Enhancement of pacemaker induced stochastic resonance by an autapse in a scale-free neuronal network

An autapse is an unusual synapse that occurs between the axon and the soma of the same neuron. Mathematically, it can be described as a self-delayed feedback loop that is defined by a specific time-delay and the so-called autaptic coupling strength. Recently, the role and function of autapses within the nervous system has been studied extensively. Here, we extend the scope of theoretical research by investigating the effects of an autapse on the transmission of a weak localized pacemaker activity in a scale-free neuronal network. Our results reveal that by mediating the spiking activity of the pacemaker neuron, an autapse increases the propagation of its rhythm across the whole network, if only the autaptic time delay and the autaptic coupling strength are properly adjusted. We show that the autapse-induced enhancement of the transmission of pacemaker activity occurs only when the autaptic time delay is close to an integer multiple of the intrinsic oscillation time of the neurons that form the network. In particular, we demonstrate the emergence of multiple resonances involving the weak signal, the intrinsic oscillations, and the time scale that is dictated by the autapse. Interestingly, we also show that the enhancement of the pacemaker rhythm across the network is the strongest if the degree of the pacemaker neuron is lowest. This is because the dissipation of the localized rhythm is contained to the few directly linked neurons, and only afterwards, through the secondary neurons, it propagates further. If the pacemaker neuron has a high degree, then its rhythm is simply too weak to excite all the neighboring neurons, and propagation therefore fails.     

Transition of electric activity of neurons induced by chemical and electric autapses

Autapse connected to the neuron can change the electric activity of neuron. The effect of autapse on neuronal activity is often described by adding an additive forcing current along a close loop, which is described by a time-delayed feedback on the membrane potential. Neuron often responds to electric autapse forcing sensitively and quickly, while the chemical autapse changes the electric activity of neuron slowly. By applying external forcing, a shift transition of electric activity can be more easily induced by the electric autapse than the chemical autapse. Our results confirm that chemical autapse can enhance and/or suppress the transition of electric activity with excitable or inhibitory type driven by electric autapse, vice versa. It indicates that an appropriate switch-off-on for autapse can make the neuron give different types of response to external forcing. Particularly, cooperation and competition between chemical and electric autapse help neuron response to external forcing in the most reliable way.     

Dynamics of electric activities in neuron and neurons of network induced by autapses

The effect of autapse on adjusting the membrane of potentials of neuron is described by imposing a time-delayed feedback on the membrane of neuron in a close loop type,and the Hindmarsh-Rose(HR)neuron under autapse is investigated.Firstly,the electric activity of single HR neuron under electric autapse and chemical autapse is investigated.It is found that quiescent neuron is activated due to appropriate time delay and feedback gain in the autapse,and the autapse plays an important role in waking up neuron.The parameter region for periodic,chaotic activity of neuron under autapse is calculated in a numerical way,and transition from spiking to bursting is observed by increasing the feedback gain and time delay carefully.Furthermore,the collective electric activities of neurons in a ring network is investigated and abundant electric activities are observed due to the competition between the autapse and the time-delayed coupling between adjacent neurons in the network,and time delay in coupling between neurons also plays an important role in enhancing synchronization in the network.     

Preparation and performance of dye-sensitized solar cells based on ZnO-modified TiO_2 electrodes

The ZnO-modified TiO 2 electrode was prepared by adding Zn(CH 3 COO) 2 ·2H 2 O to the TiO 2 colloid during the sol-gel production process,and was used in dye-sensitized solar cells (DSCs).The open circuit voltage (V OC) and fill factor (ff) of the cells were improved significantly.The performances of the ZnO-modified TiO 2 electrode such as dark current,transient photocurrent,impedance,absorption spectra,and flat band potential (V fb) were investigated.It is found that the interface charge recombination imp...     

Emergence of higher-level neuron properties using a hierarchical statistical distribution model

Essential to visual tasks such as object recognition is the formation of effective representations that generalize from specific instances of visual input. Neurons in primary visual cortex are typically hypothesized to efficiently encode image structures such as edge and textures from natural scenes. Here this paper proposed a novel hierarchical statistical distribution model to generalize higher-level neuron properties and encode distributed regularities that characterize local image regions. Two layers of our hierarchical model are presented to extract spiking activities of excitatory neurons decorrelated by inhibitory neurons and to construct the statistical patterns of input data, respectively. Trained on whitened natural images, parameters including neural connecting weights and distribution coding weights are estimated by their corresponding learning rules. To prove the feasibility and effectiveness of our model, several experiments on natural images are conducted. Adapting our model to natural scenes yields a distributed representation for higher-order statistical regularities. Comparison results provide insight into higher-level neurons which encode more abstract and invariant properties.     

