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Isotopes

Distribution by Scientific Domains
Earth and Environmental Science23%
Chemistry22%
Life Sciences21%
Humanities and Social Sciences8%
Engineering7%
Medical Sciences7%
Physics and Astronomy6%
3 Other Domains6%
Distribution within Earth and Environmental Science
General Aquaculture, Fisheries & Fish Science17%
Geochemistry & Mineralogy13%
Geology & Geophysics8%

Kinds of Isotopes

  • carbon isotope
  • environmental isotope
  • nitrogen isotope
    		•
  • nitrogen stable isotope
  • oxygen isotope
  • radioactive isotope
    		•
  • stable carbon isotope
  • stable isotope
  • sulfur isotope
    		•
  • water isotope

    • Terms modified by Isotopes

  • isotope analysis
  • isotope approach
  • isotope composition
  • isotope content
  • isotope data
  • isotope dilution
  • isotope dilution analysis
  • isotope dilution mass spectrometry
  • isotope dilution method
  • isotope discrimination
    		•
  • isotope effect
  • isotope effects
  • isotope enrichment
  • isotope evidence
  • isotope exchange
  • isotope fractionation
  • isotope geochemistry
  • isotope incorporation
  • isotope labeling
  • isotope labelling
    		•
  • isotope measurement
  • isotope pattern
  • isotope probing
  • isotope ratio
  • isotope ratio analysis
  • isotope ratio mass spectrometer
  • isotope ratio mass spectrometry
  • isotope record
  • isotope shift
  • isotope signal
    		•
  • isotope signature
  • isotope stage
  • isotope studies
  • isotope study
  • isotope value
  • isotope variation

    • Selected Abstracts

    STABLE ISOTOPES IN HUMAN NUTRITION

    JOURNAL OF HUMAN NUTRITION & DIETETICS, Issue 1 2004
    Les Bluck
    [source]

    POTENTIAL TOOLS FOR TRACKING OCEAN CLIMATE: VARIABILITY IN STABLE ISOTOPES IN LIVING CORALLINE ALGAE

    JOURNAL OF PHYCOLOGY, Issue 2000
    R.A. Dunn
    Our ability to track long term climate change in coastal regions is limited in temperate and polar regions. Physical oceanographic dynamics in temperature and upwelling events can be recorded as carbon and oxygen stable isotope signals in carbonate producing organisms. Because coralline algae photosynthesize, produce calcium carbonate and are widely distributed, they may provide a new tool for detecting short-term change. However, little is known about how coralline algae incorporate stable isotopes into their calcite thallus structure. The objectives of this study were to determine if growth and isotopic signature differ in articulated coralline algae grown in different oceanographic regimes in Monterey Bay. The articulated alga Calliarthron cheiliospororioides was outplanted at three locations varying in seawater temperature and upwelling strength. New algal growth was measured by staining the algae with Alizarin Red and enumerating the amount of accumulated material at the branch tips. Growth rates varied seasonally and spatially. Low-upwelling daily growth rates averaged 0.044,0.056 mm day,1, while high-upwelling growth rates were 0.083 mm day,1. Isotope ratios were obtained by analyzing microsampled portions of the alga in a mass spectrometer. Changes in the 18O/16O and 13C/12C ratios appear to reflect change in seawater temperature and upwelling strength, respectively. [source]

    DIET-TISSUE FRACTIONATION OF STABLE CARBON AND NITROGEN ISOTOPES IN PHOCID SEALS

    MARINE MAMMAL SCIENCE, Issue 1 2002
    VÉRONIQUE Lesage
    Diet-tissue isotopic fractionation of carbon (C) and nitrogen (N) isotopes in short- and longer-term diet integrators of diet (i. e., blood serum and red cells), that involve non-invasive sampling techniques was examined using three species of phocid seals (harbor seals, gray seals, and harp seals) fed a known diet. Variability in diet-tissue fractionation values within and between species was also scrutinized to determine the legitimacy of using values obtained from one species to explore trophic positions and diets of other related species. All captive seals raised on a constant diet had tissues enriched in 13C and 15N relative to their diet. Diet-tissue isotopic fractionation values were generally consistent among conspecifics and among phocid species for a given tissue. Trophic isotopic enrichment in 13C was significantly higher in red blood cells (+1.5%±) than in blood serum (+0.8%±), whereas the reverse was observed for nitrogen isotopes (+1.7%± in red cells vs. +3.1%± in serum). However, 13C-depleted lipids were not extracted from blood tissues in this study. This results in a downward bias in the diet-tissue fractionation factors for carbon for both red cells and blood serum, particularly the latter because of their significantly higher lipid contents (x,± SD = 14.6 ± 2.3%; n= 20; red blood cells 3.8 ± 0.9%±; n= 50, muscle 7.7 ± 2.0; n= 21) in marine mammals. [source]

    ON THE ROAD TO PARADIS: NEW INSIGHTS FROM AMS DATES AND STABLE ISOTOPES AT LE DÉHUS, GUERNSEY, AND THE CHANNEL ISLANDS MIDDLE NEOLITHIC

    OXFORD JOURNAL OF ARCHAEOLOGY, Issue 2 2010
    RICK J. SCHULTING
    Summary We here report the results of a programme of AMS dating and stable isotope analysis on human remains from the chambered tomb of Le Déhus, Guernsey. An early use-phase in the range 4100,3900 BC is indicated, confirming the monument's attribution to the Middle Neolithic II as defined in western France. Late Neolithic burial activity is also identified. Stable carbon isotope measurements provide little or no evidence for the consumption of marine foods, although stable nitrogen isotope values are unusually high. These results are situated in the wider context of Neolithic mortuary monuments of the Channel Islands and Normandy. [source]

