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。     

具有多重定态的化学反应中的相变及临界点分类

研究了具有多重定态的化学反应中的相变及其临界现象。参照Landau相变理论的基本精神,提出了以判断临界点的稳定性及其热力学函数的连续性为准则,来对临界点进行分类,从而说明了化学多重定态中相变和临界现象的多样性。一般来说,多稳性的级次越高,相变和临界点的式样也越多。最后,对一个在非理想情形下可能具有三稳态的自催化反应模式中的相变和临界现象进行了考察。     

多定态转变化学反应体系与环境传热-扩散耦合导致的环面型化学振荡

以Schlögl模型作为多定态转变化学反应体系的范例, 研究了通过传热及扩散与环境耦合的多定态转变化学反应体系中诱发的新动力学行为, 其中特别重要的是沿慢变量方向的环面型化学振荡的出现. 建立了慢流型上的准定态的线形化稳定性分析法, 揭示了由极限环振荡蜕变为环面型振荡的动力学机制, 不同于小寄生参数存在引起的非连续极限环振荡. 通过以慢流型上准定态稳定性分区为基础的定性分析, 进一步揭示了该类体系中可能出现间歇性、反复持续式和骤发式3种亚类环面振荡. 最后以第三亚类作为示例, 以相应的计算机模拟证实理论分析的正确性.     

热补偿恒温控制条件下铂电极BZ反应体系中的电化学时间自组织——从极限环型电化学振荡到环面跳跃型非连续电化学振荡

在实验室的热补偿恒温控制条件下, 理论预测的等温恒电流(电压)电化学振荡实际上将发生变异. 用慢流型上准定态的线性化稳定性分析法全面分析了此类恒温控制条件下铂电极BZ反应系在以温度为慢变参数的慢流型上的准稳定性及绕温度轴慢变轨迹的动力学行为. 发现在温度围绕控制值上下往复波动的每一个周期内, 准定态点将穿梭跨越于振荡区与非振荡区之间, 表现为间隙性的沿温度轴的环面型电化学振荡. 计算机模拟结果证实了上述理论分析.     

平衡态向周期态的分支和副热带流型的两类低频振荡

本文在低谱途径的非绝热项中,引进对流凝结加热参数化,用以估计湿过程对平衡态向周期态分支的影响。在一定的参数集合,牛顿加热形式的强迫下,不能激发出周期态分支;但含有对流凝结加热的非绝热强迫,却可以激发出时间尺度以2—3周为主的周期态分支。对流凝结加热并使周期态分支运动的时间尺度缩短,振幅增长加快。对流上层副热带气压分布均匀的基态失稳,可形成两种类型的低频振荡。一类是高压中心的东西振荡;另一类是高压中心强度的低频振荡。这时,高压中心位置呈准定常状态。对流凝结加热对这两类低频振荡均具有一定的影响能力。     

铁-联吡啶体系化学振荡的研究及其在价态分析中的应用

试验发现,铁-联吡啶体系中存在化学振荡,初步探讨了该体系的化学振荡规律,并找出氟化铵为有效的振荡抑制剂。加入抑制剂后,在Fe（Ⅲ）存在下,铁-联吡啶分光光度法能准确测定Fe（Ⅱ）。方法用于人工样品中铁的价态分析,测得Fe（Ⅱ）的回收率为99．0％～99．7％,Fe（Ⅲ）的回收率为99．5％～103．0％。     

PHOTO-INDUCED ELECTRON TRANSFER FROM TRANSITION METAL CATIONS TO EXCITED STATES OF THE 10-METHYLACRIDINIUM ION

Abstract— Photo-induced electron transfer from cuprous ion to electronically excited 10-methyiacridinium tetrafluoroborate in acetonitrile-water solutions is described. The final photoproducts are Cu²⁺ (aq) and 10,10'-dimethyl-9,9'-biacridane. The proposed mechanism, based on microsecond flash excitation and fluorimetry experiments, is one-electron transfer from Cu⁺ to the 10-methylacridinium ion triplet state (and possibly the singlet state), followed by dimerization of the neutral acridinyl radical. Because the high energy photoproducts revert slowly to reactants, the system may have potential for storage and controlled recovery of light energy.     

A STUDY ON MULTIPLE METAL TO METAL BONDS IN TRANSITION METAL COMPLEXES

<正> We report here the calculation on electronic structures of model compounds of dimetal tetracarboxylate M2(O2CH)4 (M=V, Cr, Mo) by means of a DPS8 computer CNDO program. On the basis of molecular orbital components and contour maps of wave functions the character of the multiple metal to metal bonds are analysed and discussed.     

