Thermoelectric response near a quantum critical point of ß-YbAlB4 and YbRh2Si2: a comparative study.

The thermoelectric coefficients have been measured down to a very low temperature for the Yb-based heavy-fermion compounds ß-YbAlB4 and YbRh2Si2, often considered as model systems for the local quantum criticality case. We observe a striking difference in the behavior of the Seebeck coefficient S in the vicinity of their respective quantum critical point (QCP). Approaching the critical field, S/T is enhanced in ß-YbAlB4, but drastically reduced in YbRh2Si2. The ratio of thermopower to specific heat remains constant for ß-YbAlB4, but it is significantly reduced near the QCP in YbRh2Si2. In both systems, on the other hand, the Nernst coefficient shows a diverging behavior near the QCP. The interplay between valence and magnetic quantum criticality and the additional possibility of a Lifshitz transition crossing the critical field under magnetic field are discussed as the origin of the different behaviors of these compounds.

Quantum critical Kondo quasiparticles probed by ESR in ß-YbAlB4.

Electron spin resonance (ESR) can probe conduction electrons (CE) and local moment (LM) spin systems in different materials. A CE spin resonance (CESR) is observed in metallic systems based on light elements or with enhanced Pauli susceptibility. LM ESR can be seen in compounds with paramagnetic ions and localized d or f electrons. Here we report a remarkable and unprecedented ESR signal in the heavy-fermion superconductor ß-YbAlB4 [S. Nakatsuji et al., Nature Phys. 4, 603 (2008)] which behaves as a CESR at high temperatures and acquires characteristics of the Yb³âº LM ESR at low temperature. This dual behavior strikes as an in situ unique observation of the Kondo quasiparticles in a quantum critical regime. The proximity to a quantum critical point may favor the appearance of this dual character of the ESR signal in ß-YbAlB4.

Strong valence fluctuation in the quantum critical heavy fermion superconductor ß-YbAlB4: a hard x-ray photoemission study.

Electronic structures of the quantum critical superconductor ß-YbAlB4 and its polymorph α-YbAlB4 are investigated by using bulk-sensitive hard x-ray photoemission spectroscopy. From the Yb 3d core level spectra, the values of the Yb valence are estimated to be ∼2.73 and ∼2.75 for α- and ß-YbAlB4, respectively, thus providing clear evidence for valence fluctuations. The valence band spectra of these compounds also show Yb2+ peaks at the Fermi level. These observations establish an unambiguous case of a strong mixed valence at quantum criticality for the first time among heavy fermion systems, calling for a novel scheme for a quantum critical model beyond the conventional Doniach picture in ß-YbAlB4.

Conduction electron spin resonance in the α-Yb1-xFexAlB4 (0 ⩽ x ⩽ 0.50) and α-LuAlB4 compounds.

ß-YbAlB4 has become one of the most studied heavy fermion systems since its discovery due to its remarkable physical properties. This system is the first reported Yb-based heavy-fermion superconductor (HFS) for which the low-T superconducting state emerges from a non-fermi-liquid (NFL) normal state associated with quantum criticality Nakatsuji et al 2008 Nature 4 603. Additionally, it presents a striking and unprecedented electron spin resonance (ESR) signal which behaves as a conduction electron spin resonance (CESR) at high temperatures and acquires features of the Yb(3+) local moment ESR at low temperatures. The latter, also named Kondo quasiparticles spin resonance (KQSR), has been defined as a 4f-ce strongly coupled ESR mode that behaves as a local probe of the Kondo quasiparticles in a quantum critical regime, Holanda et al 2011 Phys. Rev. Lett. 107 026402. Interestingly, ß-YbAlB4 possesses a previously known structural variant, namely the α-YbAlB4, phase which is a paramagnetic Fermi liquid (FL) at low temperatures Macaluso et al 2007 Chem. Mater. 19 1918. However, it has been recently suggested that the α-YbAlB4 phase may be tuned to NFL behavior and/or magnetic ordering as the compound is doped with Fe. Here we report ESR studies on the α-Yb1-xFexAlB4 (0 â©½ x â©½ 0.50) series as well as on the reference compound α-LuAlB4. For all measured samples, the observed ESR signal behaves as a CESR in the entire temperature range (10 K â‰² T â‰² 300 K) in clear contrast with what has been observed for ß-YbAlB4. This striking result indicates that the proximity to a quantum critical point is crucial to the occurrence of a KQSR signal.

