818 research outputs found

    SCUBA - A submillimetre camera operating on the James Clerk Maxwell Telescope

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    The Submillimetre Common-User Bolometer Array (SCUBA) is one of a new generation of cameras designed to operate in the submillimetre waveband. The instrument has a wide wavelength range covering all the atmospheric transmission windows between 300 and 2000 microns. In the heart of the instrument are two arrays of bolometers optimised for the short (350/450 microns) and long (750/850 microns) wavelength ends of the submillimetre spectrum. The two arrays can be used simultaneously, giving a unique dual-wavelength capability, and have a 2.3 arc-minute field of view on the sky. Background-limited performance is achieved by cooling the arrays to below 100 mK. SCUBA has now been in active service for over a year, and has already made substantial breakthroughs in many areas of astronomy. In this paper we present an overview of the performance of SCUBA during the commissioning phase on the James Clerk Maxwell Telescope (JCMT).Comment: 14 pages, 13 figures (1 JPEG), Proc SPIE vol 335

    Talking about weight talk : primary care practitioner knowledge, attitudes and practice

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    Background: Primary care practitioners (PCPs) have a vital role in patient weight management. This study investigates knowledge, attitudes and practice of UK PCPs regarding patient weight management. Methods: A cross-sectional questionnaire assessed PCP perceived knowledge, self-reported practice, attitudes towards overweight/obesity and actual knowledge regarding overweight and obesity management. Practitioners from NE Scotland were invited to participate. Results: Participants comprised 107 PCPs. Most participants viewed management of overweight and obesity as core to their roles and 75% reported discussing weight with overweight/obese patients. Management techniques included discussion and advice provision. Behavioural change techniques (BCTs) were reported infrequently, despite perceptions that patients lacked motivation to lose weight. A quarter of participants reported a lack of training and a third reported inadequate skills to manage overweight/obese patients. Mean percent correct for knowledge questions was approximately 53%. Barriers to patient weight management included lack of specialists for referral and limited time. Conclusions: This study confirmed a primary care role in managing weight in overweight/obese patients. Our finding that most participants reported discussing weight with their overweight or obese patients is unsupported by previously published research, however, a more comprehensive sample of practitioners is required to scrutinize this disparity. Incongruence exists between practitioners’ perceptions of difficulties associated with patient weight loss and the tools they use to address them. Inclusion of training in BCT, the provision of weight care specialists, or referral on to commercial weight loss organizations may provide more effective pathways for PCPs to assist weight loss for overweight/obese patients in primary care.PostprintPeer reviewe

    Keeping Unwanted Gulls Away - A Progress Report

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    Nearly 50 years ago, wires were strung over fish ponds to discourage fish-eating birds from taking fish destined for other uses (McAtee and Piper 1936). Twenty years ago, overwiring of open ditches began on airports to keep ducks from using them and causing hazards to aircraft (Solman 1973). Both techniques used coarse wires spaced closely enough to form a physical barrier to prevent ducks and herons from landing on or taking off from the water

    Social attention with real versus reel stimuli: toward an empirical approach to concerns about ecological validity

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    Cognitive neuroscientists often study social cognition by using simple but socially relevant stimuli, such as schematic faces or images of other people. Whilst this research is valuable, important aspects of genuine social encounters are absent from these studies, a fact that has recently drawn criticism. In the present review we argue for an empirical approach to the determination of the equivalence of different social stimuli. This approach involves the systematic comparison of different types of social stimuli ranging in their approximation to a real social interaction. In garnering support for this cognitive ethological approach, we focus on recent research in social attention that has involved stimuli ranging from simple schematic faces to real social interactions. We highlight both meaningful similarities and differences in various social attentional phenomena across these different types of social stimuli thus validating the utility of the research initiative. Furthermore, we argue that exploring these similarities and differences will provide new insights into social cognition and social neuroscience

    Behaviour of three charged particles on a plane under perpendicular magnetic field

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    We consider the problem of three identical charged particles on a plane under a perpendicular magnetic field and interacting through Coulomb repulsion. This problem is treated within Taut's framework, in the limit of vanishing center of mass vector R⃗→0⃗\vec{R} \to \vec{0}, which corresponds to the strong magnetic field limit, occuring for example in the Fractional Quantum Hall Effect. Using the solutions of the biconfluent Heun equation, we compute the eigenstates and show that there is two sets of solutions. The first one corresponds to a system of three independent anyons which have their angular momenta fixed by the value of the magnetic field and specified by a dimensionless parameter C≃lBl0C \simeq \frac{l_B}{l_0}, the ratio of lBl_B, the magnetic length, over l0l_0, the Bohr radius. This anyonic character, consistent with quantum mechanics of identical particles in two dimensions, is induced by competing physical forces. The second one corresponds to the case of the Landau problem when C→0C \to 0. Finally we compare these states with the quantum Hall states and find that the Laughlin wave functions are special cases of our solutions under certains conditions.Comment: 15 pages, 3 figures, Accepeted in JP

    Inverting the handedness of circularly polarized luminescence from light-emitting polymers using film thickness

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    The emission of circularly polarized light is central to many applications, including data storage, optical quantum computation, biosensing, environmental monitoring, and display technologies. An emerging method to induce (chiral) circularly polarized (CP) electroluminescence from the active layer of polymer light-emitting diodes (polymer OLEDs; PLEDs) involves blending achiral polymers with chiral small-molecule additives, where the handedness/sign of the CP light is controlled by the absolute stereochemistry of the small molecule. Through the in-depth study of such a system we report an interesting chiroptical property: the ability to tune the sign of CP light as a function of active layer thickness for a fixed enantiomer of the chiral additive. We demonstrate that it is possible to achieve both efficient (4.0 cd/A) and bright (8000 cd/m2) CP-PLEDs, with high dissymmetry of emission of both left-handed (LH) and right-handed (RH) light, depending on thickness (thin films, 110 nm: gEL = 0.51, thick films, 160 nm: gEL = -1.05, with the terms "thick" and "thin" representing the upper and lower limits of the thickness regime studied), for the same additive enantiomer. We propose that this arises due to an interplay between localized CP emission originating from molecular chirality and CP light amplification or inversion through a chiral medium. We link morphological, spectroscopic, and electronic characterization in thin films and devices with theoretical studies in an effort to determine the factors that underpin these observations. Through the control of active layer thickness and device architecture, this study provides insights into the mechanisms that result in CP luminescence and high performance from CP-PLEDs, as well as demonstrating new opportunities in CP photonic device design

    Classical phase space and statistical mechanics of identical particles

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    Starting from the quantum theory of identical particles, we show how to define a classical mechanics that retains information about the quantum statistics. We consider two examples of relevance for the quantum Hall effect: identical particles in the lowest Landau level, and vortices in the Chern-Simons Ginzburg-Landau model. In both cases the resulting {\em classical} statistical mechanics is shown to be a nontrivial classical limit of Haldane's exclusion statistics.Comment: 40 pages, Late

    Fractional Exclusion Statistics and Anyons

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    Do anyons, dynamically realized by the field theoretic Chern-Simons construction, obey fractional exclusion statistics? We find that they do if the statistical interaction between anyons and anti-anyons is taken into account. For this anyon model, we show perturbatively that the exchange statistical parameter of anyons is equal to the exclusion statistical parameter. We obtain the same result by applying the relation between the exclusion statistical parameter and the second virial coefficient in the non-relativistic limit.Comment: 9 pages, latex, IFT-498-UN
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