Changes in hydrogen isotope ratios in sequential plumage stages: an implication for the creation of isotope-base maps for tracking migratory birds.

PubMed

Duxbury, J M; Holroyd, G L; Muehlenbachs, K

2003-09-01

Accurate reference maps are important in the use of stable-isotopes to track the movements of migratory birds. Reference maps created by the analysis of samples collected from young at the nest site are more accurate than simply referring to naturally occurring patterns of hydrogen isotope ratios created by precipitation cycles. Ratios of hydrogen isotopes in the nutrients incorporated early in the development of young birds can be derived from endogenous, maternal sources. Base-maps should be created with the analysis of tissue samples from hatchlings after local the isotopic signature of exogenous nutrients is dominant. Migratory species such as Peregrine Falcons are known to use endogenous sources in the creation of their eggs, therefore knowledge of what plumage stage best represents the local hydrogen ratios would assist in the planning of nest visits. We conducted diet manipulation experiments involving Japanese Quail and Peregrine Falcons to determine the plumage stage when hydrogen isotope ratios were indicative of a switch in their food source. The natal down of both the quail and falcons reflected the diet of breeding adult females. The hydrogen isotope ratios of a new food source were dominant in the juvenile down of the young falcons, although a further shift was detected in the final juvenile plumage. The juvenile plumage is grown during weeks 3-4 after hatch on Peregrine Falcons. Nest visits for the purpose of collecting feathers for isotope-base-map creation should be made around 4 weeks after the presumed hatch of the young falcons.

Rapid determination of actinides in asphalt samples

DOE PAGES

Maxwell, Sherrod L.; Culligan, Brian K.; Hutchison, Jay B.

2014-01-12

A new rapid method for the determination of actinides in asphalt samples has been developed that can be used in emergency response situations or for routine analysis If a radiological dispersive device (RDD), Improvised Nuclear Device (IND) or a nuclear accident such as the accident at the Fukushima Nuclear Power Plant in March, 2011 occurs, there will be an urgent need for rapid analyses of many different environmental matrices, including asphalt materials, to support dose mitigation and environmental clean up. The new method for the determination of actinides in asphalt utilizes a rapid furnace step to destroy bitumen and organicsmore » present in the asphalt and sodium hydroxide fusion to digest the remaining sample. Sample preconcentration steps are used to collect the actinides and a new stacked TRU Resin + DGA Resin column method is employed to separate the actinide isotopes in the asphalt samples. The TRU Resin plus DGA Resin separation approach, which allows sequential separation of plutonium, uranium, americium and curium isotopes in asphalt samples, can be applied to soil samples as well.« less

Determination of cadmium in sediments by diluted HCI extraction and isotope dilution ICP-MS.

PubMed

Terán-Baamonde, Javier; Soto-Ferreiro, Rosa-María; Carlosena, Alatzne; Andrade, José-Manuel; Prada, Darío

2018-08-15

Isotope dilution ICP-MS is proposed to measure the mass fraction of Cd extracted by diluted HCl in marine sediments, using a fast and simple extraction procedure based on ultrasonic probe agitation. The 111 Cd isotope was added before the extraction to achieve isotope equilibration with native Cd solubilized from the sample. The parameters affecting trueness and precision of isotope ratio measurements were evaluated carefully and subsequently corrected in order to minimize errors; they were: detector dead time, spectral interferences, mass discrimination factor and optimum sample/spike ratio. The mass fraction of Cd extracted was compared with the sum of the certified contents of the three steps of the sequential extraction procedure of the Standards, Measurements and Testing Programme (SM&T) analysing the BCR 701 sediment to validate the method. The certified and measured values agreed, giving a measured / certified mass fraction ratio of 1.05. Further, the extraction procedure itself was studied by adding the enriched isotope after the extraction step, which allowed verifying that analyte losses occurred during this process. Two additional reference sediments with certified total cadmium contents were also analysed. The method provided very good precision (0.9%, RSD) and a low detection limit, 1.8 ng g -1 . The procedural uncertainty budget was estimated following the EURACHEM Guide by means of the 'GUM Workbench' software, obtaining a relative expanded uncertainty of 1.5%. The procedure was applied to determine the bioaccessible mass fraction of Cd in sediments from two environmentally and economically important areas of Galicia (rias of Arousa and Vigo, NW of Spain). Copyright © 2018 Elsevier B.V. All rights reserved.

Improved radiocarbon analyses of modern human hair to determine the year-of-death by cross-flow nanofiltered amino acids: common contaminants, implications for isotopic analysis, and recommendations.

PubMed

Santos, Guaciara M; De La Torre, Hector A Martinez; Boudin, Mathieu; Bonafini, Marco; Saverwyns, Steven

2015-10-15

In forensic investigation, radiocarbon ((14)C) measurements of human tissues (i.e., nails and hair) can help determine the year-of-death. However, the frequent use of cosmetics can bias hair (14)C results as well as stable isotope values. Evidence shows that hair exogenous impurities percolate beyond the cuticle layer, and therefore conventional pretreatments are ineffective in removing them. We conducted isotopic analysis ((14)C, δ(13)C, δ(15)N and C/N) of conventionally treated and cross-flow nanofiltered amino acid (CFNAA)-treated samples (scalp- and body-hair) from a single female subject using fingernails as a reference. The subject studied frequently applies a permanent dark-brown dye kit to her scalp-hair and uses other care products for daily cleansing. We also performed pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) analyses of CFNAA-treated scalp-hair to identify contaminant remnants that could possibly interfere with isotopic analyses. The conventionally treated scalp- and body-hair showed (14)C offsets of ~21‰ and ~9‰, respectively. These offsets confirm the contamination by petrochemicals in modern human hair. A single CFNAA extraction reduced those offsets by ~34%. No significant improvement was observed when sequential extractions were performed, as it appears that the procedure introduced some foreign contaminants. A chromatogram of the CFNAA scalp-hair pyrolysis products showed the presence of petroleum and plant/animal compound residues, which can bias isotopic analyses. We have demonstrated that CFNAA extractions can partially remove cosmetic contaminants embedded in human hair. We conclude that fingernails are still the best source of keratin protein for year-of-death determinations and isotopic analysis, with body-hair and/or scalp-hair coupled with CFNAA extraction a close second. Copyright © 2015 John Wiley & Sons, Ltd.

Comparative analysis of monoclonal antibody N-glycosylation using stable isotope labelling and UPLC-fluorescence-MS.

PubMed

Millán Martín, Silvia; Delporte, Cédric; Farrell, Amy; Navas Iglesias, Natalia; McLoughlin, Niaobh; Bones, Jonathan

2015-03-07

A twoplex method using (12)C6 and (13)C6 stable isotope analogues (Δmass = 6 Da) of 2-aminobenzoic acid (2-AA) is described for quantitative analysis of N-glycans present on monoclonal antibodies and other glycoproteins using ultra performance liquid chromatography with sequential fluorescence and accurate mass tandem quadrupole time of flight (QToF) mass spectrometric detection.

A protocol to correct for intra- and interspecific variation in tail hair growth to align isotope signatures of segmentally cut tail hair to a common time line.

PubMed

Burnik Šturm, Martina; Pukazhenthi, Budhan; Reed, Dolores; Ganbaatar, Oyunsaikhan; Sušnik, Stane; Haymerle, Agnes; Voigt, Christian C; Kaczensky, Petra

2015-06-15

In recent years, segmental stable isotope analysis of hair has been a focus of research in animal dietary ecology and migration. To correctly assign tail hair segments to seasons or even Julian dates, information on tail hair growth rates is a key parameter, but is lacking for most species. We (a) reviewed the literature on tail hair growth rates in mammals; b) made own measurements of three captive equid species; (c) measured δ(2)H, δ(13)C and δ(15)N values in sequentially cut tail hairs of three sympatric, free-ranging equids from the Mongolian Gobi, using isotope ratio mass spectrometry (IRMS); and (d) collected environmental background data on seasonal variation by measuring δ(2)H values in precipitation by IRMS and by compiling pasture productivity measured by remote sensing via the normalized difference vegetation index (NDVI). Tail hair growth rates showed significant inter- and intra-specific variation making temporal alignment problematic. In the Mongolian Gobi, high seasonal variation of δ(2)H values in precipitation results in winter lows and summer highs of δ(2)H values of available water sources. In water-dependent equids, this seasonality is reflected in the isotope signatures of sequentially cut tails hairs. In regions which are subject to strong seasonal patterns we suggest identifying key isotopes which show strong seasonal variation in the environment and can be expected to be reflected in the animal tissue. The known interval between the maxima and minima of these isotope values can then be used to correctly temporally align the segmental stable isotope signature for each individual animal. © 2015 The Authors. Rapid Communications in Mass Spectrometry published by John Wiley & Sons Ltd.

A protocol to correct for intra- and interspecific variation in tail hair growth to align isotope signatures of segmentally cut tail hair to a common time line

PubMed Central

Burnik Šturm, Martina; Pukazhenthi, Budhan; Reed, Dolores; Ganbaatar, Oyunsaikhan; Sušnik, Stane; Haymerle, Agnes; Voigt, Christian C; Kaczensky, Petra

2015-01-01

Rationale In recent years, segmental stable isotope analysis of hair has been a focus of research in animal dietary ecology and migration. To correctly assign tail hair segments to seasons or even Julian dates, information on tail hair growth rates is a key parameter, but is lacking for most species. Methods We (a) reviewed the literature on tail hair growth rates in mammals; b) made own measurements of three captive equid species; (c) measured δ2H, δ13C and δ15N values in sequentially cut tail hairs of three sympatric, free-ranging equids from the Mongolian Gobi, using isotope ratio mass spectrometry (IRMS); and (d) collected environmental background data on seasonal variation by measuring δ2H values in precipitation by IRMS and by compiling pasture productivity measured by remote sensing via the normalized difference vegetation index (NDVI). Results Tail hair growth rates showed significant inter- and intra-specific variation making temporal alignment problematic. In the Mongolian Gobi, high seasonal variation of δ2H values in precipitation results in winter lows and summer highs of δ2H values of available water sources. In water-dependent equids, this seasonality is reflected in the isotope signatures of sequentially cut tails hairs. Conclusions In regions which are subject to strong seasonal patterns we suggest identifying key isotopes which show strong seasonal variation in the environment and can be expected to be reflected in the animal tissue. The known interval between the maxima and minima of these isotope values can then be used to correctly temporally align the segmental stable isotope signature for each individual animal. © 2015 The Authors. Rapid Communications in Mass Spectrometry published by John Wiley & Sons Ltd. PMID:26044272

Enrichment and geochemical mobility of heavy metals in bottom sediment of the Hoedong reservoir, Korea and their source apportionment.

PubMed

Lee, Pyeong-Koo; Kang, Min-Ju; Yu, Soonyoung; Ko, Kyung-Seok; Ha, Kyoochul; Shin, Seong-Cheon; Park, Jung Han

2017-10-01

Physicochemical characteristics of bottom sediment in the Hoedong reservoir were studied to evaluate the effectiveness of the reservoir as traps for trace metals. Roadside soil, stream sediment and background soil were also studied for comparison. Sequential extractions were carried out, and lead isotopic compositions of each extraction were determined to apportion Pb sources. Besides, particle size distribution of roadside soil, and metal concentrations and Pb isotopes of each size group were determined to characterize metal contamination. In result, Zn and Cu were enriched in sediment through roadside soil. The data on metal partitioning implied that Zn posed potential hazards for water quality. Meanwhile, the noticeable reduction of the 206 Pb/ 207 Pb isotopic ratio in the acid-soluble fraction in the size group 200 μm - 2 mm of national roadside soil indicated that this size group was highly contaminated by automotive emission with precipitation of acid-soluble secondary minerals during evaporation. Based on the Pb isotopic ratios, the dry deposition of Asian dust (AD) and non-Asian dust (NAD) affected roadside soil, while the effects of AD and NAD on bottom sediment appeared to be low given the low metal concentrations in sediment. Metal concentrations and Pb isotopic compositions indicated that sediments were a mixture of background and roadside soil. Source apportionment calculations showed that the average proportion of traffic Pb in bottom and stream sediments was respectively 34 and 31% in non-residual fractions, and 26 and 28% in residual fraction. The residual fraction of sediments appeared to be as contaminated as the non-residual fractions. Copyright © 2017 Elsevier Ltd. All rights reserved.

A novel procedure for Rubidium separation and its isotope measurements on geological samples by MC-ICP-MS

NASA Astrophysics Data System (ADS)

Ma, J.; Zhang, Z.; Wei, G.; Zhang, L.

2017-12-01

A method including a novel column Rb separation procedure and high-precision Rb isotope measurement in geological materials by using multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS) in standard-sample-bracketing (SSB) mode has been developed. Sr-Spec resin was employed, in which the distribution coefficients for Rb, K, Ba and Sr are different in nitric acid, to sequentially separate them from the matrix. The dissolved samples were loaded on the column in 3 M HNO3, the main matrix such as Al, Ca, Fe, Mg, Mn and Na were removed by rinsing with 4.5 mL HNO3, Rb and K were then sequentially eluted by 3 M HNO3 in different volumes. After that, Ba was eluted by 8 M HNO3, and Sr was finally eluted by Milli-Q water. This enable us to collect the pure Rb, K, Ba and Sr one by one with recovery close to 100% for their isotopic compositions measurement on MC-ICP-MS. We here focus on Rb isotope measurement. The measurement using MC-ICP-MS yielded an internal precision for δ87Rb of < ± 0.03‰ (2SE), and the external precision was generally better than ± 0.06‰ (2SD) based on the long-term results of the Rb standard solutions NIST SRM 984. A series of geological rock standards, were analyzed using this method, and the results indicate significant Rb isotope differences in different geologic materials. This will provide a powerful tool to investigate Rb isotope fractionation during geological processes.Based on this method, Rb isotope compositions from a basaltic weathering profile were carried out. The data show the lighter Rb (85Rb) isotope is preferentially leached from the weathering profile and remains heavy Rb isotope (87Rb) in the weathered residues during the incipient weathering stage. From the moderate to advanced weathering stage, the significant variations of Rb isotope were observed and multiple factors, such as leaching, adsorption, desorption, and precipitation, should play important role in fractionating Rb isotope.

High-precision isotopic characterization of USGS reference materials by TIMS and MC-ICP-MS

NASA Astrophysics Data System (ADS)

Weis, Dominique; Kieffer, Bruno; Maerschalk, Claude; Barling, Jane; de Jong, Jeroen; Williams, Gwen A.; Hanano, Diane; Pretorius, Wilma; Mattielli, Nadine; Scoates, James S.; Goolaerts, Arnaud; Friedman, Richard M.; Mahoney, J. Brian

2006-08-01

The Pacific Centre for Isotopic and Geochemical Research (PCIGR) at the University of British Columbia has undertaken a systematic analysis of the isotopic (Sr, Nd, and Pb) compositions and concentrations of a broad compositional range of U.S. Geological Survey (USGS) reference materials, including basalt (BCR-1, 2; BHVO-1, 2), andesite (AGV-1, 2), rhyolite (RGM-1, 2), syenite (STM-1, 2), granodiorite (GSP-2), and granite (G-2, 3). USGS rock reference materials are geochemically well characterized, but there is neither a systematic methodology nor a database for radiogenic isotopic compositions, even for the widely used BCR-1. This investigation represents the first comprehensive, systematic analysis of the isotopic composition and concentration of USGS reference materials and provides an important database for the isotopic community. In addition, the range of equipment at the PCIGR, including a Nu Instruments Plasma MC-ICP-MS, a Thermo Finnigan Triton TIMS, and a Thermo Finnigan Element2 HR-ICP-MS, permits an assessment and comparison of the precision and accuracy of isotopic analyses determined by both the TIMS and MC-ICP-MS methods (e.g., Nd isotopic compositions). For each of the reference materials, 5 to 10 complete replicate analyses provide coherent isotopic results, all with external precision below 30 ppm (2 SD) for Sr and Nd isotopic compositions (27 and 24 ppm for TIMS and MC-ICP-MS, respectively). Our results also show that the first- and second-generation USGS reference materials have homogeneous Sr and Nd isotopic compositions. Nd isotopic compositions by MC-ICP-MS and TIMS agree to within 15 ppm for all reference materials. Interlaboratory MC-ICP-MS comparisons show excellent agreement for Pb isotopic compositions; however, the reproducibility is not as good as for Sr and Nd. A careful, sequential leaching experiment of three first- and second-generation reference materials (BCR, BHVO, AGV) indicates that the heterogeneity in Pb isotopic compositions, and concentrations, could be directly related to contamination by the steel (mortar/pestle) used to process the materials. Contamination also accounts for the high concentrations of certain other trace elements (e.g., Li, Mo, Cd, Sn, Sb, W) in various USGS reference materials.

Impacts of Dust on Tropical Volcanic Soil Formation: Insights from Strontium and Uranium-Series Isotopes in Soils from Basse-Terre Island, French Guadeloupe

NASA Astrophysics Data System (ADS)

Pereyra, Y.; Ma, L.; Sak, P. B.; Gaillardet, J.; Buss, H. L.; Brantley, S. L.

2015-12-01

Dust inputs play an important role in soil formation, especially for thick soils developed on tropical volcanic islands. In these regions, soils are highly depleted due to intensive chemical weathering, and mineral nutrients from dusts have been known to be important in sustaining soil fertility and productivity. Tropical volcanic soils are an ideal system to study the impacts of dust inputs on the ecosystem. Sr and U-series isotopes are excellent tracers to identify sources of materials in an open system if the end-members have distinctive isotope signatures. These two isotope systems are particularly useful to trace the origin of atmospheric inputs into soils and to determine rates and timescales of soil formation. This study analyzes major elemental concentrations, Sr and U-series isotope ratios in highly depleted soils in the tropical volcanic island of Basse-Terre in French Guadeloupe to determine atmospheric input sources and identify key soil formation processes. We focus on three soil profiles (8 to 12 m thick) from the Bras-David, Moustique Petit-Bourg, and Deshaies watersheds; and on the adjacent rivers to these sites. Results have shown a significant depletion of U, Sr, and major elements in the deep profile (12 to 4 m) attributed to rapid chemical weathering. The top soil profiles (4 m to the surface) all show addition of elements such as Ca, Mg, U, and Sr due to atmospheric dust. More importantly, the topsoil profiles have distinct Sr and U-series isotope compositions from the deep soils. Sr and U-series isotope ratios of the top soils and sequential extraction fractions confirm that the sources of the dust are from the Saharan dessert, through long distance transport from Africa to the Caribbean region across the Atlantic Ocean. During the transport, some dust isotope signatures may also have been modified by local volcanic ashes and marine aerosols. Our study highlights that dusts and marine aerosols play important roles in element cycles and nutrient sources in the highly depleted surface soils of tropical oceanic islands.

Multi isotopic characterization (Li-Cu-Zn-Pb) of waste waters pollution in a small watershed (Loire River basin, France)

NASA Astrophysics Data System (ADS)

Millot, R.; Desaulty, A. M.; Perret, S.; Bourrain, X.

2016-12-01

The goal of this study is to use multi-isotopic signature to track the pollution in surface waters, and to understand the complex processes causing the metals mobilization and transport in the environment. In the present study, we investigate waste water releases from a hospital water treatment plant and its potential impact in a small river basin near Orléans in France (Egoutier watershed: 15 km²and 5 km long). We decided to monitor this small watershed which is poorly urbanized in the Loire river basin. Its spring is located in a pristine area (forested area), while it is only impacted some kilometers further by the releases rich in metals coming from a hospital water treatment plant. A sampling of these liquid effluents as well as dissolved load and sediment from upstream to downstream was realized and their concentrations and isotopic data were determined. Isotopic ratios were measured using a MC-ICP-MS at BRGM, after a specific protocol of purification for each isotopic systematics. Lithium isotopic compositions are rather homogeneous in river waters along the main course of the stream. The waste water signal is very different from the natural background with significant heavy lithium contribution (high δ7Li). Lead isotopic compositions are rather homogenous in river waters and sediments with values close to geologic background. For Zn, the sediments with high concentrations and depleted isotopic compositions (low δ66Zn), typical of an anthropic pollution, are strongly impacted. The analyses of Cu isotopes in sediments show the impact of waster waters, but also isotopic fractionations due to redox processes in the watershed. To better understand these processes controlling the release of metals in water, sequential extractions on sediments are in progress under laboratory conditions and will provide important constraints for metal distribution in this river basin.

Sclerochronological analysis of Saxidomus gigantea: Implications for reconstructing past seasonality and sea ice extent in the Northern Pacific Ocean

NASA Astrophysics Data System (ADS)

Bassett, C.; Andrus, C. F. T.

2015-12-01

Sclerochronological analysis of biogenic carbonates provides valuable paleoenvironmental information. Oxygen isotope analysis of bivalve shell yields information on the temperature of the water in which the organism grew. However, in coastal environments, variations in δ18Owater may complicate the interpretation of shell isotope profiles. Measuring and comparing the length of seasonal shell growth in select species of bivalves may complement isotopic analysis, together providing a more precise paleoclimate reconstruction. This project aims to determine the reliability of sclerochronological analysis of bivalves in reconstructing seasonality along the Northwest Coast of North America. To compare bivalves growing at different seasonal temperature conditions, samples of Saxidomus gigantea were collected from southern Alaska and northern British Columbia. Winter cessation lines were identified using oxygen isotope (δ18O) peaks from a profile of variation over the life of the clam, which was sampled sequentially from a section of its shell. Shell growth stops below ~4-5°C and so each winter cessation indicates temperatures lower than this threshold. Lunar-daily growth lines were counted between these winter growth cessation breaks, which quantitatively measure the length of the growing season. The resulting data were compared between habitats to assess if this is a useful method of determining the length of the growing season. If this method of assessing seasonality appears valid, it can be applied to ancient shells abundant in archaeological shell middens to make inferences about past seawater conditions and potentially indicate the presence or absence of the conditions necessary for sea ice accumulation.

Metal distribution and mobility in lateritic soils affected by Cu-Co smelting in the Copperbelt district, Zambia

NASA Astrophysics Data System (ADS)

Ettler, Vojtech; Mihaljevic, Martin; Majer, Vladimir; Kribek, Bohdan; Sebek, Ondrej

2010-05-01

The copper smelting activities in the Copperbelt mining district (Zambia) left a huge pollution related to the disposal sites of smelting waste (slags) and to the continuous deposition of the smelter stack particulates in the soil systems. We sampled 196 surface and subsurface soils in the vicinity of the Nkana copper smelter at Kitwe and a 110 cm deep lateritic soil profile in order to assess the regional distribution of metallic contaminants and their vertical mobility. The content of contaminants in soil samples were measured by ICP techniques and the lead isotopic compositions (206Pb/207Pb and 208Pb/206Pb ratios) were determined by ICP-MS. The spatial distribution of the major contaminants (Cu, Co, Pb, Zn) indicated the highest contamination NW of the smelter stack corresponding to the direction of prevailing winds in the area. The highest metal concentrations in soils were: 27410 ppm Cu, 606 ppm Co, 480 ppm Pb, 450 ppm Zn. Lead isotopes helped to discriminate the extent of metallic pollution related to the smelter emissions having similar 206Pb/207Pb ratio of 1.17-1.20 in contrast to the regional background value of 1.32. The investigation of the lateritic soil profile sampled in the near vicinity of the Nkana smelter indicated that contamination is mostly located in the uppermost soil horizons enriched in organic matter (< 10 cm). The sequential extraction procedure indicated that up to 33% of Cu and <10% of Co, Pb and Zn was mobile in the profile, being bound in the exchangeable fraction. However, in the deeper parts of the soil profile, metals were mostly bound in reducible fraction, presumably to hydrous ferric oxides. The combination of sequential extraction and lead isotopic determination indicated that the "mobile" fractions of Pb in the soil profile corresponded to the signatures of smelter particulate emissions (206Pb/207Pb = 1.17-1.20), which means that the anthropogenic emissions are the important source of mobile (and potentially bioavailable) metals.

Heterogeneity of the Caribbean plateau mantle source: Sr, O and He isotopic compositions of olivine and clinopyroxene from Gorgona Island

NASA Astrophysics Data System (ADS)

Révillon, S.; Chauvel, C.; Arndt, N. T.; Pik, R.; Martineau, F.; Fourcade, S.; Marty, B.

2002-12-01

The composition of the mantle plumes that created large oceanic plateaus such as Ontong Java or the Caribbean is still poorly known. Geochemical and isotopic studies on accreted portions of the Caribbean plateau have shown that the plume source was heterogeneous and contained isotopically depleted and relatively enriched portions. A distinctive feature of samples from the Caribbean plateau is their unusual Sr isotopic compositions, which, at a given Nd isotopic ratio, are far higher than in samples from other oceanic plateaus. Sr, O and He isotopic compositions of whole rocks and magmatic minerals (clinopyroxene or olivine) separated from komatiites, gabbros and peridotites from Gorgona Island in Colombia were determined to investigate the origin of these anomalously radiogenic compositions. Sequentially leached clinopyroxenes have Sr isotopic compositions in the range 87Sr/ 86Sr=0.70271-0.70352, systematically lower than those of leached and unleached whole rocks. Oxygen isotopic ratios of clinopyroxene vary within the range δ 18O=5.18-5.35‰, similar to that recorded in oceanic island basalts. He isotopic ratios are high ( R/ Ra=8-19). The lower 87Sr/ 86Sr ratios of most of the clinopyroxenes shift the field of the Caribbean plateau in Nd-Sr isotope diagrams toward more 'normal' values, i.e. a position closer to the field defined by mid-ocean ridge basalts and oceanic-island basalts. Three clinopyroxenes have slightly higher 87Sr/ 86Sr ratios that cannot be explained by an assimilation model. The high 87Sr/ 86Sr and variations of 143Nd/ 144Nd are interpreted as a source characteristic. Trace-element ratios, however, are controlled mainly by fractionation during partial melting. We combine these isotopic data in a heterogeneous plume source model that accounts for the diversity of isotopic signatures recorded on Gorgona Island and throughout the Caribbean plateau. The heterogeneities are related to old recycled oceanic lithosphere in the plume source; the high 3He/ 4He ratios may indicate that the source material once resided in the lower mantle.

Geochemical and multi-isotopic ( 87Sr/ 86Sr, 143Nd/ 144Nd, 238U/ 235U) perspectives of sediment sources, depositional conditions, and diagenesis of the Marcellus Shale, Appalachian Basin, USA

DOE PAGES

Phan, Thai T.; Gardiner, James B.; Capo, Rosemary C.; ...

2017-10-25

Here, we investigate sediment sources, depositional conditions and diagenetic processes affecting the Middle Devonian Marcellus Shale in the Appalachian Basin, eastern USA, a major target of natural gas exploration. Multiple proxies, including trace metal contents, rare earth elements (REE), the Sm-Nd and Rb-Sr isotope systems, and U isotopes were applied to whole rock digestions and sequentially extracted fractions of the Marcellus shale and adjacent units from two locations in the Appalachian Basin. The narrow range of εNd values (from –7.8 to –6.4 at 390 Ma) is consistent with derivation of the clastic sedimentary component of the Marcellus Shale from amore » well-mixed source of fluvial and eolian material of the Grenville orogenic belt, and indicate minimal post-depositional alteration of the Sm-Nd system. While silicate minerals host >80% of the REE in the shale, data from sequentially extracted fractions reflect post-depositional modifications at the mineralogical scale, which is not observed in whole rock REE patterns.« less

Advances in stable isotope assisted labeling strategies with information science.

PubMed

Kigawa, Takanori

2017-08-15

Stable-isotope (SI) labeling of proteins is an essential technique to investigate their structures, interactions or dynamics by nuclear magnetic resonance (NMR) spectroscopy. The assignment of the main-chain signals, which is the fundamental first step in these analyses, is usually achieved by a sequential assignment method based on triple resonance experiments. Independently of the triple resonance experiment-based sequential assignment, amino acid-selective SI labeling is beneficial for discriminating the amino acid type of each signal; therefore, it is especially useful for the signal assignment of difficult targets. Various combinatorial selective labeling schemes have been developed as more sophisticated labeling strategies. In these strategies, amino acids are represented by combinations of SI labeled samples, rather than simply assigning one amino acid to one SI labeled sample as in the case of conventional amino acid-selective labeling. These strategies have proven to be useful for NMR analyses of difficult proteins, such as those in large complex systems, in living cells, attached or integrated into membranes, or with poor solubility. In this review, recent advances in stable isotope assisted labeling strategies will be discussed. Copyright © 2017 Elsevier Inc. All rights reserved.

Geochemical and multi-isotopic ( 87Sr/ 86Sr, 143Nd/ 144Nd, 238U/ 235U) perspectives of sediment sources, depositional conditions, and diagenesis of the Marcellus Shale, Appalachian Basin, USA

DOE Office of Scientific and Technical Information (OSTI.GOV)

Phan, Thai T.; Gardiner, James B.; Capo, Rosemary C.

Here, we investigate sediment sources, depositional conditions and diagenetic processes affecting the Middle Devonian Marcellus Shale in the Appalachian Basin, eastern USA, a major target of natural gas exploration. Multiple proxies, including trace metal contents, rare earth elements (REE), the Sm-Nd and Rb-Sr isotope systems, and U isotopes were applied to whole rock digestions and sequentially extracted fractions of the Marcellus shale and adjacent units from two locations in the Appalachian Basin. The narrow range of εNd values (from –7.8 to –6.4 at 390 Ma) is consistent with derivation of the clastic sedimentary component of the Marcellus Shale from amore » well-mixed source of fluvial and eolian material of the Grenville orogenic belt, and indicate minimal post-depositional alteration of the Sm-Nd system. While silicate minerals host >80% of the REE in the shale, data from sequentially extracted fractions reflect post-depositional modifications at the mineralogical scale, which is not observed in whole rock REE patterns.« less

Simulation of dual carbon-bromine stable isotope fractionation during 1,2-dibromoethane degradation.

PubMed

Jin, Biao; Nijenhuis, Ivonne; Rolle, Massimo

2018-06-01

We performed a model-based investigation to simultaneously predict the evolution of concentration, as well as stable carbon and bromine isotope fractionation during 1,2-dibromoethane (EDB, ethylene dibromide) transformation in a closed system. The modelling approach considers bond-cleavage mechanisms during different reactions and allows evaluating dual carbon-bromine isotopic signals for chemical and biotic reactions, including aerobic and anaerobic biological transformation, dibromoelimination by Zn(0) and alkaline hydrolysis. The proposed model allowed us to accurately simulate the evolution of concentrations and isotope data observed in a previous laboratory study and to successfully identify different reaction pathways. Furthermore, we illustrated the model capabilities in degradation scenarios involving complex reaction systems. Specifically, we examined (i) the case of sequential multistep transformation of EDB and the isotopic evolution of the parent compound, the intermediate and the reaction product and (ii) the case of parallel competing abiotic pathways of EDB transformation in alkaline solution.

New technique for study on isotopic fractionation between sea water and foraminiferal growing processes

NASA Astrophysics Data System (ADS)

Cang, Shuxi; Shackleton, N. J.

1990-12-01

The stable isotopic δ18O and δ13C composition of foraminiferal shell calcite varies as a function of many factors including temperature and salinity. In order to understand and interpret the variations in the isotopic composition of foraminiferal shell calcite, research has been recently focused on the role of the “vital effects”. Our examination of the lamella structure of several recent planktonic foraminifera indicates that the secretion of sequential lamellae results in multiple lamillae on earlier chambers and a single lamella on the final chamber. We used a very simple procedure to separate the individual whole test of foraminifera into several chambers and measured the isotopic composition of each growth stage chamber. The results indicate that the stable isotopic composition (carbon and oxygen), particularly that of the last two chambers, of the foraminiferal test varies as a function of the individual growing process.

Validation of a single biopsy approach and bolus protein feeding to determine myofibrillar protein synthesis in stable isotope tracer studies in humans

PubMed Central

2011-01-01

Background Minimizing the number of muscle biopsies has important methodological implications and minimizes subject discomfort during a stable isotope amino acid infusion. We aimed to determine the reliability of obtaining a single muscle biopsy for the calculation of muscle protein fractional synthetic rate (FSR) as well as the amount of incorporation time necessary to obtain that biopsy after initiating a stable isotope infusion (Study 1). The calculation of muscle protein FSR requires tracer steady-state during the stable isotope infusion. Therefore, a second aim was to examine if steady-state conditions are compromised in the precursor pools (plasma free or muscle intracellular [IC]) after ingestion of a tracer enriched protein drink and after resistance exercise (Study 2). Methods Sixteen men (23 ± 3 years; BMI = 23.8 ± 2.2 kg/m2, means ± SD) were randomized to perform Study 1 or Study 2 (n = 8, per study). Subjects received a primed, constant infusion of L-[ring-13C6]phenylalanine coupled with muscle biopsies of the vastus lateralis to measure rates of myofibrillar protein synthesis (MPS). Subjects in Study 2 were fed 25 g of whey protein immediately after an acute bout of unilateral resistance exercise. Results There was no difference (P = 0.3) in rates of MPS determined using the steady-state precursor-product equation and determination of tracer incorporation between sequential biopsies 150 min apart or using plasma protein as the baseline enrichment, provided the infusion length was sufficient (230 ± 0.3 min). We also found that adding a modest amount of tracer (4% enriched), calculated based on the measured phenylalanine content of the protein (3.5%) in the drink, did not compromise steady-state conditions (slope of the enrichment curve not different from zero) in the plasma free or, more importantly, the IC pool (both P > 0.05). Conclusions These data demonstrate that the single biopsy approach yields comparable rates of muscle protein synthesis, provided a longer incorporation time is utilized, to that seen with a traditional two biopsy approach. In addition, we demonstrate that enriching protein-containing drinks with tracer does not disturb isotopic steady-state and thus both are reliable techniques to determine rates of MPS in humans. PMID:21388545

Determining the isotopic compositions of uranium and fission products in radioactive environmental microsamples using laser ablation ICP-MS with multiple ion counters.

PubMed

Boulyga, Sergei F; Prohaska, Thomas

2008-01-01

This paper presents the application of a multicollector inductively coupled plasma mass spectrometer (MC-ICP-MS)--a Nu Plasma HR--equipped with three ion-counting multipliers and coupled to a laser ablation system (LA) for the rapid and sensitive determination of the 235U/238U, 236U/238U, 145Nd/143Nd, 146Nd/143Nd, 101Ru/(99Ru+99Tc) and 102Ru/(99Ru+99Tc) isotope ratios in microsamples collected in the vicinity of Chernobyl. Microsamples with dimensions ranging from a hundred mum to about 1 mm and with surface alpha activities of 3-38 mBq were first identified using nuclear track radiography. U, Nd and Ru isotope systems were then measured sequentially for the same microsample by LA-MC-ICP-MS. The application of a zoom ion optic for aligning the ion beams into the ion counters allows fast switching between different isotope systems, which enables all of the abovementioned isotope ratios to be measured for the same microsample within a total analysis time of 15-20 min (excluding MC-ICP-MS optimization and calibration). The 101Ru/(99Ru+99Tc) and 102Ru/(99Ru+99Tc) isotope ratios were measured for four microsamples and were found to be significantly lower than the natural ratios, indicating that the microsamples were contaminated with the corresponding fission products (Ru and Tc). A slight depletion in 146Nd of about 3-5% was observed in the contaminated samples, but the Nd isotopic ratios measured in the contaminated samples coincided with natural isotopic composition within the measurement uncertainty, as most of the Nd in the analyzed samples originates from the natural soil load of this element. The 235U/238U and 236U/238U isotope ratios were the most sensitive indicators of irradiated uranium. The present work yielded a significant variation in uranium isotope ratios in microsamples, in contrast with previously published results from the bulk analysis of contaminated samples originating from the vicinity of Chernobyl. Thus, the 235U/238U ratios measured in ten microsamples varied in the range from 0.0073 (corresponding to the natural uranium isotopic composition) to 0.023 (corresponding to initial 235U enrichment in reactor fuel). An inverse correlation was observed between the 236U/238U and 235U/238U isotope ratios, except in the case of one sample with natural uranium. The heterogeneity of the uranium isotope composition is attributed to the different burn-up grades of uranium in the fuel rods from which the microsamples originated.

Strontium Isotopes of Gaskiers Cap Carbonate, Avalon, Newfoundland: Sequential Digestion Aids Interpretation of Petrologic Complexity

NASA Astrophysics Data System (ADS)

Tang, T.; Raub, T. D.; Wang, Z.

2013-12-01

Strontium isotope chemostratigraphy in limestones appear to track a near monotonic rising trend from the tail of the breakup of the supercontinent Rodinia at ~750 Ma into the latest Ediacaran Period at ~ 550 Ma (Halverson et al., 2007). This offers a potentially powerful tool to date carbonates occurring within this time period of stepwise environmental oxidation. Furthermore, aspects of the Snowball Earth hypothesis predict that some magnitude of 87Sr/86Sr excursions of seawater is expected at multiple intervals during this time, because balancing influences from prolonged synglacial hydrothermal input in entombed oceans, deglacial freshwater plumes of varying temperature and salinity, and enhanced postglacial silicate weathering from the continents can leave multiple isotopic trends plausible during these critical intervals. The positions of these deglaciations appear to correlate specifically to marine oxidation events, with cause/effect relations still under investigation. To capitalize on all of these interpretive possibilities, it is crucial to establish a high-precision and high-resolution strontium chemostratigraphic record over both short and long timescales. However, difficulties in establishing such a record based on carbonates are associated with 1) diagenetic influence over extensive geological time; and 2) petrologic complexities of the studied samples. Using a sequential digestion technique, Liu et al. (2013) demonstrated that these hurdles can be overcome, and that primary 87Sr/86Sr ratios of contemporaneous seawater can be obtained from Marinoan cap dolostones (~635 Ma), which have considerably less Sr than limestones, and whose Sr isotope compositions are commonly ignored in the strontium chemostratigraphic record. This leads to several viable, specific interpretations about the origin of Marinoan cap carbonate: either 1) very fast deposition; 2) slow deposition in a long-Sr-residence-time ocean; 3) mid-cap deposition in a freshwater "Glacial Lake Harland" of high-Ca, Sr composition; or 4) brine-influenced diagenesis exploiting specific horizons in the cap. As a broader implication, many extant Sr-isotope chemostratigraphies of Marinoan cap carbonate may be inaccurate, and in general, recrystallized impure (and low-Sr) carbonates, and dolomites in particular, are probably best studied with the serial digestion technique. We apply this sequential digestion technique to another Ediacaran cap carbonate with significant siliciclastic content, the anomalous cap limestone synchronous with deglaciation of ~581 Ma Gaskiers ice age in Newfoundland's Avalon zone. Although some textural and compositional differences exist between ~635 Ma Nuccaleena and ~581 Ma Gaskiers cap, the sequential digestion technique again appears to provide clarity by suggesting less-altered and more-altered fractions from various sample levels. We will discuss implications for the nature of Gaskiers glaciation and accompanying environmental oxidation, its global correlations, and the utility of the existing Ediacaran Sr-chemostratigraphic reference curve.

Assessing of distribution, mobility and bioavailability of exogenous Pb in agricultural soils using isotopic labeling method coupled with BCR approach.

PubMed

Huang, Zhi-Yong; Xie, Hong; Cao, Ying-Lan; Cai, Chao; Zhang, Zhi

2014-02-15

The contamination of Pb in agricultural soils is one of the most important ecological problems, which potentially results in serious health risk on human health through food chain. Hence, the fate of exogenous Pb contaminated in agricultural soils is needed to be deeply explored. By spiking soils with the stable enriched isotopes of (206)Pb, the contamination of exogenous Pb(2+) ions in three agricultural soils sampled from the estuary areas of Jiulong River, China was simulated in the present study, and the distribution, mobility and bioavailability of exogenous Pb in the soils were investigated using the isotopic labeling method coupled with a four-stage BCR (European Community Bureau of Reference) sequential extraction procedure. Results showed that about 60-85% of exogenous Pb was found to distribute in reducible fractions, while the exogenous Pb in acid-extractable fractions was less than 1.0%. After planting, the amounts of exogenous Pb presenting in acid-extractable, reducible and oxidizable fractions in rhizospheric soils decreased by 60-66%, in which partial exogenous Pb was assimilated by plants while most of the metal might transfer downward due to daily watering and applying fertilizer. The results show that the isotopic labeling technique coupled with sequential extraction procedures enables us to explore the distribution, mobility and bioavailability of exogenous Pb contaminated in soils, which may be useful for the further soil remediation. Copyright © 2014 Elsevier B.V. All rights reserved.

Sequential extraction procedure for determination of uranium, thorium, radium, lead and polonium radionuclides by alpha spectrometry in environmental samples

NASA Astrophysics Data System (ADS)

Oliveira, J. M.; Carvalho, F. P.

2006-01-01

A sequential extraction technique was developed and tested for common naturally-occurring radionuclides. This technique allows the extraction and purification of uranium, thorium, radium, lead, and polonium radionuclides from the same sample. Environmental materials such as water, soil, and biological samples can be analyzed for those radionuclides without matrix interferences in the quality of radioelement purification and in the radiochemical yield. The use of isotopic tracers (232U, 229Th, 224Ra, 209Po, and stable lead carrier) added to the sample in the beginning of the chemical procedure, enables an accurate control of the radiochemical yield for each radioelement. The ion extraction procedure, applied after either complete dissolution of the solid sample with mineral acids or co-precipitation of dissolved radionuclide with MnO2 for aqueous samples, includes the use of commercially available pre-packed columns from Eichrom® and ion exchange columns packed with Bio-Rad resins, in altogether three chromatography columns. All radioactive elements but one are purified and electroplated on stainless steel discs. Polonium is spontaneously plated on a silver disc. The discs are measured using high resolution silicon surface barrier detectors. 210Pb, a beta emitter, can be measured either through the beta emission of 210Bi, or stored for a few months and determined by alpha spectrometry through the in-growth of 210Po. This sequential extraction chromatography technique was tested and validated with the analysis of certified reference materials from the IAEA. Reproducibility was tested through repeated analysis of the same homogeneous material (water sample).

Determination of the delta(18O/16O)of Water: RSIL Lab Code 489

USGS Publications Warehouse

Revesz, Kinga; Coplen, Tyler

2008-01-01

The purpose of the technique described by the Reston Stable Isotope Laboratory (RSIL) lab code 489 is to present a method to determine the delta(180/160), abbreviated as delta-180, of water. This delta-18O measurement of water also is a component of National Water Quality Laboratory (NWQL in USGS) schedules 1142 and 1172. Water samples are loaded into glass sample containers on a vacuum manifold to equilibrate gaseous CO2 at constant temperature (25 deg C) with water samples. After loading water samples on the vacuum manifold, air is evacuated through capillary to avoid evaporation, and CO2 is added. The samples are shaken to increase the equilibration rate of water and CO2. When isotopic equilibrium has been attained, an aliquot of CO2 is extracted sequentially from each sample container, separated from water vapor by means of a dry ice trap, and introduced into a dual-inlet isotope-ratio mass spectrometer (DI-IRMS) for determination of the delta-18O value. There is oxygen isotopic fractionation between water and CO2, but it is constant at constant temperature. The DI-IRMS is a DuPont double-focusing mass spectrometer. It has a double collector. One ion beam passes through a slit in a forward collector and is collected in the rear collector. The other ion beams are collected in the front collector. The instrument is capable of measuring mass/charge (m/z) 44 and 45 or 44 and 46 by changing the ion-accelerating voltage under computer control. The ion beams from these m/z values are as follows: m/z 44=CO2=12C16O16O, m/z 45=CO2=13C16O16O primarily, and m/z 46 = CO2=12C16O18O primarily. The data acquisition and control software calculates delta-18O values.

Sequential chemical treatment of radium species in TENORM waste sludge produced from oil and natural gas production.

PubMed

El Afifi, E M; Awwad, N S; Hilal, M A

2009-01-30

This paper is dedicated to the treatment of sludge occurring in frame of the Egyptian produced from oil and gas production. The activity levels of three radium isotopes: Ra-226 (of U-series), Ra-228 and Ra-224 (of Th-series) in the solid TENORM waste (sludge) were first evaluated and followed by a sequential treatment for all radium species (fractions) presented in TENORM. The sequential treatment was carried out based on two approaches 'A' and 'B' using different chemical solutions. The results obtained indicate that the activity levels of all radium isotopes (Ra-226, Ra-228 and Ra-224) of the environmental interest in the TENORM waste sludge were elevated with regard to exemption levels established by IAEA [International Atomic Energy Agency (IAEA), International basic safety standards for the protection against ionizing radiation and for the safety of radiation sources. GOV/2715/Vienna, 1994]. Each approach of the sequential treatment was performed through four steps using different chemical solutions to reduce the activity concentration of radium in a large extent. Most of the leached radium was found as an oxidizable Ra species. The actual removal % leached using approach B was relatively efficient compared to A. It is observed that the actual removal percentages (%) of Ra-226, Ra-228 and Ra-224 using approach A are 78+/-2.8, 64.8+/-4.1 and 76.4+/-5.2%, respectively. Whereas in approach A, the overall removal % of Ra-226, Ra-228 and Ra-228 was increased to approximately 91+/-3.5, 87+/-4.1 and 90+/-6.2%, respectively.

Early-life sexual segregation: ontogeny of isotopic niche differentiation in the Antarctic fur seal

NASA Astrophysics Data System (ADS)

Kernaléguen, L.; Arnould, J. P. Y.; Guinet, C.; Cazelles, B.; Richard, P.; Cherel, Y.

2016-09-01

Investigating the ontogeny of niche differentiation enables to determine at which life-stages sexual segregation arises, providing insights into the main factors driving resource partitioning. We investigated the ontogeny of foraging ecology in Antarctic fur seals (Arctocephalus gazella), a highly dimorphic species with contrasting breeding strategies between sexes. Sequential δ13C and δ15N values of whiskers provided a longitudinal proxy of the foraging niche throughout the whole life of seals, from weaning, when size dimorphism is minimal to the age of 5. Females exhibited an early-life ontogenetic shift, from a total segregation during their first year at-sea, to a similar isotopic niche as breeding females as early as age 2. In contrast, males showed a progressive change in isotopic niche throughout their development such that 5-year-old males did not share the same niche as territorial bulls. Interestingly, males and females segregated straight after weaning with males appearing to feed in more southerly habitats than females. This spatial segregation was of similar amplitude as observed in breeding adults and was maintained throughout development. Such early-life niche differentiation is an unusual pattern and indicates size dimorphism and breeding constraints do not directly drive sexual segregation contrary to what has been assumed in otariid seals.

Oxygen isotopic fractionation of O₂ during adsorption and desorption processes using molecular sieve at low temperatures.

PubMed

Ahn, Insu; Kusakabe, Minoru; Lee, Jong Ik

2014-06-15

Cryogenic trapping using molecular sieves is commonly used to collect O2 extracted from silicates for (17)O/(16)O and (18)O/(16)O analyses. However, gases which interfere with (17)O/(16)O analysis, notably NF3, are also trapped and their removal is essential for accurate direct measurement of the (17)O/(16)O ratio. It is also necessary to identify and quantify any isotopic fractionation associated with the use of cryogenic trapping using molecular sieves. The oxygen isotopic compositions of O2 before and after desorption from, and adsorption onto, 13X and 5A molecular sieves (MS13X and MS5A) at 0°C, -78°C, -114°C, and -130°C were measured in order to determine the oxygen isotopic fractionation at these temperatures. We also investigated whether isotopic fractionation occurred when O2 gas was transferred sequentially into a second cold finger, also containing molecular sieve. It was confirmed that significant oxygen isotopic fractionation occurs between the gaseous O2 and that adsorbed onto molecular sieve, if desorption and adsorption are incomplete. As the fraction of released or untrapped O2 becomes smaller with decreasing trapping temperature (from 0 to -130°C), the isotopic fractionation becomes larger. Approximately half of the total adsorbed O2 is released from the molecular sieve during desorption at -114°C, which is the temperature recommended for separation from NF3 (retained on the molecular sieve), and this will interfere with (17)O/(16)O measurements. The use of a single cold finger should be avoided, because partial desorption is accompanied by oxygen isotopic fractionation, thereby resulting in inaccurate isotopic data. The use of a dual cold finger arrangement is recommended because, as we have confirmed, the transfer of O2 from the first trap to the second is almost 100%. However, even under these conditions, a small isotopic fractionation (0.18 ± 0.05‰ in δ(17)O values and 0.26 ± 0.06‰ in δ(18)O values) occurred, with O2 in the second trap being isotopically enriched in the heavier isotopes. Copyright © 2014 John Wiley & Sons, Ltd.

Assessment of the global fallout of plutonium isotopes and americium-241 in the soil of the central region of Saudi Arabia.

PubMed

Shabana, E I; Al-Shammari, H L

2001-01-01

A radiochemical technique for determination of plutonium isotopes and 241Am in soil samples is tested against IAEA-standard reference materials to determine its accuracy and precision for reliable results. The technique is then used in the investigation of topsoil samples, collected from the natural environment of the central region of Saudi Arabia, to assess the effect of fallout accumulation of these radionuclides in the region. Plutonium and americium were sequentially separated from all other components of the sample by anion-exchange chromatography and co-precipitated with Nd3+ as fluorides. The precipitates were mounted on membrane filters and measured using a high-resolution alpha-spectrometer. The results of the analysis of the reference materials showed satisfactory sensitivity and precision of the technique. The results of the analyzed soil samples show activity levels ranging from < LLD to 0.089 and from

Fukushima Daiichi reactor source term attribution using cesium isotope ratios from contaminated environmental samples.

PubMed

Snow, Mathew S; Snyder, Darin C; Delmore, James E

2016-02-28

Source term attribution of environmental contamination following the Fukushima Daiichi Nuclear Power Plant (FDNPP) disaster is complicated by a large number of possible similar emission source terms (e.g. FDNPP reactor cores 1-3 and spent fuel ponds 1-4). Cesium isotopic analyses can be utilized to discriminate between environmental contamination from different FDNPP source terms and, if samples are sufficiently temporally resolved, potentially provide insights into the extent of reactor core damage at a given time. Rice, soil, mushroom, and soybean samples taken 100-250 km from the FDNPP site were dissolved using microwave digestion. Radiocesium was extracted and purified using two sequential ammonium molybdophosphate-polyacrylonitrile columns, following which (135)Cs/(137) Cs isotope ratios were measured using thermal ionization mass spectrometry (TIMS). Results were compared with data reported previously from locations to the northwest of FDNPP and 30 km to the south of FDNPP. (135)Cs/(137)Cs isotope ratios from samples 100-250 km to the southwest of the FDNPP site show a consistent value of 0.376 ± 0.008. (135)Cs/(137)Cs versus (134)Cs/(137)Cs correlation plots suggest that radiocesium to the southwest is derived from a mixture of FDNPP reactor cores 1, 2, and 3. Conclusions from the cesium isotopic data are in agreement with those derived independently based upon the event chronology combined with meteorological conditions at the time of the disaster. Cesium isotopic analyses provide a powerful tool for source term discrimination of environmental radiocesium contamination at the FDNPP site. For higher precision source term attribution and forensic determination of the FDNPP core conditions based upon cesium, analyses of a larger number of samples from locations to the north and south of the FDNPP site (particularly time-resolved air filter samples) are needed. Published in 2016. This article is a U.S. Government work and is in the public domain in the USA.

Technical note: An inverse method to relate organic carbon reactivity to isotope composition from serial oxidation

NASA Astrophysics Data System (ADS)

Hemingway, Jordon D.; Rothman, Daniel H.; Rosengard, Sarah Z.; Galy, Valier V.

2017-11-01

Serial oxidation coupled with stable carbon and radiocarbon analysis of sequentially evolved CO2 is a promising method to characterize the relationship between organic carbon (OC) chemical composition, source, and residence time in the environment. However, observed decay profiles depend on experimental conditions and oxidation pathway. It is therefore necessary to properly assess serial oxidation kinetics before utilizing decay profiles as a measure of OC reactivity. We present a regularized inverse method to estimate the distribution of OC activation energy (E), a proxy for bond strength, using serial oxidation. Here, we apply this method to ramped temperature pyrolysis or oxidation (RPO) analysis but note that this approach is broadly applicable to any serial oxidation technique. RPO analysis directly compares thermal reactivity to isotope composition by determining the E range for OC decaying within each temperature interval over which CO2 is collected. By analyzing a decarbonated test sample at multiple masses and oven ramp rates, we show that OC decay during RPO analysis follows a superposition of parallel first-order kinetics and that resulting E distributions are independent of experimental conditions. We therefore propose the E distribution as a novel proxy to describe OC thermal reactivity and suggest that E vs. isotope relationships can provide new insight into the compositional controls on OC source and residence time.

The smallest Gliders in the Ocean- Temperature Recordings from Pteropods using SIMS

NASA Astrophysics Data System (ADS)

Keul, N.; Orland, I. J.; Valley, J. W.; Kozdon, R.; deMenocal, P. B.

2016-02-01

During the last few decades, the development, refinement and application of geochemical methods have lead to the establishment of new proxies to estimate global change. The oxygen isotope composition of carbonate shells formed by marine organisms is a widely used proxy for past ocean temperatures. Secondary ion mass spectrometry (SIMS) is a high spatial-resolution in situ technique, allowing oxygen isotope measurements on very small samples (down to 3 μm spot size). Pteropods are pelagic mollusks, producing shells made out of aragonite, which is more soluble than calcite in seawater, making them one of the first responders to climate change. They calcify closely at the aragonite- seawater equilibrium and are therefor ideal candidates to reconstruct temperatures based on their d18O. The oxygen isotopic composition of pteropod shells from sediment traps, net tows and a culture study from the Fram Strait will be presented. Specimens travelled in the Westspitsbergen Current prior to sinking into the sediment. During this transport specimens continue to grow, sequentially adding aragonite to the shell. We show that when using traditional (whole shell) δ18O measurements, the isotopic signatures of whole shells reflect the latitudinal gradient. Combining this with SIMS-derived δ18O measurements on individual shell parts, however, reveals that this is only half the story: Comparing δ18O of earlier (produced further South) and later shell parts (produced further North) shows that pteropods calcify in sequentially shallower water depths, overriding the latitudinal South to North temperature gradient. Combining traditional and novel δ18O measurements can potentially not only allow the reconstruction of temperature/ global warming, but also to assess ecological key parameters, such as habitat depth, at the same time.

RAPID DETERMINATION OF ACTINIDES IN URINE BY INDUCTIVELY-COUPLED PLASMA MASS SPECTROMETRY AND ALPHA SPECTROMETRY: A HYBRID APPROACH

DOE Office of Scientific and Technical Information (OSTI.GOV)

Maxwell, S.; Jones, V.

2009-05-27

A new rapid separation method that allows separation and preconcentration of actinides in urine samples was developed for the measurement of longer lived actinides by inductively coupled plasma mass spectrometry (ICP-MS) and short-lived actinides by alpha spectrometry; a hybrid approach. This method uses stacked extraction chromatography cartridges and vacuum box technology to facilitate rapid separations. Preconcentration, if required, is performed using a streamlined calcium phosphate precipitation. Similar technology has been applied to separate actinides prior to measurement by alpha spectrometry, but this new method has been developed with elution reagents now compatible with ICP-MS as well. Purified solutions are splitmore » between ICP-MS and alpha spectrometry so that long- and short-lived actinide isotopes can be measured successfully. The method allows for simultaneous extraction of 24 samples (including QC samples) in less than 3 h. Simultaneous sample preparation can offer significant time savings over sequential sample preparation. For example, sequential sample preparation of 24 samples taking just 15 min each requires 6 h to complete. The simplicity and speed of this new method makes it attractive for radiological emergency response. If preconcentration is applied, the method is applicable to larger sample aliquots for occupational exposures as well. The chemical recoveries are typically greater than 90%, in contrast to other reported methods using flow injection separation techniques for urine samples where plutonium yields were 70-80%. This method allows measurement of both long-lived and short-lived actinide isotopes. 239Pu, 242Pu, 237Np, 243Am, 234U, 235U and 238U were measured by ICP-MS, while 236Pu, 238Pu, 239Pu, 241Am, 243Am and 244Cm were measured by alpha spectrometry. The method can also be adapted so that the separation of uranium isotopes for assay is not required, if uranium assay by direct dilution of the urine sample is preferred instead. Multiple vacuum box locations may be set-up to supply several ICP-MS units with purified sample fractions such that a high sample throughput may be achieved, while still allowing for rapid measurement of short-lived actinides by alpha spectrometry.« less

Quantifying Uranium Isotope Ratios Using Resonance Ionization Mass Spectrometry: The Influence of Laser Parameters on Relative Ionization Probability

DOE Office of Scientific and Technical Information (OSTI.GOV)

Isselhardt, Brett H.

2011-09-01

Resonance Ionization Mass Spectrometry (RIMS) has been developed as a method to measure relative uranium isotope abundances. In this approach, RIMS is used as an element-selective ionization process to provide a distinction between uranium atoms and potential isobars without the aid of chemical purification and separation. We explore the laser parameters critical to the ionization process and their effects on the measured isotope ratio. Specifically, the use of broad bandwidth lasers with automated feedback control of wavelength was applied to the measurement of 235U/ 238U ratios to decrease laser-induced isotopic fractionation. By broadening the bandwidth of the first laser inmore » a 3-color, 3-photon ionization process from a bandwidth of 1.8 GHz to about 10 GHz, the variation in sequential relative isotope abundance measurements decreased from >10% to less than 0.5%. This procedure was demonstrated for the direct interrogation of uranium oxide targets with essentially no sample preparation. A rate equation model for predicting the relative ionization probability has been developed to study the effect of variation in laser parameters on the measured isotope ratio. This work demonstrates that RIMS can be used for the robust measurement of uranium isotope ratios.« less

Using Strontium Isotopes in Arid Agricultural Soils to Determine a Sink or Source of CO2

NASA Astrophysics Data System (ADS)

Ortiz, A. C.; Jin, L.

2014-12-01

Arid and semi-arid regions of the world are predicted to continue to expand through land degradation and prolonged drought events. Agricultural practices in these drylands degrade soils through elevated salinity, sodicity and alkalinity. Indeed, flood irrigation loads salts onto the soils including carbonate minerals in the form of calcite. Alfalfa and Pecan are salt tolerant and commonly grown in the arid El Paso region, but need irrigation using Rio Grande water with little to no contribution from local ground waters. We hypothesize that the irrigation is loading extra Ca and bicarbonate to soils and anthropogenically enhancing the precipitation of carbonates. We intend to monitor soil CO2 efflux after irrigation, characterize soil minerals, and combine them to isotopic data of soil, irrigation, and drainage waters to link the sources of Ca and C, kinetics of calcite precipitation, to irrigation events. This will include strontium isotopic analysis to determine the source of calcium in the agricultural fields, U-disequilibrium isotopes to estimate the carbonate ages, and CO2 efflux to monitor atmosphere-soil exchange. Carbon dioxide emissions are expected to change during flood irrigation when soils are saturated. After irrigation events, evaporative effects increase Ca and dissolved inorganic carbon concentration in soil waters leading to precipitation of calcite and thus elevated CO2efflux. Preliminary measurements in the pecan field show a marginally significant difference in CO2 fluxes before and after irrigation (p=0.07, t-test). Carbon dioxide emissions are lower during moist conditions (0.6 g m-2hr-1 CO2) than those in dry conditions (1.0 g m-2hr-1 CO2). Future C isotope data are needed to identify the source of extra CO2, biogenic or calcite-precipitation related. A water leachable extraction of alfalfa soils shows 87Sr/86Sr ratios ranged from 0.7101 to 0.7103, indicating Rio Grande river as a dominant calcium source. Further Sr isotopic analysis of sequential extractions from both alfalfa soils (for calcite fraction), pore waters, irrigation waters, and drainage waters will allow us to quantitatively evaluate the source of calcium in calcite therefore, defining if anthropogenic sources of calcium lead to enhanced CO2 production in agricultural fields.

Iron Cycling in Marine Sediments - New Insights from Isotope Analysis on Sequentially Extracted Fe Fractions

NASA Astrophysics Data System (ADS)

Henkel, S.; Kasten, S.; Poulton, S.; Hartmann, J.; Staubwasser, M.

2014-12-01

Reactive Fe (oxyhydr)oxides preferentially undergo early diagenetic cycling and may cause a diffusive flux of dissolved Fe2+ from sediments towards the sediment-water interface. The partitioning of Fe in sediments has traditionally been studied by applying sequential extractions based on reductive dissolution of Fe minerals. We complemented the sequential leaching method by Poulton and Canfield [1] in order to be able to gain δ56Fe data for specific Fe fractions, as such data are potentially useful to study Fe cycling in marine environments. The specific mineral fractions are Fe-carbonates, ferrihydrite + lepidocrocite, goethite + hematite, and magnetite. Leaching was performed with acetic acid, hydroxylamine-HCl, Na-dithionite and oxalic acid. The processing of leachates for δ56Fe analysis involved boiling the samples in HCl/HNO3/H2O2, Fe precipitation and anion exchange column chromatography. The new method was applied to short sediment cores from the North Sea and a bay of King George Island (South Shetland Islands, Antarctica). Downcore mineral-specific variations in δ56Fe revealed differing contributions of Fe (oxyhydr)oxides to redox cycling. A slight decrease in easily reducible Fe oxides correlating with a slight increase in δ56Fe for this fraction with depth, which is in line with progessive dissimilatory iron reduction [2,3], is visible in the top 10 cm of the North Sea core, but not in the antarctic sediments. Less reactive (dithionite and oxalate leachable) fractions did not reveal isotopic trends. The acetic acid-soluble fraction displayed pronounced δ56Fe trends at both sites that cannot be explained by acid volatile sulfides that are also extracted by acetic acid [1]. We suggest that low δ56Fe values in this fraction relative to the pool of easily reducible Fe oxides result from adsorbed Fe(II) that was open to isotopic exchange with oxide surfaces, affirming the experimental results of Crosby el al. [2]. Hence, δ56Fe analyses on marine sediments appear to be particularly useful when targeting specific Fe pools, rather than the total highly reactive Fe fraction, since isotopic trends may be masked within the latter pool. [1] Poulton and Canfield (2005), Chemical Geology 214, 209-221. [2] Crosby et al., Geobiology 5 (2007), 169-189. [3] Staubwasser et al., Geology 34 (2006), 629-632.

A Sequential Leach Method and Pb Isotope Approach to Studying Apatite Weathering in Granitoid Soils at Hubbard Brook Experimental Forest, NH, USA

NASA Astrophysics Data System (ADS)

Nezat, C. A.; Blum, J. D.

2005-12-01

Easily dissolved minerals such as calcite and apatite can be important in controlling stream and ground water chemistry even though these minerals are only present in trace amounts in granitoid rocks. Because of its solubility, apatite, a calcium phosphate mineral, may be a significant source of essential nutrients (especially phosphorous) for vegetation, and has been shown to strongly influence stream and soil water composition (e.g, calcium, strontium and rare earth elements). There are additional sources of Ca (e.g., feldspars, hornblende) and P (e.g., organic matter or bound to Fe and Al oxides) in granitoid soils. In order to distinguish the chemical constituents of apatite from other pools in the bulk soil, we selectively dissolved apatite with a dilute acid leach, and measured Pb isotopic ratios of apatite, feldspar, and leachates. We tested the leaching procedure on mineral separates and verified that a dilute nitric solution primarily dissolves apatite. Silicates were dissolved in subsequent steps by successively stronger acids. We then applied this method to bulk soils collected from several soil pits across a small watershed at the Hubbard Brook Experimental Forest (HBEF), New Hampshire, USA, to determine the spatial distribution of Ca and P pools, and determine the depth of apatite depletion in the soil. We also measured Pb isotope ratios in the soil leachates to distinguish among the various sources of Pb (e.g., apatite, feldspars and anthropogenic sources). We found that Pb in the dilute nitric leach of the HBEF organic soils is dominated by anthropogenic sources and that Pb from apatite becomes increasingly important with depth.

Using chromium stable isotope ratios to quantify Cr(VI) reduction: Lack of sorption effects

USGS Publications Warehouse

Ellis, A.S.; Johnson, T.M.; Bullen, T.D.

2004-01-01

Chromium stable isotope values can be effectively used to monitor reduction of Cr(VI) in natural waters. We investigate effects of sorption during transport of Cr(VI) which may also shift Cr isotopes values, complicating efforts to quantify reduction. This study shows that Cr stable isotope fractionation caused by sorption is negligible. Equilibrium fractionation of Cr stable isotopes between dissolved Cr-(VI) and Cr(VI) adsorbed onto ??-Al2O3 and goethite is less than 0.04???. (53Cr/52Cr) under environmentally relevant pH conditions. Batch experiments at pH 4.0 and pH 6.0 were conducted in series to sequentially magnify small isotope fractionations. A simple transport model suggests that adsorption may cause amplification of a small isotope fractionation along extreme fringes of a plume, leading to shifts in 53Cr/52Cr values. We therefore suggest that isotope values at extreme fringes of Cr plumes be critically evaluated for sorption effects. A kinetic effect was observed in experiments with goethite at pH 4 where apparently lighter isotopes diffuse into goethite clumps at a faster rate before eventually reaching equilibrium. This observed kinetic effect may be important in a natural system that has not attained equilibrium and is in need of further study. Cr isotope fractionation caused by speciation of Cr(VI) between HCrO4- and CrO42- was also examined, and we conclude that it is not measurable. In the absence of isotope fractionation caused by equilibrium speciation and sorption, most of the variation in ??53 Cr values may be attributed to reduction, and reliable estimates of Cr reduction can be made.

Ion implantation system and process for ultrasensitive determination of target isotopes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Farmer, III, Orville T.; Liezers, Martin

2016-09-13

A system and process are disclosed for ultrasensitive determination of target isotopes of analytical interest in a sample. Target isotopes may be implanted in an implant area on a high-purity substrate to pre-concentrate the target isotopes free of contaminants. A known quantity of a tracer isotope may also be implanted. Target isotopes and tracer isotopes may be determined in a mass spectrometer. The present invention provides ultrasensitive determination of target isotopes in the sample.

Method for sequential injection of liquid samples for radioisotope separations

DOEpatents

Egorov, Oleg B.; Grate, Jay W.; Bray, Lane A.

2000-01-01

The present invention is a method of separating a short-lived daughter isotope from a longer lived parent isotope, with recovery of the parent isotope for further use. Using a system with a bi-directional pump and one or more valves, a solution of the parent isotope is processed to generate two separate solutions, one of which contains the daughter isotope, from which the parent has been removed with a high decontamination factor, and the other solution contains the recovered parent isotope. The process can be repeated on this solution of the parent isotope. The system with the fluid drive and one or more valves is controlled by a program on a microprocessor executing a series of steps to accomplish the operation. In one approach, the cow solution is passed through a separation medium that selectively retains the desired daughter isotope, while the parent isotope and the matrix pass through the medium. After washing this medium, the daughter is released from the separation medium using another solution. With the automated generator of the present invention, all solution handling steps necessary to perform a daughter/parent radionuclide separation, e.g. Bi-213 from Ac-225 "cow" solution, are performed in a consistent, enclosed, and remotely operated format. Operator exposure and spread of contamination are greatly minimized compared to the manual generator procedure described in U.S. patent application Ser. No. 08/789,973, now U.S. Pat. No. 5,749,042, herein incorporated by reference. Using 16 mCi of Ac-225 there was no detectable external contamination of the instrument components.

Assessment of chloroethene biodegradation in the subsurface by microbiological, molecular and isotopic tools

NASA Astrophysics Data System (ADS)

Schmidt, K. R.; Kranzioch, I.; Heidinger, M.; Ertl, S.; Tiehm, A.

2012-04-01

A multiple lines of evidence approach to assess the biodegradation potential of contaminated sites includes - site investigation analysing pollutant distribution (compounds, concentrations, isotopic composition) and hydrochemical conditions (redox conditions) - determination of the presence of pollutant degrading bacteria in the field by microbiological (most probable number, MPN) and molecular (polymerase chain reaction, PCR) methods - analysis of degradation processes in the laboratory by microcosms with determination of site specific isotopic enrichment factors enabling the quantification of biodegradation processes in the field. Results will be shown of the application of such a multiple lines of evidence approach at a chloroethene-contaminated site in Frankenthal, Germany. In anaerobic groundwater microcosms, reductive transformation of perchloroethene (PCE) and trichloroethene (TCE) was observed to mainly proceed to cis-1,2-dichloroethene (cDCE). 16S-PCR analysis showed a wide distribution of halorespiring bacteria capable of PCE degradation to cDCE, whereas Dehalococcoides - the only organisms described so far being able of complete reductive dechlorination down to ethene - was only found in one groundwater sample. Aerobic microcosms showed metabolic degradation of the lower chlorinated compounds cDCE and vinyl chloride (VC). Co-metabolic degradation of cDCE with VC as auxiliary substrate occurred, too. Significant stable carbon isotope fractionation was observed during anaerobic degradation of PCE and TCE as well as during aerobic degradation of cDCE and VC. Compiling the results of the different assessment methods, sequential dechlorination - PCE/TCE to cDCE anaerobically and cDCE to CO2 aerobically - was demonstrated to occur at the Frankenthal site. The extent of biodegradation in the field was calculated based on the enrichment factors determined in microcosms and the 13C-isotopic composition of the contaminants on site. The application of molecular methods is continuously increasing. For example, microbiological and molecular tools showed the presence and activity of halorespiring bacteria in sediment samples of the Yangtze river, China. PCR-detection demonstrated the presence of five different halorespiring bacterial groups as well as of four different dechlorinating enzymes of Dehalococcoides. In conclusion, our study demonstrates that (i) multiple lines of evidence approaches result in a profound understanding of the biodegradation processes occurring in the field, (ii) stable isotope fractionation is suitable for assessing and quantifying anaerobic and aerobic chloroethene degradation and (iii) detection and quantification of dechlorinating bacteria and enzymes by PCR methods provide more insight into biodegradation processes. Acknowledgement The authors gratefully acknowledge financial support by the German Ministry of Education and Research (BMBF, grant no 02WN0446, 02WN0447 and 02WT1130), the German Ministry of Economics and Technology (BMWi, grant no KF2265705AK9 and KF2285302AK9) and the federal state of Rhineland-Palatinate. We thank all project partners for fruitful cooperation.

Fruits of the forest: Human stable isotope ecology and rainforest adaptations in Late Pleistocene and Holocene (∼36 to 3 ka) Sri Lanka.

PubMed

Roberts, Patrick; Perera, Nimal; Wedage, Oshan; Deraniyagala, Siran; Perera, Jude; Eregama, Saman; Petraglia, Michael D; Lee-Thorp, Julia A

2017-05-01

Sri Lanka has yielded some of the earliest dated fossil evidence for Homo sapiens (∼38-35,000 cal. years BP [calibrated years before present]) in South Asia, within a region that is today covered by tropical rainforest. Archaeozoological and archaeobotanical evidence indicates that these hunter-gatherers exploited tropical forest resources, yet the contribution of these resources to their overall subsistence strategies has, as in other Late Pleistocene rainforest settings, remained relatively unexplored. We build on previous work in this tropical region by applying both bulk and sequential stable carbon and oxygen isotope analysis to human and faunal tooth enamel from the sites of Batadomba-lena, Fa Hien-lena, and Balangoda Kuragala. Tooth enamel preservation was assessed by means of Fourier Transform Infrared Spectroscopy. We use these data to produce a detailed stable isotope ecology for Late Pleistocene-Holocene foragers in Sri Lanka from ∼36-29,000 to 3000 cal. years BP, allowing us to test the degree of human tropical forest resource reliance over a considerable time period. Given that non-human primates dominate the mammalian assemblages at these sites, we also focus on the stable isotope composition of three monkey species in order to study their ecological preferences and, indirectly, human hunting strategies. The results confirm a strong human reliance on tropical forest resources from ∼36-29,000 cal. years BP until the Iron Age ∼3 cal. years BP, while sequential tooth data show that forest resources were exploited year-round. This strategy was maintained through periods of evident environmental change at the Last Glacial Maximum and upon the arrival of agriculture. Long-term tropical forest reliance was supported by the specialised capture of non-human primates, although the isotopic data revealed no evidence for niche distinction between the hunted species. We conclude that humans rapidly developed a specialisation in the exploitation of South Asia's tropical forests following their arrival in this region. Copyright © 2017 Elsevier Ltd. All rights reserved.

