and deuteride of niobium. The isotropic component of the Knight shift tensor has the same value in the hydride phase as in the solid solution (α') phase at the same composition, indicating that no significant change in band structure details occurs as a consequence of the structural phase transition. Comparison of the measured asymmetry parameter of the quadrupole interaction with calculated values indicates that the probable Nb environment is that of the ordered NbH structure. Estimates of the activation energy for hydrogen (deuterium) diffusion are obtained from the temperature dependence of the linewidths of the spectrum features.     

Static B NMR studies of the short range order in alkali metal modified B2S3 glasses

The ¹¹B NMR spectra of xRb₂S+(1−x)B₂S₃ glasses in the range 0x0.75 and of xCs₂S+(1−x)B₂S₃ glasses in the range 0x0.60 are reported. The addition of Rb₂S to B₂S₃ creates on average approximately two and one-half tetrahedral borons for each added sulfur ion, whereas it is found that the addition of Cs₂S creates approximately 2 tetrahedral borons for each added sulfur ion. This behavior while more similar to that seen in the alkali borate glasses, contrasts that seen in the Na and K thioborate glasses, where six to eight and three, respectively, tetrahedral borons are formed for every sulfide anion added to the glass. These findings are supported by the IR and ¹¹B NMR spectra of the di-thioborate polycrystals (c-Rb₂S:2B₂S₃ and c-Cs₂S:2B₂S₃) whose structures appear to be comprised of two BS₄ tetrahedrals and two BS₃ trigonals (N₄0.5) like that in the alkali di-borate phases for both Rb and Cs. Unlike the ¹¹B NMR resonances of the sodium thioborate glasses where a single sharp line is observed for the tetrahedral boron site and a single quadrupolar broadened line is observed for all the trigonal sites, a third resonance line is observed at high alkali fractions for the rubidium and cesium thioborate glasses. This new structural feature may arise from asymmetric MBS₂ (meta-thioborate groups) or tetrahedral boron groups possessing a non-bridging sulfur.     

Two separate Li ionic motions observed by Li and B NMR in xLi2S + (1 − x)B2S3 glassy fast ionic conductors

Studies of ion dynamics in the highly conductive glassy fast ionic conductor (FIC) xLi₂S + (1 − x)B₂S₃ (x = 0.65 and 0.70) were made with NMR nuclear spin lattice relaxation (NSLR) R₁(ω, T) of both mobile ⁷Li and immobile ¹¹B ions, and ⁷Li NMR line narrowing δν(T). The possible dependence of ion dynamics on the short range order structures (SRO) and the distribution of activation energies (DAE) in this highly conductive FIC was investigated. Two Gaussian DAE were employed to fit ⁷Li NSLR data, where each Gaussian DAE was correlated to a separate ¹¹B NSLR in a BS₃ and in a BS₄ group. The long range diffusion of Li ions among BS₃ groups and a seemingly localized ionic hopping motion around BS₄ group is suggested as a microscopic model for the ion dynamics in thioborate glasses, namely a ‘two channel relaxation’.     

The physics of diamond

The accurate measurement of the thermal conductivity of metals still poses considerable experimental difficulty. The reasons for this, and the main ways in which the problem has been approached, are summarized. A detailed examination of the development in technique and methods of measurement shows that while most of the steady-state methods introduced over 50 years ago are still being improved, the emphasis in the last few years has been on the development of methods which give more rapid results, particularly at high temperatures.