Objective Coronavirus Disease 2019 (COVID-19) caused by a novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), is still spreading worldwide, which may progress to pulmonary fibrosis (PF), leading to the worsen outcome. As the markers of lung injury, the correlation of Krebs von den Lungen-6 (KL-6) and fibronectin (Fn) with pulmonary fibrosis in COVID-19 was still unclear. Methods 113 patients diagnosed as COVID-19 were enrolled in this retrospective study, and divided into three categories as mild, moderate and severe cases. The concentrations of serum KL-6 and Fn at hospital admission were tested using the method of latex agglutination assay and immunoturbidimetic assay, respectively. Results Compared with that in the non-severe COVID-19 cases and normal control subjects, serum KL-6 concentrations on admission were significantly higher in the severe group, which was positively correlated with C-reactive protein, and negatively correlated with lymphocytes count. Whereas, no obvious elevation in serum Fn concentration was investigated in COVID-19 patients with the different phenotypes. The severe cases displayed the higher incident rate of pulmonary fibrosis at hospital discharge. Compared with non-PF patients, the COVID-19 cases with PF have the higher serum KL-6 values. Conclusion Serum KL-6 concentration was significantly elevated in severe COVID-19 patients, which may be useful for evaluating the disease severity. For early prevention of the development of pulmonary fibrosis, high concentrations of serum KL-6 in the early stage of COVID-19 should be paid close attention.

Coronavirus disease 2019 (COVID‐19) is a newly emerging infectious disease. Our understanding of the clinical characteristics of liver damage and the relationship with disease severity in COVID‐19 is still limited. To investigate the serum hepatic enzyme activities in different phenotypes of COVID‐19 patients, evaluate their relationship with the illness severity and analyze the correlation of glycyrrhizin treatment and abnormal liver enzyme activities, one hundred and forty‐seven patients with COVID‐19 were enrolled in a retrospective study that investigated hepatic dysfunction. Liver alanine aminotransferase (ALT), aspartate aminotransferase (AST), lactic dehydrogenase (LDH), Y‐glutamyl transferase (GGT), superoxide dismutase (SOD), and alkaline phosphatase (ALP) were analyzed in these patients. Patients with diammonium glycyrrhizinate (DG) treatment were further investigated. Of the 147 patients, 56 (38.1%) had abnormal ALT activity and 80 (54.4%) had abnormal AST activity. The peak of abnormal hepatic enzyme activities occurred at 3 to 6 days after on admission. Serum AST and LDH levels were elevated, while the SOD level was decreased in severe and critical patients, compared with mild cases. DG treatment may alleviate the abnormal liver enzyme activities in non‐critical COVID‐19 patients. Abnormal liver functions may be observed in patients with COVID‐19, and were associated with SARS‐CoV‐2‐induced acute liver damage. Glycyrrhizin treatment may be an effective therapeutic approach for the outcome of abnormal hepatic enzyme activities in severe COVID‐19 cases. Serum hepatic enzyme tests may reflect the illness severity and should be monitored.

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Carbon was coated on the surface of molybdenum grids by ion beam assisted deposition. The electron emission characteristics from the grids with and without carbon, which were contaminated by an active electron emission substance of the cathode, was measured using an analogous diode method. The results show that electron emission from the carbon-coated Mo grid was much less than that from the Mo grid without carbon. The cathode emission substance deposited on the carbon surface of the grid was analyzed by x-ray photoelectron spectroscopy and electron probes. Analysis results revealed that the carbon-coated Mo grid could effectively reduce the accumulation of the cathode emitting substances Ba and BaO on the grid surface. The reason for the suppression of electron emission of the carbon-coated Mo grid is discussed. The carbon-coated Mo grids were used in pulsed-controlled grid traveling wave tubes and the working lifetime of the tube was increased from tens of hours to over 1000 h.