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Sulfur IsotopesChemical FractionationOxygen IsotopesCarbon IsotopesHydrogenHydrogen BondingHydrogen PeroxideHydrogen SulfideCell FractionationFractionation, Field FlowSubcellular FractionsHydrogen CyanideMolecular Sequence DataKineticsHydrogen-Ion ConcentrationModels, MolecularOxidation-ReductionMolecular WeightAmino Acid SequenceCatalaseOxidantsElectrophoresis, Polyacrylamide GelDeuterium Exchange MeasurementChromatography, GelMolecular StructureChromatographyChemistry Techniques, AnalyticalChromatography, Ion ExchangeProtein ConformationMagnetic Resonance SpectroscopyCell MembraneSulfidesCystathionine gamma-LyasePeroxidasesMass SpectrometryCrystallography, X-RayTemperatureWaterBinding SitesModels, Chemical
CompositionNitrogenLipid biosynthesisBiosynthesisDetermine isotopicGeochimica et Cosmochimica ActaAnalysesRatiosEquilibriumOxygen isotopicStable isotopesSulfideRatioBiochemicalDeuteriumProcessesOxidationVariabilityAbundancesLipidsMechanismsGeochemistryAtmosphericCompositionsPeroxideReactionsAtomsRadioactiveMolecularWaterMeasurementsAtmosphereExperimentsLaboratoryChemicalAdvances
Composition14
  • values for amorphous silica qualitatively reflect the isotopic composition of the waters and temperatures of formation. (caltech.edu)
  • The stable silicon isotopic composition (denoted by δ 30 Si ) of siliceous microfossils extracted from sediment cores can be used as an archive of past oceanic silicon cycling. (copernicus.org)
  • However, the silicon isotopic composition of biogenic silica has only been measured in diatoms, sponges and radiolarians, and isotopic fractionation relative to seawater is entirely unknown for many other silicifiers. (copernicus.org)
  • The vertical profiles of water vapor and its semi-heavy hydrogen isotope HDO provided by instruments on ExoMars Trace Gas Orbiter constitute a unique new data set to understand the Martian water cycle including its isotopic composition. (unibas.it)
  • In 2009, the Commission on Isotopic Abundances and Atomic Weights (CIAAW) of the International Union of Pure and Applied Chemistry (IUPAC) introduced the interval notation to express the standard atomic weights of elements whose isotopic composition varies significantly in nature. (degruyter.com)
  • In the absence of detailed knowledge about the isotopic composition of a material, or when such details may safely be ignored, the probability distribution assigned to the standard atomic weight intervals may be taken as rectangular (or, uniform). (degruyter.com)
  • When information about the provenance of the material, or other information about the isotopic composition needs to be taken into account, then this distribution may be non-uniform. (degruyter.com)
  • Concerning the provision that the isotopic composition of a "normal" material should not have been modified significantly in a geologically brief period, John Böhlke (2015, personal communication) has pointed out that "high and low atomic weight values of light elements commonly are due to isotopic fractionation processes that are happening every day," as arise in respiration, evaporation, and dissolution. (degruyter.com)
  • The 2009 recommendation to use interval notation did achieve the valuable educational goal of drawing attention to the fact that isotopic composition can vary among natural materials, hence so do the atomic weights [ 8 ]. (degruyter.com)
  • The oxygen and hydrogen isotopic composition δ 2 H and δ 18 O of leaf and lake water reflects the isotopic composition of source water/precipitation modified by evapo(transpi)rative enrichment. (copernicus.org)
  • Microbial Isotopic Composition as a Function of Growth Medium? (com.bo)
  • The hydrogen isotopic composition of comets are variable, and these impacts can increase the D/H ratio of surface water without atmospheric escape. (astrobites.org)
  • The research direction is the interpretation of paleoclimatic significance of the hydrogen isotopic composition of leaf wax lipids. (geobiology.cn)
  • Through extensive research of modern plants and surface sediments, the spatial distribution of the net offset of the hydrogen isotopic composition of leaf wax hydrogen and precipitation is revealed. (geobiology.cn)
Nitrogen7
  • Stable nitrogen ( 15 N/ 14 N) and carbon ( 13 C/ 12 C) isotopic compositions of amino acids in organisms have widely been employed as a powerful tool to evaluate resource utilization and trophic connection among organisms in diverse ecosystems. (springeropen.com)
  • The proposed link between nitrogen and carbon isotopes can refine our knowledge of the potential processes affecting the isotopic fractionation within diet and consumer compartments, as well as environmental samples. (springeropen.com)
