16,677 research outputs found

    Nuclear Bar, Star Formation and Gas Fueling in the Active Galaxy NGC 4303

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    A combination of Hubble Space Telescope (HST) WFPC2 and NICMOS images are used to investigate the gas/dust and stellar structure inside the central 300 pc of the nearby active galaxy NGC 4303. The NICMOS H-band (F160W) image reveals a bright core and a nuclear elongated bar-like structure of 250 pc in diameter. The bar is centered on the bright core, and its major axis is oriented in proyection along the spin axis of the nuclear gaseous rotating disk recently detected (Colina & Arribas 1999). The V-H (F606W - F160W) image reveals a complex gas/dust distribution with a two-arm spiral structure of about 225 pc in radius. The southwestern arm is traced by young star-forming knots while the northeastern arm is detected by the presence of dust lanes. These spirals do not have a smooth structure but rather they are made of smaller flocculent spirals or filament-like structures. The magnitudes and colors of the star-forming knots are typical of clusters of young stars with masses of 0.5 to 1 x 105Msolar,andagesof5to25millionyears.Theoverallstructureofthenuclearspiralsaswellasthesize,numberandmassesofthestar−formingknotsareexplainedinthecontextofamassivegaseousnucleardisksubjecttoself−gravitationalinstabilitiesandtothegravitationalfieldcreatedbythenuclearbar.Accordingtothemodel,thegaseousdiskhasamassofabout5x107Msolarinsidearadiusof400pc,thebarhasaradiusof150pcandapatternspeedofabout0.5Myr−1,andtheaveragemassaccretionrateintothecore(R<8pc)isabout0.01Msolar10^5 M_{solar}, and ages of 5 to 25 million years. The overall structure of the nuclear spirals as well as the size, number and masses of the star-forming knots are explained in the context of a massive gaseous nuclear disk subject to self-gravitational instabilities and to the gravitational field created by the nuclear bar. According to the model, the gaseous disk has a mass of about 5 x 10^7 M_{solar} inside a radius of 400 pc, the bar has a radius of 150 pc and a pattern speed of about 0.5 Myr^{-1}, and the average mass accretion rate into the core (R < 8 pc) is about 0.01 M_{solar} yr^{-1} for about 80 Myr.Comment: ApJ, in press (February 1, 2000

    Towards durable multistakeholder-generated solutions: The pilot application of a problem-oriented policy learning protocol to legality verification and community rights in Peru

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    This paper reports and reflects on the pilot application of an 11-step policy learning protocol that was developed by Cashore and Lupberger (2015) based on several years of Cashore’s multi-author collaborations. The protocol was applied for the first time in Peru in 2015 and 2016 by the IUFRO Working Party on Forest Policy Learning Architectures (hereinafter referred to as the project team). The protocol integrates insights from policy learning scholarship (Hall 1993, Sabatier 1999) with Bernstein and Cashore’s (2000, 2012) four pathways of influence framework. The pilot implementation in Peru focused on how global timber legality verification interventions might be harnessed to promote local land rights. Legality verification focuses attention on the checking and auditing of forest management units in order to verify that timber is harvested and traded in compliance with the law. We specifically asked: How can community legal ownership of, and access to, forestland and forest resources be enhanced? The protocol was designed as a dynamic tool, the implementation of which fosters iterative rather than linear processes. It directly integrated two objectives: 1) identifying the causal processes through which global governance initiatives might be harnessed to produce durable results ‘on the ground’; 2) generating insights and strategies in collaboration with relevant stakeholders. This paper reviews and critically evaluates our work in designing and piloting the protocol. We assess what seemed to work well and suggest modifications, including an original diagnostic framework for nurturing durable change. We also assess the implications of the pilot application of the protocol for policy implementation that works to enhance the influence of existing international policy instruments, rather than contributing to fragmentation and incoherence by creating new ones

    The foundations of the working alliance in assertive community treatment teams

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    Abstract Background In this study, we aimed to identify and define the fundamental components of the working alliance in multidisciplinary (Flexible) Assertive Community Treatment teams with shared caseloads, in order to support their daily practice and further research. Methods After reviewing the literature, concept mapping with professionals and clients was used to define the working alliance in (F) ACT teams. The resulting concept maps formed the basis for the working alliance assessment instrument, which was pilot tested with professionals and clients through cognitive interviews with a think-aloud procedure. Results The study led to the development of a twenty five-item assessment instrument to evaluate working alliances in multidisciplinary teams (WAM) that was comprised of three subscales: bond, task/goal and team. Two different versions were developed for clients and professionals. Conclusions The WAM instrument was developed to determine the quality of the working alliance in (F) ACT teams. Future research will focus on testing its psychometric properties and predictive value

    Towards a fully self-consistent spectral function of the nucleon in nuclear matter

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    We present a calculation of nuclear matter which goes beyond the usual quasi-particle approximation in that it includes part of the off-shell dependence of the self-energy in the self-consistent solution of the single-particle spectrum. The spectral function is separated in contributions for energies above and below the chemical potential. For holes we approximate the spectral function for energies below the chemical potential by a δ\delta-function at the quasi-particle peak and retain the standard form for energies above the chemical potential. For particles a similar procedure is followed. The approximated spectral function is consistently used at all levels of the calculation. Results for a model calculation are presented, the main conclusion is that although several observables are affected by the inclusion of the continuum contributions the physical consistency of the model does not improve with the improved self-consistency of the solution method. This in contrast to expectations based on the crucial role of self-consistency in the proofs of conservation laws.Comment: 26 pages Revtex with 4 figures, submitted to Phys. Rev.

