Tuning of optical resonances in asymmetric microtube cavities

We tune optical resonances in rolled-up SiO/SiO(2) microtube cavities by gradually modifying the tube structure through asymmetrical postdeposition of SiO(2). Spectral blueshifts followed by redshifts of the resonant modes are observed in a thin-walled microtube (tube-I), which is attributed to a competition between shape deformation and effective increase of tube wall thickness. In contrast, only a monotonic redshift is detected when asymmetrical deposition is performed on a thick-walled microtube (tube-II). Distinct wavelength-dependent tuning was revealed in both kinds of tubes. Numerical calculations based on perturbation theory are carried out to explain and confirm the experimental results.     

一种新颖的稀土-2-羟基烟酸的配合物的结构和光谱性质研究

通过水热反应合成了一种新颖的稀土2-羟基烟酸的配合物{[LaL(HL)(H2O)3]1/3(SO4)2/3(H3O)2H2O}(H2L=2-hydroxynicotinic acid)。X-ray单晶衍射分析可知,2-羟基烟酸通过羧基O和羟基O原子桥连La离子,形成二维层状结构,层与层之间通过弱作用力拓展为三维结构。二维相关光谱分析表明N—H面外弯曲振动和C—H面外弯曲振动对磁微扰比较敏感,这可能是吡啶环上π电子云在磁微扰下变形引起C—H和N—H面外弯曲振动的响应,SO24-的ν4振动和羧基不对称伸缩振动对磁微扰也比较敏感;热微扰下N—H伸缩振动比较敏感。此外还对化合物进行了紫外和热重分析。     

近红外光谱结合ELM快速检测固态发酵过程参数pH值

pH值是固态发酵过程关键参数之一,为此提出基于近红外光谱技术的秸秆蛋白饲料固态发酵过程参数pH值检测方法。利用近红外光谱系统获取140个固态发酵过程产物样本在10 000～4 000cm-1范围内的近红外光谱数据,通过酸度计测得近红外光谱预测模型的参考测量值;运用ELM算法建立pH值的预测模型,在模型建立过程中由交互验证法确定最佳主成分因子数和ELM网络隐含层节点数。试验结果显示:最佳ELM网络模型的拓扑结构为10-40-1,模型预测集相关系数(Rp)和预测均方根误差(RMSEP)分别为0.961 8和0.104 4。研究结果可为固态发酵过程参数的在线检测提供技术基础。     

Multiple-beam Ramsey interference and quantum decoherence

We study the effect of photon scattering from a path of a four-beam atomic interference setup, which is based on a cesium atomic beam and two subsequent optical Ramsey pulses projecting the atoms onto a multilevel dark state. While in two-beam interference, any attempt to keep track of an interfering path reduces the fringe contrast, we demonstrate that photon scattering in a multiple-path arrangement cannot only lead to a decrease, but - under certain conditions - also to an increase of the interference contrast. The results are confirmed by a density-matrix calculation. We are aware that in all cases the “which-path” information carried away by the scattered photons leads to a loss of information that is contained in the atomic quantum state. An approach to quantify this “which-path” information using observed fringe signals is presented; it allows for an appropriate measure of quantum decoherence in multiple-path interference. Received: 27 July 2000 / Published online: 6 December 2000     

Tuning spin-filtering,rectifying, and negative differential resistance by hydrogenation on topological edge defects of zigzag silicene nanoribbons

By first-principles calculations, we propose three heterojunction nanodevices based on zigzag silicene nanoribbons with different edge-hydrogenated topological line defects. The devices all present excellent spin-filtering properties with 100% spin polarization as well as remarkable rectifying effect (with rectification ratio around 10²) and negative differential resistance behaviors. Our findings shed new light on the design of silicon-based nanodevices with intriguing spintronic applications.     

EFFECTS OF CONSTRAINTS ON LIE SYMMETRIES AND CONSERVED QUANTITIES OF A BIRKHOFF SYSTEM

After a Birkhoff system is restricted by constraints, the determining equations, the Lie symmetries, the structure equation and the form of conserved quantities corresponding to the Lie symmetries will change. Some Lie symmetries will disappear and under certain conditions some Lie symmetries will still remain present. The condition under which Lie symmetries and conserved quantities of the system will remain is given.     

K-Pb-Tl-O复合氧化物的合成和电子结构的XPS研究

用熔盐阳极电沉积法合成了导电的复合氧化物K-Pb-Tl-O晶体.这些晶体具有纳米尺寸层状结构.用XPS对其进行了表征,并与相关的化合物进行了比较.实验表明,氧化物中的Pb和Tl都以高价态的单一价态存在,但电子结合能比相应的非导电低价化合物的低.该文用原子外弛豫效应解释了复合氧化物中的Pb和Tl的结合能的反常现象.讨论了它们的价电子结构与导电性的关系.     

基于天然氨基酸的双环手性季铵盐相转移催化剂的合成及催化性能研究

以L－脯氨酸及L－羟基脯氨酸为原料合成了4个新型手性季铵盐磁相转移催化 剂，并用于催化不对称查耳酮环氧化反应，高产率得到相应环氧化合物，ee最高达 9％。     

软珊瑚Sinularia sp.中次生代谢产物的结构鉴定

细胞毒性;软珊瑚Sinularia sp.中次生代谢产物的结构鉴定     

基于发光铜纳米团簇的多组分体系的构成及应用

铜纳米团簇(copper nanoclusters,Cu NCs)具有独特而优异的光物理性质,近年来在发光领域取得了令人瞩目的研究进展。然而,由于铜易氧化,因而难以获得结构稳定、发光强度高的Cu NCs。将Cu NCs与其他组分结合构建多组分体系,是提高稳定性、优化发光性能的可行策略之一。基于Cu NCs构筑的多组分体系,不仅能够有效弥补其缺陷和不足,而且还能实现发光体系的功能多样化,从而有助于促进该发光材料的实际应用。基于此,本文对该领域的研究进行了综述,首先介绍了CuNCs的基本结构和发光影响因素,进而分类总结了目前发光Cu NCs多组分体系的构成策略及其应用。