13,679 research outputs found
Bayes-X: a Bayesian inference tool for the analysis of X-ray observations of galaxy clusters
We present the first public release of our Bayesian inference tool, Bayes-X,
for the analysis of X-ray observations of galaxy clusters. We illustrate the
use of Bayes-X by analysing a set of four simulated clusters at z=0.2-0.9 as
they would be observed by a Chandra-like X-ray observatory. In both the
simulations and the analysis pipeline we assume that the dark matter density
follows a spherically-symmetric Navarro, Frenk and White (NFW) profile and that
the gas pressure is described by a generalised NFW (GNFW) profile. We then
perform four sets of analyses. By numerically exploring the joint probability
distribution of the cluster parameters given simulated Chandra-like data, we
show that the model and analysis technique can robustly return the simulated
cluster input quantities, constrain the cluster physical parameters and reveal
the degeneracies among the model parameters and cluster physical parameters. We
then analyse Chandra data on the nearby cluster, A262, and derive the cluster
physical profiles. To illustrate the performance of the Bayesian model
selection, we also carried out analyses assuming an Einasto profile for the
matter density and calculated the Bayes factor. The results of the model
selection analyses for the simulated data favour the NFW model as expected.
However, we find that the Einasto profile is preferred in the analysis of A262.
The Bayes-X software, which is implemented in Fortran 90, is available at
http://www.mrao.cam.ac.uk/facilities/software/bayesx/.Comment: 22 pages, 11 figure
Displaying desire and distinction in housing
The article discusses the significance of cultural capital for the understanding of the field of housing in contemporary Britain. It explores the relationship between housing and the position of individuals in social space mapped out by means of a multiple correspondence analysis. It considers the material aspects of housing and the changing contexts that are linked to the creation and display of desire for social position and distinction expressed in talk about home decoration as personal expression and individuals' ideas of a `dream house'. It is based on an empirical investigation of taste and lifestyle using nationally representative survey data and qualitative interviews. The article shows both that personal resources and the imagination of home are linked to levels of cultural capital, and that rich methods of investigation are required to grasp the significance of these normally invisible assets to broaden the academic understanding of the field of housing in contemporary culture
Band structures of rare gas solids within the GW approximation
Band structures for solid rare gases (Ne, Ar) have been calculated using the
GW approximation. All electron and pseudopotential ab initio calculations were
performed using Gaussian orbital basis sets and the dependence of particle-hole
gaps and electron affinities on basis set and treatment of core electrons is
investigated. All electron GW calculations have a smaller particle-hole gap
than pseudopotential GW calculations by up to 0.2 eV. Quasiparticle electron
and hole excitation energies, valence band widths and electron affinities are
generally in very good agreement with those derived from optical absorption and
photoemission measurements.Comment: 7 pages 1 figur
When it Pays to Rush: Interpreting Morphogen Gradients Prior to Steady-State
During development, morphogen gradients precisely determine the position of
gene expression boundaries despite the inevitable presence of fluctuations.
Recent experiments suggest that some morphogen gradients may be interpreted
prior to reaching steady-state. Theoretical work has predicted that such
systems will be more robust to embryo-to-embryo fluctuations. By analysing two
experimentally motivated models of morphogen gradient formation, we investigate
the positional precision of gene expression boundaries determined by
pre-steady-state morphogen gradients in the presence of embryo-to-embryo
fluctuations, internal biochemical noise and variations in the timing of
morphogen measurement. Morphogens that are direct transcription factors are
found to be particularly sensitive to internal noise when interpreted prior to
steady-state, disadvantaging early measurement, even in the presence of large
embryo-to-embryo fluctuations. Morphogens interpreted by cell-surface receptors
can be measured prior to steady-state without significant decrease in
positional precision provided fluctuations in the timing of measurement are
small. Applying our results to experiment, we predict that Bicoid, a
transcription factor morphogen in Drosophila, is unlikely to be interpreted
prior to reaching steady-state. We also predict that Activin in Xenopus and
Nodal in zebrafish, morphogens interpreted by cell-surface receptors, can be
decoded in pre-steady-state.Comment: 18 pages, 3 figure
Description and Operation of the A3 Subscale Facility
The purpose of this paper is to give an overview of the general design and operation of the A3 Subscale test facility. The goal is to provide the reader with a general understanding of what the major facility systems are, where they are located, and how they are used to meet the objectives supporting the design of the A3 altitude rocket test facility. This paper also provides the reader with the background information prior to reading the subsequent papers detailing the design and test results of the various systems described herein