Interruption of the Sequential Release of Small and Large Molecules from Tumor Cells by Low Temperature During Cytolysis Mediated by Immune T-Cells or Complement

PubMed Central

Martz, Eric; Burakoff, Steven J.; Benacerraf, Baruj

1974-01-01

Specific lysis of tumor cells by thymus-derived lymphocytes from alloimmunized mice (T-effector specific lysis) was studied with target cells labeled with isotopes attached to both small (14C-labeled nicotinamide) and large (51Cr-labeled) molecules. The results confirm and extend previous reports that target cells release small molecules considerably earlier than large molecules during T-effector specific lysis. After interruption of T-effector specific lysis by specific antibody and complement directed against the killer cells, or by ethylenediaminetetraacetic acid, release of both isotopes continued, eventually reaching identical levels of specific release, the value of which represents the fraction of the target cell population which had been committed to die at the time these treatments were applied. On the other hand, release of both isotopes during T-effector specific lysis stops immediately when the cultures are cooled to 0°. Thus, while ethylenediaminetetraacetic acid or specific complement-mediated lysis of the killer cells merely prevents the initiation of any new damage to target cells, cooling to 0° also stops the lytic process in already-damaged target cells. The colloid osmotic phase of target cell lysis induced by specific antibody and complement was similarly stopped at 0° in tumor cells, but not in erythrocytes. Thus, in tumor target cells, both T-effector specific lysis and complement cause a sequential release of progressively larger molecules which can be immediately stopped at any point by cooling to 0°. PMID:4359327

Feather lead concentrations and (207)Pb/(206)Pb ratios reveal lead exposure history of California Condors (Gymnogyps californianus).

PubMed

Finkelstein, M E; George, D; Scherbinski, S; Gwiazda, R; Johnson, M; Burnett, J; Brandt, J; Lawrey, S; Pessier, A P; Clark, M; Wynne, J; Grantham, J; Smith, D R

2010-04-01

Lead poisoning is a primary factor impeding the survival and recovery of the critically endangered California Condor (Gymnogyps californianus). However, the frequency and magnitude of lead exposure in condors is not well-known in part because most blood lead monitoring occurs biannually, and biannual blood samples capture only approximately 10% of a bird's annual exposure history. We investigated the use of growing feathers from free-flying condors in California to establish a bird's lead exposure history. We show that lead concentration and stable lead isotopic composition analyses of sequential feather sections and concurrently collected blood samples provided a comprehensive history of lead exposure over the 2-4 month period of feather growth. Feather analyses identified exposure events not evident from blood monitoring efforts, and by fitting an empirically derived timeline to actively growing feathers, we were able to estimate the time frame for specific lead exposure events. Our results demonstrate the utility of using sequentially sampled feathers to reconstruct lead exposure history. Since exposure risk in individuals is one determinant of population health, our findings should increase the understanding of population-level effects from lead poisoning in condors; this information may also be helpful for other avian species potentially impacted by lead poisoning.

Feather lead concentrations and 207Pb/206Pb ratios reveal lead exposure history of California Condors (Gymnogyps californianus)

USGS Publications Warehouse

Finkelstein, M.E.; George, D.; Scherbinski, S.; Gwiazda, R.; Johnson, M.; Burnett, J.; Brandt, J.; Lawrey, S.; Pessier, Allan P.; Clark, M.R.; Wynne, J.; Grantham, And J.; Smith, D.R.

2010-01-01

Lead poisoning is a primary factor impeding the survival and recovery of the critically endangered California Condor (Gymnogyps californianus). However, the frequency and magnitude of lead exposure in condors is not well-known in part because most blood lead monitoring occurs biannually, and biannual blood samples capture only ∼10% of a bird’s annual exposure history. We investigated the use of growing feathers from free-flying condors in California to establish a bird’s lead exposure history. We show that lead concentration and stable lead isotopic composition analyses of sequential feather sections and concurrently collected blood samples provided a comprehensive history of lead exposure over the 2−4 month period of feather growth. Feather analyses identified exposure events not evident from blood monitoring efforts, and by fitting an empirically derived timeline to actively growing feathers, we were able to estimate the time frame for specific lead exposure events. Our results demonstrate the utility of using sequentially sampled feathers to reconstruct lead exposure history. Since exposure risk in individuals is one determinant of population health, our findings should increase the understanding of population-level effects from lead poisoning in condors; this information may also be helpful for other avian species potentially impacted by lead poisoning.

Cross-Calibration of Secondary Electron Multiplier in Noble Gas Analysis

NASA Astrophysics Data System (ADS)

Santato, Alessandro; Hamilton, Doug; Deerberg, Michael; Wijbrans, Jan; Kuiper, Klaudia; Bouman, Claudia

2015-04-01

The latest generation of multi-collector noble gas mass spectrometers has decisively improved the precision in isotopic ratio analysis [1, 2] and helped the scientific community to address new questions [3]. Measuring numerous isotopes simultaneously has two significant advantages: firstly, any fluctuations in signal intensity have no effect on the isotope ratio and secondly, the analysis time is reduced. This particular point becomes very important in static vacuum mass spectrometry where during the analysis, the signal intensity decays and at the same time the background increases. However, when multi-collector analysis is utilized, it is necessary to pay special attention to the cross calibration of the detectors. This is a key point in order to have accurate and reproducible isotopic ratios. In isotope ratio mass spectrometry, with regard to the type of detector (i.e. Faraday or Secondary Electron Multiplier, SEM), analytical technique (TIMS, MC-ICP-MS or IRMS) and isotope system of interest, several techniques are currently applied to cross-calibrate the detectors. Specifically, the gain of the Faraday cups is generally stable and only the associated amplifier must be calibrated. For example, on the Thermo Scientific instrument control systems, the 1011 and 1012 ohm amplifiers can easily be calibrated through a fully software controlled procedure by inputting a constant electric signal to each amplifier sequentially [4]. On the other hand, the yield of the SEMs can drift up to 0.2% / hour and other techniques such as peak hopping, standard-sample bracketing and multi-dynamic measurement must be used. Peak hopping allows the detectors to be calibrated by measuring an ion beam of constant intensity across the detectors whereas standard-sample bracketing corrects the drift of the detectors through the analysis of a reference standard of a known isotopic ratio. If at least one isotopic pair of the sample is known, multi-dynamic measurement can be used; in this case the known isotopic ratio is measured on different pairs of detectors and the true value of the isotopic ratio of interest can be determined by a specific equation. In noble gas analysis, due to the decay of the ion beam during the measurement as well as the special isotopic systematic of the gases themselves, the cross-calibration of the SEM using these techniques becomes more complex and other methods should be investigated. In this work we present a comparison between different approaches to cross-calibrate multiple SEM's in noble gas analysis in order to evaluate the most suitable and reliable method. References: [1] Mark et al. (2009) Geochem. Geophys. Geosyst. 10, 1-9. [2] Mark et al. (2011) Geochim. Cosmochim. 75, 7494-7501. [3] Phillips and Matchan (2013) Geochimica et Cosmochimica Acta 121, 229-239. [4] Koornneef et al. (2014) Journal of Analytical Atomic Spectrometry 28, 749-754.

Stable Isotopic Variations in Columnar Cacti: are Responses to Climate Recorded in Spines?

NASA Astrophysics Data System (ADS)

English, N. B.; Dettman, D. L.; Williams, D. G.

2004-12-01

The behavior of the North American monsoon (NAM), particularly with respect to times of continental drought and its relationship to the Pacific-North American (PNA) teleconnection pattern and the El Nino/Southern Oscillation (ENSO) is of great interest to paleoclimatologists and water managers. Long-term instrumental precipitation and tree ring records in the southwestern United States and northwestern Mexico at low elevations are sparse and this has hindered research on NAM variability at interannual timescales. Saguaro cacti (Carnegiea gigantea) and other columnar cacti in North and South America are long-lived and have the potential to record climate variability on land with high temporal and spatial resolution. The vertical sequence of spines on the saguaro's exterior represents a high resolution (4 to 6 per year), and long (over 150 years) record of environmental change. We present results from an experiment where we tracked the oxygen isotopic values in the source waters, stem tissue waters and spine tissue for three treatments over the course of three months. These data are then compared to a previously developed mechanistic model of isotopic variation that reflects the physiological responses of Saguaro to climate variation over seasonal to century long time-scales. We also present the rationale for a new method to determine the growth rate of columnar cacti using the radiocarbon bomb spike. Our measurements reveal that oxygen and hydrogen isotopic variation among the sequentially produced and persistent spines covering the saguaro body record fluctuations in saguaro water balance. The model successfully predicts isotopic variation in spines and constrains controlling variables, yielding a powerful and high-resolution stable isotope index of water stress in the low desert. The development and refinement of an isotopic model for saguaro will serve as the basis for models applied to other species of columnar cacti in North and South America. The role of the tropics in global climate change is poorly understood and precise chronologies of tropical climate change are needed to place empirical constraints on competing theories and models. In particular, the use of continental records from columnar cacti in South America could identify ENSO periods in the last century and provide empirical constraints on the inputs of Atlantic (monsoonal) versus Pacific (winter) moisture to the Altiplano during ENSO and other important climatological phenomena.

Selenium stable isotope ratios in California agricultural drainage water management systems

USGS Publications Warehouse

Herbel, M.J.; Johnson, T.M.; Tanji, K.K.; Gao, S.; Bullen, T.D.

2002-01-01

Selenium stable isotope ratios are known to shift in predictable ways during various microbial, chemical, and biological processes, and can be used to better understand Se cycling in contaminated environments. In this study we used Se stable isotopes to discern the mechanisms controlling the transformation of oxidized, aqueous forms of Se to reduced, insoluble forms in sediments of Se-affected environments. We measured 80Se/76Se in surface waters, shallow ground waters, evaporites, digested plants and sediments, and sequential extracts from several sites where agricultural drainage water is processed in the San Joaquin Valley of California. Selenium isotope analyses of samples obtained from the Tulare Lake Drainage District flow-through wetland reveal small isotopic contrasts (mean difference 0.7%o) between surface water and reduced Se species in the underlying sediments. Selenium in aquatic macrophytes was very similar isotopically to the NaOH and Na2SO3 sediment extracts designed to recover soluble organic Se and Se(O), respectively. For the integrated on-farm drainage management sites, evaporite salts were slightly (approximately 0.6%o) enriched in the heavier isotope relative to the inferred parent waters, whereas surface soils were slightly (approximately 1.4%o) depleted. Bacterial or chemical reduction of Se(VI) or Se(IV) may be occurring at these sites, but the small isotopic contrasts suggest that other, less isotopically fractionating mechanisms are responsible for accumulation of reduced forms in the sediments. These findings provide evidence that Se assimilation by plants and algae followed by deposition and mineralization is the dominant transformation pathway responsible for accumulation of reduced forms of Se in the wetland sediments.

Improved constraints on in situ rates and on quantification of complete chloroethene degradation from stable carbon isotope mass balances in groundwater plumes

NASA Astrophysics Data System (ADS)

Höhener, Patrick; Elsner, Martin; Eisenmann, Heinrich; Atteia, Olivier

2015-11-01

Spills of chloroethenes (CEs) at industrial and urban sites can create groundwater plumes in which tetrachloro- and trichloroethene sequentially degrade to dichloroethenes, vinyl chloride (VC) and ethene, or ethane under reducing conditions. For detoxification, degradation must go beyond VC. Assessments based on ethene and ethane, however, are difficult because these products are volatile, may stem from alternative sources, can be further transformed and are not always monitored. To alternatively quantify degradation beyond VC, stable carbon isotope mass balances have been proposed where concentration-weighted CE isotope ratios are summed up and compared to the original source isotope ratio. Reported assessments, however, have provided not satisfactorily quantified results entailing greatly differing upper and lower estimates. This work proposes an integrative approach to better constrain the extent of total chloroethene degradation in groundwater samples. It is based on fitting of measured concentration and compound-specific stable carbon isotope data to an analytical reactive transport equation simulating steady-state plumes in two dimensions using an EXCEL spreadsheet. The fitting also yields estimates of degradation rates, of source width and of dispersivities. The approach is validated using two synthetic benchmark cases where the true extent of degradation is well known, and using data from two real field cases from literature.

Speciation of strontium in particulates and sediments from the Mississippi River mixing zone

NASA Astrophysics Data System (ADS)

Xu, Yingfeng; Marcantonio, Franco

2004-06-01

Sequential extractions were performed on small amounts of particulate and sediment samples (6 to10 mg) from the Mississippi River mixing zone. The leachates were analyzed for Sr concentration and 87Sr/ 86Sr isotope ratio. Mn and Fe contents were also measured as their oxyhydroxides are potential carrier phases for Sr. The largest fraction of Sr in the solid phase (particulates and sediments) was found to be present in the residual, refractory fraction (>70% of total). By comparison with the corresponding sediment, particulates appear to have higher concentrations of nonresidual, labile Sr (30% vs. 15%). Carbonate components seem to play an important role as carriers for labile Sr in particulates and sediments. Changes in the composition and content of the solid phase may significantly modify both the 87Sr/ 86Sr isotope ratio of the total labile fractions and that of the bulk components. However, such modifications, under normal conditions, exert little measurable influence on the Sr isotope composition of the dissolved phase.

Physical and Biological Carbon Isotope Fractionation in Methane During Gas-Push-Pull-Tests

NASA Astrophysics Data System (ADS)

Gonzalez-Gil, G.; Schroth, M. H.; Gomez, K.; Zeyer, J.

2005-12-01

Stable isotope analyses have become a common tool to assess microbially-mediated processes in subsurface environments. We investigated if stable carbon isotope analysis can be used as a tool to complement gas push-pull tests (GPPTs), a novel technique that was recently developed and tested for the in-situ quantification of CH4 oxidation in soils. During a GPPT a gas mixture containing CH4, O2 and nonreactive tracer gases is injected into the soil, where CH4 is oxidized by indigenous microorganisms. Thereafter, a blend of injected gas mixture and soil air is extracted from the same location, and CH4 oxidation is quantified from an analysis of extracted CH4 and tracer gases. To assess the magnitude of physical isotope fractionation due to molecular diffusion during GPPTs, we conducted laboratory experiments in the absence of microbial activity in a 1m-high, 1m-diameter tank filled with dry sand. During the GPPTs' extraction phase, the isotopic composition of methane was analyzed. Results indicated strong carbon isotope fractionation (>20 per mil) during GPPTs. To assess the combined effect of physical and biological isotope fractionation, numerical simulations of GPPTs were conducted in which microbial CH4 isotope fractionation was simulated using first-order rate constants and microbial kinetic isotope fractionation factors previously reported for methane oxidation in landfill environments. Results of these simulations indicated that for small CH4 oxidation rates, overall isotope fractionation in CH4 is dominated by physical fractionation. Conversely, for high CH4 oxidation rates, overall fractionation is dominated by biological fractionation. Thus, CH4 isotope fractionation data alone from a single GPPT cannot be used to assess microbial CH4 oxidation. However, biological fractionation may be quantified if physical fractionation due to diffusion is known. This can be achieved by conducting two sequential GPPTs, with microbial activity being inhibited in the second test.

Modelling phytoremediation by the hyperaccumulating fern, Pteris vittata, of soils historically contaminated with arsenic.

PubMed

Shelmerdine, Paula A; Black, Colin R; McGrath, Steve P; Young, Scott D

2009-05-01

Pteris vittata plants were grown on twenty-one UK soils contaminated with arsenic (As) from a wide range of natural and anthropogenic sources. Arsenic concentration was measured in fern fronds, soil and soil pore water collected with Rhizon samplers. Isotopically exchangeable soil arsenate was determined by equilibration with (73)As(V). Removal of As from the 21 soils by three sequential crops of P. vittata ranged between 0.1 and 13% of total soil As. Ferns grown on a soil subjected to long-term sewage sludge application showed reduced uptake of As because of high available phosphate concentrations. A combined solubility-uptake model was parameterised to enable prediction of phytoremediation success from estimates of soil As, 'As-lability' and soil pH. The model was used to demonstrate the remediation potential of P. vittata under different soil conditions and with contrasting assumptions regarding re-supply of the labile As pool from unavailable forms.

Triple oxygen isotopes in biogenic and sedimentary carbonates

NASA Astrophysics Data System (ADS)

Passey, Benjamin H.; Hu, Huanting; Ji, Haoyuan; Montanari, Shaena; Li, Shuning; Henkes, Gregory A.; Levin, Naomi E.

2014-09-01

The 17O anomaly (Δ17O) of natural waters has been shown to be sensitive to evaporation in a way analogous to deuterium excess, with evaporated bodies of water (e.g., leaf waters, lake waters, animal body waters) tending to have lower Δ17O than primary meteoric waters. In animal body water, Δ17O relates to the intake of evaporated waters, evaporative effluxes of water, and the Δ17O value of atmospheric O2, which itself carries signatures of global carbon cycling and photochemical reactions in the stratosphere. Carbonates have the potential to record the triple oxygen isotope compositions of parent waters, allowing reconstruction of past water compositions, but such investigations have awaited development of methods for high-precision measurement of Δ17O of carbonate. We describe optimized methods based on a sequential acid digestion/reduction/fluorination approach that yield Δ17O data with the high precision (∼0.010‰, 1σ) needed to resolve subtle environmental signals. We report the first high-precision Δ17O dataset for terrestrial carbonates, focusing on vertebrate biogenic carbonates and soil carbonates, but also including marine invertebrates and high-temperature carbonates. We determine apparent three-isotope fractionation factors between the O2 analyte derived from carbonate and the parent waters of the carbonate. These in combination with appropriate temperature estimates (from clumped isotope thermometry, or known or estimated body temperatures) are used to calculate the δ18O and Δ17O of parent waters. The clearest pattern to emerge is the strong 17O-depletion in avian, dinosaurian, and mammalian body water (from analyses of eggshell and tooth enamel) relative to meteoric waters, following expected influences of evaporated water (e.g., leaf water) and atmospheric O2 on vertebrate body water. Parent waters of the soil carbonates studied here have Δ17O values that are similar to or slightly lower than global precipitation. Our results suggest that Δ17O will have useful application to paleoenvironmental studies of continental environments where the effects of evaporation are important, and where vertebrate body water may record an isotopic signal of evaporated water sources and atmospheric oxygen.

A 16-ka oxygen-isotope record from Genggahai Lake on the northeastern Qinghai-Tibetan Plateau: Hydroclimatic evolution and changes in atmospheric circulation

NASA Astrophysics Data System (ADS)

Qiang, Mingrui; Song, Lei; Jin, Yanxiang; Li, Yuan; Liu, Li; Zhang, Jiawu; Zhao, Yan; Chen, Fahu

2017-04-01

Moisture source history and changes in atmospheric circulation are the most important attributes for portraying past climate changes and for estimating possible future trends. However, few climate records reflecting these attributes are available from the marginal zones of the Asian summer monsoon. Here, we present a record of the oxygen isotopic composition of authigenic carbonates (δ18Ocarb) of sequential sediments from Genggahai Lake in the northeastern Qinghai-Tibetan Plateau (QTP). Isotopic analyses were performed on the fine-grained carbonate fraction (<38 μm), mollusc shells, and stem encrustations from submerged plants. The stratigraphic variations of the δ18O record from the different carbonate components exhibit a remarkably similar pattern, probably reflecting the fact that δ18Ocarb variability was controlled primarily by changes in the oxygen isotopic composition of the lake water (δ18OLW). Disequilibrium effects and water temperature are precluded as major factors affecting the δ18Ocarb variations. Genggahai Lake is hydrologically open and characterized by a rapid discharge rate, as indicated by analysis of the hydrological setting of the lake system and by the observed significant positive correlation between δ18OLW and the oxygen isotopic composition of the inflowing water (δ18OI). Under such hydrological conditions, we argue that the isotopic signals of different moisture sources should be reflected in the carbonate isotopic composition. Furthermore, placing the δ18Ocarb record in the context of regional palaeoclimate archives, we found that the isotopic signals, particularly the negative shifts from the average values, cannot be interpreted consistently, despite a process of evaporative enrichment at the lake surface. During the early- to mid-Holocene, low δ18Ocarb values during 10.6-9.4 and 7.4-6.3 ka were associated with higher lake levels, and thus the record may have been significantly affected by a strengthened Asian summer monsoon at those times and hence by a positive moisture balance. Isotopic depletions with similar magnitudes occurred at 15-14.5, 13.8-13.3, 12.5-11.4, 5.3-4.8, 3.7-3.4, 2.8-2.3, 1.7, 1.3, and 0.6 ka, i.e., within the Lateglacial and the late Holocene. These negative shifts in δ18Ocarb corresponded to lower lake-level phases, and most likely were a response to intensification of the mid-latitude westerly circulation that may have transported significantly more 18O-depleted moisture to the region, compared to that from the Asian summer monsoon. Overall, our results suggest that the alternating influence of the Asian summer monsoon and the westerlies played a significant role in determining the pattern of atmospheric circulation on the northeastern QTP.

The reliability of using the single-biopsy approach to assess basal muscle protein synthesis rates in vivo in humans.

PubMed

Burd, Nicholas A; Groen, Bart B L; Beelen, Milou; Senden, Joan M G; Gijsen, Annemie P; van Loon, Luc J C

2012-07-01

It has recently been proposed that basal muscle protein synthesis can be effectively assessed by measuring the background enrichment in total plasma protein, thereby omitting the initial biopsy, and determining the difference in enrichment from a single muscle biopsy obtained during a primed continuous infusion of isotope-labeled amino acids. We determined the reliability of calculating basal mixed muscle protein fractional synthetic rates (FSRs) from mixed plasma proteins and a single muscle biopsy compared against the sequential muscle biopsy approach. Ten men (age, 23 ± 1 years; body mass index, 22 ± 1 kg∙m(-2)) received muscle biopsies of the vastus lateralis after 2 and 4 hours of a primed continuous infusion of l-[ring-(13)C(6)]phenylalanine. Mixed muscle protein FSR was calculated from baseline plasma enrichments and muscle protein enrichments determined from the biopsy at 2 hours (1BX SHORT) or 4 hours (1BX LONG), or between muscle protein enrichments at 2 and 4 hours (2BX) of the infusion. No differences (P = .50) were observed in mixed muscle protein FSR, using plasma [ring-(13)C(6)]phenylalanine enrichments as the precursor, between the 1BX SHORT (0.031% ± 0.010%∙h(-1)), 1BX LONG (0.032% ± 0.007%∙h(-1)), or 2BX (0.035% ± 0.011%∙h(-1)) approach. A significant correlation was observed between the calculated muscle protein FSR assessed using the 1BX LONG and 2BX approach (r = 0.7, P = .02). Our data demonstrate that the single-biopsy approach, irrespective of whether the biopsy is obtained at 2 or 4 hours, can be used as a surrogate for the sequential-biopsy approach to determine basal muscle protein synthesis in a group. Copyright © 2012 Elsevier Inc. All rights reserved.

Carbon isotopic fractionation of CH4 and CO2 during canister desorption of coal

USGS Publications Warehouse

Strapoc, D.; Schimmelmann, A.; Mastalerz, Maria

2006-01-01

Canister desorption of coal gas from freshly sampled coal is commonly used for exploratory assessment of the coalbed methane (CBM) potential of a basin or prospect, as well as for the sampling of gas for isotopic determination of the gas origin. Compositional and ??13C isotopic time-series of desorbing CBM and carbon dioxide (CO2) over 3-4 months demonstrate considerable compositional and isotopic shifts over time. Non-stationary chemical and isotopic characteristics are due to differences in diffusivity and adsorbance behavior of gas molecules and must be taken into account when attempting to reproducibly sample coal gases. Off-line gas processing on a vacuum line and on-line GC/MS analyses were performed on coal gas samples from the Springfield and Seelyville Coal Members of the Pennsylvanian age that were cored in the SE Illinois Basin in SW Indiana, USA. The coals cover a narrow range of maturity from 0.54% to 0.64% vitrinite reflectance. Methane initially desorbed faster than CO2, resulting in a 50% increase of the CO 2 content in bulk desorbing gas on the 50th day relative to the first day of desorption. After 50 days of desorption, about 90% of all coal gas was desorbed. Over the same time period, ??13C values of incrementally sampled coal gas increased by 2??? and 9???, for CH 4 and CO2, respectively, testifying to the greater retention of 13CH4 and 13CO2 relative to 12CH4 and 12CO2. An isotopic mass balance of the individual, sequentially desorbed and sampled gas amounts yielded weighted mean ??13CCH4 and ??13CCO2 values for characterizing the cumulatively desorbed gas. The overall mean ??13C values were equivalent to ??13C values of gases that desorbed at a time when half of the potentially available gas had been desorbed from coal, corresponding in this study to a time between day 5 and day 12 of canister desorption at 15-18??C. The total expected gas volume and the ???50% midpoint can thus be approximated for a desorbing coal gas sample, based on a dynamic prediction after the first five days of canister desorption. ?? 2005 Elsevier Ltd. All rights reserved.

Preparation of Authigenic Pyrite from Methane-bearing Sediments for In Situ Sulfur Isotope Analysis Using SIMS.

PubMed

Lin, Zhiyong; Sun, Xiaoming; Peckmann, Jörn; Lu, Yang; Strauss, Harald; Xu, Li; Lu, Hongfeng; Teichert, Barbara M A

2017-08-31

Different sulfur isotope compositions of authigenic pyrite typically result from the sulfate-driven anaerobic oxidation of methane (SO4-AOM) and organiclastic sulfate reduction (OSR) in marine sediments. However, unravelling the complex pyritization sequence is a challenge because of the coexistence of different sequentially formed pyrite phases. This manuscript describes a sample preparation procedure that enables the use of secondary ion mass spectroscopy (SIMS) to obtain in situ δ 34 S values of various pyrite generations. This allows researchers to constrain how SO4-AOM affects pyritization in methane-bearing sediments. SIMS analysis revealed an extreme range in δ 34 S values, spanning from -41.6 to +114.8‰, which is much wider than the range of δ 34 S values obtained by the traditional bulk sulfur isotope analysis of the same samples. Pyrite in the shallow sediment mainly consists of 34 S-depleted framboids, suggesting early diagenetic formation by OSR. Deeper in the sediment, more pyrite occurs as overgrowths and euhedral crystals, which display much higher SIMS δ 34 S values than the framboids. Such 34 S-enriched pyrite is related to enhanced SO4-AOM at the sulfate-methane transition zone, postdating OSR. High-resolution in situ SIMS sulfur isotope analyses allow for the reconstruction of the pyritization processes, which cannot be resolved by bulk sulfur isotope analysis.

Modeling 3D-CSIA data: Carbon, chlorine, and hydrogen isotope fractionation during reductive dechlorination of TCE to ethene.

PubMed

Van Breukelen, Boris M; Thouement, Héloïse A A; Stack, Philip E; Vanderford, Mindy; Philp, Paul; Kuder, Tomasz

2017-09-01

Reactive transport modeling of multi-element, compound-specific isotope analysis (CSIA) data has great potential to quantify sequential microbial reductive dechlorination (SRD) and alternative pathways such as oxidation, in support of remediation of chlorinated solvents in groundwater. As a key step towards this goal, a model was developed that simulates simultaneous carbon, chlorine, and hydrogen isotope fractionation during SRD of trichloroethene, via cis-1,2-dichloroethene (and trans-DCE as minor pathway), and vinyl chloride to ethene, following Monod kinetics. A simple correction term for individual isotope/isotopologue rates avoided multi-element isotopologue modeling. The model was successfully validated with data from a mixed culture Dehalococcoides microcosm. Simulation of Cl-CSIA required incorporation of secondary kinetic isotope effects (SKIEs). Assuming a limited degree of intramolecular heterogeneity of δ 37 Cl in TCE decreased the magnitudes of SKIEs required at the non-reacting Cl positions, without compromising the goodness of model fit, whereas a good fit of a model involving intramolecular CCl bond competition required an unlikely degree of intramolecular heterogeneity. Simulation of H-CSIA required SKIEs in H atoms originally present in the reacting compounds, especially for TCE, together with imprints of strongly depleted δ 2 H during protonation in the products. Scenario modeling illustrates the potential of H-CSIA for source apportionment. Copyright © 2017 The Authors. Published by Elsevier B.V. All rights reserved.

Improved constraints on in situ rates and on quantification of complete chloroethene degradation from stable carbon isotope mass balances in groundwater plumes.

PubMed

Höhener, Patrick; Elsner, Martin; Eisenmann, Heinrich; Atteia, Olivier

2015-11-01

Spills of chloroethenes (CEs) at industrial and urban sites can create groundwater plumes in which tetrachloro- and trichloroethene sequentially degrade to dichloroethenes, vinyl chloride (VC) and ethene, or ethane under reducing conditions. For detoxification, degradation must go beyond VC. Assessments based on ethene and ethane, however, are difficult because these products are volatile, may stem from alternative sources, can be further transformed and are not always monitored. To alternatively quantify degradation beyond VC, stable carbon isotope mass balances have been proposed where concentration-weighted CE isotope ratios are summed up and compared to the original source isotope ratio. Reported assessments, however, have provided not satisfactorily quantified results entailing greatly differing upper and lower estimates. This work proposes an integrative approach to better constrain the extent of total chloroethene degradation in groundwater samples. It is based on fitting of measured concentration and compound-specific stable carbon isotope data to an analytical reactive transport equation simulating steady-state plumes in two dimensions using an EXCEL spreadsheet. The fitting also yields estimates of degradation rates, of source width and of dispersivities. The approach is validated using two synthetic benchmark cases where the true extent of degradation is well known, and using data from two real field cases from literature. Copyright © 2015 Elsevier B.V. All rights reserved.

The origin of volatile element depletion in early solar system material: Clues from Zn isotopes in chondrules

NASA Astrophysics Data System (ADS)

Pringle, Emily A.; Moynier, Frédéric; Beck, Pierre; Paniello, Randal; Hezel, Dominik C.

2017-06-01

Volatile lithophile elements are depleted in the different planetary materials to various degrees, but the origin of these depletions is still debated. Stable isotopes of moderately volatile elements such as Zn can be used to understand the origin of volatile element depletions. Samples with significant volatile element depletions, including the Moon and terrestrial tektites, display heavy Zn isotope compositions (i.e. enrichment of 66Zn vs. 64Zn), consistent with kinetic Zn isotope fractionation during evaporation. However, Luck et al. (2005) found a negative correlation between δ66Zn and 1/[Zn] between CI, CM, CO, and CV chondrites, opposite to what would be expected if evaporation caused the Zn abundance variations among chondrite groups. We have analyzed the Zn isotope composition of multiple samples of the major carbonaceous chondrite classes: CI (1), CM (4), CV (2), CO (4), CB (2), CH (2), CK (4), and CK/CR (1). The bulk chondrites define a negative correlation in a plot of δ66Zn vs 1/[Zn], confirming earlier results that Zn abundance variations among carbonaceous chondrites cannot be explained by evaporation. Exceptions are CB and CH chondrites, which display Zn systematics consistent with a collisional formation mechanism that created enrichment in heavy Zn isotopes relative to the trend defined by CI-CK. We further report Zn isotope analyses of chondrite components, including chondrules from Allende (CV3) and Mokoia (CV3), as well as an aliquot of Allende matrix. All chondrules are enriched in light Zn isotopes (∼500 ppm on 66Zn/64Zn) relative to the bulk, contrary to what would be expected if Zn were depleted during evaporation, on the other hand the matrix has a complementary heavy isotope composition. We report sequential leaching experiments in un-equilibrated ordinary chondrites, which show sulfides are isotopically heavy compared to silicates and the bulk meteorite by ca. +0.65 per mil on 66Zn/64Zn. We suggest isotopically heavy sulfides were removed from either chondrules or their precursors, thereby producing the light Zn isotope enrichments in chondrules.

Utilization of Sugarcane Habitat by Feral Pig (Sus scrofa) in Northern Tropical Queensland: Evidence from the Stable Isotope Composition of Hair

PubMed Central

Wurster, Christopher M.; Robertson, Jack; Westcott, David A.; Dryden, Bart; Zazzo, Antoine; Bird, Michael I.

2012-01-01

Feral pigs (Sus scrofa) are an invasive species that disrupt ecosystem functioning throughout their introduced range. In tropical environments, feral pigs are associated with predation and displacement of endangered species, modification of habitat, and act as a vector for the spread of exotic vegetation and disease. Across many parts of their introduced range, the diet of feral pigs is poorly known. Although the remote location and difficult terrain of far north Queensland makes observing feral pig behavior difficult, feral pigs are perceived to seek refuge in World Heritage tropical rainforests and seasonally ‘crop raid’ into lowland sugarcane crops. Thus, identifying how feral pigs are using different components of the landscape is important to the design of management strategies. We used the stable isotope composition of captured feral pigs to determine the extent of rainforest and sugarcane habitat usage. Recently grown hair (basal hair) from feral pigs captured in remote rainforest indicated pigs met their dietary needs solely within this habitat. Stable carbon and nitrogen isotope values of basal hair from feral pigs captured near sugarcane plantations were more variable, with some individuals estimated to consume over 85% of their diet within a sugarcane habitat, while a few consumed as much as 90% of their diet from adjacent forested environments. We estimated whether feral pigs switch habitats by sequentially sampling δ 13C and δ 15N values of long tail hair from a subset of seven captured animals, and demonstrate that four of these individuals moved between habitats. Our results indicate that feral pigs utilize both sugarcane and forest habitats, and can switch between these resources. PMID:22957029

Source Identification of Zn Contamination around a Zn-smelting Facility in Korea

NASA Astrophysics Data System (ADS)

Lee, S.; Jeon, S. K.

2016-12-01

With massive production of Zn for various industrial purposes, Zn release into the environment becomes highly possible, some of which might require a proper countermeasure depending on the residual concentration in environmental media. In order to set up an effective countermeasure, identification of contaminant source should be essential for determining the target object to be managed, and delineating the extent of necessary remedial work. In this study, we focus on a Zn-smelting facility located in eastern Korea where Zn concentrations in surrounding soils have been reported to exceed the contamination criteria. An abandoned mine which had been explored for Zn ores was located adjacent to the facility, and background concentration of Zn in the area was naturally high. The objective of the present study is to identify the major source of Zn contamination in the area, and to estimate the relative contributions of multiple sources, if so. In order to achieve these goals, we analyzed and compared the stable isotope ratios of Pb in the soil samples collected at different distances from the facility and the Zn concentrates (ZnS, sphalerite) of raw material in the facility. The Pb isotope ratios were further investigated by performing sequential extraction for each sample and comparing the isotopes ratios observed in each fraction of soil. In addition, possible presence of ZnS in the samples, which could be an evidence of Zn contamination by the smelting facility, was estimated by X-ray diffraction (XRD) analysis and scanning electron microscopy equipped with energy dispersive X-ray spectrometry (SEM-EDS) after separating the soil sample into the fractions with different particle sizes

Stable carbon and nitrogen isotope trophic enrichment factors for Steller sea lion vibrissae relative to milk and fish/invertebrate diets

USGS Publications Warehouse

Stricker, Craig A.; Christ, Aaron M.; Wunder, Michael B.; Doll, Andrew C.; Farley, Sean D.; Rea, Lorrie D.; Rosen, David A. S.; Scherer, R. D.; Tollit, Dominic J.

2015-01-01

Nutritional constraints have been proposed as a contributor to population declines in the endangered Steller sea lion Eumetopias jubatus in some regions of the North Pacific. Isotopic analysis of vibrissae (whiskers) is a potentially useful approach to resolving the nutritional ecology of this species because long-term (up to 8 yr) dietary information is sequentially recorded and metabolically inert once formed. Additionally, vibrissae are grown in utero, potentially offering indirect inference on maternal diet. However, diet reconstruction using isotopic techniques requires a priori knowledge of trophic enrichment factors (TEFs), which can vary relative to diet quality and among animal species. In this study, we provide new TEF estimates for (1) maternal relative to pup vibrissae during both gestation and nursing and (2) adult vibrissae relative to a complex diet. Further, we refine vibrissa-milk TEFs based on an additional 76 animals with an age distribution ranging from 1 to 20 mo. Mother-pup vibrissae TEF values during gestation and nursing were near zero for δ13C and averaged 0.8 and 1.6‰, respectively, for δ15N. In contrast, vibrissa-fish/invertebrate TEFs averaged 3.3 (± 0.3 SD) and 3.7‰ (±0.3) for lipid-free δ13C and δ15N, respectively. Average lipid-free δ13C and δ15N vibrissa-milk TEFs were 2.5 (±0.9) and 1.8‰ (±0.8), respectively, and did not differ among metapopulations. Empirically determined TEFs are critical for accurate retrospective diet modeling, particularly for evaluating the hypothesis of nutritional deficiency contributing to the lack of Steller sea lion population recovery in some regions of Alaska.

A latitudinal study of oxygen isotopes within horsehair

NASA Astrophysics Data System (ADS)

Thompson, E.; Bronk Ramsey, C.; McConnell, J. R.

2016-12-01

This study aims to explore the hypothesis that 'if oxygen isotope ratios deplete with decreasing temperature then a study of oxygen isotope ratios within horsehair from Oxfordshire to Iceland will show a latitudinal depletion gradient'. By looking at oxygen isotope values at different geographical positions, we can track the relationship with latitude and with different regional climate features. This will provide a firmer understanding of how to compare climate records from different locations. Additionally, a comparison of the horse breeds from this study to those analysed within previous studies will create an even better understanding of the intra-species variation within the δ18O values of horsehair. A total of 24 horses were sampled on the 7th March from Thordale Stud in Shetland, the Icelandic Food And Veterinary Authority in Iceland, the Exmoor Pony Centre in Exmoor and the Pigeon House Equestrian Centre in Oxfordshire. By starting the sampling process from the most recent growth at the follicle, the sampling date becomes a chronological marker, temporally fixing the first sample within a sequential set of data points extending for one year or longer, depending on the length of each individual hair. The samples were analysed for oxygen isotope values using an IRMS coupled within a Sercon HTEA. Preliminary results show a latitudinal gradient is evident on comparison between the locations, consistent with the findings of Darling and Talbot's study of fresh water isotopes in the British Isles (2003). These results support the hypothesis, showing that a study of oxygen isotope ratios within horse hair from Oxfordshire to Iceland showing a latitudinal depletion gradient, consistent with a depletion of oxygen isotope ratios due to decreasing temperatures. Darling, W. and Talbot, J. (2003). The O and H stable isotope composition of freshwaters in the British Isles. 1. Rainfall. Hydrol. Earth System Science, 7(2), pp.163-181.

Coal fly ash interaction with environmental fluids: Geochemical and strontium isotope results from combined column and batch leaching experiments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brubaker, Tonya M; Stewart, Brian W; Capo, Rosemary C

2013-05-01

The major element and Sr isotope systematics and geochemistry of coal fly ash and its interactions with environmental waters were investigated using laboratory flow-through column leaching experiments (sodium carbonate, acetic acid, nitric acid) and sequential batch leaching experiments (water, acetic acid, hydrochloric acid). Column leaching of Class F fly ash samples shows rapid release of most major elements early in the leaching procedure, suggesting an association of these elements with soluble and surface bound phases. Delayed release of certain elements (e.g., Al, Fe, Si) signals gradual dissolution of more resistant silicate or glass phases as leaching continues. Strontium isotope resultsmore » from both column and batch leaching experiments show a marked increase in {sup 87}Sr/{sup 86}Sr ratio with continued leaching, yielding a total range of values from 0.7107 to 0.7138. For comparison, the isotopic composition of fluid output from a fly ash impoundment in West Virginia falls in a narrow range around 0.7124. The experimental data suggest the presence of a more resistant, highly radiogenic silicate phase that survives the combustion process and is leached after the more soluble minerals are removed. Strontium isotopic homogenization of minerals in coal does not always occur during the combustion process, despite the high temperatures encountered in the boiler. Early-released Sr tends to be isotopically uniform; thus the Sr isotopic composition of fly ash could be distinguishable from other sources and is a useful tool for quantifying the possible contribution of fly ash leaching to the total dissolved load in natural surface and ground waters.« less

High-precision Pb isotopic measurements of teeth and environmental samples from Sofia (Bulgaria): insights for regional lead sources and possible pathways to the human body

NASA Astrophysics Data System (ADS)

Kamenov, George D.

2008-08-01

High-precision Pb isotopic measurements on teeth and possible sources in a given area can provide important insights for the lead (Pb) sources and pathways in the human body. Pb isotopic analyses on soils from the area of Sofia, Bulgaria show that Pb is contributed by three end-members represented by two natural sources and leaded gasoline. Sequential leaching experiments reveal that the alumosilicate fraction of the soils is mainly controlled by natural Pb derived from two mountain massifs bordering the city. Around 1/3 to a half of the Pb in the soil leachates, however, can be explained by contamination from leaded gasoline. Contemporary teeth from Sofia residents show very similar Pb isotopic compositions to the soil leachates, also indicating that around 1/3 to a half of the Pb can be explained by derivation from leaded gasoline. The remarkable isotopic similarities between the teeth and the most labile fractions of the local soils suggest that the lead can be derived from the latter. Pb incorporation in the human body via soil-plant-human or soil-plant-animal-human chains is unlikely due to the fact that no significant farming occurs in the city area. The isotopic compositions of the local soil labile fractions can be used as approximation of the bioaccessible lead for humans. Considering all possible scenarios it appears that soil and/or soil-born dust inhalation and/or ingestion is the most probable pathway for incorporation of local soil lead in the local population. The high-precision Pb isotope data presented in this work indicate that apparently the local soil is what plays major role in the human Pb exposure.

Quantification of Labile Soil Mercury by Stable Isotope Dilution Techniques

NASA Astrophysics Data System (ADS)

Shetaya, Waleed; Huang, Jen-How; Osterwalder, Stefan; Alewell, Christine

2016-04-01

Mercury (Hg) is a toxic element that can cause severe health problems to humans. Mercury is emitted to the atmosphere from both natural and anthropogenic sources and can be transported over long distances before it is deposited to aquatic and terrestrial environments. Aside from accumulation in soil solid phases, Hg deposited in soils may migrate to surface- and ground-water or enter the food chain, depending on its lability. There are many operationally-defined extraction methods proposed to quantify soil labile metals. However, these methods are by definition prone to inaccuracies such as non-selectivity, underestimation or overestimation of the labile metal pool. The isotopic dilution technique (ID) is currently the most promising method for discrimination between labile and non-labile metal fractions in soil with a minimum disturbance to soil-solid phases. ID assesses the reactive metal pool in soil by defining the fraction of metal both in solid and solution phases that is isotopically-exchangeable known as the 'E-value'. The 'E-value' represents the metal fraction in a dynamic equilibrium with the solution phase and is potentially accessible to plants. This is carried out by addition of an enriched metal isotope to soil suspensions and quantifying the fraction of metal that is able to freely exchange with the added isotope by measuring the equilibrium isotopic ratio by ICP-MS. E-value (mg kg-1) is then calculated as follows: E-Value = (Msoil/ W) (CspikeVspike/ Mspike) (Iso1IAspike -Iso2IAspikeRss / Iso2IAsoil Rss - Iso1IAsoil) where M is the average atomic mass of the metal in the soil or the spike, W is the mass of soil (kg), Cspike is the concentration of the metal in the spike (mg L-1), Vspike is the volume of spike (L), IA is isotopic abundance, and Rss is the equilibrium ratio of isotopic abundances (Iso1:Iso2). Isotopic dilution has been successfully applied to determine E-values for several elements. However, to our knowledge, this method has not yet been applied to estimate the labile pool of mercury in contaminated soils. We performed a series of soil incubations spiked with 196Hg2+aiming at measuring and modelling the progressive assimilation of Hg ions into less labile forms. Soils with a wide range of characteristics are taken for our research purpose, inclusive of Hg concentrations ranging from 0.1 to 390 mg kg-1, pH between 3.5 - 7.5 and total organic carbon (TOC) between 2.5 - 8 %. In parallel, the labile pool of Hg estimated using ID will be compared with that determined using conventional extraction methods, e.g. sequential extraction procedures. These altogether allows us to answer (1) how the E-value of Hg in soils is comparable to those estimated based on selective extraction methods, (2) how the labile Hg correlates with the total soil Hg, soil pH and TOC, and (3) how the solubility of added Hg (e.g. via rainfall) decreased in soils of different properties during aging. The obtained results fills the knowledge gap concerning Hg biogeochemistry in the terrestrial environment and serves as a basis for estimating (and predicting) the risk of soil Hg diffusion from a point source to the adjacent environments.

Discrimination of Geographical Origin of Asian Garlic Using Isotopic and Chemical Datasets under Stepwise Principal Component Analysis.

PubMed

Liu, Tsang-Sen; Lin, Jhen-Nan; Peng, Tsung-Ren

2018-01-16

Isotopic compositions of δ 2 H, δ 18 O, δ 13 C, and δ 15 N and concentrations of 22 trace elements from garlic samples were analyzed and processed with stepwise principal component analysis (PCA) to discriminate garlic's country of origin among Asian regions including South Korea, Vietnam, Taiwan, and China. Results indicate that there is no single trace-element concentration or isotopic composition that can accomplish the study's purpose and the stepwise PCA approach proposed does allow for discrimination between countries on a regional basis. Sequentially, Step-1 PCA distinguishes garlic's country of origin among Taiwanese, South Korean, and Vietnamese samples; Step-2 PCA discriminates Chinese garlic from South Korean garlic; and Step-3 and Step-4 PCA, Chinese garlic from Vietnamese garlic. In model tests, countries of origin of all audit samples were correctly discriminated by stepwise PCA. Consequently, this study demonstrates that stepwise PCA as applied is a simple and effective approach to discriminating country of origin among Asian garlics. © 2018 American Academy of Forensic Sciences.

Protein-protein interactions and metabolite channelling in the plant tricarboxylic acid cycle

PubMed Central

Zhang, Youjun; Beard, Katherine F. M.; Swart, Corné; Bergmann, Susan; Krahnert, Ina; Nikoloski, Zoran; Graf, Alexander; Ratcliffe, R. George; Sweetlove, Lee J.; Fernie, Alisdair R.; Obata, Toshihiro

2017-01-01

Protein complexes of sequential metabolic enzymes, often termed metabolons, may permit direct channelling of metabolites between the enzymes, providing increased control over metabolic pathway fluxes. Experimental evidence supporting their existence in vivo remains fragmentary. In the present study, we test binary interactions of the proteins constituting the plant tricarboxylic acid (TCA) cycle. We integrate (semi-)quantitative results from affinity purification-mass spectrometry, split-luciferase and yeast-two-hybrid assays to generate a single reliability score for assessing protein–protein interactions. By this approach, we identify 158 interactions including those between catalytic subunits of sequential enzymes and between subunits of enzymes mediating non-adjacent reactions. We reveal channelling of citrate and fumarate in isolated potato mitochondria by isotope dilution experiments. These results provide evidence for a functional TCA cycle metabolon in plants, which we discuss in the context of contemporary understanding of this pathway in other kingdoms. PMID:28508886

Bifurcations on Potential Energy Surfaces of Organic Reactions

PubMed Central

Ess, Daniel H.; Wheeler, Steven E.; Iafe, Robert G.; Xu, Lai; Çelebi-Ölçüm, Nihan; Houk, K. N.

2009-01-01

A single transition state may lead to multiple intermediates or products if there is a post-transition state reaction path bifurcation. These bifurcations arise when there are sequential transition states with no intervening energy minimum. For such systems, the shape of the potential energy surface and dynamic effects control selectivity rather than transition state energetics. This minireview covers recent investigations of organic reactions exhibiting reaction pathway bifurcations. Such phenomena are surprisingly general and affect experimental observables such as kinetic isotope effects and product distributions. PMID:18767086

Chemical and isotopic composition of secondary organic aerosol generated by α-pinene ozonolysis

NASA Astrophysics Data System (ADS)

Meusinger, Carl; Dusek, Ulrike; King, Stephanie M.; Holzinger, Rupert; Rosenørn, Thomas; Sperlich, Peter; Julien, Maxime; Remaud, Gerald S.; Bilde, Merete; Röckmann, Thomas; Johnson, Matthew S.

2017-05-01

Secondary organic aerosol (SOA) plays a central role in air pollution and climate. However, the description of the sources and mechanisms leading to SOA is elusive despite decades of research. While stable isotope analysis is increasingly used to constrain sources of ambient aerosol, in many cases it is difficult to apply because neither the isotopic composition of aerosol precursors nor the fractionation of aerosol forming processes is well characterised. In this paper, SOA formation from ozonolysis of α-pinene - an important precursor and perhaps the best-known model system used in laboratory studies - was investigated using position-dependent and average determinations of 13C in α-pinene and advanced analysis of reaction products using thermal-desorption proton-transfer-reaction mass spectrometry (PTR-MS). The total carbon (TC) isotopic composition δ13C of the initial α-pinene was measured, and the δ13C of the specific carbon atom sites was determined using position-specific isotope analysis (PSIA). The PSIA analysis showed variations at individual positions from -6.9 to +10. 5 ‰ relative to the bulk composition. SOA was formed from α-pinene and ozone in a constant-flow chamber under dark, dry, and low-NOx conditions, with OH scavengers and in the absence of seed particles. The excess of ozone and long residence time in the flow chamber ensured that virtually all α-pinene had reacted. Product SOA was collected on two sequential quartz filters. The filters were analysed offline by heating them stepwise from 100 to 400 °C to desorb organic compounds that were (i) detected using PTR-MS for chemical analysis and to determine the O : C ratio, and (ii) converted to CO2 for 13C analysis. More than 400 ions in the mass range 39-800 Da were detected from the desorbed material and quantified using a PTR-MS. The largest amount desorbed at 150 °C. The O : C ratio of material from the front filter increased from 0.18 to 0.25 as the desorption temperature was raised from 100 to 250 °C. At temperatures above 250 °C, the O : C ratio of thermally desorbed material, presumably from oligomeric precursors, was constant. The observation of a number of components that occurred across the full range of desorption temperatures suggests that they are generated by thermal decomposition of oligomers. The isotopic composition of SOA was more or less independent of desorption temperature above 100 °C. TC analysis showed that SOA was enriched in 13C by 0.6-1.2 ‰ relative to the initial α-pinene. According to mass balance, gas-phase products will be depleted relative to the initial α-pinene. Accordingly, organic material on the back filters, which contain adsorbed gas-phase compounds, is depleted in 13C in TC by 0.7 ‰ relative to the initial α-pinene, and by 1.3 ‰ compared to SOA collected on the front filter. The observed difference in 13C between the gas and particle phases may arise from isotope-dependent changes in the branching ratios in the α-pinene + O3 reaction. Alternatively, some gas-phase products involve carbon atoms from highly enriched and depleted sites, as shown in the PSIA analysis, giving a non-kinetic origin to the observed fractionations. In either case, the present study suggests that the site-specific distribution of 13C in the source material itself governs the abundance of 13C in SOA.

Molecular controls on Cu and Zn isotopic fractionation in Fe-Mn crusts

NASA Astrophysics Data System (ADS)

Little, S. H.; Sherman, D. M.; Vance, D.; Hein, J. R.

2014-06-01

The isotopic systems of the transition metals are increasingly being developed as oceanic tracers, due to their tendency to be fractionated by biological and/or redox-related processes. However, for many of these promising isotope systems the molecular level controls on their isotopic fractionations are only just beginning to be explored. Here we investigate the relative roles of abiotic and biotic fractionation processes in controlling modern seawater Cu and Zn isotopic compositions. Scavenging to Fe-Mn oxides represents the principal output for Cu and Zn to sediments deposited under normal marine (oxic) conditions. Using Fe-Mn crusts as an analogue for these dispersed phases, we investigate the phase association and crystal chemistry of Cu and Zn in such sediments. We present the results of an EXAFS study that demonstrate unequivocally that Cu and Zn are predominantly associated with the birnessite (δ-MnO2) phase in Fe-Mn crusts, as previously predicted from sequential leaching experiments (e.g., Koschinsky and Hein, 2003). The crystal chemistry of Cu and Zn in the crusts implies a reduction in coordination number in the sorbed phase relative to the free metal ion in seawater. Thus, theory would predict equilibrium fractionations that enrich the heavy isotope in the sorbed phase (e.g., Schauble, 2004). In natural samples, Fe-Mn crusts and nodules are indeed isotopically heavy in Zn isotopes (at ∼1‰) compared to deep seawater (at ∼0.5‰), consistent with the predicted direction of equilibrium isotopic fractionation based on our observations of the coordination environment of sorbed Zn. Further, ∼50% of inorganic Zn‧ is chloro-complexed (the other ∼50% is present as the free Zn2+ ion), and complexation by Cl- is also predicted to favour equilibrium partitioning of light Zn isotopes into the dissolved phase. The heavy Zn isotopic composition of Fe-Mn crusts and nodules relative to seawater can therefore be explained by an inorganic fractionation during uptake. However, Cu in Fe-Mn crusts is isotopically light (at ∼0.3 to 0.5‰) compared to the dissolved phase in seawater (at ∼0.9‰). We suggest that this is because dissolved Cu in the oceans is overwhelmingly complexed to strong organic ligands, which are better competitors for the heavy isotope.

Filling the gap in Ca input-output budgets in base-poor forest ecosystems: The contribution of non-crystalline phases evidenced by stable isotopic dilution

NASA Astrophysics Data System (ADS)

van der Heijden, Gregory; Legout, Arnaud; Mareschal, Louis; Ranger, Jacques; Dambrine, Etienne

2017-07-01

In terrestrial ecosystems, plant-available pools of magnesium and calcium are assumed to be stored in the soil as exchangeable cations adsorbed on the surface of mineral and/or organic particles. The pools of exchangeable magnesium and calcium are measured by ion-exchange soil extractions. These pools are sustained in the long term by the weathering of primary minerals in the soil and atmospheric inputs. This conceptual model is the base of input-output budgets from which soil acidification and the sustainability of soil chemical fertility is inferred. However, this model has been questioned by data from long-term forest ecosystem monitoring sites, particularly for calcium. Quantifying the contribution of atmospheric inputs, ion exchange and weathering of both primary, secondary and non-crystalline phases to tree nutrition in the short term is challenging. In this study, we developed and applied a novel isotopic dilution technique using the stable isotopes of magnesium and calcium to study the contribution of the different soil phases to soil solution chemistry in a very acidic soil. The labile pools of Mg and Ca in the soil (pools in equilibrium with the soil solution) were isotopically labeled by spraying a solution enriched in 26Mg and 44Ca on the soil. Labeled soil columns were then percolated with a dilute acid solution during a 3-month period and the isotopic dilution of the tracers was monitored in the leaching solution, in the exchangeable (2 sequential 1 mol L-1 ammonium acetate extractions) and non-crystalline (2 sequential soil digestions: oxalic acid followed by nitric acid) phases. Significant amounts of Mg and Ca isotope tracer were recovered in the non-crystalline soil phases. These phases represented from 5% to 25% and from 24% to 50%, respectively, of the Mg and Ca labile pools during the experiment. Our results show that non-crystalline phases act as both a source and a sink of calcium and magnesium in the soil, and contribute directly to soil solution chemistry on very short-term time scales. These phases are very abundant in acid soils and, in the present study, represent a substantial calcium pool (equivalent in size to the Ca exchangeable pool). The gradual isotopic dilution of Mg and Ca isotope ratios in the leaching solution during the experiment evidenced an input flux of Mg and Ca originating from a pool other than the labile pool. While the Mg input flux originated primarily from the weathering of primary minerals and secondarily from the non-crystalline phases, the Ca input flux originated primarily from the non-crystalline phases. Our results also show that the net calcium release flux from these phases may represent a significant source of calcium in forest ecosystems and actively contribute to compensating the depletion of Ca exchangeable pools in the soil. Non-crystalline phases therefore should be taken into account when computing input-output nutrient budgets and soil acid neutralizing capacity.

Sr isotope characterization of atmospheric inputs to soils along a climate gradient of the Chilean Coastal Range

NASA Astrophysics Data System (ADS)

Oeser, Ralf; Schuessler, Jan A.; Floor, Geerke H.; von Blanckenburg, Friedhelm

2017-04-01

The rate and degree of rock weathering controls the release, distribution, and cycling of mineral nutrients at the Earth's surface, being essential for developing and sustaining of ecosystems. Climate plays an important role as water flow and temperature determine both the biological community and activity, and also set the speed of weathering. Because of this double control by climate, the impact of biological activity on rock weathering and the feedbacks between the geosphere and the biosphere under different climatic conditions are not well understood. We explore the impact of biota on rock weathering in the four EarthShape primary study areas which are situated along the Chilean Coastal Range, featuring an outstanding vegetation gradient controlled by climate, ranging over 2000 km from hyper-arid, to temperate, to humid conditions. The study sites are within 80 km of the Pacific coast and are located in granitic lithology. Moreover, the sites were unglaciated during the last glacial maximum. However, as substrates get depleted in mineral nutrients, ecosystems are increasingly nourished by atmospheric inputs, sources, such as solutes contained in rain, dust, and volcanic ash. We aim to quantify the primary nutrient inputs to the ecosystem from these different potential sources. Radiogenic strontium (Sr) isotope ratios are a powerful tool to trace chemical weathering, soil formation, as well as cation provenance and mobility [1]. We determined 87Sr/86Sr ratios on bulk bedrock, saprolite, and soil and performed sequential extractions of the the easily bioavailable soil phases up to 2 m depth on two soil depth profiles in each of the four study sites. Our first results from the La Campana study site indicate that the radiogenic Sr isotope ratios of saprolite samples decrease from 0.70571 (n = 4) at the base of the profile to lower values of 0.70520 (n = 4) at the top of the immobile saprolite, indicating increasing biotite weathering. 87Sr/86Sr increases in the mobile soil layer to 0.70571 (n = 25). We find that atmospheric sources (87Sr/86Srseawater = 0.709234; [2]) contribute about 13 % of Sr to the soil and are a minor but not negligible fraction in comparison to weathering supply from saprolite. Furthermore, the 87Sr/86Sr ratios determined for saprolite samples are in good agreement with the values reported for the local Illapel Plutonic Complex [3]. Hence, the top-soil atmospheric inputs are potentially influencing the plant's strategies of nutrient uplift, ultimately controlled by the plants' nutrient demand as a function of climate. [1] Capo, R. C., Stewart, B. W., and Chadwick, O. A., 1998, Strontium isotopes as tracers of ecosystem processes: theory and methods: Geoderma, v. 82, no. 1-3, p. 197-225. [2] DePaolo, D. J., and Ingram, B. L., 1985, High-resolution stratigraphy with strontium isotopes: Science, v. 227, no. 4689, p. 938-941. [3] Parada, M. A., Nyström, J. O., and Levi, B., 1999, Multiple sources for the Coastal Batholith of central Chile (31-34˚ S): geochemical and Sr-Nd isotopic evidence and tectonic implications: Lithos, v. 46, no. 3, p. 505-521.

Authigenic oxide Neodymium Isotopic composition as a proxy of seawater: applying multivariate statistical analyses.

NASA Astrophysics Data System (ADS)

McKinley, C. C.; Scudder, R.; Thomas, D. J.

2016-12-01

The Neodymium Isotopic composition (Nd IC) of oxide coatings has been applied as a tracer of water mass composition and used to address fundamental questions about past ocean conditions. The leached authigenic oxide coating from marine sediment is widely assumed to reflect the dissolved trace metal composition of the bottom water interacting with sediment at the seafloor. However, recent studies have shown that readily reducible sediment components, in addition to trace metal fluxes from the pore water, are incorporated into the bottom water, influencing the trace metal composition of leached oxide coatings. This challenges the prevailing application of the authigenic oxide Nd IC as a proxy of seawater composition. Therefore, it is important to identify the component end-members that create sediments of different lithology and determine if, or how they might contribute to the Nd IC of oxide coatings. To investigate lithologic influence on the results of sequential leaching, we selected two sites with complete bulk sediment statistical characterization. Site U1370 in the South Pacific Gyre, is predominantly composed of Rhyolite ( 60%) and has a distinguishable ( 10%) Fe-Mn Oxyhydroxide component (Dunlea et al., 2015). Site 1149 near the Izu-Bonin-Arc is predominantly composed of dispersed ash ( 20-50%) and eolian dust from Asia ( 50-80%) (Scudder et al., 2014). We perform a two-step leaching procedure: a 14 mL of 0.02 M hydroxylamine hydrochloride (HH) in 20% acetic acid buffered to a pH 4 for one hour, targeting metals bound to Fe- and Mn- oxides fractions, and a second HH leach for 12 hours, designed to remove any remaining oxides from the residual component. We analyze all three resulting fractions for a large suite of major, trace and rare earth elements, a sub-set of the samples are also analyzed for Nd IC. We use multivariate statistical analyses of the resulting geochemical data to identify how each component of the sediment partitions across the sequential extractions. Here we present results comparing the two sites, and examine how the composition of the sediment impacts the resulting Nd IC.

Analysis of filter tuning techniques for sequential orbit determination

NASA Technical Reports Server (NTRS)

Lee, T.; Yee, C.; Oza, D.

1995-01-01

This paper examines filter tuning techniques for a sequential orbit determination (OD) covariance analysis. Recently, there has been a renewed interest in sequential OD, primarily due to the successful flight qualification of the Tracking and Data Relay Satellite System (TDRSS) Onboard Navigation System (TONS) using Doppler data extracted onboard the Extreme Ultraviolet Explorer (EUVE) spacecraft. TONS computes highly accurate orbit solutions onboard the spacecraft in realtime using a sequential filter. As the result of the successful TONS-EUVE flight qualification experiment, the Earth Observing System (EOS) AM-1 Project has selected TONS as the prime navigation system. In addition, sequential OD methods can be used successfully for ground OD. Whether data are processed onboard or on the ground, a sequential OD procedure is generally favored over a batch technique when a realtime automated OD system is desired. Recently, OD covariance analyses were performed for the TONS-EUVE and TONS-EOS missions using the sequential processing options of the Orbit Determination Error Analysis System (ODEAS). ODEAS is the primary covariance analysis system used by the Goddard Space Flight Center (GSFC) Flight Dynamics Division (FDD). The results of these analyses revealed a high sensitivity of the OD solutions to the state process noise filter tuning parameters. The covariance analysis results show that the state estimate error contributions from measurement-related error sources, especially those due to the random noise and satellite-to-satellite ionospheric refraction correction errors, increase rapidly as the state process noise increases. These results prompted an in-depth investigation of the role of the filter tuning parameters in sequential OD covariance analysis. This paper analyzes how the spacecraft state estimate errors due to dynamic and measurement-related error sources are affected by the process noise level used. This information is then used to establish guidelines for determining optimal filter tuning parameters in a given sequential OD scenario for both covariance analysis and actual OD. Comparisons are also made with corresponding definitive OD results available from the TONS-EUVE analysis.

Determination of technetium-99 in environmental samples: a review.

PubMed

Shi, Keliang; Hou, Xiaolin; Roos, Per; Wu, Wangsuo

2012-01-04

Due to the lack of a stable technetium isotope, and the high mobility and long half-life, (99)Tc is considered to be one of the most important radionuclides in safety assessment of environmental radioactivity as well as nuclear waste management. (99)Tc is also an important tracer for oceanographic research due to the high technetium solubility in seawater as TcO(4)(-). A number of analytical methods, using chemical separation combined with radiometric and mass spectrometric measurement techniques, have been developed over the past decades for determination of (99)Tc in different environmental samples. This article summarizes and compares recently reported chemical separation procedures and measurement methods for determination of (99)Tc. Due to the extremely low concentration of (99)Tc in environmental samples, the sample preparation, pre-concentration, chemical separation and purification for removal of the interferences for detection of (99)Tc are the most important issues governing the accurate determination of (99)Tc. These aspects are discussed in detail in this article. Meanwhile, the different measurement techniques for (99)Tc are also compared with respect to advantages and drawbacks. Novel automated analytical methods for rapid determination of (99)Tc using solid extraction or ion exchange chromatography for separation of (99)Tc, employing flow injection or sequential injection approaches are also discussed. Copyright © 2011 Elsevier B.V. All rights reserved.

Geochemical and multi-isotopic (87Sr/86Sr, 143Nd/144Nd, 238U/235U) perspectives of sediment sources, depositional conditions, and diagenesis of the Marcellus Shale, Appalachian Basin, USA

NASA Astrophysics Data System (ADS)

Phan, Thai T.; Gardiner, James B.; Capo, Rosemary C.; Stewart, Brian W.

2018-02-01

We investigate sediment sources, depositional conditions and diagenetic processes affecting the Middle Devonian Marcellus Shale in the Appalachian Basin, eastern USA, a major target of natural gas exploration. Multiple proxies, including trace metal contents, rare earth elements (REE), the Sm-Nd and Rb-Sr isotope systems, and U isotopes were applied to whole rock digestions and sequentially extracted fractions of the Marcellus shale and adjacent units from two locations in the Appalachian Basin. The narrow range of εNd values (from -7.8 to -6.4 at 390 Ma) is consistent with derivation of the clastic sedimentary component of the Marcellus Shale from a well-mixed source of fluvial and eolian material of the Grenville orogenic belt, and indicate minimal post-depositional alteration of the Sm-Nd system. While silicate minerals host >80% of the REE in the shale, data from sequentially extracted fractions reflect post-depositional modifications at the mineralogical scale, which is not observed in whole rock REE patterns. Limestone units thought to have formed under open ocean (oxic) conditions have δ238U values and REE patterns consistent with modern seawater. The δ238U values in whole rock shale and authigenic phases are greater than those of modern seawater and the upper crust. The δ238U values of reduced phases (the oxidizable fraction consisting of organics and sulfide minerals) are ∼0.6‰ greater than that of modern seawater. Bulk shale and carbonate cement extracted from the shale have similar δ238U values, and are greater than δ238U values of adjacent limestone units. We suggest these trends are due to the accumulation of chemically and, more likely, biologically reduced U from anoxic to euxinic bottom water as well as the influence of diagenetic reactions between pore fluids and surrounding sediment and organic matter during diagenesis and catagenesis.

The altitudinal mobility of wild sheep at the Epigravettian site of Kalavan 1 (Lesser Caucasus, Armenia): Evidence from a sequential isotopic analysis in tooth enamel.

PubMed

Tornero, Carlos; Balasse, Marie; Bălăşescu, Adrian; Chataigner, Christine; Gasparyan, Boris; Montoya, Cyril

2016-08-01

Kalavan 1 is an Epigravettian hunting campsite in the Aregunyats mountain chain in northeastern Armenia (Lesser Caucasus). The site lies at an elevation of 1640 m in a bottleneck that controls the descent into the Barepat Valley from the alpine meadows above. The lithic and faunal assemblages show evidence of the production of hunting weapons, the hunting and targeting of wild sheep (Ovis orientalis), and the constitution of animal product reserves. A seasonal occupation of the site was proposed within a model of occupation by Epigravettian hunter-gatherers that involved a search for obsidian resources in high altitude sources from the spring to the summer and settling at Kalavan 1 at the end of summer or during autumn to coincide with the migration of wild herds from the alpine meadows to the valley. A key parameter of this model is wild sheep ethology, with a specifically seasonal vertical mobility, based on observations from contemporary mouflon populations from the surrounding areas. In this study, the vertical mobility of Paleolithic wild sheep was directly investigated through sequential isotope analysis (δ(18)O, δ(13)C) in teeth. A marked seasonality of birth is suggested that reflects a physiological adaptation to the strong environmental constraints of this mountainous region. Most importantly, a recurrent altitudinal mobility was demonstrated on a seasonal basis, which confirms that wild sheep migrated from lowland areas that they occupied in the winter and then moved to higher altitude meadows during the summer. Last, low inter-individual variability in the stable isotope sequences favors a hypothesis of accumulation for these faunal remains over a short time period. Overall, this new dataset strengthens the previous interpretations for Kalavan 1 and contributes to an understanding of the pattern of occupation of mountain territories by Epigravettian communities. Copyright © 2016 Elsevier Ltd. All rights reserved.

Iron speciation and isotope fractionation during silicate weathering and soil formation in an alpine glacier forefield chronosequence

NASA Astrophysics Data System (ADS)

Kiczka, Mirjam; Wiederhold, Jan G.; Frommer, Jakob; Voegelin, Andreas; Kraemer, Stephan M.; Bourdon, Bernard; Kretzschmar, Ruben

2011-10-01

The chemical weathering of primary Fe-bearing minerals, such as biotite and chlorite, is a key step of soil formation and an important nutrient source for the establishment of plant and microbial life. The understanding of the relevant processes and the associated Fe isotope fractionation is therefore of major importance for the further development of stable Fe isotopes as a tracer of the biogeochemical Fe cycle in terrestrial environments. We investigated the Fe mineral transformations and associated Fe isotope fractionation in a soil chronosequence of the Swiss Alps covering 150 years of soil formation on granite. For this purpose, we combined for the first time stable Fe isotope analyses with synchrotron-based Fe-EXAFS spectroscopy, which allowed us to interpret changes in Fe isotopic composition of bulk soils, size fractions, and chemically separated Fe pools over time in terms of weathering processes. Bulk soils and rocks exhibited constant isotopic compositions along the chronosequence, whereas soil Fe pools in grain size fractions spanned a range of 0.4‰ in δ 56Fe. The clay fractions (<2 μm), in which newly formed Fe(III)-(hydr)oxides contributed up to 50% of the total Fe, were significantly enriched in light Fe isotopes, whereas the isotopic composition of silt and sand fractions, containing most of the soil Fe, remained in the range described by biotite/chlorite samples and bulk soils. Iron pools separated by a sequential extraction procedure covered a range of 0.8‰ in δ 56Fe. For all soils the lightest isotopic composition was observed in a 1 M NH 2OH-HCl-25% acetic acid extract, targeting poorly-crystalline Fe(III)-(hydr)oxides, compared with easily leachable Fe in primary phyllosilicates (0.5 M HCl extract) and Fe in residual silicates. The combination of the Fe isotope measurements with the speciation data obtained by Fe-EXAFS spectroscopy permitted to quantitatively relate the different isotope pools forming in the soils to the mineral weathering reactions which have taken place at the field site. A kinetic isotope effect during the Fe detachment from the phyllosilicates was identified as the dominant fractionation mechanism in young weathering environments, controlling not only the light isotope signature of secondary Fe(III)-(hydr)oxides but also significantly contributing to the isotope signature of plants. The present study further revealed that this kinetic fractionation effect can persist over considerable reaction advance during chemical weathering in field systems and is not only an initial transient phenomenon.

