Nernst Sign Reversal in the Hexatic Vortex Phase of Weakly Disordered a-MoGe Thin Films.

The hexatic phase is an intermediate stage in the melting process of a 2D crystal due to topological defects. Recently, this exotic phase was experimentally identified in the vortex lattice of 2D weakly disordered superconducting MoGe by scanning tunneling microscopic measurements. Here, we study this vortex state by the Nernst effect, which is an effective and sensitive tool to detect vortex motion, especially in the superconducting fluctuation regime. We find a surprising Nernst sign reversal at the melting transition of the hexatic phase. We propose that they are a consequence of vortex dislocations in the hexatic state which diffuse preferably from the cold to hot.

Universal Voltage Fluctuations in Disordered Superconductors.

The Aharonov-Casher effect is the analogue of the Aharonov-Bohm effect that applies to neutral particles carrying a magnetic moment. This effect can be manifested by vortices or fluxons flowing in trajectories that encompass an electric charge. These vortices have been predicted to result in a persistent voltage that fluctuates for different sample realizations. Here, we show that disordered superconductors exhibit reproducible voltage fluctuation, which is antisymmetrical with respect to the magnetic field, as a function of various parameters such as the magnetic field amplitude, field orientations, and gate voltage. These results are interpreted as the vortex equivalent of the universal conductance fluctuations typical of mesoscopic disordered metallic systems. We analyze the data in the framework of random matrix theory and show that the fluctuation correlation functions and curvature distributions exhibit behavior that is consistent with Aharonov-Casher physics. The results demonstrate the quantum nature of the vortices in highly disordered superconductors, both above and below T_{c}.

Quantum Criticality at the Superconductor-Insulator Transition Probed by the Nernst Effect.

The superconductor-insulator transition (SIT) is an excellent example of a quantum phase transition at zero temperature, dominated by quantum fluctuations. These are expected to be very prominent close to the quantum critical point. So far, most of the experimental studies of the SIT have concentrated on transport properties and tunneling experiments that provide indirect information on criticality close to the transition. Here we present an experiment uniquely designed to study the evolution of quantum fluctuations through the quantum critical point. We utilize the Nernst effect, which has been shown to be effective in probing superconducting fluctuation. We measure the Nernst coefficient in amorphous indium oxide films tuned through the SIT and find a large signal on both the superconducting and the insulating sides, which peaks close to the critical point. The transverse Peltier coefficient α_{xy}, which is the thermodynamic quantity extracted from these measurements, follows quantum critical scaling with critical exponents ν∼0.7 and z∼1. These exponents are consistent with a clean X-Y model in 2+1 dimensions.

Publisher's Note: Glassy Dynamics in Disordered Electronic Systems Reveal Striking Thermal Memory Effects [Phys. Rev. Lett. 117, 116601 (2016)].

This corrects the article DOI: 10.1103/PhysRevLett.117.116601.

Glassy Dynamics in Disordered Electronic Systems Reveal Striking Thermal Memory Effects.

Memory is one of the unique qualities of a glassy system. The relaxation of a glass to equilibrium contains information on the sample's excitation history, an effect often refer to as "aging." We demonstrate that under the right conditions a glass can also possess a different type of memory. We study the conductance relaxation of electron glasses that are fabricated at low temperatures. Remarkably, the dynamics are found to depend not only on the ambient measurement temperature but also on the maximum temperature to which the system was exposed. Hence the system "remembers" its highest temperature. This effect may be qualitatively understood in terms of energy barriers and local minima in configuration space and therefore may be a general property of the glass state.

Measurement of a superconducting energy gap in a homogeneously amorphous insulator.

We present tunneling spectroscopy measurements that directly reveal the existence of a superconducting gap in the insulating state of homogenously disordered amorphous indium oxide films. Two films on both sides of the disorder induced superconductor to insulator transition show the same energy gap scale. This energy gap persists up to relatively high magnetic fields and is observed across the magnetoresistance peak typical of disordered superconductors. The results provide useful information for understanding the nature of the insulating state in the disorder induced superconductor to insulator transition.

Coexistence of Coulomb blockade and zero bias anomaly in a strongly coupled nanodot.

The current-voltage characteristics through a metallic nanoparticle which is well coupled to a metallic lead are measured. It is shown that the I-V curves are composed of two contributions. One is a suppression of the tunneling conductivity at the Fermi level, and the second is an oscillating feature which shifts with gate voltage. The results indicate that zero-bias anomaly and Coulomb blockade phenomena coexist in an asymmetric strongly coupled zero-dimensional system.

New and innovative interventions in the management of pemphigus.

