2,382 research outputs found

    Breaking the mass / anisotropy degeneracy in the Coma cluster

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    We provide the first direct lifting of the mass/anisotropy degeneracy for a cluster of galaxies, by jointly fitting the line of sight velocity dispersion and kurtosis profiles of the Coma cluster, assuming an NFW tracer density profile, a generalized-NFW dark matter profile and a constant anisotropy profile. We find that the orbits in Coma must be quasi-isotropic, and find a mass consistent with previous analyses, but a concentration parameter 50% higher than expected in cosmological N-body simulations. We then test the accuracy of our method on realistic non-spherical systems with substructure and streaming motions, by applying it to the ten most massive structures in a cosmological N-body simulation. We find that our method yields fairly accurate results on average (within 20%), although with a wide variation (factor 1.7 at 1 sigma) for the concentration parameter, with decreased accuracy and efficiency when the projected mean velocity is not constant with radius.Comment: 5 pages, oral presentation at IAU Colloquium 195, Outskirts of Galaxy Clusters: intense life in the suburbs, ed. A. Diaferi

    Development and initial validation of a sensory threshold examination protocol (STEP) for phenotyping canine pain syndromes

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    Objective To study feasibility and test-retest repeatability of a sensory threshold examination protocol (STEP) and report quantitative sensory threshold distributions in healthy dogs. Study design Prospective, observational, cohort study. Animals Twenty-five healthy client-owned dogs. Methods Tactile sensitivity (TST) (von Frey filaments), mechanical thresholds (MT with 2, 4 and 8 mm probes), heat thresholds (HT) and responsiveness to cold stimulus (CT at 0 °C) were quantitatively assessed for five body areas (BA: tibias, humeri, neck, thoracolumbar region and abdomen) in a randomized order on three different occasions. Linear Mixed Model and Generalised Linear Mixed models were used to evaluate the effects of body weight category, age, sex, BA, occasion, feasibility score and investigator experience. Test-retest repeatability was evaluated with the Intra-class Correlation Coefficient (ICC). Results The STEP lasted 90 minutes without side effects. The BA affected most tests (p = 0.001). Higher thresholds and longer cold latencies were scored in the neck (p = 0.024) compared to other BAs. Weight category affected all thresholds (p = 0.037). Small dogs had lower MT (~1.4 N mean difference) and HT (1.1 0C mean difference) than other dogs (p = 0.029). Young dogs had higher HT than adults (2.2 0C mean difference) (p = 0.035). Gender also affected TST, MT and HT (p < 0.05) (females versus males: TST OR= 0.5, MT= 1.3 N mean difference, HT= 2.2 0C mean difference). Repeatability was substantial to moderate for all tests, but poor for TST. There was no difference in thresholds between occasions, except for CT. Test-retest repeatability was slightly better with the 2 mm MT probe compared to other diameters and improved with operator experience. Conclusions and clinical relevance The STEP was feasible, well tolerated and showed substantial test-retest repeatability in healthy dogs. Further validation is needed in dogs suffering pain

    Comment on "Theory of tailoring sonic devices: Diffraction dominates over refraction"

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    Recently N. Garcia et al. (Phys. Rev. E 67, 046606 (2003)) theoretically studied several acoustic devices with dimensions on de order of several wavelenghts. The authors discussed on experimental results previously reported by several of us (F. Cervera et al., Phys. Rev. Lett. 88, 023902 (2002)). They concluded that diffraction and not refraction is the ominating mechanism that explain the focusing effects observed in those experiments. In this Comment we reexamined their calculations and discussed why some of their interpretations of our results are misleading.Comment: 2 pages, 2 figures, a comment on an articl

    Overview of ASDEX Upgrade results

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    The ASDEX Upgrade (AUG) programme is directed towards physics input to critical elements of the ITER design and the preparation of ITER operation, as well as addressing physics issues for a future DEMO design. Since 2015, AUG is equipped with a new pair of 3-strap ICRF antennas, which were designed for a reduction of tungsten release during ICRF operation. As predicted, a factor two reduction on the ICRF-induced W plasma content could be achieved by the reduction of the sheath voltage at the antenna limiters via the compensation of the image currents of the central and side straps in the antenna frame. There are two main operational scenario lines in AUG. Experiments with low collisionality, which comprise current drive, ELM mitigation/suppression and fast ion physics, are mainly done with freshly boronized walls to reduce the tungsten influx at these high edge temperature conditions. Full ELM suppression and non-inductive operation up to a plasma current of Ip = 0.8 MA could be obtained at low plasma density. Plasma exhaust is studied under conditions of high neutral divertor pressure and separatrix electron density, where a fresh boronization is not required. Substantial progress could be achieved for the understanding of the confinement degradation by strong D puffing and the improvement with nitrogen or carbon seeding. Inward/outward shifts of the electron density profile relative to the temperature profile effect the edge stability via the pressure profile changes and lead to improved/decreased pedestal performance. Seeding and D gas puffing are found to effect the core fueling via changes in a region of high density on the high field side (HFSHD). The integration of all above mentioned operational scenarios will be feasible and naturally obtained in a large device where the edge is more opaque for neutrals and higher plasma temperatures provide a lower collisionality. The combination of exhaust control with pellet fueling has been successfully demonstrated. High divertor enrichment values of nitrogen EN 10 have been obtained during pellet injection, which is a prerequisite for the simultaneous achievement of good core plasma purity and high divertor radiation levels. Impurity accumulation observed in the all-metal AUG device caused by the strong neoclassical inward transport of tungsten in the pedestal is expected to be relieved by the higher neoclassical temperature screening in larger devices.European Commission (EUROfusion 633053

