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.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.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.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.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.Carbon Dioxide: A colorless, odorless gas that can be formed by the body and is necessary for the respiration cycle of plants and animals.Methyl Chloride: A hydrocarbon used as an industrial solvent. It has been used as an aerosal propellent, as a refrigerant and as a local anesthetic. (From Martindale, The Extra Pharmacopoeia, 31st ed, p1403)Atmosphere: The gaseous envelope surrounding a planet or similar body. (From Random House Unabridged Dictionary, 2d ed)Fossils: Remains, impressions, or traces of animals or plants of past geological times which have been preserved in the earth's crust.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)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)Ethylene Dichlorides: Toxic, chlorinated, saturated hydrocarbons. Include both the 1,1- and 1,2-dichloro isomers. The latter is considerably more toxic. It has a sweet taste, ethereal odor and has been used as a fumigant and intoxicant among sniffers. Has many household and industrial uses.Paleontology: The study of early forms of life through fossil remains.Xanthobacter: A genus of gram-negative, aerobic, rod-shaped bacteria found in wet soil containing decaying organic material and in water. Cells tend to be pleomorphic if grown on media containing succinate or coccoid if grown in the presence of an alcohol as the sole carbon source. (From Bergey's Manual of Determinative Bacteriology, 9th ed)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)Pinus taeda: A plant species of the genus PINUS which is the subject of genetic study.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)Peptococcaceae: A family of bacteria found in the mouth and intestinal and respiratory tracts of man and other animals as well as in the human female urogenital tract. Its organisms are also found in soil and on cereal grains.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)Carbon Monoxide: Carbon monoxide (CO). A poisonous colorless, odorless, tasteless gas. It combines with hemoglobin to form carboxyhemoglobin, which has no oxygen carrying capacity. The resultant oxygen deprivation causes headache, dizziness, decreased pulse and respiratory rates, unconsciousness, and death. (From Merck Index, 11th ed)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)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)Carbon Cycle: The cycle by which the element carbon is exchanged between organic matter and the earth's physical environment.Nanotubes, Carbon: Nanometer-sized tubes composed mainly of CARBON. Such nanotubes are used as probes for high-resolution structural and chemical imaging of biomolecules with ATOMIC FORCE MICROSCOPY.Carbon Compounds, Inorganic: Inorganic compounds that contain carbon as an integral part of the molecule but are not derived from hydrocarbons.Epitestosterone: The 17-alpha isomer of TESTOSTERONE, derived from PREGNENOLONE via the delta5-steroid pathway, and via 5-androstene-3-beta,17-alpha-diol. Epitestosterone acts as an antiandrogen in various target tissues. The ratio between testosterone/epitestosterone is used to monitor anabolic drug abuse.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)Flaveria: A plant genus of the family ASTERACEAE that is used for experiments in molecular genetic studies in plant physiology and development.Rhamnus: A plant genus of the family RHAMNACEAE. Several species have been reclassified to the FRANGULA genus. It is often called buckthorn but should not be confused with other plants called that.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)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.History, Ancient: The period of history before 500 of the common era.Myrtus: A plant genus of the family MYRTACEAE. Members contain PHYTOHEMAGGLUTININS.Hyphomicrobium: A genus of rod-shaped, oval, or bean-shaped bacteria found in soil and fresh water. Polar prosthecae are present and cells reproduce by budding at the tips of the prosthecae. Cells of this genus are aerobic and grow best with one-carbon compounds. (From Bergey's Manual of Determinative Bacteriology, 9th ed)Doping in Sports: Illegitimate use of substances for a desired effect in competitive sports. It includes humans and animals.Seawater: The salinated water of OCEANS AND SEAS that provides habitat for marine organisms.Biodegradation, Environmental: Elimination of ENVIRONMENTAL POLLUTANTS; PESTICIDES and other waste using living organisms, usually involving intervention of environmental or sanitation engineers.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.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).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)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.Gas Chromatography-Mass Spectrometry: A microanalytical technique combining mass spectrometry and gas chromatography for the qualitative as well as quantitative determinations of compounds.Plant Stomata: Closable openings in the epidermis of plants on the underside of leaves. They allow the exchange of gases between the internal tissues of the plant and the outside atmosphere.Phosphoenolpyruvate Carboxylase: An enzyme with high affinity for carbon dioxide. It catalyzes irreversibly the formation of oxaloacetate from phosphoenolpyruvate and carbon dioxide. This fixation of carbon dioxide in several bacteria and some plants is the first step in the biosynthesis of glucose. EC 4.1.1.31.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.Rain: Water particles that fall from the ATMOSPHERE.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.Extinction, Biological: The ceasing of existence of a species or taxonomic groups of organisms.Fresh Water: Water containing no significant amounts of salts, such as water from RIVERS and LAKES.Ribulose-Bisphosphate Carboxylase: A carboxy-lyase that plays a key role in photosynthetic carbon assimilation in the CALVIN-BENSON CYCLE by catalyzing the formation of 3-phosphoglycerate from ribulose 1,5-biphosphate and CARBON DIOXIDE. It can also utilize OXYGEN as a substrate to catalyze the synthesis of 2-phosphoglycolate and 3-phosphoglycerate in a process referred to as photorespiration.Carbon Monoxide Poisoning: Toxic asphyxiation due to the displacement of oxygen from oxyhemoglobin by carbon monoxide.Deuterium: Deuterium. The stable isotope of hydrogen. It has one neutron and one proton in the nucleus.Poaceae: A large family of narrow-leaved herbaceous grasses of the order Cyperales, subclass Commelinidae, class Liliopsida (monocotyledons). Food grains (EDIBLE GRAIN) come from members of this family. RHINITIS, ALLERGIC, SEASONAL can be induced by POLLEN of many of the grasses.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)Trees: Woody, usually tall, perennial higher plants (Angiosperms, Gymnosperms, and some Pterophyta) having usually a main stem and numerous branches.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.Chiroptera: Order of mammals whose members are adapted for flight. It includes bats, flying foxes, and fruit bats.Climate: The longterm manifestations of WEATHER. (McGraw-Hill Dictionary of Scientific and Technical Terms, 6th 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.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.Sulfates: Inorganic salts of sulfuric acid.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)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.Carbon Tetrachloride: A solvent for oils, fats, lacquers, varnishes, rubber waxes, and resins, and a starting material in the manufacturing of organic compounds. Poisoning by inhalation, ingestion or skin absorption is possible and may be fatal. (Merck Index, 11th ed)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.Anaerobiosis: The complete absence, or (loosely) the paucity, of gaseous or dissolved elemental oxygen in a given place or environment. (From Singleton & Sainsbury, Dictionary of Microbiology and Molecular Biology, 2d ed)Carbon Sequestration: Any of several processes for the permanent or long-term artificial or natural capture or removal and storage of carbon dioxide and other forms of carbon, through biological, chemical or physical processes, in a manner that prevents it from being released into the atmosphere.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)Carbon Disulfide: A colorless, flammable, poisonous liquid, CS2. It is used as a solvent, and is a counterirritant and has local anesthetic properties but is not used as such. It is highly toxic with pronounced CNS, hematologic, and dermatologic effects.Seasons: Divisions of the year according to some regularly recurrent phenomena usually astronomical or climatic. (From McGraw-Hill Dictionary of Scientific and Technical Terms, 6th ed)Diet: Regular course of eating and drinking adopted by a person or animal.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.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.Mass Spectrometry: An analytical method used in determining the identity of a chemical based on its mass using mass analyzers/mass spectrometers.Biological Evolution: The process of cumulative change over successive generations through which organisms acquire their distinguishing morphological and physiological characteristics.Phylogeny: The relationships of groups of organisms as reflected by their genetic makeup.Carbon Tetrachloride PoisoningKinetics: The rate dynamics in chemical or physical systems.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)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.Carbon Footprint: A measure of the total greenhouse gas emissions produced by an individual, organization, event, or product. It is measured in units of equivalent kilograms of CARBON DIOXIDE generated in a given time frame.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).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.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.Evolution, Planetary: Creation and development of bodies within solar systems, includes study of early planetary geology.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)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.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)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)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).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.Geological Phenomena: The inanimate matter of Earth, the structures and properties of this matter, and the processes that affect it.Soot: A dark powdery deposit of unburned fuel residues, composed mainly of amorphous CARBON and some HYDROCARBONS, that accumulates in chimneys, automobile mufflers and other surfaces exposed to smoke. It is the product of incomplete combustion of carbon-rich organic fuels in low oxygen conditions. It is sometimes called lampblack or carbon black and is used in INK, in rubber tires, and to prepare CARBON NANOTUBES.CarboxyhemoglobinCatalysis: The facilitation of a chemical reaction by material (catalyst) that is not consumed by the reaction.Chromatography, Liquid: Chromatographic techniques in which the mobile phase is a liquid.

An examination of coaxial stacking of helical stems in a pseudoknot motif: the gene 32 messenger RNA pseudoknot of bacteriophage T2. (1/7271)

The RNA pseudoknot located at the 5' end of the gene 32 messenger RNA of bacteriophage T2 contains two A-form helical stems connected by two loops, in an H-type pseudoknot topology. A combination of multidimensional NMR methods and isotope labeling were used to investigate the pseudoknot structure, resulting in a more detailed structural model than provided by earlier homonuclear NMR studies. Of particular significance, the interface between the stacked helical stems within the pseudoknot motif is described in detail. The two stems are stacked in a coaxial manner, with an approximately 18 degrees rotation of stem1 relative to stem2 about an axis that is parallel to the helical axis. This rotation serves to relieve what would otherwise be a relatively close phosphate-phosphate contact at the junction of the two stems, while preserving the stabilizing effects of base stacking. The ability of the NMR data to determine pseudoknot bending was critically assessed. The data were found to be a modestly precise indicator of pseudoknot bending, with the angle between the helical axes of stem1 and stem2 being in the range of 15+/-15 degrees. Pseudoknot models with bend angles within this range are equally consistent with the data, since they differ by only small amounts in the relatively short-range interproton distances from which the structure was derived. The gene 32 messenger RNA pseudoknot was compared with other RNA structures with coaxial or near-coaxial stacked helical stems.  (+info)

Prior protein intake may affect phenylalanine kinetics measured in healthy adult volunteers consuming 1 g protein. kg-1. d-1. (2/7271)

Study of the amino acid metabolism of vulnerable groups, such as pregnant women, children and patients, is needed. Our existing protocol is preceded by 2 d of adaptation to a low 13C formula diet at a protein intake of 1 g. kg-1. d-1 to minimize variations in breath 13CO2 enrichment and protein metabolism. To expand on our potential study populations, a less invasive protocol needs to be developed. We have already established that a stable background 13CO2 enrichment can be achieved on the study day without prior adaptation to the low 13C formula. Therefore, this study investigates phenylalanine kinetics in response to variations in prior protein intake. Healthy adult subjects were each fed nutritionally adequate mixed diets containing 0.8, 1.4 and 2.0 g protein. kg-1. d-1 for 2 d. On d 3, subjects consumed an amino acid-based formula diet containing the equivalent of 1 g protein. kg-1. d-1 hourly for 10 h and primed hourly oral doses of L-[1-13C]phenylalanine for the final 6 h. Phenylalanine kinetics were calculated from plasma-free phenylalanine enrichment and breath 13CO2 excretion. A significant quadratic response of prior protein intake on phenylalanine flux (P = 0.012) and oxidation (P = 0.009) was identified, such that both variables were lower following adaptation to a protein intake of 1.4 g. kg-1. d-1. We conclude that variations in protein intake, between 0.8 and 2.0 g. kg-1. d-1, prior to the study day may affect amino acid kinetics and; therefore, it is prudent to continue to control protein intake prior to an amino acid kinetics study.  (+info)

Carbon 13 NMR study of nonenzymatic reactions of pyridoxal 5'-phosphate with selected amino acids and of related reactions. (3/7271)

Carbon 13 nuclear magnetic resonance spectroscopy has been used to monitor the nonenzymatic reactions of pyridoxal 5'-phosphate with glycine, alanine, valine, serine, and with several other model compounds. Isotopically enriched amino acids were employed so that low concentrations could be utilized while still allowing relatively rapid acquisition of spectral data. The results for alanine and serine are particularly noteworthy in that alanine is deaminated to pyruvate and pyruvate is aminated to alanine, but contrary to the enzymatic reactions of various serine dehydratases wherein serine is converted to pyruvate, the nonenzymatic reaction utilizing serine results in hydroxypruvate rather than pyruvate formation. In the reverse reaction, hydroxypyruvate is aminated to serine but very inefficiently relative to the amination of pyruvate to alanine. The experimental results have been formulated into a proposed reaction mechanism for deamination of amino acids by pyridoxal-P.  (+info)

The Ice Man's diet as reflected by the stable nitrogen and carbon isotopic composition of his hair. (4/7271)

Establishing the diets of ancient human populations is an integral component of most archaeological studies. Stable isotope analysis of well-preserved bone collagen is the most direct approach for a general assessment of paleodiet. However, this method has been limited by the scarcity of well-preserved skeletal materials for this type of destructive analysis. Hair is preserved in many burials, but is often overlooked as an alternative material for isotopic analysis. Here we report that the stable carbon and nitrogen isotope values for the hair of the 5200 year-old Ice Man indicates a primarily vegetarian diet, in agreement with his dental wear pattern. Whereas previous investigations have focused on bone collagen, the stable isotope composition of hair may prove to be a more reliable proxy for paleodiet reconstruction, particularly when skeletal remains are not well preserved and additional archaeological artifacts are unavailable.  (+info)

European interlaboratory comparison of breath 13CO2 analysis. (5/7271)

The BIOMED I programme Stable Isotopes in Gastroenterology and Nutrition (SIGN) has focused upon evaluation and standardisation of stable isotope breath tests using 13C labelled substrates. The programme dealt with comparison of 13C substrates, test meals, test conditions, analysis techniques, and calculation procedures. Analytical techniques applied for 13CO2 analysis were evaluated by taking an inventory of instrumentation, calibration protocols, and analysis procedures. Two ring tests were initiated measuring 13C abundances of carbonate materials. Evaluating the data it was found that seven different models of isotope ratio mass spectrometers (IRMS) were used by the participants applying both the dual inlet system and the continuous flow configuration. Eight different brands of certified 13C reference materials were used with a 13C abundance varying from delta 13CPDB -37.2 to +2.0/1000. CO2 was liberated from certified material by three techniques and different working standards were used varying from -47.4 to +0.4/1000 in their delta 13CPDB value. The standard deviations (SDs) found for all measurements by all participants were 0.25/1000 and 0.50/1000 for two carbonates used in the ring tests. The individual variation for the single participants varied from 0.02 /1000 (dual inlet system) to 0.14/1000 (continuous flow system). The measurement of the difference between two carbonates showed a SD of 0.33/1000 calculated for all participants. Internal precision of IRMS as indicated by the specifications of the different instrument suppliers is < 0.3/1000 for continuous flow systems. In this respect it can be concluded that all participants are working well within the instrument specifications even including sample preparation. Increased overall interlaboratory variation is therefore likely to be due to non-instrumental conditions. It is possible that consistent differences in sample handling leading to isotope fractionation are the causes for interlaboratory variation. Breath analysis does not require sample preparation. As such, interlaboratory variation will be less than observed for the carbonate samples and within the range indicated as internal precision for continuous flow instruments. From this it is concluded that pure analytical interlaboratory variation is acceptable despite the many differences in instrumentation and analytical protocols. Coordinated metabolic studies appear possible, in which different European laboratories perform 13CO2 analysis. Evaluation of compatibility of the analytical systems remains advisable, however.  (+info)