Pemphigus is a rare autoimmune blistering disease usually treated with systemic glucocorticoids with adjuvant immunosuppressants or anti-inflammatories. However significant morbidity and mortality is associated with these treatments. This review discusses conventional therapeutic options, as well as new and emerging therapies that may be safer alternatives to broad-based immunosuppression.

Setup for pressurizing thin films through the superconductor-insulator transition.

We describe an experimental setup designed for transport measurement of thin disordered superconducting films as a function of pressure up to several GPa. We use a specially designed single screw diamond anvil cell that allows the gradual increase of high pressure at cryogenic temperatures. By depositing amorphous films of disordered superconducting indium oxide directly on the diamond, we avoid the effect of pressure-induced structural changes in the substrate. Using this technique, we are able to drive thin films through a pressure tuned superconductor-insulator transition.

AC measurement of the Nernst effect of thin films at low temperatures.

We describe an alternating current method to measure the Nernst effect in superconducting thin films at low temperatures. The Nernst effect is an important tool in the understanding of superconducting fluctuations and, in particular, vortex motion near critical points. However, in most materials, the Nernst signal in a typical experimental setup rarely exceeds a few µV, in some cases being as low as a few nV. DC measurements of such small signals require extensive signal processing and protection against stray pickups and offsets, limiting the sensitivity of such measurements to >1 nV. Here, we describe a method utilizing a one-heater-two-thermometer setup with the heating element and thermometers fabricated on-chip with the sample, which helped to reduce the thermal load and temperature lag between the substrate and the thermometer. Using AC heating power and 2ω measurement, we are able to achieve sub-nanovolt sensitivity in 20 nm-30 nm thin superconducting films on a glass substrate, compared to a sensitivity of ∼10 nV using DC techniques on the same setup.

Imaging quantum fluctuations near criticality.

A quantum phase transition (QPT) occurs between two competing phases of matter at zero temperature, driven by quantum fluctuations. Though the presence of these fluctuations is well established, they have not been locally imaged in space and their local dynamics has not been studied so far. We use a scanning superconducting quantum interference device to image quantum fluctuations in the vicinity of the QPT from a superconductor to an insulator. We find fluctuations of the diamagnetic response in both space and time that survive well below the transition temperature, demonstrating their quantum nature. The fluctuations appear as telegraph-like noise with a range of characteristic times and a non-monotonic temperature dependence, revealing unexpected quantum granularity. The lateral dimension of these fluctuations grows towards criticality, offering a new measurable length scale. Our results provide physical insight about the reorganization of phases across a QPT, with implications for any theoretical description. This paves a new route for future quantum information applications.

Multiple periodicity in a nanoparticle-based single-electron transistor.

A single-electron transistor is a nano-device with large potential for low-power applications that can be used as logic elements in integrated circuits. In this device, the conductance oscillates with a well-defined period due to the Coulomb blockade effect. By using a unique technique, we explore single-electron transistors based on a single metallic nanoparticle with tunable coupling to electric leads. We demonstrate a unique regime in which the transistor is characterized by multi-periodic oscillations of the conductance with gate voltage where the additional periods are harmonics of the basic periodicity of the Coulomb blockade and their relative strength can be controllably tuned. These harmonics correspond to a charge change on the dot by a fraction of the electron charge. The presence of multiple harmonics makes these transistors potential elements in future miniaturization of nano-sized circuit elements.Single-electron transistors are elements for nanoscale electronics. Employing single-electron transistors based on gold nanoparticles, Bitton et al., report a fabrication technique that allows precise control over the coupling between a nanodot and leads, resulting in new transport characteristics.

Quantum criticality at the superconductor-insulator transition revealed by specific heat measurements.

The superconductor-insulator transition (SIT) is considered an excellent example of a quantum phase transition that is driven by quantum fluctuations at zero temperature. The quantum critical point is characterized by a diverging correlation length and a vanishing energy scale. Low-energy fluctuations near quantum criticality may be experimentally detected by specific heat, cp, measurements. Here we use a unique highly sensitive experiment to measure cp of two-dimensional granular Pb films through the SIT. The specific heat shows the usual jump at the mean field superconducting transition temperature marking the onset of Cooper pairs formation. As the film thickness is tuned towards the SIT, is relatively unchanged, while the magnitude of the jump and low-temperature specific heat increase significantly. This behaviour is taken as the thermodynamic fingerprint of quantum criticality in the vicinity of a quantum phase transition.

Formation of a three-dimensional microstructure of Fe3O4-poly(vinyl alcohol) composite by evaporating the hydrosol under a magnetic field.

