Low-density series expansions for directed percolation I: A new efficient algorithm with applications to the square lattice

A new algorithm for the derivation of low-density series for percolation on directed lattices is introduced and applied to the square lattice bond and site problems. Numerical evidence shows that the computational complexity grows exponentially, but with a growth factor \lambda < \protect{\sqrt[8]{2}}, which is much smaller than the growth factor \lambda = \protect{\sqrt[4]{2}} of the previous best algorithm. For bond (site) percolation on the directed square lattice the series has been extended to order 171 (158). Analysis of the series yields sharper estimates of the critical points and exponents.Comment: 20 pages, 8 figures (3 of them > 1Mb

Numerical renormalization group study of the symmetric Anderson-Holstein model: phonon and electron spectral functions

We study the symmetric Anderson-Holstein (AH) model at zero temperature with Wilson's numerical renormalization group (NRG) technique to study the interplay between the electron-electron and electron-phonon interactions. An improved method for calculating the phonon propagator using the NRG technique is presented, which turns out to be more accurate and reliable than the previous works in that it calculates the phonon renormalization explicitly and satisfies the boson sum rule better. The method is applied to calculate the renormalized phonon propagators along with the electron propagators as the onsite Coulomb repulsion $U$ and electron-phonon coupling constant $g$ are varied. As $g$ is increased, the phonon mode is successively renormalized, and for $g \gtrsim g_{co}$ crosses over to the regime where the mode splits into two components, one of which approaches back to the bare frequency and the other develops into a soft mode. The initial renormalization of the phonon mode, as $g$ is increased from 0, depends on $U$ and the hybridization $\Delta$; it gets softened (hardened) for $U \gtrsim (\lesssim) U_s (\Delta)$. Correlated with the emergence of the soft mode is the central peak of the electron spectral function severely suppressed. These NRG calculations will be compared with the standard Green's function results for the weak coupling regime to understand the phonon renormalization and soft mode.Comment: 18 pages, 4 figures. Submitted to Phys. Rev.

A highly active and redox stable novel ceramic anode with in-situ exsolution of nanocatalysts

Layered perovskite novel ceramic anode (referred to as SGNM) phases were evaluated for use in solid oxide fuel cells (SOFCs). Hydrogen temperature programmed reduction (H2-TPR) analysis of the SGNM materials revealed that significant exsolution of Ni nanoparticles occurred. Consistently, the SGNM on the LSGM electrolyte showed low electrode polarization resistance in H2 at 800 °C. Moreover, after 10 redox cycles at 750 °C, the electrode area specific resistance of the SGNM anode in H2 slightly increased during cycle, indicating excellent redox stability in both reducing and oxidizing atmospheres. An LSGM-electrolyte supported SOFC employing an SGNM-based anode yielded a high power density of ~1 W cm-2 at 800 °C, which is the best performance among the any SOFCs with Ruddlesden-Popper based ceramic anodes to date. After performance measurement, we observed that metallic Ni nanoparticles (~ 25 nm) were grown in situ and homogeneously distributed on the SGNM anode surface. These exsolved nanocatalysts are believed to significantly enhance the hydrogen oxidation activity of the SGNM material. These results demonstrate that the novel SGNM material is promising as a high catalytically active and redox-stable anode for SOFCs.. Please click Additional Files below to see the full abstract

Type and Severity of Migraine Determines Risk of Atrial Fibrillation in Women

OBJECTIVE: To evaluate sex differences in the risk of atrial fibrillation (AF) according to the type and severity of migraine. METHODS: We analyzed the nationwide health screening recipients in 2009 without previous AF diagnosis from the Korean National Health Insurance Service data. The diagnosis, type, and severity of migraine were determined using claims data. Newly developed AF was identified during a 10-year follow-up. Sex-difference in the effect of migraine on AF was evaluated. RESULTS: A total of 4,020,488 subjects were enrolled from January 1, to December 31, 2009 and followed-up through December 31, 2018; 4,986 subjects had migraine with aura (age 50.6 ± 14.0 years, men 29.3%); and 105,029 had migraine without aura (age 51.6 ± 14.3 years, men 30.9%). Risk of AF in a mild degree of migraine was similar to that in the control group, regardless of sex or the presence of aura. Severe migraine without aura modestly but significantly increased the risk of AF in both men and women compared to controls, with increase in AF risk being most prominent in women who had severe migraine with aura [incidence rate (IR) = 3.39, hazard ratio (HR)(adjust) = 1.48, 95% confidence intervals (CI) = 1.18–1.85]. No significant association according to aura was observed in men with severe migraines (p for interaction 0.011). CONCLUSION: Severe migraine with aura significantly increased the risk of incident AF in women, but not in men. Surveillance for incident AF and prompt lifestyle modification may be beneficial, particularly for young women suffering from severe migraine with aura

Associations between obesity parameters and the risk of incident atrial fibrillation and ischaemic stroke in the different age groups

