61 research outputs found
Electron Correlations in the Quasi-Two-Dimensional Organic Conductor -(BEDT-TTF)I investigated by C NMR
We report a C-NMR study on the ambient-pressure metallic phase of the
layered organic conductor -(BEDT-TTF)I [BEDT-TTF:
bisethylenedithio-tetrathiafulvalene], which is expected to connect the physics
of correlated electrons and Dirac electrons under pressure. The orientation
dependence of the NMR spectra shows that all BEDT-TTF molecules in the unit
cell are to be seen equivalent from a microscopic point of view. This feature
is consistent with the orthorhombic symmetry of the BEDT-TTF sublattice and
also indicates that the monoclinic sublattice, which should make three
molecules in the unit cell nonequivalent, is not practically influential on the
electronic state in the conducting BEDT-TTF layers at ambient pressure. There
is no signature of charge disproportionation in opposition to most of the
-type BEDT-TTF salts.
The analyses of NMR Knight shift, , and the nuclear spin-lattice
relaxation rate, , revealed that the degree of electron correlation,
evaluated by the Korringa ratio [)], is in an
intermediate regime. However, NMR relaxation rate is enhanced above
200K, which possibly indicates that the system enters into a quantum
critical regime of charge-order fluctuations as suggested theoretically.Comment: 19pages, 6figure
Excitonic instability of two-dimensional tilted Dirac cones
The electron-electron Coulomb interaction in Dirac-Weyl semimetals harbours a
novel paradigm of correlation effects that hybridizes diverse realms of
solid-state physics with their relativistic counterpart. Driving spontaneous
mass acquisition, the excitonic condensate of strongly-interacting massless
Dirac fermions is one such example whose exact nature remains debated. Here, by
focussing on the two-dimensional tilted Dirac cones in the organic salt
-(BEDT-TTF)I, we show that the excitonic instability is
controlled by a small chemicalpotential shift and an in-plane magnetic field.
In combined analyses based on renormalization-group approaches and ladder
approximation, we demonstrate that the nuclear relaxation rate is an excellent
probe of excitonic-spin fluctuations in an extended parameter region.
Comparative nuclear magnetic resonance (NMR) experiments show good agreements
with this result, jointly revealing the importance of intervalley nesting
between field-induced, spin-split Fermi pockets of opposite charge polarities.
Our work provides an accurate framework to search for excitonic instability of
strongly-interacting massless fermions.Comment: 26 pages, 5 figures, 1 supplementary file (9 pages, 3 figures
Phenomenological interaction between current quarks
We construct a phenomenological model which describes the dynamical chiral
symmetry breaking (DCSB) of QCD vacuum and reproduces meson spectra. Quark
condensates, the pion decay constant, and meson spectra are well reproduced by
phenomenological interaction which consists of a linear confining potential, a
Coulombic potential, and the 't Hooft determinant interaction. In this model,
the 't Hooft determinant interaction plays a important role not to only
\eta,\eta' mass difference, but other meson masses through DCSB.Comment: 18 pages, LaTe
Nuclear Photoabsorption at Photon Energies between 300 and 850 Mev
We construct the formula for the photonuclear total absorption cross section
using the projection method and the unitarity relation. Our treatment is very
effective when interference effects in the absorption processes on a nucleon
are strong. The disappearance of the peak around the position of the
resonance in the nuclear photoabsorption can be explained with the cooperative
effect of the interference in two-pion production processes,the Fermi motion,
the collision broadenings of and , and the pion distortion in the
nuclear medium. The change of the interference effect by the medium plays an
important role.Comment: 22pages,7figures,revtex
Analysis of Delayed Bleeding after Endoscopic Submucosal Dissection for Gastric Epithelial Neoplasms
