Phonon softening and double-well potential formation due to electron-phonon interaction in heavy-fermion systems

We investigate the periodic Anderson-Holstein model by using the dynamical mean-field theory combined with the exact diagonalization method. For the strong electron-phonon coupling g\simg g_c, the system shows an anomalous heavy-fermion behaviour which is accompanied by a large lattice fluctuation and an extreme phonon softening. We also calculate an effective potential for the ions and find that a simple harmonic potential for g\siml g_c changes into a double-well potential for g\simg g_c. The effective pairing interaction between the conduction electrons shows a maximum at $g \approx g_c$ where the superconducting transition temperature is expected to be maximum.Comment: 5 pages, 4 figures, accepted for publication in Physica

Teanol, a new brominated sesquiterpene from the Thailand Laurencia mariannensis

We examined the constitution of Laurencia mariannensis collected from the east coast of Tean Island, Thailand. The structure of a new brominated rearranged cyclolaurane-type sesquiterpene, named teanol (1), is reported. This is the first report on biology and chemistry of the Thailand red algal genus Laurencia (Rhodomelaceae, Ceramiales)

日本维持性血液透析患者蛋白质能量消耗的患病率和诊断标准评估

Background and Objectives: The International Society of Renal Nutrition and Metabolism (ISRNM) has recently recommended the use of the term “protein-energy wasting” (PEW). PEW is a state of malnutrition with decreased body stores of protein and energy fuel in hemodialysis patients and is known as a risk factor for morbidity and mortality. We examined the prevalence of PEW and the characteristics of PEW patients in a hemodialysis center in Japan. Methods and Study Design: Fifty-nine outpatients undergoing maintenance hemodialysis at Iga City General Hospital were evaluated. We observed their biochemical data, body composition, dietary intake, and the number of steps prospectively. PEW was defined according to ISRNM criteria. Results: Nine patients (15% of total) were diagnosed as having PEW. Among indicators of PEW criteria, the relevance ratios of “reduced muscle mass” and “unintentional low dietary energy intake” were significantly higher in PEW than in non-PEW. The number of steps was lower, and serum levels of glucose and C-reactive protein were higher in PEW. Conclusion: About 15% of Japanese hemodialysis patients are estimated to have PEW. Our results suggested that major contributing factors to PEW were reduced muscle mass, unintentional low dietary energy intake, lower amount of exercise, insulin resistance, and chronic inflammation.背景与目的：国际肾营养与代谢协会（ISRNM）最近推荐使用术语“蛋白质能量消耗（PEW）”。PEW 是血液透析患者体内蛋白质和能量储存减少的一种营养不良状态，并且被认为是患病率和死亡率的危险因素。我们在日本的一个血液透析中心研究了PEW 的患病率和PEW 患者的特征。方法与研究设计：我们评估了58 名在伊贺市综合医院做维持性血液透析的门诊患者，并观察了他们的生化数据、体成分、膳食摄入量和行走的步数。根据ISRNM 标准诊断PEW。结果：9 名（占总数的15%）患者被诊断为PEW。在PEW 诊断标准指标中，PEW 患者“肌肉量减少”和“无意识的低膳食能量摄入”的比例高于非PEW 患者。PEW 患者中行走的步数较低，而血清葡萄糖和C-反应蛋白水平较高。结论：约有15%的日本血液透析患者患有PEW。我们的研究结果表明：引起PEW 的主要因素是肌肉量减少、无意识的低膳食能量摄入、运动量低、胰岛素抵抗和慢性炎症

Magnetic Phase Diagram and Metal-Insulator Transition of NiS2-xSex

Magnetic phase diagram of NiS2-xSex has been reexamined by systematic studies of electrical resistivity, uniform magnetic susceptibility and neutron diffraction using single crystals grown by a chemical transport method. The electrical resistivity and the uniform magnetic susceptibility exhibit the same feature of temperature dependence over a wide Se concentration. A distinct first order metal-insulator (M-I) transition accompanied by a volume change was observed only in the antiferromagnetic ordered phase for 0.50<x<0.59. In this region, the M-I transition makes substantial effects to the thermal evolution of staggered moments. In the paramagnetic phase, the M-I transition becomes broad; both the electrical resistivity and the uniform magnetic susceptibility exhibit a broad maximum around the temperatures on the M-I transition-line extrapolated to the paramagnetic phase.Comment: 6 pages, 8 figures, corrected EPS fil

Cooperative Effect of Coulomb Interaction and Electron-Phonon Coupling on the Heavy Fermion State in the Two-Orbital Periodic Anderson Model