OBJECTIVE: Obesity and aging are important predisposing factors to atrial fibrillation (AF) and ischaemic stroke (IS). However, limited data comprehensively evaluated the relationships between obesity measurements and AF and IS in different ages. METHODS: A total of 9,432,332 adults from the Korean National Health Insurance Service Database were included. The study population was categorized into the six age subgroups by an increase every decade from the twenties. We evaluated AF and IS risk according to body mass index (BMI) and waist circumference (WC) in the different age groups. RESULTS: During a mean follow-up of 8.2 ± 1.0 years, BMI-AF presented a J-shaped association across ages. The highest hazard ratio (HR) of the BMI ≥ 30 kg/m(2) group was observed in subjects aged 30–39 years [HR 1.80, 95% CI 1.63–1.98, p 60 years. Among the BMI ≥ 30 kg/m(2) groups, subjects aged 20–29 years presented the highest risk of IS [HR 3.00, 95% CI (2.34–3.84), p < 0.001]. Overall, WC-AF and WC-IS showed positive linear correlations, but the WC-IS association was weak in subjects aged ≥ 40 years. CONCLUSION: The higher risks of AF and IS according to an increment of BMI and WC were most apparent among the young ages. The association between obesity measurements and IS was not significantly above the midlife. Weight management in the young and integrated risk factor management in the elderly are warranted

Clinicopathologic characteristics and treatment outcomes of hepatoid adenocarcinoma of the stomach, a rare but unique subtype of gastric cancer

<p>Abstract</p> <p>Background</p> <p>Gastric hepatoid adenocarcinoma (HAC) is a special type of gastric cancer that morphologically mimics hepatocellular carcinoma. In this study, we performed an evaluation of clinicopathologic characteristics, treatment outcome, and prognosis in patients with gastric HAC.</p> <p>Methods</p> <p>We consecutively enrolled patients with pathologically proven gastric HAC at Seoul National University Hospital between January 1996 and December 2008 and conducted a retrospective review. Among 15,253 patients with gastric cancer, 26 patients (0.17%) were diagnosed as gastric HAC.</p> <p>Results</p> <p>Among 26 patients, 22 were male and the median age was 63. Stage at diagnosis was stage IB in 3 patients, stage II in 6 patients, stage III in 7 patients, and stage IV in 10 patients. Eight patients out of 18 patients with stage IB, II, III, and IV relapsed after curative surgery. Relapse-free survival for these patients was 16.67 months. The most common metastatic site was intraabdominal lymph nodes (n = 9), followed by the liver (n = 8). Thirteen patients received palliative chemotherapy. The most commonly used regimen was a combination of fluoropyrimidine and platinum. Partial response was observed in one patient and stable disease in 5 patients. Median overall survival and progression free survival of these patients were 8.03 (95% CI: 6.59-9.47) and 3.47 months (95% CI: 0.65-6.29), respectively.</p> <p>Conclusions</p> <p>Gastric HAC is a very rare but unique type of stomach cancer. Early detection of this type of cancer is of critical importance to patient prognosis. Additional studies to reveal the biology of this tumor are warranted.</p

Diagnostic performance of contrast enhanced CT and 18F-FDG PET/CT in suspicious recurrence of biliary tract cancer after curative resection

<p>Abstract</p> <p>Background</p> <p>Because of the late clinical presentation of biliary tract cancer (BTC), only 10% of patients are eligible for curative surgery. Even among those patients who have undergone curative surgery, most patients develop recurrent cancer. This study is to determine the clinical role of ¹⁸F-FDG PET/CT during post-operative surveillance of suspected recurrent BTC based on symptoms, laboratory findings and contrast-enhanced CT (ceCT) findings.</p> <p>Methods</p> <p>We consecutively enrolled 50 patients with BTC who underwent curative surgery. An ¹⁸F-FDG PET/CT was obtained for assessment of recurrence based on clinical suspicion during post-operative surveillance. The final confirmation of recurrence was determined pathologically or clinically. When a pathologic confirmation was impossible or inconclusive, a clinical confirmation was used by radiologic correlation with subsequent follow-up ceCT at a minimum of 3-month intervals. Diagnostic efficacy was evaluated by comparing the results of ceCT and ¹⁸F-FDG PET/CT with the final diagnosis.</p> <p>Results</p> <p>Among the 50 patients, 34(68%) were confirmed to have a recurrence. PET/CT showed higher sensitivity (88% <it>vs</it>. 76%, <it>p </it>= 0.16) and accuracy (82% <it>vs</it>. 66%, <it>p </it>= 0.11) for recurrence compared to ceCT, even though the difference was not significant. The positive (86% <it>vs</it>. 74%, <it>p </it>= 0.72) and negative predictive values for recurrence (73% <it>vs</it>. 47%, <it>p </it>= 0.55) were not significantly different between PET/CT and ceCT. However, an additional PET/CT on ceCT significantly improved the sensitivity than did a ceCT alone (94% [32/34] for PET/CT on ceCT <it>vs</it>. 76% [26/34] for ceCT alone, <it>p </it>= 0.03) without increasing the specificity, positive predictive value, and negative predictive value.</p> <p>Conclusions</p> <p>¹⁸F-FDG PET/CT alone is not more sensitive or specific than ceCT in the detection of recurrent BTC after curative surgery. These results do not reach statistical significance, probably due to the low number of patients. However, an additional ¹⁸F-FDG PET/CT on ceCT significantly improves the sensitivity of detecting recurrences.</p