11,242 research outputs found

    U(1) flux tube profiles from Hamiltonian lattice gauge theory using a random walk ground-state projector

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    We use a self-guided random walk to solve the ground-state problem of Hamiltonian U(1) pure gauge theory in 2+1 dimensions in the string sector. By making use of the electric-field representation, we argue that the spatial distribution of the electric field can be more easily measured than in ordinary Monte Carlo simulations.Comment: 3 pages, contribution to Lattice 94, uuencoded compressed Postscrip

    Wavelets as a variational basis of the XY model

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    We use Daubechies' orthonormal compact wavelets as a variational basis for the XYXY model in two and three dimensions. Assuming that the fluctuations of the wavelet coefficients are Gaussian and uncorrelated, minimization of the free energy yields the fluctuation strength of wavelet coefficients at different scales, from which observables can be computed. This model is able to describe the low-temperature phase and makes a prediction about the phase transition temperature.Comment: 3 pages, postscript. Contribution to the Lattice 93 workshop (Dallas, Texas, October 1993

    HgSe, a highly electronegative stable metallic contact for semiconductor devices

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    Schottky barriers formed by the highly electronegative substance HgSe on n-ZnS and on n-ZnSe have been characterized by capacitance-voltage and photoresponse measurements. The barriers are about 0.5 eV greater than Au barriers on these n-type substrates. HgSe contacts are stable under ambient conditions and are easily fabricated, making them attractive for device use

    Finding Person Relations in Image Data of the Internet Archive

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    The multimedia content in the World Wide Web is rapidly growing and contains valuable information for many applications in different domains. For this reason, the Internet Archive initiative has been gathering billions of time-versioned web pages since the mid-nineties. However, the huge amount of data is rarely labeled with appropriate metadata and automatic approaches are required to enable semantic search. Normally, the textual content of the Internet Archive is used to extract entities and their possible relations across domains such as politics and entertainment, whereas image and video content is usually neglected. In this paper, we introduce a system for person recognition in image content of web news stored in the Internet Archive. Thus, the system complements entity recognition in text and allows researchers and analysts to track media coverage and relations of persons more precisely. Based on a deep learning face recognition approach, we suggest a system that automatically detects persons of interest and gathers sample material, which is subsequently used to identify them in the image data of the Internet Archive. We evaluate the performance of the face recognition system on an appropriate standard benchmark dataset and demonstrate the feasibility of the approach with two use cases

    Lessons learned in promoting evidence-based public health: Perspectives from managers in state public health departments

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    Evidence-based public health (EBPH) practice, also called evidence-informed public health, can improve population health and reduce disease burden in populations. Organizational structures and processes can facilitate capacity-building for EBPH in public health agencies. This study involved 51 structured interviews with leaders and program managers in 12 state health department chronic disease prevention units to identify factors that facilitate the implementation of EBPH. Verbatim transcripts of the de-identified interviews were consensus coded in NVIVO qualitative software. Content analyses of coded texts were used to identify themes and illustrative quotes. Facilitator themes included leadership support within the chronic disease prevention unit and division, unit processes to enhance information sharing across program areas and recruitment and retention of qualified personnel, training and technical assistance to build skills, and the ability to provide support to external partners. Chronic disease prevention leaders\u27 role modeling of EBPH processes and expectations for staff to justify proposed plans and approaches were key aspects of leadership support. Leaders protected staff time in order to identify and digest evidence to address the common barrier of lack of time for EBPH. Funding uncertainties or budget cuts, lack of political will for EBPH, and staff turnover remained challenges. In conclusion, leadership support is a key facilitator of EBPH capacity building and practice. Section and division leaders in public health agencies with authority and skills can institute management practices to help staff learn and apply EBPH processes and spread EBPH with partners

    VLT spectropolarimetry of two powerful radio galaxies at z~1.4: UV continuum, emission-line properties and the nature of high-redshift dust

