Uses of Radioactivity

In the years since 1940, the elements with atomic numbers greater than 92, called the transuranium elements, have been synthesized. Many of these elements have very short half-lives, as shown in Table 19.4. As a result, only a few atoms of some have ever been formed. This, of course, makes the chemical characterization of these elements extremely difficult. 

Geiger counters are often called survey meters in the industry. 

A schematic representation of a Geiger-Muller counter. The high-energy radioactive particle enters the window and ionizes argon atoms along its path. The resulting ions and electrons produce a momentary current pulse, which is amplified and counted. 

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Brigham Young researcher Scott Woodward taking a bone sampie for carbon-14 dating at an archaeoiogicai site in Egypt. 

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The most widely used experimental method for determining surface excess quantities at the liquid-vapor interface makes use of radioactive tracers. The solute to be studied is labeled with a radioisotope that emits weak beta radiation, such as H, C, or One places a detector close to the surface of the solution and measures the intensity of beta radiation. Since the penetration range of such beta emitters is small (a ut 30 mg/cm for C, with most of the adsorption occurring in the first two-tenths of the range), the measured radioactivity corresponds to the surface region plus only a thin layer of solution (about 0.06 mm for C and even less for H). 

A difficulty in the physicochemical study of penetration is that the amount of soluble component present in the monolayer is not an easily accessible quantity. It may be measured directly, through the use of radioactive labeling (Section III-6) [263, 266], but the technique has so far been used only to a limited extent. 

Monna and co-workers studied the use of radioactive isotopes as a means of dating sediments collected from the bottom of lakes and estuaries. To verify this method they analyzed a 208po standard known to have an activity of 77.5 decays/min, obtaining the following results... 

Three common quantitative applications of radiochemical methods of analysis are considered in this section the direct analysis of radioactive isotopes by measuring their rate of disintegration, neutron activation, and the use of radioactive isotopes as tracers in isotope dilution. 

The use of radioactive tracers was pioneered by Georg von Hevesy, a Hungarian physical chemist, who received the Nobel Prize in 1943 for his work on radioactive indicators (1). Radioisotopes have become indispensable components of most medical and life science research strategies, and in addition the technology is the basis for numerous industries focused on the production and detection of radioactive tracers. Thousands of radioactive tracers have been synthesized and are commercially available. These are used worldwide in tens of thousands of research laboratories. 

The diffusion coefficients of cations in metal oxides are usually measured through the use of radioactive isotopes. Because of the friable nature of oxides it is exU emely difficult to use the sectioning technique employed for metal samples. The need for this can be avoided by the application of radioisotopes which emit radiation having a well established absorption law in matter. Isotopes which emit y radiation are very useful when the cation has a relatively high diffusion coefficient because of the long-range peneU ation of y rays. The absorption law is... 

Governs the keeping and use of radioactive substances and the storage and disposal of radioactive waste. 

Diffusion has often been measured in metals by the use of radioactive tracers. The resulting parameter, DT, is related to the self-diffusion coefficient by a correlation factor/that is dependent upon the details of the crystal structure and jump geometry. The relation between DT and the self-diffusion coefficient Dsclf is thus simply... 

Antithyroid drugp or thyroid antagonists are used to treat hyperthyroidism. In addition to the antithyroid drugs, hyperthyroidism may be treated by the administration of strong iodine solutions, use of radioactive iodine (131I), or by surgical removal of some or almost all of the tiiyroid gland (subtotal thyroidectomy). 

Limitations encountered in routine use include (a) the use of radioactive materials, (b) limited sensitivity in the presence of high protein concentrations, (c) long assay time of up to 5 days,... 

Air monitoring will be required, e.g., when volatiles are handled in quantity, where use of radioactive isotopes has led to unacceptable workplace contamination, when processing plutonium or other transuranic elements, when handling unsealed sources in hospitals in therapeutic amounts, and in the use of hot cells/reactors and critical facilities. Routine monitoring of skin, notably the hands, may be required. 

