163 research outputs found
First-principles structural optimization and electronic structure of the superconductor picene for various potassium doping levels
We theoretically explore the crystal structures of Kpicene, for which a
new aromatic superconductivity has recently been discovered for , by
systematically performing first-principles full structural optimization
covering the concentration range -4. The crystal symmetry (space group) of
the pristine picene is shown to be preserved in all the optimized structures
despite significant deformations of each picene molecule and vast
rearrangements of herringbone array of molecules. For Kpicene (-4)
optimization indicates that (i) multiple structures exist in some cases, and
(ii) dopants can enter not only in the interlayer region between the stack of
herringbone structures, but also in the intralayer region. In the electronic
structure obtained with the local density approximation for the optimized
structures, the dopants are shown to affect the electronic properties not only
through the rearrangement and distortion of molecules, but also molecule-metal
atom hybridization. In other words, the rigid-band approximation is invalidated
for multifold reasons. As a consequence the resultant Fermi surface exhibits a
variety of multiband structures which take diverse topology for Kpicene and
Kpicene.Comment: 7 figures, to be published in Phys. Rev.
Electronic structure of solid coronene: differences and commonalities to picene
We have obtained the first-principles electronic structure of solid coronene,
which has been recently discovered to exhibit superconductivity with potassium
doping. Since coronene, along with picene, the first aromatic superconductor,
now provide a class of superconductors as solids of aromatic compounds, here we
compare the two cases in examining the electronic structures. In the undoped
coronene crystal, where the molecules are arranged in a herringbone structure
with two molecules in a unit cell, the conduction band above an insulating gap
is found to comprise four bands, which basically originate from the lowest two
unoccupied molecular orbitals
(doubly-degenerate, reflecting the high symmetry of the molecular shape) in
an isolated molecule but the bands are entangled as in solid picene. The Fermi
surface for a candidate of the structure of Kcoronene with , for which
superconductivity is found, comprises multiple sheets, as in doped picene but
exhibiting a larger anisotropy with different topology.Comment: 5 pages, to be published in Phys. Rev.
Implications for the Cosmic Reionization from the Optical Afterglow Spectrum of the Gamma-Ray Burst 050904 at z = 6.3
The gamma-ray burst (GRB) 050904 at z = 6.3 provides the first opportunity of
probing the intergalactic medium (IGM) by GRBs at the epoch of the
reionization. Here we present a spectral modeling analysis of the optical
afterglow spectrum taken by the Subaru Telescope, aiming to constrain the
reionization history. The spectrum shows a clear damping wing at wavelengths
redward of the Lyman break, and the wing shape can be fit either by a damped Ly
alpha system with a column density of log (N_HI/cm^{-2}) ~ 21.6 at a redshift
close to the detected metal absorption lines (z_metal = 6.295), or by almost
neutral IGM extending to a slightly higher redshift of z_{IGM,u} ~ 6.36. In the
latter case, the difference from z_metal may be explained by acceleration of
metal absorbing shells by the activities of the GRB or its progenitor. However,
we exclude this possibility by using the light transmission feature around the
Ly beta resonance, leading to a firm upper limit of z_{IGM,u} < 6.314. We then
show an evidence that the IGM was largely ionized already at z=6.3, with the
best-fit neutral fraction of IGM, x_HI = N_HI/N_H = 0.00, and upper limits of
x_HI < 0.17 and 0.60 at 68 and 95% C.L., respectively. This is the first direct
and quantitative upper limit on x_HI at z > 6. Various systematic uncertainties
are examined, but none of them appears large enough to change this conclusion.