KINETICSOF TRANSITION FROM ISOTROPIC TO CHOLESTERIC PHASE FOR A THERMOTROPIC CELLULOSE DERIVATIVE

The kinetics of mesophase formation of a thermotropic hydroxyethyl cellulose acetatefrom isotropic phase to cholesteric mesophase has been studied by means of depolariz-ing transmittance method. Avrami type analysis of the data gives an exponent n close to1, which suggests the nucleation followed by rod-like growth. It means that the kineticbehavior of phase transition from isotropic to cholesteric mesophase is very similar to thatof the mesophase formation from isotropic to nematic mesophase.     

ON THE EVIDENCE FROM HIGH-INTENSITY TWO-PHOTON LASER PHOTOLYSIS FOR ENERGY TRANSFER FROM HIGH-LYING QUASI-RYDBERG STATES OF THYMINE TO ISO-ENERGETIC STATES OF WATER

High intensity two-photon picosecond excitation at 266 nm (effective energy 9.2 eV) has been shown to cause efficient photolysis of thymine in aqueous solution. Experimental results for the quantum yield of solvated electrons, phi (eaq-), and the net consumption of thymine, phi(-Thy) have been interpreted (Oraevsky and Nikogosyan, 1985) as indicating a stoichiometric excess of solvated electrons over thymine radical-cations. To account for this under conditions in which direct two-photon photolysis of water is negligible, it has been concluded that it is necessary to postulate the occurrence of extensive energy transfer from high-lying thymine states to dissociating/ionizing states of water. This Note demonstrates that: (i) the supposed excess of eaq- depends on an implicit assumption concerning the secondary radical reactions (dimerization) such that -delta Thy = delta Thy+; if secondary radicals dismutate then -Thy = 1/2 delta Thy+, leading a stoichiometric deficit of eaq-; and (ii) the experimental results can be accounted for by a mixed dimerization/dismutation mechanism, without invoking energy transfer. Thus there is no evidence unambiguously requiring the postulate of energy transfer. But if it occurs, stoichiometry places restrictions on the extent of transfer and the nature of the secondary radical reactions.     

STEADY HYPSOCHROMIC SHIFT OF PEAK RESPONSIVITY TO ATTRACTANT LIGHT FROM 590 nm TO 560 nm IN Halobacterium halobium*

Abstract— Peak responsivity of photoattraction in Halobacterium halobium cells shows steady hypsochromic shift from 590 nm wavelength under low irradiance conditions to 560 nm under high irradiance conditions. Inversion of the photoattractant response, as dependent on blue vs red background light, is compatible with the known properties of photochromic sensory rhodopsin-I (SR-I) with ground state maximum absorption at 587 nm. Relaxation of the photoattractant response in H. halobium, as a function of wavelength and irradiance, gives a hint at an antagonistic pigment or intermediate state, different from ground state SR-I, with peak sensitivity at 620 nm or even above. The less sensitive photoattractant response at 560 nm persists without photorelaxation and represents the peak responsivity under high irradiance conditions.     

A STUDY ON MULTIPLE CENTER d-p π BOND IN OXO-CENTERED TRINUCLEAR TRANSITION METAL CARBOXYLATE COMPLEXES

<正> The self-empirical SCC-EHMO calculation has been carried out for a series of oxo-centered trinuclear metal carboxylate complexes. The results indicated that the four-center d-p ?π bonds, formed by combination of centered oxygen atom 2p2 orbital with metal atom dxz,dyz orbitals in core M3O or M2M1O (simplified as M3O in the following) ,are of importance for this class complexes. In the opinion of isolobal contrast, these bonds would be similar to four-center p-p π bonds in C(CH2)3 and can be used for explaining some characteristics of these complexes, such as stability, planar configuration of M3O core, chemical reactivity and so on .     

端基附壁高分子模型链的塌缩转变

借MonteCarlo和模拟退火方法研究了端基附壁高分子尾形链在不同温度下的形态变化 ,链的模型采用有最近邻相互吸引作用的自避行走 .计算机实验结果表明 ,对于端基附壁的高分子尾形链 ,与自由链一样 ,当温度逐渐降低时高分子链会发生从松散的无规线团到紧密球体的塌缩转变 .计算机模拟得到了端基附壁链的均方末端距及其分量 ,均方回转半径及分布随温度的变化 .由于刚性壁的影响 ,使得有限链长的高分子尾形链与自由链相比 ,其表示链尺寸 温度关系的曲线要稍低 .模拟还发现 ,在高温时壁对链形状的影响比较大 ,壁垂直方向上尺寸明显大于平行方向的尺寸 ,后者接近于自由链的尺寸分量 .然而 ,低于θ温度时 ,尤其是完全塌缩之后 ,壁对链形状的影响已经很小 .     

一个新的液晶相转变动力学理论

本文以保留系统的宏观特性为基本原则,从用动力学方法处理非稳态相转变入手,在物理化学基础上,建立了描述液晶相转变的动力学方程,提出了动力学意义上的相转变级数参数,推导出相转变级数的理论公式及参数的变化范围,丹卉将其应用于一新的聚合物体系,获得了该体系各聚合物加热过程中所经历相态的动力学相转变级数。