3,254 research outputs found
Field-induced magnetic ordering in the Haldane system PbNi2V2O8
The Haldane system PbNi2V2O8 was investigated by the temperature dependent
magnetization M(T) measurements at fields higher than H_c, with H_c the
critical fields necessary to close the Haldane gap. It is revealed that M(T)
for H > H_c exhibits a cusp-like minimum at T_{min}, below which M(T) increases
with decreasing T having a convex curve. These features have been observed for
both and , with c-axis being parallel to the chain.
These data indicate the occurrence of field-induced magnetic ordering around
T_{min}. Phase boundaries for and do not cross each
other, consistent with the theoretical calculation for negative single-ion
anisotropy D.Comment: 3 figures, submitted to Phys. Rev.
Single crystal MgB2 with anisotropic superconducting properties
The discovery of superconductor in magnesium diboride MgB2 with high Tc (39
K) has raised some challenging issues; whether this new superconductor
resembles a high temperature cuprate superconductor(HTS) or a low temperature
metallic superconductor; which superconducting mechanism, a phonon- mediated
BCS or a hole superconducting mechanism or other new exotic mechanism may
account for this superconductivity; and how about its future for applications.
In order to clarify the above questions, experiments using the single crystal
sample are urgently required. Here we have first succeeded in obtaining the
single crystal of this new MgB2 superconductivity, and performed its electrical
resistance and magnetization measurements. Their experiments show that the
electronic and magnetic properties depend on the crystallographic direction.
Our results indicate that the single crystal MgB2 superconductor shows
anisotropic superconducting properties and thus can provide scientific basis
for the research of its superconducting mechanism and its applications.Comment: 7 pages pdf fil
Multipole Expansion for Relativistic Coulomb Excitation
We derive a general expression for the multipole expansion of the
electro-magnetic interaction in relativistic heavy-ion collisions, which can be
employed in higher-order dynamical calculations of Coulomb excitation. The
interaction has diagonal as well as off-diagonal multipole components,
associated with the intrinsic and relative coordinates of projectile and
target. A simple truncation in the off-diagonal components gives excellent
results in first-order perturbation theory for distant collisions and for beam
energies up to 200 MeV/nucleon.Comment: 3 figures, Accepted for publication in Phys. Rev.
Valence and Na content dependences of superconductivity in NaxCoO2.yH2O
Various samples of sodium cobalt oxyhydrate with relatively large amounts of
Na ions were synthesized by a modified soft-chemical process in which a
NaOH aqueous solution was added in the final step of the procedure. From these
samples, a superconducting phase diagram was determined for a section of a
cobalt valence of +3.48, which was compared with a previously obtained
one of +3.40. The superconductivity was significantly affected by the
isovalent exchanger of Na and HO, rather than by variation of
Co valence, suggesting the presence of multiple kinds of Fermi surface.
Furthermore, the high-field magnetic susceptibility measurements for one sample
up to 30 T indicated an upper critical field much higher than the Pauli limit
supporting the validity of the spin-triplet pairing mechanism.Comment: 4 figures and 1 tabl
Coulomb Breakup Mechanism of Neutron-Halo Nuclei in a Time-Dependent Method
The mechanism of the Coulomb breakup reactions of the nuclei with
neutron-halo structure is investigated in detail. A time-dependent
Schr\"odinger equation for the halo neutron is numerically solved by treating
the Coulomb field of a target as an external field. The momentum distribution
and the post-acceleration effect of the final fragments are discussed in a
fully quantum mechanical way to clarify the limitation of the intuitive picture
based on the classical mechanics. The theory is applied to the Coulomb breakup
reaction of Be + Pb. The breakup mechanism is found to be
different between the channels of and
, reflecting the underlying structure of Be. The
calculated result reproduces the energy spectrum of the breakup fragments
reasonably well, but explains only about a half of the observed longitudinal
momentum difference.Comment: 15 pages,revtex, 9 figures (available upon request
Designing molecules to bypass the singlet-triplet bottleneck in the electroluminescence of organic light-emitting-diode materials
Electroluminescence in organic light emitting diode (OLED) materials occurs
via the recombination of excitonic electrons-hole pairs Only the singlet
excitons of commonly used OLED materials, e.g., Aluminum trihydroxyquinoline
(AlQ), decay radiatively, limiting the external quantum efficiency to a
maximum 25%. Thus 75% of the energy is lost due to the triplet bottleneck for
radiative recombination. We consider molecules derived from AlQ which
bypass the triplet bottleneck by designing structures which contain strong
spin-orbit coupling. As a first stage of this work, groundstate energies and
vertical excitation energies of Al-arsenoquinolines and Al-boroarsenoquinolines
are calculated. It is found that the substitution of N by As leads to very
favourable results, while the boron substitution leads to no advantage.Comment: 4 pages, 4 figue
Pathological activation of KIT in metastatic tumors of acral and mucosal melanomas
ArticleINTERNATIONAL JOURNAL OF CANCER. 124(4):862-868 (2009)journal articl
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