Information Transmitting and Cognition with a Spiking Neural Network Model

Information encoding plays a crucial role in neuroscience. One of the fundamental questions in cognitive neuroscience is how the brain encodes external stimuli in the sensory cortex. We use a network model based on the Hodgkin–Huxley type to study the information transmitting including its storage and recall. The model is inspired by psychological and neurobiological evidence on sequential memories. The model contains excitatory and inhibitory neurons with all-to-all connections whose architecture has two layers. A lower layer represents consecutive events during the information encoding process, and the upper layer is used to tag sequences of events represented in the lower layer. The spike-timing-dependent plasticity learning rule is used for sequential storage of excitatory connections between the modules. Computer simulations demonstrate that the synchronization status of multiple neurons is dependent on the network connectivity patterns, and also this model has good performance for different sequences of storage and recall.     

蒙脱土负载碘催化多组分合成咪唑衍生物

以苯偶酰(1)、苯甲醛(2a)、苯胺(3)和醋酸铵(4)为原料,蒙脱土负载碘和三乙烯二胺(DABCO)为催化剂,通过多组分法合成了6种1,2,4,5-四芳基-1,3-咪唑衍生物,其结构经1H NMR和IR确证。对反应条件进行了优化。结果表明:在最优反应条件{以10 mol%MMT/I2为催化剂,10 mol%DABCO为碱,正丁醇为溶剂,原料配比r[n(1)∶n(2a)∶n(3)∶n(4)]=1.0∶2.0∶2.0∶8.0,于110℃反应16 h}下,产率最高为91.5%。     

KINETICS OF NON-ISOTHERMAL CRYSTALLIZATION OF POLY (ETHYLENE TEREPHTHALATE) MODIFIED BY POLY (ETHYLENE GLYCOL)

The non-isothermal crystallization kinetics of poly(ethylene terephthalate) (PET) modified by poly (ethlene glycol) (PEG) were determined by DSC. The dual linear regression method was used to evaluate the relationship between the reciprocal of t 1/2 ( the half life of crystallization) and the appropriate temperature variable. The parameters such as the activation energy (Ed) for transport, the equilibrium melting temperature (T_m~0),the nucleation parameter (ψ),themaximum crystallization temperature (T_(e, max)), and the kinetic crystallizability (G) for the copolyesters were obtained. The influence of the PEG content in PET chains on the parameters characterizing crystallization kinetics and crystallization thermodynamics was discussed.     

瓜环对氨基酸的分子识别研究

使用¹H NMR和UV-Vis光谱法研究了七、八元瓜环对九种天然氨基酸盐酸盐的分子识别作用. 结果表明, 瓜环对芳香侧基取代的L-酪氨酸、L-色氨酸、L-苯丙氨酸均能进行有效识别, 而侧链上不带芳香基团的氨基酸, 如L-组氨酸、L-谷氨酸、L-蛋氨酸、L-缬氨酸、L-白氨酸、L-丙氨酸, 与这些瓜环的作用相对较弱. 对于七元瓜环, 主客体间都以1∶1化学计量比形成包结物, 并得到它们相互作用的稳定常数; 八元瓜环与L-酪氨酸及L-色氨酸也以1∶1形成包结物, 而与L-苯丙氨酸以1∶2形成包结物. L-酪氨酸、L-色氨酸和L-苯丙氨酸荧光性质研究表明, 七、八元瓜环既可成为这些氨基酸荧光性质的增敏试剂, 也可成为它们荧光淬灭试剂, 这与氨基酸的结构有关.     

八元瓜环与啡咯啉及其衍生物主客体配合物的研究

利用¹H NMR技术、荧光光谱法, 对八元瓜环与多种啡咯啉及衍生物相互作用形成的主客体配合物实体的结构进行了考察. 研究结果显示, 1,10-啡咯啉及其异构体1,7-啡咯啉、4,7-啡咯啉的盐酸盐“钻”进八元瓜环内腔, 形成2︰1自组装主客体包结物; 2,9二甲基-1,10-啡咯啉的盐酸盐部分进入八元瓜环形成一种比较稳定的主客体配合物; 而4,7-二甲基-1,10-啡咯啉、3,4,7,8-四甲基-1,10-啡咯啉以两种不同的π-π堆砌方式部分进入八元瓜环内腔, 形成包结比也是2︰1的两种较稳定的自组装主客体配合物异构体.     

