Gamma-ray bursts (GRBs) are flashes of high-energy radiation arising from energetic cosmic explosions. Bursts of long (greater than two seconds) duration are produced by the core-collapse of massive ...stars
, and those of short (less than two seconds) duration by the merger of compact objects, such as two neutron stars
. A third class of events with hybrid high-energy properties was identified
, but never conclusively linked to a stellar progenitor. The lack of bright supernovae rules out typical core-collapse explosions
, but their distance scales prevent sensitive searches for direct signatures of a progenitor system. Only tentative evidence for a kilonova has been presented
. Here we report observations of the exceptionally bright GRB 211211A, which classify it as a hybrid event and constrain its distance scale to only 346 megaparsecs. Our measurements indicate that its lower-energy (from ultraviolet to near-infrared) counterpart is powered by a luminous (approximately 10
erg per second) kilonova possibly formed in the ejecta of a compact object merger.
Double neutron star (DNS) merger events are promising candidates of short gamma-ray burst (sGRB) progenitors as well as high-frequency gravitational wave (GW) emitters. On August 17, 2017, such a ...coinciding event was detected by both the LIGO-Virgo gravitational wave detector network as GW170817 and Gamma-Ray Monitor on board NASA's Fermi Space Telescope as GRB 170817A. Here, we show that the fluence and spectral peak energy of this sGRB fall into the lower portion of the distributions of known sGRBs. Its peak isotropic luminosity is abnormally low. The estimated event rate density above this luminosity is at least Formula: see text Gpc
yr
, which is close to but still below the DNS merger event rate density. This event likely originates from a structured jet viewed from a large viewing angle. There are similar faint soft GRBs in the Fermi archival data, a small fraction of which might belong to this new population of nearby, low-luminosity sGRBs.
With the aim of gathering temporal trends on bacterial epidemiology and resistance from multiple laboratories in China, the CHINET surveillance system was organized in 2005. Antimicrobial ...susceptibility testing was carried out according to a unified protocol using the Kirby-Bauer method or automated systems. Results were analyzed according to Clinical and Laboratory Standards Institute (CLSI) 2014 definitions. Between 2005 and 2014, the number of bacterial isolates ranged between 22 774 and 84 572 annually. Rates of extended-spectrum β-lactamase production among Escherichia coli isolates were stable, between 51.7 and 55.8%. Resistance of E. coli and Klebsiella pneumoniae to amikacin, ciprofloxacin, piperacillin/tazobactam and cefoperazone/sulbactam decreased with time. Carbapenem resistance among K. pneumoniae isolates increased from 2.4 to 13.4%. Resistance of Pseudomonas aeruginosa strains against all of antimicrobial agents tested including imipenem and meropenem decreased with time. On the contrary, resistance of Acinetobacter baumannii strains to carbapenems increased from 31 to 66.7%. A marked decrease of methicillin resistance from 69% in 2005 to 44.6% in 2014 was observed for Staphylococcus aureus. Carbapenem resistance rates in K. pneumoniae and A. baumannii in China are high. Our results indicate the importance of bacterial surveillance studies.
Summary
Background
The seroclearance of hepatitis B surface antigen (HBsAg) in patients with chronic hepatitis B (CHB) is considered to be associated with favourable clinical outcomes. However, ...previous studies with inconsistent findings reported that hepatocellular carcinoma (HCC) could still develop in those patients.
Aim
To establish the proportion of HCC occurrence in CHB patients after HBsAg seroclearance, a systematic review and meta‐analysis was performed.
Methods
Databases of Medline, Web of Science and Embase were searched from inception to July 2015. The proportion of patients who developed HCC after HBsAg seroclearance was pooled by a random‐effects model.
Results
Twenty‐eight studies were finally included, involving 34 952 patients with HBsAg seroclearance. The overall pooled proportion suggested that 2.29% (95% CI: 1.19–4.37%) CHB patients would develop HCC despite HBsAg seroclearance. In HBsAg seroclearance patients without cirrhosis and HCV co‐infection, the pooled proportion of HCC development was 1.55% (95% CI: 0.92–2.61%). Moreover, patients with cirrhosis or age greater than 50 years at the time of HBsAg seroclearance were at significantly higher risk for HCC development. Nonetheless, the seroclearance of HBsAg was significantly associated with a reduced risk for HCC compared with persistently positive HBsAg (RR = 0.34, 95% CI: 0.20–0.56, P < 0.001).
Conclusions
Despite that HBsAg seroclearance can significantly reduce the risk for HCC, HCC can still develop in a proportion of CHB patient after HBsAg seroclearance. Closer attention should be paid to those patients with established cirrhosis or older age than 50 years at the time of HBsAg seroclearance.
This study reports an efficient inoculation protocol that allowed cytological analysis of the infection process of the rice false smut pathogen Ustilaginoidea virens. Examination of serial semithin ...and ultrathin sections of infected spikelets showed that the primary infection sites for the pathogen were the upper parts of the three stamen filaments located between the ovary and the lodicules. The stigma and lodicules were also occasionally infected to a limited extent. The pathogen infected the filaments intercellularly and extended intercellularly along the filament base. The host cells were degraded gradually. The pathogen did not penetrate host cell walls directly and did not form haustoria. In the balls the ovary remained alive and was never infected. This suggests that the pathogen is a biotrophic parasite that grows intercellularly in vivo.
Aims.
Gamma-ray burst (GRB) 190829A (
z
= 0.0785) was detected by
Fermi
and
Swift
and also at very high energy (VHE) by the High-Energy Stereoscopic System (H.E.S.S.) telescopes. The prompt emission ...displayed two emission episodes separated by a quiescent gap of ∼40 s. We present the 10.4 m Gran Telescopio Canarias (GTC) observations of the afterglow of GRB 190829A and its underlying supernova. We also compare GRB 190829A to GRB 180728A, a GRB with similar behaviour, and discuss the implications on underlying physical mechanisms producing these two GRBs.
Methods.
We present multi-band photometric data along with spectroscopic follow-up observations taken with the 10.4 m GTC telescope. Together with the data from the prompt emission, the 10.4 m GTC data are used to understand the emission mechanisms and possible progenitor.
Results.
A detailed analysis of the multi-band observations of the afterglow requires the cooling frequency to pass between the optical and X-ray bands at early epochs. The afterglow then transitions to the underlying supernova (SN) 2019oyw, which dominates later on.
Conclusions.
Although the prompt emission temporal properties of GRB 190829A and GRB 180728A are similar, the two pulses are different in the spectral domain. We find that SN 2019oyw associated with GRB 190829A is powered by Ni decay and is a Type Ic-BL SN. The spectroscopic and photometric properties of this SN are consistent with those observed for SN 1998bw, but evolved earlier.
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