| partial thromboplastin time | Test of the intrinsic (factors viii, ix, xi, and xii) and common (fibrinogen, prothrombin, factors v and x) pathways of coagulation in which a mixture of plasma and phospholipid platelet substitute (e.g., crude cephalins, soybean phosphatides) is recalcified and the time required for the appearance of fibrin strands measured. Activation may be provided by contact with the glass tube or exposure to activators (e.g., ellagic acid, particulate silicates such as diatomaceous earth or kaolin) before addition of the calcium chloride. It is used as a screening test and to monitor heparin therapy. (12 Dec 1998) |
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| relaxation time | Time taken for a system to return to the resting or ground state or a new equilibrium state following perturbation. Often used in context of receptor systems that have a refractory period after responding and then relax to a competent state. Can be used more precisely to mean the time for a system to change from its original equilibrium value to 1/e of this original value. (18 Nov 1997) |
| median time to elimination | <pharmacology> The time it takes one half of a drug to be eliminated from the body. (09 Oct 1997) |
| repetition time | In magnetic resonance imaging, the time between repetitions of the pulse sequence. (05 Mar 2000) |
| rise time | The time required for a pulse or echo to rise from 10% to 90% of its peak amplitude. (05 Mar 2000) |
| P-H conduction time | See: atrioventricular conduction. (05 Mar 2000) |
| running time | The time during which an activity (e.g., chromatography development) occurs. (05 Mar 2000) |
| Russell's viper venom clotting time | A clotting time determination performed on citrated platelet-poor plasma using Russell's viper venom as an activating agent. This allows activation of factor X directly without the need for other coagulation factors and is used to confirm factor X defects. See: Stypven time test. (05 Mar 2000) |
| circulation time | The time taken for the blood to pass through a given circuit of the vascular system, e.g., the pulmonary or systemic circulation, from one arm to another, from arm to tongue, or from arm to lung; it is measured by the injection into an arm vein of a substance, such as sodium dehydrocholate, ether, fluorescein, histamine, or a radium salt, which can be detected when it arrives at another point in the vascular system. (05 Mar 2000) |
| clot retraction time | The time required for a blood clot to separate from the tube wall and express serum, usually completed in 18 to 24 hours, but retarded or absent in persons with thrombocytopenic purpura. (05 Mar 2000) |
| clotting time | The time required for blood to coagulate; prolonged in haemophilia and in the presence of obstructive jaundice, some anaemias and leukaemias, and some of the infectious diseases. Synonym: clotting time. (05 Mar 2000) |
| coagulation time | The time required for blood to coagulate; prolonged in haemophilia and in the presence of obstructive jaundice, some anaemias and leukaemias, and some of the infectious diseases. Synonym: clotting time. (05 Mar 2000) |
| 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) |
| 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) |