| collision time | <radiobiology> Typical time which passes between two consecutive collision events for a given particle. Inverse of the collision frequency, equal to the mean free path divided by the particle's velocity. In plasmas, the (Coulomb) collision time decreases with increasing density, and increases with increasing temperature. (09 Oct 1997) |
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| whole blood coagulation time | Measurement of the time required by whole blood to produce a visible clot. Factors that could influence the test are all but III, vii, and xiii. Activation may be by contact with the glass tube or exposure to diatomaceous earth. Delay of onset of coagulation may be achieved by use of nonwettable plastic or silicone-coated glass tubes. It is used for monitoring heparin therapy and as a bedside screening test for deficiencies in the intrinsic coagulation pathway. "activated coagulation time" is sometimes referred to as act. (12 Dec 1998) |
| confinement time | <radiobiology> There are several types. The general definition is tau = [total]/[loss per unit time], hence Tau_E = [total energy]/[energy loss per unit time]. Tau_[E, N,.] is the amount of time the plasma is contained (for example, by magnetic fields) before its [energy (E), particles (N or P)] leak / dissipate away. The different types are, in general, similar but not equal. (N.B., Tau_E is NOT electron confinement time!) (09 Oct 1997) |
| continuous time model | <epidemiology> A model in which the system changes continuously over time. Derivatives (e.g. DY/dt ) are the mathematical formalism for describing such continuous change. The differential equation which embodies a model provides the values of these derivatives at any particular time point; calculus or a computer can then be used to move the state of the model forwards in time. Continuous models have the advantage over discrete time models in that they are more amenable to algebraic manipulation, although they are slightly harder to implement on a computer. The same as a differential equation model. (05 Dec 1998) |
| half-time | The time, in a first-order chemical (or enzymic) reaction, for half of the substance (substrate) to be converted or to disappear. Compare: half-life. (05 Mar 2000) |
| prothrombin time | Measurement of clotting time of plasma recalcified in the presence of excess tissue thromboplastin. Factors measured are fibrinogen, prothrombin, and factors v, vii, and x. It is used for monitoring anticoagulant therapy with coumarins. (12 Dec 1998) |
| sensation time | The minimal time a visual image must be exposed in order to be perceived. (05 Mar 2000) |
| H-R conduction time | Conduction of the cardiac impulse through the ventricular myocardium, represented by the QRS complex in the electrocardiogram. H-R conduction time is from the onset of the first high frequency component of the His bundle electrogram to the onset of the QRS complex of the surface electrocardiogram (normally 43 ± 12 msec); H-V conduction time is from the onset of the first high frequency component of the His bundle electrogram to the onset of the ventricular electrogram (normally approximates the H-R interval but may be a little shorter). Synonym: ventricular conduction. (05 Mar 2000) |
| H-V conduction time | Conduction of the cardiac impulse through the ventricular myocardium, represented by the QRS complex in the electrocardiogram. H-R conduction time is from the onset of the first high frequency component of the His bundle electrogram to the onset of the QRS complex of the surface electrocardiogram (normally 43 ± 12 msec); H-V conduction time is from the onset of the first high frequency component of the His bundle electrogram to the onset of the ventricular electrogram (normally approximates the H-R interval but may be a little shorter). Synonym: ventricular conduction. (05 Mar 2000) |
| sinoatrial conduction time | <cardiology, physiology> The time required for an impulse to travel from the sinoatrial node to the atrium; estimated indirectly during asystole by halving the average interval from the premature beat to the following normal sinus beat of the atrium. (05 Mar 2000) |
| sinoatrial recovery time | <cardiology, physiology> Interval from the last paced P wave to the first succeeding spontaneous P wave (after 2 to 5 minutes of right atrial pacing at 120 to 140 beats per minute, and when expressed as percentage of control cycle length, it normally ranges from 115 to 159%). (05 Mar 2000) |
| space-time clustering | A statistically significant excess of cases of a disease, occurring within a limited space-time continuum. (12 Dec 1998) |
| Stypven time test | A test measuring the clotting time of plasma after addition of Russell's viper venom, useful in evaluating patients with deficiencies in factor X. Origin: Trade name styptic + venom (05 Mar 2000) |
| survival time | The period elapsing between the completion or institution of any procedure and death, the life-span of biologically or physically marked erythrocytes or other cells. (05 Mar 2000) |
| systolic time intervals | See: electromechanical systole, left ventricular ejection time, preejection period. (05 Mar 2000) |