1,250 research outputs found
Out-of-hospital cardiac arrest and survival in a patient with Noonan syndrome and multiple lentigines: a case report
BACKGROUND: A 9-year-old Arabic boy attending middle school presented with an out-of-hospital cardiac arrest due to ventricular fibrillation recorded by Holter electrocardiographic monitoring. He had a background history of Noonan syndrome with multiple lentigines (also known as LEOPARD syndrome), a rare condition of autosomal dominant inheritance with approximately 200 cases reported worldwide. CASE PRESENTATION: Apart from characteristic features, the boy was known to have asymmetric septal hypertrophy with a maximum wall thickness of 24 mm measured by cardiovascular magnetic resonance imaging. A day prior to the event, he attended cardiology follow-up at our institution, and Holter monitoring was commenced. Following cardiopulmonary resuscitation by bystanders and paramedics, he reverted back into sinus rhythm after a total downtime of 24 min. He was initially treated in the intensive care unit and underwent implantable cardioverter defibrillator implantation. He has made a full recovery and remains at the top of his class. CONCLUSION: This case demonstrates that sudden cardiac arrest in patients with secondary forms of hypertrophic cardiomyopathy is not necessarily protected by apparently favorable phenotypes and that events may be preceded by non-sustained ventricular tachycardia observed by Holter monitoring. Implantable cardioverter defibrillator implantation plays a critical role in both primary and secondary prevention in patients at high risk of out-of-hospital cardiac arrest
Cluster Evolution in the ROSAT North Ecliptic Pole Survey
The deepest region of the ROSAT All-Sky Survey, at the North Ecliptic Pole,
has been studied to produce a complete and unbiased X-ray selected sample of
clusters of galaxies. This sample is used to investigate the nature of cluster
evolution and explore potential implications for large-scale structure models.
The survey is 99.6% optically identified. Spectroscopic redshifts have been
measured for all the extragalactic identifications. In this Letter, first
results on cluster evolution are presented based on a comparison between the
number of the observed clusters in the North Ecliptic Pole survey and the
number of expected clusters assuming no-evolution models. At z>0.3 there is a
deficit of clusters with respect to the local universe which is significant at
> 4.7sigma. The evolution appears to commence at L_{0.5-2.0} > 1.8x10^{44} erg
s^{-1} in our data. The negative evolution goes in the same direction as the
original EMSS result, the results from the 160 deg^{2} survey by Vikhlinin et
al. (1998) and the recent results from the RDCS (Rosati et al. 2000). At lower
redshifts there is no evidence for evolution, a result in agreement with these
and other cluster surveys.Comment: 17 pages, 3 figures. Accepted for publication in ApJ Letter
Discovery of a new cataclysmic variable through optical variability and X-ray emission
Aims: We present discovery observations of the new cataclysmic variable star
(CV) 1RXS J092737.4-191529, as well as spectra and photometry of SY Vol. The
selection technique that turned up these two CVs is described; it should be
efficient for finding dwarf novae with high outburst duty cycles. Methods: Two
very common observational features of CVs, namely optical variability and X-ray
emission, are combined to select targets for follow-up observations. Long-slit
spectra were taken to identify CVs in the sample. Results: Two out of three
objects selected in this way are CVs. One of these is the known dwarf nova SY
Vol, while the second system, 1RXS J092737.4-191529, is a new discovery. We
present medium resolution spectra, magnitudes, and high-speed
photometry for both these CVs. Rapid flickering in the light curve of 1RXS
J092737.4-191529 confirms the mass transferring binary nature of this object;
it is probably a dwarf nova that was in quiescence during our observations.Comment: 4 pages, 5 figures, accepted to A&
The Effect of Hot Gas in WMAP's First Year Data
By cross-correlating templates constructed from the 2 Micron All Sky Survey
(2MASS) Extended Source (XSC) catalogue with WMAP's first year data, we search
for the thermal Sunyaev-Zel'dovich signature induced by hot gas in the local
Universe. Assuming that galaxies trace the distribution of hot gas, we select
regions on the sky with the largest projected density of galaxies. Under
conservative assumptions on the amplitude of foreground residuals, we find a
temperature decrement of -35 7 K ( detection level,
the highest reported so far) in the 26 square degrees of the sky
containing the largest number of galaxies per solid angle. We show that most of
the reported signal is caused by known galaxy clusters which, when convolved
with the average beam of the WMAP W band channel, subtend a typical angular
size of 20--30 arcmins. Finally, after removing from our analyses all pixels
associated with known optical and X-ray galaxy clusters, we still find a tSZ
decrement of -96 37 K in pixels subtending about 0.8 square
degrees on the sky. Most of this signal is coming from five different cluster
candidates in the Zone of Avoidance (ZoA), present in the Clusters In the ZoA
(CIZA) catalogue. We found no evidence that structures less bound than clusters
contribute to the tSZ signal present in the WMAP data.Comment: 10 pages, 4 figures, matches accepted version in ApJ Letter
Opening the random forest black box by the analysis of the mutual impact of features
