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This study investigates the aerosol transmission in queuing and dining scenarios in canteens and explores the effectiveness of control measures. An improved Wells-Riley equation is adopted to calculate the infection risk. The dilution of exhaled aerosols is difficult in the crowded queuing scenario, where the replacement of queuing positions increases the cross-infection risk. The highest infection risk is 1.16% and 1.08% for the linear-queue and cross-queue condition, respectively. Shortening the queuing duration, increasing the separation distance, and wearing masks can considerably reduce the infection risk. In the dining scenario, the effect of increasing ACH is limited on reducing the local concentration. An exhaust vent installed close to the top of the partition can effectively remove the local high-concentration aerosols. Intermittent occupation of a seat can considerably reduce the transmission risk between the consecutive dinners taking that seat. These findings should contribute to improved control of infectious transmission in canteens.
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In order to comprehensively understand the epidemiological situation of bovine coronavirus (BCoV) in beef cattle herds in Jilin Province, blood, nasal swabs, fecal swabs and tissue organs of clinically diseased and dead cattle were collected in different seasons from 12 counties and cities in the east, central and western regions of Jilin Province, using serological and molecular diagnostic testing techniques to conduct an epidemiological investigation of BCoV in the The epidemiological situation of BCoV in some areas of Jilin Province. A total of 1 298 clinical serum samples, 462 clinical samples (including fecal samples, liver, lung, spleen, trachea and other tissue samples) were collected, and PCR detection of clinical samples was performed by applying commercial BCoV antibody detection kits to detect serum antibodies and a novel detection technique of nano-PCR, and sequencing and analysis of positive results detected by nucleic acid. The results showed that the serum positive rate of BCoV antibodies was 1.08%, and the positive rate of clinical samples such as feces and liver was 21.10%. The BCoV prevalent strain in the investigated area was more than 99% homologous to the prevalent strain in Sichuan, China, after sequencing analysis. This study provides a comprehensive survey of BCoV prevalence in central Jilin Province, which enriches the epidemiological survey data of bovine coronavirus and lays the foundation for guiding the prevention and control of bovine coronavirus.Copyright © 2023 Acta Veterinaria et Zootechnica Sinica. All rights reserved.
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COVID-19 is reshaping the relationship between humans and their living environment, potentially generating a profound impact on human physical and mental health and quality of life. The objective of this study was to explore how outdoor activities and the campus landscape impacted the subjective well-being (SWB) of Chinese university students in the pre-COVID-19 era (before December 2019) and during the COVID-19 era (from December 2019 to early December 2022). This study collected 439 valid questionnaires from students at a Chinese university, with the questions focusing on the frequency and length of time that university students of different genders, grades, and abilities to cover their living expenses participated in outdoor activities in the pre- and COVID-19 eras, as well as the changes in their SWB. Paired sample t tests revealed a significant decrease in SWB during the COVID-19 era compared with the pre-COVID-19 era, while independent sample t tests and a one-way ANOVA showed that changes in the SWB of university students pre- and during COVID-19 were not related to their gender or their ability to cover their living expenses, but were related to their grades. Hierarchical linear regression showed that outdoor activities in the COVID-19 era had a significant effect on mitigating the decline in students' SWB. These results suggest a proactive way to increase resilience to future public health challenges and other crises of human life safety. © 2023 by the authors.
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Due to the globalization of the economy, studying abroad has been widely recognized as bringing many benefits to students. However, the closure of campuses and borders around the world since the COVID-19 pandemic, which began in 2020, has brought about significant changes in studying abroad as learning has moved online. In the context of emergency management, a new way of studying online has arisen. Despite this change, few studies have focused on the value perception of and satisfaction with online study abroad (OSA) in the context of the pandemic or have focused on students enrolled in overseas universities. To address this gap, this study proposed six research hypotheses and a hypothesis model based on the situated expectancy-value theory. The study used the snowballing technique to survey Chinese university faculty members who had studied online at overseas universities during the pandemic. A total of 481 valid data were collected, including 214 (44.5%) male and 267 (55.5%) female respondents. The data were then confirmed to have reliability and validity, and the research model was tested. Results indicated that all of the research hypotheses were supported. More specifically, the perceived value of OSA can be positively predicted by academic and career self-efficacy. Academic and career self-efficacy can be positively predicted by OSA motivation. The perceived value of OSA is positively related to satisfaction with OSA. This shows that promoting satisfaction with OSA for international students is a feasible international education program when international mobility is not possible in particular situations. © 2023 by the authors.
