416 research outputs found
Detection of an X-Ray Hot Region in the Virgo Cluster of Galaxies with ASCA
Based on mapping observations with ASCA, an unusual hot region with a spatial
extent of 1 square degree was discovered between M87 and M49 at a center
coordinate of R. A. = 12h 27m 36s and Dec. = (J2000). The X-ray
emission from the region has a 2-10 keV flux of ergs
s cm and a temperature of keV, which is
significantly higher than that in the surrounding medium of keV. The
internal thermal energy in the hot region is estimated to be ergs with a gas density of cm. A power-law
spectrum with a photon index is also allowed by the data. The hot
region suggests there is an energy input due to a shock which is probably
caused by the motion of the gas associated with M49, infalling toward the M87
cluster with a velocity km s.Comment: 12 pages, 3 figures, accepted to ApJ
Detection of Bulk Motions in the ICM of the Centaurus Cluster
Several recent numerical simulations of off-center cluster mergers predict
that significant angular momentum with associated velocities of a few x 10^{3}
km/s can be imparted to the resulting cluster. Such gas bulk velocities can be
detected by the Doppler shift of X-ray spectral lines with ASCA spectrometers.
Using two ASCA observations of the Centaurus cluster, we produced a velocity
map for the gas in the cluster's central regions. We also detected radial and
azimuthal gradients in temperature and metal abundance distributions, which
seem to be associated with the infalling sub-group centered at NGC 4709 (Cen
45). More importantly, we found a significant (>99.8% confidence level)
velocity gradient along a line near-perpendicular to the direction of the
incoming sub-group and with a maximum velocity difference of ~3.4+-1.1 x 10^{3}
km/s. It is unlikely (P < 0.002) that the observed velocity gradient is
generated by gain fluctuations across the detectors. While the observed
azimuthal temperature and abundance variations can be attributed to the
interaction with Cen 45, we argue that the intracluster gas velocity gradient
is more likely due to a previous off-center merging event in the main body of
the Centaurus cluster.Comment: 13 pages in emulateapj5 style, 8 postscript figures; Accepted by ApJ;
Revised version with minor change
Recommended from our members
Near-realtime quantitative precipitation estimation and prediction (RealPEP)
Flash floods in small- to medium-sized catchments and intense precipitation over cities
caused by severe local storms pose increasing threats to our society. For the timely prediction of such events, the value of high-resolution and high-quality QPE and corresponding
forecasts cannot be overrated. Seamless predictions harmonizing nowcasting and numerical
weather prediction (NWP) across forecast lead times from minutes to days would greatly help
to improve the value and efficiency of warnings. Organized by the Research Unit on Near-Realtime Precipitation Estimation and Prediction (RealPEP, www2.meteo.uni-bonn.de/realpep)
and supported by the Project on Seamless Integrated Forecasting System (SINFONY, www.dwd
.de/DE/forschung/forschungsprogramme/sinfony_iafe/sinfony_node.html) of the German Meteorological Service (DWD), an international 3-day online conference was held from 5 to 7 October 2020,
dedicated to Precipitation and Flash-Flood Predictions from Minutes to Days (https://indico
.scc.kit.edu/event/883/). Most speakers agreed to have their presentations recorded, which we
uploaded to YouTube for further distribution (see, e.g., on the conference homepage, https://
indico.scc.kit.edu/event/883/page/588-recorded-talks).
The speakers were both invited experts in the respective research fields and researchers
from the RealPEP and SINFONY projects. Talks and discussions could be followed on video
stream. Interaction between the about 250 participants was enabled by entering written questions and comments via a dedicated tool, which allowed for voting and thus also ranking
questions. Registered participants could enter chat rooms from where they could be moved to
the speaker room for posing the questions directly to the speakers and the auditorium. On the
last day of the conference podium discussions with selected speakers summarized talks and
discussions and elaborated on overarching problems, ideas, and developments in the fields
of quantitative precipitation estimation (QPE), quantitative precipitation nowcasting (QPN),
quantitative precipitation forecasting (QPF), flash-flood prediction (FFP), and their organization into seamless prediction systems, which also constituted the topics of the five sessions
during the conference. We report here in particular on the outcomes of the panel discussions
How uncertain are precipitation and peak flow estimates for the July 2021 flooding event?
