3,243 research outputs found
20 cm VLA Radio-Continuum Study of M31 - Images and Point Source Catalogues DR2: Extraction of a supernova remnant sample
We present Data Release 2 of the Point Source Catalogue created from a series
of previously constructed radio-continuum images of M31 at lambda=20 cm (nu=1.4
GHz) from archived VLA observations. In total, we identify a collection of 916
unique discrete radio sources across the field of M31. Comparing these detected
sources to those listed by Gelfand et al. (2004) at lambda=92 cm, the spectral
index of 98 sources has been derived. The majority (73%) of these sources
exhibit a spectral index of alpha <-0.6, indicating that their emission is
predominantly non-thermal in nature, which is typical for background objects
and Supernova Remnants (SNRs). Additionally, we investigate the presence of
radio counterparts for some 156 SNRs and SNR candidates, finding a total of
only 13 of these object in our images within a 5 arcsec search area. Auxiliary
optical, radio and X-ray catalogs were cross referenced highlighting a small
population of SNR and SNR candidates common to multi-frequency domains
An XMM-Newton view of Planetary Nebulae in the Small Magellanic Cloud. The X-ray luminous central star of SMP SMC 22
During an X-ray survey of the Small Magellanic Cloud, carried out with the
XMM-Newton satellite, we detected significant soft X-ray emission from the
central star of the high-excitation planetary nebula SMP SMC 22. Its very soft
spectrum is well fit with a non local thermodynamical equilibrium model
atmosphere composed of H, He, C, N, and O, with abundances equal to those
inferred from studies of its nebular lines. The derived effective temperature
of 1.5x10^5 K is in good agreement with that found from the optical/UV data.
The unabsorbed flux in the 0.1-0.5 keV range is about 3x10^{-11} erg cm^-2
s^-1, corresponding to a luminosity of 1.2x10^37 erg/s at the distance of 60
kpc. We also searched for X-ray emission from a large number of SMC planetary
nebulae, confirming the previous detection of SMP SMC 25 with a luminosity of
(0.2-6)x10^35 erg/s (0.1-1 keV). For the remaining objects that were not
detected, we derived flux upper limits corresponding to luminosity values from
several tens to hundreds times smaller than that of SMP SMC 22. The
exceptionally high X-ray luminosity of SMP SMC 22 is probably due to the high
mass of its central star, quickly evolving toward the white dwarf's cooling
branch, and to a small intrinsic absorption in the nebula itself.Comment: Accepted for publication on Astronomy and Astrophysic
Transfer of patients with ruptured abdominal aortic aneurysm from general hospitals to specialist vascular centres: results of a Delphi consensus study
An analysis of the FIR/RADIO Continuum Correlation in the Small Magellanic Cloud
The local correlation between far-infrared (FIR) emission and radio-continuum
(RC) emission for the Small Magellanic Cloud (SMC) is investigated over scales
from 3 kpc to 0.01 kpc. Here, we report good FIR/RC correlation down to ~15 pc.
The reciprocal slope of the FIR/RC emission correlation (RC/FIR) in the SMC is
shown to be greatest in the most active star forming regions with a power law
slope of ~1.14 indicating that the RC emission increases faster than the FIR
emission. The slope of the other regions and the SMC are much flatter and in
the range of 0.63-0.85. The slopes tend to follow the thermal fractions of the
regions which range from 0.5 to 0.95. The thermal fraction of the RC emission
alone can provide the expected FIR/RC correlation. The results are consistent
with a common source for ultraviolet (UV) photons heating dust and Cosmic Ray
electrons (CRe-s) diffusing away from the star forming regions. Since the CRe-s
appear to escape the SMC so readily, the results here may not provide support
for coupling between the local gas density and the magnetic field intensity.Comment: 19 pages, 7 Figure
XMM-Newton observation of SNR J0533-7202 in the Large Magellanic Cloud
Aims. We present an X-ray study of the supernova remnant SNR J0533-7202 in
the Large Magellanic Cloud (LMC) and determine its physical characteristics
based on its X-ray emission. Methods. We observed SNR J0533-7202 with
XMM-Newton (flare-filtered exposure times of 18 ks EPIC-pn and 31 ks
EPIC-MOS1/MOS2). We produced X-ray images of the SNR, performed an X-ray
spectral analysis, and compared the results to multi-wavelength studies.
Results. The distribution of X-ray emission is highly non-uniform, with the
south-west region brighter than the north-east. The X-ray emission is
correlated with the radio emission from the remnant. We determine that this
morphology is likely due to the SNR expanding into a non-uniform ambient medium
and not an absorption effect. We estimate the size to be 53.9 (\pm 3.4) x 43.6
(\pm 3.4) pc, with the major axis rotated ~64 degrees east of north. We find no
spectral signatures of ejecta and infer that the X-ray plasma is dominated by
swept-up interstellar medium. Using the spectral fit results and the Sedov
self-similar solution, we estimate an age of ~17-27 kyr, with an initial
explosion energy of (0.09-0.83) x 10^51 erg. We detected an X-ray source
located near the centre of the remnant, namely XMMU J053348.2-720233. The
source type could not be conclusively determined due to the lack of a
multi-wavelength counterpart and low X-ray counts. We find that it is likely
either a background active galactic nucleus or a low-mass X-ray binary in the
LMC. Conclusions. We detected bright thermal X-ray emission from SNR J0533-7202
and determined that the remnant is in the Sedov phase of its evolution. The
lack of ejecta emission prohibits us from typing the remnant with the X-ray
data. Therefore, the likely Type Ia classification based on the local stellar
population and star formation history reported in the literature cannot be
improved upon.Comment: 7 pages, 4 figures, accepted for publication in Astronomy and
Astrophysic
Innate immune responses to acute viral infection during pregnancy
Immunological adaptations in pregnancy allow maternal tolerance of the semi-allogeneic fetus but also increase maternal susceptibility to infection. At implantation, the endometrial stroma, glands, arteries and immune cells undergo anatomical and functional transformation to create the decidua, the specialised secretory endometrium of pregnancy. The maternal decidua and the invading fetal trophoblast constitute a dynamic junction that facilitates a complex immunological dialogue between the two. The decidual and peripheral immune systems together assume a pivotal role in regulating the critical balance between tolerance and defence against infection.