    THE USE OF OXYGEN ISOTOPES IN SHEEP MOLARS TO INVESTIGATE PAST HERDING PRACTICES AT THE NEOLITHIC SETTLEMENT OF ÇATALHÖYÜK, CENTRAL ANATOLIA

    ARCHAEOMETRY, Issue 3 2010
    E. HENTON
    This paper presents a pilot study designed to test the use of oxygen isotopes for investigating aspects of early herding practices in the Neolithic of western Asia, using the site of Çatalhöyük in central Anatolia as a case study. Time-sequenced ,18O values in dental enamel of archaeological sheep are assessed for post-depositional diagenetic effects and compared with seasonal ,18O meteoric water values in the region today. The evidence is used to indicate the environmental conditions in which individual sheep spent their first year, enabling management of breeding and birthing seasons, and movement to seasonal pastures, to be investigated. [source]

    ON ISOTOPES AND OLD BONES*

    ARCHAEOMETRY, Issue 6 2008
    J. A. LEE-THORP
    This review charts the developments and progress made in the application of stable light isotope tools to palaeodietary adaptations from the 1970s onwards. It begins with an outline of the main principles governing the distribution of stable light isotopes in foodwebs and the quality control issues specific to the calcified tissues used in these analyses, and then proceeds to describe the historical landmark studies that have marked major progress, either in their archaeological applications or in enhancing our understanding of the tools. They include the adoption of maize agriculture, marine-focused diets amongst coastal hunter,gatherers, trophic level amongst Glacial-period modern humans and Neanderthals, and the use of savannah resources by early hominins in Africa. Particular attention is given to the progress made in addressing the challenges that have arisen out of these studies, including issues related to the routing of dietary nutrients. I conclude with some firm, and some more speculative, pointers about where the field may be heading in the next decade or so. [source]

    Isotopes in Biogenic Silica (IBiS),

    JOURNAL OF QUATERNARY SCIENCE, Issue 4 2008
    Melanie J. Leng
    This special issue of the Journal of Quaternary Science comprises a selection of papers from the third meeting of a series on ,ISOtopes in PALaeoenvironmental reconstruction' (ISOPAL), themed around Isotopes and Biogenic silica (IBiS). The meeting was held at the British Geological Survey (Nottingham, UK) in April 2007, and consisted of a series of presentations giving methodological approaches to using isotopes in biogenic silica but also specific examples of the application, the majority of which are presented in this issue. © Natural Environment Research Council (NERC) copyright 2008. Reproduced with the permission of NERC. Published by John Wiley & Sons Ltd. [source]

    The ,Malbouffe' Saga La Saga de la ,Malbouffe' Die Saga von ,Malbouffe"

