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Potential Configuration (potential + configuration)
Selected AbstractsRole of Ca2+ -Activated Cl, Current in Ventricular Action Potentials of Sheep During Adrenoceptor StimulationEXPERIMENTAL PHYSIOLOGY, Issue 2 2001Arie O. Verkerk Adrenoceptor stimulation enhances repolarising and depolarising membrane currents to different extents in cardiac myocytes. We investigated the opposing effects of the repolarising Ca2+ -activated Cl, current (ICl(Ca)) and depolarising L-type Ca2+ current (ICa,L) on the action potential configuration of sheep ventricular myocytes stimulated with noradrenaline. Whole-cell current-clamp recordings revealed that noradrenaline accelerated and prolonged phase-1 repolarisation. We define the minimal potential at the end of phase-1 repolarisation as ,notch level'. Noradrenaline (1 ,M) caused the notch level to fall from 14 ± 2.6 to 7.8 ± 2.8 mV (n= 24), but left action potential duration, resting membrane potential or action potential amplitude unaffected. Whole-cell voltage-clamp recordings showed that 1 ,M noradrenaline increased both ICa,L and ICl(Ca), but it had no significant effect on the principal K+ currents. Blockage of ICl(Ca) by 0.5 mM 4,4,-diisothiocyanatostilbene-2,2,-disulphonic acid (DIDS) in both the absence and the presence of noradrenaline abolished phase-1 repolarisation. In the presence of noradrenaline, DIDS caused elevation of the plateau phase amplitude and an increase in the action potential duration. In conclusion, elevation of the plateau phase amplitude and action potential prolongation associated with an increased ICa,L upon adrenoceptor stimulation is prevented by an increased ICl(Ca) in sheep ventricular myocytes. [source] Regional Differences in Arrhythmogenic Aftereffects of High Intensity DC Stimulation in the VentriclesPACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 5 2000ITSUO KODAMA Regional differences of the aftereffects of high intensity DC stimulation were investigated in isolated rabbit hearts stained with a voltage-sensitive dye (di-4-ANEPPS). Optical action potential signals were recorded from the epicardial surface of the right and left ventricular free wall (RVep, LVep) and from the right endocardial surface of the interventricular septum (IVS). Ten-millisecond monophasic DC stimulation (S2, 20,120 V) was applied to the signal recording spots during the early plateau phase of the action potential induced by basic stimuli (S1, 2.5 Hz). There was a linear relationship between S2 voltage and the S2 field intentisy (FI). S2 caused postshock additional depolarization. giving rise to a prolongation of the shocked action potential. With S2, 40 V (FI ,,20 V/cm), terminal repolarization of action potential was inhibited, and subsequent postshock S1 action potentials for 1,5 minutes were characterized by a decrease in the maximum diastolic potential and a decrease in the amplitude and a slowing of their upstroke phase. The higher the S2 voltage, the larger the aftereffects. The changes in postshock action potential configuration in RVep were significantly greater than those observed in LVep and IVS when compared at the same levels of S2 intensity. In RVep, 12 of 20 shocks of 120 V resulted in a prolonged refractoriness to S1 (> 1 s), and the arrest was often followed by oscillation of membrane potential. Ventricular tachycardia or fibrillation ensued from the oscillation in five cases. No such long arrest or serious arrhythmias were elicited in LVep and IVS. These results suggest that RVep is more susceptible than LVep and IVS for arrhythmogenic aftereffects of high intensity DC stimulation. [source] Oscillatory transient inward currents in ventricular myocytes of healthy versus myopathic Syrian hamsterCLINICAL AND EXPERIMENTAL PHARMACOLOGY AND PHYSIOLOGY, Issue 10 2004Sze-Hsueh Wu Summary 1.,The present experiments were performed in order to study abnormal action potential configuration and ion channel activity in ventricular myocytes obtained from 23 male myopathic Syrian hamsters (Biobreeders strain 14.6, 32,52 weeks old) compared with 10 age-matched healthy control hamsters (Biobreeders F1B) by means of whole-cell patch-clamp techniques. 2.,The results show that the myopathic myocytes had a longer action potential duration, a reduced transient outward K+ current on depolarization and a smaller transient inward current on repolarization after prolonged depolarizing pulses (> 500 msec). However, the L-type Ca2+ current and the inwardly rectifing K+ current were not significantly different from those of healthy myocytes. 3.,The oscillatory transient inward currents could be diminished by treatment with ryanodine (0.01,1 µmol/L), a sarcoplasmic reticulum (SR) Ca2+ release channel blocker, or with Na+ -free superfusate. 4.,We conclude that the hereditary myopathic hamsters are less likely to develop delayed afterdepolarization-related transient inward currents and triggered arrhythmias owing to a smaller SR Ca2+ content. [source] Design and integration of eco-industrial parks for managing water resourcesENVIRONMENTAL PROGRESS & SUSTAINABLE ENERGY, Issue 2 2009Eva M. Lovelady Abstract This work is aimed at developing an optimization-based approach to the design and integration of eco-industrial parks (EIPs). Focus is given to the management of water among multiple processes in a common EIP facility. Recycle, reuse, and separation using interception devices are considered as possible strategies for managing wastewater. A source-interception-sink structural representation is used to embed potential configurations of interest. The representation accounts for the possibilities of direct recycle, material (waste) exchange, mixing and segregation of different streams, separation and treatment in interception units, and allocation to process users (sinks). Then, the EIP design problem is formulated as an optimization program whose objective is to minimize cost of the EIP while determining optimal recycle and separation strategies. A case study is solved to illustrate the applicability of the devised approach. © 2009 American Institute of Chemical Engineers Environ Prog, 2009 [source] Potential-based path planning for robot manipulatorsJOURNAL OF FIELD ROBOTICS (FORMERLY JOURNAL OF ROBOTIC SYSTEMS), Issue 6 2005Chien-Chou Lin In this paper, a potential-based path-planning algorithm for a high DOF robot manipulator is proposed. Unlike some c-space-based approaches, which often require expensive preprocessing for the construction of the c-space, the proposed approach uses the workspace information directly. The approach computes, similar to that done in electrostatics, repulsive force and torque between objects in the workspace. A collision-free path of a manipulator will then be obtained by locally adjusting the manipulator configuration to search for minimum potential configurations using that force and torque. The proposed approach is efficient because these potential gradients are analytically tractable. Simulation results show that the proposed algorithm works well, in terms of computation time and collision avoidance, for manipulators up to 9 degrees of freedom (DOF). © 2005 Wiley Periodicals, Inc. [source] Disjunctive optimization design models for complex liquid,liquid multistage extractorsAICHE JOURNAL, Issue 10 2001Juan A. Reyes-Labarta A new method for the optimal design of multicomponent liquid,liquid extraction processes using multistage countercurrent extractor systems is proposed. The method determines the optimum number of equilibrium stages and flow rates needed to obtain a specified product separation and recovery, and accounts for the possibility of side feed streams and product extractions. A superstructure is proposed that has embedded all potential configurations and interconnections. Based on this superstructure representation, the problem is formulated as an optimization problem using generalized disjunctive programming (GDP) to minimize the total cost of the process, subject to design specifications. The robustness and computational efficiency of the model is illustrated with different cases involving single and complex countercurrent cascades in a quaternary liquid,liquid system. [source] | |||||||||||||