Labyrinthine pattern formation in magnetic fluids

A quasi two-dimensional drop of a magnetic fluid (ferrofluid) in a magnetic field is one example of the many systems, including amphiphilic monolayers, thin magnetic films, and type I superconductors, that form labyrinthine patterns. The formation of the ferrofluid labyrinth was examined both experimentally and theoretically. Labyrinth formation was found to be sensitively dependent on initial conditions, indicative of a space of configurations having a vast number of local energy minima. Certain geometric characteristics of the labyrinths suggest that these multiple minima have nearly equivalent energies. Kinetic effects on pattern selection were found in studies of fingering in the presence of timedependent magnetic fields. The dynamics of this pattern formation was studied within a simple model that yields shape evolutions in qualitative agreement with experiment.     

Primary afferent depolarization evoked by a painful stimulus

Pulses of intense radiant heat applied to the plantar pad of unanesthetized spinal cats produced negative dorsal root potentials, increased excitability of cutaneous A fibers, and marked activation of ipsilateral flexor motoneurons. The same effects were obtained during cold block of A fiber conduction in the appropriate peripheral nerve. We conclude that adequate noxious activation of cutaneous C fibers depolarizes cutaneous A fibers.     

Global pattern formation and ethnic/cultural violence

We identify a process of global pattern formation that causes regions to differentiate by culture. Violence arises at boundaries between regions that are not sufficiently well defined. We model cultural differentiation as a separation of groups whose members prefer similar neighbors, with a characteristic group size at which violence occurs. Application of this model to the area of the former Yugoslavia and to India accurately predicts the locations of reported conflict. This model also points to imposed mixing or boundary clarification as mechanisms for promoting peace.     

Spatial pattern formation in an insect host-parasitoid system

Spatial models in ecology predict that populations may form patchy distributions within continuous habitats, through strong predator-prey or host-parasitoid interactions combined with limited dispersal. Empirical support of these models is provided. Parasitoids emanating from a population outbreak of tussock moths (Orgyia vetusta) suppressed the growth of nearby experimental populations of the moth, while experimental populations farther away were able to grow. This result explains the observed localized nature of tussock moth outbreaks and illustrates how population distributions can be regulated by dynamic spatial processes.     

大孔吸附树脂纯化矮牵牛花红色素

比较了大孔吸附树脂D61和X-5对牵牛花红色素的吸附效果及纯化牵牛花红色素的方法。结果表明：X-5树脂吸附牵牛花红色素的能力较强，吸附量为76．1mg／g湿树脂；洗脱液以甲醇洗脱效果最佳，洗脱回收率92％左右。     

高效液相色谱法测定小米中黄色素的含量

小米中的黄色素是一类类胡萝卜素化合物。作为杂粮食品中的重要功能性成分,其成分和含量分析受到极大关注。建立了小米中黄色素物质的反相高效液相色谱分析方法。色谱分离柱采用YMCTM Carotenoid S-5(250×4.6 mm ID,5μm),流动相采用三元溶剂梯度洗脱模式,样品中目标组分采用甲基叔丁基醚(MTBE)超声波辅助萃取处理。色谱分离获得了较好的选择性,各黄色素组分17 min内完成基线分离,并在0.5~50.0μg·m L-1浓度范围内呈现良好的线性关系,方法叶黄素、玉米黄素和β-隐黄素的检测限分别为0.3,0.4和0.4μg·m L-1。该方法样品前处理简便,重现性好,结果准确。     

Reaction-diffusion model as a framework for understanding biological pattern formation

The Turing, or reaction-diffusion (RD), model is one of the best-known theoretical models used to explain self-regulated pattern formation in the developing animal embryo. Although its real-world relevance was long debated, a number of compelling examples have gradually alleviated much of the skepticism surrounding the model. The RD model can generate a wide variety of spatial patterns, and mathematical studies have revealed the kinds of interactions required for each, giving this model the potential for application as an experimental working hypothesis in a wide variety of morphological phenomena. In this review, we describe the essence of this theory for experimental biologists unfamiliar with the model, using examples from experimental studies in which the RD model is effectively incorporated.     

Modulation instability and pattern formation in spatially incoherent light beams

We report on the experimental observation of modulation instability of partially spatially incoherent light beams in noninstantaneous nonlinear media and show that in such systems patterns can form spontaneously from noise. Incoherent modulation instability occurs above a specific threshold that depends on the coherence properties (correlation distance) of the wave packet and leads to a periodic train of one-dimensional filaments. At a higher value of nonlinearity, the incoherent one-dimensional filaments display a two-dimensional instability and break up into self-ordered arrays of light spots. This discovery of incoherent pattern formation reflects on many other nonlinear systems beyond optics. It implies that patterns can form spontaneously (from noise) in diverse nonlinear many-body systems involving weakly correlated particles, such as atomic gases at (or near) Bose-Einstein condensation temperatures and electrons in semiconductors at the vicinity of the quantum Hall regime.     

