Propylene Polymerization Catalyzed by Bis(R_3-indenyl) Zirconium Dichloride/Aluminoxane──Synthesis of Metallocenes and Influence ofSolvent Polarity on Polymerization

Three unbridged metallocenes, bis(2,4,7-Me3-indenyl)zirconium dichloride(1) , bis(2-Me-4, 7-Et2-indenyl)zirconium dichloride (2) and bis (2, 4, 6-Me3-indenyl) zirconium dichloride (3) were synthesized. The effect of solvent polarity on propylene polymerization catalyzed by the metallocenes in the presence of methylaluminoxane(MAO) and triisobutylaluminum(TIBA) was investigated in the toluene/CH2Cl2 mixed solvent. Changing the solvent polarity was found to influence the catalytic activity, polymer molecular weight and stereospecificity of the catalysts. The changes in the position of the substituents on the ligand caused the different responses of the catalyst to the changes in solvent polarity. The isotactic stereosequence of polypropylene was found to increase with the increase in the polarity of the reaction medium.     

自适应超静定桁架结构强度控制的研究

以超静定桁架结构为背景研究了自适应结构的承载能力,探讨作动器和杆单元的共同工作,用以进行结构分析和控制结构承载能力,后者意指通过作动器的主动变形调控结构的内力分布以获得更加合理的工作状态。     

红外焦平面阵列非线性校正曲线测量方法

针对红外焦平面阵列强度响应的非线性失真现象,本文提出了一种基于单波长激光器测定红外焦平面阵列非线性校正曲线的方法,设计出用于测量的实验装置,并通过实验研究获得了实测的非线性校正曲线。结果表明,该方法规避了红外焦平面阵列光谱响应不均匀性的影响,满足了装置器件在工程技术中通用性和实用性的需要,在简单易行的同时保证了较高的测量精度。     

熔石英再沉积层结构的纳米级表征和杂质分析

利用原子力显微镜观察熔石英不同蚀刻时间的表面形貌,结合二次离子质谱分析,研究了熔石英的再沉积层结构和杂质分布。结果表明,熔石英表面深度10nm的再沉积层内存在大量微裂纹和杂质,经蚀刻展开形成nm级划痕和坑点,其分布随着深度增加呈指数衰减。根据nm级划痕密度、宽深比随蚀刻深度变化的规律,估算出再沉积层厚度,估算结果与二次离子质谱测得的杂质嵌入深度基本一致。杂质元素嵌入深度与抛光微裂纹分布特征的关联性表明,杂质很有可能藏匿在抛光微裂纹中。     

Preliminary Frequency Comparison of Two 40^Ca^＋ Optical Frequency Standards

Frequency comparison is one of the most efficient ways to evaluate the performance of a frequency standard. Based on the pre-existing 40^Ca＋ optical frequency standard, we set up the second 40^Ca^＋ optical frequency standard, which has been improved in the materials and structure of ion traps for better control of the magnetic field. After the compensation, the residual magnetic field at the position of the ion is adjusted to be～500nT with a long time jitter of～10nT, which is better than the pre-existing 40^Ca^＋ optical frequency standard. We realize the ＇4-point-closed-loop locking＇ on the second 40^Ca＋ optical frequency standard after a series of preparatory works. Through half an hour of measurement time, the two frequency standards exhibited a stability of 2.1 × 10^-13.τ^1/2 and a relative frequency difference of 1.5 （2.9）Hz.     

Mimetic Preparation of Analogues of Territrem B, A Potent Acetylcholinesterase Inhibitor

One of the strategies of bettering Alzheimer's Disease is focused on cholinergic compound based on the cholinergic hypothesis1. An important approach to cholinergic augmentation is administration of cholinesterase inhibitors such as Huperzine A2. Territrem B is a potent AChE inhibitor (IC50 47 nM, H. Zea AchE)3, and its inhibitory mechanism is totally different with the known AChE inhibitors4. In the last report we have described three routes of synthesizing Territrem B analogues, whic…     

红外焦平面阵列非线性校正曲线测量方法

针对红外焦平面阵列强度响应的非线性失真现象,本文提出了一种基于单波长激光器测定红外焦平面阵列非线性校正曲线的方法,设计出用于测量的实验装置,并通过实验研究获得了实测的非线性校正曲线。结果表明,该方法规避了红外焦平面阵列光谱响应不均匀性的影响,满足了装置器件在工程技术中通用性和实用性的需要,在简单易行的同时保证了较高的测量精度。     

Transient competition between photocatalysis and carrier recombination in TiO_2 nanotube film loaded with Au nanoparticles

Highly ordered TiO2 nanotube array(TNA) films are fabricated by using an anodic oxidation method. Au nanoparticles(NPs) films are decorated onto the top of TNA films with the aid of ion-sputtering and thermal annealing. An enhanced photocatalytic activity under ultraviolet C(UVC, 266 nm) light irradiation is obtained compared with that of the pristine TNA, which is shown by the steady-state photoluminescence(PL) spectra. Furthermore, a distinct blue shift in the nanosecond time-resolved transient photoluminescence(NTRT-PL) spectra is observed. Such a phenomenon could be well explained by considering the competition between the surface photocatalytic process and the recombination of the photo-generated carriers. The enhanced UV photocatalytic activities of the Au–TNA composite are evaluated through photo-degradation of methyl orange(MO) in an aqueous solution with ultraviolet–visible absorption spectrometry. Our current work may provide a simple strategy to synthesize defect-related composite photocatalytic devices.