Isotopes: Atomic species differing in mass number but having the same atomic number. (Grant & Hackh's Chemical Dictionary, 5th ed)Isotope Labeling: Techniques for labeling a substance with a stable or radioactive isotope. It is not used for articles involving labeled substances unless the methods of labeling are substantively discussed. Tracers that may be labeled include chemical substances, cells, or microorganisms.Nitrogen Isotopes: Stable nitrogen atoms that have the same atomic number as the element nitrogen, but differ in atomic weight. N-15 is a stable nitrogen isotope.Oxygen Isotopes: Stable oxygen atoms that have the same atomic number as the element oxygen, but differ in atomic weight. O-17 and 18 are stable oxygen isotopes.Carbon Isotopes: Stable carbon atoms that have the same atomic number as the element carbon, but differ in atomic weight. C-13 is a stable carbon isotope.Zinc Isotopes: Stable zinc atoms that have the same atomic number as the element zinc, but differ in atomic weight. Zn-66-68, and 70 are stable zinc isotopes.Killer Cells, Natural: Bone marrow-derived lymphocytes that possess cytotoxic properties, classically directed against transformed and virus-infected cells. Unlike T CELLS; and B CELLS; NK CELLS are not antigen specific. The cytotoxicity of natural killer cells is determined by the collective signaling of an array of inhibitory and stimulatory CELL SURFACE RECEPTORS. A subset of T-LYMPHOCYTES referred to as NATURAL KILLER T CELLS shares some of the properties of this cell type.Sulfur Isotopes: Stable sulfur atoms that have the same atomic number as the element sulfur, but differ in atomic weight. S-33, 34, and 36 are stable sulfur isotopes.Deuterium: Deuterium. The stable isotope of hydrogen. It has one neutron and one proton in the nucleus.Iron Isotopes: Stable iron atoms that have the same atomic number as the element iron, but differ in atomic weight. Fe-54, 57, and 58 are stable iron isotopes.Strontium Isotopes: Stable strontium atoms that have the same atomic number as the element strontium, but differ in the atomic weight. Sr-84, 86, 87, and 88 are the stable strontium isotopes.Radioisotope Dilution Technique: Method for assessing flow through a system by injection of a known quantity of radionuclide into the system and monitoring its concentration over time at a specific point in the system. (From Dorland, 28th ed)Mass Spectrometry: An analytical method used in determining the identity of a chemical based on its mass using mass analyzers/mass spectrometers.Indicator Dilution Techniques: Methods for assessing flow through a system by injection of a known quantity of an indicator, such as a dye, radionuclide, or chilled liquid, into the system and monitoring its concentration over time at a specific point in the system. (From Dorland, 28th ed)Kinetics: The rate dynamics in chemical or physical systems.Biological Products: Complex pharmaceutical substances, preparations, or matter derived from organisms usually obtained by biological methods or assay.Gas Chromatography-Mass Spectrometry: A microanalytical technique combining mass spectrometry and gas chromatography for the qualitative as well as quantitative determinations of compounds.Mercury Isotopes: Stable mercury atoms that have the same atomic number as the element mercury, but differ in atomic weight. Hg-196, 198-201, and 204 are stable mercury isotopes.Evolution, Planetary: Creation and development of bodies within solar systems, includes study of early planetary geology.Deuterium Oxide: The isotopic compound of hydrogen of mass 2 (deuterium) with oxygen. (From Grant & Hackh's Chemical Dictionary, 5th ed) It is used to study mechanisms and rates of chemical or nuclear reactions, as well as biological processes.Molecular Sequence Data: Descriptions of specific amino acid, carbohydrate, or nucleotide sequences which have appeared in the published literature and/or are deposited in and maintained by databanks such as GENBANK, European Molecular Biology Laboratory (EMBL), National Biomedical Research Foundation (NBRF), or other sequence repositories.Hydrogen: The first chemical element in the periodic table. It has the atomic symbol H, atomic number 1, and atomic weight [1.00784; 1.00811]. It exists, under normal conditions, as a colorless, odorless, tasteless, diatomic gas. Hydrogen ions are PROTONS. Besides the common H1 isotope, hydrogen exists as the stable isotope DEUTERIUM and the unstable, radioactive isotope TRITIUM.Ecosystem: A functional system which includes the organisms of a natural community together with their environment. (McGraw Hill Dictionary of Scientific and Technical Terms, 4th ed)Radioisotopes: Isotopes that exhibit radioactivity and undergo radioactive decay. (From Grant & Hackh's Chemical Dictionary, 5th ed & McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)Geologic Sediments: A mass of organic or inorganic solid fragmented material, or the solid fragment itself, that comes from the weathering of rock and is carried by, suspended in, or dropped by air, water, or ice. It refers also to a mass that is accumulated by any other natural agent and that forms in layers on the earth's surface, such as sand, gravel, silt, mud, fill, or loess. (McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed, p1689)Chromatography, Liquid: Chromatographic techniques in which the mobile phase is a liquid.Carbon: A nonmetallic element with atomic symbol C, atomic number 6, and atomic weight [12.0096; 12.0116]. It may occur as several different allotropes including DIAMOND; CHARCOAL; and GRAPHITE; and as SOOT from incompletely burned fuel.Carbon Radioisotopes: Unstable isotopes of carbon that decay or disintegrate emitting radiation. C atoms with atomic weights 10, 11, and 14-16 are radioactive carbon isotopes.Food Chain: The sequence of transfers of matter and energy from organism to organism in the form of FOOD. Food chains intertwine locally into a food web because most organisms consume more than one type of animal or plant. PLANTS, which convert SOLAR ENERGY to food by PHOTOSYNTHESIS, are the primary food source. In a predator chain, a plant-eating animal is eaten by a larger animal. In a parasite chain, a smaller organism consumes part of a larger host and may itself be parasitized by smaller organisms. In a saprophytic chain, microorganisms live on dead organic matter.Molecular Structure: The location of the atoms, groups or ions relative to one another in a molecule, as well as the number, type and location of covalent bonds.Meteoroids: Any solid objects moving in interplanetary space that are smaller than a planet or asteroid but larger than a molecule. Meteorites are any meteoroid that has fallen to a planetary surface. (From McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)Natural Language Processing: Computer processing of a language with rules that reflect and describe current usage rather than prescribed usage.Catalysis: The facilitation of a chemical reaction by material (catalyst) that is not consumed by the reaction.Oxidation-Reduction: A chemical reaction in which an electron is transferred from one molecule to another. The electron-donating molecule is the reducing agent or reductant; the electron-accepting molecule is the oxidizing agent or oxidant. Reducing and oxidizing agents function as conjugate reductant-oxidant pairs or redox pairs (Lehninger, Principles of Biochemistry, 1982, p471).Geological Phenomena: The inanimate matter of Earth, the structures and properties of this matter, and the processes that affect it.Zinc Radioisotopes: Unstable isotopes of zinc that decay or disintegrate emitting radiation. Zn atoms with atomic weights 60-63, 65, 69, 71, and 72 are radioactive zinc isotopes.Natural Killer T-Cells: A specialized subset of T-LYMPHOCYTES that exhibit features of INNATE IMMUNITY similar to that of NATURAL KILLER CELLS. They are reactive to glycolipids presented in the context of the major histocompatibility complex (MHC) class I-like molecule, CD1D ANTIGEN.Conservation of Natural Resources: The protection, preservation, restoration, and rational use of all resources in the total environment.Time Factors: Elements of limited time intervals, contributing to particular results or situations.Tandem Mass Spectrometry: A mass spectrometry technique using two (MS/MS) or more mass analyzers. With two in tandem, the precursor ions are mass-selected by a first mass analyzer, and focused into a collision region where they are then fragmented into product ions which are then characterized by a second mass analyzer. A variety of techniques are used to separate the compounds, ionize them, and introduce them to the first mass analyzer. For example, for in GC-MS/MS, GAS CHROMATOGRAPHY-MASS SPECTROMETRY is involved in separating relatively small compounds by GAS CHROMATOGRAPHY prior to injecting them into an ionization chamber for the mass selection.Models, Biological: Theoretical representations that simulate the behavior or activity of biological processes or diseases. For disease models in living animals, DISEASE MODELS, ANIMAL is available. Biological models include the use of mathematical equations, computers, and other electronic equipment.Proteomics: The systematic study of the complete complement of proteins (PROTEOME) of organisms.Volcanic Eruptions: The ash, dust, gases, and lava released by volcanic explosion. The gases are volatile matter composed principally of about 90% water vapor, and carbon dioxide, sulfur dioxide, hydrogen, carbon monoxide, and nitrogen. The ash or dust is pyroclastic ejecta and lava is molten extrusive material consisting mainly of magnesium silicate. (From McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)Models, Chemical: Theoretical representations that simulate the behavior or activity of chemical processes or phenomena; includes the use of mathematical equations, computers, and other electronic equipment.TritiumRadiometric Dating: Techniques used to determine the age of materials, based on the content and half-lives of the RADIOACTIVE ISOTOPES they contain.Atmosphere: The gaseous envelope surrounding a planet or similar body. (From Random House Unabridged Dictionary, 2d ed)Water: A clear, odorless, tasteless liquid that is essential for most animal and plant life and is an excellent solvent for many substances. The chemical formula is hydrogen oxide (H2O). (McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)Geology: The science of the earth and other celestial bodies and their history as recorded in the rocks. It includes the study of geologic processes of an area such as rock formations, weathering and erosion, and sedimentation. (From McGraw-Hill Dictionary of Scientific and Technical Terms, 6th ed)Intestinal Absorption: Uptake of substances through the lining of the INTESTINES.Oceans and Seas: A great expanse of continuous bodies of salt water which together cover more than 70 percent of the earth's surface. Seas may be partially or entirely enclosed by land, and are smaller than the five oceans (Atlantic, Pacific, Indian, Arctic, and Antarctic).Amino Acid Sequence: The order of amino acids as they occur in a polypeptide chain. This is referred to as the primary structure of proteins. It is of fundamental importance in determining PROTEIN CONFORMATION.Nitrogen: An element with the atomic symbol N, atomic number 7, and atomic weight [14.00643; 14.00728]. Nitrogen exists as a diatomic gas and makes up about 78% of the earth's atmosphere by volume. It is a constituent of proteins and nucleic acids and found in all living cells.Magnetic Resonance Spectroscopy: Spectroscopic method of measuring the magnetic moment of elementary particles such as atomic nuclei, protons or electrons. It is employed in clinical applications such as NMR Tomography (MAGNETIC RESONANCE IMAGING).Chemical Fractionation: Separation of a mixture in successive stages, each stage removing from the mixture some proportion of one of the substances, for example by differential solubility in water-solvent mixtures. (McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)History, Ancient: The period of history before 500 of the common era.Cytotoxicity, Immunologic: The phenomenon of target cell destruction by immunologically active effector cells. It may be brought about directly by sensitized T-lymphocytes or by lymphoid or myeloid "killer" cells, or it may be mediated by cytotoxic antibody, cytotoxic factor released by lymphoid cells, or complement.Natural History: A former branch of knowledge embracing the study, description, and classification of natural objects (as animals, plants, and minerals) and thus including the modern sciences of zoology, botany, and mineralogy insofar as they existed at that time. In the 17th, 18th, and 19th centuries it was much used for the generalized pursuit of certain areas of science. (Webster, 3d ed; from Dr. James H. Cassedy, NLM History of Medicine Division)Hydrogen-Ion Concentration: The normality of a solution with respect to HYDROGEN ions; H+. It is related to acidity measurements in most cases by pH = log 1/2[1/(H+)], where (H+) is the hydrogen ion concentration in gram equivalents per liter of solution. (McGraw-Hill Dictionary of Scientific and Technical Terms, 6th ed)Selection, Genetic: Differential and non-random reproduction of different genotypes, operating to alter the gene frequencies within a population.Natural Cytotoxicity Triggering Receptor 1: A 46-kD stimulatory receptor found on resting and activated NATURAL KILLER CELLS. It has specificity for VIRAL HEMAGGLUTININS that are expressed on infected cells.Stereoisomerism: The phenomenon whereby compounds whose molecules have the same number and kind of atoms and the same atomic arrangement, but differ in their spatial relationships. (From McGraw-Hill Dictionary of Scientific and Technical Terms, 5th ed)Genetic Variation: Genotypic differences observed among individuals in a population.Geography: The science dealing with the earth and its life, especially the description of land, sea, and air and the distribution of plant and animal life, including humanity and human industries with reference to the mutual relations of these elements. (From Webster, 3d ed)Phylogeny: The relationships of groups of organisms as reflected by their genetic makeup.Amino Acids: Organic compounds that generally contain an amino (-NH2) and a carboxyl (-COOH) group. Twenty alpha-amino acids are the subunits which are polymerized to form proteins.Methane: The simplest saturated hydrocarbon. It is a colorless, flammable gas, slightly soluble in water. It is one of the chief constituents of natural gas and is formed in the decomposition of organic matter. (Grant & Hackh's Chemical Dictionary, 5th ed)Mummies: Bodies preserved either by the ancient Egyptian technique or due to chance under favorable climatic conditions.Animal Migration: Periodic movements of animals in response to seasonal changes or reproductive instinct. Hormonal changes are the trigger in at least some animals. Most migrations are made for reasons of climatic change, feeding, or breeding.Carbon Dioxide: A colorless, odorless gas that can be formed by the body and is necessary for the respiration cycle of plants and animals.Paleontology: The study of early forms of life through fossil remains.Radioactive Tracers: Radioactive substances added in minute amounts to the reacting elements or compounds in a chemical process and traced through the process by appropriate detection methods, e.g., Geiger counter. Compounds containing tracers are often said to be tagged or labeled. (Hawley's Condensed Chemical Dictionary, 12th ed)Ecology: The branch of science concerned with the interrelationship of organisms and their ENVIRONMENT, especially as manifested by natural cycles and rhythms, community development and structure, interactions between different kinds of organisms, geographic distributions, and population alterations. (Webster's, 3d ed)Carbon-Carbon Lyases: Enzymes that catalyze the cleavage of a carbon-carbon bond by means other than hydrolysis or oxidation. This subclass contains the DECARBOXYLASES, the ALDEHYDE-LYASES, and the OXO-ACID-LYASES. EC 4.1.Absorption: The physical or physiological processes by which substances, tissue, cells, etc. take up or take in other substances or energy.Species Specificity: The restriction of a characteristic behavior, anatomical structure or physical system, such as immune response; metabolic response, or gene or gene variant to the members of one species. It refers to that property which differentiates one species from another but it is also used for phylogenetic levels higher or lower than the species.Substrate Specificity: A characteristic feature of enzyme activity in relation to the kind of substrate on which the enzyme or catalytic molecule reacts.Chromatography, High Pressure Liquid: Liquid chromatographic techniques which feature high inlet pressures, high sensitivity, and high speed.Soil: The unconsolidated mineral or organic matter on the surface of the earth that serves as a natural medium for the growth of land plants.Escherichia coli: A species of gram-negative, facultatively anaerobic, rod-shaped bacteria (GRAM-NEGATIVE FACULTATIVELY ANAEROBIC RODS) commonly found in the lower part of the intestine of warm-blooded animals. It is usually nonpathogenic, but some strains are known to produce DIARRHEA and pyogenic infections. Pathogenic strains (virotypes) are classified by their specific pathogenic mechanisms such as toxins (ENTEROTOXIGENIC ESCHERICHIA COLI), etc.Fresh Water: Water containing no significant amounts of salts, such as water from RIVERS and LAKES.Diet: Regular course of eating and drinking adopted by a person or animal.Biological Evolution: The process of cumulative change over successive generations through which organisms acquire their distinguishing morphological and physiological characteristics.Fossils: Remains, impressions, or traces of animals or plants of past geological times which have been preserved in the earth's crust.Temperature: The property of objects that determines the direction of heat flow when they are placed in direct thermal contact. The temperature is the energy of microscopic motions (vibrational and translational) of the particles of atoms.Bacteria: One of the three domains of life (the others being Eukarya and ARCHAEA), also called Eubacteria. They are unicellular prokaryotic microorganisms which generally possess rigid cell walls, multiply by cell division, and exhibit three principal forms: round or coccal, rodlike or bacillary, and spiral or spirochetal. Bacteria can be classified by their response to OXYGEN: aerobic, anaerobic, or facultatively anaerobic; by the mode by which they obtain their energy: chemotrophy (via chemical reaction) or PHOTOTROPHY (via light reaction); for chemotrophs by their source of chemical energy: CHEMOLITHOTROPHY (from inorganic compounds) or chemoorganotrophy (from organic compounds); and by their source for CARBON; NITROGEN; etc.; HETEROTROPHY (from organic sources) or AUTOTROPHY (from CARBON DIOXIDE). They can also be classified by whether or not they stain (based on the structure of their CELL WALLS) with CRYSTAL VIOLET dye: gram-negative or gram-positive.Base Sequence: The sequence of PURINES and PYRIMIDINES in nucleic acids and polynucleotides. It is also called nucleotide sequence.Proteome: The protein complement of an organism coded for by its genome.Spectrometry, Mass, Electrospray Ionization: A mass spectrometry technique used for analysis of nonvolatile compounds such as proteins and macromolecules. The technique involves preparing electrically charged droplets from analyte molecules dissolved in solvent. The electrically charged droplets enter a vacuum chamber where the solvent is evaporated. Evaporation of solvent reduces the droplet size, thereby increasing the coulombic repulsion within the droplet. As the charged droplets get smaller, the excess charge within them causes them to disintegrate and release analyte molecules. The volatilized analyte molecules are then analyzed by mass spectrometry.Models, Molecular: Models used experimentally or theoretically to study molecular shape, electronic properties, or interactions; includes analogous molecules, computer-generated graphics, and mechanical structures.Receptors, Natural Killer Cell: Receptors that are specifically found on the surface of NATURAL KILLER CELLS. They play an important role in regulating the cellular component of INNATE IMMUNITY.Plant Leaves: Expanded structures, usually green, of vascular plants, characteristically consisting of a bladelike expansion attached to a stem, and functioning as the principal organ of photosynthesis and transpiration. (American Heritage Dictionary, 2d ed)Archaeology: The scientific study of past societies through artifacts, fossils, etc.Liver: A large lobed glandular organ in the abdomen of vertebrates that is responsible for detoxification, metabolism, synthesis and storage of various substances.Feces: Excrement from the INTESTINES, containing unabsorbed solids, waste products, secretions, and BACTERIA of the DIGESTIVE SYSTEM.Solar System: The group of celestial bodies, including the EARTH, orbiting around and gravitationally bound by the sun. It includes eight planets, one minor planet, and 34 natural satellites, more than 1,000 observed comets, and thousands of lesser bodies known as MINOR PLANETS (asteroids) and METEOROIDS. (From Academic American Encyclopedia, 1983)Protons: Stable elementary particles having the smallest known positive charge, found in the nuclei of all elements. The proton mass is less than that of a neutron. A proton is the nucleus of the light hydrogen atom, i.e., the hydrogen ion.Population Dynamics: The pattern of any process, or the interrelationship of phenomena, which affects growth or change within a population.Environment: The external elements and conditions which surround, influence, and affect the life and development of an organism or population.Biological Availability: The extent to which the active ingredient of a drug dosage form becomes available at the site of drug action or in a biological medium believed to reflect accessibility to a site of action.Sequence Analysis, DNA: A multistage process that includes cloning, physical mapping, subcloning, determination of the DNA SEQUENCE, and information analysis.Trees: Woody, usually tall, perennial higher plants (Angiosperms, Gymnosperms, and some Pterophyta) having usually a main stem and numerous branches.Solvents: Liquids that dissolve other substances (solutes), generally solids, without any change in chemical composition, as, water containing sugar. (Grant & Hackh's Chemical Dictionary, 5th ed)Seawater: The salinated water of OCEANS AND SEAS that provides habitat for marine organisms.Nature: The system of all phenomena in space and time; the totality of physical reality. It is both a scientific and philosophic concept appearing in all historic eras. (Webster 2d; Dr. James H. Cassedy, NLM History of Medicine Division)Plants: Multicellular, eukaryotic life forms of kingdom Plantae (sensu lato), comprising the VIRIDIPLANTAE; RHODOPHYTA; and GLAUCOPHYTA; all of which acquired chloroplasts by direct endosymbiosis of CYANOBACTERIA. They are characterized by a mainly photosynthetic mode of nutrition; essentially unlimited growth at localized regions of cell divisions (MERISTEMS); cellulose within cells providing rigidity; the absence of organs of locomotion; absence of nervous and sensory systems; and an alternation of haploid and diploid generations.Mathematics: The deductive study of shape, quantity, and dependence. (From McGraw-Hill Dictionary of Scientific and Technical Terms, 6th ed)Reproducibility of Results: The statistical reproducibility of measurements (often in a clinical context), including the testing of instrumentation or techniques to obtain reproducible results. The concept includes reproducibility of physiological measurements, which may be used to develop rules to assess probability or prognosis, or response to a stimulus; reproducibility of occurrence of a condition; and reproducibility of experimental results.Peptides: Members of the class of compounds composed of AMINO ACIDS joined together by peptide bonds between adjacent amino acids into linear, branched or cyclical structures. OLIGOPEPTIDES are composed of approximately 2-12 amino acids. Polypeptides are composed of approximately 13 or more amino acids. PROTEINS are linear polypeptides that are normally synthesized on RIBOSOMES.Sulfides: Chemical groups containing the covalent sulfur bonds -S-. The sulfur atom can be bound to inorganic or organic moieties.Ammonium Compounds: Inorganic compounds that include a positively charged tetrahedral nitrogen (ammonium ion) as part of their structure. This class of compounds includes a broad variety of simple ammonium salts and derivatives.Climate: The longterm manifestations of WEATHER. (McGraw-Hill Dictionary of Scientific and Technical Terms, 6th ed)Reference Standards: A basis of value established for the measure of quantity, weight, extent or quality, e.g. weight standards, standard solutions, methods, techniques, and procedures used in diagnosis and therapy.Forensic Sciences: Disciplines that apply sciences to law. Forensic sciences include a wide range of disciplines, such as FORENSIC TOXICOLOGY; FORENSIC ANTHROPOLOGY; FORENSIC MEDICINE; FORENSIC DENTISTRY; and others.Hair: A filament-like structure consisting of a shaft which projects to the surface of the SKIN from a root which is softer than the shaft and lodges in the cavity of a HAIR FOLLICLE. It is found on most surfaces of the body.Gas, Natural: A combustible, gaseous mixture of low-molecular weight PARAFFIN hydrocarbons, generated below the surface of the earth. It contains mostly METHANE and ETHANE with small amounts of PROPANE; BUTANES; and higher hydrocarbons, and sometimes NITROGEN; CARBON DIOXIDE; HYDROGEN SULFIDE; and HELIUM. (from McGraw-Hill Dictionary of Scientific and Technical Terms, 6th ed)Proteins: Linear POLYPEPTIDES that are synthesized on RIBOSOMES and may be further modified, crosslinked, cleaved, or assembled into complex proteins with several subunits. The specific sequence of AMINO ACIDS determines the shape the polypeptide will take, during PROTEIN FOLDING, and the function of the protein.Recombinant Proteins: Proteins prepared by recombinant DNA technology.Mutation: Any detectable and heritable change in the genetic material that causes a change in the GENOTYPE and which is transmitted to daughter cells and to succeeding generations.Food Analysis: Measurement and evaluation of the components of substances to be taken as FOOD.Zinc: A metallic element of atomic number 30 and atomic weight 65.38. It is a necessary trace element in the diet, forming an essential part of many enzymes, and playing an important role in protein synthesis and in cell division. Zinc deficiency is associated with ANEMIA, short stature, HYPOGONADISM, impaired WOUND HEALING, and geophagia. It is known by the symbol Zn.Feeding Behavior: Behavioral responses or sequences associated with eating including modes of feeding, rhythmic patterns of eating, and time intervals.Deuterium Exchange Measurement: A research technique to measure solvent exposed regions of molecules that is used to provide insight about PROTEIN CONFORMATION.Binding Sites: The parts of a macromolecule that directly participate in its specific combination with another molecule.Technetium: The first artificially produced element and a radioactive fission product of URANIUM. Technetium has the atomic symbol Tc, atomic number 43, and atomic weight 98.91. All technetium isotopes are radioactive. Technetium 99m (m=metastable) which is the decay product of Molybdenum 99, has a half-life of about 6 hours and is used diagnostically as a radioactive imaging agent. Technetium 99 which is a decay product of technetium 99m, has a half-life of 210,000 years.Uranium: Uranium. A radioactive element of the actinide series of metals. It has an atomic symbol U, atomic number 92, and atomic weight 238.03. U-235 is used as the fissionable fuel in nuclear weapons and as fuel in nuclear power reactors.Cell Line: Established cell cultures that have the potential to propagate indefinitely.Earth (Planet): Planet that is the third in order from the sun. It is one of the four inner or terrestrial planets of the SOLAR SYSTEM.Radionuclide Imaging: The production of an image obtained by cameras that detect the radioactive emissions of an injected radionuclide as it has distributed differentially throughout tissues in the body. The image obtained from a moving detector is called a scan, while the image obtained from a stationary camera device is called a scintiphotograph.Water Pollutants, Radioactive: Pollutants, present in water or bodies of water, which exhibit radioactivity.Biodegradation, Environmental: Elimination of ENVIRONMENTAL POLLUTANTS; PESTICIDES and other waste using living organisms, usually involving intervention of environmental or sanitation engineers.Biocatalysis: The facilitation of biochemical reactions with the aid of naturally occurring catalysts such as ENZYMES.Methods: A series of steps taken in order to conduct research.Pacific OceanNatural Cytotoxicity Triggering Receptor 3: A 30 kDa stimulatory receptor found on resting and activated NATURAL KILLER CELLS.Structure-Activity Relationship: The relationship between the chemical structure of a compound and its biological or pharmacological activity. Compounds are often classed together because they have structural characteristics in common including shape, size, stereochemical arrangement, and distribution of functional groups.Oxygen: An element with atomic symbol O, atomic number 8, and atomic weight [15.99903; 15.99977]. It is the most abundant element on earth and essential for respiration.Cells, Cultured: Cells propagated in vitro in special media conducive to their growth. Cultured cells are used to study developmental, morphologic, metabolic, physiologic, and genetic processes, among others.Calibration: Determination, by measurement or comparison with a standard, of the correct value of each scale reading on a meter or other measuring instrument; or determination of the settings of a control device that correspond to particular values of voltage, current, frequency or other output.Predatory Behavior: Instinctual behavior pattern in which food is obtained by killing and consuming other species.Antigens, CD56: The 140 kDa isoform of NCAM (neural cell adhesion molecule) containing a transmembrane domain and short cytoplasmic tail. It is expressed by all lymphocytes mediating non-MHC restricted cytotoxicity and is present on some neural tissues and tumors.Nuclear Magnetic Resonance, Biomolecular: NMR spectroscopy on small- to medium-size biological macromolecules. This is often used for structural investigation of proteins and nucleic acids, and often involves more than one isotope.Protein Binding: The process in which substances, either endogenous or exogenous, bind to proteins, peptides, enzymes, protein precursors, or allied compounds. Specific protein-binding measures are often used as assays in diagnostic assessments.Aquatic Organisms: Organisms that live in water.Biomass: Total mass of all the organisms of a given type and/or in a given area. (From Concise Dictionary of Biology, 1990) It includes the yield of vegetative mass produced from any given crop.Phenotype: The outward appearance of the individual. It is the product of interactions between genes, and between the GENOTYPE and the environment.Sulfates: Inorganic salts of sulfuric acid.Leucine: An essential branched-chain amino acid important for hemoglobin formation.Water Microbiology: The presence of bacteria, viruses, and fungi in water. This term is not restricted to pathogenic organisms.Carbonates: Salts or ions of the theoretical carbonic acid, containing the radical CO2(3-). Carbonates are readily decomposed by acids. The carbonates of the alkali metals are water-soluble; all others are insoluble. (From Grant & Hackh's Chemical Dictionary, 5th ed)Photosynthesis: The synthesis by organisms of organic chemical compounds, especially carbohydrates, from carbon dioxide using energy obtained from light rather than from the oxidation of chemical compounds. Photosynthesis comprises two separate processes: the light reactions and the dark reactions. In higher plants; GREEN ALGAE; and CYANOBACTERIA; NADPH and ATP formed by the light reactions drive the dark reactions which result in the fixation of carbon dioxide. (from Oxford Dictionary of Biochemistry and Molecular Biology, 2001)Reproduction: The total process by which organisms produce offspring. (Stedman, 25th ed)Acetates: Derivatives of ACETIC ACID. Included under this heading are a broad variety of acid forms, salts, esters, and amides that contain the carboxymethane structure.Natural Orifice Endoscopic Surgery: Surgical procedures performed through a natural opening in the body such as the mouth, nose, urethra, or anus, and along the natural body cavities with which they are continuous.Cattle: Domesticated bovine animals of the genus Bos, usually kept on a farm or ranch and used for the production of meat or dairy products or for heavy labor.Gold Isotopes: Stable gold atoms that have the same atomic number as the element gold, but differ in atomic weight. Au-197 is a stable isotope.Geological Processes: Events and activities of the Earth and its structures.Environmental Monitoring: The monitoring of the level of toxins, chemical pollutants, microbial contaminants, or other harmful substances in the environment (soil, air, and water), workplace, or in the bodies of people and animals present in that environment.Lead Radioisotopes: Unstable isotopes of lead that decay or disintegrate emitting radiation. Pb atoms with atomic weights 194-203, 205, and 209-214 are radioactive lead isotopes.Mammoths: An extinct genus of large mammals in the family Elephantidae that fed by grazing on low vegetation. Most died out at the end of the last ice age.Immunity, Innate: The capacity of a normal organism to remain unaffected by microorganisms and their toxins. It results from the presence of naturally occurring ANTI-INFECTIVE AGENTS, constitutional factors such as BODY TEMPERATURE and immediate acting immune cells such as NATURAL KILLER CELLS.Sulfur: An element that is a member of the chalcogen family. It has an atomic symbol S, atomic number 16, and atomic weight [32.059; 32.076]. It is found in the amino acids cysteine and methionine.Models, Theoretical: Theoretical representations that simulate the behavior or activity of systems, processes, or phenomena. They include the use of mathematical equations, computers, and other electronic equipment.Time: The dimension of the physical universe which, at a given place, orders the sequence of events. (McGraw-Hill Dictionary of Scientific and Technical Terms, 6th ed)Evolution, Chemical: Chemical and physical transformation of the biogenic elements from their nucleosynthesis in stars to their incorporation and subsequent modification in planetary bodies and terrestrial biochemistry. It includes the mechanism of incorporation of biogenic elements into complex molecules and molecular systems, leading up to the origin of life.Iron: A metallic element with atomic symbol Fe, atomic number 26, and atomic weight 55.85. It is an essential constituent of HEMOGLOBINS; CYTOCHROMES; and IRON-BINDING PROTEINS. It plays a role in cellular redox reactions and in the transport of OXYGEN.Fishes: A group of cold-blooded, aquatic vertebrates having gills, fins, a cartilaginous or bony endoskeleton, and elongated bodies covered with scales.Water Pollutants, Chemical: Chemical compounds which pollute the water of rivers, streams, lakes, the sea, reservoirs, or other bodies of water.Evolution, Molecular: The process of cumulative change at the level of DNA; RNA; and PROTEINS, over successive generations.Algorithms: A procedure consisting of a sequence of algebraic formulas and/or logical steps to calculate or determine a given task.Marine Biology: The study of the origin, structure, development, growth, function, genetics, and reproduction of organisms which inhabit the OCEANS AND SEAS.Plant Transpiration: The loss of water vapor by plants to the atmosphere. It occurs mainly from the leaves through pores (stomata) whose primary function is gas exchange. The water is replaced by a continuous column of water moving upwards from the roots within the xylem vessels. (Concise Dictionary of Biology, 1990)Body Water: Fluids composed mainly of water found within the body.Potassium Radioisotopes: Unstable isotopes of potassium that decay or disintegrate emitting radiation. K atoms with atomic weights 37, 38, 40, and 42-45 are radioactive potassium isotopes.Soil Microbiology: The presence of bacteria, viruses, and fungi in the soil. This term is not restricted to pathogenic organisms.Selenium Radioisotopes: Unstable isotopes of selenium that decay or disintegrate emitting radiation. Se atoms with atomic weights 70-73, 75, 79, 81, and 83-85 are radioactive selenium isotopes.Molecular Conformation: The characteristic three-dimensional shape of a molecule.Hydrolysis: The process of cleaving a chemical compound by the addition of a molecule of water.Glucose: A primary source of energy for living organisms. It is naturally occurring and is found in fruits and other parts of plants in its free state. It is used therapeutically in fluid and nutrient replacement.Rivers: Large natural streams of FRESH WATER formed by converging tributaries and which empty into a body of water (lake or ocean).Enzymes: Biological molecules that possess catalytic activity. They may occur naturally or be synthetically created. Enzymes are usually proteins, however CATALYTIC RNA and CATALYTIC DNA molecules have also been identified.Tooth: One of a set of bone-like structures in the mouth used for biting and chewing.Thermodynamics: A rigorously mathematical analysis of energy relationships (heat, work, temperature, and equilibrium). It describes systems whose states are determined by thermal parameters, such as temperature, in addition to mechanical and electromagnetic parameters. (From Hawley's Condensed Chemical Dictionary, 12th ed)Tropical Climate: A climate which is typical of equatorial and tropical regions, i.e., one with continually high temperatures with considerable precipitation, at least during part of the year. (McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)Natural Cytotoxicity Triggering Receptor 2: A 44-kD stimulatory receptor found on activated NATURAL KILLER CELLS. It has specificity for VIRAL HEMAGGLUTININS that are expressed on infected cells.Chemistry, Organic: The study of the structure, preparation, properties, and reactions of carbon compounds. (McGraw-Hill Dictionary of Scientific and Technical Terms, 6th ed)Bacterial Proteins: Proteins found in any species of bacterium.Flow Cytometry: Technique using an instrument system for making, processing, and displaying one or more measurements on individual cells obtained from a cell suspension. Cells are usually stained with one or more fluorescent dyes specific to cell components of interest, e.g., DNA, and fluorescence of each cell is measured as it rapidly transverses the excitation beam (laser or mercury arc lamp). Fluorescence provides a quantitative measure of various biochemical and biophysical properties of the cell, as well as a basis for cell sorting. Other measurable optical parameters include light absorption and light scattering, the latter being applicable to the measurement of cell size, shape, density, granularity, and stain uptake.Potassium Isotopes: Stable potassium atoms that have the same atomic number as the element potassium, but differ in atomic weight. K-41 is a stable potassium isotope.Cyclization: Changing an open-chain hydrocarbon to a closed ring. (McGraw-Hill Dictionary of Scientific and Technical Terms, 5th ed)Pneumoencephalography: Radiographic visualization of the cerebral ventricles by injection of air or other gas.Hydroxybenzoate Ethers: Benzoate derivatives that contain one or more alkyl or aryl groups linked to the benzene ring structure by OXYGEN.Computer Simulation: Computer-based representation of physical systems and phenomena such as chemical processes.Hydrogen Bonding: A low-energy attractive force between hydrogen and another element. It plays a major role in determining the properties of water, proteins, and other compounds.KetonesLigands: A molecule that binds to another molecule, used especially to refer to a small molecule that binds specifically to a larger molecule, e.g., an antigen binding to an antibody, a hormone or neurotransmitter binding to a receptor, or a substrate or allosteric effector binding to an enzyme. Ligands are also molecules that donate or accept a pair of electrons to form a coordinate covalent bond with the central metal atom of a coordination complex. (From Dorland, 27th ed)Toluene: A widely used industrial solvent.DNA, Bacterial: Deoxyribonucleic acid that makes up the genetic material of bacteria.Biodiversity: The variety of all native living organisms and their various forms and interrelationships.Spleen: An encapsulated lymphatic organ through which venous blood filters.Lymphocyte Activation: Morphologic alteration of small B LYMPHOCYTES or T LYMPHOCYTES in culture into large blast-like cells able to synthesize DNA and RNA and to divide mitotically. It is induced by INTERLEUKINS; MITOGENS such as PHYTOHEMAGGLUTININS, and by specific ANTIGENS. It may also occur in vivo as in GRAFT REJECTION.