    EUROCHOICES, Issue 1 2007
    Alain Rérat
    summary The ,Malbouffe' Saga After the end of the Second World War, a marked increase in animal and plant production was observed in France, little by little considered by consumers to be obtained at the expense of product quality. The pejorative term ,malbouffe' soon emerged, in connection not only with the hygiene of food, but also with its organoleptic and technological characteristics. This article focuses on food safety in France, with special attention paid to the incidence of toxi-infections and food contaminations of biological and chemical origin. The Mad Cow outbreak is reviewed, along with its consequences for human health in the form of new variant Creutzfeldt-Jakob's disease. It is emphasized that food-related human mortality , almost exclusively due to biological contaminations , represented only 647 cases in 1995, i.e., 0.12 per cent of the overall mortality rate. The main contaminants were Salmonella, whose number is steadily decreasing, and Campylobacter, but parasite and phycotoxic risks are increasing. Mortality due to chemical contaminants is very low i.e., 10 cases or 0.002 per cent of overall mortality These contaminants, either accidental (dioxin, hydrocarbons, radioactive isotopes) or unavoidable (residues from phytochemicals, fertilisers) may be at the source of acute or chronic intoxications with sometimes unknown consequences. Nevertheless, food safety in France does not merit the spiteful term ,malbouffe'. Nach dem Ende des Zweiten Weltkriegs war in Frankreich im Bereich der Tier- und Pflanzenproduktion ein deutlicher Zuwachs zu beobachten, welcher in den Augen der Verbraucher zunehmend auf Kosten der Produktqualität erreicht wurde. Der abwertende Begriff ,Malbouffe" (in etwa ,schlechtes Essen") entstand bald darauf nicht nur im Hinblick auf die Nahrungsmittelhygiene, sondern auch in Bezug auf die organoleptischen und technologischen Eigenschaften der Nahrungsmittel. Dieser Beitrag konzentriert sich auf die Nahrungsmittelsicherheit in Frankreich unter besonderer Berücksichtigung der aufgetretenen Infektionen durch Giftstoffe und der Kontamination von Nahrungsmitteln biologischen und chemischen Ursprungs. Der BSE-Ausbruch und dessen Auswirkungen auf die Gesundheit des Menschen in Form von einer neuen Variante der Creutzfeldt-Jakob-Krankheit werden noch einmal betrachtet. Es wird hervor gehoben, dass die nahrungsmittelbedingte Sterblichkeit bei Menschen, die nahezu ausschließlich auf biologische Kontaminationen zurückzuführen ist, 1995 bei nur 647 Fällen lag, d.h. bei 0,12 Prozent der gesamten Sterblichkeitsrate. Die Nahrungsmittel wurden hauptsächlich durch Salmonellen (die Anzahl dieser Fälle nimmt kontinuierlich ab) und Campylobacter kontaminiert, die parasitären und phykotoxischen Risiken nehmen jedoch zu. Die auf chemische Kontaminationen zurückzuführende Sterblichkeit ist sehr gering und macht zehn Fälle oder 0,002 Prozent der gesamten Sterblichkeitsrate aus. Bei diesen Kontaminationen, die entweder zufällig herbei geführt werden (durch Dioxin, Kohlenwasserstoff, radioaktive Isotope) oder unvermeidbar sind (durch Rückstände pfl anzenchemischer Substanzen, Düngemittel), könnte es sich um die Ursache für akute oder chronische Vergiftungen handeln, welche zum Teil unbekannte Konsequenzen nach sich ziehen. Dennoch hat die Nahrungsmittelsicherheit in Frankreich den verächtlichen Begriff ,Malbouffe" nicht verdient. Après la fi n de la deuxième guerre mondiale, l'agriculture française a connu une augmentation spectaculaire des rendements des productions animale et végétale, rapidement accusée d'avoir été obtenue aux dépens de la qualité des produits consommés. Ainsi est apparue le terme barbare de «malbouffe», lié dans l'esprit des consommateurs, non seulement aux qualités hygiéniques de l'alimentation, mais également à ses caractéristiques sensorielles, voire technologiques. Ce rapport se focalise uniquement sur la salubrité alimentaire en France, soulignant, en particulier, l'évolution de l'incidence des toxi-infections et des contaminations alimentaires d'origine biologique et chimique. Après avoir rappelé l'épizootie de la vache folle (1000 cas en France depuis 1996 et actuellement en cours d'extinction) et de ses conséquences sur la santé humaine (nouvelle variante de la maladie de Creutzfeldt-Jakob) limitées actuellement à 13 cas mortels dans notre pays, ce rapport précise que la mortalité humaine liée à l'alimentation , presque totalement due à des contaminations biologiques - ne représentait en 1995 que 647 cas, i.e. 0.12% de la mortalité générale. Pour l'essentiel, ces contaminants sont des salmonelles, en baisse constante, et des campylobacter, mais on peut craindre la progression des risques parasitaires et phycotoxiques, encore réduits actuellement. La mortalité liée aux contaminants chimiques est très faible (10 cas, i.e. 0.002% de la mortalité générale); mais ces contaminants -qu'ils soient accidentels (dioxine, hydrocarbures, isotopes radio-actifs,) ou inévitables (résidus de phytosanitaires, d'engrais,)- peuvent être à l'origine de crises aiguës ou d'intoxications chroniques dont on ne connaît pas toujours les implications. Néanmoins, dans l'ensemble, la salubrité alimentaire en France ne mérite nullement la connotation malveillante du terme «malbouffe». [source]

    Variability of Isotope and Major Ion Chemistry in the Allequash Basin, Wisconsin

    GROUND WATER, Issue 7 2003
    John F. Walker
    As part of ongoing research conducted at one of the U.S. Geological Survey's Water, Energy, and Biogeochem-ical Budgets sites, work was undertaken to describe the spatial and temporal variability of stream and ground water isotopic composition and cation chemistry in the Trout Lake watershed, to relate the variability to the watershed flow system, and to identify the linkages of geochemical evolution and source of water in the watershed. The results are based on periodic sampling of sites at two scales along Allequash Creek, a small headwater stream in northern Wisconsin. Based on this sampling, there are distinct water isotopic and geochemical differences observed at a smaller hillslope scale and the larger Allequash Creek scale. The variability was larger than expected for this simple watershed, and is likely to be seen in more complex basins. Based on evidence from multiple isotopes and stream chemistry, the flow system arises from three main source waters (terrestrial-, lake-, or wetland-derived recharge) that can be identified along any flowpath using water isotopes together with geochemical characteristics such as iron concentrations. The ground water chemistry demonstrates considerable spatial variability that depends mainly on the flow-path length and water mobility through the aquifer. Calcium concentrations increase with increasing flowpath length, whereas strontium isotope ratios increase with increasing extent of stagnation in either the unsaturated or saturated zones as waters move from source to sink. The flowpath distribution we identify provides important constraints on the calibration of ground water flow models such as that undertaken by Pint et al. (this issue). [source]

    Evaluation of TCE and MTBE in situ Biodegradation: Integrating Stable Isotope, Metabolic Intermediate, and Microbial Lines of Evidence

