Objective: To systematically evaluate the prevalence and influencing factors of screen exposure among preschool children in China, so as to provide evidence for formulating scientific intervention strategies. Methods: Retrieve relevant studies on screen exposure among preschool children from PubMed, Web of Science, Embase, Cochrane Library, China Biomedical Literature Database, CNKI, VIP, and Wanfang databases from the time of estaldishment to June 29, 2025. Meta analysis was performed using Stata 16.0 software. Results: A total of 43 studies were included. Meta analysis showed that the prevalence of screen exposure among preschool children in China was 46.0% (95% CI = 38.9 %-53.1%, P <0.01). Girls, non only child, father s age<35 years, both parents having an educational level of high school or below, being cared for by grandparents, rural residence, parents having no exercise habit, parental support for the use of screen devices, and parental screen time>1 h/d were influencing factors for screen exposure among preschool children [ OR (95% CI ) were 0.85(0.78-0.92), 1.09(1.04-1.15), 1.45(1.22-1.71), 1.38(1.24- 1.54 ), 1.78(1.32-2.40), 1.39(1.16-1.65), 1.38(1.13-1.69), 1.67(1.40-1.98), 1.70(1.38-2.10), 1.59(1.04-2.43), all P <0.05]. Conclusion The prevalence of screen exposure among preschool children in China is relatively high, and relevant child health promotion strategies should be formulated to reduce its occurrence.

Public hospitals bear the responsibility of ensuring people's health and promoting their healthy lives.New media have emerged as a pivotal platform for health science popularization in public hospitals.Under these contexts,the Science Popularization Base for Health and Chronic Disease Prevention of the First Hospital of Lanzhou University established a multidisci-plinary team model for science popularization,mainly relying on the WeChat official account to disseminate health knowledge and dispel rumors.This article explored the experiences and practices of health science popularization under this model,focusing on the"meticulous selection for science popularization"strategy employed on their WeChat official account.

Objective To investigate the efficacy of antibacterial photodynamic therapy(aPDT)as an adjunct to subgingival scaling and root planning in the treatment of chronic periodontitis.Methods This study followed medical ethics guidelines,and informed consent was obtained from all patients.Sixteen patients were recruited for this random-ized split-mouth controlled trial.The control group underwent subgingival scaling and root planning(SRP),while the ex-perimental group received subgingival scaling and root planing plus aPDT treatment using Perowave? with a toluidine blue O solution photosensitizer.The probing pocket depth(PD),recession,plaque index(PLI),bleeding index(BI)and proportion of positive sites of bleeding on probing(BOP)(BOP%)at all sites were examined at baseline(before treat-ment)and at 1,3 and 6 months after treatment.Results Follow-up was completed for 13 patients.On the control side,356 teeth were tested at 2 136 sites.A total of 360 teeth on the test side and 2 160 sites were included in the study.Before treatment,there was no significant difference in the baseline indicators between the two groups.After treatment,both groups showed significant improvement in clinical parameters,including PD,PLI,BI,and BOP%,compared with baseline.At 3 months,the BOP%and PLI in the experimental group were significantly lower than those in the control group(P＜0.05).The improvement in BOP%and PLI in the experimental group was significantly greater than that in the control group 3 months after treatment(P＜0.05).Conclusion aPDT,as an adjuvant treatment to SRP for chronic periodontitis,can improve gingival bleeding and control periodontal inflammation in the early stage.

Objective:To provide basis for preventing flight safety accidents caused by hypoxia by exploring the subjective and objective performance of pilots in hypobaric hypoxia environment.Methods:The relevant data of pilots′ high altitude physiological training were retrospectively analyzed and a symptom questionnaire upon the training were summarized. The pilots were divided into excellent group (time of useful consciousness >6 min), good group (3 min ≤time of useful consciousness <6 min) and qualified group (2 min ≤time of useful consciousness <3 min) according to the time of useful consciousness. The hypoxia symptoms and physiological parameters of pilots in each group were statistically analyzed.Results:A total of 919 pilots were included, in which 416 were in excellent group, 490 were in good group and 13 were in qualified group. Among the 25 hypoxia symptoms, there were significant differences in the components of numbness and difficulty in calculation among 3 groups ( χ2=6.04, 7.79, P=0.049, 0.020), but there were no significant differences in the components of the other 23 hypoxia symptoms (all P>0.05). The changes of blood oxygen saturation were significant in group main effect, time main effect and their interaction ( F=25.65, 1 039.77, 25.22, all P<0.001). The change of heart rate was statistically significant in the main effect of time ( F=66.41, P<0.001) but in time main effect and their interaction (both P>0.05). There was no significant difference in respiratory rate among group main effect, time main effect and their interaction (all P>0.05). The distribution and variation of blood oxygen saturation were statistically significant differences among the 3 groups in the ranges of 81%-90%, 71%-80% and 65%-70% ( H=125.93, 372.83, 13.10, all P≤0.001) unlike the range of 91%-100% ( H=2.48, P=0.289). Conclusions:The excellent group showed better blood oxygen saturation maintaining and useful consciousness time enduring capabilities, and those imply them in better performance and consciousness that enable the operation in hypoxic environment with more ease.