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For the rapid development of the cruise industry, the cruise disaster relief supply chain has attracted extensive attention, especially because COVID-19 cases on international cruise ships occurred. In this paper, we propose an idea of coordination layout for cruise ship emergency supplies, the problem optimized two objective functions of maximizing coverage satisfaction and minimizing the total cost, addressing the low efficiency of resource utilization at the same. By applying to cruise ship emergency supplies layout of Northeast Asia cruise port group system, using expert scoring method and AHP to evaluate cruise port security vulnerability. The NSGA-II algorithm is used to solve the multi-objective programming model. A numerical example shows that the optimization design model and method are valid and feasible, and the algorithm is efficient for solving the above collaborative location and allocation problem of sectional reserves, which can also offer a variety of decision-making options. © 2023 the Author(s), licensee AIMS Press
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As segmentation labels are scarce, extensive researches have been conducted to train segmentation networks with domain adaptation, semi-supervised or self-supervised learning techniques to utilize abundant unlabeled dataset. However, these approaches appear different from each other, so it is not clear how these approaches can be combined for better performance. Inspired by recent multi-domain image translation approaches, here we propose a novel segmentation framework using adaptive instance normalization (AdaIN), so that a single generator is trained to perform both domain adaptation and semi-supervised segmentation tasks via knowledge distillation by simply changing task-specific AdaIN codes. Specifically, our framework is designed to deal with difficult situations in chest X-ray radiograph (CXR) segmentation, where labels are only available for normal data, but the trained model should be applied to both normal and abnormal data. The proposed network demonstrates great generalizability under domain shift and achieves the state-of-the-art performance for abnormal CXR segmentation.
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The COVID-19 lockdown has opened a unique window for investigating aerosol formation and evolution with controlled anthropogenic emissions in urban areas. Here, variations of PM2.5 chemical compositions, gaseous pollutants, meteorological conditions, and secondary organic aerosol (SOA) molecular tracers were monitored during three stages at an urban site (Pudong) and a suburban site (Qingpu) in Shanghai, which were defined as pre-COVID lockdown (PL), during COVID lockdown (DL), and after COVID lockdown (AL) in 2020. Abundances of pollutants during the same periods back in 2019 were also analyzed for a more comprehensive intercomparison and evaluation of the impact of the 2020 COVID-19 lockdown on regional air quality. With the sudden cessation of anthropogenic activities during the lockdown, significant reductions in PM2.5 were observed compared to both PL in 2020 (32% in Pudong and 36% in Qingpu) and the DL period back in 2019 (31% in Pudong and 35% in Qingpu), which was accompanied by the significantly reduced PM2.5 components (29-44% and 14-44% reductions in sulfate, nitrate, ammonium, organic carbon, and elemental carbon for Pudong and Qingpu, respectively). In particular, with the reduced secondary inorganic aerosol (SIA), the time series of SOA molecular tracers also underwent significant reduction that was characteristic to the lockdown. Amid the uncontrolled biogenic emissions and even slightly enhanced atmospheric oxidation capacity during the 2020 DL period, controlling anthropogenic emissions exhibits synergistic effects on the reduction of SIA and SOA, which could be further attributed to the changes in the aerosol aqueous-phase environment, such as aerosol liquid water content (ALWC), ionic strength, sulfate content, and particulate NH4+. Based on thermodynamic modeling, greatly reduced ALWC was observed during 2020 DL, which can prevent the partitioning of oxygenated organics into the condensed phase as well as the aqueous-phase formation of SOA. Higher ionic strength in 2020 DL may have a "salting-out" effect on gas- particle partitioning of oxygenated organics. The reduced SOA during 2020 DL at both sites can generally be reflected by the predicted heterogeneous reaction kinetics (gamma) of the isoprene SOA formation pathway. Overall, our study showed a synergistic effect in suppressing SIA and SOA formation upon the reduction of anthropogenic emissions during the COVID-19 lockdown, which shed light on the importance of controlling anthropogenic emissions in regulating secondary aerosol formation in typical urban areas of East China.
