- 1. That relation of events which is expressed by the terms past, present, and future, and measured by units such as minutes, hours, days, months, or years. 2. A certain period during which something definite or determined is done. SYN: tempus (2). [A.S. tima]- activated clotting t. (ACT) the most common test used for coagulation t. in cardiovascular surgery.- activated partial thromboplastin t. (aPTT) the t. needed for plasma to form a fibrin clot following the addition of calcium and a phospholipid reagent; used to evaluate the intrinsic clotting system.- biologic t. the concept that our appreciation of t. varies with age and is governed by the neural organization of the individual; it obeys a logarithmic rather than an arithmetic law.- bleeding t. the t. interval between the appearance of the first drop of blood and the removal of the last drop following puncture of the ear lobe or the finger, usually 1–3 min; it provides a global but imprecise evaluation of platelet and capillary function.- circulation t. the t. 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.- clot retraction t. the t. required for a blood clot to separate from the tube wall and express serum, usually completed in 18–24 hours, but retarded or absent in persons with thrombocytopenic purpura.- clotting t. SYN: coagulation t..- doubling t. the t. it takes for the number of cells in a neoplasm to double, with shorter doubling times implying more rapid growth.- euglobulin clot lysis t. a measure of the ability of plasminogen activators and plasmin to lyse a clot; normally, clot lysis is determined by the balance of factors which activate fibrinolysis (plasminogen activators and plasmin) and those which inhibit lysis; in certain conditions ( e.g., carcinoma or hepatic insufficiency) activating factors predominate and can be measured by noting the t. it takes the euglobulin fraction of plasma (excluding inhibitors of fibrinolysis) to clot.- fading t. the t. required for a constant stimulus applied to a fixed area of the peripheral visual field to stop.- t. of flight the t. for a photon created by annihilation of a positron-electron pair to reach a detector; since annihilation photons are created in pairs and travel in opposite directions at about 3 × 1010 cm/sec, measurement of the difference in arrival t. at detectors with subnanosecond resolution allows calculation of the location of the event; the basic physics of positron emission tomography.- forced expiratory t. (FET) the t. taken to expire a given volume or a given fraction of vital capacity during measurement of forced vital capacity; subscripts specify the exact parameters measured.- half-t. half-t..- inertia t. the interval elapsing between the reception of the stimulus from a nerve and the contraction of the muscle.- intraatrial conduction t. 1. the total duration of electrical activity of the atria in one cardiac cycle; 2. the t. between right atrial and left atrial activation. SYN: interatrial conduction t..- left ventricular ejection t. (LVET) the t. measured clinically from onset to incisural notch of the carotid or other pulse; properly, the t. of ejection of blood from the left ventricle beginning with aortic valve opening and ending with aortic valve closure.- prothrombin t. (PT) the t. required for clotting after thromboplastin and calcium are added in optimal amounts to blood of normal fibrinogen content; if prothrombin is diminished, the clotting t. increases; used to evaluate the extrinsic clotting system. SEE ALSO: prothrombin test.- reaction t. the interval between the presentation of a stimulus and the responsive reaction to it.- recognition t. the interval between the application of a stimulus and the recognition of its nature.- relaxation t. (τ) the t. required for the substrate in an enzymatic or chemical reaction to fall to 1/e of its initial value.- repetition t. (TR) in magnetic resonance imaging, the t. between repetitions of the pulse sequence.- rise t. 1. the t. required for a pulse or echo to rise from onset to its peak amplitude; 2. the t. required for a pulse or echo to rise from 10–90% peak amplitude.- Russell's viper venom clotting t. a clotting t. 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 ALSO: Stypven t. test.- sinoatrial conduction t. (SACT) the t. required for an impulse to travel from sinus node to atrium; estimated indirectly during reset nodus sinuatrialis period by halving the average interval from the premature beat to the following normal sinus beat of the atrium.- sinoatrial recovery t. (SART) interval from the last paced P wave to the first succeeding spontaneous P wave (after 2–5 min of right atrial pacing at 120–140 beats/min, and when expressed as percentage of control cycle length, it normally ranges from 115–159%).- survival t. 1. the period elapsing between the completion or institution of any procedure and death; 2. the lifespan of biologically or physically marked erythrocytes or other cells.- thrombin t. the t. needed for a fibrin clot to form after the addition of thrombin to citrated plasma; prolonged thrombin t. is seen in patients receiving heparin therapy.- tissue thromboplastin inhibition t. a test used to identify lupus anticoagulant; the thromboplastin source used in the prothrombin test is diluted to increase sensitivity to inhibitors.- utilization t. the minimum duration of a stimulus of rheobasic strength that is just sufficient to produce excitation. SYN: temps utile.* * *Teaching Immunization for Medical Education [study]; Treatment of Infarcting Myocardium Early [trials]
* * *time 'tīm n1 a) the measured or measurable period during which an action, process, or condition exists or continues see bleeding time, COAGULATION TIME, PROTHROMBIN TIME, REACTION TIMEb) a continuum which lacks spatial dimensions and in which events succeed one another from past through present to future2) the point or period when something occurs3) a moment, hour, day, or year as indicated by a clock or calendar <what \time is it>
* * *(t) (tīm) [A.S. tīma] a measure of duration.
Medical dictionary. 2011.