Even 253Es, which would be created by the beta decay of natural 253Cf, is already here.) There are no missing isotopes of any ... But looking at isotopes from Tl to Ra, the missing isotopes are: 206Tl, 207Tl, 208Tl, 210Tl, 211Pb, 214Pb, 211Bi, 214Bi, 215Bi ... Actually I would like these shortlived natural isotopes to be listed in this article as well (in a separate section), I think ... Maybe some of the trans-plutonium isotopes that have recently been determined to be natural (see Wikiproject Elements ...
isotope(s)[n 2]. nuclear. spin. representative. isotopic. composition. (mole fraction). range of natural. variation. (mole ... Thallium (81Tl) has 37 isotopes with atomic masses that range from 176 to 212. 203Tl and 205Tl are the only stable isotopes and ... List of isotopes[edit]. nuclide. symbol. historic. name. Z(p). N(n). isotopic mass (u). half-life. decay. mode(s)[5][n 1]. ... N. E. Holden (2004). "Table of the Isotopes". In D. R. Lide. CRC Handbook of Chemistry and Physics (85th ed.). CRC Press. ...
Isotopes[edit]. Main article: Isotopes of ytterbium. Natural ytterbium is composed of seven stable isotopes: 168Yb, 170Yb, 171 ... Natural ytterbium is a mixture of seven stable isotopes, which altogether are present at concentrations of 3 parts per million ... The 169Yb isotope (with a half-life of 32 days), which is created along with the short-lived 175Yb isotope (half-life 4.2 days ... The primary decay mode of ytterbium isotopes lighter than the most abundant stable isotope, 174Yb, is electron capture, and the ...
... λ is a constant that depends on the particular isotope; for a given isotope it is equal to the reciprocal of the mean-life - i. ... Man-made and Natural Radioactivity in Environmental Pollution and Radiochronology. Dordrecht: Kluwer Academic Publishers. pp. ... The equation governing the decay of a radioactive isotope is: N = N 0 e − λ t {\displaystyle N=N_{0}e^{-\lambda t}\,} where N0 ... Naturally occurring radioactive isotopes can also form the basis of dating methods, as with potassium-argon dating, argon-argon ...
Isotopes. Natural concentrations. Main article: Isotopes of uranium. Natural uranium consists of three major isotopes: uranium- ... "Uranium Isotopes". Retrieved 14 March 2012.. *^ "WWW Table of Radioactive Isotopes". Lawrence Berkeley National Laboratory, ... The most common isotopes in natural uranium are uranium-238 (which has 146 neutrons and accounts for over 99% of uranium on ... Another fissile isotope, uranium-233, can be produced from natural thorium and is also important in nuclear technology. Uranium ...
Natural uranium consists of three isotopes; the majority (99.274%) is U-238, while approximately 0.72% is fissile U-235 and the ... If natural uranium is enriched to contain 3% U-235, it can be used as fuel for light water nuclear reactors. If it is enriched ... Separation of uranium isotopes requires a centrifuge that can spin at 1,500 revolutions per second (90,000 RPM). If we assume a ... The Zippe-type centrifuge is a gas centrifuge designed to enrich the rare fissile uranium isotope Uranium-235 out of the ...
Isotopes Division, Radiological Safety Branch, AEC. Morgan, G. W. (1955). The Control of Radioisotopes. Modern Sanitation, 7(11 ... Natural radiation exposure in UK dwellings. National Radiological Protection Board, Chilton (UK), 1988. O'Riordan, M. C. (1988 ... MORGAN, G.W. (1955). Facilities and equipment for isotopes program. Hospitals, 29(3), 103. Morgan, K. Z., POLLARD, E., COWAN, F ... Circular B-3 (January 1948), obtainable from Isotopes Division, US Atomic Energy Commission, PO Box E, Oak Ridge, Tennessee. ...
2003). "α activity of natural tungsten isotopes". Phys. Rev. C. 67 (1): 014310. doi:10.1103/PhysRevC.67.014310. Fazzini T.; et ... For example, the first indication of the natural alpha activity of tungsten (alpha decay of 180W) had been found in 2003 with ...
F.A. Danevich et al., "α activity of natural tungsten isotopes" Phys. Rev. C 67 (2003) 014310 Yu.G. Zdesenko et al., " ... F.A.Danevich et al., " Quest for double beta decay of 160Gd and Ce isotopes" Nucl. Phys. A 694 (2001) 375. F.A.Danevich et al ... F.A. Danevich et al., "Search for 2β decay of cadmium and tungsten isotopes: Final results of the Solotvina experiment Phys. ... isotope 180W); investigation of rare beta decay of 113Cd; search for neutrinoless double beta decay of 160Gd and 186W. ...
Five isotopes of zinc occur in nature. 64Zn is the most abundant isotope (48.63% natural abundance). That isotope has such a ... 69mZn has the longest half-life, 13.76 h. The superscript m indicates a metastable isotope. The nucleus of a metastable isotope ... The isotopes 65 Zn, 71 Zn, 77 Zn and 78 Zn each have only one excited metastable state. The most common decay mode of a ... Anthropogenic and natural emissions occur at a ratio of 20 to 1. Zinc in rivers flowing through industrial and mining areas can ...
Carbon-14 is a natural radioactive isotope with a half-life of 5,730 years. 23 isotopes of silicon have been discovered. Five ... followed by the stable isotope tin-118, the stable isotope tin-116, the stable isotope tin-119, the stable isotope tin-117, the ... followed by the stable isotope germanium-72, the stable isotope germanium-70, and the stable isotope germanium-73. The isotope ... These isotopes are tin-121, tin-123, tin-125, and tin-126. 38 isotopes of lead have been discovered. 9 of these are naturally ...
Formicidae, Dolichoderinae) a L'aide de Radio-isotopes. Bull. Soc. Zool. Fr. 117: 21-30. Wang, T.B., Patel, A., Vu, F. & Nonacs ... According to Ramos-Elorduy & Levieux (1992), L. occidentale in natural environments forage an areas as large as 2,000 m2, but ... Bulletin of the American Museum of Natural History 21:321-333. Wheeler, W. M. (1917) The mountain ants of western North America ... P. (2010). Natural history observations on the velvety tree ants (Liometopum occidentale) unicoloniality and mating flights. ...
2003). "α activity of natural tungsten isotopes". Phys. Rev. C. 67: 014310. arXiv:nucl-ex/0211013 . Bibcode:2003PhRvC..67a4310D ...
Natural uranium is a mix of three isotopes; mainly U-238, with some U-235, and trace amounts of U-234. The neutrons released in ... of natural lithium. These lower energy neutrons will cause breeding in Li-6, which could be concentrated from the natural ... As a natural side-effect of the size of the fuel elements and their resulting explosions, ICF designs use a very large reaction ... "Wholesale Electricity and Natural Gas Market Data". Energy Information Administration. 19 March 2015. The Future of nuclear ...
Of these natural isotopes, 90Zr is the most common, making up 51.45% of all zirconium. 96Zr is the least common, comprising ... 93Zr is the longest-lived artificial isotope, with a half-life of 1.53×106 years. 110Zr, the heaviest isotope of zirconium, is ... Radioactive isotopes at or above mass number 93 decay by electron emission, whereas those at or below 89 decay by positron ... Five isotopes occur naturally, three of which are stable. Zirconium compounds have no known biological role. Zirconium is a ...
isotope(s)[n 2] nuclear. spin and. parity representative. isotopic. composition. (mole fraction) range of natural. variation. ( ... All other isotopes have half-lives less than 12 days, most less than 20 hours. The shortest-lived isotope, 108Xe,[6] has a half ... Naturally occurring xenon (54Xe) is made of eight stable isotopes and one very long-lived isotope. (124Xe, 126Xe, and 134Xe are ... Because xenon is a tracer for two parent isotopes, Xe isotope ratios in meteorites are a powerful tool for studying the ...
