44 research outputs found
The Eerdmans Bible Dictionary
Reviewed Book: Myers, Allen C. The Eerdmans Bible Dictionary. Grand Rapids: Eerdmans, 1987
Chandra and XMM-Newton observations of the merging cluster of galaxies PLCK G036.7+14.9
We present Chandra and XMM-Newton observations of PLCK G036.7+14.9 from the
Chandra-Planck Legacy Program. The high resolution X-ray observations reveal
two close subclusters, G036N and G036S, which were not resolved by previous
ROSAT, optical, or recent Planck observations. We perform detailed imaging and
spectral analyses and use a simplified model to study the kinematics of this
system. The basic picture is that PLCK G036.7+14.9 is undergoing a major merger
(mass ratio close to unity) between the two massive subclusters, with the
merger largely along the line-of-sight and probably at an early stage. G036N
hosts a small, moderate cool-core, while G036S has at most a very weak
cool-core in the central 40 kpc region. The difference in core cooling times is
unlikely to be caused by the ongoing merger disrupting a pre-existing cool-core
in G036S. G036N also hosts an unresolved radio source in the center, which may
be heating the gas if the radio source is extended. The Planck derived mass is
higher than the X-ray measured mass of either subcluster, but is lower than the
X-ray measured mass of the whole cluster, due to the fact that Planck does not
resolve PLCK G036.7+14.9 into subclusters and interprets it as a single
cluster. This mass discrepancy could induce significant bias to the mass
function if such previously unresolved systems are common in the Planck cluster
sample. High resolution X-ray observations are necessary to identify the
fraction of such systems and correct such a bias for the purpose of precision
cosmological studies.Comment: 23 pages, 8 figures (low resolution) with additional 12 figures in
the Appendix, accepted for publication in Ap
LoCuSS: The Sunyaev-Zel'dovich Effect and Weak Lensing Mass Scaling Relation
We present the first weak-lensing-based scaling relation between galaxy
cluster mass, M_wl, and integrated Compton parameter Y_sph. Observations of 18
galaxy clusters at z~0.2 were obtained with the Subaru 8.2-m telescope and the
Sunyaev-Zel'dovich Array. The M_wl-Y_sph scaling relations, measured at
Delta=500, 1000, and 2500 rho_c, are consistent in slope and normalization with
previous results derived under the assumption of hydrostatic equilibrium (HSE).
We find an intrinsic scatter in M_wl at fixed Y_sph of 20%, larger than both
previous measurements of M_HSE-Y_sph scatter as well as the scatter in true
mass at fixed Y_sph found in simulations. Moreover, the scatter in our
lensing-based scaling relations is morphology dependent, with 30-40% larger
M_wl for undisturbed compared to disturbed clusters at the same Y_sph at r_500.
Further examination suggests that the segregation may be explained by the
inability of our spherical lens models to faithfully describe the
three-dimensional structure of the clusters, in particular, the structure along
the line-of-sight. We find that the ellipticity of the brightest cluster
galaxy, a proxy for halo orientation, correlates well with the offset in mass
from the mean scaling relation, which supports this picture. This provides
empirical evidence that line-of-sight projection effects are an important
systematic uncertainty in lensing-based scaling relations.Comment: Accepted versio
Weighing the Giants - I. Weak-lensing masses for 51 massive galaxy clusters: project overview, data analysis methods and cluster images
This is the first in a series of papers in which we measure accurate
weak-lensing masses for 51 of the most X-ray luminous galaxy clusters known at
redshifts 0.15<z<0.7, in order to calibrate X-ray and other mass proxies for
cosmological cluster experiments. The primary aim is to improve the absolute
mass calibration of cluster observables, currently the dominant systematic
uncertainty for cluster count experiments. Key elements of this work are the
rigorous quantification of systematic uncertainties, high-quality data
reduction and photometric calibration, and the "blind" nature of the analysis
to avoid confirmation bias. Our target clusters are drawn from RASS X-ray
catalogs, and provide a versatile calibration sample for many aspects of
cluster cosmology. We have acquired wide-field, high-quality imaging using the
Subaru and CFHT telescopes for all 51 clusters, in at least three bands per
cluster. For a subset of 27 clusters, we have data in at least five bands,
allowing accurate photo-z estimates of lensed galaxies. In this paper, we
describe the cluster sample and observations, and detail the processing of the
SuprimeCam data to yield high-quality images suitable for robust weak-lensing
shape measurements and precision photometry. For each cluster, we present
wide-field color optical images and maps of the weak-lensing mass distribution,
the optical light distribution, and the X-ray emission, providing insights into
the large-scale structure in which the clusters are embedded. We measure the
offsets between X-ray centroids and Brightest Cluster Galaxies in the clusters,
finding these to be small in general, with a median of 20kpc. For offsets
<100kpc, weak-lensing mass measurements centered on the BCGs agree well with
values determined relative to the X-ray centroids; miscentering is therefore
not a significant source of systematic uncertainty for our mass measurements.
