ABSTRACT
Objective@#To investigate the status and trend of low vision of junior and senior high school students in Beijing from 2009 to 2018, and to provide evidence for myopia prevention.@*Methods@#Data came from the results of physical examination of eyesight in 2009-2018 in Beijing, which were cdlected among juncor and senior high school students in March every year. Detection rate of low vision of students and the difference across different districts and counties were analyzed.@*Results@#From 2009 to 2018, the rate of low vision of high school and college entrance examination students in Beijing was on the rise, with the average rate of low vision of 86.07% and 76.36% respectively. Similar trend was found in the rate of high myopia(16.39% and 18.64%,respectively), while that of light and medium myopia tends to be stable. The highest rate of low vision among junior middle school students was in Xicheng (84.75%) District and Chaoyang District (84.03%), and for high middle school students,the highest rate of myopia was found in Fengtai District (91.17%) and Dongcheng District (89.92%).@*Conclusion@#In Beijing, the detection rate of low vision of middle school and college entrance examination students increased steadily, especially the high myopia. The health education of eyesight protection is of great significance to students. It is necessary to strengthen the extensive intervention of eyesight protection in middle and college entrance examination students.
ABSTRACT
The generally thought unstable diol compound tetrazyl gem-diol (1, H2DTMdiol·2H2O), was firstly obtained in crystalline form by culturing the filtrate for ten days after acidification and filtration of aqueous solution of potassium salt of ketone (2, [K(HDTMone)·2H2O]n). The stability of this novel gem-diol compound is found owning to the hydrogen bonds with lattice water molecules and electrophilic tetrazolyl groups. Meanwhile, the undissolved ketone (3, H2DTMone) was separated during the filtration in the process of gem-diol compound production. Surprisingly, the crystal-to-crystal perfect transition phenomena from gem-diol (1) to ketone (3) were firstly observed after heating up to 120 °C as evidenced by X-ray single crystal diffraction and powder X-ray diffraction. These results found here might open new revenues for methylene oxidation and alkanediol chemistry.
