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.

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.

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
References in periodicals archive ?
According to Tor Bjornstad, Chief Scientist at the Institute for Energy Technology in Kjeller, Norway before the use of nuclear tracers scientists relied on seismic mapping, which delivered less precise data.
Accordingly, on the basis of a decision by BISP Management Board, BISP has initiated a tracer study to evaluate the performance of training provider which includes verification of the institute, attendance of trainees and quality of training etc, to validate the trainings imparted to beneficiaries.
The PS and PP macromolecule tracers were injected directly to the extruder instead of the masterbatches and marked as PS-tracer and PP-tracer, respectively.
The tracer released indoors in the atrium redistributed to the North and South wings in a roughly 2:1 ratio, as shown in Figure 3a.
Having peace of mind that--when the construction crews backfill--the tracer wire will not be displaced to the opposite side of the trench, will easily allow you to record on your as-built maps that the tracer wire is four inches to the house side or four inches to the road side of the gas pipe being installed.
As a follow-on to FOPEN, the TRACER system can be tailored to specific missions by providing a variety of SAR images including strip maps and spotlight and circle images.
The key point here is that tracer concentration has meaning only with respect to the carrier species for which it functions as a tracer.
By collecting real-time data and providing actionable information at incredible speeds, Tracer XT integrates with existing Tracer controls to allow for faster decision making about management of data center functions, including critical systems.
The tracer gas method was used to investigate the exposure risk on commercial flights, and was found to be suitable for use as a substitute of microorganisms.
This implies that a small molecule tracer will do as a good job as a macromolecular tracer if it can be well dispersed in the polymer matrix.
After exposing chicks to a loud noise for 48 hours, they administered radioactive thymidine as a tracer that is incorporated into replicating DNA, permitting detection of dividing cells.
Taking a unique approach by providing the reader with a systematic and state of the art description of natural and artificial tracers, the book also covers key analytical techniques and applications, and modern tracer methods in the context of systematic hydrology.