一类非线性信号动力学趋化模型的非线性不稳定性

应用嵌入定理,能量估计方法和bootstrp技巧,讨论一类非线性信号动力学趋化模型的不稳定正常数平衡解附近的非线性动力学性态.对正常数平衡解失稳初期时空斑图的非线性演化给出严格的定量刻画.

心电动力学信号数据特征提取与模式识别的研究进展

现代控制理论和计算机技术的进步,为深入研究心电信号内在动态病理特征创造了良好条件,并推动了相关学者在基于心电信号转化数据的神经网络模型构建、心电信号异质度特征的量化指标提取、心脏疾病辅助诊断等方面的早期探索。本文综述了心电动力学信号数据特征的研究现状,并介绍了心电动力学信号数据特征的提取方法、模式识别及其在心肌缺血辅助诊断、心肌缺血引发心脏疾病早期筛查和疗效评估等方面的应用。

钙离子信号及细胞调控信号网络动力学

钙离子(Ca^(2+))是细胞内广泛存在的一种重要的第二信使,参与并控制着几乎所有的生命活动过程.细胞信号分子网络对细胞正常和病理生理活动过程进行着精密调控,确保细胞各项生理功能有序地进行.本文综述了近些年本课题组关于细胞内钙信号及细胞信号网络动力学模型方面的研究进展,包括集团化钙离子通道释放局域钙信号、细胞全局钙波信号、内质网和线粒体钙微域调控钙信号和钙信号调控细胞凋亡信号网络动力学,以及细胞信号调控网络动力学等.这些理论工作为研究钙信号和蛋白质信号网络调控细胞复杂生命过程的动力学机制提供了方向和思路.

基于功能近红外光谱成像的协调运动想象识别研究

基于功能近红外光谱成像的脑机接口(fNIRS-BCI)是一种较为新颖的脑机交互技术。为了探究不同肢体协调运动想象血液动力学信号的可分性以及不同组合特征的分类效果,研究采集了10名健康受试者站立、行走想象以及休息状态的血液动力学信号,提取了氧合血红蛋白(HbO2)信号的均值、峰值、均方根、方差和标准差的组合作为分类特征。构建了基于最小二乘支持向量机(LS-SVM)的分类模型,对站立、行走想象和休息状态的HbO2进行了测量和分类。试验结果表明,均值&峰值、均值&均方根、标准差&均值、方差&均方根的分类准确率明显高于其他组合特征,分别为77.3%±5.5%、74.8%±6.1%、71.7%±6.5%和73%±3.9%。这表明多个肢体的协调运动想象具有可分性,有望为fNIRS-BCI控制外部设备增加新的指令,该研究可能为fNIRS-BCI在下肢康复的应用提供帮助。

一类Keller-Segel趋化模型的分支结构

应用局部分支方法,讨论一类带Logistic源项的具有非线性信号动力学趋化模型在二维空间中局部分支解的存在性,并且在分支点附近确定分支方向。

反相胶束介质中漆酶催化反应中间体信息的捕捉及其解析

利用反相胶束独特的介质特性 ,捕捉到漆酶催化反应的中间体光谱动力学信号 ,实现了对酶催化反应过程的在线光谱研究 .通过解析反应过程中在线测得的动力学光谱数据矩阵 ,解得中间体的生成和衰减均为一级反应 ,并求出实验条件下的反应速率常数 .

