Reentrant behavior in the superconducting phase-dependent resistance of a disordered 2-dimensional electron gas

We have investigated the bias-voltage dependence of the phase-dependent differential resistance of a disordered T-shaped 2-dimensional electron gas coupled to two superconducting terminals. The resistance oscillations first increase upon lowering the energy. For bias voltages below the Thouless energy, the resistance oscillations are suppressed and disappear almost completely at zero bias voltage. We find a qualitative agreement with the calculated reentrant behavior of the resistance and discuss quantitative deviations.Comment: 4 pages, 5 figures, to be published in Phys. Rev.

Sensitivity and responsiveness of the EQ-5D-3L in patients with uncontrolled focal seizures: an analysis of Phase III trials of adjunctive brivaracetam.

PURPOSE: Preference-based measures are required to measure the impact of interventions for cost-effectiveness analysis. This study assessed the psychometric performance of the EQ-5D-3L in adults with uncontrolled focal (partial-onset) seizures. METHODS: Data from three Phase III studies of an antiepileptic drug (adjunctive brivaracetam; n = 1095) were used. Analysis included correlations between EQ-5D-3L and Quality of Life in Epilepsy Inventory (QOLIE-31P) and seizure frequency. Known group validity was based on ability of the EQ-5D-3L to discriminate between baseline QOLIE-31P total scores, seizure type and number of antiepileptic drugs using effect sizes (ES). Responsiveness assessed proportions reporting highest or lowest scores, overall change using standardized response means (SRM) and change by responder and clinician/patient evaluation groups using ES. RESULTS: Correlations were weak to moderate (ρ = 0.2-0.4) between EQ-5D-3L dimensions and QOLIE-31P subscales, apart from medication effects (ρ < 0.1); seizure frequency was not associated with either measure. Known group analysis had small ES. A quarter (24.9%) of patients had a baseline EQ-5D-3L utility score of 1 (full health) but lower average QOLIE-31P scores. SRMs were small (<0.1) in EQ-5D-3L compared with 0.1-0.4 for QOLIE-31P subscales. Results across the studies were mixed for responder status and clinician/patient evaluation of improvement for EQ-5D-3L. CONCLUSIONS: EQ-5D-3L had weak-to-moderate correlations with QOLIE-31P and varied with QOLIE-31P severity groups, but showed less responsiveness than QOLIE-31P. Given this lack of sensitivity, EQ-5D-3L may not be appropriate for measuring the impact of interventions in cost-effectiveness analysis in this population and disease-specific preference-based measures may be more appropriate

Experimental determination of the quasi-particle decay length ξSm\xi_{\text{Sm}} in a superconducting quantum well

We have investigated experimentally the electronic transport properties of a two-dimensional electron gas (2DEG) present in an AlSb/InAs/AlSb quantum well, where part of the toplayer has been replaced by a superconducting Nb strip, with an energy gap $\Delta_0$. By measuring the lateral electronic transport underneath the superconductor, and comparing the experimental results with a model based on the Bogoliubov-de Gennes equation and the Landauer-B\"uttiker formalism, we obtain a decay length $\xi_{\text{Sm}} \approx 100~\text{nm}$ for electrons. This decay length corresponds to an interface transparency $T_{\text{SIN}}=0.7$ between the Nb and InAs. Using this value, we infer an energy gap in the excitation spectrum of the SQW of $\Delta_{\text{eff}} = 0.97 \Delta_0 = 0.83~\text{meV}$.Comment: Revtex, 3 PostScript figure

Experimental Separation of Rashba and Dresselhaus Spin-Splittings in Semiconductor Quantum Wells

The relative strengths of Rashba and Dresselhaus terms describing the spin-orbit coupling in semiconductor quantum well (QW) structures are extracted from photocurrent measurements on n-type InAs QWs containing a two-dimensional electron gas (2DEG). This novel technique makes use of the angular distribution of the spin-galvanic effect at certain directions of spin orientation in the plane of a QW. The ratio of the relevant Rashba and Dresselhaus coefficients can be deduced directly from experiment and does not relay on theoretically obtained quantities. Thus our experiments open a new way to determine the different contributions to spin-orbit coupling

Boosting the Figure Of Merit of LSPR-based refractive index sensing by phase-sensitive measurements