  • Nitrogen isotopes with amino acids undergo varying degrees of isotopic discrimination (Δ δ 15 N AA ) during trophic transfer (e.g. (springeropen.com)
  • The chemical evolution observed to occur in molecular clouds is summarised and a model for dense core collapse that can plausibly account for the isotopic fractionation of hydrogen, nitrogen, oxygen and carbon measured in primitive solar system materials is presented. (activeboard.com)
  • The scientists believe the xenolith, which shows unprecedented isotopic variations of nitrogen, may offer insight into the solar system's formation and say it poses serious problems for current models of light element isotopic fractionation. (activeboard.com)
  • Giacomo Briani and colleagues measured the light element isotopic ratios of hydrogen, carbon and nitrogen in the xenolith, called PX-18. (activeboard.com)
  • A method for the oxidation and nitrogen isotopic analysis of photopigments (chlorophyll and phaeophytin) has been developed. (uncg.edu)
Lipid biosynthesis4
Biosynthesis2
  • The Studium Research Associate will contribute to all these projects by bringing an original expertise on isotopes biochemistry that will advance our understanding of the intimate mechanisms during biosynthesis that affect the isotopic record of environmental parameters through organic biochemicals. (lestudium-ias.com)
  • He/she will specifically coordinate all aspects concerning the biochemical fractionation of hydrogen isotopes from water absorption to chemical biosynthesis. (lestudium-ias.com)
Determine isotopic2
  • Furthermore, the biochemical pathways and mechanisms that determine isotopic fractionation during biosilicification remain poorly understood. (copernicus.org)
  • No experiments have been completed to determine isotopic shifts induced by Se(-II) oxidation, but results from the S isotope literature suggest they should be small. (chempedia.info)
Geochimica et Cosmochimica Acta1
  • A. L. Sessions and Hayes, J. M. , " Calculation of hydrogen isotopic fractionations in biogeochemical systems " , Geochimica Et Cosmochimica Acta , vol. 69, no. 3, pp. 593-597, 2005. (whoi.edu)
Analyses3
  • Granular microcrystalline quartz, the most common constituent of chert, has been found to contain hydroxyl groups particularly suitable for hydrogen isotope analyses. (caltech.edu)
  • This session aims to bring together scientists from different fields applying single and dual oxygen and hydrogen isotope approaches on environmental-derived compounds for the reconstruction of climatic and biological processes that go beyond standard isotope analyses of water. (copernicus.org)
  • Compound-specific hydrogen isotopic analyses for unravelling present and past hydrological regimes. (lestudium-ias.com)
Ratios5
  • Often, these stable isotopic compositions represent discernible ratios and thus can be useful for characterizing and quantifying any given process in the biosphere (e.g. (springeropen.com)
  • Sulfur isotope analysis has been used to investigate sources and chemical processes of sulfur dioxide and sul- fate in the atmosphere, however interpretation of measured sulfur isotope ratios is challenging due to a lack of reliable information on the isotopic fractionation involved in ma- jor transformation pathways. (documents.pub)
  • Light element isotopic ratios are the result of formation mechanisms and particular physical and chemical conditions. (activeboard.com)
  • Oxygen isotopes appear in anomalous ratios in atmospheric ozone, resulting from mass-independent fractionation . (detailedpedia.com)
  • Because the lead isotopes are created by decay of different transuranic elements, the ratios of the four lead isotopes to one another can be very useful in tracking the source of melts in igneous rocks , the source of sediments and even the origin of people via isotopic fingerprinting of their teeth, skin and bones. (detailedpedia.com)
Equilibrium4
  • The fraction of the water or hydroxyl groups that is most resistant to exchange and most difficult to drive off is that water or hydroxyl group most likely to contain the hydrogen which was in equilibrium with the waters from which the silica formed. (caltech.edu)
  • Cherts are usually not in isotopic equilibrium with their coexisting carbonates, and the somewhat insensitive chert-calcite oxygen isotope fractionation thus cannot be used to obtain meaningful temperatures. (caltech.edu)
  • This method allows for the determination of the concentration of free sulfide that is in equilibrium with hydrogen sulfide . (chempedia.info)
