5,835 research outputs found
Effect of Dzyaloshinskii Moriya interaction on magnetic vortex
The effect of the Dzyaloshinskii Moriya interaction on the vortex in magnetic
microdisk was investigated by micro magnetic simulation based on the Landau
Lifshitz Gilbert equation. Our results show that the DM interaction modifies
the size of the vortex core, and also induces an out of plane magnetization
component at the edge and inside the disk. The DM interaction can destabilizes
one vortex handedness, generate a bias field to the vortex core and couple the
vortex polarity and chirality. This DM-interaction-induced coupling can
therefore provide a new way to control vortex polarity and chirality
Growth-regulated expression of D-type cyclin genes in human diploid fibroblasts
The human CCND1 cyclin D1/PRAD1 gene was previously identified by a genetic screen for G1 cyclin function in Saccharomyces cerevisiae and also was identified as the putative BCL1 oncogene. However, its role in human cell proliferation is not known. To determine if expression of human D-type cyclin genes correlates with the state of cell growth, we examined the level of mRNAs for CCND1 and a related gene, CCND3, in normal human diploid fibroblasts (HDF). The levels of both mRNAs decrease upon serum depletion or at high cell densities. Following stimulation of quiescent fibroblasts with serum, the mRNA levels increase gradually to a peak at about 12 hr, prior to the onset of S phase. Induction of cyclin gene expression by serum is reduced concomitantly with the decline in FOS induction in aging HDFs, suggesting a possible relationship to the decrease in the proliferative response to mitogens during cellular senescence. Cycloheximide partially blocks the induction of CCND1 and CCND3 gene expression by serum, suggesting that both de novo protein synthesis-dependent and -independent pathways contribute to induction. Treatment of HDFs with defined growth factors suggests a correlation between CCND mRNA induction and DNA synthesis. However, induction of these genes is not sufficient for the transition from quiescence through G1 into S phase
Troubleshooting Arterial-Phase MR Images of Gadoxetate Disodium-Enhanced Liver.
Gadoxetate disodium is a widely used magnetic resonance (MR) contrast agent for liver MR imaging, and it provides both dynamic and hepatobiliary phase images. However, acquiring optimal arterial phase images at liver MR using gadoxetate disodium is more challenging than using conventional extracellular MR contrast agent because of the small volume administered, the gadolinium content of the agent, and the common occurrence of transient severe motion. In this article, we identify the challenges in obtaining high-quality arterial-phase images of gadoxetate disodium-enhanced liver MR imaging and present strategies for optimizing arterial-phase imaging based on the thorough review of recent research in this field
Thermophysical and elastic properties of Cu50Zr50 and (Cu50Zr50)95Al5 bulk-metallic-glass-forming alloys
By employing a containerless high-temperature high-vacuum electrostatic levitation technique, the thermophysical properties, including the ratio between the specific heat capacity and the hemispherical total emissivity, the specific volume, and the viscosity, of Cu50Zr50 and (Cu50Zr50)95Al5 bulk-metallic-glass (BMG)-forming liquids have been measured. Compared with Cu50Zr50, the improved glass-forming ability of (Cu50Zr50)95Al5 can be attributed to its dense liquid structure and its high value of viscosity. Additionally, the relationship between the viscosity of various BMG forming liquids at the melting temperature and the elastic properties of the corresponding glasses at room temperature will be compared
Gap Structure of the Spin-Triplet Superconductor Sr2RuO4 Determined from the Field-Orientation Dependence of Specific Heat
We report the field-orientation dependent specific heat of the spin-triplet
superconductor Sr2RuO4 under the magnetic field aligned parallel to the RuO2
planes with high accuracy. Below about 0.3 K, striking 4-fold oscillations of
the density of states reflecting the superconducting gap structure have been
resolved for the first time. We also obtained strong evidence of multi-band
superconductivity and concluded that the superconducting gap in the active
band, responsible for the superconducting instability, is modulated with a
minimum along the [100] direction.Comment: 4 pages, 4 figure
Field induced state and marginal stability of high-Tc superconductors
It is shown that the {\em complex} component is generated in d-wave
superconductor in the magnetic field. As one enters superconducting state at
finite field the normal to superconducting transition occurs into bulk
state . The driving force for the transition is the
linear coupling between magnetic field and non zero magnetization of the
condensate. The external magnetic field violates parity
and time reversal symmetries and the nodal quasiparticle states respond by
generating the component of the order parameter, with the magnitude
estimated to be on the order of few Kelvin. Parity (P) and time reversal (T)
symmetries are violated in this state.Comment: 4 pages, latex file with two eps figure file
Superconducting Gap Structure of Spin-Triplet Superconductor Sr_2RuO_4 Studied by Thermal Conductivity
To clarify the superconducting gap structure of the spin-triplet
superconductor Sr_2RuO_4, the in-plane thermal conductivity has been measured
as a function of relative orientations of the thermal flow, the crystal axes,
and a magnetic field rotating within the 2D RuO_2 planes. The in-plane
variation of the thermal conductivity is incompatible with any model with line
nodes vertical to the 2D planes and indicates the existence of horizontal
nodes. These results place strong constraints on models that attempt to explain
the mechanism of the triplet superconductivity.Comment: 5 pages, 4 figures, to be published in Phys. Rev. Let
Upper critical field for electrons in two-dimensional lattice
We address a problem of the upper critical field in a lattice described by a
two-dimensional tight-binding model with the on-site pairing. We develop a
finite-system-approach which enables investigation of magnetic and
superconducting properties of electrons on clusters, consisting of a few
thousand sites. We discuss how the quasiparticle density of states changes with
the applied external magnetic field and present the temperature dependence of
the upper critical field. We also briefly discuss possible extension of the
model to account for the properties of high-temperature superconductors.Comment: 4 pages, 3 postscript figures, revte
Theory of de Haas-van Alphen Effect in Type-II Superconductors
Theory of quasiparticle spectra and the de Haas-van Alphen (dHvA) oscillation
in type-II superconductors are developed based on the Bogoliubov-de Gennes
equations for vortex-lattice states. As the pair potential grows through the
superconducting transition, each degenerate Landau level in the normal state
splits into quasiparticle bands in the magnetic Brillouin zone. This brings
Landau-level broadening, which in turn leads to the extra dHvA oscillation
damping in the vortex state. We perform extensive numerical calculations for
three-dimensional systems with various gap structures. It is thereby shown that
(i) this Landau-level broadening is directly connected with the average gap at
H=0 along each Fermi-surface orbit perpendicular to the field H; (ii) the extra
dHvA oscillation attenuation is caused by the broadening around each extremal
orbit. These results imply that the dHvA experiment can be a unique probe to
detect band- and/or angle-dependent gap amplitudes. We derive an analytic
expression for the extra damping based on the second-order perturbation with
respect to the pair potential for the Luttinger-Ward thermodynamic potential.
This formula reproduces all our numerical results excellently, and is used to
estimate band-specific gap amplitudes from available data on NbSe_2, Nb_3Sn,
and YNi_2B_2C. The obtained value for YNi_2B_2C is fairly different from the
one through a specific-heat measurement, indicating presence of gap anisotropy
in this material. C programs to solve the two-dimensional Bogoliubov-de Gennes
equations are available at http://phys.sci.hokudai.ac.jp/~kita/index-e.html .Comment: 16 pages, 11 figure
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