B5N3 and B7N5 Monolayers with High Carrier Mobility and Excellent Optical Performance.

An ab initio evolutionary search algorithm was combined with density functional theory (DFT) calculations to predict a series of 2-D BxNy (1 < x/y ≤ 2). Particularly, B5N3 and B7N5 monolayers have sufficiently low formation enthalpy and excellent dynamic stability that make them promising for synthesis in experiments. Electronic structure calculations reveal that B5N3 and B7N5 monolayers possess an indirect band gap of 1.99 eV and a direct band gap of 2.40 eV, respectively. The calculated absorption coefficients for B5N3 and B7N5 monolayers are significantly improved in the low end of the visible region compared with that of 2-D h-BN. Moreover, our calculations reveal that both B5N3 and B7N5 monolayers have high electron carrier mobilities. The narrow band gaps, high carrier mobilities, strong near-ultraviolet absorption, and high synthesis possibility of B5N3 and B7N5 monolayers render them promising new materials for application in novel electronics and environmentally benign solar energy conversion.

[Establishment and application of school-based health promotion and intervention model of schistosomiasis in lake-type endemic area].

OBJECTIVE: To establish an intervention model of school health promotion, and apply it in developing "schistosomiasis-free schools". METHODS: At the pilot stage, all students of Henghu primary school and Banshan primary school in Xinjian County of Jiangxi Province were selected as experiment group and control group, respectively. A baseline survey covered knowledge and attitude on schistosomiasis control, water contact behaviors and Schistosoma japonicum infection rate. Two health promotion intervention models, i.e. "information communication + training of protection skill + reward & punishment" (model A, 1993-1999) and "information communication + behavior participation + encouragement" (model B, 2000-2007), were implemented in Henghu school. The effect of two models was compared by infection rate. At the application stage, all students of 8 schools in Xinjian County, Nanchang County, and Jinxian County were chosen for evaluation of the effectiveness of Model B with same methods and index. RESULTS: Before intervention there was no significant statistical difference on the passed rate of anti-schistosomiasis knowledge, correct rate of anti-schistosomiasis attitude, frequency of infested water exposure and the infection rate between Henghu and Banshan schools (P > 0.05). In Henghu school, the intervention showed significant effect on the scores of knowledge and attitude after one year (P < 0.01), raised from 9.0% and 55.1% before intervention to 94.4% and 98.9% after intervention, respectively. The frequency of infested water exposure and the infection rate significantly decreased from 14.6% and 13.5% before intervention to 1.9% and 2.3%, respectively (P < 0.01). In 2-7 years after intervention, there were only one or two schistosomiasis cases each year. At the application stage, no schistosomiasis cases were found among Model B target population in two successive years after intervention. CONCLUSION: The practice of Model B can be extended to other schools in endemic area to develop "schistosomiasis-free schools".