Assessment by autonomic blockade of age-related changes of the sinus node function and autonomic regulation in sick sinus syndrome.

Age-related changes of the sinus node (SN) function and the autonomic influence on the SN function were evaluated in 65 patients with sick sinus syndrome (range 14 to 84 years). Heart rate (HR), corrected SN recovery time and sinoatrial conduction time were measured before (basic) and after (intrinsic) autonomic blockade (propranolol 0.2 mg/kg plus atropine 0.04 mg/kg intravenously). Percent of autonomic chronotropies of the SN function were calculated by the following formulas: (1)--(intrinsic HR--basic HR/intrinsic HR) X 100; (2) (intrinsic corrected SN recovery time--basic corrected SN recovery time/intrinsic corrected SN recovery time) X 100; (3) (intrinsic sinoatrial conduction time--basic sinoatrial conduction time/intrinsic sinoatrial conduction time) X 100. Basic HR, basic corrected SN recovery time and basic sinoatrial conduction time did not vary with age. Intrinsic HR decreased with age, but this correlation was weak (r = -0.54, p less than 0.001). Intrinsic corrected SN recovery time and intrinsic sinoatrial conduction time tended to increase with age (r = 0.26, p less than 0.05; r = 0.29, p less than 0.05, respectively). Percent chronotropies of HR, corrected SN recovery time and sinoatrial conduction time were negative values in younger patients and positive values in elderly patients; they correlated positively with age (r = 0.59, p less than 0.001; r = 0.60, p less than 0.001; r = 0.43, p less than 0.001, respectively). Thus, the basic SN function did not change with age, while the intrinsic SN function deteriorated with age.(ABSTRACT TRUNCATED AT 250 WORDS)

New observations on the mechanisms of antiarrhythmic actions of disopyramide on cardiac membranes.

Electrophysiologic effects of disopyramide on cardiac membranes were studied using the microelectrode technique applied to papillary muscles and the suction pipette whole-cell clamp method applied to isolated ventricular myocytes from guinea-pig hearts. In contrast to previous reports, the development and recovery from the Vmax blocks of action potentials by disopyramide and lidocaine were best expressed by 2 exponential functions, not 1, suggesting that there might be 2 different processes for the sodium current block. A near-therapeutic concentration (11 microM) of disopyramide depressed Vmax at frequencies of 0.1 to 2.0 Hz decreased action potential amplitude and shortened plateau phase in ventricular myocytes. Action potential duration was prolonged by the drug in most of the preparations but shortened in some. Disopyramide prolonged the refractory period and increased threshold current for excitation. The drug was also shown to depress both the calcium current and the delayed outward potassium current. These multiple actions of disopyramide may explain its variety of antiarrhythmic properties.

Aneurysm of patent ductus arteriosus in an adult case: findings of cardiac catheterization, angiography, and pathology.

A 42-year-old male was admitted to our hospital for evaluation of a left precordial continuous murmur. Results of catheterization revealed a step-up of oxygen content in the pulmonary arteries and the calculated left-to-right shunt flow was 40% of the pulmonary arterial flow. Furthermore, aortography unexpectedly revealed an aneurysm of the patent ductus arteriosus. During surgery, the aneurysm was discovered to arise from the frontal wall of the ductus arteriosus, and histological observation showed focal necrosis and mucoid degeneration of the media of the aneurysmal wall in contrast to a thickened intimal fibroelastosis of the adjacent ductal wall. This is presumed to be the first adult case of patent ductal aneurysm ever reported in which antemortem diagnosis and surgical treatment were successfully conducted. Our case may suggest that the fragility of the ductal wall following the structural change in an incomplete closing process is considered as a potential pathogenesis of ductal aneurysm formation.

Intraocular hemorrhage developing during interferon therapy.

A 43-year-old man with chronic active hepatitis C was treated with interferon-beta (IFN-beta) at a dosage of 6 x 10(6) IU/day for a planned 6-week period. Ocular hyperemia, ophthalmalgia, and increased intraocular pressure in the right eye developed 20 days after the start of treatment. Intraocular pressure remained high, even after discontinuation of IFN therapy, laser therapy, and iridectomy. Two days later, the right eye was removed because perforation had occurred. The ocular symptoms that developed in this case were thought to have been caused and exacerbated by IFN administration.

