10,977 research outputs found
XMM-Newton study of 30 Dor C and a newly identified MCSNR J0536-6913 in the Large Magellanic Cloud
Aims: We present a study of the superbubble (SB) 30 Dor C and the newly
identified MCSNR J0536-6913 in the LMC. Methods: All available XMM-Newton data
(exposure times of 420 ks EPIC-pn, 556 ks EPIC-MOS1, 614 ks EPIC-MOS2) were
used to characterise the thermal X-ray emission in the region. An analysis of
the non-thermal X-rays is also presented and discussed in the context of
emission mechanisms previously suggested in the literature. These data are
supplemented by X-ray data from Chandra, optical data from the MCELS, and radio
data from ATCA and MOST. Results: The brightest thermal emission was found to
be associated with a new supernova remnant, MCSNR J0536-6913. X-ray spectral
analysis of MCSNR J0536-6913 suggested an ejecta-dominated remnant with lines
of O, Ne, Mg, and Si, and a total 0.3-10 keV luminosity of ~8E+34 erg/s. Based
on derived ejecta abundance ratios, we determined the mass of the stellar
progenitor to be either ~18 M_sun or as high as >40 M_sun, though the spectral
fits were subject to assumptions (e.g., uniform temperature and well-mixed
ejecta). The thermal emission from the SB exhibited enrichment by alpha-process
elements, evidence for a recent core-collapse SNR interaction with the SB
shell. We detected non-thermal X-ray emission throughout 30 Dor C, with the
brightest regions being highly correlated with the H-alpha and radio shells. We
created a non-thermal spectral energy distribution for the north-eastern shell
of 30 Dor C which was best-fit with an exponentially cut-off synchrotron model.
Conclusions: Thermal X-ray emission from 30 Dor C is very complex, consisting
of a large scale SB emission at the eastern shell wall with the brightest
emission due to MCSNR J0536-6913. The fact that the non-thermal spectral energy
distribution of the SB shell was observed to roll-off is further evidence that
the non-thermal X-rays from 30 Dor C are synchrotron in origin.Comment: 22 pages, 21 figures, accepted for publication in Astronomy and
Astrophysic
Modified Hemagglutination Tests for COVID-19 Serology in Resource-Poor Settings: Ready for Prime-Time?
During the ongoing COVID-19 pandemic, serology has suffered several manufacturing and budget bottlenecks. Kode technology exposes exogenous antigens on the surface of cells; in the case of red blood cells, modified cells are called kodecytes, making antibody\u2013antigen reactions detectable by the old-fashioned hemagglutination test. In this commentary, we review evidence supporting the utility of SARS-CoV-2 Spike kodecytes for clinical diagnostic purposes and serosurveys in resource-poor settings
Interestingness of traces in declarative process mining: The janus LTLPf Approach
Declarative process mining is the set of techniques aimed at extracting behavioural constraints from event logs. These constraints are inherently of a reactive nature, in that their activation restricts the occurrence of other activities. In this way, they are prone to the principle of ex falso quod libet: they can be satisfied even when not activated. As a consequence, constraints can be mined that are hardly interesting to users or even potentially misleading. In this paper, we build on the observation that users typically read and write temporal constraints as if-statements with an explicit indication of the activation condition. Our approach is called Janus, because it permits the specification and verification of reactive constraints that, upon activation, look forward into the future and backwards into the past of a trace. Reactive constraints are expressed using Linear-time Temporal Logic with Past on Finite Traces (LTLp f). To mine them out of event logs, we devise a time bi-directional valuation technique based on triplets of automata operating in an on-line fashion. Our solution proves efficient, being at most quadratic w.r.t. trace length, and effective in recognising interestingness of discovered constraints
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
The population of X-ray supernova remnants in the Large Magellanic Cloud
We present a comprehensive X-ray study of the population of supernova
remnants (SNRs) in the LMC. Using primarily XMM-Newton, we conduct a systematic
spectral analysis of LMC SNRs to gain new insights on their evolution and the
interplay with their host galaxy. We combined all the archival XMM observations
of the LMC with those of our Very Large Programme survey. We produced X-ray
images and spectra of 51 SNRs, out of a list of 59. Using a careful modelling
of the background, we consistently analysed all the X-ray spectra and measure
temperatures, luminosities, and chemical compositions. We investigated the
spatial distribution of SNRs in the LMC and the connection with their
environment, characterised by various SFHs. We tentatively typed all LMC SNRs
to constrain the ratio of core-collapse to type Ia SN rates in the LMC. We
compared the X-ray-derived column densities to HI maps to probe the
three-dimensional structure of the LMC. This work provides the first
homogeneous catalogue of X-ray spectral properties of LMC SNRs. It offers a
complete census of LMC SNRs exhibiting Fe K lines (13% of the sample), or
revealing contribution from hot SN ejecta (39%). Abundances in the LMC ISM are
found to be 0.2-0.5 solar, with a lower [/Fe] than in the Milky Way.
