Poly（dA）h·poly（dT）结构的喇曼光谱和晶格动力学研究

我们成功地获得了溶液中 poly(d A)·poly(d T)的喇曼光谱 ,并利用晶格动力学方法对于异规模型进行了简正分析。根据势能分布矩阵 (PED)对每一个模式进行了指定。结果表明异规模型的简振频率和 poly(d A)·poly(d T)的喇曼光谱符合得相当好 ,这说明溶液中的 poly(d A)· poly(d T)完全有可能保留了固体纤维中的异规模型结构。     

三链核酸poly(U)·poly(A)·poly(U)主链的振动位移

基于三链核酸 poly(U)· poly(A)·poly(U)的螺旋对称性 ,利用晶格动力学方法 ,计算了三链核酸分子 poly(U)·poly(A)·poly(U)主链振动的本征矢 ,探讨了振动位移矢量和线二色光谱的关系。结果表明 ,对应着磷酸双氧的反对称振动谱线可以用于直接确定磷酸根的取向 ,精度大约为 1°。其他谱线必须通过对分子的简正分析来帮助确定分子的结构。     

Poly(dA)·poly(dT)结构的喇曼光谱和晶格动力学研究

我们成功地获得了溶液中poly(dA)·poly(dT)的喇曼光谱,并利用晶格动力学方法对于异规模型进行了简正分析.根据势能分布矩阵(PED)对每一个模式进行了指定.结果表明异规模型的简振频率和poly(dA)·poly(dT)的喇曼光谱符合得相当好,这说明溶液中的poly(dA)·poly(dT)完全有可能保留了固体纤维中的异规模型结构.     

三螺旋DNA分子poly(dT)·poly(dA)·poly(dT)的构型和振动谱

我们计算了ｐｏｌｙ（ｄＴ）·ｐｏｌｙ（ｄＡ）·ｐｏｌｙ（ｄＴ）的Ｈｏｗａｒｄ模型的原子笛卡尔坐标，并利用晶格动力学方法对模型进行了简正分析。结果发现其０ Ｐ ０对称振动模式位于８０４ｃｍ－１，这和８１０ｃｍ－１附近没有拉曼和红外谱线的实验结果不符。在８００～１０００ｃｍ－１的范围内只有四个振动模式，明显少于拉曼和红外光谱在该范围内的谱线数目。所以我们认为Ｈｏｗａｒｄ模型需要进一步地完善和修正，ｐｏｌｙ（ｄＴ）·ｐｏｌｙ（ｄＡ）·ｐｏｌｙ（ｄＴ）必须具有三条不完全一致的脊骨     

三螺旋核酸polyU*polyA*polyU的喇曼光谱和晶格动力学研究

由于三螺旋核酸在医疗、诊断和生物技术应用中的重要性 ,越来越受到人们的关注 .对溶于 0 .2 5mol/ L的 Na Cl磷酸缓冲液的三螺旋核酸 poly U· poly A· poly U的喇曼光谱进行了测量 ,在 750～ 1 2 50 cm- 1范围内获得了高信噪比的光谱图 .利用晶格动力学方法计算了Anott模型的主链振动模式 .根据势能分布矩阵对每一个喇曼谱线进行了指定 .结果表明poly U· poly A· poly U的三条单链具有相似的简正模式 ,没有一条喇曼线独属于某个单链 .理论同实验符合的事实说明溶液中的 poly U· poly A· poly U采用了 A型结构     

Rb(NTO)·(H_2O)的合成,表征,FT-IR和Raman光谱

首次用碳酸铷与NTO在水溶液中直接合成了Rb+ 与NTO- 的配合物。采用元素分析和化学分析确定配合物的组成为Rb(NTO)·(H2 O)。用X 射线粉末衍射谱的测试与分析对该配合物进行了结构和性质的表征。给出了FTIR和Raman光谱 ,分析了各种谱线的归属。从结构角度讨论了配合物中不同键的形成。     

T_(1u)h_gJahn-Teller系统中的频率约化矩阵

在研究C60 的电声相互作用中 ,最重要的应是T1u电子态与hg 振动模式的偶合 ,俗称作T1u hgJahn Teller(JT)系统 .线性的T1u hgJT系统的势能面上只有势槽的存在 ,而当非线性耦合项加入后 ,势能面将被扭曲成具有D3d或D5d对称性的势阱 .在振动频率的各向同性假设下 ,势阱中hg 的五个振动分量相等 .但实际上并非如此 .hg 振动模式在电声偶合下将按阱中的对称性分裂成不同频率的振动模式 .而这些振动模式又可通过约化矩阵写成五个本征振动频率的叠加 .通过群论及 pik Pryce方法找出了分裂hg 振动模式的全部约化矩阵 .它们对C-60 离子的各向异性研究有着特别的应用价值 .     