    GROUND WATER MONITORING & REMEDIATION, Issue 4 2007
    Jennifer R. McKelvie
    Compound specific isotope analysis (CSIA) was used to investigate biodegradation of trichloroethene (TCE) and methyl tert -butyl ether (MTBE) at contaminated field sites in Alaska and New York State, respectively. At both sites, geochemical conditions and the presence of metabolic intermediates (cis -1-2-dichloroethene and tert -butyl alcohol [TBA]) suggested the potential for biodegradation of TCE and MTBE, respectively. Given that in both cases these metabolic intermediates could also have been present as cocontaminants in the source zone, CSIA was undertaken to evaluate the possibility of in situ biodegradation. At the TCE-contaminated field site in Alaska, ,13C values of TCE in ground water determined in this study showed no evidence of biodegradation (mean ,13C of ,27.0 ± 1.0, for nine wells), and quantitative-polymerase chain reaction analyses of ground water from four wells found no evidence of dechlorinator Dehalococcoides sp. at this site. At the MTBE-contaminated field site in New York, TBA was present in the ground water but was not present in gasoline sampled from underground storage tanks (UST) on-site, suggesting that at this site, TBA was potentially a metabolite of MTBE biodegradation rather than a cocontaminant. However, at all sampling times and locations, ,13C and ,2H values of MTBE in ground water were within range of published values for undegraded MTBE in gasoline. While the occurrence of a small extent of in situ MTBE biodegradation cannot be ruled out, the findings suggest that it is more likely that multiple gasoline spills occurred through time, and while present day USTs do not contain TBA as a cocontaminant, gasoline spilled at the site in the past may have. At both contaminated field sites, CSIA, chemical, and microbiological lines of evidence suggest that biodegradation was not a significant attenuation process. The results of these two studies underscore the need for an integrated approach to site assessment that draws on measurements of metabolic intermediates, analysis of stable isotopes, and microbial evidence to give a reliable assessment of in situ biodegradation at contaminated field sites. [source]

    Isotope labeled ,HEA/HEE' moiety in the synthesis of labeled HIV-protease inhibitors,Part II

    JOURNAL OF LABELLED COMPOUNDS AND RADIOPHARMACEUTICALS, Issue 3 2005
    I. Victor Ekhato
    Abstract [2H5]-Amprenavir and [2H 5]-saquinavir have been prepared from a common labeled precursor (1S, 2S)-(1-oxiranyl-2-[2H5]phenylethyl)-carbamic acid tert- butyl ester, 1. Both of these compounds are in the ,HEA' class of HIV protease inhibitors. [2H5]-Indinavir, a representative of the ,HEE' group of protease inhibitors, has also been synthesized. In the case of indinavir, 1S-(2,2-dimethyl-8, 8a-dihydro-3aH-indeno-[1,2-d]-oxazol-3R-yl)-2-oxiranylmethyl-3-[2H5]phenylpropan-1-one, 11, provided the [phenyl- 2H5]-HEE core structure for synthesis of the desired labeled compound. Copyright © 2005 John Wiley & Sons, Ltd. [source]

    Isotope labeled ,HEA Moiety' in the synthesis of labeled HIV-protease inhibitors , Part 1

    JOURNAL OF LABELLED COMPOUNDS AND RADIOPHARMACEUTICALS, Issue 12 2004
    I. Victor Ekhato
    Abstract [(S)-1,-((N - tert -Butyloxycarbonyl)amino)-2S-[2H5]phenyl-ethyl]oxirane 11, made from [2H5]-bromobenzene, was transformed into the HIV-protease inhibitors [2H5]-DPH 153893 and [2H5]-DPH 140662. Both compounds are members of the hydroxyethylamine class of protease inhibitors (HIV-PIs). The method of synthesis is applicable to members of this class and the HEE group of HIV-PIs. Copyright © 2004 John Wiley & Sons, Ltd. [source]

    Amino-acid geochronology and the British Pleistocene: secure stratigraphical framework or a case of circular reasoning?

    JOURNAL OF QUATERNARY SCIENCE, Issue 7 2002
    Danny McCarroll
    Abstract Aminostratigraphy is central to the recently revised correlation of Quaternary deposits in the British Isles, providing a link between terrestrial deposits and marine Oxygen Isotope Stages. The central tenet of British aminostratigraphy, however, that shells from the same interglacial yield very similar ratios, so that the characteristic ratios from different interglacials are distinct, remains uncertain. The data available suggest that amino-acid ratios from different interglacials do not fall into discrete groups, but overlap considerably. It is therefore not valid to assign individual shells to Oxygen Isotope Stages simply on the basis of their amino-acid ratios, which means that filtering data to remove high or low values, on the assumption that they represent reworked shells, is unacceptable. The range of ,characteristic ratios' assigned to British warm stages may have been underestimated and the degree of separation between them overestimated. Amino-acid ratios should be treated as sample data that are naturally variable. Copyright © 2002 John Wiley & Sons, Ltd. [source]

    Isotope and disorder effects in the Raman spectra of LiHxD1,x crystals

    JOURNAL OF RAMAN SPECTROSCOPY, Issue 8 2001
    V. G. Plekhanov
    Most of the physical properties of a solid depend on its isotopic composition in some way or another. Scientific interest, technological promise and increased availability of highly enriched isotopes have led to a sharp rise in the number of experimental and theoretical studies with isotopically controlled crystals. A great number of stable isotopes and well-developed methods for their separation have made it possible to grow crystals of C, LiH, ZnO, ZnSe, CuCl, GaN, GaAs, CdS, Cu2O, Si, Ge and ,-Sn with a controllable isotopic composition. Among these compounds, LiH possesses the largest value of the isotope effect. The great number of theoretical and experimental data suggest that the isotopic composition of a crystal lattice exerts some influence on the vibrational properties of crystals. These effects are fairly large and can be readily measured by modern experimental techniques (ultrasound, Brillouin and Raman scattering and neutron scattering). In addition, crystals of different isotopic compositions possess different Debye temperatures. This difference between an LiH crystal and its deuterated analogue exceeds a 100 K. Very pronounced and general effects of isotopic substitution are observed in phonon spectra. The scattering lines in isotopically mixed crystals are not only shifted (the shift of LO lines exceeds 100 cm,1) but are also broadened. This broadening is related to the isotopic disorder of the crystal lattice. It is shown that the degree of a change in the scattering potential is different for different isotopic mixed crystals. In the case of germanium and diamond crystals, phonon scattering is weak, which allows one to apply successfully the coherent potential approximation (CPA) for describing the shift and broadening of scattering lines. In the case of lithium hydride, the change in the scattering potential is so strong that it results in phonon localization, which is directly observed in experiments. The common nature of the isotopic and disorder effects in a wide range of crystals is emphasized. Copyright © 2001 John Wiley & Sons, Ltd. [source]

