half-life definition
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- 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.
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What does a Drug's Half-Life Mean? Biological and Plasma Half-Life. There are two ways to quantify the half-life of a medication. The biological or elimination half-life is the time it takes for the bioactivity of the drug to reduce by 50% of its initial value. In contrast, the plasma half-life is the time it takes for the concentration of the drug in the bloodstream to reduce by 50%. Two related terms are clearance and volume of distribution.
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- The half life of a radioactive isotope is the time taken for the number of radioactive atoms in the samp…le to decay to one half. Half lives vary hugely, from times like 10-21 seconds, to the very long, approaching the age of our solar system at 4.5x1012 years.
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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]
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half-life half-life, effective, n the half-life of a radioactive isotope in a biologic organism, resulting from the combination of radioactive decay and biologic elimination. half-life, physical, n the average time required for the decay of half the atoms in a given amount of a radioactive substance.
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Can you predict when a specific atom will decay? <br /><br /> The half-life is the time that it will take for half of the atoms in a sample of a radioactive isotope to decay into another element or isotope. This is a constant property of the isotope and does not depend on the sample size.
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Definition of half life of drugs The tissue for which the half-life of a drug is determined should always be specified, e.g., “serum half-life”; the half-life of a drug in muscle, kidney, etc., or in the whole organism can be determined.
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ABC's of Nuclear Science The time required for half of the atoms in any given quantity of a radioactive isotope to decay is the half-life of that isotope. Each particular isotope has its own half-life. For example, the half-life of 238 U is 4.5 billion years.
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- All radioactive atoms undergo radioactive decay. However, they do so spontaneously. Thus, half-life is an estimate of how long it will take a sample of a radioactive element to undergo radioactive decay.
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half-life 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.
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Basic Physics of Nuclear Medicine/The Radioactive Decay Law N t = N 0 2 {\displaystyle N_{t}={\frac {N_{0}}{2}}}. the time taken is the Half Life: Note that the half-life does not express how long a material will remain radioactive but simply the length of time for its radioactivity to halve. Examples of the half lives of some radioisotopes are given in the following table.
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half-life Part of the Computing fundamentals glossary: In science, a half-life (also, as a noun, spelled half life) is the amount of time it takes for half of a substance or entity to undergo some specified process.
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half-life half-life. 1. The period in which the radioactivity or number of atoms of a radioactive substance decreases by half; similarly applied to any substance whose quantity decreases exponentially with time. Compare: half-time. 2.
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What is Nuclear Half-Life? The half-life of Cobalt-60 has a half-life of 5.3 years. You find a 20.0 g sample that has been decaying for 21.2 years. Based on this information calculate the size of the original sample. Think about it: 1  21.2 years total divided by 5.3 years per half-life means the sample completed 3 half lives.
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Half-life Half-life, in radioactivity, the interval of time required for one-half of the atomic nuclei of a radioactive sample to decay (change spontaneously into other nuclear species by emitting particles and energy), or, equivalently, the time interval required for the number of disintegrations per second of a radioactive material to decrease by one-half.
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Biomolecules (Introduction, Structure and Functions)- Carbohydrates A half-life is defined as the amount of time required for one-half or 50% of the radioactive atoms to undergo a radioactive decay. This is also known as the “radioactive” or “physical” half-life.
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What is Half-Life? Now it is time to put those math skills to good use. At one half-life, you would have approximately 50% Carbon-14 and 50% Nitrogen-14. In other words, half (50%) of the Carbon-14 you started with has decayed into the daughter isotope Nitrogen-14.
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Half life Half life. The title speaks for itself, but anyway; in this set there will be the definitions and examples of half life... Flashcards.
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- In a medical context, the half-life may also describe the time that it takes for the concentration in blood plasma of a substance to reach one-half of its steady-state value (the plasma half-life).
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- Not all of the atoms of a radioisotope decay at the same time, but they decay at a rate that is characteristic to the isotope. The rate of decay is a fixed rate called a half-life. The half-life of a radioisotope describes how long it takes for half of the atoms in a given mass to decay.Some isotopes decay very rapidly and, therefore, have a high specific activity.Others decay at a much slower rate. The term half-life describes how long it will take for half of the atoms to decay, and is constant for a given isotope. 2  The curie the unit of measure used to describe the radioactivity of radioactive material. (1C = 3.7 X 1010 disintegrations/sec).
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- 1 The Definition of Half Life The definition of half-life refers to the amount of time it takes for half of the parent isotope in a sample to decay. 2  Isotopes are variations in the atoms of an element base…. 3  The Periodic Table of Elements Life is sustained by a number of chemical elements.
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Drug Half-Life Explained The half-life is the amount of time necessary for the concentration of the drug in the bloodstream of the body to be reduced by one-half. The time it will take for a drug to reach a steady state, or full effectiveness, in the system is based on that half-life.he length of a drug's half-life is significant when the medication is used to treat chronic symptoms, or when a patient's body needs to be clear of the drug in order to take the next step in treatment. For example, some medications are known for having short half-lives, which means the body eliminates them quickly.
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What are Half Lives and Mean Lives? Original May 2003 by Don Koks. Specifying the half life or mean life of a process is a way of quantifying how fast it is occurring, when the whole process would in principle take forever to complete.
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- The term half-life describes how long it will take for half of the atoms to decay, and is constant for a given isotope. The curie the unit of measure used to describe the radioactivity of radioactive material. (1C = 3.7 X 1010 disintegrations/sec)
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Introduction Pharmacology: Half-life of Drugs. Toggle Navigation. The duration of action of a drug is known as its half life. This is the period of time required for the concentration or amount of drug in the body to be reduced by one-half. We usually consider the half life of a drug in relation to the amount of the drug in plasma. A drug's plasma half-life depends on how quickly the drug is eliminated from the plasma. A drug molecule that leaves plasma may have any of several fates. It can be eliminated from the body, or it can be translocated to another body fluid compartment such as the intracellular fluid or it can be destroyed in the blood.
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Half-life For example, if there are 3 radioactive atoms with a half-life of one second, there will not be 1.5 atoms left after one second. Instead, the half-life is defined in terms of probability: Half-life is the time required for exactly half of the entities to decay on average.