Pattern languages in HCI: A critical review
This article presents a critical review of patterns and pattern languages in human-computer interaction (HCI). In recent years, patterns and pattern languages have received considerable attention in HCI for their potential as a means for developing and communicating information and knowledge to support good design. This review examines the background to patterns and pattern languages in HCI, and seeks to locate pattern languages in relation to other approaches to interaction design. The review explores four key issues: What is a pattern? What is a pattern language? How are patterns and pattern languages used? and How are values reflected in the pattern-based approach to design? Following on from the review, a future research agenda is proposed for patterns and pattern languages in HCI
Recovering the Primordial Density Fluctuations: A comparison of methods
We present a comparative study of six different methods for reversing the
gravitational evolution of a cosmological density field to recover the
primordial fluctuations: linear theory, the Gaussianization mapping scheme, two
different quasi-linear dynamical schemes based on the Zel'dovich approximation,
a Hybrid dynamical-Gaussianization method and the Path Interchange Zel'dovich
Approximation (PIZA). The final evolved density field from an N-body simulation
constitutes our test case. We use a variety of statistical measures to compare
the initial density field recovered from it to the true initial density field,
using each of the six different schemes. These include point-by-point
comparisons of the density fields in real space, the individual modes in
Fourier space, as well as global statistical properties such as the genus, the
PDF of the density, and the distribution of peak heights and their shapes. We
find linear theory to be the most inaccurate of all the schemes. The
Gaussianization scheme is the least accurate after linear theory. The two
quasi-linear dynamical schemes are more accurate than Gaussianization, although
they break down quite drastically when used outside their range of validity -
the quasi-linear regime. The complementary beneficial aspects of the dynamical
and the Gaussianization schemes are combined in the Hybrid method. We find this
Hybrid scheme to be more accurate and robust than either Gaussianization or the
dynamical method alone. The PIZA scheme performs substantially better than the
others in all point-by-point comparisons. However, it produces an oversmoothed
initial density field, with a smaller number of peaks than expected, but
recovers the PDF of the initial density with impressive accuracy on scales as
small as 3Mpc/h.Comment: 39 pages, including 13 Figures, submitted to Ap
CHANGE IN FOOTSTRIKE POSITION IS RELATED TO ALTERATIONS IN RUNNING ECONOMY IN TRIATHLETES
Biomechanical factors are likely related to the impairment in running economy frequently observed in triathletes when running after cycling (Millet et al., 2000). Cycling has been shown to interfere with muscle recruitment during subsequent running in some highly-trained triathletes (Chapman et al., 2008), but the implications of this on run performance are unknown. Links between muscle recruitment and running economy have been established during isolated running (Paavolainen et al., 1999), which compel the proposition that any change in muscle recruitment following cycling might be associated with running economy. Stride frequency, stride length and hip and knee angles have been reported to be unchanged after cycling (Quigley & Richards, 1996; Hue et al., 1997), however, muscle recruitment and limb movement have not been simultaneously measured in previous studies that have investigated the relationship between biomechanical factors and running economy after cycling. The purpose of the current investigation was to evaluate changes in neuromuscular control (muscle and movement control) during running after a 45 min high-intensity cycle and their relationships to alterations in running economy
SHORT-TERM PLYOMETRIC TRAINING IMPROVES ALTERED NEUROMOTOR CONTROL DURING RUNNING AFTER CYCLING IN TRIATHLETES
Cycling has a direct negative effect on some highly-trained triathletes’ ability to execute optimal neuromotor strategies specific to running (Chapman et al., 2008). The presence of altered neuromotor control when running off-the-bike has been associated with exercise-related leg pain (Chapman et al., 2010). Accordingly, identification of training interventions that could minimise this interference may aid in prevention of injury and augmentation of performance during running following cycling. Plyometric training is a specific form of strength training that has been reported to improve running economy by enhancing neuromuscular function (Paavolainen et al., 1999). The primary aim of this study was to examine the effect of plyometric training on triathletes neuromotor control and running economy in those in which neuromotor control is aberrant during running after cycling
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