锯齿型石墨烯带缺陷改性方法研究

采用基于密度泛函理论的非平衡格林函数, 对具有不同缺陷构型的锯齿型石墨烯带(zigzag graphene nanoribbon, ZGNR) 的输运性质进行了理论计算与模拟. 研究表明, 相同数目、 不同构型缺陷结构对ZGNR的导电特性将产生不同的影响. 如A-B构型双空缺对ZGNR电导的影响最为显著, 而A-A构型双空缺对其电导的影响最小. 更为重要的是, 当引入碳环构型缺陷时, ZGNR将被改性, 即由原本的金属性质转变为半导体性质, 为缺陷调控石墨烯导电特性提供了理论依据.     

基于AFM的药物刺激前后淋巴瘤活细胞的形貌及弹性的变化

原子力显微镜(AFM)的发明为研究单个活细胞的形貌结构及物理特性提供了新的技术手段.然而,由于缺少合适的固定方法,利用AFM对动物悬浮活细胞的形貌进行高分辨率成像还面临着巨大的挑战.本文提出一种基于微柱阵列和静电吸附相结合的动物悬浮细胞固定方法.通过微柱阵列的机械钳制和多聚赖氨酸的静电吸附实现了对单个淋巴瘤B细胞的固定,并在此基础上利用AFM动态观测了不同浓度Rituximab刺激下淋巴瘤B细胞的表面形貌及弹性的变化.经过0.2 mg·mL-1的Rituximab刺激2 h后,细胞表面的褶皱增加,细胞的杨氏模量从196 kPa减小到183 kPa.经过0.5 mg·mL-1的Rituximab刺激2 h后,细胞形貌发生显著变化并出现突起结构,细胞的杨氏模量从234 kPa减小到175 kPa.实验结果表明淋巴瘤细胞形貌和弹性变化的幅度随着Rituximab刺激浓度的增加而增加,加深了对Rituximab作用效果的认识.     

针对电子极化子迁移的哈伯德U修正受限密度泛函理论方法：TiO2实例研究

极化子的形成和迁移对过渡金属氧化物的物理和化学性质有重要影响. 含哈伯德$U$修正的密度泛函理论和受限密度泛函理论方法经常被应用于小极化子迁移性质的理论研究. 本文在投影缀加波框架中实现了哈伯德$U$修正的受限密度泛函理论(cDFT+U),并将其应用于体相TiO₂中的极化子迁移性质的计算. 确认了哈伯德U的取值对极化子性质的理论预测有重要影响. 采用基于cDFT计算所获得的哈伯德U值,可对TiO₂金红石和锐钛矿相中的极化子性质获得与实验符合很好的描述. 本文表明,使用与理论上一致的方式计算获得的哈伯德U值,cDFT+U有望成为一种有效的不需经验输入而计算过渡金属氧化物极化子性质的第一性原理方法.     

Effect of f-c hybridization on the $\gamma\to \alpha$ phase transition of cerium studied by lanthanum doping

The hybridization between the localized 4f level (f) with conduction (c) electrons in $\gamma $-Ce upon cooling has been previously revealed in single crystalline thin films experimentally and theoretically, whereas its influence on the $\gamma \to \alpha $ phase transition was not explicitly verified, due to the fact that the phase transition happened in the bulk-layer, leaving the surface in the $\gamma $ phase. Here in our work, we circumvent this issue by investigating the effect of alloying addition of La on Ce, by means of crystal structure, electronic transport and angle resolved photoemission spectroscopy measurements, together with a phenomenological periodic Anderson model and a modified Anderson impurity model. Our current researches indicate that the weakening of f-c hybridization is the major factor in the suppression of $\gamma \to \alpha $ phase transition by La doping. The consistency of our results with the effects of other rare earth and actinide alloying additions on the $\gamma \to \alpha $ phase transition of Ce is also discussed. Our work demonstrates the importance of the interaction between f and c electrons in understanding the unconventional phase transition in Ce, which is intuitive for further researches on other rare earth and actinide metals and alloys with similar phase transition behaviors.     

Planning and control of 3-D nano-manipulation

The use of atomic force microscope (AFM) as a nanomanipulator has been evolving for various kinds of nano-manipulation tasks. Due to the bow effect of the piezo scanner of the AFM, the AFM space is different from the Cartesian space. Traditional nanomanipulation based on AFM is only a 2-D operation and does not consider the bow effect of the piezotube. In this paper, different 3-D nanomanipulation tasks using AFM such as nanolithography, pushing and cutting have been discussed. 3-D path planning is performed directly in the AFM space and the 3-D paths are generated based on the 3-D topography information of the surface represented in the AFM space. This approach can avoid the mappings between the AFM space and Cartesian space in planning. By following the generated motion paths, the tip can either follow the topography of the surface or move across the surface by avoiding collision with bumps. Nanomanipulation using this method can be considered as the “true“ 3-D operations since the cantilever tip can be controlled to follow any desired 3-D trajectory within the range of AFM space. The experimental study shows the effectiveness of the planning and control scheme.     

三角级数的解析求解与应用

利用欧拉公式,将三角级数可以转化为幂级数,进而利用泰勒展开等手段,得到幂级数的收敛函数．利用三角函数的周期性,还可以得到一些级数的解析结果．通过几个例题,可以加深对此类问题的理解．