红曲霉产红曲色素工艺优化

[目的]优化红曲米生产工艺,提高红曲米红曲色素含量。[方法]以加水量(A)、灭菌温度(B)、灭菌时间(C)、浸泡时间(D)作为试验因素,设计4因素3水平正交试验,优化米饭制作方式。[结果]4种因素均对红曲菌产红曲色素产量具有极显著影响,最优组合为A_1B_2C_2D_2,即加水量30 m L、灭菌温度121℃、灭菌时间23 min、浸泡时间24 h,在此条件下红曲色阶达2 884 U/g。[结论]该研究对红曲米生产企业具有实践指导意义。     

橘皮色素提取的响应面优化及其稳定性研究

采用Box-Behnken中心组合试验和响应面分析法,研究醇提法提取橘皮色素中料液比、提取温度和提取时间对提取效果的影响,并分析橘皮色素的稳定性。结果表明:以95%乙醇为提取溶剂,在料液比为1∶20(g/mL)、温度为75℃、提取时间为120min条件下提取效果最佳;橘皮色素的稳定性研究表明,橘皮色素在光照条件下稳定性较差,因此贮藏中应适当避光;Mg2+、K+、Na+、Mn2+和Ca2+等金属离子对色素无不良影响;常用食品添加剂葡萄糖和柠檬酸溶液对色素的稳定性几乎无影响;橘皮色素对氧化剂和还原剂亦较为稳定;橘皮色素在酸性条件下比较敏感,在碱性条件下颜色加深。     

溶剂法提取辣椒红色素工艺研究

研究了溶剂法(异丙醇和乙醇)提取辣椒红色素的的工艺,结果表明,异丙醇对辣椒红色素吸光度的影响程度从大到小依次为提取温度、提取次数、料液比、提取时间,其提取辣椒红色素的最佳工艺条件为:提取时间2 h/次,料液比1∶15,提取温度40℃,提取次数3次;95%乙醇对辣椒红色素吸光度的影响程度从大到小依次为提取时间、提取温度、料液比、提取次数,其提取辣椒红色素的最佳工艺条件为:提取时间3 h/次,料液比1∶2,提取温度70℃,提取次数1次。     

Dendrites, viscous fingers, and the theory of pattern formation

There has emerged recently a new theoretical picture of the way in which patterns are formed in dendritic crystal growth and in the closely analogous phenomenon of viscous fingering in fluids. Some interesting questions that arise in connection with this theory include: How broad is its range of validity? How do we understand dynamic stability in systems of this kind? What is the origin of sidebranches? Can weak noise, or even microscopic thermal fluctuations, play a role in determining the macroscopic features of these systems?     

Sonic hedgehog control of size and shape in midbrain pattern formation

Little is known about how patterns of cell types are organized to form brain structures of appropriate size and shape. To study this process, we employed in vivo electroporation during midbrain development to create ectopic sources of Sonic Hedgehog, a signaling molecule previously shown to specify different neuronal cell types in a concentration-dependent manner in vitro. We provide direct evidence that a Sonic Hedgehog source can control pattern at a distance in brain development and demonstrate that the size, shape, and orientation of the cell populations produced depend on the geometry of the morphogen source. Thus, a single regulatory molecule can coordinate tissue size and shape with cell-type identity in brain development.     

Controlling chemical turbulence by global delayed feedback: pattern formation in catalytic CO oxidation on Pt(110)

Control of spatiotemporal chaos is one of the central problems of nonlinear dynamics. We report on suppression of chemical turbulence by global delayed feedback using, as an example, catalytic carbon monoxide oxidation on a platinum (110) single-crystal surface and carbon monoxide partial pressure as the controlled feedback variable. When feedback intensity was increased, spiral-wave turbulence was transformed into new intermittent chaotic regimes with cascades of reproducing and annihilating local structures on the background of uniform oscillations. The global feedback further led to the development of cluster patterns and standing waves and to the stabilization of uniform oscillations. These findings are reproduced by theoretical simulations.     

正交法超声波提取密蒙花黄色素

以水为介质，应用超声波技术提取密蒙花黄色素。实验结果表明，超声波处理密蒙花有利于黄色素的浸出，黄色素提取率可达14．1％。在超声波频率40KHz下，最佳提取条件为：提取温度75℃，超声波提取时间45min，浸提固液比1：30。