Boron/nitrogen pairs Co-doping in metallic carbon nanotubes: a first-principle study

By using the first-principles calculations, the electronic structure and quantum transport properties of metallic carbon nanotubes with B/N pairs co-doping have been investigated. It is shown that the total energies of metallic carbon nanotubes are sensitive to the doping sites of the B/N pairs. The energy gaps of the doped metallic carbon nanotubes decrease with decreasing the concentration of the B/N pair not only along the tube axis but also around the tube. Moreover, the I--V characteristics and transmissions of the doped tubes are studied. Our results reveal that the conducting ability of the doped tube decreases with increasing the concentrations of the B/N pairs due to symmetry breaking of the system. This fact opens a new way to modulate band structures of metallic carbon nanotubes by doping B/N pair with suitable concentration and the novel characteristics are potentially useful in future applications.     

酱鸭加工过程中肌肉质构特性和蛋白降解的变化

酱鸭加工过程(盐腌、酱制、收汁、灭菌)中质构特性(硬度、弹性)和肌肉蛋白(肌浆蛋白、肌原纤维蛋白)降解的变化规律。结果表明:在盐腌过程中,鸭肉硬度呈现先升高后降低趋势,盐腌6h硬度最高,12h硬度最低;盐腌过程中的弹性总体呈下降趋势,腌制9h后弹性最低。酱制、收汁、灭菌过程鸭肉硬度明显高于盐腌过程,在酱制阶段,硬度变化不显著,经过灭菌后的酱鸭硬度有所下降;该过程中的鸭肉弹性低于盐腌过程,变化不显著。SDSPAGE电泳分析显示:在盐腌阶段,鸭肉肌原纤维蛋白中的α-肌动蛋白素条带比较稳定,其余的肌原纤维蛋白和肌浆蛋白均发生着不同程度的降解;而经过酱制、收汁、灭菌后,肌原纤维蛋白条带变少,肌浆蛋白中原先的蛋白条带消失,出现了一些新的蛋白条带。从盐腌开始到酱制结束,非蛋白氮含量下降,灭菌后含量增加;鸭肉重量在加工过程中下降,特别是经过0.5h的酱制后,鸭肉重量显著降低。     

高压相BeO晶体的电子结构和光学性质

应用基于密度泛函理论的第一性原理研究方法,考虑广义梯度近似(GGA)下的交换关联势,模拟计算了高压下纤维锌矿(WZ)、闪锌矿(ZB)和岩盐(RS)结构氧化铍(BeO)晶体的电子结构和光学性质等.计算结果表明,随着压力的增加,同种结构下原子间的键长和电荷转移有所减小,并且价带和导带分别向低能和高能方向移动,禁带展宽.与常压下的BeO相比,随着压力的增加,三种结构的BeO晶体的光学性质有一定的变化,介电函数、吸收系数、折射率以及电子能量损失谱曲线出现更多的精细结构,峰的数量增多;各高压相结构的吸收谱和能量损失谱宽度逐次展宽;吸收系数曲线的吸收峰及其位于低能区域的吸收边以及电子能量损失谱峰的位置均发生一定程度的蓝移.     

A simple Scheme for Generating an n-Qubit W State in a Trapped-Ion System without a Lamb-Dicke Limit

A simple and scalable scheme is proposed to generate a n-qubit W state in a trapped-ion system without the Lamb-Dicke limit. The n-qubit W state can be generated by the interaction between the ions and the laser field if the collective mode is initially prepared in the single-phonon state and each ion is in the ground state. The scheme only requires a single laser and avoids laser manipulation of the individual ion. The time required to complete the process decreases with the number of ions. The present scheme is not limited to small values of the LD parameter, which greatly enhances operation speeds.     

