Influx velocity

Generally the airflow rate per cross-sectional area of openings or the influx velocity in the opening (equal distribution across the whole area assumed)... 

IS used as a design base. As a first assumption an influx velocity of Z ij, = 0.1 to 0.2 m s should be used. Based on the total area of all openings the necessary airflow rate, can be calculated as... 

At this step in the design procedure, it is necessary to consider the type of contaminant emission that the booth is designed to control. With the above assumption of influx velocity (0.1 to 0.2 m s ), all emitted material should remain in the booth. With these velocities, it will not be possible to draw in any contaminants that escape the booth. In case of doubt, the influx velocity, zv , should be increased and the necessary hood flow rate should be recalculated. 

Mecfianism of Action An antiarrhythmic that decreases sodium influx during depolarization, potassium efflux during repolarization, and reduces calcium transport across the myocardial cell membrane.Decreases myocardial excitability, conduction velocity, and contractility Therapeutic Effect Suppresses arrhythmias. Pharmacokinetics Almost completely absorbed after PO administration. Protein binding 80%-90%. Metabolized in liver. Excreted in urine. Removed by hemodialysis. Half-life 6-8 hr. 

Direct effects on the heart are determined largely by Bi receptors, although B2 and to a lesser extent a receptors are also involved, especially in heart failure. Beta-receptor activation results in increased calcium influx in cardiac cells. This has both electrical and mechanical consequences. Pacemaker activity—both normal (sinoatrial node) and abnormal (eg, Purkinje fibers)—is increased (positive chronotropic effect). Conduction velocity in the atrioventricular node is increased (positive dromotropic effect), and the refractory period is decreased. Intrinsic contractility is increased (positive inotropic effect), and relaxation is accelerated. As a result, the twitch response of isolated cardiac muscle is increased in tension but abbreviated in duration. In the intact heart, intraventricular pressure rises and falls more rapidly, and ejection time is decreased. These direct effects are easily demonstrated in the absence of reflexes evoked by changes in blood pressure, eg, in isolated myocardial preparations and in patients with ganglionic blockade. In the presence of normal reflex activity, the direct effects on heart rate may be dominated by a reflex response to blood pressure changes. Physiologic stimulation of the heart by catecholamines tends to increase coronary blood flow. 

The number of sodium channels available for activation determines the conduction velocity of the action potential in cardiac cells. The more sodium channels available for activation, the faster the conduction velocity occurs. At resting membrane potential of ventricular, atrial, and Purkinje cells (-85 mV), the m gate is closed, preventing any influx of sodium therefore, no action potential develops (Resting). With an... 

The limiting equations applicable at low concentrations are obtained by assuming a finite but negative J0 which we write as - /0, where /0 is the influx, Dt is a constant (which equals molecular diffusion coefficient D if there is no stirring or convection), and W= - u, another constant equal to the relative velocity of the liquid and the surface. The absolute value forms are used to allow the positive coordinate axis to point into the flow from the barrier or interface to which we assign coordinate position y = 0. 

Temporal changes in the PSDF may also reflect conditions both within and outside the aquifer. For both storms, dmax reaches a maximum at the same time that TSS peaks, a reflection of maximum flow velocity. The maximum particle size decreases from 8 to 12 hours after rainfall, possibly indicating that an initial flush of water from one source is later followed by an influx from another source. The late flush of clay minerals for storm 2, seen both in the mineralogy and as an increase in N4,jin, indicates a newly accessed source of clay minerals. 

Recent interesting information on this problem has come from work by Crompton and his associates [121,122] who found that a-adrenergic stimulation of rats increased the velocity of Ca influx via the electrophoretic uniporter in isolated... 

MOA For both class lA and IC-rDecrease influx of sodium during repolariiation reduces conduction velocity ... 

Class IV Calcium channel lockers Blocks calcium influx slows conduction velocity, decreases myocardial contractility (negative inotropic), and increases refraction in the AV node Verapamil HC1 (Calan) (Constipation, dizziness, lightheadedness, headache, asthenia [loss of strength, energy]) Diltiazem (Cardizem) (Peripheral edema, dizziness, lightheadedness, headache, bradycardia, asthenia [loss of strength, weakness], nausea, constipation, flushing, altered ECG)... 

The giant axon of the squid is very large, typically 0.5 mm in diameter, and the conduction velocity is about 25 m/s. During such an action potential, an influx of 3.7 pmol/cm of Na is offset by a subsequent efflux of 4.3 pmol/cm of K. ... 

More difficult in BLMs, refined HPTS assays exist to address the special cases of selective transport of protons [11] and electrons [17] in LUVs. In the conventional HPTS assay (Fig. 11.5c), the apparent activity of proton channels decreases with increasing proton selectivity because the rate ofthe disfavored cation (M ) influx influences the detected velocity more than the favored proton efflux. Disfavored potassium influx can, however, be accelerated with the potassium carrier vaiinomycin (Fig. 11.8). Increasing activity in the presence of vaiinomycin identifies proton channels with H > K+ selectivity being at least as high as the maximal measurable increase (in unpolarized LUVs of course, compare Section 11.3.4). Important controls include evidence for low enough vaiinomycin concentrations to exclude activity without the proton channel (due to disfavored H+ efflux). The proton carrier FCCP is often used as complementary additive to confirm M+ > H+ selectivity (e.g. amphotericin B). 

Not all cells in the cardiac conduction system rely on sodium influx for initial depolarization. Some tissues depolarize in response to a slower inward ionic current caused by calcium influx. These calcium-dependent tissues are found primarily in the SA and AV nodes (both L- and T-channels) and possess distinct conduction properties in comparison with the sodium-dependent fibers. Calcium-dependent cells generally have a less negative RMP (-40 to -60 mV) and a slower conduction velocity. Furthermore, in calcium-dependent tissues, recovery of excitability outlasts full repolarization, whereas in sodium-dependent tissues, recovery is prompt after repolarization. These two types of electrical fibers also differ dramatically in how drugs modify their conduction properties (see below). 

Answer B. Calcium channel antagonists decrease myocardial contractility by blocking the influx of Ca2+ ions through voltage-dependent L-type channels in the cardiac cell membrane. CCBs have no effects on Na+ channels, they do not change intracellular K+ levels, and they decrease not increase) conduction velocity. 

The third member of this class IB trio, mexiletine (No. 5), which was marketed in 1986, was first found to have anticonvulsant properties. Examination of its electrophysiological behavior led to its characterization as a strong ventricular antiarrhythmic. As the other drugs in this subclass, mexiletine blocks Na+ influx and reduces the maximal impulse velocity of phase O of the action potential. 

---