The length of time for half the amount of a radioactive nucleus to spontaneously disintegrate.
The amount of time that must elapse until half the principal amount of a block of bonds has been retired ( via a sinking fund or other Process).
A half-life is the amount of time it takes for a radioactive substance to decay by releasing radioactive particles or waves, and to lose one-half of its radioactivity. Half-lives for different substances vary from millionths of a second to billions of years. Iodine-131 has a half-life of eight days. At the end of eight days, half of the Iodine-131 becomes stable xenon-131. After another eight days, half of the remaining Iodine 131 will decay into stable xenon-131, and so on. When an atom decays and becomes stable, it is no longer radioactive.
1. The time required for a pollutant to lose half its effect on the environment. For example, the biochemical half-life of DDT in the environment is 15 years. The half-life of Radium is 1,580 years. 2. The time required for half of the atoms of a radioactive element to undergo self-transmutation or decay. 3. The time required for elimination of one-half a total dose from the body.
Time in which one half of the nuclei in a radioisotope emits its radiation. Half-lives for radioisotopes vary from millionths of a second to billion of years.
the time required for the radioactive decay of one half of the atoms of a radioactive substance
The time required for half the quantity of a drug to be metabolized or eliminated from an organism.
The time taken for the amount of drug in the body (or its concentration in plasma or within cells) to be reduced by 50% as a result of metabolism and excretion.
Subject: Geology The time required to reduce the number of parent atoms by one-half as a result of radioactive decay. Reference : Skinner B.J., S.C.Porter & J.Park (2004), DYNAMIC EARTH, 5thedition, Jon Wiley & Sons [ Pics List
The time for the activity of a radioactive isotope to decay to half its original value. Each radioactive isotope has a characteristic half-life, e.g. U-235 = 0.7038 x 109 years; U-238 = 4.468 x 109 years. See decay.
the time required for one-half of a given number of a radionuclide to decay (= t 1/2). where is the decay constant is the decay equation used to determine half life.
Time in which the concentration of a substance (especially if radioactive) is reduced by 50%.
The time required for half of the residue to lose its analytical identity whether through dissipation, decomposition, metabolic alteration or other factors. The half-life concept may be applied to residues in crops, soil, water, animals or specific tissues.
The amount of time it takes for half of the existing amount of a radioactive element to decay to non-radioactive products.
The time taken for the concentration of a xenobiotic in a body fluid to decrease by half.
The period required for the decay of half of the atoms in a given amount of a specific radioactive substance.
The time taken for the blood concentration of a drug to drop by half
The time required for a chemical to degrade to half its initial concentration
This is the amount of time it takes for a radioactive substance to lose one-half of its radioactivity. Iodine-131 has a half-life of eight days. At the end of eight days, half of the iodine-131 atoms have undergone decay and converted to stable xenon-131. Half of the remaining iodine-131 will decay into stable xenon-131 in another eight days, and so on. When an atom decays and becomes stable, it is no longer radioactive. Some radioactive substances decay quickly into non-radioactive materials. Others decay over long periods of time into other radioactive materials which, in turn, undergo radioactive decay. For example, uranium-238 has a half-life of 4.5 billion years and undergoes more than a dozen changes before becoming a stable form of lead. [Back to Module 2
the time it takes for 50 percent of the plasma concentration of a drug to be eliminated from the body.
the time it takes for the reactant concentration to decrease by one-half of its initial value in a reaction. The time it takes for one-half of the nuclei in a sample to decay
The average time required for the disappearance or decay of one-half of any amount of a given substance. haploid cell( hap-loyd) [Gk. haploos, single + ploion, vessel] A cell containing only one set of chromosomes (n).
t1/2): Time in which the concentration of a substance will be reduced by half, assuming a first order elimination process or radioactive decay.
the time required for one-half of the atoms of a radioisotope to undergo radioactive decay.
Time needed for one-half of the nuclei in a radioisotope to emit its radiation. Each radioisotope has a characteristic half-life, which may range from a few millionths of a second to several billion years. See radioisotope.
The time required for half the atoms of a particular radionuclide to decay to another nuclear state.
The time it takes for half the atoms in a radioactive source to decay. Half-lives vary from a fraction of a second to billions of years.
The time required for half of something to undergo a process. With respect to a drug, this is the time required for half the amount of the drug in or introduced into a living system to be eliminated or disintegrated by natural processes
(HALF·life). The average length of time it takes for one half the atoms of any given amount of radioactive substance to decay or disintegrate.
The amount of time it takes for half a dose of any drug to be eliminated from the body.
used of plant virus inoculum for the time taken to lose half its infectivity on ageing, or in heat inactivation studies. Also used to express the progressive decline in transmission of some viruses by their vectors as the period between acquisition and inoculation feeding increases.