Enzymatic synthesis of natural and 13C enriched linear poly-N-acetyllactosamines as ligands for galectin-1. (6/7271)

As part of a study of protein-carbohydrate interactions, linear N-acetyl-polyllactosamines [Galbeta1,4GlcNAcbeta1,3]nwere synthesized at the 10-100 micromol scale using enzymatic methods. The methods described also provided specifically [1-13C]-galactose-labeled tetra- and hexasaccharides ([1-13C]-Galbeta1,4GlcNAcbeta1,3Galbeta1,4Glc and Galbeta1, 4GlcNAcbeta1,3[1-13C]Galbeta1,4GlcNAcbeta1,3Galbeta 1,4Glc) suitable for NMR studies. Two series of oligosaccharides were produced, with either glucose or N-acetlyglucosamine at the reducing end. In both cases, large amounts of starting primer were available from human milk oligosaccharides (trisaccharide primer GlcNAcbeta1,3Galbeta1, 4Glc) or via transglycosylation from N-acetyllactosamine. Partially purified and immobilized glycosyltransferases, such as bovine milk beta1,4 galactosyltransferase and human serum beta1,3 N- acetylglucosaminyltransferase, were used for the synthesis. All the oligo-saccharide products were characterized by1H and13C NMR spectroscopy and MALDI-TOF mass spectrometry. The target molecules were then used to study their interactions with recombinant galectin-1, and initial1H NMR spectroscopic results are presented to illustrate this approach. These results indicate that, for oligomers containing up to eight sugars, the principal interaction of the binding site of galectin-1 is with the terminal N-acetyllactosamine residues.  (+info)

Documenting the diet in ancient human populations through stable isotope analysis of hair. (7/7271)

Fundamental to the understanding of human history is the ability to make interpretations based on artefacts and other remains which are used to gather information about an ancient population. Sequestered in the organic matrices of these remains can be information, for example, concerning incidence of disease, genetic defects and diet. Stable isotopic compositions, especially those made on isolates of collagen from bones, have been used to help suggest principal dietary components. A significant problem in the use of collagen is its long-term stability, and the possibility of isotopic alteration during early diagenesis, or through contaminating condensation reactions. In this study, we suggest that a commonly overlooked material, human hair, may represent an ideal material to be used in addressing human diets of ancient civilizations. Through the analysis of the amino-acid composition of modern hair, as well as samples that were subjected to radiation (thus simulating ageing of the hair) and hair from humans that is up to 5200 years old, we have observed little in the way of chemical change. The principal amino acids observed in all of these samples are essentially identical in relative abundances and content. Dominating the compositions are serine, glutamic acid, threonine, glycine and leucine, respectively accounting for approximately 15%, 17%, 10%, 8% and 8% of the total hydrolysable amino acids. Even minor components (for example, alanine, valine, isoleucine) show similar constancy between the samples of different ages. This constancy clearly indicates minimal alteration of the amino-acid composition of the hair. Further, it would indicate that hair is well preserved and is amenable to isotopic analysis as a tool for distinguishing sources of nutrition. Based on this observation, we have isotopically characterized modern individuals for whom the diet has been documented. Both stable nitrogen and carbon isotope compositions were assessed, and together provide an indication of trophic status, and principal type (C3 or C4) of vegetation consumed. True vegans have nitrogen isotope compositions of about 7/1000 whereas humans consuming larger amounts of meat, eggs, or milk are more enriched in the heavy nitrogen isotope. We have also analysed large cross-sections of modern humans from North America and Europe to provide an indication of the variability seen in a population (the supermarket diet). There is a wide diversity in both carbon and nitrogen isotope values based at least partially on the levels of seafood, corn-fed beef and grains in the diets. Following analysis of the ancient hair, we have observed similar trends in certain ancient populations. For example, the Coptics of Egypt (1000 BP) and Chinchorro of Chile (5000-800 BP) have diets of similar diversity to those observed in the modern group but were isotopically influenced by local nutritional sources. In other ancient hair (Egyptian Late Middle Kingdom mummies, ca. 4000 BP), we have observed a much more uniform isotopic signature, indicating a more constant diet. We have also recognized a primary vegetarian component in the diet of the Neolithic Ice Man of the Oetztaler Alps (5200 BP). In certain cases, it appears that sulphur isotopes may help to further constrain dietary interpretations, owing to the good preservation and sulphur content of hair. It appears that analysis of the often-overlooked hair in archaeological sites may represent a significant new approach for understanding ancient human communities.  (+info)

NMR studies on the 46-kDa dimeric protein, 3,4-dihydroxy-2-butanone 4-phosphate synthase, using 2H, 13C, and 15N-labelling. (8/7271)

3,4-Dihydroxy-2-butanone 4-phosphate synthase catalyses the release of C-4 from the substrate, ribulose phosphate, via a complex series of rearrangement reactions. The cognate ribB gene of Escherichia coli was hyperexpressed in a recombinant E. coli strain. The protein was shown to be a 46-kDa homodimer by hydrodynamic analysis. A variety of protein samples labelled with different grades of 13C, 15N and 2H, i.e. one with 100% 2H and 15N, one with 75% 2H, 99% 13C, 15N, and one with 100% 2H, 99% 13C,15N were prepared. Despite the large molecular size, 2- and 3-dimensional NMR spectra of reasonable quality were obtained. Attempts at the assignment of individual 13C, 15N and 1H signals show, in principle, the feasibility of structure determination. The number of NMR signals shows unequivocally that the homodimeric protein obeys strict C2 symmetry.  (+info)