[Fe_3O(Ala)_6(H_2O)_3](ClO_4)_7和[Fe_3O(Gly)_6(H_2O)_3](NO_3)7·3H_2O的顺磁共振谱及变温磁化率研究

本文通过对 [Fe3 O(Ala) 6(H2 O) 3 ](Cl O4) 7和 [Fe3 O(Gly) 6(H2 O) 3 ](NO3 ) 7· 3H2 O的 ESR谱的解析及变温磁化率的研究 ,得出它们的 ESR谱具有各向同性的特点 ;朗德因子分别为 2 .0 19和 1.997;两种配合物中铁离子间有反铁磁相互作用     

描述甲烷在Pt(110)-(21)表面的化学吸附解离的密度泛函评估

本文探讨了几种梯度近似(GGA)密度泛函及元梯度近似(meta-GGA)密度泛函在描述甲烷在重构的Pt(110)-(2×1)上的解离化学吸附作用的适用性. 金属的体相和表面结构、甲烷的吸附能量和解离能垒等被用来评估泛函的可靠性. 另外,在从头算分子动力学计算中,采用范德瓦尔斯矫正的GGA函数(optPBE-vdW)和范德瓦尔斯矫正的meta-GGA函数(MS-PBEl-rVV10）计算粘附概率. 计算结果表明,使用这两种泛函能更好地与现有的实验结果吻合,从而为发展甲烷在Pt(110)-(2×1)表面解离的可靠机器学习势能面打下重要基础.     

自学·探究·辅导教学法在高中物理 教学中的实践研究

在全面推进素质教育和课程改革的背景下,结合新建学校的实际情况,依托选用教材以及自编《高中 物理教学讲义》,采用自学·探究·辅导教学法在教学中对普通高中物理课程标准(实验) 的实施进行实践性尝试. 介绍2010 - 2013 年实践过程中的基本实施程序、原则及效果等情况,并对实践过程中反映出的一些相关问题进行 分析讨论     

三链DNA分子poly（dT）.poly（dA）.poly（dT）的低频振动模式

利用晶格动力学方法，首次计算了具有三螺旋结构的ｐｏｌｙ（ｄＴ）．ｐｏｌｙ（ｄＡ）．ｐｏｌｙ（ｄＴ）的低频振动模式，结果表明Ｗａｔｓｏｎ－Ｃｒｉｃｋ氢键的呼吸模式位于９０ｃｍ＾－＾１附近，而Ｈｏｏｇｅｎｓｔｅｅｎ氢键除了在９０ｃｍ＾－＾１附近存在模式外，还在更低频率上存在着几个更为强烈的呼吸模式，这一结果定性地解释了低盐度下ｐｏｌｙ（ｄＴ）．ｐｏｌｙ（ｄＡ）．ｐｏｌｙ（ｄＴ）的两步热融化。     

聚对苯二甲酸丁二醇酯/聚(对苯二甲酸丁二醇酯-e-己内酯)二元结晶共混体系的相容性和结晶行为

聚对苯二甲酸丁二醇酯(PBT)/聚(对苯二甲酸丁二醇酯-e-己内酯)(PBT-PCl)是一个新制备的具有分子间排斥相互作用的A/AxB1?x型两元结晶共混体系. 根据两元平均场模型,报道对苯二甲酸丁二醇酯(BT)与"-己内酯(CL)结构单元的相互作用参数为0.305. DSC研究发现,此共混物呈现了与典型的共聚物/均聚物共混物不同的结晶特征. PBT-PCL影响PBT链的活动力和晶片堆积;同时PBT-PCL的结晶受到先期结晶的PBT晶粒的阻滞. 尽管拥有相同的BT单元,共混的两组分在组成变化范围内仍没有形     

Turbulent Drag Reduction Efficiency and Mechanical Degradation of Poly(Acrylamide)

Abstract

Turbulent drag reduction (DR) efficiency and mechanical degradation of high‐molecular‐weight poly(acrylamide) (PAAM) was investigated in a rotating disk apparatus. Drag reduction efficiency of PAAM was measured as a function of rotational speed, polymer concentration, and temperature and then compared with that of poly(ethylene oxide) (PEO). The PAAM exhibited relatively high shear resistance, and its mechanical degradation behavior in a turbulent flow was examined by using both an exponential and a fractional exponential decay equation.     