The disastrous July 2021 flooding event made us question the ability of current hydrometeorological tools in providing timely and reliable flood forecasts for unprecedented events. This is an urgent concern since extreme events are increasing due to global warming, and existing methods are usually limited to more frequently observed events with the usual flood generation processes. For the July 2021 event, we simulated the hourly
streamflows of seven catchments located in western Germany by combining
seven partly polarimetric, radar-based quantitative precipitation estimates
(QPEs) with two hydrological models: a conceptual lumped model (GR4H) and a
physically based, 3D distributed model (ParFlowCLM). GR4H parameters were
calibrated with an emphasis on high flows using historical discharge
observations, whereas ParFlowCLM parameters were estimated based on
landscape and soil properties. The key results are as follows. (1) With no
correction of the vertical profiles of radar variables, radar-based QPE
products underestimated the total precipitation depth relative to rain
gauges due to intense collision–coalescence processes near the surface, i.e., below the height levels monitored by the radars. (2) Correcting the vertical profiles of radar variables led to substantial improvements. (3) The probability of exceeding the highest measured peak flow before July 2021 was highly impacted by the QPE product, and this impact depended on the catchment for both models. (4) The estimation of model parameters had a
larger impact than the choice of QPE product, but simulated peak flows of
ParFlowCLM agreed with those of GR4H for five of the seven catchments. This
study highlights the need for the correction of vertical profiles of
reflectivity and other polarimetric variables near the surface to improve
radar-based QPEs for extreme flooding events. It also underlines the large
uncertainty in peak flow estimates due to model parameter estimation.</p
Spatially-resolved X-ray spectroscopy of the core of the Centaurus cluster
We present Chandra data from a 31.7 ks observation of the Centaurus cluster,
using the ACIS-S detector. Images of the X-ray emission show a plume-like
feature at the centre of the cluster, of extent 60 arcsec (20 kpc in
projection). The feature has the same metallicity as gas at a similar radius,
but is cooler. Using adaptive binning, we generate temperature, abundance and
absorption maps of the cluster core. The radial abundance profile shows that
the previously known, steep abundance gradient peaks with a metallicity of
1.3-1.8 Zsolar at a radius of about 45 arcsec (15 kpc), before falling back to
0.4 Zsolar at the centre of the cluster. A radial temperature profile shows
that the temperature decreases inwards. We determine the spatial distributions
of each of two temperature components, where applicable. The radiative cooling
time of the cooler component within the inner 10 arcsec (3 kpc) is less than
2x10^7 yr. X-ray holes in the image coincident with the radio lobes are seen,
as well as two outer sharp temperature drops, or cold fronts. The origin of the
plume is unclear. The existence of the strong abundance gradient is a strong
constraint on extensive convection or gas motion driven by a central radio
source.Comment: 11 pages, 14 figures (3 colour), accepted by MNRAS, high res. version
at http://www-xray.ast.cam.ac.uk/papers/cen1_accptd.pdf . Updated version
includes a section considering a non-thermal componen
Chandra and XMM-Newton X-ray observations of AWM 7 - I: Investigating X-ray surface brightness fluctuations
We investigate the levels of small scale structure in surface brightness
images of the core of the X-ray bright cool-core galaxy cluster AWM 7. After
subtraction of a model of the smooth cluster emission, we find a number of
approximately radial surface brightness depressions which are not present in
simulated images and are seen in both the Chandra and XMM-Newton data. The
depressions are most strongly seen in the south of the cluster and have a
magnitude of around 4 per cent in surface brightness. We see these features in
both an energy band sensitive to the density (0.6 to 5 keV) and a band more
sensitive to the pressure (3.5 to 7.5 keV). Histograms of surface brightness in
the data, when compared to realisations of a smooth model, reveal stronger
surface brightness variations. We use the Delta-variance technique to
characterise the magnitude of the fluctuations as a function of length scale.