In this paper, we report on the self-assembly formation of three-dimensional microstructures of Fe3O4 hydrosol. First, we perform new, facile, and direct fabrication of a stable hydrosol of Fe3O4 nanoparticles, based on the sonolysis of an aqueous solution of iron acetate in the presence of PVA-100,000. This is then followed by investigations of the formation of different microstructures obtained on drying a drop of the water suspension on a glass microscope substrate. The evaporation was carried out both without and in the presence of an external magnetic field.

Fabrication and magnetic properties of Ni nanospheres encapsulated in a fullerene-like carbon.

A very simple, efficient, and economical synthetic technique, which produces fascinating fullerene-like Ni-C (graphitic) core-shell nanostructures at a relatively low temperature, is reported. The thermal dissociation of Ni acetylacetonate is carried out in a closed vessel cell (Swagelok) that was heated at 700 degrees C for 3 h. The encapsulation of ferromagnetic Ni nanospheres into the onion structured graphitic layers is obtained in a one-stage, single precursor reaction, without a catalyst, that possesses interesting magnetic properties. The magnetoresistance (MR) property of Ni nanospheres encapsulated in a fullerene-like carbon was measured, which shows large negative MR, of the order of 10%. The proposed mechanism for the formation of the Ni-C core-shell system is based on the segregation and the surface flux formed in the Ni and carbon particles during the reaction under autogenic pressure at elevated temperature.

Influence of rifampin on the pharmacokinetics of pefloxacin.

Pefloxacin and rifampin are frequently associated in the antibiotic therapy of deep-seated, and especially bone-located, infections. The influence of rifampin, a potent drug metabolism enzyme inducer, on the pharmacokinetics of pefloxacin was studied in a randomized crossover trial involving eight young healthy male volunteers. Every volunteer received either pefloxacin alone (period A) or pefloxacin after a 10-day induction by rifampin (period B) given as a 900 mg daily oral dose, and both periods were separated by a 3-week washout period. During both periods, pefloxacin was given during 3 days as a 400 mg b.i.d. oral dose (six doses) followed by a 400 mg intravenous dose on the fourth day. The kinetics of pefloxacin are significantly influenced by rifampin: The minimum (12-hour) plasma concentration, area under the concentration-time curve, and elimination half-life decreased respectively from 4.26 +/- 1.57 to 2.70 +/- 1.00 mg/L, 78.91 +/- 22.82 to 57.81 +/- 16.69 mg.hr/L, 14.46 +/- 3.46 to 10.08 +/- 2.44 hours (p less than 0.05). The renal clearance of pefloxacin was unchanged, but the plasma clearance increased from 94.04 +/- 39.04 to 126.82 +/- 47.36 ml/min (p less than 0.05). The plasma clearance of N-demethyl and N-oxide metabolites were similar for both periods, but the cumulative renal excretion (0 to 96 hours) decreased significantly (p less than 0.01) for period B versus period A. This definite but moderate inductive effect of rifampin on the pharmacokinetics of pefloxacin does not suggest a dose modification of pefloxacin in therapeutic association with rifampin, but pefloxacin assay in plasma seems to be advisable.

Total and free ketoprofen in serum and synovial fluid after intramuscular injection.

Free and total ketoprofen levels in serum and synovial fluid were determined in 37 patients after a single intramuscular injection of ketoprofen, 100 mg. Free drug was separated by equilibrium dialysis. Ketoprofen was assayed by HPLC. Ketoprofen penetrated into the joints rapidly and significant concentrations were found at 15 minutes. The equilibrium time was about 3 1/2 hours. The AUC for total ketoprofen was greater in serum than in synovial fluid. On the other hand, the free fraction AUC in the serum and synovial fluid were quite similar. The mean residence time in the joint was about three times that in the systemic circulation. Ketoprofen was strongly bound to proteins and the percentage of free ketoprofen was not significantly different between serum and synovial fluid. These results provide a possible explanation for duration of the therapeutic effect of ketoprofen despite the short elimination half-life from the serum.

Synthesis and characterization of the antitumor activities of analogues of meridine, a marine pyridoacridine alkaloid.

Marine compounds with pyridoacridine skeletons are known to exhibit interesting antitumor activities. Among these compounds, meridine has already been reported as having significant antitumor activities in vitro. We synthesized 24 analogues of meridine substituted on ring A with the aim of obtaining compounds that display significantly higher in vitro antitumor activities than meridine. The 24 compounds and meridine used as a control compound were tested at 6 different concentrations on 12 different human cancer cell lines including various histopathological types (glioblastomas and breast, colon, lung, prostate, and bladder cancers). The IC(50) value (i.e., the drug concentration inhibiting the mean growth value of the 12 cell lines by 50%) of these 25 compounds ranged over 5 log concentrations, i.e., between 10 and 0.0001 microM, with four of the compounds exhibiting a significantly higher in vitro antitumor activity than meridine. These compounds will now be subjected to further pharmacological investigation including in vivo testing on both conventional murine tumors and human tumors grafted onto nude mice.

