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Oxygen-18
Oxygen-18 (, Ω) is a natural, stable isotope of oxygen and one of the environmental isotopes. is an important precursor for the production of fluorodeoxyglucose (FDG) used in positron emission tomography (PET). Generally, in the radiopharmaceutical industry, enriched water () is bombarded with hydrogen ions in either a cyclotron or linear accelerator, producing fluorine-18. This is then synthesized into FDG and injected into a patient. It can also be used to make an extremely heavy version of water when combined with tritium (hydrogen-3): or . This compound has a density almost 30% greater than that of natural water. The accurate measurements of rely on proper procedures of analysis, sample preparation and storage. Paleoclimatology In ice cores, mainly Arctic and Antarctic, the ratio of to (known as δ) can be used to determine the temperature of precipitation through time. Assuming that atmospheric circulation and elevation has not changed significantly over the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Oxygen
Oxygen is a chemical element; it has chemical symbol, symbol O and atomic number 8. It is a member of the chalcogen group (periodic table), group in the periodic table, a highly reactivity (chemistry), reactive nonmetal (chemistry), nonmetal, and a potent oxidizing agent that readily forms oxides with most elements as well as with other chemical compound, compounds. Oxygen is abundance of elements in Earth's crust, the most abundant element in Earth's crust, making up almost half of the Earth's crust in the form of various oxides such as water, carbon dioxide, iron oxides and silicates.Atkins, P.; Jones, L.; Laverman, L. (2016).''Chemical Principles'', 7th edition. Freeman. It is abundance of chemical elements, the third-most abundant element in the universe after hydrogen and helium. At standard temperature and pressure, two oxygen atoms will chemical bond, bind covalent bond, covalently to form dioxygen, a colorless and odorless diatomic gas with the chemical formula ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Environmental Isotopes
The environmental isotopes are a subset of isotopes, both Stable isotope ratio, stable and Radioactive isotopes, radioactive, which are the object of isotope geochemistry. They are primarily used as tracers to see how things move around within the ocean-atmosphere system, within terrestrial biomes, within the Earth's surface, and between these broad domains. Isotope geochemistry Chemical elements are defined by their number of protons, but the atomic mass, mass of the atom is determined by the number of protons and neutrons in the nucleus. Isotopes are atoms that are of a specific element, but have different numbers of neutrons and thus different mass numbers. The ratio between isotopes of an element varies slightly in the world, so in order to study isotopic ratio changes across the world, changes in isotope ratios are defined as deviations from a standard, multiplied by 1000. This unit is a "per mil". As a convention, the ratio is of the heavier isotope to the lower isotope. \d ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fluorodeoxyglucose
[]Fluorodeoxyglucose (International Nonproprietary Name, INN), or fluorodeoxyglucose F 18 (United States Adopted Name, USAN and United States Pharmacopeia, USP), also commonly called fluorodeoxyglucose and abbreviated []FDG, 2-[]FDG or FDG, is a radiopharmaceutical, specifically a radiotracer, used in the medical imaging modality positron emission tomography (PET). Chemically, it is 2-deoxy-2-[]fluoro-D-glucose, a glucose analog (chemistry), analog, with the positron-emitting radionuclide fluorine-18 substituted for the normal hydroxyl group at the C-2 position in the glucose molecule. The uptake of []FDG by tissues is a marker for the tissue Glucose uptake, uptake of glucose, which in turn is closely correlated with certain types of tissue metabolism. After []FDG is injected into a patient, a PET scanner can form two-dimensional or three-dimensional images of the distribution of []FDG within the body. Since its development in 1976, []FDG had a profound influence on r ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fluorine-18
Fluorine-18 (18F, also called radiofluorine) is a fluorine radioisotope which is an important source of positrons. It has a mass of 18.0009380(6) u and its half-life is 109.771(20) minutes. It decays by positron emission 96.7% of the time and electron capture 3.3% of the time. Both modes of decay yield stable oxygen-18. Natural occurrence is a natural trace radioisotope produced by cosmic ray spallation of atmospheric argon as well as by reaction of protons with natural oxygen: 18O + p → 18F + n.sup>18Oater with high energy protons (typically ~18 MeV). The fluorine produced is in the form of a water solution of 18F">sup>18F luoride, which is then used in a rapid chemical synthesis of various radio pharmaceuticals. The organic oxygen-18 pharmaceutical molecule is not made before the production of the radiopharmaceutical, as high energy protons destroy such molecules ( radiolysis). Radiopharmaceuticals using fluorine must therefore be synthesized after the fluorine-18 has ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Δ18O
In geochemistry, paleoclimatology and paleoceanography ''δ''18O or delta-O-18 is a measure of the deviation in ratio of stable isotopes oxygen-18 (18O) and oxygen-16 (16O). It is commonly used as a measure of the temperature of precipitation, as a measure of groundwater/mineral interactions, and as an indicator of processes that show isotopic fractionation, like methanogenesis. In paleosciences, 18O:16O data from corals, foraminifera and ice cores are used as a proxy for temperature. It is defined as the deviation in "per mil" (‰, parts per thousand) between a sample and a standard: :\delta \ce = \left( \frac - 1 \right) \times 1000 ‰ where the standard has a known isotopic composition, such as Vienna Standard Mean Ocean Water (VSMOW). The fractionation can arise from kinetic, equilibrium, or mass-independent fractionation. Mechanism Foraminifera shells are composed of calcium carbonate (CaCO3) and are found in many common geological environments. The rat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Heavy Water