We investigate the two-orbital periodic Anderson model, where the local orbital fluctuations of f-electrons couple with a two-fold degenerate Jahn-Teller phonon, by using the dynamical mean-field theory. It is found that the heavy fermion state caused by the Coulomb interaction between f-electrons U is largely enhanced due to the electron-phonon coupling g, in contrast to the case with the single-orbital periodic Anderson model where the effects of U and g compete to each other. In the heavy fermion state for large $U$ and g, both the orbital and lattice fluctuations are enhanced, while the charge (valence) and spin fluctuations are suppressed. In the strong coupling regime, a sharp soft phonon mode with a large spectral weight is observed for small U, while a broad soft phonon mode with a small spectral weight is observed for large U. The cooperative effect of U and g for half-filling with two f-electrons per atom $n_f=2$ is more pronounced than that for quarter-filling with $n_f=1$.Comment: 8 pages, 11 figures, accepted for publication in JPS

Comparing shocks in planetary nebulae with the solar wind termination shock

We show that suprathermal particles, termed pick-up ions (PUIs), might reduce the postshock temperature of the fast wind and jets in some planetary nebulae (PNs) and in symbiotic systems. The goal is to explain the finding that the temperature of the hot bubble formed by the post-shock gas in some PNs and symbiotic nebulae is lower, sometimes by more than an order of magnitude, than the value expected from simple hydrodynamical calculations. Although various explanations have been proposed, there is as yet no prefered solution for this low tempeature problem. PUIs have been invoked to explain the low temperature behind the termination shock of the solar wind. While in the case of the solar wind the neutral atoms that turn into PUIs penetrate the pre-shock solar wind region from the interstellar medium (ISM), in PNs the PUI source is more likely slowly moving clumps embedded in the fast wind or jets. These clumps are formed by instabilities or from backflowing cold gas. Our estimates indicate that in young PNs these PUIs will thermalize before leaving the system. Only in older PNs whose sizes exceed ~5000 AU and for which the fast-wind mass loss rate is below ~10^{-7} Mo/yr do we expect the PUIs to be an efficient carrier of energy out of the postshock region (the hot bubble).Comment: Accepted for publication in Ap

Impact of phase angle on postoperative prognosis

Objective Phase angle (PhA), by bioelectrical impedance analysis, has been used in patients with several diseases; however, its prognostic value in patients with gastrointestinal and hepatobiliary–pancreatic (HBP) cancer is unclear. The present study aimed to investigate the impact of PhA on postoperative short-term outcomes and long-term survival in these patients. Research Methods & Procedures This retrospective study reviewed data of 501 patients with gastrointestinal and HBP cancers who underwent first resection surgery and divided the data into the following groups according to the preoperative PhA quartile values by sex: high-PhA group with the highest quartile (Q4), normal-PhA group with middle quartiles (Q3 and Q2), and low-PhA group with the lowest quartile (Q1). Preoperative nutritional statuses, postoperative short-term outcomes during hospitalization, and 5-year survival between three groups were compared. Cox proportional hazard models were used to evaluate the prognostic effect of PhA. Results PhA positively correlated with body weight, skeletal muscle mass, and handgrip strength, and negatively correlated with age and C-reactive protein levels. The low-PhA group showed a high prevalence of malnutrition (48%) than normal-PhA (25%), and high-PhA (9%) (P < 0.001). The incidence of postoperative severe complications was 10% in all patients [14% in low-PhA, 12% in normal-PhA, and 4% in high-PhA (P = 0.018)]. The incidence of prolonged postoperative high care unit or/and intensive care unit stays was 8% in all patients [16% in low-PhA, 8% in normal-PhA, and 2% in high-PhA (P < 0.001)]. The 5-year survival rate was 74% in all patients [68% in low-PhA, 74% in normal-PhA, and 79% in high-PhA (P < 0.001)]. The multivariate analysis demonstrated that a low-PhA group was an independent risk factor for mortality (hazard ratio, 1.99; 95% confidence interval 1.05–3.90; P = 0.034). Conclusion PhA is a useful short-term and long-term postoperative prognostic marker for patients with gastrointestinal and HBP cancers

Mott Transition, Compressibility Divergence and P-T Phase Diagram of Layered Organic Superconductors: An Ultrasonic Investigation

The phase diagram of the organic superconductor $\kappa$-(BEDT-TTF)$_2$Cu[N(CN)$_2$Cl has been investigated by ultrasonic velocity measurements under helium gas pressure. Different phase transitions were identified trough several elastic anomalies characterized from isobaric and isothermal sweeps. Our data reveal two crossover lines that end on the critical point terminating the first-order Mott transition line. When the critical point is approached along these lines, we observe a dramatic softening of the velocity which is consistent with a diverging compressibility of the electronic degrees of freedom.Comment: 4 pages, 5 figure