The amount of time it takes for half of a drug concentration to be eliminated from the body. Withdrawal reactions associated with drugs with a longer half-life are more gradual and may be less severe.
The amount of time it takes half of a given quantity of a radioactive element to decay.
The time required for the activity of a radionuclide to decrease by decay to one half of its initial value; radionuclides may be referred to as "short-lived" or "long-lived", etc
The amount of time needed for half of the atoms in a quantity of a radioisotope to decay.
3/4 The time in which the activity of a radioactive nuclide decays to half its initial value.
the time required for the decay of one-half the unstable atoms initially present (see Table 26.3)
The time required for the amount of a reactant to decrease to half its initial value.
The time in which half the atoms of a given quantity of a particular radioactive substance disintegrate to another nuclear form. Measured half-lives vary from millionths of a second to billions of years. Similarly, the time in which half the molecules of a chemical substance disappear as a result of chemical or biochemical transformation. [S. L. Brown
The period of time necessary for one half of a substance introduced to a living system or ecosystem to be eliminated or disintegrated by natural processes.
The half-life of a chemical reaction is the time take for the reaction to reach 50 % completion. See also: Rate Integrated Rate Law Differential Rate Law
For a given reaction the half life 1/2 of a reactant is the time required for its concentration to reach a value that is the arithmetic mean of its initial and final (equilibrium) value. In nuclear chemistry, (radioactive) half life is defined, for a simple radioactive decay process, as the time required for the activity to decrease to half its value by that process. = 0/2
The time taken for the level of radioactivity in an element to halve.
The half-life of a reaction is the time required for the concentration of one of the reactants to decrease to half of its initial value.
The amount of time that it takes half of the atoms of the parent isotope found in a mineral to decay and form stable daughter isotopes.
Amount of time necessary for one-half of a given mass of a radioactive isotope to decay into another element.
the time it takes for the body to eliminate half of the drug that reaches the bloodstream
The average time required for one-half of the amount of radioactivity of a radionuclide to undergo radioactive decay. For material with a half-life of one week, half of the original amount of activity will remain after one week; half of that (one-quarter of the original amount) will remain after two weeks; and so on.
the amount of time required for one half of an amount of a substance to be lost through biologic processes.
The amount of time that a radioactive atom has a probability of 1/2 of surviving without decaying.
Time required to reduce by one half the amount of a chemical absorbed by the body. Half-life can be calculated accurately only for those substances eliminated linearly, independent of concentration. For linearly eliminated substances, it takes approximately 3.5 half-lives to eliminate 90% of the substance. [LaDou, p.183
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)
a measure of the average lifetime of a radioactive substance, and specifies the time it takes for one-half of the original atoms to decay
a measure of time required for an amount of radioactive material to decrease by one-half of its initial amount
the time it takes for half the radioactive atoms in a sample to decay to a stable product
Time, in years, until half of the purchased principal has been repaid.
the time any substance takes to decay by half of its original amount. See also biological half-life, decay constant, effective half-life, radioactive half-life.
The time during which radioactivity or some other property of substances falls to half of its original value (UN, 1997).
The time required for the decay of half of a sample of particles of a radionucleotide or elementary particle.
The time it takes for half the clotting activity of infused factor to disappear (e.g., a product with a half-life of 12 hours is only half as effective 12 hours after being infused).
The amount of time a substance (hormone, medication, etc.) in the body takes until one-half its initial concentration has been metabolized or eliminated.
The time in which half the atoms of a particular radioactive nuclide disintegrate. The half-life is a characteristic property of each radioactive isotope.
The time in which half the atom of a particular radioactive substance disintegrate to another nuclear form. Also called radioactive or physical half-life.
The time required for the body to eliminate half of the material taken in by natural biological means.
The time required for a radionuclide contained in a biological system, such as a human or an animal, to reduce its activity by half as a combined result of radioactive decay and biological elimination.
The period over which the concentration of a specified chemical or drug takes to fall to half its original concentration in the specified fluid or blood.
The time it takes for one-half of a radioactive element or pesticide to decay. Halides or halogens - Chlorine, bromine, or fluorine.
The time it takes for half of any radioactive substance to disintegrate. Half-lives range from seconds to millions of years.
The time it takes to reduce the concentration of a pesticide in an organism or medium by half, through transport, degradation or transformation.
The amount of time required for half of the pesticide residue to disappear from soil, water, plants, or animals.
