Purpose: To describe changes in the prevalence of visual impairment and glasses ownership with age and as associated with income and population density for visual impairment among rural and urban migrant Chinese students.Design: Meta-analysis of 12 cross-sectional, school-based studies conducted between 2012 and 2017.Setting: Rural and urban migrant schools in seven Chinese provinces.Participants: A total of 83 273 rural and urban migrant Chinese students aged 6–17 years.Results: Prevalence of visual impairment (uncorrected visual acuity ≤6/12 in either eye) rose from 19.0% at age 6 to 66.9% at 17, with the overall age-adjusted prevalence higher for girls (35.8%) than for boys (30.1%, p<0.001). The rate of glasses ownership among students who needed them increased from 13.0% at age 6 to 63.9% (p<0.001) at 17 and was significantly higher for girls (37.0%) than boys (34.7%, p<0.001). The unmet need for glasses as a proportion of the student population peaked in junior high school (31.8%). A 1% increase in per capita gross domestic product was associated with a 4.45% rise in uncorrected visual acuity (R²=0.057, p=0.020). Population density was significantly associated with glasses ownership among children (R²=0.359, p=0.012). A 1% population density increase was associated with an increase in the glasses ownership rate of 6.83%.Conclusion: Efforts are needed to improve vision screening coverage in China’s schools, particularly junior high schools, as this is when many rural children leave school and glasses coverage is lowest.

A rich language environment is an important element of a nurturing home environment. Despite their proven importance, vocabulary and conversation have been shown to vary widely across households—even within the same socio-economic class. One significant gap in the existing literature is its nearly exclusive geographic focus on Western and developed settings, with little attention given to poorer communities in lower/middle income countries. The purpose of this study was to empirically illustrate the characteristics of the home language environment in the low SES, non-Western cultural setting of rural China. Using Language Environment Analysis (LENA) automated language-analysis system, this study measured the home language environment of 38 children aged 20-27 months in Northwest rural China. Our primary measures of the home language environment were Adult Word Count (AWC), Conversational Turn Count (CTC) and Child Vocalization Count (CVC). Multivariate linear regression models were used to examine the association between home language environment and family/child characteristics, and language skills (Measured by MacArthur-Bates Communicative Developmental Inventory score). In this paper, by comparison, we found that the home language environment of our rural sample fell far behind that of urban households. We also identify significant, positive correlations between language skills and both AWC and CTC. Our analysis finds no significant correlations between home language environment and family/child characteristics. In this paper, we present the first ever findings using the LENA system to measure the home language environment of young children from poor rural communities in China. We found that the home language environment of lower-SES household was significantly worse than high-SES households, and demonstrated the importance of the home language environment to language skills, pointing to a need for more high-quality studies of the home language environment in rural China to better understand possible mechanisms behind low levels of parent-child language engagement and ways to improve the home language environment.

Objective To estimate the effect of providing free spectacles on uncorrected visual acuity (VA) among urban migrant Chinese school children. Design Exploratory analysis from a parallel cluster-randomised clinical trial. Methods After baseline survey and VA screening, eligible children were randomised by school to receive one of the two interventions: free glasses and a teacher incentive (tablet computer if ≥80% of children given glasses were wearing them on un-announced examination) (treatment group) or glasses prescription and letter to parents (control group). The primary outcome was uncorrected logarithm of the minimal angle of resolution (LogMAR) VA at study closeout, adjusted for baseline uncorrected VA. Results Among 4376 randomly selected children, 728 (16.6%, mean age 10.9 years, 51.0% boys) at 94 schools failed VA screening and met eligibility criteria. Of these, 358 children (49.2%) at 47 schools were randomised to treatment and 370 children (50.8%) at 47 schools to control. Among these, 679 children (93.3%) completed follow-up and underwent analysis. Spectacle wear in the treatment and control groups was 68.3% and 29.3% (p<0.001), respectively. Uncorrected final VA for eyes of treatment children was significantly better than control children, adjusting only for baseline VA (difference of 0.039 LogMAR units, 95% CI: 0.008, 0.070, equivalent to 0.39 lines, p=0.014) or baseline VA and other baseline factors (0.040 LogMAR units, 95% CI 0.007 to 0.074, equivalent to 0.40 lines, p=0.020). Conclusion We found no evidence that spectacles wear worsens children’s uncorrected VA among urban migrant Chinese school children.

以多孔聚丙烯(PP)膜为原材料, 通过压缩气体膨化工艺和电晕极化方法成功制备出PP压电驻极体膜, 并研究了该功能膜的压电和声学性能. 结果表明PP压电驻极体膜厚度方向和横向的杨氏模量分别为1.4和480 MPa, 因此压电系数d33比d31和d32高2个量级以上, d33是该类压电膜压电效应的主要性能指标, 而 d31和d32可以忽略不计. PP压电驻极体膜的准静态压电系数d33在15-35 kPa的压强范围内具有良好的线性度. 在2-300 Hz的测试频率范围内, 300 Hz 下的d33是2 Hz下的81%, 这主要是由PP膜的杨氏模量随频率增大而增强引起的. 在100 Hz-100 kHz 的音频和超声波频率范围内, PP压电驻极体膜具有平坦的频响曲线; 在1 kHz下其开路电压灵敏度和压电系数d33分别为0.85 mV/Pa和164 pC/N.