摘要：In this study, we theoretically investigate the feasibility of using laser-wakefield accelerated (LWFA) electrons for the photonuclear measurement of nuclear isomers according to the characteristics of the electrons obtained from LWFA experiments conducted at the Compact Laser Plasma Accelerator (CLAPA) laboratory. The experiments at the CLAPA show that a stable electron beam with an energy of 78–135 MeV and a charge of 300-600 pC can be obtained. The bremsstrahlung spectra were simulated using Geant4, which suggests that a bremsstrahlung source with a peak intensity of 1019 photons/s can be generated. Theoretical calculations of isomer production cross-sections from the photonuclear reactions on six target nuclei, 197Au, 180Hf, 159Tb, 115In, 103Rh, and 90Zr were performed and compared with the available experimental data in EXFOR, which suggest that further experiments are required for a series of photonuclear reaction channels. Flux-averaged cross-sections and isomer ratios (IR) resulting from such bremsstrahlung sources are theoretically deduced. The results suggest that IR measurements can be used to constrain nuclear components, such as γ strength function and optical model potential. In addition, the detection of the decay characteristics was evaluated with Geant4 simulations. The use of the LWFA electron beam and its bremsstrahlung for photonuclear studies involving nuclear isomers is anticipated.
摘要：The ongoing outbreak of Coronavirus Disease 2019 (COVID-19) has become a global pandemic and crisis. SARS-coronavirus-2 (SARS-CoV-2), the causative pathogen of COVID-19, is a positive-sense single-stranded RNA virus belonging to the family Coronaviridae. For RNA viruses, virus-encoded RNA helicases have long been recognized to play pivotal roles during viral life cycles by facilitating the correct folding and replication of viral RNAs. Here, our studies show that SARS-CoV-2-encoded nonstructural protein 13 (nsp13) possesses the nucleoside triphosphate hydrolase (NTPase) and RNA helicase activities that can hydrolyze all types of NTPs and unwind RNA helices dependently of the presence of NTP, and further characterize the biochemical characteristics of these two enzymatic activities associated with SARS-CoV-2 nsp13. Moreover, we found that some bismuth salts could effectively inhibit both the NTPase and RNA helicase activities of SARS-CoV-2 nsp13 in a dose-dependent manner. Thus, our findings demonstrate the NTPase and helicase activities of SARS-CoV-2 nsp13, which may play an important role in SARS-CoV-2 replication and serve as a target for antivirals.
摘要： 新型冠状病毒肺炎目前仍在武汉和中国其他地区持续。在目前的形势下，进一步了解新型冠状病毒（SARS-CoV-2）的病毒学和病毒与宿主的相互作用，对控制感染、开发有效的治疗方法具有重要意义。RNA干扰（RNA interference，RNAi）是一种进化上保守的真核生物抗病毒免疫机制，目前已发现许多病毒编码自身的RNA干扰抑制因子作为对抗措施。在这项研究中，我们发现SARS-CoV-2编码的核衣壳蛋白（N）有效地抑制了shRNAs或siRNAs触发的RNAi。此外，与许多由其他病毒编码的VSR类似，SARS-CoV-2的VSR在体外与人类细胞中与dsRNA相互作用，显示出双链RNA（dsRNA）结合活性。综上所述，我们的研究结果表明，SARS-CoV-2的N蛋白在人类细胞中表现出VSR活性，这可能是新型冠状病毒的一个关键免疫逃避因子。
摘要：The Dark Matter Particle Explorer (DAMPE) is an upcoming scientific satellite mission for high energy gamma-ray, electron and cosmic rays detection. The silicon tracker (STK) is a sub detector of the DAMPE payload with an excellent position resolution (readout pitch of 242um), which measures the incident direction of particles, as well as charge. The STK consists 12 layers of Silicon Micro-strip Detector (SMD), equivalent to a total silicon area of 6.5m2. The total readout channels of the STK are 73728, which leads to a huge amount of raw data to be dealt. In this paper, we focus on the on-board data compression algorithm and procedure in the STK, which was initially verified by cosmic-ray measurements.