The span of time required for a thing to deteriorate to 50 per cent of its original potency: about twenty-four thousand years for plutonium atoms ... a few centuries for great civilizations ... three weeks for a hit song ... four days for your child's enthusiasm over a new £60 toy ... twenty-four hours for the fresh sense of purpose acquired at a motivational seminar . . . fifteen minutes for the warming afterglow of a 'feel-good' movie ... ten seconds for a sudden impulse to shove the papers off your desk, slug the boss and board the next plane to Tahiti.
The time it takes for 50% of a drug or drug formulation given to a patient to be eliminated or disintegrated by natural processes.
The time required for the body to eliminate half the amount of a drug.
For our purposes, the amount of time it takes for a substance to be metabolically reduced to one half of its original concentration.
the amount of time it takes for half of the nuclei matter to decay.
The amount of time it takes for one half of a substance to be broken down or excreted. Nicotine has a short half-life; therefore, frequent tobacco intake is required to maintain desired nicotine levels in the blood.
The time required for a radioactive substance to lose 50 percent of its activity by decay. The half-life of the radioisotope plutonium-239, for example, is about 24,000 years. Starting with a pound of plutonium-239, in 24,000 years there will be one-half pound of plutonium-239, in another 24,000 years there will be one-fourth pound, and so on. (A pound of material remains, but it gradually becomes a stable element.)
The time required for concentration of one substance to reach half of its initial value.The time it takes for one half of a substance to be metabolized and/or excreted from the body.
The time the body takes to metabolize and rid itself of half the ingested dosage.
Used to measure the rate of radioactive decay of disintegration. The time lapse during which a radioactive mass loses one half of its radioactivity.
The time required for half the amount of a substance (such as a drug or toxin) introduced into the body to be eliminated by the body through natural processes.
The time required for the amount of a drug in the blood to decline to half its original value, measured in hours; a drug with a longer half-life lasts longer in the body and, therefore, generally needs to be taken less often than a drug with a shorter half-life.
The period of time it takes for half the nuclei of a radioactive element to undergo decay to another nuclear form.
The time in which half the atoms of a particular radioactive substance disintegrate to another nuclear form. Measured half-lives vary from millionths of a second to billions of years. Also called physical half-life.
the time required for half the amount of a substance to be eliminated from the body or to be converted to another substance(s).
The time it takes for a radioactive isotope to deliver half of its original energy.
The time required for one-half of an original unstable radioactive element to be converted to a more stable daughter element.
The time required to reduce a drug level to half of its initial value.
the time required for half the amount of an agent (e.g., drug, virus, cell type) to be eliminated from the body.
The period of time required for the disintegration of half of the atoms in a sample of a specific radioactive substance.
The period of time it takes for the concentration of a drug to decrease to half its original concentration in the blood.
Time needed for the concentration of a particular drug in blood to decline to half its maximum level. The half-life of THC is 4.3 days on average but is faster in regular than in occasional users. Because it is highly fat soluble, THC is stored in fatty tissues, thus increasing its half life to as much as 7 to 12 days. Prolonged use of cannabis increases the period of time needed to eliminate is from the system. Even one week after use, THC metabolites may remain in the system. They are gradually metabolised in the urine (one third) and in feces (two thirds). Traces on inactive THC metabolites can be detected as many as 30 days after use.
The time need for the body/tissues to inactivate half of the amount of a drug.
The time required for half of a sample of a radioactive isotope to decay to its stable, nonradioactive form.
The rate of decay of radioactive materials.
the time required for a drug’s concentration in the bloodstream to decrease by one-half; often used in calculating the dosage interval of a drug (i.e. how often a drug is given)
The time required for half of the amount of a drug to be eliminated from the body.
The time required for one-half of a specified substance to disappear.
The length of time for a radioactive substance to lose half of its radioactivity from decay. At the end of one half-life, only 50% of the original radionuclide remains.
The time it takes for an isotope to lose half of its radioactivity.
The time in which the concentration of a chemical in the environment is reduced by half.
The time required for half the nuclei in a sample of a specific isotopic species to undergo radioactive decay.
The amount of time it takes a quantity which changes by a constant factor over time to decrease to half its initial size..
The time required for half of a given radioactive substance to decay.
The time required for one-half of a sample to decay or change into some other form.
The time in which half the atoms of a radioactive substance will have disintegrated, leaving half the original amount. Half of the residue will disintegrate in another equal period of time.
The time required for half of the atoms in a radioactive sample to decay.
The time that it takes for one half of the original concentration of a given drug to dissipate through the body. The shorter the half-life of a drug, the more frequently you have to administer the drug.
The time it takes for HALF of the radioactive element to decay (give off half of its radioactivity). Different radioactive isotopes have different half-lives.
