Leak current

Fig. 10). With the completion of the structure transition, the current should drop to zero, which is indeed the case except for peak B, where a slight leak current is seen (ascribed to the side reaction Cu++ I c > Cu+). According to the theory by Bewick, Fleischmann and Thirsk (BFT) the transients can be used to distinguish between instantaneous and progressive nucleation [45], A corresponding analysis revealed that the falling part of the transients agrees well with the model for instantaneous nucleation, while the rising part shows a systematic deviation. This was explained by the existence of surface defects on a real electrode in contrast to the ideal case of a defect-free surface assumed in the theoretical model. By including an adsorption term in the BFT theory to account for Cu deposition at defects, the experimentally obtained transients could indeed be reproduced very well [44], We shall return to the important role of surface defects in metal deposition later (sec. 3.2).

In normal atrial and ventricular myocytes, phase 4 is electrically stable, with the resting membrane potential held at approximately -90 mV and maintained by the outward potassium leak current and ion exchangers previously described. It is during phase 4 that the Na+ channels necessary for atrial and ventricular myocyte depolarization recover completely from inactivation. In myocytes capable of automaticity, the membrane potential slowly depolarizes during this period to initiate an action potential (discussed later). 

Automaticity can be defined as the ability of a cell to alter its resting membrane potential toward the excitation threshold without the influence of an external stimulus. The characteristic feature of cells with automaticity is a slow decrease in the membrane potential during diastole (phase 4) such that the membrane potential reaches threshold (Figure 16.2). During phase 4 in these pacemaker cells, the background potassium leak current decreases and an inward depolarizing current (h) is... 

Figure 26. Scheme for the control of ionic fluxes by light irradiation. trans-Azo ammonium, covering the hydrophilic oligoether parts from the outside, can stabilize the supramolecular ion channel structure, while cis cannot because of its bent structure. Therefore, trans-azo generates ion channel currents, while for c/sonly small leak currents across the membrane. 

The Hodgkin-Huxley model involves three membrane currents due to potassium, sodium, and a leak current of charge through other pathways. The model assumes linear current-voltage relationships ... 

The leak current of hydrogen ions is modeled using the Goldman-Hodgkin-Katz expression ... 

As discussed in Chapter 6, dashboards will increasingly be used to communicate process safety metrics and performance to local line management. Such dashboards may reflect current, summary, or cumulative data (such as the number of days without a leak), current conditions (such as the fill level of a tank), or the results of the most current inspection or audit. An organization s process safety metrics can evolve in a hierarchical way so that individual indicators can be rolled up from the process level to the site level and eventually even the organizational level. Dashboards can be expected to evolve similarly to report such rolled up information to upper management. 

In the dark, no anodic current was observed up to +1.5 V vs. SCE. (The current above +1.5 V is a leak current.) Under irradiation, however, an anodic photocurrent was observed at potentials more positive than -0.6 V vs. SCE. In fact, deposition of polypyrrole was observed on the semiconductor electrode when the electrode was kept at +0.5 V vs. SCE under irradiation. Therefore, the observed anodic current must include the current for oxidation of pyrrole. It was revealed in a separate experiment that most of the current is used for oxidation of pyrrole and that for the partial... 

Rabbit sciatic nerve axons A fast sodium current and a leak current was found to be sufficient to model single action potentials in the nodes of Ranvier of axons from rabbit sciatic nerve by Chiu et ai [1979]. It is likely that this model should be augmented to include potassium currents in order to model trains of action potentials accurately. 

Vertebrate retinal cone photoreceptors A model of vertebrate photoreceptor cells that includes a light-sensitive current, an L-type calcium current, a delayed rectifier potassium current, calcium-sensitive potassium and chloride currents, a hyperpolarization-activated current, a sodium-potassium pump, and a leak current in addition to the response of the cell to a channel blocker was published by Usui et al. [1996]. 

Pyloric constrictor neurons of the lobster Models of the crab lateral pyloric neuron were modified to include a fast sodium current, an A-type potassium current, a delayed rectifier potassium current, a calcium current, a calcium-dependent potassium current, and a leak current by Harris-Warrick et al. [1995] to examine the effect of the neurotransmitter dopamine on the A-type current. This model was augmented by Harris-Warrick et al. [ 1995] to include a hyperpolarization-activated current... 

Mammalian Spinal Motoneuron Halter et al. [1995] set up a detailed model of myelinated motoneurons with myelination morphology and ionic currents including a fast sodium current, fast and slow delayed rectifier potassium currents, and a leak current... 

Pituitary Gonadotrophs and Corticotrophs Li et al. [1995] have constructed a model of membrane fluxes and calcium release from the endoplasmic reticulum of rat pituitary gonadotrophs. The membrane currents modeled include an L- and T-type calcium currents, delayed rectifier and calcium-sensitive potassium currents and a leak current. A modification of this model was used by LeBeau et al. [1997] to model pituitary corticotroph cells. 

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