C4 grasses form the foundation of warm-climate grasslands and savannas and provide important food crops such as corn, but their Neogene rise to dominance is still not fully understood. Carbon isotope ratios of tooth enamel, soil carbonate, carbonate cements, and plant lipids indicate a late Miocene-Pliocene (8-2 Ma) transition from C3 vegetation to dominantly C4 grasses at many sites around the world. However, these isotopic proxies cannot identify whether the C4 grasses replaced woody vegetation (trees and shrubs) or C3 grasses. Here we propose a method for reconstructing the carbon isotope ratio of Neogene grasses using the carbon isotope ratio of organic matter trapped in plant silica bodies (phytoliths). Although a wide range of plants produce phytoliths, we hypothesize that in grass-dominated ecosystems the majority of phytoliths will be derived from grasses, and will yield a grass carbon isotope signature. Phytolith extracts can be contaminated by non-phytolith silica (e.g., volcanic ash). ...
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The chlorofluorocarbons CFC-11 (CFCl3) and CFC-12 (CF2Cl2) are stable atmospheric compounds that are produced at the earths surface, but removed only at high altitudes in the stratosphere by photolytic reactions. Their removal liberates atomic chlorine that then catalytically destroys stratospheric ozone. For such long-lived compounds, isotope effects in the stratospheric removal reactions have a large effect on their global isotope budgets. We have demonstrated a photolytic isotope fractionation for stable carbon isotopes of CFC-11 and CFC-12 in laboratory experiments using broadband UV-C (190-230 nm) light. 13C/12C isotope fractionations (e) range from (-23.8±0.9) to (-17.7±0.4) ‰ for CFC-11 and (-66.2±3.1) to (-51.0±2.9) \permil for CFC-12 between 203 and 288 K, a temperature range relevant to conditions in the troposphere and stratosphere. These results suggest that CFCs should become strongly enriched in 13C with decreasing mixing ratio in the stratosphere, similar to what has been ...
In the last year, the stable isotope ratio analysis has become a useful tool with many applications in different scientific area. In particular the characteristic isotope signature of materials has permitted to identify authenticity and traceability of food sample and isotope composition has become a valuable marker in environmental studies. This work shows the applicability of analytical methods for isotopic carbon determination in food and environmental samples and the innovative use of δ13C in cultural heritage as valuable tool to trace pollutant fate. The first part is dedicated to the improvement of spectroscopic methods as Fourier Transform Infrared (FT-IR) and Non-Dispersive Infrared spectroscopy (NDIRS) and their application to identify geographical origin in sample like pasta, cocoa, olive oil. The results conducted in order to assess the robustness of the two alternative methods respecting IRMS showed a strong correlation like a demonstration of the positive relationship between the ...
Lakes are a source of methane, an important greenhouse gas in the atmosphere. In order to understand increasing methane emissions in the present, it is important to study the variations of methane release during past periods of climate change. However, records of methane release from lakes over time scales longer ... read more than a few years are extremely rare. In this thesis a method is explored to reconstruct past methane availability in lakes based on the stable carbon isotope composition (delta 13C) of aquatic invertebrate remains. Methane-derived 13C-depleted carbon can be an alternative carbon source to plant-derived material for invertebrates in the sediment and water column of lakes, that can lead to markedly depleted delta 13C values in invertebrate tissues. Using culturing experiments, it was demonstrated that methane-derived carbon is incorporated into chironomid head capsules. Also, it was shown that chemical pre-treatments that are commonly used for sediment processing do not have ...
RATIONALE: Recent advances in stable isotope probing (SIP) have allowed direct linkage of microbial population structure and function. This paper details a new development of SIP, Stable Isotope Switching (SIS), which allows the simultaneous assessment of carbon (C) uptake, turnover and decay, and the elucidation of soil food webs within complex soils or sedimentary matrices. METHODS: SIS utilises a stable isotope labelling approach whereby the 13C-labelled substrate is switched part way through the incubation to a natural abundance substrate. A 13CH4 SIS study of landfill cover soils from Odcombe (Somerset, UK) was conducted. Carbon assimilation and dissimilation processes were monitored through bulk elemental analysis isotope ratio mass spectrometry and compound-specific gas chromatography/combustion/isotope ratio mass spectrometry, targeting a wide range of biomolecular components including: lipids, proteins and carbohydrates. RESULTS: Carbon assimilation by primary consumers (methanotrophs) ...
is a valuable tracer for studying the processes controlling the autotrophic (FRa) and heterotrophic (FRh) contributions to ecosystem respiration (FR) and the influence of photosynthesis on FR. There is increasing interest in quantifying the temporal variability of the carbon isotope composition of ecosystem respiration (δR) because it contains information about the sources contributing to respiration and is an important parameter used for partitioning net ecosystem CO2 exchange using stable isotope methods. In this study, eddy covariance, flux gradient, automated chambers, and stable carbon isotope techniques were used to quantify and improve our understanding of the temporal variability in FR and δR in a C3/C4agricultural ecosystem. Six years (2004-2009) of isotope flux-gradient measurements indicated that δR had a very consistent annual pattern during both C3 (soybean) and C4(corn) growing seasons due to significant contributions from FRa, which was strongly influenced by the isotope ...
The data presented here comprise Ryazanian-Valanginian carbon isotope ratios analyzed from fossil wood and belemnites from the shallow marine Boyarka River succession in Siberia. Additional belemnite carbon isotope ratios from the Izhma River succession (also Ryazanian-Valanginian) in Russia are also presented. The wood-derived and belemnite-derived isotope ratios are considered to primarily reflect changes in the terrestrial and marine carbon isotope reservoirs respectively. The δ13Ccarb and δ13Cwood records reveal a distinct mid-Valanginian positive carbon isotope excursion, with the initiation occurring near the Boreal Russian michalskii-polyptychus zone boundary, which is broadly time-equivalent Tethyan campylotoxus-verrucosum boundary. The Ryazanian-Valanginian δ13Ccarb values fluctuate between c. −1 and +1.5‰ but reach a maximum of +4.1‰ in the Late Valanginian, whilst the δ13Cwood values fluctuate between c. −27 and −23.5‰ and reach a Late Valanginian maximum of ...
Semantic Scholar extracted view of Forensic Examination of Australian Papers Using Isotope Ratio Mass Spectrometry by Kylie Jones et al.
Background:You are what you eat is an accurate summary for humans and animals when it comes to carbon isotope abundance. In biological material, natural13C/12C ratio is subject to minute variations due to diet composition (mainly from ingestion of C3 and C4 metabolism plants) and to the discrimination between light and heavy isotopes during biochemical reactions (isotope effects and isotopic fractionation).Methodology/Principal Findings:Carbon isotopic abundance was measured in ZDF (fa/+) and ZDF (fa/fa), (lean and obese-diabetic rats respectively) fed the same diet. By analysing plasma metabolites (glucose and non-esterified fatty acids), breath and liver tissue by high-precision isotope ratio mass spectrometry, we demonstrate for the first time statistically distinguishable metabolic carbon isotope abundance between ZDF (fa/+) and ZDF (fa/fa) rats based on plasma glucose, palmitic, oleic, linoleic, arachidonic acids and bulk analysis of liver tissue (P|0.005) resulting into clear isotopic
Supplemental material: Oxygen and Carbon Isotopic Composition of Silurian Brachiopods: Implications for Coeval Seawater and Glaciations
Oxygen and carbon isotope ratios were measured for hydrothermal minerals (silica, clay and calcite) from fractures and vugs in altered rhyolite, located between 28 and 129 m below surface (in situ temperatures ranging from 81 to 199??C) in Yellowstone drill holes. The purpose of this study was to investigate the mechanism of formation of these minerals. The ??18O values of the thirty-two analyzed silica samples (quartz, chalcedony, ??-cristobalite, and ??-cristobalite) range from -7.5 to +2.8???. About one third of the silica 7samples have ??18O values that are consistent with isotopic equilibrium with present thermal waters; most of the other silica samples appear to have precipitated from water enriched in 18O (up to 4.7???) relative to present thermal water, assuming precipitation at present in situ temperatures. Available data on fluid-inclusion homogenization temperatures in hydrothermal quartz indicate that silica precipitation occurred mostly at temperatures above those measured during drilling
The concept of metabolic compartmentation describes the presence in a tissue of functionally different and chemically distinct pools of a given substrate. These separate pools equilibrate only very slowlyt if at a11, and exhibit different turnover and flux rates. Such heterogeneous functional pools of amino acids were coming under investigation in microorganisms (Britten et al. 1955; Cowie, Walton 1956; Cowie, McClure 1959), plants (Steward et al. 1956; Maclennan et al. 1963), and animal tissues (Korner, Tarver 1957; Green, Lowther 1959; Kipnis et al. 1961) at about the same time that we began our studies on glutamate-glutamine metabolism in brain. The first reference to the term metabolic compartmentstion trat we have noted is in the work of Stuart et al. (1956). In their studies on the carrot root explant, they found that glutamic acid derived from [U-l4C]glutamine had a higher specific activity (counts/min/μmol, SA) than the glutamine isolated from the tissue, a situation opposite to that which
The 2nd Annual USADA Symposium on Anti-Doping Science was to discuss the use of GC-C-IRMS in the identification of exogenous substances entering the native metabolic pool.
Thomas Whelan, Harry H. Roberts; Carbon isotope composition of diagenetic carbonate nodules from freshwater swamp sediments. Journal of Sedimentary Research ; 43 (1): 54-58. doi: https://doi.org/10.1306/74D726DF-2B21-11D7-8648000102C1865D. Download citation file:. ...
Background/Question/Methods. The partitioning of net ecosystem exchange of CO2 (NEE) measured via the eddy covariance technique into gross photosynthesis (GPP) and ecosystem respiration (Reco) can be challenging and is often associated with unknown amounts of uncertainty. In order to estimate GPP from NEE, typically nighttime measurements of Reco are extrapolated to the day using a temperature function. Then Reco is subtracted from NEE to obtain GPP (i.e., GPP = NEE - Reco). However, recent evidence employing stable carbon isotopes of CO2 has shown that this practice can strongly overestimate GPP and Reco, from 10-100%. This is due to reduced leaf respiration during the day, aka the Kok effect. One key parameter for partitioning NEE using stable carbon isotopes is the isotopic composition of carbon respiration by the ecosystem, δ13Cr. δ13Cr is typically estimated using a Keeling plot with nighttime data either sampled via a profile method or single-inlet sampling where measurements are ...
The stable carbon isotopic analysis of tree-rings for environmental, plant physiological and archaeological applications using conventional methods is occasionally limited by physical constraints (narrow rings) or administrative concerns (requirement for non-destructive sampling) that prevent researcher access to scientifically valuable wood samples. Analysis of such archives by laser-ablation can potentially address these issues and facilitate access to restricted archives. Smaller quantities of wood are required for analysis by laser ablation, hence the approach may be considered less-invasive and is virtually non-destructive compared to standard preparation methods. High levels of intra-annual isotopic variability reported elsewhere mean that a single measurement may not faithfully represent the inter-annual isotopic signal, so before such an approach can be used with confidence it is necessary to compare the stable carbon isotopic data produced using these two methods. This paper presents ...
Hoins, M. , Eberlein, T. , Van de Waal, D. B. , Sluijs, A. , Reichart, G. J. and Rost, B. (2016): CO2-dependent carbon isotope fractionation in dinoflagellates relates to their inorganic carbon fluxes , Journal of Experimental Marine Biology and Ecology ...
Steude, J. S., C.P. Sullivan, R. C. Chaney, M. McKee, L. E. OShea. 1990. "Tracer Experiments in Saturated Sand by Computed Tomography and Inductively Coupled Plasma," Physico-Chemical Aspects of Soil and Related Materials, ASTM STP 1095, K. B. Hoddinott and R.O. Lamb, Eds., American Society for Testing and Materials, Philadelphia, 1990, pp. 171-184.. ...
Los Gatos Research is developing a simple robust methodology for the determination of carbon isotope ratios in small gas samples. This new measurement scheme is inherently compact and rugged and offers a great potential for adaptation into space vehicles. With such a sensitive method of accurately determining carbon isotope levels we hope to significantly advance the prospects for making in-situ tests for evidence of life on nearby planets, such as Mars. The isotope ratio is known to be a sensitive indicator of biologic activity. The new innovative advancement we propose to make will make such measurements potentially much easier than currently possible. We will demonstrate the new absorption analysis technique at wavelengths of 1.5 microns in Phase I and demonstrate that the approach can be used to record the relative isotopic abundance of carbon 12 and 13 with great accuracy ...
The ratio of 13C to 12C in marine sedimentary rocks holds important clues to the evolution of the carbon cycle through Earth history. Isotopic analyses are traditionally carried out using isotope ratio mass spectrometry (IRMS), but this technique is labor-intensive, expensive and requires expert know-how. He
ABSTRACT: In freshwater food webs, a substantial contribution of methane-derived carbon for the nutrition of larvae of the macroinvertebrate species Chironomus plumosus has been proposed from stable carbon isotope analysis. We investigated if the larvae feed on methanogenic Archaea or methane-oxidising bacteria (MOB), and whether the carbon transfer is based on digestion of the microbial biomass or on a symbiotic relationship. Fluorescence in situ hybridisation (FISH) with larval tissue thin sections showed that the larvae are not inhabited by methanogens or MOB as symbionts or part of their tissue and gut microflora. Furthermore, clone libraries for the bacterial 16S rRNA gene from larval tissue and comparative denaturing gradient gel electrophoresis (DGGE) of sediment and larval DNA samples showed that the eubacterial community present in the larval gut is dominated by anaerobic and facultatively anaerobic bacteria, whereas MOB were only rarely found. Additionally, comparative quantitative PCR ...
D7026-13 Standard Guide for Sampling and Reporting of Results for Determination of Biobased Content of Materials via Carbon Isotope Analysis carbon content~ carbon isotope analysis~
Abstract Mud gas data represent the first breath of a well being drilled. However, despite significant progress in technology, techniques and theoretical understanding of mud gas detection and analysis, such data are still largely under-utilized b
A survey of Mesozoic organic-rich shales in space and time indicates that they are widely distributed through much of the era but are concentrated especially at two levels: Upper Jurassic (Kimmeridgian-Volgian/Tithonian) and Middle Cretaceous (Aptian-Turonian). Stable carbon isotope studies prove to be a particularly useful tool in both palaeoenvironmental and diagenetic analysis. Anoxic events in the ocean may be characterized by high concentrations of δ13 carbonate carbon. The carbon isotope values obtained may, however, reflect diagenesis in the sulphate reduction zone rather than conditions in the original sea water. Calcite concretions formed at successive stages in diagenesis may record a change from strongly negative to strongly positive values of δ13C, indicating a switch from the sulphate-reduction to the fermentation zone.. Analysis of benthic palaeoecology leads to a classification of marine mudrocks into barren laminite, shelly laminite, shelly shale and shelly mudstone, of which ...
Potter KE, Ono S, Prinn RG. 2013. Fully automated, high-precision instrumentation for the isotopic analysis of tropospheric N2O using continuous flow isotope ratio mass spectrometry.. Rapid communications in mass spectrometry : RCMRapid communications in mass spectrometry : RCM. 27(15):1723-38. ...
Deep continental subsurface fracture water systems, ranging from 1.1 to 3.3 km below land surface (kmbls), were investigated to characterize the indigenous microorganisms and elucidate microbial carbon sources and their cycling. Analysis of phospholipid fatty acid (PLFA) abundances and direct cell counts detected varying biomass that was not correlated with depth. Compound-specific carbon isotope analyses (δ13C and Δ14C) of the phospholipid fatty acids (PLFAs) and carbon substrates combined with genomic analyses did identify, however, distinct carbon sources and cycles between the two depth ranges studied. In the shallower boreholes at circa 1 kmbls, isotopic evidence indicated microbial incorporation of biogenic CH4 by the in situ microbial community. At the shallowest site, 1.05 kmbls in Driefontein mine, this process clearly dominated the isotopic signal. At slightly deeper depths, 1.34 kmbls in Beatrix mine, the isotopic data indicated the incorporation of both biogenic CH4 and dissolved ...