On the cross-sensitivity between water vapor mixing ratio and stable isotope measurements of in-situ analyzers

NASA Astrophysics Data System (ADS)

Parkes, Stephen; Wang, Lixin; McCabe, Matthew

2015-04-01

In recent years there has been an increasing amount of water vapor stable isotope data collected using in-situ instrumentation. A number of papers have characterized the performance of these in-situ analyzers and suggested methods for calibrating raw measurements. The cross-sensitivity of the isotopic measurements on the mixing ratio has been shown to be a major uncertainty and a variety of techniques have been suggested to characterize this inaccuracy. However, most of these are based on relating isotopic ratios to water vapor mixing ratios from in-situ analyzers when the mixing ratio is varied and the isotopic composition kept constant. An additional correction for the span of the isotopic ratio scale is then applied by measuring different isotopic standards. Here we argue that the water vapor cross-sensitivity arises from different instrument responses (span and offset) of the parent H2O isotope and the heavier isotopes, rather than spectral overlap that could cause a true variation in the isotopic ratio with mixing ratio. This is especially relevant for commercial laser optical instruments where absorption lines are well resolved. Thus, the cross-sensitivity determined using more conventional techniques is dependent on the isotopic ratio of the standard used for the characterization, although errors are expected to be small. Consequently, the cross-sensitivity should be determined by characterizing the span and zero offset of each isotope mixing ratio. In fact, this technique makes the span correction for the isotopic ratio redundant. In this work we model the impact of changes in the span and offset of the heavy and light isotopes and illustrate the impact on the cross-sensitivity of the isotopic ratios on water vapor. This clearly shows the importance of determining the zero offset for the two isotopes. The cross-sensitivity of the isotopic ratios on water vapor is then characterized by determining the instrument response for the individual isotopes for a number of different in-situ analyzers that employ different optical methods. We compare this simplified calibration technique to more conventional characterization of both the cross-sensitivity determined in isotopic ratio space and the isotopic ratio span. Utilizing this simplified calibration approach with improved software control can lead to a significant reduction in time spent calibrating in-situ instrumentation or enable an increase in calibration frequency as required to minimize measurement uncertainty.

Beta-lactamase-catalyzed aminolysis of depsipeptides: Proof of the nonexistence of a specific D-phenylalanine/enzyme complex by double-label isotope trapping

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pazhanisamy, S.; Pratt, R.F.

The steady-state kinetics of the Enterobacter cloacae P99 beta-lactamase-catalyzed aminolysis of the depsipeptide m-(((phenylacetyl)glycyl)oxy)benzoic acid by D-phenylalanine were consistent with an ordered sequential mechanism with D-phenylalanine binding first. In terms of this mechanism, the kinetics data required that in 20 mM MOPS buffer, pH 7.5, the dissociation constant of the initially formed enzyme/D-phenylalanine complex be around 1.3 mM; at pH 9.0 in 0.1 M carbonate buffer, the complex should be somewhat more stable. Attempts to detect this complex in a binary mixture by spectroscopic methods (fluorescence, circular dichroic, and nuclear magnetic resonance spectra) failed. Kinetic methods were also unsuccessful--the presencemore » of 20 mM D-phenylalanine did not appear to affect beta-lactamase activity nor inhibition of the enzyme by phenylmethanesulfonyl fluoride, phenylboronic acid, or (3-dansylamidophenyl)boronic acid. Equilibrium dialysis experiments appeared to indicate that the dissociation constant of any binary enzyme/D-phenylalanine complex must be somewhat higher than the kinetics allowed (greater than 2 mM). Since the kinetics also required that, at high depsipeptide concentrations, and again with the assumption of the ordered sequential mechanism, the reaction of the enzyme/D-phenylalanine complex to aminolysis products be faster than its reversion to enzyme and D-phenylalanine, a double-label isotope-trapping experiment was performed.« less

Control of electron excitation and localization in the dissociation of H2(+) and its isotopes using two sequential ultrashort laser pulses.

PubMed

He, Feng; Ruiz, Camilo; Becker, Andreas

2007-08-24

We study the control of dissociation of the hydrogen molecular ion and its isotopes exposed to two ultrashort laser pulses by solving the time-dependent Schrödinger equation. While the first ultraviolet pulse is used to excite the electron wave packet on the dissociative 2psigma{u} state, a second time-delayed near-infrared pulse steers the electron between the nuclei. Our results show that by adjusting the time delay between the pulses and the carrier-envelope phase of the near-infrared pulse, a high degree of control over the electron localization on one of the dissociating nuclei can be achieved (in about 85% of all fragmentation events). The results demonstrate that current (sub-)femtosecond technology can provide a control over both electron excitation and localization in the fragmentation of molecules.

Mass spectrometric-based stable isotopic 2-aminobenzoic acid glycan mapping for rapid glycan screening of biotherapeutics.

PubMed

Prien, Justin M; Prater, Bradley D; Qin, Qiang; Cockrill, Steven L

2010-02-15

Fast, sensitive, robust methods for "high-level" glycan screening are necessary during various stages of a biotherapeutic product's lifecycle, including clone selection, process changes, and quality control for lot release testing. Traditional glycan screening involves chromatographic or electrophoretic separation-based methods, and, although reproducible, these methods can be time-consuming. Even ultrahigh-performance chromatographic and microfluidic integrated LC/MS systems, which work on the tens of minute time scale, become lengthy when hundreds of samples are to be analyzed. Comparatively, a direct infusion mass spectrometry (MS)-based glycan screening method acquires data on a millisecond time scale, exhibits exquisite sensitivity and reproducibility, and is amenable to automated peak annotation. In addition, characterization of glycan species via sequential mass spectrometry can be performed simultaneously. Here, we demonstrate a quantitative high-throughput MS-based mapping approach using stable isotope 2-aminobenzoic acid (2-AA) for rapid "high-level" glycan screening.

DEEP WATER ISOTOPIC CURRENT ANALYZER

DOEpatents

Johnston, W.H.

1964-04-21

A deepwater isotopic current analyzer, which employs radioactive isotopes for measurement of ocean currents at various levels beneath the sea, is described. The apparatus, which can determine the direction and velocity of liquid currents, comprises a shaft having a plurality of radiation detectors extending equidistant radially therefrom, means for releasing radioactive isotopes from the shaft, and means for determining the time required for the isotope to reach a particular detector. (AEC)

Lead Isotopes in Olivine-Phyric Shergottite Tissint: Implications for the Geochemical Evolution of the Shergottite Source Mantle

NASA Technical Reports Server (NTRS)

Moriwaki, R.; Usui, T.; Simon, J. I.; Jones, J. H.; Yokoyama, T.

2015-01-01

Geochemically-depleted shergottites are basaltic rocks derived from a martian mantle source reservoir. Geochemical evolution of the martian mantle has been investigated mainly based on the Rb-Sr, Sm-Nd, and Lu-Hf isotope systematics of the shergottites [1]. Although potentially informative, U-Th- Pb isotope systematics have been limited because of difficulties in interpreting the analyses of depleted meteorite samples that are more susceptible to the effects of near-surface processes and terrestrial contamination. This study conducts a 5-step sequential acid leaching experiment of the first witnessed fall of the geochemically-depleted olivinephyric shergottite Tissint to minimize the effect of low temperature distrubence. Trace element analyses of the Tissint acid residue (mostly pyroxene) indicate that Pb isotope compositions of the residue do not contain either a martian surface or terrestrial component, but represent the Tissint magma source [2]. The residue has relatively unradiogenic initial Pb isotopic compositions (e.g., 206Pb/204Pb = 10.8136) that fall within the Pb isotope space of other geochemically-depleted shergottites. An initial µ-value (238U/204Pb = 1.5) of Tissint at the time of crystallization (472 Ma [3]) is similar to a time-integrated mu- value (1.72 at 472 Ma) of the Tissint source mantle calculated based on the two-stage mantle evolution model [1]. On the other hand, the other geochemically-depleted shergottites (e.g., QUE 94201 [4]) have initial µ-values of their parental magmas distinctly lower than those of their modeled source mantle. These results suggest that only Tissint potentially reflects the geochemical signature of the shergottite mantle source that originated from cumulates of the martian magma ocean

Stable Isotopes Provide Insight into Population Structure and Segregation in Eastern North Atlantic Sperm Whales

PubMed Central

Borrell, Asunción; Velásquez Vacca, Adriana; Pinela, Ana M.; Kinze, Carl; Lockyer, Christina H.; Vighi, Morgana; Aguilar, Alex

2013-01-01

In pelagic species inhabiting large oceans, genetic differentiation tends to be mild and populations devoid of structure. However, large cetaceans have provided many examples of structuring. Here we investigate whether the sperm whale, a pelagic species with large population sizes and reputedly highly mobile, shows indication of structuring in the eastern North Atlantic, an ocean basin in which a single population is believed to occur. To do so, we examined stable isotope values in sequential growth layer groups of teeth from individuals sampled in Denmark and NW Spain. In each layer we measured oxygen- isotope ratios (δ18O) in the inorganic component (hydroxyapatite), and nitrogen and carbon isotope ratios (δ15N: δ13C) in the organic component (primarily collagenous). We found significant differences between Denmark and NW Spain in δ15N and δ18O values in the layer deposited at age 3, considered to be the one best representing the baseline of the breeding ground, in δ15N, δ13C and δ18O values in the period up to age 20, and in the ontogenetic variation of δ15N and δ18O values. These differences evidence that diet composition, use of habitat and/or migratory destinations are dissimilar between whales from the two regions and suggest that the North Atlantic population of sperm whales is more structured than traditionally accepted. PMID:24324782

Lead Isotope Compositions of Acid Residues from Olivine-Phyric Shergottite Tissint: Implications for Heterogeneous Shergottite Source Reservoirs

NASA Technical Reports Server (NTRS)

Moriwaki, R.; Usui, T.; Yokoyama, T.; Simon, J. I.; Jones, J. H.

2015-01-01

Geochemical studies of shergottites suggest that their parental magmas reflect mixtures between at least two distinct geochemical source reservoirs, producing correlations between radiogenic isotope compositions and trace element abundances. These correlations have been interpreted as indicating the presence of a reduced, incompatible element- depleted reservoir and an oxidized, incompatible- element-enriched reservoir. The former is clearly a depleted mantle source, but there is ongoing debate regarding the origin of the enriched reservoir. Two contrasting models have been proposed regarding the location and mixing process of the two geochemical source reservoirs: (1) assimilation of oxidized crust by mantle derived, reduced magmas, or (2) mixing of two distinct mantle reservoirs during melting. The former requires the ancient Martian crust to be the enriched source (crustal assimilation), whereas the latter requires isolation of a long-lived enriched mantle domain that probably originated from residual melts formed during solidification of a magma ocean (heterogeneous mantle model). This study conducts Pb isotope and trace element concentration analyses of sequential acid-leaching fractions (leachates and the final residues) from the geochemically depleted olivine-phyric shergottite Tissint. The results suggest that the Tissint magma is not isotopically uniform and sampled at least two geochemical source reservoirs, implying that either crustal assimilation or magma mixing would have played a role in the Tissint petrogenesis.

Assessing human weaning practices with calcium isotopes in tooth enamel

PubMed Central

Tacail, Théo; Thivichon-Prince, Béatrice; Martin, Jeremy E.; Charles, Cyril; Viriot, Laurent

2017-01-01

Weaning practices differ among great apes and likely diverged during the course of human evolution, but behavioral inference from the fossil record is hampered by a lack of unambiguous biomarkers. Here, we show that early-life dietary transitions are recorded in human deciduous tooth enamel as marked variations in Ca isotope ratios (δ44/42Ca). Using a sequential microsampling method along the enamel growth axis, we collected more than 150 enamel microsamples from 51 deciduous teeth of 12 different modern human individuals of known dietary histories, as well as nine enamel samples from permanent third molars. We measured and reconstructed the evolution of 44Ca/42Ca ratios in enamel from in utero development to first months of postnatal development. We show that the observed variations of δ44/42Ca record a transition from placental nutrition to an adult-like diet and that Ca isotopes reflect the duration of the breastfeeding period experienced by each infant. Typically, the δ44/42Ca values of individuals briefly or not breastfed show a systematic increase during the first 5–10 mo, whereas individuals with long breastfeeding histories display no measurable variation in δ44/42Ca of enamel formed during this time. The use of Ca isotope analysis in tooth enamel allows microsampling and offers an independent approach to tackle challenging questions related to past population dynamics and evolution of weaning practices in hominins. PMID:28559355

A comparison of lead-isotope measurements on exploration-type samples using inductively coupled plasma and thermal ionization mass spectrometry

USGS Publications Warehouse

Gulson, B.L.; Meier, A.L.; Church, S.E.; Mizon, K.J.

1989-01-01

Thermal ionization mass spectrometry (TI-MS) has long been the method of choice for Pb-isotope determinations. More recently, however, inductively coupled plasma mass spectrometry (ICP-MS) has been used to determine Pb-isotope ratios for mineral exploration. The ICP-MS technique, although not as precise as TI-MS, may promote a wider application of Ph-isotope ratio methods because it allows individual isotopes to be determined more rapidly, generally without need for chemical separation (e.g., Smith et al., 1984; Hinners et al., 1987). To demonstrate the utility of the ICP-MS method, we have conducted a series of Pb-isotope measurements on several suites of samples using both TI-MS and ICP-MS. ?? 1989.

20 CFR 404.1520 - Evaluation of disability in general.

Code of Federal Regulations, 2010 CFR

2010-04-01

...-step sequential evaluation process we use to decide whether you are disabled, as defined in § 404.1505...-step sequential evaluation process. The sequential evaluation process is a series of five “steps” that... severe medically determinable physical or mental impairment that meets the duration requirement in § 404...

Individual specialization in the foraging habits of female bottlenose dolphins living in a trophically diverse and habitat rich estuary

USGS Publications Warehouse

Rossman, Sam; Ostrom, Peggy H.; Stolen, Megan; Barros, Nélio B.; Gandhi, Hasand; Stricker, Craig A.; Wells, Randall S.

2015-01-01

We examine individual specialization in foraging habits (foraging habitat and trophic level) of female bottlenose dolphins (Tursiops truncatus) resident in Sarasota Bay, Florida, USA, by analyzing time series of stable isotope (δ15N and δ13C) values in sequential growth layer groups within teeth. The isotope data provide a chronology of foraging habits over the lifetime of the individual and allowed us to show that female bottlenose dolphins exhibit a high degree of individual specialization in both foraging habitat and trophic level. The foraging habits used by adult females are similar to those they used as calves and may be passed down from mother to calf through social learning. We also characterized the foraging habits and home range of each individual by constructing standard ellipses from isotope values and dolphin sightings data (latitude and longitude), respectively. These data show that Sarasota Bay bottlenose dolphins forage within a subset of the habitats in which they are observed. Moreover, females with similar observational standard ellipses often possessed different foraging specializations. Female bottlenose dolphins may demonstrate individual specialization in foraging habits because it reduces some of the cost of living in groups, such as competition for prey.

Heterologous expression of Cenchritis muricatus protease inhibitor II (CmPI-II) in Pichia pastoris system: Purification, isotopic labeling and preliminary characterization.

PubMed

Cabrera-Muñoz, Aymara; Rojas, Laritza; Gil, Dayrom F; González-González, Yamile; Mansur, Manuel; Camejo, Ayamey; Pires, José R; Alonso-Del-Rivero Antigua, Maday

2016-10-01

Cenchritis muricatus protease inhibitor II (CmPI-II) is a tight-binding serine protease inhibitor of the Kazal family with an atypical broad specificity, being active against several proteases such as bovine pancreatic trypsin, human neutrophil elastase and subtilisin A. CmPI-II 3D structures are necessary for understanding the molecular basis of its activity. In the present work, we describe an efficient and straightforward recombinant expression strategy, as well as a cost-effective procedure for isotope labeling for NMR structure determination purposes. The vector pCM101 containing the CmPI-II gene, under the control of Pichia pastoris AOX1 promoter was constructed. Methylotrophic Pichia pastoris strain KM71H was then transformed with the plasmid and the recombinant protein (rCmPI-II) was expressed in benchtop fermenter in unlabeled or (15)N-labeled forms using ammonium chloride ((15)N, 99%) as the sole nitrogen source. Protein purification was accomplished by sequential cation exchange chromatography in STREAMLINE DirectHST, anion exchange chromatography on Hitrap Q-Sepharose FF and gel filtration on Superdex 75 10/30, yielding high quantities of pure rCmPI-II and (15)N rCmPI-II. Recombinant proteins displayed similar functional features as compared to the natural inhibitor and NMR spectra indicated folded and homogeneously labeled samples, suitable for further studies of structure and protease-inhibitor interactions. Copyright © 2016 Elsevier Inc. All rights reserved.

History of Animals using Isotope Records (HAIR): A 6-year dietary history of one family of African elephants

PubMed Central

Cerling, Thure E.; Wittemyer, George; Ehleringer, James R.; Remien, Christopher H.; Douglas-Hamilton, Iain

2009-01-01

The dietary and movement history of individual animals can be studied using stable isotope records in animal tissues, providing insight into long-term ecological dynamics and a species niche. We provide a 6-year history of elephant diet by examining tail hair collected from 4 elephants in the same social family unit in northern Kenya. Sequential measurements of carbon, nitrogen, and hydrogen isotope rations in hair provide a weekly record of diet and water resources. Carbon isotope ratios were well correlated with satellite-based measurements of the normalized difference vegetation index (NDVI) of the region occupied by the elephants as recorded by the global positioning system (GPS) movement record; the absolute amount of C4 grass consumption is well correlated with the maximum value of NDVI during individual wet seasons. Changes in hydrogen isotope ratios coincided very closely in time with seasonal fluctuations in rainfall and NDVI whereas diet shifts to relatively high proportions of grass lagged seasonal increases in NDVI by ≈2 weeks. The peak probability of conception in the population occurred ≈3 weeks after peak grazing. Spatial and temporal patterns of resource use show that the only period of pure browsing by the focal elephants was located in an over-grazed, communally managed region outside the protected area. The ability to extract time-specific longitudinal records on animal diets, and therefore the ecological history of an organism and its environment, provides an avenue for understanding the impact of climate dynamics and land-use change on animal foraging behavior and habitat relations. PMID:19365077

History of Animals using Isotope Records (HAIR): a 6-year dietary history of one family of African elephants.

PubMed

Cerling, Thure E; Wittemyer, George; Ehleringer, James R; Remien, Christopher H; Douglas-Hamilton, Iain

2009-05-19

The dietary and movement history of individual animals can be studied using stable isotope records in animal tissues, providing insight into long-term ecological dynamics and a species niche. We provide a 6-year history of elephant diet by examining tail hair collected from 4 elephants in the same social family unit in northern Kenya. Sequential measurements of carbon, nitrogen, and hydrogen isotope rations in hair provide a weekly record of diet and water resources. Carbon isotope ratios were well correlated with satellite-based measurements of the normalized difference vegetation index (NDVI) of the region occupied by the elephants as recorded by the global positioning system (GPS) movement record; the absolute amount of C(4) grass consumption is well correlated with the maximum value of NDVI during individual wet seasons. Changes in hydrogen isotope ratios coincided very closely in time with seasonal fluctuations in rainfall and NDVI whereas diet shifts to relatively high proportions of grass lagged seasonal increases in NDVI by approximately 2 weeks. The peak probability of conception in the population occurred approximately 3 weeks after peak grazing. Spatial and temporal patterns of resource use show that the only period of pure browsing by the focal elephants was located in an over-grazed, communally managed region outside the protected area. The ability to extract time-specific longitudinal records on animal diets, and therefore the ecological history of an organism and its environment, provides an avenue for understanding the impact of climate dynamics and land-use change on animal foraging behavior and habitat relations.

Preliminary Report on U-Th-Pb Isotope Systematics of the Olivine-Phyric Shergottite Tissint

NASA Technical Reports Server (NTRS)

Moriwaki, R.; Usui, T.; Yokoyama, T.; Simon, J. I.; Jones, J. H.

2014-01-01

Geochemical studies of shergottites suggest that their parental magmas reflect mixtures between at least two distinct geochemical source reservoirs, producing correlations between radiogenic isotope compositions, and trace element abundances.. These correlations have been interpreted as indicating the presence of a reduced, incompatible-element- depleted reservoir and an oxidized, incompatible-element-rich reservoir. The former is clearly a depleted mantle source, but there has been a long debate regarding the origin of the enriched reservoir. Two contrasting models have been proposed regarding the location and mixing process of the two geochemical source reservoirs: (1) assimilation of oxidized crust by mantle derived, reduced magmas, or (2) mixing of two distinct mantle reservoirs during melting. The former clearly requires the ancient martian crust to be the enriched source (crustal assimilation), whereas the latter requires a long-lived enriched mantle domain that probably originated from residual melts formed during solidification of a magma ocean (heterogeneous mantle model). This study conducts Pb isotope and U-Th-Pb concentration analyses of the olivine-phyric shergottite Tissint because U-Th-Pb isotope systematics have been intensively used as a powerful radiogenic tracer to characterize old crust/sediment components in mantle- derived, terrestrial oceanic island basalts. The U-Th-Pb analyses are applied to sequential acid leaching fractions obtained from Tissint whole-rock powder in order to search for Pb isotopic source components in Tissint magma. Here we report preliminary results of the U-Th-Pb analyses of acid leachates and a residue, and propose the possibility that Tissint would have experienced minor assimilation of old martian crust.

Comparison of ERBS orbit determination accuracy using batch least-squares and sequential methods

NASA Technical Reports Server (NTRS)

Oza, D. H.; Jones, T. L.; Fabien, S. M.; Mistretta, G. D.; Hart, R. C.; Doll, C. E.

1991-01-01

The Flight Dynamics Div. (FDD) at NASA-Goddard commissioned a study to develop the Real Time Orbit Determination/Enhanced (RTOD/E) system as a prototype system for sequential orbit determination of spacecraft on a DOS based personal computer (PC). An overview is presented of RTOD/E capabilities and the results are presented of a study to compare the orbit determination accuracy for a Tracking and Data Relay Satellite System (TDRSS) user spacecraft obtained using RTOS/E on a PC with the accuracy of an established batch least squares system, the Goddard Trajectory Determination System (GTDS), operating on a mainframe computer. RTOD/E was used to perform sequential orbit determination for the Earth Radiation Budget Satellite (ERBS), and the Goddard Trajectory Determination System (GTDS) was used to perform the batch least squares orbit determination. The estimated ERBS ephemerides were obtained for the Aug. 16 to 22, 1989, timeframe, during which intensive TDRSS tracking data for ERBS were available. Independent assessments were made to examine the consistencies of results obtained by the batch and sequential methods. Comparisons were made between the forward filtered RTOD/E orbit solutions and definitive GTDS orbit solutions for ERBS; the solution differences were less than 40 meters after the filter had reached steady state.

Comparison of ERBS orbit determination accuracy using batch least-squares and sequential methods

NASA Astrophysics Data System (ADS)

Oza, D. H.; Jones, T. L.; Fabien, S. M.; Mistretta, G. D.; Hart, R. C.; Doll, C. E.

1991-10-01

The Flight Dynamics Div. (FDD) at NASA-Goddard commissioned a study to develop the Real Time Orbit Determination/Enhanced (RTOD/E) system as a prototype system for sequential orbit determination of spacecraft on a DOS based personal computer (PC). An overview is presented of RTOD/E capabilities and the results are presented of a study to compare the orbit determination accuracy for a Tracking and Data Relay Satellite System (TDRSS) user spacecraft obtained using RTOS/E on a PC with the accuracy of an established batch least squares system, the Goddard Trajectory Determination System (GTDS), operating on a mainframe computer. RTOD/E was used to perform sequential orbit determination for the Earth Radiation Budget Satellite (ERBS), and the Goddard Trajectory Determination System (GTDS) was used to perform the batch least squares orbit determination. The estimated ERBS ephemerides were obtained for the Aug. 16 to 22, 1989, timeframe, during which intensive TDRSS tracking data for ERBS were available. Independent assessments were made to examine the consistencies of results obtained by the batch and sequential methods. Comparisons were made between the forward filtered RTOD/E orbit solutions and definitive GTDS orbit solutions for ERBS; the solution differences were less than 40 meters after the filter had reached steady state.

Sediment Sources, Depositional Environment, and Diagenetic Alteration of the Marcellus Shale, Appalachian Basin, USA: Nd, Sr, Li and U Isotopic Constraints

NASA Astrophysics Data System (ADS)

Phan, T. T.; Capo, R. C.; Gardiner, J. B.; Stewart, B. W.

2017-12-01

The organic-rich Middle Devonian Marcellus Shale in the Appalachian Basin, eastern USA, is a major target of natural gas exploration. Constraints on local and regional sediment sources, depositional environments, and post-depositional processes are essential for understanding the evolution of the basin. In this study, multiple proxies, including trace metals, rare earth elements (REE), the Sm-Nd and Rb-Sr isotope systems, and U and Li isotopes were applied to bulk rocks and authigenic fractions of the Marcellus Shale and adjacent limestone/sandstone units from two locations separated by 400 km. The range of ɛNd values (-7.8 to -6.4 at 390 Ma) is consistent with a clastic sedimentary component derived from a well-mixed source of fluvial and eolian material of the Grenville orogenic belt. The Sm-Nd isotope system and bulk REE distributions appear to have been minimally affected by post-depositional processes, while the Rb-Sr isotope system shows evidence of limited post-depositional redistribution. While REE are primarily associated with silicate minerals (80-95%), REE patterns of sequentially extracted fractions reflect post-depositional alteration at the intergranular scale. Although the chemical index of alteration (CIA = 54 to 60) suggests the sediment source was not heavily weathered, Li isotope data are consistent with progressively increasing weathering of the source region during Marcellus Shale deposition. δ238U values in bulk shale and reduced phases (oxidizable fraction) are higher than those of modern seawater and upper crust. The isotopically heavy U accumulated in these authigenic phases can be explained by the precipitation of insoluble U in anoxic/euxinic bottom water. Unlike carbonate cement within the shale, the similarity between δ238U values and REE patterns of the limestone units and those of modern seawater indicates that the limestone formed under open ocean (oxic) conditions.

Predictions on the modes of decay of even Z superheavy isotopes within the range 104 ≤ Z ≤ 136

NASA Astrophysics Data System (ADS)

Santhosh, K. P.; Nithya, C.

2018-01-01

The decay modes and half lives of all the even Z isotopes of superheavy elements within the range 104 ≤ Z ≤ 136 have been predicted by comparing the alpha decay half-lives with the spontaneous fission half-lives. The Coulomb and proximity potential model for deformed nuclei (CPPMDN) and the shell-effect-dependent formula of Santhosh et al. are used to calculate the alpha half-lives and spontaneous fission half-lives respectively. For theoretical comparison the alpha decay half-lives are also calculated using Coulomb and proximity potential model (CPPM), the Viola-Seaborg-Sobiczewski semi-empirical (VSS) relation, the universal (UNIV) curve of Poenaru et al., the analytical formula of Royer and the universal decay law (UDL) of Qi et al. Another tool used for the evaluation of spontaneous fission half-lives is the semi-empirical formula of Xu et al. The nuclei with alpha decay half-lives less than spontaneous fission half-lives will survive fission and hence decay through alpha emission. The predicted half lives and decay modes are compared with the available experimental results. The one-proton and two-proton separation energies of all the isotopes are calculated to find nuclei which lie beyond the proton drip line. Among 1119 even Z nuclei within the range 104 ≤ Z ≤ 136, 164 nuclei show sequential alpha emission followed by subsequent spontaneous fission. Since the isotopes decay through alpha decay chain and the half-lives are in measurable range, these isotopes are predicted to be synthesized and detected in laboratory via alpha decay. 2 nuclei will decay by alpha decay followed by proton emission, 54 nuclei show full alpha chains, 642 nuclei will decay through spontaneous fission, 166 nuclei exhibit proton decay and 91 isotopes are found to be stable against alpha decay. All the isotopes are tabulated according to their decay modes. The study is intended to enhance further experimental investigations in superheavy region.

Phosphorus cycling in forest ecosystems: insights from oxygen isotopes in phosphate

NASA Astrophysics Data System (ADS)

Pistocchi, Chiara; Tamburini, Federica; Bünemann, Else; Frossard, Emmanuel

2015-04-01

The current view on the phosphorus (P) cycle in forest ecosystems relies mostly on measurements and correlations of pools, and to a lower extent on measurement of fluxes. We have no direct insight into the processes phosphate goes through at the ecosystem level, and into the relative importance of organic and mineral pools in sustaining P nutrition of trees. The analysis of oxygen isotopes associated to P (18Op) is expected to bring this type of information. The German Priority Program SPP 1685 aims to test the overall hypothesis that the P-depletion of soils drives forest ecosystems from P acquiring systems (efficient mobilization of P from the mineral phase) to P recycling systems (highly efficient cycling of P). Our contribution to this project will consist in studying the relative importance of biological and geochemical processes in controlling the P cycle in temperate beech forest ecosystems in Germany along a gradient of decreasing soil P availability. We will follow the fate of phosphate from litter fall to the uptake of P by plants via P release by decomposition of organic matter or after release from P-containing minerals, by using a multi-isotope approach (O in water and phosphate plus 33P). To address our research question we will rely on measurements in experimental forest sites and on laboratory incubations of the organic layer or the mineral soil. We present here the first results issued from the 2014 sampling on three study sites, where we characterized the P pools in surface soil horizons by a sequential extraction (modified after Tiessen and Moir, 2007) and we analysed the 18Op of the resin extractable- and microbial-P fractions. Contrary to what was previously found (e.g. Tamburini et al. 2012) the isotopic composition of these fractions in most of the samples does not reflect the equilibrium value (as the result of the dominance of the pyrophosphatase activity on the other enzymatic processes, Blake et al. 2005). Depending on the P availability in the soil, deviations from the equilibrium are more or less pronounced. We hypothesized that the 18Op is the result of other processes such the mineralization of organic P by phosphatases. These first results of 18Op on forest soils are suggesting that isotopic equilibrium driven by biological cycling (pyrophosphatase) is not always overprinting other processes. In addition, together with information on P speciation/concentration, 18Op seems to provide direct insights on P cycling at the ecosystem level. Blake R.E., Neil J.R.O., Surkov A.V. (2005) Biogeochemical cycling of phosphorus: insights from oxygen isotope effects of phosphoenzymes. American Journal of Science 305: 596-620 Moir J.O., Tiessen H. Characterization of available P by sequential extraction. Soil Sampling and Methods of Analysis, Second Edition. Ed. by M.R. Carter and E.G. Gregorich CRC Press 2007 Tamburini F., Pfahler V, Bünemann E.K., Guelland K., Bernasconi S.M., Frossard E. (2012) Oxygen Isotopes Unravel the Role of Microorganisms in Phosphate Cycling in Soils. Environmental Science & Technology 46: 5956-5962

Application of stable isotope tools for evaluating natural and stimulated biodegradation of organic pollutants in field studies.

PubMed

Fischer, Anko; Manefield, Mike; Bombach, Petra

2016-10-01

Stable isotope tools are increasingly applied for in-depth evaluation of biodegradation of organic pollutants at contaminated field sites. They can be divided into three methods i) determination of changes in natural abundance of stable isotopes using compound-specific stable isotope analysis (CSIA), ii) detection of incorporation of stable-isotope label from a stable-isotope labelled target compound into degradation and/or mineralisation products and iii) determination of stable-isotope label incorporation into biomarkers using stable isotope probing (SIP). Stable isotope tools have been applied as key monitoring tools for multiple-line-of-evidence-approaches (MLEA) for sensitive evaluation of pollutant biodegradation. This review highlights the application of CSIA, SIP and MLEA including stable isotope tools for assessing natural and stimulated biodegradation of organic pollutants in field studies dealing with soil and groundwater contaminations. Copyright © 2016 Elsevier Ltd. All rights reserved.

Biogeochemical cycling in an organic-rich coastal marine basin. 8. A sulfur isotopic budget balanced by differential diffusion across the sediment-water interface

USGS Publications Warehouse

Chanton, J.P.; Martens, C.S.; Goldhaber, M.B.

1987-01-01

The sulfur isotopic composition of the sulfur fluxes occurring in the anoxic marine sediments of Cape Lookout Bight, N.C., U.S.A., was determined, and the result of isotopic mass balance was obtained via the differential diffusion model. Seasonal pore water sulfate ??34S measurements yielded a calculated sulfate input of 0.6%.. Sulfate transported into the sediments via diffusion appeared to be enriched in the lighter isotope because its concentration gradient was steeper, due to the increase in the measured isotopic composition of sulfate with depth. Similarly, the back diffusion of dissolved sulfide towards the sediment-water interface appeared enriched in the heavier isotope. The isotopic composition of this flux was calculated from measurements of the ??34S of dissolved sulfide and was determined to be 15.9%.. The isotopic composition of buried sulfide was determined to be -5.2%. and the detrital sulfur input was estimated to be -6.2%.. An isotope mass balance equation based upon the fluxes at the sediment-water interface successfully predicted the isotopic composition of the buried sulfur flux within 0.5%., thus confirming that isotopes diffuse in response to their individual concentration gradients. ?? 1987.

Three- α particle correlations in quasi-projectile decay in 12C + 24Mg collisions at 35A MeV

NASA Astrophysics Data System (ADS)

Quattrocchi, L.; Acosta, L.; Amorini, F.; Anzalone, A.; Auditore, L.; Berceanu, I.; Cardella, G.; Chbihi, A.; De Filippo, E.; De Luca, S.; Dell'Aquila, D.; Francalanza, L.; Gnoffo, B.; Grzeszczuk, A.; Lanzalone, G.; Lombardo, I.; Martel, I.; Martorana, N. S.; Minniti, T.; Norella, S.; Pagano, A.; Pagano, E. V.; Papa, M.; Pirrone, S.; Politi, G.; Porto, F.; Rizzo, F.; Rosato, E.; Russotto, P.; Trifirò, A.; Trimarchi, M.; Verde, G.; Veselsky, M.; Vigilante, M.

2017-11-01

Two and multi particle correlations have been studied in peripheral 12C + 24Mg collisions at 35A MeV with CHIMERA 4 π multi detector, in order to explore resonances produced in light nuclei. Correlations techniques have become a tool to explore nuclear structure properties but also to evaluate the competition between simultaneous and sequential channels in decay of light isotopes. The exploration of features such as branching ratios with respect to different decay channels (sequential vs. simultaneous) could provide information on in-medium effects on nuclear structure properties, an important perspective for research on the nuclear interaction. The performed experiment is preliminary to further studies to be performed by coupling of CHIMERA to FARCOS (Femtoscope ARray for COrrelations and Spectroscopy, FARCOS TDR available at https://drive.google.com/file/d/0B5CgGWz8LpOOc3pGTWdOcDBoWFE) array devoted to measurements of two and multi particle correlations with high energy and angular resolutions.

Evaluation of TDRSS-user orbit determination accuracy using batch least-squares and sequential methods

NASA Technical Reports Server (NTRS)

Oza, D. H.; Jones, T. L.; Hodjatzadeh, M.; Samii, M. V.; Doll, C. E.; Hart, R. C.; Mistretta, G. D.

1991-01-01

The development of the Real-Time Orbit Determination/Enhanced (RTOD/E) system as a prototype system for sequential orbit determination on a Disk Operating System (DOS) based Personal Computer (PC) is addressed. The results of a study to compare the orbit determination accuracy of a Tracking and Data Relay Satellite System (TDRSS) user spacecraft obtained using RTOD/E with the accuracy of an established batch least squares system, the Goddard Trajectory Determination System (GTDS), is addressed. Independent assessments were made to examine the consistencies of results obtained by the batch and sequential methods. Comparisons were made between the forward filtered RTOD/E orbit solutions and definitive GTDS orbit solutions for the Earth Radiation Budget Satellite (ERBS); the maximum solution differences were less than 25 m after the filter had reached steady state.

Hydrochemical and isotopic effects associated with petroleum fuel biodegradation pathways in a chalk aquifer.

PubMed

Spence, Michael J; Bottrell, Simon H; Thornton, Steven F; Richnow, Hans H; Spence, Keith H

2005-09-01

Hydrochemical data, compound specific carbon isotope analysis and isotopic enrichment trends in dissolved hydrocarbons and residual electron acceptors have been used to deduce BTEX and MTBE degradation pathways in a fractured chalk aquifer. BTEX compounds are mineralised sequentially within specific redox environments, with changes in electron acceptor utilisation being defined by the exhaustion of specific BTEX components. A zone of oxygen and nitrate exhaustion extends approximately 100 m downstream from the plume source, with residual sulphate, toluene, ethylbenzene and xylene. Within this zone complete removal of the TEX components occurs by bacterial sulphate reduction, with sulphur and oxygen isotopic enrichment of residual sulphate (epsilon(s) = -14.4 per thousand to -16.0 per thousand). Towards the plume margins and at greater distance along the plume flow path nitrate concentrations increase with delta15N values of up to +40 per thousand indicating extensive denitrification. Benzene and MTBE persist into the denitrification zone, with carbon isotope enrichment of benzene indicating biodegradation along the flow path. A Rayleigh kinetic isotope enrichment model for 13C-enrichment of residual benzene gives an apparent epsilon value of -0.66 per thousand. MTBE shows no significant isotopic enrichment (delta13C = -29.3 per thousand to -30.7 per thousand) and is isotopically similar to a refinery sample (delta13C = -30.1 per thousand). No significant isotopic variation in dissolved MTBE implies that either the magnitude of any biodegradation-induced isotopic fractionation is small, or that relatively little degradation has taken place in the presence of BTEX hydrocarbons. It is possible, however, that MTBE degradation occurs under aerobic conditions in the absence of BTEX since no groundwater samples were taken with co-existing MTBE and oxygen. Low benzene delta13C values are correlated with high sulphate delta34S, indicating that little benzene degradation has occurred in the sulphate reduction zone. Benzene degradation may be associated with denitrification since increased benzene delta13C is associated with increased delta15N in residual nitrate. Re-supply of electron acceptors by diffusion from the matrix into fractures and dispersive mixing is an important constraint on degradation rates and natural attenuation capacity in this dual-porosity aquifer.

Landsat-4 (TDRSS-user) orbit determination using batch least-squares and sequential methods

NASA Technical Reports Server (NTRS)

Oza, D. H.; Jones, T. L.; Hakimi, M.; Samii, M. V.; Doll, C. E.; Mistretta, G. D.; Hart, R. C.

1992-01-01

TDRSS user orbit determination is analyzed using a batch least-squares method and a sequential estimation method. It was found that in the batch least-squares method analysis, the orbit determination consistency for Landsat-4, which was heavily tracked by TDRSS during January 1991, was about 4 meters in the rms overlap comparisons and about 6 meters in the maximum position differences in overlap comparisons. The consistency was about 10 to 30 meters in the 3 sigma state error covariance function in the sequential method analysis. As a measure of consistency, the first residual of each pass was within the 3 sigma bound in the residual space.

Site fidelity and condition metrics suggest sequential habitat use by early juvenile snook

USGS Publications Warehouse

Brame, Adam B.; McIvor, Carole; Peebles, Ernst B; Hollander, David J.

2014-01-01

The common snook Centropomus undecimalis is an estuarine-dependent fish that relies on landward wetlands as nursery habitat. Despite its economic importance, portions of the snook's early life history are poorly understood. We compared habitat use of young-of-the-year (YOY) snook in 2 geomorphic mesohabitats (tidal pond and tidal creek) along an estuarine gradient (upstream vs. downstream) within a single wetland during fall recruitment. We used abundance, length, condition indices, and stable isotopes to assess ontogenetic mesohabitat use and site fidelity. We found that (1) YOY snook were more abundant within the upstream creek and ponds; (2) the smallest snook were found only in ponds; (3) snook from ponds had lower condition (Fulton's K and hepatosomatic index); (4) snook began moving from ponds to the creek at ~40 mm standard length; and (5) snook from the 2 mesohabitats were isotopically distinct, indicating high site fidelity at rather small spatial scales. Collectively, these data identified sequential use of mesohabitats, wherein seaward-spawned YOY snook moved landward and recruited to pond habitats, where they dedicated energy to growth (as length) before making an ontogenetic habitat shift to the creek. Once in the creek, YOY snook condition improved as they approached maturity and started the downstream return towards seaward locations. The wetland network that was previously viewed as generalized nursery habitat instead consists of mesohabitats that support different life stages in sequence. This represents ontogenetic habitat complementation, in which lower availability of a required mesohabitat type may limit the entire wetland's contribution to the adult population.

Beta-lactamase-catalyzed aminolysis of depsipeptides: proof of the nonexistence of a specific D-phenylalanine/enzyme complex by double-label isotope trapping.

PubMed

Pazhanisamy, S; Pratt, R F

1989-08-22

The steady-state kinetics of the Enterobacter cloacae P99 beta-lactamase-catalyzed aminolysis of the depsipeptide m-[[(phenylacetyl)glycyl]oxy]benzoic acid by D-phenylalanine were consistent with an ordered sequential mechanism with D-phenylalanine binding first [Pazhanisamy, S., Govardhan, C. P., & Pratt, R. F. (1989) Biochemistry (first of three papers in this issue)]. In terms of this mechanism, the kinetics data required that in 20 mM MOPS buffer, pH 7.5, the dissociation constant of the initially formed enzyme/D-phenylalanine complex be around 1.3 mM; at pH 9.0 in 0.1 M carbonate buffer, the complex should be somewhat more stable. Attempts to detect this complex in a binary mixture by spectroscopic methods (fluorescence, circular dichroic, and nuclear magnetic resonance spectra) failed. Kinetic methods were also unsuccessful--the presence of 20 mM D-phenylalanine did not appear to affect beta-lactamase activity nor inhibition of the enzyme by phenylmethanesulfonyl fluoride, phenylboronic acid, or (3-dansylamidophenyl)boronic acid. Equilibrium dialysis experiments appeared to indicate that the dissociation constant of any binary enzyme/D-phenylalanine complex must be somewhat higher than the kinetics allowed (greater than 2 mM). Since the kinetics also required that, at high depsipeptide concentrations, and again with the assumption of the ordered sequential mechanism, the reaction of the enzyme/D-phenylalanine complex to aminolysis products be faster than its reversion to enzyme and D-phenylalanine, a double-label isotope-trapping experiment was performed.(ABSTRACT TRUNCATED AT 250 WORDS)

A validated ultra-high-performance liquid chromatography-tandem mass spectrometry method for the selective analysis of free and total folate in plasma and red blood cells.

PubMed

Kiekens, Filip; Van Daele, Jeroen; Blancquaert, Dieter; Van Der Straeten, Dominique; Lambert, Willy E; Stove, Christophe P

2015-06-12

A stable isotope dilution LC-MS/MS method is the method of choice for the selective quantitative determination of several folate species in clinical samples. By implementing an integrated approach to determine both the plasma and red blood cell (RBC) folate status, the use of consumables and time remains limited. Starting from a single 300μl whole blood sample, the folate status in plasma and RBCs can be determined after separating plasma and RBCs and sequential washing of the latter with isotonic buffer, followed by reproducible lysis using an ammonium-based buffer. Acidification combines both liberation of protein bound folates and protein precipitation. Sample cleanup is performed using a 96-well reversed-phase solid-phase extraction procedure, similar for both plasma and RBC samples. Analyses are performed by UHPLC-MS/MS. Method validation was successfully performed based on EMA-guidelines and encompassed selectivity, carry-over, linearity, accuracy, precision, recovery, matrix effect and stability. Plasma and RBC folates could be quantified in the range of 1-150nmol/l and 5-1500nmol/l, respectively. This method allows for the determination of 6 folate monoglutamates in both plasma and RBCs. It can be used to determine short and long term folate status in both normal and severely deficient subjects in a single analytical sequence. Copyright © 2015 Elsevier B.V. All rights reserved.

Effects of Training Auditory Sequential Memory and Attention on Reading.

ERIC Educational Resources Information Center

Klein, Pnina S.; Schwartz, Allen A.

To determine if auditory sequential memory (ASM) in young children can be improved through training and to discover the effects of such training on the reading scores of children with reading problems, a study was conducted involving 92 second and third graders. For purposes of this study, auditory sequential memory was defined as the ability to…

Sequential and simultaneous SLAR block adjustment. [spline function analysis for mapping

NASA Technical Reports Server (NTRS)

Leberl, F.

1975-01-01

Two sequential methods of planimetric SLAR (Side Looking Airborne Radar) block adjustment, with and without splines, and three simultaneous methods based on the principles of least squares are evaluated. A limited experiment with simulated SLAR images indicates that sequential block formation with splines followed by external interpolative adjustment is superior to the simultaneous methods such as planimetric block adjustment with similarity transformations. The use of the sequential block formation is recommended, since it represents an inexpensive tool for satisfactory point determination from SLAR images.

TDRSS-user orbit determination using batch least-squares and sequential methods

NASA Astrophysics Data System (ADS)

Oza, D. H.; Jones, T. L.; Hakimi, M.; Samii, Mina V.; Doll, C. E.; Mistretta, G. D.; Hart, R. C.

1993-02-01

The Goddard Space Flight Center (GSFC) Flight Dynamics Division (FDD) commissioned Applied Technology Associates, Incorporated, to develop the Real-Time Orbit Determination/Enhanced (RTOD/E) system on a Disk Operating System (DOS)-based personal computer (PC) as a prototype system for sequential orbit determination of spacecraft. This paper presents the results of a study to compare the orbit determination accuracy for a Tracking and Data Relay Satellite System (TDRSS) user spacecraft, Landsat-4, obtained using RTOD/E, operating on a PC, with the accuracy of an established batch least-squares system, the Goddard Trajectory Determination System (GTDS), and operating on a mainframe computer. The results of Landsat-4 orbit determination will provide useful experience for the Earth Observing System (EOS) series of satellites. The Landsat-4 ephemerides were estimated for the January 17-23, 1991, timeframe, during which intensive TDRSS tracking data for Landsat-4 were available. Independent assessments were made of the consistencies (overlap comparisons for the batch case and covariances and the first measurement residuals for the sequential case) of solutions produced by the batch and sequential methods. The forward-filtered RTOD/E orbit solutions were compared with the definitive GTDS orbit solutions for Landsat-4; the solution differences were less than 40 meters after the filter had reached steady state.

TDRSS-user orbit determination using batch least-squares and sequential methods

NASA Technical Reports Server (NTRS)

Oza, D. H.; Jones, T. L.; Hakimi, M.; Samii, Mina V.; Doll, C. E.; Mistretta, G. D.; Hart, R. C.

1993-01-01

The Goddard Space Flight Center (GSFC) Flight Dynamics Division (FDD) commissioned Applied Technology Associates, Incorporated, to develop the Real-Time Orbit Determination/Enhanced (RTOD/E) system on a Disk Operating System (DOS)-based personal computer (PC) as a prototype system for sequential orbit determination of spacecraft. This paper presents the results of a study to compare the orbit determination accuracy for a Tracking and Data Relay Satellite System (TDRSS) user spacecraft, Landsat-4, obtained using RTOD/E, operating on a PC, with the accuracy of an established batch least-squares system, the Goddard Trajectory Determination System (GTDS), and operating on a mainframe computer. The results of Landsat-4 orbit determination will provide useful experience for the Earth Observing System (EOS) series of satellites. The Landsat-4 ephemerides were estimated for the January 17-23, 1991, timeframe, during which intensive TDRSS tracking data for Landsat-4 were available. Independent assessments were made of the consistencies (overlap comparisons for the batch case and covariances and the first measurement residuals for the sequential case) of solutions produced by the batch and sequential methods. The forward-filtered RTOD/E orbit solutions were compared with the definitive GTDS orbit solutions for Landsat-4; the solution differences were less than 40 meters after the filter had reached steady state.

Uranium isotopes quantitatively determined by modified method of atomic absorption spectrophotometry

NASA Technical Reports Server (NTRS)

Lee, G. H.

1967-01-01

Hollow-cathode discharge tubes determine the quantities of uranium isotopes in a sample by using atomic absorption spectrophotometry. Dissociation of the uranium atoms allows a large number of ground state atoms to be produced, absorbing the incident radiation that is different for the two major isotopes.

Cryogenic Calcite: A Morphologic and Isotopic Analog to the ALH84001 Carbonates

NASA Technical Reports Server (NTRS)

Niles, P. B.; Leshin, L. A.; Socki, R. A.; Guan, Y.; Ming, D. W.; Gibson, E. K.

2004-01-01

Martian meteorite ALH84001 carbonates preserve large and variable microscale isotopic compositions, which in some way reflect their formation environment. These measurements show large variations (>20%) in the carbon and oxygen isotopic compositions of the carbonates on a 10-20 micron scale that are correlated with chemical composition. However, the utilization of these data sets for interpreting the formation conditions of the carbonates is complex due to lack of suitable terrestrial analogs and the difficulty of modeling under non-equilibrium conditions. Thus, the mechanisms and processes are largely unknown that create and preserve large microscale isotopic variations in carbonate minerals. Experimental tests of the possible environments and mechanisms that lead to large microscale isotopic variations can help address these concerns. One possible mechanism for creating large carbon isotopic variations in carbonates involves the freezing of water. Carbonates precipitate during extensive CO2 degassing that occurs during the freezing process as the fluid s decreasing volume drives CO2 out. This rapid CO2 degassing results in a kinetic isotopic fractionation where the CO2 gas has a much lighter isotopic composition causing an enrichment of 13C in the remaining dissolved bicarbonate. This study seeks to determine the suitability of cryogenically formed carbonates as analogs to ALH84001 carbonates. Specifically, our objective is to determine how accurately models using equilibrium fractionation factors approximate the isotopic compositions of cryogenically precipitated carbonates. This includes determining the accuracy of applying equilibrium fractionation factors during a kinetic process, and determining how isotopic variations in the fluid are preserved in microscale variations in the precipitated carbonates.

Determination of chemical purity and isotopic composition of natural and carbon-13-labeled arsenobetaine bromide standards by quantitative(1)H-NMR.

PubMed

Le, Phuong-Mai; Ding, Jianfu; Leek, Donald M; Mester, Zoltan; Robertson, Gilles; Windust, Anthony; Meija, Juris

2016-10-01

In this study, we report the characterization of three arsenobetaine-certified reference materials by quantitative NMR. We have synthesized an arsenobetaine bromide high-purity standard of natural isotopic composition (ABET-1) and two carbon-13-labeled isotopic standards (BBET-1 and CBET-1). Assignments of the chemical purity and isotopic composition are not trivial in the case of arsenobetaine, and in this study we utilized quantitative(1)H-NMR techniques for the determination of the mass fractions (chemical purity). The isotopic purity of all three standards was also assessed by NMR from the carbon-13 satellite signals. The standards are non-hygroscopic, high-purity (ca. 0.99 g/g), and the carbon-13 enrichment for both isotopic standards is x((13)C)≈0.99. These standards are designed for use as primary calibrators for mass spectrometric determination of arsenobetaine in environmental samples.

An isotopic comparison of cross-latitudinal horse hair data

NASA Astrophysics Data System (ADS)

Thompson, Elisabeth; Ramsey, Christopher

2017-04-01

This study explores whether the Rayleigh distillation process latitude effect, of depleted δ18O in precipitation toward the poles, can be observed in horse hair. This study specifically compares δ18O values in horse hair with meteorological variables, and examines whether regional changes in global climate can be observed. The sampling sites and the pony breeds used in this study will add to the increasing network of isotopic horse hair data and will create an even better understanding of the intra-species variation within the δ18O values of horse hair. By directly correlating the meteorological variables to δ18O variations, the effects of specific weather events at different latitudes can also be explored at a very high resolution. 24 horses were sampled within approximately 24 hours on the 7th March 2016 from Thordale Stud in Shetland; the Icelandic Food And Veterinary Authority in Iceland; the Exmoor Pony Centre in Exmoor; and the Pigeon House Equestrian Centre in Oxfordshire. Starting the sampling process from the most recent growth at the follicle, the sampling date becomes a chronological marker, temporally fixing the first sample within a sequential set of data points extending for one year or longer, depending on the length of each individual hair. Preliminary results confirm the hypothesis, demonstrating that a study of oxygen isotope ratios in horse hair from Oxfordshire to Iceland shows a latitudinal depletion gradient, consistent with a depletion of oxygen isotope ratios due to decreasing temperatures.

Biomedical applications of laser photoionization

NASA Astrophysics Data System (ADS)

Xiong, Xiaoxiong; Moore, Larry J.; Fassett, John R.; O'Haver, Thomas C.

1991-07-01

Trace elements are important for many essential metabolic functions. Zinc is a structural/functional component in more than 200 enzymes active in the biochemistry of cell division and tissue growth, neurology and endocrine control. Calcium is involved in intracellular control mechanisms and in skeletal bone building and resorption processes related to osteoporosis. Sensitive and selective laser photoionization is being developed to understand mechanisms in smaller samples and biological units approaching the cellular domain. Zinc has an ionization potential of 9.4 eV, or 75766.8 cm-1. Several processes are being explored, including two-photon resonant, three- photon ionization utilizing sequential UV transitions, e.g., 4s2 1S0 yields 4s4p 3P1 and 4s4p 3P1 yields 4s5d 3D1. Preliminary zinc stable isotope ratio data obtained by thermal atomization and laser photoionization agree with accepted values within 2 to 5%, except for anomalous 67Zn. Photoionization of calcium is being studied for isotope enrichment and ratio measurement using narrow and medium bandwidth lasers. Several ionization pathways, e.g., 4s2 1S0 - 2hv1 yields 4s10s - hv2 yields Ca+ (4s2S), are being investigated for isotopically selective ionization. Auto-ionization pathways are explored for greater efficiency in isotopic analysis. All studies have utilized a Nd:YAG- pumped laser system with one or two frequency-doubled tunable dye lasers coupled either to a magnetic sector or time-of-flight mass spectrometer.

Stable mercury isotope ratios as tracers for Hg cycling at the inoperative New Idria Hg mine, California

NASA Astrophysics Data System (ADS)

Wiederhold, J. G.; Jew, A. D.; Brown, G. E.; Bourdon, B.; Kretzschmar, R.

2010-12-01

The seven stable isotopes of Hg are fractionated in the environment as a result of mass-dependent (MDF) and mass-independent (MIF) fractionation processes that can be studied in parallel by analyzing the ratios of even and odd mass Hg isotopes. MDF and MIF Hg isotope signatures of natural samples may provide a new tool to trace sources and transformations in environmental Hg cycling. However, the mechanisms controlling the extent of kinetic and equilibrium Hg isotope fractionations are still only partially understood. Thus, development of this promising tracer requires experimental calibration of relevant fractionation factors as well as assessment of natural variations of Hg isotope ratios under different environmental conditions. The inoperative Hg mine in New Idria (California, USA) represents an ideal case study to explore Hg isotope fractionation during Hg transformation and transport processes. More than a century of Hg mining and on-site thermal refining to obtain elemental Hg until 1972 produced large volumes of contaminated mine wastes which now represent sources of Hg pollution for the surrounding ecosystems. Here, we present Hg isotope data from various materials collected at New Idria using Cold-Vapor-MC-ICPMS with a long-term δ202Hg reproducibility of ±0.1‰ (2SD). Uncalcined mine waste samples were isotopically similar to NIST-3133 and did not exhibit any MIF signatures. In contrast, calcine samples, which represent the residue of the thermal ore processing at 700°C, had significantly heavier δ202Hg values of up to +1.5‰. In addition, we observed small negative MIF anomalies of the odd-mass Hg isotopes in the calcine samples, which could be caused either by nuclear volume fractionation or a magnetic isotope effect during or after the roasting process. The mass-dependent enrichment of heavy Hg isotopes in the calcine materials indicates that light Hg isotopes were preferentially removed during the roasting process, in agreement with a previous study by Stetson et al. (ES&T, 2009, 43:7331-7336). In order to further elucidate the Hg isotope signatures of the New Idria samples, we performed a three-step sequential extraction procedure to separate different Hg pools. The calcine samples exhibited a higher proportion of leachable Hg phases compared with the unrefined ore waste samples. The most soluble Hg pool (HAc/HCl, pH 2) had a significantly heavier MDF and more negative MIF signature than the bulk calcine samples, suggesting that the dissolution of more soluble Hg phases from calcine materials results in an enhanced flux of leached Hg which is isotopically distinct from the original ore. Moreover, this finding demonstrates that the Hg isotope fractionation during the ore roasting cannot be solely explained by a kinetic Rayleigh-type process which removes light Hg isotopes, but must additionally involve the formation of isotopically heavy secondary Hg phases in the calcine. The analysis of additional samples will enable us to test this hypothesis and to gain further insights into the applicability of stable Hg isotope ratios as source and process tracers in Hg-contaminated environments.

Growth patterns of an intertidal gastropod as revealed by oxygen isotope analysis

NASA Astrophysics Data System (ADS)

Bean, J. R.; Hill, T. M.; Guerra, C.

2007-12-01

The size and morphology of mollusk shells are affected by environmental conditions. As a result, it is difficult to assess growth rate, population age structure, shell morphologies associated with ontogenetic stages, and to compare life history patterns across various environments. Oxygen isotope analysis is a useful tool for estimating minimum ages and growth rates of calcium carbonate secreting organisms. Calcite shell material from members of two northern California populations of the intertidal muricid gastropod Acanthinucella spirata was sampled for isotopic analysis. Individual shells were sampled from apex to margin, thus providing a sequential record of juvenile and adult growth. A. spirata were collected from a sheltered habitat in Tomales Bay and from an exposed reef in Bolinas. Abiotic factors, such as temperature, wave exposure, and substrate consistency, and biotic composition differ significantly between these sites, possibly resulting in local adaptations and variation in life history and growth patterns. Shell morphology of A. spirata changes with age as internal shell margin thickenings of denticle rows associated with external growth bands are irregularly accreted. It is not known when, either seasonally and/or ontogentically, these thickenings and bands form or whether inter or intra-populational variation exists. Preliminary results demonstrate the seasonal oxygen isotopic variability present at the two coastal sites, indicating 5-6 degC changes from winter to summertime temperatures; these data are consistent with local intertidal temperature records. Analysis of the seasonal patterns indicate that: 1) differences in growth rate and seasonal growth patterns at different ontogenetic stages within populations, and 2) differences in growth patterns and possibly age structure between the two A. spirata populations. These findings indicate that isotopic analyses, in addition to field observations and morphological measurements, are necessary to assess life history strategies and compare population dynamics under varying environmental conditions.

Medium rare or well done - how would you like your snail? Influence of cooking practices on the isotopic composition of land snails' shells

NASA Astrophysics Data System (ADS)

Kwiecien, O.; Breitenbach, S. F. M.

2017-12-01

Since the seminal work of Goodfriend (1992, EPSL 11), several studies confirmed a relation between the isotopic composition (δ18O, δ13C) of land snail shell carbonate, and environmental parameters like precipitation amount, moisture source, temperature and vegetation. This relation, however, is not straightforward and, importantly, site dependent. The choice of sampling strategy (discrete or bulk sampling), cleaning procedure, and/or pre-depositional history further complicate the shell analysis. The advantage of using snail shells as environmental archive lies in their limited mobility, and thus an intrinsic aptitude of recording local and site-specific conditions. However, snail shells found at archaeological sites, even if of local origin, often represent a dietary component and boiling/roasting could potentially alter the isotopic signature of aragonite material. While thermal processing affects the clumped isotope composition of carbonates, its influence on traditional isotopes is still debated (Ritter et al. 2017, Sedimentology; Müller et al. 2017, Scientific Reports). Consequently, a proper sampling strategy is of great importance and should be chosen according to scientific question. Horizontal high-resolution shell sampling (drill holes along growth axis, across growth lines) provides insights into the amplitude of seasonal variability, while vertical high-resolution sampling (multiple drill holes along the same growth line) produces reproducible results. We took advantage of this reproducibility and, on a yet unprecedented scale, experimentally and sequentially tested the influence of boiling on the δ18O and δ13C signature of shells of modern Helix pomatia. Our results challenge recent reports on alteration due to boiling (Müller et al., 2017, Scientific Reports) and support uncompromised application of snail shells from archeological sites for paleoenvironmental reconstructions.

System and method for high precision isotope ratio destructive analysis

DOEpatents

Bushaw, Bruce A; Anheier, Norman C; Phillips, Jon R

2013-07-02

A system and process are disclosed that provide high accuracy and high precision destructive analysis measurements for isotope ratio determination of relative isotope abundance distributions in liquids, solids, and particulate samples. The invention utilizes a collinear probe beam to interrogate a laser ablated plume. This invention provides enhanced single-shot detection sensitivity approaching the femtogram range, and isotope ratios that can be determined at approximately 1% or better precision and accuracy (relative standard deviation).

Distinguishing wild vs. stocked lake trout (Salvelinus namaycush) in Lake Ontario: Evidence from carbon and oxygen stable isotope values of otoliths

USGS Publications Warehouse

Schaner, T.; Patterson, W.P.; Lantry, B.F.; O'Gorman, R.

2007-01-01

We investigated the potential for using carbon and oxygen isotope values of otolith carbonate as a method to distinguish naturally produced (wild) lake trout (Salvelinus namaycush) from hatchery-reared lake trout in Lake Ontario. We determined δ 13C(CaCO3) and δ 18O(CaCO3) values of otoliths from juvenile fish taken from two hatcheries, and of otoliths from wild yearlings. Clear differences in isotope values were observed between the three groups. Subsequently we examined otoliths from large marked and unmarked fish captured in the lake, determining isotope values for regions of the otolith corresponding to the first year of life. Marked (i.e., stocked) fish showed isotope ratios similar to one of the hatchery groups, whereas unmarked fish, (wild fish or stocked fish that lost the mark) showed isotope ratios similar either to one of the hatchery groups or to the wild group. We interpret these data to suggest that carbon and oxygen isotope values can be used to determine the origin of lake trout in Lake Ontario, if a catalogue of characteristic isotope values from all candidate years and hatcheries is compiled.

Simultaneous determination of nitroimidazoles, benzimidazoles, and chloramphenicol components in bovine milk by ultra-high performance liquid chromatography-tandem mass spectrometry.

PubMed

Wang, Yuanyuan; Li, Xiaowei; Zhang, Zhiwen; Ding, Shuangyang; Jiang, Haiyang; Li, Jiancheng; Shen, Jianzhong; Xia, Xi

2016-02-01

A sensitive, confirmatory ultra-high performance liquid chromatography-tandem mass spectrometric method was developed and validated to detect 23 veterinary drugs and metabolites (nitroimidazoles, benzimidazoles, and chloramphenicol components) in bovine milk. Compounds of interest were sequentially extracted from milk with acetonitrile and basified acetonitrile using sodium chloride to induce liquid-liquid partition. The extract was purified on a mixed mode solid-phase extraction cartridge. Using rapid polarity switching in electrospray ionization, a single injection was capable of detecting both positively and negatively charged analytes in a 9 min chromatography run time. Recoveries based on matrix-matched calibrations and isotope labeled internal standards for milk ranged from 51.7% to 101.8%. The detection limits and quantitation limits of the analytical method were found to be within the range of 2-20 ng/kg and 5-50 ng/kg, respectively. The recommended method is simple, specific, and reliable for the routine monitoring of nitroimidazoles, benzimidazoles, and chloramphenicol components in bovine milk samples. Copyright © 2015 Elsevier Ltd. All rights reserved.

First Observation of Three-Neutron Sequential Emission from 25O

NASA Astrophysics Data System (ADS)

Sword, C.; Brett, J.; Deyoung, P. A.; Frank, N.; Karrick, H.; Kuchera, A. N.; MoNA Collaboration

2017-09-01

An active area of nuclear physics research is to evaluate models of the nuclear force by studying the structure of neutron-rich isotopes. In this experiment, a 101.3 MeV/u 27Ne beam from the National Superconducting Cyclotron Laboratory collided with a liquid deuterium target. The collision resulted in two-proton removal from the 27Ne beam which created excited 25O that decayed into three neutrons and an 22O fragment. The neutrons were detected by arrays of scintillating plastic bars, while a 4-Tesla dipole magnet placed directly after the target redirected charged fragments to a series of charged-particle detectors. From measured velocities of the neutrons and 22O fragments, the decay energy of 25O was calculated on an event-by-event basis with invariant mass spectroscopy. Using GEANT4, we simulated the decay of all nuclei that could have been created by the beam collision. By successfully fitting simulated decay processes to experimental data, we determined the decay processes present in the experiment. This work is supported by the National Science Foundation under Grants No. PHY-1306074 and No. PHY-1613188.

Examination of the Relation between TEOG Score of Turkish Revolution History and Kemalism Course and Reading Comprehension Skill (An Example of Explanatory Sequential Mixed Design)

ERIC Educational Resources Information Center

Yuvaci, Ibrahim; Demir, Selçuk Besir

2016-01-01

This paper is aimed to determine the relation between reading comprehension skill and TEOG success. In this research, a mixed research method, sequential explanatory mixed design, is utilized to examine the relation between reading comprehension skills and TEOG success of 8th grade students throughly. In explanatory sequential mixed design…

Quantitative Determination of Isotope Ratios from Experimental Isotopic Distributions

PubMed Central

Kaur, Parminder; O’Connor, Peter B.

2008-01-01

Isotope variability due to natural processes provides important information for studying a variety of complex natural phenomena from the origins of a particular sample to the traces of biochemical reaction mechanisms. These measurements require high-precision determination of isotope ratios of a particular element involved. Isotope Ratio Mass Spectrometers (IRMS) are widely employed tools for such a high-precision analysis, which have some limitations. This work aims at overcoming the limitations inherent to IRMS by estimating the elemental isotopic abundance from the experimental isotopic distribution. In particular, a computational method has been derived which allows the calculation of 13C/12C ratios from the whole isotopic distributions, given certain caveats, and these calculations are applied to several cases to demonstrate their utility. The limitations of the method in terms of the required number of ions and S/N ratio are discussed. For high-precision estimates of the isotope ratios, this method requires very precise measurement of the experimental isotopic distribution abundances, free from any artifacts introduced by noise, sample heterogeneity, or other experimental sources. PMID:17263354

Determination of lithium isotopes at natural abundance levels by atomic absorption spectrometry

USGS Publications Warehouse

Meier, A.L.

1982-01-01

The relationships of the absorption of 6Li and 7Li hollow cathode lamp emissions are used to determine lithium isotopic composition in the natural abundance range of geologic materials. Absorption was found to have a nonlinear dependence upon total lithium concentration and isotopic composition. A method using nonlinear equations to describe the relationship of the absorption of 6Li and 7Li lamp radiation is proposed as a means of calculating isotopic composition that is independent of total lithium concentration.

Improved solution accuracy for TDRSS-based TOPEX/Poseidon orbit determination

NASA Technical Reports Server (NTRS)

Doll, C. E.; Mistretta, G. D.; Hart, R. C.; Oza, D. H.; Bolvin, D. T.; Cox, C. M.; Nemesure, M.; Niklewski, D. J.; Samii, M. V.

1994-01-01

Orbit determination results are obtained by the Goddard Space Flight Center (GSFC) Flight Dynamics Division (FDD) using a batch-least-squares estimator available in the Goddard Trajectory Determination System (GTDS) and an extended Kalman filter estimation system to process Tracking and Data Relay Satellite (TDRS) System (TDRSS) measurements. GTDS is the operational orbit determination system used by the FDD in support of the Ocean Topography Experiment (TOPEX)/Poseidon spacecraft navigation and health and safety operations. The extended Kalman filter was implemented in an orbit determination analysis prototype system, closely related to the Real-Time Orbit Determination System/Enhanced (RTOD/E) system. In addition, the Precision Orbit Determination (POD) team within the GSFC Space Geodesy Branch generated an independent set of high-accuracy trajectories to support the TOPEX/Poseidon scientific data. These latter solutions use the geodynamics (GEODYN) orbit determination system with laser ranging and Doppler Orbitography and Radiopositioning integrated by satellite (DORIS) tracking measurements. The TOPEX/Poseidon trajectories were estimated for November 7 through November 11, 1992, the timeframe under study. Independent assessments were made of the consistencies of solutions produced by the batch and sequential methods. The batch-least-squares solutions were assessed based on the solution residuals, while the sequential solutions were assessed based on primarily the estimated covariances. The batch-least-squares and sequential orbit solutions were compared with the definitive POD orbit solutions. The solution differences were generally less than 2 meters for the batch-least-squares and less than 13 meters for the sequential estimation solutions. After the sequential estimation solutions were processed with a smoother algorithm, position differences with POD orbit solutions of less than 7 meters were obtained. The differences among the POD, GTDS, and filter/smoother solutions can be traced to differences in modeling and tracking data types, which are being analyzed in detail.

Mass-spectrometric mining of Hadean zircons by automated SHRIMP multi-collector and single-collector U/Pb zircon age dating: The first 100,000 grains

NASA Astrophysics Data System (ADS)

Holden, Peter; Lanc, Peter; Ireland, Trevor R.; Harrison, T. Mark; Foster, John J.; Bruce, Zane

2009-09-01

The identification and retrieval of a large population of ancient zircons (>4 Ga; Hadean) is of utmost priority if models of the early evolution of Earth are to be rigorously tested. We have developed a rapid and accurate U-Pb zircon age determination protocol utilizing a fully automated multi-collector ion microprobe, the ANU SHRIMP II, to screen and date these zircons. Unattended data acquisition relies on the calibration of a digitized sample map to the Sensitive High Resolution Ion MicroProbe (SHRIMP) sample-stage co-ordinate system. High precision positioning of individual grains can be produced through optical image processing of a specified mount location. The focal position of the mount can be optimized through a correlation between secondary-ion steering and the spot position on the target. For the Hadean zircon project, sample mounts are photographed and sample locations (normally grain centers) are determined off-line. The sample is loaded, reference points calibrated, and the target positions are then visited sequentially. In SHRIMP II multiple-collector mode, zircons are initially screened (ca. 5 s data acquisition) through their 204Pb corrected 207Pb/206Pb ratio; suitable candidates are then analyzed in a longer routine to obtain better measurement statistics, U/Pb, and concentration data. In SHRIMP I and SHRIMP RG, we have incorporated the automated analysis protocol to single-collector measurements. These routines have been used to analyze over 100,000 zircons from the Jack Hills quartzite. Of these, ca. 7%, have an age greater than 3.8 Ga, the oldest grain being 4372 +/- 6 Ma (2[sigma]), and this age is part of a group of analyses around 4350 Ma which we interpret as the age when continental crust first began to coalesce in this region. In multi-collector mode, the analytical time taken for a single mount with 400 zircons is approximately 6 h; whereas in single-collector mode, the analytical time is ca. 17 h. With this productivity, we can produce significant numbers of zircons for statistically limited studies including correlations between age and morphology, mineral-inclusion paragenesis, as well as isotopic studies including Hf and O isotopic compositions, Pu-Xe, and Sm-Nd isotopes.

Isotopic Composition of the Neolithic Alpine Iceman's Tooth Enamel and Clues to his Origin

NASA Astrophysics Data System (ADS)

Muller, W.; Muller, W.; Halliday, A. N.

