11,604 research outputs found

    Observed characteristics of sudden commencement absorption.

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    Shot Noise in Mesoscopic Transport Through Localised States

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    We show that shot noise can be used for studies of hopping and resonant tunnelling between localised electron states. In hopping via several states, shot noise is seen to be suppressed compared with its classical Poisson value SI=2eIS_I=2eI (II is the average current) and the suppression depends on the distribution of the barriers between the localised states. In resonant tunnelling through a single impurity an enhancement of shot noise is observed. It has been established, both theoretically and experimentally, that a considerable increase of noise occurs due to Coulomb interaction between two resonant tunnelling channels.Comment: 7 pages, 5 figures; Proceedings of the 10th Conference on Hopping and Related Phenomena (Trieste 2003); requires Wiley style files (included

    Diagnostic Tests for Alzheimer's Disease: Rationale, Methodology, and Challenges

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    There has been a large increase in the amount of research seeking to define or diagnose Alzheimer's disease before patients develop dementia. If successful, this would principally have clinical benefits both in terms of treatment as well as risk modification. Moreover, a better method for diagnosing predementia disease would assist research which seeks to develop such treatments and risk modification strategies. The evidence-based definition of a diagnostic test's accuracy is fundamental to achieve the above goals and to address this, the Cochrane Collaboration has established a Diagnostic Test Accuracy group dedicated to examining the utility and accuracy of proposed tests in dementia and cognitive impairment. We present here the assumptions and observations underpinning the chosen methodology as well as the initial methodological approach decided upon

    Men's experience of a guided self-help intervention for hot flushes associated with prostate cancer treatment

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    Up to 80% of men who receive androgen deprivation therapy report hot flushes and for many these are associated with reduced quality of life. However it is recognised that there are a number of barriers to men’s engagement with support to manage symptoms and improve quality of life. This qualitative study was embedded within a larger randomised controlled trial (MANCAN) of a guided self-help cognitive behavioural intervention to manage hot flushes resulting among men receiving androgen deprivation therapy. The study aimed to explore the engagement and experiences with the guided self-help intervention. Twenty men recruited from the treatment arm of the MANCAN trial participated in a semi-structured interview exploring acceptability of the intervention, factors affecting engagement and perceived usefulness of the intervention. Interviews were audio-recorded, transcribed verbatim and analysed using a Framework approach. Over two thirds of respondents (69%) reported reading the intervention booklet in full and over 90% reporting practising the relaxation CD at least once a week. Analysis of the interviews identified three super-ordinate themes and these related to changes in hot flush symptomatology (learned to cope with hot flushes in new ways), the skills that participants had derived from the intervention (promoting relaxation and reducing stressors), and to a broader usefulness of the intervention (broader impact of the intervention and skills). The present study identified positive engagement with a guided self-help intervention and that men applied the skills developed through the intervention to help them undertake general lifestyle changes. Psycho-educational interventions (e.g. cognitive behaviour therapy, relaxation, and positive lifestyle elements) offer the potential to be both effective and well received by male cancer survivors

    Scoping studies: towards a methodological framework

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    This paper focuses on scoping studies, an approach to reviewing the literature which to date has received little attention in the research methods literature. We distinguish between different types of scoping studies and indicate where these stand in relation to full systematic reviews. We outline a framework for conducting a scoping study based on our recent experiences of reviewing the literature on services for carers for people with mental health problems. Where appropriate, our approach to scoping the field is contrasted with the procedures followed in systematic reviews. We emphasize how including a consultation exercise in this sort of study may enhance the results, making them more useful to policy makers, practitioners and service users. Finally, we consider the advantages and limitations of the approach and suggest that a wider debate is called for about the role of the scoping study in relation to other types of literature reviews

    Theory of the in-plane photoelectric effect in a two-dimensional electron system

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    A new photoelectric phenomenon, the in-plane photoelectric (IPPE) effect, has been recently discovered at terahertz (THz) frequencies in a GaAs/Alx_xGa1x_{1-x}As heterostructure with a two-dimensional (2D) electron gas (W. Michailow et al., Science Advances, DOI: 10.1126/sciadv.abi8398). In contrast to the conventional PE phenomena, the IPPE effect is observed at normal incidence of radiation, the height of the in-plane potential step, which electrons overcome after absorption of a THz photon, is electrically tunable by gate voltages, and the effect is maximal at a negative electron "work function", when the Fermi energy lies above the potential barrier. Based on the discovered phenomenon, efficient detection of THz radiation has been demonstrated. In this work we present a detailed theory of the IPPE effect providing analytical results for the THz wave generated photocurrent, the quantum efficiency, and the internal responsivity of the detector, in dependence on the frequency, the gate voltages, and the geometrical parameters of the detector. The calculations are performed for macroscopically wide samples at zero temperature. Results of the theory are applicable to any semiconductor systems with 2D electron gases, including III-V structures, silicon-based field effect transistors, and the novel 2D layered, graphene-related materials.Comment: 21 pages, 15 figures, substantially revised improved versio
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