relaxation time


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re·lax·a·tion time (τ),

the time required for the substrate in an enzymatic or chemical reaction to fall to 1/e of its initial value.

relaxation time

in magnetic resonance imaging, the characteristic time it takes for a sample of atoms, whose nuclei have first been aligned along a static magnetic field and then excited to a higher-energy state by a radiofrequency (rf) signal, to return to a lower-energy equilibrium state. Two time parameters are used to describe the return, or relaxation, to the equilibrium state once the rf signal is turned off: T1 describes the relaxation of the system of spins into a condition of thermal equilibrium with its surroundings. T2 describes the relaxation of the energy that is traded within the system itself. Maps of the values of T1 or T2 as a function of position in the cross-sectional view constitute magnetic resonance images. Also called transverse relaxation time.

relaxation time

An MRI term for the post-excitation return of spins to their equilibrium distribution, in which there is no transverse magnetisation and the longitudinal magnetisation is at its maximum value and oriented in the direction of the static magnetic field. Transverse magnetisation decays toward zero after excitation at a characteristic time constant T2; longitudinal magnetisation returns toward equilibrium with a characteristic time constant T1.

re·lax·a·tion time

(τ) (rē'lak-sā'shŭn tīm)
The time required for the substrate in an enzymatic or chemical reaction to fall to 1/e of its initial value.
References in periodicals archive ?
4 are linear, meaning that the temperature dependent relaxation time follows an Arrhenius-type temperature dependence for all the observed relaxations.
When we compared the scores among groups, we found an accelerated progression of T2 relaxation times in those who were the most physically active," said Thomas M.
The relaxation time observed with 2-phenoxyethanol was less (299 [+ or -] 56 sec), and less dispersal was observed for clove oil at the 0.
The cured soy flour/water sample has a smaller fractional percentage of rapidly relaxing carbons as compared with the neat soy flour and also has much faster relaxation times for both fractional components.
The relaxation time was nondimensionalized by dividing it with the time that the inlet isothermal sound of the vapor phase takes in travelling through the inlet width.
The relaxation time of samples with any degree of aging is longer than the typical cycle length of accelerated weathering, thus the memory of one cycle will be carried over into the next.
It is oriented to a pursuit of those things that help people to savor time--vacation travel time, relaxation time.
Try and manage your time and give yourself plenty of relaxation time.
Moreover, the photon-beam experiments proposed to use the polarized target with CLAS detector place specific demands which are an appropriate target material thickness, maximal amount of polarizable nuclei, high polarization value, and, in case of the frozen mode, long enough relaxation time.
At a time when the public's confidence is shaken by headlines reporting the breach of trust by corporate executives, it is important, during the public's relaxation time, for there to be maintained a sense of impartiality and professionalism in commercial sports performances,'' Nader wrote.