648 research outputs found

    Separating the scales in a compressible interstellar medium

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    We apply Gaussian smoothing to obtain mean density, velocity, magnetic and energy density fields in simulations of the interstellar medium based on three-dimensional magnetohydrodynamic equations in a shearing box 1×1×2 kpc1\times1\times2 \, \rm{kpc} in size. Unlike alternative averaging procedures, such as horizontal averaging, Gaussian smoothing retains the three-dimensional structure of the mean fields. Although Gaussian smoothing does not obey the Reynolds rules of averaging, physically meaningful central statistical moments are defined as suggested by Germano (1992). We discuss methods to identify an optimal smoothing scale ℓ\ell and the effects of this choice on the results. From spectral analysis of the magnetic, density and velocity fields, we find a suitable smoothing length for all three fields, of ℓ≈75 pc\ell \approx 75 \, \rm{pc}. We discuss the properties of third-order statistical moments in fluctuations of kinetic energy density in compressible flows and suggest their physical interpretation. The mean magnetic field, amplified by a mean-field dynamo, significantly alters the distribution of kinetic energy in space and between scales, reducing the magnitude of kinetic energy at intermediate scales. This intermediate-scale kinetic energy is a useful diagnostic of the importance of SN-driven outflows

    The Experiences of Staff Who Support People with Intellectual Disability on Issues About Death, Dying, and Bereavement:a metasynthesis

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    Background: Historically, people with intellectual disabilities have tended to be excluded from knowing about death, dying, and bereavement. Staff in intellectual disability services can play a valuable role in improving understanding of these issues in those they support. This qualitative metasynthesis aimed to understand the experiences of staff supporting adults with intellectual disabilities with issues of death, dying, and bereavement. Method: Thirteen papers were identified following a systematic review of six databases. Results: Three themes were developed following a lines-of-argument synthesis: (1) Talking about death is hard: Negotiating the uncertainty in death, dying, and bereavement; (2) The commitment to promoting a “good death”; and (3) The grief behind the professional mask. “A cautious silence: The taboo of death,” was an overarching theme. Conclusions: A more open culture around issues of death, dying, and bereavement in intellectual disability settings is essential and could be promoted through staff training and support

    First-principles extrapolation method for accurate CO adsorption energies on metal surfaces

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    We show that a simple first-principles correction based on the difference between the singlet-triplet CO excitation energy values obtained by DFT and high-level quantum chemistry methods yields accurate CO adsorption properties on a variety of metal surfaces. We demonstrate a linear relationship between the CO adsorption energy and the CO singlet-triplet splitting, similar to the linear dependence of CO adsorption energy on the energy of the CO 2π\pi* orbital found recently {[Kresse {\em et al.}, Physical Review B {\bf 68}, 073401 (2003)]}. Converged DFT calculations underestimate the CO singlet-triplet excitation energy ΔES−T\Delta E_{\rm S-T}, whereas coupled-cluster and CI calculations reproduce the experimental ΔES−T\Delta E_{\rm S-T}. The dependence of EchemE_{\rm chem} on ΔES−T\Delta E_{\rm S-T} is used to extrapolate EchemE_{\rm chem} for the top, bridge and hollow sites for the (100) and (111) surfaces of Pt, Rh, Pd and Cu to the values that correspond to the coupled-cluster and CI ΔES−T\Delta E_{\rm S-T} value. The correction reproduces experimental adsorption site preference for all cases and obtains EchemE_{\rm chem} in excellent agreement with experimental results.Comment: Table sent as table1.eps. 3 figure

    The Spatial Origin of a Perceptual Transition in Binocular Rivalry

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    When the left and the right eye are simultaneously presented with incompatible images at overlapping retinal locations, an observer typically reports perceiving only one of the two images at a time. This phenomenon is called binocular rivalry. Perception during binocular rivalry is not stable; one of the images is perceptually dominant for a certain duration (typically in the order of a few seconds) after which perception switches towards the other image. This alternation between perceptual dominance and suppression will continue for as long the images are presented. A characteristic of binocular rivalry is that a perceptual transition from one image to the other generally occurs in a gradual manner: the image that was temporarily suppressed will regain perceptual dominance at isolated locations within the perceived image, after which its visibility spreads throughout the whole image. These gradual transitions from perceptual suppression to perceptual dominance have been labeled as traveling waves of perceptual dominance. In this study we investigate whether stimulus parameters affect the location at which a traveling wave starts. We varied the contrast, spatial frequency or motion speed in one of the rivaling images, while keeping the same parameter constant in the other image. We used a flash-suppression paradigm to force one of the rival images into perceptual suppression. Observers waited until the suppressed image became perceptually dominant again, and indicated the position at which this breakthrough from suppression occurred. Our results show that the starting point of a traveling wave during binocular rivalry is highly dependent on local stimulus parameters. More specifically, a traveling wave most likely started at the location where the contrast of the suppressed image was higher than that of the dominant one, the spatial frequency of the suppressed image was lower than that of the dominant one, and the motion speed of the suppressed image was higher than that of the dominant one. We suggest that a breakthrough from suppression to dominance occurs at the location where salience (the degree to which a stimulus element stands out relative to neighboring elements) of the suppressed image is higher than that of the dominant one. Our results further show that stimulus parameters affecting the temporal dynamics during continuous viewing of rival images described in other studies, also affect the spatial origin of traveling waves during binocular rivalry

