Research progress in nonlinear analysis of heart electric activities

1INTRODUCTION THE WORLD IS NONLINEAR,AND THE HUMAN LIFE ACTIVITY IS ALSO NONLINEAR.FROM THE VIEWPOINT OF SYSTEM,HUMAN BEINGS(OR THE OTHER HIGHER ANIMAL)ARE THE MOST COM-PLEX SYSTEM IN THE NATURE.FOR SUCH A PHYSIOLOGICAL SYS-TEM WITH THE UTTERMOST COMPLEXI…     

Nonlinearity degree of short-term heart rate variability signal

A nonlinear autoregressive (NAR) model is built to model the heartbeat interval time series and the optimum model degree is proposed to be taken to evaluate the nonlinearity degree of heart rate variability (HRV). A group of healthy persons are studied and the results indicate that this method can effectively get nonlinear information from short (6—7 min) heartbeat series and consequently reflect the degree of heart rate variability, which supplies convenience in clinical application. Finally, a comparison with the traditional time domain method shows that the NAR model method can reflect the complexity of the whole signal and lessen the influence of noise and instability, in the signal.     

高原公路驾驶员心率变异性试验分析

为了揭示驾驶员在高原公路行车时的心率变异性的变化情况,寻求提高行车安全性的途径,利用生物反馈仪在高原公路上进行了实地行车测试。以频域指标LF/HF作为高原公路驾驶员心率变异性指标,在分析驾驶时间、海拔高度与驾驶员心率变异性指标之间关系的基础上,建立了相关模型。分析结果表明：驾驶员在高原公路行车时,心率变异性受到高原低氧环境和驾驶时间的双重影响;海拔越高,驾驶时间越长,驾驶员交感神经张力越大,使驾驶员疲劳程度增大,安全隐患增大。     

Characterization of rhinovirus subviral A particles via capillary electrophoresis, electron microscopy and gas-phase electrophoretic mobility molecular analysis: Part I

During infection, enteroviruses, such as human rhinoviruses (HRVs), convert from the native, infective form with a sedimentation coefficient of 150S to empty subviral particles sedimenting at 80S (B particles). B particles lack viral capsid protein 4 (VP4) and the single-stranded RNA genome. On the way to this end stage, a metastable intermediate particle is observed in the cell early after infection. This subviral A particle still contains the RNA but lacks VP4 and sediments at 135S. Native (150S) HRV serotype 2 (HRV2) as well as its empty (80S) capsid have been well characterized by capillary electrophoresis. In the present paper, we demonstrate separation of at least two forms of subviral A particles on the midway between native virions and empty 80S capsids by CE. For one of these intermediates, we established a reproducible way for its preparation and characterized this particle in terms of its electrophoretic mobility and its appearance in transmission electron microscopy (TEM). Furthermore, the conversion of this intermediate to 80S particles was investigated. Gas-phase electrophoretic mobility molecular analysis (GEMMA) yielded additional insights into sample composition. More data on particle characterization including its protein composition and RNA content (for unambiguous identification of the detected intermediate as subviral A particle) will be presented in the second part of the publication.     

草原公路路侧景观对驾驶员心率变异的影响研究

为了研究草原公路路侧景观的变化对驾驶员心率变异性的影响,在草原公路上进行实地行车试验。运用多导生理记录仪MP150实时记录心率参数,采集驾驶员行驶过程中的心电信号;结合生理学和人机工程学等方面的理论研究,利用心率变异时频域分析方法,对驾驶员在不同路侧景观环境下的心率变异(HRV)进行分析。研究结果表明:在两种景观下,驾驶员的时域指标R-R间期差值的均方根(RMSSD)在较小范围内平稳波动,其平均值之间无显著差异;在景观Ⅱ中低频与高频比值(LF/HF)变化较大,两种景观下的平均值之间有显著差异;驾驶员在相对单调的路侧景观路段精神负荷较大。     

心率变异性现代谱估计对不同年龄段正常人的分析

比较了经典谱估计与现代谱估计在心率变异性分析中的应用,指出了经典谱估计具有频率分辨率低和旁瓣泄漏的固有缺点,采用以自回归模型为代表的现代谱估计对心率变异性信号特别是短时心率变异性信号分析具有优越性,并对不同年龄段正常人的心率变异信号进行了分析和比较,分析结果表明:自回归模型功率谱估计在心率变异性分析中的有效性优于当前所使用的传统谱估计方法;随着年龄增长,HRV信号总能量及各频段能量明显减少.     

