Conduction time

The thermal conductivity of copper having an electrical conductivity of 100% lACS is 391 W/ (m-K) at 20°C. The Wiedemann-Eranz ratio of thermal conductivity and the product of electrical conductivity times absolute temperature are approximately constant. Many copper alloys have increasing thermal conductivity with increase in temperature, whereas electrical conductivity decreases. 

Fig. 5.2. Current-versus-time records for x-cut quartz impact loaded to stresses of 2.5, 3.9, 4.5, 5.9, 6.5, and 9.0 GPa are shown, illustrating the drastic changes occurring with mechanical yielding and conduction. Time increases from right to left. The current pulses are in the center of each record and are characterized by a brief horizontal trace (zero current before impact) followed by a rapid jump to a current value (after Graham [74G01]).

Figure 2.12 From voltage-clamp to current-clamp micro-electrode recordings of synaptic current (/, lower trace) and synaptic potential with superimposed action potential (V, upper trace) from a neuron in an isolated rat superior cervical sympathetic ganglion following a single stimulus (S) applied to the preganglionic nerve trunk. The interval between the stimulus and the postsynaptic response includes the conduction time along the unmyelinated axons of the preganglionic nerve trunk. (SJ Marsh and DA Brown, unpublished)...

To confirm the proposed mechanism calculated conductance-time curves were compared with the experimental ones. The agreement is satisfactory up to at least 50 % reaction over a fairly wide range of experimental conditions. 

Figure 9.3b Conductivity/time curves (a) of cements, showing maxima. Prepared from ZnO ignited at 600 C with A-.-A dry eugenol 0...0 eugenol + 1% water O-.-O eugenol + 1% chloracetic acid ... eugenol+1% acetic acid ... eugenol+1% acetic acid+1% water. Cement powder/liquid ratio = 2-5 g cm (Crisp, Ambersley Wilson, 1980).

If effective porosity and other parameters are known, the time of travel (TOT) for a molecule of waste transported by flowing water through the soil liner can be calculated. TOT equals the length of the particular flow path times the effective porosity, divided by the hydraulic conductivity times the hydraulic gradient (Figure 26.10). 

Hence, the conduction time is the most significant of all, and it controls ignition. In general, thermal conductivity is directly related to density for solids, so... 

In addition to the above hemodynamic measurements, intraventricular, intra-arterial and atrioventricular conduction times and velocities can be measured using epicar-dial electrodes in the anesthetized and thoracotomized dog. 

The authors did not analyse their data and D. W. Gratton found the second-order nature of the reactions by an order-analysis of their conductivity-time curves. 

Nervous system Conduction time Nerve conduction Rat Homer et al.192... 

The quinolinone derivative, OPC-88117 (73), is yet another compound described as possessing both Class I and Class III electrophysiological activities. Studies in guinea-pig papillary muscle showed that OPC-88117 at 30 increased APDgo by about 15% and decreased F ,ax by only 4% however, at 100 /iM APDgo was prolonged by 23 % and was decreased by 23 % [206]. Further experiments in isolated rabbit hearts demonstrated that OPC-88117 increased atrio-His bundle (A-H) and His bundle-ventricle (H-V) conduction times and refractory periods with a profile that was similar to, but more potent than that of lidocaine [207]. 

Adenosine Adenosine slows conduction time through the AV node and can interrupt the reentry pathways through the AV node. 

Pharmacology Therapeutic concentrations of lidocaine attenuate phase 4 diastolic depolarization, decrease automaticity and cause a decrease or no change in excitability and membrane responsiveness. Action potential duration and effective refractory period (ERP) of Purkinje fibers and ventricular muscle are decreased, while the ratio of ERP to action potential duration is increased. Lidocaine raises ventricular fibrillation threshold. AV nodal conduction time is unchanged or shortened. Lidocaine increases the electrical stimulation threshold of the ventricle during diastole. 

Cardiovascular disorders Use with extreme caution in patients with cardiovascular disorders because of the possibility of conduction defects, arrhythmias, CHF, sinus tachycardia. Ml, strokes, and tachycardia. These patients require cardiac surveillance at all dose levels of the drug. In high doses, TCAs may produce arrhythmias, sinus tachycardia, conduction defects, and prolonged conduction time. Tachycardia and postural hypotension may occur more frequently with protriptyline. Hyperthyroid patients Hyperthyroid patients or those receiving thyroid medication require close supervision because of the possibility of cardiovascular toxicity, including arrhythmias. 

The AV node lies directly above the insertion of the septal leaflet of the tricuspid valve and anterior to the ostium of the coronary sinus. It is part of the AV junction area, which is divided into three regions. The transitional cells, or nodal approaches, connect the atrial myocardium to the compact portion of the AV node. The slowest conduction time occurs within the AV node [8]. At its distal end, the compact portion of the AV node enters the central fibrous body, becoming the penetrating portion, or His-bundle [9]. 

The atrioventricular conduction time, measured as the A-H interval, is prolonged by flecainide as is the His-Purkinje or H-V interval. 

Amiodarone, like its major metabolite desethylamiodarone, increases A-V nodal conduction time and refractory period. 

Chronotropic effect negative. Ethanol (50%) extract of the fresh leaf, administered by gastric intubation to rats at a dose of 40 mL/kg, produced weak activity. Results were significant at p < 0.05 level ". Glycerin/ ethanol extract of the fresh leaf, administered intragastrically to dogs at a dose of 20 mg/kg, produced an increase in length of sinusal cycle (16%), sinoatrial conduction time (27%), and sinus node recovery time (31%) . 

Mechanism of Action A cardiac agent that slows impulse formation in the SA node and conduction time through the AV node. Adenosine also acts as a diagnostic aid in myocardial perfusion imaging or stress echocardiography. Therapeutic Effect Depresses left ventricular function and restores normal sinus rhythm. 

Tricyclic antidepressants have effects on heart rate (HR), blood pressure (BP), and three distinct measures of the electrocardiogram (EKG). The EKG parameters affected are (1) the PR interval, which represents depolarization of the aorta (2) the QRS duration, which represents intraventricular conduction time and (3) the QTc, which represents the depolarization and subsequent repolarization of the ventricles, corrected for cardiac rate. 

Biederman et al. (1989a,b) also found desipramine (at the relatively high mean dose of 4.6 mg/kg/day) to be safe and effective for treatment of ADD. Despite these positive results, however, concerns about prolonged cardiac conduction times and the reports of several sudden deaths of children on desipramine have left many clinicians and parents reluctant to use the drug (Riddle, et ah, 1993). Another less well-studied tricyclic, nortriptyline, which some believe to have less potential cardiotoxicity, has shown promise in a retrospective study in children with ADHD plus tic disorder (Spencer et al., 1993b). 

As conduction times are prolonged, the chance of developing reentry arrhythmias grows. Malignant ventricular arrhythmias are uncommon in mild or moderate overdoses, but they are more likely in severe cases. 

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