Physical properties of a new cuprate superconductor Pr_2Ba_4Cu_7O_{15-\delta}

We present studies of the thermal, magnetic and electrical transport properties of reduced polycrystalline Pr_2Ba_4Cu_7O_{15-\delta} (Pr247) showing a superconducting transition at Tc = 10 - 16 K and compare them with those of as-sintered non-superconducting Pr247. The electrical resistivity in the normal state exhibited T2 dependence up to approximately 150 K. A clear specific heat anomaly was observed at Tc for Pr247 reduced in a vacuum for 24 hrs, proving the bulk nature of the superconducting state. By the reduction treatment, the magnetic ordering temperature TN of Pr moments decreased from 16 to 11 K, and the entropy associated with the ordering increased, while the effective paramagnetic moments obtained from the DC magnetic susceptibility varied from 2.72 to 3.13 mB. The sign of Hall coefficient changed from positive to negative with decreasing temperature in the normal state of a superconducting Pr247, while that of as-sintered one was positive down to 5 K. The electrical resistivity under high magnetic fields was found to exhibit T^a dependence (a = 0.08 - 0.4) at low temperatures. A possibility of superconductivity in the so-called CuO double chains is discussed.Comment: Science and Technology of Advanced Materials (in press

Functional Materials Synthesis and Physical Properties

A citrate pyrolysis technique is a unique route to prepare reactive precursor mixtures through an ignition process of concentrated aqueous solution. This procedure enables to synthesize highly homogeneous and fine powders for functional materials. The double-chain based superconductor Pr2Ba4Cu7O15−δ and double perovskite photocatalytic semiconductor Ba2Tb(Bi,Sb)O6 were synthesized by using the citrate pyrolysis technique. For the present sample with a reduction treatment for 72 h, a sharp superconducting transition appeared at an onset temperature Tc,on=26 K accompanied by a zero-resistance state at Tc,zero=22 K. The superconducting volume fraction estimated from the magnetization measurement showed an excellent value of ∼58%. Both reduction treatment in a vacuum and subsequent quenching procedure are needed to realize higher superconductivity due to further oxygen defects. The polycrystalline samples for Ba2Tb(Bi1−x,Sbx)O6 (x=0 and 0.5) were formed in the monoclinic and cubic crystal structures. We conducted the gaseous 2-propanol (IPA) and methylene blue (MB) degradation experiments under a visible light irradiation, to evaluate photocatalytic activities of the powder samples. For the Sb50% substituted sample, the highest performance of MB degradation was observed. The effect of Sb-substitution on the photocatalytic degradation of MB is in direct contrast to that on the IPA decomposition under visible light irradiation. The enhanced photocatalytic properties in the citrate samples are attributed to their morphology, where fine particles are homogeneously distributed with a submicron order

Post-intervention Status in Patients With Refractory Myasthenia Gravis Treated With Eculizumab During REGAIN and Its Open-Label Extension

OBJECTIVE: To evaluate whether eculizumab helps patients with anti-acetylcholine receptor-positive (AChR+) refractory generalized myasthenia gravis (gMG) achieve the Myasthenia Gravis Foundation of America (MGFA) post-intervention status of minimal manifestations (MM), we assessed patients' status throughout REGAIN (Safety and Efficacy of Eculizumab in AChR+ Refractory Generalized Myasthenia Gravis) and its open-label extension. METHODS: Patients who completed the REGAIN randomized controlled trial and continued into the open-label extension were included in this tertiary endpoint analysis. Patients were assessed for the MGFA post-intervention status of improved, unchanged, worse, MM, and pharmacologic remission at defined time points during REGAIN and through week 130 of the open-label study. RESULTS: A total of 117 patients completed REGAIN and continued into the open-label study (eculizumab/eculizumab: 56; placebo/eculizumab: 61). At week 26 of REGAIN, more eculizumab-treated patients than placebo-treated patients achieved a status of improved (60.7% vs 41.7%) or MM (25.0% vs 13.3%; common OR: 2.3; 95% CI: 1.1-4.5). After 130 weeks of eculizumab treatment, 88.0% of patients achieved improved status and 57.3% of patients achieved MM status. The safety profile of eculizumab was consistent with its known profile and no new safety signals were detected. CONCLUSION: Eculizumab led to rapid and sustained achievement of MM in patients with AChR+ refractory gMG. These findings support the use of eculizumab in this previously difficult-to-treat patient population. CLINICALTRIALSGOV IDENTIFIER: REGAIN, NCT01997229; REGAIN open-label extension, NCT02301624. CLASSIFICATION OF EVIDENCE: This study provides Class II evidence that, after 26 weeks of eculizumab treatment, 25.0% of adults with AChR+ refractory gMG achieved MM, compared with 13.3% who received placebo

