Puddle formation and persistent gaps across the non-mean-field breakdown of superconductivity in overdoped (Pb,Bi)2Sr2CuO6+δ.

The cuprate high-temperature superconductors exhibit many unexplained electronic phases, but the superconductivity at high doping is often believed to be governed by conventional mean-field Bardeen-Cooper-Schrieffer theory1. However, it was shown that the superfluid density vanishes when the transition temperature goes to zero2,3, in contradiction to expectations from Bardeen-Cooper-Schrieffer theory. Our scanning tunnelling spectroscopy measurements in the overdoped regime of the (Pb,Bi)2Sr2CuO6+δ high-temperature superconductor show that this is due to the emergence of nanoscale superconducting puddles in a metallic matrix4,5. Our measurements further reveal that this puddling is driven by gap filling instead of gap closing. The important implication is that it is not a diminishing pairing interaction that causes the breakdown of superconductivity. Unexpectedly, the measured gap-to-filling correlation also reveals that pair breaking by disorder does not play a dominant role and that the mechanism of superconductivity in overdoped cuprate superconductors is qualitatively different from conventional mean-field theory.

Electrochemical Scanning Tunneling Microscopy Study of Bismuth Chalcogenide Single Crystals.

We use electrochemical scanning tunneling microscopy (EC-STM) to image single-crystal surfaces of the layered bismuth chalcogenide Sn0.01Bi1.99Te2Se in situ under electrochemical control for the first time. The Bi chalcogenides are of interest for their thermoelectric properties and as model topological insulators (TIs). We show that oxidative dissolution takes place via the progressive nucleation of pits in the initially smooth surface terraces rather than at their edges. Nanometer-resolution EC-STM images show that the pit depth is generally equal to the thickness of a complete chalcogenide quintuple layer. The preferential redeposition of dissolved components at step and defect edges on application of a more negative potential after oxidation is observed. Our work demonstrates the ability to control and characterize the surface morphology of single-crystal TIs in an electrochemical environment.

Clinical evaluation of left ventricular function and morphology using an accelerated k-t sensitivity encoding method in cardiovascular magnetic resonance.

OBJECTIVES: To provide clinical validation of a recent 2D SENSE-based accelerated cardiovascular magnetic resonance (CMR) sequence (accelerated k-t SENSE), investigating whether this technique accurately quantifies left ventricle (LV) volumes, function, and mass as compared to 2D cine steady-state free precession (2D-SSFP). METHODS: Healthy volunteers (n = 16) and consecutive heart failure patients (n = 26) were scanned using a 1.5 T MRI system. Two LV short axis (SA) stacks were acquired: (1) accelerated k-t SENSE (5-6 breath-holds; temporal/spatial resolution: 37 ms/1.82 × 1.87 mm; acceleration factor = 4) and (2) standard 2D-SSFP (10-12 breath-holds; temporal/spatial resolution: 49 ms/1.67 × 1.87 mm, parallel imaging). Ascending aorta phase-contrast was performed on all volunteers as a reference to compare LV stroke volumes (LVSV) and validate the sequences. An image quality score for SA images was used, with lower scores indicating better quality (from 0 to 18). RESULTS: There was a high agreement between accelerated k-t SENSE and 2D-SSFP for LV measurements: bias (limits of agreement) of 2.4% (- 5.4% to 10.1%), 6.9 mL/m2 (- 4.7 to 18.6 mL/m2), - 1.5 (- 8.3 to 5.2 mL/m2), and - 0.2 g/m2 (- 11.9 to 12.3 g/m2) for LV ejection fraction, end-diastolic volume index, end-systolic volume index, and mass index, respectively. LVSV by accelerated k-t SENSE presented good agreement with aortic flow. Interobserver and intraobserver variabilities for all LV parameters were also high. CONCLUSION: The accelerated k-t SENSE CMR sequence is clinically feasible and accurately quantifies LV volumes, function, and mass, with short acquisition time and good image quality.

Electrochemical Modification and Characterization of Topological Insulator Single Crystals.

We compare electrochemically modified or thiol-functionalized single-crystal samples of the topological insulator (TI) Bi2Te0.9Se2.1 to freshly cleaved/air-exposed control samples and use X-ray photoelectron spectroscopy (XPS) to investigate the extent of any surface oxidation. XPS spectra for a TI sample maintained at an appropriate potential for 2 h demonstrate the feasibility of protecting the TI surface from oxidation while working in an electrochemical environment. Deliberate electrochemical oxidation, in contrast, generates prominent Bi, Te, and Se peaks associated with oxidation. However, this change is reversible, as further XPS spectra following electrochemical reduction are similar to those measured for an in situ cleaved sample. XPS also shows that adsorption of pentanedithiol (PDT) protects the TI surface from oxidation. Cyclic voltammetry shows that PDT adsorption suppresses electrochemical oxidation and reduction, while electrochemical impedance spectroscopy shows that it increases the charge transfer resistance significantly. Our work demonstrates the ability to control and characterize the surface chemistry of single-crystal TIs in an electrochemical environment for the first time.

