CuSO4-KSCN-H2O2-NaOH反应体系双节律的周期调制

研究了ＣｕＳＯ４－ＫＳＣＮ－Ｈ２Ｏ２－ＮａＯＨ反应体系,新发现了两种双节律现象。继而以流速作为扰动参数,对双节律Ⅱ中两个不同振荡态的不同流速点进行了周期调制,发现在临界区（接近实现ＯＳＳ１→ＯＳＳ２或ＯＳＳ２→ＯＳＳ１的流速点）只能实现单向跃迁;在ＯＳＳ１态的ｋｆ＾０＝４．０ｍＬ／ｍｉｎ和ＯＳＳ２态的ｄｆ＾０＝３．０ｍＬ／ｍｉｎ,能实现在两振荡态间的双向跃迁,而且ＯＳＳ２态比ＯＳＳ１态稳定。     

H+H2体系的态(R)-态(TS)-态(P)理论研究

H+H₂体系的辛准经典轨迹(SQCT)计算表明: 碰撞轨迹分为A, B两种类型, A型是经过过渡态鞍点的, B型是不经过过渡态鞍点的. A型轨迹不全发生反应, B型轨迹却也可发生反应. A, B两种类型轨迹的配分及其反应性, 与反应物初始态(R)有关. 这种轨迹类型A, B影响着产物态(P)(即振转态)分布及其角度分布. 初步建立了化学反应态(R)-态(TS)-态(P)理论研究的雏形, 深化了对Eyring过渡态理论的理解.     

封闭型简单反应系统中复杂动力学行为的模拟

研究了一个只涉及双分子反应步骤(A+B→C+D, B+C→2B)和单分反应步骤(B→p, E→A, G→B, A→D, C→P)的封闭反应系统的动力学行为, 尤其是各种状态之间的跃迁行为. 在用准定态分析方法得到的准定态分岔图的基础上, 进行了大量的数值模拟, 模拟结果和难定态分岔图预言的结果基本一致. 这些结果能定性解释近年来在封闭反应体系中发现的各种动力学现象, 如化学振荡, 多重稳定性以及定态激发现象等。     

过氧化氢氧化硫化钠反应体系的复杂振荡

研究了过氧化氢和硫化钠反应体系在连续流动搅拌反应器中的复杂振荡行为. 观察到11型振荡、12型振荡、非周期振荡以及衰减振荡; 在振荡周期内, 拐点附近区域H+扰动产生的延迟与振荡相位pH有关. 在完全基于硫价态变化的经验速率方程模型的基础上进行数值模拟, 得到的各种复杂振荡行为与实验现象基本一致, 证明了硫价态变化可驱动复杂非线性动力学行为.     

从多重定态到化学振荡

通过对化学反应体系动力学模型的分析, 论证了通过在多重定态体系中引入适当慢反馈步骤设计化学振荡体系的可能性, 提出了这类体系的动力学方程具有振荡解的判据以及在参数平面内划分振荡区域的方法。采用这种途径具体分析了一氧化碳在铂催化剂上氧化产生振荡现象的机理。     

pH探针在亚氯酸盐-硫代硫酸钠非线性反应体系研究 中的应用

当pH探针应用于ClO2^--S2O3^2-非线性反应体系动力学研究时,发现了封闭体系的pH准振荡和CSTR中的pH稳态振荡现象,在CSTR中振荡的pH与铂电位同相位,且与闭系中小峰性质相同,反应机理包括氯氧化合物自身反应,氯氧化合物-硫化合物反应,硫-硫反应。以硫价态变化驱使的动力学模型模拟出闭系准振荡和CSTR中pH稳态振荡。该模型也为解释反应-扩散体系中的pH前沿波提供模型机理。     

