19,961 research outputs found

    The use of conversation mapping to frame key perceptual issues facing the general dental practice system in England

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    <b>Objective</b>: To demonstrate the use of a novel qualitative methodology namely conversation mapping, which can be used to capture differences in stakeholder perspectives and give a root definition of the problem in a complex policy area. The methodology is used in the context of the changes introduced in the English general dental practice system in April 2006, to investigate the key issues facing the system, as perceived by general dental practitioners (GDPs). <b>Basic research design</b>: From a broad trigger statement, three transformational statements were produced. Each participant recorded their contribution on a hard diagrammatic form as a ‘map’, with others responding with their own written comment, thus generating three conversation maps. Thematic analysis resulted in the generation of a preliminary model summarising key perceptual issues. <b>Results</b>: The five emergent themes identified were: financing, dentists’ wants/needs, the role of the public and patients, system goals and policy level decision making. Financing was identified as the core category to which all other categories were related. <b>Conclusions</b>: Conversation mapping, a methodology arising from a systems approach, can be used to develop a ‘rich picture’ of an oral health care system in order to define the core problem within this policy area. Findings suggest that GDPs identify the financing of the system as a fundamental source of problems within the general dental practice system. This appears to be at variance with the perception of policy makers, who report a more limited view, identifying the system of remuneration as the ‘heart of the problem’

    Effects of Interactions on the Critical Temperature of a Trapped Bose Gas

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    We perform high-precision measurements of the condensation temperature of a harmonically-trapped atomic Bose gas with widely-tuneable interactions. For weak interactions we observe a negative shift of the critical temperature in excellent agreement with mean-field theory. However for sufficiently strong interactions we clearly observe an additional positive shift, characteristic of beyond-mean-field critical correlations. We also discuss non-equilibrium effects on the apparent critical temperature for both very weak and very strong interactions.Comment: 4 pages, 4 figure

    Comparative Negligence

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    This note will discuss briefly the policy considerations underlying a choice between comparative negligence and contributory negligence, and will attempt to predict the effects, both procedural and substantive, of the new Act on practice in Washington

    SAGA: A project to automate the management of software production systems

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    The Software Automation, Generation and Administration (SAGA) project is investigating the design and construction of practical software engineering environments for developing and maintaining aerospace systems and applications software. The research includes the practical organization of the software lifecycle, configuration management, software requirements specifications, executable specifications, design methodologies, programming, verification, validation and testing, version control, maintenance, the reuse of software, software libraries, documentation, and automated management

    Efficient Production of Large 39K Bose-Einstein Condensates

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    We describe an experimental setup and the cooling procedure for producing 39K Bose-Einstein condensates of over 4x10^5 atoms. Condensation is achieved via a combination of sympathetic cooling with 87Rb in a quadrupole-Ioffe-configuration (QUIC) magnetic trap, and direct evaporation in a large volume crossed optical dipole trap, where we exploit the broad Feshbach resonance at 402 G to tune the 39K interactions from weak and attractive to strong and repulsive. In the same apparatus we create quasi-pure 87Rb condensates of over 8x10^5 atoms.Comment: 7 pages, 5 figures; figure font compatibility improve

    Rate of Diffusion of Radioactive Ions in Gels

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    A simple gel-to-gel method is described for the estimation of diffusion coefficients (D) of radio-isotopic chemicals. Cold and hot gel cylinders, enclosed in small hypodermic syringes with their needle ends cut off, were carefully joined together, and diffusion was allowed to proceed for several hours. Slices of gels were then obtained for counting of activities. Application of the classical theory of diffusion permitted calculations of D values

    The 6dF Galaxy Survey: Dependence of halo occupation on stellar mass

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    In this paper we study the stellar-mass dependence of galaxy clustering in the 6dF Galaxy Survey. The near-infrared selection of 6dFGS allows more reliable stellar mass estimates compared to optical bands used in other galaxy surveys. Using the Halo Occupation Distribution (HOD) model, we investigate the trend of dark matter halo mass and satellite fraction with stellar mass by measuring the projected correlation function, wp(rp)w_p(r_p). We find that the typical halo mass (M1M_1) as well as the satellite power law index (α\alpha) increase with stellar mass. This indicates, (1) that galaxies with higher stellar mass sit in more massive dark matter halos and (2) that these more massive dark matter halos accumulate satellites faster with growing mass compared to halos occupied by low stellar mass galaxies. Furthermore we find a relation between M1M_1 and the minimum dark matter halo mass (MminM_{\rm min}) of M122MminM_1 \approx 22\,M_{\rm min}, in agreement with similar findings for SDSS galaxies. The satellite fraction of 6dFGS galaxies declines with increasing stellar mass from 21% at Mstellar=2.6×1010h2MM_{\rm stellar} = 2.6\times10^{10}h^{-2}\,M_{\odot} to 12% at Mstellar=5.4×1010h2MM_{\rm stellar} = 5.4\times10^{10}h^{-2}\,M_{\odot} indicating that high stellar mass galaxies are more likely to be central galaxies. We compare our results to two different semi-analytic models derived from the Millennium Simulation, finding some disagreement. Our results can be used for placing new constraints on semi-analytic models in the future, particularly the behaviour of luminous red satellites. Finally we compare our results to studies of halo occupation using galaxy-galaxy weak lensing. We find good overall agreement, representing a valuable crosscheck for these two different tools of studying the matter distribution in the Universe.Comment: 17 pages, 11 figures. arXiv admin note: text overlap with arXiv:1104.2447 by other author

    Quantum-Inspired Tempering for Ground State Approximation using Artificial Neural Networks

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    A large body of work has demonstrated that parameterized artificial neural networks (ANNs) can efficiently describe ground states of numerous interesting quantum many-body Hamiltonians. However, the standard variational algorithms used to update or train the ANN parameters can get trapped in local minima, especially for frustrated systems and even if the representation is sufficiently expressive. We propose a parallel tempering method that facilitates escape from such local minima. This methods involves training multiple ANNs independently, with each simulation governed by a Hamiltonian with a different "driver" strength, in analogy to quantum parallel tempering, and it incorporates an update step into the training that allows for the exchange of neighboring ANN configurations. We study instances from two classes of Hamiltonians to demonstrate the utility of our approach using Restricted Boltzmann Machines as our parameterized ANN. The first instance is based on a permutation-invariant Hamiltonian whose landscape stymies the standard training algorithm by drawing it increasingly to a false local minimum. The second instance is four hydrogen atoms arranged in a rectangle, which is an instance of the second quantized electronic structure Hamiltonian discretized using Gaussian basis functions. We study this problem in a minimal basis set, which exhibits false minima that can trap the standard variational algorithm despite the problem's small size. We show that augmenting the training with quantum parallel tempering becomes useful to finding good approximations to the ground states of these problem instances.Comment: 13 pages, 6 figures. v2: updated Figs. 3, 4, and 5. v3. included two new QPT schemes. Updated format to SciPost format. 30 pages, 11 figures. Submission to SciPos
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