BACKGROUND: Improvement of water-use efficiency (WUE) can effectively reduce production losses caused by drought stress. A better understanding of the genetic determination of WUE in crops under drought stress has great potential value for developing cultivars adapted to arid regions. To identify the genetic loci associated with WUE and reveal genes responsible for the trait in apple, we aim to map the quantitative trait loci (QTLs) for carbon isotope composition, the proxy for WUE, applying two contrasting irrigating regimes over the two-year experiment and search for the candidate genes encompassed in the mapped QTLs. RESULTS: We constructed a high-density genetic linkage map with 10,172 markers of apple, using single nucleotide polymorphism (SNP) markers obtained through restriction site-associated DNA sequencing (RADseq) and a final segregating population of 350 seedlings from the cross of Honeycrisp and Qinguan. In total, 33 QTLs were identified for carbon isotope composition in apple under ...
Thermo Delta Plus Isotope Ratio Mass Spectrometer used extensively for the measurement of 2H/1H in water using a chromium reduction inlet. This magnetic sector instrument is optimized for hydrogen isotope ratio analysis of water samples between 0.2 and 1 g, although analysis of samples as small as 1 uL can be performed. The precision of the d2H measurement is 0.5 permil or 0.08 ppm.. Thermo Delta V Isotope Ratio Mass Spectrometer used extensively for the measurement of 13C/12C, 15N/14N, 18O/16O. The instrument is equipped with gas bench and elemental analyzer inlets. The gas bench is used for measurement of 13C/12C in carbon dioxide, and 18O/16O in water by equilibration with carbon dioxide. Specimen size for carbon dioxide is 0.05 mL (STP) and water is 1 g. Precisions are d13C = 0.1 permil (1 ppm) and d18O = 0.1 permil (0.06 ppm). The elemental analyzer is used for bulk sample analysis of 13C/12C and 15N/14N. Sample size is 0.5 mg of organic material. Precisions are d13C = 0.1 permil (1 ppm) ...
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At the Curití Quarry, Eastern Cordillera of Colombia, a 23.35 m section includes a 6.3 m interval of organic-rich marlstones, calcareous clay-shales and clay-shales devoid of benthic fossils and bioturbation, at the base of the Paja Formation. It overlies carbonate ramp deposits of the Rosablanca Formation, with the topmost layer containing reworked and phosphatized assemblages of middle Barremian to lowest Aptian ammonites of the genera Pulchellia, Gerhardtia, Toxancycloceras, Karsteniceras and Prodeshayesites. High-resolution analyses of the section, including total inorganic carbon (TIC, 0.09-50 wt%), total organic carbon (TOC, up to 8.4%) and stable carbon isotope measurements (δ13Corg between −22.05‰ and −20.47‰) allow the determination of the stratigraphic relationship between the organic-rich level within the Paja Formation and Oceanic Anoxic Event-1a (OAE-1a). The range of values and the overall pattern of the δ13Corg curve are comparable with the Lower Aptian interval C7. ...
This series of activities is designed to introduce students to the role of sediments and sedimentary rocks in the global carbon cycle. Students learn how stable carbon isotopes can be used to reconstruct ancient sedimentary environments. Students will make some simple calculations, formulate hypotheses, and think about the implications of their results. The activity includes an optional demonstration of the density separation of a sediment sample into a light, organic fraction and a heavier, mineral fraction.. ...
This series of activities is designed to introduce students to the role of sediments and sedimentary rocks in the global carbon cycle. Students learn how stable carbon isotopes can be used to reconstruct ancient sedimentary environments. Students will make some simple calculations, formulate hypotheses, and think about the implications of their results. The activity includes an optional demonstration of the density separation of a sediment sample into a light, organic fraction and a heavier, mineral fraction.. ...
Deng J, McCalley CK, Frolking S, Chanton J, Crill P, Varner R, Tyson GW, Rich V, Hines M, Saleska SR et al.. 2017. Adding stable carbon isotopes improves model representation of the role of microbial communities in peatland methane cycling. Journal of Advances in Modeling Earth Systems. 9(2):1412-1430. ...
Oxygen and carbon isotopic compositions have been determined from the belemnite genera Acroteuthis and Hibolites sampled from the early Cretaceous (Ryazanian-Hauterivian) interval of the Speeton Clay Formation, Filey Bay, England. The Speeton Clay Formation consists of a series of claystones and calcareous mudrocks deposited in an epicontinental sea. delta(18)O values from belemnites, which met petrographic and chemical criteria for well preserved skeletal carbonate, indicate warm marine palaeotemperatures (c. 12-15 degrees C) for much of the early Valanginian whilst cool temperatures (,9 degrees C) are inferred for the earliest Hauterivian. During the remainder of the Hauterivian, temperatures fluctuated considerably and rose to a maximum of 15.5 degrees C. Changes in kaolinite and smectite abundances, considered to reflect humid and arid phases of climate, correlate with warm and cool episodes. The palaeotemperature record, appears to contradict evidence from cephalopod faunas, which show a ...
Use the "nitrogen tree": Turn heat on high. Set pressure regulator on tank to 2-4 psi. Flow gauge should read 8 L/min for two samples. Clean capillary tips with ethanol, unscrew white plastic, move metal shaft down (may need to wipe with ethanol to allow this), insert capillary tip into glass sample vial (close to liquid but not touching), screw plastic threading back to lock the metal shaft in place. Leave heating block on. Move sample vial up hourly as liquid evaporates ...
Use the "nitrogen tree": Turn heat on high. Set pressure regulator on tank to 2-4 psi. Flow gauge should read 8 L/min for two samples. Clean capillary tips with ethanol, unscrew white plastic, move metal shaft down (may need to wipe with ethanol to allow this), insert capillary tip into glass sample vial (close to liquid but not touching), screw plastic threading back to lock the metal shaft in place. Leave heating block on. Move sample vial up hourly as liquid evaporates ...
carbon isotope ratio: A measure of the proportion of the carbon-14 isotope to the carbon-12 isotope. Living material contains carbon-14 and carbon-12 in the same ...
松本 公平 , 山田 桂太 , 奈良岡 浩 , 石渡 良志 質量分析 = Mass spectroscopy 45(6), 641-648, 1997-12-01 J-STAGE 参考文献22件 被引用文献1件 ...
Tenders Electronic Daily (TED) − the European public procurement journal. 192932-2017 - Belgium-Geel: Supply and maintenance of an elemental analyser - isotope ratio mass spectrometer (EA-IRMS)
The idea that mitochondrial metabolism of glucose generates important signals for insulin secretion has been supported by various kinds of experiments for many years (23-25). However, the specific metabolic pathways in mitochondria that participate in the generation of coupling factors for insulin secretion remains uncertain.. The approach that we have taken to this problem is apply the tool of NMR-based metabolic analysis to our robustly and poorly glucose-responsive INS-1−derived cell lines (22). Four independent cell lines with clearly distinguishable capacities for GSIS were incubated with varying concentrations of [U-13C]glucose, followed by NMR-based mass isotopomer analysis of extracted glutamate. Measurements of GSIS were performed on the same set of cells used for NMR analysis. As shown in Fig. 3, we observed a tight correlation between PC-catalyzed pyruvate cycling activity and GSIS in the four cell lines. In contrast, entry of pyruvate into the TCA cycle via PDH did not correlate ...
13CFLUX is a universal software toolkit to quantify in-vivo metabolic activities in living cells comprising facilities for simulation, flux estimation statistical analysis and experimental design of 13C-labeling experiments.
A short-term simulated weathering experiment was performed on two crude oils and two heavy fuel oils under natural conditions to evaluate the effects of natural weathering processes by using gas chromatography mass spectrometry combined with gas chromatography isotopic ratio mass spectrometry. The results of diagnostic ratios of n-alkanes show that only odd to even predominance (OEP1, OPE2) and carbon preference index (CPI) remain stabilized during the 28 d weathering process, but they cannot effectively distinguish the four types of oils. Statistical analyses based on paired sample t-test and principal component analysis (PCA) revealed that stable carbon isotope compositions of n-alkanes in the four studied oils have no significant changes over the weathering time, and that the carbon isotope discrimination (Delta delta C-13) of n-alkanes is , 3 parts per thousand. We have provided evidence that the stable carbon isotope compositions of n-alkanes compared to n-alkanes diagnostic ratios ...
Helichrysum italicum (Roth) G. Don fil. subsp. italicum oils, coming from Sicily and Corsica and growing up, at equal geographical area, at the same edaphic and climatic conditions, were investigated by GC-MS, GC-FID and gas chromatography carbon isotope ratio mass spectrometry (GC-C-IRMS). GC-MS and GC-FID analyses on the oils terpene fraction have evidenced two different compositional finger prints (chemotypes). Investigating the carbon isotope ratio of the main and common terpene compounds, were also highlighted different plants genetic behaviors. The i-stds elaboration has permitted to investigate on the plants genetic changes, taking into account only the secondary biogenetic pathways, in which the terpenes formation occurs ...
We used stable carbon isotopes to analyse individual variation in arctic fox diet. We extracted collagen from bones (the lower jaw), and measured stable carbon isotopes. The foxes came from three different localities: Iceland, where both microtines and reindeer are rare; west Greenland, where microtines are absent; and Sweden, where seat analyses showed the primary food to be microtine rodents and reindeer. The Icelandic samples included foxes from both coastal and inland habitats, the Swedish sample came from an inland area, and the Greenland sample from coastal sites. The spatial variation in the isotopic pattern followed a basic division between marine and terrestrial sources of protein. Arctic foxes from inland sites had delta(13)C values of -21.4 (Ice land) and -20.4 parts per thousand (Sweden), showing typical terrestrial values. Coastal foxes from Greenland had typical marine Values of -14.9 parts per thousand, whereas coastal foxes from Iceland had intermediate values of -17.7 parts per ...
The increasing number of bomb attacks involving improvised explosive devices, as well as the nature of the explosives, give rise to concern among safety and law enforcement agencies. The substances used in explosive charges are often everyday products diverted from their primary licit applications. Thus, reducing or limiting their accessibility for prevention purposes is difficult. Ammonium nitrate, employed in agriculture as a fertiliser, is used worldwide in small and large homemade bombs. Black powder, dedicated to hunting and shooting sports, is used illegally as a filling in pipe bombs causing extensive damage. If the main developments of instrumental techniques in explosive analysis have been constantly pushing the limits of detection, their actual contribution to the investigation of explosives in terms of source discrimination is limited. Forensic science has seen the emergence of a new technology, isotope ratio mass spectrometry (IRMS), that shows promising results. Its very f
Stable carbon isotope analyses of the humin fraction of the soil organic matter were conducted on more than 160 soil profiles from Tikal, Guatemala. The profiles were collected from near areas associated with the earthworks of Tikal; an ancient ditch and parapet construction hypothesized to have formed ancient boundaries of the polity. In addition to the isotope analyses, the physical and chemical characteristics of the horizons were determined. Maize, a C4 plant, formed an integral part of the ancient Maya diet and is the only known C4 plant cultivated by the Maya. Prior to and subsequent to the ancient Maya occupation of Tikal, the landscape was dominated by C3 forest vegetation. Over the centuries C4 plant biomass including rhizodeposition decomposed to form soil organic matter that contains a distinct C4 signature reflecting the vegetation history of the area. Forested areas anciently cleared for agriculture were identified through interpretation of significant isotopic shifts that signaled past
The major source of carbon to the bacterial community in a seagrass (Thalassia testudinum) dominated region of Lower Laguna Madre, Texas was determined with the isotopic composition of bacterial phospholipid fatty acids. Rough estimates of bacterial abundance were also obtained from total phospholipid fatty acid concentrations. Core samples came from three differing habitat types consisting of a bare area, a transitional area, and a vegetated area. Five depth intervals of 0-0.5 cm, 0.5-2.5 cm, 4.5-6.5 cm, 8.5-10.5 cm, and 18.5-20.5 cm from each core were used for analyses. Bacterial abundance was significantly higher in the vegetated habitat compared with bare or transitional habitats, which showed little difference from one another. The stable carbon isotope ratios ([ð]¹³C) of branched chain fatty acids, iso- and anteiso-15:0 (i&a15:0) found only in bacteria were used to assess carbon utilization. The [ð]¹³C of total organic carbon (TO¹³C) and the ubiquitous fatty acid 16:0 were used as ...
Carbon isotope effects were investigated for the reaction catalyzed by the glycine decarboxylase complex (GDC; EC 2.1.2.10). Mitochondria isolated from leaves of pea (Pisum sativum L.) and spinach (Spinacia oleracea L.) were incubated with glycine, and the CO2 evolved was analyzed for the carbon isotope ratio (delta C-13). Within the range of parameters tested (temperature, pH, combination of cofactors NAD(+), ADP, pyridoxal 5-phosphate), carbon isotope shifts of CO2 relative to the C-1-carboxyl carbon of glycine varied from +14 parts per thousand to -7 parts per thousand. The maximum effect of cofactors was observed for NAD(+), the removal of which resulted in a strong C-12 enrichment of the CO2 evolved. This indicates the possibility of isotope effects with both positive and negative signs in the GDC reaction. The measurement of delta C-13 in the leaves of the GDC-deficient barley ( Hordeum vulgare L.) mutant (LaPr 87/30) plants indicated that photorespiratory carbon isotope fractionation, ...
We investigated the relationships between foliar stable carbon isotope discrimination (Delta), % foliar N, and predawn water potentials ((water potential symbol)pd) and midday stomatal conductance (g(s)) of Larrea tridentata across five Mojave Desert soils with different age-specific surface and sub-surface horizon development and soil hydrologies. We wished to elucidate how this long-lived evergreen shrub optimizes leaf-level physiological performance across soils with physicochemical characteristics that affect the distribution of limiting water and nitrogen resources. We found that in young, coarse alluvial soils that permit water infiltration to deeper soil horizons, % foliar N was highest and Delta, g(s) and psgrpd were lowest, while %N was lowest and Delta, g(s) and (water potential symbol)pd were highest in fine sandy soils; Larrea growing in older soils with well-developed surface and sub-surface horizons exhibited intermediate values for these parameters. Delta showed negative linear
Across a wide range of environmental conditions, forest types and tree species we found carbon isotope ratios of wood to be a strong and reliable indicator of past drought occurrence (Fig. 2a). However, despite this clear physiological signal of drought on δ13C, we only found a weak and context-dependent effect of these same drought events on tree growth (Fig. 2b). Previous studies have suggested that the relationship between carbon isotopes and growth might not be a simple one (Ferrio et al. 2003; Peñuelas et al. 2008; Jansen et al. 2013; Hentschel et al. 2016; Shestakova et al. 2017), but to our knowledge none had explored the relationship across a broad enough range of species and environmental conditions to draw this conclusion robustly. The relatively small declines in growth we observed in response to drought suggest that most European tree species are - on average - able to maintain growth under conditions of low soil water availability.. This is not to say that water availability is ...
Enamel stable carbon isotope analyses were conducted on the large fossil ape Gigantopithecus blacki and an associated mammalian megafauna from Longgudong Cave in Jianshi and Juyuandong Cave in Liuchen
NUCLEAR MAGNETIC RESONANCE IMAGING + NUCLEAR MAGNETIC RESONANCE TOMOGRAPHY (MEDICAL DIAGNOSTICS); NMR-MIKROSKOPIE, NMR-ABBILDUNDSVERFAHREN; CARBON-13 NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY; NUTRITION + NUTRITIONAL SCIENCE; BONE MARROW (CYTOLOGY, HISTOLOGY); KNOCHENMARK (CYTOLOGIE, HISTOLOGIE); ERNÄHRUNG + ERNÄHRUNGSWISSENSCHAFT; FETTSÄUREN (BIOCHEMIE); FATTY ACIDS (BIOCHEMISTRY); MUSKELZELLEN (CYTOLOGIE, HISTOLOGIE); KOHLENSTOFF-13-KERNRESONANZSPEKTROSKOPIE; KERNSPINRESONANZ-ABBILDUNGSVERFAHREN + KERNSPINRESONANZ-TOMOGRAPHIE (MEDIZINISCHE DIAGNOSTIK); MUSCLE CELLS (CYTOLOGY, HISTOLOGY); NMR MICROSCOPY, NMR ...
