half-life

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half-life

(hăf′līf′, häf′-)
n.
1. Physics The time required for half the nuclei in a sample of a specific isotopic species to undergo radioactive decay.
2. Biology
a. The time required for half the quantity of a drug or other substance deposited in a living organism to be metabolized or eliminated by normal biological processes. Also called biological half-life.
b. The time required for the radioactivity of material taken in by a living organism to be reduced to half its initial value by a combination of biological elimination processes and radioactive decay.

half-life

n
1. (General Physics) the time taken for half of the atoms in a radioactive material to undergo decay. Symbol: τ
2. (Biology) the time required for half of a quantity of radioactive material absorbed by a living tissue or organism to be naturally eliminated (biological half-life) or removed by both elimination and decay (effective half-life)

half′-life`

or half′ life`,



n., pl. -lives (-ˌlaɪvz)
1. the time required for one half the atoms of a given amount of a radioactive substance to decay.
2. the time required for the activity of a substance taken into the body to lose one half its initial effectiveness.
[1905–10]

half-life

(hăf′līf′)
The average time needed for half the nuclei in a sample of a radioactive substance to undergo radioactive decay. The half-life of a substance does not equal half of its full duration of radioactivity. For example, if one starts with 100 grams of radium 229, whose half-life is 4 minutes, then after 4 minutes only 50 grams of radium will be left in the sample, after 8 minutes 25 grams will be left, after 12 minutes 12.5 grams will be left, and so on.

half-life

The time required for the activity of a given radioactive species to decrease to half of its initial value due to radioactive decay. The half-life is a characteristic property of each radioactive species and is independent of its amount or condition. The effective half-life of a given isotope is the time in which the quantity in the body will decrease to half as a result of both radioactive decay and biological elimination.

half-life

1. A substance which undergoes exponential decay decays by the same ratio in equal intervals of time. The constant ratio is the half-life. The rate of radioactive decay of a substance is defined by its half-life.
2. The time in which half the atoms in a radioactive isotope decay.
ThesaurusAntonymsRelated WordsSynonymsLegend:
Noun1.half-life - the time required for something to fall to half its initial value (in particular, the time for half the atoms in a radioactive substance to disintegrate)
period, period of time, time period - an amount of time; "a time period of 30 years"; "hastened the period of time of his recovery"; "Picasso's blue period"
Translations

half-life

[ˈhɑːflaɪf] N (half-lives (pl)) (Phys) → media vida f

half-life

[ˌhɑːfˈlaɪf] n (Phys) → tempo di dimezzamento

half-life

1. n. vida media, tiempo requerido para que la mitad de una sustancia ingerida o inyectada en el organismo se elimine por medios naturales;
2. semidesintegración, tiempo requerido por una sustancia radioactiva para perder la mitad de su radioactividad por desintegración.

half-life

n vida media
References in periodicals archive ?
All three effects may contribute to the observation of increasing apparent half-lives in initially highly exposed cohorts that were observed for several decades (Masuda 2001) (Table 3).
The article entitled "Engineered Human IgG Antibodies with Longer Serum Half-lives in Primates," by Paul R.
A review of each subject's self-reported diseases and medications did not provide additional evidence of possible associations with the half-lives of serum elimination.
For many persistent chemicals, information about human elimination half-lives is scarce (Wolff 1999), and available data exhibit a high degree of uncertainty.
We are now planning experiments to actually measure their decay half-lives.
Both companies have a large number of compounds with much greater potency and longer pharmacokinetic half-lives, which will be more appropriate for clinical development than CX516.
The half-lives of the new isotopes range from seconds to tens of seconds, the researchers estimate.
Although monoclonal antibodies have reasonably long half-lives, market pressures for less frequent dosing schedules can reduce efficacy.
However, the authors also noted substantial variation in estimated half-lives among individuals, which may reflect ongoing exposures among some participants (e.
These half-lives are at least 10 times longer than those previously observed for a seaborgium isotope.
PDL) (NASDAQ: PDLI) said today that four of its human and humanized monoclonal antibodies have half-lives of two weeks or longer in Rhesus monkeys.
The maximal tissue concentration of drug would be reached in three to five half-lives, or approximately 33 to 55 days.