Localized surface plasmon resonances possess very interesting properties for a wide variety of sensing applications. In many of the existing applications only the intensity of the reflected or transmitted signals is taken into account, while the phase information is ignored. At the center frequency of a (localized) surface plasmon resonance, the electron cloud makes the transition between in- and out-of-phase oscillation with respect to the incident wave. Here we show that this information can experimentally be extracted by performing phase-sensitive measurements, which result in linewidths that are almost one order of magnitude smaller than those for intensity based measurements. As this phase transition is an intrinsic property of a plasmon resonance, this opens up many possibilities for boosting the figure of merit (FOM) of refractive index sensing by taking into account the phase of the plasmon resonance. We experimentally investigated this for two model systems: randomly distributed gold nanodisks and gold nanorings on top of a continuous gold layer and a dielectric spacer and observed FOM values up to 8.3 and 16.5 for the respective nanoparticles

Unintentional high density p-type modulation doping of a GaAs/AlAs core-multi-shell nanowire

Achieving significant doping in GaAs/AlAs core/shell nanowires (NWs) is of considerable technological importance but remains a challenge due to the amphoteric behavior of the dopant atoms. Here we show that placing a narrow GaAs quantum well in the AlAs shell effectively getters residual carbon acceptors leading to an \emph{unintentional} p-type doping. Magneto-optical studies of such a GaAs/AlAs core multi-shell NW reveal quantum confined emission. Theoretical calculations of NW electronic structure confirm quantum confinement of carriers at the core/shell interface due to the presence of ionized carbon acceptors in the 1~nm GaAs layer in the shell. Micro-photoluminescence in high magnetic field shows a clear signature of avoided crossings of the $n=0$ Landau level emission line with the $n=2$ Landau level TO phonon replica. The coupling is caused by the resonant hole-phonon interaction, which points to a large 2D hole density in the structure.Comment: just published in Nano Letters (http://pubs.acs.org/doi/full/10.1021/nl500818k

The ESR1 (6q25) locus is associated with calcaneal ultrasound parameters and radial volumetric bone mineral density in European men

&lt;p&gt;&lt;b&gt;Purpose:&lt;/b&gt; Genome-wide association studies (GWAS) have identified 6q25, which incorporates the oestrogen receptor alpha gene (ESR1), as a quantitative trait locus for areal bone mineral density (BMD(a)) of the hip and lumbar spine. The aim of this study was to determine the influence of this locus on other bone health outcomes; calcaneal ultrasound (QUS) parameters, radial peripheral quantitative computed tomography (pQCT) parameters and markers of bone turnover in a population sample of European men.&lt;/p&gt; &lt;p&gt;&lt;b&gt;Methods:&lt;/b&gt; Eight single nucleotide polymorphisms (SNP) in the 6q25 locus were genotyped in men aged 40-79 years from 7 European countries, participating in the European Male Ageing Study (EMAS). The associations between SNPs and measured bone parameters were tested under an additive genetic model adjusting for centre using linear regression.&lt;/p&gt; &lt;p&gt;&lt;b&gt;Results:&lt;/b&gt; 2468 men, mean (SD) aged 59.9 (11.1) years had QUS measurements performed and bone turnover marker levels measured. A subset of 628 men had DXA and pQCT measurements. Multiple independent SNPs showed significant associations with BMD using all three measurement techniques. Most notably, rs1999805 was associated with a 0.10 SD (95%CI 0.05, 0.16; p = 0.0001) lower estimated BMD at the calcaneus, a 0.14 SD (95%CI 0.05, 0.24; p = 0.004) lower total hip BMD(a), a 0.12 SD (95%CI 0.02, 0.23; p = 0.026) lower lumbar spine BMD(a) and a 0.18 SD (95%CI 0.06, 0.29; p = 0.003) lower trabecular BMD at the distal radius for each copy of the minor allele. There was no association with serum levels of bone turnover markers and a single SNP which was associated with cortical density was also associated with cortical BMC and thickness.&lt;/p&gt; &lt;p&gt;&lt;b&gt;Conclusions:&lt;/b&gt; Our data replicate previous associations found between SNPs in the 6q25 locus and BMD(a) at the hip and extend these data to include associations with calcaneal ultrasound parameters and radial volumetric BMD.&lt;/p&gt