472 research outputs found
Reliability of Clinician Rated Physical Effort Determination During Functional Capacity Evaluation in Patients with Chronic Musculoskeletal Pain
Introduction Functional capacity evaluation (FCE) can be used to make clinical decisions regarding fitness-for-work. During FCE the evaluator attempts to assess the amount of physical effort of the patient. The aim of this study is to analyze the reliability of physical effort determination using observational criteria during FCE. Methods Twenty-one raters assessed physical effort in 18 video-recorded FCE tests independently on two occasions, 10 months apart. Physical effort was rated on a categorical four-point physical effort determination scale (P-ED) based on the Isernhagen criteria, and a dichotomous submaximal effort determination scale (S-ED). Cohen's Kappa, squared weighted Kappa and % agreement were calculated. Results Kappa values for intra-rater reliability of P-ED and S-ED for all FCE tests were 0.49 and 0.68 respectively. Kappa values for inter-rater reliability of P-ED for all FCE tests in the first and the second session were 0.51, and 0.72, and for S-ED Kappa values were 0.68 and 0.77 respectively. The inter-rater reliability of P-ED ranged from kappa = 0.02 to kappa = 0.99 between FCE tests. Acceptable reliability scores (kappa > 0.60, agreement a parts per thousand yen80 %) for each FCE test were observed in 38 % of scores for P-ED and 67 % for S-ED. On average material handling tests had a higher reliability than postural tolerance and ambulatory tests. Conclusion Dichotomous ratings of submaximal effort are more reliable than categorical criteria to determine physical effort in FCE tests. Regular education and training may improve the reliability of observational criteria for effort determination
Purification and characterization of a new cytosolic glutathione S-transferase (glutathione S-transferase X) from rat liver
Star formation in the early universe: beyond the tip of the iceberg
We present late-time Hubble Space Telescope imaging of the fields of six
Swift GRBs lying at 5.0<z<9.5. Our data includes very deep observations of the
field of the most distant spectroscopically confirmed burst, GRB 090423, at
z=8.2. Using the precise positions afforded by their afterglows we can place
stringent limits on the luminosities of their host galaxies. In one case, that
of GRB 060522 at z=5.11, there is a marginal excess of flux close to the GRB
position which may be a detection of a host at a magnitude J(AB)=28.5. None of
the others are significantly detected meaning that all the hosts lie below
L\star at their respective redshifts, with star formation rates SFR<4Mo/yr in
all cases. Indeed, stacking the five fields with WFC3-IR data we conclude a
mean SFR<0.17Mo/yr per galaxy. These results support the proposition that the
bulk of star formation, and hence integrated UV luminosity, at high redshifts
arises in galaxies below the detection limits of deep-field observations.
Making the reasonable assumption that GRB rate is proportional to UV luminosity
at early times allows us to compare our limits with expectations based on
galaxy luminosity functions derived from the Hubble Ultra-Deep Field (HUDF) and
other deep fields. We infer that a luminosity function which is evolving
rapidly towards steeper faint-end slope (alpha) and decreasing characteristic
luminosity (L\star), as suggested by some other studies, is consistent with our
observations, whereas a non-evolving LF shape is ruled out at >90% confidence.
Although it is not yet possible to make stronger statements, in the future,
with larger samples and a fuller understanding of the conditions required for
GRB production, studies like this hold great potential for probing the nature
of star formation, the shape of the galaxy luminosity function, and the supply
of ionizing photons in the early universe.Comment: ApJ in press. 14 pages, 6 figures. (small updates from version 1
The zCOSMOS 10k-sample: the role of galaxy stellar mass in the colour-density relation up to z=1
[Abridged] With the first 10000 spectra of the flux limited zCOSMOS sample
(I<=22.5) we study the evolution of environmental effects on galaxy properties
since z=1.0, and disentangle the dependence among galaxy colour, stellar mass
and local density (3D local density contrast `delta', computed with the 5th
nearest neighbour approach). We confirm that within a luminosity-limited sample
(M_B=1) galaxies 'f_red' depends on delta
at least up to z=1, with red galaxies residing mainly in high densities. This
trend weakens for increasing z, and it is mirrored by the behaviour of the
fraction of galaxies with D4000A break >=1.4. We also find that up to z=1 the
fraction of galaxies with log(EW[OII]) >=1.15 is higher for lower delta, and
also this dependence weakens for increasing z. Given the triple dependence
among galaxy colours, stellar mass and delta, the colour-delta relation found
in the luminosity-selected sample can be due to the broad range of stellar
masses. Thus, we fix the stellar mass and we find that in this case the
colour-delta relation is flat up to z=1 for galaxies with log(M/M_sun)>=10.7.
