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This is a list of radioactive nuclides (sometimes also called isotopes), ordered by half-life from shortest to longest, in seconds, minutes, hours, days and years. Current methods make it difficult to measure half-lives between approximately 10 −19 and 10 −10 seconds.
In this situation it is generally uncommon to talk about half-life in the first place, but sometimes people will describe the decay in terms of its "first half-life", "second half-life", etc., where the first half-life is defined as the time required for decay from the initial value to 50%, the second half-life is from 50% to 25%, and so on.
In clinical practice, this means that it takes 4 to 5 times the half-life for a drug's serum concentration to reach steady state after regular dosing is started, stopped, or the dose changed. So, for example, digoxin has a half-life (or t 1 / 2 ) of 24–36 h; this means that a change in the dose will take the best part of a week to ...
In principle a half-life, a third-life, or even a (1/√2)-life, could be used in exactly the same way as half-life; but the mean life and half-life t 1/2 have been adopted as standard times associated with exponential decay. Those parameters can be related to the following time-dependent parameters:
Neptunium-236 has 143 neutrons and a half-life of 154,000 years. It can decay by the following methods: Electron capture: the decay energy is 0.93 MeV and the decay product is uranium-236. This usually decays (with a half-life of 23 million years) to thorium-232. Beta emission: the decay energy is 0.48 MeV and the decay product is plutonium-236.
Plutonium-244 is the most stable isotope of plutonium, with a half-life of about 80 million years. It is not significantly produced in nuclear reactors because 243 Pu has a short half-life, but some is produced in nuclear explosions. 244 Pu has been found in interstellar space [13] and has the second longest half-life of any non-primordial ...
[5] [6] An increase of alcohol intake by ~20 g ethanol/day will raise the PEth 16:0/18:1 concentration by ~0.10 μmol/L, and vice versa if the alcohol consumption has decreased. However, it has been demonstrated that there can be significant inter-personal variation, leading to potential misclassification between moderate and heavy drinkers. [ 7 ]
Beryllium-10 has a half-life of 1.39 × 10 6 y, and decays by beta decay to stable boron-10 with a maximum energy of 556.2 keV. [ 7 ] [ 8 ] It is formed in the Earth's atmosphere mainly by cosmic ray spallation of nitrogen and oxygen.