278 research outputs found
Insights into the mechanism for gold catalysis: behaviour of gold(i) amide complexes in solution
We report the synthesis and activity of new mononuclear and dinuclear gold amide complexes . The dinuclear complexes and were characterised by single crystal X-ray analysis. We also report solution NMR and freezing point depression experiments to rationalise their behaviour in solution and question the de-ligation process invoked in gold catalysis
Diffuse light and building history of the galaxy cluster Abell 2667
We have searched for diffuse intracluster light in the galaxy cluster Abell
2667 (z=0.233) from HST images in three filters. We have applied to these
images an iterative multi-scale wavelet analysis and reconstruction technique,
which allows to subtract stars and galaxies from the original images. We detect
a zone of diffuse emission south west of the cluster center (DS1), and a second
faint object (ComDif), within DS1. Another diffuse source (DS2) may be
detected, at lower confidence level, north east of the center. These sources of
diffuse light contribute to 10-15% of the total visible light in the cluster.
Whether they are independent entities or are part of the very elliptical
external envelope of the central galaxy remains unclear. VLT VIMOS integral
field spectroscopy reveals a faint continuum at the positions of DS1 and ComDif
but do not allow to compute a redshift. A hierarchical substructure detection
method reveals the presence of several galaxy pairs and groups defining a
similar direction as the one drawn by the DS1-central galaxy-DS2 axis. The
analysis of archive XMM-Newton and Chandra observations shows X-ray emission
elongated in the same direction. The X-ray temperature map shows the presence
of a cool core, a broad cool zone stretching from north to south and hotter
regions towards the north east, south west and north west. This possibly
suggests shock fronts along these directions produced by infalling material.
These various data are consistent with a picture in which diffuse sources are
concentrations of tidal debris and harassed matter expelled from infalling
galaxies by tidal stripping and undergoing an accretion process onto the
central cluster galaxy; as such, they are expected to be found along the main
infall directions.Comment: Accepted for publication in Astronomy and Astrophysic
Large scale diffuse light in the Coma cluster: a multi-scale approach
We have obtained wide field images of the Coma cluster in the B, V, R and I
bands with the CFH12K camera at CFHT. In order to search for large scale
diffuse emission, we have applied to these images an iterative multi scale
wavelet analysis and reconstruction technique which allowed to model all the
sources (stars and galaxies) and subtract them from the original images. We
found various concentrations of diffuse emission present in the central zone
around the central galaxies NGC4874 and NGC4889. We characterize the positions,
sizes and colors of these concentrations. Some sources do not seem to have
strong star formation, while another one probably exhibits spiral-like color.
One possible origin for the star forming diffuse emission sources is that in
the region of the two main galaxies NGC4874 and NGC4889 spiral galaxies have
recently been disrupted and star formation is still active in the dispersed
material. We also use the characteristics of the sources of diffuse emission to
trace the cluster dynamics. A scenario in which the group around NGC 4874 is
moving north is consistent with our data.Comment: 11 pages, accepted in A&A, jpg figure
How does a cadaver model work for testing ultrasound diagnostic capability for rheumatic-like tendon damage?
To establish whether a cadaver model can serve as an effective surrogate for the detection of tendon damage characteristic of rheumatoid arthritis (RA). In addition, we evaluated intraobserver and interobserver agreement in the grading of RA-like tendon tears shown by US, as well as the concordance between the US findings and the surgically induced lesions in the cadaver model. RA-like tendon damage was surgically induced in the tibialis anterior tendon (TAT) and tibialis posterior tendon (TPT) of ten ankle/foot fresh-frozen cadaveric specimens. Of the 20 tendons examined, six were randomly assigned a surgically induced partial tear; six a complete tear; and eight left undamaged. Three rheumatologists, experts in musculoskeletal US, assessed from 1 to 5 the quality of US imaging of the cadaveric models on a Likert scale. Tendons were then categorized as having either no damage, (0); partial tear, (1); or complete tear (2). All 20 tendons were blindly and independently evaluated twice, over two rounds, by each of the three observers. Overall, technical performance was satisfactory for all items in the two rounds (all values over 2.9 in a Likert scale 1-5). Intraobserver and interobserver agreement for US grading of tendon damage was good (mean Îș values 0.62 and 0.71, respectively), with greater reliability found in the TAT than the TPT. Concordance between US findings and experimental tendon lesions was acceptable (70-100 %), again greater for the TAT than for the TPT. A cadaver model with surgically created tendon damage can be useful in evaluating US metric properties of RA tendon lesions
Bayesian modelling of clusters of galaxies from multi-frequency pointed Sunyaev--Zel'dovich observations
We present a Bayesian approach to modelling galaxy clusters using
multi-frequency pointed observations from telescopes that exploit the
Sunyaev--Zel'dovich effect. We use the recently developed MultiNest technique
(Feroz, Hobson & Bridges, 2008) to explore the high-dimensional parameter
spaces and also to calculate the Bayesian evidence. This permits robust
parameter estimation as well as model comparison. Tests on simulated Arcminute
Microkelvin Imager observations of a cluster, in the presence of primary CMB
signal, radio point sources (detected as well as an unresolved background) and
receiver noise, show that our algorithm is able to analyse jointly the data
