451 research outputs found
Mott gap excitations in twin-free YBa2Cu3O7-d (Tc = 93 K) studied by RIXS
Mott gap excitations in the high-Tc superconductor of the optimal doped
YBa2Cu3O7-d (Tc = 93 K) have been studied by the resonant inelastic x-ray
scattering method. Anisotropic spectra in the ab-plane are observed in a
twin-free crystal. The excitation from the one-dimensional CuO chain is
enhanced at 2 eV near the zone boundary of the b* direction, while the
excitation from the CuO2 plane is broad at 1.5-4 eV and almost independent of
the momentum transfer. Theoretical calculation based on the one-dimensional and
two-dimensional Hubbard model reproduces the observed spectra by taking the
different parameters of the on-site Coulomb energy. The fact of the Mott gap of
the CuO chain site is much smaller than that of CuO2 plane site is observed for
the first time
Neutron Diffraction Study of Field Cooling Effects on Relaxor Ferroelectrics Pb[(Zn_{1/3} Nb_{2/3})_{0.92} Ti_{0.08}] O_{3}
High-temperature (T) and high-electric-field (E) effects on Pb[(Zn_{1/3}
Nb_{2/3})_{0.92} Ti_{0.08}]O_3 (PZN-8%PT) were studied comprehensively by
neutron diffraction in the ranges 300 <= T <= 550 K and 0 <= E <= 15 kV/cm. We
have focused on how phase transitions depend on preceding thermal and
electrical sequences. In the field cooling process (FC, E parallel [001] >= 0.5
kV/cm), a successive cubic (C) --> tetragonal (T) --> monoclinic (M_C)
transition was observed. In the zero field cooling process (ZFC), however, we
have found that the system does not transform to the rhombohedral (R) phase as
widely believed, but to a new, unidentified phase, which we call X. X gives a
Bragg peak profile similar to that expected for R, but the c-axis is always
slightly shorter than the a-axis. As for field effects on the X phase, we found
an irreversible X --> M_C transition via another monoclinic phase (M_A) as
expected from a previous report [Noheda et al. Phys. Rev. Lett. 86, 3891
(2001)]. At a higher electric field, we confirmed a c-axis jump associated with
the field-induced M_C --> T transition, which was observed by strain and x-ray
diffraction measurements.Comment: 8 pages, 9 figures, revise
Polarization-analyzed resonant inelastic x-ray scattering of the orbital excitations in KCuF3
We report a Cu K-edge resonant inelastic x-ray scattering (RIXS) study of
orbital excitations in KCuF3 . By performing the polarization analysis of the
scattered photons, we disclose that the excitation between the eg orbitals and
the excitations from t2g to eg exhibit distinct polarization dependence. The
polarization dependence of the respective excitations is interpreted based on a
phenomenological consideration of the symmetry of the RIXS process that yields
a necessary condition for observing the excitations. In addition, we show that
the orbital excitations are dispersionless within our experimental resolution.Comment: 5 pages, 3 figure
Resonant inelastic x-ray scattering study of hole-doped manganites La1-xSrxMnO3 (x=0.2 and 0.4)
Electronic excitations near the Fermi energy in the hole doped manganese
oxides (La1-xSrxMnO3, x=0.2 and 0.4) have been elucidated by using the resonant
inelastic x-ray scattering (RIXS) method. A doping effect in the strongly
correlated electron systems has been observed for the first time. The
scattering spectra show that a salient peak appears in low energies indicating
the persistence of the Mott gap. At the same time, the energy gap is partly
filled by doping holes and the energy of the spectral weight shifts toward
lower energies. The excitation spectra show little change in the momentum space
as is in undoped LaMnO3, but the scattering intensities in the low energy
excitations of x=0.2 are anisotropic as well as temperature dependent, which
indicates a reminiscence of the orbital nature
Serum Levels of Testosterone in Patients with Poly-cythemia Vera