两亲嵌段共聚物P(St)-b-P(HEA)的合成、表征及其胶束化行为研究

以2-溴代异丁酸乙酯(EBiB)为引发剂,溴化亚铜(CuBr)和α,α′-联吡啶(bpy)分别为催化剂和配体,通过原子转移自由基聚合法(ATRP)制备了两亲嵌段共聚物P(St)-b-P(HEA)。利用FT-IR、GPC和TG/DTG对产物进行了表征,确定合成产物为P(St)-b-P(HEA)两嵌段共聚物。用透射电镜(TEM)观察了其在5∶95(VTHF∶VH2O)混合溶剂中的胶束化行为,发现其胶束呈分散球状体和链状聚集体两种形态。     

磷脂酶C活性测定方法及其应用的研究

以对——硝基苯磷酸胆碱(NPPC)为基质,用Hepes 代替Tris-Hcl 缓冲液对磷脂酶C(PLC)活性进行测定.最大反应速度(V_(?))由71.43nM/min 增高到212.76nM/min.用此法证明了多粘菌素B 增强PLC 活性;夹竹桃霉素的影响和药物浓度密切相关.     

Ribbon-like Cu doped V_6O_(13) as Cathode Material for High-performance Lithium Ion Batteries

Ribbon-like Cu doped V_6O_(13) was synthesized via a simple solvothermal approach followed by heat treatment in air.As an cathode material for lithium ion battery,the ribbon-like Cu doped V_6O_(13 )electrode exhibited good capacity retention with a reversible capacity of over 313 m Ah?g~(-1) for up to 50 cycles at 0.1C,as well as a high charge capacity of 306 m Ah?g~(-1) at a high current rate of 1 C,in comparison to undoped V_6O_(13 )electrode(267 m Ah?g~(-1) at 0.1C and 273 m Ah?g~(-1) at 1 C).The high rate capability and better cycleability of the doped electrode can be attributed to the influence of the Cu ions on the mophology and the electronic conductivity of V_6O_(13) during the lithiation and delithiation process.     

500kV交流输电线下工频电场对人体的影响

采用有限元分析软件ANSYS建立了近似人体的二维仿真模型,分析计算了在500 kV交流输电线路下工频电场对人体的影响,得出了人体感应电场及总感应电流的分布情况.仿真结果表明,无论人体接地与否,人体最大感应电流密度和人体内部最大电场强度均小于国际非电离辐射防护委员会（ICNIRP）规定的安全限值.     

Effects of channel blocks on the spiking regularity in clustered neuronal networks

In this paper,we discuss the influences of channel blocks on the spiking regularity in a clustered neuronal network by applying stochastic Hodgkin-Huxley neuronal models as the building blocks.With the aid of simulation results,we reveal that the spiking regularity of the clustered neuronal network could be resonantly enhanced via fine-tuning of the non-blocked potassium channel fraction xK.While the non-blocked sodium channel fraction xNa can enhance the spiking regularity of the clustered neuronal network in most cases.These results indicate that not only sodium channel blocks but also potassium channel blocks could have great influences on the regularity of spike timings in the clustered neuronal networks.Considering the importance of spike timings in neuronal information transforming processes,our results may give some implications for understanding the nonnegligible role of randomness in ion channels in neuronal systems.     

聚氧乙烯─聚氧丙烯多嵌段聚合物合成和导电性能

用聚乙二醇（分子量６００）、聚丙二醇（分子量１０００）和二氯甲烷在氢氧化钾存在下合成了氧亚甲基连接的聚氧乙烯－聚氧丙烯多嵌段聚合物（（ＰＥＯ－ＰＰＯ）ｎ），研究了它与ＬｉＣｌＯ４络合物的离子导电性能，以电导率最高的络合物为电解质，Ｎａ（１＋ｘ）Ｖ３Ｏ８复合物和Ｌｉ片分别为正、负极组装了薄型锂电池并测定其放电性能。     

Effects of Compaction Temperature on the Volumetric Properties and Compaction Energy Efforts of Polymer-Modified Asphalt Mixtures

In order to determine a proper compaction temperature that affects the workability and compactibility of the polymer-modified asphalt(PMA), the effect of compaction temperature was examined on the volumetric properties and the compaction energy indices. Change in compaction temperature shows an important influence on the maximum specific gravity of mixture(G_(mm)) by internal volume change of PMA. The change in G_(mm) mainly affects the effective volume of the aggregate(V_(Eff)). Reduction in V_(Eff) from Zero shear viscosity(ZSV) to superpave temperature allows 0.1%-0.15% of the asphalt binder to occupy highly the external voids of aggregates. The volumetric properties for all compaction specimens meet superpave criteria, but the energy efforts were the lowest at ZSV temperature. Lower energy efforts at the ZSV temperature reflect easier compaction than those at excessively high temperature. Clearly, excessive compaction temperature may not be necessary to improve the compactibility and to reduce the compaction efforts.     

