Caffeine induces a transient inward current in cultured cardiac cells

Electrical excitation of cardiac muscle may sometimes be due to initiation of inward current by the presence of Ca2+ ions at the inner surface of the cell membrane. During digitalis toxicity and other conditions that abnormally augment cellular Ca2+ stores, premature release of Ca2+ from the sarcoplasmic reticulum leads to a transient inward current, which is large enough to initiate premature beats and is accompanied by a transient contractile response. This inward current may be mediated either by electrogenic sodium-calcium exchange or by specific Ca2+-activated cation channels that have recently been characterized in tissue cultures of cardiac myocytes. An obvious question raised by these observations is whether release of the sequestered Ca2+ stores during each normal beat exerts a similar influence on membrane potential. To explore this, chick embryonic myocardial cell aggregates were voltage-clamped during abrupt exposure to caffeine, which is known to release Ca2+ from the sarcoplasmic reticulum. The speed of the perfusion system and the relative absence of diffusion barriers in the tissue-cultured cells allowed the effects of caffeine-induced Ca2+ release to be studied on a time scale comparable to that of a single normal beat. We report here that abrupt exposure of the cells to caffeine produced a transient inward current having similar features to that of digitalis toxicity, and which was both large enough and rapid enough to potentially contribute to the action potential.     

PMSM伺服控制的数字电流环研究

研究了永磁同步电动机（ＰＭＳＭ）伺服系统的一种新型数字电流环方案，该方案采用了规则采样法生成ＰＷＭ波的比例型电流调节器，提出用前馈补偿和变电流环增益技术才能提高电流调节性能，给出了数字仿真和实验结果。     

一种地面目标的相关跟踪方法

提出了一种用多子模板对目标进行相关跟踪的方法，该方法建立了综合多子模板相关结果、目标跟踪判断及自适应刷新模板等准则，较好地解决了相关跟踪中如何判断目标锁定、部分遮挡、相似目标出现及模板的刷新等问题。     

非共轭齿面鼓形齿联轴器运动分析

建立了非共轭齿面鼓形齿联轴器的内外齿面方程，根据非共轭齿面的啮合条件进行了啮合状态的计算分析，得出了若干运动学分析的结论．     

新型高效冷风机翅片管紧固效果的试验研究

采用网格法测量了冷风机翅片冲压加工的变形量，确定了翅片材料的成形极限。用塑性大应变计测试了不同工况下冷风机翅片管胀管变形的全过程，建立了分析冷风机翅片管紧固效果的特征曲线方法，提出了用宽裕度作为胀头过盈量设计取值的概念，综合评价了不同翅片管的紧固效果。     

Fault lubrication during earthquakes

The determination of rock friction at seismic slip rates (about 1?m?s(-1)) is of paramount importance in earthquake mechanics, as fault friction controls the stress drop, the mechanical work and the frictional heat generated during slip. Given the difficulty in determining friction by seismological methods, elucidating constraints are derived from experimental studies. Here we review a large set of published and unpublished experiments (～300) performed in rotary shear apparatus at slip rates of 0.1-2.6?m?s(-1). The experiments indicate a significant decrease in friction (of up to one order of magnitude), which we term fault lubrication, both for cohesive (silicate-built, quartz-built and carbonate-built) rocks and non-cohesive rocks (clay-rich, anhydrite, gypsum and dolomite gouges) typical of crustal seismogenic sources. The available mechanical work and the associated temperature rise in the slipping zone trigger a number of physicochemical processes (gelification, decarbonation and dehydration reactions, melting and so on) whose products are responsible for fault lubrication. The similarity between (1) experimental and natural fault products and (2) mechanical work measures resulting from these laboratory experiments and seismological estimates suggests that it is reasonable to extrapolate experimental data to conditions typical of earthquake nucleation depths (7-15?km). It seems that faults are lubricated during earthquakes, irrespective of the fault rock composition and of the specific weakening mechanism involved.