    A heavy quark effective field lagrangian keeping particle and antiparticle mixed sectors

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    We derive a tree-level heavy quark effective Lagrangian keeping particle-antiparticle mixed sectors allowing for heavy quark-antiquark pair annihilation and creation. However, when removing the unwanted degrees of freedom from the effective Lagrangian one has to be careful in using the classical equations of motion obeyed by the effective fields in order to get a convergent expansion on the reciprocal of the heavy quark mass. Then the application of the effective theory to such hard processes should be sensible for special kinematic regimes as for example heavy quark pair production near threshold.Comment: LaTeX, 14 pages, 1 EPS figure

    Power scaling rules for charmonia production and HQEFT

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    We discuss the power scaling rules along the lines of a complete Heavy Quark Effective Field Theory (HQEFT) for the description of heavy quarkonium production through a color-octet mechanism. To this end, we firstly derive a tree-level heavy quark effective Lagrangian keeping both particle-antiparticle mixed sectors allowing for heavy quark-antiquark pair annihilation and creation, but describing only low-energy modes around the heavy quark mass. Then we show the consistency of using HQEFT fields in constructing four-fermion local operators a la NRQCD, to be identified with standard color-octet matrix elements. We analyze some numerical values extracted from charmonia production by different authors and their hierarchy in the light of HQEFT.Comment: LaTeX, 19 pages, 3 EPS figure

    Using micro-geography data to identify town-centre space in Great Britain

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    We often talk about ‘Town Centres’, but defining their location and extent is surprisingly difficult. Their boundaries are hard to pin down and intrinsically fuzzy. Nevertheless, the British government introduced very specific policies for them in 1996 – Town Centre First Policies (TCFP) – without defining them. The semi-official definitions introduced in 2004 did not cover Scotland, only England and Wales. Using a range of variables available for the whole of Great Britain that capture all the dimensions of ‘town centredness’, we start by replicating the definitions for England and Wales. Then, we use an alternative list of towns and cities and apply our estimated coefficients to predict their size. Our models yield high correlations between the semi-official DCLG values and our predicted values, so we then move on to identify Town Centres for all three countries of GB. Our method is a contribution in its own right but is also an essential step if there is to be a rigorous evaluation of TCFP since it makes it possible to compare changes in the ‘policy treated’ Town Centres of England and Wales with changes in the ‘policy untreated’ ones of Scotland

    (IN)Convenient Stores? What do policies pushing stores to town centres actually do?

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    England®s Town Centre First Policy, introduced in 1996, restricted the opening of new retail and other ‘traditional town centre activities’ to ‘Town Centre’ (TC) locations. The aim was to halt the decay of high streets. We explore the impact of the policy on the supply and location of grocery shops and patterns of shopping by comparing English with Scottish TCs before and after the policy change in England. Using store level census data, we show first that supply trends for grocery stores in TCs were similar in both countries prior to the implementation of the policy. After the policy took effect, however, stores in TCs increased relatively more strongly in England, but with no change in grocery employment. Second, using survey data, we show that the policy changed the composition of shops in TCs in favour of convenience-type shops supplied by the “big four” grocery chains. However, although it increased the number of TC shops, the policy had no effect on the number of shoppers choosing TC locations

    (In)convenient stores? What do policies pushing stores to town centres actually do?

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    England®s Town Centre First Policy, introduced in 1996, restricted the opening of new retail and other ‘traditional town centre activities’ to ‘Town Centre’ (TC) locations. The aim was to halt the decay of high streets. We explore the impact of the policy on the supply and location of grocery shops and patterns of shopping by comparing English with Scottish TCs before and after the policy change in England. Using store level census data, we show first that supply trends for grocery stores in TCs were similar in both countries prior to the implementation of the policy. After the policy took effect, however, stores in TCs increased relatively more strongly in England, but with no change in grocery employment. Second, using survey data, we show that the policy changed the composition of shops in TCs in favour of convenience-type shops supplied by the “big four” grocery chains. However, although it increased the number of TC shops, the policy had no effect on the number of shoppers choosing TC locations
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