A study of ventricular contraction sequence in complete right bundle branch block by phase analysis.

Twenty-four patients with complete right bundle branch block (CRBBB) combined with and without left axis deviation (LAD) on ECG, were compared with 17 normal subjects to evaluate the right ventricular contraction sequence and pattern in detail. Blood pool scintigrams were obtained in the left anterior oblique projection, and these images were analyzed by first component Fourier harmonics. In the normal subjects, the phase value distribution representing the pattern of ventricular contraction was almost homogeneous in both the right and left ventricles (RV & LV). In the CRBBB patients without LAD, the phase images showed apparent phase delay in the right ventricle. In the CRBBB patients with LAD, the phase images showed many different contraction patterns varying from normal to RV phase delay, owing to the effects of the hemi-block. Quantitative analysis of the absolute values, showed that the mean (RV-LV) value was 6.6 +/- 8.4 msec in the normal subjects. In the CRBBB patients without LAD, the duration of the QRS complex correlated with the mean (RV-LV) value, whereas no difference was observed between the duration of the QRS complex and the standard deviation of the right ventricle. Using phase analysis the degree of the RBBB can be determined from the phase images, and can be quantitatively analyzed as in electrical studies.

Prognostic value of peritoneal lavage cytology and chemotherapy during surgery for advanced gastric cancer.

BACKGROUND: The prognostic value of intra-operative peritoneal lavage cytology and chemotherapy was evaluated retrospectively. METHOD: Lavage cytology was performed in 257 patients. Prognosis was investigated in 85 of pT3 and pT4 patients with radical gastrectomy. Intra-operative chemotherapy was selected according to the cytology and exploration of the peritoneal cavity. For patients forecasted to have peritoneal recurrence, intraperitoneal injection of cisplatin was performed. RESULTS: No free cancer cells (cy(-)) were found in pTis, pT1 and pT2. In pT3 and pT4, cy(-) were 82.8% of the cases without macroscopic metastasis (P(-)), and the presence of free cancer cells (cy(+)) were 89.3% of the cases with macroscopic metastasis (P(+)). Intraperitoneal injection was performed in about 60% of P(-)/cy(+) and P(+) cases. Five-year survival rate of P(-)/cy(-) was 41.7% and that of P(-)/cy(+) was 33.3%. All of P(+) died within 3 years. CONCLUSION: Patients of P(-)/cy(+) probably had microscopic residual disease and might benefit from intraperitoneal chemotherapy.

[The heart rate alternative sequence during pharmacologic total autonomic blockade in patients with sick sinus syndrome: differential effects in relation to age].

To study the age-related changes of the sinus node function and the variations of influence of autonomic nervous system, pharmacologic total autonomic blockade (TAB) was conducted in 35 patients with symptomatic sinus bradycardia (21 men and 14 women, 50 +/- 21 years, mean +/- SD). Twenty-one patients [Group I, consisting of 14 patients younger than 60 years (group IY) nd 7 patients 60 years or older (group IE)] had a normal intrinsic heart rate (IHRo), and 14 patients had an abnormal IHRo [Group II, consisting of 8 patients younger than 60 years (group IIY) and 5 patients 60 years or older (group IIE)]. The basic cycle length was significantly longer in group II than in group I, suggesting that intrinsic sinus node function was more seriously deteriorated in group II in spite of the compensatory effect of autonomic regulation. In group II it was characteristic that the cycle length (CL) after atropine sulfate administration was longer than the CL of the predicted intrinsic heart rate (IHRp). Otherwise, some group II patients might be regarded as normal by atropine sulfate administration alone. Parasympathetic tone showed a negative correlation with age, and it was most enhanced in group IIY, suggesting that parasympathetic negative chronotropy was stronger in this group. In the course of propranolol administration, prolongation of CL was significantly larger in group IIE than in group IIY, but there was no age-related difference in group I. In group II, beta-adrenergic blockade with propranolol administration showed that sympathetic positive chronotropy was a critical compensatory factor around the upper limit of the CL of IHRp.(ABSTRACT TRUNCATED AT 250 WORDS)

[Class-I antiarrhythmic drugs].

