Space Charge Characteristics and Breakdown Properties of Nanostructured SiO2/PP Composites.

Polypropylene (PP) has gained attention in the industry as an environmentally friendly material. However, its electrical properties are compromised due to space charge accumulation during operation, limiting its application in high-voltage DC cable insulation. This study investigates the effect and mechanism of SiO2 with a DDS surface hydrophobic treatment on space charge suppression and the electrical properties of PP composites. The PP matrix was doped with SiO2 nanostructures, both with a DDS surface hydrophobic treatment and untreated as a control group. The functional group structure and dispersion of nanostructured SiO2 in the matrix were characterized. The findings reveal that the incorporation of SiO2 nanostructures effectively mitigates charge accumulation in PP composites. However, a high concentration of unsurfaced nanostructures tends to agglomerate, resulting in inadequate space charge suppression and a diminished DC breakdown field strength. Nonetheless, surface treatment improves the dispersion of SiO2 within the matrix. Notably, the composite containing 1.0 wt% of surface hydrophobic SiO2 exhibits the least space charge accumulation. Compared to the base material PP, the average charge density is reduced by 83.9% after the 1800 s short-circuit discharges. Moreover, its DC breakdown field strength reaches 3.45 × 108 V/m, surpassing pure PP by 19.4% and untreated SiO2/PP composites of the same proportion by 24.0%.

Value Of Anteroposterior-To-Transverse Ratio in Ultrasonic Diagnosis of Thyroid Nodule in Different Locations.

PURPOSE: To investigate the value of anteroposterior-to-transverse ratio (ATR) and the effect on features of nodules in ultrasound (US) diagnosis of thyroid nodules in different locations.  Methods: The nodules were divided into three groups according to the different nodule location: isthmus group; upper and lower poles of bilobed thyroid group; and the middle of the bilobed thyroid group. The diameters of the nodules were recorded, and ATR of the nodule was calculated on the transverse and longitudinal sections. The transverse and the longitudinal sections of ATR of thyroid nodules in different groups were compared.  Result: The transverse section of ATR was significantly different among the three groups (p = 0.001). In addition, there are significant differences in many US features among three groups, including nodule composition, thyroid parenchyma, morphology, echogenicity, shape, calcifications, vascularity, nodule ACR TI-RADS and histopathologic (all p < 0.05). In the group of upper and lower poles of bilobed thyroid, significant difference was found between the transverse and the longitudinal section of ATR (p = 0.019). The cut-off values of transverse section and longitudinal section of ATR were 0.967 and 0.750, respectively.  Conclusion: The transverse section of ATR at different location of thyroid may be a predictor for malignancy with clinical diagnostic significance.

Myopia of primary school students in Suqian before and after COVID-19 epidemic / 中国学校卫生

Objective@#To compare myopia prevalence among primary school students in Suqian before and after COVID-19 epidemic, so as to provide a reference for prevention and scientific propaganda of myopia.@*Methods@#Mass sampling was conducted for pupils from 39 primary schools in Suqian during 2019-2020 for ophthalmic examination, including measurement of uncorrected visial acuity and noncycloplegic refractometry. The data of 76 823 and 76 039 students aged 6 to 12 years were statistically analyzed, and the differences of myopia prevalence in two years were compared under different demographic characteristics.@*Results@#The myopic rate before and after the epidemic was 30.2% and 36.9%, respectively.The two examinations all obtained that the myopic rate increased with age, the myopic rate of girls (32.3%, 40.0%) was higher than that of boys(28.3%, 34.2%), and the myopic rate of urban students(34.3%, 41.5%) was higher than that of rural students( 26.5 %, 32.2%). The myopic rate increased significantly at all ages, with students aged 9 to 11 accounted for the most(by 8.6 to 10.7 percentage point), the myopic rate by genders and areas increased significantly, among which female and urban students increased the most(7.7, 7.2 percentage point).@*Conclusion@#After the epidemic, the myopic rate was 1.2 times that of 2019. The myopic rate increased significantly under different demographic characteristics.The myopic situation was not optimistic.

Changes of awareness of tuberculosis and access to tuberculosis-related information among students in Zhejiang Province in the year of 2014 and 2018 / 中国学校卫生

Objective@#To explore the changes of awareness of tuberculosis and access to tuberculosis-related information among students in Zhejiang Province.@*Methods@#There were 554 students younger than 30 y were included in the study during April to sept. of 2014 and during sept. to Nov. of 2018. Univariate and multivariate Logistic regression were conducted to find the related factors of knowing about tuberculosis and related knowledge. Chi-square test was used to analyze the changes of ways access to tuberculosis-related information.@*Results@#There were 440 participants (79.4%) aware of tuberculosis, including 215(85.7%) in 2014 and 225(74.3%) in 2018. The factors affecting awareness on tuberculosis were female ( AOR=1.60, 95%CI =1.04-2.47) vs male; and junior middle school( AOR=1.99, 95%CI =1.03-3.85), high school( AOR=3.27, 95%CI =1.57-6.81), college or higher ( AOR=6.73，95%CI =2.55-17.76) vs primary school or lower; year 2018 ( AOR=0.50, 95%CI =0.31-0.80) vs 2014. There was no significant statistical difference in the overall knowledge scores of tuberculosis between the students in the two surveys. In 2018, the proportion of tuberculosisrelated information accessed from the Internet (forum, WeChat, Weibo.) and community activities (assembly promotion)(75.10%, 26.70%) was higher than that of 2014(36.20%, 13.10%)( χ 2=68.88, 12.79, P <0.05).@*Conclusion@#The proportion of students aware of tuberculosis and TB control in Zhejiang Province were not significantly improved. Higher proportion of students get tuberculosis-related information from the new media. Therefore, it is necessary to strengthen health education of tuberculosis in schools, especially through the usage of new media apart from traditional pathways.