Objective:To provide scientific basis for pilots′ hypoxia training by comparing and analyzing the effects of hypoxia training under normobaric and hypobaric environments.Methods:Forty-two healthy subjects were selected. The pilot reduced oxygen breathing device and hypobaric chamber were used to simulate 7 500 m hypoxia training, and blood oxygen saturation, heart rate, respiratory rate and hypoxia endurance time were monitored and recorded. The hypoxia symptom questionnaire was filled out by the subjects after 2 training sessions. The hypoxia endurance time and hypoxia tolerance grade of normobaric and hypobaric hypoxia training were analyzed, and the differences of blood oxygen saturation and hypoxia symptoms were compared between 2 hypoxia trainings.Results:Forty-two subjects completed the normobaric and hypobaric hypoxia trainings. The survival curve analysis of hypoxia endurance time showed that the median hypoxia endurance time of normobaric and hypobaric hypoxia training was [3.17(2.70, 3.64)] min and [3.67(3.46, 3.88)] min respectively, with no significant difference ( P>0.05). There was no significant difference in the grade distribution of hypoxia tolerance between 2 hypoxia trainings ( P>0.05). The blood oxygen saturation curves of 2 hypoxia trainings were basically consistent. There was no significant difference between 2 hypoxia trainings on blood oxygen saturation, heart rate and respiratory rate (all P>0.05). There were significant differences in difficulty in calculation, difficulty in concentration and with palpitation ( χ2=4.81, 3.97, 3.98, P=0.028, 0.046, 0.046). Conclusions:The analysis showed that most physiological responses and subjective symptoms of pilots are quite similar in the normobaric and hypobaric hypoxia training at simulated 7 500 m. Both normobaric and hypobaric exposures show the similar hypoxia training effect.

Objective:To provide basis for preventing flight safety accidents caused by hypoxia by exploring the subjective and objective performance of pilots in hypobaric hypoxia environment.Methods:The relevant data of pilots′ high altitude physiological training were retrospectively analyzed and a symptom questionnaire upon the training were summarized. The pilots were divided into excellent group (time of useful consciousness >6 min), good group (3 min ≤time of useful consciousness <6 min) and qualified group (2 min ≤time of useful consciousness <3 min) according to the time of useful consciousness. The hypoxia symptoms and physiological parameters of pilots in each group were statistically analyzed.Results:A total of 919 pilots were included, in which 416 were in excellent group, 490 were in good group and 13 were in qualified group. Among the 25 hypoxia symptoms, there were significant differences in the components of numbness and difficulty in calculation among 3 groups ( χ2=6.04, 7.79, P=0.049, 0.020), but there were no significant differences in the components of the other 23 hypoxia symptoms (all P>0.05). The changes of blood oxygen saturation were significant in group main effect, time main effect and their interaction ( F=25.65, 1 039.77, 25.22, all P<0.001). The change of heart rate was statistically significant in the main effect of time ( F=66.41, P<0.001) but in time main effect and their interaction (both P>0.05). There was no significant difference in respiratory rate among group main effect, time main effect and their interaction (all P>0.05). The distribution and variation of blood oxygen saturation were statistically significant differences among the 3 groups in the ranges of 81%-90%, 71%-80% and 65%-70% ( H=125.93, 372.83, 13.10, all P≤0.001) unlike the range of 91%-100% ( H=2.48, P=0.289). Conclusions:The excellent group showed better blood oxygen saturation maintaining and useful consciousness time enduring capabilities, and those imply them in better performance and consciousness that enable the operation in hypoxic environment with more ease.