    Evaluating the Provenance of Metasedimentary Rocks of the Jiangxian Group from the Zhongtiao Mountain Using Whole-Rock Geochemistry and Detrital Zircon Hf Isotope

    ACTA GEOLOGICA SINICA (ENGLISH EDITION), Issue 3 2009
    Qiugen LI
    Abstract: In this study, whole-rock geochemical and Nd isotopic data, as well as detrital zircon Hf isotopes of Palaeoproterozoic metasedimentary rocks from the Jiangxian Group are presented to evaluate the characteristics of their provenance and the tectonic history. The major and trace element compositions are comparable to Post-Archean upper continental crust (PA-UCC), but have slight enrichment in the LILE, with the exception of Cs and Sr, and a slight depletion in ferromagnesian elements, HFS elements, such as Nb and Ta, and some major elements, such as CaO and Na2O. The geochemical data reveal that the collected metasedimentary rocks have experienced intermediate source weathering with chemical index of alteration values ranging from 72 to 78, varying degrees of K-metasomatism, and post-depositional loss of Na, as well as negligible sorting, and are derived from the weathering of mostly felsic and non-mafic rocks. The selected Lu,Hf isotopic analysis on detrital zircon points to both the Trans-North China Orogen and Eastern Block of the north China craton as the most likely sources for the metasedimentary rocks of the Jiangxian Group. However, a contribution of detritus from the Western Block of the north China craton can be ruled out. The sediments were probably deposited in a back-arc basin within an active continental margin setting. [source]

    Environmental Isotopes as Indicators for Ground Water Recharge to Fractured Granite

    GROUND WATER, Issue 6 2004
    Article first published online: 9 OCT 200
    First page of article [source]

    ,Distribution of oxygen-18 and deuterium in river waters across the United States

    HYDROLOGICAL PROCESSES, Issue 7 2001
    Carol Kendall
    Abstract Reconstruction of continental palaeoclimate and palaeohydrology is currently hampered by limited information about isotopic patterns in the modern hydrologic cycle. To remedy this situation and to provide baseline data for other isotope hydrology studies, more than 4800, depth- and width-integrated, stream samples from 391 selected sites within the USGS National Stream Quality Accounting Network (NASQAN) and Hydrologic Benchmark Network (HBN) were analysed for ,18O and ,2H (http://water.usgs.gov/pubs/ofr/ofr00-160/pdf/ofr00-160.pdf). Each site was sampled bimonthly or quarterly for 2·5 to 3 years between 1984 and 1987. The ability of this dataset to serve as a proxy for the isotopic composition of modern precipitation in the USA is supported by the excellent agreement between the river dataset and the isotopic compositions of adjacent precipitation monitoring sites, the strong spatial coherence of the distributions of ,18O and ,2H, the good correlations of the isotopic compositions with climatic parameters, and the good agreement between the ,national' meteoric water line (MWL) generated from unweighted analyses of samples from the 48 contiguous states of ,2H=8·11,18O+8·99 (r2=0·98) and the unweighted global MWL of sites from the Global Network for Isotopes in Precipitation (GNIP) of the International Atomic Energy Agency and the World Meteorological Organization (WMO) of ,2H=8·17,18O+10·35. The national MWL is composed of water samples that arise in diverse local conditions where the local meteoric water lines (LMWLs) usually have much lower slopes. Adjacent sites often have similar LMWLs, allowing the datasets to be combined into regional MWLs. The slopes of regional MWLs probably reflect the humidity of the local air mass, which imparts a distinctive evaporative isotopic signature to rainfall and hence to stream samples. Deuterium excess values range from 6 to 15, in the eastern half of the USA, along the northwest coast and on the Colorado Plateau. In the rest of the USA, these values range from ,2 to 6,, with strong spatial correlations with regional aridity. The river samples have successfully integrated the spatial variability in the meteorological cycle and provide the best available dataset on the spatial distributions of ,18O and ,2H values of meteoric waters in the USA. Published in 2001 by John Wiley & Sons, Ltd. [source]

    10th International symposium on the synthesis and applications of Isotopes and Isotopically labelled compounds

    JOURNAL OF LABELLED COMPOUNDS AND RADIOPHARMACEUTICALS, Issue 5-6 2010
    John W. Kennington
    No abstract is available for this article. [source]

    Isotopes in Biogenic Silica (IBiS),

    JOURNAL OF QUATERNARY SCIENCE, Issue 4 2008
    Melanie J. Leng
    This special issue of the Journal of Quaternary Science comprises a selection of papers from the third meeting of a series on ,ISOtopes in PALaeoenvironmental reconstruction' (ISOPAL), themed around Isotopes and Biogenic silica (IBiS). The meeting was held at the British Geological Survey (Nottingham, UK) in April 2007, and consisted of a series of presentations giving methodological approaches to using isotopes in biogenic silica but also specific examples of the application, the majority of which are presented in this issue. © Natural Environment Research Council (NERC) copyright 2008. Reproduced with the permission of NERC. Published by John Wiley & Sons Ltd. [source]

