ression analysis showed that gender, professional title, educational level, job satisfaction, chronic diseases, daily sleep duration, average weekly overtime, physical activity time, and sugary beverage intake were the influencing factors of negative emotions(P<0.05). Male, primary and below, never working overtime and daily physical activity time more than 30 minutes were protective factors for negative emotions(OR vale were 0.79, 0.68, 0.39 and 0.63, respectively, P<0.05). Bachelor degree or above, poor job satisfaction, chronic disease, daily sleep duration less than eight hours and drinking one to three sugary drinks a week were the risk factors for negative emotion(OR vale were1.21, 4.32, 2.16, 2.75 and 1.20, respectively, P<0.05). Conclusion Due to the influence of work pressure, lifestyle, chronic diseases and other factors, young employees in CDC have a certain degree of negative emotions at work, which should be paid enough attention. Meanwhile, corresponding measures should be taken according to the influencing factors to reduce the occurrence of negative emotions.


Introduction
Negative emotions such as depression and anxiety caused by workplace stress have become important factors that increase the risk of developing the disease and accelerate its progression [1]. Previous studies have found that, medical and health practitioners are more prone to occupational stress and burnout because of high workload and strained interpersonal relationship [2]. It develops further when there is no relief, developing a tendency for negative emotions in the form of anxiety and depression at work [3]. The survey on perceived stress of residents in 15 provinces of China shows that the perceived stress of adult residents is related to age, marriage, working status, income and physical activity [4]. Although studies have found the young employees in public health and disease control institutions often suffer from great work pressure, especially in the process of dealing with public health emergencies [5][6]. However, they mainly focus on status of job burnout and bad mood [7], and there are few studies on large sample sizes of in uencing factors.
The main objective of this study was to describe the current situation of negative emotions among young employees in CDC, and to analyze the in uencing factors of this situation. This data can help us develop targeted health education programs to reduce the risk of related diseases.

Materials And Methods
Subjects 6,099 employees aged 20 to 40 years from 32 provincial CDC were recruited to participate in this survey.
The survey period was from October to November 2019. The protocols used in this study were approved by the Ethical Committee of Chinese Center for Disease Control and Prevention.

Questionnaire design and survey methods
The questionnaire was designed by the research team based on the survey needs and previous research, and contained 72 questions from four dimensions, including basic information, ideological status, emotion and health-related behavior [8][9], and details have been descried in our previous study [10]. Negative emotions at work include depression, anxiety and irritability [11]. In the design of the questionnaire, all sensitive questions are dealt with fuzzily.
In this study, the cluster sampling method was adopted to carry out a self-made online questionnaire survey, and relevant data were collected online by "scanning two-dimensional code or logging in to the survey link". Before the survey, the investigators were trained and instructed to ll in the form online. The questionnaire data will be cleaned and coded by special personnel, and the questionnaires with inconsistent, incomplete and abnormal information will be eliminated.

Statistical analysis
The results are presented as the mean values ± standard deviation(SD), One-way ANOVA was used for comparisons between groups. The in uencing factors were analyzed by Two-category Logistic multifactor analysis. All of the statistical analyses were performed using the Statistical Product and Service Solutions13.0 software, and signi cance was set to the α= 0.05 error rate.  Table 3.

