A New Type of Electron Nuclear-Spin Interaction from Resistively Detected NMR in the Fractional Quantum Hall Effect Regime

Two dimensional electron gases in narrow GaAs quantum wells show huge longitudinal resistance (HLR) values at certain fractional filling factors. Applying an RF field with frequencies corresponding to the nuclear spin splittings of {69}Ga, {71}Ga and {75}As leads to a substantial decreases of the HLR establishing a novel type of resistively detected NMR. These resonances are split into four sub lines each. Neither the number of sub lines nor the size of the splitting can be explained by established interaction mechanisms.Comment: 4 pages, 3 figure

Fine structure and optical pumping of spins in individual semiconductor quantum dots

We review spin properties of semiconductor quantum dots and their effect on optical spectra. Photoluminescence and other types of spectroscopy are used to probe neutral and charged excitons in individual quantum dots with high spectral and spatial resolution. Spectral fine structure and polarization reveal how quantum dot spins interact with each other and with their environment. By taking advantage of the selectivity of optical selection rules and spin relaxation, optical spin pumping of the ground state electron and nuclear spins is achieved. Through such mechanisms, light can be used to process spins for use as a carrier of information

Land surface phenological response to decadal climate variability across Australia using satellite remote sensing

© 2014 Author(s). Land surface phenological cycles of vegetation greening and browning are influenced by variability in climatic forcing. Quantitative spatial information on phenological cycles and their variability is important for agricultural applications, wildfire fuel accumulation, land management, land surface modeling, and climate change studies. Most phenology studies have focused on temperature-driven Northern Hemisphere systems, where phenology shows annually recurring patterns. However, precipitation-driven non-annual phenology of arid and semi-arid systems (i.e., drylands) received much less attention, despite the fact that they cover more than 30% of the global land surface. Here, we focused on Australia, a continent with one of the most variable rainfall climates in the world and vast areas of dryland systems, where a detailed phenological investigation and a characterization of the relationship between phenology and climate variability are missing. To fill this knowledge gap, we developed an algorithm to characterize phenological cycles, and analyzed geographic and climate-driven variability in phenology from 2000 to 2013, which included extreme drought and wet years. We linked derived phenological metrics to rainfall and the Southern Oscillation Index (SOI). We conducted a continent-wide investigation and a more detailed investigation over the Murray-Darling Basin (MDB), the primary agricultural area and largest river catchment of Australia. Results showed high inter-and intra-annual variability in phenological cycles across Australia. The peak of phenological cycles occurred not only during the austral summer, but also at any time of the year, and their timing varied by more than a month in the interior of the continent. The magnitude of the phenological cycle peak and the integrated greenness were most significantly correlated with monthly SOI within the preceding 12 months. Correlation patterns occurred primarily over northeastern Australia and within the MDB, predominantly over natural land cover and particularly in floodplain and wetland areas. Integrated greenness of the phenological cycles (surrogate of vegetation productivity) showed positive anomalies of more than 2 standard deviations over most of eastern Australia in 2009-2010, which coincided with the transition from the El Niño-induced decadal droughts to flooding caused by La Niña

Numerical study of duality and universality in a frozen superconductor

The three-dimensional integer-valued lattice gauge theory, which is also known as a "frozen superconductor," can be obtained as a certain limit of the Ginzburg-Landau theory of superconductivity, and is believed to be in the same universality class. It is also exactly dual to the three-dimensional XY model. We use this duality to demonstrate the practicality of recently developed methods for studying topological defects, and investigate the critical behavior of the phase transition using numerical Monte Carlo simulations of both theories. On the gauge theory side, we concentrate on the vortex tension and the penetration depth, which map onto the correlation lengths of the order parameter and the Noether current in the XY model, respectively. We show how these quantities behave near the critical point, and that the penetration depth exhibits critical scaling only very close to the transition point. This may explain the failure of superconductor experiments to see the inverted XY model scaling.Comment: 17 pages, 18 figures. Updated to match the version published in PRB (http://link.aps.org/abstract/PRB/v67/e014525) on 27 Jan 200

A systematic literature review and meta-analysis of community pharmacist-led interventions to optimise the use of antibiotics.