Classification, mechanism of action, pharmacokinetic properties and clinical applications of class-I antiarrhythmic agents were summarized. Class-I drugs were subdivided into three groups, Ia, Ib, Ic. This subclassification is based on their action to modify the action potential duration. In the Cardiac Arrhythmia Suppression Trial (CAST), flecainide and encainide were associated with greater mortality than placebo in patients with non-life threatening arrhythmias. Results of CAST and other megatrials suggested that antiarrhythmic agents were unsafe in some groups of patients and the limitation of antiarrhythmic therapy. Proarrhythmia and combination therapy of antiarrhythmic agents were mentioned.

Conduction electron spin resonance in AlB2.

This work reports on electron spin resonance experiments in oriented single crystals of the hexagonal AlB2 diboride compound (P6/mmm, D16h structure) which display conduction electron spin resonance. The X-band electron spin resonance spectra showed a metallic Dysonian resonance with g-value and intensity independent of temperature. The thermal broadening of the anisotropic electron spin resonance linewidth ΔH tracks the T-dependence of the electrical resistivity below T is approximately equal to 100 K. These results confirm the observation of a conduction electron spin resonance in AlB2 and are discussed in comparison with other boride compounds. Based on our main findings for AlB2 and the calculated electronic structure of similar layered honeycomb-like structures, we conclude that any array of covalent B-B layers potentially results in a conduction electron spin resonance signal. This observation may shed new light on the nature of the non-trivial conduction electron spin resonance-like signals of complex f-electron systems such as ß-YbAlB4.

Spin-orbital short-range order on a honeycomb-based lattice.

Frustrated magnetic materials, in which local conditions for energy minimization are incompatible because of the lattice structure, can remain disordered to the lowest temperatures. Such is the case for Ba(3)CuSb(2)O(9), which is magnetically anisotropic at the atomic scale but curiously isotropic on mesoscopic length and time scales. We find that the frustration of Wannier's Ising model on the triangular lattice is imprinted in a nanostructured honeycomb lattice of Cu(2+) ions that resists a coherent static Jahn-Teller distortion. The resulting two-dimensional random-bond spin-1/2 system on the honeycomb lattice has a broad spectrum of spin-dimer-like excitations and low-energy spin degrees of freedom that retain overall hexagonal symmetry.

Crystal growth, structure, and physical properties of Ln(Cu,Al)12 (Ln = Y, Ce, Pr, Sm, and Yb) and Ln(Cu, Ga)12 (Ln = Y, Gd-Er, and Yb).

Single crystals of Ln(Cu,Al)12 and Ln(Cu,Ga)12 compounds (Ln = Y, Ce-Nd, Sm, Gd-Ho, and Yb for Al and Ln = Y, Gd-Er, Yb for Ga) have been grown by flux-growth methods and characterized by means of single-crystal x-ray diffraction, complemented with microprobe analysis, magnetic susceptibility, resistivity and heat capacity measurements. Ln(Cu,Ga)12 and Ln(Cu,Al)12 of the ThMn12 structure type crystallize in the tetragonal I4/mmm space group with lattice parameters a approximately 8.59 Šand c approximately 5.15 Šand a approximately 8.75 Šand c approximately 5.13 Šfor Ga and Al containing compounds, respectively. For aluminium containing compounds, magnetic susceptibility data show Curie-Weiss paramagnetism in the Ce and Pr analogues down to 50 K with no magnetic ordering down to 3 K, whereas the Yb analogue shows a temperature-independent Pauli paramagnetism. Sm(Cu,Al)12 orders antiferromagnetically at T(N)approximately 5 K and interestingly exhibits Curie-Weiss behaviour down to 10 K with no Van Vleck contribution to the susceptibility. Specific heat data show that Ce(Cu,Al)12 is a heavy fermion antiferromagnet with T(N) approximately 2 K and with an electronic specific heat coefficient γ0 as large as 390 mJ K2 mol(-1). In addition, this is the first report of Pr(Cu,Al)12 and Sm(Cu,Al)12 showing an enhanced mass (approximately 80 and 120 mJ K(2) mol(-1)). For Ga containing analogues, magnetic susceptibility data also show the expected Curie-Weiss behaviour from Gd to Er, with the Yb analogue being once again a Pauli paramagnet. The antiferromagnetic transition temperatures range over 12.5, 13.5, 6.7, and 3.4 K for Gd, Tb, Dy, and Er. Metallic behaviour is observed down to 3 K for all Ga and Al analogues. A large positive magnetoresistance up to 150% at 9 T is also observed for Dy(Cu,Ga)12. The structure, magnetic, and transport properties of these compounds will be discussed.