Spectral gap of segments of periodic waveguides

We consider a periodic strip in the plane and the associated quantum waveguide with Dirichlet boundary conditions. We analyse finite segments of the waveguide consisting of $L$ periodicity cells, equipped with periodic boundary conditions at the ``new'' boundaries. Our main result is that the distance between the first and second eigenvalue of such a finite segment behaves like $L^{-2}$.Comment: 3 page

Continuous integral kernels for unbounded Schroedinger semigroups and their spectral projections

By suitably extending a Feynman-Kac formula of Simon [Canadian Math. Soc. Conf. Proc, 28 (2000), 317-321], we study one-parameter semigroups generated by (the negative of) rather general Schroedinger operators, which may be unbounded from below and include a magnetic vector potential. In particular, a common domain of essential self-adjointness for such a semigroup is specified. Moreover, each member of the semigroup is proven to be a maximal Carleman operator with a continuous integral kernel given by a Brownian-bridge expectation. The results are used to show that the spectral projections of the generating Schroedinger operator also act as Carleman operators with continuous integral kernels. Applications to Schroedinger operators with rather general random scalar potentials include a rigorous justification of an integral-kernel representation of their integrated density of states - a relation frequently used in the physics literature on disordered solids.Comment: 41 pages. Final version. Dedicated to Volker Enss on the occasion of his 60th birthda

Spectral asymptotics of the Laplacian on supercritical bond-percolation graphs

We investigate Laplacians on supercritical bond-percolation graphs with different boundary conditions at cluster borders. The integrated density of states of the Dirichlet Laplacian is found to exhibit a Lifshits tail at the lower spectral edge, while that of the Neumann Laplacian shows a van Hove asymptotics, which results from the percolating cluster. At the upper spectral edge, the behaviour is reversed.Comment: 16 pages, typos corrected, to appear in J. Funct. Ana

How common and severe are six withdrawal effects from, and addiction to, antidepressants? The experiences of a large international sample of patients

Introduction: The incidence and severity of withdrawal effects when coming off antidepressants (ADs) have recently received considerable attention. National guidelines on the topic have proven to be inaccurate. This paper reports the largest direct-to-patient international survey on these issues. Methods: Data generated by an online survey from 867 people from 31 countries, who had taken ADs continuously for at least one month, and had tried to come off (successfully or not) was analysed. Results: The majority (59%) had taken ADs for more than three years. Of those who were still taking them, 29% had been doing so for at least 20 years. 61% reported some degree of withdrawal effects, and 44% of these described the effects as ‘severe’. The most common of six listed withdrawal effects were anxiety/panic (66%) and irritability (62%). The most common spontaneously reported ‘other’ withdrawal effect was suicidality (2%). 40% reported that they felt addicted, with 39% of these describing their addiction as ‘severe’. Over half (55%) reported some degree of difficulty coming off, with 27% ticking ‘very difficult’, and 11% ‘very easy’. Duration of treatment was related to withdrawal, addiction and difficulty coming off. Younger people experienced more frequent withdrawal effects. Only six people (0.7%) recalled being told anything about withdrawal, dependence or addiction by the initial prescriber. Conclusions: These findings confirm previous studies, using a range of methodologies, finding high incidences of withdrawal effects, frequently at severe levels. National guidelines, and those of professional organisations, urgently need to be updated to reflect this evidence

On the AC spectrum of one-dimensional random Schroedinger operators with matrix-valued potentials

We consider discrete one-dimensional random Schroedinger operators with decaying matrix-valued, independent potentials. We show that if the l^2-norm of this potential has finite expectation value with respect to the product measure then almost surely the Schroedinger operator has an interval of purely absolutely continuous (ac) spectrum. We apply this result to Schroedinger operators on a strip. This work provides a new proof and generalizes a result obtained by Delyon, Simon, and Souillard.Comment: (1 figure

The effectiveness of web-based interventions designed to decrease alcohol consumption – a systematic review

OBJECTIVE To review the published literature on the effectiveness of web-based interventions designed to decrease consumption of alcohol and/or prevent alcohol abuse. METHOD Relevant articles published up to, and including, May 2006 were identified through electronic searches of Medline, PsycInfo, Embase, Cochrane Library, ASSIA, Web of Science and Science Direct. Reference lists of all articles identified for inclusion were checked for articles of relevance. An article was included if its stated or implied purpose was to evaluate a web-based intervention designed to decrease consumption of alcohol and/or to prevent alcohol abuse. Studies were reliably selected and quality-assessed, and data were independently extracted and interpreted by two authors. RESULTS Initial searches identified 191 articles of which 10 were eligible for inclusion. Of these, five provided a process evaluation only, with the remaining five providing some pre-to post-intervention measure of effectiveness. In general the percentage quality criteria met was relatively low and only one of the 10 articles selected was a randomized control trial. CONCLUSION The current review provides inconsistent evidence on the effectiveness of eIectronic screening and brief intervention (eSBI) for alcohol use. Process research suggests that web-based interventions are generally well received. However further controlled trials are needed to fully investigate their efficacy, to determine which elements are keys to outcome and to understand if different elements are required in order to engage low- and high-risk drinkers

Quark Soup al dente: Applied Superstring Theory

We discuss the application of the AdS/CFT correspondence to possibly gain new physical insights for the strongly coupled quark-gluon plasma. This article provides an informal summary of a talk given by RCM at the 18th International Conference on General Relativity and Gravitation in July 2007.Comment: This article provides an informal summary of a talk given by RCM at the 18th International Conference on General Relativity and Gravitation in July 200

The (Mis)appropriation of HIV/AIDS advocacy strategies in Global Mental Health: towards a more nuanced approach

Background: Mental health is increasingly finding a place on global health and international development agendas. Advocates for Global Mental Health (GMH), and international organizations such as the World Health Organization (WHO) and the World Bank, argue that treatments available in high-income countries should also be made available in low- and middle-income countries. Such arguments are often made by comparing mental health to infectious diseases, including the relative disease and economic burdens they impose, and pointing to the applicability of the right to access treatment for mental health, not only infectious diseases. HIV/AIDS advocacy in particular has been held up by GMH advocates as offering an appropriate strategy for generating global commitment. Discussion: There is a need to assess how health issues are framed not only in relation to social goods outside of health (such as human rights, security or development), but also in relation to other health or disease models, and how health policy and practice is shaped as a result. The article debates the merits and consequences of likening mental health to HIV/AIDS, and identifies four major problems with the model for GMH advocacy being developed through these analogies: 1. An inappropriately universalizing global approach to context-specific problems; 2. A conception of human rights that focuses on the right to access treatment at the expense of the right to refuse it; 3. A tendency to treat poverty as a psychiatric issue, rather than recognizing that mental distress can be the result of poverty and other forms of inequality; 4. The prioritization of destigmatization of disease over social justice models. Conclusion: There are significant problems with the wholesale adoption of an (often simplified) version of HIV/AIDS advocacy as a model for GMH. Yet critical engagement with the important and nuanced differences between HIV/AIDS and mental health may nevertheless point to some possibilities for productive engagement and cross-fertilisation between advocates, activists and scholars in both fields