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tracer

tracer, an identifiable substance used to follow the course of a physical, chemical, or biological process. In chemistry the ideal tracer has the same chemical properties as the molecule it replaces and undergoes the same reactions but can at all times be detectible and quantitatively assessed. In biochemistry tracers have been in use since the beginning of the 20th cent. Using synthetic methods, Franz Knoop in 1904 made various derivatives of fatty acids, the degradation of which he studied by feeding the derivatives to dogs and by monitoring the appearance of unusual products in the dogs' urine. From these studies were obtained the first descriptions of the metabolic pathway for fatty acid catabolism. About these sorts of experiments, however, the argument could always be made that the derivatives were "unphysiological," that is, did not occur naturally and might be handled by the enzymes of the body differently than "physiological" compounds. This difficulty was overcome in 1935 when Rudolf Schoenheimer and David Rittenberg described the use of the isotope deuterium (identical to the hydrogen atom except that it contains an extra neutron) in following biochemical reactions. They argued persuasively that deuterium-labeled compounds (those having a deuterium atom substituted for a hydrogen) were essentially indistinguishable from nonlabeled compounds as far as metabolic processes were concerned but that the amount of deuterium in any given sample could be quantitatively determined by the properties of the water produced upon combustion of the sample. Although this was the first declaration of the general usefulness of the approach, George Hevesy in 1923 was the first investigator to use an isotope in metabolic studies; he explored lead transport in the bean plant using radioactive thorium. Radioactive isotopes are more easily detected than nonradioactive ones, such as deuterium; therefore, when the radioactive isotopes of various atoms commonly occurring in organic molecules became widely available after World War II, metabolic studies proliferated. Isotopes in common use today include carbon-14, iodine-131, nitrogen-15, oxygen-17, phosphorus-32, sulfur-35, tritium (hydrogen-3), iron-59, and sodium-24.

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"tracer." The Columbia Encyclopedia, 6th ed.. . Encyclopedia.com. 26 Jun. 2017 <http://www.encyclopedia.com>.

"tracer." The Columbia Encyclopedia, 6th ed.. . Encyclopedia.com. (June 26, 2017). http://www.encyclopedia.com/reference/encyclopedias-almanacs-transcripts-and-maps/tracer

"tracer." The Columbia Encyclopedia, 6th ed.. . Retrieved June 26, 2017 from Encyclopedia.com: http://www.encyclopedia.com/reference/encyclopedias-almanacs-transcripts-and-maps/tracer

tracer

trac·er / ˈtrāsər/ • n. a person or thing that traces something or by which something may be traced, in particular: ∎  a bullet or shell whose course is made visible in flight by a trail of flames or smoke, used to assist in aiming. ∎  a substance introduced into a biological organism or other system so that its subsequent distribution can be readily followed from its color, fluorescence, radioactivity, or other distinctive property. ∎  a device that transmits a signal and so can be located when attached to a moving vehicle or other object.

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"tracer." The Oxford Pocket Dictionary of Current English. . Encyclopedia.com. 26 Jun. 2017 <http://www.encyclopedia.com>.

"tracer." The Oxford Pocket Dictionary of Current English. . Encyclopedia.com. (June 26, 2017). http://www.encyclopedia.com/humanities/dictionaries-thesauruses-pictures-and-press-releases/tracer-0

"tracer." The Oxford Pocket Dictionary of Current English. . Retrieved June 26, 2017 from Encyclopedia.com: http://www.encyclopedia.com/humanities/dictionaries-thesauruses-pictures-and-press-releases/tracer-0

tracer

tracer A substance that is used to follow the passage of groundwater in places where it cannot be observed directly. Typical tracers include fluorescent dyes and salt. The presence of radioactive isotopes, e.g. tritium and carbon-14, may also be used as tracers in that they allow the age of groundwater to be determined. The presence of small amounts of other substances may also be used to make deductions about the origin and flow path of groundwaters.

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"tracer." A Dictionary of Earth Sciences. . Encyclopedia.com. 26 Jun. 2017 <http://www.encyclopedia.com>.

"tracer." A Dictionary of Earth Sciences. . Encyclopedia.com. (June 26, 2017). http://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/tracer

"tracer." A Dictionary of Earth Sciences. . Retrieved June 26, 2017 from Encyclopedia.com: http://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/tracer

tracer

tracer A substance that is used to follow the passage of groundwater in places where it cannot be observed directly. Typical tracers include fluorescent dyes and salt. The presence of radioactive isotopes (e.g. tritium and carbon-14) may also be used as tracers in that they allow the age of groundwater to be determined. The presence of small amounts of other substances may also be used to make deductions about the origin and flow path of groundwater.

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"tracer." A Dictionary of Ecology. . Encyclopedia.com. 26 Jun. 2017 <http://www.encyclopedia.com>.

"tracer." A Dictionary of Ecology. . Encyclopedia.com. (June 26, 2017). http://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/tracer-0

"tracer." A Dictionary of Ecology. . Retrieved June 26, 2017 from Encyclopedia.com: http://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/tracer-0

tracer

tracer (tray-ser) n. a substance that is introduced into the body and whose progress can subsequently be followed so that information is gained about metabolic processes. Radioactive tracers, which are substances labelled with radionuclides, are used for a variety of purposes in nuclear medicine.

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"tracer." A Dictionary of Nursing. . Encyclopedia.com. 26 Jun. 2017 <http://www.encyclopedia.com>.

"tracer." A Dictionary of Nursing. . Encyclopedia.com. (June 26, 2017). http://www.encyclopedia.com/caregiving/dictionaries-thesauruses-pictures-and-press-releases/tracer

"tracer." A Dictionary of Nursing. . Retrieved June 26, 2017 from Encyclopedia.com: http://www.encyclopedia.com/caregiving/dictionaries-thesauruses-pictures-and-press-releases/tracer

tracer

traceramasser, gasser, macassar, Makassar, Mombasa, Nasser •relaxer, waxer •salsa •cancer, romancer •piazza • necromancer • madrasa •Kinshasa, Lhasa, passer, Tarrasa, Vaasa •advancer, answer, chancer, dancer, enhancer, lancer, prancer •tazza •addresser, aggressor, assessor, compressor, confessor, contessa, depressor, digresser, dresser, guesser, intercessor, lesser, Odessa, oppressor, possessor, professor, represser, successor, transgressor, Vanessa •Alexa, flexor, vexer •Elsa, Kielce •censer, censor, dispenser, fencer, Mensa, sensor, Spenser •seltzer •Faenza, Henze •indexer • hairdresser • predecessor •microprocessor, processor •acer, bracer, chaser, debaser, embracer, facer, macer, mesa, pacer, placer, racer, spacer, tracer •Ailsa • steeplechaser •greaser, Lisa, Nerissa, piecer, Raisa, releaser •pizza

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"tracer." Oxford Dictionary of Rhymes. . Encyclopedia.com. 26 Jun. 2017 <http://www.encyclopedia.com>.

"tracer." Oxford Dictionary of Rhymes. . Encyclopedia.com. (June 26, 2017). http://www.encyclopedia.com/humanities/dictionaries-thesauruses-pictures-and-press-releases/tracer

"tracer." Oxford Dictionary of Rhymes. . Retrieved June 26, 2017 from Encyclopedia.com: http://www.encyclopedia.com/humanities/dictionaries-thesauruses-pictures-and-press-releases/tracer