Minimal Symptom Expression' in Patients With Acetylcholine Receptor Antibody-Positive Refractory Generalized Myasthenia Gravis Treated With Eculizumab

The efficacy and tolerability of eculizumab were assessed in REGAIN, a 26-week, phase 3, randomized, double-blind, placebo-controlled study in anti-acetylcholine receptor antibody-positive (AChR+) refractory generalized myasthenia gravis (gMG), and its open-label extension

Physical properties of a new cuprate superconductor Pr2Ba4Cu7O15−δ

We present studies of the thermal, magnetic, and electrical transport properties of reduced polycrystalline Pr2Ba4Cu7O15−δ (Pr247) showing a superconducting transition at Tc=10–16 K, and compare them with those of as-sintered non-superconducting Pr247. The electrical resistivity in the normal state exhibited T2 dependence up to approximately 150 K. A clear specific heat anomaly was observed at Tc for Pr247 reduced in a vacuum for 24 h, proving the bulk nature of the superconducting state. By the reduction treatment, the magnetic ordering temperature TN of Pr moments decreased from 16 to 11 K, and the entropy associated with the ordering increased, while the effective paramagnetic moments obtained from the DC magnetic susceptibility varied from 2.72 to 3.13μB. The sign of Hall coefficient changed from positive to negative with decreasing temperature in the normal state of a superconducting Pr247, while that of the as-sintered one was positive down to 5 K. The electrical resistivity under high magnetic fields was found to exhibit Tα dependence (α=0.08–0.4) at low temperatures. A possibility of superconductivity in the so-called CuO double chains is discussed

Electronic properties and crystal structures of double-perovskites, Ba2BiIIIBiVO6,Ba2PrBiO6, and Ba2PrSbO6: First-principles study

In recent experiments, a significant band gap widening was observed when Sb was substituted for Bi in the double-perovskite Ba _2 PrBiO _6 . In this work, we study a series of double-perovskites, Ba _2 Bi ^III Bi ^V O _6 , Ba _2 PrBiO _6 , and Ba _2 PrSbO _6 using the first-principles density functional theory with the Heyd-Scuseria-Ernzerhof hybrid functional to investigate the substitution effect on the structural and electronic properties. We find that the two topmost valence bands are disappeared on the substitution of Pr ^III for Bi ^III , and the two bottommost conduction bands are disappeared on the substitution of Sb ^V for Bi ^V , causing the significant band gap widening. Further, our calculation suggests that the Ba _2 PrPr _Bi O _6 is a possible candidate as a source of the Pr ^IV signal observed in the experiment. We find that the B -site disordering atomic configuration, Ba _2 B ″ ^V B ′ ^III O _6 , are restored to those of the original structures. On the other hand, our results also suggest the importance of the partial B -site disorder to explain the experimentally observed band gaps

Changes in the Superior Vena Cava Area During Inspiration and Expiration in Relation to Emphysema

<p><i>Background:</i> In patients with emphysema, increased intrathoracic pressure is closely related to hyperinflation and leads to hemodynamic impairments. Both intrathoracic pressure and hemodynamics such as venous return are affected by the respiratory phase. Therefore, respiratory variations in hemodynamics may be associated with the extent of emphysema that causes increased intrathoracic pressure. The current study was designed to evaluate the relationship between respiratory phasic variations in the area of the superior vena cava (SVC) and the extent of emphysema. <i>Methods:</i> We measured the SVC area and calculated the ratio of the SVC area in inspiratory and expiratory scans (i/e-SVC ratio) in 101 patients with emphysema who underwent both inspiratory and expiratory CT. The correlation of the i/e-SVC ratio with the extent of emphysema (%LAA) obtained by CT images was evaluated. Multiple linear regression analysis using i/e-SVC ratio as the dependent variable was performed. <i>Results:</i> The i/e-SVC ratio had a significant positive correlation with%LAA (ρ = 0.582, <i>p</i> <0.0001). The i/e-SVC ratio was significantly higher in patients with severe emphysema (0.86 ± 0.13) than in patients with mild-moderate emphysema (0.69 ± 0.13) (<i>p</i> <0.0001). Multiple linear regression analysis showed that%LAA was the only independent predictors of the i/e-SVC ratio (r² = 0.471, <i>p</i> = 0.0006). <i>Conclusion:</i> Respiratory phasic variations in the SVC area are significantly correlated with the extent of emphysema.</p