2001-12-01

Five small enamel fragments from three teeth of the upper right jaw from the mummy of the Neolithic Alpine Iceman have been investigated for their isotopic composition in order to shed light on his geographic origins. Soils from approximately contemporaneous sites were sampled for comparison. Tooth enamel forms ontogenetically very early and is not re-mineralized during later lifetime (unlike with bone material). Therefore, unique insights into the Iceman's childhood can be acquired. Enamel also is the densest tissue of a human body and is thus less susceptible to post-mortem alteration. Both radiogenic (Sr, Pb, Nd) and stable isotopes (O, C) are investigated. Radiogenic isotopes allow reconstruction of the local geological background, because humans incorporate Sr, Pb and Nd from their local environment by eating local food. Stable isotopes provide information about altitude and/or position relative to the main Alpine watershed. High spatial-resolution laser-ablation ICPMS profiles reveal that most elements are distributed in a manner that is essentially similar to modern human teeth except of that La, Ce, Nd (LREE) show up to a 100-fold enrichment towards the outer enamel surface. These uptake-profiles may reflect interaction with melt water, consistent with data for the composition of samples of the Iceman's skin. Biogenic apatites (enamel, bone) have very low in-vivo LREE concentrations, but take up LREEs post-mortem from the burial environment. Ice core samples from the finding site show concentrations up to 400 ppt Ce. Such high uptake of the LREEs precludes the derivation of an in-vivo Nd isotopic signal, but both other radiogenic tracers, Sr and Pb, show pristine (in-vivo) concentrations of 87 ppm and 0.1 ppm, respectively. Strontium isotopic compositions were determined on fragments from the canine, the first and second premolar (1 - 9 mg) and two hip bone samples, utilizing three sequential leaching steps for each sample to detect possible alteration-related disturbance. Enamel fragments from three teeth are characterized by virtually similar and high 87Sr/^{86}Sr ratios of 0.7203-0.7206, consistent with the compositions of crystalline gneisses and schists close to the finding site. Sites overlying bedrock built up by limestone from further south or north can clearly be excluded as the Iceman's childhood area. Among the three teeth, enamel mineralized approximately during a 2-3 year interval starting with the canine at the age of ~2 years. Hence, during this period, the food source for the Iceman must have remained essentially constant. Two compact bone samples from the damaged hip region have 87Sr/^{86}Sr ratios of 0.7175 and 0.7181, significantly lower than that of the enamel. The internal variation in the Iceman's bone Sr isotopic composition argues for somewhat different Sr turnover times within the skeleton, but it is evident that during the last 1-3 decades of his life, food from a different region was utilized. The 87Sr/^{86}Sr ratios of the initial bone leachates point towards post-mortem alteration with water having 87Sr/^{86}Sr ratios higher than ~0.718, consistent with that measured for contemporaneous ice samples (0.720-0.723). These Sr isotopic variations among ice samples may have implications for the post depositional (climate) history of the Iceman's finding site, since it appears unlikely that substantial compositional differences among adjacent ice samples would be preserved if the site had thawed near completely during e.g. the Roman warm period.

Transient signal isotope analysis: validation of the method for isotope signal synchronization with the determination of amplifier first-order time constants.

PubMed

Gourgiotis, Alkiviadis; Manhès, Gérard; Louvat, Pascale; Moureau, Julien; Gaillardet, Jérôme

2015-09-30

During transient signal acquisition by Multi-Collection Inductively Coupled Plasma Mass Spectrometry (MC-ICPMS), an isotope ratio increase or decrease (isotopic drift hereafter) is often observed which is related to the different time responses of the amplifiers involved in multi-collection. This isotopic drift affects the quality of the isotopic data and, in a recent study, a method of internal amplifier signal synchronization for isotope drift correction was proposed. In this work the determination of the amplifier time constants was investigated in order to validate the method of internal amplifier signal synchronization for isotope ratio drift correction. Two different MC-ICPMS instruments, the Neptune and the Neptune Plus, were used, and both the lead transient signals and the signal decay curves of the amplifiers were investigated. Our results show that the first part of the amplifier signal decay curve is characterized by a pure exponential decay. This part of the signal decay was used for the effective calculation of the amplifier first-order time constants. The small differences between these time constants were compared with time lag values obtained from the method of isotope signal synchronization and were found to be in good agreement. This work proposes a way of determining amplifier first-order time constants. We show that isotopic drift is directly related to the amplifier first-order time constants and the method of internal amplifier signal synchronization for isotope ratio drift correction is validated. Copyright © 2015 John Wiley & Sons, Ltd.

Physics-based, Bayesian sequential detection method and system for radioactive contraband

DOEpatents

Candy, James V; Axelrod, Michael C; Breitfeller, Eric F; Chambers, David H; Guidry, Brian L; Manatt, Douglas R; Meyer, Alan W; Sale, Kenneth E

2014-03-18

A distributed sequential method and system for detecting and identifying radioactive contraband from highly uncertain (noisy) low-count, radionuclide measurements, i.e. an event mode sequence (EMS), using a statistical approach based on Bayesian inference and physics-model-based signal processing based on the representation of a radionuclide as a monoenergetic decomposition of monoenergetic sources. For a given photon event of the EMS, the appropriate monoenergy processing channel is determined using a confidence interval condition-based discriminator for the energy amplitude and interarrival time and parameter estimates are used to update a measured probability density function estimate for a target radionuclide. A sequential likelihood ratio test is then used to determine one of two threshold conditions signifying that the EMS is either identified as the target radionuclide or not, and if not, then repeating the process for the next sequential photon event of the EMS until one of the two threshold conditions is satisfied.

Precise and accurate isotope ratio measurements by ICP-MS.

PubMed

Becker, J S; Dietze, H J

2000-09-01

The precise and accurate determination of isotope ratios by inductively coupled plasma mass spectrometry (ICP-MS) and laser ablation ICP-MS (LA-ICP-MS) is important for quite different application fields (e.g. for isotope ratio measurements of stable isotopes in nature, especially for the investigation of isotope variation in nature or age dating, for determining isotope ratios of radiogenic elements in the nuclear industry, quality assurance of fuel material, for reprocessing plants, nuclear material accounting and radioactive waste control, for tracer experiments using stable isotopes or long-lived radionuclides in biological or medical studies). Thermal ionization mass spectrometry (TIMS), which used to be the dominant analytical technique for precise isotope ratio measurements, is being increasingly replaced for isotope ratio measurements by ICP-MS due to its excellent sensitivity, precision and good accuracy. Instrumental progress in ICP-MS was achieved by the introduction of the collision cell interface in order to dissociate many disturbing argon-based molecular ions, thermalize the ions and neutralize the disturbing argon ions of plasma gas (Ar+). The application of the collision cell in ICP-QMS results in a higher ion transmission, improved sensitivity and better precision of isotope ratio measurements compared to quadrupole ICP-MS without the collision cell [e.g., for 235U/238U approximately 1 (10 microg x L(-1) uranium) 0.07% relative standard deviation (RSD) vs. 0.2% RSD in short-term measurements (n = 5)]. A significant instrumental improvement for ICP-MS is the multicollector device (MC-ICP-MS) in order to obtain a better precision of isotope ratio measurements (with a precision of up to 0.002%, RSD). CE- and HPLC-ICP-MS are used for the separation of isobaric interferences of long-lived radionuclides and stable isotopes by determination of spallation nuclide abundances in an irradiated tantalum target.

A carbon isotope mass balance for an anoxic marine sediment: Isotopic signatures of diagenesis

NASA Technical Reports Server (NTRS)

Boehme, Susan E.

1993-01-01

A carbon isotope mass balance was determined for the sediments of Cape Lookout Bight, NC to constrain the carbon budgets published previously. The diffusive, ebullitive and burial fluxes of sigma CO2 and CH4, as well as the carbon isotope signatures of these fluxes, were measured. The flux-weighted isotopic signature of the remineralized carbon (-18.9 plus or minus 2.7 per mil) agreed with the isotopic composition of the remineralized organic carbon determined from the particulate organic carbon (POC) delta(C-13) profiles (-19.2 plus or minus 0.2), verifying the flux and isotopic signature estimates. The measured delta(C-13) values of the sigma CO2 and CH4 diffusive fluxes were significantly different from those calculated from porewater gradients. The differences appear to be influenced by methane oxidation at the sediment-water interface, although other potential processes cannot be excluded. The isotope mass balance provides important information concerning the locations of potential diagenetic isotope effects. Specifically, the absence of downcore change in the delta(C-13) value of the POC fraction and the identical isotopic composition of the POC and the products of remineralization indicate that no isotopic fractionation is expressed during the initial breakdown of the POC, despite its isotopically heterogeneous composition.

Analysis of plutonium isotope ratios including 238Pu/239Pu in individual U-Pu mixed oxide particles by means of a combination of alpha spectrometry and ICP-MS.

PubMed

Esaka, Fumitaka; Yasuda, Kenichiro; Suzuki, Daisuke; Miyamoto, Yutaka; Magara, Masaaki

2017-04-01

Isotope ratio analysis of individual uranium-plutonium (U-Pu) mixed oxide particles contained within environmental samples taken from nuclear facilities is proving to be increasingly important in the field of nuclear safeguards. However, isobaric interferences, such as 238 U with 238 Pu and 241 Am with 241 Pu, make it difficult to determine plutonium isotope ratios in mass spectrometric measurements. In the present study, the isotope ratios of 238 Pu/ 239 Pu, 240 Pu/ 239 Pu, 241 Pu/ 239 Pu, and 242 Pu/ 239 Pu were measured for individual Pu and U-Pu mixed oxide particles by a combination of alpha spectrometry and inductively coupled plasma mass spectrometry (ICP-MS). As a consequence, we were able to determine the 240 Pu/ 239 Pu, 241 Pu/ 239 Pu, and 242 Pu/ 239 Pu isotope ratios with ICP-MS after particle dissolution and chemical separation of plutonium with UTEVA resins. Furthermore, 238 Pu/ 239 Pu isotope ratios were able to be calculated by using both the 238 Pu/( 239 Pu+ 240 Pu) activity ratios that had been measured through alpha spectrometry and the 240 Pu/ 239 Pu isotope ratios determined through ICP-MS. Therefore, the combined use of alpha spectrometry and ICP-MS is useful in determining plutonium isotope ratios, including 238 Pu/ 239 Pu, in individual U-Pu mixed oxide particles. Copyright © 2016 Elsevier B.V. All rights reserved.

Determining and quantifying specific sources of light alkane

NASA Astrophysics Data System (ADS)

Bill, M.; Conrad, M. E.

2015-12-01

Determining and quantifying specific sources of emission of methane (an important greenhouse gas) and light alkanes from abandoned gas and oil wells, hydraulic fracturing or associated with CO2 sequestration are a challenge in determining their contribution to the atmospheric greenhouse gas budget or to identify source of groundwater contamination. Here, we review organic biogeochemistry proprieties and isotopic fingerprinting of C1-C5 alkanes to address this problem. For instance, the concentration ratios of CH4 to C2-C5 alkanes can be used to distinguish between thermogenic and microbial generated CH4. Together C and H isotopes of CH4 are used to differentiate bacterial generated sources and thermogenic CH4 and may also identify processes such as alteration and source mixing. Carbon isotope ratios pattern of C1-C5 alkanes highlight sources and oxidation processes in the gas reservoirs. Stable carbon isotope measurements are a viable tool for monitoring the degradation progress of methane and light hydrocarbons. The carbon isotope ratios of the reactants and products are independent of the concentration and only depend on the relative progress of the particular reaction. Oxidation/degradation of light alkanes are typically associated with increasing ð13C values. Isotopic mass balances offer the possibility to independently determine the fractions coming from microbial versus thermogenic and would also permit differentiation of the isotope fractionations associated with degradation. Unlike conventional concentration measurements, this approach is constrained by the different isotopic signatures of various sources and sinks.

Freeze-dried Lactobacillus plantarum 299v increases iron absorption in young females—Double isotope sequential single-blind studies in menstruating women

PubMed Central

Önning, Gunilla; Hulthén, Lena

2017-01-01

Background The probiotic strain Lactobacillus plantarum 299v has earlier been shown to increase iron absorption when added to foods. However, it is not known if the same probiotic strain in a freeze-dried format included in a capsule increases the iron absorption. Objective The aim of this study was to test the hypotheses that non-heme iron absorption from a light meal is promoted by a simultaneous intake of freeze-dried Lactobacillus plantarum 299v (Lp299v, DSM 9843). Study design With a single blinded placebo controlled sequential design, iron absorption from a light breakfast meal administered with or without capsules containing 1010 cfu freeze-dried Lp299v was studied in healthy female volunteers of fertile age. The methodology used was a double isotope technique (59Fe and 55Fe). Two studies were performed using the same protocol. Results In study 1, the absorption of iron from a meal without Lp299v was found to be 17.4 ± 13.4%, and from an identical meal with Lp299v was found to be 22.4 ± 17.3% (mean ± SD). This difference was statistically significant (p = 0.040, n = 14). In study 2, the absorption of iron from a meal without Lp299v was found to be 20.9 ± 13.1%, and from an identical meal with Lp299v found to be 24.5 ± 12.0% (mean ± SD, n = 28), which again was statistically significant (p = 0.003). Conclusion Freeze-dried Lp299v enhances the absorption of iron when administered together with a meal with a high iron bioavailability. Trial registration ClinicalTrials.gov Identifier: NCT02131870 PMID:29236734

Malic enzyme: Tritium isotope effects with alternative dinucleotide substrates and divalent metal ions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Karsten, W.E.; Harris, B.G.; Cook, P.F.

1992-01-01

The NAD-malic enzyme from Ascaris suum catalyzes the divalent metal ion dependent oxidative decarboxylation of L-malate to yield pyruvate, carbon dioxide and NADH. Multiple isotope effect studies suggest a stepwise chemical mechanism with hydride transfer from L-malate to NAD occurring first to form oxalacetate, followed by decarboxylation. Utilizing L-malate-2-T, tritium V/K isotope effects have been determined for the hydride transfer step using a variety of alternative dinucleotide substrates and divalent metal ions. Combination of these data with deuterium isotope effects data and previously determined [sup 13]C isotope effects has allowed the calculation of intrinsic isotope effects for the malic enzymemore » catalyzed reaction. The identity of both the dinucleotide substrate and divalent metal ion has an effect of the size of the intrinsic isotope effect for hydride transfer.« less

Analysis of Inter- and Intra-individual Variation in Foraging Habits of the Endangered Hawaiian Petrel Using Stables Isotopes

NASA Astrophysics Data System (ADS)

Morra, K. E.; Ostrom, P. H.; Wiley, A. E.; James, H. F.; Stricker, C. A.; Gandhi, H.

2014-12-01

Stable isotope analysis of the endangered Hawaiian petrel's (Pterodroma sandwichensis, HAPE) feathers provides otherwise intractable information regarding non-breeding season foraging habits. Adult HAPE spend 3.5-6 months at sea during the non-breeding season, at which time they sequentially molt their flight feathers. Because feathers are metabolically inert once synthesized, they capture isotopic signals while they are grown, providing an opportunity to study foraging habits over time. Here we use stable hydrogen (δD), carbon (δ13C) and nitrogen (δ15N) isotopes to assess variation in foraging habits within and between individuals, and among four breeding colonies. δD is an indicator of prevalence of fish vs. invertebrates in the diet. In one analysis, we observed large variation in feather δD (125‰), with adults from Maui and Kauai having significantly higher δD values than corresponding hatch-year birds, indicating significant dietary differences between age groups. In a second analysis, we utilized δ13C and δ15N of Hawaii, Maui and Lanai adults, values which vary with trophic level and also at the base of the food web across HAPE's foraging range, potentially revealing information about feeding location, as well as diet. Furthermore, because the sequence of molt is known, we are able to determine whether individual foraging specialization (continued use of the same foraging behavior over time) exists in this species. To do this, we analyzed two primary feathers, P1 and P6, which reflect the beginning and the middle of the non-breeding season, respectively. We did not find significant differences in δ13C or δ15N between P1 and P6, suggesting consistent foraging habits within individuals over time. This provides evidence that individual foraging specialization exists within these populations. Analysis of a secondary feather grown late in the molt sequence would further illuminate the extent of foraging specialization. Finally, δ15N differs significantly between Hawaii and Maui adults, suggesting foraging segregation between these two populations. HAPE may be sensitive to changes in prey availability, given evidence of foraging specialization. However, conserving HAPE populations with apparently different foraging habits may be critical to preserve ecological diversity within the species.

Effects of must concentration techniques on wine isotopic parameters.

PubMed

Guyon, Francois; Douet, Christine; Colas, Sebastien; Salagoïty, Marie-Hélène; Medina, Bernard

2006-12-27

Despite the robustness of isotopic methods applied in the field of wine control, isotopic values can be slightly influenced by enological practices. For this reason, must concentration technique effects on wine isotopic parameters were studied. The two studied concentration techniques were reverse osmosis (RO) and high-vacuum evaporation (HVE). Samples (must and extracted water) have been collected in various French vineyards. Musts were microfermented at the laboratory, and isotope parameters were determined on the obtained wine. Deuterium and carbon-13 isotope ratios were studied on distilled ethanol by nuclear magnetic resonance (NMR) and isotope ratio mass spectrometry (IRMS), respectively. The oxygen-18 ratio was determined on extracted and wine water using IRMS apparatus. The study showed that the RO technique has a very low effect on isotopic parameters, indicating that this concentration technique does not create any isotopic fractionation, neither at sugar level nor at water level. The effect is notable for must submitted to HVE concentration: water evaporation leads to a modification of the oxygen-18 ratio of the must and, as a consequence, ethanol deuterium concentration is also modified.

A Method to Determine 18O Kinetic Isotope Effects in the Hydrolysis of Nucleotide Triphosphates

PubMed Central

Du, Xinlin; Ferguson, Kurt; Sprang, Stephen R.

2007-01-01

A method to determine 18O kinetic isotope effects (KIE) in the hydrolysis of GTP is described that is generally applicable to reactions involving other nucleotide triphosphates. Internal competition, wherein the substrate of the reaction is a mixture of 18O-labeled and unlabeled nucleotides, is employed and the change in relative abundance of the two species in the course of the reaction is used to calculate KIE. The nucleotide labeled with 18O at sites of mechanistic interest also contains 13C at all carbon positions, while the 16O-nucleotide is depleted of 13C. The relative abundance of the labeled and unlabeled substrates or products is reflected in the carbon isotope ratio (13C/12C) in GTP or GDP, which is determined by use of a liquid chromatography-coupled isotope ratio mass spectrometer (LC-coupled IRMS). The LC is coupled to the IRMS by an Isolink™ interface (ThermoFinnigan). Carbon isotope ratios can be determined with accuracy and precision greater than 0.04%, and are consistent over an order of magnitude in sample amount. KIE values for Ras/NF1333-catalyzed hydrolysis of [β18O3,13C]GTP were determined by change in the isotope ratio of GTP or GDP or the ratio of the isotope ratio of GDP to that of GTP. KIE values computed in the three ways agree within 0.1%, although the method using the ratio of isotope ratios of GDP and GTP gives superior precision (< 0.1%). A single KIE measurement can be conducted in 25 minutes with less than 5 μg nucleotide reaction product. PMID:17963711

Evaluation strategies for isotope ratio measurements of single particles by LA-MC-ICPMS.

PubMed

Kappel, S; Boulyga, S F; Dorta, L; Günther, D; Hattendorf, B; Koffler, D; Laaha, G; Leisch, F; Prohaska, T

2013-03-01

Data evaluation is a crucial step when it comes to the determination of accurate and precise isotope ratios computed from transient signals measured by multi-collector-inductively coupled plasma mass spectrometry (MC-ICPMS) coupled to, for example, laser ablation (LA). In the present study, the applicability of different data evaluation strategies (i.e. 'point-by-point', 'integration' and 'linear regression slope' method) for the computation of (235)U/(238)U isotope ratios measured in single particles by LA-MC-ICPMS was investigated. The analyzed uranium oxide particles (i.e. 9073-01-B, CRM U010 and NUSIMEP-7 test samples), having sizes down to the sub-micrometre range, are certified with respect to their (235)U/(238)U isotopic signature, which enabled evaluation of the applied strategies with respect to precision and accuracy. The different strategies were also compared with respect to their expanded uncertainties. Even though the 'point-by-point' method proved to be superior, the other methods are advantageous, as they take weighted signal intensities into account. For the first time, the use of a 'finite mixture model' is presented for the determination of an unknown number of different U isotopic compositions of single particles present on the same planchet. The model uses an algorithm that determines the number of isotopic signatures by attributing individual data points to computed clusters. The (235)U/(238)U isotope ratios are then determined by means of the slopes of linear regressions estimated for each cluster. The model was successfully applied for the accurate determination of different (235)U/(238)U isotope ratios of particles deposited on the NUSIMEP-7 test samples.

Determination of tin isotope ratios in cassiterite by femtosecond laser ablation multicollector inductively coupled plasma mass spectrometry

NASA Astrophysics Data System (ADS)

Schulze, Marie; Ziegerick, Marco; Horn, Ingo; Weyer, Stefan; Vogt, Carla

2017-04-01

In comparison to isotope analysis of dissolved samples femtosecond laser ablation multicollector inductively coupled plasma mass spectrometry (fs-LA-MC-ICP-MS) enables precise isotope ratio analyses consuming much less sample material and with a minimum effort in sample preparation. This is especially important for the investigation of valuable historical objects for which visual traces of sampling are unwanted. The present study provides a basis for tin isotope ratio measurements using LA-MC-ICP-MS technique. For this, in house isotope standards had to be defined. Investigations on interferences and matrix effects illustrate that beside Sb only high Te contents (with values above those to be expected in cassiterite) result in a significant shift of the measured tin isotope ratios. This effect can partly be corrected for using natural isotope abundances. However, a natural isotope fractionation of Te cannot be excluded. Tin beads reduced from cassiterite were analysed by laser ablation and after dissolution. It was shown that tin isotope ratios can be determined accurately by using fs-LA-MC-ICP-MS. Furthermore the homogeneity of tin isotope ratios in cassiterite was proven.

INCORPORATING CONCENTRATION DEPENDENCE IN STABLE ISOTOPE MIXING MODELS

EPA Science Inventory

Stable isotopes are frequently used to quantify the contributions of multiple sources to a mixture; e.g., C and N isotopic signatures can be used to determine the fraction of three food sources in a consumer's diet. The standard dual isotope, three source linear mixing model ass...

INCORPORATING CONCENTRATION DEPENDENCE IN STABLE ISOTOPE MIXING MODELS

EPA Science Inventory

Stable isotopes are often used as natural labels to quantify the contributions of multiple sources to a mixture. For example, C and N isotopic signatures can be used to determine the fraction of three food sources in a consumer's diet. The standard dual isotope, three source li...

Diagnosis and assessment of skeletal related disease using calcium 41

DOEpatents

Hillegonds, Darren J [Oakland, CA; Vogel, John S [San Jose, CA; Fitzgerald, Robert L [Encinitas, CA; Deftos, Leonard J [Del Mar, CA; Herold, David [Del Mar, CA; Burton, Douglas W [San Diego, CA

2012-05-15

A method of determining calcium metabolism in a patient comprises the steps of administering radioactive calcium isotope .sup.41Ca to the patient, allowing a period of time to elapse sufficient for dissemination and reaction of the radioactive calcium isotope .sup.41Ca by the patient, obtaining a sample of the radioactive calcium isotope .sup.41Ca from the patient, isolating the calcium content of the sample in a form suitable for precise measurement of isotopic calcium concentrations, and measuring the calcium content to determine parameters of calcium metabolism in the patient.

Diagnosis and assessment of skeletal related disease using calcium 41

DOEpatents

Hillegonds, Darren J.; Vogel, John S.; Fitzgerald, Robert L.; Deftos, Leonard J.; Herold, David; Burton, Douglas W.

2013-03-05

A method of determining calcium metabolism in a patient comprises the steps of administering radioactive calcium isotope .sup.41Ca to the patient, allowing a period of time to elapse sufficient for dissemination and reaction of the radioactive calcium isotope .sup.41Ca by the patient, obtaining a sample of the radioactive calcium isotope .sup.41Ca from the patient, isolating the calcium content of the sample in a form suitable for precise measurement of isotopic calcium concentrations, and measuring the calcium content to determine parameters of calcium metabolism in the patient.

Enhanced forensic discrimination of pollutants by position-specific isotope analysis using isotope ratio monitoring by (13)C nuclear magnetic resonance spectrometry.

PubMed

Julien, Maxime; Nun, Pierrick; Höhener, Patrick; Parinet, Julien; Robins, Richard J; Remaud, Gérald S

2016-01-15

In forensic environmental investigations the main issue concerns the inference of the original source of the pollutant for determining the liable party. Isotope measurements in geochemistry, combined with complimentary techniques for contaminant identification, have contributed significantly to source determination at polluted sites. In this work we have determined the intramolecular (13)C profiles of several molecules well-known as pollutants. By giving additional analytical parameters, position-specific isotope analysis performed by isotope ratio monitoring by (13)C nuclear magnetic resonance (irm-(13)C NMR) spectrometry gives new information to help in answering the major question: what is the origin of the detected contaminant? We have shown that isotope profiling of the core of a molecule reveals both the raw materials and the process used in its manufacture. It also can reveal processes occurring between the contamination site 'source' and the sampling site. Thus, irm-(13)C NMR is shown to be a very good complement to compound-specific isotope analysis currently performed by mass spectrometry for assessing polluted sites involving substantial spills of pollutant. Copyright © 2015 Elsevier B.V. All rights reserved.

A multi-method approach toward de novo glycan characterization: a Man-5 case study.

PubMed

Prien, Justin M; Prater, Bradley D; Cockrill, Steven L

2010-05-01

Regulatory agencies' expectations for biotherapeutic approval are becoming more stringent with regard to product characterization, where minor species as low as 0.1% of a given profile are typically identified. The mission of this manuscript is to demonstrate a multi-method approach toward de novo glycan characterization and quantitation, including minor species at or approaching the 0.1% benchmark. Recently, unexpected isomers of the Man(5)GlcNAc(2) (M(5)) were reported (Prien JM, Ashline DJ, Lapadula AJ, Zhang H, Reinhold VN. 2009. The high mannose glycans from bovine ribonuclease B isomer characterization by ion trap mass spectrometry (MS). J Am Soc Mass Spectrom. 20:539-556). In the current study, quantitative analysis of these isomers found in commercial M(5) standard demonstrated that they are in low abundance (<1% of the total) and therefore an exemplary "litmus test" for minor species characterization. A simple workflow devised around three core well-established analytical procedures: (1) fluorescence derivatization; (2) online rapid resolution reversed-phase separation coupled with negative-mode sequential mass spectrometry (RRRP-(-)-MS(n)); and (3) permethylation derivatization with nanospray sequential mass spectrometry (NSI-MS(n)) provides comprehensive glycan structural determination. All methods have limitations; however, a multi-method workflow is an at-line stopgap/solution which mitigates each method's individual shortcoming(s) providing greater opportunity for more comprehensive characterization. This manuscript is the first to demonstrate quantitative chromatographic separation of the M(5) isomers and the use of a commercially available stable isotope variant of 2-aminobenzoic acid to detect and chromatographically resolve multiple M(5) isomers in bovine ribonuclease B. With this multi-method approach, we have the capabilities to comprehensively characterize a biotherapeutic's glycan array in a de novo manner, including structural isomers at >/=0.1% of the total chromatographic peak area.

Arsenic and metallic trace elements cycling in the surface water-groundwater-soil continuum down-gradient from a reclaimed mine area: Isotopic imprints

NASA Astrophysics Data System (ADS)

Khaska, Mahmoud; Le Gal La Salle, Corinne; Sassine, Lara; Cary, Lise; Bruguier, Olivier; Verdoux, Patrick

2018-03-01

One decade after closure of the Salsigne mine (SW France), As contamination persisted in surface water, groundwater and soil near and down-gradient from the reclaimed ore processing site (OPS). We assess the fate of As and other associated chalcophilic MTEs, and their transport in the surface-water/groundwater/soil continuum down-gradient from the reclaimed OPS, using Sr-isotopic fingerprinting. The Sr-isotope ratio was used as a tracer of transfer processes in this hydro-geosystem and was combined to sequential extraction of soil samples to evaluate the impact of contaminated soil on the underlying phreatic groundwater. The contrast in Sr isotope compositions of the different soil fractions reflects several Sr sources in the soil. In the complex hydro-geosystem around the OPS, the transport of As and MTEs is affected by a succession of factors, such as (1) Existence of a reducing zone in the aquifer below the reclaimed OPS, where groundwater shows relatively high As and MTEs contents, (2) Groundwater discharge into the stream near the reclaimed OPS causing an increase in As and MTE concentrations in surface water; (3) Partial co-precipitation of As with Fe-oxyhydroxides, contributing to some attenuation of As contents in surface water; (4) Infiltration of contaminated stream water into the unconfined aquifer down-gradient from the reclaimed OPS; (5) Accumulation of As and MTEs in soil irrigated with contaminated stream- and groundwater; (6) Release of As and MTEs from labile soil fractions to underlying the groundwater.

MIXING MODELS IN ANALYSES OF DIET USING MULTIPLE STABLE ISOTOPES: A CRITIQUE

EPA Science Inventory

Stable isotopes have become widely used in ecology to quantify the importance of different sources based on their isotopic signature. One example of this has been the determination of food webs, where the isotopic signatures of a predator and various prey items can be used to de...

Investigation of mass dependence effects for the accurate determination of molybdenum isotope amount ratios by MC-ICP-MS using synthetic isotope mixtures.

PubMed

Malinovsky, Dmitry; Dunn, Philip J H; Petrov, Panayot; Goenaga-Infante, Heidi

2015-01-01

Methodology for absolute Mo isotope amount ratio measurements by multicollector inductively coupled plasma-mass spectrometry (MC-ICP-MS) using calibration with synthetic isotope mixtures (SIMs) is presented. For the first time, synthetic isotope mixtures prepared from seven commercially available isotopically enriched molybdenum metal powders ((92)Mo, (94)Mo, (95)Mo, (96)Mo, (97)Mo, (98)Mo, and (100)Mo) are used to investigate whether instrumental mass discrimination of Mo isotopes in MC-ICP-MS is consistent with mass-dependent isotope distribution. The parent materials were dissolved and mixed as solutions to obtain mixtures with accurately known isotope amount ratios. The level of elemental impurities in the isotopically enriched molybdenum metal powders was quantified by ICP-MS by using both high-resolution and reaction cell instruments to completely resolve spectral interferences. The Mo isotope amount ratio values with expanded uncertainty (k = 2), determined by MC-ICP-MS for a high-purity Mo rod from Johnson Matthey, were as follows: (92)Mo/(95)Mo = 0.9235(9), (94)Mo/(95)Mo = 0.5785(8), (96)Mo/(95)Mo = 1.0503(9), (97)Mo/(95)Mo = 0.6033(6), (98)Mo/(95)Mo = 1.5291(20), and (100)Mo/(95)Mo = 0.6130(7). A full uncertainty budget for the measurements is presented which shows that the largest contribution to the uncertainty budget comes from correction for elemental impurities (∼51%), followed by the contribution from weighing operations (∼26 %). The atomic weight of molybdenum was calculated to be 95.947(2); the uncertainty in parentheses is expanded uncertainty with the coverage factor of 2. A particular advantage of the developed method is that calibration factors for all six Mo isotope amount ratios, involving the (95)Mo isotope, were experimentally determined. This allows avoiding any assumption on mass-dependent isotope fractions in MC-ICP-MS, inherent to the method of double spike previously used for Mo isotope amount ratio measurements. However, data obtained in this study show that instrumental mass discrimination in MC-ICP-MS is consistent with mass-dependent Mo isotope fractionation. This was demonstrated by a good agreement between experimentally obtained and theoretically expected values of the exponent of isotope fractionation, β, for each triad of Mo isotopes.

Thermal Diffusion Fractionation of Cr and V Isotope in Silicate Melt

NASA Astrophysics Data System (ADS)

Lin, X.; Lundstrom, C.

2017-12-01

Earth's mantle is isotopically heavy relative to chondrites for V, Cr and some other siderophile elements. A possible solution is that isotopic fractionation by thermal diffusion occurs in a thermal boundary layer between solid mantle and an underlying basal magma ocean (BMO:Labrosse et al.,2007). If so, isotopically light composition might partition into the core, resulting in a complimentary isotopically heavy solid mantle. To verify how much fractionation could happen in this process, piston cylinder experiment were conducted to investigate the fractionation of Cr and V isotope ratios in partially molten silicate under an imposed temperature gradient from 1650 °C to 1350 °C at 1 GPa for 10 to 50 hours to reach a steady state isotopic profile. The temperature profile for experiments was determined by the spinel-growth method at the same pressure and temperature. Experimental runs result in 100% glass at the hot end progressing to nearly 100 % olivine at the cold end. Major and minor element concentrations of run products show systematic changes with temperature. Glass MgO contents increase and Al2O3 and CaO contents decrease by several weight percent as temperature increases across the charge. These are well modeled using IRIDIUM (Boudreau 2003) to simulate the experiments. Isotopic composition measurements of Cr and V at different temperatures are in progress, providing the first determinations of thermal diffusion isotopic sensitivity, Ω (permil isotopic fractionation per temperature offset per mass unit) for these elements. These results will be compared with previously determined Ω for network formers and modifiers and used in a BMO-based thermal diffusion model for formation of Earth's isotopically heavy mantle.

Isotopic determinations of rhenium and osmium in meteorites by using fusion, distillation and ion-exchange separations

USGS Publications Warehouse

Morgan, J.W.; Walker, R.J.

1989-01-01

A stable isotope-dilution method using resonance ionization mass spectrometry is suitable for the determination of rhenium and osmium abundances and osmium isotopic composition in carbonaceous chondrites and iron meteorites. The chemical procedure involves sodium peroxide fusion, followed by distillation of osmium from sulfuric acid/hydrogen peroxide and subsequent anion-exchange separation of rhenium from the same solution. ?? 1989.

Redefining the utility of the three-isotope method

NASA Astrophysics Data System (ADS)

Cao, Xiaobin; Bao, Huiming

2017-09-01

The equilibrium isotope fractionation factor αeq is a fundamental parameter in the study of stable isotope effects. Experimentally, it has been difficult to establish that a system has attained equilibrium. The three-isotope method, using the initial trajectory of changing isotope ratios (e.g. 16O, 17O, and 18O) to deduce the final equilibrium point of isotope exchange, has long been hailed as the most rigorous experimental approach. However, over the years some researchers have cautioned on the limitations of this method, but the foundation of three-isotope method has not been properly examined and the method is still widely used in calibrating αeq for both traditional and increasingly non-traditional isotope systems today. Here, using water-water and dissolved CO2-water oxygen exchange as model systems, we conduct an isotopologues-specific kinetic analysis of the exchange processes and explore the underlying assumptions and validity of the three-isotope method. We demonstrate that without knowing the detailed exchange kinetics a priori the three-isotope method cannot lead to a reliable αeq. For a two-reservoir exchanging system, α determined by this method may be αeq, kinetic isotope effect, or apparent kinetic isotope effect, which can all bear different values. When multiple reservoirs exist during exchange, the evolving trajectory can be complex and hard to predict. Instead of being a tool for αeq determination, three-isotope method should be used as a tool for studying kinetic isotope effect, apparent kinetic isotope effect, and detailed exchange kinetics in diverse systems.

Development of particle induced gamma-ray emission methods for nondestructive determination of isotopic composition of boron and its total concentration in natural and enriched samples.

PubMed

Chhillar, Sumit; Acharya, Raghunath; Sodaye, Suparna; Pujari, Pradeep K

2014-11-18

We report simple particle induced gamma-ray emission (PIGE) methods using a 4 MeV proton beam for simultaneous and nondestructive determination of the isotopic composition of boron ((10)B/(11)B atom ratio) and total boron concentrations in various solid samples with natural isotopic composition and enriched with (10)B. It involves measurement of prompt gamma-rays at 429, 718, and 2125 keV from (10)B(p,αγ)(7)Be, (10)B(p, p'γ)(10)B, and (11)B(p, p'γ)(11)B reactions, respectively. The isotopic composition of boron in natural and enriched samples was determined by comparing peak area ratios corresponding to (10)B and (11)B of samples to natural boric acid standard. An in situ current normalized PIGE method, using F or Al, was standardized for total B concentration determination. The methods were validated by analyzing stoichiometric boron compounds and applied to samples such as boron carbide, boric acid, carborane, and borosilicate glass. Isotopic compositions of boron in the range of 0.247-2.0 corresponding to (10)B in the range of 19.8-67.0 atom % and total B concentrations in the range of 5-78 wt % were determined. It has been demonstrated that PIGE offers a simple and alternate method for total boron as well as isotopic composition determination in boron based solid samples, including neutron absorbers that are important in nuclear technology.

Evaluation of Landsat-4 orbit determination accuracy using batch least-squares and sequential methods

NASA Astrophysics Data System (ADS)

Oza, D. H.; Jones, T. L.; Feiertag, R.; Samii, M. V.; Doll, C. E.; Mistretta, G. D.; Hart, R. C.

The Goddard Space Flight Center (GSFC) Flight Dynamics Division (FDD) commissioned Applied Technology Associates, Incorporated, to develop the Real-Time Orbit Determination/Enhanced (RTOD/E) system on a Disk Operating System (DOS)-based personal computer (PC) as a prototype system for sequential orbit determination of spacecraft. This paper presents the results of a study to compare the orbit determination accuracy for a Tracking and Data Relay Satellite (TDRS) System (TDRSS) user spacecraft, Landsat-4, obtained using RTOD/E, operating on a PC, with the accuracy of an established batch least-squares system, the Goddard Trajectory Determination System (GTDS), operating on a mainframe computer. The results of Landsat-4 orbit determination will provide useful experience for the Earth Observing System (EOS) series of satellites. The Landsat-4 ephemerides were estimated for the May 18-24, 1992, timeframe, during which intensive TDRSS tracking data for Landsat-4 were available. During this period, there were two separate orbit-adjust maneuvers on one of the TDRSS spacecraft (TDRS-East) and one small orbit-adjust maneuver for Landsat-4. Independent assessments were made of the consistencies (overlap comparisons for the batch case and covariances and the first measurement residuals for the sequential case) of solutions produced by the batch and sequential methods. The forward-filtered RTOD/E orbit solutions were compared with the definitive GTDS orbit solutions for Landsat-4; the solution differences were generally less than 30 meters after the filter had reached steady state.

Evaluation of Landsat-4 orbit determination accuracy using batch least-squares and sequential methods

NASA Technical Reports Server (NTRS)

Oza, D. H.; Jones, T. L.; Feiertag, R.; Samii, M. V.; Doll, C. E.; Mistretta, G. D.; Hart, R. C.

1993-01-01

The Goddard Space Flight Center (GSFC) Flight Dynamics Division (FDD) commissioned Applied Technology Associates, Incorporated, to develop the Real-Time Orbit Determination/Enhanced (RTOD/E) system on a Disk Operating System (DOS)-based personal computer (PC) as a prototype system for sequential orbit determination of spacecraft. This paper presents the results of a study to compare the orbit determination accuracy for a Tracking and Data Relay Satellite (TDRS) System (TDRSS) user spacecraft, Landsat-4, obtained using RTOD/E, operating on a PC, with the accuracy of an established batch least-squares system, the Goddard Trajectory Determination System (GTDS), operating on a mainframe computer. The results of Landsat-4 orbit determination will provide useful experience for the Earth Observing System (EOS) series of satellites. The Landsat-4 ephemerides were estimated for the May 18-24, 1992, timeframe, during which intensive TDRSS tracking data for Landsat-4 were available. During this period, there were two separate orbit-adjust maneuvers on one of the TDRSS spacecraft (TDRS-East) and one small orbit-adjust maneuver for Landsat-4. Independent assessments were made of the consistencies (overlap comparisons for the batch case and covariances and the first measurement residuals for the sequential case) of solutions produced by the batch and sequential methods. The forward-filtered RTOD/E orbit solutions were compared with the definitive GTDS orbit solutions for Landsat-4; the solution differences were generally less than 30 meters after the filter had reached steady state.

Sm-Nd isotopic compositions of LREE minerals for use as reference materials for in situ analysis by LA-MC-ICPMS

NASA Astrophysics Data System (ADS)

Fisher, C. M.; McFarlane, C. R.; Sylvester, P.; Hanchar, J. M.; Lam, R.; Schmitz, M. D.

2009-12-01

Recent work has demonstrated the possibility of obtaining both accurate and precise in situ Sm-Nd isotopic data in light rare earth enriched (LREE) accessory minerals including apatite, titanite, and monazite, using laser ablation-multicollector-inductively coupled plasma mass spectrometry (LA-MC-ICPMS). A distinct advantage of using LA-MC-ICPMS is that Sm-Nd isotopic data from these minerals can be determined in sub-grain domains potentially avoiding problems of isotopic mixing from inherited or xenocrystic components and allowing both valuable tracer isotope and geochronologic data to be obtained. However, a number of analytical obstacles complicate accurate Sm-Nd determination by LA-MC-ICPMS including mass bias corrections, the 144Sm isobaric interference on 144Nd, and potential offset (ca. 20-40 ppm) from thermal ionization mass spectrometry (TIMS) determination of similar materials. Thus, in order to verify Sm-Nd isotopic determination from unknowns, matrix-matched quality control standards (i.e., reference materials) must be developed to test the data handling protocol. This talk will present new Sm-Nd isotopic data determined by both TIMS as well as LA-MC-ICPMS of a number of natural potential reference minerals including Durango apatite, Fish Canyon titanite, Daibosatsu allanite, Trebilcock monazite, as well as a monazite from the Doi Inthanon core complex in northern Thailand. Our preliminary LA-MC-ICPMS results demonstrate that Durango apatite, Fish Canyon titanite, and Thailand monazite show both inter- and intra-grain homogeneity at current levels of precision (ca. 0.3-0.5 ɛNd) and close agreement with our TIMS data.

Tracer study of oxygen and hydrogen uptake by Mg alloys in air with water vapor

DOE PAGES

Brady, M. P.; Fayek, M.; Meyer, H. M.; ...

2015-05-15

We studied the pure oxidation of Mg, Mg–3Al–1Zn (AZ31B), and Mg–1Zn–0.25Zr–<0.5Nd (ZE10A) at 85 °C in humid air using sequential exposures with H 2 18O and D 2 16O for water vapor. Incorporation of 18O in the hydroxide/oxide films indicated that oxygen from water vapor participated in the reaction. Moreover, penetration of hydrogen into the underlying metal was observed, particularly for the Zr- and Nd-containing ZE10A. Isotopic tracer profiles suggested a complex mixed inward/outward film growth mechanism.

Determination of phenylalanine isotope ratio enrichment by liquid chromatography/time- of-flight mass spectrometry.

PubMed

Wu, Zhanpin; Zhang, Xiao-Jun; Cody, Robert B; Wolfe, Robert R

2004-01-01

The application of time-of-flight mass spectrometry to isotope ratio measurements has been limited by the relatively low dynamic range of the time-to-digital converter detectors available on commercial LC/ToF-MS systems. Here we report the measurement of phenylalanine isotope ratio enrichment by using a new LC/ToF-MS system with wide dynamic range. Underivatized phenylalanine was injected onto a C18 column directly with 0.1% formic acid/acetonitrile as the mobile phase. The optimal instrument parameters for the time-of-flight mass spectrometer were determined by tuning the instrument with a phenylalanine standard. The accuracy of the isotope enrichment measurement was determined by the injection of standard solutions with known isotope ratios ranging from 0.02% to 9.2%. A plot of the results against the theoretical values gave a linear curve with R2 of 0.9999. The coefficient of variation for the isotope ratio measurement was below 2%. The method is simple, rapid, and accurate and presents an attractive alternative to traditional GC/MS applications.

Sequential water molecule binding enthalpies for aqueous nanodrops containing a mono-, di- or trivalent ion and between 20 and 500 water molecules† †Electronic supplementary information (ESI) available: Detailed description of the experimental and computational modeling methods. Isolation, BIRD and UVPD sequence for [Ru(NH3)6]3+·(H2O)169–171, nanoESI spectra for 2+ and 3+ ions. Detailed description of the isotope distribution simulation program. Comparison between experimental and simulated 1+, 2+ and 3+ ion isotope distributions. Wavelength dependence of the deduced sequential binding enthalpies. Comparison of experimental UVPD binding enthalpies to the liquid drop model at different temperatures. Complete list of binding enthalpies and average number of water molecules lost upon UVPD. See DOI: 10.1039/c6sc04957e Click here for additional data file.

PubMed Central

Heiles, Sven; Cooper, Richard J.; DiTucci, Matthew J.

2017-01-01

Sequential water molecule binding enthalpies, ΔH n,n–1, are important for a detailed understanding of competitive interactions between ions, water and solute molecules, and how these interactions affect physical properties of ion-containing nanodrops that are important in aerosol chemistry. Water molecule binding enthalpies have been measured for small clusters of many different ions, but these values for ion-containing nanodrops containing more than 20 water molecules are scarce. Here, ΔH n,n–1 values are deduced from high-precision ultraviolet photodissociation (UVPD) measurements as a function of ion identity, charge state and cluster size between 20–500 water molecules and for ions with +1, +2 and +3 charges. The ΔH n,n–1 values are obtained from the number of water molecules lost upon photoexcitation at a known wavelength, and modeling of the release of energy into the translational, rotational and vibrational motions of the products. The ΔH n,n–1 values range from 36.82 to 50.21 kJ mol–1. For clusters containing more than ∼250 water molecules, the binding enthalpies are between the bulk heat of vaporization (44.8 kJ mol–1) and the sublimation enthalpy of bulk ice (51.0 kJ mol–1). These values depend on ion charge state for clusters with fewer than 150 water molecules, but there is a negligible dependence at larger size. There is a minimum in the ΔH n,n–1 values that depends on the cluster size and ion charge state, which can be attributed to the competing effects of ion solvation and surface energy. The experimental ΔH n,n–1 values can be fit to the Thomson liquid drop model (TLDM) using bulk ice parameters. By optimizing the surface tension and temperature change of the logarithmic partial pressure for the TLDM, the experimental sequential water molecule binding enthalpies can be fit with an accuracy of ±3.3 kJ mol–1 over the entire range of cluster sizes. PMID:28451364

Tables for determining lead, uranium, and thorium isotope ages

NASA Technical Reports Server (NTRS)

Schonfeld, E.

1974-01-01

Tables for determining lead, uranium, and thorium isotope ages are presented in the form of computer printouts. Decay constants, analytical expressions for the functions evaluated, and the precision of the calculations are briefly discussed.

Kullback-Leibler information function and the sequential selection of experiments to discriminate among several linear models. Ph.D. Thesis

NASA Technical Reports Server (NTRS)

Sidik, S. M.

1972-01-01

A sequential adaptive experimental design procedure for a related problem is studied. It is assumed that a finite set of potential linear models relating certain controlled variables to an observed variable is postulated, and that exactly one of these models is correct. The problem is to sequentially design most informative experiments so that the correct model equation can be determined with as little experimentation as possible. Discussion includes: structure of the linear models; prerequisite distribution theory; entropy functions and the Kullback-Leibler information function; the sequential decision procedure; and computer simulation results. An example of application is given.

77 FR 64143 - Manufacturer of Controlled Substances; Notice of Registration; Cambridge Isotope Lab

Federal Register 2010, 2011, 2012, 2013, 2014

2012-10-18

...; Notice of Registration; Cambridge Isotope Lab By Notice dated June 18, 2012, and published in the Federal Register on June 26, 2012, 77 FR 38086, Cambridge Isotope Lab, 50 Frontage Road, Andover, Massachusetts....C. 823(a) and determined that the registration of Cambridge Isotope Lab to manufacture the listed...

Comparison of IRMS and NMR spectrometry for the determination of intramolecular 13C isotope composition: application to ethanol.

PubMed

Gilbert, Alexis; Hattori, Ryota; Silvestre, Virginie; Wasano, Nariaki; Akoka, Serge; Hirano, Satoshi; Yamada, Keita; Yoshida, Naohiro; Remaud, Gérald S

2012-09-15

Isotopic (13)C NMR is a relatively recent technique which allows the determination of intramolecular (13)C isotope composition at natural abundance. It has been used in various scientific fields such as authentication, counterfeiting or plant metabolism. Although its precision has already been evaluated, the determination of its trueness remains still challenging. To deal with that issue, a comparison with another normalized technique must be achieved. In this work, we compare the intramolecular (13)C isotope distribution of ethanol from different origins obtained using both Isotope Ratio Mass Spectrometry (IRMS) and Nuclear Magnetic Resonance (NMR) spectrometry techniques. The IRMS approach consists of the oxidation of ethanol to acetic acid followed by the degradation of the latter for the analysis of each fragments formed. We show here that the oxidation of ethanol to acetic acid does not bring any significant error on the determination of the site-specific δ(13)C (δ(13)C(i)) of ethanol using the IRMS approach. The difference between the data obtained for 16 samples from different origins using IRMS and NMR approaches is not statistically significant and remains below 0.3‰. These results are encouraging for the future studies using isotopic NMR, especially in combination with the IRMS approach. Copyright © 2012. Published by Elsevier B.V.

REFINING THE DUAL ISOTOPE APPROACH TO DETERMINE FIELD ESTIMATES OF LITTER, ROOT, AND SOM COMPONENTS OF SOIL CO2 EFFLUX

EPA Science Inventory

Stable isotopes have become an important tool for determining the relative importance of CO2 sources and sinks contributing to the global carbon budget. Of particular importance is the determination of the terrestrial CO2 flux which is difficult to decipher without determining t...

EFFECT OF TEMPERATURE ON THE C ISOTOPIC VALUE OF MICROBIAL LIPIDS APPLIED TO DETERMINE C USAGE IN MICROBIAL COMMUNITIES

EPA Science Inventory

The combination of compound specific stable isotopic analysis with phospholipid fatty acid (PLFAS) analysis is useful in determining the source of organic carbon used by groups of a microbial community. Determination of the effect of certain environmental parameters is important ...

100,000-year-long terrestrial record of millennial-scale linkage between eastern North American mid-latitude paleovegetation shifts and Greenland ice-core oxygen isotope trends

USGS Publications Warehouse

Litwin, Ronald J.; Smoot, Joseph P.; Pavich, Milan J.; Markewich, Helaine Walsh; Brook, George; Durika, Nancy J.

2013-01-01

We document frequent, rapid, strong, millennial-scale paleovegetation shifts throughout the late Pleistocene, within a 100,000+ yr interval (~ 115–15 ka) of terrestrial sediments from the mid-Atlantic Region (MAR) of North America. High-resolution analyses of fossil pollen from one core locality revealed a continuously shifting sequence of thermally dependent forest assemblages, ranging between two endmembers: subtropical oak-tupelo-bald cypress-gum forest and high boreal spruce-pine forest. Sedimentary textural evidence indicates fluvial, paludal, and loess deposition, and paleosol formation, representing sequential freshwater to subaerial environments in which this record was deposited. Its total age"depth model, based on radiocarbon and optically stimulated luminescence ages, ranges from terrestrial oxygen isotope stages (OIS) 6 to 1. The particular core sub-interval presented here is correlative in trend and timing to that portion of the oxygen isotope sequence common among several Greenland ice cores: interstades GI2 to GI24 (≈ OIS2–5 d). This site thus provides the first evidence for an essentially complete series of "Dansgaard"Oeschger" climate events in the MAR. These data reveal that the ~ 100,000 yr preceding the Late Glacial and Holocene in the MAR of North America were characterized by frequently and dynamically changing climate states, and by vegetation shifts that closely tracked the Greenland paleoclimate sequence.

Comparison of secondary ion mass spectrometry and micromilling/continuous flow isotope ratio mass spectrometry techniques used to acquire intra-otolith delta18O values of wild Atlantic salmon (Salmo salar).

PubMed

Hanson, N N; Wurster, C M; Todd, C D

2010-09-15

The chemical signals in the sequential layers of fish otoliths have the potential to provide fisheries biologists with temporal and spatial details of migration which are difficult to obtain without expensive tracking methods. Signal resolution depends, however, on the extraction technique used. We compared the use of mechanical micromilling and continuous flow isotope ratio mass spectrometry (CF-IRMS) methods with secondary ion mass spectrometry (SIMS) to obtain delta(18)O profiles from otoliths of wild Atlantic salmon (Salmo salar) and used these to corroborate the time of freshwater emigration of the juvenile with macroscopic patterns within the otolith. Both techniques showed the transition occurring at the same visible feature on the otolith, allowing future analyses to easily identify the juvenile (freshwater) versus adult (marine) life-stages. However, SIMS showed a rapid and abrupt transition whereas micromilling provided a less distinct signal. The number of samples that could be obtained per unit area sampled using SIMS was 2 to 3 times greater than that when using micromilling/CF-IRMS although the delta(18)O values and analytical precisions (approximately 0.2 per thousand) of the two methods were comparable. In addition, SIMS delta(18)O results were used to compare otolith aragonite values with predicted values calculated using various isotope fractionation equations. Copyright 2010 John Wiley & Sons, Ltd.

Can We Untangle the Weather? Stable Water Isotope Controls on the Juneau Icefield

NASA Astrophysics Data System (ADS)

Ihle, A. C.; Keenan, E.; Yong, C.; Bridgers, S. L.; Markle, B. R.; Hamel, J.; Klein, E. S.

2017-12-01

Stable water isotopes in snow and ice provide a reliable proxy for past weather and climate. However, untangling weather and climate signals from water isotopes on the Juneau Icefield, Alaska, has proven difficult due to consistent summer melt and rain. The Juneau Icefield is a large glaciated region consisting of complex terrain and sharp climatic gradients. Here we study how topographic steepness and elevation influence stable water isotope ratios on the Juneau Icefield using vertical snowpit profiles collected from water year 2017's snowpack. As terrain steepens, we expect gradients in isotope ratios to intensify. In addition, we aim to determine how post-depositional metamorphism, particularly precipitation, affects water isotope ratios. We anticipate rain events to increase the proportion of heavy water isotopes. Lastly, we compare model output and remote sensing observations of storm origin to vertical stratigraphy of stable isotope ratios in the snowpack in order to determine if it is possible to use isotopes to identify past storm tracks on the Juneau Icefield. Snowpack isotope stratigraphy ratios can likely be linked to seasonal trends of storm characteristics. Given this enhanced understanding of how stable water isotopes behave on the Juneau Icefield, we contribute to the understanding of past weather and climate, both here and elsewhere, and explore the possibility for future deep ice cores on the Juneau Icefield.

Wading bird guano enrichment of soil nutrients in tree islands of the Florida Everglades.

PubMed

Irick, Daniel L; Gu, Binhe; Li, Yuncong C; Inglett, Patrick W; Frederick, Peter C; Ross, Michael S; Wright, Alan L; Ewe, Sharon M L

2015-11-01

Differential distribution of nutrients within an ecosystem can offer insight of ecological and physical processes that are otherwise unclear. This study was conducted to determine if enrichment of phosphorus (P) in tree island soils of the Florida Everglades can be explained by bird guano deposition. Concentrations of total carbon, nitrogen (N), and P, and N stable isotope ratio (δ(15)N) were determined on soil samples from 46 tree islands. Total elemental concentrations and δ(15)N were determined on wading bird guano. Sequential chemical extraction of P pools was also performed on guano. Guano contained between 53.1 and 123.7 g-N kg(-1) and 20.7 and 56.7 g-P kg(-1). Most of the P present in guano was extractable by HCl, which ranged from 82 to 97% of the total P. Total P of tree islands classified as having low or high P soils averaged 0.71 and 40.6 g kg(-1), respectively. Tree island soil with high total P concentration was found to have a similar δ(15)N signature and total P concentration as bird guano. Phosphorus concentrations and δ(15)N were positively correlated in tree island soils (r = 0.83, p< 0.0001). Potential input of guano with elevated concentrations of N and P, and (15)N enriched N, relative to other sources suggests that guano deposition in tree island soils is a mechanism contributing to this pattern. Copyright © 2015. Published by Elsevier B.V.

Cost-effectiveness of simultaneous versus sequential surgery in head and neck reconstruction.

PubMed

Wong, Kevin K; Enepekides, Danny J; Higgins, Kevin M

2011-02-01

To determine whether simultaneous (ablation and reconstruction overlaps by two teams) head and neck reconstruction is cost effective compared to sequentially (ablation followed by reconstruction) performed surgery. Case-controlled study. Tertiary care hospital. Oncology patients undergoing free flap reconstruction of the head and neck. A match paired comparison study was performed with a retrospective chart review examining the total time of surgery for sequential and simultaneous surgery. Nine patients were selected for both the sequential and simultaneous groups. Sequential head and neck reconstruction patients were pair matched with patients who had undergone similar oncologic ablative or reconstructive procedures performed in a simultaneous fashion. A detailed cost analysis using the microcosting method was then undertaken looking at the direct costs of the surgeons, anesthesiologist, operating room, and nursing. On average, simultaneous surgery required 3 hours 15 minutes less operating time, leading to a cost savings of approximately $1200/case when compared to sequential surgery. This represents approximately a 15% reduction in the cost of the entire operation. Simultaneous head and neck reconstruction is more cost effective when compared to sequential surgery.

Steps toward identifying a biogeochemical signal in non-equilibrium methane clumped isotope measurements

NASA Astrophysics Data System (ADS)

Douglas, P. M.; Eiler, J. M.; Sessions, A. L.; Dawson, K.; Walter Anthony, K. M.; Smith, D. A.; Lloyd, M. K.; Yanay, E.

2016-12-01

Microbially produced methane is a globally important greenhouse gas, energy source, and biological substrate. Methane clumped isotope measurements have recently been developed as a new analytical tool for understanding the source of methane in different environments. When methane forms in isotopic equilibrium clumped isotope values are determined by formation temperature, but in many cases microbial methane clumped isotope values deviate strongly from expected equilibrium values. Indeed, we observe a very wide range of clumped isotope values in microbial methane, which are likely strongly influenced by kinetic isotope effects, but thus far the biological and environmental parameters controlling this variability are not understood. We will present data from both culture experiments and natural environments to explore patterns of variability in non-equilibrium clumped isotope values on temporal and spatial scales. In methanogen batch cultures sampled at different time points along a growth curve we observe significant variability in clumped isotope values, with values decreasing from early to late exponential growth. Clumped isotope values then increase during stationary growth. This result is consistent with previous work suggesting that differences in the reversibility of methanogenesis related to metabolic rates control non-equilibrium clumped isotope values. Within single lakes in Alaska and Sweden we observe substantial variability in clumped isotope values on the order of 5‰. Lower clumped isotope values are associated with larger 2H isotopic fractionation between water and methane, which is also consistent with a kinetic isotope effect determined by the reversibility of methanogenesis. Finally, we analyzed a time-series clumped isotope compositions of methane emitted from two seeps in an Alaskan lake over several months. Temporal variability in these seeps is on the order of 2‰, which is much less than the observed spatial variability within the lake. Comparing carbon isotope fractionation between CO2 and CH4 with clumped isotope data suggests the temporal variability may result from changes in methane oxidation.

Determination of nitrogen-15 isotope fractionation in tropine: evaluation of extraction protocols for isotope ratio measurement by isotope ratio mass spectrometry.

PubMed

Molinié, Roland; Kwiecień, Renata A; Silvestre, Virginie; Robins, Richard J

2009-12-01

N-Demethylation of tropine is an important step in the degradation of this compound and related metabolites. With the purpose of understanding the reaction mechanism(s) involved, it is desirable to measure the 15N kinetic isotope effects (KIEs), which can be accessed through the 15N isotope shift (Deltadelta15N) during the reaction. To measure the isotope fractionation in 15N during tropine degradation necessitates the extraction of the residual substrate from dilute aqueous solution without introducing artefactual isotope fractionation. Three protocols have been compared for the extraction and measurement of the 15N/14N ratio of tropine from aqueous medium, involving liquid-liquid phase partitioning or silica-C18 solid-phase extraction. Quantification was by gas chromatography (GC) on the recovered organic phase and delta15N values were obtained by isotope ratio measurement mass spectrometry (irm-MS). Although all the protocols used can provide satisfactory data and both irm-EA-MS and irm-GC-MS can be used to obtain the delta15N values, the most convenient method is liquid-liquid extraction from a reduced aqueous volume combined with irm-GC-MS. The protocols are applied to the measurement of 15N isotope shifts during growth of a Pseudomonas strain that uses tropane alkaloids as sole source of carbon and nitrogen. The accuracy of the determination of the 15N/14N ratio is sufficient to be used for the determination of 15N-KIEs. Copyright 2009 John Wiley & Sons, Ltd.

Calibration strategies for the determination of stable carbon absolute isotope ratios in a glycine candidate reference material by elemental analyser-isotope ratio mass spectrometry.

PubMed

Dunn, Philip J H; Malinovsky, Dmitry; Goenaga-Infante, Heidi

2015-04-01

We report a methodology for the determination of the stable carbon absolute isotope ratio of a glycine candidate reference material with natural carbon isotopic composition using EA-IRMS. For the first time, stable carbon absolute isotope ratios have been reported using continuous flow rather than dual inlet isotope ratio mass spectrometry. Also for the first time, a calibration strategy based on the use of synthetic mixtures gravimetrically prepared from well characterised, highly (13)C-enriched and (13)C-depleted glycines was developed for EA-IRMS calibration and generation of absolute carbon isotope ratio values traceable to the SI through calibration standards of known purity. A second calibration strategy based on converting the more typically determined delta values on the Vienna PeeDee Belemnite (VPDB) scale using literature values for the absolute carbon isotope ratio of VPDB itself was used for comparison. Both calibration approaches provided results consistent with those previously reported for the same natural glycine using MC-ICP-MS; absolute carbon ratios of 10,649 × 10(-6) with an expanded uncertainty (k = 2) of 24 × 10(-6) and 10,646 × 10(-6) with an expanded uncertainty (k = 2) of 88 × 10(-6) were obtained, respectively. The absolute carbon isotope ratio of the VPDB standard was found to be 11,115 × 10(-6) with an expanded uncertainty (k = 2) of 27 × 10(-6), which is in excellent agreement with previously published values.

Sequential contrast-enhanced MR imaging of the penis.

PubMed

Kaneko, K; De Mouy, E H; Lee, B E

1994-04-01

To determine the enhancement patterns of the penis at magnetic resonance (MR) imaging. Sequential contrast material-enhanced MR images of the penis in a flaccid state were obtained in 16 volunteers (12 with normal penile function and four with erectile dysfunction). Subjects with normal erectile function showed gradual and centrifugal enhancement of the corpora cavernosa, while those with erectile dysfunction showed poor enhancement with abnormal progression. Sequential contrast-enhanced MR imaging provides additional morphologic information for the evaluation of erectile dysfunction.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cohn, J.S.; Wagner, D.A.; Cohn, S.D.

Six normolipidemic male subjects, after an 8-h overnight fast, were given a bolus injection and then a 15-h constant intravenous infusion of (D3)L-leucine. Subjects were studied in the fasted state and on a second occasion in the fed state (small, physiological meals were given every hour for 15 h). Apolipoproteins were isolated by preparative gradient gel electrophoresis from plasma lipoproteins separated by sequential ultracentrifugation. Incorporation of (D3)L-leucine into apolipoproteins was monitored by negative ionization, gas chromatography-mass spectrometry. Production rates were determined by multiplying plasma apolipoprotein pool sizes by fractional production rates calculated as the rate of isotopic enrichment (IE) ofmore » each protein as a fraction of IE achieved by VLDL (d less than 1.006 g/ml) apo B-100 at plateau. VLDL apo B-100 production was greater, and LDL (1.019 less than d less than 1.063 g/ml) apo B-100 production was less in the fed compared with the fasted state (9.9 +/- 1.7 vs. 6.4 +/- 1.7 mg/kg per d, P less than 0.01, and 8.9 +/- 1.2 vs. 13.1 +/- 1.2 mg/kg per d, P less than 0.05, respectively). No mean change was observed in high density lipoprotein apo A-I production. We conclude that: (a) this stable isotope, endogenous-labeling technique, for the first time allows for the in vivo measurement of apolipoprotein production in the fasted and fed state; and (b) since LDL apo B-100 production was greater than VLDL apo B-100 production in the fasted state, this study provides in vivo evidence that LDL apo B-100 can be produced independently of VLDL apo B-100 in normolipidemic subjects.« less

Comparison of Performance of Eight-Year-Old Children on Three Auditory Sequential Memory Tests.

ERIC Educational Resources Information Center

Chermak, Gail D.; O'Connell, Vickie I.

1981-01-01

Twenty normal children were administered three tests of auditory sequential memory. A Pearson product-moment correlation of .50 and coefficients of determination showed all but one relationship to be nonsignificant and predictability between pairs of scores to be poor. (Author)

EM reconstruction of dual isotope PET using staggered injections and prompt gamma positron emitters

PubMed Central

Andreyev, Andriy; Sitek, Arkadiusz; Celler, Anna

2014-01-01

Purpose: The aim of dual isotope positron emission tomography (DIPET) is to create two separate images of two coinjected PET radiotracers. DIPET shortens the duration of the study, reduces patient discomfort, and produces perfectly coregistered images compared to the case when two radiotracers would be imaged independently (sequential PET studies). Reconstruction of data from such simultaneous acquisition of two PET radiotracers is difficult because positron decay of any isotope creates only 511 keV photons; therefore, the isotopes cannot be differentiated based on the detected energy. Methods: Recently, the authors have proposed a DIPET technique that uses a combination of radiotracer A which is a pure positron emitter (such as 18F or 11C) and radiotracer B in which positron decay is accompanied by the emission of a high-energy (HE) prompt gamma (such as 38K or 60Cu). Events that are detected as triple coincidences of HE gammas with the corresponding two 511 keV photons allow the authors to identify the lines-of-response (LORs) of isotope B. These LORs are used to separate the two intertwined distributions, using a dedicated image reconstruction algorithm. In this work the authors propose a new version of the DIPET EM-based reconstruction algorithm that allows the authors to include an additional, independent estimate of radiotracer A distribution which may be obtained if radioisotopes are administered using a staggered injections method. In this work the method is tested on simple simulations of static PET acquisitions. Results: The authors’ experiments performed using Monte-Carlo simulations with static acquisitions demonstrate that the combined method provides better results (crosstalk errors decrease by up to 50%) than the positron-gamma DIPET method or staggered injections alone. Conclusions: The authors demonstrate that the authors’ new EM algorithm which combines information from triple coincidences with prompt gammas and staggered injections improves the accuracy of DIPET reconstructions for static acquisitions so they reach almost the benchmark level calculated for perfectly separated tracers. PMID:24506645

"Application of Tunable Diode Laser Spectrometry to Isotopic Studies for Exobiology"

NASA Technical Reports Server (NTRS)

Sauke, Todd B.

1999-01-01

Computer-controlled electrically-activated valves for rapid gas-handling have been incorporated into the Stable Isotope Laser Spectrometer (SILS) which now permits rapid filling and evacuating of the sample and reference gas cells, Experimental protocols have been developed to take advantage of the fast gas handling capabilities of the instrument and to achieve increased accuracy which results from reduced instrumental drift during rapid isotopic ratio measurements. Using these protocols' accuracies of 0.5 del (0.05%) have been achieved in measurements of 13C/12C in carbon dioxide. Using the small stable isotope laser spectrometer developed in a related PIDDP project of the Co-I, protocols for acquisition of rapid sequential calibration spectra were developed which resulted in 0.5 del accuracy also being achieved in this less complex instrument. An initial version of software for automatic characterization of tunable diode lasers has been developed and diodes have been characterized in order to establish their spectral output properties. A new state-of-the-art high operating temperature (200 K) mid infrared diode laser was purchased (through NASA procurement) and characterized. A thermo-electrically cooled mid infrared tunable diode laser system for use with high temperature operation lasers was developed. In addition to isotopic ratio measurements of carbon and oxygen, measurements of a third biologically important element (15N/14N in N2O gas) have been achieved to a preliminary accuracy of about 0.2%. Transfer of the basic SILS technology to the commercial sector is proceeding under an unfunded Space Act Agreement between NASA and SpiraMed, a medical diagnostic instrument company. Two patents have been issued. Foreign patents based on these two US patents have been applied for and are expected to be issued. A preliminary design was developed for a thermo-electrically cooled SILS instruments for application to planetary space flight exploration missions.

Losing a dime with a satisfied mind: positive affect predicts less search in sequential decision making.

PubMed

von Helversen, Bettina; Mata, Rui

2012-12-01

We investigated the contribution of cognitive ability and affect to age differences in sequential decision making by asking younger and older adults to shop for items in a computerized sequential decision-making task. Older adults performed poorly compared to younger adults partly due to searching too few options. An analysis of the decision process with a formal model suggested that older adults set lower thresholds for accepting an option than younger participants. Further analyses suggested that positive affect, but not fluid abilities, was related to search in the sequential decision task. A second study that manipulated affect in younger adults supported the causal role of affect: Increased positive affect lowered the initial threshold for accepting an attractive option. In sum, our results suggest that positive affect is a key factor determining search in sequential decision making. Consequently, increased positive affect in older age may contribute to poorer sequential decisions by leading to insufficient search. 2013 APA, all rights reserved

Comparing isotope signatures of prey fish: does gut removal affect δ13C or δ15N?

USGS Publications Warehouse

Chipps, Steven R.; Fincel, Mark J.; VanDeHey, Justin A.; Wuestewald, Andrew

2011-01-01

Stable isotope analysis is a quick and inexpensive method to monitor the effects of food web changes on aquatic communities. Traditionally, whole specimens have been used when determining isotope composition of prey fish or age-0 recreational fishes. However, gut contents of prey fish could potentially alter isotope composition of the specimen, especially when recent foraging has taken place or when the gut contains non-assimilated material that would normally pass through fishes undigested. To assess the impacts of gut content on prey fish isotope signatures, we examined the differences in isotopic variation of five prey fish species using whole fish, whole fish with the gut contents removed, and dorsal muscle only. We found significant differences in both δ15N and δ13C between the three tissue treatments. In most cases, muscle tissue was enriched compared to whole specimens or gut-removed specimens. Moreover, differences in mean δ15N within a species were up to 2‰ among treatments. This would result in a change of over half a trophic position (TP) based on a 3.4‰ increase per trophic level. However, there were no apparent relationships between tissue isotope values in fish with increased gut fullness (more prey tissue present). We suggest that muscle tissue should be used as the standard tissue for determining isotope composition of prey fish or age-0 recreational fishes, especially when determining enrichment for mixing models, calculating TP, or constructing aquatic food webs.

Evaluation of laser ablation double-focusing SC-ICPMS for “common” lead isotopic measurements in silicate glasses and mineral

USGS Publications Warehouse

Pietruszka, Aaron J.; Neymark, Leonid

2017-01-01

An analytical method for the in situ measurement of “common” Pb isotope ratios in silicate glasses and minerals using a 193-nm excimer laser ablation (LA) system with a double-focusing single-collector (SC)-ICPMS is presented and evaluated as a possible alternative to multiple-collector (MC)-ICPMS. This LA-SC-ICPMS technique employs fast-scanning ion deflectors to sequentially place a series of flat-topped isotope peaks into a single ion-counting detector at a fixed accelerating voltage and magnetic field strength. Reference materials (including NIST, MPI-DING, and USGS glasses) are used to identify two analytical artifacts on the Pb isotope ratios (expressed here as heavier/lighter isotopes) when corrected for mass bias relative to NIST SRM610. The first artifact is characterized by anomalously low Pb isotope ratios (~0.1%/AMU) when SRM610 is analyzed in raster mode as an unknown at small spot sizes (<25 µm), which may indicate that (1) SRM610 is isotopically heterogeneous on a small length scale and/or (2) there is a non-spectral matrix effect on the Pb isotope ratios related to differences in spot size. The second artifact is characterized by anomalously high Pb isotope ratios (<0.1%/AMU) for NIST SRM612 (in raster mode) and some Fe-rich glass reference materials (BCR-2G, GOR132-G, and T1-G). These offsets are thought to be caused by one or more non-spectral matrix effects related to differences in the ablation behavior, composition, or physical properties of these reference materials compared to the bracketing SRM610 standard. The precision (±2SD) of our LA-SC-ICPMS Pb isotopic measurements is similar to (207Pb/206Pb and 208Pb/206Pb, or 20XPb/206Pb) or better than (206Pb/204Pb,207Pb/204Pb, and 208Pb/204Pb, or 20XPb/204Pb) a series of published studies that used a different type of SC-ICPMS and obtained a factor of ~3-4 higher sensitivity for Pb. An increase in the sensitivity of our LA-SC-ICPMS would likely improve the precision of the 20XPb/206Pb and 20XPb/204Pb ratios for low-Pb materials (<5 ppm), possibly making the technique broadly similar to LA-MC-ICPMS (particularly compared to methods that rely upon at least one ion-counting detector). Further improvement in the precision of the 20XPb/206Pb and 20XPb/204Pb ratios for high-Pb materials (>5 ppm) by LA-SC-ICPMS is unlikely, and in this case, LA-MC-ICPMS remains the preferable analytical technique.

