RECOVERY OF AMORPHOUS POLY(ETHYLENE TEREPHTHALATE)FILM UNIAXIALLY DRAWN JUST BELOW THE GLASS TRANSITION TEMPERATURE*

Isothermal recovery in the macroscopic length of homogeneously deformed specimens of amorphous poly(ethyleneterephthalate) (PET) film sample uniaxially drawn at 69℃ to the draw ratios λ_0=1.26～2.20 were studied at temperaturesaround the glass transition temperature (T_g = 73℃). Experimental results indicate that the length recovery took place in twodistinct steps: a fast first step (fast relaxation) followed by a slow second step (slow relaxation). The relaxation processeswere accompanied by the reversion of trans-conformers (1340 cm~(-1)) to gauche, and the dichroic function of the 1340 cm~(-1)band characterizing the segmental orientation along the chain direction decreased to a very low value at the end of the fastrelaxation. This fact led us to assign the fast relaxation as the segmental orientation while the slow relaxation as relaxation ofthe global chain orientation. It was found that the slow relaxation follows a single exponential function, with relaxation timesstrongly dependent on the temperature resembling the glass transition process. The fast relaxation does not follow a singleexponential decay, presumably a distribution of relaxation times is involved.     

The effect of mechanical drawing on optical and structural properties of nylon 6 fibres

The Pluta polarizing double-refracting interference microscope was attached to a mechanical drawing device to study the effect of cold drawing on the optical and structural properties of nylon 6 fibres. The microscope was used in its two positions for determining the refractive indices and birefringence of fibres. Different applied stresses and strain rates were obtained using the mechanical-drawing device. The effect of the applied stresses on the optical and physical parameters was investigated. The resulting optical parameters were utilized to investigate the polarizability per unit volume, the optical orientation factor, the orientation angle and the average work per chain. The refractive index and birefringence profiles were measured. Relationships between the average work per chain and optical parameters at different strains rates were determined. An empirical formula was deduced for these fibres. Micro-interferograms are given for illustration.     

聚甲基丙烯酸-对-甲氧基偶氮苯氧己基酯的液晶及光响应行为

合成并表征了侧链液晶高分子聚甲基丙烯酸－对－甲氧基偶氮苯氧己基酯（ＰＭＡＡＺＯ６），在不同条件下对其进行了光响应测试。发现紫外光易诱导体系发生相转变；增加辐照光波长有利于分子发生整体取向，不同温度下的光响应测试表明，样品处于玻璃化转变温度之下是保持分子取向的前提。     

基于SIFT特征区域的抗几何攻击图像水印算法

提出了一种基于局部特征区域的抗几何攻击图像水印算法.首先利用尺度不变特征变换在载体图像的尺度空间上提取特征点并形成特征区域,该区域具有缩放、平移不变性;然后通过主方向归一化,使这些区域具有旋转不变性;最后将水印信息重复嵌入到多个不重叠的局部特征区域的DFT中频系数中.仿真结果表明,该算法在获得较好的不可见性的同时,对几何攻击和常规信号处理均具有良好的鲁棒性.     

Effects of molecular orientation of fluorescently-labeled duplex DNA on emission anisotropy

The molecular orientation of Cy5-labeled target DNA hybridized on a probe DNA layer was studied on a planar waveguide in the Kretchmann configuration at various target DNA bulk concentration. Optical waveguide fluorescence spectroscopy (OWFS) was employed to evaluate the fluorescence emission anisotropy by analyzing two polarized modes, i.e., TM and TE modes propagating in a waveguide. In this way, the orientational order parameter S could be determined. It was found that the orientation of DNA duplex molecules is disordered at lower concentrations, while relatively ordered at higher concentrations.     

pH对磷脂膜中Slc11a1跨膜区二级结构和取向的影响

采用圆二色光谱、 荧光光谱、 红外衰减全反射光谱和差示扫描量热分析等方法对不同pH条件下膜蛋白Slc11a1(溶质转运蛋白家族11成员1)的第二、 第三和第四跨膜区(TMD2~TMD4)在磷脂膜[二肉豆蔻酰磷脂酰胆碱(DMPC)和二肉豆蔻酰磷脂酰甘油(DMPG)的摩尔比为2∶1]中的二级结构和取向进行了研究. 结果表明, TMD3的二级结构及在磷脂膜内的位置与pH密切相关, 在pH=7时TMD3主要为β股结构, 在膜中埋入较浅; 而在pH=5.5时TMD3形成部分α螺旋结构, 并较深地埋入膜中. 对TMD3进行E139A突变后的结果证明, TMD3的这些性质与位于中间的谷氨酸的质子化性质密切相关. 实验结果还表明, TMD2和TMD4在不同pH条件下都形成α螺旋结构并分别以26°和35°的倾斜角插入磷脂膜内, 它们在磷脂膜内的位置基本不受pH影响.     

