1,264 research outputs found
Labor Markets in Professional Sports
Many interesting elements of supply and demand are starkly observable in professional athletics. Understanding institutional arrangements, competitive balance and labor-management relations requires a basic understanding of sports labor markets and the struggle for control of those markets between interest groups. In this paper we treat historical and contemporary labor issues in North America and Europe, from reserve rules and free agency, high levels of player pay and work stoppages, to the distribution of playing talents across teams. We discuss the relationship between personal productivity and pay; relative versus absolute demand; competitive and cooperative interactions across firms (teams); factor substitutions; player mobility and the Coase theorem. We briefly consider how property rights affect supply, athletic talent, arms races and restrictions on competition. The problem of (excess) incentives to compete leading to externalities and inefficiencies are noted throughout the paper. Restrictive agreements such as reverse-order drafts, payroll caps and revenue sharing may constrain these forces, but they also redistribute rents from players to owners. All of these schemes, in one way or another, punish success. The European approach -- promotion of better-performing teams and relegation of those with the poorest records -- punishes failure. It remains an interesting economic question as to which system is better.
An alternative formulation of lyapunov exponents for computing lagrangian coherent structures
pre-printLagrangian coherent structures are time-evolving surfaces that highlight areas in flow fields where neighboring advected particles diverge or converge. The detection and understanding of such structures is an important part of many applications such as in oceanography where there is a need to predict the dispersion of oil and other materials in the ocean. One of the most widely used tools for revealing Lagrangian coherent structures has been to calculate the finite-time Lyapunov exponents, whose maximal values appear as ridgelines to reveal Lagrangian coherent structures. In this paper we explore an alternative formulation of Lyapunov exponents for computing Lagrangian coherent structures
X-ray modelling of galaxy cluster gas and mass profiles
We present a parametric analysis of the intracluster medium and gravitating
mass distribution of a statistical sample of 20 galaxy clusters using the
phenomenological cluster model of Ascasibar and Diego. We describe an effective
scheme for the estimation of errors on model parameters and derived quantities
using bootstrap resampling. We find that the model provides a good description
of the data in all cases and we quantify the mean fractional intrinsic scatter
about the best-fit density and temperature profiles, finding this to have
median values across the sample of 2 and 5 per cent, respectively. In addition,
we demonstrate good agreement between r500 determined directly from the model
and that estimated from a core-excluded global spectrum. We compare cool core
and non-cool core clusters in terms of the logarithmic slopes of their gas
density and temperature profiles and the distribution of model parameters and
conclude that the two categories are clearly separable. In particular, we
confirm the effectiveness of the logarithmic gradient of the gas density
profile measured at 0.04 r500 in differentiating between the two types of
cluster.Comment: 8 pages, 7 figures, accepted for publication in MNRA
Probing the dark matter profile of hot clusters and the M-T relation with XMM-Newton
We present results based on XMM-Newton observations of a small sample of hot
galaxy clusters. Making a full use of XMM-Newton's spectro-imaging
capabilities, we have extracted the radial temperature profile and gas density
profile, and with this information, calculated the total mass profile of each
cluster (under the assumption of hydrostatic equilibrium and spherical
symmetry). Comparing the individual scaled total mass profiles, we have probed
the Universality of rich cluster mass profiles over a wide range of radii (from
0.01 to 0.7 the virial radius). We have also tested the shape of cluster mass
profiles by comparing with the predicted profiles from numerical simulations of
hierarchical structure formation. We also derived the local mass-temperature
(M-T) scaling relation over a range of temperature going from 4 to 9 keV, that
we compare with theoretical predictions.Comment: 7 pages, 2 figures, Advances in Space Research in press (proceedings
of the COSPAR 2004 Assembly, Paris
NHS procurement and the origins of the personal protective equipment crisis
COVID-19 has thrown NHS procurement into the limelight, but the shortage of personal protective equipment (PPE) has complex origins. This article explores the long-lasting struggle for centralisation in NHS procurement and its impact on the current PPE crisis
Bayesian modelling of the cool core galaxy group NGC 4325
We present an X-ray analysis of the radio-quiet cool-core galaxy group NGC
4325 (z=0.026) based on Chandra and ROSAT observations. The Chandra data were
analysed using XSPEC deprojection, 2D spectral mapping and forward-fitting with
parametric models. Additionally, a Markov chain Monte Carlo method was used to
perform a joint Bayesian analysis of the Chandra and ROSAT data. The results of
the various analysis methods are compared, particularly those obtained by
forward-fitting and deprojection. The spectral mapping reveals the presence of
cool gas displaced up to 10 kpc from the group centre. The Chandra X-ray
surface brightness shows the group core to be highly disturbed, and indicates
the presence of two small X-ray cavities within 15 kpc of the group core. The
XSPEC deprojection analysis shows that the group has a particularly steep
entropy profile, suggesting that an AGN outburst may be about to occur. With
the evidence of prior AGN activity, but with no radio emission currently
observed, we suggest that the group in in a pre-outburst state, with the
cavities and displaced gas providing evidence of a previous, weak AGN outburst.Comment: 12 pages, 10 figures; accepted for publication in MNRA
Measuring the dark matter velocity anisotropy in galaxy clusters
The Universe contains approximately 6 times more dark matter than normal
baryonic matter, and a directly observed fundamental difference between dark
matter and baryons would both be significant for our understanding of dark
matter structures and provide us with information about the basic
characteristics of the dark matter particle. We discuss one distinctive feature
of dark matter structures in equilibrium, namely the property that a local dark
matter temperature may depend on direction. This is in stark contrast to
baryonic gases. We used X-ray observations of two nearby, relaxed galaxy
clusters, under the assumptions of hydrostatic equilibrium and identical dark
matter and gas temperatures in the outer cluster region, to measure this dark
matter temperature anisotropy beta_dm, with non-parametric Monte Carlo methods.