Depositionally controlled recycling of iron and sulfur in marine sediments and its isotopic consequences

NASA Astrophysics Data System (ADS)

Riedinger, N.; Formolo, M.; Arnold, G. L.; Vossmeyer, A.; Henkel, S.; Sawicka, J.; Kasten, S.; Lyons, T. W.

2011-12-01

The continental margin off Uruguay and Argentina is characterized by highly dynamic depositional conditions. This variable depositional regime significantly impacts the biogeochemical cycles of iron and sulfur. Mass deposit related redeposition of reduced minerals can lead to the reoxidation of these phases and thus to an overprint of their geochemical primary signatures. Due to rapid burial these oxidized phases are still present in deeper subsurface sediments. To study the effects of sediment relocation on the sulfur and iron inventory we collected shallow and deep subsurface sediment samples via multicorer and gravity cores, respectively, in the western Argentine Basin during the RV Meteor Expedition M78/3 in May-July 2009. The samples were retrieved from shelf, slope and deep basin sites. The concentration and sulfur isotope composition of acid volatile sulfur (AVS), chromium reducible sulfur (CRS), elemental sulfur and total organic sulfur were determined. Furthermore, sequential iron extraction techniques were applied assess the distribution of iron oxide phases within the sediment. The investigated sediments are dominated by terrigenous inputs, with high amounts of reactive ferric iron minerals and only low concentrations of calcium carbonate. Total organic carbon concentrations show strong variation in the shallow subsurface sediments ranging between approximately 0.7 and 6.4 wt% for different sites. These concentrations do not correlate with water depths. Pore water accumulations of hydrogen sulfide are restricted to an interval at the sulfate-methane transition (SMT) zone a few meters below the sediment surface. In these deeper subsurface sediments pyrite is precipitated in this zone of hydrogen sulfide excess, whereas the accumulation of authigenic AVS and elemental sulfur (up to 2000 ppm) occurs at the upper and lower boundary of the sulfidic zone due the reaction of iron oxides with limited amounts of sulfide. Furthermore, our preliminary results indicate that there is a link between modern deposition in the shallow subsurface sediments and the long-term signals being buried and preserved in the deep subsurface layers. The data show that the burial of elemental sulfur into deep subsurface sediments can fuel the deep biosphere and has consequences for isotopic overprints tied, for example, to oxidation and disproportionation processes in the deeper sediments.

Hadean Oceanography: Experimental Constraints on the Development of the Terrestrial Hydrosphere and the Origin of Life on Earth

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ryerson, F J

The oxygen isotopic compositions of the world's oldest mineral grains, zircon, have recently been used to infer the compositions of the rocks from which they crystallized. The results appear to require a source that had once experienced isotopic fractionation between clay minerals and liquid water, thereby implying the presence of liquid water at the Earth's surface prior to 4.4 billion years ago, less than 2 million years after accretion. This observation has important implications for the development of the Earth's continental crust. The inferred composition of the zircon source rock is directly dependent upon the oxygen isotopic fractionation between zirconmore » and melt, and zircon and water. These fractionation factors have not been determined experimentally, however, constituting the weak link in this argument. A series of experiments to measure these fractionation factors has been conducted. The experiments consist of finely powdered quartz, a polished single crystal of zircon and isotopically-enriched or isotopically normal water to provide a range of isotopic compositions. The experiments will be run until quartz is in isotopic equilibrium with water. Zircon was expected to partially equilibrate producing an oxygen isotopic diffusion profile perpendicular to the surface. Ion probe spot analysis of quartz and depth profiling of zircon will determine the bulk and surface isotopic compositions of the phases, respectively. The well-known quartz-water isotopic fractionation factors can be used to calculate the oxygen isotopic composition of the fluid, and with the zircon surface composition, the zircon-water fractionation factor. Run at temperatures up to 1000 C for as long as 500 hours have not produced diffusion profiles longer than 50 nm. The steep isotopic gradient at the samples surface precludes use of the diffusion profile for estimation on the surface isotopic composition. The short profiles may be the result of surface dissolution, although such dissolution cannot be resolved in SEM images. The sluggish nature of diffusion in zircon may require that fractionation factors be determined by direct hydrothermal synthesis of zircon rather than by mineral-fluid exchange.« less

Acute Toxicity and Efficacy of Current Medical Countermeasures against VM in Guinea Pigs: A Comparison to VX and VR

DTIC Science & Technology

2013-05-01

and diazepam with and without pretreatment with pyridostigmine bromide . The 24 hr median lethal dose (MLD) of VM was determined using a sequential... pyridostigmine bromide . The 24 hr median lethal dose (MLD) of VM was determined using a sequential stage approach. The efficacy of medical...with and without pyridostigmine bromide (PB) pretreatment against lethal intoxication with VM, VR or VX. Methods Animals: Adult male Hartley

Mechanical System Reliability and Cost Integration Using a Sequential Linear Approximation Method

NASA Technical Reports Server (NTRS)

Kowal, Michael T.

1997-01-01

The development of new products is dependent on product designs that incorporate high levels of reliability along with a design that meets predetermined levels of system cost. Additional constraints on the product include explicit and implicit performance requirements. Existing reliability and cost prediction methods result in no direct linkage between variables affecting these two dominant product attributes. A methodology to integrate reliability and cost estimates using a sequential linear approximation method is proposed. The sequential linear approximation method utilizes probability of failure sensitivities determined from probabilistic reliability methods as well a manufacturing cost sensitivities. The application of the sequential linear approximation method to a mechanical system is demonstrated.

Efficacy of passive sampler collection for atmospheric NO2 isotopes under simulated environmental conditions.

PubMed

Coughlin, Justin G; Yu, Zhongjie; Elliott, Emily M

2017-07-30

Nitrogen oxides or NO x (NO x = NO + NO 2 ) play an important role in air quality, atmospheric chemistry, and climate. The isotopic compositions of anthropogenic and natural NO 2 sources are wide-ranging, and they can be used to constrain sources of ambient NO 2 and associated atmospheric deposition of nitrogen compounds. While passive sample collection of NO 2 isotopes has been used in field studies to determine NO x source influences on atmospheric deposition, this approach has not been evaluated for accuracy or precision under different environmental conditions. The efficacy of NO 2 passive sampler collection for NO 2 isotopes was evaluated under varied temperature and relative humidity (RH) conditions in a dynamic flux chamber. The precision and accuracy of the filter NO 2 collection as nitrite (NO 2 - ) for isotopic analysis were determined using a reference NO 2 gas tank and through inter-calibration with a modified EPA Method 7. The bacterial denitrifer method was used to convert 20 μM of collected NO 2 - or nitrate (NO 3 - ) into N 2 O and was carried out on an Isoprime continuous flow isotope ratio mass spectrometer. δ 15 N-NO 2 values determined from passive NO 2 collection, in conditions of 11-34 °C, 1-78% RH, have an overall accuracy and precision of ±2.1 ‰, and individual run precision of ±0.6 ‰. δ 18 O-NO 2 values obtained from passive NO 2 sampler collection, under the same conditions, have an overall precision of ± 1.3 ‰. Suitable conditions for passive sampler collection of NO 2 isotopes are in environments ranging from 11 to 34 °C and 1 to 78% RH. The passive NO 2 isotope measurement technique provides an accurate method to determine variations in atmospheric δ 15 N-NO 2 values and a precise method for determining atmospheric δ 18 O-NO 2 values. The ability to measure NO 2 isotopes over spatial gradients at the same temporal resolution provides a unique perspective on the extent and seasonality of fluctuations in atmospheric NO 2 isotopic compositions. Copyright © 2017 John Wiley & Sons, Ltd. Copyright © 2017 John Wiley & Sons, Ltd.

Uses of stable isotopes in fish ecology

EPA Science Inventory

Analyses of fish tissues (other than otoliths) for stable isotope ratios can provide substantial information on fish ecology, including physiological ecology. Stable isotopes of nitrogen and carbon frequently are used to determine the mix of diet sources for consumers. Stable i...

Eyewitness confidence in simultaneous and sequential lineups: a criterion shift account for sequential mistaken identification overconfidence.

PubMed

Dobolyi, David G; Dodson, Chad S

2013-12-01

Confidence judgments for eyewitness identifications play an integral role in determining guilt during legal proceedings. Past research has shown that confidence in positive identifications is strongly associated with accuracy. Using a standard lineup recognition paradigm, we investigated accuracy using signal detection and ROC analyses, along with the tendency to choose a face with both simultaneous and sequential lineups. We replicated past findings of reduced rates of choosing with sequential as compared to simultaneous lineups, but notably found an accuracy advantage in favor of simultaneous lineups. Moreover, our analysis of the confidence-accuracy relationship revealed two key findings. First, we observed a sequential mistaken identification overconfidence effect: despite an overall reduction in false alarms, confidence for false alarms that did occur was higher with sequential lineups than with simultaneous lineups, with no differences in confidence for correct identifications. This sequential mistaken identification overconfidence effect is an expected byproduct of the use of a more conservative identification criterion with sequential than with simultaneous lineups. Second, we found a steady drop in confidence for mistaken identifications (i.e., foil identifications and false alarms) from the first to the last face in sequential lineups, whereas confidence in and accuracy of correct identifications remained relatively stable. Overall, we observed that sequential lineups are both less accurate and produce higher confidence false identifications than do simultaneous lineups. Given the increasing prominence of sequential lineups in our legal system, our data argue for increased scrutiny and possibly a wholesale reevaluation of this lineup format. PsycINFO Database Record (c) 2013 APA, all rights reserved.

ASSESSMENT OF A SEQUENTIAL EXTRACTION PROCEDURE FOR PERTURBED LEAD-CONTAMINATED SAMPLES WITH AND WITHOUT PHOSPHOROUS AMENDMENTS

EPA Science Inventory

Sequential extraction procedures are used to determine the solid-phase association in which elements of interest exist in soil and sediment matrices. Foundational work by Tessier et al. (1) has found widespread acceptance and has worked tolerably as an operational definition for...

J-adaptive estimation with estimated noise statistics

NASA Technical Reports Server (NTRS)

Jazwinski, A. H.; Hipkins, C.

1973-01-01

The J-adaptive sequential estimator is extended to include simultaneous estimation of the noise statistics in a model for system dynamics. This extension completely automates the estimator, eliminating the requirement of an analyst in the loop. Simulations in satellite orbit determination demonstrate the efficacy of the sequential estimation algorithm.

Reduction of chemical formulas from the isotopic peak distributions of high-resolution mass spectra.

PubMed

Roussis, Stilianos G; Proulx, Richard

2003-03-15

A method has been developed for the reduction of the chemical formulas of compounds in complex mixtures from the isotopic peak distributions of high-resolution mass spectra. The method is based on the principle that the observed isotopic peak distribution of a mixture of compounds is a linear combination of the isotopic peak distributions of the individual compounds in the mixture. All possible chemical formulas that meet specific criteria (e.g., type and number of atoms in structure, limits of unsaturation, etc.) are enumerated, and theoretical isotopic peak distributions are generated for each formula. The relative amount of each formula is obtained from the accurately measured isotopic peak distribution and the calculated isotopic peak distributions of all candidate formulas. The formulas of compounds in simple spectra, where peak components are fully resolved, are rapidly determined by direct comparison of the calculated and experimental isotopic peak distributions. The singular value decomposition linear algebra method is used to determine the contributions of compounds in complex spectra containing unresolved peak components. The principles of the approach and typical application examples are presented. The method is most useful for the characterization of complex spectra containing partially resolved peaks and structures with multiisotopic elements.

A Cerenkov-delta E-Cerenkov detector for high energy cosmic ray isotopes and an accelerator study of Ar-40 and Fe-56 fragmentation. Ph.D. Thesis

NASA Technical Reports Server (NTRS)

Lau, K. H.

1985-01-01

A high energy cosmic ray detector--the High Energy Isotope Spectrometer Telescope (HEIST) is described. It is a large area (0.25 m(swp 2) SR) balloon borne isotope spectrometer designed to make high resolution measurements of isotopes in the element range from neon to nickel (10 Z 28) at energies of about 2 GeV/nucleon. HEIST determines the mass of individual nuclei by measuring both the change in the Lorentz factor (delta gamma) that results from traversing the NaI stack, and the energy loss (delta E) in the stack. Since the total energy of an isotope is given by E = (gamma M), the mass M can be determined by M = delta E/delta, gamma. The instrument is designed to achieve a typical mass resolution of 0.2 amu. The isotopic composition of the fragments from the breakup of high energy An-40 and Fe-56 nuclei are measured experimentally. Isotope yields are compared with calculated yields based on semi-empirical cross-section formulae.

Laser ablation molecular isotopic spectroscopy (LAMIS) towards the determination of multivariate LODs via PLS calibration model of 10B and 11B Boric acid mixtures

NASA Astrophysics Data System (ADS)

Harris, C. D.; Profeta, Luisa T. M.; Akpovo, Codjo A.; Johnson, Lewis; Stowe, Ashley C.

2017-05-01

A calibration model was created to illustrate the detection capabilities of laser ablation molecular isotopic spectroscopy (LAMIS) discrimination in isotopic analysis. The sample set contained boric acid pellets that varied in isotopic concentrations of 10B and 11B. Each sample set was interrogated with a Q-switched Nd:YAG ablation laser operating at 532 nm. A minimum of four band heads of the β system B2∑ -> Χ2∑transitions were identified and verified with previous literature on BO molecular emission lines. Isotopic shifts were observed in the spectra for each transition and used as the predictors in the calibration model. The spectra along with their respective 10/11B isotopic ratios were analyzed using Partial Least Squares Regression (PLSR). An IUPAC novel approach for determining a multivariate Limit of Detection (LOD) interval was used to predict the detection of the desired isotopic ratios. The predicted multivariate LOD is dependent on the variation of the instrumental signal and other composites in the calibration model space.

A cost and policy analysis comparing immediate sequential cataract surgery and delayed sequential cataract surgery from the physician perspective in the United States.

PubMed

Neel, Sean T

2014-11-01

A cost analysis was performed to evaluate the effect on physicians in the United States of a transition from delayed sequential cataract surgery to immediate sequential cataract surgery. Financial and efficiency impacts of this change were evaluated to determine whether efficiency gains could offset potential reduced revenue. A cost analysis using Medicare cataract surgery volume estimates, Medicare 2012 physician cataract surgery reimbursement schedules, and estimates of potential additional office visit revenue comparing immediate sequential cataract surgery with delayed sequential cataract surgery for a single specialty ophthalmology practice in West Tennessee. This model should give an indication of the effect on physicians on a national basis. A single specialty ophthalmology practice in West Tennessee was found to have a cataract surgery revenue loss of $126,000, increased revenue from office visits of $34,449 to $106,271 (minimum and maximum offset methods), and a net loss of $19,900 to $91,700 (base case) with the conversion to immediate sequential cataract surgery. Physicians likely stand to lose financially, and this loss cannot be offset by increased patient visits under the current reimbursement system. This may result in physician resistance to converting to immediate sequential cataract surgery, gaming, and supplier-induced demand.

Sequential biases in accumulating evidence

PubMed Central

Huggins, Richard; Dogo, Samson Henry

2015-01-01

Whilst it is common in clinical trials to use the results of tests at one phase to decide whether to continue to the next phase and to subsequently design the next phase, we show that this can lead to biased results in evidence synthesis. Two new kinds of bias associated with accumulating evidence, termed ‘sequential decision bias’ and ‘sequential design bias’, are identified. Both kinds of bias are the result of making decisions on the usefulness of a new study, or its design, based on the previous studies. Sequential decision bias is determined by the correlation between the value of the current estimated effect and the probability of conducting an additional study. Sequential design bias arises from using the estimated value instead of the clinically relevant value of an effect in sample size calculations. We considered both the fixed‐effect and the random‐effects models of meta‐analysis and demonstrated analytically and by simulations that in both settings the problems due to sequential biases are apparent. According to our simulations, the sequential biases increase with increased heterogeneity. Minimisation of sequential biases arises as a new and important research area necessary for successful evidence‐based approaches to the development of science. © 2015 The Authors. Research Synthesis Methods Published by John Wiley & Sons Ltd. PMID:26626562

Fundamental studies on kinetic isotope effect (KIE) of hydrogen isotope fractionation in natural gas systems

USGS Publications Warehouse

Ni, Y.; Ma, Q.; Ellis, G.S.; Dai, J.; Katz, B.; Zhang, S.; Tang, Y.

2011-01-01

Based on quantum chemistry calculations for normal octane homolytic cracking, a kinetic hydrogen isotope fractionation model for methane, ethane, and propane formation is proposed. The activation energy differences between D-substitute and non-substituted methane, ethane, and propane are 318.6, 281.7, and 280.2cal/mol, respectively. In order to determine the effect of the entropy contribution for hydrogen isotopic substitution, a transition state for ethane bond rupture was determined based on density function theory (DFT) calculations. The kinetic isotope effect (KIE) associated with bond rupture in D and H substituted ethane results in a frequency factor ratio of 1.07. Based on the proposed mathematical model of hydrogen isotope fractionation, one can potentially quantify natural gas thermal maturity from measured hydrogen isotope values. Calculated gas maturity values determined by the proposed mathematical model using ??D values in ethane from several basins in the world are in close agreement with similar predictions based on the ??13C composition of ethane. However, gas maturity values calculated from field data of methane and propane using both hydrogen and carbon kinetic isotopic models do not agree as closely. It is possible that ??D values in methane may be affected by microbial mixing and that propane values might be more susceptible to hydrogen exchange with water or to analytical errors. Although the model used in this study is quite preliminary, the results demonstrate that kinetic isotope fractionation effects in hydrogen may be useful in quantitative models of natural gas generation, and that ??D values in ethane might be more suitable for modeling than comparable values in methane and propane. ?? 2011 Elsevier Ltd.

Oxygen Isotope Composition of Nitrate Produced by Freshwater Nitrification

NASA Astrophysics Data System (ADS)

Boshers, D.; Granger, J.; Bohlke, J. K.

2016-12-01

Measurements of the naturally occurring nitrogen and oxygen stable isotope ratios of nitrate (NO3-), δ15N and δ18O, can be used to determine the source, dispersal, and fate of natural and contaminant NO3- in aquatic environments. To this end, it is necessary to know the extent to which NO3- isotopologues are modified by biological reactions, as heavy and light isotopes have different reaction rates. The purpose of this study was to determine the influence of the δ18O of ambient water on the isotope composition of NO3- produced during nitrification, the biological oxidation of ammonium (NH4+) to nitrite (NO2-) and then NO3-, which is poorly constrained in freshwater systems. To determine the δ18O of NO3- produced by nitrification in freshwater, we collected water from a stream in New England, which we amended with NH4+ and with increments of 18O-enriched water, to monitor the isotope composition of NO3- produced by a natural consortium of nitrifiers. Added NH4+ was completely oxidized to NO3- over 26 days. The final δ18O of nitrified NO3- revealed sensitivity to the δ18O of water mediated by (a) isotopic equilibration between water and NO2- and (b) kinetic isotope fractionation during O-atom incorporation from water into NO2- and NO3-. Our results concur with nitrifying culture experiments that have demonstrated analogous sensitivity of the δ18O of nitrified NO3- to equilibrium and kinetic O isotope effects (Buchwald et al. 2012), as well as show that these dynamics need to be considered to interpret NO3- isotope distribution in freshwater environments.

The Application of Methane Clumped Isotope Measurements to Determine the Source of Large Methane Seeps in Alaskan Lakes

NASA Astrophysics Data System (ADS)

Douglas, P. M.; Stolper, D. A.; Eiler, J. M.; Sessions, A. L.; Walter Anthony, K. M.

2014-12-01

Natural methane emissions from the Arctic present an important potential feedback to global warming. Arctic methane emissions may come from either active microbial sources or from deep fossil reservoirs released by the thawing of permafrost and melting of glaciers. It is often difficult to distinguish between and quantify contributions from these methane sources based on stable isotope data. Analyses of methane clumped isotopes (isotopologues with two or more rare isotopes such as 13CH3D) can complement traditional stable isotope-based classifications of methane sources. This is because clumped isotope abundances (for isotopically equilibrated systems) are a function of temperature and can be used to identify pathways of methane generation. Additionally, distinctive effects of mixing on clumped isotope abundances make this analysis valuable for determining the origins of mixed gasses. We find large variability in clumped isotope compositions of methane from seeps in several lakes, including thermokarst lakes, across Alaska. At Lake Sukok in northern Alaska we observe the emission of dominantly thermogenic methane, with a formation temperature of at least 100° C. At several other lakes we find evidence for mixing between thermogenic methane and biogenic methane that forms in low-temperature isotopic equilibrium. For example, at Eyak Lake in southeastern Alaska, analysis of three methane samples results in a distinctive isotopic mixing line between a high-temperature end-member that formed between 100-170° C, and a biogenic end-member that formed in isotopic equilibrium between 0-20° C. In this respect, biogenic methane in these lakes resembles observations from marine gas seeps, oil degradation, and sub-surface aquifers. Interestingly, at Goldstream Lake in interior Alaska, methane with strongly depleted clumped-isotope abundances, indicative of disequilibrium gas formation, is found, similar to observations from methanogen culture experiments.

Revisiting streamside trees that do not use stream water: can the two water worlds hypothesis and snowpack isotopic effects explain a missing water source?: Riparian tree water sources

DOE PAGES

Bowling, David R.; Schulze, Emily S.; Hall, Steven J.

2016-10-14

We revisit a classic ecohydrological study that showed streamside riparian trees in a semiarid mountain catchment did not use perennial stream water. The original study suggested that mature individuals of Acer negundo, Acer grandidentatum, and other species were dependent on water from “deeper strata,” possibly groundwater. We used a dual stable isotope approach (δ 18O and δ 2H) to further examine the water sources of these trees. We tested the hypothesis that groundwater was the main tree water source, but found that neither groundwater nor stream water matched the isotope composition of xylem water during two growing seasons. Soil watermore » (0–1 m depth) was closest to and periodically overlapped with xylem water isotope composition, but overall, xylem water was isotopically enriched compared to all measured water sources. The “two water worlds” hypothesis postulates that soil water comprises isotopically distinct mobile and less mobile pools that do not mix, potentially explaining this disparity. We further hypothesized that isotopic effects during snowpack metamorphosis impart a distinct isotope signature to the less mobile soil water that supplies summer transpiration. Depth trends in water isotopes following snowmelt were consistent with the two water worlds hypothesis, but snow metamorphic isotope effects could not explain the highly enriched xylem water. Thus, the dual isotope approach did not unambiguously determine the water source(s) of these riparian trees. Further exploration of physical, geochemical, and biological mechanisms of water isotope fractionation and partitioning is necessary to resolve these data, highlighting critical challenges in the isotopic determination of plant water sources.« less

Revisiting streamside trees that do not use stream water: can the two water worlds hypothesis and snowpack isotopic effects explain a missing water source?: Riparian tree water sources

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bowling, David R.; Schulze, Emily S.; Hall, Steven J.

We revisit a classic ecohydrological study that showed streamside riparian trees in a semiarid mountain catchment did not use perennial stream water. The original study suggested that mature individuals of Acer negundo, Acer grandidentatum, and other species were dependent on water from “deeper strata,” possibly groundwater. We used a dual stable isotope approach (δ 18O and δ 2H) to further examine the water sources of these trees. We tested the hypothesis that groundwater was the main tree water source, but found that neither groundwater nor stream water matched the isotope composition of xylem water during two growing seasons. Soil watermore » (0–1 m depth) was closest to and periodically overlapped with xylem water isotope composition, but overall, xylem water was isotopically enriched compared to all measured water sources. The “two water worlds” hypothesis postulates that soil water comprises isotopically distinct mobile and less mobile pools that do not mix, potentially explaining this disparity. We further hypothesized that isotopic effects during snowpack metamorphosis impart a distinct isotope signature to the less mobile soil water that supplies summer transpiration. Depth trends in water isotopes following snowmelt were consistent with the two water worlds hypothesis, but snow metamorphic isotope effects could not explain the highly enriched xylem water. Thus, the dual isotope approach did not unambiguously determine the water source(s) of these riparian trees. Further exploration of physical, geochemical, and biological mechanisms of water isotope fractionation and partitioning is necessary to resolve these data, highlighting critical challenges in the isotopic determination of plant water sources.« less

Statistical characteristics of the sequential detection of signals in correlated noise

NASA Astrophysics Data System (ADS)

Averochkin, V. A.; Baranov, P. E.

1985-10-01

A solution is given to the problem of determining the distribution of the duration of the sequential two-threshold Wald rule for the time-discrete detection of determinate and Gaussian correlated signals on a background of Gaussian correlated noise. Expressions are obtained for the joint probability densities of the likelihood ratio logarithms, and an analysis is made of the effect of correlation and SNR on the duration distribution and the detection efficiency. Comparison is made with Neumann-Pearson detection.

Applications of stable isotopes in clinical pharmacology

PubMed Central

Schellekens, Reinout C A; Stellaard, Frans; Woerdenbag, Herman J; Frijlink, Henderik W; Kosterink, Jos G W

2011-01-01

This review aims to present an overview of the application of stable isotope technology in clinical pharmacology. Three main categories of stable isotope technology can be distinguished in clinical pharmacology. Firstly, it is applied in the assessment of drug pharmacology to determine the pharmacokinetic profile or mode of action of a drug substance. Secondly, stable isotopes may be used for the assessment of drug products or drug delivery systems by determination of parameters such as the bioavailability or the release profile. Thirdly, patients may be assessed in relation to patient-specific drug treatment; this concept is often called personalized medicine. In this article, the application of stable isotope technology in the aforementioned three areas is reviewed, with emphasis on developments over the past 25 years. The applications are illustrated with examples from clinical studies in humans. PMID:21801197

Using cumulative diet data and stable isotope analysis to determine trophic position of walleye Sander vitreus in a large, complex system

USGS Publications Warehouse

Fincel, Mark J.; James, Daniel A.; Chipps, Steven R.; Davis, Blake A.

2014-01-01

Diet studies have traditionally been used to determine prey use and food web dynamics, while stable isotope analysis provides for a time-integrated approach to evaluate food web dynamics and characterize energy flow in aquatic systems. Direct comparison of the two techniques is rare and difficult to conduct in large, species rich systems. We compared changes in walleye Sander vitreus trophic position (TP) derived from paired diet content and stable isotope analysis. Individual diet-derived TP estimates were dissimilar to stable isotope-derived TP estimates. However, cumulative diet-derived TP estimates integrated from May 2001 to May 2002 corresponded to May 2002 isotope-derived estimates of TP. Average walleye TP estimates from the spring season appear representative of feeding throughout the entire previous year.

The biosynthesis of 4-hydroxycoumarin and dicoumarol by Aspergillus fumigatus Fresenius.

PubMed

Bye, A; King, H K

1970-04-01

A strain of Aspergillus fumigatus Fresenius, isolated from spoiled hay, converts melilotic acid (o-hydroxyphenylpropionic acid) and o-coumaric acid into 4-hydroxycoumarin and dicoumarol. The sequence is shown to be melilotic acid (I) [Formula: see text] coumaric acid (IV) [Formula: see text] beta-hydroxymelilotic acid (II) [Formula: see text] beta-oxomelilotic acid (III) [Formula: see text] 4-hydroxycoumarin (VI), on the basis of (1) studies on the formation of postulated intermediates, (2) experiments with isotopically labelled materials and (3) sequential enzyme induction. In the presence of semicarbazide, o-coumaraldehyde is formed from o-coumaric acid: there is no evidence, however, that this lies on the normal metabolic pathway.

SOURCE PARTITIONING USING STABLE ISOTOPES: COPING WITH TOO MANY SOURCES

EPA Science Inventory

Stable isotopes are increasingly being used as tracers in environmental studies. One application is to use isotopic ratios to quantitatively determine the proportional contribution of several sources to a mixture, such as the proportion of various pollution sources in a waste st...

Use of stable isotope analysis in determining aquatic food webs

EPA Science Inventory

Stable isotope analysis is a useful tool for describing resource-consumer dynamics in ecosystems. In general, organisms of a given trophic level or functional feeding group will have a stable isotope ratio identifiable different than their prey because of preferential use of one ...

Oxygen isotope corrections for online δ34S analysis

USGS Publications Warehouse

Fry, B.; Silva, S.R.; Kendall, C.; Anderson, R.K.

2002-01-01

Elemental analyzers have been successfully coupled to stable-isotope-ratio mass spectrometers for online measurements of the δ34S isotopic composition of plants, animals and soils. We found that the online technology for automated δ34S isotopic determinations did not yield reproducible oxygen isotopic compositions in the SO2 produced, and as a result calculated δ34S values were often 1–3‰ too high versus their correct values, particularly for plant and animal samples with high C/S ratio. Here we provide empirical and analytical methods for correcting the S isotope values for oxygen isotope variations, and further detail a new SO2-SiO2 buffering method that minimizes detrimental oxygen isotope variations in SO2.

Nd Isotope and U-Th-Pb Age Mapping of Single Monazite Grains by Laser Ablation Split Stream Analysis

NASA Astrophysics Data System (ADS)

Fisher, C. M.; Hanchar, J. M.; Miller, C. F.; Phillips, S.; Vervoort, J. D.; Martin, W.

2015-12-01

Monazite is a common accessory mineral that occurs in medium to high grade metamorphic and Ca-poor felsic igneous rocks, and often controls the LREE budget (including Sm and Nd) of the host rock in which it crystallizes. Moreover, it contains appreciable U and Th, making it an ideal mineral for determining U-Th-Pb ages and Sm-Nd isotopic compositions, both of which are readily determined using in situ techniques with very high spatial resolution like LA-MC-ICPMS. Here, we present the results of laser ablation split stream analyses (LASS), which allows for simultaneous determination of the age and initial Nd isotopic composition in a single analysis. Analyses were done using a 20mm laser spot that allowed for detailed Nd isotope mapping of monazite grains (~30 analyses per ~250mm sized grain). Combined with LREE ratios (e.g., Sm/Nd, Ce/Gd, and Eu anomalies) these results yield important petrogenetic constraints on the evolution of peraluminous granites from the Old Woman-Piute batholith in southeastern California. Our findings also allow an improved understanding of the causes of isotope heterogeneity in granitic rocks. U-Th-Pb age mapping across the crystals reveals a single Cretaceous age for all grains with precision and accuracy typical of laser ablation analyses (~2%). In contrast, the concurrent Nd isotope mapping yields homogeneous initial Nd isotope compositions for some grains and large initial intra-grain variations of up to 8 epsilon units in others. The grains that yield homogeneous Nd isotope compositions have REE ratios suggesting that they crystallized in a fractionally crystallizing magma. Conversely, other grains, which also record fractional crystallization of both feldspar and LREE rich minerals, demonstrate a change in the Nd isotope composition of the magma during crystallization of monazite. Comparison of inter- and intra-grain Nd isotope compositions reveals further details on the potential mechanisms responsible for isotope heterogeneity present in single rock samples. This method highlights the potential of single grain isotope mapping of LREE phases such as monazite, allanite, and titanite for understanding both igneous and metamorphic petrogenesis.

STABLE CHLORINE ISOTOPIC COMPOSITIONS OF AROCLORS AND ARCLOR-CONTAMINATED SEDIMENT

EPA Science Inventory

An exploratory investigation was conducted to evaluate if stable chlorine isotopic ratios of polychlorinated biphenyls (PCBs) could be useful in studying the processes that determine their transport and fate in the environment. First, we determined the variability of 37Cl in the...

The Determination of Molecular Structure from Rotational Spectra

DOE R&D Accomplishments Database

Laurie, V. W.; Herschbach, D. R.

1962-07-01

An analysis is presented concerning the average molecular configuration variations and their effects on molecular structure determinations. It is noted that the isotopic dependence of the zero-point is often primarily governed by the isotopic variation of the average molecular configuration. (J.R.D.)

Isotopic composition analysis and age dating of uranium samples by high resolution gamma ray spectrometry

NASA Astrophysics Data System (ADS)

Apostol, A. I.; Pantelica, A.; Sima, O.; Fugaru, V.

2016-09-01

Non-destructive methods were applied to determine the isotopic composition and the time elapsed since last chemical purification of nine uranium samples. The applied methods are based on measuring gamma and X radiations of uranium samples by high resolution low energy gamma spectrometric system with planar high purity germanium detector and low background gamma spectrometric system with coaxial high purity germanium detector. The ;Multigroup γ-ray Analysis Method for Uranium; (MGAU) code was used for the precise determination of samples' isotopic composition. The age of the samples was determined from the isotopic ratio 214Bi/234U. This ratio was calculated from the analyzed spectra of each uranium sample, using relative detection efficiency. Special attention is paid to the coincidence summing corrections that have to be taken into account when performing this type of analysis. In addition, an alternative approach for the age determination using full energy peak efficiencies obtained by Monte Carlo simulations with the GESPECOR code is described.

Radiochemical sampling and analysis of shallow ground water and sediment at the BOMARC Missile Facility, east-central New Jersey, 1999-2000

USGS Publications Warehouse

Szabo, Zoltan; Zapecza, Otto S.; Oden, Jeannette H.; Rice, Donald E.

2005-01-01

A field sampling experiment was designed using low-flow purging with a portable pump and sample-collection equipment for the collection of water and sediment samples from observation wells screened in the Kirkwood-Cohansey aquifer system to determine radionuclide or trace-element concentrations for various size fractions. Selected chemical and physical characteristics were determined for water samples from observation wells that had not been purged for years. The sampling was designed to define any particulate, colloidal, and solution-phase associations of radionuclides or trace elements in ground water by means of filtration and ultrafiltration techniques. Turbidity was monitored and allowed to stabilize before samples were collected by means of the low-flow purging technique rather than by the traditional method of purging a fixed volume of water at high-flow rates from the observation well. A minimum of four water samples was collected from each observation well. The samples of water from each well were collected in the following sequence. (1) A raw unfiltered sample was collected within the first minutes of pumping. (2) A raw unfiltered sample was collected after at least three casing volumes of water were removed and turbidity stabilized. (3) A sample was collected after the water was filtered with a 0.45-micron filter. (4) A sample was collected after the water passed through a 0.45-micron filter and a 0.003-micron tangential-flow ultrafilter in sequence. In some cases, a fifth sample was collected after the water passed through a 0.45-micron filter and a 0.05-micron filter in sequence to test for colloids of 0.003 microns to 0.05 microns in size. The samples were analyzed for the concentration of manmade radionuclides plutonium-238 and -239 plus -240, and americium-241. The samples also were analyzed for concentrations of uranium-234, -235, and -238 to determine whether uranium-234 isotope enrichment (resulting from industrial processing) is present. A subset of samples was analyzed for concentrations of thorium-232, -230, and -228 to determine if thorium-228 isotope enrichment, also likely to result from industrial processing, is present. Concentrations of plutonium isotopes and americium-241 in the water samples were less than 0.1 picocurie per liter, the laboratory reporting level for these manmade radionuclides, with the exception of one americium-241 concentration from a filtered sample. A sequential split sample from the same well did not contain a detectable concentration of americium-241, however. Other filtered and unfiltered samples of water from the same well did not contain quantities of americium-241 nearly as high as 0.1 pCi/L. Therefore, the presence of americium-241 in a quantifiable concentration in water samples from this well could not be confirmed. Neither plutonium nor americium was detected in samples of settled sediment collected from the bottom of the wells. Concentrations of uranium isotopes (maximum of 0.05 and 0.08 picocuries per liter of uranium-238 and uranium-234, respectively) were measurable in unfiltered samples of turbid water from one well and in the settled bottom sediment from 6 wells (maximum concentrations of 0.25 and 0.20 picocuries per gram of uranium-238 and uranium-234, respectively). The uranium-234/uranium-238 isotopic ratio was near 1:1, which indicates natural uranium. The analytical results, therefore, indicate that no manmade radionuclide contamination is present in any of the well-bottom sediments, or unfiltered or filtered water samples from any of the sampled wells. No evidence of manmade radionuclide contamination was observed in the aquifer as settled or suspended particulates, colloids, or in the dissolved phase.

Visualizing Single Cell Biology: Nanosims Studies of Carbon and Nitrogen Metabolism in Diazotrophic Cyanobacteria

NASA Astrophysics Data System (ADS)

Pett-Ridge, J.; Finzi, J. A.; Capone, D. G.; Popa, R.; Nealson, K. H.; Ng, W.; Spormann, A. M.; Hutcheon, I. D.; Weber, P. K.

2007-12-01

Filamentous nitrogen fixing (diazotrophic) cyanobacteria are key players in global nutrient cycling, but the relationship between CO2- and N2-fixation and intercellular exchange of these elements remains poorly understood in many genera. These bacteria are faced with the challenge of isolating regions of N-fixation (O2 inhibited) and photosynthetic (O2 producing) activity. We used isotope labeling in conjunction with a high-resolution isotope and elemental mapping technique (NanoSIMS) to quantitatively describe 13C and 15N uptake and transport in two aquatic cyanobacteria grown on NaH13CO3 and 15N2. The technical challenges of tracing isotopes within individual bacteria can be overcome with high resolution Secondary Ion Mass Spectrometry (NanoSIMS). In NanoSIMS analysis, samples are sputtered with an energetic primary beam (Cs+, O-) liberating secondary ions that are separated by the mass spectrometer and detected in a suite of electron multipliers. Five isotopic species may be analyzed concurrently with spatial resolution as fine as 50nm. A high sensitivity isotope ratio 'map' can then be generated for the analyzed area. Using sequentially harvested cyanobacteria in conjunction with enriched H13CO3 and 15N2 incubations, we measured temporal enrichment patterns that evolve over the course of a day's growth and suggest tightly regulated changes in fixation kinetics. With a combination of TEM, SEM and NanoSIMS analyses, we also mapped the distribution of C, N and Mo (a critical nitrogenase co-factor) isotopes in intact cells. Our results suggest that NanoSIMS mapping of metal enzyme co-factors may be a powerful method of identifying physiological and morphological characteristics within individual bacterial cells, and could be used to provide a 3-dimensional context for more traditional analyses such as immunogold labeling. Finally, we resolved patterns of isotope enrichment at multiple spatial scales: sub-cellular variation, cell-cell differences along filaments, inter-species transfers (with Rhizobium epibionts), and within-cell depth profiles. Spatial enrichment patterns were correlated with morphological features evidenced in TEM images of microtomed filaments. These features indicate how 15N and 13C "hotspots" are dispersed throughout individual cells in different species, and may indicate isolated locations of increased N2 fixation, sites of amino acid/protein synthesis, or cyanophycin storage granules. This combination of Nano-Secondary Ion Mass Spectrometry (NanoSIMS) analysis and high resolution microscopy allows isotopic analysis to be linked to morphological features and holds great promise for fine-scale studies of bacteria metabolism.

Accurate experimental determination of the isotope effects on the triple point temperature of water. I. Dependence on the 2H abundance

NASA Astrophysics Data System (ADS)

Faghihi, V.; Peruzzi, A.; Aerts-Bijma, A. T.; Jansen, H. G.; Spriensma, J. J.; van Geel, J.; Meijer, H. A. J.

2015-12-01

Variation in the isotopic composition of water is one of the major contributors to uncertainty in the realization of the triple point of water (TPW). Although the dependence of the TPW on the isotopic composition of the water has been known for years, there is still a lack of a detailed and accurate experimental determination of the values for the correction constants. This paper is the first of two articles (Part I and Part II) that address quantification of isotope abundance effects on the triple point temperature of water. In this paper, we describe our experimental assessment of the 2H isotope effect. We manufactured five triple point cells with prepared water mixtures with a range of 2H isotopic abundances encompassing widely the natural abundance range, while the 18O and 17O isotopic abundance were kept approximately constant and the 18O  -  17O ratio was close to the Meijer-Li relationship for natural waters. The selected range of 2H isotopic abundances led to cells that realised TPW temperatures between approximately  -140 μK to  +2500 μK with respect to the TPW temperature as realized by VSMOW (Vienna Standard Mean Ocean Water). Our experiment led to determination of the value for the δ2H correction parameter of A2H  =  673 μK / (‰ deviation of δ2H from VSMOW) with a combined uncertainty of 4 μK (k  =  1, or 1σ).

[Approach to percutaneous nephrolithotomy. Comparison of the procedure in a one-shot versus the sequential with metal dilata].

PubMed

Sedano-Portillo, Ismael; Ochoa-León, Gastón; Fuentes-Orozco, Clotilde; Irusteta-Jiménez, Leire; Michel-Espinoza, Luis Rodrigo; Salazar-Parra, Marcela; Cuesta-Márquez, Lizbeth; González-Ojeda, Alejandro

2017-01-01

Percutaneous nephrolithotomy is an efficient approach for treatment of different types of kidney stones. Various types of access techniques have been described like sequential dilatation and one-shot procedure. To determine the differences in time of exposure to X-rays and hemoglobin levels between techniques. Controlled clinical trial. Patients older than 18 years with complex/uncomplicated kidney stones, without urine infection were included. They were assigned randomly to one of the two techniques. Response variables were determined before and 24 h after procedures. 59 patients were included: 30 underwent one-shot procedure (study-group) and 29 sequential dilatation (control-group). Baseline characteristics were similar. Study group had a lower postoperative hemoglobin decline than control group (0.81 vs. 2.03 g/dl, respectively; p < 0.001); X-ray exposure time (69.6 vs. 100.62 s; p < 0.001) and postoperative creatinine serum levels (0.93 ± 0.29 vs. 1.13 ± 0.4 mg/dl; p = 0.039). No significant differences in postoperative morbidity were found. One-shot technique demonstrated better results compared to sequential dilatation.

Delta(13)C, delta(15)N and delta(2)H isotope ratio mass spectrometry of ephedrine and pseudoephedrine: application to methylamphetamine profiling.

PubMed

Collins, Michael; Cawley, Adam T; Heagney, Aaron C; Kissane, Luke; Robertson, James; Salouros, Helen

2009-07-01

Conventional chemical profiling of methylamphetamine has been used for many years to determine the synthetic route employed and where possible to identify the precursor chemicals used. In this study stable isotope ratio analysis was investigated as a means of determining the origin of the methylamphetamine precursors, ephedrine and pseudoephedrine. Ephedrine and pseudoephedrine may be prepared industrially by several routes. Results are presented for the stable isotope ratios of carbon (delta(13)C), nitrogen (delta(15)N) and hydrogen (delta(2)H) measured in methylamphetamine samples synthesized from ephedrine and pseudoephedrine of known provenance. It is clear from the results that measurement of the delta(13)C, delta(15)N and delta(2)H stable isotope ratios by elemental analyzer/thermal conversion isotope ratio mass spectrometry (EA/TC-IRMS) in high-purity methylamphetamine samples will allow determination of the synthetic source of the ephedrine or pseudoephedrine precursor as being either of a natural, semi-synthetic, or fully synthetic origin. Copyright (c) 2009 Commonwealth of Australia.

Determination of nitrite and nitrate in water samples by an automated hydrodynamic sequential injection method.

PubMed

Somnam, Sarawut; Jakmunee, Jaroon; Grudpan, Kate; Lenghor, Narong; Motomizu, Shoji

2008-12-01

An automated hydrodynamic sequential injection (HSI) system with spectrophotometric detection was developed. Thanks to the hydrodynamic injection principle, simple devices can be used for introducing reproducible microliter volumes of both sample and reagent into the flow channel to form stacked zones in a similar fashion to those in a sequential injection system. The zones were then pushed to the detector and a peak profile was recorded. The determination of nitrite and nitrate in water samples by employing the Griess reaction was chosen as a model. Calibration graphs with linearity in the range of 0.7 - 40 muM were obtained for both nitrite and nitrate. Detection limits were found to be 0.3 muM NO(2)(-) and 0.4 muM NO(3)(-), respectively, with a sample throughput of 20 h(-1) for consecutive determination of both the species. The developed system was successfully applied to the analysis of water samples, employing simple and cost-effective instrumentation and offering higher degrees of automation and low chemical consumption.

Experimental determination of iron isotope fractionations among Fe aq 2 + -FeSaq-Mackinawite at low temperatures: Implications for the rock record

NASA Astrophysics Data System (ADS)

Wu, Lingling; Druschel, Greg; Findlay, Alyssa; Beard, Brian L.; Johnson, Clark M.

2012-07-01

The Fe isotope fractionation factors among aqueous ferrous iron (Fe aq 2 +), aqueous FeS clusters (FeSaq), and nanoparticulate mackinawite under neutral and mildly acidic and alkaline pH conditions have been determined using the three-isotope method. Combined voltammetric analysis and geochemical modeling were used to determine the Fe speciation in the experimental systems. The equilibrium 56Fe/54Fe fractionation factor at 20 °C and pH 7 has been determined to be -0.32 ± 0.29 (2σ)‰ between Fe aq 2 + (minor FeSaq also present in the experiment) and mackinawite. This fractionation factor was essentially constant when pH was changed to 6 or 8. When equal molarity of HS- and Fe aq 2 + were added to the system, however, the isotopic fractionation at pH 7 changed to -0.64 ± 0.36 (2σ)‰, correlating with a significant increase in the proportion of FeHS+ and FeSaq. These results highlight a more important role of aqueous Fe-S speciation in the equilibrium Fe isotope fractionation factor than recognized in previous studies. The isotopic fractionation remained constant when temperature was increased from 20 °C to 35 °C for fractionation factors between Fe aq 2 + , and mackinawite and between dominantly FeHS+ and mackinawite. Synthesis experiments similar to those of Butler et al. (2005) and Guilbaud et al. (2010) at pH 4 show consistent results: over time, the aqueous Fe-mackinawite fractionation decreases but even after 38 days of aging the fractionation factor is far from the equilibrium value inferred using the three-isotope method. In contrast, at near-neutral pH the fractionation factor for the synthesis experiment reached the equilibrium value in 38 days. These differences are best explained by noting that at low pH the FeS mackinawite particles coarsen more rapidly via particle aggregation, which limits isotopic exchange, whereas at higher pH mackinawite aggregation is limited, and Fe isotope exchange occurs more rapidly, converging on the equilibrium value. These results suggest that mackinawite formed in natural environments at near-neutral or alkaline pH are unlikely to retain kinetic isotope fractionations, but are more likely to reflect equilibrium isotope compositions. This in turn has important implications for interpreting iron isotope compositions of Fe sulfides in natural systems.

The stable Cr isotopic compositions of chondrites and silicate planetary reservoirs

NASA Astrophysics Data System (ADS)

Schoenberg, Ronny; Merdian, Alexandra; Holmden, Chris; Kleinhanns, Ilka C.; Haßler, Kathrin; Wille, Martin; Reitter, Elmar

2016-06-01

The depletion of chromium in Earth's mantle (∼2700 ppm) in comparison to chondrites (∼4400 ppm) indicates significant incorporation of chromium into the core during our planet's metal-silicate differentiation, assuming that there was no significant escape of the moderately volatile element chromium during the accretionary phase of Earth. Stable Cr isotope compositions - expressed as the ‰-difference in 53Cr/52Cr from the terrestrial reference material SRM979 (δ53/52CrSRM979 values) - of planetary silicate reservoirs might thus yield information about the conditions of planetary metal segregation processes when compared to chondrites. The stable Cr isotopic compositions of 7 carbonaceous chondrites, 11 ordinary chondrites, 5 HED achondrites and 2 martian meteorites determined by a double spike MC-ICP-MS method are within uncertainties indistinguishable from each other and from the previously determined δ53/52CrSRM979 value of -0.124 ± 0.101‰ for the igneous silicate Earth. Extensive quality tests support the accuracy of the stable Cr isotope determinations of various meteorites and terrestrial silicates reported here. The uniformity in stable Cr isotope compositions of samples from planetary silicate mantles and undifferentiated meteorites indicates that metal-silicate differentiation of Earth, Mars and the HED parent body did not cause measurable stable Cr isotope fractionation between these two reservoirs. Our results also imply that the accretionary disc, at least in the inner solar system, was homogeneous in its stable Cr isotopic composition and that potential volatility loss of chromium during accretion of the terrestrial planets was not accompanied by measurable stable isotopic fractionation. Small but reproducible variations in δ53/52CrSRM979 values of terrestrial magmatic rocks point to natural stable Cr isotope variations within Earth's silicate reservoirs. Further and more detailed studies are required to investigate whether silicate differentiation processes, such as partial mantle melting and crystal fractionation, can cause stable Cr isotopic fractionation on Earth and other planetary bodies.

Biodegradation of Chlorofluorocarbons in a Groundwater Plume using Compound Specific Carbon Isotope Analysis

NASA Astrophysics Data System (ADS)

Phillips, E.; Manna, J.; Horst, A.; Gilevska, T.; Sherwood Lollar, B.; Mack, E. E.; Seger, E.; Lutz, E. J.; Norcoss, S.; Morgan, S. E.; West, K. A.; Dworatzek, S.; Webb, J.

2017-12-01

Compound specific isotope analysis (CSIA) measures isotope ratios of organic hydrocarbons to monitor intrinsic bioremediation processes that can transform contaminants in field settings. The fraction of original contaminant remaining can be determined using the measured isotope ratio of the contaminant by an experimentally determined fractionation factor. In this study, two separate biotransformation experiments were performed in the Stable Isotope Laboratory at the University of Toronto using CSIA. In these two experiments, a mixed culture derived from a contaminated site was amended with trichlorotrifluoroethane (CFC-113), or trichlorofluoromethane (CFC-11), respectively. The concentrations and carbon isotope ratios of CFC-113, or CFC-11 were analyzed to calculate the fractionation factor for the transformation of each compound. Subsequently, groundwater samples from 9 wells at a historically contaminated site were collected and analyzed. The experimentally determined fractionation factors were then used to evaluate the extent of transformation that had occurred at the field site. In the laboratory studies, significant carbon isotope fractionation was observed for both CFC-113 and CFC-11 as biotransformation proceeded. This significant fractionation is beneficial when evaluating biotransformation at field sites as it can be clearly differentiated from the effects of other physical processes such as transport, or volatilization. Although there was significant variation in the carbon isotope values of CFC-113 between different well locations at the field site, these variations may be due to differences in source carbon isotope signatures. For CFC-11, much more significant isotopic variation was observed within the same well and between wells, showing trends consistent with in situ biotransformation. Results from this study demonstrate that CSIA can be successfully applied to evaluate the extent of transformation of chlorofluorocarbons (CFCs) at contaminated field sites, which has not been shown previously. This study also demonstrates that biotransformation may play a more significant role in the natural attenuation of CFCs than has previously been recognized.

Carbon Monoxide Stable Isotopes: Extraction Technique Development and Urban Atmospheric Analysis

NASA Astrophysics Data System (ADS)

Vimont, Isaac Josef

We have developed an extraction system to analyze isotopes of carbon monoxide (CO). We then analyzed CO isotopes for two years at Indianapolis, IN, USA. These measurements were done at three towers, one of which measured incoming, background air into the city. We quantitatively removed the background signal and determined the urban CO mole fraction and isotopic enhancements. During the winter months, we constrained the isotopic signature and concluded that the majority of CO produced during the winter was produced by fossil fuel combustion. We found that the Indianapolis fossil fuel signature differed from that of studies done in Europe. Further, we performed a limited traffic study to look at CO isotopes from traffic. While this was not conclusive, it did support our hypothesis that a larger fraction of the Indianapolis vehicle fleet may have malfunctioning catalytic systems, which biases the isotopic results, particularly for delta18O. We used the wintertime fossil fuel isotopic signature to help constrain the summertime budget. It was hypothesized that a second source of CO was significant during the summer months. Oxidation of biogenically produced volatile organic compounds (BVOC's) was one possible source. Oxidized BVOC's were consistent with the changes between our winter and summer isotopic source signatures. We then used the isotopic signatures to determine that between zero and sixty percent of the summertime CO budget was produced from oxidized VOC's. This provided the first direct evidence of a larger percentage of urban CO being produced by oxidized VOC's.

USSR Report, Chemistry

DTIC Science & Technology

1985-08-19

No 2, Mar-Apr 85) 15 Factors Which Determine Activity of Catalysts of Various Chemical Types in Hydrogen Oxidation Reactions . Part 1: Oxidation ...Factors Which Determine Activity of Catalysts of Various Chemical Types in Hydrogen Oxidation Reactions . Part 2: Oxidation and Isotope Exchange of...FACTORS WHICH DETERMINE ACTIVITY OF CATALYSTS OF VARIOUS CHEMICAL TYPES IN HYDROGEN OXIDATION REACTIONS . PART 1: OXIDATION AND ISOTOPE EXCHANGE OF

[Rapid analysis of the radionuclides plutonium and americium-241 in soils].

PubMed

Egorov, A V; Klochkova, N V

2009-01-01

The paper shows it possible to perform a rapid analysis of the isotopes of plutomium and americium-241. The basis of the developed rapid analysis is X-spectrometric determination of the amount of plutonium isotopes and gamma-spectrometric determination of the radionuclide 241AM.

Improvements in the MGA Code Provide Flexibility and Better Error Analysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ruhter, W D; Kerr, J

2005-05-26

The Multi-Group Analysis (MGA) code is widely used to determine nondestructively the relative isotopic abundances of plutonium by gamma-ray spectrometry. MGA users have expressed concern about the lack of flexibility and transparency in the code. Users often have to ask the code developers for modifications to the code to accommodate new measurement situations, such as additional peaks being present in the plutonium spectrum or expected peaks being absent. We are testing several new improvements to a prototype, general gamma-ray isotopic analysis tool with the intent of either revising or replacing the MGA code. These improvements will give the user themore » ability to modify, add, or delete the gamma- and x-ray energies and branching intensities used by the code in determining a more precise gain and in the determination of the relative detection efficiency. We have also fully integrated the determination of the relative isotopic abundances with the determination of the relative detection efficiency to provide a more accurate determination of the errors in the relative isotopic abundances. We provide details in this paper on these improvements and a comparison of results obtained with current versions of the MGA code.« less

High-precision measurement of variations in calcium isotope ratios in urine by multiple collector inductively coupled plasma mass spectrometry

USGS Publications Warehouse

Morgan, J.L.L.; Gordon, G.W.; Arrua, R.C.; Skulan, J.L.; Anbar, A.D.; Bullen, T.D.

2011-01-01

We describe a new chemical separation method to isolate Ca from other matrix elements in biological samples, developed with the long-term goal of making high-precision measurement of natural stable Ca isotope variations a clinically applicable tool to assess bone mineral balance. A new two-column procedure utilizing HBr achieves the purity required to accurately and precisely measure two Ca isotope ratios (44Ca/42Ca and 44Ca/43Ca) on a Neptune multiple collector inductively coupled plasma mass spectrometer (MC-ICPMS) in urine. Purification requirements for Sr, Ti, and K (Ca/Sr > 10000; Ca/Ti > 10000000; and Ca/K > 10) were determined by addition of these elements to Ca standards of known isotopic composition. Accuracy was determined by (1) comparing Ca isotope results for samples and standards to published data obtained using thermal ionization mass spectrometry (TIMS), (2) adding a Ca standard of known isotopic composition to a urine sample purified of Ca, and (3) analyzing mixtures of urine samples and standards in varying proportions. The accuracy and precision of δ44/42Ca measurements of purified samples containing 25 μg of Ca can be determined with typical errors less than ±0.2‰ (2σ).

Spinel-olivine-pryoxene equilibrium iron isotopic fractionation and applications to natural peridotites

DOE Office of Scientific and Technical Information (OSTI.GOV)

Roskosz, Mathieu; Sio, Corliss K. I.; Dauphas, Nicolas

2015-11-15

Eight spinel-group minerals were synthesized by a flux-growth method producing spinels with varying composition and Fe3+/Fe-tot ratios. The mean force constants of iron bonds in these minerals were determined by synchrotron nuclear resonant inelastic X-ray scattering (NRIXS) in order to determine the reduced isotopic partition function ratios (beta-factors) of these spinels. The mean force constants are strongly dependent on the Fe3+/Fe-tot of the spinel but are independent, or weakly dependent on other structural and compositional parameters. From our spectroscopic data, it is found that a single redox-dependent calibration line accounts for the effects of Fe3+/Fe-tot on the beta-factors of spinels.more » This calibration successfully describes the equilibrium Fe isotopes fractionation factors between spinels and silicates (olivine and pyroxenes). Our predictions are in excellent agreement with independent determinations for the equilibrium Fe isotopic fractionations for the magnetite- fayalite and the magnetite-hedenbergite couples. Our calibration applies to the entire range of Fe3+/Fe-tot ratios found in natural spinels and provides a basis for interpreting iron isotopic variations documented in mantle peridotites. Except for a few exceptions, most of the samples measured so far are in isotopic disequilibrium, reflecting metasomatism and partial melting processes.« less

Compound-specific isotope analysis: Questioning the origins of a trichloroethene plume

USGS Publications Warehouse

Eberts, S.M.; Braun, C.; Jones, S.

2008-01-01

Stable carbon isotope ratios of trichloroethene (TCE), cis-1,2- dichloroethene, and trans-1,2-dichloroethene were determined by use of gas chromatography-combustion-isotope ratio mass spectroscopy to determine whether compound-specific stable carbon isotopes could be used to help understand the origin and history of a TCE groundwater plume in Fort Worth, TX. Calculated ??13C values for total chlorinated ethenes in groundwater samples, which can approximate the ??13C of a spilled solvent if all degradation products are accounted for, were useful for determining whether separate lobes of the plume resulted from different sources. Most notably, values for one lobe, where tetrachloroethene (PCE) has been detected periodically, were outside the range for manufactured TCE but within the range for manufactured PCE, whereas values for a separate lobe, which is downgradient of reported TCE spills, were within the range for manufactured TCE. Copyright ?? Taylor & Francis Group, LLC.

Intrinsic ratios of glucose, fructose, glycerol and ethanol 13C/12C isotopic ratio determined by HPLC-co-IRMS: toward determining constants for wine authentication.

PubMed

Guyon, François; Gaillard, Laetitia; Salagoïty, Marie-Hélène; Médina, Bernard

2011-09-01

High-performance liquid chromatography linked to isotope ratio mass spectrometry (HPLC-co-IRMS) via a Liquiface© interface has been used to simultaneously determine (13)C isotope ratios of glucose (G), fructose (F), glycerol (Gly) and ethanol (Eth) in sweet and semi-sweet wines. The data has been used the study of wine authenticity. For this purpose, 20 authentic wines from various French production areas and various vintages have been analyzed after dilution in pure water from 20 to 200 times according to sugar content. If the (13)C isotope ratios vary according to the production area and the vintage, it appears that internal ratios of (13)C isotope ratios (R((13)C)) of the four compounds studied can be considered as a constant. Thus, ratios of isotope ratios are found to be 1.00 ± 0.04 and 1.02 ± 0.08 for R((13)C(G/F)) and R((13)C(Gly/Eth)), respectively. Moreover, R((13)C(Eth/Sugar)) is found to be 1.15 ± 0.10 and 1.16 ± 0.08 for R((13)C(Gly/Sugar)). Additions of glucose, fructose and glycerol to a reference wine show a variation of the R((13)C) value for a single product addition as low as 2.5 g/L(-1). Eighteen commercial wines and 17 concentrated musts have been analyzed. Three wine samples are suspicious as the R((13)C) values are out of range indicating a sweetening treatment. Moreover, concentrated must analysis shows that (13)C isotope ratio can be also used directly to determine the authenticity of the matrix.

Environmentally friendly microwave-assisted sequential extraction method followed by ICP-OES and ion-chromatographic analysis for rapid determination of sulphur forms in coal samples.

PubMed

Mketo, Nomvano; Nomngongo, Philiswa N; Ngila, J Catherine

2018-05-15

A rapid three-step sequential extraction method was developed under microwave radiation followed by inductively coupled plasma-optical emission spectroscopic (ICP-OES) and ion-chromatographic (IC) analysis for the determination of sulphur forms in coal samples. The experimental conditions of the proposed microwave-assisted sequential extraction (MW-ASE) procedure were optimized by using multivariate mathematical tools. Pareto charts generated from 2 3 full factorial design showed that, extraction time has insignificant effect on the extraction of sulphur species, therefore, all the sequential extraction steps were performed for 5 min. The optimum values according to the central composite designs and counter plots of the response surface methodology were 200 °C (microwave temperature) and 0.1 g (coal amount) for all the investigated extracting reagents (H 2 O, HCl and HNO 3 ). When the optimum conditions of the proposed MW-ASE procedure were applied in coal CRMs, SARM 18 showed more organic sulphur (72%) and the other two coal CRMs (SARMs 19 and 20) were dominated by sulphide sulphur species (52-58%). The sum of the sulphur forms from the sequential extraction steps have shown consistent agreement (95-96%) with certified total sulphur values on the coal CRM certificates. This correlation, in addition to the good precision (1.7%) achieved by the proposed procedure, suggests that the sequential extraction method is reliable, accurate and reproducible. To safe-guard the destruction of pyritic and organic sulphur forms in extraction step 1, water was used instead of HCl. Additionally, the notorious acidic mixture (HCl/HNO 3 /HF) was replaced by greener reagent (H 2 O 2 ) in the last extraction step. Therefore, the proposed MW-ASE method can be applied in routine laboratories for the determination of sulphur forms in coal and coal related matrices. Copyright © 2018 Elsevier B.V. All rights reserved.

Melting point of high-purity germanium stable isotopes

NASA Astrophysics Data System (ADS)

Gavva, V. A.; Bulanov, A. D.; Kut'in, A. M.; Plekhovich, A. D.; Churbanov, M. F.

2018-05-01

The melting point (Tm) of germanium stable isotopes 72Ge, 73Ge, 74Ge, 76Ge was determined by differential scanning calorimetry. With the increase in atomic mass of isotope the decrease in Tm is observed. The decrease was equal to 0.15 °C per the unit of atomic mass which qualitatively agrees with the value calculated by Lindemann formula accounting for the effect of "isotopic compression" of elementary cell.

Isotope Ratio Monitoring Gas Chromatography Mass Spectrometry (IRM-GCMS)

NASA Technical Reports Server (NTRS)

Freeman, K. H.; Ricci, S. A.; Studley, A.; Hayes, J. M.

1989-01-01

On Earth, the C-13 content of organic compounds is depleted by roughly 13 to 23 permil from atmospheric carbon dioxide. This difference is largely due to isotope effects associated with the fixation of inorganic carbon by photosynthetic organisms. If life once existed on Mars, then it is reasonable to expect to observe a similar fractionation. Although the strongly oxidizing conditions on the surface of Mars make preservation of ancient organic material unlikely, carbon-isotope evidence for the existence of life on Mars may still be preserved. Carbon depleted in C-13 could be preserved either in organic compounds within buried sediments, or in carbonate minerals produced by the oxidation of organic material. A technique is introduced for rapid and precise measurement of the C-13 contents of individual organic compounds. A gas chromatograph is coupled to an isotope-ratio mass spectrometer through a combustion interface, enabling on-line isotopic analysis of isolated compounds. The isotope ratios are determined by integration of ion currents over the course of each chromatographic peak. Software incorporates automatic peak determination, corrections for background, and deconvolution of overlapped peaks. Overall performance of the instrument was evaluated by the analysis of a mixture of high purity n-alkanes of know isotopic composition. Isotopic values measured via IRM-GCMS averaged withing 0.55 permil of their conventionally measured values.

Simultaneous versus sequential penetrating keratoplasty and cataract surgery.

PubMed

Hayashi, Ken; Hayashi, Hideyuki

2006-10-01

To compare the surgical outcomes of simultaneous penetrating keratoplasty and cataract surgery with those of sequential surgery. Thirty-nine eyes of 39 patients scheduled for simultaneous keratoplasty and cataract surgery and 23 eyes of 23 patients scheduled for sequential keratoplasty and secondary phacoemulsification surgery were recruited. Refractive error, regular and irregular corneal astigmatism determined by Fourier analysis, and endothelial cell loss were studied at 1 week and 3, 6, and 12 months after combined surgery in the simultaneous surgery group or after subsequent phacoemulsification surgery in the sequential surgery group. At 3 and more months after surgery, mean refractive error was significantly greater in the simultaneous surgery group than in the sequential surgery group, although no difference was seen at 1 week. The refractive error at 12 months was within 2 D of that targeted in 15 eyes (39%) in the simultaneous surgery group and within 2 D in 16 eyes (70%) in the sequential surgery group; the incidence was significantly greater in the sequential group (P = 0.0344). The regular and irregular astigmatism was not significantly different between the groups at 3 and more months after surgery. No significant difference was also found in the percentage of endothelial cell loss between the groups. Although corneal astigmatism and endothelial cell loss were not different, refractive error from target refraction was greater after simultaneous keratoplasty and cataract surgery than after sequential surgery, indicating a better outcome after sequential surgery than after simultaneous surgery.

Isotopic composition of Pb and Th in interplinian volcanics from Somma-Vesuvius volcano, Italy

USGS Publications Warehouse

Cortini, M.; Ayuso, R.A.; de Vivo, B.; Holden, P.; Somma, R.

2004-01-01

We present a detailed isotopic study of volcanic rocks emitted from Somma-Vesuvius volcano during three periods of interplinian activity: "Protohistoric" (3550 y B.P. to 79 A.D.), "Ancient Historic" (79 to 472 A.D.) and "Medieval" (472 to 1631 A.D.). Pb isotopic compositions of two acid leached fractions and whole rock residues of 37 whole rock samples (determined by Somma et al., 2001) show that each of the three interplinian periods is distinguished by small, systematic, and unique uranogenic and thorogenic Pb isotopic trends. This key and novel feature is compatible with the notion that the Pb isotopic data reflect small-scale source heterogeneity operating over relatively short periods of time. From this representative group of samples, a selected set of nine whole rocks were analysed for Th isotopes. 232Th/238U ratios in the source can be obtained independently from Pb and from Th isotopes. Those obtained from Pb isotopes represent source ratios, time-integrated over the whole age of the Earth; they range from 3.9 to 4.1. 232Th/238U obtained from Th isotopes are those of the present source. They are lower, and cluster around 3.5; this difference probably indicates recent U enrichment of the present source. The behaviour of Pb, as inferred by its isotopic ratios, is quite distinct from that of Sr and Nd isotopes: Pb isotope variations are not correlated to Sr or Nd isotope variations. The isotopic contrast is compatible with the idea that the isotopes were decoupled during magmatic production, evolution, and ascent through the crust. Thus, the Pb isotopes do not reflect the effects of the same processes as in the case of the Sr and Nd isotopes, or, as we also favor, they do not necessarily reflect the same source contributions into the magmas. Moreover, the Pb isotopic evolution of the interplinian rocks chiefly reflects mixing, driven by processes that are superimposed on, and independent of, other source contributions that determine the isotopic compositions of Sr and Nd. We suggest that reactions between magmas and fluids transported Pb and U, but not Sr. These data show that isotope mixing in the mantle is active at different times and scales. ?? Springer-Verlag 2004.

USING STABLE ISOTOPES FOR FISH DIETARY ANALYSES: COPING WITH TOO MANY SOURCES

EPA Science Inventory

Stable isotope analysis can provide a useful tool for determining time-integrated measures of proportional food source contributions to fish diets. Ratios of stable (non-radioactive) isotopes of common elements (e.g., C,N,S) vary among food sources, and tissues of consumers (e.g...

Soil drying effects on the carbon isotope composition of soil respiration

EPA Science Inventory

Stable isotopes are used widely as a tool for determining sources of carbon (C) fluxes in ecosystem C studies. Environmental factors that change over time, such as moisture, can create dynamic changes in the isotopic composition of C assimilated by plants, and offers a unique opp...

76 FR 77257 - Manufacturer of Controlled Substances; Notice of Registration

Federal Register 2010, 2011, 2012, 2013, 2014

2011-12-12

... 18, 2011, 76 FR 51400, Cambridge Isotope Lab, 50 Frontage Road, Andover, Massachusetts 01810, made... determined that the registration of Cambridge Isotope Lab to manufacture the listed basic class of controlled substance is consistent with the public interest at this time. DEA has investigated Cambridge Isotope Lab to...

Isotopic Compositions of the Elements, 2001

NASA Astrophysics Data System (ADS)

Böhlke, J. K.; de Laeter, J. R.; De Bièvre, P.; Hidaka, H.; Peiser, H. S.; Rosman, K. J. R.; Taylor, P. D. P.

2005-03-01

The Commission on Atomic Weights and Isotopic Abundances of the International Union of Pure and Applied Chemistry completed its last review of the isotopic compositions of the elements as determined by isotope-ratio mass spectrometry in 2001. That review involved a critical evaluation of the published literature, element by element, and forms the basis of the table of the isotopic compositions of the elements (TICE) presented here. For each element, TICE includes evaluated data from the "best measurement" of the isotope abundances in a single sample, along with a set of representative isotope abundances and uncertainties that accommodate known variations in normal terrestrial materials. The representative isotope abundances and uncertainties generally are consistent with the standard atomic weight of the element Ar(E) and its uncertainty U[Ar(E)] recommended by CAWIA in 2001.

Isotopic variations of dissolved copper and zinc in stream waters affected by historical mining

USGS Publications Warehouse

Borrok, D.M.; Nimick, D.A.; Wanty, R.B.; Ridley, W.I.

2008-01-01

Zinc and Cu play important roles in the biogeochemistry of natural systems, and it is likely that these interactions result in mass-dependent fractionations of their stable isotopes. In this study, we examine the relative abundances of dissolved Zn and Cu isotopes in a variety of stream waters draining six historical mining districts located in the United States and Europe. Our goals were to (1) determine whether streams from different geologic settings have unique or similar Zn and Cu isotopic signatures and (2) to determine whether Zn and Cu isotopic signatures change in response to changes in dissolved metal concentrations over well-defined diel (24-h) cycles. Average ??66Zn and ??65Cu values for streams varied from +0.02??? to +0.46??? and -0.7??? to +1.4???, respectively, demonstrating that Zn and Cu isotopes are heterogeneous among the measured streams. Zinc or Cu isotopic changes were not detected within the resolution of our measurements over diel cycles for most streams. However, diel changes in Zn isotopes were recorded in one stream where the fluctuations of dissolved Zn were the largest. We calculate an apparent separation factor of ???0.3??? (66/64Zn) between the dissolved and solid Zn reservoirs in this stream with the solid taking up the lighter Zn isotope. The preference of the lighter isotope in the solid reservoir may reflect metabolic uptake of Zn by microorganisms. Additional field investigations must evaluate the contributions of soils, rocks, minerals, and anthropogenic components to Cu and Zn isotopic fluxes in natural waters. Moreover, rigorous experimental work is necessary to quantify fractionation factors for the biogeochemical reactions that are likely to impact Cu and Zn isotopes in hydrologic systems. This initial investigation of Cu and Zn isotopes in stream waters suggests that these isotopes may be powerful tools for probing biogeochemical processes in surface waters on a variety of temporal and spatial scales.

