491 research outputs found
Non-Fermi Liquid behavior at the Orbital Ordering Quantum Critical Point in the Two-Orbital Model
The critical behavior of a two-orbital model with degenerate and
orbitals is investigated by multidimensional bosonization. We find
that the corresponding bosonic theory has an overdamped collective mode with
dynamical exponent , which appears to be a general feature of a
two-orbital model and becomes the dominant fluctuation in the vicinity of the
orbital-ordering quantum critical point. Since the very existence of this
overdamped collective mode induces non-Fermi liquid behavior near the quantum
critical point, we conclude that a two-orbital model generally has a sizable
area in the phase diagram showing non-Fermi liquid behavior. Furthermore, we
show that the bosonic theory resembles the continuous model near the d-wave
Pomeranchuk instability, suggesting that orbital order in a two-orbital model
is identical to nematic order in a continuous model. Our results can be applied
to systems with degenerate and orbitals such as iron-based
superconductors and bilayer strontium ruthenates SrRuO.Comment: 5 pages, 2 figure
Pomeranchuk Instability in a non-Fermi Liquid from Holography
The Pomeranchuk instability, in which an isotropic Fermi surface distorts and
becomes anisotropic due to strong interactions, is a possible mechanism for the
growing number of experimental systems which display transport properties that
differ along the and axes. We show here that the gauge-gravity duality
can be used to describe such an instability in fermionic systems. Our
holographic model consists of fermions in a background which describes the
causal propagation of a massive neutral spin-two field in an asymptotically AdS
spacetime. The Fermi surfaces in the boundary theory distort spontaneously and
become anisotropic once the neutral massive spin-two field develops a
normalizable mode in the bulk. Analysis of the fermionic correlators reveals
that the low-lying fermionic excitations are non-Fermi liquid-like both before
and after the Fermi surface shape distortion. Further, the spectral weight
along the Fermi surface is angularly dependent and can be made to vanish along
certain directions.Comment: Updated version to appear in PRD. New version has WKB analysis of
spectral intensity in ordered phas
Experimental investigation of flow-induced vibration of a rotating circular cylinder
While flow-induced vibration of bluff bodies has been extensively studied over the last half-century, only limited attention has been given to flow-induced vibration of elastically mounted rotating cylinders. Since recent low-Reynolds-number numerical work suggests that rotation can enhance or suppress the natural oscillatory response, the former could find applications in energy harvesting and the latter in vibration control. The present experimental investigation characterises the dynamic response and wake structure of a rotating circular cylinder undergoing vortex-induced vibration at a low mass ratio (m∗ = 5.78) over the reduced velocity range leading to strong oscillations. The experiments were conducted in a free-surface water channel with the cylinder vertically mounted and attached to a motor that provided constant rotation. Springs and an air-bearing system allow the cylinder to undertake low-damped transverse oscillations. Under cylinder rotation, the normalised frequency response was found to be comparable to that of a freely vibrating non-rotating cylinder. At reduced velocities consistent with the upper branch of a non-rotating transversely oscillating cylinder, the maximum oscillation amplitude increased with non-dimensional rotation rate up to α ≈ 2. Beyond this, there was a sharp decrease in amplitude. Notably, this critical value corresponds approximately to the rotation rate at which vortex shedding ceases for a non-oscillating rotating cylinder. Remarkably, at α = 2 there was approximately an 80% increase in the peak amplitude response compared to that of a non-rotating cylinder. The observed amplitude response measured over the Reynolds-number range of (1100 Re 6300) is significantly different from numerical predictions and other experimental results recorded at significantly lower Reynolds numbers
Experimental investigation of flow-induced vibration of a sinusoidally rotating circular cylinder
The present experimental investigation characterises the dynamic response and wake structure of a sinusoidally rotating circular cylinder with a low mass ratio (defined as the ratio of the total oscillating mass to the displaced fluid mass) undergoing cross-stream flow-induced vibration (FIV). The study covers a wide parameter space spanning the forcing rotary oscillation frequency ratio
Rates of metachronous adenoma after curative resection for left-sided or right-sided colon cancer
