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). ...

Read Stable carbon isotope ratio in xylotrophic fungi and their substrates, Russian Journal of Ecology on DeepDyve, the largest online rental service for scholarly research with thousands of academic publications available at your fingertips.

Abstract. A method for the determination of the stable carbon isotopic composition of atmospheric nitrophenols in the gas and particulate phases is presented. It has been proposed to use the combination of concentration and isotope ratio measurements of precursor and product to test the applicability of results of laboratory studies to the atmosphere. Nitrophenols are suspected to be secondary products formed specifically from the photooxidation of volatile organic compounds. XAD-4TM resin was used as an adsorbent on quartz filters to sample ambient phenols using conventional high volume air samplers at York University in Toronto, Canada. Filters were extracted in acetonitrile, with a HPLC (high-performance liquid chromatography) clean-up step and a solid phase extraction step prior to derivatization with BSTFA (bis(trimethylsilyl) trifluoroacetamide). Concentration measurements were done with gas chromatography-mass spectrometry and gas chromatography-isotope ratio mass spectrometry was used ...

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.

Compound-specific carbon and hydrogen isotope ratios are routinely measured on extractable organic matter to decipher biogeochemical processes and events in Earth history. To deliver accurate interpretations, it is paramount that isotopic values are derived from indigenous compounds and are not the result of contamination. However, distinguishing between compounds from these different provenances can be difficult, especially if a degree of mixing occurred. In this study, we assess the impact of hydrocarbon contamination on the carbon and hydrogen isotopic composition of n-alkanes from similar to 820 Ma Precambrian evaporitic drill core samples through exterior/interior (E/I) rock extraction experiments. In these experiments, exterior and interior portions of the same rock samples were separately crushed to powder, extracted and processed. Compound-specific isotope values of n-alkanes from the different rock portions were subsequently measured and compared. In most cases, n-alkanes from exterior ...

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

Yu ZQ,Sheng GY,Piu JM,et al. Determination of porphyrin carbon isotopic composition using gas chromatography-isotope ratio monitoring mass spectrometry[J]. Journal of Chromatography A,2000,903(1-2):183-191 ...

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

Freeman, Katherine H., Mueller, Kevin E., Diefendorf, Aaron F., Wing, Scott L., and Koch, Paul L. 2011. Clarifying the influence of water availability and plant types on carbon isotope discrimination by C3 plants. Proceedings of the National Academy of Sciences of the United States of America. 108 (16):E59-E60. https://doi.org/10.1073/pnas.1102556108 ...

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:. ...

If you have a question about this talk, please contact Julia Montes-Landa.. Abstract not available. This talk is part of the Pitt-Rivers Archaeological Science Seminar Series series.. ...

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

TY - JOUR. T1 - Land use driven change in soil pH affects microbial carbon cycling processes. AU - Malik, Ashish A.. AU - Puissant, Jeremy. AU - Buckeridge, Kate M.. AU - Goodall, Tim. AU - Jehmlich, Nico. AU - Chowdhury, Somak. AU - Gweon, Hyun Soon. AU - Peyton, Jodey M.. AU - Mason, Kelly E.. AU - van Agtmaal, Maaike. AU - Blaud, Aimeric. AU - Clark, Ian M.. AU - Whitaker, Jeanette. AU - Pywell, Richard F.. AU - Ostle, Nick. AU - Gleixner, Gerd. AU - Griffiths, Robert I.. N1 - A.A.M. has received funding from the European Unions Horizon 2020 research and innovation program under the Marie Skłodowska-Curie grant no. 655240 and all other UK-based authors were funded by the UK Natural Environment Research Council under a Soil Security Programme grant (NE/M017125/1). We also acknowledge Kathleen Eismann for her help in sample preparation for metaproteomic analysis; Heiko Moossen, Petra Linke and Steffen Ruehlow for assistance with stable carbon isotope analyses and all the land owners who ...

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 ...

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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Die Universität zu Köln ist eine Exzellenzuniversität mit dem klassischen Fächerspektrum einer Volluniversität. Als eine der größen Hochschulen Europas arbeitet sie in Forschung und Lehre auch international auf höchstem Niveau.

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 ...

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

Arı́stegui J, Duarte CM, Agustı́ S, Doval M, Álvarez-Salgado XA, Hansell DA. 2002. Dissolved organic carbon support of respiration in the dark ocean. Science. 298(5600):1967-1967. doi:10.1126/science.1076746.. Boyd PW, Sherry ND, Berges JA, Bishop JKB, Calvert SE, Charette MA, Giovannoni SJ, Goldblatt R, Harrison PJ, Moran SB, et al. 1999. Transformations of biogenic particulates from the pelagic to the deep ocean realm. Deep Sea Res, Part II. 46(11):2761-2792. doi:10.1016/S0967-0645(99)00083-1.. Carter JF, Barwick VJ, editors. 2011. Good practice guide for isotope ratio mass spectrometry. 1st edition. Bristol: FIRMS.. Cavan EL, Trimmer M, Shelley F, Sanders R. 2017. Remineralization of particulate organic carbon in an ocean oxygen minimum zone. Nat Commun. 8(1):1-9. doi:10.1038/ncomms14847.. Cifuentes LA, Sharp JH, Fogel ML. 1988. Stable carbon and nitrogen isotope biogeochemistry in the Delaware estuary: Carbon and nitrogen isotopes. Limnol Oceanogr. 33(5):1102-1115. ...