Mass spectrometry of long-lived radionuclides

NASA Astrophysics Data System (ADS)

Becker, Johanna Sabine

2003-10-01

The capability of determining element concentrations at the trace and ultratrace level and isotope ratios is a main feature of inorganic mass spectrometry. The precise and accurate determination of isotope ratios of long-lived natural and artificial radionuclides is required, e.g. for their environmental monitoring and health control, for studying radionuclide migration, for age dating, for determining isotope ratios of radiogenic elements in the nuclear industry, for quality assurance and determination of the burn-up of fuel material in a nuclear power plant, for reprocessing plants, nuclear material accounting and radioactive waste control. Inorganic mass spectrometry, especially inductively coupled plasma mass spectrometry (ICP-MS) as the most important inorganic mass spectrometric technique today, possesses excellent sensitivity, precision and good accuracy for isotope ratio measurements and practically no restriction with respect to the ionization potential of the element investigated—therefore, thermal ionization mass spectrometry (TIMS), which has been used as the dominant analytical technique for precise isotope ratio measurements of long-lived radionuclides for many decades, is being replaced increasingly by ICP-MS. In the last few years instrumental progress in improving figures of merit for the determination of isotope ratio measurements of long-lived radionuclides in ICP-MS has been achieved by the application of a multiple ion collector device (MC-ICP-MS) and the introduction of the collision cell interface in order to dissociate disturbing argon-based molecular ions, to reduce the kinetic energy of ions and neutralize the disturbing noble gas ions (e.g. of 129Xe + for the determination of 129I). The review describes the state of the art and the progress of different inorganic mass spectrometric techniques such as ICP-MS, laser ablation ICP-MS vs. TIMS, glow discharge mass spectrometry, secondary ion mass spectrometry, resonance ionization mass spectrometry and accelerator mass spectrometry for the determination of long-lived radionuclides in quite different materials.

Apparatus and method for quantitative assay of generic transuranic wastes from nuclear reactors

DOEpatents

Caldwell, J.T.; Kunz, W.E.; Atencio, J.D.

1982-03-31

A combination of passive and active neutron measurements which yields quantitative information about the isotopic composition of transuranic wastes from nuclear power or weapons material manufacture reactors is described. From the measurement of prompt and delayed neutron emission and the incidence of two coincidentally emitted neutrons from induced fission of fissile material in the sample, one can quantify /sup 233/U, /sup 235/U and /sup 239/Pu isotopes in waste samples. Passive coincidence counting, including neutron multiplicity measurement and determination of the overall passive neutron flux additionally enables the separate quantitative evaluation of spontaneous fission isotopes such as /sup 240/Pu, /sup 244/Cm and /sup 252/Cf, and the spontaneous alpha particle emitter /sup 241/Am. These seven isotopes are the most important constituents of wastes from nuclear power reactors and once the mass of each isotope present is determined by the apparatus and method of the instant invention, the overall alpha particle activity can be determined to better than 1 nCi/g from known radioactivity data. Therefore, in addition to the quantitative analysis of the waste sample useful for later reclamation purposes, the alpha particle activity can be determined to decide whether permanent low-level burial is appropriate for the waste sample.

Apparatus and method for quantitative assay of generic transuranic wastes from nuclear reactors

DOEpatents

Caldwell, John T.; Kunz, Walter E.; Atencio, James D.

1984-01-01

A combination of passive and active neutron measurements which yields quantitative information about the isotopic composition of transuranic wastes from nuclear power or weapons material manufacture reactors is described. From the measurement of prompt and delayed neutron emission and the incidence of two coincidentally emitted neutrons from induced fission of fissile material in the sample, one can quantify .sup.233 U, .sup.235 U and .sup.239 Pu isotopes in waste samples. Passive coincidence counting, including neutron multiplicity measurement and determination of the overall passive neutron flux additionally enables the separate quantitative evaluation of spontaneous fission isotopes such as .sup.240 Pu, .sup.244 Cm and .sup.252 Cf, and the spontaneous alpha particle emitter .sup.241 Am. These seven isotopes are the most important constituents of wastes from nuclear power reactors and once the mass of each isotope present is determined by the apparatus and method of the instant invention, the overall alpha particle activity can be determined to better than 1 nCi/g from known radioactivity data. Therefore, in addition to the quantitative analysis of the waste sample useful for later reclamation purposes, the alpha particle activity can be determined to decide whether "permanent" low-level burial is appropriate for the waste sample.

Improvements in Precise and Accurate Isotope Ratio Determination via LA-MC-ICP-MS by Application of an Alternative Data Reduction Protocol

NASA Astrophysics Data System (ADS)

Fietzke, J.; Liebetrau, V.; Guenther, D.; Frische, M.; Zumholz, K.; Hansteen, T. H.; Eisenhauer, A.

2008-12-01

An alternative approach for the evaluation of isotope ratio data using LA-MC-ICP-MS will be presented. In contrast to previously applied methods it is based on the simultaneous responses of all analyte isotopes of interest and the relevant interferences without performing a conventional background correction. Significant improvements in precision and accuracy can be achieved when applying this new method and will be discussed based on the results of two first methodical applications: a) radiogenic and stable Sr isotopes in carbonates b) stable chlorine isotopes of pyrohydrolytic extracts. In carbonates an external reproducibility of the 87Sr/86Sr ratios of about 19 ppm (RSD) was achieved, an improvement of about a factor of 5. For recent and sub-recent marine carbonates a mean radiogenic strontium isotope ratio 87Sr/86Sr of 0.709170±0.000007 (2SE) was determined, which agrees well with the value of 0.7091741±0.0000024 (2SE) reported for modern sea water [1,2]. Stable chlorine isotope ratios were determined ablating pyrohydrolytic extracts with a reproducibility of about 0.05‰ (RSD). For basaltic reference material JB1a and JB2 chlorine isotope ratios were determined relative to SMOC (standard mean ocean chlorinity) δ37ClJB-1a = (-0.99±0.06) ‰ and δ37ClJB-1a = (-0.60±0.03) ‰ (SD), respectively, in accordance with published data [3]. The described strategies for data reduction are considered to be generally applicable for all isotope ratio measurements using LA-MC-ICP-MS. [1] J.M. McArthur, D. Rio, F. Massari, D. Castradori, T.R. Bailey, M. Thirlwall, S. Houghton, Palaeogeo. Palaeoclim. Palaeoeco., 2006, 242 (126), doi: 10.1016/j.palaeo.2006.06.004 [2] J. Fietzke, V. Liebetrau, D. Guenther, K. Guers, K. Hametner, K. Zumholz, T.H. Hansteen and A. Eisenhauer, J. Anal. At. Spectrom., 2008, 23, 955-961, doi:10.1039/B717706B [3] J. Fietzke, M. Frische, T.H. Hansteen and A. Eisenhauer, J. Anal. At. Spectrom., 2008, 23, 769-772, doi:10.1039/B718597A

Isotope ratio mass spectrometry coupled to liquid and gas chromatography for wine ethanol characterization.

PubMed

Cabañero, Ana I; Recio, Jose L; Rupérez, Mercedes

2008-10-01

Two new procedures for wine ethanol 13C/12C isotope ratio determination, using high-performance liquid chromatography and gas chromatography isotope ratio mass spectrometry (HPLC/IRMS and GC/IRMS), have been developed to improve isotopic methods dedicated to the study of wine authenticity. Parameters influencing separation of ethanol from wine matrix such as column, temperature, mobile phase, flow rates and injection mode were investigated. Twenty-three wine samples from various origins were analyzed for validation of the procedures. The analytical precision was better than 0.15 per thousand, and no significant isotopic fractionation was observed employing both separative techniques coupled to IRMS. No significant differences and a very strong correlation (r = 0.99) were observed between the 13C/12C ratios obtained by the official method (elemental analyzer/isotope ratio mass spectrometry) and the proposed new methodology. The potential advantages of the developed methods over the traditional one are speed (reducing time required from hours to minutes) and simplicity. In addition, these are the first isotopic methods that allow 13C/12C determination directly from a liquid sample with no previous ethanol isolation, overcoming technical difficulties associated with sample treatment.

Isotope fractionation during the anaerobic consumption of acetate by methanogenic and sulfate-reducing microorganisms

NASA Astrophysics Data System (ADS)

Gövert, D.; Conrad, R.

2009-04-01

During the anaerobic degradation of organic matter in anoxic sediments and soils acetate is the most important substrate for the final step in production of CO2 and/or CH4. Sulfate-reducing bacteria (SRB) and methane-producing archaea both compete for the available acetate. Knowledge about the fractionation of 13C/12C of acetate carbon by these microbial groups is still limited. Therefore, we determined carbon isotope fractionation in different cultures of acetate-utilizing SRB (Desulfobacter postgatei, D. hydrogenophilus, Desulfobacca acetoxidans) and methanogens (Methanosarcina barkeri, M. acetivorans). Including literature values (e.g., Methanosaeta concilii), isotopic enrichment factors (epsilon) ranged between -35 and +2 permil, possibly involving equilibrium isotope effects besides kinetic isotope effects. The values of epsilon were dependent on the acetate-catabolic pathway of the particular microorganism, the methyl or carboxyl position of acetate, and the relative availability or limitation of the substrate acetate. Patterns of isotope fractionation in anoxic lake sediments and rice field soil seem to reflect the characteristics of the microorganisms actively involved in acetate catabolism. Hence, it might be possible using environmental isotopic information to determine the type of microbial metabolism converting acetate to CO2 and/or CH4.

Application of Stable Isotope-Assisted Metabolomics for Cell Metabolism Studies

PubMed Central

You, Le; Zhang, Baichen; Tang, Yinjie J.

2014-01-01

The applications of stable isotopes in metabolomics have facilitated the study of cell metabolisms. Stable isotope-assisted metabolomics requires: (1) properly designed tracer experiments; (2) stringent sampling and quenching protocols to minimize isotopic alternations; (3) efficient metabolite separations; (4) high resolution mass spectrometry to resolve overlapping peaks and background noises; and (5) data analysis methods and databases to decipher isotopic clusters over a broad m/z range (mass-to-charge ratio). This paper overviews mass spectrometry based techniques for precise determination of metabolites and their isotopologues. It also discusses applications of isotopic approaches to track substrate utilization, identify unknown metabolites and their chemical formulas, measure metabolite concentrations, determine putative metabolic pathways, and investigate microbial community populations and their carbon assimilation patterns. In addition, 13C-metabolite fingerprinting and metabolic models can be integrated to quantify carbon fluxes (enzyme reaction rates). The fluxome, in combination with other “omics” analyses, may give systems-level insights into regulatory mechanisms underlying gene functions. More importantly, 13C-tracer experiments significantly improve the potential of low-resolution gas chromatography-mass spectrometry (GC-MS) for broad-scope metabolism studies. We foresee the isotope-assisted metabolomics to be an indispensable tool in industrial biotechnology, environmental microbiology, and medical research. PMID:24957020

Fluid flow in deforming media: interpreting stable isotope signatures of marbles

NASA Astrophysics Data System (ADS)

Bond, C. E.

2016-12-01

Fluid flow in the crust is controlled by permeable networks. These networks can be created and destroyed dynamically during rock deformation. Rock deformation is therefore critical in controlling fluid pathways in the crust and hence the location of mineral and other resources. Here, evidence for deformation-enhanced fluid infiltration shows that a range of deformation mechanisms control fluid flow and chemical and isotopic equilibration. The results attest to localised fluid infiltration within a single metamorphic terrain (12km) over a range of metamorphic grades; ecologite- blueschist to greenschist. For fluid infiltrating marbles during ductile deformation, chemical and isotopic signatures are now homogenous; whilst fluid infiltration associated with brittle deformation results in chemical and isotopic heterogeneity at a microscale. The findings demonstrate how ductile deformation enhances equilibration of δ18O at a grain scale whilst brittle deformation does not. The control of deformation mechanisms in equilibrating isotopic and chemical heterogeneities have implications for the understanding of fluid-rock interaction in the crust. Interpretation of bulk stable isotope data, particularly in the use of isotope profiles to determine fluid fluxes into relatively impermeable units that have been deformed need to be used with care when trying to determine fluid fluxes and infiltration mechanisms.

Determination of the mechanism of demethylenation of (methylenedioxy)phenyl compounds by cytochrome P450 using deuterium isotope effects

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fukuto, J.M.; Kumagai, Y.; Cho, A.K.

1991-09-01

The mechanism of demethylenation of (methylenedioxy)benzene (MDB), (methylenedioxy)amphetamine (MDA), and (methylenedioxy)methamphetamine (MDMA) by purified rabbit liver cytochrome P450IIB4 has been investigated by using deuterium isotope effects. A comparison of the magnitude and direction of the observed kinetic isotope effects indicates that the three compounds are demethylenated by different mechanisms. The different mechanisms of demethylenation have been proposed on the basis of comparisons of the observed biochemical isotope effects with the isotope effects from purely chemical systems.

Metal stable isotopes in low-temperature systems: A primer

USGS Publications Warehouse

Bullen, T.D.; Eisenhauer, A.

2009-01-01

Recent advances in mass spectrometry have allowed isotope scientists to precisely determine stable isotope variations in the metallic elements. Biologically infl uenced and truly inorganic isotope fractionation processes have been demonstrated over the mass range of metals. This Elements issue provides an overview of the application of metal stable isotopes to low-temperature systems, which extend across the borders of several science disciplines: geology, hydrology, biology, environmental science, and biomedicine. Information on instrumentation, fractionation processes, data-reporting terminology, and reference materials presented here will help the reader to better understand this rapidly evolving field.

Radiation detection method and system using the sequential probability ratio test

DOEpatents

Nelson, Karl E [Livermore, CA; Valentine, John D [Redwood City, CA; Beauchamp, Brock R [San Ramon, CA

2007-07-17

A method and system using the Sequential Probability Ratio Test to enhance the detection of an elevated level of radiation, by determining whether a set of observations are consistent with a specified model within a given bounds of statistical significance. In particular, the SPRT is used in the present invention to maximize the range of detection, by providing processing mechanisms for estimating the dynamic background radiation, adjusting the models to reflect the amount of background knowledge at the current point in time, analyzing the current sample using the models to determine statistical significance, and determining when the sample has returned to the expected background conditions.

Stable isotope ratio determination of the origin of vanillin in vanilla extracts and its relationship to vanillin/potassium ratios

DOE Office of Scientific and Technical Information (OSTI.GOV)

Martin, G.E.; Alfonso, F.C.; Figert, D.M.

A method is described for isolating vanillin from vanilla extract, followed by stable isotope ratio analysis to determine the amount of natural vanillin contained in adulterated vanilla extracts. After the potassium content is determined, the percent Madagascar and/or Java vanilla beans incorporated into the extract may then be approximated from the vanillin/potassium ratio.

The Effects of Partial Reinforcement in the Acquisition and Extinction of Recurrent Serial Patterns.

ERIC Educational Resources Information Center

Dockstader, Steven L.

The purpose of these 2 experiments was to determine whether sequential response pattern behavior is affected by partial reinforcement in the same way as other behavior systems. The first experiment investigated the partial reinforcement extinction effects (PREE) in a sequential concept learning task where subjects were required to learn a…

Exploring Liquid Sequential Injection Chromatography to Teach Fundamentals of Separation Methods: A Very Fast Analytical Chemistry Experiment

ERIC Educational Resources Information Center

Penteado, Jose C.; Masini, Jorge Cesar

2011-01-01

Influence of the solvent strength determined by the addition of a mobile-phase organic modifier and pH on chromatographic separation of sorbic acid and vanillin has been investigated by the relatively new technique, liquid sequential injection chromatography (SIC). This technique uses reversed-phase monolithic stationary phase to execute fast…

Determination of 241Am in sediments by isotope dilution high resolution inductively coupled plasma mass spectrometry (ID HR ICP-MS).

PubMed

Agarande, M; Benzoubir, S; Bouisset, P; Calmet, D

2001-08-01

Trace levels (pg kg(-1)) of 241Am in sediments were determined by isotope dilution high resolution inductively coupled plasma mass spectrometry (ID HR ICP-MS) using a microconcentric nebulizer. 241Am was isolated from major elements like Ca and Fe by different selective precipitations. In further steps. Am was first separated from other transuranic elements and purified by anion exchange and extraction chromatography prior to the mass spectrometric measurements. The ID HR ICP-MS results are compared with isotope dilution alpha spectrometry.

Mechanistic Analysis of Oxidative C–H Cleavages Using Inter- and Intramolecular Kinetic Isotope Effects

PubMed Central

Jung, Hyung Hoon; Floreancig, Paul E.

2009-01-01

A series of monodeuterated benzylic and allylic ethers were subjected to oxidative carbon–hydrogen bond cleavage to determine the impact of structural variation on intramolecular kinetic isotope effects in DDQ-mediated cyclization reactions. These values are compared to the corresponding intermolecular kinetic isotope effects that were accessed through subjecting mixtures of non-deuterated and dideuterated substrates to the reaction conditions. The results indicate that carbon–hydrogen bond cleavage is rate determining and that a radical cation is most likely a key intermediate in the reaction mechanism. PMID:20640173

Normalization of oxygen and hydrogen isotope data

USGS Publications Warehouse

Coplen, T.B.

1988-01-01

To resolve confusion due to expression of isotopic data from different laboratories on non-corresponding scales, oxygen isotope analyses of all substances can be expressed relative to VSMOW or VPDB (Vienna Peedee belemnite) on scales normalized such that the ??18O of SLAP is -55.5% relative to VSMOW. H3+ contribution in hydrogen isotope ratio analysis can be easily determined using two gaseous reference samples that differ greatly in deuterium content. ?? 1988.

Environmental Survey of the B-3 and Ford’s Farm Ranges,

DTIC Science & Technology

1983-08-01

reported have an estimated analytical error of *35% unless noted otherwise. 14 Isotopic Analysis The isotopic uranium analysis procedure used by UST...sulfate buffer and elec- trodeposited on a stainless steel disc, and isotopes of uranium (234U, 23 5U, and 2 38U) were determined by pulse height analysis ...measurements and some environmental sampling. Several special studies were also conducted, including analyses of the isotopic composition of uranium in

Equilibrium Tin Isotope Fractionation during Metal-Sulfide-Silicate Differentiation: A Nuclear Resonant Inelastic X-ray Scattering Approach

NASA Astrophysics Data System (ADS)

Roskosz, M.; Amet, Q.; Fitoussi, C.; Laporte, D.; Hu, M. Y.; Alp, E. E.

2016-12-01

Metal-silicate differentiation was recently addressed through the insight of the isotopic composition of siderophile elements (mainly Fe, Si and Cr isotopes) of planetary and extraterrestrial bodies. A key limitation of this approach is however the knowledge of equilibrium fractionation factors between coexisting phases (metal alloys, silicates and sulfides) used to interpret data on natural samples. These properties are difficult to determine experimentally. In this context, tin is generally classified as a chalcophile element but it is also siderophile and volatile. We applied a synchrotron-based method to circumvent difficulties related to determination of equilibrium isotope fractionation. The nuclear resonant inelastic x-ray scattering (NRIXS) was used to measure the phonon excitation spectrum and then to derive the force constant and finally the fractionation factors of Sn-bearing geomaterials. Spectroscopic measurements were carried out at room pressure at Sector 30-ID (APS, USA). A range of Fe-Ni alloys, rhyolitic and basaltic glasses and iron sulfides containing isotopically enriched 119Sn were synthesized. The tin content and the redox conditions prevailing during the synthesis were varied. The data evaluation was carried out using PHOENIX and SciPhon programs. A strong effect of both the redox state and the tin content was measured. In addition, the composition of the silicate glasses was found to be another important factor determining the tin isotope metal-silicate-sulfide fractionation factors. Our results are consistent with trends previously observed in the case of iron isotopes [1,2]. We will discuss the implications of our experimental results in terms of tin isotope planetary signatures. References: [1] Dauphas et al. (2014), EPSL, 398, 127-140; [2] Roskosz et al. (2015), GCA, 169, 184-199.

Growth versus metabolic tissue replacement in mouse tissues determined by stable carbon and nitrogen isotope analysis

NASA Astrophysics Data System (ADS)

Macavoy, S. E.; Jamil, T.; Macko, S. A.; Arneson, L. S.

2003-12-01

Stable isotope analysis is becoming an extensively used tool in animal ecology. The isotopes most commonly used for analysis in terrestrial systems are those of carbon and nitrogen, due to differential carbon fractionation in C3 and C4 plants, and the approximately 3‰ enrichment in 15N per trophic level. Although isotope signatures in animal tissues presumably reflect the local food web, analysis is often complicated by differential nutrient routing and fractionation by tissues, and by the possibility that large organisms are not in isotopic equilibrium with the foods available in their immediate environment. Additionally, the rate at which organisms incorporate the isotope signature of a food through both growth and metabolic tissue replacement is largely unknown. In this study we have assessed the rate of carbon and nitrogen isotopic turnover in liver, muscle and blood in mice following a diet change. By determining growth rates, we were able to determine the proportion of tissue turnover caused by growth versus that caused by metabolic tissue replacement. Growth was found to account for approximately 10% of observed tissue turnover in sexually mature mice (Mus musculus). Blood carbon was found to have the shortest half-life (16.9 days), followed by muscle (24.7 days). Liver carbon turnover was not as well described by the exponential decay equations as other tissues. However, substantial liver carbon turnover was observed by the 28th day after diet switch. Surprisingly, these tissues primarily reflect the carbon signature of the protein, rather than carbohydrate, source in their diet. The nitrogen signature in all tissues was enriched by 3 - 5‰ over their dietary protein source, depending on tissue type, and the isotopic turnover rates were comparable to those observed in carbon.

Differential soil water sourcing of managed Loblolly Pine and Sweet Gum revealed by stable isotopes in the Upper Coastal Plain, USA

NASA Astrophysics Data System (ADS)

Brockman, L. E.; Younger, S. E.; Jackson, C. R.; McDonnell, J.; Janzen, K. F.

2017-12-01

Stable isotope signatures of stem water can illuminate where in the soil profile different types of trees are accessing soil water and thereby contribute to our understanding of water movement through the soil plant atmosphere continuum. The objective of this study was to use 2H and 18O isotopes to characterize water sources of fourteen-year-old intensively managed Loblolly Pine and Sweet Gum stands in replicated (n=3) paired plots. In order to differentiate the isotopic signatures of tree and soil water, both species and five soil depths were sampled monthly for one year. Tree sap and soil water were extracted cryogenically and their isotopic signatures were determined. Although plant water uptake is generally considered a non-fractionating process, our dataset suggests a source of fractionation in 2H signatures in both species and during most of the thirteen sampling events. As a result, only the 18O isotopic data were used to determine the vertical distribution of soil water contributions to stem water. Statistically, we grouped the five soil sampling depths into three isotopic horizons. Shallow, intermediate and deep soil represent sampling depths of 0-10cm, 30-70cm and 100-125cm, respectively. These isotopic horizons were used in a direct inference approach and Bayesian mixing model analysis to determine the origin of stem water. In this study, Loblolly Pine used more water from intermediate and deep soil while Sweet Gum used more water from shallow and intermediate soil. In the winter months, January through March, Loblolly Pine transpired primarily deep soil where as Sweet Gum mainly utilized shallow soil for transpiration. These results indicate that both species have opportunistic water use patterns with seasonal variation.

Geographic variation of stable isotopes in African elephant ivory

NASA Astrophysics Data System (ADS)

Ziegler, S.; Merker, S.; Jacob, D.

2012-04-01

In 1989, the international community listed the African elephant in Appendix I of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) thus prohibiting commercial ivory trade. Recent surveillance data show that the illegal trade in ivory has been growing worldwide. Long-term preservation of many of the African elephant populations can be supported with a control mechanism that helps with the implementation of remedial conservation action. Therefore, setting up a reference database that predicts the origin of ivory specimens can assist in determining smuggling routes and the provenance of illegal ivory. Our research builds on earlier work to seek an appropriate method for determining the area of origin for individual tusks. Several researchers have shown that the provenance of elephant ivory can be traced by its isotopic composition, but this is the first attempt to produce an integrated isotopic reference database of elephant ivory provenance. We applied a combination of various routine geochemical analyses to measure the stable isotope ratios of hydrogen, carbon, nitrogen, oxygen, and sulphur. Up to now, we analysed 606 ivory samples of known geographical origin from African range states, museums and private collections, comprising 22 African elephant range states. The isotopic measurements were superimposed with data layers from vegetation, geology and climate. A regression function for the isotope composition of the water isotopes in precipitation and collagen in ivory was developed to overcome the problem of imprecise origin of some of the sampled material. Multivariate statistics, such as nearest neighborhood and discriminate analysis were applied to eventually allow a statistical determination of the provenance for ivory of unknown origin. Our results suggest that the combination of isotopic parameters have the potential to provide predictable and complementary markers for estimating the origin of seized elephant ivory.

Isotope dilution ICP-MS with laser-assisted sample introduction for direct determination of sulfur in petroleum products.

PubMed

Boulyga, Sergei F; Heilmann, Jens; Heumann, Klaus G

2005-08-01

Inductively coupled plasma isotope dilution mass spectrometry (ICP-IDMS) with direct laser-assisted introduction of isotope-diluted samples into the plasma, using a laser ablation system with high ablation rates, was developed for accurate sulfur determinations in different petroleum products such as 'sulfur-free' premium gasoline, diesel fuel, and heating oil. Two certified gas oil reference materials were analyzed for method validation. Two different 34S-enriched spike compounds, namely, elementary sulfur dissolved in xylene and dibenzothiophene in hexane, were synthesized and tested for their usefulness in this isotope dilution technique. The isotope-diluted sample was adsorbed on a filter-paper-like material, which was fixed in a special holder for irradiation by the laser beam. Under these conditions no time-dependent spike/analyte fractionation was only observed for the dibenzothiophene spike during the laser ablation process, which means that the measured 34S/32S isotope ratio of the isotope-diluted sample remained constant-a necessary precondition for accurate results with the isotope dilution technique. A comparison of LA-ICP-IDMS results with the certified values of the gas oil reference materials and with results obtained from ICP-IDMS analyses with wet sample digestion demonstrated the accuracy of the new LA-ICP-IDMS method in the concentration range of 9.2 microg g(-1) ('sulfur-free' premium gasoline) to 10.4 mg g(-1) (gas oil reference material BCR 107). The detection limit for sulfur by LA-ICP-IDMS is 0.04 microg g(-1) and the analysis time is only about 10 min, which therefore also qualifies this method for accurate determinations of low sulfur contents in petroleum products on a routine level.

Three-body dissociation of OCS3+: Separating sequential and concerted pathways

NASA Astrophysics Data System (ADS)

Kumar, Herendra; Bhatt, Pragya; Safvan, C. P.; Rajput, Jyoti

2018-02-01

Events from the sequential and concerted modes of the fragmentation of OCS3+ that result in coincident detection of fragments C+, O+, and S+ have been separated using a newly proposed representation. An ion beam of 1.8 MeV Xe9+ is used to make the triply charged molecular ion, with the fragments being detected by a recoil ion momentum spectrometer. By separating events belonging exclusively to the sequential mode of breakup, the electronic states of the intermediate molecular ion (CO2+ or CS2+) involved are determined, and from the kinetic energy release spectra, it is shown that the low lying excited states of the parent OCS3+ are responsible for this mechanism. An estimate of branching ratios of events coming from sequential versus concerted mode is presented.

Determination of Multiple φ-Torsion Angles in Proteins by Selective and Extensive 13C Labeling and Two-Dimensional Solid-State NMR

NASA Astrophysics Data System (ADS)

Hong, Mei

1999-08-01

We describe an approach to efficiently determine the backbone conformation of solid proteins that utilizes selective and extensive 13C labeling in conjunction with two-dimensional magic-angle-spinning NMR. The selective 13C labeling approach aims to reduce line broadening and other multispin complications encountered in solid-state NMR of uniformly labeled proteins while still enhancing the sensitivity of NMR spectra. It is achieved by using specifically labeled glucose or glycerol as the sole carbon source in the protein expression medium. For amino acids synthesized in the linear part of the biosynthetic pathways, [1-13C]glucose preferentially labels the ends of the side chains, while [2-13C]glycerol labels the Cα of these residues. Amino acids produced from the citric-acid cycle are labeled in a more complex manner. Information on the secondary structure of such a labeled protein was obtained by measuring multiple backbone torsion angles φ simultaneously, using an isotropic-anisotropic 2D correlation technique, the HNCH experiment. Initial experiments for resonance assignment of a selectively 13C labeled protein were performed using 15N-13C 2D correlation spectroscopy. From the time dependence of the 15N-13C dipolar coherence transfer, both intraresidue and interresidue connectivities can be observed, thus yielding partial sequential assignment. We demonstrate the selective 13C labeling and these 2D NMR experiments on a 8.5-kDa model protein, ubiquitin. This isotope-edited NMR approach is expected to facilitate the structure determination of proteins in the solid state.

Seawater osmium isotope evidence for a middle Miocene flood basalt event in ferromanganese crust records

USGS Publications Warehouse

Klemm, V.; Frank, M.; Levasseur, S.; Halliday, A.N.; Hein, J.R.

2008-01-01

Three ferromanganese crusts from the northeast, northwest and central Atlantic were re-dated using osmium (Os) isotope stratigraphy and yield ages from middle Miocene to the present. The three Os isotope records do not show evidence for growth hiatuses. The reconstructed Os isotope-based growth rates for the sections older than 10??Ma are higher than those determined previously by the combined beryllium isotope (10Be/9Be) and cobalt (Co) constant-flux methods, which results in a decrease in the maximum age of each crust. This re-dating does not lead to significant changes to the interpretation of previously determined radiogenic isotope neodymium, lead (Nd, Pb) time series because the variability of these isotopes was very small in the records of the three crusts prior to 10??Ma. The Os isotope record of the central Atlantic crust shows a pronounced minimum during the middle Miocene between 15 and 12??Ma, similar to a minimum previously observed in two ferromanganese crusts from the central Pacific. For the other two Atlantic crusts, the Os isotope records and their calibration to the global seawater curve for the middle Miocene are either more uncertain or too short and thus do not allow for a reliable identification of an isotopic minimum. Similar to pronounced minima reported previously for the Cretaceous/Tertiary and Eocene/Oligocene boundaries, possible interpretations for the newly identified middle Miocene Os isotope minimum include changes in weathering intensity and/or a meteorite impact coinciding with the formation of the No??rdlinger Ries Crater. It is suggested that the eruption and weathering of the Columbia River flood basalts provided a significant amount of the unradiogenic Os required to produce the middle Miocene minimum. ?? 2008 Elsevier B.V.

Determining the N and O isotope effects of microbial nitrite reduction: the global N cycle implications of an enzyme-dependent isotope effect

NASA Astrophysics Data System (ADS)

Martin, T. S.; Casciotti, K. L.

2014-12-01

The marine nitrogen (N) cycle is a dynamic system of critical importance, since nitrogen is the limiting nutrient in over half of the world's oceans. Denitrification and anammox, the main N loss processes from the ocean, have different effects on carbon cycling and greenhouse gas emission. Understanding the balance between the two processes is vital to understanding the role of the N cycle in global climate change. One approach for investigating these processes is by using stable isotope analysis to estimate the relative magnitudes of N fluxes, particularly for biologically mediated processes. In order to make the most of the currently available isotope analysis techniques, it is necessary to know the isotope effects for each processes occurring in the environment. Nitrite reduction is an important step in denitrification. Previous work had begun to explore the N isotope effects for nitrite reduction, but no oxygen (O) isotope effect has been measured. Additionally, no consideration has been given to the type of nitrite reductase carrying out the reaction. There are two main types of respiratory nitrite reductase, one that is Cu-based and another that is Fe-based. We performed batch culture experiments with denitrifier strains possessing either a Cu-type or Fe-type nitrite reductase. Both N and O isotope effects for nitrite reduction were determined for each of these experiments by measuring the NO2- concentration, as well as the N and O isotopes of nitrite and applying a Rayleigh fractionation model. Both the N and O isotope effects were found to be significantly different between the two types of enzymes. This enzyme-linked difference in isotope effects emphasizes the importance of microbial community composition within the global N cycle.

Quantification of in Situ Biodegradation Rate Constants Using a Novel Combined Isotope Approach

NASA Astrophysics Data System (ADS)

Blum, P.; Sültenfuß, J.; Martus, P.

2014-12-01

Numerous studies have shown the enormous potential of the compound-specific isotope analysis (CSIA) for studying the biodegradation of organic compounds such as monoaromatic hydrocarbons (BTEX), polyaromatic hydrocarbons (PAH), chlorinated solvents and other organic contaminants and environmental transformation mechanisms in groundwater. In addition, two-dimensional isotope analysis such as carbon and hydrogen have been successfully studied indicating the potential to also investigate site-specific reaction mechanisms. The main objective of the current study however is to quantify real effective in situ biodegradation rate constants in a coal-tar contaminated aquifer by combining compound-specific isotope analysis (CSIA) and tracer-based (3H-3He) ground-water dating (TGD). Hence, groundwater samples are used to determine groundwater residence times, and carbon and hydrogen stable isotopes are analyzed for selected BTEX and PAH. The results of the hydrogen stable isotopes surprisingly indicate no isotope fractionation and therefore no biodegradation. In contrast, for stable carbon isotopes of selected BTEX such as o-xylene and toluene, isotope shifts are detected indicating active biodegradation under sulfate-reducing conditions. These and previous results of stable carbon isotopes show that only for o-xylene a clear evidence for biodegradation is possible for the studied site. Nevertheless, in combining these results with the groundwater residence times, which range between 1 year for the shallow wells (20 m below surface) and 41 years for the deeper wells (40 m below surface), it is feasible to effectively determine in situ biodegradation rate constants for o-xylene. Conversely, the outcome also evidently demonstrate the major limitations of the novel combined isotope approach for a successful implementation of monitored natural attenuation (MNA) at such field sites.

Protein classification using sequential pattern mining.

PubMed

Exarchos, Themis P; Papaloukas, Costas; Lampros, Christos; Fotiadis, Dimitrios I

2006-01-01

Protein classification in terms of fold recognition can be employed to determine the structural and functional properties of a newly discovered protein. In this work sequential pattern mining (SPM) is utilized for sequence-based fold recognition. One of the most efficient SPM algorithms, cSPADE, is employed for protein primary structure analysis. Then a classifier uses the extracted sequential patterns for classifying proteins of unknown structure in the appropriate fold category. The proposed methodology exhibited an overall accuracy of 36% in a multi-class problem of 17 candidate categories. The classification performance reaches up to 65% when the three most probable protein folds are considered.

Sequential behavior and its inherent tolerance to memory faults.

NASA Technical Reports Server (NTRS)

Meyer, J. F.

1972-01-01

Representation of a memory fault of a sequential machine M by a function mu on the states of M and the result of the fault by an appropriately determined machine M(mu). Given some sequential behavior B, its inherent tolerance to memory faults can then be measured in terms of the minimum memory redundancy required to realize B with a state-assigned machine having fault tolerance type tau and fault tolerance level t. A behavior having maximum inherent tolerance is exhibited, and it is shown that behaviors of the same size can have different inherent tolerance.

An NMR Study of Isotope Effect on Keto-Enol Tautomerization: A Physical Organic Chemistry Experiment

ERIC Educational Resources Information Center

Atkinson, D.; Chechik, V.

2004-01-01

Isotope substitution often affects the rate of an organic reaction and can be used to reveal the underlying mechanism. A series of experiments that use (super 1)H NMR to determine primary and secondary isotope effects, activation parameters, and the regioselectivity of butanone enolization are described.

USE OF GC-MS/COMBUSTION/IRMS TO IDENTIFY AND DETERMINE THE STABLE CARBON ISOTOPIC RATIO OF INDIVIDUAL LIPIDS

EPA Science Inventory

A system that couples a gas chromatograph (GC) via a split to a quadrapole mass spectrometer (MS) and, through a combustion interface, to an isotope ratio mass spectrometer (IRMS) allows the simultaneous detection of electron impact mass spectra and stable carbon isotope ratio an...

Comparative analysis of 1-phenyl-2-propanone (P2P), an amphetamine-type stimulant precursor, using stable isotope ratio mass spectrometry: presented in part as a poster at the 2nd meeting of the Joint European Stable Isotope User Meeting (JESIUM), Giens, France, September 2008.

PubMed

Schneiders, S; Holdermann, T; Dahlenburg, R

2009-06-01

The isotope ratios of amphetamine type stimulants (ATS) depend as well on the precursor as the synthetic pathway. For clandestine production of amphetamine and methamphetamine, 1-phenyl-2-propanone (P2P, benzylmethylketone) is a commonly used precursor. Our aim was to determine the variation of the isotope ratios within precursor samples of one manufacturer and to compare seized samples of unknown sources to these values. delta13C(V-PDB), delta2H(V-SMOW) and delta118O(V-SMOW) isotope ratios were determined using elemental analysis (EA) and gas chromatography (GC) coupled toan isotope ratio mass spectrometer (IRMS). The comparison of all seized samples to the data of the samples of one manufacturer revealed considerable differences. The results show that IRMS provides a high potential in differentiating between precursors from different manufacturers for the clandestine production of ATS and identifying corresponding sources.

Mn-53-Cr-53 Systematics of R-Chondrite NWA 753

NASA Technical Reports Server (NTRS)

Jogo, K.; Shih, C-Y.; Reese, Y. D.; Nyquist, L. E.

2006-01-01

Chondrules and chondrites are interpreted as objects formed in the early solar system, and it is important to study them in order to elucidate its evolution. Here, we report the study of the Mn-Cr systematics of the R-Chondrite NWA753 and compare the results to other chondrite data. The goal was to determine Cr isotopic and age variations among chondrite groups with different O-isotope signatures. The Mn-53-Cr-53 method as applied to individual chondrules [1] or bulk chondrites [2] is based on the assumption that 53Mn was initially homogeneously distributed in that portion the solar nebula where the chondrules and/or chondrites formed. However, different groups of chondrites formed from regions of different O-isotope compositions. So, different types of chondrites also may have had different initial Mn-53 abundances and/or Cr isotopic compositions. Thus, it is important to determine the Cr isotopic systematics among chondrites from various chondrite groups. We are studying CO-chondrite ALH83108 and Tagish Lake in addition to R-Chondrite NWA753. These meteorites have very distinct O-isotope compositions (Figure 1).

Frontiers of QC Laser spectroscopy for high precision isotope ratio analysis of greenhouse gases

NASA Astrophysics Data System (ADS)

Emmenegger, Lukas; Mohn, Joachim; Harris, Eliza; Eyer, Simon; Ibraim, Erkan; Tuzson, Béla

2016-04-01

An important milestone for laser spectroscopy was achieved when isotope ratios of greenhouse gases were reported at precision levels that allow addressing research questions in environmental sciences. Real-time data with high temporal resolution at moderate cost and instrument size make the optical approach highly attractive, complementary to the well-established isotope-ratio mass-spectrometry (IRMS) method. Especially appealing, in comparison to IRMS, is the inherent specificity to structural isomers having the same molecular mass. Direct absorption in the MIR in single or dual QCL configuration has proven highly reliable for the sta-ble isotopes of CO2, N2O and CH4. The longest time series of real-time measurements is currently available for δ13C and δ18O in CO2 at the high-alpine station Jung-fraujoch. At this well-equipped site, QCL based direct absorption spectroscopy (QCLAS) measurements are ongoing since 2008 1,2. Applications of QCLAS for N2O and CH4 stable isotopes are considerably more challenging because of the lower atmospheric mixing ratios, especially for the less abundant species, such as N218O and CH3D. For high precision (< 0.1 ‰) measurements in ambient air, QCLAS may be combined with a fully automated preconcentration unit yielding an up to 500 times concentration increase and the capability to separate the target gas from spectral interferants by se-quential desorption 3. Here, we review our recent developments on high precision isotope ratio analysis of greenhouse gases, with special focus on the isotopic species of N2O and CH4. Furthermore, we show environ-mental applications illustrating the highly valuable information that isotope ratios of atmospheric trace gases can carry. For example, the intramolecular distribution of 15N in N2O gives important information on the geochemical cycle of N2O4-6, while the analysis of δ13C and δ D in CH4 may be applied to disentangle microbial, fossil and landfill sources 7. 1 Sturm, P., Tuzson, B., Henne, S. & Emmenegger, L. Tracking isotopic signatures of CO2 at the high altitude site Jungfraujoch with laser spectroscopy: Analytical improvements and representative re-sults. Atmospheric Measurement Techniques 6, 1659-1671 (2013). 2 Tuzson, B. et al. Continuous isotopic composition measurements of tropospheric CO2 at Jungfraujoch (3580 m a.s.l.), Switzerland: real-time observation of regional pollution events. Atmospheric Chemistry and Physics 11, 1685-1696 (2011). 3 Mohn, J. et al. A liquid nitrogen-free preconcentration unit for measurements of ambient N2O isotopomers by QCLAS. Atmospheric Measurement Techniques 3, 609-618 (2010). 4 Wolf, B. et al. First on-line isotopic characterization of N2O above intensively managed grassland. Biogeosciences 12, 2517-1960 (2015). 5 Harris, E. et al. Nitrous oxide and methane emissions and nitrous oxide isotopic composition from waste incineration in Switzerland. Waste Management 35, 135-140 (2015). 6 Harris, E. et al. Isotopic evidence for nitrous oxide production pathways in a partial nitritation-anammox reactor. Water Research 83, 258-270 (2015). 7 Eyer, S. et al. Real-time analysis of δ13C- and δ D-CH4 in ambient air with laser spectroscopy: method development and first intercomparison results. Atmos. Meas. Tech. Discuss. 8, 8925-8970 (2015).

Isotopic compositions of the elements, 2001

USGS Publications Warehouse

Böhlke, J.K.; De Laeter, J. R.; De Bievre, P.; Hidaka, H.; Peiser, H.S.; Rosman, K.J.R.; Taylor, P.D.P.

2005-01-01

The Commission on Atomic Weights and Isotopic Abundances of the International Union of Pure and Applied Chemistry completed its last review of the isotopic compositions of the elements as determined by isotope-ratio mass spectrometry in 2001. That review involved a critical evaluation of the published literature, element by element, and forms the basis of the table of the isotopic compositions of the elements (TICE) presented here. For each element, TICE includes evaluated data from the “best measurement” of the isotope abundances in a single sample, along with a set of representative isotope abundances and uncertainties that accommodate known variations in normal terrestrial materials. The representative isotope abundances and uncertainties generally are consistent with the standard atomic weight of the element Ar(E)">Ar(E)Ar(E) and its uncertainty U[Ar(E)]">U[Ar(E)]U[Ar(E)] recommended by CAWIA in 2001.

Isotope pattern deconvolution as a tool to study iron metabolism in plants.

PubMed

Rodríguez-Castrillón, José Angel; Moldovan, Mariella; García Alonso, J Ignacio; Lucena, Juan José; García-Tomé, Maria Luisa; Hernández-Apaolaza, Lourdes

2008-01-01

Isotope pattern deconvolution is a mathematical technique for isolating distinct isotope signatures from mixtures of natural abundance and enriched tracers. In iron metabolism studies measurement of all four isotopes of the element by high-resolution multicollector or collision cell ICP-MS allows the determination of the tracer/tracee ratio with simultaneous internal mass bias correction and lower uncertainties. This technique was applied here for the first time to study iron uptake by cucumber plants using 57Fe-enriched iron chelates of the o,o and o,p isomers of ethylenediaminedi(o-hydroxyphenylacetic) acid (EDDHA) and ethylenediamine tetraacetic acid (EDTA). Samples of root, stem, leaves, and xylem sap, after exposure of the cucumber plants to the mentioned 57Fe chelates, were collected, dried, and digested using nitric acid. The isotopic composition of iron in the samples was measured by ICP-MS using a high-resolution multicollector instrument. Mass bias correction was computed using both a natural abundance iron standard and by internal correction using isotope pattern deconvolution. It was observed that, for plants with low 57Fe enrichment, isotope pattern deconvolution provided lower tracer/tracee ratio uncertainties than the traditional method applying external mass bias correction. The total amount of the element in the plants was determined by isotope dilution analysis, using a collision cell quadrupole ICP-MS instrument, after addition of 57Fe or natural abundance Fe in a known amount which depended on the isotopic composition of the sample.

The Determination of the Natural Abundance of the Isotopes of Chlorine: An Introductory Experiment in Mass Spectrometry.

ERIC Educational Resources Information Center

O'Malley, Rebecca M.

1982-01-01

Describes a laboratory experiment which introduces basic principles and experimental techniques of mass spectrometry for fourth year undergraduate (B.Sc.) students. Laboratory procedures, background information, and discussion of results are provided for the experiment in which the natural isotopic abundance of chlorine is determined. (Author/JN)

CORRESPONDENCE OF STABLE ISOTOPE AND GUT CONTENTS ANALYSES IN DETERMINING TROPHIC POSITION OF STREAM FISHES

EPA Science Inventory

It is generally accepted that both stable isotope analysis (SIA) and gut contents analysis (GCA) be used in food web studies; however, few researchers have analyzed these data in concert. We utilized SIA and GCA to determine if longitudinal and seasonal variation in diet affects...

Experimental Evaluation of Stable Isotope Fractionation in Fish Muscle and Otoliths

EPA Science Inventory

We investigated an unresolved question in the use of stable isotopes to determine diet and trophic position of fish using both muscle and otoliths. We determined: i) the degree of fractionation of δ13C and δ15N between diet and muscle, and assessed if fractionation was consistent...

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lemonidou, Angeliki A.; Vagia, Ekaterini C.; Lercher, Johannes A.

Reforming of acetic acid was investigated on Rh supported on CeO2-ZrO2 modified with 3 wt % La. The active catalyst converted acetic acid to H-2-rich gas and hardly formed coke. The low rate of coke formation is concluded to be related to the presence of redox-active oxygen limiting the concentration of coke precursors. Temperature-programmed O-18(2)) isotope exchange measurements showed that the La2O3 and Rh enhanced the mobility of lattice oxygen compared with that of the parent CeO2-ZrO2. Ketonization and decarboxylation of acetic acid are the dominating reactions over the latter up to 600 degrees C, whereas above 600 degrees C,more » steam reforming and water gas shift also contribute. Over 0.5 wt % Rh on La2O3/CeO2-ZrO2, reforming and water gas shift reactions dominate, even below 300 degrees C, producing mostly H-2 and CO2. Using isotope labeling, it is shown that acetic acid adsorbs dissociatively on Rh, forming acetates, which sequentially decarboxylate and form surface methyl groups. The latter are in turn converted to CO, CO2, and H-2.« less

Diet-tissue stable isotope (Δ(13)C and Δ(15)N) discrimination factors for multiple tissues from terrestrial reptiles.

PubMed

Steinitz, Ronnie; Lemm, Jeffrey M; Pasachnik, Stesha A; Kurle, Carolyn M

2016-01-15

Stable isotope analysis is a powerful tool for reconstructing trophic interactions to better understand drivers of community ecology. Taxon-specific stable isotope discrimination factors contribute to the best use of this tool. We determined the first Δ(13)C and Δ(15)N values for Rock Iguanas (Cyclura spp.) to better understand isotopic fractionation and estimate wild reptile foraging ecology. The Δ(13)C and Δ(15)N values between diet and skin, blood, and scat were determined from juvenile and adult iguanas held for 1 year on a known diet. We measured relationships between iguana discrimination factors and size/age and quantified effects of lipid extraction and acid treatment on stable isotope values from iguana tissues. Isotopic and elemental compositions were determined by Dumas combustion using an elemental analyzer coupled to an isotope ratio mass spectrometer using standards of known composition. The Δ(13)C and Δ(15)N values ranged from -2.5 to +6.5‰ and +2.2 to +7.5‰, respectively, with some differences among tissues and between juveniles and adults. The Δ(13)C values from blood and skin differed among species, but not the Δ(15)N values. The Δ(13)C values from blood and skin and Δ(15)N values from blood were positively correlated with size/age. The Δ(13)C values from scat were negatively correlated with size (not age). Treatment with HCl (scat) and lipid extraction (skin) did not affect the isotope values. These results should aid in the understanding of processes driving stable carbon and nitrogen isotope discrimination factors in reptiles. We provide estimates of Δ(13)C and Δ(15)N values and linear relationships between iguana size/age and discrimination factors for the best interpretation of wild reptile foraging ecology. Copyright © 2015 John Wiley & Sons, Ltd.

Potassium Isotopic Compositions of NIST Potassium Standards and 40Ar/39Ar Mineral Standards

NASA Technical Reports Server (NTRS)

Morgan, Leah; Tappa, Mike; Ellam, Rob; Mark, Darren; Higgins, John; Simon, Justin I.

2013-01-01

Knowledge of the isotopic ratios of standards, spikes, and reference materials is fundamental to the accuracy of many geochronological methods. For example, the 238U/235U ratio relevant to U-Pb geochronology was recently re-determined [1] and shown to differ significantly from the previously accepted value employed during age determinations. These underlying values are fundamental to accurate age calculations in many isotopic systems, and uncertainty in these values can represent a significant (and often unrecognized) portion of the uncertainty budget for determined ages. The potassium isotopic composition of mineral standards, or neutron flux monitors, is a critical, but often overlooked component in the calculation of K-Ar and 40Ar/39Ar ages. It is currently assumed that all terrestrial materials have abundances indistinguishable from that of NIST SRM 985 [2]; this is apparently a reasonable assumption at the 0.25per mille level (1s) [3]. The 40Ar/39Ar method further relies on the assumption that standards and samples (including primary and secondary standards) have indistinguishable 40K/39K values. We will present data establishing the potassium isotopic compositions of NIST isotopic K SRM 985, elemental K SRM 999b, and 40Ar/39Ar biotite mineral standard GA1550 (sample MD-2). Stable isotopic compositions (41K/39K) were measured by the peak shoulder method with high resolution MC-ICP-MS (Thermo Scientific NEPTUNE Plus), using the accepted value of NIST isotopic SRM 985 [2] for fractionation [4] corrections [5]. 40K abundances were measured by TIMS (Thermo Scientific TRITON), using 41K/39K values from ICP-MS measurements (or, for SRM 985, values from [2]) for internal fractionation corrections. Collectively these data represent an important step towards a metrologically traceable calibration of 40K concentrations in primary 40Ar/39Ar mineral standards and improve uncertainties by ca. an order of magnitude in the potassium isotopic compositions of standards.

OpenMebius: an open source software for isotopically nonstationary 13C-based metabolic flux analysis.

PubMed

Kajihata, Shuichi; Furusawa, Chikara; Matsuda, Fumio; Shimizu, Hiroshi

2014-01-01

The in vivo measurement of metabolic flux by (13)C-based metabolic flux analysis ((13)C-MFA) provides valuable information regarding cell physiology. Bioinformatics tools have been developed to estimate metabolic flux distributions from the results of tracer isotopic labeling experiments using a (13)C-labeled carbon source. Metabolic flux is determined by nonlinear fitting of a metabolic model to the isotopic labeling enrichment of intracellular metabolites measured by mass spectrometry. Whereas (13)C-MFA is conventionally performed under isotopically constant conditions, isotopically nonstationary (13)C metabolic flux analysis (INST-(13)C-MFA) has recently been developed for flux analysis of cells with photosynthetic activity and cells at a quasi-steady metabolic state (e.g., primary cells or microorganisms under stationary phase). Here, the development of a novel open source software for INST-(13)C-MFA on the Windows platform is reported. OpenMebius (Open source software for Metabolic flux analysis) provides the function of autogenerating metabolic models for simulating isotopic labeling enrichment from a user-defined configuration worksheet. Analysis using simulated data demonstrated the applicability of OpenMebius for INST-(13)C-MFA. Confidence intervals determined by INST-(13)C-MFA were less than those determined by conventional methods, indicating the potential of INST-(13)C-MFA for precise metabolic flux analysis. OpenMebius is the open source software for the general application of INST-(13)C-MFA.

Determination of the total oxygen isotopic composition of nitrate and the calibration of a Δ17Ο nitrate reference material

USGS Publications Warehouse

Michalski, Greg; Savarino, Joel; Böhlke, J.K.; Thiemens , Mark

2002-01-01

A thermal decomposition method was developed and tested for the simultaneous determination of δ18O and δ17Ο in nitrate. The thermal decomposition of AgNO3 allows for the rapid and accurate determination of 18O/16O and 17O/16O isotopic ratios with a precision of ±1.5‰ for δ18O and ±0.11‰ for Δ17Ο (Δ17Ο = δ17Ο − 0.52 × δ18O). The international nitrate isotope reference material IAEA-NO3 yielded a δ18O value of +23.6‰ and Δ17Ο of −0.2‰, consistent with normal terrestrial mass-dependent isotopic ratios. In contrast, a large sample of NaNO3 from the Atacama Desert, Chile, was found to have Δ17Ο = 21.56 ± 0.11‰ and δ18O = 54.9 ± 1.5‰, demonstrating a substantial mass-independent isotopic composition consistent with the proposed atmospheric origin of the desert nitrate. It is suggested that this sample (designated USGS-35) can be used to generate other gases (CO2, CO, N2O, O2) with the same Δ17Ο to serve as measurement references for a variety of applications involving mass-independent isotopic compositions in environmental studies.

An on-line potentiometric sequential injection titration process analyser for the determination of acetic acid.

PubMed

van Staden, J F; Mashamba, Mulalo G; Stefan, Raluca I

2002-09-01

An on-line potentiometric sequential injection titration process analyser for the determination of acetic acid is proposed. A solution of 0.1 mol L(-1) sodium chloride is used as carrier. Titration is achieved by aspirating acetic acid samples between two strong base-zone volumes into a holding coil and by channelling the stack of well-defined zones with flow reversal through a reaction coil to a potentiometric sensor where the peak widths were measured. A linear relationship between peak width and logarithm of the acid concentration was obtained in the range 1-9 g/100 mL. Vinegar samples were analysed without any sample pre-treatment. The method has a relative standard deviation of 0.4% with a sample frequency of 28 samples per hour. The results revealed good agreement between the proposed sequential injection and an automated batch titration method.

Calcium and Titanium Isotope Fractionation in CAIS: Tracers of Condensation and Inheritance in the Early Solar Protoplanetary Disk

NASA Technical Reports Server (NTRS)

Simon, J. I.; Jordan, M. K.; Tappa, M. J.; Kohl, I. E.; Young, E. D.

2016-01-01

The chemical and isotopic compositions of calcium-aluminum-rich inclusions (CAIs) can be used to understand the conditions present in the protoplantary disk where they formed. The isotopic compositions of these early-formed nebular materials are largely controlled by chemical volatility. The isotopic effects of evaporation/sublimation, which are well explained by both theory and experimental work, lead to enrichments of the heavy isotopes that are often exhibited by the moderately refractory elements Mg and Si. Less well understood are the isotopic effects of condensation, which limits our ability to determine whether a CAI is a primary condensate and/or retains any evidence of its primordial formation history.

Multiconfiguration calculations of electronic isotope shift factors in Al i

NASA Astrophysics Data System (ADS)

Filippin, Livio; Beerwerth, Randolf; Ekman, Jörgen; Fritzsche, Stephan; Godefroid, Michel; Jönsson, Per

2016-12-01

The present work reports results from systematic multiconfiguration Dirac-Hartree-Fock calculations of electronic isotope shift factors for a set of transitions between low-lying levels of neutral aluminium. These electronic quantities together with observed isotope shifts between different pairs of isotopes provide the changes in mean-square charge radii of the atomic nuclei. Two computational approaches are adopted for the estimation of the mass- and field-shift factors. Within these approaches, different models for electron correlation are explored in a systematic way to determine a reliable computational strategy and to estimate theoretical error bars of the isotope shift factors.

Development of high through-put Sr isotope analysis for monitoring reservoir integrity for CO{sub 2} storage.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wall, Andy; Jain, Jinesh; Stewart, Brian

2012-01-01

Recent innovations in multi-collector ICP-mass spectrometry (MC-ICP-MS) have allowed for rapid and precise measurements of isotope ratios in geological samples. Naturally occurring Sr isotopes has the potential for use in Monitoring, Verification, and Accounting (MVA) associated with geologic CO2 storage. Sr isotopes can be useful for: Sensitive tracking of brine migration; Determining seal rock leakage; Studying fluid/rock reactions. We have optimized separation chemistry procedures that will allow operators to prepare samples for Sr isotope analysis off site using rapid, low cost methods.

Lead isotopes in iron and manganese oxide coatings and their use as an exploration guide for concealed mineralization

USGS Publications Warehouse

Gulson, B.L.; Church, S.E.; Mizon, K.J.; Meier, A.L.

1992-01-01

Lead isotopes from Fe and Mn oxides that coat stream pebbles from around the Mount Emmons porphyry molybdenum deposit in Colorado were studied to assess the feasibility of using Pb isotopes to detect concealed mineral deposits. The Fe/Mn oxide coatings were analyzed to determine their elemental concentrations using ICP-AES. The Pb isotope compositions of solutions from a selected suite of samples were measured, using both thermal ionization and ICP mass spectrometry, to compare results determined by the two analytical methods. Heavy mineral concentrates from the same sites were also analyzed to compare the Pb isotope compositions of the Fe/Mn coatings with those found in panned concentrates. The Fe/Mn and 206Pb/204Pb ratios of the oxide coatings are related to the lithology of the host rocks; Fe/Mn oxide coatings on pebbles of black shale have higher Fe/Mn values than do the coatings on either sandstone or igneous rocks. The shale host rocks have a more radiogenic signature (e.g. higher 206Pb/ 204Pb) than the sandstone or igneous host rocks. The Pb isotope data from sandstone and igneous hosts can detect concealed mineralized rock on both a regional and local scale, even though there are contributions from: (1) metals from the main-stage molybdenite ore deposit; (2) metals from the phyllic alteration zone which has a more radiogenic Pb isotope signature reflecting hydrothermal leaching of Pb from the Mancos Shale; (3) Pb-rich base metal veins with a highly variable Pb isotope signature; and (4) sedimentary country rocks which have a more radiogenic Pb isotope signature. An investigation of within-stream variation shows that the Pb isotope signature of the molybdenite ore zone is retained in the Fe/Mn oxide coatings and is not camouflaged by contributions from Pb-rich base-metal veins that crop out upstream. In another traverse, the Pb isotope data from Fe/Mn oxide coatings reflect a complex mixing of Pb from the molybdenite ore zone and its hornfels margin, Pb-rich base-metal veins, and sedimentary country rocks. Stream-sediment anomalies detected using oxalic acid leaches can be evaluated using Pb isotope analysesof selected geochemical anomalies. Such an evaluation procedure, given regional target Pb isotope signatures for concealed mineralization, can greatly reduce the cost of exploration for undiscovered ore deposits concealed beneath barren overburden. Lead isotope measurements on aliquots of the same solutions showed that ICP-MS determinations are of low precision and vary non-systematically when compared with the Pb isotope values of the higher precision thermal ionization method. These variations and lower precision of the ICP-MS measurements are attributed to matrix effects. ?? 1992.

Phosphorus Concentrations in Sequentially Fractionated Soil Samples as Affected by Digestion Methods

PubMed Central

do Nascimento, Carlos A. C.; Pagliari, Paulo H.; Schmitt, Djalma; He, Zhongqi; Waldrip, Heidi

2015-01-01

Sequential fractionation has helped improving our understanding of the lability and bioavailability of P in soil. Nevertheless, there have been no reports on how manipulation of the different fractions prior to analyses affects the total P (TP) concentrations measured. This study investigated the effects of sample digestion, filtration, and acidification on the TP concentrations determined by ICP-OES in 20 soil samples. Total P in extracts were either determined without digestion by ICP-OES, or ICP-OES following block digestion, or autoclave digestion. The effects of sample filtration, and acidification on undigested alkaline extracts prior to ICP-OES were also evaluated. Results showed that, TP concentrations were greatest in the block-digested extracts, though the variability introduced by the block-digestion was the highest. Acidification of NaHCO3 extracts resulted in lower TP concentrations, while acidification of NaOH randomly increased or decreased TP concentrations. The precision observed with ICP-OES of undigested extracts suggests this should be the preferred method for TP determination in sequentially extracted samples. Thus, observations reported in this work would be helpful in appropriate sample handling for P determination, thereby improving the precision of P determination. The results are also useful for literature data comparison and discussion when there are differences in sample treatments. PMID:26647644

Type I and Type II Error Rates and Overall Accuracy of the Revised Parallel Analysis Method for Determining the Number of Factors

ERIC Educational Resources Information Center

Green, Samuel B.; Thompson, Marilyn S.; Levy, Roy; Lo, Wen-Juo

2015-01-01

Traditional parallel analysis (T-PA) estimates the number of factors by sequentially comparing sample eigenvalues with eigenvalues for randomly generated data. Revised parallel analysis (R-PA) sequentially compares the "k"th eigenvalue for sample data to the "k"th eigenvalue for generated data sets, conditioned on"k"-…

Determination of ambroxol hydrochloride, methylparaben and benzoic acid in pharmaceutical preparations based on sequential injection technique coupled with monolithic column.

PubMed

Satínský, Dalibor; Huclová, Jitka; Ferreira, Raquel L C; Montenegro, Maria Conceição B S M; Solich, Petr

2006-02-13

The porous monolithic columns show high performance at relatively low pressure. The coupling of short monoliths with sequential injection technique (SIA) results in a new approach to implementation of separation step to non-separation low-pressure method. In this contribution, a new separation method for simultaneous determination of ambroxol, methylparaben and benzoic acid was developed based on a novel reversed-phase sequential injection chromatography (SIC) technique with UV detection. A Chromolith SpeedROD RP-18e, 50-4.6 mm column with 10 mm precolumn and a FIAlab 3000 system with a six-port selection valve and 5 ml syringe were used for sequential injection chromatographic separations in our study. The mobile phase used was acetonitrile-tetrahydrofuran-0.05M acetic acid (10:10:90, v/v/v), pH 3.75 adjusted with triethylamine, flow rate 0.48 mlmin(-1), UV-detection was at 245 nm. The analysis time was <11 min. A new SIC method was validated and compared with HPLC. The method was found to be useful for the routine analysis of the active compounds ambroxol and preservatives (methylparaben or benzoic acid) in various pharmaceutical syrups and drops.

Influences of large-scale convection and moisture source on monthly precipitation isotope ratios observed in Thailand, Southeast Asia

NASA Astrophysics Data System (ADS)

Wei, Zhongwang; Lee, Xuhui; Liu, Zhongfang; Seeboonruang, Uma; Koike, Masahiro; Yoshimura, Kei

2018-04-01

Many paleoclimatic records in Southeast Asia rely on rainfall isotope ratios as proxies for past hydroclimatic variability. However, the physical processes controlling modern rainfall isotopic behaviors in the region is poorly constrained. Here, we combined isotopic measurements at six sites across Thailand with an isotope-incorporated atmospheric circulation model (IsoGSM) and the Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model to investigate the factors that govern the variability of precipitation isotope ratios in this region. Results show that rainfall isotope ratios are both correlated with local rainfall amount and regional outgoing longwave radiation, suggesting that rainfall isotope ratios in this region are controlled not only by local rain amount (amount effect) but also by large-scale convection. As a transition zone between the Indian monsoon and the western North Pacific monsoon, the spatial difference of observed precipitation isotope among different sites are associated with moisture source. These results highlight the importance of regional processes in determining rainfall isotope ratios in the tropics and provide constraints on the interpretation of paleo-precipitation isotope records in the context of regional climate dynamics.

Synthetic isotope mixtures for the calibration of isotope amount ratio measurements of carbon

NASA Astrophysics Data System (ADS)

Russe, K.; Valkiers, S.; Taylor, P. D. P.

2004-07-01

Synthetic isotope mixtures for the calibration of carbon isotope amount ratio measurements have been prepared by mixing carbon tetrafluoride highly enriched in 13C with carbon tetrafluoride depleted in 13C. Mixing procedures based on volumetry and gravimetry are described. The mixtures served as primary measurement standards for the calibration of isotope amount ratio measurements of the Isotopic Reference Materials PEF1, NBS22 and USGS24. Thus SI-traceable measurements of absolute carbon isotope amount ratios have been performed for the first time without any hypothesis needed for a correction of oxygen isotope abundances, such as is the case for measurements on carbon dioxide. As a result, "absolute" carbon isotope amount ratios determined via carbon tetrafluoride have smaller uncertainties than those published for carbon dioxide. From the measurements of the Reference Materials concerned, the absolute carbon isotope amount ratio of Vienna Pee Dee Belemnite (VPDB)--the hypothetical material upon which the scale for relative carbon isotope ratio measurements is based--was calculated to be R13(VPDB) = (11 101 +/- 16) × 10-6.

Atomic vapor laser isotope separation process

DOEpatents

Wyeth, R.W.; Paisner, J.A.; Story, T.

1990-08-21

A laser spectroscopy system is utilized in an atomic vapor laser isotope separation process. The system determines spectral components of an atomic vapor utilizing a laser heterodyne technique. 23 figs.

Reconstruction of an aquatic food web: Viking Haithabu vs. Medieval Schleswig.

PubMed

von Steinsdorff, Katja; Grupe, Gisela

2006-09-01

In the last two decades, the analysis of stable isotopes of carbonate and collagen from archaeological bone finds became a useful tool in the reconstruction of ancient food webs. Nevertheless there is still only little information available about aquatic food webs, in particular concerning brackish water ecosystems. The Schlei Fjord in Schleswig-Holstein, Germany, is such an ecosystem and was investigated to determine stable isotopic values for nitrogen, carbon and oxygen from bone collagen and carbonate in archaeological bone finds. Wild birds, mammals and fish bones from the Viking settlement Haithabu and the medieval town of Schleswig have been analyzed in this study to determine stable isotope values for marine and limnic species and to investigate possible isotopic gradients for mixing fresh water and salt water ecosystems.

Patterns of local and nonlocal water resource use across the western U.S. determined via stable isotope intercomparisons

USDA-ARS?s Scientific Manuscript database

The stable isotope ratios of hydrogen (H) and oxygen (O) are valuable tracers of the origin of biological materials and water sources. Application of these environmental tracers is largely based on the distinct and pervasive spatial patterns of precipitation isotopes, which are preserved in many hy...

[Sources of Methane in the Boreal Region

NASA Technical Reports Server (NTRS)

1998-01-01

In determining the global methane budget the sources of methane must be balanced with the sinks and atmospheric inventory. The approximate contribution of the different methane sources to the budget has been establish showing the major terrestrial inputs as rice, wetlands, bogs, fens, and tundra. Measurements and modeling of production in these sources suggest that temperature, water table height and saturation along with substratum composition are important in controlling methane production and emission. The isotopic budget of 13 C and D/H in methane can be used as a tool to clarify the global budget. This approach has achieved success at constraining the inputs. Studies using the isotopic approach place constraints on global methane production from different sources. Also, the relation between the two biogenic production pathways, acetate fermentation and CO2 reduction, and the effect of substratum composition can be made using isotope measurements shows the relation between the different biogenic, thermogenic and anthropogenic sources of methane as a function of the carbon and hydrogen isotope values for each source and the atmosphere, tropospheric composition. Methane emissions from ponds and fens are a significant source in the methane budget of the boreal region. An initial study in 1993 and 1994 on the isotopic composition of this methane source and the isotopic composition in relation to oxidation of methane at the sediment surface of the ponds or fen was conducted as part of our BOREAS project. The isotopic composition of methane emitted by saturated anoxic sediment is dependent on the sediment composition and geochemistry, but will be influenced by in situ oxidation, in part, a function of rooted plant activity. The influence of oxidation mediated by rooted plant activities on the isotopic composition of methane is not well known and will depend on the plant type, sediment temperature, and numerous other variables. Information on this isotopic composition is important in both understanding the bio-geochemistry of the system and also in determining the regional and global inputs for the methane isotope budget. In determining the destruction of methane for balancing the atmospheric methane budget soil oxidation must be considered.

Native Frames: Disentangling Sequential from Concerted Three-Body Fragmentation

NASA Astrophysics Data System (ADS)

Rajput, Jyoti; Severt, T.; Berry, Ben; Jochim, Bethany; Feizollah, Peyman; Kaderiya, Balram; Zohrabi, M.; Ablikim, U.; Ziaee, Farzaneh; Raju P., Kanaka; Rolles, D.; Rudenko, A.; Carnes, K. D.; Esry, B. D.; Ben-Itzhak, I.

2018-03-01

A key question concerning the three-body fragmentation of polyatomic molecules is the distinction of sequential and concerted mechanisms, i.e., the stepwise or simultaneous cleavage of bonds. Using laser-driven fragmentation of OCS into O++C++S+ and employing coincidence momentum imaging, we demonstrate a novel method that enables the clear separation of sequential and concerted breakup. The separation is accomplished by analyzing the three-body fragmentation in the native frame associated with each step and taking advantage of the rotation of the intermediate molecular fragment, CO2 + or CS2 + , before its unimolecular dissociation. This native-frame method works for any projectile (electrons, ions, or photons), provides details on each step of the sequential breakup, and enables the retrieval of the relevant spectra for sequential and concerted breakup separately. Specifically, this allows the determination of the branching ratio of all these processes in OCS3 + breakup. Moreover, we find that the first step of sequential breakup is tightly aligned along the laser polarization and identify the likely electronic states of the intermediate dication that undergo unimolecular dissociation in the second step. Finally, the separated concerted breakup spectra show clearly that the central carbon atom is preferentially ejected perpendicular to the laser field.

A modified lead-matrix separation procedure shown for lead isotope analysis in Trojan silver artefacts as an example.

PubMed

Vogl, Jochen; Paz, Boaz; Koenig, Maren; Pritzkow, Wolfgang

2013-03-01

A modified Pb-matrix separation procedure using NH4HCO3 solution as eluent has been developed and validated for determination of Pb isotope amount ratios by thermal ionization mass spectrometry. The procedure is based on chromatographic separation using the Pb·Spec resin and an in-house-prepared NH4HCO3 solution serving as eluent. The advantages of this eluent are low Pb blanks (<40 pg mL(-1)) and the property that NH4HCO3 can be easily removed by use of a heating step (>60 °C). Pb recovery is >95 % for water samples. For archaeological silver samples, however, the Pb recovery is reduced to approximately 50 %, but causes no bias in the determination of Pb isotope amount ratios. The validated procedure was used to determine lead isotope amount ratios in Trojan silver artefacts with expanded uncertainties (k = 2) <0.09 %.

Measurement of plutonium isotope ratios in nuclear fuel samples by HPLC-MC-ICP-MS

NASA Astrophysics Data System (ADS)

Günther-Leopold, I.; Waldis, J. Kobler; Wernli, B.; Kopajtic, Z.

2005-04-01

Radioactive isotopes are traditionally quantified by means of radioactivity counting techniques ([alpha], [beta], [gamma]). However, these methods often require extensive matrix separation and sample purification before the identification of specific isotopes and their relative abundance is possible as it is necessary in the frame of post-irradiation examinations on nuclear fuel samples. The technique of multicollector inductively coupled plasma mass spectrometry (MC-ICP-MS) is attracting much attention because it permits the precise measurement of the isotope compositions for a wide range of elements combined with excellent limits of detection due to high ionization efficiencies. The present paper describes one of the first applications of an online high-performance liquid chromatographic separation system coupled to a MC-ICP-MS in order to overcome isobaric interferences for the determination of the plutonium isotope composition and concentrations in irradiated nuclear fuels. The described chromatographic separation is sufficient to prevent any isobaric interference between 238Pu present at trace concentrations and 238U present as the main component of the fuel samples. The external reproducibility of the uncorrected plutonium isotope ratios was determined to be between 0.04 and 0.2% (2 s) resulting in a precision in the [per mille sign] range for the isotopic vectors of the irradiated fuel samples.