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Understanding how interurban movements can modify the spatial distribution of the population is important for transport planning but is also a fundamental ingredient for epidemic modeling. We illustrate this on vacation trips for all transportation modes in China during the Lunar New Year and compare the results for 2019 with the ones for 2020 where travel bans were applied for mitigating the spread of a novel coronavirus (COVID-19). We first show that inter-urban travel flows are broadly distributed and display both large temporal and spatial fluctuations, making their modeling very difficult. When flows are larger, they appear to be more dispersed over a larger number of origins and destinations, creating de facto hubs that can spread an epidemic at a large scale. These movements quickly induce (in about a week for this case) a very strong population concentration in a small set of cities. We characterize quantitatively the return to the initial distribution by defining a pendular ratio which allows us to show that this dynamics is in general very slow and even stopped for the 2020 Lunar New Year due to travel restrictions. Travel restrictions obviously limit the spread of the diseases between different cities, but have thus the counter-effect of keeping high concentration in a small set of cities, a priori favoring intra-city spread, unless individual contacts are strongly limited. These results shed some light on the statistics of interurban movements and how they modify the national distribution of populations, a crucial ingredient for devising effective control strategies at a national level. Copyright © 2022 Ye, Hu, Ji and Barthelemy.
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Numerous short-term exposure events in public spaces were reported during the COVID-19 pandemic, especially during the spread of Delta and Omicron. However, the currently used exposure risk assessment models and mitigation measures are mostly based on the assumption of steady-state and complete-mixing conditions. The present study investigates the dynamics of airborne transmission in short-term events when a steady state is not reached before the end of the events. Large-eddy simulation (LES) is performed to predict the airborne transmission in short-term events, and three representative physical distances between two occupants are examined. Both time-averaged and phase-averaged exposure indices are used to evaluate the exposure risk. The results present that the exposure index in the short-term events constantly varies over time, especially within the first 1/ACH (air changes per hour) hour of exposure between occupants in close proximity, posing high uncertainty to the spatial and temporal evolutions of the risk of cross-infection. The decoupling analysis of the direct and indirect airborne transmission routes indicates that the direct airborne transmission is the predominated route in short-term events. It suggests also that the general dilution ventilation has a relatively limited efficiency in mitigating the risk of direct airborne transmission, but determines largely the occurrence time of the indirect one. Given the randomness, discreteness, localization, and high-risk characteristics of direct airborne transmission, a localized method that has a direct interference on the respiratory flows would be better than dilution ventilation for short-term events, in terms of both efficiency and cost.
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After the outbreak of COVID-19, it is worrisome that how to cope with the spread of the pandemic. Ventilation is the most important engineering control measure, ASHRAE, REHVA, SHASE and authoritative institutions in China have issued many documents on how to apply HVAC system to prevent and control the spread of COVID-19, and thus this paper summarizes the contents related to the ventilation rate and air distribution. Besides, traditional total volume ventilation has the disadvantages of insufficient ventilation rate, less efficiency for short-term exposure events at short range and high energy consumption during the pandemic. Source control based on advanced air distribution has the advantages of high control efficiency, personalized adjustable, fast response and high energy saving potential, which can make up the disadvantages of the total volume ventilation scheme. Therefore, this paper systematically summarizes the technical types of source control based on advanced air distribution in coping the spread of respiratory infectious diseases. Considering that the design of ventilation system in the post-pandemic era is facing the development of "combination of normal time and pandemic period", the advantages of applying source control in the post-pandemic era and the application schemes of source control in high-risk scenarios are discussed, and the directions that need to be further explored in order to implement the design concept of"combination of normal time and pandemic period" are also discussed. This paper aims to provide a reference for the compilation of subsequent guidelines, and to bring some new ideas and enlightenments to the ventilation design for future pandemic prevention. © 2022, Editorial Department of Journal of Hunan University. All right reserved.
