Neural Signal Tuned by Random Long-range Connections in Coupled FitzHugh-Nagumo Neurons Systems

We investigate the effect of random long-range connections on signal propagation in an array of coupled FitzHugh- Nagumo （FHN） neurons. The neural network can be obtained by randomly adding a small fraction of shortcuts in an originally locally coupled one-dimensional chain. It is shown that when the first neuron is subjected to external stimuli, it fires and excites its connected neighbours, such that the neural signal may propagate along the chain favoured by the shortcuts. Moreover, there exists an optimal number of shortcuts which can lead to the most synchronous behaviour. In addition, how the region of the fraction of shortcuts varies with the coupling strength is also discussed. These results suggest that topological disorder in the neural network may play a vital role in helping information processing in living systems.     

Synchronization and Pattern Dynamics of Coupled Chaotic Maps on Complex Networks

The synchronization and pattern dynamics of coupled logistic maps on a certain type of complex network, constructed by adding random shortcuts to a regular ring, is investigated. For parameters where an isolated map is fully chaotic, the defect turbulence, which is dominant in the regular network, can be tamed into ordered periodic patterns or synchronized chaotic states when random shortcuts are added, and the patterns formed on the complex network can be grouped into two or three branches depending on the coupling strength.     

细胞体系中内噪声对弱信号检测的积极作用

在小尺度的生物化学反应体系中内噪声是普遍存在的,本文采用化学Langevin方程研究了细胞体系中内噪声对弱信号检测的作用. 研究发现, 在Hopf分岔点附近, 当弱信号非常小以至于不能独立地激发细胞内的钙尖峰振荡时, 内噪声能够帮助细胞内的钙振荡信号越过一个域值, 并且在一个最佳的内噪声强度下, 内噪声、内噪声诱导的钙振荡和弱信号之间会产生共振现象, 由此极大地增强了细胞体系对弱信号的检测能力. 由于内噪声是通过细胞尺度变化而改变的, 因此这种现象也说明了在对弱信号检测行为中最佳细胞尺度的存在. 研究还发现最佳的细胞尺度与真正的细胞体积是相吻合的, 并且基本不随外界刺激的改变而改变, 这具有重要的生物学意义.     

A new cytotoxic cholesterol sulfate from marine sponge Halichondria rugosa

A new steroid, 24xi,25-dimethyl-3alpha-hydroxyl-cholest-5-ene-2beta-ol sodium sulfate (1), together with a known steroid, 24xi,25-dimethyl-cholest-5-ene-2beta,3alpha-diol disodium sulfate (2), was isolated from the ethanol extract of marine sponge Halichondria rugosa. Their structures were elucidated on the base of spectroscopic analysis. Both compounds showed cytotoxicity to four human cancer cell lines (BEL-7402, HT-29, SPC-A1 and U-251) with IC(50) values between 6.5 and 23.1 microM.     

Dysidavarones A-D, new sesquiterpene quinones from the marine sponge Dysidea avara

Dysidavarones A-D (1-4), four new sesquiterpene quinones possessing the unprecedented "dysidavarane" carbon skeleton, were isolated from the South China Sea sponge Dysidea avara. The structures were established by spectroscopic methods, and the absolute configurations were determined using quantum mechanical calculation of the electronic circular dichroic (ECD) spectrum and exciton chirality CD method. Their cytotoxic activity against four human cancer cell lines and PTP1B inhibitory activity were also evaluated.     

Adaptive co-evolution of strategies and network leading to optimal cooperation level in spatial prisoner’s dilemma game

We study evolutionary prisoner's dilemma game on adaptive networks where a population of players co-evolves with their interaction networks. During the co-evolution process, interacted players with opposite strategies either rewire the link between them with probability $p$ or update their strategies with probability $1-p$ depending on their payoffs. Numerical simulation shows that the final network is either split into some disconnected communities whose players share the same strategy within each community or forms a single connected network in which all nodes are in the same strategy. Interestingly, the density of cooperators in the final state can be maximised in an intermediate range of $p$ via the competition between time scale of the network dynamics and that of the node dynamics. Finally, the mean-field analysis helps to understand the results of numerical simulation. Our results may provide some insight into understanding the emergence of cooperation in the real situation where the individuals' behaviour and their relationship adaptively co-evolve.     

电氧化甲酸反应体系的随机共振调制

采用甲酸电氧化的反应模型对随机共振的调制进行了研究。反应模型中有驱动电流和CO的饱和覆盖率两个控制参量。当弱信号和噪声同时作用于驱动电流时,固定信号强度,体系输出的脉冲间隔分布可以在合适的噪声强度时最有序,表明出现了随机共振现象。对CO的饱和覆盖率施加周期性信号的作用可以对随机共振行为进行调制,调制的结果取决于调制信号的周期及初相位。     

Best Spatiotemporal Performance Sustained by Optimal Number of Random Shortcuts on Complex Networks

The spatial synchronization and temporal coherence of FitzHugh-Nagumo （FHN） neurons on complex networks are numerically investigated. When an optimal number of random shortcuts are added to a regular neural chain, the system can reach a state which is nearly periodic in time and almost synchronized in space. More shortcuts do not increase the spatial synchronization too much, but will obviously destroy the temporal regularity.     

Pellynols M−O,cytotoxic polyacetylenic alcohols from a Niphates sp. marine sponge

Three new polyacetylenic alcohols, pellynols M?O (1–3), along with two known ones, melyne A (4) and melyne B (5), were isolated from a Niphates sp. marine sponge collected off the South China Sea. The structures of new compounds were determined based on a combination of 1D and 2D NMR analysis, ESI-MSⁿ fragmentation, and chemical (ozonolysis) method. Their absolute configurations were assigned by modified Mosher's method. All the isolates showed potent cytotoxic activity against PC9 and HepG2 human cancer cell lines with IC₅₀ values of 2.9–7.6?μM.     

Simplexolides A–E and plakorfuran A,six butyrate derived polyketides from the marine sponge Plakortis simplex

Six new polyketides, simplexolides A–E (1–5) and a furan ester, plakorfuran A (6), together with four known furanylidenic methyl esters (7–10) were isolated from the marine sponge Plakortis simplex. Compounds 1–5 feature a tetrahydrofuran ring opened seco-plakortone skeleton. These new structures, including relative configurations, were determined on the basis of extensive analysis of spectroscopic data. The absolute configurations of 1–6 were established by the modified Mosher’s method, and the CD exciton chirality method. However, configurations of the remote stereocenters at C-8 in compounds 1–5 were not determined. Antifungal, cytotoxicity, antileismanial, and antimalarial activities of these polyketides were evaluated.