Pattern dynamics in cellular perception

By using a giant amoeboid cell of the Physarum plasmodium, changes in the intracellular distribution of chemical components are studied in relation to information processing in cell behavior. Various kinds of metabolites oscillate, and so the protoplasm should be a collection of chemical oscillators. Spatially, characteristic chemical patterns are self-organized for different cell shapes, and hence cell behavior. New phase waves propagate throughout the cell upon local stimulation, their direction being opposite for attraction and repulsion. Locomotion is inhibited when the coherence of the oscillators breaks. Thus, pattern dynamics is correlated with information processing in the amoeboid cell.     

Compatibilization of Poly(Trimethylene Terephthalate)/Polycarbonate Blends by Epoxy. Part 2. Melting Behavior and Spherulite Morphology

The melting behaviors of poly(trimethylene terephthalate)/polycarbonate (PTT/PC) blends, compatibilized by epoxy, and PTT spherulite morphology in the blends were investigated. When epoxy was present during blending, the melting behaviors of PTT/PC blends changed substantially; glass transition temperatures (T_g's) and cold crystallization temperature (T_cc's) of the PTT‐rich phase shifted to higher temperatures, while T_m's shifted slightly to lower temperatures, indicating that epoxy suppressed considerably all processes of dynamic movements pertinent to molecular (or segmental) movements. The cold crystallization process responded sensitively to thermal history. Changes of T_cc's with composition suggested that the epoxy's compatibilization effect was pronounced when PTT and PC were in near equal content.

Recrystallization or reorganization exotherms appeared before melting for isothermally crystallized PTT/PC and PTT/PC epoxy (E) blends. A wide angle X‐ray diffraction (WAXD) analysis showed that, although the perfection of PTT crystallites was influenced either by PC content and the presence of compatibilizer or by the crystallization temperature and crystallization time, PTT's crystal structure was independent of these variables.

The polarized light microscopy (PLM) observations showed that PTT spherulite morphology was very sensitive to blend composition. Epoxy addition interfered severely with the growth of PTT spherulites, causing them to be much less developed. When the spherulites grew under a condition of varied composition, they would exhibit diversified spherulite morphology, though in one spherulite.     

Empirical study of the scaling behavior of the amplitude–frequency distribution of the Hilbert–Huang transform and its application in sunspot time series analysis

Investigating long-range correlation by the Hurst exponent, H$H$, is crucial in the study of time series. Recently, empirical-mode-decomposition-based arbitrary-order Hilbert spectral analysis (EMD-HSA) has been proposed to numerically obtain without proof a scaling relationship, generated from the amplitude–frequency distribution, related to H$H$. We propose a formalism to empirically study EMD-HSA, to deduce its scaling exponent ξ(q)$\xi \left(q\right)$ from the perspective of EMD-based arbitrary-order Hilbert marginal spectrum (EMD-HMS), and to numerically compare the results with the expected H$H$. EMD-HSA and EMD-HMS experiments show that, by incompletely removing (quasi-)periodic trends, the sunspot series should have an H$H$ value around 0.12.     

路径约束条件下车辆行为的时空演化模型

复杂地理环境下车辆运行线路具有空间三维特征, 它对车辆行为的约束是显然的, 非一维空间和二维空间所能描述. 将复杂地理环境下车辆运行线路抽象为空间曲线, 引入微分几何理论, 利用弧长、曲率和挠率等几何不变量参数建立沿空间曲线运动的Serret-Frenet活动标架; 然后, 对空间曲线上任意一点处Serret-Frenet标架具有时变属性的动态行为进行数学描述, 进而建立路径约束条件下车辆行为的时空演化模型, 并在数学上严格证明了所建时空演化模型适用于车辆(Serret-Frenet标架)直线运行和做匀速圆周运动的特殊情形. 为后续复杂地理环境中交通线路上的车辆跟驰、变道等微观行为和交通流宏观行为研究, 奠定了理论基础.     

电磁波在大面积等离子体片中传播特性的分析

脉冲磁约束线形空心阴极放电形成的大面积等离子体片可应用于等离子体天线、隐身及模拟超音速飞行器表面的等离子体鞘套. 本文首次利用实测等离子体片电子密度时空分布和横向场传播矩阵法, 研究了电磁波在等离子体片中反射率、透射率、吸收率随频率及脉冲放电时间的变化特征. 结果表明: 极化方向平行磁场的电磁波, 在小于截止频率的低频带内具有较高的反射率和吸收率, 增大电流, 反射率增加, 吸收率下降, 在大于截止频率的高频带内反射率和吸收率较低, 增大电流, 透射率下降, 吸收率升高; 极化方向垂直磁场的电磁波在高混杂谐振频率附近存在吸收率明显增强的吸收带, 谐振吸收峰值与放电电流无关; 脉冲放电期间, 电磁波的反射率、透射率与吸收率由不稳定过渡到稳定的时间约为100 μs, 过渡时间随着放电电流的增加而增大, 极化方向垂直磁场、小于截止频率的电磁波在稳定放电阶段谐振吸收较强. 本文的研究成果对利用等离子体片实现对电磁波的稳定高反射作用具有重要意义.     