辉长岩中的类流态研究

在天然辉长岩中, 观察到介观尺度的天然非线性振荡现象. 在金相显微镜下显示出复杂的形态变化过程; XRD原位分析证实该试样随时间推移, 某些衍射峰的位置和强度发生振荡式变化, 说明了其晶胞发生膨胀和收缩, 同时还伴有旋转和“流”的作用; 在原子力显微镜下观察, 同样发现振荡、旋转和流的特征. 初步分析了固体材料中可能存在着的一种未被人们认知的, 除固、液、气态之外的状态——类流态. 在类流态出现的临界点附近, 不同位置的空间能量涨落不是相互独立的, 而是彼此关联. 这种涨落因某种未知的非线性机制自反馈放大成巨涨落, 形成在特定条件和特定区域的自组织现象, 甚至可以导致生成纳米管.     

Au-MgB2-Au纳米结点的负微分电阻效应

运用密度泛函理论结合非平衡格林函数的方法对MgB2直线原子链与两半无限Au（100）电极构成纳米结点的电子输运特性进行了第一性原理计算．在模拟Au-MgB2-Au纳米结点的拉伸过程中,计算了结点在不同距离下的结合能与电导．结果发现结点的Au-B键长为1．90A,B-Mg键长为2．22A时,结合能最大,结构最稳定,此时结点平衡电导为0．51G0（G0=2e^0／h）．通过计算投影态密度发现电子通过结点时主要是通过B、Mg原子的px和py电子轨道形成的π键进行传输的．在-1．5～1．5V的电压范围内,结点的电流-电压近似为线性关系,表现出类似金属的导电性质,而当正负电压高于15V时,电流对称性逐渐减小,即存在负微分电阻效应,从不同电压下透射谱的变化对负微分电阻现象进行了分析与讨论．     

He-LiH体系转动非弹性碰撞的理论研究

在单双迭代耦合簇CCSD(T)势能面的基础上,运用密耦方法讨论了He-LiH体系的转动非弹性碰撞.计算结果表明,对LiH分子j=0→j′跃迁,跃迁截面主要由各向异性的短程相互作用和长程的“软”排斥共同作用的结果,未见明显的长程吸引势贡献.态－态跃迁总截面表现出振荡结构,长程“软”排斥分波只对j=0向j′=1、2、3的跃迁总截面有较大贡献,而j′≥ 4跃迁的积分截面则几乎由各向异性的短程部分贡献.     

酞菁氧钛/N,N-二甲苯基苝酰亚胺复合薄膜的光伏极性反转

用表面光电压谱和电场诱导表面光电压谱相结合的方法, 研究了酞菁氧钛/N,N-二甲苯基苝酰亚胺复合薄膜的表面光伏行为, 发现加入N,N-二甲苯基苝酰亚胺使复合薄膜在可见光区和近红外光区均产生负的光伏响应, 可归结为光伏极性反转现象. 该响应随着外加偏压方向的改变而改变正负值, 表现出表面态跃迁的特征.  根据N,N-二甲苯基苝酰亚胺n型半导体的性质,  从价带到表面态和从表面态到导带的跃迁能量的差别以及依赖于偏压方向的电场诱导表面光伏响应,  确认表面态来自N,N-二甲苯基苝酰亚胺组分.     

Marginal states in a cubic autocatalytic reaction

Marginal steady state belongs to a special class of states in nonlinear dynamics. To realize this state we consider a cubic autocatalytic reaction A + 2B → 3B in a continuous-stirred-tank-reactor, where the flow rate of the reactant A can be controlled to manipulate the dynamical behavior of the open system. We demonstrate that when the flow rate is weakly noisy the autocatalytic reaction admits of a steady state which is marginal in nature and is surrounded by infinite number of periodic trajectories. When the uncatalyzed reaction A → B is included in the reaction scheme, there exists a marginal steady state which is a critical state corresponding to the point of transition between the flow branch and the equilibrium branch, similar to gas-liquid critical point of transition. This state loses its stability in the weak noise limit.     