We find that the spectrum in the 0.6 to 5 keV band is flatter than expected for
Kolmogorov index fluctuations. If characterised by a power spectrum, on large
scales it would have an index around -1.7, rather than -3.7. The implied 3D
density fluctuations have a standard deviation of around 4 per cent. The
implied 3D pressure variations are at most 4 per cent. Most of the longer-scale
power in the density spectrum is contributed by the southern half of the
cluster, where the depressions are seen. The density variations implied by the
spectrum of the northern sector have a standard deviation of about 2 per cent.Comment: 17 pages, accepted by MNRAS, high resolution version available at
http://www-xray.ast.cam.ac.uk/papers/awm7.pd
The effect of parental consanguinity and inbreeding in Hirado, Japan
A census of Hirado, Japan in the summer of 1964 produced data on the reproductive performances of husbands and wives for 10,530 marriages where either the husband, the wife, or both were alive and residing in the city at the time of the census. Approximately one in every 6 of these marriages involves spouses who are biologically related to one another, and in some 10 per cent of marriages the husband, wife, or both are inbred. Analysis of the effects of length of cohabitation, socio-economic status, and consanguinity and inbreeding on total pregnancies, total livebirths, and “net fertility” (total livebirths minus non-accidental deaths in the first 21 years of life) revealed the following insofar as marriages contracted in the years 1920–1939 are concerned: 1. Total pregnancies and total livebirths were significantly increased with consanguinity, but “net fertility” was not when allowance is made for the role of socio-economic factors, and religious affiliation is ignored. The latter finding is thought to reflect the increased risk of death to liveborn children born to consanguineous marriages. Among Buddhists, the only religious group large enough to warrant separate analysis, total pregnancies, total livebirths and “net fertility” are all significantly and positively associated with parental relationship. However, the regression coefficient associated with “net fertility” is less than half the value associated with either total pregnancies or total livebirths.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/47633/1/439_2004_Article_BF00286995.pd
Radio Bubbles in Clusters
We extend our earlier work on cluster cores with distinct radio bubbles,
adding more active bubbles, i.e. those with Ghz radio emission, to our sample,
and also investigating ``ghost bubbles,'' i.e. those without GHz radio
emission. We have determined k, which is the ratio of the total particle energy
to that of the electrons radiating between 10 MHz and 10 GHz. Constraints on
the ages of the active bubbles confirm that the ratio of the energy factor, k,
to the volume filling factor, f lies within the range 1 < k/f < 1000. In the
assumption that there is pressure equilibrium between the radio-emitting plasma
and the surrounding thermal X-ray gas, none of the radio lobes has
equipartition between the relativistic particles and the magnetic field. A
Monte-Carlo simulation of the data led to the conclusion that there are not
enough bubbles present in the current sample to be able to determine the shape
of the population. An analysis of the ghost bubbles in our sample showed that
on the whole they have higher upper limits on k/f than the active bubbles,
especially when compared to those in the same cluster. A study of the Brightest
55 cluster sample shows that 17, possibly 20, clusters required some form of
heating as they have a short central cooling time, t_cool < 3 Gyr, and a large
central temperature drop, T_centre/T_outer< 1/2. Of these between 12 (70 per
cent) and 15 (75 per cent), contain bubbles. This indicates that the duty cycle
of bubbles is large in such clusters and that they can play a major role in the
heating process.Comment: 12 pages, Accepted for publication in MNRA
