1,246 research outputs found
A review of strength and conditioning internships: the UKSCA’s State of the Nation survey
Internships within the strength and conditioning (S&C) industry have become a ‘right of passage’ for any junior or student coach wanting to gain employment. They have recently been described as ‘the new degree’, implying that formal education is no longer sufficient enough to gain employment on its own. Given the importance of practical skills required to successfully deliver S&C coaching, there is an expectation that applicants for professional jobs possess an appropriate level of experience. The UKSCA decided to conduct a survey of S&C interns in order to discover just exactly what kind of experiences they receive during their internships. The results are presented and discussed below
Application of ERTS-1 imagery to the harvest model of the US Menhaden fishery
Preliminary results of an experiment to demonstrate the utility of ERTS-1 imagery for providing significant information to the harvest model of the menhaden industry are reported. Fisheries and related environmental data were obtained discontinuously throughout the 1973 menhaden (a surface schooling, coastal species) fishing season in Mississippi Sound. The unexpected complexity of the physical environment in Mississippi Sound precluded simplistic analysis of fish/environment relationships. Preliminary indications are that an association does exist between fish availability and differences in water transparency (turbidity) within the Sound. A clearer relationship is developing between major turbid features, imaged by ERTS-1 and location of successful fishing attempts. On all occasions where relatively cloudfree ERTS-1 overflight days coincided with fishery activity, overlays of catch location of ERTS-1 images show an association of school position with interfaces between imaged turbid features. Analysis is currently underway to determine persistence of such associations in an attempt to define minimum satellite return time necessary to maintain continuity of associations
Manipulating O3/P2 phase ratio in bi-phasic sodium layered oxides via ionic radius control
Funding: This work was supported by the Faraday Institution (Grant number FIRG018). The authors would like to thank Dr. David Rochester at Lancaster University for conducting the ICP-OES experiments. A.B.N. would like to acknowledge funding by the Engineering and Physical Sciences Research Council under grant numbers EP/L017008/1, EP/R023751/1, and EP/T019298/1 for the electron microscopy analysis.Bi-phasic O3/P2 sodium layered oxides have emerged as leading candidates for the commercialisation of next-generation sodium-ion batteries. However, beyond simply altering the sodium content, rational control of the O3/P2 ratio in these materials has proven particularly challenging despite being crucial for the realization of high-performance electrode materials. Here, using abundant elements, we manipulate the O3/P2 ratio using the average ionic radius of the transition metal layer and different synthesis conditions. These methods allow deterministic control over the O3/P2 ratio, even for constant Na contents. In addition, tuning the O3/P2 ratio yields high-performing materials with different performance characteristics, with a P2-rich material achieving high rate capabilities and excellent cycling stability (92% retention, 50 cycles), while an O3-rich material displayed an energy density up to 430 Wh kg−1, (85%, 50 cycles). These insights will help guide the rational design of future high-performance materials for sodium-ion batteries.Publisher PDFPeer reviewe
Chandra Measurements of a Complete Sample of X-ray Luminous Galaxy Clusters: The Luminosity-Mass Relation
We present the results of work involving a statistically complete sample of
34 galaxy clusters, in the redshift range 0.15z0.3 observed with
. We investigate the luminosity-mass () relation for the cluster
sample, with the masses obtained via a full hydrostatic mass analysis. We
utilise a method to fully account for selection biases when modeling the
relation, and find that the relation is significantly different than the
relation modelled when not account for selection effects. We find that the
luminosity of our clusters is 2.20.4 times higher (when accounting for
selection effects) than the average for a given mass, its mass is 30% lower
than the population average for a given luminosity. Equivalently, using the
relation measured from this sample without correcting for selection biases
would lead to the underestimation by 40% of the average mass of a cluster with
a given luminosity. Comparing the hydrostatic masses to mass estimates
determined from the parameter, we find that they are entirely
consistent, irrespective of the dynamical state of the cluster.Comment: 31 pages, 43 figures, accepted for publication in MNRA
An XMM and Chandra view of massive clusters of galaxies to z=1