This means that for these masses the colour-delta relation found in a
luminosity-selected sample is the result of the combined colour-mass and
mass-delta relations. In contrast, we find that for 0.1<=z<=0.5 and
log(M/M_sun)<=10.7 'f_red' depends on delta even at fixed mass. In these mass
and z ranges, environment affects directly also galaxy colours. We suggest a
scenario in which the colour depends primarily on stellar mass, but for
relatively low mass galaxies the local density modulates this dependence. These
galaxies formed more recently, in an epoch when evolved structures were already
in place, and their longer SFH allowed environment-driven physical processes to
operate during longer periods of time.Comment: 19 pages, 12 figures, submitted to A&A, revised version after referee
comment
Detection of three gamma-ray burst host galaxies at z ⌠6
The American Astronomical Society. All rights reserved.Long-duration gamma-ray bursts (GRBs) allow us to pinpoint and study star-forming galaxies in the early universe, thanks to their orders of magnitude brighter peak luminosities compared to other astrophysical sources, and their association with the deaths of massive stars. We present Hubble Space Telescope Wide Field Camera 3 detections of three Swift GRB host galaxies lying at redshifts z = 5.913 (GRB 130606A), z = 6.295 (GRB 050904), and z = 6.327 (GRB 140515A) in the F140W (wide-JH band, λobs ⌠1.4ÎŒm) filter. The hosts have magnitudes (corrected for Galactic extinction) of mλobsAB = 26.34-0.16+0.14, 27.56-0.22+0.18, and 28.30-0.33+0.25, respectively. In all three cases, the probability of chance coincidence of lower redshift galaxies is âČ2%, indicating that the detected galaxies are most likely the GRB hosts. These are the first detections of high-redshift () GRB host galaxies in emission. The galaxies have luminosities in the range 0.1-0.6 Lz=6â(with M1600â = -20.95±0.12) and half-light radii in the range 0.6-0.9 kpc. Both their half-light radii and luminosities are consistent with existing samples of Lyman-break galaxies at zâŒ6. Spectroscopic analysis of the GRB afterglows indicate low metallicities ([M/H]âČ-1) and low dust extinction (AV âČ 0.1) along the line of sight. Using stellar population synthesis models, we explore the implications of each galaxy's luminosity for its possible star-formation history and consider the potential for emission line metallicity determination with the upcoming James Webb Space Telescope. © 2016
The zCOSMOS redshift survey: how group environment alters global downsizing trends
Context. Groups of galaxies are a common environment, bridging the gap between starforming field galaxies and quiescent cluster galaxies. Within groups secular processes could be at play, contributing to the observed strong decrease of star formation with cosmic time in the global galaxy population.
Aims. We took advantage of the wealth of information provided by the first ~10â000 galaxies of the zCOSMOS-bright survey and its group catalogue to study in detail the complex interplay between group environment and galaxy properties.
Methods. The classical indicator F_(blue), i.e.,âthe fraction of blue galaxies, proved to be a simple but powerful diagnostic tool. We studied its variation for different luminosity and mass selected galaxy samples, divided as to define groups/field/isolated galaxy subsamples.
Results. Using rest-frame evolving B-band volume-limited samples, the groups galaxy population exhibits significant blueing as redshift increases, but maintains a systematic difference (a lower F_(blue)) with respect to the global galaxy population, and an even larger difference with respect to the isolated galaxy population. However moving to mass selected samples it becomes apparent that such differences are largely due to the biased view imposed by the B-band luminosity selection, being driven by the population of lower mass, bright blue galaxies for which we miss the redder, equally low mass, counterparts. By carefully focusing the analysis on narrow mass bins such that mass segregation becomes negligible we find that only for the lowest mass bin explored, i.e., log(M_*/M_â) †10.6, does a significant residual difference in color remain as a function of environment, while this difference becomes negligible toward higher masses.