Malonic acid concentration as a control parameter in the kinetic analysis of the Belousov-Zhabotinsky reaction under batch conditions

The influence of the initial malonic acid concentration [MA]0 (8.00 x 10(-3) < or = [MA]0 < or = 4.30 x 10(-2) mol dm(-3)) in the presence of bromate (6.20 x 10(-2) mol dm(-3)), bromide (1.50 x 10(-5) mol dm(-3)), sulfuric acid (1.00 mol dm(-3)) and cerium sulfate (2.50 x 10(-3) mol dm(-3)) on the dynamics and the kinetics of the Belousov-Zhabotinsky (BZ) reactions was examined under batch conditions at 30.0 degrees C. The kinetics of the BZ reaction was analyzed by the earlier proposed method convenient for the examinations of the oscillatory reactions. In the defined region of parameters where oscillograms with only large-amplitude relaxation oscillations appeared, the pseudo-first order of the overall malonic acid decomposition with a corresponding rate constant of 2.14 x 10(-2) min(-1) was established. The numerical results on the dynamics and kinetics of the BZ reaction, carried out by the known skeleton model including the Br2O species, were in good agreement with the experimental ones. The already found saddle node infinite period (SNIPER) bifurcation point in transition from a stable quasi-steady state to periodic orbits and vice versa is confirmed by both experimental and numerical investigations of the system under consideration. Namely, the large-amplitude relaxation oscillations with increasing periods between oscillations in approaching the bifurcation points at the beginning and the end of the oscillatory domain, together with excitability of the stable quasi-steady states in their vicinity are obtained.     

Mathematical analysis of the smallest chemical reaction system with Hopf bifurcation

Recently we presented an up to now unstudied three-dimensional dynamical system which is, according to our given definition, the smallest chemical reaction system with Hopf bifurcation. We here study the Hopf bifurcation in detail and prove that near the bifurcation point a stable limit cycle arises. In the analysis we use the methods of local bifurcation theory, especially the center manifold and the normal form theorem. In a similar way we analyse the also occurring transcritical bifurcation. Besides studying local stability, we give the proofs for global stability of the trivial steady state in the whole positive phase space and for the nontrivial steady state in a closed domain containing the steady state point.     

Spatial bistability in a pH autocatalytic system: from long to short range activation

The acid-auto-activated chlorite-tetrathionate reaction is studied in a one-side-fed spatial reactor. It was previously shown that in these conditions the unstirred reaction-diffusion system can generate oscillatory and excitable states even though under well-stirred nonequilibrium conditions only steady-state bistability is observed. Numerical simulations suggest that these temporal reaction-diffusion instabilities result from long-range activation by rapidly diffusing protons. We study here experimentally and numerically the effect of introducing into this reaction-diffusion system macromolecular carboxylate species that reduce the effective diffusivity of protons. Consistent with the original assumption, the introduction of such slow mobility proton-binding species quenches both oscillatory and excitability dynamics. Within the bistability domain the direction of the propagation of an interface between the two steady states depends on control parameter value. We elaborate on the fact that beyond a low critical concentration of macromolecular carboxylate species, the stability limit of the "thermodynamic" branch of spatial steady state does not depend on this concentration. Despite the relative simplicity of the kinetic model used in the numerical simulations, the results are in quasi-quantitative agreement with the experimental observations.     

Oscillatory dynamics protect enzymes and possibly cells against toxic substances

We have used the oscillating peroxidase-oxidase (PO) reaction as a model system to study how oscillatory dynamics may affect the influence of toxic reaction intermediates on enzyme stability. In the peroxidase-oxidase reaction reactive intermediates, such as hydrogen peroxide, superoxide, and hydroxyl radical are formed. Such intermediates inactivate many cellular macromolecules such as proteins and nucleic acids. These reaction intermediates also react with peroxidase itself to form an inactive enzyme. The fact that the PO reaction shows bistability between an oscillatory and a steady state gives us a unique possibility to compare such inactivation when the system is in one of these two states. We show that inactivation of peroxidase is slower when the system is in an oscillatory state, and using numerical simulations we provide evidence that oscillatory dynamics lower the average concentration of the reactive intermediates.     