Discussion
Due to the nature of medical and health work, practitioners suffer from a high level of work stress and psychological stress, many studies have shown that long-term high-load work can easily cause negative emotions and increase the risk of depression and chronic diseases [7,12−13]. CDC is the primary agency for dealing with public health emergencies, especially SAS, avian in uenza and COVID-19 [14], in which young people are the main force. Therefore, paying attention to the physical and mental health of young practitioners is not only of great signi cance to individuals, but also to the overall quality of disease control.
Previous studies have found that during the COVID-19 pandemic, the proportion of employees in CDC with anxiety was 33.87% and that of with depression was 38.88% [15]. In this study, we found that the proportion of anxiety and other negative emotions among young practitioners was 53.60%, slightly lower than the results above, suggesting that the high workload brought by the epidemic increased the occurrence of negative emotions. Our study also found that the female employees have a higher proportion of negative situations, reaching 68.51%, which is basically consistent with the result (63.0%) obtained by Qiu Qianwen et al in 2020 [7]. Walter Wurm et al. [16] in 2016 also found this phenomenon and believed that compared with men, women's physical and mental health were more easily affected by the environment, so they were more prone to negative emotions.
In a survey of 1344 employees from four coal mines in Xinjiang, Xian Tingyong et al [17]. found that weekly working hours, positions and duties were signi cant factors contributing to increased occupational stress among practitioners. Our study also found that those who often work overtime are more likely to have negative emotions than those who never work overtime. This may be related to the fact that overtime takes up more spare time and young people are unable to obtain psychological relaxation from leisure time [18]. At the same time, the study found that physical activity of 30 minutes or more per day was a protective factor against negative emotions compared with those who did not exercise and those who rarely exercised. Huglles CW et al [19]. observed 30 teenagers with major depression who experienced signi cant relief after 12 weeks of intense exercise. A survey of Health risks in 2014 also found that regular exercise reduced the incidence of depression in young people [20].
On the other hand, this study found that poor job satisfaction and daily sleep duration less than eight hours were risk factors for negative emotions. People with poor job satisfaction were more likely to experience negative emotions than those with higher job satisfaction, which may be related to complaining more about their jobs. Previous studies have found that the higher the occupational selfconcept and dedication, the lower the incidence of occupational burnout [7]. Because stress comes from work overload and the inability to juggle work and family, people with high job satisfaction are more likely to nd a balance and put more energy into their work.
Studies have found an association between the quality and duration of sleep and depression [21]. Healthy China Initiative (2019-2030) calls for mental health promotion actions to slow the rise of insomnia, anxiety and depression, and advocate getting 7-8 hours of sleep a day [4]. Li Yinghua et al. conducted a study on the relationship between work status and depression among occupational population in Beijing and found that people with average or poor sleep quality had a greater risk of depression than those with good sleep quality, and people with good sleep quality had a lower incidence of depression [22]. In this study, it was also found that people who slept more than 8 hours had a lower proportion of negative emotions, suggesting that lack of sleep was a risk factor. However, lack of sleep among CDC employees was also associated with heavier workloads and frequent overtime. Therefore, to address these problems fundamentally, consideration should be given to reducing the workload of young practitioners.

Conclusion
There may be some bias in this study due to the in uence of sample size, which may affect the accuracy and credibility of the results. Despite some limitations, our ndings still represent a signi cant step forward, especially for nding out the possible in uencing factors, and then put forward targeted solutions.

Declarations
Ethics approval and consent to participate All methods are implemented in accordance with relevant guidelines and regulations. All experimental protocols were approved by the designated licensing Committee(Ethics Committee of China Center for Disease Control and Prevention). Informed consent was obtained from all subjects.
Consent for publication Not applicable.
Availability of data and materials The datasets used and analysed during the current study are available from the corresponding author on reasonable request.
Competing interests The authors declare that they have no con ict of interest.
Funding This work was supported by the Scienti c research project of Chinese Center for Disease Control and Prevention (grant number JY18-2-40).
Authors' contributions HL is the rst author.ZY initiated the concepts of the study.LT,LQand NR collected the data. LT,LQ,and NR analyzed the data. HL drafted the manuscript.ZY contributed to the interpretation of the results and critical revision of the manuscript for important intellectual content and approved the nal version of the manuscript. LQ,LT,NR,WQ,and ZL reviews and suggests the manuscript.All authors have read and approved the nal manuscript. HL and ZY are the study guarantors.RIKEN Center for Advanced Photonics (RAP) is helping to realize the dream of making the invisible visible. As one example, stroboscopes, which allow us to see high-speed phenomena by pulsing light in a short duration, cannot catch the movements of molecules or atoms because they simply move too fast. However, thanks to research in photonics, lasers developed to generate pulses at even shorter duration such as 10-15 second (1