Introduction
The world is in a critical situation because of the COVID-19 pandemic that is threatening human lives as 60% of the population is likely to be infected in the absence of effective treatment [1, 2]. The pandemic has caused physical, mental, and emotional distress, depression, and anxiety among people worldwide, especially healthcare personnel [1, 2, 3]. The pandemic will likely lead to a weakened immune system and reduce the ability to fight the disease [4, 5]. Considering the impact of COVID-19 on the economy and political and social life of all nations globally, studying the psychological effects of this disease on the mental health of individuals in the healthcare profession is of crucial importance [5]. Due to the extensive exposure to patients with COVID-19, nurses are at high risk of getting psychological distress and anxiety [6]. They are at increased risk of mental health disorders because of a stressful environment, leading to a decline in job satisfaction, commitment, and emotional attachment to their family and relatives [7]. These can affect nurses during the pandemic in at least 3 ways: a) clinical performance, b) psychological knowledge and experience, and c) job security. The assessment of this condition contributes significantly to the diagnosis and management of individuals affected by the pandemic [25]. The objective of this analytical and descriptive study is to investigate the relationships between psychological capital, self-reported job satisfaction, and the mediating role of psychological security in enhancing nurses’ clinical performance at an average-sized medical center in Arak City, Iran.
Methods
We recruited 100 volunteer nurses who practiced on wards serving patients with coronavirus infection at a major medical center in Arak City, Iran. They reviewed the ethically approved study protocol before participating in the study. Upon their consent, they completed 3 questionnaires focused on psychological capital [21], psychological security [18], and clinical performance [22]. The first questionnaire, measuring the critical elements of hope, optimism, self-efficacy, and resilience had 24 items scored on a 5-point Likert scale [23, 24]. 
The second questionnaire contained 5 items, scored on a 6-point Likert scale, measuring the perceived psychological security [4, 25]. The third questionnaire (evidence-based practice questionnaire) assessed the quality of nurses’ clinical performance on a 5-point Likert scale [22]. We statistically analyzed the data and assessed the compliance, using the confirmatory factor analysis with the partial least squares method via the smart PLS3 software. In addition, we tested the normality of the data for the questionnaires. The path analysis test, the t test, and the regression β coefficient were used to examine the 4 hypotheses: a) psychological capital has a significant effect on nurses’ evidence-based clinical performance when faced with COVID-19 patients; b) psychological capital has a significant effect on psychological security based on nurses’ evidence of facing the COVID-19 patients; c) psychological security has a significant effect on clinical performance based on nurses’ evidence when faced with COVID-19 patients; and d) psychological security mediates the positive effect of psychological capital on nurses’ clinical performance.
Results
Regarding the demographic characteristics of the nurses, 78 were female and 22 were men. The participants were in the age range of 20 to 30 (55%) years, 30 to 40 (35%) years, and 40 to 50 (10%) years. Of these, 87% had a bachelor’s degree and 13% had a nursing certificate. 
The analyzed data representing the nurses’ statements based on the first hypothesis confirmed that psychological capital had a positive and significant impact on nurses’ clinical performance (P‌<‌0.05). The similar data for the second hypothesis indicated that psychological capital had a significant effect on psychological security (P‌<‌0.05). The data demonstrated that nurses’ psychological security had significant effects on their clinical performance (P‌<‌0.05). Table 1 represents the estimation of the statistically analyzed results of the path coefficient β, T value, and significance for the first, second, and third hypotheses. 


Regarding the fourth hypothesis, psychological security mediated the effect of psychological capital on clinical performance. To analyze the data on the fourth hypothesis, we used the Baron and Kenny method. As shown in Table 2, the results indicated a significant relationship among the first 3 steps.


For the entry of the mediator variable (fourth step), the results indicated that in the presence of the psychological security variable, the standard β for the relationship between psychological capital and clinical performance was significantly reduced from 0.684 to 0.507. Therefore, the role of psychological security was partially mediatory, which confirmed the fourth hypothesis of the study.
4. Discussion 
This study investigated the effects of psychological capital on improving clinical performance and psychological security in nurses who worked with infected patients in coronavirus wards during the pandemic. The study’s hypotheses were proposed and tested successfully. The results established this study as an experimental and conceptual model on this psychological subject. Specifically, we demonstrated the effective interaction of psychological capital with the clinical performance and psychological security of nurses [26, 27]. Nurses with higher psychological knowledge have fewer worries and fears compared to those who lack that knowledge [32]. Such nurses are more resourceful and can provide significantly better professional care for patients with coronavirus infection compared to those who lack the extra knowledge [32]. Therefore, providing continuing education programs to improve the psychological knowledge of nurses will raise their resilience and hope for providing excellent clinical services to all patients, regardless of their diagnosis [33].
This study enabled the exchange of positive and constructive feedback among the nurses, increased their hope, and led them to improve their sense of self-efficacy, security, and trust [34, 35, 36, 37]. This exercise also led to their heightened sense of job satisfaction and professional commitment. Given the complexity of clinical environments, the participating nurses believed that developing a nursing plan of care for patients with coronavirus infection during the pandemic should be based on valid and updated scientific evidence [38, 39, 40]. They requested holding regular continuing education sessions on psychological principles [39, 40]. If nurses receive social support from others, they will feel a greater sense of adequacy to overcome their professional challenges [40]. 

Ethical Considerations
Compliance with ethical guidelines
The study protocol was reviewed and approved by the Ethics Committee of Arak University of Medical Sciences (Ethics Code: IR.ARAKMU.REC.1399.321).

Funding
This study was financially supported by Arak University of Medical Sciences (Project No.: 3848).


Authors contributions
All authors contributed equally to the design, conduction, and writing of the drafts of the Persian manuscript.

Conflicts of interest
The authors had no conflict of interest with any internal or external entity in conducting this study.

Acknowledgements
The authors are grateful to the nurses and the management of Amir-Al-Momenin General Hospital in Arak City, Iran for their support and participation in this study. The authors are thankful to MERCI Editors & Consultants, Virginia, USA, for the native English translation of the manuscript.