Andreev reflection at the interface with an oxide in the quantum Hall regime

Quantum Hall/superconductor junctions have been an attractive topic as the two macroscopically quantum states join at the interface. Despite longstanding efforts, however, experimental understanding of this system has not been settled yet. One of the reasons is that most semiconductors hosting high-mobility two-dimensional electron systems (2DES) usually form Schottky barriers at the metal contacts, preventing efficient proximity between the quantum Hall edge states and Cooper pairs. Only recently have relatively transparent 2DES/superconductor junctions been investigated in graphene. In this study, we propose another material system for investigating 2DES/superconductor junctions, that is ZnO-based heterostrcuture. Due to the ionic nature of ZnO, a Schottky barrier is not effectively formed at the contact with a superconductor MoGe, as evidenced by the appearance of Andreev reflection at low temperatures. With applying magnetic field, while clear quantum Hall effect is observed for ZnO 2DES, conductance across the junction oscillates with the filling factor of the quantum Hall states. We find that Andreev reflection is suppressed in the well developed quantum Hall regimes, which we interpret as a result of equal probabilities of normal and Andreev reflections as a result of multiple Andreev reflection at the 2DES/superconductor interface.Comment: 18 pages, 8 figure

Thinning or thickening? Multiple rheological regimes in dense suspensions of soft particles

The shear rheology of dense colloidal and granular suspensions is strongly nonlinear, as these materials exhibit shear-thinning and shear-thickening, depending on multiple physical parameters. We numerically study the rheology of a simple model of soft repulsive particles at large densities, and show that nonlinear flow curves reminiscent of experiments on real suspensions can be obtained. By using dimensional analysis and basic elements of kinetic theory, we rationalize these multiple rheological regimes and disentangle the relative impact of thermal fluctuations, glass and jamming transitions, inertia and particle softness on the flow curves. We characterize more specifically the shear-thickening regime and show that both particle softness and the emergence of a yield stress at the jamming transition compete with the inertial effects responsible for the observed thickening behaviour. This allows us to construct a dynamic state diagram, which can be used to analyze experiments.Comment: 6 pages, 3 figure

SOLVENT ISOTOPE EFFECT ON NUCLEOPHILIC ATTACK OF METHOXIDE ION ON sp² CARBON ATOM OF trans-3- METHOXY OR trans-3- METHYLTHIO-ACRYLOPHENONES

The second-order rate constants for the base-catalysed reactions of methanol with 3-methoxy- and 3-methylthio-acrylophenones (MeOAcr and MeSAcr) have been determined in methanol and in methanol-OD at 25℃. Non-catalytic terms were not detected. Inverse kinetic solvent isotope effects on attack of methoxide ion on MeOAcr and MeSAcr of 0.62 and 0.57, respectively, are compared with earlier data for attack of methoxide ion on a substituted N -benzylideneaniline. The rate constants depend on electrophiles, but the solvent isotope effects, ca. 0.6, are fairly constant, irrespective of the 10⁴ fold variance of the rate constants. The results are discussed in terms of solvent reorganisation. The solvent isotope effect for the reaction of hydroxide ion in water was also determined.Article信州大学教養部紀要. 26: 157-162(1992)departmental bulletin pape

KINETICS OF THE REACTION OF trans-3- METHYLTHIOACRYLOPHENONE WITH HYDROXIDE ION. DETECTION OF CARBANION INTERMEDIATE BY THE DIFFERENCE SPECTRUM.

Reaction of trans-3-methylthioacrylophenone (MeSAcr) with hydroxide ion was followed spectrophotometric ally in aqueous solution. The reaction was found to be a typical series reaction : MeSAcr → benzoylacetaldehyde enolate → acetophenone. A carbanion intermediate, the enolate ion, was detected by the coincidence of difference spectra between the spectra in basic reaction solutions and in their acidified solutions with those between the spectra of benzoylacetaldehyde enolate and of the parent aldehyde. The first step of reaction in eq. (3) was kinetically first order in MeSAcr and first order in hydroxide ion. The second-order rate constants were obtained for MeSAcr-hydroxide ion combination reactions. The first-order rate coefficients for the second step of reaction in eq. (3) were obtained at the later stage of reaction where almost all MeSAcr was consumed. The rate coefficients are expressed as: k_ = K₀ + k_⁻[OH⁻]. This is completely consistent with a mechanism for the hydrolysis of enolates of dicarbonyl compounds.Article信州大学教養部紀要. 27: 249-256(1993)departmental bulletin pape

Strategyproof matching with regional minimum and maximum quotas

This paper considers matching problems with individual/regional minimum/maximum quotas. Although such quotas are relevant in many real-world settings, there is a lack of strategyproof mechanisms that take such quotas into account. We first show that without any restrictions on the regional structure, checking the existence of a feasible matching that satisfies all quotas is NP-complete. Then, assuming that regions have a hierarchical structure (i.e., a tree), we show that checking the existence of a feasible matching can be done in time linear in the number of regions. We develop two strategyproof matching mechanisms based on the Deferred Acceptance mechanism (DA), which we call Priority List based Deferred Acceptance with Regional minimum and maximum Quotas (PLDA-RQ) and Round-robin Selection Deferred Acceptance with Regional minimum and maximum Quotas (RSDA-RQ). When regional quotas are imposed, a stable matching may no longer exist since fairness and nonwastefulness, which compose stability, are incompatible. We show that both mechanisms are fair. As a result, they are inevitably wasteful. We show that the two mechanisms satisfy different versions of nonwastefulness respectively; each is weaker than the original nonwastefulness. Moreover, we compare our mechanisms with an artificial cap mechanism via simulation experiments, which illustrate that they have a clear advantage in terms of nonwastefulness and student welfare

Andreev Reflection at the Interface with an Oxide in the Quantum Hall Regime

Quantum Hall/superconductor junctions have been an attractive topic as the two macroscopically quantum states join at the interface. Despite longstanding efforts, however, experimental understanding of this system has not been settled yet. One of the reasons is that most semiconductors hosting high-mobility two-dimensional electron systems (2DES) usually form Schottky barriers at the metal contacts, preventing efficient proximity between the quantum Hall edge states and Cooper pairs. Only recently have relatively transparent 2DES/superconductor junctions been investigated in graphene. In this study, we propose another material system for investigating 2DES/superconductor junctions, that is ZnO-based heterostructure. Due to the ionic nature of ZnO, a Schottky barrier is not effectively formed at the contact with a superconductor MoGe, as evidenced by the appearance of Andreev reflection at low temperatures. With applying magnetic field, while clear quantum Hall effect is observed for ZnO 2DES, conductance across the junction oscillates with the filling factor of the quantum Hall states. We find that Andreev reflection is suppressed in the well developed quantum Hall regimes, which we interpret as a result of equal probabilities of normal and Andreev reflections as a result of multiple Andreev reflection at the 2DES/superconductor interface

Synergistic effects of cardiac resynchronization therapy and Bachmann’s bundle pacing on heart failure with atrial tachyarrhythmias

Cardiac resynchronization therapy (CRT) is electrical resynchronization of the ventricles. Bachmann’s bundle (BB) pacing is considered to be electrical resynchronization of the atria. Atrial fibrillation (AF) and congestive heart failure (HF) often coexist in the same patient. A 69 year-old man who underwent CRT combined with BB pacing for HF and atrial tachycardias or atrial fibrillation (AF) improved HF symptoms. The combined therapy reduced the number of admissions and occurrence of atrial tachyarrhythmias. It is possible that CRT combined with BB pacing could provide synergistic, beneficial effects on symptoms in patients with HF and AF and hence break a vicious circle