Throughout pregnancy, this equilibrium is repeatedly subjected to microbial challenge. Acute viral infection in pregnancy is associated with a wide spectrum of adverse consequences for both mother and fetus. Vertical transmission from mother to fetus can cause developmental anomalies, growth restriction, preterm birth and stillbirth, while the mother is predisposed to heightened morbidity and maternal death. A rapid, effective response to invasive pathogens is therefore essential in order to avoid overwhelming maternal infection and consequent fetal compromise.
This sentinel response is mediated by the innate immune system: a heritable, highly evolutionarily conserved system comprising physical barriers, antimicrobial peptides and a variety of immune cells – principally neutrophils, macrophages, dendritic cells and natural killer cells – which express pattern-receptors that detect invariant molecular signatures unique to pathogenic micro-organisms. Recognition of these signatures during acute infection triggers signalling cascades that enhance antimicrobial properties such as phagocytosis, secretion of pro-inflammatory cytokines and activation of the complement system. As well as coordinating the initial immune response, macrophages and dendritic cells present microbial antigens to lymphocytes, initiating and influencing the development of specific, long-lasting adaptive immunity.
Despite extensive progress in unravelling the immunological adaptations of pregnancy, pregnant women remain particularly susceptible to certain acute viral infections and continue to experience mortality rates equivalent to those observed in pandemics several decades ago. Here, we focus specifically on the pregnancy-induced vulnerabilities in innate immunity that contribute to the disproportionately high maternal mortality observed in the following acute viral infections: Lassa fever, Ebola virus disease, dengue fever, hepatitis E, influenza, and novel coronavirus infections
XMM-Newton EPIC Observation of SMC SNR 0102-72.3
Results from observations of the young oxygen-rich supernova remnant SNR 0102-72.3 in the Small Magellanic Cloud during the calibration phase of the XMM-Newton Observatory are presented. Both EPIC-PN and MOS observations show a ringlike structure with a radius of ~15'' already known from Einstein, ROSAT and Chandra observations. Spectra of the entire SNR as well as parts in the eastern half were analyzed confirming shocked hot plasma in non-uniform ionization stages as the origin of the X-ray emission. The spectra differ in the northeastern and the southeastern part of the X-ray ring, showing emission line features of different strength. The temperature in the northeastern part is significantly higher than in the southeast, reflected by the lines of higher ionization stages and the harder continuum. Comparison to radio data shows the forward shock of the blast wave dominating in the northern part of the SNR, while the southern emission is most likely produced by the recently formed reverse shock in the ejecta. In the case of the overall spectrum of SNR 0102-72.3, the two-temperature non-equilibrium ionization model is more consistent with the data in comparison to the single plane-parallel shock model. The structure of SNR 0102-72.3 is complex due to variations in shock propagation leading to spatially differing X-ray spectra
Targeting higher intraoperative blood pressures does not reduce adverse cardiovascular events following noncardiac surgery
ALMA CO Observations of Supernova Remnant N63A in the Large Magellanic Cloud: Discovery of Dense Molecular Clouds Embedded within Shock-Ionized and Photoionized Nebulae
We carried out new CO( = 1-0, 3-2) observations of a N63A supernova
remnant (SNR) from the LMC using ALMA and ASTE. We find three giant molecular
clouds toward the northeast, east, and near the center of the SNR. Using the
ALMA data, we spatially resolved clumpy molecular clouds embedded within the
optical nebulae in both the shock-ionized and photoionized lobes discovered by
previous H and [S II] observations. The total mass of the molecular
clouds is for the shock-ionized region and
for the photoionized region. Spatially resolved X-ray spectroscopy
reveals that the absorbing column densities toward the molecular clouds are
- cm, which are - times less
than the averaged interstellar proton column densities for each region. This
means that the X-rays are produced not only behind the molecular clouds, but
also in front of them. We conclude that the dense molecular clouds have been
completely engulfed by the shock waves, but have still survived erosion owing
to their high-density and short interacting time. The X-ray spectrum toward the
gas clumps is well explained by an absorbed power-law or high-temperature
plasma models in addition to the thermal plasma components, implying that the
shock-cloud interaction is efficiently working for both the cases through the
shock ionization and magnetic field amplification. If the hadronic gamma-ray is
dominant in the GeV band, the total energy of cosmic-ray protons is calculated
to be - erg with the estimated ISM proton density
of cm, containing both the shock-ionized gas and
neutral atomic hydrogen.Comment: 18 pages, 4 tables, 8 figures, accepted for publication in The
Astrophysical Journal (ApJ
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