简易OMA系统光响应参数的测量

用一维CCD摄像头、多色仪及通用微机组成了简易价廉的光学多道分析仪系统（OMA），测量了该系统的光响应参数，对测量结果进行了讨论。     

含氮氟化类金刚石(FN-DLC)薄膜的研究:(Ⅰ)sp结构与化学键分析

以CF4,CH4和N2为源气体,利用射频等离子体增强化学气相沉积法,在不同功率下制备了含氮氟化类金刚石膜.用俄歇电子能谱、拉曼光谱、X射线光电子能谱和傅里叶变换红外光谱对薄膜的电子结构和化学键进行了表征,并结合高斯分峰拟合方法分析了薄膜中sp2,sp3结构比率.结果表明,制备的薄膜属于类金刚石结构,不同沉积功率下,薄膜内的sp2/sp3值在2.0—9.0之间,随着沉积功率的增加薄膜内sp2的相对含量增加.膜内主要有C—Fx(x=1,2),C—C,CC和CN等化学键.沉积功率增加,C—C基团增加,膜内F的浓度降低,C—F基团减少,薄膜的关联加强,稳定性提高.     

一维长程关联无序系统中的电子态

利用傅里叶滤波法在一维Anderson无序系统中产生了具有幂律谱密度公式s(q)∝q^-p形式的长程关联随机能量序列，并利用传输矩阵方法计算了系统中引入了长程关联后的局域长度，同时应用负本征值理论对系统中的电子态密度进行了分析，并分别把计算结果与系统中不具有长程关联时的局域长度与电子态密度进行了比较.结果表明，长程幂律关联的引入对电子态的性质产生了很大的影响，当关联指数p≥2.0时，在系统能带中心范围内发生了部分局域态向退局域态的转变，而同时电子态密度也发生了很大的变化，出现了六个范霍夫奇点，系统的能带范围也相应地得到展宽. 关键词： 无序系统 长程关联 局域长度 电子态密度     

含氮氟化类金刚石(FN-DLC)薄膜的研究：(Ⅱ)射频功率对薄膜光学带隙的影响

以CF₄,CH₄和N₂为源气体，采用射频等离子体增强化学气相沉积法，在不同射频功率下制备了含氮氟化类金刚石薄膜样品.原子力显微形貌显示，低功率下沉积样品表面致密均匀.拉曼及傅里叶变换红外光谱分析显示，随着射频功率的改变，薄膜的结构和组分也随之变化.紫外-可见光透射光谱证明薄膜具有紫外强吸收特性，通过计算得到其光学带隙在1.89—2.29 eV之间.结果表明，射频功率增加，薄膜内sp²C含量增加，或者说C=C交联相对浓度增加、F的相对浓度降低，导致薄膜内π-π^*带边态密度增大，光学带隙减小. 关键词： 含氮氟化类金刚石薄膜 射频功率 光学带隙     

氮分压对氮化铜薄膜结构及光学带隙的影响

在不同的氮分压r(r=N₂/［N₂+Ar］)和射频功率P下，使用反应射频磁控溅射法，在玻璃基片上制备了氮化铜薄膜样品.用台阶仪测得了薄膜的厚度，用原子力显微镜、X射线衍射仪、紫外-可见光谱仪对薄膜的表面形貌、结构及光学性质进行了表征分析.结果表明，薄膜的沉积速率随P和r的增加而增大.薄膜表面致密均匀，晶粒尺寸为30nm左右.随着r的增加，薄膜颗粒增大，且薄膜由(111)晶面转向(100)晶面择优生长.薄膜的光学带隙E_g在1.47—1.82eV之间，随r的增加而增大. 关键词： 氮化铜薄膜 反应射频磁控溅射 晶体结构 光学带隙     

Electronic Transport in Molecular Junction Based on C20 Cages

Choosing closed-ended armchair （5, 5） single-wall carbon nanotubes （CCNTs） as electrodes, we investigate the electron transport properties across an all-carbon molecular junction consisting of C20 molecules suspended between two semi-infinite carbon nanotubes. It is shown that the conductances are quite sensitive to the number of C20 molecules between electrodes for both configuration CF1 and double-bonded models： the conductances of C20 dimers are markedly smaller than those of monomers. The physics is that incident electrons easily pass the C20 molecules and are predominantly scattered at the C20-C20 junctions. Moreover, we study the doping effect of such molecular junction by doping nitrogen atoms substitutionally. The bonding property of the molecular junction with configuration CF1 has been analysed by calculating the Mulliken atomic charges. Our results have revealed that the C atoms in N-doped junctions are more ionic than those in pure-carbon ones, leading to the fact that N-doped junctions have relatively large conductance.