    Strontium Isotopes in the Investigation of Early Glass Production: Byzantine and Early Islamic Glass from the Near East,

    ARCHAEOMETRY, Issue 1 2003
    I. C. Freestone
    87Sr/86Sr ratios have been determined for glasses from four production sites, dated to between the sixth and the 11th centuries, in the Eastern Mediterranean region. On the basis of elemental analyses, the glasses at each location are believed to have been melted from different raw materials. Two glass groups, from Bet Eli,ezer and Bet She,an, in Israel, are believed to have been based upon mixtures of Levantine coastal sands and natron, and have 87Sr/86Sr ratios close to 0.7090, plus high elemental strontium, confirming a high concentration of modern marine shell (87Sr/86Sr ~ 0.7092) in the raw materials. The isotopic compositions of these two groups of glasses differ slightly, however, probably reflecting a varying ratio of limestone to shell because the sands that were utilized were from different coastal locations. Natron-based glasses from a workshop at Tel el Ashmunein, Middle Egypt, have 87Sr/86Sr values of 0.70794,0.70798, and low elemental strontium, consistent with the use of limestone or limestone-rich sand in the batch. High-magnesia glasses based on plant ash, from Banias, Israel, have 87Sr/86Sr values of 0.70772,0.70780, probably reflecting the isotopic composition of the soils that were parental to the plants that were ashed to make the glass. Strontium and its isotopes offer an approach to identifying both the raw materials and the origins of ancient glasses, and are a potentially powerful tool in their interpretation. [source]

    Detecting Altitudinal Migration Events in Neotropical Birds Using Stable Isotopes

    BIOTROPICA, Issue 3 2008
    Kevin C. Fraser
    ABSTRACT We evaluated the utility of stable-hydrogen isotope ratios in tropical bird tissues for detecting altitudinal migration events. Our results identified two of five species as altitudinal migrants in Nicaragua. This approach may circumvent the current limitations of mark,recapture techniques and enhance our ability to study this poorly characterized behavior. RESUMEN Hemos evaluado la utilidad de los índices de isótopos de hidrógenos estables en los tejidos de aves tropicales para detectar eventos de migraciones altitudinales. Nuestros resultados identificaron 2 de 5 especies como migrantes altitudinales en Nicaragua. Este enfoque podría superar las limitaciones actuales en técnicas de anillamiento , recaptura y resaltar nuestra capacidad para estudiar esta conducta pobremente investigada. [source]

    Geology, Geochemistry and Minerogenesis of the Shijuligou Zinc,Copper Deposit in Gansu, China

    ACTA GEOLOGICA SINICA (ENGLISH EDITION), Issue 6 2009
    LI Wenyuan
    Abstract: The Shijuligou deposit was separated by an arcuate ductile shear zone cross the center of the deposit region, resulting in the difference between the southern and northern ore bodies. The lead (Pb) isotopic data of ores of the Shijuligou copper deposit have averages of 206Pb/204Pb, 207Pb/204Pb, and 208Pb/204Pb in 17.634, 15.444, and 37.312, respectively. It has been shown that ore-forming metals originated from intrusive and extrusive rocks in the upper part of ophiolites. The sulfur isotopic data of pyrite and chalcopyrite in the northern part change from +7.61, to +8.09, and +4.95, to +8.88, in the southern part. Isotopes of ,18O in the Shijuligou copper deposit are between +11.1, and +18.6,, with the calculated ,18OH2O at +0.65,. It is suggested that the mineralized fluid is a mixture of magma fluid, meteorological water, and seawater through circulating and leaching metals from the volcanic rocks. The zircon uranium-lead (U,Pb) dating of gabbro is 457.9±1.2 Ma, and the lower crossing age of the discordant and concordia curves of pyroxene spilite of zircon is 454±15 Ma. It is indicated that the Shijuligou deposit formed in a new ocean crust (ophiolite) of the back-arc basin in the late Ordovician. Mineralization should occur in the intermittence period after strong volcanic activity, and the age should be the late Ordovician. Moreover, the mineralization of ophiolite-hosted massive sulfide deposits in the ancient orogenic belt of the late Ordovician in the northern Qilian Mountains was controlled by the primary fault/fracture, with the forming of a metallogenic hydrothermal system by a mixture of volcanic magma fluid and seawater, which circularly leached the metallogenic metals from the volcanic rocks, resulting in their accumulation. The ore bodies were transformed with morphology and metallogenic elements. Jasperoid is an important sign for prospecting such deposits. There were many island arcs in the continent of China. This study provides evidence for understanding and exploration of ophiolite-hosted massive sulfide deposits in western China, especially in the area of northern Qilian Mountains. [source]

    Oxygen and Hydrogen Isotopes of Waters in the Ordos Basin, China: Implications for Recharge of Groundwater in the North of Cretaceous Groundwater Basin