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Federated learning, which shares the weights of the neural network across clients, is gaining attention in the healthcare sector as it enables training on a large corpus of decentralized data while maintaining data privacy. For example, this enables neural network training for COVID-19 diagnosis on chest X-ray (CXR) images without collecting patient CXR data across multiple hospitals. Unfortunately, the exchange of the weights quickly consumes the network bandwidth if highly expressive network architecture is employed. So-called split learning partially solves this problem by dividing a neural network into a client and a server part, so that the client part of the network takes up less extensive computation resources and bandwidth. However, it is not clear how to find the optimal split without sacrificing the overall network performance. To amalgamate these methods and thereby maximize their distinct strengths, here we show that the Vision Transformer, a recently developed deep learning architecture with straightforward decomposable configuration, is ideally suitable for split learning without sacrificing performance. Even under the non-independent and identically distributed data distribution which emulates a real collaboration between hospitals using CXR datasets from multiple sources, the proposed framework was able to attain performance comparable to data-centralized training. In addition, the proposed framework along with heterogeneous multi-task clients also improves individual task performances including the diagnosis of COVID-19, eliminating the need for sharing large weights with innumerable parameters. Our results affirm the suitability of Transformer for collaborative learning in medical imaging and pave the way forward for future real-world implementations. © 2021 Neural information processing systems foundation. All rights reserved.
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Background and Purpose of Research Adolescents use their smartphones for various purposes, for example, following distance/online learning, especially during the COVID-19 pandemic, staying in touch with friends, having fun using social media tools. According to the social ecological model, risk behaviors, like substance consumption, are regarded as behavior problems. Relatively, etiology is derived of youths’ embeddedness surrounded by their social networks, mainly throughout sensitive development periods (Bishop et al., 2020). Given the prevalence of smartphone addiction among young students, previous studies have explored the relationships between smartphone addiction and students’ learning and indicated there is negative outcomes of smartphone resulting from overuse of mobile phones, including poor sleep quality. However, there some antecedents of smartphone addiction which has not extendedly studied, for example, parenting style, thus, the present study aimed to explore the correlates between parenting styles, academic achievement and smartphone addiction. Parenting that reflects a combination of support and behavioral control has been linked to numerous indices of academic well-being and live functioning from early childhood through adolescence. In regarding the term helicopter parenting indicated that parents involve hovering behaviors and are potentially over-involved in the lives of their child or in their academic work (Padilla-Walker & Nelson, 2012). But empirical research has not adequately used these two construct from other controlling parenting practices to predict children’s smartphone addiction, thus, the present study applied two types of helicopter parenting: Live hovering and academic hovering of parenting for of emerging adults, to explain the prediction of children’s smartphone addiction. According to Bronfenbrenner (1979) micro ecological system that discusses the association between person-process-content (PPC), who described “person-process-context model” (PPCM) that occurs variability in development procedure as considered in this paper as a functional context (mobile phone usage), person (parenting styles) and process (academic achievement). Not only has cultural ecology be likely to pursue its complications in issues originating from social and cultural topics, but intricate schools of understanding of culture-nature relationship have developed for certain risk behavior. For example, helicopter parenting is more obvious in Chinese families than Western ones, even though the parents want their children to grow up to be independent and think for themselves. Particularly, Chinese parents are more concerned about their children’s schoolwork when they are teenagers, which leads to increased helicopter parenting problems, exacerbating issues such as lack of independence, lack of control, and not knowing how to self-manage smartphone use, which can in turn lead to smartphone addiction. If parents are in constant hovering of their children’s lives or schoolwork, children develop dependent behaviors. Some studies have indicated