Measurements of small variations in the natural abundances of deuterium, along with those of the stable heavy oxygen isotopes ... Isotopes of hydrogen Complete table of nuclides. Deuterium (or hydrogen-2, symbol 2. H. or D. , also known as heavy hydrogen) ... Suspicion of lighter element isotopes[edit]. The existence of nonradioactive isotopes of lighter elements had been suspected in ... This is thought to be a result of natural isotope separation processes that occur from solar heating of ices in comets. Like ...
Dauphas, N.; Rouxel, O. (2006). "Mass spectrometry and natural variations of iron isotopes" (PDF). Mass Spectrometry Reviews. ... Natural Gas Liquids and Natural Gasoline to Offshore Process Piping: High Performance Alloys. CRC Press. pp. 166-167. ISBN 978- ... Of these stable isotopes, only 57Fe has a nuclear spin (−​1⁄2). The nuclide 54Fe theoretically can undergo double electron ... Naturally occurring iron consists of four stable isotopes: 5.845% of 54Fe, 91.754% of 56Fe, 2.119% of 57Fe and 0.282% of 58Fe. ...
Examples include the natural isotopes of polonium and radium. Cosmogenic isotopes, such as carbon-14, are present because they ... This list covers common isotopes, most of which are available in very small quantities to the general public in most countries ... A radionuclide (radioactive nuclide, radioisotope or radioactive isotope) is an atom that has excess nuclear energy, making it ... Interactive Chart of Nuclides - A chart of all nuclides National Isotope Development Center - U.S. Government source of ...
The atomic mass of different isotopes affect their chemical kinetic behavior, leading to natural isotope separation processes. ... The ratios of isotopes in a sample material are measured by isotope-ratio mass spectrometry. This process is called isotope ... Carbon isotopes: you are what you eat Hair-rising research Ayacucho Archaeo Isotope Project The pursuit of isotopic and ... The rate of exchange of surface isotopes with the environment has to be taken in account. Lead consists of four stable isotopes ...
... is a low-abundant, natural, stable isotope of oxygen (0.0373% in seawater; approximately twice as abundant as ... Natural water starts out with 373 ppm of O-17; heavy water starts out incidentally enriched to about 550 ppm of oxygen-17. The ... The isotope was first hypothesized and subsequently imaged by Patrick Blackett in Rutherford's lab 1924: Of the nature of the ... Finally its natural abundance in earth atmosphere was detected in 1929 by Giauque and Johnson in absorption spectra. Mass ...
The only natural occurring radioactive isotope of lutetium 176 71 Lu {\displaystyle {\ce {^{176}_{71}Lu}}} decays in the ... The two isotopes, 176Lu and 176Hf, in the system are measured as ratio to the reference stable isotope of 177Hf. The measured ... The technique of isotope dilution is often necessary for precise determination of concentrations. Isotope dilution is done by ... However, the process and extent of depletion could not be concluded based on a few isotope characteristics, as some isotope ...
Natural abundance of isotopes of a chemical element in nature.. ...
... is the "quasi-stable" isotope of bismuth with the longest known half-life of any radioisotope that undergoes α- ... "Experimental detection of α-particles from the radioactive decay of natural bismuth". Nature. 422 (6934): 876-878. Bibcode: ... Isotopes of bismuth 4.48 grams = 8900000000 * (1 - 0.5 ^ (13798000000 / (600 * (10 ^ 24) / 31557600))) 8,900 metric tons * ... All of the primordial bismuth is of this isotope. It is also the β− daughter of lead-209. 209 82Pb → 209 83Bi + e− Bismuth-209 ...
Maslin, Mark A.; Swann, George E.A. (2006). "Isotopes in marine sediments". In Leng, Melanie J. Isotopes in Palaeoenvironmental ... Man-made and Natural Radioactivity in Environmental Pollution and Radiochronology. Dordrecht: Kluwer Academic Publishers. pp. ... The depletion of 13 C relative to 12 C is proportional to the difference in the atomic masses of the two isotopes, so once the ... ISBN 978-1-4020-2503-7. Rasskazov, Sergei V.; Brandt, Sergei Borisovich; Brandt, Ivan S. (2009). Radiogenic Isotopes in ...
A food web (or food cycle) is a natural interconnection of food chains and a graphical representation (usually an image) of ... The technique has been improved through the use of stable isotopes to better trace energy flow through the web.[14] It was once ... It is explicitly understood that natural systems are 'sloppy' and that food web trophic positions simplify the complexity of ...
Geochemical and strontium isotope characterization of produced waters from Marcellus Shale natural gas extraction. Environ Sci ... The process of natural gas extraction. Natural gas extraction of shale gas reserves may involve multiple activities occurring ... 624 active natural gas wells in Washington County. Of these natural gas wells, 95% were horizontally drilled (Pennsylvania ... 1 km from a natural gas well suggests that airborne irritant exposures related to natural gas extraction activities could be ...
USGS Releases New Standards for Natural Gas USGS now has the new standard for natural gas. ...
... natural isotope is U-238. Many elements have both natural and artificial isotopes (e.g. hydrogen has three natural isotopes ... Stable isotope Environmental isotopes "Natural Isotopes". www.soest.hawaii.edu. Retrieved 2015-12-13. "Isotopes - Chemwiki". ... Natural isotopes are either stable isotopes, radioactive isotopes that have a sufficiently long half-life to allow them to ... Natural isotopes must be either stable, have a half-life exceeding about 7*107 years (there are 34 isotopes in this category, ...
High-precision optical measurements of 13C/12C isotope ratios in organic compounds at natural abundance. Richard N. Zare, ... If the bulk isotope ratio rather than the compound-specific isotope ratio is desired, the separation procedure can be omitted. ... High-precision optical measurements of 13C/12C isotope ratios in organic compounds at natural abundance ... High-precision optical measurements of 13C/12C isotope ratios in organic compounds at natural abundance ...
... a further complication to the use of variations in the natural abundance of 15N for tracer studies - Volume 90 Issue 1 - K. W. ... Fractionation of nitrogen isotopes by animals: a further complication to the use of variations in the natural abundance of 15N ... Rennie, D. A. & Paul, E. A. (1975). Nitrogen isotope ratios in surface and subsurface soil horizons. In Isotope ratios as ... Use of variation of natural nitrogen isotope abundance for environmental studies: a questionable approach. Science 177, 453-4. ...
... has made it possible to analyze natural stable isotope ratios (e.g., 13C/12C, 15N/14N, 2H/1H) of individual organic ... Gas chromatography-isotope ratio mass spectrometry (GC-IRMS) ... has made it possible to analyze natural stable isotope ratios ( ... Isotope effects reflect the energy difference of isotopologues (i.e., molecules carrying a light versus a heavy isotope in a ... Stable isotope fractionation. to investigate natural transformation mechanisms of organic contaminants: principles, prospects ...
Compound specific isotope analysis (CSIA) has proven t ... Compound specific isotope analysis (CSIA) has proven to be a ... Mineral identity, natural organic matter, and repeated contaminant exposures do not affect the carbon and nitrogen isotope ... Mineral identity, natural organic matter, and repeated contaminant exposures do not affect the carbon and nitrogen isotope ... natural organic matter presence, and repeated exposures to DNAN. Though rate constants varied, N and C apparent kinetic isotope ...
Radio-isotopes (isotopes) naturally decay into more stable substances over time, some more quickly than others (the decay is ... Tc-99m, which is obtained from the decay of its parent isotope molybdenum-99 (Mo-99), is the most widely used medical isotope ... A dedicated isotope facility based on a private sector cost-recovery model would be a good solution, assuming a private-sector ... The Report of the Expert Review Panel on Medical Isotope Production. The Panel found that a sustainable supply of Tc-99m would ...
Validation of carbon isotope fractionation in algal lipids as a pCO2 proxy using a natural CO2 seep (Shikine Island, Japan) ... This research demonstrates new approaches for exploring past pCO2 via the carbon isotope fractionation in general algal lipids ...
Those methods share the application of the stable carbon isotope 13C, using either local changes in natural abundance of 13CO2 ... We conclude that the applicability of natural stable isotope methods is still limited in forest ecosystems because only in a ... Still, especially the combination of Free Air Carbon Enrichment (FACE) with dual δ13C and δ18O stable isotope approach has the ... Method of natural abundance. The heavier stable isotope 13C is much less abundant than the lighter 12C.13C ≈ 1.10% of the total ...
The influence of oxygen isotope exchange between CO2 and H2O in natural CO2-rich spring waters : implications for ... Oxygen isotope ratio (δ18O) value deviations from the Meteoric Water Line with no significant change in the hydrogen isotope ( ... natural waters previously interpreted as geothermal based on their oxygen isotope composition may actually have acquired their ... The influence of oxygen isotope exchange between CO2 and H2O in natural CO2-rich spring waters : implications for ...