TY - GEN. T1 - Carbon isotope signatures and their possible link to upwelling, Middle Mississippian crinoidal-bryozoan carbonates, Illinois Basin. AU - Lasemi, Z.. N1 - hand-typed from author-received information. PY - 2018. Y1 - 2018. KW - ISGS. M3 - Conference contribution. SP - 88. BT - Book of Abstracts. CY - Quebec City, Canada. ER - ...
0057] The presence of 14C, the content of biomaterial, the content of biocarbon or the content of organic carbon of renewable origin of a material is determined on the basis of standards ASTM D 6866 (ASTM D 6866-06) and ASTM D 7026 (ASTM D 7026-04). Standard ASTM D 6866 relates to "Determining the Biobased Content of Natural Range Materials Using Radiocarbon and Isotope Ratio Mass Spectrometry Analysis", whereas standard ASTM D 7026 relates to "Sampling and Reporting of Results for Determination of Biobased Content of Materials via Carbon Isotope Analysis". The second standard refers in its first paragraph to the first standard. The first standard describes a test for measuring the 14C/12C ratio of a sample and compares it with the 14C/12C ratio of a reference sample of 100% renewable origin, to give a relative percentage of C of renewable origin in the sample. The standard is based on the same concepts as 14C dating, but without applying dating equations. The ratio thus calculated is designated ...
Scheele, N. and Hoefs, J. (1992): Carbon isotope fractionation between calcite, graphite and CO2 an experimental study , Contrib Mineral Petrol ...
We present new carbon and oxygen isotope curves from sections in the Bakony Mts. (Hungary), constrained by biostratigraphy and magnetostratigraphy in order to evaluate whether carbon isotopes can provide a tool to help establish and correlate the last system boundary remaining undefined in the Phanerozoic as well provide data to better understand the carbon cycle history and environmental drivers during the Jurassic-Cretaceous interval. We observe a gentle decrease in carbon isotope values through the Late Jurassic. A pronounced shift to more positive carbon isotope values does not occur until the Valanginian, corresponding to the Weissert event. In order to place the newly obtained stable isotope data into a global context, we compiled 31 published and stratigraphically constrained carbon isotope records from the Pacific, Tethyan, Atlantic, and Boreal realms, to produce a new global δ13C stack for the Late Oxfordian through Early Hauterivian interval. Our new data from Hungary is consistent ...
The Waikato Stable Isotope Unit (WSIU) offers precision analyses of isotopes of carbon and nitrogen in biological, geological, and chemical materials by isotope ratio mass spectrometry. Isotopic abundance analysis is carried out on two fully automated Europa Scientific 20/20 isotope analysers. Materials may be submitted as solids, liquids, or gases, for example, for breath analyses. Precision analyses of carbon and nitrogen content in solid or liquid samples are also provided with a LECO TruSpec Carbon/Nitrogen Determinator fitted with an autosampler for liquids.. The WSIU provides commercial analyses and also services the needs of scientists at the University of Waikato and their collaborators, promoting the use of stable isotopes in all branches of research. Staff are highly experienced in the use of stable isotopes, both natural abundance and enriched tracers, particularly in biological and environmental research. In 2006 the WSIU was accredited by the International Atomic Energy Agency for ...
Fossils of many species are common all the way across the landscape," Ambrose said. "But this species is missing in action from the east side of the distribution.". Isotopic analysis of teeth found on the site gave a more complete picture of the habitat of the animals that lived and died there, Ambrose said.. "The distribution of plant carbon isotope ratios conveniently separates out grasslands from forests," he said. "And it also separates out grazing animals, like zebras, from browsing animals that eat the leaves off of trees, like giraffes.". The distribution of the fossil browsers and grazers echoed that of the habitat, he said.. "On the west we find lots of Ardipithecus fossils and theyre associated with a lot of woodland and forest animals," he said. "And then theres a break; Ardipithecus and most of the monkeys that live in trees disappear, and grass-eating animals become more abundant.". The carbon isotope ratios of the Ardipithecus teeth also tell the story of a woodland creature, he ...
Håkon Mosby Mud Volcano (HMMV, SW Barents Sea slope, 1280 m) is one of the numerous cold methane-venting seeps existing along the continental margins. Analyses of videoguided core samples revealed extreme differences in the diversity and density of the metazoan meiobenthic communities associated with the different sub-habitats (centre, microbial mats, Pogonophora field, outer rim) of this mud volcano. Diversity was lowest in the sulphidic, microbial mat sediments that supported the highest standing stock, with unusually high densities (11 000 ind. 10 cm-2) of 1 nematode species related to Geomonhystera disjuncta. Stable carbon isotope analyses revealed that this nematode species was thriving on chemosynthetically derived food sources in these sediments. Ovoviviparous reproduction has been identified as an important adaptation of parents securing the survival and development of their brood in this toxic environment. The proliferation of this single species in exclusive association with ...
We measure stable isotope ratios of carbon and nitrogen in organic matrix using conventional isotope ratio mass spectrometers. For a price offer, please contact the corresponding network partner. Animal tissue: --, Dr. Christian C. Voigt at: [email protected] Plant material: --, Dr. Zachary Kayler at: [email protected] Historic samples --, Dr. Ulrich Struck at: [email protected] ...
The Chrono Centre undergo Isotope Ratio Mass Spectrometry (EA-IRMS) using a Thermo Delta V Advantage IRMS machine and accompanying Flash 112 elemental analyser.
All 3795 co-registered samples were analyzed for their soluble major anion content (Cl-, NO3-, SO42-) by ion chromatography (IC) and for trace elements (Na, Mg, Ca, Sr, Cd, Cs, Ba, La, Ce, Pr, Pb, Bi, U, As, Al, S, Ti, V, Cr, Mn, Fe, Co, Cu, Zn) by inductively coupled plasma sector field mass spectrometry (ICP-MS). Major anions were analyzed on a Dionex DX-500 ion chromatograph coupled to a Gilson autosampler, and concentrations are reported in ug/L (ppb). Trace elements analyses were performed with the University of Maine Thermo Electron Element2 ICP-MS coupled to a Cetac Model ASX- 260 autosampler. Isotopes were measured in low and medium resolution (GIVE range ppt-ppq). The ICP-MS samples were acidified to 1% with double-distilled HN03 under a class-100 High Efficiency Particle Air (HEPA) clean bench and allowed to react with the acid for approximately 1 week before being frozen. Approximately every fifth sample (713 total) was analyzed for dD by isotope ratio mass spectrometry (IRMS) using a ...
As most of the uses of plants are intimately linked to their metabolic output or activity, there is a renewed interest in understanding the behavior and regulation of plant metabolic networks. The only direct measure of metabolic activity, and the facet most closely related to biological function, is flux through the metabolic network (Libourel and Shachar-Hill, 2008). There has been a considerable research effort in the last few years to develop and refine methods that allow fluxes in large metabolic networks to be determined. The best established of these methods, steady-state metabolic flux analysis (MFA), involves measuring the redistribution of a supplied stable isotope, usually 13C, at metabolic and isotopic steady state (Ratcliffe and Shachar-Hill, 2006; Allen et al., 2009a). Flux maps of a range of heterotrophic plant cells and tissues have been produced, providing information on the operation of different flux modes (Sriram et al., 2004, 2007; Schwender et al., 2006; Allen et al., ...
STICKSTOFFORGANISCHE UMWELTSCHADSTOFFE; ABBAU, ZERSETZUNG, UMWANDLUNG, PERSISTENZ VON UMWELTSCHADSTOFFEN (UMWELTPROBLEME); TRIAZIN-DERIVATE (PESTIZIDWIRKSTOFFE); REDUKTION (CHEMISCHE REAKTIONEN); PHOTOCHEMISCHE REAKTIONEN (CHEMISCHE REAKTIONEN); ISOTOPIEEFFEKT (CHEMISCHE KINETIK); STICKSTOFF-15-ISOTOP; NITROGEN ORGANIC ENVIRONMENTAL POLLUTANTS; DEGRADATION, DECOMPOSITION, TRANSFORMATION, PERSISTENCE OF POLLUTANTS (ENVIRONMENTAL PROBLEMS); TRIAZINE-DERIVATIVES (PESTICIDE AGENTS); REDUCTION (CHEMICAL REACTIONS); PHOTOCHEMICAL REACTIONS (CHEMICAL REACTIONS); ISOTOPE EFFECT (CHEMICAL KINETICS); NITROGEN-15- ...
The first one is the mineralogical and geochemical investigation of ore and non-ore deposits in Slovakia and elsewhere in the World. Traditional analytical methods (electron probe micro-analysis, X-ray diffraction) are employed to characterize raw and dump materials mineralogically, chemically and structurally. Apart from this, fluid inclusion microthermometry, isotope ratio mass spectrometry combined with thermodynamic modeling are employed to decipher age and formation conditions of raw materials. This approach was applied to genetic studies of polymetallic ore deposits of Central Slovakian volcanics, magnesite, siderite, barite and stibnite deposits in Ore Mountains of Slovakia, and a polymetallic ore deposit in Kosovo. Recently, we are studying genesis of a phosphate deposit in Mozambique ...
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We hypothesize that the rapid onset of the carbon isotope excursion (CIE) at the Paleocene/Eocene boundary (V55 Ma) may have resulted from the accretion of a significant amount of 12C-enriched carbon from the impact of a V10 km comet, an event that would also trigger greenhouse warming leading to the Paleocene/Eocene thermal maximum and, possibly, thermal dissociation of seafloor methane hydrate. Indirect evidence of an impact is the unusual abundance of magnetic nanoparticles in kaolinite-rich shelf sediments that closely coincide with the onset and nadir of the CIE at three drill sites on the Atlantic Coastal Plain. After considering various alternative mechanisms that could have produced the magnetic nanoparticle assemblage and by analogy with the reported detection of iron-rich nanophase material at the Cretaceous/Tertiary boundary, we suggest that the CIE occurrence was derived from an impact plume condensate. The sudden increase in kaolinite is thus thought to represent the redeposition on the
We are investigating how the carbon isotope composition of fossil land plants and fossil organic matter can be used to infer climate change in ancient ecosystems.. M.T. Rabanus-Wallace, M.J. Wooller, G.D. Zazula, E. Shute, A.H. Jahren, P. Kosintsev, J.A. Burns, J. Breen, B. Llamas and A. Cooper. 2017. Megafaunal isotopes reveal role of increased moisture on rangeland during Late Pleistocene extinctions. Nature Ecology & Evolution, 1, 0125, DOI: 10.1038/s41559-017-0215. (view/download pdf). B.A. Schubert% and A.H. Jahren. 2013. Reconciliation of marine and terrestrial carbon isotope excursions based on changing atmospheric CO2 levels. Nature Communications, 4:1653, DOI: 10.1038/ncomms2659. (view/download pdf). A.H. Jahren, B.A. Schubert%, L. Marynowski and J.P. Wilson*. The carbon isotope organic geochemistry of Early Ordovician rocks from the Annascaul Formation, County Kerry. Irish Journal of Earth Sciences, 31: 1-12; doi: 10.3318/IJES.2013.31. (view/download pdf).. G.J. Retallack and A.H. ...
We are investigating how the carbon isotope composition of fossil land plants and fossil organic matter can be used to infer climate change in ancient ecosystems.. M.T. Rabanus-Wallace, M.J. Wooller, G.D. Zazula, E. Shute, A.H. Jahren, P. Kosintsev, J.A. Burns, J. Breen, B. Llamas and A. Cooper. 2017. Megafaunal isotopes reveal role of increased moisture on rangeland during Late Pleistocene extinctions. Nature Ecology & Evolution, 1, 0125, DOI: 10.1038/s41559-017-0215. (view/download pdf). B.A. Schubert% and A.H. Jahren. 2013. Reconciliation of marine and terrestrial carbon isotope excursions based on changing atmospheric CO2 levels. Nature Communications, 4:1653, DOI: 10.1038/ncomms2659. (view/download pdf). A.H. Jahren, B.A. Schubert%, L. Marynowski and J.P. Wilson*. The carbon isotope organic geochemistry of Early Ordovician rocks from the Annascaul Formation, County Kerry. Irish Journal of Earth Sciences, 31: 1-12; doi: 10.3318/IJES.2013.31. (view/download pdf).. G.J. Retallack and A.H. ...
Abstract: We construct an interaction between a (2,0) tensor multiplet in six dimensions and a self-dual string. The interaction is a sum of a Nambu-Goto term, with the tension of the string given by the modulus of the scalar fields of the tensor multiplet, and a non-local Wess-Zumino term, that encodes the electromagnetic coupling of the string to the two-form gauge field of the tensor multiplet. The interaction is invariant under global (2,0) supersymmetry, modulo the equations of motion of a free tensor multiplet. It is also invariant under a local fermionic kappa-symmetry, as required by the BPS-property of the string ...
Natural-abundance 13C nuclear magnetic resonance spectra of ten common nucleotides in neutral, aqueous solutions have been determined and interpreted. The spectra of two of these substances were also determined in acidic solutions, and several of the carbon chemical shifts were found to depend markedly on pH. Within the limited range of concentrations employed, there were observed no carbon chemical-shift changes which could be ascribed to base-stacking or base-pairing phenomena. ...
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Heterogeneous and homogeneous processes in the formation of diamond at low pressures, where diamond is a metastable modification of carbon, are discussed. Data on the kinetics of the growth of diamond from hydrocarbons under conditions which give codeposition with graphite are reported, together with data on the influence of hydrogen on this process and on the resulting fractionation of the stable carbon isotopes. Chemical and plasma-chemical methods of preparing diamond and diamond-like layers are discussed, as well as methods based on the use of atomic and ionic beams. The most recent theoretical and experimental results on the homogeneous formation of diamond in the gas phase are presented ...
Researchers have achieved the first long temperature reconstruction for the eastern Mediterranean using the stable carbon isotopes found in tree rings found in the region.
Liu, Junwen,Mo, Yangzhi,Ding, Ping,Li, Jun,Shen, Chengde,&Zhang, Gan.(2018).Dual carbon isotopes (C-14 and C-13) and optical properties of WSOC and HULIS-C during winter in Guangzhou, China.SCIENCE OF THE TOTAL ENVIRONMENT,633,1571-1578 ...
Ordovician Carbon Isotope Curve By Bergstrom, S.M., Xu Chen, Gutierrez-Marco, J.C., and Dronov, A., 2008, Lethaia, DOI: 10.1111/j.1502-39 Click HERE t
ISOFLEX supplies stable and radioactive isotopes. With competitive pricing, certified isotopic enrichment, expedited processing and delivery and exemplary customer service, ISOFLEX is your premier isotope supplier. Contact us with your specific requirements.
The STRI Soils Laboratory in Panama operates an Isotope Ratio Mass Spectrometer (IRMS) for the determination of stable isotopes of carbon, hydrogen, oxygen and nitrogen in environmental samples. A variety of samples can be analyzed, including soils, plant and animal tissue, geological samples, gases, and waters. We also operate a cavity ring-down spectrometer for high precision determination of δ18O and δ2H in liquids.. ...
^12C. ^13C, and ^14C. The heaviest isotope shown has a half life of about 6000 years (this is from memory, so check). The ^13C isotope is abundant enough (approx. 1%) to make ^13C NMR spectroscopy a routine method of characterization for organic chemists. Most universities would have 1 or more ^13C NMR spectrometers. ^12C isotope is the bog standard, naturally abundant one that you sprinkle on your cornflakes when it (the isotope) is bound to oxygen and hydrogen.
Scientists engaged in climate research, biochemistry, forensics and oilgas exploration can now analyze the isotopic anatomy of molecules using a new high-resolution isotope ratio mass spectrometer from Thermo Fisher Scientific . This new instrument will allow scientists to access the direct conditions under which molecules were formed,...
Scientists engaged in climate research, biochemistry, forensics and oilgas exploration can now analyze the isotopic anatomy of molecules using a new high-resolution isotope ratio mass spectrometer from Thermo Fisher Scientific . This new instrument will allow scientists to access the direct conditions under which molecules were formed,...
In a study published in the journal Geology, Dr. Peter Swart if the University of Miami Rosenstiel School of Marine and Atmospheric Science suggests that the large changes in the carbon isotopic composition of carbonates which occurred prior to the major climatic event more than 500 million years ago, known as
C4 photosynthesis calls for metabolic compartmentation which is in turn linked to specialised anatomy (Figure 2.4). Three biochemical subtypes of C4 photosynthesis have evolved which probably derive from subtle differences in the original physiology and leaf anatomy of their C3 progenitors.CO2 assimilation by all three C4 subtypes (Figure 2.8) involves five stages:
The technique of 13C-NMR spectroscopy of oriented systems to problems of biological importance has been suggested and used to investigate non-planar distortions in substituted amides-models for peptides. The studies in conjunction with the proton magnetic resonance data on 5N-[13C]methyl[13C]formamide oriented in a nematic solvent provide all the direct dipolar couplings between the interacting nuclei in the system. When the 13C- and the 1H-NMR experiments are performed under non-identical conditions, 22 different direct dipolar couplings are obtained. It is demostrated that they can be used to determine unambiguously non-planar distortions around the nitrogen atom together with other geometrical data and the molecular order.. ...