The length of time it takes a substance to diminish to one-half its initial amount.
The time required for half of a reactant to be converted into product(s). The time required for half of a given sample to undergo radioactive decay.
the time required for half the atoms of a radioactive substance to disintegrate or the length of time it takes for a radioactive substance to lose one-half of its radioactivity. Radioactive isotopes have half-lives ranging from split seconds to thousands of years.
The rate of decay for a radioactive isotope; the amount of time it takes for a sample of a radioactive substance to decrease by half.
the time taken for half the quantity of a radioactive isotope in a sample to decay (see also radioactive decay).
The average time taken for half the atoms in a sample of a radioactive substance to decay. It is also the time for the count rate to halve. Radioactivity
The time taken for a radiopharmaceutical to loose it's half of its radioactivity. If the word you are looking for is not in our imaging encyclopaedia, please email us with a word recommendation.
Amount of time it takes for something to become half as radioactive as it was to begin with (e.g. Iodine-131's half life is 8.05 days. Uranium-235's half life is 710 million years).
The time required for the body to eliminate one-half of an administered dosage of any substance by regular process of elimination. Approximately the same for both stable and radioactive isotopes of a particular element.
The time required for a radioactive substance to lose 50 percent of its activity by decay. Each radionuclide has a unique half-life.
The time required for a population of atoms of a given radionuclide to decrease, by radioactive decay, to exactly one-half of its original number is called the radionuclide's half-life. No operation, either chemical or physical, can change the decay rate of a radioactive substance. Half-lives range from much less than a microsecond to more than a billion years. The longer the half-life the more stable the nuclide. After one half-life, half the original atoms will remain; after two half-lives, one fourth (or 1/2 of 1/2) will remain; after three half-lives one eighth of the original number (1/2 of 1/2 of 1/2) will remain; and so on. back to
the amount of time that it takes for half of a particular radioactive substance to decay into a different substance.
amount of time necessary for a radioactive element to lose half of its radioactivity.
Amount of time for a storage device to weaken to half its strength.
Measure of the amount of time it takes for half the radioactive atoms in an element to decay to a more stable form. The half-life of plutonium-239, for example, is about 24,000 years. After one half-life, half the radioactive atoms in a sample remain radioactive; after two half-lives, one quarter remain radioactive; after three half-lives, one-eighth remain radioactive; and so on. Half-lives range from a fraction of a second to billions of years.
The time it takes for half of the activity of a molecule to decay.
the time required for one-half of a radioactive material to decay to a more stable material (it is NOT one-half the age of the rock!).
Each radioactive isotope decays at a specific rate defined as the time it takes for half of the atoms to decay. This decay rate remains the same, and is independent of the amount of the radioactive isotope (p.210-211).
The amount of time required for a radioactive material to lose its strength down to one-half of its initial value.
A measure of how long a drug stays in the blood. The length of time it takes for the blood concentration to drop to 50% of Cmax.
The time required for the disintegration of half the atoms in a sample of a radioactive isotope of an element.
The period required for half of the atoms of a particular radioactive isotope to decay and become an isotope of another element.
Refers to the amount of time required for half of a given concentration of drug to be eliminated from the body.
The time taken for the activity of a radionuclide to lose half its value by decay. Symbol ½.
The time required for half of the substance present at the beginning to dissipate or disintegrate.
the amount of time taken for half of the drug to be eliminated by the body.
1. The time required for a pollutant to lose one-half of its original coconcentrationor example, the biochemical half-life of DDT in the environment is 15 years. 2. The time required for half of the atoms of a radioactive element to undergo self-transmutation or decay (half-life of radium is 1620 years). 3. The time required for the elimination of half a total dose from the body.
The time required for half of the radioactive atoms in a sample to disintegrate.
The amount of time it takes for one-half of the atoms of a radioactive material to decay to a stable form. For example, the half-life of carbon-14 is 5,568 years.
The time it takes for half of a group of a radioactive element's isotopes to decay.
The half-life of a radioisotope is the amount of time it takes for half of the radioisotope to decay.
The time over which the number of radioactive nuclei of a given species decays exponentially to half its initial value. Half-lives range from small fractions of a second to billions of years. Half-life is also applied to any exponential decay. That is, if a physical quantity at any time is related to its initial value 0 by the half-life for this process is Ï„ ln 2, where Ï„ is the mean life.
the time required for the number of nuclides in a radioactive sample to reach half the original number of nuclides.
The half-life of a quantity subject to exponential decay is the time required for the quantity to decay to half of its initial value. The concept originated in the study of radioactive decay, but applies to many other fields as well, including phenomena which are described by non-exponential decays.