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  2. Half-life - Wikipedia

    en.wikipedia.org/wiki/Half-life

    Half-life (symbol t½) is the time required for a quantity (of substance) to reduce to half of its initial value. The term is commonly used in nuclear physics to describe how quickly unstable atoms undergo radioactive decay or how long stable atoms survive. The term is also used more generally to characterize any type of exponential (or, rarely ...

  3. Biological half-life - Wikipedia

    en.wikipedia.org/wiki/Biological_half-life

    Biological half-life (elimination half-life, pharmacological half-life) is the time taken for concentration of a biological substance (such as a medication) to decrease from its maximum concentration (C max) to half of C max in the blood plasma. [1][2][3][4][5] It is denoted by the abbreviation . [2][4] This is used to measure the removal of ...

  4. Exponential decay - Wikipedia

    en.wikipedia.org/wiki/Exponential_decay

    A more intuitive characteristic of exponential decay for many people is the time required for the decaying quantity to fall to one half of its initial value. (If N(t) is discrete, then this is the median life-time rather than the mean life-time.) This time is called the half-life, and often denoted by the symbol t 1/2. The half-life can be ...

  5. Specific activity - Wikipedia

    en.wikipedia.org/wiki/Specific_activity

    Specific activity. Specific activity (symbol a) is the activity per unit mass of a radionuclide and is a physical property of that radionuclide. [1][2] It is usually given in units of becquerel per kilogram (Bq/kg), but another commonly used unit of specific activity is the curie per gram (Ci/g). In the context of radioactivity, activity or ...

  6. Tritium - Wikipedia

    en.wikipedia.org/wiki/Tritium

    Tritium (from Ancient Greek τρίτος (trítos) 'third') or hydrogen-3 (symbol T or 3 H) is a rare and radioactive isotope of hydrogen with half-life ~12.3 years. The tritium nucleus (t, sometimes called a triton) contains one proton and two neutrons, whereas the nucleus of the common isotope hydrogen-1 (protium) contains one proton and no neutrons, and that of non-radioactive hydrogen-2 ...

  7. Effective half-life - Wikipedia

    en.wikipedia.org/wiki/Effective_half-life

    Effective half-life. In pharmacokinetics, the effective half-life is the rate of accumulation or elimination of a biochemical or pharmacological substance in an organism; it is the analogue of biological half-life when the kinetics are governed by multiple independent mechanisms. This is seen when there are multiple mechanisms of elimination ...

  8. K–Ar dating - Wikipedia

    en.wikipedia.org/wiki/K–Ar_dating

    remaining. The long half-life of 40 K allows the method to be used to calculate the absolute age of samples older than a few thousand years. [1] The quickly cooled lavas that make nearly ideal samples for K–Ar dating also preserve a record of the direction and intensity of the local magnetic field as the sample cooled past the Curie ...

  9. Elimination rate constant - Wikipedia

    en.wikipedia.org/wiki/Elimination_rate_constant

    Elimination rate constant. The elimination rate constant K or Ke is a value used in pharmacokinetics to describe the rate at which a drug is removed from the human system. [1] It is often abbreviated K or Ke. It is equivalent to the fraction of a substance that is removed per unit time measured at any particular instant and has units of T −1.