[abridged]Comment: 26 pages, 19 figures (Appendix C not included). Accepted after minor
revisio
Abell 1758N from an optical point of view: new insights on a merging cluster with diffuse radio emission
We seek to explore the internal dynamics of the cluster Abell 1758N, which
has been shown to host a radio halo and two relics, and is known to be a
merging bimodal cluster. Our analysis is mainly based on new redshift data for
137 galaxies acquired at the Telescopio Nazionale Galileo, only four of which
have redshifts previously listed in the literature. We also used photometric
data from the Sloan Digital Sky Survey and from the Canada-France-Hawaii
Telescope archive. We combined galaxy velocities and positions to select 92
cluster galaxies and analyzed the internal cluster dynamics. We estimate a
cluster redshift of =0.2782 and quite a high line-of-sight (LOS) velocity
dispersion of ~ 1300 km/s. Our 2D analysis confirms the presence of a bimodal
structure along the NW-SE direction. We add several pieces of information to
the previous merging scenario: the two subclusters (here A1758N(NW) and
A1758N(SE)) cannot be separated in the velocity analyses and we deduce a small
LOS velocity difference of ~300 km/s in the cluster rest-frame. The velocity
information successfully shows that A1758N is surrounded by two small groups
and active galaxies infalling onto, or escaping from, the cluster. Removing the
two groups, we estimate ~1000 km/s and ~800 km/s for the velocity dispertions
of A1758N(NW) and A1758N(SE), respectively. We find that Abell 1758N is a very
massive cluster with a range of M=2-3 10^15 solar masses, depending on the
adopted model. As expected for clusters that host powerful, extended, diffuse
radio emissions, Abell 1758N is a major cluster merger just forming a massive
system.Comment: Accepted for publication on Astronomy & Astrophysic
LOFAR discovery of a double radio halo system in Abell 1758 and radio/X-ray study of the cluster pair
Radio halos and radio relics are diffuse synchrotron sources that extend over Mpc-scales and are found in a number of merger galaxy clusters. They are believed to form as a consequence of the energy that is dissipated by turbulence and shocks in the intra-cluster medium (ICM). However, the precise physical processes that generate these steep synchrotron spectrum sources are still poorly constrained. We present a new LOFAR observation of the double galaxy cluster Abell 1758. This system is composed of A1758N, a massive cluster hosting a known giant radio halo, and A1758S, which is a less massive cluster whose diffuse radio emission is confirmed here for the first time. Our observations have revealed a radio halo and a candidate radio relic in A1758S, and a suggestion of emission along the bridge connecting the two systems which deserves confirmation. We combined the LOFAR data with archival VLA and GMRT observations to constrain the spectral properties of the diffuse emission. We also analyzed a deep archival Chandra observation and used this to provide evidence that A1758N and A1758S are in a pre-merger phase. The ICM temperature across the bridge that connects the two systems shows a jump which might indicate the presence of a transversal shock generated in the initial stage of the merger
Postcopulatory sexual selection
The female reproductive tract is where competition between the sperm of different males takes place, aided and abetted by the female herself. Intense postcopulatory sexual selection fosters inter-sexual conflict and drives rapid evolutionary change to generate a startling diversity of morphological, behavioural and physiological adaptations. We identify three main issues that should be resolved to advance our understanding of postcopulatory sexual selection. We need to determine the genetic basis of different male fertility traits and female traits that mediate sperm selection; identify the genes or genomic regions that control these traits; and establish the coevolutionary trajectory of sexes
Modelling of grain size transition with alloy concentration in solidified Al-Si alloys
The transition in grain size with Si content in Al-Si alloys has been systematically investigated by the Cellular Automaton-Finite control Volume Method (CAFVM) to understand the operating mechanisms for this behavior. Three aspects: growth restriction factor (GRF), the chemical driving force (CDF) and the constitutional undercooling (Delta T-C) have been demonstrated to affect the microstructure formation, and among them the Delta T-C plays the most important role. Furthermore, it is also shown that the surface modification of the nucleant particles by silicon significantly influences the grain formation. However, the combined effects of the investigated factors on the grain size were not sufficiently strong to cause a grain size change similar to that observed experimentally. This implies that there could be other mechanisms that control the transition
Gefitinib for oesophageal cancer progressing after chemotherapy (COG): a phase 3, multicentre, double-blind, placebo-controlled randomised trial
Background
Evidence is scarce for the effectiveness of therapies for oesophageal cancer progressing after chemotherapy, and no randomised trials have been reported. We aimed to compare gefitinib with placebo in previously treated advanced oesophageal cancer.