Performance and Optimization for a Ground-Coupled Liquid Loop Heat Recovery Ventilation System

Ground-coupled heat pumps(GCHP) arecommonly used in residential heating system. To mitigatethe boreholes temperature dropping with operating time, anew exhaust-air recharging system is developed. The newrecharging system can be used in three operational modes.In this paper, a ground-coupled heat recovery ventilation(HRV) model is discussed. A thermal model is set up tofind the optimal brine flow rate and heat transfer allocationratio between exhaust and supply coils for maximum heatrecovery efficiency. Contrary to the conventional liquid-loopHRV systems, the brine temperature entering the exhaustcoil never goes blow zero(0℃), and hence defrosting isneedless in the ground-coupled HRV system. This can makethe ground-coupled HRV system over 20% more efficientthan a conventional HRV system at low outdoortemperatures.     

Similarity Changes Analysis for Heart Rate Fluctuation Regularity as a New Screening Method for Congestive Heart Failure

Congestive heart failure (CHF) is a chronic cardiovascular condition associated with dysfunction of the autonomic nervous system (ANS). Heart rate variability (HRV) has been widely used to assess ANS. This paper proposes a new HRV analysis method, which uses information-based similarity (IBS) transformation and fuzzy approximate entropy (fApEn) algorithm to obtain the fApEn_IBS index, which is used to observe the complexity of autonomic fluctuations in CHF within 24 h. We used 98 ECG records (54 health records and 44 CHF records) from the PhysioNet database. The fApEn_IBS index was statistically significant between the control and CHF groups (p < 0.001). Compared with the classical indices low-to-high frequency power ratio (LF/HF) and IBS, the fApEn_IBS index further utilizes the changes in the rhythm of heart rate (HR) fluctuations between RR intervals to fully extract relevant information between adjacent time intervals and significantly improves the performance of CHF screening. The CHF classification accuracy of fApEn_IBS was 84.69%, higher than LF/HF (77.55%) and IBS (83.67%). Moreover, the combination of IBS, fApEn_IBS, and LF/HF reached the highest CHF screening accuracy (98.98%) with the random forest (RF) classifier, indicating that the IBS and LF/HF had good complementarity. Therefore, fApEn_IBS effusively reflects the complexity of autonomic nerves in CHF and is a valuable CHF assessment tool.     

基于驾驶人生理心理参数的午餐后驾驶疲劳分析

为找出午餐前后驾驶人疲劳特征变化规律,选取6名驾驶人开展了驾驶模拟试验。对驾驶人午餐前后的体温、心率变异性、深度知觉、速度知觉等生理、心理特征参数进行了测定,并通过问卷方式获取了驾驶人对自身疲劳状况的主观感受,分析了午餐前后驾驶疲劳特征的变化。生理参数分析结果表明:驾驶人心率变异性指标在午餐后1~1.5 h内呈升高趋势,随后下降至正常水平;体温指标在午餐后出现一个低谷,随后恢复正常;PERCLOS指标值午餐后均有所增大,其中67%受试者PERCLOS值增幅明显。心理特征参数变化表明:午餐后受试者认知能力出现了不同程度的降低,主要体现为深度知觉能力下降、反应时间延长和速度判断力下降。这些都将影响驾驶人对道路环境信息的获取,进而会增加驾驶不安全因素。     

指数分布在心率变异临床分析中的应用

近20年来,心率变异(HRV)分析作为一种无创检测心脏功能,特别是自主神经系统活动状况的重要手段,成为临床和理论研究的热点之一.笔者提出在时频平面上研究HRV,能够显示HRV信号各频率分量随时间变化的信息,满足HRV分析对时间分辨率和频率分辨率的要求,选择指数分布来抑制交叉项造成的影响.将指数分布应用于药物试验HRV信号的分析,得到了一些有益的结论.