Stable Isotopes are a full range of neutron absorbing and reflecting materials for the nuclear power industry and semiconductor ... We produce ultra-high purity (UHP) grades of natural and enriched boron to meet the specialized needs of the silicon wafer ... 3M™ Stable Isotopes * Ceradyne Inc., a 3M company (formerly Boron Products, LLC), is a leading global commercial processor of ... Our portfolio includes the 11Boron isotope, which is used as an additive to semiconductor-grade silicon as a "doping" agent. ...
My PhD thesis involved determining kinetic isotope effects (KIE) for aromatic electrophilic substitution reactions in an effort ... "High-Precision Simultaneous Determination of Multiple Small Kinetic Isotope Effects at Natural Abundance", Journal of the ... Isotopes, Kinetic isotope effect, Nuclear physics, Physical organic chemistry, shell solutions ... The inverse isotope effects are greater for the more completely formed bond (to C1) than for the lagging bond (to C4). They are ...
Natural Hazards. How low should we go when warning for earthquakes?. *. Archaeology. Excavating Uruk ... Sieving hydrogen isotopes through two-dimensional crystals. By M. Lozada-Hidalgo, S. Hu, O. Marshall, A. Mishchenko, A. N. ... Sieving hydrogen isotopes through two-dimensional crystals. By M. Lozada-Hidalgo, S. Hu, O. Marshall, A. Mishchenko, A. N. ... 2 Isotope separation by electrochemical pumping of hydrons through graphene.. (A) Schematic of our mass spectrometry setup. (B ...
20.3 Natural Radioactivity. 20.4 Nuclear Transmutation. 20.5 Nuclear Fission. 20.6 Nuclear Fusion. 20.7 Uses of Isotopes. 20.8 ... 2.3 Atomic Number, Mass Number, and Isotopes. 2.4 Average Atomic Mass 2.5 The Periodic Table 2.6 The Mole and Molar Masses. ...
As stable isotopes are transported in well-defined manners up the food chain, natural abundances of stable isotopes are widely ... Natural abundance of stable isotopes. Stable isotope analyses demonstrated a higher proportion of host-independent food sources ... 2005) and were confirmed by natural abundances of stable isotopes. Stable isotopes have been used to study nutrient fluxes ... Natural abundances of stable isotopes. Mean ± SE of abundances of δ 15N (a) and of δ 13C (b) are displayed in per mil [‰]. ...
Example of Natural Gas Isotope Log showing subsurface depth variations in carbon isotopic composition of C1 through C4 n- ... Natural Gas Isotope Logs (NGIL) developed by GCHEM provide the information necessary to develop a template for the distribution ... These diagrams are particularly useful for identifying potential zones of leakage of natural gas. One area of application is in ... Because the isotopic composition of natural gases, including methane, ethane, propane and butane, among other molecules, varies ...
Natural gas development impacts and best practices. The Mobile Methane Analyzer. Photo by Christi Turner. ... Stable Isotopes in the Biosphere. Carbon isotope ratios of organic material are useful tools in ecology and ecosystem science. ... Stable Isotope Laboratory. Research. The INSTAAR Stable Isotope Lab is a focal point of interdisciplinary research programs: we ... Stable isotopes are very useful for understanding sources and sinks due to processes that discriminate against one isotope over ...
Even 253Es, which would be created by the beta decay of natural 253Cf, is already here.) There are no missing isotopes of any ... But looking at isotopes from Tl to Ra, the missing isotopes are: 206Tl, 207Tl, 208Tl, 210Tl, 211Pb, 214Pb, 211Bi, 214Bi, 215Bi ... Actually I would like these shortlived natural isotopes to be listed in this article as well (in a separate section), I think ... Maybe some of the trans-plutonium isotopes that have recently been determined to be natural (see Wikiproject Elements ...
College of Agriculture and Natural Resources. Plant Isotope Ecologist. UWYO Stable Isotope Facility. [email protected] Phone: (307 ...
Natural History Museum. Pohjoinen Rautatiekatu 13. open Tue-Sun. entrance 14/11/7 € ... CARATE - tree-ring carbon isotopes tell stories of past climate evolution. Markku Oinonen, docent, laboratory manager & Laura ... Stability of climate signal in carbon and oxygen isotope records and ring width from Scots pine (Pinus sylvestris L.) in ... a 7500-year record of climate and tree response to climate forcing in Northern Finland on the basis of the carbon isotope ...
2.91 Strontium has four stable isotopes. Strontium-84 has a very low natural abundance, but 86Sr, 87Sr, and 88S.... Chemistry ...
Review of Use of Isotopes in Studying the Natural History of Puerto Rico. Thu, 01/19/2012 - 13:43 - leonmi Evaristo J. Review ... isotopes. Evaluation of the fidelity of isotope records as an environmental proxy in the coral Montastraea. Tue, 01/24/2012 - ... Using stable carbon isotope techniques, we tracked the loss of the old soil organic C from the previous C4 land use (SOC4) and ... Pett-Ridge J. C., Derry L. A. and Kurtz A. C. (2009) Sr isotopes as. a tracer of weathering processes and dust inputs in a ...
Isotope geochemistry is an aspect of geology based upon the study of natural variations in the relative abundances of isotopes ... National Isotope Development Center Reference information on isotopes, and coordination and management of isotope production, ... ISBN 0-13-272790-0. "USGS -- Isotope Tracers -- Resources -- Isotope Geochemistry". Retrieved 2009-01-18. "Carbon isotope (d13C ... USGS Tritium/Helium-3 Dating Hydrologic Isotope Tracers - Helium Cosmogenic isotopes Environmental isotopes Geochemistry ...
  • Little is known about the environmental and public health impact of unconventional natural gas extraction activities, including hydraulic fracturing, that occur near residential areas. (nih.gov)
  • Tc-99m, which is obtained from the decay of its parent isotope molybdenum-99 (Mo-99), is the most widely used medical isotope for medical imaging and accounts for approximately 80 percent of nuclear medicine diagnostic procedures. (gc.ca)
  • With the National Reactor Universal (NRU) in Chalk River, Ontario, ceasing production of medical isotopes in October 2016, Canada risks losing a major medical industry that has supplied 40%-50% of the world's molybdenum-99 (Mo-99) for imaging and 85% of the world's cobalt-60 for radiotherapy. (cmaj.ca)
  • In Canada, home to the NRU reactor located in Chalk River, Ontario, the medical isotope supply chain has been complex and has involved a combination of both public- and private-sector organizations. (gc.ca)
  • Uncertainties shroud medical isotope supply. (ebscohost.com)
  • Iso-trace is equipped with a six isotope ratio mass spectrometers and a range of preparation devices including elemental analysers, and a gas chromatograph combustion isotope ratio mass spectrometer (GC-C-IRMS) for compound specific analysis. (otago.ac.nz)
  • Though rate constants varied, N and C apparent kinetic isotope effects (AKIEs) remained consistent across all experiments (averaged values of 15 N-AKIE = 1.0317 ± 0.0064 and 13 C-AKIE = 1.0008 ± 0.0005) and revealed significant 15 N- and minimal 13 C-enrichment in agreement with previous work on nitroaromatic compounds. (rsc.org)
  • My PhD thesis involved determining kinetic isotope effects (KIE) for aromatic electrophilic substitution reactions in an effort to learn more about the nature of the transition states involved. (imperial.ac.uk)
  • We also produce complementary chemical isotopes used in the normal operation and control of nuclear power plants. (3m.com)
  • The artificial isotope 135 Xe is of considerable significance in the operation of nuclear fission reactors . (wikipedia.org)
  • The isotope 56 Fe is the isotope with the lowest mass per nucleon, 930.412 MeV/c 2 , though not the isotope with the highest nuclear binding energy per nucleon, which is nickel-62 . (archive.org)
  • The isotope 57 Fe is widely used in Mössbauer spectroscopy and the related nuclear resonance vibrational spectroscopy due to the low natural variation in energy of the 14.4 keV nuclear transition. (archive.org)
  • At least 1,000 radioactive isotopes occur in nature or have been produced synthetically in particle accelerators (atom-smashers) or nuclear reactors (devices used to control the release of energy from nuclear reactions). (encyclopedia.com)
  • In sufficient concentration, these isotopes maintain a sustained nuclear chain reaction . (wikipedia.org)
  • Stable isotopes are not radioactive, whereas unstable isotopes undergo radioactive decay and release nuclear radiation. (reference.com)
  • Isotope masses from Ame2003 Atomic Mass Evaluation by G. Audi, A.H. Wapstra, C. Thibault, J. Blachot and O. Bersillon in Nuclear Physics A729 (2003). (thefullwiki.org)
  • In addition to lutetium-176, and not counting nuclear isomers, 33 more radioactive isotopes of lutetium are known. (britannica.com)
  • The most important radioactive isotopes, 89Sr and 90Sr, are formed during nuclear reactor operations and during nuclear explosions by the nuclear fission of 235U, 238U, or 239Pu. (cdc.gov)
  • A FRIB's rare-isotope beams of unprecedented intensity and its sophisticated detector arrays would allow experimentalists to explore the limits of nuclear stability. (nap.edu)
  • Applied Radiation and Isotopes provides a high quality medium for the publication of substantial, original and scientific and technological papers on the development and peaceful application of nuclear, radiation and radionuclide techniques in chemistry, physics, biochemistry, biology, medicine, security. (elsevier.com)