AIMS: The aim of this systematic review is to assess the effects of community pharmacist-led interventions to optimise the use of antibiotics and identify which interventions are most effective. METHODS: This review was conducted according to the PRISMA guidelines (PROSPERO: CRD42020188552). PubMed, EMBASE and the Cochrane Central Register of Controlled Trials were searched for (randomised) controlled trials. Included interventions were required to target antibiotic use, be set in the community pharmacy context, and be pharmacist-led. Primary outcomes were quality of antibiotic supply and adverse effects while secondary outcomes included patient-reported outcomes. Risk of bias was assessed using the 'Cochrane suggested risk of bias criteria' and narrative synthesis of primary outcomes conducted. RESULTS: Seventeen studies were included covering in total 3822 patients (mean age 45.6 years, 61.9% female). Most studies used educational interventions. Three studies reported on primary outcomes, 12 on secondary outcomes and two on both. Three studies reported improvements in quality of dispensing, interventions led to more intensive symptom assessment (up to 30% more advice given) and a reduction of over-the-counter supply up to 53%. Three studies led to higher consumer satisfaction, effects on adherence from nine studies were mixed (risk difference 0.04 [-0.02, 0.10]). All studies had unclear or high risks of bias across at least one domain, with large heterogeneity between studies. CONCLUSIONS: Our review suggests some positive results from pharmacist-led interventions, but the interventions do not seem sufficiently effective as currently implemented. This review should be interpreted as exploratory research, as more high-quality research is needed

Triplet-Singlet Spin Relaxation via Nuclei in a Double Quantum Dot

The spin of a confined electron, when oriented originally in some direction, will lose memory of that orientation after some time. Physical mechanisms leading to this relaxation of spin memory typically involve either coupling of the electron spin to its orbital motion or to nuclear spins. Relaxation of confined electron spin has been previously measured only for Zeeman or exchange split spin states, where spin-orbit effects dominate relaxation, while spin flips due to nuclei have been observed in optical spectroscopy studies. Using an isolated GaAs double quantum dot defined by electrostatic gates and direct time domain measurements, we investigate in detail spin relaxation for arbitrary splitting of spin states. Results demonstrate that electron spin flips are dominated by nuclear interactions and are slowed by several orders of magnitude when a magnetic field of a few millitesla is applied. These results have significant implications for spin-based information processing

Critical Behavior of Nuclear-Spin Diffusion in GaAs/AlGaAs Heterostructures near Landau Level Filling \nu=1

Thermal measurements on a GaAs/AlGaAs heterostructure reveal that the state of the confined two-dimensional electrons dramatically affects the nuclear-spin diffusion near Landau level filling factor \nu=1. The experiments provide quantitative evidence that the sharp peak in the temperature dependence of heat capacity near \nu=1 is due to an enhanced nuclear-spin diffusion from the GaAs quantum wells into the AlGaAs barriers. We discuss the physical origin of this enhancement in terms the possible Skyrme solid-liquid phase transition.Comment: 1 LateX file, 3 figures, submitte

(G)hosting television: Ghostwatch and its medium

This article’s subject is Ghostwatch (BBC, 1992), a drama broadcast on Halloween night of 1992 which adopted the rhetoric of live non-fiction programming, and attracted controversy and ultimately censure from the Broadcasting Standards Council. In what follows, we argue that Ghostwatch must be understood as a televisually-specific artwork and artefact. We discuss the programme’s ludic relationship with some key features of television during what Ellis (2000) has termed its era of ‘availability’, principally liveness, mass simultaneous viewing, and the flow of the television super-text. We trace the programme’s television-specific historicity whilst acknowledging its allusions and debts to other media (most notably film and radio). We explore the sophisticated ways in which Ghostwatch’s visual grammar and vocabulary and deployment of ‘broadcast talk’ (Scannell 1991) variously ape, comment upon and subvert the rhetoric of factual programming, and the ends to which these strategies are put. We hope that these arguments collectively demonstrate the aesthetic and historical significance of Ghostwatch and identify its relationship to its medium and that medium’s history. We offer the programme as an historically-reflexive artefact, and as an exemplary instance of the work of art in television’s age of broadcasting, liveness and co-presence