卟啉取代侧链在LB膜结构中的取向研究

本文研究了５，１０，１５，２０－四（对－山嵛酸乙酯－α－氧代苯基）卟啉在气－液界面的成膜性能。在优化实验条件下制备了该化合物的多层ＬＢ膜。利用偏振ＦＴ－ＩＲ谱测定了卟啉上脂链取代基在ＬＢ膜结构中的取向。结果表明脂链轴线与载片法线间夹角为２７°。     

FRS-XRSA与SAXS研究硬弹性聚丙烯的结晶度、取向与超结构——Ⅰ.退火时间的影响

硬弹性材料是近二十年发展起来的一种新型的、具有开发前景的高聚物材料,但目前只利用其多孔透气性而作人工肺等。为了开发这种硬弹性,人们对其加工-结构-物性之间的关系仍在进行着不懈的研究。本文利用FRS-XRSA与SAXS研究退火条件对HEPP结晶、取向与超结构的影响。FRS-XRSA是作者为研完择优取向聚合物结晶与取向而提出的一种理论分析。结果指出:当T_(an)取130℃,则获得稳定结构的t_(an)应大于40min。与前人工作不同之点是,HEPP纤维中的片晶不是伸展的,而是扭曲或双重取向的。当退火时间增加,扭曲的片晶逐渐伸展。从SAXS得到的长周期与从WAXD得到的结晶度与晶粒度指出,片晶是由两层晶粒砌成。     

Melt shear rheology of carbon nanofiber/polystyrene composites

The rheological behavior and morphology of carbon nanofiber/polystyrene (CNF/PS) composites in their melt phase have been characterized both through experimental measurements and modeling. Composites prepared in the two different processes of solvent casting and melt blending are contrasted; melt-blended and solvent-cast composites were each prepared with CNF loadings of 2, 5, and 10 wt%. A morphological study revealed that the melt blending process results in composites with shorter CNFs than in the solvent-cast composites, due to damage caused by the higher stresses the CNFs encounter in melt blending, and that both processes retain the diameter of the as-received CNFs. The addition of carbon nanofiber to the polystyrene through either melt blending or solvent casting increases the linear viscoelastic moduli, G′ and G″, and steady-state viscosity, η, in the melt phase monotonically with CNF concentration, more so in solvent cast composites with their longer CNFs. The melt phase of solvent-cast composites with higher CNF concentrations exhibit a plateau of the elastic modulus, G′, at low frequencies, an apparent yield stress, and large first normal stress difference, N ₁, at low strain rates, which can be attributed to contact-based network nanostructure formed by the long CNFs. A nanostructurally-based model for CNF/PS composites in their melt phase is presented which considers the composite system as rigid rods in a viscoelastic fluid matrix. Except for two coupling parameters, all material constants in the model for the composite systems are deduced from morphological and shear flow measurements of its separate nanofiber and polymer melt constituents of the composite. These two coupling parameters are polymer–fiber interaction parameter, σ, and interfiber interaction parameter, C _I. Through comparison with our experimental measurements of the composite systems, we deduce that σ is effectively 1 (corresponding to no polymer–fiber interaction) for all CNF/PS nanocomposites studied. The dependence of CNF orientation on strain rate which we observe in our experiments is captured in the model by considering the interfiber interaction parameter, C _I, as a function of strain rate. Applied to shear flows, the model predicts the melt-phase, steady-state viscosities, and normal stress differences of the CNF/PS composites as functions of shear rate, polymer matrix properties, fiber length, and mass concentration consistent with our experimental measurements.     

不同管径聚乙烯管的旋转挤出

通过口模旋转挤出制备3种管径聚乙烯(PE)管,系统研究其结构与性能。结果表明,相较于传统挤出PE管内串晶平行与轴向,旋转挤出过程中聚合物熔体的流动是轴向牵引流动和环向拖曳流动的叠加,其方向偏离轴向,可诱导串晶偏离轴向排列,从而提高PE管的环向取向度,实现PE管的环向增强,抑制裂纹在PE管内沿轴向扩展。随PE管管径的增加,在相同旋转角速度下环向流动线速度增大,串晶偏离轴向的夹角增加,环向取向度更高,因而旋转挤出制备的大口径PE管具有更优的性能。     

Variation of fiber orientation in turbulent flow inside a planar contraction with different shapes