that a child’s dependent behaviors result in lower motivation to learn and reduced academic achievement. In line with this, drawn on PPCM to understanding the role of academic hovering and live hovering affect participants’ smartphone addiction mediated by academic achievement, hypotheses are proposed as follows. Hypotheses (1) Live hovering has a negative effect on academic achievement. (2) Academic hovering has a negative effect on academic achievement. (3) Academic achievement has a negative effect on smartphone addiction. (4) Live hovering has a positive effect on smartphone addiction. (5) Academic hovering has a positive effect on smartphone addiction. Methodology Questionnaire was designed by adapting and translated from previous researched and gave to domain experts to ensure the content validity. Afterward, a purposive sampling was adapted in this study, a total of 400 questionnaires were distributed to 4 vocational senior high schools located in Taipei City. 354 of which were collected, resulting in a questionnaire collection rate of 88.5%. After 64 invalid questionnaires were excluded, 290 valid questionnaires remained, resulting in a valid questionnaire collection rate of 81.92%. Factor analysis was conducted on the valid questionnaires. Results First, helicopter parenting, live and academic hovering had a negative association with academic achievement, with an explanatory power of 20.8%. Second, academic achievement had a negative association with smartphone addiction, with an explanatory power of 38.6%. Third, helicopter parenting had a negative association with smartphone addiction. Fourth, academic hovering had a negative association with smartphone addiction mediated by academic achievement, with an explanatory power of 20.8%. The results of the study thus indicate that young people who are not independent in life or schoolwork tend to rely on their parents, are less able to control their smartphone use, and are more likely to develop smartphone addiction. By contrast, young people who are independent in life and schoolwork and do not need to rely on their parents have control over their smartphone use and are less likely to develop smartphone addiction. Conclusions and Recommendations The results of this study demonstrate that if vocational senior high school students are overly dependent on their parents in life or schoolwork, they may have lower academic achievement and therefore, they are not motivated to achieve strong academic results and will not restrain their desire to spend time on using smartphone, resulting in a tendency toward smartphone addiction. However, when vocational senior high school students do not have to rely on their parents to a great extent in life or schoolwork, they are able to act independently, attain high academic achievement, determine what they want to achieve, and arrange how they will accomplish their goals. Therefore, they have the ability to control the time they spend using their phones and will not develop smartphone addiction. This study suggests that parents should let their children learn to be independent and autonomous, which should help to effectively reduce the problem of smartphone addiction. Finally, conducting this study highlighted possibilities for future research. Some studies suggest that fathers and mothers do not necessarily share the same parenting style, and hence, it is suggested that in a questionnaire survey, the hovering styles of fathers and mothers could be differentiated and then analyzed through a differential analysis. In addition, some smartphone use can be designed with time of use to control using time (e.g., Chinese government limited the hours for children to use smartphone). However, how is the effect of the regulation to students’ smartphone addiction should be further studied. © 2021, National Taiwan Normal University. All rights reserved.
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Under the background of the spread of COVID-19, there has been a shift from offline education to online education. Online education is rapidly becoming large-scale in a short time, and its related hardware and software markets are expanding rapidly. The development of this kind of online education hardware carrier represented by children’s robot has become a hot spot in the industry at this time, but there are still some problems in its design, such as ignoring the emotional needs of users. This study first focuses on the user’s function and emotional needs through market research and user research, then uses the method of Kansei engineering to select a certain sample of existing children’s robots, conducts Kansei vocabulary research through SD method, and analyzes the data results through SPSS, so as to summarize the modeling semantic keywords. Finally, from the perspective of Kansei Engineering, a new practical design scheme of children’s accompanying robot is proposed. The feasibility and effectiveness of the design practice are verified by the satisfaction survey. © 2021, Springer Nature Switzerland AG.