Conclusions. Our results indicate that red galaxies of mass log(M_*/M_â) â„ 10.8 are already in place at z ~ 1 and do not exhibit any strong environmental dependence, possibly originating from so-called nature or internal mechanisms. In contrast, for lower galaxy masses and redshifts lower than z ~ 1, we observe the emergence in groups of a population of nurture red galaxies: slightly deviating from the trend of the downsizing scenario followed by the global galaxy population, and more so with cosmic time. These galaxies exhibit signatures of group-related secular physical mechanisms directly influencing galaxy evolution. Our analysis implies that these mechanisms begin to significantly influence galaxy evolution after z ~ 1, a redshift corresponding to the emergence of structures in which these mechanisms take place
The zCOSMOS redshift survey : Influence of luminosity, mass and environment on the galaxy merger rate
The contribution of major mergers to galaxy mass assembly along cosmic time
is an important ingredient to the galaxy evolution scenario. We aim to measure
the evolution of the merger rate for both luminosity/mass selected galaxy
samples and investigate its dependence with the local environment. We use a
sample of 10644 spectroscopically observed galaxies from the zCOSMOS redshift
survey to identify pairs of galaxies destined to merge, using only pairs for
which the velocity difference and projected separation of both components with
a confirmed spectroscopic redshift indicate a high probability of merging. We
have identified 263 spectroscopically confirmed pairs with r_p^{max} = 100
h^{-1} kpc. We find that the density of mergers depends on luminosity/mass,
being higher for fainter/less massive galaxies, while the number of mergers a
galaxy will experience does not depends significantly on its intrinsic
luminosity but rather on its stellar mass. We find that the pair fraction and
merger rate increase with local galaxy density, a property observed up to
redshift z=1. We find that the dependence of the merger rate on the luminosity
or mass of galaxies is already present up to redshifts z=1, and that the
evolution of the volumetric merger rate of bright (massive) galaxies is
relatively flat with redshift with a mean value of 3*10^{-4} (8*10^{-5}
respectively) mergers h^3 Mpc^{-3} Gyr^{-1}. The dependence of the merger rate
with environment indicates that dense environments favors major merger events
as can be expected from the hierarchical scenario. The environment therefore
has a direct impact in shapping-up the mass function and its evolution
therefore plays an important role on the mass growth of galaxies along cosmic
time.Comment: submitted to A&A, 17 pages, 12 figure
The optical spectra of 24 ÎŒm galaxies in the COSMOS field. I. Spitzer MIPS bright sources in the zCOSMOS-bright 10k catalog
We study zCOSMOS-bright optical spectra for 609 Spitzer MIPS 24 ÎŒm-selected galaxies with S_(24) ÎŒ m > 0.30 mJy and I 10^(11) Lï galaxies at 0.6 < z < 0.7 are ~0.6 dex higher than the average ratio of all zCOSMOS galaxies at similar redshifts. Massive star formation and AGNs could simultaneously be present in those galaxies with the highest ionizing fluxes. (5) Roughly 1/3 of the galaxies with metallicity measurements at 0.5 < z < 0.7 lie below the general mass-metallicity relation at the corresponding redshifts. The strengths of the 4000 Ă
break and the HÎŽ EW of our galaxies show that secondary bursts of star formation are needed to explain the spectral properties of most IR sources. The LIRG and ULIRG phases occur, on average, between 10^7 and 10^8 yr after the onset of a starburst on top of underlying older stellar populations. These results are valid for galaxies of different IR luminosities at 0.6 < z < 1.0 and seem independent of the mechanisms triggering star formation
K+a galaxies in the zCOSMOS Survey: Physical properties of systems in their post-starburst phase
The identities of the main processes triggering and quenching star-formation
in galaxies remain unclear. A key stage in evolution, however, appears to be
represented by post-starburst galaxies. To investigate their impact on galaxy
evolution, we initiated a multiwavelength study of galaxies with k+a spectral
features in the COSMOS field. We examine a mass-selected sample of k+a galaxies
at z=0.48-1.2 using the spectroscopic zCOSMOS sample. K+a galaxies occupy the
brightest tail of the luminosity distribution. They are as massive as quiescent
galaxies and populate the green valley in the colour versus luminosity (or