The Yangtze Platform preserves relatively thick carbonate successions and excellent fossil records across the Ediacaran-Cambrian boundary interval. The intensely studied Meishucun section in East Yunnan was one of the Global Stratotype Section candidates for the Precambrian-Cambrian boundary. However, depositional breaks were suspected in the section and the first appearance of small shelly fossils could not be verified. The Laolin section located in NE Yunnan is more continuous and shows great potential for global correlation of carbon isotope features across the Precambrian-Cambrian boundary. However, the stratigraphic framework and correlations were controversial. We studied and systematically sampled the Laolin section and present here new carbon isotope data for this section. The Laolin section consists of, in ascending order, the Baiyanshao dolostone of the Dengying Formation, the Daibu siliceous dolostone, Zhongyicun dolomitic phosphorite, lower Dahai dolostone and upper Dahai limestone ...
Major endogenous reserves and pool materials generally are oxidized during early periods of endogenous respiration in the absence of an exogenous substrate. Once these reserves are utilized ribonucleic acid and protein frequently are utilized as endogenous substrates. In general, the pattern of endogenous metabolism is a reflection of the nutritional condition of the cell but may be modified by environmental factors. The rate of endogenous respiration decreases as the cells age but may be maintained at higher levels if the cells are fed continuously as they age. Endogenous respiration generally continues, often at reduced rates, in the presence of an exogenous substrate and may be essential for the maintenance of the living cell. (Author)(*MICROORGANISMS
Costech ECS140 Elemental Analzyer with ConFlo-III interface to Finnegan Delta XL isotope ratio mass spectrometer (ir-MS also equipped with automated carbonate prep system and Gas Bench for analysis of carbonates and waters, maintained by Prof. Stephen Burns) ...
Reports from the NHS suggest that the number of flu victims this winter has been higher than seen for nearly a decade. A healthy robust immune system is the best protection against falling victim to the latest flu virus and a big part of the solution may be a daily dose of Vitamin C.
Suppliers List, E-mail/RFQ Form, Molecular Structure, Weight, Formula, IUPAC, Synonyms for D-[4-13C]FRUCTOSE (CAS No. 84270-09-7)
A detailed analysis of the 35Cl/37Cl isotope shifts induced in the 128.8 MHz 195Pt NMR resonances of [PtCl n(H2O)6 - n]4 - n complexes (n = 6,5,4) in acidic solution at 293 K, shows that the unique isotopologue and isotopomer ...
By amending methodology to utilize eVol® for sample preparation processes for GC-C-IRMS C isotope ratio analysis, the ISORA department has: improved sample preparation conditions and the GC-C-IRMS ...
This activity guides the analysis of a published scientific figure from a study on prehistoric human food sources. In this study, scientists used carbon isotopes to determine how the advent of agriculture affected human diets.. ...
We present an advanced system for on-line position-specific carbon isotope analysis. The main limitation of on-line intramolecular isotope ratio measurements has been that optimal pyrolytic fragments are obtained mostly at temperatures where the analyte has not completely reacted. As a result of undetermined isotopic fractionation, the isotopic signatures of the pyrolysis products are not strictly equal to these of the equivalent moieties in the parent molecule. We designed a pyrolytic unit in which both temperature and reaction time are variable parameters, enabling determination of the enrichment factor of the pyrolysis at optimal temperature by construction of a Rayleigh plot. In the case of methyl tert-butyl ether (MTBE) presented here, a pre-pyrolysis fractionation of MTBE leading to a depletion of 0.9 parts per thousand was discovered and the enrichment factor of the optimal pyrolysis reaction was determined at -1.7 parts per thousand. Absolute delta C-13 values of two functional groups ...
0036]The stable carbon isotope ratio (13C/12C) provides a complementary route to source discrimination and apportionment. The 13C/12C ratio in a given biosourced material is a consequence of the 13C/12C ratio in atmospheric carbon dioxide at the time the carbon dioxide is fixed and also reflects the precise metabolic pathway. Regional variations also occur. Petroleum, C3 plants (the broadleaf), C4 plants (the grasses), and marine carbonates all show significant differences in 13C/12C and the corresponding δ 13C values. Furthermore, lipid matter of C3 and C4 plants analyze differently than materials derived from the carbohydrate components of the same plants as a consequence of the metabolic pathway. Within the precision of measurement, 13C shows large variations due to isotopic fractionation effects, the most significant of which for the instant invention is the photosynthetic mechanism. The major cause of differences in the carbon isotope ratio in plants is closely associated with differences ...
In order to investigate mid-Cretaceous terrestrial climates of low paleolatitudes, Moroccan, Tunisian and Brazilian vertebrate apatites have been analyzed for their oxygen and carbon isotope compositions of phosphates (delta O-18(p)) and carbonates (delta O-18(c), delta C-18(c)). At each site, coexisting theropod dinosaurs, titanosaurid sauropods, pterosaurs, crocodilians, turtles and fish have distinct delta O-18(p) and delta C-18(c) values reflecting their ecologies, diets and foraging environments. Oxygen isotope compositions of surface waters (delta O-18(w)) estimated from turtle and crocodile delta O-18(p) values range from -5.0 +/- 1.0 parts per thousand to -2.4 +/- 1.0 parts per thousand, which do not differ from mean annual rainwater values occurring today under inter-tropical sub-arid to arid climates. High water temperatures ranging from 21 +/- 6 degrees C to 34 +/- 2 degrees C deduced from fish delta O-18(p) values are in agreement with those published for mid-Cretaceous low ...
TY - GEN. T1 - Stable isotope analysis of breath using the optogalvanic effect. AU - Murnick, Daniel E.. AU - Colgan, M. J.. AU - Lie, H. P.. AU - Stoneback, D.. PY - 1996/1/1. Y1 - 1996/1/1. N2 - A new technique based on the optogalvanic effect has been developed for the measurement of stable isotope ratios in the carbon dioxide of exhaled breath. Data obtained before and after ingestion of harmless stable isotope labeled compounds, metabolized to carbon dioxide, can be used for sensitive noninvasive diagnostics of various disease conditions. The technique uses the specificity of laser resonance spectroscopy and achieves sensitivity and accuracy typical of sophisticated isotope ratio mass spectrometers. Using fixed frequency carbon dioxide lasers, 13C/ 12C ratios can be determined with a precision of 2 ppm with 100 second averaging times. Multiple samples can be analyzed simultaneously providing real time continuous calibration. In a first application, analysis of 13C/ 12C ratios in exhaled ...
1.During infusion of [5-15N]glutamine in patients with gastrointestinal cancer we unexpectedly observed a gradual decrease in time of the appearance rate (Ra) of glutamine in plasma. Here we investigate whether the failure to achieve a plateau isotopic enrichment in plasma is, among other factors, due to incomplete equilibration of the glutamine tracer with the large intramuscular free glutamine pool.. 2.Plasma and intramuscular glutamine enrichment were measured during 6-11 ;h infusions of L-[5-15N]glutamine and L-[1-13C]glutamine in post-absorptive patients admitted to hospital for elective abdominal surgery. L-[1-13C]Leucine and L-[ring-2H5]phenylalanine were infused to measure the proportion of glutamine appearing in plasma directly due to its release from protein.. 3.The glutamine tracer entered muscle, but the rise in intramuscular glutamine enrichment was small, presumably as a result of the enormous size of the intramuscular glutamine pool and the limited speed of entry of glutamine into ...
Sudden pulse-like events of rapidly increasing CO2-efflux occur in soils under seasonally dry climates in response to rewetting after drought. These occurrences, termed "Birch effect", can have a marked influence on the ecosystem carbon balance. Current hypotheses indicate that the "Birch" pulse is caused by rapidly increased respiration and mineralization rates in response to changing moisture conditions but the underlying mechanisms are still unclear. Here, we present data from an experimental field study using straight-forward stable isotope methodology to gather new insights into the processes induced by rewetting of dried soils and evaluate current hypotheses for the "Birch"-CO2-pulse. Two irrigation experiments were conducted on bare soil, root-free soil and intact vegetation during May and August 2005 in a semi-arid Mediterranean holm oak forest in southern Portugal. We continuously monitored CO2-fluxes along with their isotopic compositions before, during and after the irrigation. d13C ...
We have in our lab a Finnegan 253 isotope ratio mass spectrometer with GC-combustion interface, a Finnegan Delta Plus IRMS with dual inlet and continuous flow GC interfaces, two standalone HP 6890 GCs, and a Pfeiffer quadrupole mass spectrometer. There is also an Ionicon high resolution proton transfer time of flight mass spectrometer (HR-PTRTOFMS) (shared with D. Knopf).. We have two cryogenic vacuum extraction lines for the separation and quantification of specific trace gases, such as isoprene, methanol, carbon monoxide and methane. We have developed our own preconcentration systems for the analysis of selective trace species via continuous flow isotope ratio mass spectrometry (IRMS); this allows us to quantify the isotopic composition of gases from ice core samples (e.g., Mak and Yang, 1998; Wang and Mak, 2010; Wang et al., 2010). We are currently funded to analyze the stable isotopic composition of CO from Antarctic Ice cores (e.g., SPICE), as well as Greenland ice.. We are also involved in ...
Isotopes. Main article: Isotopes of carbon. Isotopes of carbon are atomic nuclei that contain six protons plus a number of ... Carbon can form very long chains of interconnecting carbon-carbon bonds, a property that is called catenation. Carbon-carbon ... naturally occurring isotopes.[15] The isotope carbon-12 (12C) forms 98.93% of the carbon on Earth, while carbon-13 (13C) forms ... The paths of carbon in the environment form the carbon cycle. For example, photosynthetic plants draw carbon dioxide from the ...
The ratio of carbon-13 and carbon-12 isotopes in these types of plants is as follows: C4 plants: -16 to -10 ‰ CAM plants: -20 ... Carbon isotopes: you are what you eat Hair-rising research Ayacucho Archaeo Isotope Project The pursuit of isotopic and ... The ratios of isotopes in a sample material are measured by isotope-ratio mass spectrometry. This process is called isotope ... In addition, there are two types of plants with different biochemical pathways; the C3 carbon fixation, where the isotope ...
C3 plants preferentially use the lighter of two isotopes of carbon in the atmosphere, 12C, which is more readily involved in ... O'Leary, Marion (May 1988). "Carbon Isotopes in Photosynthesis". BioScience. 38 (5): 328-336. doi:10.2307/1310735. JSTOR ... being closer to C3 plants if they fix most carbon in the day and closer to C4 plants if they fix all their carbon at night. It ... The enzyme RuBisCO is responsible for "fixing" CO2 - that is, it attaches it to a carbon-based molecule to form a sugar, which ...
ISBN 978-1-4443-3301-5. Mook, W. G., & Tan, F. C. (1991). Stable carbon isotopes in rivers and estuaries. Biogeochemistry of ... This signal is also a function of the amount of carbon burial; when organic carbon is buried, more 12C is locked out of the ... O'Leary, M. H. (1988). "Carbon Isotopes in Photosynthesis". BioScience. 38 (5): 328-336. doi:10.2307/1310735. JSTOR 1310735. ... δ18O δ15N δ34S Isotopic signature Isotope analysis Isotope geochemistry Isotopic labeling Libes, Susan M. (1992). Introduction ...
Stable isotope analysis monitors the ratio of carbon 13 to carbon 12 (13C/12C), which is expressed as parts per mil (per ... Nitrogen isotopes in bone collagen are ultimately derived from dietary protein, while carbon can be contributed by protein, ... Stable isotope analysis of carbon and nitrogen in human bone collagen allows bioarchaeologists to carry out dietary ... Rounick, J.S.; Winterbourn, M.J. (1986). "Stable Isotopes and Carbon Flow in Ecosystems". BioScience. 36 (3): 171-77. doi: ...
Carbon isotopes indicate "dry woodland" conditions. This seeming contradiction between the seasonally dry climate and tropical ...
Klein, R.G. (2013). "Stable carbon isotopes and human evolution". PNAS. 110: 10470-2. doi:10.1073/pnas.1307308110. Semaw, S.; ... More direct stable isotope evidence from Neanderthal bodies also indicate indicates a heavy, though by no means exclusive ... This is corroborated by stable carbon isotopic evidence indicating the consumption of plants found along riversides and under ... More recent techniques have been introduced such as Carbon Isotopic Analysis of recovered bones, which can be used as direct ...
Carbon has three naturally occurring isotopes. About 99% of carbon on Earth is carbon-12 (12C), about 1% is carbon-13 (13C), ... The Suess effect is a change in the ratio of the atmospheric concentrations of heavy isotopes of carbon (13C and 14C) by the ... doi:10.1016/0160-4120(79)90005-9. Farquhar, G.D., Ehleringer, J.R. and Hubick, K.T. "Carbon Isotope Discrimination and ... and a trace amount is carbon-14 (14C). The 12C and 13C isotopes are stable, while 14C decays radioactively to nitrogen-14 (14N ...
Other more neutron-deficient and more unstable isotopes can be formed by the irradiation of platinum with carbon nuclei.[55] ... Isotopes[edit]. Main article: Isotopes of polonium. Polonium has 42 known isotopes, all of which are radioactive. They have ... Atterling, H.; Forsling, W. (1959). "Light Polonium Isotopes from Carbon Ion Bombardments of Platinum". Arkiv för Fysik. 15 (1 ... Not specified is the isotope under study, but at the time polonium-210 was the most readily available polonium isotope. The DoE ...
... which prefers carbon-12 over carbon-13, resulting in carbon isotope fractionation in the rock record. Sedimentary rocks ... Stable Isotopes and Plant Carbon-Water Relations. Elsevier. 2012-12-02. ISBN 9780080918013. McCollom, Thomas M. (2013-01-01). " ... Isotope tracers can be used to track biochemical reactions to understand microbial metabolism. Isotope natural abundance in ... Stable isotopes of water are sometimes used as tracers of water sources and flow paths between the physical environment and the ...
Karhu, J.A.; Holland, H.D. (1 October 1996). "Carbon isotopes and the rise of atmospheric oxygen". Geology. 24 (10): 867-870. ... The flow of carbon dioxide from the atmosphere to the soil is therefore regulated with the help of living beings. When CO2 ... Carbon precipitation, solution and fixation are influenced by the bacteria and plant roots in soils, where they improve gaseous ... The Ukrainian geochemist was one of the first scientists to recognize that the oxygen, nitrogen, and carbon dioxide in the ...
Characterization of photobiont associations in lichens using carbon isotope discrimination techniques. Stable Isotopes and ... algal and cyanobacterial photobionts of lichen associations was also identified using gas exchange and carbon isotope isotopes ... In sea water for example, the pH is such that dissolved inorganic carbon (DIC) is mainly found in the form of HCO3−. The net ... From there on, the pyrenoid was studied in the wider context of carbon acquisition in algae, but has yet to be given a precise ...
Hayes made the first measurements of the distribution of the isotopes of carbon within biolipids. This innovation provided a ... Hayes, John M. (2001). "Fractionation of Carbon and Hydrogen Isotopes in Biosynthetic Processes". Reviews in Mineralogy and ... Hayes, John M; Waldbauer, Jacob R (2006). "The carbon cycle and associated redox processes through time". Philosophical ... Hayes's studies of the carbon cycle bear strongly on the development of the global environment and provide evidence about the ...
His work uses stable isotopes of carbon (carbon-13 and oxygen (Δ18O) to integrate carbon and hydrological cycles for individual ... Seibt, Ulli; Rajabi, Abazar; Griffiths, Howard; Berry, Joseph A. (2008). "Carbon isotopes and water use efficiency: sense and ... Measurements of gas exchange and of carbon isotope ratio and their ecological implications". Oecologia. 53 (1): 68-78. doi: ... He has investigated carbon concentrating mechanisms (see photosynthesis) in algae and hornworts, focusing on the molecular ...
Isotopes are nuclides having the same number of protons; e.g. carbon-12 and carbon-13. Isobars are nuclides having the same ... In contrast, the proton numbers for which there are no stable isotopes are 43, 61, and 83 or more. This is related to nuclear ... ISBN 0-486-65622-5. via File:NuclideMap_stitched.png; note also Isotopes of bismuth. ... boron-12 and carbon-13 nuclei both contain 7 neutrons, and so are isotones . Similarly, 36S, 37Cl, 38Ar, 39K, and 40Ca nuclei ...
Even when compounds only contain elements with less intense isotope peaks (carbon or oxygen), the distribution of these peaks ... Isotope effects[edit]. Isotope peaks within a spectrum can help in structure elucidation. Compounds containing halogens ( ... The same requirements for McLafferty rearrangement apply to ortho rearrangement except for the strong α,β carbon-carbon double ... An example is the cleavage of carbon-carbon bonds next to a heteroatom. In this depiction, single-electron movements are ...