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    (Abridged) Deep VLT spectropolarimetric observations are presented for two powerful radio galaxies, 0850-206 and 1303+091. These observations cover the rest-frame wavelength range ~ 1450 - 3750 A. New radio observations and continuum images of the same sources are also presented. These galaxies are the first two observed from a complete sample of nine radio sources with redshifts in the range 1.3 < z < 1.5 (selected from the equatorial sample of powerful radio sources of Best, Rottgering & Lehnert), as part of a project aimed to investigate the multi-component nature of the UV continuum in radio galaxies and any variations of the continuum properties with the radio source age. The larger radio source of the two, 0850-206, presents a high continuum fractional polarization, averaging 17% across the observed wavelength range and reaching 24% at rest-frame wavelengths of <2000 A. The smaller radio source, 1303+091, shows a lower continuum polarization, averaging 8% and rising to 11% for rest-frame wavelengths >3000 A. For both galaxies, the position angle of the electric vector is generally constant with wavelength and within ~15 degrees of perpendicular to the radio axis. Both their total flux spectra and polarized flux spectra reveal the 2200 A dust feature, and comparison with dust scattering models suggests that the composition of the dust in these galaxies is similar to that of Galactic dust. In 0850-206, scattered quasar radiation dominates the UV continuum emission, with the nebular continuum accounting for no more than ~22% and no requirement for any additional emission component such as emission from young stars. By contrast, in 1303+091, unpolarized radiation could be a major constituent of the UV continuum emission, with starlight accounting for up to ~50% and the nebular continuum accounting for ~11%.Comment: 20 pages, including 14 figures. MNRAS accepte

    Measurement of 25Mg(p; gamma)26Al resonance strengths via gamma spectrometry

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    The COMPTEL instrument performed the first mapping of the 1.809 MeV photons in the Galaxy, triggering considerable interest in determing the sources of interstellar 26Al. The predicted 26Al is too low compared to the observation, for a better understanding more accurate rates for the 25Mg(p; gamma)26Al reaction are required. The 25Mg(p;gamma)26Al reaction has been investigated at the resonances at Er= 745; 418; 374; 304 keV at Ruhr-Universitat-Bochum using a Tandem accelerator and a 4piNaI detector. In addition the resonance at Er = 189 keV has been measured deep underground laboratory at Laboratori Nazionali del Gran Sasso, exploiting the strong suppression of cosmic background. This low resonance has been studied with the 400 kV LUNA accelerator and a HPGe detector. The preliminary results of the resonance strengths will be reported.Comment: Accepted for publication in Journal of Physics

    Deep radio observations of 3C324 and 3C368: evidence for jet-cloud interactions

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    High resolution, deep radio images are presented for two distant radio galaxies, 3C324 (z=1.206) and 3C368 (z=1.132), which are both prime examples of the radio-optical alignment effect seen in powerful radio galaxies with redshifts z > 0.6. Radio observations were made using the Very Large Array in A-array configuration at 5 and 8 GHz, and using the MERLIN array at 1.4 and 1.65 GHz. Radio spectral index, radio polarisation, and rotation measure maps are presented for both sources. Radio core candidates are detected in each source, and by aligning these with the centroid of the infrared emission the radio and the optical/infrared images can be related astrometrically with 0.1 arcsec accuracy. In each source the radio core is located at a minimum of the optical emission, probably associated with a central dust lane. Both sources also exhibit radio jets which lie along the directions of the bright strings of optical knots seen in high resolution Hubble Space Telescope images. The northern arm of 3C368 shows a close correlation between the radio and optical emission, whilst along the jet direction of 3C324 the bright radio and optical knots are co-linear but not co-spatial. These indicate that interactions between the radio jet and its environment play a key role in producing the excess ultraviolet emission of these sources, but that the detailed mechanisms vary from source to source. 3C368 is strongly depolarised and has an average rest-frame rotation measure of a few hundred rad/m^2, reaching about 1000 rad/m^2 close to the most depolarised regions. 3C324 has weaker depolarisation, and an average rest-frame rotation measure of between 100 and 200 rad/m^2. Both sources show large gradients in their rotation measure structures, with variations of up to 1000 rad/m^2 over distances of about 10 kpc.Comment: 15 pages including 4 figures. LaTeX. Accepted for publication in MNRA

    Transfer Function Approximations for Large Highly Coupled Elastic Boosters with Fuel Slosh

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    Transfer function approximations for large highly coupled flexible body launch vehicles with liquid fuel slos
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