Quantum waveguides with a lateral semitransparent barrier: spectral and scattering properties

We consider a quantum particle in a waveguide which consists of an infinite straight Dirichlet strip divided by a thin semitransparent barrier on a line parallel to the walls which is modeled by a $\delta$ potential. We show that if the coupling strength of the latter is modified locally, i.e. it reaches the same asymptotic value in both directions along the line, there is always a bound state below the bottom of the essential spectrum provided the effective coupling function is attractive in the mean. The eigenvalues and eigenfunctions, as well as the scattering matrix for energies above the threshold, are found numerically by the mode-matching technique. In particular, we discuss the rate at which the ground-state energy emerges from the continuum and properties of the nodal lines. Finally, we investigate a system with a modified geometry: an infinite cylindrical surface threaded by a homogeneous magnetic field parallel to the cylinder axis. The motion on the cylinder is again constrained by a semitransparent barrier imposed on a ``seam'' parallel to the axis.Comment: a LaTeX source file with 12 figures (11 of them eps); to appear in J. Phys. A: Math. Gen. Figures 3, 5, 8, 9, 11 are given at 300 dpi; higher resolution originals are available from the author

Learning in the Palaver Hut: The ‘Africa Study Visit’ as teaching tool.

noThe aim of this article is to assess the experiential learning environment of the African Study Visit (ASV). It presents a theoretically grounded analysis of the ASV. Although field visits are not a new phenomenon within Higher Education, they seem, but with few exceptions, to be considered as an add-on teaching method. By drawing from the experiential learning literature, we demonstrate that there are sound pedagogical reasons for incorporating field visits like the ASV into the curriculum as stand-alone components. Thus, the original contribution of this article is to place the ASV within the experiential learning literature such that the theoretical, practical and conceptual benefits for students are understood. Its significance is that this article offers a set of practices from an experiential learning perspective that can be used for deepening the levels of comprehension of political issues in Africa for international studies students

A study of patent thickets

Report analysing whether entry of UK enterprises into patenting in a technology area is affected by patent thickets in the technology area

Concordance of sibling's recall of measures of childhood socioeconomic position

<p>Abstract</p> <p>Background</p> <p>Studies of socioeconomic determinants of health often rely on recalled information on childhood socioeconomic position, despite limited evidence of the validity of this information. This study examined concordance between siblings of recalled measures of childhood socioeconomic position.</p> <p>Methods</p> <p>This cross-sectional study examined reports by 1280 adult sibling pairs in the National Survey of Midlife Development in the United States of seven measures of childhood socioeconomic position: father's occupation (in 9 categories), father having a professional occupation, father being a supervisor at work, father's education level, mother's education level, receipt of welfare payments, and subjective appraisal of being better or worse off financially than others.</p> <p>Results</p> <p>Concordance was high for father's professional occupation (0.97; 95% confidence interval (CI) 0.96, 0.98), father's occupation in 9 categories (0.76; 95% CI 0.73, 0.80), and receipt of welfare payments (0.95; 95% CI 0.93, 0.97). Concordance was lower for father's and mother's education level, and lowest for subjective appraisal of socioeconomic position (0.60; 95% CI 0.57, 0.64). Concordance of parental education was lower for sibling pairs with high school educations or less.</p> <p>Conclusion</p> <p>Concordance of recalled measures of childhood socioeconomic position by siblings is generally but not uniformly high.</p

The Leeds Evaluation of Efficacy of Detoxification Study (LEEDS) Prisons Project Study: protocol for a randomised controlled trial comparing methadone and buprenorphine for opiate detoxification

<p>Abstract</p> <p>Background</p> <p>In the United Kingdom (UK), there is an extensive market for the class 'A' drug heroin and many heroin users spend time in prison. People addicted to heroin often require prescribed medication when attempting to cease their drug use. The most commonly used detoxification agents in UK prisons are currently buprenorphine and methadone, both are recommended by national clinical guidelines. However, these agents have never been compared for opiate detoxification in the prison estate and there is a general paucity of research evaluating the most effective treatment for opiate detoxification in prisons. This study seeks to address this paucity by evaluating the most routinely used interventions amongst drug users within UK prisons.</p> <p>Methods/Design</p> <p>This study uses randomised controlled trial methodology to compare the open use of buprenorphine and methadone for opiate detoxification, given in the context of routine care, within three UK prisons. Prisoners who are eligible and give informed consent will be entered into the trial. The primary outcome will be abstinence status eight days after detoxification, as determined by a urine test. Secondary outcomes will be recorded during the detoxification and then at one, three and six months post-detoxification.</p> <p>Trial registration</p> <p>Current Controlled Trials ISRCTN58823759</p

Regressor and random-effects dependencies in multilevel models

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/72623/1/j.0039-0402.2003.00254.x.pd