To get further information on the reionization, it is important to increase the
sample size of z >~ 6 GRBs, in order to find GRBs with low column densities
(log N_HI <~ 20) within their host galaxies, and for statistical studies of Ly
alpha line emission from host galaxies.Comment: Matches the published version in PASJ. The version with full
resolution figures is available upon request to Totani or at
http://www.kusastro.kyoto-u.ac.jp/~totani/up/grb050904-paper2-astroph-v3.pd
Treatment with Corticosteroid for Pericardial Effusion in a Patient with Advanced Synchronous Esophageal and Gastric Cancers following Chemoradiotherapy
Severe late toxicity following chemoradiotherapy in esophageal cancer, especially cardiac toxicity, is sometimes difficult to treat and is associated with mortality. However there is little published information with regard to patients with delayed pericardial effusion following chemoradiotherapy and its management. We herein report the case of a 63-year-old man with advanced synchronous esophageal and gastric cancers. This patient presented with pericardial effusion with cardiac tamponade after definitive chemoradiotherapy and was successfully treated with corticosteroid after pericardiocentesis. No instances of pericardial and pleural effusions were observed during the 2-year follow-up period until his death from cancer relapses
Effects of ezetimibe add-on therapy for high-risk patients with dyslipidemia
<p>Abstract</p> <p>Background</p> <p>Ezetimibe (Zetia<sup>®</sup>) is a potent inhibitor of cholesterol absorption that has been approved for the treatment of hypercholesterolemia. Statin, an inhibitor of cholesterol synthesis, is the first-choice drug to reduce low-density lipoprotein-cholesterol (LDL-C) for patients with hypercholesterolemia, due to its strong effect to lower the circulating LDL-C levels. Because a high dose of statins cause concern about rhabdomyolysis, it is sometimes difficult to achieve the guideline-recommended levels of LDL-C in high-risk patients with hypercholesterolemia treated with statin monotherapy. Ezetimibe has been reported to reduce LDL-C safely with both monotherapy and combination therapy with statins.</p> <p>Results</p> <p>To investigate the effect of ezetimibe as "add-on" therapy to statin on hypercholesterolemia, we examined biomarkers and vascular endothelial function in 14 patients with hypercholesterolemia before and after the 22-week ezetimibe add-on therapy. Ezetimibe add-on therapy reduced LDL-C by 24% compared with baseline (p < 0.005), with 13 patients (93%) reaching their LDL cholesterol goals. Of the Ezetimibe add-on therapy significantly improved not only LDL-C, high-density lipoprotein-cholesterol (HDL-C), and apolipoprotein (apo)B levels, but also reduced levels of triglyceride (TG), the ratio of LDL/HDL-C, the ratio of apoB/apoA-I, and a biomarker for oxidative stress (d-ROMs). Furthermore, ezetimibe add-on therapy improved vascular endothelial function in high-risk patients with hypercholesterolemia.</p> <p>Conclusion</p> <p>In conclusion, ezetimibe as add-on therapy to statin might be a therapeutic good option for high-risk patients with atherosclerosis.</p
Advanced moderately differentiated neuroendocrine carcinoma of the rectum with favorable prognosis by postoperative chemoradiation
Rectal neuroendocrine carcinoma is rare with poor prognosis. We report herein a case of advanced moderately differentiated neuroendocrine carcinoma of the rectum with relatively favorable prognosis treated by postoperative adjuvant chemoradiation therapy. A 58-year-old Japanese female was referred and colonofiberscopy revealed an easy-bleeding irregular tumor in the lower rectum, which was pathologically diagnosed as a neuroendocrine carcinoma. Surgical treatment consisted of abdominoperineal resection and lymph node dissection. The tumor invaded deeply into perirectal tissues, and 9 of 11 lymph node metastases were observed. Immunohistochemically, chromogranin A showed diffuse and strong staining, and the MIB-1 labeling index was 18.3 ± 5.6, supporting the high proliferation of the tumor. Some nucleus of the tumor showed positive staining for p21/WAF1. A total dose of 46 Gy of radiotherapy was delivered with 800 mg of daily oral doxifluridine. At 5 years post-surgery, the patient demonstrated no clinical evidence of intrapelvic recurrence or distant metastases
- …