哺乳动物心血管系统参数的指数标度律

目的 :研究生物系统异速生长的基本规律。方法 :提出了一种适合分析生物系统动力学特征的量纲分析方法。结果 :使用本文提出的理论方法所得结果与资料实验数据基本一致。结论 :蕴涵物体动力学过程因果关系的量纲关系可以阐述生物体生长、发育的基本规律。     

An improved robust stability result for uncertain neural networks with multiple time delays

This paper proposes a new alternative sufficient condition for the existence, uniqueness and global asymptotic stability of the equilibrium point for the class of delayed neural networks under the parameter uncertainties of the neural system. The existence and uniqueness of the equilibrium point is proved by using the Homomorphic mapping theorem. The asymptotic stability of the equilibrium point is established by employing the Lyapunov stability theorems. The obtained robust stability condition establishes a new relationship between the network parameters of the system. We compare our stability result with the previous corresponding robust stability results derived in the past literature. Some comparative numerical examples together with some simulation results are also given to show the applicability and advantages of our result.     

重症急性胰腺炎大鼠肺损伤的病理生理变化及机制研究

目的观察重症急性胰腺炎大鼠肺损伤的病理生理变化并探讨其发生机制。方法选取2008年1月至2009年1月健康雄性SD(Sprague-Dawley)大鼠240只,按照随机数字表随机均分为8组,每组30只,即重症急性胰腺炎(SAP)不同时间点组(SAP 1 h、3 h、6 h、9 h、12 h、18 h、24 h组)和对照组。比较各组血清淀粉酶、肺组织湿/干重比、肺髓过氧化物酶(myeloperoxidase,MPO)活性、肺通透性指数的变化。结果观察组大鼠肺损伤组织评分、肺组织湿干重比以及肺髓过氧化物酶(MPO)水平随着时间的延续逐渐升高,各时间点组均明显高于对照组(P<0.05),观察组肺通透性指数随时间延续呈逐渐降低趋势,均低于对照组,差异均有统计学意义(P<0.05)。肺组织MPO水平与肺损伤评分存在正相关(r=0.946,P<0.01),肺湿干重比与肺损伤评分呈正相关(r=0.879,P<0.01),肺通透性指数与肺损伤评分存在负相关(r=-0.859,P<0.01)。结论重症急性胰腺炎大鼠肺损伤的损伤程度随SAP病程延长而逐渐增加,肺组织MPO水平持续升高。     

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目的    计算嚼肌在牙尖交错位（ICP）紧咬时表面肌电的最大Lyapunov指数,引入一个新的量化指标,分析咀嚼系统肌电信号的混沌特征。方法    于2009年5—7月在中山大学医学院在校学生中选取20名口颌系统基本正常的个体,其中男、女各10名。在ICP位紧咬时采集其左、右嚼肌的表面肌电,利用小数据量法计算嚼肌肌电信号的最大Lyapunov指数,并进行统计学分析。结果    男性个体左、右两侧嚼肌最大Lyapunov指数分别为17.882±1.7498和18.244±1.3028,女性为14.839±1.8198和14.866±1.3947。 对数据进行两因素析因设计的方差分析,性别差异具有统计学意义,女性的最大Lyapunov指数小于男性（F = 41.158,P＜0.001）;左、右侧部位差异无统计学意义（F = 0.151,P = 0.700）。结论    嚼肌在ICP位紧咬时表面肌电具有混沌特征,适合用非线性动力学方法进行分析。     

Characteristic time scales of electroencephalograms of narcoleptic patients and healthy controls

Sleep electroencephalograms (EEGs) typically showed correlated fluctuations that became random-like oscillations beyond a characteristic time scale. To investigate this behavior quantitatively, the detrended fluctuation analysis (DFA) was applied to EEGs of 10 narcoleptic patients (; 6 males) and 8 healthy controls (; 5 males). The characteristic time scales of the narcoleptics and controls were estimated as 1.8±0.7 and , respectively (significance level, p<0.01). We further performed DFA of the EEGs segmented into 30 s epochs and found that the DFA scaling exponents increased in deep sleep stages. These results were verified with power spectrum and auto-correlation analysis, and reproduced by a mathematical model. We thus concluded that characteristics of EEGs of narcoleptic patients could be differentiated from those of healthy subjects, suggesting a potential application of DFA in diagnosing narcolepsy.     

