Electrostatic tailoring of magnetic interference in quantum point contact ballistic Josephson junctions

The magneto-electrostatic tailoring of the supercurrent in quantum point contact ballistic Josephson junctions is demonstrated. An etched InAs-based heterostructure is laterally contacted to superconducting niobium leads and the existence of two etched side gates permits, in combination with the application of a perpendicular magnetic field, to modify continuously the magnetic interference pattern by depleting the weak link. For wider junctions the supercurrent presents a Fraunhofer-like interference pattern with periodicity h/2e whereas by shrinking electrostatically the weak link, the periodicity evolves continuously to a monotonic decay. These devices represent novel tunable structures that might lead to the study of the elusive Majorana fermions.Comment: 4.5 pages, 4 color figure

Assessing the Efficiency of Mother-to-Child HIV Prevention in Low- and Middle-Income Countries using Data Envelopment Analysis

AIDS is one of the most significant health care problems worldwide. Due to the difficulty and costs involved in treating HIV, preventing infection is of paramount importance in controlling the AIDS epidemic. The main purpose of this paper is to explore the potential of using Data Envelopment Analysis (DEA) to establish international comparisons on the efficiency implementation of HIV prevention programmes. To this effect we use data from 52 low- and middle-income countries regarding the prevention of mother-to-child transmission of HIV. Our results indicate that there is a remarkable variation in efficiency of prevention services across nations, suggesting that a better use of resources could lead to more and improved services, and ultimately, prevent the infection of thousands of children. These results also demonstrate the potential strategic role of DEA for the efficient and effective planning of scarce resources to fight the epidemic.HIV Prevention; DEA; Mother-to-Child HIV Transmission.

Numerical study of the localization length critical index in a network model of plateau-plateau transitions in the quantum Hall effect

We calculate numerically the localization length critical index within the Chalker-Coddington (CC) model for plateau-plateau transitions in the quantum Hall effect. Lyapunov exponents have been calculated with relative errors on the order $10^{-3}$. Such high precision was obtained by considering the distribution of Lyapunov exponents for large ensembles of relatively short chains and calculating the ensemble average values. We analyze thoroughly finite size effects and find the localization length critical index $\nu= 2.517\pm 0.018$.Comment: 4 pages, 4 figure

Exploring the use of data envelopment analysis for evaluation in primary care

Primary care is currently at the heart of the National Health Service policy. The newly established organisations, known as Primary Care Groups and Trusts (PCG/Ts), have the crucial role of improving the efficiency and equity in primary care delivery. However, not many studies have focused on performance assessment in primary care provision. In this thesis we aim to contribute to a discussion regarding appropriate ways to compare the performance of primary care providers and the effective ways to use these results in order to improve performance in primary care. Following a review of the literature, a conceptual framework for performance assessment in primary care was developed in collaboration with a sample of PCG/Ts. This framework aims to establish a link between the local needs, the resources used, the services delivered and the outcomes achieved in primary care. Based on the relationships between these elements, four performance assessment criteria were defined: equity, efficiency, service effectiveness and cost effectiveness. DEA is then proposed to measure efficiency, service effectiveness and cost effectiveness, given the fact that it can handle multiple inputs and outputs without requiring the specification of a functional form. Following the Government’s policy of focusing on the management of chronic diseases, this conceptual framework is then applied to compare the performance of a sample of GP surgeries in terms of their delivery of diabetes care. An exploratory and formative comparison is undertaken in order to investigate why certain surgeries appear to perform better than others, and in order to identify ways in which some of the surgeries can improve their performance. The relationships between the different performance criteria are also investigated, together with the ways in which an adequate balance between the different criteria can be achieved. Several conclusions are arrived at and several contributions arc made to this research area. The usefulness of complementing efficiency analysis with equity and effectiveness analysis; the usefulness of following a formative methodology in the use of DEA; the importance of estimating the costs involved in achieving speciality based outcomes; the importance of area deprivation in the achievement of effectiveness and the limitations of the data available in primary care in England

New ground-based observational methods and instrumentation for asteroseismology

Space instrumentation like SOHO, MOST, CoRoT and Kepler has been and is being built to attain very high precision data to be used for asteroseismic analysis. Nonetheless, there is a very strong need for providing additional information, especially on mode identification. With this contribution I will review the efforts been put on new ground-based instrumentation and the methodology that can be used to achieve this aim.Comment: 6 pages. Review contribution to be published in Astrophysics and Space Science Proceedings series (ASSP), in the proceedings of "20th Stellar Pulsation Conference Series: Impact of new instrumentation and new insights in stellar pulsations", 5-9 September 2011, Granada, Spai

On the relationship of the scaled phase space and Skyrme-coherent state treatments of proton antiproton annihilation at rest

We discuss pion multiplicities and single pion momentum spectra from proton antiproton annihilation at rest. Both the scaled phase space model and the Skyrme-coherent state approach describe these observables well. In the coherent state approach the puzzling size of the scale parameter relating the phase space integrals for different multiplicities is replaced by a well defined weight function. The strength of this function is determined by the intensity of the classical pion field and its spatial extent is of order 1 fm.Comment: 11 pages including 4 figures(postscript

Circularly Polarized Resonant Rayleigh Scattering and Skyrmions in the ν\nu = 1 Quantum Hall Ferromagnet

We use the circularly polarized resonant Rayleigh scattering (RRS) to study the quantum Hall ferromagnet at $\nu$ = 1. At this filling factor we observe a right handed copolarized RRS which probes the Skyrmion spin texture of the electrons in the photoexcited grounds state. The resonant scattering is not present in the left handed copolarization, and this can be related to the correlation between Skymionic effects, screening and spin wave excitations. These results evidence that RRS is a valid method for the study of the spin texture of the quantum Hall states