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Objective@#To investigate the visual acuity of primary and middle school students in Ningxia by using decision tree model and logistic regression, and to provide evidence for the prevention and control of visual acuity.@*Methods@#Using stratified cluster sampling method, 3 257 children aged 7-18 years were randomly selected from Yinchuan and Wuzhong in Ningxia. Visual acuity test and questionnaire survey were conducted. The C 5.0 algorithm in Clementine12.0 and Logistic regression were used to analyze the factors associated with visual acuity.@*Results@#The overall rate of low vision of the middle school of Ningxia was 62.6%, with girls (68.1%) higher than that of boys(56.8%)(P<0.01). There was a significant difference in the prevalence of low vision among different educational stages(P<0.01), with high school students had the highest detection rate(82.2%). Results of decision tree C 5.0 algorithm showed that educational stage, gender, time to do homework after school and frequency of moderate intensity exercise per week associated with poor eyesight of primary and secondary school students. Logistic regression results showed that girls, the distance between the eyes and the computer display screen <66 cm(OR=1.24, 95%CI=1.00-1.52), and the distance between the eyes and the textbook when reading was less than one foot (OR=2.05, 95%CI=1.23-3.40) were positively associated with poor vision. Low grade students and homework time <2 hours after school (OR=0.76, 95%CI=0.62-0.92) were negatively associated with lower risk of poor vision.@*Conclusion@#Educational stage, gender and time of homework after school are associated with the visual acuity of primary and secondary school students in Ningxia. It is suggested that prevention of myopia should start from the low-grade students, reducing after-school work for primary and secondary school students, and increasing outdoor activities. All the girls should be encouraged to engage in more outdoor activities, to prevent the occurrence and development of myopia.
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Objective To evaluate the hemocompatibility of polydioxanone(PDO)bioabsorbable stents.Methods Whole blood clotting time,prothrombin time(PT),activated partial thromboplastin time(APTT),platelet adhesion and hemolysis were used to evaluate the hemocompatibility of PDO bioabsorbable stents,and the results were compared with those of 316L stainless stents which are widely used clinically.Results The anticoagulant property of PDO bioabsorbable stents was similar to that of 316L stainless stents.Both PDO bioabsorbable and 316L stainless stents were not prone to activate blood coagulation factors.Compared with 316L stainless stents,PDO bioabsorbable stents had weaker platelet adhesion and activation.Hemolysis ratios of two groups were less than 5%.Conclusions PDO bioabsorbable stents had good hemocompatibility in vitro.