Guard Cell Signaling Dynamics and Rapid Chip-based Cloning of Ion Accumulation Mutants

Guard cells have been developed as a model system for dissecting hormone,ion channel and calcium signal transduction in response to physiological stimuli. Abscisic acid causes elevations in the cytosolic Ca^2+ concentration in guard cells. We identified reactive oxygen species（ROS) activation of Ca^2+-permeable

Diagnostic efficacy of gadoxetic acid-enhanced MRI for hepatocellular carcinoma and dysplastic nodule

AIM:To evaluate the relationship between the signal intensity of hepatobiliary phase images on gadoxetic acid-enhanced magnetic resonance imaging(MRI)and histological grade.METHODS:Fifty-nine patients with 82 hepatocellular lesions were evaluated retrospectively.Hepatobiliary phase images on gadoxetic acid-enhanced MRI were classified into 3 groups:low,iso or high.Angiographyassisted computed tomography(CT)findings were also classified into 3 groups:CT during arterial portography,and CT hepatic arteriography:A:iso,iso or low;B:slightly low,iso or low;;and C:low,high.We correlated angiography-assisted CT,hepatobiliary phase findings during gadoxetic acid-enhanced MRI and histological grades.Furthermore,correlations between MRI findings and histological grade for each hemodynamic pattern were performed.Correlations among radiologicaland pathological findings were statistically evaluated using the chi-square test and Fisher's exact test.RESULTS:There was a significant correlation between histological grade and hemodynamic pattern(P<0.05).There was a significant correlation between histological grade and signal intensity in the hepatobiliary phase(P<0.05)in group A lesions.There was no significant correlation between histological grade and signal intensity in the hepatobiliary phase in group B or C lesions(P>0.05).CONCLUSION:Signal intensity in the hepatobiliary phase correlated with histological grade in the lesions that maintained portal blood flow,but did not correlate in lesions that showed decreased or defective portal blood flow.

Dynamics of Meandering Spiral Waves Driven by Two-Point Feedback

We numerically study the dynamics of meandering spiral waves in the excitable system subjected to a feedback signal coming from two measuring points located on a straight line together with the initial spiral core. The core location and size radius of the final attractors are computed, and they change with the position of the moving measuring point in a unique way. By the Fourier Spectral analysis, we find the frequency-locked behaviors different from the driving scheme of the external periodic force. It when the moving measuring point approaches closely is also found that the meandering spiral wave can be eliminated the boundary and its feedback gain is large enough. This offers an effective and convenient method for eliminating meandering spiral waves.

Neural network identification for underwater vehicle motion control system based on hybrid learning algorithm

Based on the structure of Elman and Jordan neural networks, a new dynamic neural network is constructed. The network can remember the past state of the hidden layer and adjust the effect of the past signal to the current value in real-time. And in order to enhance the signal processing capabilities, the feedback of output layer nodes is increased. A hybrid learning algorithm based on genetic algorithm （GA） and error back propagation algorithm （BP） is used to adjust the weight values of the network, which can accelerate the rate of convergence and avoid getting into local optimum. Finally, the improved neural network is utilized to identify underwater vehicle （UV） ＇ s hydrodynamic model, and the simulation results show that the neural network based on hybrid learning algorithm can improve the learning rate of convergence and identification nrecision.

The dynamics of color signals in male threespine sticklebacks Gasterosteus aculeatus

Body coloration and color patterns are ubiquitous throughout the animal kingdom and vary be- tween and within species. Recent studies have dealt with individual dynamics of various aspects of coloration, as it is in many cases a flexible trait and changes in color expression may be context-de- pendent. During the reproductive phase, temporal changes of coloration in the visible spectral range （400-700 nm） have been shown for many animals but corresponding changes in the ultravio- let （UV） waveband （300-400 nm） have rarely been studied. Threespine stickleback Gasterosteus aculeatus males develop conspicuous orange-red breeding coloration combined with UV reflect- ance in the cheek region. We investigated dynamics of color patterns including UV throughout a male breeding cycle, as well as short-term changes in coloration in response to a computer- animated rival using reflectance spectrophotometry and visual modeling, to estimate how colors would be perceived by conspecifics. We found the orange-red component of coloration to vary during the breeding cycle with respect to hue （theta/R50） and intensity （achieved chroma/red chroma）. Furthermore, color intensity in the orange-red spectral part （achieved chroma） tended to be increased after the presentation of an artificial rival. Dynamic changes in specific measures of hue and intensity in the UV waveband were not found. In general, the orange-red component of the signal seems to be dynamic with respect to color intensity and hue. This accounts in particular for color changes during the breeding cycle, presumably to signal reproductive status, and with limitations as well in the intrasexual context, most likely to signal dominance or inferiority.