    Simulated Basic Skills Training: Graduate Nursing Students Teaching Medical Students: A Work in Progress

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    For a number of years, Advanced Practice Nursing (APN) students have taught interested 1st year medical students to perform intramuscular injections prior to their participation in community flu clinics. When several 4th year medical students needed documentation of competency in intravenous (IV) cannulation prior to participating in an elective rotation at another institution, the Medical School\u27s Dean of Students called the Director of Interdisciplinary Partnerships in the Graduate School of Nursing to request assistance. In fact, all medical students need IV therapy training prior to graduation, not just those who seek out visiting clerkships at other medical schools. Integration of IV training into the Undergraduate Medical Education Surgery Clerkship Curriculum supports the clinical objectives of the Surgery Clerkship along with the developing use of simulation within in the medical school. This need led to the development of this interdisciplinary simulation education initiative. Presented at the 2008 Society on Simulation in Healthcare Conference

    Evidence for a novel Kit adhesion domain mediating human mast cell adhesion to structural airway cells

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    Background: Human lung mast cells (HLMCs) infiltrate the airway epithelium and airway smooth muscle (ASM) in asthmatic airways. The mechanism of HLMC adhesion to both cell types is only partly defined, and adhesion is not inhibited by function-blocking anti-Kit and anti-stem cell factor (SCF) antibodies. Our aim was to identify adhesion molecules expressed by human mast cells that mediate adhesion to human ASM cells (HASMCs) and human airway epithelial cells. Methods: We used phage-display to isolate single chain Fv (scFv) antibodies with adhesion-blocking properties from rabbits immunised with HLMC and HMC-1 membrane proteins. Results: Post-immune rabbit serum labelled HLMCs in flow cytometry and inhibited their adhesion to human BEAS-2B epithelial cells. Mast cell-specific scFvs were identified which labelled mast cells but not Jurkat cells by flow cytometry. Of these, one scFv (A1) consistently inhibited mast cell adhesion to HASMCs and BEAS-2B epithelial cells by about 30 %. A1 immunoprecipitated Kit (CD117) from HMC-1 lysates and bound to a human Kit-expressing mouse mast cell line, but did not interfere with SCF-dependent Kit signalling. Conclusion: Kit contributes to human mast cell adhesion to human airway epithelial cells and HASMCs, but may utilise a previously unidentified adhesion domain that lies outside the SCF binding site. Targeting this adhesion pathway might offer a novel approach for the inhibition of mast cell interactions with structural airway cells, without detrimental effects on Kit signalling in other tissues

    Measurements of Higgs boson production and couplings in diboson final states with the ATLAS detector at the LHC

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    Measurements are presented of production properties and couplings of the recently discovered Higgs boson using the decays into boson pairs, H →γ γ, H → Z Z∗ →4l and H →W W∗ →lνlν. The results are based on the complete pp collision data sample recorded by the ATLAS experiment at the CERN Large Hadron Collider at centre-of-mass energies of √s = 7 TeV and √s = 8 TeV, corresponding to an integrated luminosity of about 25 fb−1. Evidence for Higgs boson production through vector-boson fusion is reported. Results of combined fits probing Higgs boson couplings to fermions and bosons, as well as anomalous contributions to loop-induced production and decay modes, are presented. All measurements are consistent with expectations for the Standard Model Higgs boson

    Standalone vertex nding in the ATLAS muon spectrometer

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    A dedicated reconstruction algorithm to find decay vertices in the ATLAS muon spectrometer is presented. The algorithm searches the region just upstream of or inside the muon spectrometer volume for multi-particle vertices that originate from the decay of particles with long decay paths. The performance of the algorithm is evaluated using both a sample of simulated Higgs boson events, in which the Higgs boson decays to long-lived neutral particles that in turn decay to bbar b final states, and pp collision data at √s = 7 TeV collected with the ATLAS detector at the LHC during 2011
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