Quasi-classical Trajectory Study of the Intramolecular Isotope Effect in the Reaction O（3p）＋H2/HD

Theoretical studies of the dynamics of the reactions O（3p）＋H2/HD（ν=0, j=0）→OH＋H have been performed with quasi-classical trajectory method （QCT） on an ab initio potential surface for the lowest triplet electronic state of H2O（aA＂）. The QCT-calculated integral cross sections are in good agreement with the earlier time-dependent quantum mechanics results. The state-resolved rotational distributions reveal that the product OH rotational distributions for O＋HD have a preference for populating highly internally excited states compared with the O＋H2 reaction. Distributions of differential cross sections show that directions of scattering are strongly dependent on the choice of quantum state. The polarization dependent generalized differential cross-sections and the distributions were calculated and a pronounced isotopic effect is revealed. The calculated results indicate that the product polarization is very sensitive to the mass factor.     

Study of the rotational diffusivity coefficient of fibres in planar contracting flows with varying turbulence levels

The Fokker–Planck equation is solved by describing the evolution of a 3D fibre orientation state along a planar contraction. A constant value of the effective rotational diffusion coefficient was determined for four different turbulent flow cases in planar contractions, reported experimentally in the literature. Two hypotheses for the non-dimensional rotational diffusivity are presented, each based on two different turbulent time scales, i.e. the Kolmogorov time scales and the time scale associated with large energy bearing eddies. These hypotheses are dependent on either the Reynolds number, based on the Taylor micro-scale, and/or a non-dimensional fibre length. The hypothesis, based on the assumption of long fibres, _Lf/η?25$L_{\text{f}}/\eta ?25$, compared to the Kolmogorov scale and in the limit of large _Reλ${\mathit{Re}}_{\lambda }$ seems to capture the basic trends presented in the literature. This hypothesis has also the feature of predicting effects of varying fibre length within certain limits. Accordingly, by modeling the variation of turbulent quantities along the contraction in a CFD analysis, local values of rotational diffusivity can be evaluated with the mentioned hypothesis, based on either Kolmogorov time scale or Eulerian integral time scale.     

膨化柞蚕丝内部形态和结构的研究

利用扫描电镜(SEM), 结合拉曼(Raman)光谱、 衰减全反射傅里叶变换红外(ATR-FTIR)光谱和X射线衍射(XRD)等方法研究了膨化型柞蚕丝的内部形态和结构, 表征了其热性能和力学性能. 结果表明, 虽然经过了相应的膨化处理, 柞蚕丝素蛋白分子链仍表现出具有高度取向的反平行β-折叠构象, 而其单丝是由许多带状微纤沿纤维轴平行组装而成, 且具有较高力学性能的纤维.     

Measurement of ordered associate of protonated tetraphenylporphine formed at toluene/aqueous H2SO4 interface by attenuated total internal reflection spectroscopy with polarized light

Attenuated total internal reflection (ATR) spectroscopy with an s- or p-polarized visible light was examined for some species of protonated 5,10,15,20-tetraphenylporphine (tpp) at toluene/aqueous H₂SO₄ (3-6 mol dm⁻³) interface. Tpp initially dissolved in the toluene phase was diprotonated at the interface to form monomeric H₂tpp²⁺, the absorption peak of which was 438 nm. At the same time, a long H₂tpp²⁺ oligomer was formed, the absorption peak of which was 448 nm. The two interfacial species were transient. Just after their disappearance, a rod-shaped H₂tpp²⁺ associate was formed at the interface, the absorption peak of which was 417 and 478 nm. The former and latter wavelengths corresponded to H- and J-bands of the associate, respectively. Theoretical calculation of the strength of electric field of light at the interface allowed one to estimate the interfacial concentration of the three species with measured reflection absorbance (A_R). The monomeric H₂tpp²⁺ and its oligomer were at sub-monolayer levels, whereas the associate was at a multilayer level. Reflection absorption anisotropy (K_R), which was calculated from A_R with the s- and p-polarized lights, was adopted for the evaluation of out-of-plane orientation of the interfacial species for the first time. The K_R value suggested that the rod-shaped associate lay at the interface.