Nonlinear Dynamics of Permanent-magnet Synchronous Motor with v/f Control

The nonlinear dynamics of permanent-magnet synchronous motor(PMSM) with v/f control signals is investigated intensively.First,the equilibria and steady-state characteristics of the system are formulated by analytical analysis.Then,some of its basic dynamical properties,such as characteristic eigenvalues,Lyapunov exponents and phase trajectories are studied by varying the values of system parameters.It is found that when the values of the system parameters are smaller,the PMSM operates in stable domains,no matter what the values of control gains are.With the values of parameters increasing,the unstability appears and PMSM falls into chaotic operation.Furthermore,the complex dynamic behaviors are verified by means of simulation.

Investigation of the spike-stall warning method using the blade passing signal

The vaned-diffuser usually brings compressor instability problems under the small flow rate, for instance the spike-type rotating stall phenomenon which restricts the operation range and may cause the trouble of blade fatigue. Since it is difficult to mathematically predict the spike-type stall for its randomness, finding out a practical method to warning this stall precursor appears to be meaningful. The paper explains the relationship between the spike-type precursor and the blade passing irregularity coefficient to analyze whether this coefficient is appropriate for the spike-stall warning inside a centrifugal compressor with the vaned-diffuser. The advanced wireless measurements were conducted on a 1.5 stages test centrifugal compressor to capture the unsteady behavior progressing from the design to stall inception within the region between the impeller trailing edge(TE) and diffuser leading edge(LE). The circumferential distribution of the blade passing irregularity has been quantitatively revealed.The steep increase of the blade passing irregularity at some "special locations", which is responsible for the onset of the spiketype precursor, is highlighted. Also, to further understand the spike precursor inside the diffuser passage corresponding to the circumferential "special location" with maximum irregularity, the high-response transient measurement within this passage is presented. With the help of full-annulus computational fluid dynamics(CFD) simulation and the mathematical model, it is proved that the blade passing irregularity precisely reflects the flow characteristics during the spike precursor, which presents the guidance for this stall warning method.

A full-length 3D structure for MAPK/ERK kinase 2 (MEK2)

As a pivotal signal pathway,the Ras/Raf/MEK/ERK cascade can be activated by multiple extracellular stimuli and can transmit signals to diverse substrates.It remains to be elucidated how so many different signals can be variously transferred by only two MEK molecules(MEK1 and MEK2) .Because of technological limitations the complete structures of the MEKs are still unavailable.Here,we report the full-length structure of MEK2 obtained by homology modeling and molecular dynamics simulations.The simulations show that the N-terminal part of MEK2 is highly flexible and this flexibility may enable MEK2 to interact with ERKs and other ligands in diverse manners that correspond to various upstream signals and downstream consequences.

The molecular dynamics of neural metabolism during the action potential

Neural information processing is tightly coupled to both energy consumption and derivation from substrates.In this study,the energy function of the neuron during the action potential(AP)is described and analyzed.It has been observed that energy consumption during the AP does not match predictions of the conventional theory of neural energy dynamics.On short time scales,neural energy expenditure shifts between positive and negative phases.During the AP,the energy source switches from neuronal stores(positive expenditure or net consumption)to exploitation of external substrates,specifically the glucose and oxygen carried in cerebral blood(the negative consumption phase).Based on the idea of reductionism,this paper demonstrates how ion channels,membrane pumps and transporters,ionotropic and metabotropic receptor signaling pathways,astrocyte glycolysis and the production lactate,and the glutamate-glutamine cycle all serve to relate cerebral blood flow and neuronal metabolism to neuronal activity and so maintain neuronal energy charge during the AP.