Objective　To examine whether ischemia preconditioning (IPC) can decrease ischemia reperfusion(I/R) injury in retina and investigate the mechanism. Methods　Retinal ischemia was induced in SD rats by increasing the intraocular pressure to 14.63kPa for 60 minutes via cannulation into the anterior chamber. Retinal ischemia for 5 minutes constituted the preconditioning stimulus. Rats first underwent IPC and 60 minutes of ische- mia 30 minutes, 24 or 72 hours later or they underwent a 5-minute sham PC and 60 minutes of ischemia 24 hours later. Their electroretinography(ERG), Light microscopy(LM),transmission electron microscopy (EM) and the expression of heat shock protein 70(HSP70) were observed and the content of malandialdehyde(MDA) in rat retinas were measured 24 or 72 hours later after 60 minutes ischemia.Results　Ischemia induced histologic damage was completely prevented when IPC was performed 24 or 72 hours (but not 30 minutes) before ischemia. In contrast to the sham PC group, the amplitudes had complete recovery of b-waves with preischemia basline amplitudes (P<0.01),and the content of MDA was significantly decreased (P<0.01).Conclusion　IPC provides protection against retinal I/R injury just during limited period of time.

Purpose/Significance To explore the changes,challenges,key application scenarios and future development directions of generative artificial intelligence(AI)represented by ChatGPT in the field of hospital management,and to provide references for the ap-plication of AI natural language processing(NLP)technology in the field of hospital management in China.Method/Process Through literature review and analysis,the changes and challenges brought about by the rapid development of generative AI in the field of hospital management are sorted out,its key application scenarios and future development directions in the field of hospital management are empha-sized and explored.Result/Conclusion AI has broad application prospects in the field of hospital management,and it should focus on exploring its practical application scenarios and strategic directions to provide reference and guidance for promoting the high-quality de-velopment of public hospitals.

Objective:By analyzed the transmission patterns of 4 out of the 51 COVID-19 cluster cases in Shaanxi province to provide evidences for the COVID-19 control and prevention.Methods:The epidemiological data of RT-PCR test-confirmed COVID-19 cases were collected. Transmission chain was drawn and the transmission process was analyzed.Results:Cluster case 1 contained 13 cases and was caused by a family of 5 who traveled by car to Wuhan and returned to Shaanxi. Cluster case 2 had 5cases and caused by initial patient who participated family get-together right after back from Wuhan while under incubation period. Cluster case 3 contained 10 cases and could be defined as nosocomial infection. Cluster case 4 contained 4 cases and occurred in work place.Conclusion:Higher contact frequency and smaller places were more likely to cause a small-scale COVID-19 cluster outbreak, with potential longer incubation period. COVID-19 control strategies should turn the attention to infection prevention and control in crowded places, management of enterprise resumption and prevention of nosocomial infection.