电晕放电法无损检测技术中检测参数对检测结果的影响

本文从实验结果出发,探讨了电晕放电法无损检测技术中检测延迟时间t、极间直流电压V_(DC)和相对湿度R.H.三个检测参数的变化对检测结果的影响情况,得到了对确定材料的参考性规律,并对规律进行了定性地说明。     

系统可靠性分配的模糊数学方法

基于模糊数学理论,建立了串联系统可靠性的模糊分配方法。将影响系统可靠性分配的各种因素综合在一起,并予以量化,从而对系统可靠性进行科学、合理的分配。     

STBC-VBLAST系统发射天线选择算法研究

分析STBC(Space-Time Block Code)与V-BLAST混合编码系统中基于STBC子系统性能最优准则的发射天线选择算法,提出通过提高STBC子系统的调制阶数,可以使STBC子系统和V-BLAST子系统性能基本平衡的方法.该方法同时也可提高全系统的频谱效率。计算机仿真结果证明,该方法有效。     

零状态可探测与非线性系统的镇定

研究零状态可探测性在非线性系统镇定中的作用。运用李雅谱诺夫稳定原理,证明了以光滑正定适定函数为库函数的无源系统,通过输出负反馈可镇定当且仅当其零状态可探测;运用零状态可探测性到一类从驱动联级系统的镇定,提出了较弱的充分条件,仅要求从动系统的非受控动态临界稳定而不必全局渐近稳定;为了镇定设计需要给出了无源系统零状态可探测的两个几何判据。中举例说明了所得结果的实用性。     

二值神经网的逻辑理论

提出了二值神经网的逻辑理论，它包括二状判决、弱推理、推理规则、规则类型和强度、一致和矛盾等。该理论表明：神经网是自主的、开放的、柔性限制的和自适应的约束满足网；神经网运行的根本原因是网络中存在着优势矛盾。     

施主掺杂BaTiO_3陶瓷的正电子湮没和顺磁共振研究

本文用正电子湮没和电子顺磁共振相结合的方法对施主掺杂BaTiO_3陶瓷的缺陷进行了研究。正电子湮没寿命测量说明与Ba/Ti=1的样品相比Ba过量或Ti过量都会引起材料中的空位增加。顺磁共振图谱表明,g=1.997峰的强度在铁电相变为顺电相后,强度有很大的增长(约20倍)。该峰强度随Ba/Ti的变化与正电子捕获率随Ba/Ti的变化相同。因此该峰是由阳离子空位(V_(Ba)和V_(Ti))引起的。它实质上是由O~-产生的,随施主掺量的增加g=1.997峰急剧增强,这很可能是由于施主增加引起V_(Ti)大量生成的缘故。     

一类非线性感知器的设计与应用

本文设计出一类比传统感知器更加接近实际的生物感知器,根据相应的学习规则,它能够成功的执行非线性分类任务。根据突触连接的不同,如纯兴奋突触连接或等比率的兴奋与抑制突触连接,考虑三种不同的模型,得出相应的决策支持界。应用所得的学习规则,此类单层感知器也能够执行非线性的分类任务,如异或问题（XOR）的解决。     

受电弓弓头悬挂系统的随机跳跃与分岔

基于随机平均法研究考虑刚度非线性时DSA X型受电弓弓头悬挂子系统的随机动力学特性.建立弓头悬挂子系统的非线性动力学模型,基于受电弓的结构参数计算获得非线性刚度.弓网间接触压力简化为对弓头悬挂系统的周期和随机组合外激励,建立描述弓头悬挂动态行为的非线性随机微分方程.基于随机平均法得到弓头悬挂子系统的稳态响应统计量,研究非线性强度对稳态响应的影响规律.结果表明,弓头滑板的稳态响应出现随机跳跃,随着非线性强度的变化随机跳跃会产生或消失,即发生分岔.