High-Temperature Atomic Diffusion and Specific Heat in Quasicrystals.

A quasicrystal is an ordered but nonperiodic structure understood as a projection from a higher-dimensional periodic structure. Some physical properties of quasicrystals are different from those of conventional solids. An anomalous increase in heat capacity at high temperatures has been discussed for over two decades as a manifestation of a hidden high dimensionality of quasicrystals. A plausible candidate for this origin has been the phason, which has excitation modes originating from the additional atomic rearrangements introduced by the quasiperiodic order, which can be understood in terms of shifting a higher-dimensional lattice. However, most theoretical studies of phasons have used toy models. A theoretical study of the heat capacity of realistic quasicrystals or their approximants has yet to be conducted because of the huge computational complexity. To bridge this gap between experiment and theory, we show experiments and molecular simulations on the same material, an Al-Pd-Ru quasicrystal, and its approximants. We show that at high temperatures, aluminum atoms diffuse with discontinuouslike jumps, and the diffusion paths of the aluminum can be understood in terms of jumps corresponding to hyperatomic-fluctuations-associated atomic rearrangements of the phason degrees of freedom. It is concluded that the anomaly in the heat capacity of quasicrystals arises from the hyperatomic fluctuations that play a role in diffusive Nambu-Goldstone modes.

Deep Learning Enables Rapid Identification of a New Quasicrystal from Multiphase Powder Diffraction Patterns.

Since the discovery of the quasicrystal, approximately 100 stable quasicrystals are identified. To date, the existence of quasicrystals is verified using transmission electron microscopy; however, this technique requires significantly more elaboration than rapid and automatic powder X-ray diffraction. Therefore, to facilitate the search for novel quasicrystals, developing a rapid technique for phase-identification from powder diffraction patterns is desirable. This paper reports the identification of a new Al-Si-Ru quasicrystal using deep learning technologies from multiphase powder patterns, from which it is difficult to discriminate the presence of quasicrystalline phases even for well-trained human experts. Deep neural networks trained with artificially generated multiphase powder patterns determine the presence of quasicrystals with an accuracy >92% from actual powder patterns. Specifically, 440 powder patterns are screened using the trained classifier, from which the Al-Si-Ru quasicrystal is identified. This study demonstrates an excellent potential of deep learning to identify an unknown phase of a targeted structure from powder patterns even when existing in a multiphase sample.

Crystal structures of five compounds in the aluminium-ruthenium-silicon system.

Single crystals of five compounds with approximate compositions ∼Ru16(Al0.78Si0.22)47, (I), ∼Ru9(Al0.70Si0.30)32, (II), ∼Ru10(Al0.67Si0.33)41, (III), ∼Ru(Al0.57Si0.43)5, (IV), and ∼Ru2(Al0.46Si0.54)9, (V), were obtained from polycrystalline lumps mainly composed of the target compounds, and their crystal structures were determined by means of single-crystal X-ray diffraction. The crystal structure of (I) can be related to that of a cubic rational crystalline approximant to an icosa-hedral quasicrystal through crystallographic shear and then unit-cell twinning. The crystal structure of (II) is isotypic with that of a phase with composition ∼Fe9(Al,Si)32. The crystal structure of (III) is comprised of edge-sharing Ru(Al,Si)9-11 polyhedra with disordered chains along edges of polyhedra. The crystal structure of (IV) is of the LiIrSn4 type. The crystal structure of (V) can be viewed as a crystallographic shear structure derived from that of (IV).

Phase stability and thermoelectric properties of semiconductor-like tetragonal FeAl2.

Tetragonal FeAl2 is a high-pressure phase and is predicted to exhibit semiconductor-like behavior. We investigated the pressure and temperature synthesizing conditions of tetragonal FeAl2, supported by in situ X-ray diffractions, using synchrotron radiation during heating the sample under a pressure of 20 GPa. Based on the determined optimal conditions, we synthesized the bulk polycrystalline samples of tetragonal FeAl2 at 7.5 GPa and 873 K, using a multi-anvil press and measured its thermoelectric properties. The Seebeck coefficient of tetragonal FeAl2 showed a large negative value of - 105 µV/K at 155 K and rapidly changed to a positive value of 75 µV/K at 400 K. Although these values are the largest among those of Fe-Al alloys, the maximum power factor remained at 0.41 mW/mK2 because the carrier concentration was not tuned. A comparison of the Gibbs free energy of tetragonal FeAl2, triclinic FeAl2 and FeAl+Fe2Al5 revealed that tetragonal FeAl2 became unstable as the temperature increased, because of its smaller contribution of vibrational entropy.

Thermoelectric properties and electronic structure of the Zintl phase Sr5Al2Sb6.