Methods
For this phase 3, parallel, randomised, placebo-controlled trial, eligible patients were adults with advanced oesophageal cancer or type I/II Siewert junctional tumours, histologically confirmed squamous-cell carcinoma or adenocarcinoma, who had progressed after chemotherapy, with WHO performance status 0–2, and with measurable or evaluable disease on CT scan. Participants were recruited from 48 UK centres and randomly assigned (1:1) to gefitinib (500 mg) or matching placebo by simple randomisation with no stratification factors. Patients, clinicians, and trial office staff were masked to treatment allocation. Treatment continued until disease progression, unacceptable toxicity, or patient choice. The primary outcome was overall survival, analysed by intention to treat. This trial is registered, number ISRCTN29580179.
Findings
Between March 30, 2009, and Nov 18, 2011, 450 patients were randomly assigned to treatment groups (one patient withdrew consent; 224 patients allocated gefitinib and 225 allocated placebo included in analyses). Overall survival did not differ between groups (median 3·73 months, 95% CI 3·23–4·50, for gefitinib vs 3·67 months, 95% CI 2·97–4·37, for placebo; hazard ratio [HR] 0·90, 95% CI 0·74–1·09, p=0·29). Among the prespecified patient-reported outcomes (110 patients on gefitinib and 121 on placebo completed both baseline and 4 week questionnaires and were included in analyses), odynophagia was significantly better in the gefitinib group (adjusted mean difference −8·61, 95% CI −14·49 to −2·73; n=227; p=0·004), whereas the other outcomes were not significantly improved compared with placebo: global quality of life (2·69, 95% CI −2·33 to 7·72, n=231, p=0·293), dysphagia (−3·18, 95% CI −8·36 to 2·00, n=231, p=0·228), and eating (−4·11, 95% CI −9·96 to 1·75, n=229, p=0·168). Median progression-free survival was marginally longer with gefitinib than it was with placebo (1·57 months, 95% CI 1·23–1·90 in the gefitinib group vs 1·17 months, 95% CI 1·07–1·37 in the placebo group; HR 0·80, 95% CI 0·66–0·96, p=0·020). The most common toxicities were diarrhoea (36 [16%] of 224 patients on gefitinib vs six [3%] of 225 on placebo) and skin toxicity (46 [21%] vs two [1%]), both mostly grade 2. The commonest grade 3–4 toxicities were fatigue (24 [11%] vs 13 [6%] patients) and diarrhoea (13 [6%] vs two [1%]). Serious adverse events were reported in 109 (49%) of 224 patients assigned to gefitinib and 101 (45%) of 225 on placebo. 54 (24%) of patients in the gefitinib group achieved disease control at 8 weeks, as did 35 (16%) of patients on placebo (p=0·023).
Interpretation
The use of gefitinib as a second-line treatment in oesophageal cancer in unselected patients does not improve overall survival, but has palliative benefits in a subgroup of these difficult-to-treat patients with short life expectancy. Future research should focus on identification of predictive biomarkers to identify this subgroup of benefiting patients