The X-ray properties of a sample of high redshift (z>0.6), massive clusters
observed with XMM-Newton and Chandra are described, including two exceptional
systems. One, at z=0.89, has an X-ray temperature of T=11.5 (+1.1, -0.9) keV
(the highest temperature of any cluster known at z>0.6), an estimated mass of
(1.4+/-0.2)x10^15 solar masses and appears relaxed. The other, at z=0.83, has
at least three sub-clumps, probably in the process of merging, and may also
show signs of faint filamentary structure at large radii,observed in X-rays. In
general there is a mix of X-ray morphologies, from those clusters which appear
relaxed and containing little substructure to some highly non-virialized and
probably merging systems. The X-ray gas metallicities and gas mass fractions of
the relaxed systems are similar to those of low redshift clusters of the same
temperature, suggesting that the gas was in place, and containing its metals,
by z=0.8. The evolution of the mass-temperature relation may be consistent with
no evolution or with the ``late formation'' assumption. The effect of point
source contamination in the ROSAT survey from which these clusters were
selected is estimated, and the implications for the ROSAT X-ray luminosity
function discussed.Comment: 9 pages, in Carnegie Observatories Astrophysics Series, Vol. 3:
Clusters of Galaxies: Probes of Cosmological Structure and Galaxy Evolution,
ed. J. S. Mulchaey, A. Dressler, and A. Oemler. See
http://www.ociw.edu/ociw/symposia/series/symposium3/proceedings.html for a
full-resolution versio
Separating the BL Lac and Cluster X-ray Emissions in Abell 689 with Chandra
We present the results of a Chandra observation of the galaxy cluster Abell
689 (z=0.279). Abell 689 is one of the most luminous clusters detected in the
ROSAT All Sky Survey (RASS), but was flagged as possibly including significant
point source contamination. The small PSF of the Chandra telescope allows us to
confirm this and separate the point source from the extended cluster X-ray
emission. For the cluster we determine a bolometric luminosity of
L_{bol}=(3.3+/-0.3)x10^{44} erg s-1 and a temperature of kT=5.1^{+2.2}_{-1.3}
keV when including a physically motivated background model. We compare our
measured luminosity for A689 to that quoted in the Rosat All Sky Survey (RASS)
and find L_{0.1-2.4,keV}=2.8x10^{44} erg s-1, a value \sim10 times lower than
the ROSAT measurement. Our analysis of the point source shows evidence for
significant pileup, with a pile-up fraction of ~60%. SDSS spectra and HST
images lead us to the conclusion that the point source within Abell 689 is a BL
Lac object. Using radio and optical observations from the VLA and HST archives,
we determine {\alpha}_{ro}=0.50, {\alpha}_{ox}=0.77 and {\alpha}_{rx}=0.58 for
the BL Lac, which would classify it as being of 'High-energy peak BL Lac' (HBL)
type. Spectra extracted of A689 show a hard X-ray excess at energies above 6
keV that we interpret as inverse Compton emission from aged electrons that may
have been transported into the cluster from the BL Lac.Comment: 11 pages, 15 figures, MNRAS in pres
Self-similar scaling and evolution in the galaxy cluster X-ray Luminosity-Temperature relation
We investigate the form and evolution of the X-ray luminosity-temperature
(LT) relation of a sample of 114 galaxy clusters observed with Chandra at
0.1<z<1.3. The clusters were divided into subsamples based on their X-ray
morphology or whether they host strong cool cores. We find that when the core
regions are excluded, the most relaxed clusters (or those with the strongest
cool cores) follow an LT relation with a slope that agrees well with simple
self-similar expectations. This is supported by an analysis of the gas density
profiles of the systems, which shows self-similar behaviour of the gas profiles
of the relaxed clusters outside the core regions. By comparing our data with
clusters in the REXCESS sample, which extends to lower masses, we find evidence
that the self-similar behaviour of even the most relaxed clusters breaks at
around 3.5keV. By contrast, the LT slopes of the subsamples of unrelaxed
systems (or those without strong cool cores) are significantly steeper than the
self-similar model, with lower mass systems appearing less luminous and higher
mass systems appearing more luminous than the self-similar relation. We argue
that these results are consistent with a model of non-gravitational energy
input in clusters that combines central heating with entropy enhancements from
merger shocks. Such enhancements could extend the impact of central energy
input to larger radii in unrelaxed clusters, as suggested by our data. We also
examine the evolution of the LT relation, and find that while the data appear
inconsistent with simple self-similar evolution, the differences can be
plausibly explained by selection bias, and thus we find no reason to rule out
self-similar evolution. We show that the fraction of cool core clusters in our