4π-periodic Andreev bound states in a Dirac semimetal.

Although signatures of superconductivity in Dirac semimetals have been reported, for instance by applying pressure or using point contacts, our understanding of the topological aspects of Dirac semimetal superconductivity is still developing. Here, we utilize nanoscale phase-sensitive junction technology to induce superconductivity in the Dirac semimetal Bi1-xSbx. Our radiofrequency irradiation experiments then reveal a significant contribution of 4π-periodic Andreev bound states to the supercurrent in Nb-Bi0.97Sb0.03-Nb Josephson junctions. The conditions for a substantial 4π contribution to the supercurrent are favourable because of the Dirac cone's very broad transmission resonances and a measurement frequency faster than the quasiparticle poisoning rate. In addition, we show that a magnetic field applied in the plane of the junction allows tuning of the Josephson junctions from 0 to π regimes. Our results open the technologically appealing avenue of employing the topological bulk properties of Dirac semimetals for topological superconductivity research and topological quantum computer development.

Direct bulk-sensitive probe of 5f symmetry in URu2Si2.

The second-order phase transition into a hidden order phase in URu2Si2 goes along with an order parameter that is still a mystery, despite 30 years of research. However, it is understood that the symmetry of the order parameter must be related to the symmetry of the low-lying local electronic [Formula: see text]-states. Here, we present results of a spectroscopic technique, namely core-level nonresonant inelastic X-ray scattering (NIXS). This method allows for the measurement of local high-multipole excitations and is bulk-sensitive. The observed anisotropy of the scattering function unambiguously shows that the 5[Formula: see text] ground-state wave function is composed mainly of the [Formula: see text] with majority [Formula: see text] = [Formula: see text] + [Formula: see text] and/or [Formula: see text] singlet states. The incomplete dichroism indicates the possibility that quantum states of other irreducible representation are mixed into the ground state.

Existence, character, and origin of surface-related bands in the high temperature iron pnictide superconductor BaFe(2-x)Co(x)As2.

Low energy electron diffraction (LEED) experiments, LEED simulations, and finite slab density functional calculations are combined to study the cleavage surface of Co doped BaFe(2-x)Co(x)As2 (x = 0.1,0.17). We demonstrate that the energy dependence of the LEED data can only be understood from a terminating 1/2 Ba layer accompanied by distortions of the underlying As-Fe2-As block. As a result, surface-related Fe 3d states are present in the electronic structure, which we identify in angle resolved photoemission spectroscopy (ARPES) experiments. The close proximity of the surface-related states to the bulk bands inevitably leads to broadening of the ARPES signals, which excludes the use of the BaFe(2-x)Co(x)As2 system for accurate determination of self-energies using ARPES.

The safety and efficacy of zileuton controlled-release tablets as adjunctive therapy to usual care in the treatment of moderate persistent asthma: a 6-month randomized controlled study.

This study was conducted to assess the safety and efficacy of zileuton controlled release [CR] 1,200 mg BID added to usual care (UC) in 926 patients with moderate asthma (619 patients randomized to zileuton CR and 307 to placebo). Sustained improvements in AM and PM peak expiratory flow (PEF) were observed in the zileuton CR group compared to placebo. The adverse event profile was similar in the two treatment groups. Eleven patients (1.8%) receiving zileuton CR and 2 (0.7%) receiving placebo experienced elevations of alanine aminotransferase (ALT) >or= 3X the upper limit of normal (ULN). These elevations typically occurred (81.8%) during the first 3 months of exposure and most resolved within 21 days after discontinuation.

Surgical complications caused by inaccurate scotopic preoperative pupillary measurement in cataract and lasik surgery: case report and review of the literature.

Accurate scotopic preoperative pupillary measurements in both cataract and lasik surgery cases are critical to avoid in individuals with naturally briskly dilating pupils under scotopic conditions postoperative visual disability related to low light reflections, disabling illuminance, glare disability, halos, starbursts, and diplopia with night vision. Both edge reflections of the pseudophakos implant in cataract surgery and the ablated corneal margin in lasik surgery can contribute to serious visual disability in patients who have larger scotopic pupils exposing the edge of the implanted lens or the surgical optical zone of the ablated cornea to the entrance pupil. A case is presented in which cataract surgery was performed initially with a 5.5-mm-diameter optic lens in one eye and later a 7.0-mm-diameter optic lens in the other eye. Because of a naturally briskly dilating pupil of 7.0 mm, the eye with the smaller implant experienced significant night vision difficulties because of edge reflections of the exposed implant. The other eye in the very same patient with the larger lens implant was asymptomatic. This case underscores the importance of accurate preoperative pupillary measurements under scotopic conditions to avoid this preventable disabling surgical complication in both cataract and lasik cases.