  • They include the development and use of α- and β-particles, X-rays and γ-rays, neutrons and other nuclear particles and radiations from all sources, including radionuclides, synchrotron sources, cyclotrons and reactors and from the natural environment. (elsevier.com)
  • The article reports on the possible decrease in the supply of medical isotopes such as technetium-99, which are used to treat a range of cancers after the Nuclear Research and Consultancy Group (NRG) in Petten, the Netherlands, shut down a reactor. (ebscohost.com)
  • According to Robert Atcher, president-elect of the Society for Nuclear Medicine, the shutdown at Petten, threatens the ability of countries across the globe to access and obtain radioactive isotopes. (ebscohost.com)
  • This article reports that continued shortage of medical isotopes could lead to more invasive and expensive imaging techniques in the diagnosis of patients, according to speakers at a press conference held by the Society of Nuclear Medicine (SNM). (ebscohost.com)
  • Drawing on research from ecology, biology, and limnology, this paper outlines some of the complexities of freshwater ecosystem biogeochemistry in order to address key areas of investigation in archaeology, including prehistoric human aquatic resource use and anthropogenic and natural changes in past aquatic ecosystems. (frontiersin.org)
  • Radiogenic isotopes provide powerful tracers for studying the ages and origins of Earth systems. (wikipedia.org)
  • In this paper, we show that both methods produce similar source water fraction values, implying the usefulness of both despite their shortcomings, and fortifying the use of hydrodynamic tracers to model transport in a natural system. (mdpi.com)
  • It is shown how such position-specific isotope effects are "diluted out" in the compound average measured by GC-IRMS , and how a careful evaluation in mechanistic scenarios and by dual isotope plots can recover the underlying mechanistic information. (rsc.org)
  • Despite its ubiquity on Earth today, the evidence for MSO in the rock record is sparse as it is generally considered to yield small sulfur isotope enrichments between the sulfide consumed and the sulfate produced ( 4 ). (sciencemag.org)
  • Until recently, foreign vendors supplied 100 percent of the parent isotope, which was mostly produced using HEU. (ornl.gov)
  • This study presents comprehensive strontium stable isotope ( 88 Sr/ 86 Sr) data, measured by multiple-collector inductively-coupled plasma mass spectrometry (MC-ICP-MS), for a suite of carbonaceous chondrites, differentiated meteorites, lunar, martian and terrestrial samples. (open.ac.uk)
  • Still, especially the combination of Free Air Carbon Enrichment (FACE) with dual δ 13 C and δ 18 O stable isotope approach has the potential to provide new answers on the response sensitivity of turnover dynamics of the largest belowground soil carbon storage to elevated temperature and CO 2 . (sisef.it)
  • where a higher δ 13 C stands for more heavy stable isotopes than the standard (enrichment) and a lower δ 13 C means less heavy stable isotopes than the standard (depletion). (sisef.it)
  • Traditionally, the interaction of CO2 and water in a natural CO2-rich groundwater setting has only been associated with water 18O depletion and this is the first study to consider 18O enrichment. (strath.ac.uk)
  • We present a spectroscopic approach for making high-precision CSIA measurements of the 13 C/ 12 C isotope ratio of organic compounds, which is less expensive, does not require trained personnel, and is portable. (pnas.org)
  • The isotope measurements, along with concentrations of greenhouse gases in our atmosphere, constrain models of these gases, and increase their predictive capability for understanding future climate regimes and making policy decisions. (colorado.edu)
  • To advance our ability to reconstruct this signature, we present methodological developments that allow us to make precise and accurate Pb isotope measurements on deep-sea coral aragonite, and apply our approach to generate the first Pb isotope record for the glacial to deglacial mid-depth Southern Ocean. (caltech.edu)
  • From 1970 to the present day, projected trends agree with tropospheric measurements, suggesting that within analytical uncertainties, a constant average emission isotope delta (δ) is a compatible scenario. (atmos-chem-phys.net)
  • So, rather than needing sophisticated isotope separation technology, the two metals can be separated by well-known metal processing chemistry (such as the PUREX method which involves dissolving them in acid, reacting both metals with an organic compound, extracting the organic compounds into kerosene and selectively reducing the plutonium so that it can be re-extracted back into water). (ferret.com.au)
  • Harold Urey's interest in isotope chemistry goes back to the late 1920's when he and I.I. Rabi returned from Europe and established themselves at Columbia to introduce the then brand-new concepts of quantum mechanics to students in the United States. (minsocam.org)
  • Urey followed up his initial important discovery with many other experimental and theoretical contributions to isotope chemistry. (minsocam.org)
  • Xenon isotopes are also a powerful tool for understanding terrestrial differentiation . (wikipedia.org)
  • ionizing radiation from natural sources, such as terrestrial radiation due to radionuclides in the soil or cosmic radiation originating in outer space. (cdc.gov)
  • Whereas neodymium (Nd) isotopes in the Southern Ocean respond to global ocean circulation changes between glacial and interglacial periods, Pb isotopes record more localised mixing within the Antarctic Circumpolar Current, potentially further modulated by climate through changing terrestrial inputs from southern Africa or Australia. (caltech.edu)
  • Cernusak LA, Ubierna N, Winter K et al (2013) Environmental and physiological determinants of carbon isotope discrimination in terrestrial plants. (springer.com)
  • The TRIUMF-led cyclotron consortium is among several cyclotron and linear accelerator isotope solutions that have received $60 million from the federal government from 2010-2016. (cmaj.ca)
  • The calibrated accuracy for methane, ethane, and propane is within 3‰ of the values determined using isotope ratio mass spectrometry (IRMS), which is the current method of choice for compound-specific isotope analysis. (pnas.org)
  • In addition to the stable isotope analysis, we are involved with the coring, processing , and modeling/analysis of the data. (colorado.edu)
  • Sources of dissolved inorganic and organic N in water samples using stable isotope analysis of d15N will be determined. (epa.gov)
  • Here we perform a meta-analysis of plant xylem water stable isotope (δ 2 H and δ 18 O, n = 7367) information from 138 published papers - representing 251 genera, and 414 species of angiosperms ( n = 376) and gymnosperms ( n = 38). (nature.com)
  • In a collaborative SNF-Sinergia project, we aim at elucidating the fate of pesticides by multi-element isotope analysis on the field scale. (eawag.ch)
  • Furthermore, for a typical 500 mg coral sample with low Pb concentrations (∼6-10 ppb yielding ∼3-5 ng Pb for analysis), we obtain a comparable internal precision of ∼150-250 ppm for ^(206,207,208)Pb/^(204)Pb, indicating a good sensitivity for tracing natural Pb sources to the oceans. (caltech.edu)
  • Oxygen isotopes: (R. Greenwood, OU ) analysis of a sample leached with ethanolamine thioglycollate gave δ 18 O=3.67, δ 17 O=-1.14, Δ 17 O= -3.04. (usra.edu)
  • Here we present a novel method for organic authentication based on stable isotope ratio analysis of oxygen in plant-derived sulphate. (dtu.dk)
  • We combined this method with stable isotope ratio analysis of bulk plant tissue and plant-derived nitrate to discriminate organic and conventional potato, carrot, and cabbage from rigidly controlled long-term field trials and from a case study using retail potatoes. (dtu.dk)
  • The classification power of sulphate isotope analysis was superior compared to known bulk tissue isotope markers and nitrate isotope values. (dtu.dk)
  • In conclusion, oxygen isotope analysis of plant-derived sulphate represents a promising new method for authentication of organic vegetables. (dtu.dk)
  • In 1995 Dan Singleton and Allen Thomas reported an elegant strategy to this very problem by proposing a remarkably simple method for obtaining KIE using natural isotopic abundances. (imperial.ac.uk)
  • This publication presents the proceedings of the latest IAEA symposium on isotopes in hydrology, marine ecosystems and climate change studies. (iaea.org)
  • We present two case studies from Daylesford (Australia) and Pah Tempe (Utah, USA) mineral springs, where we use a numerical geochemical modelling approach to resolve the influence of low temperature water-rock interactions and CO2 equilibration on the observed oxygen isotope ranges observed in the mineral waters. (strath.ac.uk)
  • Stable isotopes of precipitation are a proxy for temperature when the snow fell, making ice cores a rich paleoclimate archives. (colorado.edu)
  • These observations indicate that for G. sacculifer , at least, there is no effect of temperature on Sr stable isotope uptake, but the species specific, and/or shell size effects need to be considered in order to retrieve seawater δ 88 Sr values from foraminiferal tests. (open.ac.uk)
  • With the information discovered by Nier and his co-workers that limestones were about 3 percent richer in 18 O than ocean water, and with his calculations of the temperature coefficient for the isotope exchange reaction between CaCO 3 and H 2 O, Urey realized that it might be possible to apply these concepts to determining the paleotemperatures of the oceans. (minsocam.org)