  • Harold Urey's equally seminal contribution was his classic paper "The thermodynamic properties of isotopic substances", also published in 1947, in which he calculated the equilibrium separation factors for isotopes of the light elements in chemical reactions and solid-liquid-vapor phase equilibria, based on quantum mechanics and spectroscopic data on isotopic molecules. (balzan.org)
Oxygen isotopic2
  • Calcitic Crinoid fragments in a chert nodule from the Mississippian Burlington limestone yielded an oxygen isotopic temperature of 25°C, indicating that fossil fragments encased within chert nodules may be protected from post-depositional exchange with ground waters and thus suitable for isotopic paleo-temperature analysis. (caltech.edu)
  • That the flowering of oxygen isotopic climatology began in Urey's Chicago laboratory was due to another, and perhaps equally improbable impact, which similarly caused the demise of the conventional scientific wisdom on the glacial and interglacial climatic cycles during the Pleistocene Epoch. (balzan.org)
Stable isotopes1
  • Within the context of building an understanding of relationships between past changes in the water cycle and developments in societies, we have initiated an ambitious project at ISTO based on our recent technological advances that allow the measurement of hydrogen stable isotopes (deuterium/hydrogen ratio or dD) on single biomolecules extracted from geological archives (peats, soils, sediments) or living plants. (lestudium-ias.com)
Sulfide4
  • GC/FPD has been used to measure hydrogen sulfide, free disulfide, and dissolved metal sulfide complexes in water (Radford-Knoery and Cutter 1993). (chempedia.info)
  • Hydrogen sulfide was measured in the headspace of the sample (100 mL) with a detection limit of 0.6 pmol/L. A detection limit of 0.2 pmol/L was obtained for total dissolved sulfide. (chempedia.info)
  • Canfield (2001) reviewed previous work on oxidation of dissolved sulfide and concluded that little isotopic fractionation occurs in this process. (chempedia.info)
  • Hydrogen sulfide occurs in natural gas. (chempedia.info)
Ratio6
  • As water vapor undergoes hydrogen isotopic fractionation upon deposition (but not sublimation), the D/H isotopic ratio in water is a tracer of phase transitions, and a key quantity to understand the long-term history of water on Mars. (unibas.it)
  • Our work provides evidence that the variability of the D/H ratio in the lower and middle atmosphere of Mars is controlled by fractionation on water ice clouds, and thus modulated by diurnally and seasonally varying cloud formation. (unibas.it)
  • The term is most commonly met in connection with deuterium solvent isotope effects, when the fractionation factor Φ expresses the ratio: \[\varPhi = \frac{(x_{\text{D}}/x_{\text{H}})_{\text{solute}}}{(x_{\text{D}}/x_{\text{H}})_{\text{solvent}}} \] for the exchangeable hydrogen atoms in the chemical species (or sites) concerned. (iupac.org)
  • Specifically, the authors examine the ratio of deuterium to hydrogen (D/H) and see how it changes over time. (astrobites.org)
  • The D/H ratio is a good tracer of water content due to a process called fractionation. (astrobites.org)
  • Variations in isotopic abundance are measured by isotope ratio mass spectrometry , and can reveal information about the ages and origins of rock, air or water bodies, or processes of mixing between them. (detailedpedia.com)
Biochemical1
  • Our results highlight that there is a taxonomic component to silicon isotope fractionation during biosilicification, possibly via a shared or related biochemical transport pathway. (copernicus.org)
Deuterium1
  • As water is cycled between the atmosphere and surface water, we expect some water molecules with normal hydrogen to be lost from the atmosphere, while heavier water molecules with deuterium are retained. (astrobites.org)
Processes2
  • 2013 ). Isotopic discrimination is frequently quantified by the kinetic isotope effect ( α ) and flux ( F ) of the processes (e.g. (springeropen.com)
  • We further examined the effects of pressure on the isotope enrichment factors of carbon and hydrogen isotopes and propose that the dual isotope derived lambda index, calculated based on bacterial growth pressure, can serve as a diagnostic tool for delineating microbially-driven biogeochemical processes in the deep ocean and deep biosphere. (geochemicalperspectivesletters.org)
Oxidation1
  • Natural mixed matrix samples exhibited irreproducible isotopic results following both extractions and oxidation. (uncg.edu)
Variability1
  • We have been examining these problems by modeling the effects of loading the atmosphere with H2, characterizing the stable isotopic (D/H) variability of atmospheric H2, and determining the isotopic characteristics of H2 of different origins. (caltech.edu)
Abundances2