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Purpose To meet the rapidly increasing demand for medical treatment during the outbreak of COVID-19, Huoshengshan and Leishenshan Hospital are rapidly built (9-12 days) in Wuhan. These two urgent emergency projects are unprecedented. In general, substantial literature suggests that the possibility of shortening a schedule by more than a quarter of its original duration is implausible. By contrast, the two projects had successfully compressed the schedules from months and years to about ten days. This study aims to investigate how this was done and provide references for future projects. Design/methodology/approach The study uses qualitative case study techniques to analyze the project practices in two urgent emergency projects. Data were gathered through semi-structured interviews and archival research. During interviews, interviewees were asked to describe the project practices adopted to overcome the challenges and freely share their experiences and knowledge. Findings The results illustrate that a high degree of schedule compression is achievable through tactful crashing, substitution and overlapping applications. The successful practices heavily rely on the high capacity of participants and necessary organization, management and technology innovations, such as three-level matrix organizational structure, reverse design method, site partition, mock-up room first strategies and prefabricated construction technology. For instance, the reverse design method is one of the most significant innovations to project simplification and accelerate and worthy of promotion for future emergency projects. Practical implications The empirical findings are significant as they evoke new thinking and direction for addressing the main challenges of sharp schedule compression and provide valuable references for future emergency projects, including selecting high-capacity contractors and replacing the conventional design methods with reverse design. Originality/value Substantial studies indicate that the maximum degree of schedule compression is highly unlikely to exceed 25%, but this study suggests that sharp compression is possible. Although with flaws in its beauty (i.e. compressing schedule at the expense of construction cost and quality), it is also a breakthrough. It provides the building block for future research in this fertile and unexplored area.
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The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) causes a respiratory disease called coronavirus disease (COVID)-19 in infected individuals. Since its first outbreak at the end of 2019, COVID-19 has rapidly evolved into a global pandemic and has infected more than 85 million (M) people worldwide and has resulted in over 1.85 M deaths. The pandemic has led to the race for finding therapeutics and vaccines, and to date, there have been two vaccines approved within the United States and the potential for more to follow in the coming months. In addition, this has also forced clinical researchers to look into the impact this may have on ongoing trials, given the risk of COVIDrelated complications confounding with the efficacy and safety outcomes and necessitating the collection of additional data and evaluating alternate ways of analyzing trial results. This is of particular concern in patients with cancer who are often immunosuppressed as a result of both their disease and the treatment they receive, which puts them at increased risk of severe complications from COVID-19. In this session, we will focus on two important but very distinct topics that have emerged due to the onset of the pandemic: (1) the issues and challenges related to vaccine development including trial design, rapid execution, real-time regulatory feedback, and overall interpretation of trial results and (2) understanding potential impact of COVID-related deaths in Oncology trials, on time to event endpoints of overall survival and progression-free survival. Topic 1: Challenges with COVID-19 Vaccine development The SARS-CoV-2, first identified in December 2019, has caused a worldwide pandemic leading to widespread morbidity and mortality. There was no Food and Drug Administration-approved vaccine for the prevention of the coronavirus disease 2019 (COVID-19), the disease caused by SARS-CoV-2. The urgent need for safe and effective interventions to mitigate the global spread of SARS-CoV-2 has prompted international efforts to develop antivirals and vaccines. Numerous vaccine candidates based on traditional and new platforms are currently being evaluated including nucleic acid (DNA and RNA), viral vector (replicating and non-replicating), virus-like particles, peptide-based, recombinant protein, and live attenuated and inactivated virus modalities. COVID-19 vaccines are in various stages of clinical development, with several candidates in pivotal phase 3 clinical trials, including mRNA-based vaccines, of which two vaccines, one developed by Pfizer and the other by Moderna recently received the emergency use authorization from the Food and Drug Administration in December 2020. In this session, we will share experiences and challenges in the development of these two vaccines. We will share the practical and statistical challenges and considerations when designing COVID-19 vaccine studies, such as target population(s), endpoint selection and