stellar mass) distribution. A small percentage (<8%) of these galaxies have
radio and/or X-ray counterparts (implying an upper limit to the SFR of
~8Msun/yr). Over the entire redshift range explored, the class of k+a galaxies
is morphologically a heterogeneous population with a similar incidence of
bulge-dominated and disky galaxies. This distribution does not vary with the
strength of the Hdelta absorption line but instead with stellar mass in a way
reminiscent of the well-known mass-morphology relation. Although k+a galaxies
are also found in underdense regions, they appear to reside typically in a
similarly rich environment as quiescent galaxies on a physical scale of
~2-8Mpc, and in groups they show a morphological early-to-late type ratio
similar to the quiescent galaxy class. With the current data set, we do not
find evidence of statistical significant evolution in either the number/mass
density of k+a galaxies at intermediate redshift with respect to the local
values, or the spectral properties. Those galaxies, which are affected by a
sudden quenching of their star-formation activity, may increase the stellar
mass of the red-sequence by up to a non-negligible level of ~10%.Comment: 17 pages, 9 figures. Accepted for publication in Astronomy and
Astrophysics on 09/09/2009 (no changes wrt v1
The zCOSMOS survey: the role of the environment in the evolution of the luminosity function of different galaxy types
Aims. An unbiased and detailed characterization of the galaxy luminosity function (LF) is a basic requirement in many astrophysical issues: it is of particular interest in assessing the role of the environment in the evolution of the LF of different galaxy types.
Methods. We studied the evolution in the B band LF to redshift z ~ 1 in the zCOSMOS 10k sample, for which both accurate galaxy classifications (spectrophotometric and morphological) and a detailed description of the local density field are available.
Results. The global B band LF exhibits a brightening of ~0.7 mag in M^* from z ~ 0.2 to z ~ 0.9. At low redshifts (z -20), while the bright end is populated mainly by spectrophotometric early types. At higher redshift, spectrophotometric late-type galaxies evolve significantly and, at redshift z ~ 1, the contribution from the various types to the bright end of the LF is comparable. The evolution for spectrophotometric early-type galaxies is in both luminosity and normalization: M* brightens by ~0.6 mag but Ï^â decreases by a factor ~1.7 between the first and the last redshift bin. A similar behaviour is exhibited by spectrophotometric late-type galaxies, but with an opposite trend for the normalization: a brightening of ~0.5 mag is present in M^*, while Ï^â increases by a factor ~1.8.â©Studying the role of the environment, we find that the global LF of galaxies in overdense regions has always a brighter M^* and a flatter slope. In low density environments, the main contribution to the LF is from blue galaxies, while for high density environments there is an important contribution from red galaxies to the bright end.â©The differences between the global LF in the two environments are not due to only a difference in the relative numbers of red and blue galaxies, but also to their relative luminosity distributions: the value of M^* for both types in underdense regions is always fainter than in overdense environments. These results indicate that galaxies of the same type in different environments have different properties.â©We also detect a differential evolution in blue galaxies in different environments: the evolution in their LF is similar in underdense and overdense regions between z ~ 0.25 and z ~ 0.55, and is mainly in luminosity. In contrast, between z ~ 0.55 and z ~ 0.85 there is little luminosity evolution but there is significant evolution in Ï^â, that is, however, different between the two environments: in overdense regions Ï^â increases by a factor ~1.6, while in underdense regions this increase reaches a factor ~2.8. Analyzing the blue galaxy population in more detail, we find that this evolution is driven mainly by the bluest types.
Conclusions. The âspecularâ evolution of late- and early-type galaxies is consistent with a scenario where a part of blue galaxies is transformed in red galaxies with increasing cosmic time, without significant changes in the fraction of intermediate-type galaxies. The bulk of this tranformation in overdense regions probably happened before z ~ 1, while it is still ongoing at lower redshifts in underdense environments
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