731 research outputs found
Insulin-like growth factor binding protein-5 as a biomarker for detection of early liver disease
Study identifying an Insulin-like growth factor binding protein-5 as a biomarker for detection of early liver disease presented at the annual congress of the british toxicology societ
Hyperfine Interactions in the Heavy Fermion CeMIn_5 Systems
The CeMIn_5 heavy fermion compounds have attracted enormous interest since
their discovery six years ago. These materials exhibit a rich spectrum of
unusual correlated electron behavior, and may be an ideal model for the high
temperature superconductors. As many of these systems are either
antiferromagnets, or lie close to an antiferromagnetic phase boundary, it is
crucial to understand the behavior of the dynamic and static magnetism. Since
neutron scattering is difficult in these materials, often the primary source of
information about the magnetic fluctuations is Nuclear Magnetic Resonance
(NMR). Therefore, it is crucial to have a detailed understanding of how the
nuclear moments interact with conduction electrons and the local moments
present in these systems. Here we present a detailed analysis of the hyperfine
coupling based on anisotropic hyperfine coupling tensors between nuclear
moments and local moments. Because the couplings are symmetric with respect to
bond axes rather than crystal lattice directions, the nuclear sites can
experience non-vanishing hyperfine fields even in high symmetry sites.Comment: 15 pages, 5 figure
Nuclear spin-spin coupling in La_{2-x}Sr_{x}CuO_{4} studied by stimulated echo decay
We have performed copper NQR experiments in high temperature superconductors
YBa_{2}Cu_{4}O_{8}, YBa_{2}Cu_{3}O_{7}, and La_{2-x}Sr_{x}CuO_{4} (x=0.12 and
0.15), using the stimulated echo technique. The stimulated echo intensity is
analyzed by a model that includes the spin-lattice relaxation process (T_ {1
}-process) and the fluctuating local field due to nuclear spin-spin coupling.
The model gives quantitative account of the experimental results in Y-based
compounds using the known values of 1/T_{1} and 1/T_{2G}, the gaussian decay
rate of the spin echo intensity. The same model applied to LSCO enables us to
extract the value of T_{2G}. Our results indicate that T_{1}T/T_{2G} is
independent of temperature, implying that the dynamic exponent is one in
La_{2-x}Sr_{x}CuO_{4}.Comment: 14 pages, 11 fugures, The bibliography field is correcte
A Universal Intrinsic Scale of Hole Concentration for High-Tc Cuprates
We have measured thermoelectric power (TEP) as a function of hole
concentration per CuO2 layer, Ppl, in Y1-xCaxBa2Cu3O6 (Ppl = x/2) with no
oxygen in the Cu-O chain layer. The room-temperature TEP as a function of Ppl,
S290(Ppl), of Y1-xCaxBa2Cu3O6 behaves identically to that of La2-zSrzCuO4 (Ppl
= z). We argue that S290(Ppl) represents a measure of the intrinsic equilibrium
electronic states of doped holes and, therefore, can be used as a common scale
for the carrier concentrations of layered cuprates. We shows that the Ppl
determined by this new universal scale is consistent with both hole
concentration microscopically determined by NQR and the hole concentration
macroscopically determined by the Cu valency. We find two characteristic
scaling temperatures, TS* and TS2*, in the TEP vs. temperature curves that
change systematically with doping. Based on the universal scale, we uncover a
universal phase diagram in which almost all the experimentally determined
pseudogap temperatures as a function of Ppl fall on two common curves; upper
pseudogap temperature defined by the TS* versus Ppl curve and lower pseudogap
temperature defined by the TS2* versus Ppl curve. We find that while pseudogaps
are intrinsic properties of doped holes of a single CuO2 layer for all high-Tc
cuprates, Tc depends on the number of layers, therefore the inter-layer
coupling, in each individual system.Comment: 11 pages, 9 figures, accepted for publication in Physical Review
Superconductivity of the spin ladder system: Are the superconducting pairing and the spin-gap formation of the same origin?
