Spiral and Antispiral Waves in Reaction-Diffusion Systems

Spiral waves are ubiquitous phenomena in nonlinear chemical, physical, and biological systems. But antispiral waves are infrequent to date. The transition between spiral and antispiral waves has been rarely explored. We have analyzed the extended Brusselator model and the extended Oregonator model by linear stability analysis. We have demonstrated that it is possible and plausible to realize the transition between them by control of diffusion coefficient of inactivator from theoretical analysis and numerical simulations.     

Cyclopropylidenes,bicyclopropylidenes, and vinylcarbenes -- some modes of formation and preparative applications

The routes of transformation of the simplest bicyclopropylidene into the derivatives of the second and third generations and synthesis of perspirocyclopropanated [3]rotane and linear spiral [4]- and [5]triangulanes are discussed.     

Atomic force microscopy observation of the condensates of the spermidine-DNA complexes

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The Influence of Pair Spiral Extrusion Equipment on Thermoplastic Potato Starch

Owing to contain a great deal of hydroxyl in Potato Starch, between the molecules and inside of molecules have very strong hydroxyl action. Thus, the liquate temperature is higher than disintegrate temperature, so it is difficult to process. Under the microscope, the microcosmic construction is a polar crystal molecule, and it appears globe predicament.To make the original potato starch into possession thermoplastic, we must make molecule of starch to change construct into amorphous state to form thermoplastic starch colophony. Besides auxiliary agent, shearing stress, temperature, time, pressure and hydrous quantity can affect the quality of starch thermoplastic too. The pair spiral extrude machine is used widely as the machines that are based of the pressure difference, and this extrude course may suffice require.Using the machine of pair spiral extrude of specific combination in the test of thermoplastic starch, the potato starch can be turned into thermoplastic starch of denaturalization preferably under auxiliary agent, shearing stress, temperature, pressure and the certain hydrous quantity.By the action of the technology process condition and the spiral combination, potato starch grains expand and fragmentate; hydroxyl bond cleave between and inside of molecules. Thus, crystallize state is changed into amorphous state. The transmutation of starch molecule property may be seen clearly from X diffraction chart and analyses of the construction property,By means of the denaturation, the crystal area of potato starch is broken,its crystallization degree is decreased,and its molecular chains are in amorphous state. The hydrogen bond among the molecular chain is broken or removed so that the starch structure is changed, making the starch thermoplastic.The processing of thermoplastic starch advances a higher requirement of ingredient water content, and technical conditions. A remodeled twin-screw extruder is used to create an environment to realize the condition of denaturalizing and plasticizing reactions. After the continuous probing, we have successfully developed three types of thermoplastics starch plastic from the potato starch (starch content of all of them is greater than 90%). The fluidity of the thermoplastics starch will be better if the processing is performed under the condition of 4.0-6.0Mpa (pressure) and 80-110℃ (temperature). By doing so, it is shown that there is the possibility of further thermoplastic fabrication upon it.     

环域反馈下复Ginzburg-Landau系统的螺旋波动力学行为

针对自激振荡系统的复金兹伯格-朗道(Complex Ginzbury-Landau, 简称CGL)方程, 研究圆形环域与方形环域两种反馈控制下的螺旋波动力学。结果表明: 圆形环域反馈控制下, 螺旋波波头通常经过一段过渡漂移后进入圆形吸引子, 圆形吸引子的半径以及反馈刚启动时波头的漂移方向随环域参数呈周期性变化, 过渡漂移阶段波头轨道的平缓程度与复反馈信号模的时间函数中钟形部分的陡度有关, 且反馈增益的正负与大小也会影响受控螺旋波的动力学行为。方形环域反馈控制下的螺旋波波头的吸引子更为丰富, 主要包括方形吸引子、小的极限环吸引子、菱形吸引子以及点吸引子, 点吸引子通常位于方形环域的两条对角线上, 且波头运动随环域控制参数呈现规律性变换。     

Spatiotemporal dynamics of the polarisation state of laser radiation performed by lens-axicon combinations

Spatiotemporal dynamics of the polarisation state of laser radiation performed by lens-axicon combinations were investigated theoretically and numerically in the paraxial regime. We demonstrate that in this case, while the static polarisation state does not change, various features are observed in the temporal dynamics, including spiral trajectories of the field components, transformation of the polarisation state and the “disappearance” of the light field at some time moments of the harmonic period. The results obtained can be useful for understanding the effects of spatiotemporal polarisation transformations of laser radiation, which is crucial in the field of ultrastrong and ultrashort laser-matter interactions.     

从碳中心到硅中心:手性螺环双膦配体研究的发展

手性螺环配体和催化剂已被公认是一类优势手性配体和催化剂。手性螺环配体的相关研究，促进了不对称催化领域的发展。根据螺环骨架类型进行分类，分别讨论具有螺[4.4]壬烷骨架、螺二氢茚骨架、螺[4.4]壬二烯骨架以及螺二色烷骨架的手性螺环双膦配体的合成及在不对称催化反应中的应用，为今后发展新的不对称催化体系提供了重要参考。     

介质阻挡放电中同心圆环斑图的产生机理

在氩气空气混合气体介质阻挡放电中, 得到了同心圆环斑图. 采用高速照相机拍摄了同心圆环斑图在外加电压半周期时间尺度内的放电照片, 发现放电丝是构成同心圆环斑图的基本单元. 通过对比高速照相机拍摄的连续三个正半周期和负半周期的六张放电图像, 证实肉眼看到的同心圆环斑图是由不同半周期放电位置和不同的大量放电丝长时间积累叠加产生的. 随着外加电压升高, 同心圆环斑图会演化成螺旋波, 然后重新转变成同心圆环斑图. 通过对两种斑图的形成和转化特点进行分析, 推断该螺旋波应具有和同心圆环斑图相似的动力学机理. 计算了两种斑图的放电功率, 发现功率随外加电压增加近似满足线性增长的关系. 利用相关计算的方法计算并对比了不同延迟时间下两种斑图的互相关系数, 结果表明, 同心圆环斑图的互相关系数相对较低且无明显规律, 螺旋波的互相关系数稍高且具有随延迟时间增大呈现振荡的特点.     

非对称耦合两层可激发介质中的螺旋波动力学

本文采用Bär-Eiswirth模型研究了两层可激发介质中螺旋波的动力学, 两层介质采用抑制和兴奋性非对称耦合. 数值模拟结果表明: 兴奋性非对称耦合可以促进两个不同频率的螺旋波锁频, 即使初始频率相差大, 两螺旋波也能实现锁频, 这种耦合使两个螺旋波具有最强的锁频能力; 当两层介质采用抑制性非对称耦合时, 只有当两个初始螺旋波的频率差比较小才能实现锁频, 而且比一般扩散耦合的锁频范围窄, 两螺旋波锁频能力达到最低水平; 当耦合强度和控制参数适当选取时, 抑制性和兴奋性非对称耦合既可以使其中一层介质维持螺旋波态, 使另一层介质中的螺旋波演化到静息态或低频靶波态, 也可以使两层介质中的螺旋波都漫游, 或都转变成靶波, 最后这两个靶波要么消失, 要么转变成平面波状的振荡斑图, 而且两层介质振荡是反相的, 此外在模拟中还观察到两螺旋波局部间歇锁频现象, 这些结果有助于人们理解在心脏系统中出现的复杂现象.