tracer


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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

[′trā·sər]
(chemistry)
A foreign substance, usually radioactive, that is mixed with or attached to a given substance so the distribution or location of the latter can later be determined; used to trace chemical behavior of a natural element in an organism. Also known as tracer element.
(engineering)
A thread of contrasting color woven into the insulation of a wire for identification purposes.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.

tracer

Med any radioactive isotope introduced into the body to study metabolic processes, absorption, etc., by following its progress through the body with a gamma camera or other detector
Collins Discovery Encyclopedia, 1st edition © HarperCollins Publishers 2005
References in periodicals archive ?
Radio tracers are particularly prepared to perform a certain task.
The Tracer's chassis geometry is inclined towards stability rather than quick response and it's a well-suited balance with the long travel suspension.
As each tracer estimates the same soil ingestion behavior, high inter-tracer consistency in soil ingestion values would be expected if each tracer reliably estimated soil ingestion (Calabrese et al.
Tracer pebbles were filled with iron and coated with paraffin.
To determine the amount of tracer injected into the flow that can generate a minimum detectable concentration in the spectrofluorometer and conductivity meter, a simulation was first made using the Gaussian analytic solution of the diffusion-advection equation.
Various shots, WHO contact tracers walking through neighbourhood streets
The indoor tracer would be compared to the concentrations of the PFTs released outdoors.
The inexpensive device simply snaps onto a gas meter incoming service line, protecting the “locating” tracer wire from getting, cut, torn out, lost or damaged.
The current management is also working on processing the payments of those service providers/training institutes in 9 districts of Khyber Pakhtunkhwa where Tracer Study has been completed.
Dr Shangula said that the main purpose of the Tracer Study was to gain information on the current employment and economic status of the graduates and their assessment of the relevance and quality of their education within their work context.