The Mexican consensus on the diagnosis and treatment of ulcerative colitis
The guidelines presented herein are an updated version of the recommendations published in 2007. Since then, there has been a rapid advance in the knowledge about the pathophysiology of ulcerative colitis and its therapeutic options. New drugs have been approved, novel targeted therapies have emerged, and new strategies have been developed to improve the previously available approaches to the disease.The aim of the present consensus is to promote the current knowledge of and Mexican perspective on the epidemiology, diagnosis, and medical and surgical treatment of chronic idiopathic ulcerative colitis.The final vote on the statements and their ultimate modifications were carried out at the consensus working group meeting. Evidence was evaluated through the GRADE classification. Resumen: Estas guías constituyen una actualización de las guías publicadas en 2007. Desde ese año, los conocimientos acerca de la fisiopatología, así como las opciones terapéuticas, han evolucionado rápidamente, con la aprobación de nuevos agentes, la aparición de nuevos blancos terapéuticos y nuevas estrategias para mejorar los abordajes disponibles previamente.El objetivo de este consenso es promover una actualización y perspectiva mexicana sobre la epidemiología, el diagnóstico así como el tratamiento médico y quirúrgico de la colitis ulcerosa crónica idiopática.Los enunciados fueron finalmente votados y se realizaron las modificaciones finales en la junta de consenso. La evaluación de la evidencia por la clasificación GRADE se realizó al momento del consenso. Keywords: Chronic idiopathic ulcerative colitis, Diagnosis, Treatment, Epidemiology, Colectomy, Pouchitis, Palabras clave: Colitis ulcerosa crónica idiopática, Diagnóstico, Tratamiento, Epidemiología, Colectomía, Pouchiti
Transcript levels of Toll-Like receptors 5, 8 and 9 correlate with inflammatory activity in Ulcerative Colitis
<p>Abstract</p> <p>Background</p> <p>Dysregulation of innate immune response by Toll-Like Receptors (TLRs) is a key feature in Ulcerative Colitis (UC). Most studies have focused on <it>TLR2, TLR3</it>, and <it>TLR4 </it>participation in UC. However, few studies have explored other TLRs. Therefore, the aim of this study was to evaluate the mRNA profiles of <it>TLR1 to 9 </it>in colonic mucosa of UC patients, according to disease activity.</p> <p>Methods</p> <p>Colonic biopsies were taken from colon during colonoscopy in 51 patients with Ulcerative Colitis and 36 healthy controls. mRNA levels of <it>TLR1 to 9, Tollip</it>, inflammatory cytokines <it>IL6 </it>and <it>TNF </it>were assessed by RT-qPCR with hydrolysis probes. Characterization of <it>TLR9 </it>protein expression was performed by Immunohistochemistry.</p> <p>Results</p> <p>Toll-like receptors <it>TLR8, TLR9</it>, and <it>IL6 </it>mRNA levels were significantly higher in the colonic mucosa from UC patients (both quiescent and active) as compared to healthy individuals (p < 0.04). In the UC patients group the <it>TLR2, TLR4, TLR8 </it>and <it>TLR9 </it>mRNA levels were found to be significantly lower in patients with quiescent disease, as compared to those with active disease (p < 0.05), whereas <it>TLR5 </it>showed a trend (p = 0.06). <it>IL6 </it>and <it>TNF </it>mRNA levels were significantly higher in the presence of active disease and help to discriminate between quiescent and active disease (p < 0.05). Also, <it>IL6 </it>and <it>TNF </it>mRNA positively correlate with TLRs mRNA with the exception for <it>TLR3</it>, with stronger correlations for <it>TLR5, TLR8</it>, and <it>TLR9 </it>(p < 0.0001). <it>TLR9 </it>protein expression was mainly in the lamina propria infiltrate.</p> <p>Conclusions</p> <p>This study demonstrates that <it>TLR2, TLR4, TLR8</it>, and <it>TLR9 </it>expression increases in active UC patients, and that the mRNA levels positively correlate with the severity of intestinal inflammation as well as with inflammatory cytokines.</p
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