Energy Dispersive X-ray Diffraction (Edxd) Investigation Of Amorphous Poly(phenylacetylene) (Ppa)

The application of wide-angle x-ray diffraction in energy-dispersive modality (EDXD) to the investigation of the static structure of amorphous poly(phenylacetylene) (PPA) is discussed. The structural investigation was carried out through the systematic comparison of the measured functions (the reduced interference function and the radial distribution function) and the same functions calculated from three-dimensional theoretical models, suitably optimized. Possible configurations and conformations, coming from the combination of the polymeric repeating units, were analyzed separately. Consistent with the literature, a general agreement for a cis-transoidal head-to-tail configuration was achieved. Possible coexistence of trans-transoidal head-to-head with cis-transoidal head-to-tail configuration is also discussed. Several simple models were investigated to gain information about the chain packing. Moreover, a first quantitative investigation of the dependence of the interference function upon mechanical compression of PPA was performed.     

POLYMERIZATION,MORPHOLOGY, AND CRYSTAL STRUCTURE OF POLY(p-BENZAMIDE)*

Isothermal polymerization of acetaminobenzoic acid at various temperatures in bulk and solution was monitored by acetic acid evolution. The polymerization took place initially in a homogeneous phase, but it soon changed to heterogeneous as the polymer precipitated from the melt or solution. The reaction course consisted of a short induction period, followed by a fast second-order reaction and a third slow, also second-order, reaction. The different polymerization rates in the second and third stage were due to polymer precipitation. The degree of polymerization of the resulting polymer was generally low, usually less than 5. The polymer was highly crystalline and prone to decarboxylation at temperatures above 300°C. Sample structure and morphology were characterized by various lamellar formations similar to those seen previously in many aromatic polyesters. Epitaxial solution polymerization/crystallization on mica resulted in three different morphologies, the most unique being shish kebab–type structures. Polybenzamide [poly(p-aminobenzoate)] is polymorphic; the most frequently seen hk0 electron diffraction patterns were similar to those from phase I of aromatic polyesters. Phase II of polybenzamide was seen only rarely. Simulation, using Cerius², suggested equal agreement with [001], [100], and fiber electron diffraction (ED) patterns and X-ray powder patterns for two different orthorhombic unit cells (a = 7.71, b = 5.35, c = 12.94 Å, ρ = 1.55 g/cm³); both have a parallel packing of adjacent molecules, but in one, successive phenyl rings along a given chain are parallel, while in the other they are twisted at ±30°. For both unit cells, neighboring molecules were displaced by ±0.14 Å along c to obtain better agreement with the observed patterns. The [010] patterns could distinguish between the two cells, but were not obtainable.

     

Influence of Blend Composition on Crystallization of Poly(L-Lactic Acid)/Poly (Ethylene Oxide) Crystalline/Crystalline Blends

The effect of blend composition on crystallization morphology and behavior of a crystalline/crystalline blend, poly(l-lactic acid) (PLLA)/poly(ethylene oxide) (PEO), during slow, non-isothermal crystallization was studied by polarized light microscopy (PLM) connected with a hot-stage and differential scanning calorimetry (DSC). The results showed that all of the PLLA/PEO blends produced spherulites which gradually became bigger and looser, as well as coarser, with the increment of the PEO content, indicating that the PEO crystals was resided in the interlamellar or interfibrillar (between clusters of commonly oriented lamellae) regions of the PLLA spherulites. In the (25/75) and (10/90) blends, the nucleation and growth processes of the PEO spherulites could be clearly observed in the pre-existing PLLA spherulites. The onset crystallization temperature and the melting point of one component decreased with increasing the content of the other one owing to the good miscibility of the two components in the non-crystalline state and the interaction between their macromolecules, indicating that the crystallization of each component was influenced by the other one.     

聚对苯二甲酸丙二醇酯(PPT)纤维的偏振红外光谱取向研究

聚对苯二甲酸丙二醇酯 (PPT)是一种全新的高分子材料。本文采用偏振衰减全反射红外光谱法 ,对不同拉伸工艺条件下的PPT纤维进行了取向研究。结果表明 ,PPT纤维的二向色性比和取向函数都随拉伸速度提高而增大 ,但当拉伸速度高于 2 5 0 0m·min- 1 以后二向色性比基本不变。     

Crystallization of Poly(Ethylene Oxide) in Thin Films

Crystallization of poly(ethylene oxide) (PEO) in thin films was studied using hot-stage polarized optical microscopy. Isothermal linear crystal growth rates were measured for various film thicknesses at various degrees of undercooling. At a given crystallization temperature, the linear crystal growth rate decreased exponentially with decreasing film thickness below a film thickness of 80 nm. Films showed similar spherulitic morphology down to a film thickness of 30 nm. Control experiments on hydrophilic and hydrophobic surfaces showed that surface chemistry affects stability of the polymer films and causes a competition between crystallization and dewetting.