分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： We present the first observation of a solar filament formed by magnetic reconnection and associated chromospheric evaporation and subsequent coronal condensation. Driven by shearing motion during flux emergence, a sequential tether-cutting reconnection processes occurred and resulted in an M1.3 confined flare accompany with the formation of a sigmoid structure. It is found that the flare had a conjugate compact footpoint brightenings, which correspond to the footpoints of the sigmoid. Furthermore, observational evidence of explosive evaporation is well diagnosed at the conjugate footpoint brightenings in the impulsive phase of the flare. After the flare, continuous cool condensations formed at about the middle section of the sigmoid and then moved in opposite directions along the sigmoid, eventually leading to the formation of the filament. These observations suggest that magnetic reconnection not only can form the magnetic field structure of the filament, but also heat their chromospheric footpoints during their formation and drive chromospheric evaporation. As a result, the heated chromospheric plasma may be evaporated into the magnetic field structure of the filament, where the accumulated hot plasma might suffer from thermal instability or thermal non-equilibrium, causing catastrophic cooling and coronal condensation to form the cool dense material of the filament. This observation lends strong support to the evaporative-condensation model and highlights the crucial role of magnetic reconnection in forming both the magnetic field structure and the cool dense material of filaments.
分类： 医学、药学 >> 临床医学 提交时间： 2020-02-28
Zikuan Leng
Rongjia Zhu
Wei Hou
Yingmei Feng
Yanlei Yang
Qin Han
Guangliang Shan
Fanyan Meng
Dongshu Du
Shihua Wang
Junfen Fan
Wenjing Wang
Luchan Deng
Hongbo Shi
Hongjun Li
Zhongjie Hu
Fengchun Zhang
Jinming Gao
Hongjian Liu
Xiaoxia Li
摘要： A coronavirus (HCoV-19) has caused the novel coronavirus disease (COVID-19) outbreak in Wuhan, China, Preventing and reversing the cytokine storm may be the key to save the patients with severe COVID-19 pneumonia. Mesenchymal stem cells (MSCs) have been shown to possess a comprehensive powerful immunomodulatory function. This study aims to investigate whether MSC transplantation improve the outcome of 7 enrolled patients with COVID-19 pneumonia in Beijing YouAn Hospital, China from Jan 23, 2020. to Feb 16, 2020. The clinical outcomes, as well as changes of inflammatory and immune function levels and adverse effects of 7 enrolled patients were assessed for 14 days after MSC injection. MSCs could cure or significantly improve the functional outcomes of seven patients with COVID-19 pneumonia in 14 days without observed adverse effect. The pulmonary function and symptoms of all patients with COVID-19 pneumonia were significantly improved in 2 days after MSC transplantation. Among them, two common and one severe patient were recovered and discharged in 10 days after treatment. After treatment, the peripheral lymphocytes were increased and the overactivated cytokine-secreting immune cells CXCR3 CD4 T cells, CXCR3 CD8 T cells, and CXCR3 NK cells were disappeared in 3-6 days. And a group of CD14 CD11c CD11bmid regulatory DC cell population dramatically increased. Meanwhile, the level TNF-α is significantly decreased while IL-10 increased in MSC treatment group compared to the placebo control group. Furthermore, the gene expression profile showed MSCs were ACE2- and TMPRSS2- which indicated MSCs are free from COVID-19 infection. Thus, the intravenous transplantation of MSCs was safe and effective for treatment in patients with COVID-19 pneumonia, especially for the patients in critically severe condition.
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