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 ...

TY - JOUR. T1 - Measurement of δ18O and δ2H values of fluid inclusion water in speleothems using cavity ring-down spectroscopy compared with isotope ratio mass spectrometry. AU - Arienzo, Monica M.. AU - Swart, Peter K.. AU - Vonhof, Hubert B.. N1 - Copyright: Copyright 2013 Elsevier B.V., All rights reserved.. PY - 2013/12/15. Y1 - 2013/12/15. N2 - RATIONALE The hydrogen and oxygen isotopic analyses (δ2H and δ18O values) of water trapped within speleothem carbonate (fluid inclusions) have traditionally been conducted utilizing dual-inlet isotope ratio mass spectrometry (IRMS) or continuous-flow (CF)-IRMS methods. The application of cavity ring-down spectroscopy (CRDS) to the δ2H and δ18O analysis of water in fluid inclusions has been investigated at the University of Miami as an alternative method to CF-IRMS. METHODS An extraction line was developed to recover water from the fluid inclusions consisting of a crusher, sample injection port and an expansion volume (either 100 or 50 cm3) ...

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 - ...

In this study, we analyzed settling particles collected from March 2011 to February 2012 for long-chain n-alkanes and their stable carbon isotope ratio (δ13C) to investigate sources of terrestrial organic carbon in the Ulleung basin (East Sea). The settling particles were collected with 10 to 17-day intervals at 1000 m and 2300 m water depths. In general, the n-alkanes showed strong odd carbon number predominance at both water depths with higher fluxes of long-chain n-alkanes (C25-C35, 0.4-12.0 μg/m2/day at 1000 m water depth and 0.7-13.6 μg/m2/day at 2300 m water depth) than those of short-chain n-alkanes (C15-C23, 0.04-1.1 μg/m2/day at 1000 m water depth and 0.1-0.9 μg/m2/day at 2300 m water depth). The δ13C signatures of n-C27, n-C29, and n-C31 at 1000 m and 2300 m water depths were -31.0±0.5‰, -32.1±0.4‰, -32.4±0.8‰ and -30.9±0.9‰, -31.7±0.5‰, -32.3±0.4‰, respectively, indicating a large contribution of C3 plant as the main source of n-alkanes. The carbon Preference ...

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 ...

Diverse interpretations have been made of carbon isotope time series in speleothems, reflecting multiple potential controls. Here we study the dynamics of 13C and 12C cycling in a particularly well-constrained site to improve our understanding of processes affecting speleothem δ13C values. The small, tubular Grotta di Ernesto cave (NE Italy) hosts annually-laminated speleothem archives of climatic and environmental changes. Temperature, air pressure, pCO2, dissolved inorganic carbon (DIC) and their C isotopic compositions were monitored for up to five years in soil water and gas, cave dripwater and cave air. Mass-balance models were constructed for CO2 concentrations and tested against the carbon isotope data. Air advection forces winter pCO2 to drop in the cave air to ca. 500 ppm from a summer peak of ca. 1500 ppm, with a rate of air exchange between cave and free atmosphere of approximately 0.4 days. The process of cave ventilation forces degassing of CO2 from the dripwater, prior to any ...

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.

This publication was developed by an international group of experts as an integral part of the IAEAs efforts to contribute to the transfer of technology and knowledge in nutrition. Its aim is to assist Member States in their efforts to combat malnutrition by facilitating the use of relevant nuclear techniques. The stable (non-radioactive) isotope technique has been developed to assess intake of human milk in breastfed infants. The practical application of the stable isotope technique, based on analysis of deuterium by Fourier transform infrared spectrometry (FTIR), is presented in this book.. ...

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 ...

to 1) assess winter habitat dynamics and validate the use of stable carbon isotopes as a measure of ... effects from winter habitat on arrival timing, reproduction, and post-fledging survival, and 3) explore ... carry-over effects between breeding events, molt, and subsequent winter habitat use. Combined, my results .... ...

to 1) assess winter habitat dynamics and validate the use of stable carbon isotopes as a measure of ... effects from winter habitat on arrival timing, reproduction, and post-fledging survival, and 3) explore ... carry-over effects between breeding events, molt, and subsequent winter habitat use. Combined, my results .... ...