Equation does not contain the concentration of A, so the half-life of a first-order reaction is a constant that is independent of how much A is present. The decomposition reactions of radioactive isotopes provide excellent examples of first-order processes, as Example illustrates. We describe the use of radioactive isotopes and their half-lives to determine the age of an object in more detail in Chapter 22. 

Until the advent of modem physical methods for surface studies and computer control of experiments, our knowledge of electrode processes was derived mostly from electrochemical measurements (Chapter 12). By clever use of these measurements, together with electrocapillary studies, it was possible to derive considerable information on processes in the inner Helmholtz plane. Other important tools were the use of radioactive isotopes to study adsorption processes and the derivation of mechanisms for hydrogen evolution from isotope separation factors. Early on, extensive use was made of optical microscopy and X-ray diffraction (XRD) in the study of electrocrystallization of metals. In the past 30 years enormous progress has been made in the development and application of new physical methods for study of electrode processes at the molecular and atomic level. 

Despite the advantages that sand-based systems provide for estimating rhizodeposition, studies in soil are still required. These are far more technically demanding and are heavily biased toward the use of radioactive tracer methods. 

The use of radioactive isotopes in industry is covered by government legislation, see hse.gov.uk/pubns. 

If the excess of lanthanide is sufficiently great, overloading of the transport system occurs and colloidal aggregates of large size are formed by hydrolysis. The interstitial or intracavitary formation of immobilized lanthanide colloids labeled with relatively short-lived radioisotopes was the basis for the attempted use of radioactive lanthanides as internal sources of therapeutic radiation (Kyker, 1962a, 1962b). 

Pressman, D., and Keighley, G. (1948) The zone of activity of antibodies as determined by the use of radioactive tracers. The zone of activity of nephritoxic antikidney serum. /. Immunol 59, 141-146. 

In 1987, CL started to be applied in DNA hybridization assays as an alternative to the use of radioactive tags. These assays are based on the specificity of a binding process that of DNA strands for each other. An unknown DNA can be identified with the Southern blot method in which the strands of the analyte are separated and allowed to interact with labeled probe DNA strands on nitrocellulose filter paper. If the label on the probe is detected, the DNA can be identified and, in some cases, quantitated. Conventionally, radioactive tags were used be-... 

A prerequisite to pharmacokinetic/pharmacodynamic studies is the availability of a sufficiently selective and sensitive assay. The assay must be capable of detecting and accurately quantifying the therapeutic protein in the presence of a complex soup of contaminant molecules characteristic of tissue extracts/body fluids. As described in Chapter 7, specific proteins are usually detected and quantified either via immunoassay or bioassay. Additional analytical approaches occasionally used include liquid chromatography (e.g. HPLC) or the use of radioactively labelled protein. 

Diffusion is followed by tracking the movements of tracer species through the solid to obtain the tracer diffusion coefficient, written as D when the tracer is identical to one of the components of the crystal, and D% when an impurity or foreign atom A is the tracer. Earlier studies made extensive use of radioactive isotopes because the progress... 

The use of radioactive ionization sources in areas subject to explosion or fire is undesirable because of the potential for area contamination with radioactive material which could be disseminated in the event of an explosion or fire. With proper precautions, however, electrical ionizing systems can be safely and effectively utilized while processing electrostatically sensitive energetic materials. Ions are generated electrically by corona discharge... 

Although B12 can be assayed biologically in mice, chicks, and rats, especially with the use of radioactive cobalt, the microbiologic method of assay is preferred because it is economical and sensitive. One serious drawback of bacterial Bi2 assay procedures is the lack of specificity and sensitivity. The extreme sensitivity (1 X 10 12 g) and relative freedom of stimulation in blood, serum, and urine make protozoa the choice assay tools (B17, F3, H19). The most specific is O. malhamensis (B17, F3) Euglena is known to be stimulated by pseudo-B12 (F2). Serum and blood from normal subjects have a growth-promoting effect on Euglena (M12) above that seen with Ochromonas. The reason for such... 

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