assessment, statistical analysis method, timing of interim analyses, and questions continuously to be answered after receiving the emergency use authorization and/or during the Biologics License Application review. We show that, when planning a vaccine pivotal study against a novel virus causing ongoing worldwide pandemic, special consideration needs to be given for the designing of interim analyses related to efficacy, so that a vaccine with favorable benefit-risk profile can be made available as early as possible;special attention also needs to be given for an independent data safety monitoring board for vaccine-associated enhanced respiratory disease and other safety signal monitoring to mitigate the risk for trial participants during an ongoing pandemic. Topic 2: Impact of COVID-19 on Oncology trial outcomes using overall survival or progression-free survival Simulations were conducted to assess (1) the impact of the COVID-19-related death and (2) missed RECIST visits on the statistical analysis of time-to-event outcomes in randomized phase 3 oncology trials and explore mitigation options for this r sk when COVID- 19 cohort is well-defined. Two simulated case studies of Phase 3 randomized controlled trials ongoing during the pandemic outbreak were used to evaluate five approaches (1, ITT approach;2, modified ITT excluding COVID-19-related deaths;3, censoring COVID-19- related deaths with target number of non-COVID-19- related deaths;4, censoring COVID-19-related deaths with original date-cut-off;5, Fine & Gray modeling of competing risk approach to treat COVID-19-related death and non-COVID-19-related death separately), at presence of COVID-19-related deaths with different pandemic onsets relative to timing of analysis and varying pandemic durations, the impact of COVID-19- related death due to pandemic, on the primary endpoints of overall survival and/or progression-free survival in terms of type 1 error, power, and hazard ratio estimates. It was found that COVID-19-related deaths would impact time-to-event analysis in terms of type 1 error and power for log rank test, and provide biased treatment effect estimation from Cox model if ITT approach is used;impact would be more severe if there was an imbalance in COVID-19-related deaths mainly in experimental arm. With same number of COVID-19- related deaths, the earlier the timing of the pandemic window, will lead to greater loss in power. Approaches censoring COVID-19-related deaths would minimize impact on power loss and bias in hazard ratio estimation, particularly if data cut-off was extended to mitigate for events loss due to censoring. The simulations conducted in this analysis provide a framework to help understand how to mitigate the risk to the randomized oncology trials in which COVID-19- related deaths are observed in the blinded assessment during the COVID-19 pandemic.
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This study aims to improve control schemes for COVID-19 by a numerical model with estimation of parameters. We established a multi-level and multi-objective nonlinear SEIDR model to simulate the virus transmission. The early spread in Japan was adopted as a case study. The first 96 days since the infection were divided into five stages with parameters estimated. Then, we analyzed the trend of the parameter value, age structure ratio, and the defined PCR test index (standardization of the scale of PCR tests). It was discovered that the self-healing rate and confirmed rate were linear with the age structure ratio and the PCR test index using the stepwise regression method. The transmission rates were related to the age structure ratio, PCR test index, and isolation efficiency. Both isolation measures and PCR test medical screening can effectively reduce the number of infected cases based on the simulation results. However, the strategy of increasing PCR test medical screening would encountered a bottleneck effect on the virus control when the index reached 0.3. The effectiveness of the policy would decrease and the basic reproduction number reached the extreme value at 0.6. This study gave a feasible combination for isolation and PCR test by simulation. The isolation intensity could be adjusted to compensate the insufficiency of PCR test to control the pandemic.
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The impacts of anthropogenic emissions on the reduction of source-specific equivalent black carbon (eBC) aerosols and their direct radiative effects (DREs) were investigated during the lockdown of the coronavirus outbreak in a megacity of China in 2020. Five eBC sources were identified using a hybrid environmental receptor model. Results showed that biomass burning, traffic-related emissions, and coal combustion were the dominant contributors to eBC. The generalized additive model indicated that the reduction of traffic-related eBC during the lockdown was entirely attributed to the decrease of emissions. Decreased biomass-burning activities and favorable meteorological factors are both important drivers for the biomass-burning eBC reduction during the lockdown. A radiative transfer model showed that the DRE efficiency of eBC from biomass burning was the strongest, followed by coal combustion and traffic-related emissions. This study highlights that aggressive reduction in the consumption of residential solid fuels would be effective in achieving climate change mitigation.