Comparison of the pharmacokinetic profiles of three low molecular mass heparins--dalteparin, enoxaparin and nadroparin--administered subcutaneously in healthy volunteers (doses for prevention of thromboembolism).

The present trial was designed to comparatively investigate the pharmacokinetic profile and evaluate the apparent bioavailability pattern of three already marketed low molecular mass heparins (LMMHs): dalteparin (Fragmin), nadroparin (Fraxiparin), and enoxaparin (Lovenox) given by subcutaneous route. The study was carried out in 20 healthy young volunteers given, according to a cross over design, a single subcutaneous injection of the doses recommended for the prophylaxis of deep vein thrombosis (commercial preparations, prefilled syringes): dalteparin 2,500 IU (= 2,500 IU anti-Xa), nadroparin 7,500 ICU (= 3,075 IU anti-Xa), enoxaparin 20 mg (= 2,000 IU anti-Xa) and enoxaparin 40 mg (= 4,000 IU anti-Xa). Of the markers used, activated partial thromboplastin time (APTT), thrombin clotting time (TCT), Heptest, anti-thrombin (aIIa) activity and anti-Xa (aXa) activity, the most pertinent parameter (from a biodynamic viewpoint) is plasma aXa activity. We demonstrated that dalteparin, nadroparin and enoxaparin exhibit statistically significantly different pharmacokinetic and overall disposition patterns. Normalized to the same injected dose (1,000 IU aXa), the relative actual amount of plasma anti-Xa activity generated by enoxaparin is 1.48 times greater (p < 0.001) than that of nadroparin and 2.28 times greater (p < 0.001) than that of dalteparin while the plasma amount induced by nadroparin is 1.54 times greater (p < 0.001) than that of dalteparin. The apparent total body clearance of enoxaparin doses (CL/F = 16.7 +/- 5.5 and 13.8 +/- 3.2 ml/min) is significantly smaller than those of nadroparin (CL/F = 21.4 +/- 7.0 ml/min; p < 0.01) and dalteparin (CL/F = 33.3 +/- 11.8 ml/min; p < 0.001) while dalteparin apparent clearance is about 1.5-fold greater (p < 0.001) than that of nadroparin. These LMMHs also differ by their renal excretion pattern: more fragments exhibiting an anti-Xa activity are recovered in urine following enoxaparin doses (6.4 and 8.7% of the dose, respectively) than following nadroparin (3.9%) and dalteparin (3.4%) injection. These differences in the disposition profiles explain why the apparent elimination half life t1/2 values of the LMMHs compared here are different: dalteparin: 2.8 h; nadroparin: 3.7 h; and enoxaparin: 4.1 h. Whether or not these differences may contribute to explain the different safety/efficacy balance of each of these antithrombotic medications remains to be discussed and needs further studies.

Pharmacokinetics of nicorandil.

This report presents the findings of some studies on single intravenous and oral dosing performed in healthy volunteers to determine the pharmacokinetics and preliminary metabolism of nicorandil, a new vasodilator acting via increase of both membrane potassium conductance and intracellular cyclic guanosine monophosphate in vascular smooth muscle. Nicorandil (5 to 40 mg) is rapidly and completely absorbed after oral administration. Absolute bioavailability is 75 +/- 23% (mean +/- standard deviation) indicating that no significant hepatic first-pass effect exists; peak plasma levels occur within 0.30 to 1.0 hours after dosing. Maximal concentration and area under the plasma concentration time curve of the parent drug are linearly related to a dose range of 5 to 40 mg, which covers the therapeutic regimen proposed for the treatment of patients with angina pectoris. The apparent distribution volume is about 1.4 liters/kg and the plasma concentrations decline according to 2 different processes: (1) a rapid elimination phase (apparent t1/2 beta congruent to 1 hour) that involves about 96% of the dose found in plasma, and a slower phase between the eighth and twenty-fourth hour that could be the consequence of the vascular affinity of the compound. Nicorandil is weakly bound to human plasma proteins (free fraction greater than 75%) and its mean residence time is close to 1.25 hour. Both in animals and in humans, preliminary metabolic studies show that the main biotransformation pathways are denitration and then introduction into the nicotinamide metabolism. However, unchanged nicorandil and denitrated metabolite excreted into the urine represent only about 1 and 4% of the dose, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)