Layer IV of the primary somatosensory cortex has the highest complexity under anesthesia and cortical complexity is modulated by specific thalamic inputs

The system complexity, as calculated from correlation dimension, embedded in each layer and its modulation by specific inputs and general excitatory state are not yet known. The aims of present study were to estimate the system complexity across the cortical layers by analyzing intracortical EEG signals using a nonlinear analytical method, and to identify how layer-related complexity varies with the alteration of thalamic input and brain state. Male Sprague-Dawley rats were anesthetized under l% halothane. Sixteen channels of evoked or spontaneous EEG signals were recorded simultaneously across the six cortical layers in the somatosensory cortex with a single Michigan probe. The system complexity was assessed by computing correlation dimension, D(2), based on the Nonlinear Time Series Analysis data analysis program. Cortical layer IV exhibited a D(2) value, 3.24, that was significantly higher than that of the other cortical layers. The D(2) values in layers IV and II/III were significantly reduced after reversible deactivation of the ventral posterior lateral thalamic nucleus. D(2) decreased with increases in administered halothane concentration from 0.75% to 2.0%, particularly in layer IV. The present findings suggest that cortical layer IV maintains a higher complexity than the other layers and that the complexity of the mid-cortical layers is subject to regulation from specific thalamic inputs and more sensitive to changes in the general state of brain excitation.     

航空发动机分布式控制系统指数稳定性分析

建立具有时延与数据包丢失的航空发动机分布式控制系统模型为一类异步动态系统,基于Lyapunov第二法和线性矩阵不等式方法推导了系统的指数稳定性判定定理,根据该判据可以得到分布式控制系统的指数稳定意义下的状态反馈控制律,数字仿真说明了该判据的有效性。     

Top marine predators track Lagrangian coherent structures

Meso- and submesoscales (fronts, eddies, filaments) in surface ocean flow have a crucial influence on marine ecosystems. Their dynamics partly control the foraging behavior and the displacement of marine top predators (tuna, birds, turtles, and cetaceans). In this work we focus on the role of submesoscale structures in the Mozambique Channel in the distribution of a marine predator, the Great Frigatebird. Using a newly developed dynamic concept, the finite-size Lyapunov exponent (FSLE), we identified Lagrangian coherent structures (LCSs) present in the surface flow in the channel over a 2-month observation period (August and September 2003). By comparing seabird satellite positions with LCS locations, we demonstrate that frigatebirds track precisely these structures in the Mozambique Channel, providing the first evidence that a top predator is able to track these FSLE ridges to locate food patches. After comparing bird positions during long and short trips and different parts of these trips, we propose several hypotheses to understand how frigatebirds can follow these LCSs. The birds might use visual and/or olfactory cues and/or atmospheric current changes over the structures to move along these biologic corridors. The birds being often associated with tuna schools around foraging areas, a thorough comprehension of their foraging behavior and movement during the breeding season is crucial not only to seabird ecology but also to an appropriate ecosystemic approach to fisheries in the channel.     

Decreased chaos of heart rate time series in children of patients with panic disorder

This study examined the differences of heart rate variability measures between children of parents with panic disorder and children of healthy controls using linear as well as nonlinear techniques. Supine and standing heart rate variability indices were measured in all children using power spectral analysis and a measure of chaos, the largest Lyapunov exponent (LLE) of heart rate time series. No significant differences emerged between the children of panic disorder parents and children of normal controls on any of the spectral heart rate variability measures. However, children of patients with panic disorder had significantly lower LLE of heart rate time series in supine posture, suggesting a relative decrease of cardiac vagal function in this group of children. This suggests a possible heritable effect of certain measures of heart rate variability, as previous studies showed decreased heart rate variability in patients with panic disorder using spectral as well as nonlinear techniques. Recent evidence also suggests that some of these nonlinear measures are superior or of additional value to the traditional time and frequency domain measures of heart rate variability to predict serious ventricular arrhythmias and sudden death.     

Accuracy and Precision of Pharmacodynamic Exponent

Pharmaceutical Research -