  • At its 2009 meeting in Vienna, the IUPAC Commission on Isotopic Abundances and Atomic Weights (CIAAW) resolved to express the standard atomic weight of ten elements - including hydrogen, carbon, and oxygen - by means of intervals that characterize the span of their atomic-weight values in so-called "normal" materials. (degruyter.com)
  • Are all the isotopic studies based on the abundances on Earth with the assumption that at formation the abundances were uniform across the solar system? (astrobites.org)
Lipids1
  • The mechanism of controlling the hydrogen isotope fractionation of lipids is also discussed to provide insights for its application in paleoclimate. (geobiology.cn)
Mechanisms1
  • However, little is known about the physiological factors or mechanisms responsible for determining the isotopic discrimination (particularly for carbon) within amino acids of organisms. (springeropen.com)
Geochemistry2
  • Stable isotope geochemistry is largely concerned with isotopic variations arising from mass-dependent isotope fractionation , whereas radiogenic isotope geochemistry is concerned with the products of natural radioactivity . (detailedpedia.com)
  • Lead isotope geochemistry is useful for providing isotopic dates on a variety of materials. (detailedpedia.com)
Atmospheric1
  • In this paper, the authors attempt to constrain the amount of water lost through atmospheric escape over the Martian geological history by examining hydrogen isotopes in Martian meteorites . (astrobites.org)
Compositions1
  • The chert-water oxygen isotope fractionation with temperature was estimated from published experimental data and from the isotopic compositions of cherts which formed at approximately known temperatures. (caltech.edu)
Peroxide2
  • Hydrogen peroxide dimers and the production of O 2 in icy satellite surfaces. (astrochymist.org)
  • This method first uses extraction and purification of photopigments by column chromatography, followed by UV irradiation to convert photopigment N to nitrate and nitrite in the presence of hydrogen peroxide. (uncg.edu)
Reactions1
  • Polyakov, VB , Horita, J & Cole, DR 2005, ' Isotopic self-exchange reactions of water: Evaluation of the rule of the geometric mean in liquid-vapor isotope partitioning ', Journal of Physical Chemistry A , vol. 109, no. 38, pp. 8642-8645. (ttu.edu)
Atoms1
  • Fusion is the opposite, creating vast amounts of energy by fusing atoms of hydrogen together, but we're still many years away from large-scale, commercial fusion reactors. (veteranstoday.com)
Radioactive1
  • The main advantage of using tritium ( 3 H), the radioactive isotope of hydrogen, is that it is readily available and easily assayed by scintillation counting. (humankinetics.com)
Molecular2
  • Molecular hydrogen (H2) is the tenth most abundant molecule in earth's atmosphere, and the second most abundant reduced gas, after methane. (caltech.edu)
  • Surface Coverage Effects on the Formation of Molecular Hydrogen on a Graphite Surface via an Eley-Rideal Mechanism. (astrochymist.org)
Water3
  • A new experimental technique, called Differential Isotopic Analysis (D.I.A.), has been developed which allows the isotopic exchange characteristics of water in different sites in hydrous silica to be determined. (caltech.edu)
  • Outgassing is expected to surpress the fractionation of isotopes, so more water should have been lost than estimated. (astrobites.org)
  • Deviations from the random distribution of hydrogen isotopes among isotopic species of liquid and vapor water (the rule of the geometric mean) were critically assessed theoretically and experimentally from the triple to critical point of water. (ttu.edu)
Measurements1
  • Here, we present the first measurements of the silicon isotopic fractionation during biosilicification by loricate choanoflagellates, a group of protists closely related to animals. (copernicus.org)
Atmosphere1
  • Earlier in the solar system's history, the intense UV radiation from the Sun could have reduced D/H fractionation due to escape of both isotopes of hydrogen from the atmosphere. (astrobites.org)
Experiments1
  • We also expect that he/she proposes and realises alternative and additional experiments allowing a better understanding of these fractionations. (lestudium-ias.com)
Laboratory1
  • For isotopic analysis, the resulting nitrate/nitrite was converted to N2O at the USGS Reston Stable Isotope Laboratory (RSIL) using a strain of bacteria Pseudomonas aureofaciens, which lacks N2O-reductase activity. (uncg.edu)
Chemical1
Advances1
  • We also encourage people working with all techniques (IRMS-, NMR- or spectroscopy-based) to present advances in methods, as well as researchers focusing on improving oxygen and hydrogen isotope-based models to discuss their approaches. (copernicus.org)