Random forest is a popular machine learning approach for the analysis of
high-dimensional data because it is flexible and provides variable importance
measures for the selection of relevant features. However, the complex
relationships between the features are usually not considered for the selection
and thus also neglected for the characterization of the analysed samples. Here
we propose two novel approaches that focus on the mutual impact of features in
random forests. Mutual forest impact (MFI) is a relation parameter that
evaluates the mutual association of the featurs to the outcome and, hence, goes
beyond the analysis of correlation coefficients. Mutual impurity reduction
(MIR) is an importance measure that combines this relation parameter with the
importance of the individual features. MIR and MFI are implemented together
with testing procedures that generate p-values for the selection of related and
important features. Applications to various simulated data sets and the
comparison to other methods for feature selection and relation analysis show
that MFI and MIR are very promising to shed light on the complex relationships
between features and outcome. In addition, they are not affected by common
biases, e.g. that features with many possible splits or high minor allele
frequencies are prefered
A Sample of X-Ray active extragalactic Sources suitable for NIR Adaptive Optics Observations
Recent X-ray surveys have now resolved most of the X-ray background (XRB)
into discrete sources. While this represents a break- through in the
understanding of the XRB, the astrophysical nature of these sources still
remains mysterious. In this article we present a sample of X-ray/optically
selected extragalactic objects which are suitable for adaptive optics
observations in the near infrared (NIR) at highest angu- lar resolution. The
sample is based on a cross-correlation of the Sloan Digital Sky Survey and the
ROSAT All Sky Survey. The NIR properties can help to disentangle the nature of
the X-ray bright, partially absorbed and spectroscopically passive background
objects and their hosts.Comment: 4 pages with 1 figure, LateX, uses newpasp.sty, to appear in "AGN
Physics with the Sloan Digital Sky Survey", ed. G. T. Richards and P. B. Hall
(San Francisco: ASP), 200
The ROSAT North Ecliptic Pole Survey: The Optical Identifications
The X-ray data around the North Ecliptic Pole (NEP) of the ROSAT All Sky
Survey have been used to construct a contiguous area survey consisting of a
sample of 445 individual X-ray sources above a flux of ~2x10^-14 erg cm^-2 s^-1
in the 0.5-2.0 keV energy band. The NEP survey is centered at RA (2000) = 18h
00m, DEC(2000) = +66deg 33arcmin and covers a region of 80.7 sq. deg at a
moderate Galactic latitude of b = 29.8deg. Hence, the NEP survey is as deep and
covers a comparable solid angle to the ROSAT serendipitous surveys, but is also
contiguous. We have identified 99.6% of the sources and determined redshifts
for the extragalactic objects. In this paper we present the optical
identifications of the NEP catalog of X-ray sources including basic X-ray data
and properties of the sources. We also describe with some detail the optical
identification procedure. The classification of the optical counterparts to the
NEP sources is very similar to that of previous surveys, in particular the
Einstein Extended Medium Sensitivity Survey (EMSS). The main constituents of
the catalog are active galactic nuclei (~49%), either type 1 or type 2
according to the broadness of their permitted emission lines. Stellar
counterparts are the second most common identification class (~34%). Clusters
and groups of galaxies comprise 14%, and BL Lacertae objects 2%. One non-AGN
galaxy, and one planetary nebula have also been found. The NEP catalog of X-ray
sources is a homogeneous sample of astronomical objects featuring complete
optical identification.Comment: Accepted for publication in the ApJS; 33 pages including 12
postscript figures and 3 tables; uses emulateapj.sty. On-line source catalog
at http://www.eso.org/~cmullis/research/nep-catalog.htm
The North Ecliptic Pole Supercluster
We have used the ROSAT All-Sky Survey to detect a known supercluster at
z=0.087 in the North Ecliptic Pole region. The X-ray data greatly improve our
understanding of this supercluster's characteristics, approximately doubling
our knowledge of the structure's spatial extent and tripling the cluster/group
membership compared to the optical discovery data. The supercluster is a rich
structure consisting of at least 21 galaxy clusters and groups, 12 AGN, 61 IRAS
galaxies, and various other objects. A majority of these components were
discovered with the X-ray data, but the supercluster is also robustly detected
in optical, IR, and UV wavebands. Extending 129 x 102 x 67 (1/h50 Mpc)^3, the
North Ecliptic Pole Supercluster has a flattened shape oriented nearly edge-on
to our line-of-sight. Owing to the softness of the ROSAT X-ray passband and the
deep exposure over a large solid angle, we have detected for the first time a
significant population of X-ray emitting galaxy groups in a supercluster. These
results demonstrate the effectiveness of X-ray observations with contiguous
coverage for studying structure in the Universe.Comment: Accepted for publication in The Astrophysical Journal; 5 pages with 2
embedded figures; uses emulateapj.sty; For associated animations, see
http://www.ifa.hawaii.edu/~mullis/nep3d.html; A high-resolution color
postscript version of the full paper is available at
http://www.ifa.hawaii.edu/~mullis/papers/nepsc.ps.g
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