Objective:To provide scientific basis for pilots′ hypoxia training by comparing and analyzing the effects of hypoxia training under normobaric and hypobaric environments.Methods:Forty-two healthy subjects were selected. The pilot reduced oxygen breathing device and hypobaric chamber were used to simulate 7 500 m hypoxia training, and blood oxygen saturation, heart rate, respiratory rate and hypoxia endurance time were monitored and recorded. The hypoxia symptom questionnaire was filled out by the subjects after 2 training sessions. The hypoxia endurance time and hypoxia tolerance grade of normobaric and hypobaric hypoxia training were analyzed, and the differences of blood oxygen saturation and hypoxia symptoms were compared between 2 hypoxia trainings.Results:Forty-two subjects completed the normobaric and hypobaric hypoxia trainings. The survival curve analysis of hypoxia endurance time showed that the median hypoxia endurance time of normobaric and hypobaric hypoxia training was [3.17(2.70, 3.64)] min and [3.67(3.46, 3.88)] min respectively, with no significant difference ( P>0.05). There was no significant difference in the grade distribution of hypoxia tolerance between 2 hypoxia trainings ( P>0.05). The blood oxygen saturation curves of 2 hypoxia trainings were basically consistent. There was no significant difference between 2 hypoxia trainings on blood oxygen saturation, heart rate and respiratory rate (all P>0.05). There were significant differences in difficulty in calculation, difficulty in concentration and with palpitation ( χ2=4.81, 3.97, 3.98, P=0.028, 0.046, 0.046). Conclusions:The analysis showed that most physiological responses and subjective symptoms of pilots are quite similar in the normobaric and hypobaric hypoxia training at simulated 7 500 m. Both normobaric and hypobaric exposures show the similar hypoxia training effect.

Thymoma complicated with polymyositis and myasthenia gravis is a rare case, which can be clearly diagnosed and given symptomatic treatment according to its own diagnostic criteria, imaging and laboratory examinations. This paper reports the clinical data of a thymoma patient with polymyositis and myasthenia gravis admitted to the Seventh Affiliated Hospital of Sun Yat-Sen University, and discusses the possible pathogenesis and treatment methods.

Objective:To study the simplified oxygen supply protection scheme below 15.0 km, and to evaluate its protection performance through tests.Methods:The parameter of YX-5 oxygen system was modified, by reducing its total oxygen supply pressure and closing a large number of oxygen supply mechanisms, and compensatory suit was cancelled. A dummy and 4 volunteers with helmet and oxygen mask using modified YX-5 oxygen system underwent 5 tests in hypobaric chamber, included ① normal oxygen supply performance test at 0-10.0 km; ② pure oxygen supply performance test at 0-10.0 km; ③ positive pressure supplying oxygen performance test at 13.0, 15.0, 16.0 km; ④ impact test of pressured oxygen supply; ⑤ pressured oxygen supplying performance physiological test at 15.0 km.Results:Under the normal oxygen supply, the oxygen pressure of modified YX-5 oxygen system below 12.0 km was >21.0 kPa. When high-altitude pressurized oxygen supply was used, the oxygen pressure was >15.8 kPa at 12.0-15.0 km. Inspiration resistance of modified YX-5 oxygen system was <0.34 kPa when the dummy′s respiration ventilation rate was 20 L/min. The impact pressure of mask was 1.25 kPa when pressured oxygen supply switched on but without compensatory suit connected to modified YX-5 oxygen system. Four volunteers completed the human physiological test up to 15.0 km high-altitude pressurized oxygen supply to verify the protective performance of the scheme, and they had no adverse physiological reactions after the test.Conclusions:The simplified protection scheme can provide protection against hypoxia for pilots at 0-15.0 km altitude.

Objective:To evaluate the protection performance of military transport aircraft oxygen system for aircrew and provide the physiological tests basis for product design finalization.Methods:Four dummies and 4 healthy volunteers who were equipped with individual protection equipment and military transport aircraft oxygen system completed 4 tests in altitude chamber including the oxygen supply performance physical test of oxygen system, the rapid decompression physical test of oxygen system, the physiological tests of oxygen continuously supplying for 6 h and oxygen supply performance test in rapid decompression at 12.0 km. Oxygen concentration, respiratory resistance, safety pressure, peak value, peak duration and steady pressure of mask under rapid decompression were tested. Electrocardiograph and oxygen saturation of volunteers were monitored.Results:The oxygen partial pressure provided by military transport aircraft oxygen system under 12.0 km was ≥19.1 kPa corresponding to the respiration ventilation volume of 20 L/min of dummy. The expiratory resistance was no higher than 441.3 Pa and the inspiration resistance was no higher than 490.3 Pa before the safety pressure connected. The peak pressure value in rapid decompression with 1.0 L lung volume of dummy was no higher than 5.8 kPa. The oxygen partial pressure provided by military transport aircraft oxygen system for volunteers was over 21.9 kPa in the 6 h cruising flight. All 4 volunteers successfully completed the rapid decompression physiological tests at 12.0 km with good subjective and objective responses.Conclusions:The protection performance of military transport aircraft oxygen system for aircrew can provide enough protection against the hypoxia up to 12.0 km