The Zintl phase Sr5Al2Sb6 has a large, complex unit cell and is composed of relatively earth-abundant and non-toxic elements, making it an attractive candidate for thermoelectric applications. The structure of Sr5Al2Sb6 is characterized by infinite oscillating chains of AlSb4 tetrahedra. It is distinct from the structure type of the previously studied Ca5M2Sb6 compounds (M = Al, Ga or In), all of which have been shown to have promising thermoelectric performance. The lattice thermal conductivity of Sr5Al2Sb6 (~0.55 W mK(-1) at 1000 K) was found to be lower than that of the related Ca5M2Sb6 compounds due to its larger unit cell (54 atoms per primitive cell). Density functional theory predicts a relatively large band gap in Sr5Al2Sb6, in agreement with the experimentally determined band gap of E(g) ~ 0.5 eV. High temperature electronic transport measurements reveal high resistivity and high Seebeck coefficients in Sr5Al2Sb6, consistent with the large band gap and valence-precise structure. Doping with Zn(2+) on the Al(3+) site was attempted, but did not lead to the expected increase in carrier concentration. The low lattice thermal conductivity and large band gap in Sr5Al2Sb6 suggest that, if the carrier concentration can be increased, thermoelectric performance comparable to that of Ca5Al2Sb6 could be achieved in this system.

Pulmonary thromboembolism in a patient with an anomalous right coronary artery as a cause of unusual biventricular myocardial infarction.

This report presents the first case of an unusual biventricular myocardial infarction caused by pulmonary thromboembolism in a 55-year-old woman who had an anomalous origin of the right coronary artery (RCA) from the left coronary sinus. The RCA consequently courses between the aorta and pulmonary trunk, and dilatation of the pulmonary artery because of elevated pulmonary artery pressure compressed the proximal portion of the RCA. The consequent reduced right coronary oxygen supply and sudden increase in right ventricular afterload contributed to the characteristic right ventricular infarction, in addition to a left ventricular infero-posterior infarction. Her anginal symptoms disappeared following successful anticoagulation therapy and insertion of an inferior vena caval filter, without coronary bypass. This pathophysiologic phenomenon is rare, but can be fatal.

Impact of a preoperative mitral regurgitation scoring system on outcome of surgical repair for mitral valve prolapse.

The optimal timing of surgical correction of severe mitral regurgitation (MR) is important for improved morbidity and mortality. We utilized a scoring system to decide the timing of procedures. Based on clinical features and echocardiographic data, we hypothesized that preoperative semi-quantitation of MR using this scoring system may be useful for predicting prognosis after repair. The MR score was composed of 6 parameters associated with disease severity (i.e., history of heart failure, atrial fibrillation, pulmonary hypertension, left ventricular end-systolic dimension, fractional shortening, and left atrial dimension). The maximum score was 6. Of 267 patients who underwent mitral valve repair in the last 10 years, 191 patients with mitral valve prolapse were studied. Patients were categorized into 2 groups according to MR score (group low [L] : 0 to 2.5 and group high [H]: >/=3.0) irrespective of New York Heart Association functional class. A significant difference in postoperative event-free survival was observed between both groups (p = 0.0014); the adjusted risk ratio was 3.4 (95% confidence interval 1.6 to 7.2). Postoperative echocardiography showed larger left ventricular systolic dimensions (p <0.0001), lower fractional shortening (p = 0.0016), and larger left atrial dimensions (p <0.0001) in group H than group L. Thus, an MR score is a simple way to predict the prognosis of severe MR independently of subjective symptoms in patients undergoing mitral valve repair.

Echocardiographic prediction of left ventricular dysfunction after mitral valve repair for mitral regurgitation as an indicator to decide the optimal timing of repair.

OBJECTIVES: This study sought to determine whether echocardiography before mitral valve repair (MVR) for mitral regurgitation (MR) was predictive of postoperative left ventricular (LV) dysfunction and useful for deciding the optimal timing of repair. BACKGROUND: Some reports have shown that the preoperative echocardiographic data of left ventricular ejection fraction (LVEF) and left ventricular end-systolic diameter (LVDs) were good predictors of postoperative LV dysfunction. However, few reports were based on long-term follow-up data of large numbers of patients who underwent MVR in the last decade. METHODS: A total of 274 patients with moderate or severe MR underwent MVR between October 1, 1991, and September 30, 2000. Among them, 171 patients who had both an operation for isolated MR due to degenerative pathology and a postoperative echocardiogram were studied. Postoperative echocardiograms were performed 3.9 +/- 2.4 years after the operation. The LVEF decreased from 66 +/- 10% before surgery to 63 +/- 11% after surgery (p < 0.0001). On univariate analysis, preoperative LVEF and LVDs correlated with postoperative LVEF (r = 0.41 and r = -0.39, respectively). Overall, postoperative LV dysfunction (defined as LVEF <50%) was not frequent (12%). However, the incidence of postoperative LV dysfunction was high in patients with preoperative LVEF <55% (38%) or LVDs > or =40 mm (23%). CONCLUSIONS: In patients with MR, the echocardiographic data of LVEF and LVDs were good predictors of postoperative LV dysfunction. When a decrease in LVEF or an increase in LVDs is detected, MVR should be considered to preserve postoperative LV function.