We find that beta_dm is greater than the value predicted for baryonic gases,
beta_gas=0, at more than 3 sigma confidence. The observed value of the
temperature anisotropy is in fair agreement with the results of cosmological
N-body simulations and shows that the equilibration of the dark matter
particles is not governed by local point-like interactions in contrast to
baryonic gases.Comment: 5 pages, 3 figures, extended discussions, matches accepted versio
Abundance profiles and cool cores in galaxy groups
Using data from the Two Dimensional XMM-Newton Group Survey (2dXGS), we have
examined the abundance profile properties of both cool core (CC) and non cool
core (NCC) galaxy groups. The ten NCC systems in our sample represent a
population which to date has been poorly studied in the group regime. Fitting
the abundance profiles as a linear function of log radius, we find steep
abundance gradients in cool core (CC) systems, with a slope of -0.54+/-0.07. In
contrast, non cool core (NCC) groups have profiles consistent with uniform
metallicity. Many CC groups show a central abundance dip or plateau, and we
find evidence for anticorrelation between the core abundance gradient and the
1.4 GHz radio power of the brightest group galaxy (BGG) in CC systems. This may
indicate the effect of AGN-driven mixing within the central ~0.1r_500. It is
not possible to discern whether such behaviour is present in the NCC groups,
due to the small and diverse sample with the requisite radio data. The lack of
strong abundance gradients in NCC groups, coupled with their lack of cool core,
and evidence for enhanced substructure, leads us to favour merging as the
mechanism for disrupting cool cores, although we cannot rule out disruption by
a major AGN outburst. Given the implied timescales, the disruptive event must
have occurred within the past few Gyrs in most NCC groups.Comment: 15 pages, 12 figures, accepted for publication in MNRA
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A NATIONAL COLLABORATORY TO ADVANCE THE SCIENCE OF HIGH TEMPERATURE PLASMA PHYSICS FOR MAGNETIC FUSION
This report summarizes the work of the University of Utah, which was a member of the National Fusion Collaboratory (NFC) Project funded by the United States Department of Energy (DOE) under the Scientific Discovery through Advanced Computing Program (SciDAC) to develop a persistent infrastructure to enable scientific collaboration for magnetic fusion research. A five year project that was initiated in 2001, it the NFC built on the past collaborative work performed within the U.S. fusion community and added the component of computer science research done with the USDOE Office of Science, Office of Advanced Scientific Computer Research. The project was itself a collaboration, itself uniting fusion scientists from General Atomics, MIT, and PPPL and computer scientists from ANL, LBNL, and Princeton University, and the University of Utah to form a coordinated team. The group leveraged existing computer science technology where possible and extended or created new capabilities where required. The complete finial report is attached as an addendum. The In the collaboration, the primary technical responsibility of the University of Utah in the collaboration was to develop and deploy an advanced scientific visualization service. To achieve this goal, the SCIRun Problem Solving Environment (PSE) is used on FusionGrid for an advanced scientific visualization service. SCIRun is open source software that gives the user the ability to create complex 3D visualizations and 2D graphics. This capability allows for the exploration of complex simulation results and the comparison of simulation and experimental data. SCIRun on FusionGrid gives the scientist a no-license-cost visualization capability that rivals present day commercial visualization packages. To accelerate the usage of SCIRun within the fusion community, a stand-alone application built on top of SCIRun was developed and deployed. This application, FusionViewer, allows users who are unfamiliar with SCIRun to quickly create visualizations and perform analysis of their simulation data from either the MDSplus data storage environment or from locally stored HDF5 files. More advanced tools for visualization and analysis also were created in collaboration with the SciDAC Center for Extended MHD Modeling. Versions of SCIRun with the FusionViewer have been made available to fusion scientists on the Mac OS X, Linux, and other Unix based platforms and have been downloaded 1163 times. SCIRun has been used with NIMROD, M3D, BOUT fusion simulation data as well as simulation data from other SciDAC application areas (e.g., Astrophysics). The subsequent visualization results - including animations - have been incorporated into invited talks at multiple APS/DPP meetings as well as peer reviewed journal articles. As an example, SCIRun was used for the visualization and analysis of a NIMROD simulation of a disruption that occurred in a DIII-D experiment. The resulting animations and stills were presented as part of invited talks at APS/DPP meetings and the SC04 conference in addition to being highlighted in the NIH/NSF Visualization Research Challenges Report. By achieving its technical goals, the University of Utah played a key role in the successful development of a persistent infrastructure to enable scientific collaboration for magnetic fusion research. Many of the visualization tools developed as part of the NFC continue to be used by Fusion and other SciDAC application scientists and are currently being supported and expanded through follow-on up on SciDAC projects (Visualization and Analytics Center for Enabling Technology, and the Visualization and Analysis in Support of Fusion SAP)
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