Measurement of isotope ratios on transient signals by MC-ICP-MS.

PubMed

Günther-Leopold, Ines; Wernli, Beat; Kopajtic, Zlatko; Günther, Detlef

2004-01-01

Precise and accurate isotope ratio measurements are an important task in many applications such as isotope-dilution mass spectrometry, bioavailability studies, or the determination of isotope variations in geological or nuclear samples. The technique of MC-ICP-MS has attracted much attention because it permits the precise measurement of isotope compositions for a wide range of elements combined with excellent detection limits due to high ionisation efficiencies. However, the results are based mainly on measurements using continuous sample introduction. In the present study the determination of isotope ratios on various transient signals with a time duration of 30 to 60 s has been achieved by coupling high-performance liquid chromatography to a multicollector inductively coupled plasma mass spectrometer. In order to investigate the origin of ratio drifts across the transient signals for this hyphenated technique, measurements with the same standard solutions were also carried out using a flow-injection device for sample introduction. As a result of this application it could be concluded that the main source of the bias in the measured isotope ratios is within the ICP-MS instead of fractionation effects on the chromatographic column material. Preliminary studies on short transient signals of gaseous samples (dry plasma) showed a reverse fractionation effect compared with wet plasma conditions (flow injection and HPLC).

Development of an enantiomer-specific stable carbon isotope analysis (ESIA) method for assessing the fate of α-hexachlorocyclo-hexane in the environment.

PubMed

Badea, Silviu-Laurentiu; Vogt, Carsten; Gehre, Matthias; Fischer, Anko; Danet, Andrei-Florin; Richnow, Hans-Hermann

2011-05-30

α-Hexachlorocyclohexane (α-HCH) is the only chiral isomer of the eight 1,2,3,4,5,6-HCHs and we have developed an enantiomer-specific stable carbon isotope analysis (ESIA) method for the evaluation of its fate in the environment. The carbon isotope ratios of the α-HCH enantiomers were determined for a commercially available α-HCH sample using a gas chromatography-combustion-isotope ratio mass spectrometry (GC-C-IRMS) system equipped with a chiral column. The GC-C-IRMS measurements revealed δ-values of -32.5 ± 0.8‰ and -32.3 ± 0.5‰ for (-) α-HCH and (+) α-HCH, respectively. The isotope ratio of bulk α-HCH was estimated to be -32.4 ± 0.6‰ which was in accordance with the δ-values obtained by GC-C-IRMS (-32.7 ± 0.2‰) and elemental analyzer-isotope ratio mass spectrometry (EA-IRMS) of the bulk α-HCH (-32.1 ± 0.1‰). The similarity of the isotope ratio measurements of bulk α-HCH by EA-IRMS and GC-C-IRMS indicates the accuracy of the chiral GC-C-IRMS method. The linearity of the α-HCH ESIA method shows that carbon isotope ratios can be obtained for a signal size above 100 mV. The ESIA measurements exhibited standard deviations (2σ) that were mostly < ± 0.5‰. In order to test the chiral GC-C-IRMS method, the isotope compositions of individual enantiomers in biodegradation experiments of α-HCH with Clostridium pasteurianum and samples from a contaminated field site were determined. The isotopic compositions of the α-HCH enantiomers show a range of enantiomeric and isotope patterns, suggesting that enantiomeric and isotope fractionation can serve as an indicator for biodegradation and source characterization of α-HCH in the environment. Copyright © 2011 John Wiley & Sons, Ltd.

Nitrogen Isotope Evidence for a Shift in Eastern Beringian Nitrogen Cycle after the Terminal Pleistocene

NASA Astrophysics Data System (ADS)

Tahmasebi, F.; Longstaffe, F. J.; Zazula, G.

2016-12-01

The loess deposits of eastern Beringia, a region in North America between 60° and 70°N latitude and bounded by Chukchi Sea to the west and the Mackenzie River to the east, are a magnificent repository of Late Pleistocene megafauna fossils. The stable carbon and nitrogen isotope compositions of these fossils are measured to determine the paleodiet of these animals, and hence the paleoenvironment of this ecosystem during the Quaternary. For this approach to be most successful, however, requires consideration of possible changes in nutrient cycling and hence the carbon and nitrogen isotopic compositions of vegetation in this ecosystem. To test for such a shift following the terminal Pleistocene, we analyzed the stable carbon and nitrogen isotope compositions of modern plants and bone collagen of Arctic ground squirrels from Yukon Territory, and fossil plants and bones recovered from Late Pleistocene fossil Arctic ground squirrel nests. The data for modern samples provided a measure of the isotopic fractionation between ground squirrel bone collagen and their diet. The over-wintering isotopic effect of decay on typical forage grasses was also measured to evaluate its role in determining fossil plant isotopic compositions. The grasses showed only a minor change ( 0-1 ‰) in carbon isotope composition, but a major change ( 2-10 ‰) in nitrogen isotope composition over the 317-day experiment. Based on the modern carbon isotope fractionation between ground squirrel bone collagen and their diet, the modern vegetation carbon isotopic baseline provides a suitable proxy for the Late Pleistocene of eastern Beringia, after accounting for the Suess effect. However, the predicted nitrogen isotope composition of vegetation comprising the diet of fossil ground squirrels remains 2.5 ‰ higher than modern grasslands in this area, even after accounting for possible N-15 enrichment during decay. This result suggests a change in N cycling in this region since the Late Pleistocene.

Multi-Seasonal Nitrogen Recoveries from Crop Residue in Soil and Crop in a Temperate Agro-Ecosystem

PubMed Central

Hu, Guoqing; Liu, Xiao; He, Hongbo; Zhang, Wei; Xie, Hongtu; Wu, Yeye; Cui, Jiehua; Sun, Ci; Zhang, Xudong

2015-01-01

In conservation tillage systems, at least 30% of the soil surface was covered by crop residues which generally contain significant amounts of nitrogen (N). However, little is known about the multi-seasonal recoveries of the N derived from these crop residues in soil-crop systems, notably in northeastern China. In a temperate agro-ecosystem, 15N-labeled maize residue was applied to field surfaces in the 1st year (2009). From the 2nd to 4th year (2010-2012), one treatment halted the application of maize residue, whereas the soil in the second treatment was re-applied with unlabeled maize residue. Crop and soil samples were collected after each harvest, and their 15N enrichments were determined on an isotope ratio mass spectrometer to trace the allocation of N derived from the initially applied maize residue in the soil-crop systems. On average, 8.4% of the maize residue N was recovered in the soil-crop in the 1st year, and the vast majority (61.9%-91.9%) was recovered during subsequent years. Throughout the experiment, the cumulative recovery of the residue N in the crop increased gradually (18.2%-20.9%), but most of the residue N was retained in the soil, notably in the 0-10 cm soil layer. Compared to the single application, the sequential residue application significantly increased the recovery of the residue N in the soil profile (73.8% vs. 40.9%) and remarkably decreased the total and the initially applied residue derived mineral N along the soil profile. Our results suggested that the residue N was actively involved in N cycling, and its release and recovery in crop and soil profile were controlled by the decomposition process. Sequential residue application significantly enhanced the retention and stabilization of the initially applied residue N in the soil and retarded its translocation along the soil profile. PMID:26192436

Using Stable Isotope Mixing in a Great Lakes Coastal Tributary to Determine Food Web Linkages in Young Fishes

EPA Science Inventory

Our objectives were to determine whether we can detect a stable isotope gradient along the river-Great Lake hydrologic continuum in a coastal river and use it to identify changes across this gradient in the food web supporting young-of-year (YOY) and juvenile fish production. We ...

Determination of uranium isotopes in environmental samples by anion exchange in sulfuric and hydrochloric acid media.

PubMed

Popov, L

2016-09-01

Method for determination of uranium isotopes in various environmental samples is presented. The major advantages of the method are the low cost of the analysis, high radiochemical yields and good decontamination factors from the matrix elements, natural and man-made radionuclides. The separation and purification of uranium is attained by adsorption with strong base anion exchange resin in sulfuric and hydrochloric acid media. Uranium is electrodeposited on a stainless steel disk and measured by alpha spectrometry. The analytical method has been applied for the determination of concentrations of uranium isotopes in mineral, spring and tap waters from Bulgaria. The analytical quality was checked by analyzing reference materials. Copyright © 2016 Elsevier Ltd. All rights reserved.

A sequential adaptation technique and its application to the Mark 12 IFF system

NASA Astrophysics Data System (ADS)

Bailey, John S.; Mallett, John D.; Sheppard, Duane J.; Warner, F. Neal; Adams, Robert

1986-07-01

Sequential adaptation uses only two sets of receivers, correlators, and A/D converters which are time multiplexed to effect spatial adaptation in a system with (N) adaptive degrees of freedom. This technique can substantially reduce the hardware cost over what is realizable in a parallel architecture. A three channel L-band version of the sequential adapter was built and tested for use with the MARK XII IFF (identify friend or foe) system. In this system the sequentially determined adaptive weights were obtained digitally but implemented at RF. As a result, many of the post RF hardware induced sources of error that normally limit cancellation, such as receiver mismatch, are removed by the feedback property. The result is a system that can yield high levels of cancellation and be readily retrofitted to currently fielded equipment.

Diffusion-controlled magnesium isotopic fractionation of a single crystal forsterite evaporated from the solid state

NASA Technical Reports Server (NTRS)

Wang, Jianhua; Davis, Andrew M.; Hashimoto, Akihiko; Clayton, Robert N.

1993-01-01

Though the origin of calcium- and aluminum-rich inclusions (CAI's) in carbonaceous chondrites is till a disputed issue, evaporation is no doubt one of the most important processes for the formation of CAI's in the early solar nebula. The mechanism for production of large isotopic mass fractionation effects in magnesium, silicon, oxygen, and chromium in CAI's can be better understood by examining isotopic fractionation during the evaporation of minerals. New evaporation experiments were performed on single-crystal forsterite. The magnesium isotopic distribution near the evaporating surfaces of the residues using a modified AEI IM-20 ion microprobe to obtain rastered beam depth profiles was measured. A theoretical model was used to explain the profiles and allowed determination of the diffusion coefficient of Mg(++) in forsterite at higher temperatures than previous measurements. The gas/solid isotopic fractionation factor for magnesium for evaporation from solid forsterite was also determined and found to be nearly the same as that for evaporation of liquid Mg2SiO4.

Isotopic fractionation studies of uranium and plutonium using porous ion emitters as thermal ionization mass spectrometry sources

DOE PAGES

Baruzzini, Matthew L.; Hall, Howard L.; Spencer, Khalil J.; ...

2018-04-22

Investigations of the isotope fractionation behaviors of plutonium and uranium reference standards were conducted employing platinum and rhenium (Pt/Re) porous ion emitter (PIE) sources, a relatively new thermal ionization mass spectrometry (TIMS) ion source strategy. The suitability of commonly employed, empirically developed mass bias correction laws (i.e., the Linear, Power, and Russell's laws) for correcting such isotope ratio data was also determined. Corrected plutonium isotope ratio data, regardless of mass bias correction strategy, were statistically identical to that of the certificate, however, the process of isotope fractionation behavior of plutonium using the adopted experimental conditions was determined to be bestmore » described by the Power law. Finally, the fractionation behavior of uranium, using the analytical conditions described herein, is also most suitably modeled using the Power law, though Russell's and the Linear law for mass bias correction rendered results that were identical, within uncertainty, to the certificate value.« less

Isotopic fractionation studies of uranium and plutonium using porous ion emitters as thermal ionization mass spectrometry sources

DOE Office of Scientific and Technical Information (OSTI.GOV)

Baruzzini, Matthew L.; Hall, Howard L.; Spencer, Khalil J.

Investigations of the isotope fractionation behaviors of plutonium and uranium reference standards were conducted employing platinum and rhenium (Pt/Re) porous ion emitter (PIE) sources, a relatively new thermal ionization mass spectrometry (TIMS) ion source strategy. The suitability of commonly employed, empirically developed mass bias correction laws (i.e., the Linear, Power, and Russell's laws) for correcting such isotope ratio data was also determined. Corrected plutonium isotope ratio data, regardless of mass bias correction strategy, were statistically identical to that of the certificate, however, the process of isotope fractionation behavior of plutonium using the adopted experimental conditions was determined to be bestmore » described by the Power law. Finally, the fractionation behavior of uranium, using the analytical conditions described herein, is also most suitably modeled using the Power law, though Russell's and the Linear law for mass bias correction rendered results that were identical, within uncertainty, to the certificate value.« less

A new sniffer probe for the determination of hydrogen isotope ratios in the W7-AS stellarator

NASA Astrophysics Data System (ADS)

Zebisch, P.; Taglauer, E.

1999-07-01

An improved sniffer probe was constructed for measurements of the hydrogen isotope ratio and impurities in the plasma edge of the W7-AS stellarator. Details of the new design and the probe performance are presented. The new design allows changing the head without breaking the vacuum in the torus. It has a high mechanical stability, effective screening of the magnetic field and high sensitivity. The gas dynamic properties of the probe are analyzed using transmission line calculus, resulting in a rise time of 114 ms for hydrogen. During the 1997 spring measurement campaign, H/D isotope ratio measurements were carried through showing considerable outgassing of the walls during and after the discharge. He glow discharges reduce the isotope ratio drastically. Results from a typical experiment day are presented together with the analytic procedure for determining the isotope ratio in both the plasma edge and in the neutral gas region between the plasma and the vessel walls.

Carbon isotope fractionation by thermophilic phototrophic sulfur bacteria: evidence for autotrophic growth in natural populations

NASA Technical Reports Server (NTRS)

Madigan, M. T.; Takigiku, R.; Lee, R. G.; Gest, H.; Hayes, J. M.

1989-01-01

Purple phototrophic bacteria of the genus Chromatium can grow as either photoautotrophs or photoheterotrophs. To determine the growth mode of the thermophilic Chromatium species, Chromatium tepidum, under in situ conditions, we have examined the carbon isotope fractionation patterns in laboratory cultures of this organism and in mats of C. tepidum which develop in sulfide thermal springs in Yellowstone National Park. Isotopic analysis (13C/12C) of total carbon, carotenoid pigments, and bacteriochlorophyll from photoautotrophically grown cultures of C. tepidum yielded 13C fractionation factors near -20%. Cells of C. tepidum grown on excess acetate, wherein synthesis of the Calvin cycle enzyme ribulose-1,5-bisphosphate carboxylase/oxygenase ribulose bisphosphate carboxylase) was greatly repressed, were isotopically heavier, fractionation factors of ca. -7% being observed. Fractionation factors determined by isotopic analyses of cells and pigment fractions of natural populations of C. tepidum growing in three different sulfide thermal springs in Yellowstone National Park were approximately -20%, indicating that this purple sulfur bacterium grows as a photoautotroph in nature.

Temporal evolution of mechanisms controlling ocean carbon uptake during the last glacial cycle

NASA Astrophysics Data System (ADS)

Kohfeld, Karen E.; Chase, Zanna

2017-08-01

Many mechanisms have been proposed to explain the ∼85-90 ppm decrease in atmospheric carbon dioxide (CO2) during the last glacial cycle, between 127,000 and 18,000 yrs ago. When taken together, these mechanisms can, in some models, account for the full glacial-interglacial CO2 drawdown. Most proxy-based evaluations focus on the peak of the Last Glacial Maximum, 24,000-18,000 yrs ago, and little has been done to determine the sequential timing of processes affecting CO2 during the last glacial cycle. Here we use a new compilation of sea-surface temperature records together with time-sequenced records of carbon and Nd isotopes, and other proxies to determine when the most commonly proposed mechanisms could have been important for CO2 drawdown. We find that the initial major drawdown of 35 ppm 115,000 yrs ago was most likely a result of Antarctic sea ice expansion. Importantly, changes in deep ocean circulation and mixing did not play a major role until at least 30,000 yrs after the first CO2 drawdown. The second phase of CO2 drawdown occurred ∼70,000 yrs ago and was also coincident with the first significant influences of enhanced ocean productivity due to dust. Finally, minimum concentrations of atmospheric CO2 during the Last Glacial Maximum resulted from the combination of physical and biological factors, including the barrier effect of expanded Southern Ocean sea ice, slower ventilation of the deep sea, and ocean biological feedbacks.

EM reconstruction of dual isotope PET using staggered injections and prompt gamma positron emitters

DOE Office of Scientific and Technical Information (OSTI.GOV)

Andreyev, Andriy, E-mail: andriy.andreyev-1@philips.com; Sitek, Arkadiusz; Celler, Anna

2014-02-15

Purpose: The aim of dual isotope positron emission tomography (DIPET) is to create two separate images of two coinjected PET radiotracers. DIPET shortens the duration of the study, reduces patient discomfort, and produces perfectly coregistered images compared to the case when two radiotracers would be imaged independently (sequential PET studies). Reconstruction of data from such simultaneous acquisition of two PET radiotracers is difficult because positron decay of any isotope creates only 511 keV photons; therefore, the isotopes cannot be differentiated based on the detected energy. Methods: Recently, the authors have proposed a DIPET technique that uses a combination of radiotracermore » A which is a pure positron emitter (such as{sup 18}F or {sup 11}C) and radiotracer B in which positron decay is accompanied by the emission of a high-energy (HE) prompt gamma (such as {sup 38}K or {sup 60}Cu). Events that are detected as triple coincidences of HE gammas with the corresponding two 511 keV photons allow the authors to identify the lines-of-response (LORs) of isotope B. These LORs are used to separate the two intertwined distributions, using a dedicated image reconstruction algorithm. In this work the authors propose a new version of the DIPET EM-based reconstruction algorithm that allows the authors to include an additional, independent estimate of radiotracer A distribution which may be obtained if radioisotopes are administered using a staggered injections method. In this work the method is tested on simple simulations of static PET acquisitions. Results: The authors’ experiments performed using Monte-Carlo simulations with static acquisitions demonstrate that the combined method provides better results (crosstalk errors decrease by up to 50%) than the positron-gamma DIPET method or staggered injections alone. Conclusions: The authors demonstrate that the authors’ new EM algorithm which combines information from triple coincidences with prompt gammas and staggered injections improves the accuracy of DIPET reconstructions for static acquisitions so they reach almost the benchmark level calculated for perfectly separated tracers.« less

Intramolecular Isotopic Studies: Chemical Enhancements and Alternatives

NASA Astrophysics Data System (ADS)

Hayes, J. M.

2016-12-01

As mass spectroscopic and NMR-based methods now appropriately flourish, chemical techniques should not be forgotten. First, the methods developed by pioneering intramolecular analysts can be reapplied to new samples. Second, they can be extended. The synthesis of intramolecular isotopic standards is particularly important and straightforward. It requires only that a chemical reaction has no secondary products. An example is provided by the addition of carbon dioxide to a Grignard reagent. The reaction proceeds with an isotope effect. The isotopic composition of the carboxyl group in the acid which is produced is thus not equal to that of the starting carbon dioxide but the unconsumed CO2 can be recovered and analyzed. A simple titration can show that all the rest of the CO2 is in the product acid. The isotopic composition of the carboxyl group can then be calculated by difference. The product is an intramolecular isotopic standard, an organic molecule in which the isotopic composition of a specific carbon position is known accurately. Both analysts and reviewers can thus gain invaluable confidence in the accuracy of instrumental results. A second example: the haloform reaction quantitatively degrades methyl ketones, producing a carboxylic acid which can be decarboxylated to determine the isotopic composition of the parent carbonyl and a haloform (CHI3, for example) that can be combusted to determine the isotopic composition of the methyl group. Ketones thus analyzed can be combined with Grignard reagents to yield carbon skeletons in which the isotopic compositions of internal and terminal -CH2- and -CH3 groups are known accurately. In general, analysts accustomed to demanding quantitative reactions should remember the power of mass balances and recognize that many organic-chemical reactions, while not quantitative, lack side products and can be driven to the total consumption of at least one reactant.

Kinetic isotopic fractionation during diffusion of ionic species in water

NASA Astrophysics Data System (ADS)

Richter, Frank M.; Mendybaev, Ruslan A.; Christensen, John N.; Hutcheon, Ian D.; Williams, Ross W.; Sturchio, Neil C.; Beloso, Abelardo D.

2006-01-01

Experiments specifically designed to measure the ratio of the diffusivities of ions dissolved in water were used to determine DLi/DK,D/D,D/D,D/D,andD/D. The measured ratio of the diffusion coefficients for Li and K in water (D Li/D K = 0.6) is in good agreement with published data, providing evidence that the experimental design being used resolves the relative mobility of ions with adequate precision to also be used for determining the fractionation of isotopes by diffusion in water. In the case of Li, we found measurable isotopic fractionation associated with the diffusion of dissolved LiCl (D/D=0.99772±0.00026). This difference in the diffusion coefficient of 7Li compared to 6Li is significantly less than that reported in an earlier study, a difference we attribute to the fact that in the earlier study Li diffused through a membrane separating the water reservoirs. Our experiments involving Mg diffusing in water found no measurable isotopic fractionation (D/D=1.00003±0.00006). Cl isotopes were fractionated during diffusion in water (D/D=0.99857±0.00080) whether or not the co-diffuser (Li or Mg) was isotopically fractionated. The isotopic fractionation associated with the diffusion of ions in water is much smaller than values we found previously for the isotopic fractionation of Li and Ca isotopes by diffusion in molten silicate liquids. A major distinction between water and silicate liquids is that water surrounds dissolved ions with hydration shells, which very likely play an important but still poorly understood role in limiting the isotopic fractionation associated with diffusion.

High-precision 87Sr/86Sr analyses in wines and their use as a geological fingerprint for tracing geographic provenance.

PubMed

Marchionni, Sara; Braschi, Eleonora; Tommasini, Simone; Bollati, Andrea; Cifelli, Francesca; Mulinacci, Nadia; Mattei, Massimo; Conticelli, Sandro

2013-07-17

The radiogenic isotopic compositions of inorganic heavy elements such as Sr, Nd, and Pb of the food chain may constitute a reliable geographic fingerprint, their isotopic ratios being inherited by the geological substratum of the territory of production. The Sr isotope composition of geomaterials (i.e., rocks and soils) is largely variable, and it depends upon the age of the rocks and their nature (e.g., genesis, composition). In this study we developed a high-precision analytical procedure for determining Sr isotopes in wines at comparable uncertainty levels of geological data. With the aim of verifying the possibility of using Sr isotope in wine as a reliable tracer for geographic provenance, we performed Sr isotope analyses of 45 bottled wines from four different geographical localities of the Italian peninsula. Their Sr isotope composition has been compared with that of rocks from the substrata (i.e., rocks) of their vineyards. In addition wines from the same winemaker but different vintage years have been analyzed to verify the constancy with time of the (87)Sr/(86)Sr. Sr isotope compositions have been determined by solid source thermal ionization mass spectrometry following purification of Sr in a clean laboratory. (87)Sr/(86)Sr of the analyzed wines is correlated with the isotopic values of the geological substratum of the vineyards, showing little or no variation within the same vineyard and among different vintages. Large (87)Sr/(86)Sr variation is observed among wines from the different geographical areas, reinforcing the link with the geological substratum of the production territory. This makes Sr isotopes a robust geochemical tool for tracing the geographic authenticity and provenance of wine.

Determining origin in a migratory marine vertebrate: a novel method to integrate stable isotopes and satellite tracking

USGS Publications Warehouse

Vander Zanden, Hannah B.; Tucker, Anton D.; Hart, Kristen M.; Lamont, Margaret M.; Fujisaki, Ikuko; Addison, David S.; Mansfield, Katherine L.; Phillips, Katrina F.; Wunder, Michael B.; Bowen, Gabriel J.; Pajuelo, Mariela; Bolten, Alan B.; Bjorndal, Karen A.

2015-01-01

Stable isotope analysis is a useful tool to track animal movements in both terrestrial and marine environments. These intrinsic markers are assimilated through the diet and may exhibit spatial gradients as a result of biogeochemical processes at the base of the food web. In the marine environment, maps to predict the spatial distribution of stable isotopes are limited, and thus determining geographic origin has been reliant upon integrating satellite telemetry and stable isotope data. Migratory sea turtles regularly move between foraging and reproductive areas. Whereas most nesting populations can be easily accessed and regularly monitored, little is known about the demographic trends in foraging populations. The purpose of the present study was to examine migration patterns of loggerhead nesting aggregations in the Gulf of Mexico (GoM), where sea turtles have been historically understudied. Two methods of geographic assignment using stable isotope values in known-origin samples from satellite telemetry were compared: 1) a nominal approach through discriminant analysis and 2) a novel continuous-surface approach using bivariate carbon and nitrogen isoscapes (isotopic landscapes) developed for this study. Tissue samples for stable isotope analysis were obtained from 60 satellite-tracked individuals at five nesting beaches within the GoM. Both methodological approaches for assignment resulted in high accuracy of foraging area determination, though each has advantages and disadvantages. The nominal approach is more appropriate when defined boundaries are necessary, but up to 42% of the individuals could not be considered in this approach. All individuals can be included in the continuous-surface approach, and individual results can be aggregated to identify geographic hotspots of foraging area use, though the accuracy rate was lower than nominal assignment. The methodological validation provides a foundation for future sea turtle studies in the region to inexpensively determine geographic origin for large numbers of untracked individuals. Regular monitoring of sea turtle nesting aggregations with stable isotope sampling can be used to fill critical data gaps regarding habitat use and migration patterns. Probabilistic assignment to origin with isoscapes has not been previously used in the marine environment, but the methods presented here could also be applied to other migratory marine species.

Determining origin in a migratory marine vertebrate: a novel method to integrate stable isotopes and satellite tracking.

PubMed

Zanden, Hannah B Vander; Tucker, Anton D; Hart, Kristen M; Lamont, Margaret M; Fuisaki, Ikuko; Addison, David; Mansfield, Katherine L; Phillips, Katrina F; Wunder, Michael B; Bowen, Gabriel J; Pajuelo, Mariela; Bolten, Alan B; Bjorndal, Karen A

2015-03-01

Stable isotope analysis is a useful tool to track animal movements in both terrestrial and marine environments. These intrinsic markers are assimilated through the diet and may exhibit spatial gradients as a result of biogeochemical processes at the base of the food web. In the marine environment, maps to predict the spatial distribution of stable isotopes are limited, and thus determining geographic origin has been reliant upon integrating satellite telemetry and stable isotope data. Migratory sea turtles regularly move between foraging and reproductive areas. Whereas most nesting populations can be easily accessed and regularly monitored, little is known about the demographic trends in foraging populations. The purpose of the present study was to examine migration patterns of loggerhead nesting aggregations in the Gulf of Mexico (GoM), where sea turtles have been historically understudied. Two methods of geographic assignment using stable isotope values in known-origin samples from satellite telemetry were compared: (1) a nominal approach through discriminant analysis and (2) a novel continuous-surface approach using bivariate carbon and nitrogen isoscapes (isotopic landscapes) developed for this study. Tissue samples for stable isotope analysis were obtained from 60 satellite-tracked individuals at five nesting beaches within the GoM. Both methodological approaches for assignment resulted in high accuracy of foraging area determination, though each has advantages and disadvantages. The nominal approach is more appropriate when defined boundaries are necessary, but up to 42% of the individuals could not be considered in this approach. All individuals can be included in the continuous-surface approach, and individual results can be aggregated to identify geographic hotspots of foraging area use, though the accuracy rate was lower than nominal assignment. The methodological validation provides a foundation for future sea turtle studies in the region to inexpensively determine geographic origin for large numbers of untracked individuals. Regular monitoring of sea turtle nesting aggregations with stable isotope sampling can be used to fill critical data gaps regarding habitat use and migration patterns. Probabilistic assignment to origin with isoscapes has not been previously used in the marine environment, but the methods presented here could also be applied to other migratory marine species.

Use of dual carbon-chlorine isotope analysis to assess the degradation pathways of 1,1,1-trichloroethane in groundwater.

PubMed

Palau, Jordi; Jamin, Pierre; Badin, Alice; Vanhecke, Nicolas; Haerens, Bruno; Brouyère, Serge; Hunkeler, Daniel

2016-04-01

Compound-specific isotope analysis (CSIA) is a powerful tool to track contaminant fate in groundwater. However, the application of CSIA to chlorinated ethanes has received little attention so far. These compounds are toxic and prevalent groundwater contaminants of environmental concern. The high susceptibility of chlorinated ethanes like 1,1,1-trichloroethane (1,1,1-TCA) to be transformed via different competing pathways (biotic and abiotic) complicates the assessment of their fate in the subsurface. In this study, the use of a dual C-Cl isotope approach to identify the active degradation pathways of 1,1,1-TCA is evaluated for the first time in an aerobic aquifer impacted by 1,1,1-TCA and trichloroethylene (TCE) with concentrations of up to 20 mg/L and 3.4 mg/L, respectively. The reaction-specific dual carbon-chlorine (C-Cl) isotope trends determined in a recent laboratory study illustrated the potential of a dual isotope approach to identify contaminant degradation pathways of 1,1,1-TCA. Compared to the dual isotope slopes (Δδ(13)C/Δδ(37)Cl) previously determined in the laboratory for dehydrohalogenation/hydrolysis (DH/HY, 0.33 ± 0.04) and oxidation by persulfate (∞), the slope determined from field samples (0.6 ± 0.2, r(2) = 0.75) is closer to the one observed for DH/HY, pointing to DH/HY as the predominant degradation pathway of 1,1,1-TCA in the aquifer. The observed deviation could be explained by a minor contribution of additional degradation processes. This result, along with the little degradation of TCE determined from isotope measurements, confirmed that 1,1,1-TCA is the main source of the 1,1-dichlorethylene (1,1-DCE) detected in the aquifer with concentrations of up to 10 mg/L. This study demonstrates that a dual C-Cl isotope approach can strongly improve the qualitative and quantitative assessment of 1,1,1-TCA degradation processes in the field. Copyright © 2016 Elsevier Ltd. All rights reserved.

Geochemical and isotopic determination of deep groundwater contributions and salinity to the shallow groundwater and surface water systems, Mesilla Basin, New Mexico, Texas, and Mexico

NASA Astrophysics Data System (ADS)

Robertson, A.; Carroll, K. C.; Kubicki, C.; Purtshert, R.

2017-12-01

The Mesilla Basin/Conejos-Médanos aquifer system, extending from southern New Mexico to Chihuahua, Mexico, is a priority transboundary aquifer under the 2006 United States­-Mexico Transboundary Aquifer Assessment Act. Declining water levels, deteriorating water quality, and increasing groundwater use by municipal, industrial, and agricultural users on both sides of the international border raise concerns about long-term aquifer sustainability. Relative contributions of present-day and "paleo" recharge to sustainable fresh groundwater yields has not been determined and evidence suggests that a large source of salinity at the distal end of the Mesilla Basin is saline discharge from deep groundwater flow. The magnitude and distribution of those deep saline flow paths are not determined. The contribution of deep groundwater to discharge and salinity in the shallow groundwater and surface water of the Mesilla Basin will be determined by collecting discrete groundwater samples and analyzing for aqueous geochemical and isotopic tracers, as well as the radioisotopes of argon and krypton. Analytes include major ions, trace elements, the stable isotopes of water, strontium and boron isotopes, uranium isotopes, the carbon isotopes of dissolved inorganic carbon, noble gas concentrations and helium isotope ratios. Dissolved gases are extracted and captured from groundwater wells using membrane contactors in a process known as ultra-trace sampling. Gas samples are analyzed for radioisotope ratios of krypton by the ATTA method and argon by low-level counting. Effectiveness of the ultra-trace sampling device and method was evaluated by comparing results of tritium concentrations to the krypton-85 content. Good agreement between the analyses, especially in samples with undetectable tritium, indicates that the ultra-trace procedure is effective and confirms that introduction of atmospheric air has not occurred. The geochemistry data indicate a complex system of geochemical endmembers, and mixing between these endmembers. Ongoing work seeks to better constrain groundwater ages and mixing models through the coupled use of conventional aqueous geochemical and isotopic analysis and the ultra-trace constituents.

Nucleosynthetic osmium isotope anomalies in acid leachates of the Murchison meteorite

NASA Astrophysics Data System (ADS)

Reisberg, L.; Dauphas, N.; Luguet, A.; Pearson, D. G.; Gallino, R.; Zimmermann, C.

2009-01-01

We present osmium isotopic results obtained by sequential leaching of the Murchison meteorite, which reveal the existence of very large internal anomalies of nucleosynthetic origin (ɛ 184Os from - 108 to 460; ɛ 186Os from - 14.1 to 12.6; ɛ 188Os from - 2.6 to 1.6; ɛ 190Os from - 1.7 to 1.1). Despite these large variations, the isotopic composition of the total leachable osmium (weighted average of the leachates) is close to that of bulk chondrites. This is consistent with efficient large-scale mixing of Os isotopic anomalies in the protosolar nebula. The Os isotopic anomalies are correlated, and can be explained by the variable contributions of components derived from the s, r and p-processes of nucleosynthesis. Surprisingly, much of the s-process rich osmium is released by relatively mild leaching, suggesting the existence of an easily leachable s-process rich presolar phase, or alternatively, of a chemically resistant r-process rich phase. Taken together with previous evidence for a highly insoluble s-process rich carrier, such as SiC, these results argue for the presence of several presolar phases with anomalous nucleosynthetic compositions in the Murchison meteorite. The s-process composition of Os released by mild leaching diverges slightly from that released by aggressive digestion techniques, perhaps suggesting that the presolar phases attacked by these differing procedures condensed in different stellar environments. The correlation between ɛ 190Os and ɛ 188Os can be used to constrain the s-process 190Os/ 188Os ratio to be 1.275 ± 0.043. Such a ratio can be reproduced in a nuclear reaction network for a MACS value for 190Os of ~ 200 ± 22 mbarn at 30 keV. More generally, these results can help refine predictions of the s-process in the Os mass region, which can be used in turn to constrain the amount of cosmoradiogenic 187Os in the solar system and hence the age of the Galaxy. We also present evidence for extensive internal variation of 184Os abundances in the Murchison meteorite. A steep anti-correlation is observed between ɛ 184Os and ɛ 188Os. Since 184Os is formed uniquely by the p-process, this anti-correlation cannot be explained by variable addition or subtraction of s-process Os to average solar system material. Instead, this suggests that p-process rich presolar grains (e.g., supernova condensates) may be present in meteorites in sufficient quantities to influence the Os isotopic compositions of the leachates. Nevertheless, 184Os is a low abundance isotope and we cannot exclude the possibility that the measured anomalies for this isotope reflect unappreciated analytical artifacts.

Reaction paths and host phases of uranium isotopes (235U; 238U), Saanich Inlet

NASA Astrophysics Data System (ADS)

Amini, M.; Holmden, C. E.; Francois, R. H.

2009-12-01

In recent times, Uranium has become increasingly the focus of stable isotope fractionation studies. Variations in 238U/235U have been reported as a result of redox reactions [1,2] from the nuclear field shift effect [3], and a mass-dependent, microbially-mediated, kinetic isotope effect [4]. The 238U/235U variability caused by changes in environmental redox conditions leads to an increase in the 238U/235U ratios of the reduced U species sequestered into marine sediments. This points to U isotope variability as a new tool to study ancient ocean redox changes. However, the process by which reduced sediments become enriched in the heavy isotopes of U is not yet known, and hence the utility of 238U/235U as a redox tracer remains to be demonstrated. In order to further constrain sedimentary U enrichment and related isotope effect, we are investigating U isotopic compositions of water samples and fresh surface sediment grab samples over a range of redox conditions in the seasonally anoxic Saanich Inlet, on the east coast of Vancouver Island. U was sequentially extracted from sediments in order to characterize specific fractions for their isotopic composition. The measurements were carried out by MC-ICPMS using 233U/236U-double spike technique. The data are reported as δ238U relative to NBL 112a with a 238U/235U ratio of 137.88 (2sd). External precision is better than 0.10‰ (2sd). Fifteeen analyses of seawater yielded δ238U of -0.42±0.08‰ (2sd). The results for the water samples indicate a homogenous δ238U value throughout the Saanich Inlet water column that matches the global seawater signature. All of the water samples from above and below average -0.42±0.05‰ (2sd). In contrast, a plankton net sample yielded a distinctly different, (about 0.5‰ lighter) isotope value. Bacterial reduction experiments [4] have also shown isotope enrichment factors of about -0.3‰. In addition, metal isotope fractionation occurs during adsorption with the light isotope being preferentially adsorbed [5]. Whether plankton mediated chemical reduction or scavenging causes this fractionation will be further investigated by leaching experiments on sediment trap samples. By contrast, weak acidic leachates (at pH 6) of suboxic bottom sediments, tend towards higher δ238U values. For oxic sediments, U contents of this fraction were below detection limit. Stronger leaching at pH 3 removed most of the uranium from suboxic and oxic sediments. For oxic sediments, this fraction yields the seawater δ238U signature, while the U released from the suboxic sample is about 0.2‰ heavier. This matches the value for previously reported bulk analyses of suboxic sediments [1] implying that the reduced sedimentary U is released by this treatment,. Major and trace element analyses and XRD patterns will help relating this fraction to a specific mineral or reactive phase. [1] Weyer et al. (2007) GCA 72, 345-399. [2] Stirling et al. (2007) EPSL 264, 208-225. [3] Schauble (2007) GCA 71, 2170-2189. [4] Rademacher et al. (2006) Environ. Sci. Technol. 40,6943-6948. [5] Wasylenki (2009) GCA A1419.

Experimental Determination of Carbon Isotope Fractionation in C-O-H-Fluids and the Carbonate-melt - Graphite System at High Temperatures

NASA Astrophysics Data System (ADS)

Kueter, N.; Schmidt, M. W.; Lilley, M. D.; Bernasconi, S. M.

2017-12-01

The understanding of deep-earth carbon fluxes depends greatly on the investigation of carbon isotope systematics in C-O-H-fluids and carbon minerals, such as graphite and diamond (C0). The isotope fractionation factors between the different C-phases and species (in e.g. a fluid) thus govern the observed isotope fractionation patterns. C-isotope fractionation factors relevant for high temperatures are mainly derived from theoretical calculations [e.g. 1,2,3] and, with few exceptions, lack experimental determinations [e.g. 4]. Hundreds of own experiments aimed at equilibrating elemental carbon (C0, graphite/diamond) with C-O-H-fluids demonstrate that kinetics reigns as no system would be closed for H on time scales and temperatures allowing for graphite to equilibrate. To overcome this problem, we performed two studies to determine the C-isotope fractionation in 1) the CO2-CO-CH4 system and 2) the carbonate-melt - graphite system. Equilibrium C-isotope fractionation factors were obtained for CO2 - CO and CH4 - CO pairs (600 - 1200°C) and graphite - Na2CO3/CaCO3melt (900 - 1500°C). Combined with the already available fractionation data for the CaCO3-CO2 pair (400-950°C) from Chacko et al. [4], we determined experimentally based C-isotope fractionation factors for C0 - CH4 and CO2 - C0 pairs by 1) Δ13CCO2-graphite = Δ13CCO2-carbonate + Δ13CCarbonate-graphite and 2) Δ13Cgraphite-CH4 = Δ13CCO2-CH4 - Δ13CCO2-graphite . Current calculated fractionation factors relevant for mantle temperatures (1100 - 1500°C) suggest C-isotope partitioning in the CO2 - C0 pair on the order of 4.2 to 2.4‰, about 2‰ less than predicted by theoretically derived factors [3]. In contrast, our calculations suggest fractionation of about 1.4 to 1.1‰ for the C0 - CH4 pair, about 1‰ higher than expected by theory [3]. [1] Richet et al. (1977) Ann. Rev. Earth Planet. Sci.; [2] Polyakov & Kharlashina (1995) GCA; [3] Bottinga (1969) GCA; [4] Chacko et al. (2001) Rev Mineral Geochem

Isotopic ratios D/H and 15N/14N in giant planets

NASA Astrophysics Data System (ADS)

Marboeuf, Ulysse; Thiabaud, Amaury; Alibert, Yann; Benz, Willy

2018-04-01

The determination of isotopic ratios in planets is important since it allows us to investigate the origins and initial composition of materials. The present work aims to determine the possible range of values for isotopic ratios D/H and 15N/14N in giant planets. The main objective is to provide valuable theoretical assumptions on the isotopic composition of giant planets, their internal structure, and the main reservoirs of species. We use models of ice formation and planet formation that compute the composition of ices and gas accreted in the core and the envelope of planets. Assuming a single initial value for isotopic ratios in volatile species, and disruption of planetesimals in the envelope of gaseous planets, we obtain a wide variety of D/H and 15N/14N ratios in low-mass planets (≤100 Mearth) due to the migration pathway of planets, the accretion time of gas species whose relative abundance evolves with time, and isotope exchanges among species. If giant planets with mass greater than 100 Mearth have solar isotopic ratios such as Jupiter and Saturn due to their higher envelope mass, Neptune-type planets present values ranging between one and three times the solar value. It seems therefore difficult to use isotopic ratios in the envelope of these planets to get information about their formation in the disc. For giant planets, the ratios allow us to constrain the mass fraction of volatile species in the envelope needed to reproduce the observational data by assuming initial values for isotopic ratios in volatile species.

Experimentally determined isotope effect during Mg-Fe interdiffusion in olivine

NASA Astrophysics Data System (ADS)

Sio, C. K. I.; Roskosz, M.; Dauphas, N.; Bennett, N.; Mock, T. D.; Shahar, A.

2017-12-01

Isotopic fractionation provides the most direct means to investigate the nature of chemical zoning in minerals, which can be produced by either diffusive transport or crystal growth. Misinterpreting the nature of chemical zoning can result in erroneous conclusions regarding magmatic cooling rates and diffusion timescales. Isotopes are useful in this regard because the light isotopes diffuse faster than their heavier counterparts. As a result, isotopic fractionations should be associated with chemical zoning profiles if they are diffusion-driven. In contrast, little isotopic fractionation is associated with crystal growth during slow cooling at magmatic temperatures. The isotope effect for diffusion is described by β and is related to the mass (m) and diffusivity (D) of isotopes i and j of an element via: Di/Dj = (mj/mi)β. To model isotopic profiles, knowledge of β is required. Several estimates of β for Mg and Fe diffusion in olivine have been reported using natural samples but these estimates are uncertain because they depend on the choice of modeling parameters (Sio et al., 2013; Oeser et al., 2015; Collinet et al., 2017). We have experimentally determined β for Fe (βFe) in olivine as a function of crystallographic orientation, composition, and temperature. Thirty experiments have been conducted by juxtaposing crystallographically oriented olivine crystals to make Fo83.4-Fo88.8 and Fo88.8-Fo100 diffusion couples. These diffusion couples were annealed in a 1 atm gas mixing furnace at 1200 °C, 1300 °C or 1400 °C at QFM - 1.5 for up to 15 days. Chemical profiles were characterized using an electron microprobe and isotopic analyses were done using laser ablation MC-ICPMS. We found a crystallographic dependence of βFe for the Fo88.8-Fo100 couple where βFe [100] ≈ βFe [010] > βFe [001]. For the Fo83.4-Fo88.8 couple, βFe is 0.16 ± 0.09 (2σ) for all 3 major crystallographic axes. A temperature dependence of βFe could not be resolved. These experimentally determined β-values can be used in conjunction with the Mg-Fe diffusivities given in Dohmen and Chakraborty (2007) to simultaneously model the chemical-isotopic profiles of olivine to retrieve cooling and crystallization histories of magmatic rocks.

Least-squares sequential parameter and state estimation for large space structures

NASA Technical Reports Server (NTRS)

Thau, F. E.; Eliazov, T.; Montgomery, R. C.

1982-01-01

This paper presents the formulation of simultaneous state and parameter estimation problems for flexible structures in terms of least-squares minimization problems. The approach combines an on-line order determination algorithm, with least-squares algorithms for finding estimates of modal approximation functions, modal amplitudes, and modal parameters. The approach combines previous results on separable nonlinear least squares estimation with a regression analysis formulation of the state estimation problem. The technique makes use of sequential Householder transformations. This allows for sequential accumulation of matrices required during the identification process. The technique is used to identify the modal prameters of a flexible beam.

Bisubstrate inhibition: Theory and application to N-acetyltransferases.

PubMed

Yu, Michael; Magalhães, Maria L B; Cook, Paul F; Blanchard, John S

2006-12-12

Bisubstrate inhibitors represent a potentially powerful group of compounds that have found significant therapeutic utility. Although these compounds have been synthesized and tested against a number of enzymes that catalyze sequential bireactant reactions, the detailed theory for predicting the expected patterns of inhibition against the two substrates for various bireactant kinetic mechanisms has, heretofore, not been presented. We have derived the rate equations for all likely sequential bireactant mechanisms and provide two examples in which bisubstrate inhibitors allow the kinetic mechanism to be determined. Bisubstrate inhibitor kinetics is a powerful diagnostic for the determination of kinetic mechanisms.

Facile Determination of Sodium Ion and Osmolarity in Artificial Tears by Sequential DNAzymes.

PubMed

Kim, Eun Hye; Lee, Eun-Song; Lee, Dong Yun; Kim, Young-Pil

2017-12-07

Despite high relevance of tear osmolarity and eye abnormality, numerous methods for detecting tear osmolarity rely upon expensive osmometers. We report a reliable method for simply determining sodium ion-based osmolarity in artificial tears using sequential DNAzymes. When sodium ion-specific DNAzyme and peroxidase-like DNAzyme were used as a sensing and detecting probe, respectively, the concentration of Na⁺ in artificial tears could be measured by absorbance or fluorescence intensity, which was highly correlated with osmolarity over the diagnostic range ( R ² > 0.98). Our approach is useful for studying eye diseases in relation to osmolarity.

Revascularization of Left Coronary System Using a Skeletonized Left Internal Mammary Artery　- Sequential vs. Separate Grafting.

PubMed

Ji, Qiang; Shi, YunQing; Xia, LiMin; Ma, RunHua; Shen, JinQiang; Lai, Hao; Ding, WenJun; Wang, ChunSheng

2017-12-25

To evaluate in-hospital and mid-term outcomes of sequential vs. separate grafting of in situ skeletonized left internal mammary artery (LIMA) to the left coronary system in a single-center, propensity-matched study.Methods and Results:After propensity score-matching, 120 pairs of patients undergoing first scheduled isolated coronary artery bypass grafting (CABG) with in situ skeletonized LIMA grafting to the left anterior descending artery (LAD) territory were entered into a sequential group (sequential grafting of LIMA to the diagonal artery and then to the LAD) or a control group (separate grafting of LIMA to the LAD). The in-hospital and follow-up clinical outcomes and follow-up LIMA graft patency were compared. Both propensity score-matched groups had similar in-hospital and follow-up clinical outcomes. Sequential LIMA grafting was not found to be an independent predictor of adverse events. During a follow-up period of 27.0±7.3 months, 99.1% patency for the diagonal site and 98.3% for the LAD site were determined by coronary computed tomographic angiography after sequential LIMA grafting, both of which were similar with graft patency of separate grafting of in situ skeletonized LIMA to the LAD. Revascularization of the left coronary system using a skeletonized LIMA resulted in excellent in-hospital and mid-term clinical outcomes and graft patency using sequential grafting.

Sequential vs simultaneous encoding of spatial information: a comparison between the blind and the sighted.

PubMed

Ruotolo, Francesco; Ruggiero, Gennaro; Vinciguerra, Michela; Iachini, Tina

2012-02-01

The aim of this research is to assess whether the crucial factor in determining the characteristics of blind people's spatial mental images is concerned with the visual impairment per se or the processing style that the dominant perceptual modalities used to acquire spatial information impose, i.e. simultaneous (vision) vs sequential (kinaesthesis). Participants were asked to learn six positions in a large parking area via movement alone (congenitally blind, adventitiously blind, blindfolded sighted) or with vision plus movement (simultaneous sighted, sequential sighted), and then to mentally scan between positions in the path. The crucial manipulation concerned the sequential sighted group. Their visual exploration was made sequential by putting visual obstacles within the pathway in such a way that they could not see simultaneously the positions along the pathway. The results revealed a significant time/distance linear relation in all tested groups. However, the linear component was lower in sequential sighted and blind participants, especially congenital. Sequential sighted and congenitally blind participants showed an almost overlapping performance. Differences between groups became evident when mentally scanning farther distances (more than 5m). This threshold effect could be revealing of processing limitations due to the need of integrating and updating spatial information. Overall, the results suggest that the characteristics of the processing style rather than the visual impairment per se affect blind people's spatial mental images. Copyright © 2011 Elsevier B.V. All rights reserved.

Carbon, Hydrogen, and Oxygen Isotope Ratios of Cellulose from Plants Having Intermediary Photosynthetic Modes 1

PubMed Central

Sternberg, Leonel O'Reilly; Deniro, Michael J.; Ting, Irwin P.

1984-01-01

Carbon and hydrogen isotope ratios of cellulose nitrate and oxygen isotope ratios of cellulose from species of greenhouse plants having different photosynthetic modes were determined. When hydrogen isotope ratios are plotted against carbon isotope ratios, four clusters of points are discernible, each representing different photosynthetic modes: C3 plants, C4 plants, CAM plants, and C3 plants that can shift to CAM or show the phenomenon referred to as CAM-cycling. The combination of oxygen and carbon isotope ratios does not distinguish among the different photosynthetic modes. Analysis of the carbon and hydrogen isotope ratios of cellulose nitrate should prove useful for screening different photosynthetic modes in field specimens that grew near one another. This method will be particularly useful for detection of plants which show CAM-cycling. PMID:16663360

Application of zinc isotope tracer technology in tracing soil heavy metal pollution

NASA Astrophysics Data System (ADS)

Norbu, Namkha; Wang, Shuguang; Xu, Yan; Yang, Jianqiang; Liu, Qiang

2017-08-01

Recent years the soil heavy metal pollution has become increasingly serious, especially the zinc pollution. Due to the complexity of this problem, in order to prevent and treat the soil pollution, it's crucial to accurately and quickly find out the pollution sources and control them. With the development of stable isotope tracer technology, it's able to determine the composition of zinc isotope. Based on the theory of zinc isotope tracer technique, and by means of doing some latest domestic and overseas literature research about the zinc isotope multi-receiving cups of inductively coupled plasma mass spectrometer (MC-ICP-MS) testing technology, this paper summarized the latest research results about the pollution tracer of zinc isotope, and according to the deficiencies and existing problems of previous research, made outlooks of zinc isotope fractionation mechanism, repository establishment and tracer multiple solutions.

The Constructivist Approach? I Have Heard about It but I Have Never Seen It: "An Example of Exploratory Sequential Mixed Design Study"

ERIC Educational Resources Information Center

Polat, Ahmet; Dogan, Soner; Demir, Selçuk Besir

2016-01-01

The present study was undertaken to investigate the quality of education based on the views of the students attending social studies education departments at the Faculties of Education and to determine the existing problems and present suggestions for their solutions. The study was conducted according to exploratory sequential mixed method. In…

The Constructivist Approach? I Have Heard about It but I Have Never Seen It "An Example of Exploratory Sequential Mixed Design Study"

ERIC Educational Resources Information Center

Polat, Ahmet; Dogan, Soner; Demir, Selçuk Besir

2016-01-01

The present study was undertaken to investigate the quality of education based on the views of the students attending social studies education departments at the Faculties of Education and to determine the existing problems and present suggestions for their solutions. The study was conducted according to exploratory sequential mixed method. In…

Determination of 17O-excess of terrestrial silicate/oxide minerals with respect to Vienna Standard Mean Ocean Water (VSMOW).

PubMed

Tanaka, Ryoji; Nakamura, Eizo

2013-01-30

Oxygen triple isotope compositions give key information for understanding physical processes during isotopic fractionation between the geo-, hydro-, bio-, and atmosphere. For detailed discussion of these topics, it is necessary to determine precise (17)O-excess values of terrestrial silicate/oxide minerals with respect to Vienna Standard Mean Ocean Water (VSMOW). Water was fluorinated in an electrically heated Ni-metal tube into which water and BrF(5) were loaded for the quantitative extraction of oxygen. Silicate/oxide minerals were fluorinated by heating with a CO(2) laser in an atmosphere of BrF(5). The extracted oxygen was purified and isotope ratios of the oxygen triple isotope compositions were determined using a Finnigan MAT253 isotope ratio mass spectrometer. The oxygen triple isotope compositions of meteoric water and terrestrial silicate/oxide minerals fall on statistically distinguishable fractionation lines, defined as [ln(δ(17)O + 1) = λln(δ(18) O + 1) + Δ], where λ and Δ correspond to the slope and intercept, respectively. The fractionation line for meteoric water has λ = 0.5285 ± 0.0005 and Δ = 0.03 ± 0.02‰ and for terrestrial silicate/oxide minerals has λ = 0.5270 ± 0.0005 and Δ = -0.070 ± 0.005‰, at the 95% confidence limit. All the analyzed terrestrial silicate/oxide minerals including internationally accepted reference materials (NBS-28, UWG-2, and San Carlos olivine) have a negative (17)O-excess with respect to VSMOW. We propose that it is necessary to specify if the determined δ(17)O values of terrestrial and extraterrestrial samples are expressed as the difference from VSMOW or the terrestrial silicate mineral-corrected value. Copyright © 2012 John Wiley & Sons, Ltd.

ABSORPTION ANALYZER

DOEpatents

Brooksbank, W.A. Jr.; Leddicotte, G.W.; Strain, J.E.; Hendon, H.H. Jr.

1961-11-14

A means was developed for continuously computing and indicating the isotopic assay of a process solution and for automatically controlling the process output of isotope separation equipment to provide a continuous output of the desired isotopic ratio. A counter tube is surrounded with a sample to be analyzed so that the tube is exactly in the center of the sample. A source of fast neutrons is provided and is spaced from the sample. The neutrons from the source are thermalized by causing them to pass through a neutron moderator, and the neutrons are allowed to diffuse radially through the sample to actuate the counter. A reference counter in a known sample of pure solvent is also actuated by the thermal neutrons from the neutron source. The number of neutrons which actuate the detectors is a function of a concentration of the elements in solution and their neutron absorption cross sections. The pulses produced by the detectors responsive to each neu tron passing therethrough are amplified and counted. The respective times required to accumulate a selected number of counts are measured by associated timing devices. The concentration of a particular element in solution may be determined by utilizing the following relation: T2/Ti = BCR, where B is a constant proportional to the absorption cross sections, T2 is the time of count collection for the unknown solution, Ti is the time of count collection for the pure solvent, R is the isotopic ratlo, and C is the molar concentration of the element to be determined. Knowing the slope constant B for any element and when the chemical concentration is known, the isotopic concentration may be readily determined, and conversely when the isotopic ratio is known, the chemical concentrations may be determined. (AEC)

Fractionation of (137)Cs and Pu in natural peatland.

PubMed

Mihalík, Ján; Bartusková, Miluše; Hölgye, Zoltán; Ježková, Tereza; Henych, Ondřej

2014-08-01

High Cs-137 concentrations in plants growing on peatland inspired us to investigate the quantity of its bioavailable fraction in natural peat. Our investigation aims to: a) estimate the quantity of bioavailable Cs-137 and Pu present in peat, b) verify the similarity of Cs-137 and K-40 behaviours, and c) perform a quantification of Cs-137 and Pu transfer from peat to plants. We analysed the vertical distribution of Cs-137 and Pu isotopes in the peat and their concentrations in plants growing on these places. Bioavailability of radionuclides was investigated by sequential extraction. Sequential analyses revealed that it was the upper layer which contained the majority of Cs-137 in an available form while deeper layers retained Cs-137 in immobile fractions. We can conclude that 18% of all Cs-137 in the peat is still bioavailable. Despite of the low quantity of bioavailable fraction of Cs-137 its transfer factor reached extremely high values. In the case of Pu, 64% of its total amount was associated with fulvic/humic acids which resulted in the high transfer factor from peat to plants. 27 years after the Chernobyl nuclear accident, the significant part of radionuclides deposited in peatland is still bioavailable. Copyright © 2014 Elsevier Ltd. All rights reserved.

Dual tracer imaging of SPECT and PET probes in living mice using a sequential protocol

PubMed Central

Chapman, Sarah E; Diener, Justin M; Sasser, Todd A; Correcher, Carlos; González, Antonio J; Avermaete, Tony Van; Leevy, W Matthew

2012-01-01

Over the past 20 years, multimodal imaging strategies have motivated the fusion of Positron Emission Tomography (PET) or Single Photon Emission Computed Tomography (SPECT) scans with an X-ray computed tomography (CT) image to provide anatomical information, as well as a framework with which molecular and functional images may be co-registered. Recently, pre-clinical nuclear imaging technology has evolved to capture multiple SPECT or multiple PET tracers to further enhance the information content gathered within an imaging experiment. However, the use of SPECT and PET probes together, in the same animal, has remained a challenge. Here we describe a straightforward method using an integrated trimodal imaging system and a sequential dosing/acquisition protocol to achieve dual tracer imaging with 99mTc and 18F isotopes, along with anatomical CT, on an individual specimen. Dosing and imaging is completed so that minimal animal manipulations are required, full trimodal fusion is conserved, and tracer crosstalk including down-scatter of the PET tracer in SPECT mode is avoided. This technique will enhance the ability of preclinical researchers to detect multiple disease targets and perform functional, molecular, and anatomical imaging on individual specimens to increase the information content gathered within longitudinal in vivo studies. PMID:23145357

Application of isotope dilution inductively coupled plasma mass spectrometry to the analysis of marine sediments

DOE Office of Scientific and Technical Information (OSTI.GOV)

McLaren, J.W.; Beauchemin, D.; Berman, S.S.

1987-02-15

Isotope dilution inductively coupled plasma mass spectrometry (ICP-MS) has been applied to the determination of 11 trace elements (Cr, Ni, Zn, Sr, Mo, Cd, Sn, Sb, Tl, Pb, and U) in the marine sediment reference materials MESS-1 and BCSS-1. Accuracy and, especially, precision are better than those that can be easily achieved by other ICP-MS calibration strategies, as long as isotopic equilibration is achieved and the isotopes used for the ratio measurement are free of isobaric interferences by molecular species. The measurement of the isotope ratios on unspiked samples provides a sensitive diagnostic of such interferences.

Precise and traceable carbon isotope ratio measurements by multicollector ICP-MS: what next?

PubMed

Santamaria-Fernandez, Rebeca

2010-06-01

This article reviews recent developments in the use of multicollector inductively coupled plasma mass spectrometry (MC-ICP-MS) to provide high-precision carbon isotope ratio measurements. MC-ICP-MS could become an alternative method to isotope ratio mass spectrometry (IRMS) for rapid carbon isotope ratio determinations in organic compounds and characterisation and certification of isotopic reference materials. In this overview, the advantages, drawbacks and potential of the method for future applications are critically discussed. Furthermore, suggestions for future improvements in terms of precision and sensitivity are made. No doubt, this is an exciting analytical challenge and, as such, hurdles will need to be cleared.

A quantum cascade laser infrared spectrometer for CO2 stable isotope analysis: Field implementation at a hydrocarbon contaminated site under bio-remediation.

PubMed

Guimbaud, Christophe; Noel, Cécile; Chartier, Michel; Catoire, Valéry; Blessing, Michaela; Gourry, Jean Christophe; Robert, Claude

2016-02-01

Real-time methods to monitor stable isotope ratios of CO2 are needed to identify biogeochemical origins of CO2 emissions from the soil-air interface. An isotope ratio infra-red spectrometer (IRIS) has been developed to measure CO2 mixing ratio with δ(13)C isotopic signature, in addition to mixing ratios of other greenhouse gases (CH4, N2O). The original aspects of the instrument as well as its precision and accuracy for the determination of the isotopic signature δ(13)C of CO2 are discussed. A first application to biodegradation of hydrocarbons is presented, tested on a hydrocarbon contaminated site under aerobic bio-treatment. CO2 flux measurements using closed chamber method is combined with the determination of the isotopic signature δ(13)C of the CO2 emission to propose a non-intrusive method to monitor in situ biodegradation of hydrocarbons. In the contaminated area, high CO2 emissions have been measured with an isotopic signature δ(13)C suggesting that CO2 comes from petroleum hydrocarbon biodegradation. This first field implementation shows that rapid and accurate measurement of isotopic signature of CO2 emissions is particularly useful in assessing the contribution of contaminant degradation to the measured CO2 efflux and is promising as a monitoring tool for aerobic bio-treatment. Copyright © 2016. Published by Elsevier B.V.

Accurate and precise determination of isotopic ratios by MC-ICP-MS: a review.

PubMed

Yang, Lu

2009-01-01

For many decades the accurate and precise determination of isotope ratios has remained a very strong interest to many researchers due to its important applications in earth, environmental, biological, archeological, and medical sciences. Traditionally, thermal ionization mass spectrometry (TIMS) has been the technique of choice for achieving the highest accuracy and precision. However, recent developments in multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS) have brought a new dimension to this field. In addition to its simple and robust sample introduction, high sample throughput, and high mass resolution, the flat-topped peaks generated by this technique provide for accurate and precise determination of isotope ratios with precision reaching 0.001%, comparable to that achieved with TIMS. These features, in combination with the ability of the ICP source to ionize nearly all elements in the periodic table, have resulted in an increased use of MC-ICP-MS for such measurements in various sample matrices. To determine accurate and precise isotope ratios with MC-ICP-MS, utmost care must be exercised during sample preparation, optimization of the instrument, and mass bias corrections. Unfortunately, there are inconsistencies and errors evident in many MC-ICP-MS publications, including errors in mass bias correction models. This review examines "state-of-the-art" methodologies presented in the literature for achievement of precise and accurate determinations of isotope ratios by MC-ICP-MS. Some general rules for such accurate and precise measurements are suggested, and calculations of combined uncertainty of the data using a few common mass bias correction models are outlined.

A novel membrane inlet mass spectrometer method to measure ¹⁵NH4₄⁺ for isotope-enrichment experiments in aquatic ecosystems.

PubMed

Yin, Guoyu; Hou, Lijun; Liu, Min; Liu, Zhanfei; Gardner, Wayne S

2014-08-19

Nitrogen (N) pollution in aquatic ecosystems has attracted much attention over the past decades, but the dynamics of this bioreactive element are difficult to measure in aquatic oxygen-transition environments. Nitrogen-transformation experiments often require measurement of (15)N-ammonium ((15)NH4(+)) ratios in small-volume (15)N-enriched samples. Published methods to determine N isotope ratios of dissolved ammonium require large samples and/or costly equipment and effort. We present a novel ("OX/MIMS") method to determine N isotope ratios for (15)NH4(+) in experimental waters previously enriched with (15)N compounds. Dissolved reduced (15)N (dominated by (15)NH4(+)) is oxidized with hypobromite iodine to nitrogen gas ((29)N2 and/or (30)N2) and analyzed by membrane inlet mass spectrometry (MIMS) to quantify (15)NH4(+) concentrations. The N isotope ratios, obtained by comparing the (15)NH4(+) to total ammonium (via autoanalyzer) concentrations, are compared to the ratios of prepared standards. The OX/MIMS method requires only small sample volumes of water (ca. 12 mL) or sediment slurries and is rapid, convenient, accurate, and precise (R(2) = 0.9994, p < 0.0001) over a range of salinities and (15)N/(14)N ratios. It can provide data needed to quantify rates of ammonium regeneration, potential ammonium uptake, and dissimilatory nitrate reduction to ammonium (DNRA). Isotope ratio results agreed closely (R = 0.998, P = 0.001) with those determined independently by isotope ratio mass spectrometry for DNRA measurements or by ammonium isotope retention time shift liquid chromatography for water-column N-cycling experiments. Application of OX/MIMS should simplify experimental approaches and improve understanding of N-cycling rates and fate in a variety of freshwater and marine environments.

Reliable determination of oxygen and hydrogen isotope ratios in atmospheric water vapour adsorbed on 3A molecular sieve.

PubMed

Han, Liang-Feng; Gröning, Manfred; Aggarwal, Pradeep; Helliker, Brent R

2006-01-01

The isotope ratio of atmospheric water vapour is determined by wide-ranging feedback effects from the isotope ratio of water in biological water pools, soil surface horizons, open water bodies and precipitation. Accurate determination of atmospheric water vapour isotope ratios is important for a broad range of research areas from leaf-scale to global-scale isotope studies. In spite of the importance of stable isotopic measurements of atmospheric water vapour, there is a paucity of published data available, largely because of the requirement for liquid nitrogen or dry ice for quantitative trapping of water vapour. We report results from a non-cryogenic method for quantitatively trapping atmospheric water vapour using 3A molecular sieve, although water is removed from the column using standard cryogenic methods. The molecular sieve column was conditioned with water of a known isotope ratio to 'set' the background signature of the molecular sieve. Two separate prototypes were developed, one for large collection volumes (3 mL) and one for small collection volumes (90 microL). Atmospheric water vapour was adsorbed to the column by pulling air through the column for several days to reach the desired final volume. Water was recovered from the column by baking at 250 degrees C in a dry helium or nitrogen air stream and cryogenically trapped. For the large-volume apparatus, the recovered water differed from water that was simultaneously trapped by liquid nitrogen (the experimental control) by 2.6 per thousand with a standard deviation (SD) of 1.5 per thousand for delta(2)H and by 0.3 per thousand with a SD of 0.2 per thousand for delta(18)O. Water-vapour recovery was not satisfactory for the small volume apparatus. Copyright (c) 2006 John Wiley & Sons, Ltd.

Calcium inputs and transport in a base-poor forest ecosystem as interpreted by Sr isotopes

Treesearch

Scott W. Bailey; James W. Hornbeck; Charles T. Driscoll; Henri E. Gaudette

1996-01-01

Depletion of Ca in forests and its effects on forest health are poorly quantified. Depletion has been difficult to document due to limitations in determining rates at which Ca becomes available for ecosystem processes through weathering, and difficulty in determining changes in ecosystem storage. We coupled a detailed analysis of Sr isotopic composition with a mass...

Determination of the Extent of Trace Metals Pollution in Soils, Sediments and Human Hair at e-Waste Recycling Site in Ghana.

PubMed

Tokumaru, Takashi; Ozaki, Hirokazu; Onwona-Agyeman, Siaw; Ofosu-Anim, John; Watanabe, Izumi

2017-10-01

The concentrations of trace elements (Mg, Al, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, As, Se, Rb, Sr, Y, Mo, Cd, In, Sn, Sb, Cs, Ba, Tl, Pb, and Bi) in soils, sediment, human hair, and foodstuff collected around the electronic waste (e-waste) recycling sites in Accra, Ghana were detected using inductively coupled plasma-mass spectrometry (ICP-MS). High levels of Cu, Zn, Mo, Cd, In, Sn, Sb, and Pb were observed in soils collected from the e-waste recycling sites. Four sequential extraction procedures were used to evaluate the mobility and bioavailability of metals (Cu, Zn, Cd, Sb, and Pb). Especially, the results showed that Cd and Zn in soils were mostly recovered in exchangeable fraction (respectively 58.9 and 62.8%). Sediment collected from around the site had enrichment of Zn, Sn, Sb, Mo, In, Pb, and Bi. The concentrations of Cu, Mo, Cd, Sb, and Pb in human hair were significantly higher than those collected from the control site (p < 0.01). Additionally, hierarchical cluster analysis reviewed that these elements were derived from e-waste activities. The results of Pb isotopic ratios in the samples indicate that Pb in human hair possibly originated from contaminated soils, fish, and foodstuff.

Radiochemical determination of 237NP in soil samples contaminated with weapon grade plutonium

NASA Astrophysics Data System (ADS)

Antón, M. P.; Espinosa, A.; Aragón, A.

2006-01-01

The Palomares terrestrial ecosystem (Spain) constitutes a natural laboratory to study transuranics. This scenario is partially contaminated with weapon-grade plutonium since the burnout and fragmentation of two thermonuclear bombs accidentally dropped in 1966. While performing radiometric measurements in the field, the possible presence of 237Np was observed through its 29 keV gamma emission. To accomplish a detailed characterization of the source term in the contaminated area using the isotopic ratios Pu-Am-Np, the radiochemical isolation and quantification by alpha spectrometry of 237Np was initiated. The selected radiochemical procedure involves separation of Np from Am, U and Pu with ionic resins, given that in soil samples from Palomares 239+240Pu levels are several orders of magnitude higher than 237Np. Then neptunium is isolated using TEVA organic resins. After electrodeposition, quantification is performed by alpha spectrometry. Different tests were done with blank solutions spiked with 236Pu and 237Np, solutions resulting from the total dissolution of radioactive particles and soil samples. Results indicate that the optimal sequential radionuclide separation order is Pu-Np, with decontamination percentages obtained with the ionic resins ranging from 98% to 100%. Also, the addition of NaNO2 has proved to be necessary, acting as a stabilizer of Pu-Np valences.

Stable isotope ratio mass spectrometry of nanogram quantities of boron and sulfur

NASA Astrophysics Data System (ADS)

Wieser, Michael Eugene

1998-09-01

Instrumentation and analytical techniques were developed to measure isotope abundances from nanograms of sulfur and boron. Sulfur isotope compositions were determined employing continuous flow isotope ratio mass spectroscopy (CF-IRMS) procedures and AsS+ thermal ionization mass spectrometry techniques (AsS+-TIMS). Boron isotope abundances were determined by BO2/sp--TIMS. CF-IRMS measurements realized δ34S values from 10 μg sulfur with precisions of ±0.3/perthous. To extend sulfur isotope measurements to much smaller samples, a TIMS procedure was developed to measure 75As32S+ and 75As34S+ at masses 108 and 109 from 200 ng S on a Finnigan MAT 262 with an ion counter. This is possibly the smallest amount of sulfur which has been successfully analyzed isotopically. The internal precision of 32S/34S ratios measured by AsS+-TIMS was better than ±0.15 percent. δ34S-values calculated relative to the measured 32S/34S value of an IAEA AG2S standard (S-1) agreed with those determined by CF-IRMS to within ±3/perthous. The increasing sensitivity of S-isotope analyses permits hiterto impossible investigations e.g. sulfur in tree rings and ice cores. Boron isotope abundances were measured as BO2/sp- from 50 ng B using an older thermal ionization mass spectrometer which had been extensively upgraded including the addition of computer control electronics, sensitive ion current amplification and fiber optic data bus. The internal precisions of the measured 11B/10B ratios were ±0.15 percent and the precisions of δ11B values calculated relative to the accepted international standard (SRM-951) were ±3/perthous. Two applications of boron isotope abundance variations were initiated (1) ground waters of Northern Alberta and (2) coffee beans in different regions of the world. In the first it was demonstrated that boron isotopes could be used to trace boron released during steam injection of oil sands into the surrounding environment. Data from the second study suggest that boron isotopes can be used to improve cultivation of coffee particularly in regions where 'organically grown' coffee had markedly different δ11B values than beans grown with boron- containing fertilizers in neighbouring regions. A regional dependence on the δ11B values of the coffee allow the sources of commercial coffee blends to be identified.

Understanding the role of fog in forest hydrology: Stable isotopes as tools for determining input and partitioning of cloud water in montane forests

USGS Publications Warehouse

Scholl, M.; Eugster, W.; Burkard, R.