三种瓜环与4,4′-联吡啶及N,N′-二甲基4,4′-联吡啶盐酸盐相互作用的研究

以七元瓜环(Q[7])和新型椭圆型改性瓜环———对称四甲基取代六元瓜环(TM eQ[6])为主体,4,4′-联吡啶的盐酸盐(44)以及N,N′-二甲基4,4′-联吡啶的盐酸盐(dm44)为客体的主客体相互作用进行了考察.实验结果表明,Q[7]与客体44及dm44作用体系中,客体为了更有效地被主体Q[7]包结,在Q[7]内腔中呈倾斜状分布的几率最高.用核磁共振、循环伏安以及紫外吸收光谱对实验结果进行了印证和补充,验证了TM eQ[6]与客体44及dm44可发生较强的相互作用,形成一维的自组装超分子结构.核磁共振以及循环伏安方法的实验结果表明,没有观察到Q[6]与客体44及dm44的明显作用,而紫外吸收光谱方法证实,Q[6]与客体44确实存在一定的相互作用,比较主客体的结构特征,该作用体系也可能存在自组装的一维超分子结构等多种作用形式.     

瓜环与2,2''''-联吡啶衍生物的相互作用

利用~1H NMR技术、紫外吸收光谱及荧光光谱方法,考察了对六、七以及八元瓜环与多种2,2'-联吡啶衍生物相互作用形成的主客体配合物结构及光学性质.研究结果显示,不同的2,2'-联吡啶衍生物与瓜环作用不仅形成多种不同包结比的稳定包结配合物,且所形成的主客体包结配合物的结构及光谱性质也各不相同;同时用几种方法协同考察起到了互为补充、互为验证的良好效果.     

Noise Effects on Temperature Encoding of Neuronal Spike Trains in a Cold Receptor

We examine how noise interacts with encoding mechanisms of neuronal stimulus in a cold receptor. From ISI series and bifurcation diagrams it is shown that there are considerable differences in interval distributions and impulse patterns caused by purely deterministic simulations and noisy simulations. The ISI-distance can be used as an effective and powerful way to measure the noise effects on spike trains of the cold receptor quantitatively. It is also found that spike trains observed in cold receptors can be more strongly affected by noise for low temperatures than for high temperatures in some aspects; meanwhile, the spike train has greater variability with increasing noise intensity.     

瓜环与2,2'-联吡啶衍生物的相互作用

利用¹H NMR技术、紫外吸收光谱及荧光光谱方法, 考察了对六、七以及八元瓜环与多种2,2'-联吡啶衍生物相互作用形成的主客体配合物结构及光谱性质. 研究结果显示, 不同的2,2'-联吡啶衍生物与瓜环作用不仅形成多种不同包结比的稳定包结配合物, 且所形成的主客体包结配合物的结构及光谱性质也各不相同; 同时用几种方法协同考察起到了互为补充、互为验证的良好效果.     

Adaptive H∞ synchronization of chaotic systems via linear and nonlinear feedback control

Adaptive H∞ synchronization of chaotic systems via linear and nonlinear feedback control is investigated.The chaotic systems are redesigned by using the generalized Hamiltonian systems and observer approach.Based on Lyapunov’s stability theory,linear and nonlinear feedback control of adaptive H∞ synchronization is established in order to not only guarantee stable synchronization of both master and slave systems but also reduce the effect of external disturbance on an H∞-norm constraint.Adaptive H∞ synchronization of chaotic systems via three kinds of control is investigated with applications to Lorenz and Chen systems.Numerical simulations are also given to identify theeffectiveness of the theoretical analysis.