K~+-FREE INDUCED EARLY AFTERDEPOL-ARIZATION IN CARDIAC VENTRICULAR FIBERS OF GUINEA PIG AFTER COLD TREATMENT

The genesis and elimination of early afterdepolarizations (EADs) have been investigated in guinea pig cardiac ventricular fibers after a short period of cooling (5h, 2—4℃). After rewarming them to 37℃, EADs could be induced by K~+-free superfusion at an appropriate driving stimulation (0.2 Hz) in all preparations. A high level plateau, which linearly increases its duration with time, appears ahead of EADs. The critical point of the plateau occurred steadily at the level of -47±4 mV. Two types of triggered activity, all of which are the rhythmic activities in low level of membrane potential (-50 to -60 mV), appear on the platcau. There is no significant change after overdriving. Agonists of the Na-K pump (K~+ and Tl~+) could stop the rhythmic activity immediately and turn the low level of membrane potential to high one. The results showed that high level plateau is the basis of genesis of EADs, and the activation of Na-K pump plays an important part in stopping triggered rhythms arising from EADs.     

低温处理后由无钾引起的豚鼠心室肌早发后去极化

本文在短期低温处理后(5h,2—4℃)的豚鼠心室肌标本上,探讨了早发后去极化(EAD)的发生。在适当地驱动刺激(0.2Hz)下,复温后的心室肌标本经无钾溶液灌流后均可诱发EAD产生。EAD出现之前,动作电位于复极3期首先形成一新的“低位平台”。此平台可随时间呈线性增长,其拐点恒定在动作电位复极至—47±4mV的膜电位水平。由EAD触发形成的非驱动反应呈两种电位形式,但均属低膜电位水平(—50——60 mV)的节律性活动。超速驱动无明显影响,钠泵激动剂(K~+及Tl~+)可有效而迅速地终止触发性节律活动,并使低膜电位转变为高膜电位。结果表明:“低位平台”是EAD形成的基础;钠泵的激动在消除EAD触发的节律活动中起重要作用。     

我国通信光缆行业的生产管理信息化实践与发展

随着通信光缆行业的不断发展,行业内部产生了同质化竞争激烈、产能过剩等问题,制约了光缆企业和行业的发展。通过对国内主要企业在生产管理信息化方面的实践与成果进行调研分析,指出以信息化为主导的智能制造是提高企业竞争力的有效手段,也是通信光缆行业的发展方向。     

非色散位移单模光纤的鉴定与相关检测

讨论了鉴定未知光纤是否符合非色散位移单模光纤特征的检测过程。光纤种类繁多。在进行鉴定时应结合非色散位移单模光纤的特征进行系统性的检测。检测过程中可首先判断未知光纤是否属于通信用单模光纤,再通过非色散位移单模光纤与其他通信用单模光纤的技术差异进一步鉴定。鉴定过程可能涉及到光纤几何参数、色散系数、宏弯损耗等多项指标的检测,文中给出了推荐的检测方法。     

A Reevaluation of the Critical Membrane Potential of the Effective Refractory Period in Guinea Pig Ventricular Fibres

The traditional critical membrane potential (CMP), -55—-60mV, which corresponds to effective refractory period (ERP), was anew investigated in guinea pig ventricular muscle fibres. The electrical and contractile responses to the stimulus during repolarization of action potential (AP), particularly from+10 to -60 mV, were observed. One third of 35 tested cells displayed testing action potential (TAP) and local response at≥-54 mV when they were stimulated by testing pulses in 37℃ normal Tyrode's solution. Potential level of TAP which occurred earliest was at -30 mV and that of local response which appeared earliest was at 0 mV during repolarization among 95 systematic tests. Most of the TAPs belonged to the slow response potential type. The ratio of TAP evoked at ≥-54 mV initial membrane potential (IMP) was as high as 86% when the experiment was carried out in 37℃ 1.5 mmol KC1/L Tyrode's solution. In view of distribution of IMPs of TAPs, the CMP of ERP in guinea pig ventricular muscle fibres was more     

第一套国产广播电视设备(二)

《四》监视量测设备(甲)监视器监视器分为影像监视器和波形监视器两部分。前者可以独立使用,以14 RP 4 A 型显像管显示影像,后者用13 37型示波管显示同步和消隐脉冲的波形以及它们与影像信号间的波幅比例。为了使所显示影像尽可能地与实物相近,影像监视器的质量应高于接收机的,其内部视频放大器的通频带宽于.7.5兆赫。     

第一套国产广播电视设备(一)

前言今年5月1日起,北京电视台开始了实验广播。台内安装的第一套国产广播电视设备是由北京广播器材厂、广播科学研究所和清华大学无线电系三个单位合作制成的。制造过程中曾经利用了很多苏联和捷克斯洛伐克两国提供的资料,并曾得到由清华大学延聘的苏联专家     

通信用光纤可靠性影响因素分析

光纤的可靠性是保证光网络寿命的关键,可靠性由光纤的强度分布和疲劳行为共同决定.应用光纤的强度分布数据和蒙特卡洛方法,分析了筛选强度、应力腐蚀敏感性参数和载荷水平等因素对光纤可靠性的影响.分析结果表明,筛选强度的提高可改善筛选后光纤的强度分布,但同时会导致部分筛选后光纤的强度明显降低;按照基于幂定律理论的光纤疲劳行为模型...     

基于改进局部纹理特征的隐写检测算法

图像隐写是一种将信息隐藏于数字图像中的技术,而隐写检测算法试图分辨出藏有信息的图像。文中分析了现有隐写检测算法的优势,结合HUGO隐写算法的特点,提出了一种改进的基于局部纹理特征的隐写检测算法。该算法由LOCP和LPQ这两种局部纹理特征组成。由于提取到的特征维度很大,因此选用了Ensemble分类器进行训练与检测。在HUGOBOSS 1.0图像库上的实验显示,提出的隐写检测算法比原有算法更准确地区分出原始图像和隐写图像,并获得了83.65%的检测准确率。     

Characteristics of Early Afterdepolarization in Mouse Atrial Fibers

Early afterdepolarization (EAD) in mouse atrial fibers was investigated under the treatment with aconitine, 3. 0 mmol/L K+ ,quinidine, ryanodine or Bay k 8644. All of these EADs possessed the following common characteristics j all the parameters of EAD showed cycle length-dependence; take-off potential of the first triggered burst played an important role in the generation of the other parameters ; hyper-polarization of the triggered brust enhanced the end of EAD; and the second plateau response might be used as an indicator of the capability of EAD generation of myocardiac cell. All those EADs were inhibited or abolished by nifedipine, tetrodotoxin or lidocaine. Potassium channel activators, lemakalim, thalium ion, acetyl-choline or high potassium could also inhibit or abolish the EADs. It is suggested that the EADs induced by different agents may base on a common mechanism ; all currents contributing to the plateau phase of the action potential play an important role in the generation of EAD.