Dynamic states of the Bray-Liebhafsky reaction when sulfuric acid is the control parameter

Dynamic behavior of hydrogen peroxide decomposition catalyzed by iodate and hydrogen ions (the Bray-Liebhafsky reaction), in a continuous stirred tank reactor is investigated. The experimental results are obtained at one operational point in concentration phase space by varying mixed inflow concentrations of the sulfuric acid. The experimental evidences for the onset and termination of oscillatory behavior via the saddle node infinite period bifurcation as well as some kind of the Andronov-Hopf bifurcation are presented. In addition, the possibility of excitability of a stable steady state by thiamine was observed. The article is published in the original.     

钙离子体系中隐式和显式内随机共振

近年来, 细胞内钙离子信号及其产生机理已成为研究热点之一, 这是因为钙离子信号能控制细胞的生死、 传递细胞间的信息、 提高基因表达的有效性和特殊性[^1~3]. 在钙离子信号传递过程中, 受环境扰动是不可避免的. Shuai等^[4]发现噪音能够控制钙离子通道中钙离子的释放. 在过去的十年中, 无论是物理、 化学还是生物体系^[5~10]的噪音效应已被广泛研究, 其中包括对随机共振(SR)的研究^[5], 经典SR是环境噪音能够放大弱的外加信号. 但随着研究的深入, 发现有无噪音SR^[11]和内SR(ISR) ^[6]. ISR的内信号来自噪音诱导的内信号, 这种SR现象叫隐式内SR(IISR). 而我们则发现了另外一种内SR, 即显式内SR(EISR) ^[12], 它的内信号是体系固有的内信号, 而不是由噪音诱导的. 本文主要研究加入外信号将对IISR和EISR产生的影响.     

Spatial bifurcations of fixed points and limit cycles during the electrochemical oxidation of H2 on Pt ring-electrodes

Pattern formation during the oscillatory oxidation of H2 on Pt ring-electrodes in the presence of electrosorbing ions was studied under potentiostatic control for three different positions of the reference electrode (RE). The position of the RE crucially affects the degree of the global feedback which is imposed by the potentiostatic operation mode, and the three configurations selected corresponded to zero, maximum and intermediate global coupling. In the absence of global coupling, 'communication' among different positions occurs exclusively through migration coupling (the electrochemical counterpart to diffusion in reaction-diffusion systems). In this case, spatially inhomogeneous oscillations that were attributed to a spatial bifurcation of the homogeneous limit cycle were observed throughout. This implies that the system is Benjamin-Feir unstable. For the strongest global coupling adjustable, travelling pulses were found that emerged in a wave bifurcation with n = 1 from the homogeneous steady state. The pulses exhibited modulations in velocity and width that most likely resulted from the interaction between inhomogeneities of the catalytic surface and the nonlinear reaction dynamics. In the case of an intermediate global coupling strength, a diversity of spatio-temporal motions was observed. The dynamics ranged from pulses over target patterns and so-called asymmetric target patterns to mixed states where two or three of these states alternate. For some parameters these mixed states were in addition separated by bursts of the system to a nearly homogeneous unreactive state.     

Behavior of redox systems with electrostatic adsorption on electrodes in the absence of passivation

In the work, the effect of electrostatic adsorption on the stability of steady-state and appearance of monotonous instability in electrochemical systems in the absence of passivation is theoretically studied for different process modes (galvanostatic, potentiostatic, and constant potential drop). It is shown that electro-static adsorption may be the cause for appearance of multiple steady states under the galvanostatic mode and mode of constant potential drop. The corresponding diagrams of static bifurcation are constructed in the regions of different system parameters. The system under consideration tends in the potentiostatic mode to a stable steady state.