... carbon, and oxygen isotopes that must be kept away from the atmosphere.[19] The 15N:14N ratio is commonly used in stable ... The heavy isotope 15N was first discovered by S. M. Naudé in 1929, soon after heavy isotopes of the neighbouring elements ... oxygen and carbon were discovered.[26] It presents one of the lowest thermal neutron capture cross-sections of all isotopes.[27 ... Iso-tope. Abun-dance. Half-life (t1/2). Decay mode. Pro-duct. ... Like carbon tetrafluoride, it is not at all reactive and is ...
The differential uptake of the three carbon isotopes leads to 13. C/12. C and 14. C/12. C ratios in plants that differ from the ... If the carbon in freshwater is partly acquired from aged carbon, such as rocks, then the result will be a reduction in the 14. ... Dormant volcanoes can also emit aged carbon. Plants that photosynthesize this carbon also have lower 14. C/12. C ratios: for ... Volcanic eruptions eject large amounts of carbon into the air. The carbon is of geological origin and has no detectable 14. C, ...
... and isotopic compositions of carbon, nitrogen and hydrogen in organic matter; (c) multiple sulfur and oxygen isotope ratios of ... as the isotopic proportions of carbon-12 to carbon-14 in methane could distinguish between a biogenic and non-biogenic origin, ... A biosignature (sometimes called chemical fossil or molecular fossil) is any substance - such as an element, isotope, molecule ... Another example is the presence of straight-chain lipids in the form of alkanes, alcohols an fatty acids with 20-36 carbon ...
Distribution of natural isotopes of carbon in Linsley Pond and other New England lakes. Limnol. Oceanogr. 9:1-11. 1964 With M. ... Fractionation of sulfur and carbon isotopes in a meromictic lake. Science 139:407-408. 1964 With M. Stuiver. ... Carbon 13 in lake waters, and its possible bearing on paleolimnology. Am. J. Sci. 258-A:253-72. 1963 With N. Nakai and M. ... He was a creative pioneer in several areas, including quantitative palynology, cycling of natural isotopes, biogeochemistry, ...
"A 400 million year carbon isotope record of pedogenic carbonate; implications for paleoatmospheric carbon dioxide" (PDF). ... Very high atmospheric concentrations of carbon dioxide in the Late Jurassic led to high temperatures around the globe, due to ...
... using carbon and oxygen isotopes to prove their biological origin". But it was Lowenstam's 1961 discovery of "biochemically- ... During this time, the University of Chicago had emerged as the birthplace isotope geochemistry, and Harold Urey's research ... Caltech and the University of California began the building of their isotope geochemistry programs and their recruitment of ... group was making significant advancements in the use of deviations in stable isotopes to measure ancient ocean temperatures. ...
Casanova, Joel; Hillare-Marcel, Claude (1993). "Carbon and Oxygen Isotopes in African Lacustrine Stromatolites: ...
"Enriched carbon isotope labelling to trace the contribution of benthic microalgae to the nutrition of consumers in mangrove ... "Carbon pathways in estuarine foodwebs: stable isotope evidence further enriched". AMSA Conference Abstract Oral Proceedings: 26 ...
C[I=14] indicates carbon-14 isotope. Hydrogens are normally explicitly specified as a shorthand, CH4 is the SLN for methane. In ...
The technique has been improved through the use of stable isotopes to better trace energy flow through the web.[14] It was once ... A gradient exists between trophic levels running from complete autotrophs that obtain their sole source of carbon from the ... Ecologists employ stoichiometry to analyze the ratios of the main elements found in all organisms: carbon (C), nitrogen (N), ... and carbon dioxide, water, and heat). Excretion of nutrients is, therefore, basic to metabolism."[28]:1230-1231 The units in ...
The naturally occurring isotopes of carbon, of which there are three: 12C making up about 98.9 per cent; 13C about 1.1 per cent ... carbon isotopes Natural carbon is composed of three isotopes: 12C making up about 98.9%; 13C about 1.1%; and 14C whose amount ... carbon isotopes The naturally occurring isotopes of carbon, of which there are three: 12C making up about 98.9 per cent; 13C ... Carbon-isotope dating is a method of radiometric age-dating using the amount of the heavy, radioactive isotope carbon-14 ...
Carbon Isotopes, Photosynthesis, and Archaeology: Different pathways of photosynthesis cause characteristic changes in carbon ... Carbon isotope ratio data in bone collagen from human skeletons found in Illinois, Ohio, and West Virginia, dated 4,000 B.C. to ... scientists measured carbon isotopes in the collagen tissues of human skeletons from North America. ... isotope ratios that make possible the study of prehistoric human diets. American Scientist 1982; 70(6):596-606. ...
... carbon: In 1961 the isotope carbon-12 was selected to replace oxygen as the standard relative to which the atomic weights of ... Carbon-14, which is radioactive, is the isotope used in radiocarbon dating and radiolabeling. ... In carbon. In 1961 the isotope carbon-12 was selected to replace oxygen as the standard relative to which the atomic weights of ... Carbon-14, which is radioactive, is the isotope used in radiocarbon dating and radiolabeling. ...
Main isotopes of carbon .mw-parser-output .nobold{font-weight:normal}. (6C). Iso-tope Decay ... The isotopes parameter[edit]. Isotopes are to be entered by the editor in ,isotopes=. , using one subtemplate for each ... isotopes table footnote=* = [[excited state]]{{sfn,Chisté,2006}} , isotopes = {{Infobox element isotopes/isotopes stable , link ... isotopes =,!-- the parameter --, {{Infobox element isotopes/isotopes stable , mn=19 , sym=F , link=fluorine-19 , na=100 ...
The least stable isotope is 8C, with a half-life of 2.0 x 10−21 s. Carbon-11 or 11C is a radioactive isotope of carbon that ... Stable carbon isotopes in carbon dioxide are utilized differentially by plants during photosynthesis.[citation needed] Grasses ... Carbon (6C) has 15 known isotopes, from 8C to 22C, of which 12C and 13C are stable. The longest-lived radioisotope is 14C, with ... Plants find it easier to use the lighter isotopes (12C) when they convert sunlight and carbon dioxide into food. So, for ...
Los Gatos Research is developing a simple robust methodology for the determination of carbon isotope ratios in small gas ... With such a sensitive method of accurately determining carbon isotope levels we hope to significantly advance the prospects for ... The isotope ratio is known to be a sensitive indicator of biologic activity. The new innovative advancement we propose to make ... of 1.5 microns in Phase I and demonstrate that the approach can be used to record the relative isotopic abundance of carbon 12 ...
A Dual-Carbon-and-Nitrogen Stable Isotope Ratio Model Is Not Superior to a Single-Carbon Stable Isotope Ratio Model for ... For nitrogen isotopes in meat products, variability was constrained, relative to carbon isotopes. The entire range in δ15N ... We turned to carbon and nitrogen stable isotopes to tell us the origin of the animals diet, based on classical models (1, 2) ... Carbon and nitrogen stable isotopes in fast food: Signatures of corn and confinement. A. Hope Jahren and Rebecca A. Kraft ...
Carbon Isotopes in the Carbon Cycle. Since all carbon isotopes are the same chemically they can all interact with other atoms ... of carbon atoms are called Isotopes ("same type"). Chemically, they all act like carbon atoms, they all "look" like carbon ... to use the lighter isotopes of carbon: 12C over 13C over 14C. So if you took a plant and measured what isotopes it has you ... carbon-12 or 12C. But a small number of carbon atoms have an extra neutron, carbon-13, or 13C and an even smaller number of ...
The Steptoean Positive Carbon Isotope Excursion (SPICE) was a geological event which occurred about 500 million years ago at ...
Evaluating Dissolved Inorganic Carbon Cycling in a Forested Lake Watershed Using Carbon Isotopes - Volume 34 Issue 3 - Ramon ... Carbon fluxes, pCO2 and substrate weathering in a large northern river basin, Canada: carbon isotope perspectives. Chemical ... Carbon fluxes, pCO2 and substrate weathering in a large northern river basin, Canada: carbon isotope perspectives. Chemical ... A rapid and precise method for measuring stable carbon isotope ratios of dissolved inorganic carbon. Marine Chemistry, Vol. 69 ...
We compared carbon isotope ratios from four types of experimental colonies: feral, managed with and without supplemental feed, ... Kelly, J.F. (2000) Stable isotopes of carbon and nitrogen in the study of avian and mammalian trophic ecology. Can. J. Zool. 78 ... Brosi, A.R., Harkins, W.D. (1937) The abundance ratio of the isotopes in natural or isotopically separated carbon. Phys. Rev. ... Overmyer, J.P., MacNeil, M.A., Fisk, A.T. (2008) Fractionation and metabolic turnover of carbon and nitrogen stable isotopes in ...
Isotope Analysers in Agriculture focuses on an isotopic technique that scientists are using to assess the presence of carbon ... The IAEA publication Use of Laser Carbon Dioxide Carbon ... Use of Laser Carbon Dioxide Carbon Isotope Analysers in ... New IAEA Publication - Use of Laser Carbon Dioxide Carbon Isotope Analysers in Agriculture. ×. ... The recently published Use of Laser Carbon Dioxide Carbon Isotope Analysers in Agriculture focuses on this specific technique, ...
The studies show that the carbon isotope discrimination (CID), which is the ratio of the variation of carbon-13 to carbon-12 in ... INTERNATIONAL ATOMIC ENERGY AGENCY, Greater Agronomic Water Use Efficiency in Wheat and Rice Using Carbon Isotope ... Greater Agronomic Water Use Efficiency in Wheat and Rice Using Carbon Isotope Discrimination. ... Greater Agronomic Water Use Efficiency in Wheat and Rice Using Carbon Isotope Discrimination ...
Illustration of the structures of the nuclei of two isotopes each of carbon (bottom) and hydrogen (top). The nuclei are made up ... Carbon-13 (lower right) has an overall nuclear spin (unlike carbon-12), and so is used in nuclear magnetic resonance ... Hydrogen-1 (upper left) and carbon-12 (lower left) each make up over 98% of these elements. ... of nucleons (balls). There are two types of nucleon: protons (grey) and neutrons (white). Isotopes, chemically- identical ...
... to identify residency in juvenile nursery habitats with distinctive carbon isotope values. Conventional bulk... ... Stable carbon isotope analysis of amino-acid enantiomers by conventional isotope ratio mass spectrometry and combined gas- ... Carbon isotopes in otolith amino acids identify residency of juvenile snapper (Family: Lutjanidae) in coastal nurseries. ... Rodelli MR, Gearing JN, Gearing PJ, Marshall N, Sasekumar A (1984) Stable isotope ratio as a tracer of mangrove carbon in ...
One culture exhibited a change in the fractionation pattern for carbon (but not for hydrogen) midway through the... ... Methane-oxidizing bacteria, however, can significantly change the carbon isotopic composition of methane; the origin of gas ... We cultured methane-oxidizing bacteria at two different temperatures and monitored the carbon and hydrogen isotopic ... Carbon isotopic analysis of methane has become a popular technique in the exploration for oil and gas because it can be used to ...
stable isotopes, carbon fluxes, environmental factors, Planning Links:. planid: 4110 myp: ECO ltg: ECO-6 Goal: 4 obj: 405 ... Stable isotopes are used widely as a tool for determining sources of carbon (C) fluxes in ecosystem C studies. Environmental ... Stable isotopes are used widely as a tool for determining sources of carbon (C) fluxes in ecosystem C studies ... Soil drying effects on the carbon isotope composition of soil respiration. Contact. National Health and Environmental Effects ...
Conversation: Isotope changes in marine organic carbon. Subject: [ISOGEOCHEM] Isotope changes in marine organic carbon. Does ... Carbon isotope signatures were also independent of rock type and depositional environment, showing that the carbon isotope ... two positive carbon-isotope excursions in a range of materials are separated by an abrupt negative shift. Carbon-isotope ... Carbon-isotope stratigraphy proves to be most useful as a monitor of the history of the carbon-cycle during the last 200 ...
Carbon isotopes laser separation by multiple-photon dissociation O. N. Avatcov, A. B. Bakhtadze, V. Yu. Baranov, V. S. Doljikov ... "Carbon isotopes laser separation by multiple-photon dissociation," Appl. Opt. 23, 26-29 (1984) ... Laser isotope separation of rare earth elements N. V. Karlov, B. B. Krynetskii, V. A. Mishin, and A. M. Prokhorov. Appl. Opt. ... Laser Isotope Separation Using Two-Photon Selective Excitation; Its Quantum Efficiency and Separation Factor Yung S. Liu. Appl ...
The 13C isotopes reflect an organic origin for the carbon. This carbon came from the diagenesis of organic matter caused by an ... Stable carbon and oxygen isotope ratios (δ13C and δ18O) of the epibenthic foraminiferan Elphidium macellum var. aculeatum were ... Using stable isotopes of nitrogen and carbon to study seabird ecology: applications in the Mediterranean seabird community , El ... Using stable isotopes of nitrogen and carbon to study seabird ecology: applications in the Mediterranean seabird community ...
Carbon-isotope analyses of fossil plants as a chemostratigraphic and palaeoenvironmental tool. ... GRÖCKE, D. R. (1998), Carbon-isotope analyses of fossil plants as a chemostratigraphic and palaeoenvironmental tool. Lethaia, ...
To date, little isotope fractionation information is available for the... ... Compound-specific isotope analysis has been used extensively to investigate the biodegradation of various organic pollutants. ... Large hydrogen and small carbon isotope fractionation was observed for quinoline while minor carbon and hydrogen isotope ... The apparent kinetic isotope effects (AKIEC) values of carbon were 1.008 ± 0.0005 for quinoline and 1.0048 ± 0.0005 for 3- ...
Buy Carbon Isotope Techniques by David C. Coleman at TextbookX.com. ISBN/UPC: 9780121797317. Save an average of 50% on the ... Description: Carbon Isotope Techniques is a hands-on introduction to using carbon isotope tracers in experimental biology and ... and archaeology will find Carbon Isotope Techniques a valuable resource. Key Features. * Features isotopes in ecological ... The 11C, 12C, 13C, and 14C carbon isotopes are considered and standard techniques are described by established authors. This is ...
Thus far, no study has systematically examined intraindividual coupled strontium (Sr), oxygen (O), and carbon (C) isotope ... Strontium, oxygen, and carbon isotope variation in modern human dental enamel. Am J Phys Anthropol. 2020. ... Thus far, no study has systematically examined intraindividual coupled strontium (Sr), oxygen (O), and carbon (C) isotope ... MATERIAL AND METHODS: This study presents the first systematic results on intraindividual variation in Sr-O-C isotope ...
If you are a society or association member and require assistance with obtaining online access instructions please contact our Journal Customer Services team ...
  • the observed photon costs can be accommodated by assuming coupled, energy-independent inorganic carbon influx and efflux. (uvm.edu)
  • Large CO2 evasion to the atmosphere occurs as dissolved inorganic carbon (DIC) is transported from soils to streams. (diva-portal.org)
  • Changes in stable isotopes values in the biomass (δ13C, δ15N), DOC and dissolved inorganic carbon (DIC) (δ13C) arising from degradation of the DOC were tracked in both static and semi-continuous tests. (uwaterloo.ca)
  • When this evolutionary breakthrough occurred, autotrophy (growth using inorganic carbon as the sole carbon source) is believed to have already been developed. (wikipedia.org)
  • The benefits of CCM include increased tolerance to low external concentrations of inorganic carbon, and reduced losses to photorespiration. (wikipedia.org)
  • To capture inorganic carbon more effectively, some plants have adapted the anaplerotic reactions HCO3− + H+ + PEP → OAA + Pi catalyzed by PEP carboxylase (PEPC), to carboxylate phosphoenolpyruvate (PEP) to oxaloacetate (OAA) which is a C4 dicarboxylic acid. (wikipedia.org)
  • The total active pool of carbon at the Earth's surface for durations of less than 10,000 years is roughly 40,000 gigatons C (Gt C, a gigaton is one billion tons, or the weight of approximately 6 million blue whales), and about 95% (~38,000 Gt C) is stored in the ocean, mostly as dissolved inorganic carbon. (wikipedia.org)
  • The speciation of dissolved inorganic carbon in the marine carbon cycle is a primary controller of acid-base chemistry in the oceans. (wikipedia.org)
  • There are two main types of inorganic carbon that are found in the oceans. (wikipedia.org)
  • DIC can be converted to particulate inorganic carbon (PIC) through precipitation of CaCO3 (biologically or abiotically). (wikipedia.org)
  • Particulate inorganic carbon (PIC) is the other form of inorganic carbon found in the ocean. (wikipedia.org)
  • Some of the inorganic carbon species in the ocean, such as bicarbonate and carbonate, are major contributors to alkalinity, a natural ocean buffer that prevents drastic changes in acidity (or pH). (wikipedia.org)
  • In the 1970s Minze began measuring 14C in dissolved inorganic carbon in ocean water as part of The Geochemical Ocean Sections Program (GEOSECS) to study the distribution of carbon in the ocean. (wikipedia.org)
  • 12C and 13C are measured as the isotope ratio δ13C in benthic foraminifera and used as a proxy for nutrient cycling and the temperature dependent air-sea exchange of CO2 (ventilation) (Lynch-Stieglitz et al. (wikipedia.org)
  • Our model-data comparison for the middle and early Miocene suggests that during the early Neogene the seaway effect on benthic δ13C may have been superimposed by further factors such as climate regime shifts and/or terrestrial carbon cycle changes. (awi.de)
  • Such high intraspecific variability can confound the interpretation of benthic food web stable isotope values. (lancs.ac.uk)
