544 research outputs found
Investigations of supernovae and supernova remnants in the era of SKA
Two main physical mechanisms are used to explain supernova explosions:
thermonuclear explosion of a white dwarf(Type Ia) and core collapse of a
massive star (Type II and Type Ib/Ic). Type Ia supernovae serve as distance
indicators that led to the discovery of the accelerating expansion of the
Universe. The exact nature of their progenitor systems however remain unclear.
Radio emission from the interaction between the explosion shock front and its
surrounding CSM or ISM provides an important probe into the progenitor star's
last evolutionary stage. No radio emission has yet been detected from Type Ia
supernovae by current telescopes. The SKA will hopefully detect radio emission
from Type Ia supernovae due to its much better sensitivity and resolution.
There is a 'supernovae rate problem' for the core collapse supernovae because
the optically dim ones are missed due to being intrinsically faint and/or due
to dust obscuration. A number of dust-enshrouded optically hidden supernovae
should be discovered via SKA1-MID/survey, especially for those located in the
innermost regions of their host galaxies. Meanwhile, the detection of
intrinsically dim SNe will also benefit from SKA1. The detection rate will
provide unique information about the current star formation rate and the
initial mass function. A supernova explosion triggers a shock wave which expels
and heats the surrounding CSM and ISM, and forms a supernova remnant (SNR). It
is expected that more SNRs will be discovered by the SKA. This may decrease the
discrepancy between the expected and observed numbers of SNRs. Several SNRs
have been confirmed to accelerate protons, the main component of cosmic rays,
to very high energy by their shocks. This brings us hope of solving the
Galactic cosmic ray origin's puzzle by combining the low frequency (SKA) and
very high frequency (Cherenkov Telescope Array: CTA) bands' observations of
SNRs.Comment: To be published in: "Advancing Astrophysics with the Square Kilometre
Array", Proceedings of Science, PoS(AASKA14
Possible Circumstellar Interaction Origin of the Early Excess Emission in Thermonuclear Supernovae
Type Ia supernovae (SNe Ia) arise from the thermonuclear explosion in binary
systems involving carbon-oxygen white dwarfs (WDs). The pathway of WDs
acquiring mass may produce circumstellar material (CSM). Observing SNe Ia
within a few hours to a few days after the explosion can provide insight into
the nature of CSM relating to the progenitor systems. In this paper, we propose
a CSM model to investigate the effect of ejecta-CSM interaction on the
early-time multi-band light curves of SNe Ia. By varying the mass-loss history
of the progenitor system, we apply the ejecta-CSM interaction model to fit the
optical and ultraviolet (UV) photometric data of eight SNe Ia with early
excess. The photometric data of SNe Ia in our sample can be well-matched by our
CSM model except for the UV-band light curve of iPTF14atg, indicating its early
excess may not be due to the ejecta-CSM interaction. Meanwhile, the CSM
interaction can generate synchrotron radiation from relativistic electrons in
the shocked gas, making radio observations a distinctive probe of CSM. The
radio luminosity based on our models suggests that positive detection of the
radio signal is only possible within a few days after the explosion at higher
radio frequencies (e.g., ~250 GHz); at lower frequencies (e.g., ~1.5 GHz) the
detection is difficult. These models lead us to conclude that a multi-messenger
approach that involves UV, optical, and radio observations of SNe Ia a few days
past explosion is needed to address many of the outstanding questions
concerning the progenitor systems of SNe Ia.Comment: Submitted to MNRA
Influence of tensor interactions on masses and decay widths of dibaryons
The influence of gluon and Goldstone boson induced tensor interactions on the
dibaryon masses and D-wave decay widths has been studied in the quark
delocalization, color screening model. The effective S-D wave transition
interactions induced by gluon and Goldstone boson exchanges decrease rapidly
with increasing strangeness of the channel. The tensor contribution of K and
mesons is negligible in this model. There is no six-quark state in the
light flavor world studied so far that can become bound by means of these
tensor interactions besides the deuteron. The partial D-wave decay widths of
the N state to spin 0 and 1 final states
are 12.0 keV and 21.9 keV respectively. This is a very narrow dibaryon
resonance that might be detectable in relativistic heavy ion reactions by
existing RHIC detectors through the reconstruction of the vertex mass of the
decay product and by the COMPAS detector at CERN or at JHF in
Japan and the FAIR project in Germany in the future.Comment: 19 pages, 5 figure
Correlation between childhood tuberculosis and abundance of T cell gene transcription and impaired T cell function
Purpose: To investigate the relationship amongst childhood tuberculosis, abundance of T cell gene transcription and impairment of T cell function.
Methods: A total of 329 pediatric patients treated for tuberculosis in Central Hospital of Zibo, Zibo, China from 2017 to 2019 were enrolled in the study. Among them, 167 cases of tuberculosis-hospitalized children were assigned to the TB group. Additionally, 162 well- and adequately-treated patients with a previous history of tuberculosis were selected as the control group. The abundance of continuous gene transcripts in the peripheral blood of the children was analyzed. The RNA profiles were analyzed via microarray, while interferon (IFN) level was measured by enzyme linked immunosorbent assay (ELISA). The T cell proliferation was determined by thymidine assay.
Results: Within 6 months of the commencement of treatment, the differentially expressed transcripts returned the expression in children in the control group. The abundance of Talipes equinovarus, atrial septal defect, robin sequence, and the persistence of the left superior vena cava (TARP) gene transcription in the TB group was lower than in the control group on days 30, 120 and 180 (p < 0.05), while IL1R2 gene transcription abundance in the TB group was higher than in the control group on days 30, 120 ,180 (p < 0.05). The proliferation of T cells and IFNγ in tuberculosis children (TB group) were lower than in healthy controls (p < 0.05). In this study, a total of 129 genes were found to have significant differences in expression, and hence it is speculated that changes in RNA abundance altered the immune pathway.
Conclusion: The reduced abundance of T cell gene transcription and renovated T cell function in children with tuberculosis are related to acquired immunodeficiency. The results of this study provide a theoretical basis for the clinical diagnosis and treatment of tuberculosis in children
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