Heavy water (deuterium oxide, , ) is a form of water (molecule), water in which hydrogen atoms are all deuterium ( or D, also known as ''heavy hydrogen'') rather than the common hydrogen-1 isotope (, also called ''protium'') that makes up most of the hydrogen in normal water. The presence of the heavier isotope gives the water different nuclear properties, and the increase in mass gives it slightly different physical and chemical properties when compared to normal water. Deuterium is a heavy Isotopes of hydrogen, hydrogen isotope. Heavy water contains deuterium atoms and is used in nuclear reactors. Semiheavy water (HDO) is more common than pure heavy water, while heavy-oxygen water is denser but lacks unique properties. Tritiated water is radioactive due to tritium content. Heavy water has different physical properties from regular water, such as being 10.6% denser and having a higher melting point. Heavy water is less Dissociation (chemistry), dissociated at a given temperatur ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Harold Urey
Harold Clayton Urey ( ; April 29, 1893 – January 5, 1981) was an American physical chemist whose pioneering work on isotopes earned him the Nobel Prize in Chemistry in 1934 for the discovery of deuterium. He played a significant role in the development of the Nuclear weapon, atom bomb, as well as contributing to theories on the Miller–Urey experiment, development of organic life from non-living matter. Born in Walkerton, Indiana, Urey studied thermodynamics under Gilbert N. Lewis at the University of California, Berkeley. After he received his PhD in 1923, he was awarded a fellowship by the American-Scandinavian Foundation to study at the Niels Bohr Institute in Copenhagen. He was a research associate at Johns Hopkins University before becoming an associate professor of chemistry at Columbia University. In 1931, he began work with the separation of isotopes that resulted in the discovery of deuterium. During World War II, Urey turned his knowledge of isotope separation to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Radiopharmaceutical
Radiopharmaceuticals, or medicinal radiocompounds, are a group of pharmaceutical drugs containing radioactive isotopes. Radiopharmaceuticals can be used as diagnostic and therapeutic agents. Radiopharmaceuticals emit radiation themselves, which is different from contrast media which absorb or alter external electromagnetism or ultrasound. Radiopharmacology is the branch of pharmacology that specializes in these agents. The main group of these compounds are the radiotracers used to diagnose dysfunction in body tissues. While not all medical isotopes are radioactive, radiopharmaceuticals are the oldest and remain the most common of such drugs. Drug nomenclature As with other pharmaceutical drugs, there is standardization of the drug nomenclature for radiopharmaceuticals, although various standards coexist. The International Nonproprietary Names (INNs), United States Pharmacopeia (USP) names, and IUPAC names for these agents are usually similar other than trivial style diffe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tritium
Tritium () or hydrogen-3 (symbol T or H) is a rare and radioactive isotope of hydrogen with a half-life of ~12.33 years. The tritium nucleus (t, sometimes called a ''triton'') contains one proton and two neutrons, whereas the nucleus of the common isotope hydrogen-1 (''protium'') contains one proton and no neutrons, and that of non-radioactive hydrogen-2 ('' deuterium'') contains one proton and one neutron. Tritium is the heaviest particle-bound isotope of hydrogen. It is one of the few nuclides with a distinct name. The use of the name hydrogen-3, though more systematic, is much less common. Naturally occurring tritium is extremely rare on Earth. The atmosphere has only trace amounts, formed by the interaction of its gases with cosmic rays. It can be produced artificially by irradiation of lithium or lithium-bearing ceramic pebbles in a nuclear reactor and is a low-abundance byproduct in normal operations of nuclear reactors. Tritium is used as the energy source in radio ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Scallop
Scallop () is a common name that encompasses various species of marine bivalve molluscs in the taxonomic family Pectinidae, the scallops. However, the common name "scallop" is also sometimes applied to species in other closely related families within the superfamily Pectinoidea, which also includes the thorny oysters. Scallops are a cosmopolitan family of bivalves found in all of the world's oceans, although never in fresh water. They are one of the very few groups of bivalves to be primarily "free-living", with many species capable of rapidly swimming short distances and even migrating some distance across the ocean floor. A small minority of scallop species live cemented to rocky substrates as adults, while others attach themselves to stationary or rooted objects such as seagrass at some point in their lives by means of a filament they secrete called a byssal thread. The majority of species, however, live recumbent on sandy substrates, and when they sense the presence ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sensitive High-resolution Ion Microprobe
The sensitive high-resolution ion microprobe (also sensitive high mass-resolution ion microprobe or SHRIMP) is a large-diameter, double-focusing secondary ion mass spectrometer (SIMS) sector instrument that was produced by Australian Scientific Instruments in Canberra, Australia and now has been taken over by Chinese company Dunyi Technology Development Co. (DTDC) in Beijing. Similar to the IMS 1270-1280-1300 large-geometry ion microprobes produced by CAMECA, Gennevilliers, France and like other SIMS instruments, the SHRIMP microprobe bombards a sample under vacuum with a beam of primary ions that sputters secondary ions that are focused, filtered, and measured according to their energy and mass. The SHRIMP is primarily used for geological and geochemical applications. It can measure the isotopic and elemental abundances in minerals at a 10 to 30 μm-diameter scale and with a depth resolution of 1–5 μm. Thus, SIMS method is well-suited for the analysis of complex mineral ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
