Superfluid Flow Past an Array of Scatterers

We consider a model of nonlinear superfluid flow past a periodic array of point-like scatterers in one dimension. An application of this model is the determination of the critical current of a Josephson array in a regime appropriate to a Ginzburg-Landau formulation. Here, the array consists of short normal-metal regions, in the presence of a Hartree electron-electron interaction, and embedded within a one-dimensional superconducting wire near its critical temperature, $Tc$. We predict the critical current to depend linearly as $A (Tc-T)$, while the coefficient $A$ depends sensitively on the sizes of the superconducting and normal-metal regions and the strength and sign of the Hartree interaction. In the case of an attractive interaction, we find a further feature: the critical current vanishes linearly at some temperature $T*$ less than $Tc$, as well as at $Tc$ itself. We rule out a simple explanation for the zero value of the critical current, at this temperature $T*$, in terms of order parameter fluctuations at low frequencies.Comment: 23 pages, REVTEX, six eps-figures included; submitted to PR

Students as co-creators of teaching approaches, course design and curricula: implications for academic developers

Within higher education, students’ voices are frequently overlooked in the design of teaching approaches, courses and curricula. In this paper we outline the theoretical background to arguments for including students as partners in pedagogical planning processes. We present examples where students have worked collaboratively in design processes along with the beneficial outcomes of these examples. Finally we focus on some of the implications and opportunities for academic developers of proposing collaborative approaches to pedagogical planning

Large-amplitude driving of a superconducting artificial atom: Interferometry, cooling, and amplitude spectroscopy

Superconducting persistent-current qubits are quantum-coherent artificial atoms with multiple, tunable energy levels. In the presence of large-amplitude harmonic excitation, the qubit state can be driven through one or more of the constituent energy-level avoided crossings. The resulting Landau-Zener-Stueckelberg (LZS) transitions mediate a rich array of quantum-coherent phenomena. We review here three experimental works based on LZS transitions: Mach-Zehnder-type interferometry between repeated LZS transitions, microwave-induced cooling, and amplitude spectroscopy. These experiments exhibit a remarkable agreement with theory, and are extensible to other solid-state and atomic qubit modalities. We anticipate they will find application to qubit state-preparation and control methods for quantum information science and technology.Comment: 13 pages, 5 figure

Meta-analysis of type 2 Diabetes in African Americans Consortium

Type 2 diabetes (T2D) is more prevalent in African Americans than in Europeans. However, little is known about the genetic risk in African Americans despite the recent identification of more than 70 T2D loci primarily by genome-wide association studies (GWAS) in individuals of European ancestry. In order to investigate the genetic architecture of T2D in African Americans, the MEta-analysis of type 2 DIabetes in African Americans (MEDIA) Consortium examined 17 GWAS on T2D comprising 8,284 cases and 15,543 controls in African Americans in stage 1 analysis. Single nucleotide polymorphisms (SNPs) association analysis was conducted in each study under the additive model after adjustment for age, sex, study site, and principal components. Meta-analysis of approximately 2.6 million genotyped and imputed SNPs in all studies was conducted using an inverse variance-weighted fixed effect model. Replications were performed to follow up 21 loci in up to 6,061 cases and 5,483 controls in African Americans, and 8,130 cases and 38,987 controls of European ancestry. We identified three known loci (TCF7L2, HMGA2 and KCNQ1) and two novel loci (HLA-B and INS-IGF2) at genome-wide significance (4.15 × 10(-94)<P<5 × 10(-8), odds ratio (OR)  = 1.09 to 1.36). Fine-mapping revealed that 88 of 158 previously identified T2D or glucose homeostasis loci demonstrated nominal to highly significant association (2.2 × 10(-23) < locus-wide P<0.05). These novel and previously identified loci yielded a sibling relative risk of 1.19, explaining 17.5% of the phenotypic variance of T2D on the liability scale in African Americans. Overall, this study identified two novel susceptibility loci for T2D in African Americans. A substantial number of previously reported loci are transferable to African Americans after accounting for linkage disequilibrium, enabling fine mapping of causal variants in trans-ethnic meta-analysis studies.Peer reviewe

α₁-Adrenergic receptors contribute to the acute effects of 3,4-methylenedioxymethamphetamine in humans.

Preclinical studies implicate a role for α₁-noradrenergic receptors in the effects of psychostimulants, including 3,4-methylenedioxymethamphetamine (MDMA, "ecstasy"). The present study evaluated the effects of the α₁-noradrenergic receptor antagonist doxazosin on the acute pharmacodynamic and pharmacokinetic response to MDMA in 16 healthy subjects. Doxazosin (8 mg/d) or placebo was administered for 3 days before MDMA (125 mg) or placebo using a randomized, double-blind, placebo-controlled, 4-session, crossover design. Doxazosin reduced MDMA-induced elevations in blood pressure, body temperature, and moderately attenuated positive mood but enhanced tachycardia associated with MDMA. The results indicate that α₁-adrenergic receptors contribute to the acute cardiostimulant and to a minor extent possibly also to the thermogenic and euphoric effects of MDMA in humans