  • CONCLUSIONS: This is the first estimate of soil organic carbon derived from CH4 and it is comparable with levels observed in lakes that have high levels of benthic methanogenesis. (nerc.ac.uk)
  • Carbon isotope offsets between benthic foraminifer species of the genus Cibicides (Cibicidoides) in the glacial sub-Antarctic Atlantic. (pangaea.de)
  • Stratigraphic comparison of this expanded, high-resolution terrestrial carbon isotope history to the deep-sea benthic foraminiferal isotope records from Ocean Drilling Program (ODP) sites 1262 and 1263, Walvis Ridge, in the southern Atlantic Ocean corroborates the idea that the Bighorn Basin fluvial sediments record global atmospheric change. (clim-past.net)
  • Hi Tim, Using the keywords: marine, organic carbon, and atmospheric CO2 with a search on my ref database (over 30,000 refs just on stable isotopes) the selection, as given below, was generated (including abstracts). (uvm.edu)
  • Marine organic carbon lies in a range intermediate between these groups. (uvm.edu)
  • A similar pattern in the concentration of chlorophyll a (Chl-a), particulate organic nitrogen (PON) and particulat (mas) e organic carbon (POC) was observed in both mesocosms. (worldwidescience.org)
  • Existing atmospheric models underestimate concentrations of aerosol particulate matter and create gaps in our understanding of the atmospheric organic carbon budget, especially in relation to aqueous phase reactions that occur in fog and clouds. (epa.gov)
  • The outcomes of my research will provide clarification of the atmospheric organic carbon budget that could ideally be applied to total organic carbon and help ameliorate uncertainties in atmospheric models. (epa.gov)
  • 10 parts per thousand) surface-to-deep ocean delta C-13 gradient that is consistent with long-term deep ocean anoxia and the presence of a large dissolved organic carbon (DOC) reservoir. (columbia.edu)
  • A timescale for dissolved organic carbon production in equatorial {P}acific surface waters, Global Biogeochem. (clim-past.net)
  • To effectively use stable isotopes in the field, there is the need to determine the changes in stable isotope values occurring from the microbial degradation of organic components such as NAs which contribute a significant portion to the dissolved organic carbon (DOC) in reclamation sites. (uwaterloo.ca)
  • During the last 30 years, stable isotope analysis has emerged as one of most powerful tools for tracing organic carbon in food webs. (plos.org)
  • However, fatty acids account for only a small fraction of total organic carbon fluxes, and they tend to undergo degradation and transformation during food web passage . (plos.org)
  • The world's largest continental shelf, the East Siberian Shelf Sea, receives substantial input of terrestrial organic carbon (terr-OC) from both large rivers and erosion of its coastline. (biogeosciences.net)
  • To better understand the fate of this terr-OC, molecular (acyl lipid biomarkers) and isotopic tools (stable carbon and radiocarbon isotopes) have been applied to both particulate organic carbon (POC) in surface water and sedimentary organic carbon (SOC) collected from the underlying surface sediments. (biogeosciences.net)
  • The excursion maximum in the Boreal Russian bidichotomus zones corresponds with the peak of the Tethyan marine carbonate excursion in the verrucosum-peregrinus zones, the peak of a marine carbonate excursion recorded in the Argentinean atherstoni Zone and also with the peak of a terrestrial organic carbon isotope excursion in the Crimean trinodosum-callidiscus ammonite zones. (nerc.ac.uk)
  • This is interpreted as due to remineralization of organic carbon within the carbonate rocks. (lyellcollection.org)
  • Fixed carbon", "reduced carbon", and "organic carbon" are equivalent terms for various organic compounds. (wikipedia.org)
  • δ13C varies in time as a function of productivity, organic carbon burial and vegetation type. (wikipedia.org)
  • when organic carbon is buried, more 12C is locked out of the system in sediments than the background ratio. (wikipedia.org)
  • Mass extinctions are often marked by a negative δ13C anomaly thought to represent a decrease in primary productivity and release of plant-based carbon The evolution of large land plants in the late Devonian led to increased organic carbon burial and consequently a rise in δ13C. (wikipedia.org)
  • The marine carbon cycle is also biologically tied to the nitrogen and phosphorus cycles by a near-constant stoichiometric ratio C:N:P of 106:16:1, also known as the Redfield Ketchum Richards (RKR) ratio, which states that organisms tend to take up nitrogen and phosphorus incorporating new organic carbon. (wikipedia.org)
  • Organic carbon forms the backbone of key component of organic compounds such as - proteins, lipids, carbohydrates, and nucleic acids. (wikipedia.org)
  • DIC increases with depth as organic carbon particles sink and are respired. (wikipedia.org)
  • An important process called sediment diagenesis accounts for the other 9% of organic carbon that sank to the deep ocean floor, but was not permanently buried, that is 9% of the total organic carbon produced is degraded in the deep ocean. (wikipedia.org)
  • The microbial communities utilizing the sinking organic carbon as an energy source are partial to nitrogen-rich compounds because much of these bacterium are nitrogen-limited and much prefer it over carbon. (wikipedia.org)
  • As a result, the carbon to nitrogen ratio of sinking organic carbon in the deep ocean is elevated compared to fresh surface ocean organic matter that had not been degraded. (wikipedia.org)
  • Post-depositional diagenesis occurs in organic-carbon-poor marine sediments where bacteria are able to oxidize organic matter in aerobic conditions as an energy source. (wikipedia.org)
  • This has been proposed as an explanation for lower than expected C/N signatures of organic carbon in sediments that have undergone post-depositional diagenesis. (wikipedia.org)
  • citation needed] On long timescales, atmospheric CO2 concentration is determined by the balance among geochemical processes including organic carbon burial in sediments, silicate rock weathering, and volcanism. (wikipedia.org)
  • Some proposed hypotheses are as follows: Direct conversion of organic carbon under high-pressure conditions in the Earth's interior, the most common hypothesis for diamond formation Shock metamorphism induced by meteoritic impact at the Earth's surface Radiation-induced diamond formation by spontaneous fission of uranium and thorium Formation inside an earlier-generation giant star in our area, that long ago exploded in a supernova. (wikipedia.org)
  • The Steptoean Positive Carbon Isotope Excursion (SPICE) was a geological event which occurred about 500 million years ago at the end of the Cambrian Period. (wikipedia.org)
  • The δ13Ccarb and δ13Cwood records reveal a distinct mid-Valanginian positive carbon isotope excursion, with the initiation occurring near the Boreal Russian michalskii-polyptychus zone boundary, which is broadly time-equivalent Tethyan campylotoxus-verrucosum boundary. (nerc.ac.uk)
  • The Cambrian Steptoean Positive Carbon Isotope Excursion (SPICE) is a well-documented global event that marked geochemical excursions in the world's oceans and terrestrial environments. (illinois.edu)
  • Circular 600, Geochemical Preservation of the Steptoean Positive Carbon Isotope Excursion (SPICE) Event in Dolomites of the Furongian Franconia Formation in the Illinois Basin by Dana M. Labotka and Jared T. Freiburg can be downloaded from the University of Illinois IDEALS repository . (illinois.edu)
  • In diagenetic studies (see DIAGENESIS ), measurement of the ratio of carbon-13 to carbon-12 allows the recognition of carbonate precipitated from a variety of different sources. (encyclopedia.com)
  • New isotope data obtained from relatively conformable, carbonate-rich strata of the Ediacaran Yangtze platform in South China reveal substantial delta C-13 variability. (columbia.edu)
  • 34CpDB, indicating that carbon was derived in approximately equal quantities from the dissolution of marine carbonate minerals and the oxidation of organic matter during migration of hydrothermal fluid through the underlying sediment column. (usgs.gov)
  • Either there are large isotopic fractionations for carbon and hydrogen between different soluble organic phases, or the less polar components are partially of terrestrial origin. (caltech.edu)
  • Simulations of 14 C and 13 C in the ocean and terrestrial components of Earth system models (ESMs) present opportunities for model evaluation and for investigation of carbon cycling, including anthropogenic CO 2 emissions and uptake. (geosci-model-dev.net)
  • We found that δ 13 C AA patterns in contrast to bulk δ 13 C values distinguished between carbon derived from algae, seagrass, terrestrial plants, bacteria and fungi. (plos.org)
  • Since amino acids make up about half of organismal carbon, source diagnostic isotope fingerprints can be used as a new complementary approach to overcome some of the limitations of variable source bulk isotope values commonly encountered in estuarine areas and other complex environments with mixed aquatic and terrestrial inputs. (plos.org)
  • Larsen T, Ventura M, Andersen N, O'Brien DM, Piatkowski U, McCarthy MD (2013) Tracing Carbon Sources through Aquatic and Terrestrial Food Webs Using Amino Acid Stable Isotope Fingerprinting. (plos.org)
  • Cernusak LA, Ubierna N, Winter K et al (2013) Environmental and physiological determinants of carbon isotope discrimination in terrestrial plants. (springer.com)
  • Chikaraishi Y, Naraoka H, Poulson SR (2004b) Hydrogen and carbon isotopic fractionations of lipid biosynthesis among terrestrial (C3, C4 and CAM) and aquatic plants. (springer.com)
  • Stable carbon isotope studies of gas exchange within terrestrial ecosystems are commonly undertaken to determine sources and rates of carbon cycling. (nerc.ac.uk)
  • Hart, Malcolm B. . 2010 The Valanginian positive carbon isotope event in Arctic Russia : evidence from terrestrial and marine isotope records and implications for global carbon cycling. (nerc.ac.uk)
  • The synchroneity of the positive carbon isotope event between the marine and terrestrial records and between the northern and southern hemispheres and Tethys, clearly indicates a strong coupling of the ocean-atmosphere system at this time and also confirms that this was a global event, which would have affected the total exchangeable carbon reservoir. (nerc.ac.uk)
  • The magnitude of an accompanying carbon isotope excursion (CIE) can be used to constrain both the sources and amounts of carbon released during an event and also to correlate marine and terrestrial records with high precision. (clim-past.net)
  • Although the amount of carbon stored in marine biota (~3 Gt C) is very small compared with terrestrial vegetation (~610 GtC), the amount of carbon exchanged (the flux) by these groups is nearly equal - about 50 GtC each. (wikipedia.org)
  • Carbon is exchanged with varying speed with the terrestrial biosphere. (wikipedia.org)
  • In addition, an unusual signature of carbon-13 confirms the non-terrestrial origin for organic compounds found in carbonaceous chondrites, as in the Murchison meteorite. (wikipedia.org)
  • The precision of the isotope abundances and atomic mass is limited through variations. (wikipedia.org)
  • It is also important for the researcher to know the variations of isotopes within individuals, between individuals, and over time. (wikipedia.org)
  • These variations are thought to arise from biosynthetic isotope effects and different metabolic routes, especially those associated with the biosynthesis of sugars which are converted into ethanol during fermentation. (wikipedia.org)
  • Only a handful of experimental methods are capable of providing information about the mechanism of a reaction, including crossover experiments, studies of the kinetic isotope effect, and rate variations by substituent. (wikipedia.org)
  • The oxygen and carbon isotope compositions of the sediment deposits in the various Central Asian basins have already been used to decipher both the topographic and climatic changes that occurred in that region during the Cenozoic, generally concentrating on one sedimentary section and/or on a limited time range and either using multiple-type samples including sandstone calcitic cements, marine carbonates, fossils, or paleosols. (mdpi.com)
  • The apparent kinetic isotope effects (AKIE C ) values of carbon were 1.008 ± 0.0005 for quinoline and 1.0048 ± 0.0005 for 3-methylquinoline while AKIE H values of hydrogen of 1.264 ± 0.011 for quinoline and 1.0356 ± 0.0103 for 3-methylquinoline were obtained. (springer.com)
  • k_{13}]{^{13}CH3-CN}+Br^{-}}}\\{}\end{matrix}}\qquad KIE={\frac {k_{12}}{k_{13}}}=1.082\pm 0.008} The kinetic isotope effect (KIE) is the change in the reaction rate of a chemical reaction when one of the atoms in the reactants is replaced by one of its isotopes. (wikipedia.org)
  • The study of kinetic isotope effects can help the elucidation of the reaction mechanism of certain chemical reactions. (wikipedia.org)
  • The kinetic isotope effect is considered to be one of the most essential and sensitive tools for the study of reaction mechanisms, the knowledge of which allows the improvement of the desirable qualities of the corresponding reactions. (wikipedia.org)
  • For example, kinetic isotope effects can be used to reveal whether a nucleophilic substitution reaction follows a unimolecular (SN1) or bimolecular (SN2) pathway. (wikipedia.org)
  • In the reaction of methyl bromide and cyanide (shown in the introduction), the observed methyl carbon kinetic isotope effect indicates an SN2 mechanism. (wikipedia.org)
  • For the previously mentioned nucleophilic substitution reactions, primary kinetic isotope effects have been investigated for both the leaving groups, the nucleophiles, and the α-carbon at which the substitution occurs. (wikipedia.org)
  • Interpretation of the leaving group kinetic isotope effects had been difficult at first due to significant contributions from temperature independent factors. (wikipedia.org)
  • Kinetic isotope effects at the α-carbon can be used to develop some understanding into the symmetry of the transition state in SN2 reactions, although this kinetic isotope effect is less sensitive than what would be ideal, also due to contribution from non-vibrational factors. (wikipedia.org)
  • however, since kinetic isotope effects can be calculated and measured to very high precision, secondary kinetic isotope effects are still very useful for elucidating reaction mechanisms. (wikipedia.org)
  • For the aforementioned nucleophilic substitution reactions, secondary hydrogen kinetic isotope effects at the α-carbon provide a direct means to distinguish between SN1 and SN2 reactions. (wikipedia.org)
  • It has been found that SN1 reactions typically lead to large secondary kinetic isotope effects, approaching to their theoretical maximum at about 1.22, while SN2 reactions typically yield primary kinetic isotope effects that are very close to or less than unity. (wikipedia.org)
  • Kinetic isotope effects that are greater than 1 are referred to as normal kinetic isotope effects, while kinetic isotope effects that are less than one are referred to as inverse kinetic isotope effects. (wikipedia.org)
  • This mechanistic hypothesis is supported by kinetic isotope effect experiments. (wikipedia.org)
  • If the isotope is placed in the molecule at a position directly involved in the mechanism of the reaction, a kinetic isotope effect is expected. (wikipedia.org)
  • The kinetic isotope effect is a change in the rate of reaction based on the change in isotope, not a change in the mechanism of the reaction itself, so isotopic labeling generally satisfies the requirements for a valid crossover experiment. (wikipedia.org)
  • Since these essential AAs (EAAs) typically pass from food source to consumer without alteration to their carbon skeletons , , a method for tracking their origins and fluxes could greatly advance our understanding of nutrient cycling and trophic relationships. (plos.org)
  • Bowling DR, Tans PP, Monson RK (2001) Partitioning net ecosystem carbon exchange with isotopic fluxes of CO2. (springer.com)
  • Broadmeadow MSJ, Griffiths H (1993) Carbon isotope discrimination and the coupling of CO 2 fluxes within forest canopies. (springer.com)
  • Earth's plants and algae (primary producers) are responsible for the largest annual carbon fluxes. (wikipedia.org)
  • The ratio of stable carbon isotopes in the fungi depends on that in their substrates but is shifted in favor of the heavier isotope. (deepdyve.com)
  • The rate of a reaction involving a C-H bond is typically 6-10 times faster than the corresponding C-D bond, whereas a 12C reaction is only 4 percent faster than the corresponding 13C reaction (even though, in both cases, the isotope is one atomic mass unit heavier). (wikipedia.org)
  • Heavier isotopes will (classically) lead to lower vibration frequencies, or, viewed quantum mechanically, will have lower zero-point energy. (wikipedia.org)
  • the C3 carbon fixation, where the isotope separation effect is more pronounced, C4 carbon fixation, where the heavier 13C is less depleted, and Crassulacean Acid Metabolism (CAM) plants, where the effect is similar but less pronounced than with C4 plants. (wikipedia.org)
  • The electronegativity of carbon is 2.5, significantly higher than the heavier group 14 elements (1.8-1.9), but close to most of the nearby nonmetals as well as some of the second- and third-row transition metals. (wikipedia.org)
  • Like all elements heavier than lithium, the original source of nitrogen-14 and nitrogen-15 in the Universe is believed to be stellar nucleosynthesis, where they are produced as part of the carbon-nitrogen-oxygen cycle. (wikipedia.org)
  • The boiling points of the carbon group tend to get lower with the heavier elements. (wikipedia.org)