Aim. Delayed bleeding after endoscopic submucosal dissection (ESD) for gastric epithelial neoplasms is a major complication. We investigated factors related to post-ESD bleeding to identify preventive measures. Methods. The study included 161 gastric epithelial neoplasms in 142 patients from June 2007 to September 2010. Post-ESD bleeding was defined as an ulcer with active bleeding or apparent exposed vessels diagnosed by an emergency endoscopy or a planned follow-up endoscopy. We analyzed associations between bleeding and the following factors: age, sex, morphology, pathology, tumor depth, ulcer presence/absence, location, size of the resected lesion, duration of the procedure, the number of times bleeding occurred during ESD, and the use of anticoagulants and/or antiplatelet drugs. Subsequently, we examined characteristics of bleeding cases. Results. Post-ESD bleeding occurred in 21 lesions. Univariate analysis of these cases showed that ulcer presence/absence (P < 0.001), middle or lower third lesions (P = 0.036), circumference (P = 0.014), and a post-ESD ulcer with an extended lesser curve (P = 0.009) were significant predictors of bleeding. Multivariate analysis showed that ulcer presence/absence (OR 9.73, 95% CI 2.28–41.53) was the only significant predictor. Conclusion. Ulcer presence/absence was considered the most significant predictor of post-ESD bleeding
NN coupling and two-pion photoproduction on the nucleon
Effects of non-resonant photoproductions arising from two different
couplings are investigated in the reaction. We find that
the pseudoscalar (PS) coupling is generally preferable to the
pseudovector (PV) coupling and particularly the total cross sections
are successfully described by the model with the PS coupling. In order
to see the difference between the two couplings, we also show the results of
invariant mass spectra and helicity-dependent cross sections in various isospin
channels calculated with the PS and PV couplings.Comment: 35 pages, 11 figures, minor changes and version to be published in
Phys.Rev.
Nuclear translocation of the cytoplasmic domain of HB-EGF induces gastric cancer invasion
BACKGROUND: Membrane-anchored heparin-binding epidermal growth factor-like growth factor (proHB-EGF) yields soluble HB-EGF, which is an epidermal growth factor receptor (EGFR) ligand, and a carboxy-terminal fragment of HB-EGF (HB-EGF-CTF) after ectodomain shedding. We previously reported that HB-EGF-CTF and unshed proHB-EGF which has the cytoplasmic domain of proHB-EGF (HB-EGF-C), translocate from the plasma membrane to the nucleus and regulate cell cycle after shedding stimuli. However, the significance of nuclear exported HB-EGF-C in human gastric cancer is unclear. METHODS: We investigated the relationship between intracellular localization of HB-EGF-C and clinical outcome in 96 gastric cancer patients treated with gastrectomy. Moreover, we established stable gastric cancer cell lines overexpressing wild-type HB-EGF (wt-HB-EGF) and mutated HB-EGF (HB-EGF-mC), which prevented HB-EGF-C nuclear translocation after shedding. Cell motility between these 2 gastric cancer cell lines was investigated using a transwell invasion assay and a wound healing assay. RESULTS: Of the 96 gastric cancer cases, HB-EGF-C immunoreactivity was detected in both the nucleus and cytoplasm in 19 cases (19.8 %) and in the cytoplasm only in 25 cases (26.0 %). The nuclear immunoreactivity of HB-EGF-C was significantly increased in stage pT3/4 tumors compared with pT1/2 tumors (T1/2 vs. T3/4: 11.1 % vs. 36.4 %, P < 0.01). The growth of wt-HB-EGF- and HB-EGF-mC-expressing cells significantly increased compared with control cells, but the growth of HB-EGF-mC-expressing cells was significantly decreased compared with wt-HB-EGF-expressing cells. Gastric cancer cell invasion obviously increased in wt-HB-EGF-expressing cells, but invasion in HB-EGF-mC-expressing cells showed a slight increase compared with control cells. Moreover, wt-HB-EGF overexpression increased the effectiveness of wound healing, but had no significant effect in HB-EGF-mC-expressing cells. CONCLUSIONS: Both the function of HB-EGF as an EGFR ligand and a novel signal for HB-EGF-C nuclear translocation induce gastric cancer growth, whereas HB-EGF-C nuclear translocation independently plays a critical role in gastric cancer invasion. The present study demonstrated that HB-EGF-C nuclear translocation might be crucial in gastric cancer invasion. HB-EGF-C nuclear translocation may offer a prognostic marker and a new molecular target for gastric cancer therapy
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