    A graphene transmon operating at 1 T

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    A superconducting transmon qubit resilient to strong magnetic fields is an important component for proposed topological and hybrid quantum computing (QC) schemes. Transmon qubits consist of a Josephson junction (JJ) shunted by a large capacitance, coupled to a high quality factor superconducting resonator. In conventional transmon devices, the JJ is made from an Al/AlOx_x/Al tunnel junction which ceases operation above the critical magnetic field of Al, 10 mT. Alternative junction technologies are therefore required to push the operation of these qubits into strong magnetic fields. Graphene JJs are one such candidate due to their high quality, ballistic transport and electrically tunable critical current densities. Importantly the monolayer structure of graphene protects the JJ from orbital interference effects that would otherwise inhibit operation at high magnetic field. Here we report the integration of ballistic graphene JJs into microwave frequency superconducting circuits to create the first graphene transmons. The electric tunability allows the characteristic band dispersion of graphene to be resolved via dispersive microwave spectroscopy. We demonstrate that the device is insensitive to the applied field and perform energy level spectroscopy of the transmon at 1 T, more than an order of magnitude higher than previous studies.Comment: attached supplementary materia

    Ground-based variability surveys towards Centaurus A: worthwhile or not?

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    Context: Difference imaging has proven to be a powerful technique for detecting and monitoring the variability of unresolved stellar sources in M 31. Using this technique in surveys of galaxies outside the Local Group could have many interesting applications. Aims: The goal of this paper is to test difference imaging photometry on Centaurus A, the nearest giant elliptical galaxy, at a distance of 4 Mpc. Methods: We obtained deep photometric data with the Wide Field Imager at the ESO/MPG 2.2m at La Silla spread over almost two months. Applying the difference imaging photometry package DIFIMPHOT, we produced high-quality difference images and detected variable sources. The sensitivity of the current observational setup was determined through artificial residual tests. Results: In the resulting high-quality difference images, we detect 271 variable stars. We find a difference flux detection limit corresponding to m_R~24.5. Based on a simple model of the halo of Centaurus A, we estimate that a ground-based microlensing survey would detect in the order of 4 microlensing events per year due to lenses in the halo. Conclusions: Difference imaging photometry works very well at the distance of Centaurus A and promises to be a useful tool for detecting and studying variable stars in galaxies outside the local group. For microlensing surveys, a higher sensitivity is needed than achieved here, which would be possible with a large ground-based telescope or space observatory with wide-field imaging capabilities.Comment: 8 pages, 7 figures, accepted for publication in Astronomy and Astrophysic

    The effect of a goal-setting strategy with integrated feedback on goal attainment in inflammatory arthritis patients:a mixed method study

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    Patients with Inflammatory Arthritis (IA) often experience difficulties in daily life as a result of their disease. Unfortunately, outpatient consultations in daily practice tend to focus on medical topics, thereby ignoring the impact of the disease on patients’ daily lives. Patient-Reported Outcomes (PROs) can be used to understand this impact, but they are not enough for offering person-centered care. Because the patient’s true values and goals can only be ascertained during a proper conversation, which should include both medical as well as patient goals. Therefore, the aim of the study is to evaluate the effect of a goal management strategy with integrated feedback on goal attainment and Health-Related Quality of Life(HRQoL) in IA patients. IA patients with an active disease were given the opportunity to set and follow-up goals. In addition to goal setting, patients were asked to complete online questionnaires on various PROs, including HRQoL. Ninety-two IA patients participated in the study. The mean age was 51 years and most of them had rheumatoid arthritis. A total of 302 patient goals were set, of which 32% were achieved. In the entire population, HRQoL did not change over time, but patients who did not meet their goals tended to report a lower HRQoL. Incorporating a feedback mechanism in a goal-setting strategy has a positive effect on goal attainment. Yet no effect was seen on HRQoL, but this may due to the fact that general HRQoL measurement are not sensitive or specific enough to detect changes that are accompanied with goal setting and attainment.</p

    Relativistic Brueckner-Hartree-Fock calculations with explicit intermediate negative energy states

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    In a relativistic Brueckner-Hartree-Fock calculation we include explicit negative-energy states in the two-body propagator. This is achieved by using the Gross spectator-equation, modified by medium effects. Qualitatively our results compare well with other RBHF calculations. In some details significant differences occur, e.g, our equation of state is stiffer and the momentum dependence of the self-energy components is stronger than found in a reference calculation without intermediate negative energy states.Comment: 13 pages Revtex, 5 figures included seperatel

    Shot Noise of Single-Electron Tunneling in 1D Arrays

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    We have used numerical modeling and a semi-analytical calculation method to find the low frequency value S_{I}(0) of the spectral density of fluctuations of current through 1D arrays of small tunnel junctions, using the ``orthodox theory'' of single-electron tunneling. In all three array types studied, at low temperature (kT << eV), increasing current induces a crossover from the Schottky value S_{I}(0)=2e to the ``reduced Schottky value'' S_{I}(0)=2e/N (where N is the array length) at some crossover current I_{c}. In uniform arrays over a ground plane, I_{c} is proportional to exp(-\lambda N), where 1/\lambda is the single-electron soliton length. In arrays without a ground plane, I_{c} decreases slowly with both N and \lambda. Finally, we have calculated the statistics of I_{c} for ensembles of arrays with random background charges. The standard deviation of I_{c} from the ensemble average is quite large, typically between 0.5 and 0.7 of , while the dependence of on N or \lambda is so weak that it is hidden within the random fluctuations of the crossover current.Comment: RevTex. 21 pages of text, 10 postscript figure
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