(non-representative) sample decreases at z>0.5 and discuss the effect of this
on measurements of the evolution in the LT relation.Comment: 21 pages, 15 figures. Submitted to MNRAS. Comments welcom
The Evolutionary Status of Clusters of Galaxies at z ~ 1
Combined HST, X-ray, and ground-based optical studies show that clusters of
galaxies are largely "in place" by , an epoch when the Universe was
less than half its present age. High resolution images show that elliptical,
S0, and spiral galaxies are present in clusters at redshifts up to . Analysis of the CMDs suggest that the cluster ellipticals formed their
stars several Gyr earlier, near redshift 3. The morphology--density relation is
well established at , with star-forming spirals and irregulars residing
mostly in the outer parts of the clusters and E/S0s concentrated in dense
clumps. The intracluster medium has already reached the metallicity of
present-day clusters. The distributions of the hot gas and early-type galaxies
are similar in clusters, indicating both have largely virialized in
the deepest potentials wells. In spite of the many similarities between
and present-day clusters, there are significant differences. The
morphologies revealed by the hot gas, and particularly the early-type galaxies,
are elongated rather than spherical. We appear to be observing the clusters at
an epoch when the sub-clusters and groups are still assembling into a single
regular cluster. Support for this picture comes from CL0152 where the gas
appears to be lagging behind the luminous and dark mass in two merging
sub-components. Moreover, the luminosity difference between the first and
second brightest cluster galaxies at is smaller than in 93% of
present-day Abell clusters, which suggests that considerable luminosity
evolution through merging has occurred since that epoch. Evolution is also seen
in the bolometric X-ray luminosity function.Comment: 18 pages, 12 figures, to appear in Penetrating Bars through Masks of
Cosmic Dust: the Hubble Tuing Fork Strikes a New Note, eds. D.L. Block, K.C.
Freeman, I. Puerari & R. Groess. Figures degraded to meet astroph size limit;
a version with higher resolution figures may be downloaded from:
http://acs.pha.jhu.edu/~jpb/z1clusters/ford_clusters.pd
A comparison of the strong lensing properties of the Sersic and the NFW profiles
We investigate the strong lensing properties of the Sersic profile as an
alternative to the NFW profile, focusing on applications to lens modelling of
clusters. Given an underlying Sersic dark matter profile, we study whether an
NFW profile can provide an acceptable fit to strong lensing constraints in the
form of single or multiple measured Einstein radii. We conclude that although
an NFW profile that fits the lensing constraints can be found in many cases,
the derived parameters may be biased. In particular, we find that for n~2,
which corresponds to massive clusters, the mass at r_200 of the best fit NFW is
overestimated (by a factor of ~2) and the concentration is very low (c~2). The
differences are important enough to warrant the inclusion of Sersic profile for
future analysis of strong lensing clusters.Comment: 19 pages (single column format), 11 figures. Accepted for publication
by JCA
Toxicity associated with combination oxaliplatin plus fluoropyrimidine with or without cetuximab in the MRC COIN trial experience
We present the preliminary toxicity data from the MRC COIN trial, a phase III randomised controlled trial of first-line therapy in advanced colorectal cancer, with particular reference to the addition of cetuximab to an oxaliplatin–fluoropyrimidine combination. A total of 804 patients were randomised between March 2005 and July 2006 from 78 centres throughout the United Kingdom. Patients were allocated to oxaliplatin plus fluoropyrimidine chemotherapy with or without the addition of weekly cetuximab. The choice of fluoropyrimidine (either 5-fluorouracil (5FU) or capecitabine) was decided by the treating physician and patient before randomisation. Toxicity data were collected from all patients. Two hundred and three patients received 5FU plus oxaliplatin (OxMdG, 25%), 333 oxaliplatin+capecitabine (Xelox, 41%), 102 received OxMdG+cetuximab (OxMdG+C, 13%) and 166 Xelox+cetuximab (21%). Percent grade 3/4 toxicities included diarrhoea 6, 15, 13 and 25%, nausea/vomiting 3, 7, 7 and 14% for OxMdG, Xelox, OxMdG+C and Xelox+C, respectively. Sixty-day all-cause mortality was 6, 5, 5 and 7%. Statistically significant differences were evident for patients receiving Xelox+cetuximab vs Xelox alone: diarrhoea relative risk (RR) 1.69 (1.17, 2.43, P=0.005) and nausea/vomiting RR 2.01 (1.16, 3.47, P=0.012). The excess toxicity observed in the oxaliplatin-, capecitabine-, cetuximab-treated patients led the trial management group to conclude that a capecitabine dose adjustment was required to maintain safety levels when using this regimen
- …