    ACTA GEOLOGICA SINICA (ENGLISH EDITION), Issue 1 2009
    Yuncheng YANG
    Abstract: Hundreds of precipitation samples collected from meteorological stations in the Ordos Basin from January 1988 to December 2005 were used to set up a local meteoric water line and to calculate weighted average isotopic compositions of modern precipitation. Oxygen and hydrogen isotopes, with averages of ,7.8, and ,53.0, for ,18O and ,D, respectively, are depleted in winter and rich in spring, and gradually decrease in summer and fall, illustrating that the seasonal effect is considerable. They also show that the isotopic difference between south portion and north portion of the Ordos Basin are not obvious, and the isotope in the middle portion is normally depleted. The isotope compositions of 32 samples collected from shallow groundwater (less than a depth of 150 m) in desert plateau range from ,10.6, to ,6.0, with an average of ,8.4, for ,18O and from ,85, to ,46, with an average of ,63, for ,D. Most of them are identical with modern precipitation. The isotope compositions of 22 middle and deep groundwaters (greater than a depth of 275 m) fall in ranges from ,11.6, to ,8.8, with an average of ,10.2, for ,18O and from ,89, to ,63, with an average of ,76, for ,D. The average values are significantly less than those of modern precipitation, illustrating that the middle and deep groundwaters were recharged at comparatively lower air temperatures. Primary analysis of 14C shows that the recharge of the middle and deep groundwaters started at late Pleistocene. The isotopes of 13 lake water samples collected from eight lakes define a local evaporation trend, with a relatively flat slope of 3.77, and show that the lake waters were mainly fed by modern precipitation and shallow groundwater. [source]

    Quantum Diffusion of Hydrogen and Isotopes in Metals

    CHEMPHYSCHEM, Issue 9 2005
    Matthew Dyer
    Quantum diffusion constants of H and its isotopes in Pd and Nb are computed using Kubo theory applied on potential-energy surfaces obtained from density functional theory. The figure shows an excited state of H in Pd. This state is among several states which are below the classical barrier but are also delocalised between the octahedral and tetrahedral sites that contribute to quantum diffusion at low temperatures. [source]

    The benefits of oestrogens on postprandial lipid metabolism are lost in post-menopausal women with Type 2 diabetes

    DIABETIC MEDICINE, Issue 7 2006
    M. G. Masding
    Abstract Aims, Women with Type 2 diabetes appear to lose the protection against cardiovascular disease (CVD) afforded by oestrogens. We examined the effects of oestrogen hormone replacement therapy (HRT) on postprandial clearance of dietary fat in non-diabetic and diabetic post-menopausal women. Methods, In a cross-sectional study, fasting subjects [HRT+ and HRT, control and diabetic women; Type 2 diabetes (DM) HRT+n = 8, DM HRT,n = 14, control HRT+n = 7, control HRT,n = 11] consumed a meal containing the stable isotope 1,1,1,[13]C-tripalmitin, with blood and breath sampled for 6 and 24 h, respectively, in the postprandial period. Results, In diabetic women, there were no differences between the HRT+ and HRT, groups for any of these parameters. In contrast, in HRT+ compared with HRT, control women, the triglyceride (TG) area under the curve was lower [AUC; HRT+ median (range) 7.7 (4.1, 12.8) mmol/l per 6 h, HRT, 9.7 (3.9, 18.5) mmol/l per 6 h, P < 0.05] and [13]C-palmitic acid in the TG fraction was also lower [HRT+ 23.2 (10.3, 41.3) ng/ml per 6 h, HRT, 47.7 (12.6, 77.2) ng/ml per 6 h, P < 0.05], suggesting the lower postprandial triglyceridaemia associated with HRT in non-diabetic women is because of better chylomicron clearance. Conclusions, The oestrogen-associated advantage in clearance of dietary lipid we observed in non-diabetic post-menopausal women is not seen in post-menopausal diabetic women. This is likely to promote an atherogenic lipoprotein profile and may contribute to the loss of CVD protection seen in diabetic women. [source]

    Feather deuterium measurements reveal origins of migratory western loggerhead shrikes (Lanius ludovicianus excubitorides) wintering in Mexico

    DIVERSITY AND DISTRIBUTIONS, Issue 2 2007
    Guillermo E. Pérez
    ABSTRACT Understanding the winter distributions of migrant birds is important because productivity and recruitment are influenced by conditions at several locations and periods in the life cycle of individuals. The western loggerhead shrike, Lanius ludovicianus excubitorides, is a threatened species in Canada, and its decline is attributed to potential limitations on the wintering grounds. We examined patterns of stable-hydrogen isotope (,D) distributions in feathers of loggerhead shrikes, primarily of L. l. excubitorides, during winter at three regions in north and central Mexico, to establish relative abundance and origins of migrants. We also investigated potential movements of Mexican winter resident individuals. Using shrike museum specimens of known summer provenance, a shrike deuterium base map for Mexico was developed from isotopic measurement of feathers of resident shrikes and use of a recently established feather base map for raptors in North America. Stable hydrogen isotope analyses of inner secondary feather (s9) of all loggerhead shrikes examined in Mexico during winter indicated that north-central (Region A), north-eastern (Region B) and south-central (Region C) sites in Mexico consisted of 28.1%, 73.7% and 63.8% of migrant individuals from northern breeding grounds, respectively. Isotopic evidence suggested movements of a few local residents birds (7.9%) into the Chihuahuan desert from south-western USA and north-eastern Mexico to winter. [source]

    Comparing trophic position of stream fishes using stable isotope and gut contents analyses

