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Using argon as the pressure medium, the structural and elastic properties of NiO have been investigated up to 67 GPa by the in situ synchrotron x-ray diffraction in a diamond anvil cell. Up to 67 GPa, NiO remains in the rhombohedral distorted rocksalt structure without phase transition. The lattice parameters of a and c, indexed in the hexagonal lattice, were found to decrease monotonically with increasing pressure, while the c/a ratio remains almost constant. The elastic properties of NiO were studied by analyzing the linewidth of various diffraction perks, which indicates that the factor S=(S11-S12-S44/2) is negative although the single-crystal elastic compliances S11 is positive, respectively, in the investigated pressure range. [ABSTRACT FROM AUTHOR]

Recently, A2B3 type strong spin orbital coupling compounds such as Bi2Te3, Bi2Se3 and Sb2Te3 were theoretically predicated to be topological insulators and demonstrated through experimental efforts. The counterpart compound Sb2Se3 on the other hand was found to be topological trivial, but further theoretical studies indicated that the pressure might induce Sb2Se3 into a topological nontrivial state. Here, we report on the discovery of superconductivity in Sb2Se3 single crystal induced via pressure. Our experiments indicated that Sb2Se3 became superconductive at high pressures above 10 GPa proceeded by a pressure induced insulator to metal like transition at ∼3 GPa which should be related to the topological quantum transition. The superconducting transition temperature (TC) increased to around 8.0 K with pressure up to 40 GPa while it keeps ambient structure. High pressure Raman revealed that new modes appeared around 10 GPa and 20 GPa, respectively, which correspond to occurrence of superconductivity and to the change of TC slop as the function of high pressure in conjunction with the evolutions of structural parameters at high pressures. [ABSTRACT FROM AUTHOR]

We have built a high-energy-resolution monochromator for nuclear resonant scattering from the 9.4 keV nuclear transition of [sup 83]Kr. The monochromator consists of two highly asymmetric silicon single crystals arranged in a dispersive geometry and produces an energy bandwidth of 2.3 meV. This monochromator has been successfully used for a study of nuclear forward scattering and nuclear resonant inelastic scattering from a [sup 83]Kr sample that was solidified in a diamond anvil cell at 2.15 GPa and room temperature. © 2002 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Recently, A2B3 type strong spin orbital coupling compounds such as Bi2Te3, Bi2Se3 and Sb2Te3 were theoretically predicated to be topological insulators and demonstrated through experimental efforts. The counterpart compound Sb2Se3 on the other hand was found to be topological trivial, but further theoretical studies indicated that the pressure might induce Sb2Se3 into a topological nontrivial state. Here, we report on the discovery of superconductivity in Sb2Se3 single crystal induced via pressure. Our experiments indicated that Sb2Se3 became superconductive at high pressures above 10 GPa proceeded by a pressure induced insulator to metal like transition at ∼3 GPa which should be related to the topological quantum transition. The superconducting transition temperature (TC) increased to around 8.0 K with pressure up to 40 GPa while it keeps ambient structure. High pressure Raman revealed that new modes appeared around 10 GPa and 20 GPa, respectively, which correspond to occurrence of superconductivity and to the change of TC slop as the function of high pressure in conjunction with the evolutions of structural parameters at high pressures. [ABSTRACT FROM AUTHOR]

report a comprehensive high-pressure study on the triple-layer T'-La4Ni308 with a suite of experimental probes, including structure determination, magnetic, and transport properties up to 50 GPa. Consistent with a recent ab inito calculation, application of hydrostatic pressure suppresses an insulator-metal spin-state transition at Pc ≈ 6 GPa. However, a low-spin metallic phase does not emerge after the high-spin state is suppressed to the lowest temperature. For P > 20 GPa, the ambient T' structure transforms gradually to a -type structure, which involves a structural reconstruction from fluorite La-02-La blocks under low pressures to rock-salt LaO-LaO blocks under high pressures. Absence of the metallic phase under pressure has been discussed in terms of local displacements of 02- ions in the fluorite block under pressure before a global T phase is established. [ABSTRACT FROM AUTHOR]

In olfactory mitral cells, dual patch recordings show that the site of action potential initiation can shift between soma and distal primary dendrite and that the shift is dependent on the location and strength of electrode current injection. We have analyzed the mechanisms underlying this shift, using a model of the mitral cell that takes advantage of the constraints available from the two recording sites. Starting with homogeneous Hodgkin-Huxley-like Na(+)-K(+) channel distribution in the soma-dendritic region and much higher sodium channel density in the axonal region, the model's channel kinetics and density were adjusted by a fitting algorithm so that the model response was virtually identical to the experimental data. The combination of loading effects and much higher sodium channel density in the axon relative to the soma-dendritic region results in significantly lower "voltage threshold" for action potential initiation in the axon; the axon therefore fires first unless the voltage gradient in the primary dendrite is steep enough for it to reach its higher threshold. The results thus provide a quantitative explanation for the stimulus strength and position dependence of the site of action potential initiation in the mitral cell.

Three A-ring analogs of 1 alpha,25-dihydroxyvitamin D3 (1,25(OH)2D3)--2-nor-1,3-seco-1,25(OH)2D3 (2-nor analog), 2-oxa-3-deoxy-25-OH-D3 (2-oxa analog), and A-homo-3-deoxy-3,3-dimethyl-2,4-dioxa-25-OH-D3 (A-homo analog)--were tested for their ability to inhibit 25-OH-D3-1 alpha-hydroxylase (1 alpha-hydroxylase) in isolated mitochondria and to alter 25-OH-D3 metabolism in cultured chick kidney cells. The 2-nor and 2-oxa analogs were relatively potent (Kis of 60 and 30 nM, respectively, compared with 170 nM for 1,25(OH)2D3), whereas the A-homo analog was completely ineffective in inhibiting 1 alpha-hydroxylase activity. In contrast, all three analogs were able to repress 1 alpha-hydroxylase and induce 24-hydroxylase activity in cultured chick kidney cells, suggesting that this process is not one of direct action in the mitochondria, but is more likely to be a receptor-mediated one.