Background/Aims We determined the rates of metachronous colorectal neoplasm in colorectal cancer (CRC) patients after resection for right (R)-sided or left (L)-sided cancer. Methods Consecutive CRC patients who had undergone surgical resection for curative intent in our hospital between 2001 and 2004 were identified. R-sided colonic cancers refer to cancer proximal to splenic flexure whereas L-sided cancers include rectal cancers. Patients were included only if they had a clearing colonoscopy performed either before or within 6 months after the operation. Findings of surveillance colonoscopy performed up to 5 years after colonic resection were included in the analysis. Results Eight hundred and sixty-three CRC patients underwent curative surgical resection during the study period. Three hundred and twenty-seven patients (107 R-sided and 220 L-sided) fulfilled the inclusion criteria and had at least 1 postoperative surveillance colonoscopy performed. The proportion of patients who had polyp and adenoma on surveillance colonoscopy was significantly higher among patients with L-sided than R-sided cancers (polyps: 30.9% vs. 19.6%, P=0.03; adenomas: 25.5% vs. 13.1%, P=0.01). The mean number of adenoma per patient on surveillance colonoscopy was also higher for patients with L-sided than R-sided tumors (0.52; 95% confidence interval [CI], 0.37–0.68 vs. 0.22; 95% CI, 0.08–0.35; P<0.01). Multivariate analysis showed that L-sided cancers, age, male gender and longer follow-up were independent predictors of adenoma detection on surveillance colonoscopy. Conclusions Patients with Lsided cancer had a higher rate of metachronous polyps and adenoma than those with R-sided cancer on surveillance colonoscopy
The spin parameter of uniformly rotating compact stars
We study the dimensionless spin parameter of uniformly
rotating neutron stars and quark stars in general relativity. We show
numerically that the maximum value of the spin parameter of a neutron star
rotating at the Keplerian frequency is for a wide class
of realistic equations of state. This upper bound is insensitive to the mass of
the neutron star if the mass of the star is larger than about . On
the other hand, the spin parameter of a quark star modeled by the MIT bag model
can be larger than unity and does not have a universal upper bound. Its value
also depends strongly on the bag constant and the mass of the star.
Astrophysical implications of our finding will be discussed.Comment: Minor changes to match the published versio
Photo-reactive charge trapping memory based on lanthanide complex
Traditional utilization of photo-induced excitons is popularly but restricted in the fields of photovoltaic devices as well as photodetectors, and efforts on broadening its function have always been attempted. However, rare reports are available on organic field effect transistor (OFET) memory employing photo-induced charges. Here, we demonstrate an OFET memory containing a novel organic lanthanide complex Eu(tta)<sub>3</sub> ppta (Eu(tta)<sub>3</sub> = Europium(III) thenoyltrifluoroacetonate, ppta = 2-phenyl-4,6-bis(pyrazol-1-yl)-1,3,5-triazine), in which the photo-induced charges can be successfully trapped and detrapped. The luminescent complex emits intense red emission upon ultraviolet (UV) light excitation and serves as a trapping element of holes injected from the pentacene semiconductor layer. Memory window can be significantly enlarged by light-assisted programming and erasing procedures, during which the photo-induced excitons in the semiconductor layer are separated by voltage bias. The enhancement of memory window is attributed to the increasing number of photo-induced excitons by the UV light. The charges are stored in this luminescent complex for at least 10<sup>4</sup>s after withdrawing voltage bias. The present study on photo-assisted novel memory may motivate the research on a new type of light tunable charge trapping photo-reactive memory devices
Hong Kong Renal Registry Report 2012
SummaryThis report examined the characteristics and trends of dialysis and renal transplant patients among the resident population of Hong Kong who were managed by hospitals or dialysis centers of the Hospital Authority, and accounted for approximately 95% of all patients receiving renal replacement therapies (RRTs) in the territory. Patients receiving RRTs solely in the private sector were not included in this report. Data trends from 1996 to 2011 are presented. In 2011, 1115 new patients were accepted into RRT programs, and the incident rate was 157 patients per million populations (pmp). An increasing trend was noted. The incident rate was 95.1 pmp at the commencement of the annual report in 1996. The point prevalence on December 31, 2012 was 8197 with a prevalence rate of 1152.5 pmp. Overall, there were 3573 patients (43.6%) on peritoneal dialysis (PD) and 1246 patients (15.2%) on hemodialysis (HD), and 3378 patients (41.2%) were living with a functioning renal transplant. The PD/HD ratio was 74.2:25.8. The “PD First” policy was continued. The overall mortality rate among RRT patients was 9.95 patients per 100 patient-years exposed. There was a decreasing trend in mortality among PD patients. Infection and cardiovascular complications were the most common causes of death. Renal transplant was the modality with the best survival rates. The 5 years cumulative patient survival rate for patients on transplant treatment was 89.6%, whereas the corresponding patient survival rates for PD and HD patients were 50.7% and 55.7%, respectively. More than 70% of RRT patients with reports on rehabilitation were active and had normal daily activities
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