Abstract Despite its association with vascular events such as myocardial and cerebral infarction, polycythemia vera (PV) is characterized by low serum total cholesterol levels. Because several sex hormones are derived from cholesterol, statins may induce hypogodanism in male patients. Therefore, we assessed the relationship between serum total cholesterol and sex hormone levels according to gender. Medical records of 41 patients with erythrocytosis (hemoglobin concentrations: men >18.5 g/dL; women >16.5 g/dL) collected between August 2005 and December 2014 were reviewed for patient age, and gender, as well as clinical hematology, biochemistry, and endocrinology laboratory findings. Serum levels of testosterone were lower in men with PV than in patients with reactive erythrocytosis (RE) (PV: 385 ± 78 ng/mL versus RE: 529 ± 46 ng/mL). However, serum levels of testosterone in women with PV were comparable to those in patients in the nonerythrocytic group (PV: 20.5 ± 3.5 ng/mL versus non-erythrocytic group: 21.0 ± 4.3 ng/mL). Serum levels of testosterone were not related to serum levels of cholesterol. Therefore, we speculated that lower testosterone levels were not due to lower serum levels of cholesterol, a known adverse effect of statin. In conclusion, we report for the first time that serum levels of testosterone were lower in male PV patients than in those with RE; however, serum levels of testosterone in female patients with PV were not lower
Monte Carlo Study of Relaxor Systems: A Minimum Model for Pb(InNb)O}
We examine a simple model for Pb(InNb)O (PIN), which
includes both long-range dipole-dipole interaction and random local anisotropy.
A improved algorithm optimized for long-range interaction has been applied for
efficient large-scale Monte Carlo simulation. We demonstrate that the phase
diagram of PIN is qualitatively reproduced by this minimum model. Some
properties characteristic of relaxors such as nano-scale domain formation, slow
dynamics and dispersive dielectric responses are also examined.Comment: 5 pages, 4 figure
N‐Substituted Nipecotic Acids as (S )‐SNAP‐5114 Analogues with Modified Lipophilic Domains
Potential mGAT4 inhibitors derived from the lead substance (S )‐SNAP‐5114 have been synthesized and characterized for their inhibitory potency. Variations from the parent compound included the substitution of one of its aromatic 4‐methoxy and 4‐methoxyphenyl groups, respectively, with a more polar moiety, including a carboxylic acid, alcohol, nitrile, carboxamide, sulfonamide, aldehyde or ketone function, or amino acid partial structures. Furthermore, it was investigated how the substitution of more than one of the aromatic 4‐methoxy groups affects the potency and selectivity of the resulting compounds. Among the synthesized test substances (S )‐1‐{2‐[(4‐formylphenyl)bis(4‐methoxyphenyl)‐methoxy]ethyl}piperidine‐3‐carboxylic acid, that features a carbaldehyde function in place of one of the aromatic 4‐methoxy moieties of (S )‐SNAP‐5114, was found to have a pIC50 value of 5.89±0.07, hence constituting a slightly more potent mGAT4 inhibitor than the parent substance while showing comparable subtype selectivity
A continuum model of gas flows with localized density variations
We discuss the kinetic representation of gases and the derivation of macroscopic equations governing the thermomechanical behavior of a dilute gas viewed at the macroscopic level as a continuous medium. We introduce an approach to kinetic theory where spatial distributions of the molecules are incorporated through a mean-free-volume argument. The new kinetic equation derived contains an extra term involving the evolution of this volume, which we attribute to changes in the thermodynamic properties of the medium. Our kinetic equation leads to a macroscopic set of continuum equations in which the gradients of thermodynamic properties, in particular density gradients, impact on diffusive fluxes. New transport terms bearing both convective and diffusive natures arise and are interpreted as purely macroscopic expansion or compression. Our new model is useful for describing gas flows that display non-local-thermodynamic-equilibrium (rarefied gas flows), flows with relatively large variations of macroscopic properties, and/or highly compressible fluid flows
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