{"thcode":2,"term":{"code":153,"name":"chemical analysis","parent":619,"scope":"Chemical techniques used to identify the composition of substances."},"uf":[{"name":"detection (chemical)","usewith":false},{"name":"geochemical surveys","usewith":false},{"name":"leaching (analytical method)","usewith":false},{"name":"mineralogical analysis","usewith":false},{"name":"nuclear magnetic resonance spectroscopy","usewith":false},{"name":"sediment geochemistry","usewith":{"code":1199,"name":"unconsolidated deposits","parent":1005,"scope":"Loosely bound sediments such as sand, gravel, and silt which tend to accumulate in low areas or valleys."}}],"bt":[{"code":619,"name":"laboratory methods","parent":734,"scope":"Techniques to analyze and test samples in a place equipped and designed for the work."},{"code":734,"name":"methods","parent":1,"scope":"Techniques, methods, procedures, or strategies for research, management, collection, or analysis of scientific information in USGS."},{"code":1,"name":"Categories","parent":null,"scope":"Thematic terms for categorizing information resources.  This thesaurus is intended to support finding and understanding scientific information."}],"nt":[{"code":276,"name":"DNA sequencing","parent":153,"scope":"Biochemical procedure to determine the order of nucleotides in genes."},{"code":69,"name":"atomic absorption analysis","parent":153,"scope":"Technique used to identify chemicals based on the measurement of the spectra produced by atoms and molecules with absorption of electromagnetic radiation."},{"code":1342,"name":"atomic emission spectroscopy","parent":153,"scope":"Chemical detection of element concentration by examining the intensity and wavelength of light emitted from the sample when gaseous sample is ionized and maintained in a plasma state."},{"code":158,"name":"chromatography","parent":153,"scope":"Analytical techniques used to separate or partition the components of a gaseous or liquid mixture by differences in absorption rates during flow around or over surface absorbents such as columns of silica, filter papers, or gels."},{"code":328,"name":"electrophoresis","parent":153,"scope":"Analytical technique to separate and identify components in a mixture using the differential migration of molecules based on their net charge through a paper or gel medium."},{"code":400,"name":"flow cytometry","parent":153,"scope":"Laboratory technique to determine the amount of DNA in cells tagged by fluorescent dye by measuring the intensity of fluorescence under a laser beam."},{"code":711,"name":"mass spectroscopy","parent":153,"scope":"Instrumental technique to separate and identify molecules.  Gaseous ions are formed, with or without fragmentation.  Their mass\/charge ratios and relative electrical abundance are then measured or the spectra are recorded."},{"code":783,"name":"neutron activation analysis","parent":153,"scope":"Sensitive laboratory technique for both qualitative and quantitative analysis of elements in samples.  Target nuclei are bombarded with neutron beams to start nuclear reactions which emit characteristic gamma ray radiations."},{"code":872,"name":"particle-beam spectroscopy","parent":153,"scope":"Analytical technique using a concentrated beam of charged subatomic particles."},{"code":919,"name":"polymerase chain reaction","parent":153,"scope":"Biochemical technique that uses enzymes to replicate new nucleotides of DNA from DNA triphosphates using DNA as a template."},{"code":1337,"name":"x-ray diffraction","parent":153,"scope":"Study of crystals which uses short wave electromagnetic radiations (x-rays). The xrays, scattered by the crystal atoms, show a characteristic interference pattern that is dependent upon the structure of the crystal."},{"code":2001,"name":"x-ray fluorescence","parent":153,"scope":"Estimation of chemical element concentration by measuring the energy level of secondary X-rays generated when the sample is bombarded with high-energy X-rays or gamma rays."}],"rt":[{"code":89,"name":"biochemistry","parent":650,"scope":"Study of chemical processes that occur within or are mediated by living organisms."},{"code":2299,"name":"biomarkers","parent":317,"scope":"Biochemical, physiological, morphological, or histopathological characteristics of organisms that signify exposure to contaminants.  Also used for biogeochemical measurements of rocks to detect biological origin."},{"code":437,"name":"geochemistry","parent":291,"scope":"Study of the distribution of chemical elements and natural compounds on the earth and in the atmosphere and the chemical processes that affect the earth."}]}