from six frequency channels, sample the posterior space of the model and
calculate the Bayesian evidence very efficiently on a single processor. We also
illustrate the robustness of our detection process by applying it to a field
with radio sources and primordial CMB but no cluster, and show that indeed no
cluster is identified. The extension of our methodology to the detection and
modelling of multiple clusters in multi-frequency SZ survey data will be
described in a future work.Comment: 12 pages, 7 figures, submitted to MNRA
Detections of CO in Late-Type, Low Surface Brightness Spiral Galaxies
Using the IRAM 30-m telescope, we have obtained 12CO J=1-0 and 2-1 spectral
line observations toward the nuclear regions of 15 edge-on, low surface
brightness (LSB) spiral galaxies. Our sample comprises extreme late-type LSB
spirals with disk-dominated morphologies and rotational velocities V_rot<~120
km/s. We report detections of four galaxies in at least one transition
(>5sigma); for the remainder of the sample we provide upper limits on the
nuclear CO content. Adopting a standard Galactic I_CO-to-H_2 conversion factor
implies molecular gas masses of (3.3-9.8)x10**6 M_sun in the nuclear regions
(inner 1.1-1.8 kpc) of the detected galaxies. Combining our new data with
samples of late-type spirals from the literature, we find that the CO-detected
LSB spirals adhere to the same M_H2-FIR correlation as more luminous and higher
surface brightness galaxies. The amount of CO in the central regions of
late-type spirals appears to depend more strongly on mass than on central
optical surface brightness, and CO detectability declines significantly for
moderate-to-low surface brightness spirals with V_rot<~90 km/s; no LSB spirals
have so far been detected in CO below this threshold. Metallicity effects alone
are unlikely to account for this trend, and we speculate that we are seeing the
effects of a decrease in the mean fraction of a galaxy disk able to support
giant molecular cloud formation with decreasing galaxy mass.Comment: accepted to A
Interobserver reliability in musculoskeletal ultrasonography: Results from a "Teach the Teachers" rheumatologist course
Objective: To assess the interobserver reliability of the main periarticular and intra-articular ultrasonographic pathologies and to establish the principal disagreements on scanning technique and diagnostic criteria between a group of experts in musculoskeletal ultrasonography. Methods: The shoulder, wrist/hand, ankle/foot, or knee of 24 patients with rheumatic diseases were evaluated by 23 musculoskeletal ultrasound experts from different European countries randomly assigned to six groups. The participants did not reach consensus on scanning method or diagnostic criteria before the investigation. They were unaware of the patients' clinical and imaging data. The experts from each group undertook a blinded ultrasound examination of the four anatomical regions. The ultrasound investigation included the presence/absence of joint effusion/synovitis, bony cortex abnormalities, tenosynovitis, tendon lesions, bursitis, and power Doppler signal. Afterwards they compared the ultrasound findings and re-examined the patients together while discussing their results. Results: Overall agreements were 91% for joint effusion/synovitis and tendon lesions, 87% for cortical abnormalities, 84% for tenosynovitis, 83.5% for bursitis, and 83% for power Doppler signal; Îș values were good for the wrist/hand and knee (0.61 and 0.60) and fair for the shoulder and ankle/foot (0.50 and 0.54). The principal differences in scanning method and diagnostic criteria between experts were related to dynamic examination, definition of tendon lesions, and pathological v physiological fluid within joints, tendon sheaths, and bursae. Conclusions: Musculoskeletal ultrasound has a moderate to good interobserver reliability. Further consensus on standardisation of scanning technique and diagnostic criteria is necessary to improve musculoskeletal ultrasonography reproducibility
Interobserver reliability in musculoskeletal ultrasonography: Results from a "Teach the Teachers" rheumatologist course
Objective: To assess the interobserver reliability of the main periarticular and intra-articular ultrasonographic pathologies and to establish the principal disagreements on scanning technique and diagnostic criteria between a group of experts in musculoskeletal ultrasonography. Methods: The shoulder, wrist/hand, ankle/foot, or knee of 24 patients with rheumatic diseases were evaluated by 23 musculoskeletal ultrasound experts from different European countries randomly assigned to six groups. The participants did not reach consensus on scanning method or diagnostic criteria before the investigation. They were unaware of the patients' clinical and imaging data. The experts from each group undertook a blinded ultrasound examination of the four anatomical regions. The ultrasound investigation included the presence/absence of joint effusion/synovitis, bony cortex abnormalities, tenosynovitis, tendon lesions, bursitis, and power Doppler signal. Afterwards they compared the ultrasound findings and re-examined the patients together while discussing their results. Results: Overall agreements were 91% for joint effusion/synovitis and tendon lesions, 87% for cortical abnormalities, 84% for tenosynovitis, 83.5% for bursitis, and 83% for power Doppler signal; \u3ba values were good for the wrist/hand and knee (0.61 and 0.60) and fair for the shoulder and ankle/foot (0.50 and 0.54). The principal differences in scanning method and diagnostic criteria between experts were related to dynamic examination, definition of tendon lesions, and pathological v physiological fluid within joints, tendon sheaths, and bursae. Conclusions: Musculoskeletal ultrasound has a moderate to good interobserver reliability. Further consensus on standardisation of scanning technique and diagnostic criteria is necessary to improve musculoskeletal ultrasonography reproducibility
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