Examination of the choice of models for computing the extracellular potential of a single fibre in a restricted volume conductor

The paper compares the rigorous and the conventional approximate line source solution of Laplace's equation used to evaluate the potential of a single cylindrical fibre. Particular attention is given to the solutions for a radially restricted circular cylindrical volume conductor. The effect of the extent of the volume conductor b on the difference between the potentials evaluated according to the different models is examined. For values of b larger than 10 times the fibre radius, the relative difference is less than 1 per cent and the values of b around 2 times the fibre radii, the error reaches as much as 17 per cent.     

Use of surface potential spectral characteristics for solving the inverse problem in electroneurography

The changes in the power spectra of single-fibre extracellular action potentials (SFEAPs) generated in an infinite anisotropic frequency-dependent volume conductor, which occurred as a result of alterations in the propagation velocity v and duration T_in of the intracellular action potential (IAP) were analytically determined. Effects of the temporal and spatial dispersions of almost synchronously activated fibres on the power spectrum of compound extracellular potentials (CEPs) were analysed for different shapes and sizes of the activated fibres' territory. It was found that, as a result of desynchronisation in the fibres' activation, dips existed in the CEP power spectra and that the frequencies of the dips depended on the degree of desynchronisation but did not depend on the velocity. It was shown that the hypothetical power spectrum of compound IAP was sensitive to the variations in the desynchronisation in the fibres' activation and in the risetime and duration of IAP even at a great fibre electrode distance typical for surface recordings.     

左心室每搏出量的估算

为了更准确地估算左心室功能指标，作根据胸控并联导体模型和准线性弹性腔模型，从理论上得到了用胸阻抗法测算心搏出量（ＳＶ）的新算式；ＳＶ＝Ｋｐ（Ｌ／Ｚ０）＾２△Ｚ。与Ｎｙｂｏｅｒ理论所得到的心搏出量的公式：ＳＶ＝ｐ（Ｌ／Ｚ０）＾２△Ｚ所不同的是，改进后的新算式中，心搏出量不仅与胸阻抗的最大变化量（△Ｚ）有关，而且还与时间因子Ｋ有关。时间因子Ｋ定义为心动周期（Ｔ）与舒张期持续时间（Ｔｄ）之比。     

Low QRS voltage and its causes

Electrocardiographic low QRS voltage (LQRSV) has many causes, which can be differentiated into those due to the heart's generated potentials (cardiac) and those due to influences of the passive body volume conductor (extracardiac). Peripheral edema of any conceivable etiology induces reversible LQRSV, reduces the amplitude of the P waves and T waves, decreases the duration of P waves, QRS complexes, and QT intervals, and alters in turn the measurements of the signal-averaged electrocardiogram and T wave alternans, all with enormous clinical implications.     

Sensitivity of beamformer source analysis to deficiencies in forward modeling

Beamforming approaches have recently been developed for the field of electroencephalography (EEG) and magnetoencephalography (MEG) source analysis and opened up new applications within various fields of neuroscience. While the number of beamformer applications thus increases fast-paced, fundamental methodological considerations, especially the dependence of beamformer performance on leadfield accuracy, is still quite unclear. In this article, we present a systematic study on the influence of improper volume conductor modeling on the source reconstruction performance of an EEG-data based synthetic aperture magnetometry (SAM) beamforming approach. A finite element model of a human head is derived from multimodal MR images and serves as a realistic volume conductor model. By means of a theoretical analysis followed by a series of computer simulations insight is gained into beamformer performance with respect to reconstruction errors in peak location, peak amplitude, and peak width resulting from geometry and anisotropy volume conductor misspecifications, sensor noise, and insufficient sensor coverage. We conclude that depending on source position, sensor coverage, and accuracy of the volume conductor model, localization errors up to several centimeters must be expected. As we could show that the beamformer tries to find the best fitting leadfield (least squares) with respect to its scanning space, this result can be generalized to other localization methods. More specific, amplitude, and width of the beamformer peaks significantly depend on the interaction between noise and accuracy of the volume conductor model. The beamformer can strongly profit from a high signal-to-noise ratio, but this requires a sufficiently realistic volume conductor model.     

人体避雷针趣谈—针灸治病机理新说

目的：探讨针灸的治病机理。方法：运用“人是有机的整体,人与自然的统一性”这一中医基础理论来推理针灸的治病机理。结果：针灸针具具有类似避雷针效应的作用,人体的其它肌肉可能存在类似心肌的激动源。结论：针灸治病的机理可能是通过针具产生电流的刺激作用起到治病效果     

点电源圆柱形容积导体中电场分布的实验研究

目的 用实验探讨点电源圆柱形容积导体中的电场分布.方法 塑料圆桶中的稀盐水溶液作为容积导体,50 Hz交流电通过顶部和底部的输入电极加于容积导体,测量圆桶内侧壁两检测电极之间的电压,该电压除以电极间的距离,即为两电极连线上的场强.结果 两检测电极连线上的电场近似为均强电场,其大小与输入电压成正比,与检测电极连线到输入电极连线的距离成反比,但与容积导体的电阻率没有关系.结论 本实验结果可为圆柱形容积导体的应用提供基础.     

列车乘务员心电图ST—T改变及改变性质研究

掌握列车乘务工作对心电图改变的影响,为改善劳动条件和安全运输提供科学依据。方法：应用分层抽样法抽取２７０名乘务员,分别作出乘前后心电图进行对比,对心电图有改变者１年后随访,仍不能恢复者作心得安药物试验。结果：２７０名乘务员中,１６１名心电图有改变占５９．６３％,其中,３２名出乘前就有改变,经改善劳动条件或调换工种一年后,有２１例恢复正常,１１例经心得安药物实验,１０例呈阳性。所以,功能性改变者占９９．３８％。结论：列车乘务工作能使心电ＳＴ－Ｔ改变,且这种改变是功能性的。     

云南白药加冰盐水联合泮托拉唑治疗 Cushing 溃疡的临床研究

目的：观察云南白药加冰生理盐水联合泮托拉唑治疗 Cushing 溃疡的临床疗效。方法：选择2010年7月～2013年7月本院 Cushing 溃疡116例,随机分为治疗组和对照组。治疗组58例静脉滴注泮托拉唑80mg,每日2次,并口服（或鼻饲）云南白药0.5g 加冰生理盐水50ml,每日4次。对照组58例静脉滴注泮托拉唑80mg,每日2次。结果：治疗组总有效率为89.65％,对照组为65.52％,差异有统计学意义（p ＜0.05）。结论：云南白药加冰生理盐水联合泮托拉唑治疗 Cushing 溃疡的疗效显著,不良反应少,值得推广。     

交联电缆绝缘线芯质量控制关键技术分析

本文通过对交联电缆绝缘线芯导体、绝缘料、交联生产过程等技术控制过程进行分析,阐述了交联电缆绝缘线芯质量控制的要点。