Rubella-associated perimyocarditis--a case report.

Perimyocarditis represents an inflammation of both the myocardium and pericardium. Although several causative agents have been recognized, pericarditis or myocarditis associated with rubella is an unusual complication. In a 29-year-old woman, left ventricular function transiently deteriorated accompanied by ongoing cardiac inflammation a few days after illness. The titer of rubella virus increased from seronegative to more than 32-fold during the admission, and a rise in specific antirubella virus antibody was present. The patient was suspected of having perimyocarditis associated with the rubella infection. The authors also present clinical features of rubella-associated perimyocarditis and myocarditis in the literature.

Etiology of aortic valve disease and recent changes in Japan:a study of 600 valve replacement cases.

BACKGROUND: Recent studies on the etiology of aortic valve disease in the US showed a decrease in rheumatic valve disease and an increase in age-related degenerative disease. The purpose of this study was to describe the etiology of aortic valve disease and its temporal changes in Japan, based on a large number of cases. METHODS: The medical charts of all patients who underwent aortic valve replacement at our institute between 1977 and 1999 were reviewed. Among the 600 patients analyzed, 213 (36%) had pure aortic stenosis, 265 (44%) had pure aortic regurgitation, and 122 (20%) had combined stenosis and regurgitation. RESULTS: The causes were rheumatic change (49%), degenerative change (19%), bicuspid valves (18%), infective endocarditis (5%) and others (9%). Rheumatic disease continued to be the most common cause of aortic stenosis, but its frequency decreased from 100% in 1977-1979 to 37% in 1995-1999. In contrast, the frequency of degenerative change among stenotic valves increased recently from 11% in 1990-1994 to 30% in 1995-1999. Similarly, rheumatic disease remained to be the leading cause of aortic regurgitation, with a decline in frequency from 46% in 1985-1989 to 27% in 1995-1999. The percentage of degenerative change among regurgitant valves did not change appreciably. CONCLUSIONS: There was a shift in the causes of aortic valve disease, with a decrease in rheumatic disease and an increase in degenerative disease. This trend was similar to that observed in the US. These findings suggest the increasing importance of aortic valve disease due to degenerative change.

Carvedilol-induced changes in cardiac diastolic performance in a patient with isolated noncompaction of the myocardium.

Isolated ventricular noncompaction (IVNC) is an unusual congenital heart disease. The morphological features are trabeculations and intertrabecular recesses within the left ventricle. Important clinical considerations include the high mortality due to depressed cardiac function, and the instance of ventricular arrhythmia and systemic embolism. One of reasons for the high mortality is that there is still no effective therapy with the exception of the recommendation for anticoagulation therapy to prevent embolisms. Hence, we describe a 29-year-old man with IVNC presenting with chronic heart failure. Careful up-titration of carvedilol in this patient changed the parameters of cardiac diastolic performance

Effects of carvedilol on plasma levels of interleukin-6 and tumor necrosis factor-alpha in nine patients with dilated cardiomyopathy.

OBJECTIVES: Whether beta-blocker therapy changes the circulating levels of cytokines as congestive heart failure improves remains uncertain. METHODS: Nine patients with idiopathic dilated cardiomyopathy, who had previously received conventional treatment and were classified as New York Heart Association (NYHA) functional class II, received carvedilol by stepwise dose increase up to 20 mg daily, and the plasma interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-alpha) levels were measured. RESULTS: IL-6 was significantly reduced from 0.80 +/- 0.49 pg/ml before therapy to 0.21 +/- 0.08 pg/ml after carvedilol was increased to 20 mg daily (p < 0.05). Moreover, IL-6 level had already decreased significantly compared to the baseline when the dose of carvedilol had reached 10 mg daily (0.28 +/- 0.12 pg/ml, p < 0.05). TNF-alpha levels did not change significantly. CONCLUSIONS: These results demonstrate that IL-6 concentration is significantly decreased by beta-blocker therapy. The efficacy for heart failure may be related to the change of IL-6 concentration.

Normalization of left ventricular parameters following combined pimobendan and carvedilol treatment in a case of unclassified cardiomyopathy with longstanding refractory status.

A 58-year-old man with a 64-month history of unclassified cardiomyopathy developed congestive heart failure (CHF) and had been dependent on long-term intravenous positive inotropes. Combined pimobendan and carvedilol administration resulted in marked symptomatic improvement from New York Heart Association functional class IV to I. Echocardiograms showed improvement of left ventricular (LV) ejection fraction from 15 to 48%, and LV end-diastolic diameter from 6.7 to 4.9 cm. This mode of therapy not only improved LV contractile function but also normalized LV volume, which was an unusual clinical course compared with the general course of advanced CHF.