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 ?
8%, respectively, and the terminal half-lives are 24 and 31 hours.
Other unusual nuclides can have even longer half-lives than tantalum-180m.
A common challenge when using biological drugs is that they are often hampered by short plasma half-lives which can lead to reduced bioavailability, meaning that the human body clears the drug in a matter of minutes or hours.
Therapeutic proteins; strategies to modulate their plasma half-lives.
The half-lives of DCD for the 10kg and 20kg treatments (0-10cm soil depth) were not significantly different from each other for the applications made in three different seasons.
Longer half-lives allows for reduced dosing frequency, lower dosing, and potentially improved tolerability and efficacy.
Most empirical estimates of human elimination kinetics for persistent chemicals reflect apparent elimination half-lives that represent the aggregated effects of intrinsic elimination, ongoing exposure, and changes in body weight.
Methadone is difficult to dose and equianalgesia is a particular problem, be cause the analgesic and biologic half-lives don't match.
As part of Domantis' Albutherapeutics franchise, we are using the AlbudAb approach to further expand our extensive pipeline of proprietary products, both by improving existing drugs and by creating a range of entirely new drugs with exceptional half-lives.
So it may be that at least some of the nucleosides are essential in maintaining long-term suppression after you stop the medications, in a way that is perhaps beyond half-lives.
The overall half-life is determined--in the case of some of these agents by active metabolites that have lengthy half-lives, which in turn, can be associated with long-lasting daytime sedation.
As a benchmark for comparison to the preliminary results, consider the half-lives estimated for international deviations from LOP (that is, from Purchasing Power Parity) by Frankel and Rose [JIE, February 1996] who found a half-life of 4.