第一性原理计算锐钛矿型TiO2电子结构及力学性能分析

 基于第一性原理中的密度泛函理论，采用CASTEP程序包，计算分析了锐钛矿型TiO2的能带结构、电子态密度和弹性常数等性能参数. 结果表明，锐钛矿型TiO2 属间接带隙半导，最小能隙为2.2eV. Ti和O之间存在明显的电子转移现象，电子分布具有强烈的定域性，但由于存在杂化现象，Ti-O键还表现出部分共价键特征. 在四方晶系中，这种离子键和共价键混合的网络状复合键结构使材料表现出大的体积弹性模量204.44GPa，由于在TiO2晶体结构中，滑移系统较少，材料断裂时突凸显脆性，韧性差，剪切模量相对较小为64.71GPa.

IMMUNE EFFECTS OF CORDYCEPS MILITARIS MYCELIA ON MACROBRACHIUM ROSENBERGII

The Macrobrachium rosenbergii were fed with feedstuffs which contain 1%, 2%, 3% Cordyceps militaris mycelia. The results show that Cordyceps militaris mycelia can increase the phenoloxidase(PO) activity in serum, the superoxide dismutase(SOD) activity, glutathione peroxidase(GSH-Px) activity and decrease malondialdehye(MDA) concentration in muscle. The infection experiments show that Cordyceps militaris mycelia can significantly decrease the death rate of Macrobrachium rosenbergii which are infected with Aeromonas hydrophila.