Thermal Behavior of Polypropylene-g-glycidyl Methacrylate Prepared by Melt Grafting

The thermal behaviors of glycidyl methacrylate (GMA)-grafted polypropylene (PP) (PP-g-GMA) with two different grafting degrees, namely, GPP1 and GPP2, were investigated by differential scanning calorimetry (DSC), polarized optical microscopy (POM), wide-angle X-ray diffraction (WAXD), dynamic mechanical analysis (DMA), and thermogravimetrical analysis (TGA). DSC results suggested that the GMA grafted PP exhibited higher crystallization temperature T_c, higher melting temperature T_m, and higher crystallinity compared with the neat PP. The isothermal crystallization kinetics was analyzed with the Avrami equation and the total crystallization activation energy was calculated. It was concluded that the crystallization processes of PP and the grafted PP were controlled by nucleation and the values of the crystallization activation energy of PP and the grafted PP were almost identical. POM results suggested that the GMA grafted PP exhibited smaller spherulites size compared with the neat PP. WAXD patterns indicated that the neat PP encouraged the formation of γ phase, compared with the grafted PP, during the crystallization process. DMA results showed that melt grafting did not induce a clear effect on the γ-transition and β-transition of the amorphous phase but resulted in a decrease in mobility of the PP chains in the crystals. TGA curves suggested that the melt grafting slightly improved the thermal stability of PP.     

名义上无水硬玉矿物中“水”的热变异行为研究

以硬玉岩中名义上无水硬玉矿物为研究对象,通过常温和变温红外光谱测量,确定硬玉矿物结构水表征及变温过程热变异行为。研究结果显示：由M-OH伸缩振动所致的红外吸收谱带集中于3 700～3 600,3 570～3 520,3 500～3 300及3 230～3 140 cm-1波数范围内,但在不同的硬玉岩中具有不同的红外吸收。变温过程中,该吸收谱带基本在500 ℃左右相对吸收强度出现较为明显的减弱,且结构水含量也逐渐下降,进一步表征硬玉矿物中的“水”是以结构水的形式进入晶格。但此M-OH伸缩振动所致的吸收谱带、结构水含量和指纹谱均在850 ℃附近出现较为明显的变化,预示该温度硬玉矿物的成分已出现变异。硬玉矿物中“水”的热变异行为为进一步了解水分子的赋存状态与结合方式及其成岩机制提供一定的佐证。     

Phase behaviors in a binary mixture of diblock copolymers confined between two parallel walls

The phase behaviors in a binary mixture of diblock copolymers confined between two parallel walls are investigated by using a cell dynamics simulation of the time-dependent Ginzburg-Landau theory.The morphological dependence of the wall-block interaction and the distance between walls(confinement degree) has been systematically studied,and the effect of repulsive interactions between different monomers is also discussed.It is interesting that multiple novel morphological transitions are observed by changing these factors,and various multilayered sandwich structures are formed in the mixture.Furthermore,the parametric dependence and physical reasons for the microdomain growth and orientational order transitions are discussed.From the simulation,we find that much richer morphologies can form in a binary mixture of diblock copolymers than those in a pure diblock copolymer.Our results provide an insight into the phase behaviors under parallel wall confinement and may provide guidance for experimentalists.This model system can also give a simple way to realize orientational order transition in soft materials through confinement.     

深紫外激光光发射与热发射电子显微镜在热扩散阴极研究中的应用

对热扩散阴极表面微区发射状态进行原位观察和分析一直是热阴极研究的重要课题.本文着重介绍深紫外激光光发射电子/热发射电子显微镜的基本原理及其在热扩散阴极研究中的典型实例.系统配备了高温激活所用的加热装置,样品可被加热至1400℃.系统具有光发射电子、阴极热发射电子、光发射电子和阴极热发射电子联合三种电子成像模式.应用表明,对于热扩散阴极而言,深紫外激光光发射电子像适于呈现阴极表面的微观结构形貌;热发射电子像适于反映阴极表面的本征热电子发射及均匀性;光电子和热电子联合成像适于对阴极表面的有效发射点做出精确定位.     

大电流稳定发射铁电阴极的模拟与实验研究

讨论了铁电阴极的发射机理, 借助MAFIA对不同电极结构的铁电阴极表面电场分布进行了模拟计算. 计算中发现, 发射面电极结构对铁电阴极表面三界点处的场增强效应影响很大,特别是具有孤岛电极结构的铁电阴极具有更大的三界点场强,从而获得更大和更稳定的发射电流. 通过对电极结构及其工艺的改进,使用PLZT铁电阴极在实验中得到了大于100A的电流.