Pressure-induced superconductivity in a spin-ladder cuprate
SrCaCuO has not been studied on a microscopic level so
far although the superconductivity was already discovered in 1996. We have
improved high-pressure technique with using a large high-quality crystal, and
succeeded in studying the superconductivity using Cu nuclear magnetic
resonance (NMR). We found that anomalous metallic state reflecting the
spin-ladder structure is realized and the superconductivity possesses a
s-wavelike character in the meaning that a finite gap exists in the
quasi-particle excitation: At pressure of 3.5GPa we observed two excitation
modes in the normal state from the relaxation rate . One gives rise
to an activation-type component in , and the other -linear
component linking directly with the superconductivity. This gapless mode likely
arises from free motion of holon-spinon bound states appearing by hole doping,
and the pairing of them likely causes the superconductivity.Comment: to be published in Phys. Rev. Let
Neuropilin-2 expression in breast cancer: correlation with lymph node metastasis, poor prognosis, and regulation of CXCR4 expression
<p>Abstract</p> <p>Background</p> <p>Neuropilin-2 (Nrp2) is a receptor for vascular endothelial growth factor-C (VEGF-C), which is a well-known lymphangiogenic factor and plays an important role in lymph node metastasis of various human cancers, including breast cancer. Recently, Nrp2 was shown to play a role in cancer by promoting tumor cell metastasis. CXC chemokine receptor 4 (CXCR4) also promotes tumor metastasis. In the previous studies, we demonstrated that VEGF-C and cytoplasmic CXCR4 expressions were correlated with poorer patient prognosis (BMC Cancer 2008,8:340; Breast Cancer Res Treat 2005, 91:125–132).</p> <p>Methods</p> <p>The relationship between Nrp2 expression and lymph node metastasis, VEGF-C expression, CXCR4 expression, and other established clinicopathological variables (these data were cited in our previous papers), including prognosis, was analyzed in human breast cancer. Effects of neutralizing anti-Nrp2 antibody on CXCR4 expression and chemotaxis were assessed in MDA-MB-231 breast cancer cells.</p> <p>Results</p> <p>Nrp2 expression was observed in 53.1% (60 of 113) of the invasive breast carcinomas. Nrp2 expression was significantly correlated with lymph node metastasis, VEGF-C expression, and cytoplasmic CXCR4 expression. Survival curves determined by the Kaplan-Meier method showed that Nrp2 expression was associated with reduced overall survival. In multivariate analysis, Nrp2 expression emerged as a significant independent predictor for overall survival. Neutralizing anti-Nrp2 antibody blocks cytoplasmic CXCR4 expression and CXCR4-induced migration in MDA-MB-231 cells.</p> <p>Conclusion</p> <p>Nrp2 expression was correlated with lymph node metastasis, VEGF-C expression, and cytoplasmic CXCR4 expression. Nrp2 expression may serve as a significant prognostic factor for long-term survival in breast cancer. Our data also showed a role for Nrp2 in regulating cytoplasmic CXCR4 expression <it>in vitro</it>.</p
Spin dynamics and antiferromagnetic order in PrBa2Cu4O8 studied by Cu nuclear respnance
Results of the nuclear resonance experiments for the planar Cu sites in
PrBa2Cu4O8 are presented. The NMR spectrum at 1.5 K in zero magnetic field
revealed an internal field of 6.1 T, providing evidence for an
antiferromagnetic order of the planar Cu spins. This confirms that the CuO2
planes are insulating, therefore, the metallic conduction in this material is
entirely due to the one-dimensional zigzag Cu2O2 chains. The results of the
spin-lattice relaxation rates measured by zero field NQR above 245 K in the
paramagnetic state are explained by the theory for a Heisenberg model on a
square lattice.Comment: 4 pages, 2 figure
Perturbation study on the spin and charge susceptibilities of the two-dimensional Hubbard model
We investigate the spin and charge susceptibilities of the two-dimensional
Hubbard model based upon the perturbative calculation in the strength of
correlation . For comparable to a bare bandwidth, the charge
susceptibility decreases near the half-filling as hole-doping approaches zero.
This behavior suggesting the precursor of the Mott-Hubbard gap formation cannot
be obtained without the vertex corrections beyond the random phase
approximation. In the low-temperature region, the spin susceptibility deviates
from the Curie-Weiss-like law and finally turns to decrease with the decrease
of temperature. This spin-gap-like behavior is originating from the van Hove
singularity in the density of states.Comment: Revtex file + 11 figures, to appear in Phys. Rev.
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