Four-dimensional variational assimilation for SO2emission and its application around the COVID-19 lockdown in the spring 2020 over China

Emission inventories are essential for modelling studies and pollution control, but traditional emission inventories are usually updated after a few years based on the statistics of "bottom-up"approach from the energy consumption in provinces, cities, and counties. The latest emission inventories of multi-resolution emission inventory in China (MEIC) was compiled from the statistics for the year 2016 (MEIC_2016). However, the real emissions have varied yearly, due to national pollution control policies and accidental special events, such as the coronavirus disease (COVID-19) pandemic. In this study, a four-dimensional variational assimilation (4DVAR) system based on the "top-down"approach was developed to optimise sulfur dioxide (SO2) emissions by assimilating the data of SO2 concentrations from surface observational stations. The 4DVAR system was then applied to obtain the SO2 emissions during the early period of COVID-19 pandemic (from 17 January to 7 February 2020), and the same period in 2019 over China. The results showed that the average MEIC_2016, 2019, and 2020 emissions were 42.2×106, 40.1×106, and 36.4×106 kg d-1. The emissions in 2020 decreased by 9.2 % in relation to the COVID-19 lockdown compared with those in 2019. For central China, where the lockdown measures were quite strict, the mean 2020 emission decreased by 21.0 % compared with 2019 emissions. Three forecast experiments were conducted using the emissions of MEIC_2016, 2019, and 2020 to demonstrate the effects of optimised emissions. The root mean square error (RMSE) in the experiments using 2019 and 2020 emissions decreased by 28.1 % and 50.7 %, and the correlation coefficient increased by 89.5 % and 205.9 % compared with the experiment using MEIC_2016. For central China, the average RMSE in the experiments with 2019 and 2020 emissions decreased by 48.8 % and 77.0 %, and the average correlation coefficient increased by 44.3 % and 238.7 %, compared with the experiment using MEIC_2016 emissions. The results demonstrated that the 4DVAR system effectively optimised emissions to describe the actual changes in SO2 emissions related to the COVID lockdown, and it can thus be used to improve the accuracy of forecasts. Copyright: © 2022 Yiwen Hu et al.

Pandemic realism as the indispensable political precondition for global disease eradication.

This article examines the politico-scientific mechanism, which leads nations to declare an epidemic or a pandemic finished, irrespective of the actual epidemiological situation at a given time. A historical comparison is made with the famous behavior of Emperor Justinian I (482-565 CE) during the plague pandemic named after him (part of the first plague pandemic). Finally, a reference to the importance of the multidisciplinary study of the history of medicine and the intersection between pandemics and wars is made.

Research on the Relationship between Learning Engagement and Learning Completion of Online Learning Students

With the deep integration of the Internet and education, new educational models, such as micro classrooms, large-scale open online courses, and flipped classrooms have gradually appeared. In the information age, online learning has become popular in most countries all over the world, especially in the face of public crises such as the COVID-19 pandemic. Online learning can effectively connect teachers and students through the Internet. However, the low participation and low cognitive level of e-learning also affect the quality of e-learning, which depends largely on the learning investment of students. Based on selfefficacy theory and exploratory community theory, this paper puts forward the hypothesis that students' e-learning investment affects learning completion and tests the mediating effect of incorporating self-efficacy into students' e-learning investment on learning completion. The results show that the Cronbach's a coefficient is 0.968, which has high reliability. KMO value is 0.880, indicating that data information can be extracted effectively. The three aspects of students' elearning input (behavioral investment, cognitive input, and emotional input) constructed in this paper can significantly improve the learning completion level of students. The results of this study have positive value for understanding the advantages and disadvantages of e-learning, promoting the reform of e-learning methods in universities, and implementing e-learning strategies for students familiar with different e-learning years. © 2022. All Rights Reserved.

Recent sars-cov-2 seroconversion in a national prospective cohort of us adults

Background: Epidemiologic risk factors for SARS-CoV-2 infection are best characterized via prospective cohort studies, complementing case-based surveillance and cross-sectional seroprevalence studies. Methods: We estimated the cumulative incidence of SARS-CoV-2 infection and incidence rates of seroconversion in a national prospective online cohort of 6745 US adults, enrolled during March-July 2020. A subset (n=4459) underwent serologic testing (Bio-Rad Platelia Total Ab, IgA/IgM/IgG), offered initially during May-Sept. 2020 and again in Nov. 2020-Jan. 2021. Results: A total of 303 of 4459 individuals showed serologic evidence of past SARS-CoV-2 infection (6.8%, 95%CI 6.1-7.6%). Among 3280 initially seronegative participants who had a subsequent serologic test, there were 145 seroconversions over 1562 person years of follow-up (incidence rate=9.3 per 100 person-years [95%CI 7.9-11.0]). Racial/ethnic disparities in crude incidence rates were apparent through Jan. 2021 (rate ratio [RRHispanic v White]=2.1, 95%CI 1.4-3.1;RRnon-Hispanic Black v White=1.8, 95%CI 0.96- 3.1). Incidence was higher in the southern (RRSouth v Northeast=1.7, 95%CI 1.1-2.8) and midwest (RRmidwest v Northeast=1.6, 95%CI 0.98-2.7) regions, in rural v urban areas (RR=1.5, 95%CI 1.0-2.2), and among essential workers (RR=1.7, 95%CI 1.1-2.5). Household crowding (RR=1.6, 95%CI 1.1-2.3), indoor restaurant dining (RR=2.0, 95%CI 1.4-2.8), visiting places of worship (RR=2.0, 95%CI 1.3-2.9), wearing masks sometimes (v always) while grocery shopping (RR=2.5, 95%CI 1.3-4.4), not wearing masks when visiting people outside the household (RRsometimes v always=1.3, 95%CI 0.88-2.1;RRnever v always=2.0, 95%CI 1.2-3.2), gathering in groups of >10 (RRindoors v never=1.74, 95%CI 1.2-2.5;RRoutdoors v never=1.8, 95%CI 1.3-4.3), and recent air travel (RR=1.7, 95%CI 1.1-2.6) were associated with higher incidence. Among 303 seropositive persons, 27.4% had asymptomatic infections and 32% reported a positive SARSCoV- 2 PCR test or provider diagnosis. There were major gaps in the uptake of public health interventions aimed at isolation (31%) and contact tracing (asked about contacts [18%];told about exposure to a case [7.6%]). Conclusion: Modifiable risk factors and low uptake of public health strategies drive SARS-CoV-2 transmission across the US. It is critical to address inequities in incidence, reduce risk factors, and improve the reach of public health strategies.