彰显几何直观魅力,培养数学学科核心素养--以人教版教材"线段的垂直平分线的性质"为例

如何在课堂教学中让数学学科核心素养落地,是每一位数学教师关注和思考的主题.笔者以人教版教材八年级上册"13.1.2线段的垂直平分线的性质"的教学片段为例,谈谈在初中几何教学中突出几何直观,培养核心素养的教学尝试,与同行交流.     

Electrospun fluorescein/polymer composite nanofibers and their photoluminescent properties

Fluorescein/polyvinyl pyrrolidone (PVP) composite nanofibers with different fluorescein loadings (with a weight concentration of 0-5.0%) are fabricated via electrospinning. Morphologies, structures and photoluminescent (PL) properties of these straight, helical or wavelike fibers are characterized by scanning electron microscopy (SEM), fluorescence microscopy and a spectrophotometer. It is found that the maximum emission of the as-spun fluorescein/PVP fibers occurs at 510 nm. The PL intensity of the composite fiber increases with fluorescein concentration, then fluorescence quenching appears when the concentration reaches 1.67%. The mechanism of fluorescence quenching of fluorescein is discussed. In addition, the composite fibers exhibit a much stronger PL intensity than fluorescein/PVP bulk film owing to larger specific surface area, which makes them promising materials for biomedical applications such as probes and sensors.