锗薄膜透射光学二次谐波研究

本文采用固定入射角，改变入射光偏振方位角的方法从实验上了研究了锗薄膜的透射光学二次谐波产生及其变化规律，并从理论上推导了产生透射二次谐波的表达式，最后拟合求得描述面谐波电流的唯象参数ａ。     

BaZr(BO3)2:Eu的合成及发光性能研究

用硝酸盐热分解法成功制备了BaZr(BO3)2:Eu(Eu3+的掺杂量为摩尔分数5%)荧光材料,并研究了其在254及147 nm光束激发下的发光特性.254 nm光束激发下的发射主峰位于612 nm处,归属于Eu3+的5D0-7F2的电偶极跃迁,但在147 nm光束激发下的发射主峰位于592 nm处,归属于Eu3+的5D0-7F1的磁偶极跃迁.通过激发光谱分析,上述现象归因于在紫外激发下占据非对称格位Ba2+的Eu3+被优先激发,而在真空紫外激发下占据对称格位Zr4+的Eu3+被优先激发.结果表明BaZr(BO3)2:Eu并不适合作为等离子平板显示器用红色发光材料.     

Synthesis and characterization of well‐defined cyclodextrin‐centered seven‐arm star poly(ε‐caprolactone)s and amphiphilic star poly(ε‐caprolactone‐b‐ethylene glycol)s

Per‐2,3‐acetyl‐β‐cyclodextrin with seven primary hydroxyl groups was synthesized by selective modification and used as multifunctional initiator for the ring‐opening polymerization of ε‐caprolactone (CL). Well‐defined β‐cyclodextrin‐centered seven‐arm star poly(ε‐caprolactone)s (CDSPCLs) with narrow molecular weight distributions (≤1.15) have been successfully prepared in the presence of Sn(Oct)₂ at 120 °C. The molecular weight of CDSPCLs was characterized by end group ¹H NMR analyses and size‐exclusion chromatography (SEC), which could be well controlled by the molar ratio of the monomer to the initiator. Furthermore, amphiphilic seven‐arm star poly(ε‐caprolactone‐b‐ethylene glycol)s (CDSPCL‐b‐PEGs) were synthesized by the coupling reaction of CDSPCLs with carboxyl‐terminated mPEGs. ¹H NMR and SEC analyses confirmed the expected star block structures. Differential scanning calorimetry analyses suggested that the melting temperature (T_m), the crystallization temperature (T_c), and the crystallinity degree (X_c) of CDSPCLs all increased with the increasing of the molecular weight, and were lower than that of the linear poly(ε‐caprolactone). As for CDSPCL‐b‐PEGs, the T_c and T_m of the PCL blocks were significantly influenced by the PEG segments in the copolymers. Moreover, these amphiphilic star block copolymers could self‐assemble into spherical micelles with the particle size ranging from 10 to 40 nm. Their micellization behaviors were characterized by dynamic light scattering and transmission electron microscopy. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6455–6465, 2008     

氦,氖,氩气体压力对氖光谱和能级填充的影响

以＾２３８Ｐｕ为激发源，测量了不同压力下Ｎｅ、Ｈｅ－Ｎｅ、Ｈｅ－Ｎｅ－Ａｒ体系的氖光谱，并以此为基础计算了Ｎｅ的２ｐ＾５３ｐ的１０个２ｐ能级的辐射率Ⅰ、相对集居数Ｎ、填充率Ｗ，总结出相应的Ｎｅ压力、Ｈｅ压力和Ａｒ压力对Ｎｅ的５８５．２ｎｍ谱线强度和１０个２ｐ能级填充的影响规律。     

一类有迁移的SIS流行病模型

研究一类种群有迁移的流行病模型,得到了这类模型的基本再生数R0,证明了R0＜1无病平衡点是局部渐近稳定的,而当R0＞1时无病平衡点是不稳定的.进一步讨论了疾病持续存在与无病平衡点和地方病平衡点全局稳定的条件.     

Ab initio intermolecular potential-energy surface and microwave spectra for the Ne-OCS complex

An ab initio potential-energy surface for the Ne-OCS complex was calculated using the coupled-cluster singles and doubles with noniterative inclusion of connected triples [CCSD(T)] with a large basis set containing bond functions. The interaction energies were obtained by the supermolecular approach with the full counterpoise correction for the basis set superposition error. The CCSD(T) potential was found to have three minima corresponding to the T-shaped and the linear Ne-SCO and Ne-OCS structures. The two-dimensional discrete variable representation method was employed to calculate the rovibrational energy levels for five isotopomers Ne-OCS, (22)Ne-OCS, Ne-OC(34)S, Ne-O(13)CS, and Ne-(18)OCS. The calculated pure rotational transition frequencies for the vibrational ground state of the five isotopomers are in good agreement with the observed values. The corresponding microwave spectra show that the b-type transitions (deltaK(a)=+/-1) are significantly stronger than the a-type transitions (deltaK(a)=0).     

搭建紫外可见光谱仪并用于科普互动

搭建科普型可互动紫外可见光谱仪,将光谱仪的内部构造、光路和光学部件的作用展示出来,弥补了目前商业化仪器"黑盒子"的弊端。将搭建好的光谱仪与简易物理学光路和实际有色饮料样品有机结合,设计环环相扣的科普互动,展示出颜色、浓度和光之间的内在联系,可向不同人群科普化学在生活中的重要性以及分析仪器作为化学学科"放大镜"的必要性。     

Study on liquid scintillation technique for bioassay of plutonium

Simple, rapid and sensitive methods are very important for the bioassay of plutonium. In this work, modern liquid scintillation technique combined with selective extraction separation and / pulse decay discrimination were studied and evaluated for the bioassay of plutonium. After sample decomposition and partial evaporation, cyclohexanone and trialkylphosphine oxide (TRPO) were used for the separation of plutonium from matrix. Several different cocktails were tested for liquid scintillation analysis of urine samples. The minimum detectable activity (MDA) of this method was estimated to be 0.01 Bq/500ml urine with 100 minutes measuring time and 3 confident level.     

A New Fluorimetric Reagent for Determination of Trace Amounts of Europium

ＩｎｔｒｏｄｕｃｔｉｏｎＴｈｅｃｈｅｍｉｃａｌｐｒｏｐｅｒｔｉｅｓｏｆｒａｒｅ ｅａｒｔｈｅｌｅｍｅｎｔｓａｒｅｖｅｒｙｓｉｍｉｌａｒ ,ｃｏｎｓｅｑｕｅｎｔｌｙ ,ｉｔｉｓｄｉｆｆｉｃｕｌｔｔｏｄｅｔｅｃｔａｎｉｎ ｄｉｖｉｄｕａｌｉｏｎｉｎｔｈｅｉｒｍｉｘｔｕｒｅｓｏｗｉｎｇｔｏｔｈｅｉｎｔｅｒｆｅｒｅｎｃｅｏｆｏｔｈｅｒｒａｒｅ ｅａｒｔｈｅｌｅｍｅｎｔｓ .Ｄｕｅｔｏａｈｉｇｈｅｒｓｅｎｓｉｔｉｖｉｔｙａｎｄｓｅｌｅｃｔｉｖｉｔｙ ,ｆｌｕｏｒｉｍｅｔｒｉｃｍｅｔｈｏｄｓｏｆｒａｒｅ ｅａｒｔｈｅｌ…