The ratio of CC/type Ia SN in the LMC is , lower than in local SN surveys and galaxy clusters.
Comparison of X-ray luminosity functions of SNRs in Local Group galaxies
reveals an intriguing excess of bright objects in the LMC. We confirm that 30
Doradus and the LMC Bar are offset from the main disc of the LMC, to the far
and near sides, respectively. (abridged)Comment: Accepted for publication in Astronomy and Astrophysics. 54 pages, 18
figures, 12 tables. The resolution of the figures has been reduced compared
to the journal version; v2: New title, minor text edits; v3: Correct version
Dexamethasone blocks the migration of the human neuroblastoma cell line SK-N-SH
Glucocorticoids (Gc) influence the differentiation of neural crestderived cells such as those composing sympathoadrenal tumors like pheochromocytomas, as well as neuroblastomas and gangliomas. In order to obtain further information on the effects of Gc on cells evolving from the neural crest, we have used the human neuroblastoma cell line SK-N-SH to analyze: 1) the presence and the binding characteristics of Gc receptors in these cells, 2) the effect of dexamethasone (Dex) on the migration of SK-N-SH cells, and 3) the effect of Dex on the organization of the cytoskeleton of SK-N-SH cells. We show that: 1) receptors that bind [ 3 H]-Dex with high affinity and high capacity (Kd of 9.6 nM, Bmax of 47 fmol/mg cytosolic protein, corresponding to 28,303 sites/cell) are present in cytosolic preparations of SK-N-SH cells, and 2) treatment with Dex (in the range of 10 nM to 1 µM) has an inhibitory effect (from 100% to 74 and 43%, respectively) on the chemotaxis of SK-N-SH cells elicited by fetal bovine serum. This inhibition is completely reversed by the Gc receptor antagonist RU486 (1 µM), and 3) as demonstrated by fluorescent phalloidin-actin detection, the effect of Dex (100 nM) on SK-NSH cell migration is accompanied by modifications of the cytoskeleton organization that appear with stress fibers. These modifications did not take place in the presence of 1 µM RU486. The present data demonstrate for the first time that Dex affects the migration of neuroblastoma cells as well as their cytoskeleton organization by interacting with specific receptors. These findings provide new insights on the mechanism(s) of action of Gc on cells originating in the neural crest
Multi-frequency observations of a superbubble in the LMC: The case of LHA 120-N 70
We present a detailed study of new Australia Telescope Compact Array (ATCA)
and XMM-Newton observations of LHA 120-N 70 (hereafter N 70), a spherically
shaped object in the Large Magellanic Cloud (LMC) classified as a superbubble
(SB). Both archival and new observations were used to produce high quality
radio-continuum, X-ray and optical images. The radio spectral index of N 70 is
estimated to be indicating that while a supernova or
supernovae have occurred in the region at some time in the distant past, N70 is
not the remnant of a single specific supernova. N70 exhibits limited
polarisation with a maximum fractional polarisation of 9% in a small area of
the north west limb. We estimate the size of N 70 to have a diameter of 104 pc
( pc). The morphology of N 70 in X-rays closely follows that in radio
and optical, with most X-ray emission confined within the bright shell seen at
longer wavelengths. Purely thermal models adequately fit the soft X-ray
spectrum which lacks harder emission (above 1 keV). We also examine the
pressure output of N 70 where the values for the hot (PX) and warm (PHii) phase
are consistent with other studied Hii regions. However, the dust-processed
radiation pressure (PIR) is significantly smaller than in any other object
studied in Lopez et al. (2013). N70 is a very complex region that is likely to
have had multiple factors contributing to both the origin and evolution of the
entire region.Comment: 21 pages 8 figures accepted for publication in A
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