East Asian VLBI Network observations of active galactic nuclei jets:imaging with KaVA+Tianma+Nanshan

The East Asian Very Long Baseline Interferometry(VLBI) Network(EAVN) is a rapidly evolving international VLBI array that is currently promoted under joint efforts among China,Japan and Korea.EAVN aims at forming a joint VLBI Network by combining a large number of radio telescopes distributed over East Asian regions.After the combination of the Korean VLBI Network(KVN) and the VLBI Exploration of Radio Astrometry(VERA) into Ka VA,further expansion with the joint array in East Asia is actively promoted.Here we report the first imaging results(at 22 and 43 GHz) of bright radio sources obtained with Ka VA connected to Tianma 65-m and Nanshan 26-m Radio Telescopes in China.To test the EAVN imaging performance for different sources,we observed four active galactic nuclei(AGN) having different brightness and morphology.As a result,we confirmed that the Tianma 65-m Radio Telescope(TMRT) significantly enhances the overall array sensitivity,a factor of 4 improvement in baseline sensitivity and 2 in image dynamic range compared to the case of Ka VA only.The addition of the Nanshan 26-m Radio Telescope(NSRT) further doubled the east-west angular resolution.With the resulting high-dynamic-range,high-resolution images with EAVN(Ka VA+TMRT+NSRT),various fine-scale structures in our targets,such as the counter-jet in M87,a kink-like morphology of the 3 C 273 jet and the weak emission in other sources are successfully detected.This demonstrates the powerful capability of EAVN to study AGN jets and to achieve other science goals in general.Ongoing expansion of EAVN will further enhance the angular resolution,detection sensitivity and frequency coverage of the network.

Decline in subarachnoid haemorrhage volumes associated with the first wave of the COVID- 19 pandemic

Background During the COVID-19 pandemic,decreased volumes of stroke admissions and mechanical thrombectomy were reported.The study’s objective was to examine whether subarachnoid haemorrhage(SAH)hospitalisations and ruptured aneurysm coiling interventions demonstrated similar declines.Methods We conducted a cross-sectional,retrospective,observational study across 6 continents,37 countries and 140 comprehensive stroke centres.Patients with the diagnosis of SAH,aneurysmal SAH,ruptured aneurysm coiling interventions and COVID-19 were identified by prospective aneurysm databases or by International Classification of Diseases,10th Revision,codes.The 3-month cumulative volume,monthly volumes for SAH hospitalisations and ruptured aneurysm coiling procedures were compared for the period before(1 year and immediately before)and during the pandemic,defined as 1 March-31 May 2020.The prior 1-year control period(1 March-31 May 2019)was obtained to account for seasonal variation.Findings There was a significant decline in SAH hospitalisations,with 2044 admissions in the 3 months immediately before and 1585 admissions during the pandemic,representing a relative decline of 22.5%(95%CI−24.3%to−20.7%,p<0.0001).Embolisation of ruptured aneurysms declined with 1170-1035 procedures,respectively,representing an 11.5%(95%CI−13.5%to−9.8%,p=0.002)relative drop.Subgroup analysis was noted for aneurysmal SAH hospitalisation decline from 834 to 626 hospitalisations,a 24.9%relative decline(95%CI−28.0%to−22.1%,p<0.0001).A relative increase in ruptured aneurysm coiling was noted in low coiling volume hospitals of 41.1%(95%CI 32.3%to 50.6%,p=0.008)despite a decrease in SAH admissions in this tertile.Interpretation There was a relative decrease in the volume of SAH hospitalisations,aneurysmal SAH hospitalisations and ruptured aneurysm embolisations during the COVID-19 pandemic.These findings in SAH are consistent with a decrease in other emergencies,such as stroke and myocardial infarction.