In this study, we have investigated the influence of shape of planar contractions on the orientation distribution of stiff fibers suspended in turbulent flow. To do this, we have employed a model for the orientational diffusion coefficient based on the data obtained by high-speed imaging of suspension flow at the centerline of a contraction with flat walls. This orientational diffusion coefficient depends only on the contraction ratio and turbulence intensity. Our measurements show that the turbulence intensity decays exponentially independent of the contraction angle. This implies that the turbulence variation in the contraction is independent of the shape, consistent with the results by the rapid distortion theory and the experimental results of axisymmetric contractions. In order to determine the orientation anisotropy, we have solved a Fokker–Planck type equation governing the orientation distribution of fibers in turbulent flow. Although the turbulence variation and the orientational diffusion are independent of the contraction shape, the results show that the variation of the orientation anisotropy is dependent on shape. This can be explained by the variation of the rotational Péclet number, Pe_r, inside the contractions. This quantity is a measure of the importance of the mean rate of the strain relative to the orientational diffusion. We have shown that when Pe_r < 10 turbulence can significantly influence the evolution of the orientation anisotropy. Since in contractions with identical inlet conditions the streamwise position where Pe_r = 10 depends on the shape, the orientation anisotropy is dependent on the variation of rate of strain in a given contraction. We demonstrate the shape effect by considering contraction with flat walls as well as three contractions with different mean rate of strain variation.     

The auxiliary determination of the binding site of berberine binding to human serum albumin by surface-enhanced Raman scattering

We report on the joint application of fluorescence, ultraviolet-visible (UV-Vis) and Raman spectroscopy to the study of berberine with human serum albumin (HSA). We propose the surface-enhanced Raman scattering (SERS) technique to improve the understanding of the quenching interaction caused by berberine which could be applied in recognition process of fluorescent drugs with large biomolecules. The fluorescence and UV-Vis spectroscopic results show that the fluorescence intensity of HSA is significantly decreased in the presence of berberine, and the quenching mechanism is static. The SERS technique demonstrates clear advantages over direct measurements in physiological conditions. By means of this method, we are able to deduce important information concerning the binding property of berberine when interacting with HSA. We show the nitrogen atom is free but the dioxolane is involved in the spontaneously electrostatic inducement and subsequently hydrophobic binding.     

拉伸过程中晶向对银单原子线形成几率影响的分子动力学模拟

采用基于原子镶嵌势函数的分子动力学方法, 模拟了银纳米线沿[100]、[110]和[111]晶向拉伸过程中的空间原子结构和性能. 研究结果表明不同晶向的材料力学性质有显著不同, 屈服应力按照[111]、[110]和[100]依次降低. 从形变位图观察到纳米线在断裂前形成单原子线排列. 由900个分子动力学模拟样本统计得出沿三个晶向形成单原子线的几率, 其中沿[111]晶向形成单原子线的几率明显高于其他两个晶向. 本文从形变机理阐述了单原子线生成几率与晶向的依赖关系.     

锥光干涉法表征偶氮苯侧链液晶聚合物的光致取向

采用偏光显微镜在平行光和锥光条件下对液晶聚合物膜内分子的取向排列状态进行了研究,不同取向状态的膜由线偏振光或圆偏振光照射偶氮苯侧链液晶聚合物得到。结果表明,液晶聚合物膜采用线偏振光照射时,偶氮苯介晶基元沿面排列,形成单相畴面内取向态。该取向态的锥光干涉图为位于视场中心的粗黑十字,旋转载物台小于10°,该干涉图即完全退出...     

基于方向信息测度的图像边缘检测

边缘检测是图像处理中—个重要的研究课题．针对传统图像边缘检测算法对噪声敏感的问题,本文在分析图像像素灰度信息的基础上,建立了—个改进的确定方向信息测度的方法,并利用震动滤波对边缘检测图像进行增强,该方法在滤除噪声的同时,能有效地保留图像的基本目标信息,正确提取图像的边缘．     

Orientation of O(3) and SU(2)⊗CI representations in cubic point groups (Oh,Td) for application to molecular spectroscopy

We propose a detailed method for the symmetrization of the standard O(3) or SU(2)⊗C_I basis |j_τ,m〉 (τ=g or u) into the O_h or T_d point group. This is realized by means of an orientation matrix called G. The oriented basis obtained in this way allows matrix element calculations for rovibronic spectroscopic problems concerning octahedral or tetrahedral molecules. Particular attention has been put on careful phase choices. A numerical calculation of all the G matrix elements for both integer and half-integer j values up to 399/2 has been performed. Such high angular momentum values are necessary for the case of heavy molecules with high rotational excitation. To calculate the G coefficients with high precision at high j values we pre-calculated the necessary Wigner functions using symbolic MAPLE software and made then the numerical calculations with quadruple precision. The complete list of these coefficients can be obtained freely at the URL: http://www.u-bourgogne.fr/LPUB/group.html. As an illustration, we also present briefly an application to two typical spectroscopic calculations: the pure rotational levels of SF₆ in its ground vibrational state and the ν₃ band of ReF₆ (an open-shell molecule with an odd number of electrons and a fourfold degenerate electronic ground state).