Radioactive tracer such as a cell or tissue, or as a flow tracer to track fluid flow. Radioactive tracers are also used to determine the location of fractures created by hydraulic fracturing in natural gas production. Radioactive tracers form the basis of a variety of imaging systems, such as, PET scans, SPECT scans and technetium scans. Radiocarbon dating uses the naturally occurring carbon-14 isotope as an isotopic label. Isotopes of a chemical element differ only in the mass number. For example, the isotopes of hydrogen can be written as H, H and H, with the mass number at top left. When the
Sol–gel process formation of multiple phases of binary oxides as the result of differing hydrolysis and condensation rates, the entrapment of cations in a polymer network is an effective approach, generally termed the Pechini Process . In this process, a chelating agent is used, most often citric acid, to surround aqueous cations and sterically entrap them. Subsequently a polymer network is formed to immobilize the chelated cations in a gel or resin. This is most often achieved by poly-esterification using ethylene glycol. The resulting polymer is then combusted under oxidising conditions to remove organic content and yield a product oxide with homogeneously