    ECOLOGY OF FRESHWATER FISH, Issue 2 2008
    S. M. Rybczynski
    Abstract,,, Stable isotope analysis (SIA) and gut contents analysis (GCA) are commonly used in food web studies, but few studies analyse these data in concert. We used SIA (,15N) and GCA (% composition) to identify diets and trophic position (TP) of six stream fishes and to compare TP estimates between methods. Ordination analysis of gut contents identified two primary trophic groups, omnivores and predators. Significant differences in TPGCA and TPSIA were similar in direction among-species and among-trophic groups; neither method detected seasonal changes in omnivore diets. Within-species TPGCA and TPSIA were similar except for one omnivore. TPGCA was less variable than TPSIA for predators, but variation between methods was similar for omnivores. While both methods were equally robust at discriminating trophic groups of fishes, TPSIA is less laborious to estimate and may facilitate cross-stream comparisons of food web structure and energy flow. [source]

    Raman-FISH: combining stable-isotope Raman spectroscopy and fluorescence in situ hybridization for the single cell analysis of identity and function

    ENVIRONMENTAL MICROBIOLOGY, Issue 8 2007
    Wei E. Huang
    Summary We have coupled fluorescence in situ hybridization (FISH) with Raman microscopy for simultaneous cultivation-independent identification and determination of 13C incorporation into microbial cells. Highly resolved Raman confocal spectra were generated for individual cells which were grown in minimal medium where the ratio of 13C to 12C content of the sole carbon source was incrementally varied. Cells which were 13C-labelled through anabolic incorporation of the isotope exhibited key red-shifted spectral peaks, the calculated ,red shift ratio' (RSR) being highly correlated with the 13C-content of the cells. Subsequently, Raman instrumentation and FISH protocols were optimized to allow combined epifluorescence and Raman imaging of Fluos, Cy3 and Cy5-labelled microbial populations at the single cell level. Cellular 13C-content determinations exhibited good congruence between fresh cells and FISH hybridized cells indicating that spectral peaks, including phenylalanine resonance, which were used to determine 13C-labelling, were preserved during fixation and hybridization. In order to demonstrate the suitability of this technology for structure,function analyses in complex microbial communities, Raman-FISH was deployed to show the importance of Pseudomonas populations during naphthalene degradation in groundwater microcosms. Raman-FISH extends and complements current technologies such as FISH-microautoradiography and stable isotope probing in that it can be applied at the resolution of single cells in complex communities, is quantitative if suitable calibrations are performed, can be used with stable isotopes and has analysis times of typically 1 min per cell. [source]

    Dystonic Posturing Associated with Putaminal Hyperperfusion Depicted on Subtraction SPECT

    EPILEPSIA, Issue 8 2004
    Masahiro Mizobuchi
    Summary:,Purpose: Dystonic posturing (DP) is one of the most reliable lateralizing indicators for temporal lobe epilepsy (TLE). We evaluated the ictal hyperperfusional areas in patients with DP by using ictal,interictal subtraction single-photon emission computed tomography (SPECT). Methods: Ninety-seven patients were treated surgically for intractable TLE, and 39 patients underwent ictal and interictal SPECT studies with the same isotope. These patients were divided into three groups: group I with DP of the contralateral side extended to the epileptogenic focus, group II with elevated muscle tonus but without DP, and group III without DP or alteration of muscle tonus. Ictal, interictal SPECT and thin-slice magnetic resonance imaging (MRI) were overlaid by using the automatic multimodality registration program to construct ictal,interictal subtracted images of SPECT on MRI. Results: Thirteen patients belonged to group I; 14, to group II; and 12, to group III. A statistically significant difference in hyperperfusion rate was observed in the putamen (10 patients in group I, three in group II and two in group III; p < 0.01) and mesial temporal lobe (10 patients in group I, seven in group II, and two in group III; p < 0.05) on the ipsilateral side of the epileptogenic focus. No statistically significant difference was observed for other ictal symptoms except ipsilateral upper-limb automatism (eight patients in group I, three in group II, and none in group III; p < 0.01). Conclusions: A strong correlation between DP and hyperperfusion in the putamen and mesial temporal lobe was demonstrated. Some patients showed a wide hyperperfusion area extending from the mesial temporal lobe to putamen, which may correspond to the propagation of epileptic discharges. Our results suggest a correlation between hyperperfusion of putamen and contralateral dystonic posturing. [source]

    Malignant pheochromocytoma with progressive paraparesis in von Hippel,Lindau disease

    EUROPEAN JOURNAL OF NEUROLOGY, Issue 4 2000
    R. Mössner
    Pheochromocytomas are a feature of the von Hippel,Lindau disease spectrum, a multisystem disorder of autosomal dominant inheritance. Pheochromocytomas are, however, observed during life with a lower frequency than other features of this disease, such as retinal angiomas, haemangioblastomas of the CNS, and renal carcinomas. We present the highly unusual case of a patient who required an emergency operation for an intradural extramedullary thoracic tumour which was clinically suggestive initially of neurinoma. We present evidence from NMR, histological and isotope scan investigations of this being a pheochromocytoma metastasis and of an additional right-sided paraganglioma at the same height. A detailed history revealed that this patient had suffered from four other pheochromocytomas and two other paragangliomas, in addition to retinal angiomatosis of von Hippel,Lindau disease. This case is extraordinary due to (i) the unusual site of the metastasis, (ii) the neurological requirement for an emergency operation of pheochromocytoma, (iii) metastasis of pheochromocytoma in von Hippel,Lindau disease (only eight previous cases), and (iv) the number of recurrent pheochromocytomas. It clearly demonstrates the necessity for frequent and life-long follow-up in von Hippel,Lindau disease. [source]