2011-01-01

Understanding the hydrology of tropical montane cloud forests (TMCF) has become essential as deforestation of mountain areas proceeds at an increased rate worldwide. Passive and active cloud-water collectors, throughfall and stemflow collectors, visibility or droplet size measurements, and micrometeorological sensors are typically used to measure the fog water inputs to ecosystems. In addition, stable isotopes may be used as a natural tracer for fog and rain. Previous studies have shown that the isotopic signature of fog tends to be more enriched in the heavier isotopes 2H and 18O than that of rain, due to differences in condensation temperature and history. Differences between fog and rain isotopes are largest when rain is from synoptic-scale storms, and fog or orographic cloud water is generated locally. Smaller isotopic differences have been observed between rain and fog on mountains with orographic clouds, but only a few studies have been conducted. Quantifying fog deposition using isotope methods is more difficult in forests receiving mixed precipitation, because of limitations in the ability of sampling equipment to separate fog from rain, and because fog and rain may, under some conditions, have similar isotopic composition. This article describes the various types of fog most relevant to montane cloud forests and the importance of fog water deposition in the hydrologic budget. A brief overview of isotope hydrology provides the background needed to understand isotope applications in cloud forests. A summary of previous work explains isotopic differences between rain and fog in different environments, and how monitoring the isotopic signature of surface water, soil water and tree xylem water can yield estimates of the contribution of fog water to streamflow, groundwater recharge and transpiration. Next, instrumentation to measure fog and rain, and methods to determine isotopic concentrations in plant and soil water are discussed. The article concludes with the identification of some of the more pressing research questions in this field and offers various suggestions for future research. ?? 2010 This article is a US Government work and is in the public domain in the USA.

Probing Aluminum Reactions in Combustion and Explosion Via the Kinetic Isotope Effect

NASA Astrophysics Data System (ADS)

Tappan, Bryce

2015-06-01

The mechanism that controls the reaction speed of aluminum in explosion and combustion is poorly understood, and experimentally difficult to measure. Recently, work in our laboratory has demonstrated that during the combustion of nanoparticulate aluminum with H2O or D2O, different reaction rates due to the kinetic isotope effect are observed. This result is the first-ever observed kinetic isotope effect in a metal combustion reaction and verifies that chemical reaction kinetics play a major role in determining the global burning rate. During or shortly after a detonation, however, the reaction rates are dramatically faster and the physical mechanism controlling Al reaction is likely different than during combustion events. To utilize the kinetic isotope effect to probe Al reactions in detonation, formulations were produced that contain powdered Al in deuterated high explosives and high-fidelity detonation velocity were determined along with PDV measurements to observe early wall velocity expansion measurements. The JWL equation of state was solved to determine temperature, pressure and energies at specific time periods, in addition of Gurney energies, which enables the elucidation of Al reaction extent. By comparison of the Al oxidation with LiF, data indicate that Al oxidation occurs on an extremely fast time scale and isotope effects in both the HE detonation and post-detonation Al reactions are discussed.

Imaging and Radiography with Nuclear Resonance Fluorescence and Effective-Z (EZ-3D) Determination; SNM Detection Using Prompt Neutrons from Photon Induced Fission

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bertozzi, William; Hasty, Richard; Klimenko, Alexei

Four new technologies have been developed for use in non-intrusive inspection systems to detect nuclear materials, explosives and contraband. Nuclear Resonance Fluorescence (NRF) provides a three dimensional image of the isotopic content of a container. NRF determines the isotopic composition of a region and specifies the isotopic structure of the neighboring regions, thus providing the detailed isotopic composition of any threat. In transmission mode, NRF provides a two dimensional projection of the isotopic content of a container, much as standard X-ray radiography provides for density. The effective-Z method (EZ-3D) uses electromagnetic scattering processes to yield a three-dimensional map of themore » effective-Z and the density in a container. The EZ-3D method allows for a rapid discrimination based on effective Z and mass of materials such as those with high Z, as well as specifying regions of interest for other contraband. The energy spectrum of prompt neutrons from photon induced fission (PNPF) provides a unique identification of the presence of actinides and SNM. These four new technologies can be used independently or together to automatically determine the presence of hazardous materials or contraband. They can also be combined with other technologies to provide added specificity.« less

Simultaneous determination of creatinine and creatine in human serum by double-spike isotope dilution liquid chromatography-tandem mass spectrometry (LC-MS/MS) and gas chromatography-mass spectrometry (GC-MS).

PubMed

Fernández-Fernández, Mario; Rodríguez-González, Pablo; Añón Álvarez, M Elena; Rodríguez, Felix; Menéndez, Francisco V Álvarez; García Alonso, J Ignacio

2015-04-07

This work describes the first multiple spiking isotope dilution procedure for organic compounds using (13)C labeling. A double-spiking isotope dilution method capable of correcting and quantifying the creatine-creatinine interconversion occurring during the analytical determination of both compounds in human serum is presented. The determination of serum creatinine may be affected by the interconversion between creatine and creatinine during sample preparation or by inefficient chemical separation of those compounds by solid phase extraction (SPE). The methodology is based on the use differently labeled (13)C analogues ((13)C1-creatinine and (13)C2-creatine), the measurement of the isotopic distribution of creatine and creatinine by liquid chromatography-tandem mass spectrometry (LC-MS/MS) and the application of multiple linear regression. Five different lyophilized serum-based controls and two certified human serum reference materials (ERM-DA252a and ERM-DA253a) were analyzed to evaluate the accuracy and precision of the proposed double-spike LC-MS/MS method. The methodology was applied to study the creatine-creatinine interconversion during LC-MS/MS and gas chromatography-mass spectrometry (GC-MS) analyses and the separation efficiency of the SPE step required in the traditional gas chromatography-isotope dilution mass spectrometry (GC-IDMS) reference methods employed for the determination of serum creatinine. The analysis of real serum samples by GC-MS showed that creatine-creatinine separation by SPE can be a nonquantitative step that may induce creatinine overestimations up to 28% in samples containing high amounts of creatine. Also, a detectable conversion of creatine into creatinine was observed during sample preparation for LC-MS/MS. The developed double-spike LC-MS/MS improves the current state of the art for the determination of creatinine in human serum by isotope dilution mass spectrometry (IDMS), because corrections are made for all the possible errors derived from the sample preparation step.

First field determination of the 13C/12C isotope ratio in volcanic CO2 by diode-laser.

PubMed

Castrillo, A; Casa, G; van Burgel, M; Tedesco, D; Gianfrani, L

2004-12-27

Carbon isotope ratio analysis using a laser-based technique has been performed in the field, on the gaseous emissions from an active volcano. We here describe that 13CO2/12CO2 determinations can be carried out in a quasi-continuous regime using a compact, selective and sensitive diode laser spectrometer at a wavelength of 2 mum. Within the Solfatara crater (near Naples, Italy), in a very harsh environment, we were able to determine relative 13CO2/12CO2 values, on the highest flux fumarole, with an accuracy of 0.5 per thousand. Regular and frequent observations of the carbon isotopes in volcanic gases, which become possible with our methodology, are of the utmost importance for geochemical surveillance of volcanoes.

STUDIES ON ANALYTICAL METHODS FOR TRACE ELEMENTS IN METALS BY USING RADIOACTIVE ISOTOPE. III. DETERMINATION OF TANTALUM BY MEANS OF ISOTOPE DILUTION METHOD

DOE Office of Scientific and Technical Information (OSTI.GOV)

Amano, H.

1959-10-01

The determination of tantalum by the isotope dilution method in the presence of niobium was investigated by the use of the radioisotope Ta/sup 185/. Tantalum was separated from niobium as tantalum-tannin precipitate under the optimum conditions of a pH of 1.9 to 2.5 and a tantalum/niobium ratio of up to 1/ 50. If niobium was present in amounts 100 times or more that of tantalum, reprecipitation was needed. The reciprocal of the specific activity of tanthlum pentoxide precipitate was in a linear relation to the change in the amount of tantalum added. The recommended method gave an accurate result inmore » the determination of tantalum in steal. (auth)« less

Trace determination of zinc by substoichiometric isotope dilution analysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sandhya, D.; Priya, S.; Subramanian, M.O.S.

1996-09-01

A radiometric method based on substoichiometric isotope dilution analysis using 1,10-phenanthroline and a substoichiometric amount of eosin was developed for determining trace amounts of zinc. Evaluation of various metal ion interferences shows that as little as 0.2 {mu}g Zn could be determined in an aqueous-phase volume of 60 mL. The method has been successfully applied to the determination of Zn in city waste incineration ash, cadmium metal, Fourts-B tablets, Boro-plus ointment, and magnesium alloy samples. 12 refs., 3 figs., 3 tabs.

Influence of Sequential vs. Simultaneous Dual-Task Exercise Training on Cognitive Function in Older Adults.

PubMed

Tait, Jamie L; Duckham, Rachel L; Milte, Catherine M; Main, Luana C; Daly, Robin M

2017-01-01

Emerging research indicates that exercise combined with cognitive training may improve cognitive function in older adults. Typically these programs have incorporated sequential training, where exercise and cognitive training are undertaken separately. However, simultaneous or dual-task training, where cognitive and/or motor training are performed simultaneously with exercise, may offer greater benefits. This review summary provides an overview of the effects of combined simultaneous vs. sequential training on cognitive function in older adults. Based on the available evidence, there are inconsistent findings with regard to the cognitive benefits of sequential training in comparison to cognitive or exercise training alone. In contrast, simultaneous training interventions, particularly multimodal exercise programs in combination with secondary tasks regulated by sensory cues, have significantly improved cognition in both healthy older and clinical populations. However, further research is needed to determine the optimal characteristics of a successful simultaneous training program for optimizing cognitive function in older people.

Early Astronomical Sequential Photography, 1873-1923

NASA Astrophysics Data System (ADS)

Bonifácio, Vitor

2011-11-01

In 1873 Jules Janssen conceived the first automatic sequential photographic apparatus to observe the eagerly anticipated 1874 transit of Venus. This device, the 'photographic revolver', is commonly considered today as the earliest cinema precursor. In the following years, in order to study the variability or the motion of celestial objects, several instruments, either manually or automatically actuated, were devised to obtain as many photographs as possible of astronomical events in a short time interval. In this paper we strive to identify from the available documents the attempts made between 1873 and 1923, and discuss the motivations behind them and the results obtained. During the time period studied astronomical sequential photography was employed to determine the time of the instants of contact in transits and occultations, and to study total solar eclipses. The technique was seldom used but apparently the modern film camera invention played no role on this situation. Astronomical sequential photographs were obtained both before and after 1895. We conclude that the development of astronomical sequential photography was constrained by the reduced number of subjects to which the technique could be applied.

A negative excursion at 14-16 Ma in seawater osmium isotope record: Implications for paleoceanographic studies using Fe-Mn crusts

NASA Astrophysics Data System (ADS)

Goto, K. T.; Tejada, M. L. G.; Suzuki, K.

2017-12-01

Osmium isotope stratigraphy is a recently proposed method to determine the depositional age of Fe-Mn crusts [1, 2]. Seawater Os isotope (187Os/188Os) is roughly determined by the balance of riverine Os inputs with radiogenic value (187Os/188Os = 1.4), and mantle-derived and extra-terrestrial Os inputs with non-radiogenic value (187Os/188Os = 0.12) [3]. Secular variation of global seawater Os isotope (seawater Os isotope curve) has been reconstructed by the analysis of pelagic sediments and exhibits large variations ranging from 0.2 to 1.0 with several negative excursions [3]. Hence, the depositional age of Fe-Mn crusts can be approximately estimated by fitting their Os isotope depth profiles to the seawater Os isotope curve (Osmium isotope stratigraphy). However, this method allows multiple interpretations which are partly due to the lack of high-resolution seawater Os isotope curve [1, 2]. For example, the available seawater Os isotope curve does not exhibit negative anomaly during the Miocene, which contrasts with Os isotope records of Fe-Mn crusts [4]. In the present study, we obtained a high-resolution Os isotope record of Miocene seawater using hemipelagic sediments from IODP Expedition 351 SiteU1438. We found a small negative Os isotope anomaly as low as 0.7 from sediments deposited at 14-16 Ma. The magnitude of this anomaly is similar to those reported from Fe-Mn crusts. Although the extrapolation of Be-10 ages for Fe-Mn crust indicate a younger age for the anomaly ( 11 Ma) [4], we could not find any discernable isotope anomaly at 11 Ma. Our finding is consistent with the timing of major eruption of the Columbia River flood basalts (CFRB) which could provide non-radiogenic Os to seawater at 14-16 Ma [5]. Hence, we suggest that the observed isotope anomaly reflect eruption and subsequent weathering of the CFRB. As the similar Os isotope anomaly is commonly found from Fe-Mn crusts, the Os isotope anomaly at 14-16 Ma could be used as a key event to constrain depositional ages of Fe-Mn crusts. In the presentation, we will also discuss the significance of our findings to paleoceanographic studies using Fe-Mn crusts. References: [1] Klemm et al., 2005 EPSL; [2] Nielsen et al., 2009 EPSL; [3] Peucker-Ehrenbrink & Ravizza, 2012 The Geologic Time Scale 2012; [4] Klemm et al., 2008 EPSL; [5] Hopper et al., 2002 GSA Bulletin

A critical review of inductively coupled plasma-mass spectrometry for geoanalysis, geochemistry and hydrology, Part 1. Analytical performance

USGS Publications Warehouse

Brenner, I.B.; Taylor, Howard E.

1992-01-01

Present-day inductively coupled plasma-mass spectrometry (ICP-MS) instrumentation is described briefly. Emphasis is placed on performance characteristics for geoanalysis, geochemistry, and hydrology. Applications where ICP-MS would be indispensable are indicated. Determination of geochemically diagnostic trace elements (such as the rare earth elements [REE], U and Th), of isotope ratios for fingerprinting, tracer and other geo-isotope applications, and benchmark isotope dilution determinations are considered to be typical priority applications for ICP-MS. It is concluded that ICP-MS furnishes unique geoanalytical and environmental data that are not readily provided by conventional spectroscopic (emission and absorption) techniques.

Volume Measurements of Laser-generated Pits for in Situ Geochronology Using KArLE (Potassium-Argon Laser Experiment)

NASA Technical Reports Server (NTRS)

French, R. A.; Cohen, B. A.; Miller, J. S.

2014-01-01

KArLE (Potassium-­-Argon Laser Experiment) has been developed for in situ planetary geochronology using the K - Ar (potassium-­-argon) isotope system, where material ablated by LIBS (Laser-­-Induced Breakdown Spectroscopy) is used to calculate isotope abundances. We are determining the accuracy and precision of volume measurements of these pits using stereo and laser microscope data to better understand the ablation process for isotope abundance calculations. If a characteristic volume can be determined with sufficient accuracy and precision for specific rock types, KArLE will prove to be a useful instrument for future planetary rover missions.

Determination of δ13C, δ15N, or δ34S by isotope-ratio-monitoring mass spectrometry using an elemental analyzer

USGS Publications Warehouse

Johnson, Craig A.; Stricker, Craig A.; Gulbransen, Cayce A.; Emmons, Matthew P.

2018-02-14

This report describes procedures used in the Geology, Geophysics, and Geochemistry Science Center of the U.S. Geological Survey in Denver, Colorado, to determine the stable-isotope ratios 13C/12C, 15N/14N, and 34S/32S in solid materials. The procedures use elemental analyzers connected directly to gas-source isotope-ratio mass spectrometers. A different elemental–analyzer–mass-spectrometer system is used for 13C/12C and 15N/14N than is used for 34S/32S to accommodate differences in reagents, catalysts, and instrument settings.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Maxwell, Sherrod L.; Culligan, Brian K.; Hutchison, Jay B.

A new rapid fusion method for the determination of plutonium in large rice samples has been developed at the Savannah River National Laboratory (Aiken, SC, USA) that can be used to determine very low levels of plutonium isotopes in rice. The recent accident at Fukushima Nuclear Power Plant in March, 2011 reinforces the need to have rapid, reliable radiochemical analyses for radionuclides in environmental and food samples. Public concern regarding foods, particularly foods such as rice in Japan, highlights the need for analytical techniques that will allow very large sample aliquots of rice to be used for analysis so thatmore » very low levels of plutonium isotopes may be detected. The new method to determine plutonium isotopes in large rice samples utilizes a furnace ashing step, a rapid sodium hydroxide fusion method, a lanthanum fluoride matrix removal step, and a column separation process with TEVA Resin cartridges. The method can be applied to rice sample aliquots as large as 5 kg. Plutonium isotopes can be determined using alpha spectrometry or inductively-coupled plasma mass spectrometry (ICP-MS). The method showed high chemical recoveries and effective removal of interferences. The rapid fusion technique is a rugged sample digestion method that ensures that any refractory plutonium particles are effectively digested. The MDA for a 5 kg rice sample using alpha spectrometry is 7E-5 mBq g{sup -1}. The method can easily be adapted for use by ICP-MS to allow detection of plutonium isotopic ratios.« less

Sequential therapy versus standard triple-drug therapy for Helicobacter pylori eradication: a randomized study.

PubMed

Nasa, Mukesh; Choksey, Ajay; Phadke, Aniruddha; Sawant, Prabha

2013-11-01

Antimicrobial resistance has decreased eradication rates for Helicobacter pylori infection worldwide. A sequential treatment schedule has been reported to be effective, but studies published to date were performed in Italy. We undertook this study to determine whether these results could be replicated in India. A randomized, open-labeled, prospective controlled trial comparing sequential vs. standard triple-drug therapy was carried out at Lokmanya Tilak Municipal General Hospital, Mumbai. Two hundred and thirty-one patients with dyspepsia were randomized to a 10-day sequential regimen (40 mg of pantoprazole, 1 g of amoxicillin, each administered twice daily for the first 5 days, followed by 40 mg of pantoprazole, 500 mg of clarithromycin, and 500 mg of tinidazole, each administered twice daily for the remaining 5 days) or to standard 14-day therapy (40 mg of pantoprazole, 500 mg of clarithromycin, and 1 g of amoxicillin, each administered twice daily). The eradication rate achieved with the sequential regimen was significantly greater than that obtained with the triple therapy. Per-protocol eradication rate of sequential therapy was 92.4% (95% CI 85.8-96.1%) vs. 81.8% (95% CI 73.9-87.8%) (p = 0.027) for standard drug therapy. Intention-to-treat eradication rates were 88.2% (95% CI 80.9-93.0%) vs. 79.1% (95% CI 71.1-85.4%), p = 0.029, respectively. The incidence of major and minor side effects between therapy groups was not significantly different (14.6% in the triple therapy group vs. 23.5% in sequential group, p = 0.12). Follow up was incomplete in 3.3% and 4.7% patients in standard and sequential therapy groups, respectively. Sequential therapy includes one additional antibiotic (tinidazole) that is not contained in standard therapy. Sequential therapy was significantly better than standard therapy for eradicating H. pylori infection.

Hepatoblastoma Biology Using Isotope Ratio Mass Spectrometry: Utility of a Unique Technique for the Analysis of Oncological Specimens.

PubMed

Taran, Katarzyna; Frączek, Tomasz; Sitkiewicz, Anna; Sikora-Szubert, Anita; Kobos, Józef; Paneth, Piotr

2016-07-07

Hepatoblastoma is the most common primary liver tumor in children. However, it occurs rarely, with an incidence of 0.5-1.5 cases per million children. There is no clear explanation of the relationship between clinicopathologic features, therapy, and outcome in hepatoblastoma cases, so far. One of the most widely accepted prognostic factors in hepatoblastoma is histology of the tumor. The aim of the study was to determine the potential differences in biology of hepatoblastoma histological subtypes at the atomic level using the unique method of isotope ratio mass spectrometry, which is especially valuable in examination of small groups of biological samples. Twenty-four measurements of nitrogen stable isotope ratio, carbon stable isotope ratio and total carbon to nitrogen mass ratio in fetal and embryonal hepatoblastoma tissue were performed using a Sercon 20-22 Continuous Flow Isotope Ratio Mass Spectrometer (CF-IRMS) coupled with a Sercon SL elemental analyzer for simultaneous carbon-nitrogen-sulfur (NCS) analysis. A difference of about 1.781‰ in stable nitrogen isotope 15N/14N ratio was found between examined hepatoblastoma histological subtypes. The prognosis in liver tumors cases in children may be challenging particularly because of the lack of versatile methods of its evaluation. Isotope ratio mass spectrometry allows one to determine the difference between hepatoblastoma histological subtypes and clearly indicates the cases with the best outcome.

SAIL--stereo-array isotope labeling.

PubMed

Kainosho, Masatsune; Güntert, Peter

2009-11-01

Optimal stereospecific and regiospecific labeling of proteins with stable isotopes enhances the nuclear magnetic resonance (NMR) method for the determination of the three-dimensional protein structures in solution. Stereo-array isotope labeling (SAIL) offers sharpened lines, spectral simplification without loss of information and the ability to rapidly collect and automatically evaluate the structural restraints required to solve a high-quality solution structure for proteins up to twice as large as before. This review gives an overview of stable isotope labeling methods for NMR spectroscopy with proteins and provides an in-depth treatment of the SAIL technology.

Cometary and interstellar dust grains - Analysis by ion microprobe mass spectrometry and other techniques

NASA Technical Reports Server (NTRS)

Zinner, Ernst

1991-01-01

A survey of microanalytical measurements on interplanetary dust particles (IDPs) and interstellar dust grains from primitive meteorites is presented. Ion-microprobe mass spectrometry with its capability to determine isotopic compositions of many elements on a micron spatial scale has played a special role. Examples are measurements of H, N, and O isotopes and refractory trace elements in IDPs; C, N, Mg, and Si isotopes in interstellar SiC grains; and C and N isotopes and H, N, Al, and Si concentrations in interstellar graphite grains.

Evaluation of the 34S/32S ratio of Soufre de Lacq elemental sulfur isotopic reference material by continuous flow isotope-ratio mass spectrometry

USGS Publications Warehouse

Qi, H.P.; Coplen, T.B.

2003-01-01

Soufre de Lacq elemental sulfur reference material (IAEA-S-4) isotopically is homogeneous in amounts as small as 41 ??g as determined by continuous flow isotope-ratio mass spectrometry. The ??34S value for this reference material is +16.90 ?? 0.12??? (1??) on a scale (Vienna Can??on Diablo troilite, VCDT) where IAEA-S-1 Ag2S is -0.3??? and IAEA-S-2 Ag2S is +22.67???. Published by Elsevier Science B.V.

Determining Oxygen Isotopic Fractionation between the ferrous sulfate, melanterite, and aqueous sulfate

NASA Astrophysics Data System (ADS)

Shulaker, D. Z.; Kohl, I.; Coleman, M. L.

2011-12-01

Studying regions on Earth that are analogous to Mars serve as case studies for studying astrobiology and planetary surface rock formation processes. Rio Tinto, Spain is very rich in iron sulfates, and has an environment that is possibly very similar to the former environment on Mars. Certain bacteria play significant roles in accelerating pyrite oxidation rates, the products of which contribute to the formation of ferrous sulfates, such as melanterite. During mineral crystallization in an aqueous solution, there are systematic isotopic differences between dissolved species and solid phases. Quantifying this fractionation enables isotopic analysis to be used to trace the original isotopic signature of the dissolved species. Isotope fractionation has been determined for minerals such as gypsum and epsomite, and from these results and theoretical predictions, it is expected that melanterite, a mineral potentially found on Mars, would be more enriched in oxygen-18 relative to the aqueous solution from which it crystallized.Thus, determining the oxygen-18 isotopic fractionation between melanterite and dissolved sulfate has many potential benefits for understanding surface processes on Mars and its past environment. To investigate the oxygen isotope fractionation for melanterite, acidic aqueous solutions saturated with dissolved hydrated ferrous sulfate were evaporated at 25 deg C and 40 deg C and under different conditions to induce different evaporation rates. During evaporation, the aqueous solution and crystallized melanterite were sampled at different stages. Oxygen-18 isotopic compositions were then measured. However, the fractionations observed in the experiments were opposite from predictions. At 25 deg C without enhanced evaporation, the dissolved sulfate was +5.5 per mil relative to the solid, while at 40 deg C it was +4.3 per mil. With enhanced evaporation, fractionation was +2.1 per mil, while at 40 deg C it was +3.6 per mil. In addition, at 40 deg C, evaporation rates and fractionation were larger than at 25 deg C. Because no Rayleigh fractionation was observed, this system was not in equilibrium, and was most likely dominated by kinetics. Because of the unexpected results, further research will be conducted on the oxygen isotope fractionation of melanterite.

Simultaneous measurement of sulfur and lead isotopes in sulfides using nanosecond laser ablation coupled with two multi-collector inductively coupled plasma mass spectrometers

NASA Astrophysics Data System (ADS)

Yuan, Honglin; Liu, Xu; Chen, Lu; Bao, Zhian; Chen, Kaiyun; Zong, Chunlei; Li, Xiao-Chun; Qiu, Johnson Wenhong

2018-04-01

We herein report the coupling of a nanosecond laser ablation system with a large-scale multi-collector inductively coupled plasma mass spectrometer (Nu1700 MC-ICPMS, NP-1700) and a conventional Nu Plasma II MC-ICPMS (NP-II) for the simultaneous laser ablation and determination of in situ S and Pb isotopic compositions of sulfide minerals. We found that the required aerosol distribution between the two spectrometers depended on the Pb content of the sample. For example, for a sulfide containing 100-3000 ppm Pb, the aerosol was distributed between the NP-1700 and the NP-II spectrometers in a 1:1 ratio, while for lead contents >3000 and <100 ppm, these ratios were 5:1 and 1:3, respectively. In addition, S isotopic analysis showed a pronounced matrix effect, so a matrix-matched external standard was used for standard-sample bracketing correction. The NIST NBS 977 (NBS, National Bureau of Standards; NIST, National Institute of Standards & Technology) Tl (thallium) dry aerosol internal standard and the NIST SRM 610 (SRM, standard reference material) external standard were employed to obtain accurate results for the analysis of Pb isotopes. In tandem experiments where airflow conditions were similar to those employed during stand-alone analyses, small changes in the aerosol carrier gas flow did not significantly influence the accurate determination of S and Pb isotope ratios. In addition, careful optimization of the flow ratio of the aerosol carrier (He) and makeup (Ar) gases to match stand-alone analytical conditions allowed comparable S and Pb isotope ratios to be obtained within an error of 2 s analytical uncertainties. Furthermore, the results of tandem analyses obtained using our method were consistent with those of previously reported stand-alone techniques for the S and Pb isotopes of chalcopyrite, pyrite, galena, and sphalerite, thus indicating that this method is suitable for the simultaneous analysis of S and Pb isotopes of natural sulfide minerals, and provides an effective tool to determine S and Pb isotope compositions of sulfides formed through multi-stage deposition routes.

The mantle source of island arc magmatism during early subduction: Evidence from Hf isotopes in rutile from the Jijal Complex (Kohistan arc, Pakistan)

NASA Astrophysics Data System (ADS)

Ewing, Tanya A.; Müntener, Othmar

2018-05-01

The Cretaceous-Paleogene Kohistan arc complex, northern Pakistan, is renowned as one of the most complete sections through a preserved paleo-island arc. The Jijal Complex represents a fragment of the plutonic roots of the Kohistan arc, formed during its early intraoceanic history. We present the first Hf isotope determinations for the Jijal Complex, made on rutile from garnet gabbros. These lithologies are zircon-free, but contain rutile that formed as an early phase. Recent developments in analytical capabilities coupled with a careful analytical and data reduction protocol allow the accurate determination of Hf isotope composition for rutile with <30 ppm Hf for the first time. Rutile from the analysed samples contains 5-35 ppm Hf, with sample averages of 13-17 ppm. Rutile from five samples from the Jijal Complex mafic section, sampling 2 km of former crustal thickness, gave indistinguishable Hf isotope compositions with εHf(i) ranging from 11.4 ± 3.2 to 20.1 ± 5.7. These values are within error of or only slightly more enriched than modern depleted mantle. The analysed samples record variable degrees of interaction with late-stage melt segregations, which produced symplectitic overprints on the main mineral assemblage as well as pegmatitic segregations of hydrous minerals. The indistinguishable εHf(i) across this range of lithologies demonstrates the robust preservation of the Hf isotope composition of rutile. The Hf isotope data, combined with previously published Nd isotope data for the Jijal Complex garnet gabbros, favour derivation from an inherently enriched, Indian Ocean type mantle. This implies a smaller contribution from subducted sediments than if the source was a normal (Pacific-type) depleted mantle. The Jijal Complex thus had only a limited recycled continental crustal component in its source, and represents a largely juvenile addition of new continental crust during the early phases of intraoceanic magmatism. The ability to determine the Hf isotope composition of rutile with low Hf contents is an important development for zircon-free mafic lithologies. This study highlights the potential of Hf isotope analysis of rutile to characterise the most juvenile deep arc crust cumulates worldwide.

Isotopes as Tracers of the Hawaiian Coffee-Producing Regions

PubMed Central

2011-01-01

Green coffee bean isotopes have been used to trace the effects of different climatic and geological characteristics associated with the Hawaii islands. Isotope ratio mass spectrometry (IRMS) and inductively coupled plasma mass spectrometry ((MC)-ICP-SFMS and ICP-QMS) were applied to determine the isotopic composition of carbon (δ13C), nitrogen (δ15N), sulfur (δ34S), and oxygen (δ18O), the isotope abundance of strontium (87Sr/86Sr), and the concentrations of 30 different elements in 47 green coffees. The coffees were produced in five Hawaii regions: Hawaii, Kauai, Maui, Molokai, and Oahu. Results indicate that coffee plant seed isotopes reflect interactions between the coffee plant and the local environment. Accordingly, the obtained analytical fingerprinting could be used to discriminate between the different Hawaii regions studied. PMID:21838232

Bioconversion of Coal: Hydrologic indicators of the extent of coal biodegradation under different redox conditions and coal maturity, Velenje Basin case study, Slovenia

NASA Astrophysics Data System (ADS)

Kanduč, Tjaša; Grassa, Fausto; Lazar, Jerneja; Jamnikar, Sergej; Zavšek, Simon; McIntosh, Jennifer

2014-05-01

Underground mining of coal and coal combustion for energy has significant environmental impacts. In order to reduce greenhouse gas emissions, other lower -carbon energy sources must be utilized. Coalbed methane (CBM) is an important source of relatively low-carbon energy. Approximately 20% of world's coalbed methane is microbial in origin (Bates et al., 2011). Interest in microbial CBM has increased recently due to the possibility of stimulating methanogenesis. Despite increasing interest, the hydrogeochemical conditions and mechanisms for biodegradation of coal and microbial methane production are poorly understood. This project aims to examine geochemical characteristics of coalbed groundwater and coalbed gases in order to constrain biogeochemical processes to better understand the entire process of coal biodegradation of coal to coalbed gases. A better understanding of geochemical processes in CBM areas may potentially lead to sustainable stimulation of microbial methanogenesis at economical rates. Natural analogue studies of carbon dioxide occurring in the subsurface have the potential to yield insights into mechanisms of carbon dioxide storage over geological time scales (Li et al., 2013). In order to explore redox processes related to methanogenesis and determine ideal conditions under which microbial degradation of coal is likely to occur, this study utilizes groundwater and coalbed gas samples from Velenje Basin. Determination of the concentrations of methane, carbondioxide, nitrogen, oxygen, argon was performed with homemade NIER mass spectrometer. Isotopic composition of carbon dioxide, isotopic composition of methane, isotopic composition of deuterium in methane was determined with Europa-Scientific IRMS with an ANCA-TG preparation module and Thermo Delta XP GC-TC/CF-IRMS coupled to a TRACE GC analyzer. Total alkalinity of groundwater was measured by Gran titration. Major cations were analyzed by ICP-OES and anions by IC method. Isotopic composition of dissolved inorganic carbon was determined by MultiflowBio preparation module. The stable isotope composition of sulphur was determined with a Europa Scientific 20-20 continuous flow IRMS ANCA-SL preparation module. Concentrations of tritium were determined with the electrolytic enrichment method. PHREEQC for Windows was used to perform thermodynamic modelling. The average coalbed gas composition in the coalbed seam is approximately carbon dioxide: methane > 2:1, where a high proportion of CO2 is adsorbed on the lignite structure, while methane is present free in coal fractures. It can be concluded that isotopic composition of carbon in methane from -70.4‰ to -50.0‰ is generated via acetate fermentation and via reduction of carbon dioxide, while isotopic composition of carbon in methane values range from -50.0‰ to -18.8‰, thermogenic methane can be explained by secondary processes, causing enrichment of residual methane with the heavier carbon isotope. Isotopic composition of deuterium in methane range from -343.9‰ to -223.1‰. Isotopic composition of carbon in carbon dioxide values at excavation fields range from -11.0‰ to +5‰ and are endogenic and microbial in origin. The major ion chemistry, redox conditions, stable isotopes and tritium measured in groundwater from the Velenje Basin, suggest that the Pliocene and Triassic aquifers contain distinct water bodies. Groundwater in the Triassic aquifer is dominated by hydrogen carbonate, calcium, magnesium and isotopic composition of dissolved inorganic carbon indicating degradation of soil organic matter and dissolution of carbonate minerals, similar to surface waters. In addition, groundwater in the Triassic aquifer has isotopic composition of oxygen and isotopic composition of deuterium values which plot near surface waters on the local and global meteoric water lines and detectable tritium reflects recent recharge. In contrast, groundwater in the Pliocene aquifers is enriched in magnesium, sodium, calcium, potassium, and silica and has alkalinity and isotopic composition of dissolved inorganic carbon values with low sulphate and nitrate concentrations. These waters have likely been influenced by sulfate reduction and microbial methanogenesis associated with coal seams and dissolution of feldspars and magnesium-rich clay minerals. Pliocene aquifer waters are also depleted in heavier oxygen isotope and heavier deuterium isotope and have tritium concentrations near the detection limit, suggesting these waters are older. References Bates, B.L., McIntosh J.C., Lohse K.A., Brooks P.D. 2011: Influence of groundwater flowpaths, residence times, and nutrients on the extent of microbial methanogenesis in coal beds: Powder River Basin, USA, Chemical geology, 284, 45-61. Li, W., Cheng Y., Wang L., Zhou H., Wang H., Wang L. 2013: Evaluating the security of geological coalbed sequestration of supercritical CO2 reservoirs: The Haishiwan coalfield, China as a natural analogue, International Journal of Greenhouse Gas Control, 13, 102-111.

Meteoritic Sulfur Isotopic Analysis

NASA Technical Reports Server (NTRS)

Thiemens, Mark H.

1996-01-01

Funds were requested to continue our program in meteoritic sulfur isotopic analysis. We have recently detected a potential nucleosynthetic sulfur isotopic anomaly. We will search for potential carriers. The documentation of bulk systematics and the possible relation to nebular chemistry and oxygen isotopes will be explored. Analytical techniques for delta(sup 33), delta(sup 34)S, delta(sup 36)S isotopic analysis were improved. Analysis of sub milligram samples is now possible. A possible relation between sulfur isotopes and oxygen was detected, with similar group systematics noted, particularly in the case of aubrites, ureilites and entstatite chondrites. A possible nucleosynthetic excess S-33 has been noted in bulk ureilites and an oldhamite separate from Norton County. High energy proton (approximately 1 GeV) bombardments of iron foils were done to experimentally determine S-33, S-36 spallogenic yields for quantitation of isotopic measurements in iron meteorites. Techniques for measurement of mineral separates were perfected and an analysis program initiated. The systematic behavior of bulk sulfur isotopes will continue to be explored.

The Magnitude, Generality, and Determinants of Flynn Effects on Forms of Declarative Memory and Visuospatial Ability: Time-Sequential Analyses of Data from a Swedish Cohort Study

ERIC Educational Resources Information Center

Ronnlund, Michael; Nilsson, Lars-Goran

2008-01-01

To estimate Flynn effects (FEs) on forms of declarative memory (episodic, semantic) and visuospatial ability (Block Design) time-sequential analyses of data for Swedish adult samples (35-80 years) assessed on either of four occasions (1989, 1994, 1999, 2004; n = 2995) were conducted. The results demonstrated cognitive gains across occasions,…

Waste in Place. A New Sequential Curriculum Covering the Behavioral Aspects of Waste Management for Grades K-6. [Teacher Background and Seven Units].

ERIC Educational Resources Information Center

Keep America Beautiful, Inc., New York, NY.

"Waste in Place" is an interdisciplinary, sequential curriculum for kindergarten through sixth grade. The eight units in the curriculum (one offering background information for teachers and one for each grade level) offer students the opportunity to learn about proper management of solid waste and the role of the individual in determining the best…

Sequential design of discrete linear quadratic regulators via optimal root-locus techniques

NASA Technical Reports Server (NTRS)

Shieh, Leang S.; Yates, Robert E.; Ganesan, Sekar

1989-01-01

A sequential method employing classical root-locus techniques has been developed in order to determine the quadratic weighting matrices and discrete linear quadratic regulators of multivariable control systems. At each recursive step, an intermediate unity rank state-weighting matrix that contains some invariant eigenvectors of that open-loop matrix is assigned, and an intermediate characteristic equation of the closed-loop system containing the invariant eigenvalues is created.

Analyzing Communication Architectures Using Commercial Off-The-Shelf (COTS) Modeling and Simulation Tools

DTIC Science & Technology

1998-06-01

4] By 2010, we should be able to change how we conduct the most intense joint operations. Instead of relying on massed forces and sequential ...not independent, sequential steps. Data probes to support the analysis phase were required to complete the logical models. This generated a need...Networks) Identify Granularity (System Level) - Establish Physical Bounds or Limits to Systems • Determine System Test Configuration and Lineup

Ruthenium isotopic evidence for an inner Solar System origin of the late veneer

NASA Astrophysics Data System (ADS)

Fischer-Gödde, Mario; Kleine, Thorsten

2017-01-01

The excess of highly siderophile elements in the Earth’s mantle is thought to reflect the addition of primitive meteoritic material after core formation ceased. This ‘late veneer’ either comprises material remaining in the terrestrial planet region after the main stages of the Earth’s accretion, or derives from more distant asteroidal or cometary sources. Distinguishing between these disparate origins is important because a late veneer consisting of carbonaceous chondrite-like asteroids or comets could be the principal source of the Earth’s volatiles and water. Until now, however, a ‘genetic’ link between the late veneer and such volatile-rich materials has not been established or ruled out. Such genetic links can be determined using ruthenium (Ru) isotopes, because the Ru in the Earth’s mantle predominantly derives from the late veneer, and because meteorites exhibit Ru isotope variations arising from the heterogeneous distribution of stellar-derived dust. Although Ru isotopic data and the correlation of Ru and molybdenum (Mo) isotope anomalies in meteorites were previously used to argue that the late veneer derives from the same type of inner Solar System material as do Earth’s main building blocks, the Ru isotopic composition of carbonaceous chondrites has not been determined sufficiently well to rule them out as a source of the late veneer. Here we show that all chondrites, including carbonaceous chondrites, have Ru isotopic compositions distinct from that of the Earth’s mantle. The Ru isotope anomalies increase from enstatite to ordinary to carbonaceous chondrites, demonstrating that material formed at greater heliocentric distance contains larger Ru isotope anomalies. Therefore, these data refute an outer Solar System origin for the late veneer and imply that the late veneer was not the primary source of volatiles and water on the Earth.

Counting individual sulfur atoms in a protein by ultrahighresolution Fourier transform ion cyclotron resonance mass spectrometry: Experimental resolution of isotopic fine structure in proteins

PubMed Central

Shi, Stone D.-H.; Hendrickson, Christopher L.; Marshall, Alan G.

1998-01-01

A typical molecular ion mass spectrum consists of a sum of signals from species of various possible isotopic compositions. Only the monoisotopic peak (e.g., all carbons are 12C; all nitrogens are 14N, etc.) has a unique elemental composition. Every other isotope peak at approximately integer multiples of ∼1 Da higher in nominal mass represents a sum of contributions from isotope combinations differing by a few mDa (e.g., two 13C vs. two 15N vs. one 13C and one 15N vs. 34S, vs. 18O, etc., at ∼2 Da higher in mass than the monoisotopic mass). At sufficiently high mass resolving power, each of these nominal-mass peaks resolves into its isotopic fine structure. Here, we report resolution of the isotopic fine structure of proteins up to 15.8 kDa (isotopic 13C,15N doubly depleted tumor suppressor protein, p16), made possible by electrospray ionization followed by ultrahigh-resolution Fourier transform ion cyclotron resonance mass analysis at 9.4 tesla. Further, a resolving power of m/Δm50% ≈8,000,000 has been achieved on bovine ubiquitin (8.6 kDa). These results represent a 10-fold increase in the highest mass at which isotopic fine structure previously had been observed. Finally, because isotopic fine structure reveals elemental composition directly, it can be used to confirm or determine molecular formula. For p16, for example, we were able to determine (5.1 ± 0.3) the correct number (five) of sulfur atoms solely from the abundance ratio of the resolved 34S peak to the monoisotopic peak. PMID:9751700

In Situ Carbon Isotope Analysis by Laser Ablation MC-ICP-MS.

PubMed

Chen, Wei; Lu, Jue; Jiang, Shao-Yong; Zhao, Kui-Dong; Duan, Deng-Fei

2017-12-19

Carbon isotopes have been widely used in tracing a wide variety of geological and environmental processes. The carbon isotope composition of bulk rocks and minerals was conventionally analyzed by isotope ratio mass spectrometry (IRMS), and, more recently, secondary ionization mass spectrometry (SIMS) has been widely used to determine carbon isotope composition of carbon-bearing solid materials with good spatial resolution. Here, we present a new method that couples a RESOlution S155 193 nm laser ablation system with a Nu Plasma II MC-ICP-MS, with the aim of measuring carbon isotopes in situ in carbonate minerals (i.e., calcite and aragonite). Under routine operating conditions for δ 13 C analysis, instrumental bias generally drifts by 0.8‰-2.0‰ in a typical analytical session of 2-3 h. Using a magmatic calcite as the standard, the carbon isotopic composition was determined for a suite of calcite samples with δ 13 C values in the range of -6.94‰ to 1.48‰. The obtained δ 13 C data are comparable to IRMS values. The combined standard uncertainty for magmatic calcite is <0.3‰ (1s). No significant matrix effects have been identified in calcite with the amplitude of chemical composition variation (i.e., MnO, SrO, MgO, or FeO) up to 2.5 wt %. Two modern corals were investigated using magmatic calcite as the calibration standard, and the average δ 13 C values for both corals are similar to the bulk IRMS values. Moreover, coral exhibits significant heterogeneity in carbon isotope compositions, with differences up to 4.85‰ within an individual coral. This study indicates that LA-MC-ICP-MS can serve as an appropriate method to analyze carbon isotopes of carbonate minerals in situ.

Precise and accurate in situ Pb-Pb dating of apatite, monazite, and sphene by laser ablation multiple-collector ICP-MS

NASA Astrophysics Data System (ADS)

Willigers, B. J. A.; Baker, J. A.; Krogstad, E. J.; Peate, D. W.

2002-03-01

To evaluate in situ Pb dating by laser ablation multiple-collector inductively coupled plasma mass spectrometry (LA-MC-ICP-MS), we analysed apatite, sphene, and monazite from Paleoproterozoic metamorphic rocks from West Greenland. Pb isotope ratios were also determined in the National Institute of Standards and Technology (NIST) 610 glass standard and were corrected for mass fractionation by reference to the measured thallium isotope ratio. The NIST 610 glass was used to monitor Pb isotope mass fractionation in the low Tl/Pb accessory minerals. Replicate analyses of the glass (1 to 2 min) yielded ratios with an external reproducibility comparable to conventional analyses of standard reference material 981 by thermal ionisation mass spectrometry (TIMS). Mineral grains were generally analysed with a 100-μm laser beam, although some monazite crystals were analysed at smaller spot sizes (10 and 25 μm). The common Pb isotope ratios required for age calculations were either measured on coexisting plagioclase by LA-MC-ICP-MS or could be ignored, as individual crystals exhibit sufficient Pb isotopic heterogeneity to perform isochron calculations on replicate analyses of single crystals. Mean mineral ages with the 204Pb ion beam measured in the multiplier were as follows: apatite, 1715 ± 23 m.y.; sphene, 1789 ± 11 m.y.; and monazite, 1783 to 1888 m.y., with relative uncertainties on individual monazite ages of <0.2% but highly reproducible age determinations on single monazite crystals (≪1%). Isochron ages calculated from several mineral analyses without assumption of common Pb also yield precise age determinations. Apatite and monazite Pb ages determined by in situ Pb isotope analysis are identical to those determined by conventional TIMS analysis of bulk mineral separates, and the analytical uncertainties of these short laser analyses with no prior mechanical or chemical separation are comparable to those obtained by TIMS. Detailed examination of the sphene in situ age data does, however, show a small discrepancy between the LA-MC-ICP-MS and TIMS ages (˜1% younger). High-resolution mass scans of the sphene during ablation clearly showed several small and as yet unidentified isobaric interferences that overlap with the 207Pb peak at the resolution conditions for measurement of isotope ratios. These might account for the age discrepancy between the LA-MC-ICP-MS and TIMS sphene ages. LA-MC-ICP-MS is a rapid, accurate, and precise method for in situ determination of Pb isotope ratios that can be used for geochronological studies in a manner similar to an ion microprobe, albeit currently at a somewhat degraded spatial resolution. Further modifications to the LA-MC-ICP-MS system, such as improved sensitivity, ion transmission, and LA methodology, may lead to this type of instrument becoming the method of choice for many types of in situ Pb isotope dating.

The rate of decay of fresh fission products from a nuclear reactor

NASA Astrophysics Data System (ADS)

Dolan, David J.

Determining the rate of decay of fresh fission products from a nuclear reactor is complex because of the number of isotopes involved, different types of decay, half-lives of the isotopes, and some isotopes decay into other radioactive isotopes. Traditionally, a simplified rule of 7s and 10s is used to determine the dose rate from nuclear weapons and can be to estimate the dose rate from fresh fission products of a nuclear reactor. An experiment was designed to determine the dose rate with respect to time from fresh fission products of a nuclear reactor. The experiment exposed 0.5 grams of unenriched Uranium to a fast and thermal neutron flux from a TRIGA Research Reactor (Lakewood, CO) for ten minutes. The dose rate from the fission products was measured by four Mirion DMC 2000XB electronic personal dosimeters over a period of six days. The resulting dose rate following a rule of 10s: the dose rate of fresh fission products from a nuclear reactor decreases by a factor of 10 for every 10 units of time.

Heart-cutting two-dimensional gas chromatography in combination with isotope ratio mass spectrometry for the characterization of the wax fraction in plant material.

PubMed

Dumont, Emmie; Tienpont, Bart; Higashi, Nobukazu; Mitsui, Kazuhisa; Ochiai, Nobuo; Kanda, Hirooki; David, Frank; Sandra, Pat

2013-11-22

Gas chromatography coupled to isotope ratio mass spectrometry after on-line combustion (GC-C-IRMS) and high temperature conversion (GC-HTC-IRMS) is used for compound specific isotope ratio determination. This determination can only be performed successfully if the target solutes are fully resolved from other compounds. A new instrumental set-up consisting of heart-cutting two-dimensional GC based on capillary flow technology and a low thermal mass GC oven in combination with an isotope ratio mass spectrometer is presented. Capillary flow technology was also used in all column and interface connections for robust and leak-free operation. The new configuration was applied to the characterization of wax compounds in tobacco leaf and corresponding smoke samples. It is demonstrated that high accuracy is obtained, both in the determination of δ(13)C and δ(2)H values, allowing the study of biosynthesis and delivery mechanisms of naturally occurring compounds in tobacco. Copyright © 2013 Elsevier B.V. All rights reserved.

Mechanistic investigations of the hydrolysis of amides, oxoesters and thioesters via kinetic isotope effects and positional isotope exchange.

PubMed

Robins, Lori I; Fogle, Emily J; Marlier, John F

2015-11-01

The hydrolysis of amides, oxoesters and thioesters is an important reaction in both organic chemistry and biochemistry. Kinetic isotope effects (KIEs) are one of the most important physical organic methods for determining the most likely transition state structure and rate-determining step of these reaction mechanisms. This method induces a very small change in reaction rates, which, in turn, results in a minimum disturbance of the natural mechanism. KIE studies were carried out on both the non-enzymatic and the enzyme-catalyzed reactions in an effort to compare both types of mechanisms. In these studies the amides and esters of formic acid were chosen because this molecular structure allowed development of methodology to determine heavy-atom solvent (nucleophile) KIEs. This type of isotope effect is difficult to measure, but is rich in mechanistic information. Results of these investigations point to transition states with varying degrees of tetrahedral character that fit a classical stepwise mechanism. This article is part of a special issue entitled: Enzyme Transition States from Theory and Experiment. Copyright © 2014 Elsevier B.V. All rights reserved.

Seasonal oxygen isotopic variations in living planktonic foraminifera off Bermuda

DOE Office of Scientific and Technical Information (OSTI.GOV)

Williams, D.F.; Be, A.W.H.; Fairbanks, R.G.

1979-10-26

Seasonal variations in the oxygen-18/oxygen-16 ratio of calcite shells of living planktonic foraminifera in the Sargasso Sea off Bermuda are a direct function of surface water temperature. Seasonal occurrence as well as depth habitat are determining factors in the oxygen isotopic composition of planktonic foraminifera. These relationships may be used to determine the seasonal temperature contrast of oceans in the past.

Automated isotope identification algorithm using artificial neural networks

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kamuda, Mark; Stinnett, Jacob; Sullivan, Clair

There is a need to develop an algorithm that can determine the relative activities of radio-isotopes in a large dataset of low-resolution gamma-ray spectra that contains a mixture of many radio-isotopes. Low-resolution gamma-ray spectra that contain mixtures of radio-isotopes often exhibit feature over-lap, requiring algorithms that can analyze these features when overlap occurs. While machine learning and pattern recognition algorithms have shown promise for the problem of radio-isotope identification, their ability to identify and quantify mixtures of radio-isotopes has not been studied. Because machine learning algorithms use abstract features of the spectrum, such as the shape of overlapping peaks andmore » Compton continuum, they are a natural choice for analyzing radio-isotope mixtures. An artificial neural network (ANN) has be trained to calculate the relative activities of 32 radio-isotopes in a spectrum. Furthermore, the ANN is trained with simulated gamma-ray spectra, allowing easy expansion of the library of target radio-isotopes. In this paper we present our initial algorithms based on an ANN and evaluate them against a series measured and simulated spectra.« less

Automated isotope identification algorithm using artificial neural networks

DOE PAGES

Kamuda, Mark; Stinnett, Jacob; Sullivan, Clair

2017-04-12

There is a need to develop an algorithm that can determine the relative activities of radio-isotopes in a large dataset of low-resolution gamma-ray spectra that contains a mixture of many radio-isotopes. Low-resolution gamma-ray spectra that contain mixtures of radio-isotopes often exhibit feature over-lap, requiring algorithms that can analyze these features when overlap occurs. While machine learning and pattern recognition algorithms have shown promise for the problem of radio-isotope identification, their ability to identify and quantify mixtures of radio-isotopes has not been studied. Because machine learning algorithms use abstract features of the spectrum, such as the shape of overlapping peaks andmore » Compton continuum, they are a natural choice for analyzing radio-isotope mixtures. An artificial neural network (ANN) has be trained to calculate the relative activities of 32 radio-isotopes in a spectrum. Furthermore, the ANN is trained with simulated gamma-ray spectra, allowing easy expansion of the library of target radio-isotopes. In this paper we present our initial algorithms based on an ANN and evaluate them against a series measured and simulated spectra.« less

Silicon isotope ratio measurements by inductively coupled plasma tandem mass spectrometry for alteration studies of nuclear waste glasses.

PubMed

Gourgiotis, Alkiviadis; Ducasse, Thomas; Barker, Evelyne; Jollivet, Patrick; Gin, Stéphane; Bassot, Sylvain; Cazala, Charlotte

2017-02-15

High-level, long-lived nuclear waste arising from spent fuel reprocessing is vitrified in silicate glasses for final disposal in deep geologic formations. In order to better understand the mechanisms driving glass dissolution, glass alteration studies, based on silicon isotope ratio monitoring of 29 Si-doped aqueous solutions, were carried out in laboratories. This work explores the capabilities of the new type of quadrupole-based ICP-MS, the Agilent 8800 tandem quadrupole ICP-MS/MS, for accurate silicon isotope ratio determination for alteration studies of nuclear waste glasses. In order to avoid silicon polyatomic interferences, a new analytical method was developed using O 2 as the reaction gas in the Octopole Reaction System (ORS), and silicon isotopes were measured in mass-shift mode. A careful analysis of the potential polyatomic interferences on SiO + and SiO 2 + ion species was performed, and we found that SiO + ion species suffer from important polyatomic interferences coming from the matrix of sample and standard solutions (0.5M HNO 3 ). For SiO 2 + , no interferences were detected, and thus, these ion species were chosen for silicon isotope ratio determination. A number of key settings for accurate isotope ratio analysis like, detector dead time, integration time, number of sweeps, wait time offset, memory blank and instrumental mass fractionation, were considered and optimized. Particular attention was paid to the optimization of abundance sensitivity of the quadrupole mass filter before the ORS. We showed that poor abundance sensitivity leads to a significant shift of the data away from the Exponential Mass Fractionation Law (EMFL) due to the spectral overlaps of silicon isotopes combined with different oxygen isotopes (i.e. 28 Si 16 O 18 O + , 30 Si 16 O 16 O + ). The developed method was validated by measuring a series of reference solutions with different 29 Si enrichment. Isotope ratio trueness, uncertainty and repeatability were found to be <0.2%, <0.5% and <0.6%, respectively. These performances meet the requirements of the studies of nuclear glasses alteration and open up possibilities to use this method for precise determination of silicon content in natural samples by Isotope Dilution. Copyright © 2016 Elsevier B.V. All rights reserved.

MAST - A mass spectrometer telescope for studies of the isotopic composition of solar, anomalous, and galactic cosmic ray nuclei

NASA Technical Reports Server (NTRS)

Cook, Walter R.; Cummings, Alan C.; Cummings, Jay R.; Garrard, Thomas L.; Kecman, Branislav; Mewaldt, Richard A.; Selesnick, Richard S.; Stone, Edward C.; Von Rosenvinge, T. T.

1993-01-01

The Mass Spectrometer Telescope (MAST) on SAMPEX is designed to provide high resolution measurements of the isotopic composition of energetic nuclei from He to Ni (Z = 2 to 28) over the energy range from about 10 to several hundred MeV/nuc. During large solar flares MAST will measure the isotopic abundances of solar energetic particles to determine directly the composition of the solar corona, while during solar quiet times MAST will study the isotopic composition of galactic cosmic rays. In addition, MAST will measure the isotopic composition of both interplanetary and trapped fluxes of anomalous cosmic rays, believed to be a sample of the nearby interstellar medium.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aggarwal, J.K.; Palmer, M.R.

Boron isotope ratios have been determined in a variety of different geothermal waters from hydrothermal systems across Iceland. Isotope ratios from the high temperature meteoric water recharged systems reflect the isotope ratio of the host rocks without any apparent fractionation. Seawater recharged geothermal systems exhibit more positive {delta}{sup 11}B values than the meteoric water recharged geothermal systems. Water/rock ratios can be assessed from boron isotope ratios in the saline hydrothermal systems. Low temperature hydrothermal systems also exhibit more positive {delta}{sup 11}B than the high temperature systems, indicating fractionation of boron due to adsorption of the lighter isotope onto secondary minerals.more » Fractionation of boron in carbonate deposits may indicate the level of equilibrium attained within the systems.« less

Stable isotopes in mineralogy

USGS Publications Warehouse

O'Neil, J.R.

1977-01-01

Stable isotope fractionations between minerals are functions of the fundamental vibrational frequencies of the minerals and therefore bear on several topics of mineralogical interest. Isotopic compositions of the elements H, C, O, Si, and S can now be determined routinely in almost any mineral. A summary has been made of both published and new results of laboratory investigations, analyses of natural materials, and theoretical considerations which bear on the importance of temperature, pressure, chemical composition and crystal structure to the isotopic properties of minerals. It is shown that stable isotope studies can sometimes provide evidence for elucidating details of crystal structure and can be a powerful tool for use in tracing the reaction paths of mineralogical reactions. ?? 1977 Springer-Verlag.

Methods for determination of radioactive substances in water and fluvial sediments

USGS Publications Warehouse

Thatcher, Leland Lincoln; Janzer, Victor J.; Edwards, Kenneth W.

1977-01-01

Analytical methods for the determination of some of the more important components of fission or neutron activation product radioactivity and of natural radioactivity found in water are reported. The report for each analytical method includes conditions for application of the method, a summary of the method, interferences, required apparatus and reagents, analytical procedures, calculations, reporting of results, and estimation of precision. The fission product isotopes considered are cesium-137, strontium-90, and ruthenium-106. The natural radioelements and isotopes considered are uranium, lead-210, radium-226, radium-228, tritium, and carbon-14. A gross radioactivity survey method and a uranium isotope ratio method are given. When two analytical methods are in routine use for an individual isotope, both methods are reported with identification of the specific areas of application of each. Techniques for the collection and preservation of water samples to be analyzed for radioactivity are discussed.

Dissolution of barite for the analysis of strontium isotopes and other chemical and isotopic variations using aqueous sodium carbonate

USGS Publications Warehouse

Breit, G.N.; Simmons, E.C.; Goldhaber, M.B.

1985-01-01

A simple procedure for preparing barite samples for chemical and isotopic analysis is described. Sulfate ion, in barite, in the presence of high concentrations of aqueous sodium carbonate, is replaced by carbonate. This replacement forms insoluble carbonates with the cations commonly in barite: Ba, Sr, Ca and Pb. Sulfate is released into the solution by the carbonate replacement and is separated by filtration. The aqueous sulfate can then be reprecipitated for analysis of the sulfur and oxygen isotopes. The cations in the carbonate phase can be dissolved by acidifying the solid residue. Sr can be separated from the solution for Sr isotope analysis by ion-exchange chromatography. The sodium carbonate used contains amounts of Sr which will affect almost all barite 87Sr 86Sr ratios by less than 0.00001 at 1.95?? of the mean. The procedure is preferred over other techniques used for preparing barite samples for the determination of 87Sr 86Sr ratios because it is simple, rapid and enables simultaneous determination of many compositional parameters on the same material. ?? 1985.

Stable hydrogen isotope analysis of bat hair as evidence for seasonal molt and long-distance migration

USGS Publications Warehouse

Cryan, P.M.; Bogan, M.A.; Rye, R.O.; Landis, G.P.; Kester, C.L.

2004-01-01

Although hoary bats (Lasiurus cinereus) are presumed to be migratory and capable of long-distance dispersal, traditional marking techniques have failed to provide direct evidence of migratory movements by individuals. We measured the stable hydrogen isotope ratios of bat hair (δDh) and determined how these values relate to stable hydrogen isotope ratios of precipitation (δDp). Our results indicate that the major assumptions of stable isotope migration studies hold true for hoary bats and that the methodology provides a viable means of determining their migratory movements. We present evidence that a single annual molt occurs in L. cinereus prior to migration and that there is a strong relationship between δDh and δDp during the molt period. This presumably reflects the incorporation of local δDp into newly grown hair. Furthermore, we present evidence that individual hoary bats are capable of traveling distances in excess of 2,000 km and that hair is grown at a wide range of latitudes and elevations. Stable hydrogen isotope analysis offers a promising new tool for the study of bat migration.

Development of a Method to Isolate Glutamic Acid from Foodstuffs for a Precise Determination of Their Stable Carbon Isotope Ratio.

PubMed

Kobayashi, Kazuhiro; Tanaka, Masaharu; Yatsukawa, Yoichi; Tanabe, Soichi; Tanaka, Mitsuru; Ohkouchi, Naohiko

2018-01-01

Recent growing health awareness is leading to increasingly conscious decisions by consumers regarding the production and traceability of food. Stable isotopic compositions provide useful information for tracing the origin of foodstuffs and processes of food production. Plants exhibit different ratios of stable carbon isotopes (δ 13 C) because they utilized different photosynthetic (carbon fixation) pathways and grow in various environments. The origins of glutamic acid in foodstuffs can be differentiated on the basis of these photosynthetic characteristics. Here, we have developed a method to isolate glutamic acid in foodstuffs for determining the δ 13 C value by elemental analyzer-isotope-ratio mass spectrometry (EA/IRMS) without unintended isotopic fractionation. Briefly, following acid-hydrolysis, samples were defatted and passed through activated carbon and a cation-exchange column. Then, glutamic acid was isolated using preparative HPLC. This method is applicable to measuring, with a low standard deviation, the δ 13 C values of glutamic acid from foodstuffs derived from C3 and C4 plants and marine algae.

Rhenium-osmium isotope systematics of carbonaceous chondrites

USGS Publications Warehouse

Walker, R.J.; Morgan, J.W.

1989-01-01

Rhenium and osmium concentrations and Os isotopic compositions of eight carbonaceous chondrites, one LL3 ordinary chondrite, and two iron meteorites were determined by resonance ionization mass spectrometry. Iron meteorite 187Re/186Os and 187OS/186Os ratios plot on the previously determined iron meteorite isochron, but most chondrite data plot 1 to 2 percent above this meteorite isochron. This suggests either that irons have significantly younger Re-Os closure ages than chondrites or that chondrites were formed from precursor materials with different chemical histories from the precursors of irons. Some samples of Semarkona (LL3) and Murray (C2M) meteorites plot 4 to 6 percent above the iron meteorite isochron, well above the field delineated by other chondrites. Murray may have lost Re by aqueous leaching during its preterrestrial history. Semarkona could have experienced a similar loss of Re, but only slight aqueous alteration is evident in the meteorite. Therefore, the isotopic composition of Semarkona could reflect assembly of isotopically heterogeneous components subsequent to 4.55 billion years ago or Os isotopic heterogeneities in the primordial solar nebula.

The oxygen isotope partition function ratio of water and the structure of liquid water

USGS Publications Warehouse

O'Neil, J.R.; Adami, L.H.

1969-01-01

By means of the CO2-equilibration technique, the temperature dependence and absolute values of the oxygen isotope partition function ratio of liquid water have been determined, often at 1?? intervals, from -2 to 85??. A linear relationship between In (Q2/Q1) (H2O) and T-1 was obtained that is explicable in terms of the Bigeleisen-Mayer theory of isotopic fractionation. The data are incompatible with conventional, multicomponent mixture models of water because liquid water behaves isotopically as a singly structured homogeneous substance over the entire temperature range studied. A two-species model of water is proposed in which approximately 30% of the hydrogen bonds in ice are broken on melting at 0?? and in which this per cent of monomer changes by only a small amount over the entire liquid range. Because of the high precision and the fundamental property determined, the isotopic fractionation technique is particularly well suited to the detection of thermal anomalies. No anomalies were observed and those previously reported are ascribed to under-estimates of experimental error.

Calcium kinetics with microgram stable isotope doses and saliva sampling

NASA Technical Reports Server (NTRS)

Smith, S. M.; Wastney, M. E.; Nyquist, L. E.; Shih, C. Y.; Wiesmann, H.; Nillen, J. L.; Lane, H. W.

1996-01-01

Studies of calcium kinetics require administration of tracer doses of calcium and subsequent repeated sampling of biological fluids. This study was designed to develop techniques that would allow estimation of calcium kinetics by using small (micrograms) doses of isotopes instead of the more common large (mg) doses to minimize tracer perturbation of the system and reduce cost, and to explore the use of saliva sampling as an alternative to blood sampling. Subjects received an oral dose (133 micrograms) of 43Ca and an i.v. dose (7.7 micrograms) of 46Ca. Isotopic enrichment in blood, urine, saliva and feces was well above thermal ionization mass spectrometry measurement precision up to 170 h after dosing. Fractional calcium absorptions determined from isotopic ratios in blood, urine and saliva were similar. Compartmental modeling revealed that kinetic parameters determined from serum or saliva data were similar, decreasing the necessity for blood samples. It is concluded from these results that calcium kinetics can be assessed with micrograms doses of stable isotopes, thereby reducing tracer costs and with saliva samples, thereby reducing the amount of blood needed.

Liquid and gas chromatography coupled to isotope ratio mass spectrometry for the determination of 13C-valine isotopic ratios in complex biological samples.

PubMed

Godin, Jean-Philippe; Breuillé, Denis; Obled, Christiane; Papet, Isabelle; Schierbeek, Henk; Hopfgartner, Gérard; Fay, Laurent-Bernard

2008-10-01

On-line gas chromatography-combustion-isotope ratio mass spectrometry (GC-C-IRMS) is commonly used to measure isotopic ratios at natural abundance as well as for tracer studies in nutritional and medical research. However, high-precision (13)C isotopic enrichment can also be measured by liquid chromatography-isotope ratio mass spectrometry (LC-IRMS). Indeed, LC-IRMS can be used, as shown by the new method reported here, to obtain a baseline separation and to measure (13)C isotopic enrichment of underivatised amino acids (Asp, Thr-Ser, Glu, Pro, Gly, Ala, Cys and Val). In case of Val, at natural abundance, the SD(delta(13)C) reported with this method was found to be below 1 per thousand . Another key feature of the new LC-IRMS method reported in this paper is the comparison of the LC-IRMS approach with the conventional GC-C-IRMS determination. To perform this comparative study, isotopic enrichments were measured from underivatised Val and its N(O, S)-ethoxycarbonyl ethyl ester derivative. Between 0.0 and 1.0 molar percent excess (MPE) (delta(13)C= -12.3 to 150.8 per thousand), the calculated root-mean-square (rms) of SD was 0.38 and 0.46 per thousand and the calculated rms of accuracy was 0.023 and 0.005 MPE, respectively, for GC-C-IRMS and LC-IRMS. Both systems measured accurately low isotopic enrichments (0.002 atom percent excess (APE)) with an SD (APE) of 0.0004. To correlate the relative (delta(13)C) and absolute (atom%, APE and MPE) isotopic enrichment of Val measured by the GC-C-IRMS and LC-IRMS devices, mathematical equations showing the slope and intercept of the curves were established and validated with experimental data between 0.0 to 2.3 MPE. Finally, both GC-C-IRMS and LC-IRMS instruments were also used to assess isotopic enrichment of protein-bound (13)C-Val in tibial epiphysis in a tracer study performed in rats. Isotopic enrichments measured by LC-IRMS and GC-C-IRMS were not statistically different (p>0.05). The results of this work indicate that the LC-IRMS was successful for high-precision (13)C isotopic measurements in tracer studies giving (13)C isotopic enrichment similar to the GC-C-IRMS but without the step of GC derivatisation. Therefore, for clinical studies requiring high-precision isotopic measurement, the LC-IRMS is the method of choice to measure the isotopic ratio.

Microwave Ablation: Comparison of Simultaneous and Sequential Activation of Multiple Antennas in Liver Model Systems.

PubMed

Harari, Colin M; Magagna, Michelle; Bedoya, Mariajose; Lee, Fred T; Lubner, Meghan G; Hinshaw, J Louis; Ziemlewicz, Timothy; Brace, Christopher L

2016-01-01

To compare microwave ablation zones created by using sequential or simultaneous power delivery in ex vivo and in vivo liver tissue. All procedures were approved by the institutional animal care and use committee. Microwave ablations were performed in both ex vivo and in vivo liver models with a 2.45-GHz system capable of powering up to three antennas simultaneously. Two- and three-antenna arrays were evaluated in each model. Sequential and simultaneous ablations were created by delivering power (50 W ex vivo, 65 W in vivo) for 5 minutes per antenna (10 and 15 minutes total ablation time for sequential ablations, 5 minutes for simultaneous ablations). Thirty-two ablations were performed in ex vivo bovine livers (eight per group) and 28 in the livers of eight swine in vivo (seven per group). Ablation zone size and circularity metrics were determined from ablations excised postmortem. Mixed effects modeling was used to evaluate the influence of power delivery, number of antennas, and tissue type. On average, ablations created by using the simultaneous power delivery technique were larger than those with the sequential technique (P < .05). Simultaneous ablations were also more circular than sequential ablations (P = .0001). Larger and more circular ablations were achieved with three antennas compared with two antennas (P < .05). Ablations were generally smaller in vivo compared with ex vivo. The use of multiple antennas and simultaneous power delivery creates larger, more confluent ablations with greater temperatures than those created with sequential power delivery. © RSNA, 2015.

Non-lethal sampling of walleye for stable isotope analysis: a comparison of three tissues

USGS Publications Warehouse

Chipps, Steven R.; VanDeHey, J.A.; Fincel, M.J.

2012-01-01

Stable isotope analysis of fishes is often performed using muscle or organ tissues that require sacrificing animals. Non-lethal sampling provides an alternative for evaluating isotopic composition for species of concern or individuals of exceptional value. Stable isotope values of white muscle (lethal) were compared with those from fins and scales (non-lethal) in walleye, Sander vitreus (Mitchill), from multiple systems, size classes and across a range of isotopic values. Isotopic variability was also compared among populations to determine the potential of non-lethal tissues for diet-variability analyses. Muscle-derived isotope values were enriched compared with fins and depleted relative to scales. A split-sample validation technique and linear regression found that isotopic composition of walleye fins and scales was significantly related to that in muscle tissue for both δ13C and δ15N (r2 = 0.79–0.93). However, isotopic variability was significantly different between tissue types in two of six populations for δ15N and three of six populations for δ13C. Although species and population specific, these findings indicate that isotopic measures obtained from non-lethal tissues are indicative of those obtained from muscle.

[Measurements of stable isotopes in atmospheric CO2 and H2O by open-path Fourier transform infrared spectrometry].

PubMed

Wang, Wei; Liu, Wen-Qing; Zhang, Tian-Shu

2013-08-01

The development of spectroscopic techniques has offered continuous measurement of stable isotopes in the ambient air. The method of measuring environmental stable isotopes based on Fourier transform infrared spectrometry (FTIR) is described. In order to verify the feasibility of the method for continuous measurement of the stable isotopes, an open-path FTIR system was used to measure stable isotopes of CO2 and H2O in ambient air directly in a seven-day field experiment, including 12CO2, 3CO2, H2 16O and HD16 O. Also, the time course of carbon isotopic ratio delta13 C and deuterium isotope composition deltaD was calculated. The measurement precision is about 1.08 per thousand for delta13 C and 1.32 per thousand for deltaD. The measured stable isotopes of CO2 and H2O were analyzed on different time scales by Keeling plot methods, and the deuterium isotopic ratios of evapotranspiration were determined. The results of the field experiment demonstrate the potential of the open-path FTIR system for continuous measurement of stable isotopes in the air.

Calcium isotope systematics at hydrothermal conditions: Mid-ocean ridge vent fluids and experiments in the CaSO4-NaCl-H2O system

NASA Astrophysics Data System (ADS)

Scheuermann, Peter P.; Syverson, Drew D.; Higgins, John A.; Pester, Nicholas J.; Seyfried, William E.

2018-04-01

Two sets of hydrothermal experiments were performed to explore Ca isotope fractionation and exchange rates at hydrothermal conditions (410-450 °C, 31.0-50.0 MPa). The first set of experiments determined the magnitude of vapor-liquid Ca isotope fractionation and anhydrite solubility in the CaSO4-NaCl-H2O system. The data indicate no statistical difference between the Ca isotopic composition of coexisting vapor and liquid. The second set of experiments utilized an anomalous 43Ca spike to determine the rate of Ca exchange between fluid and anhydrite as a function of total dissolved Ca concentration. Results show that the rate of exchange increases with dissolved Ca concentrations (12-23 mM/kg), but no change in exchange rate is observed when the Ca concentration increases from 23 to 44 mM/kg Ca. 74-142 days are required to achieve 90% anhydrite-fluid Ca isotope exchange at the conditions investigated, while only several hours are necessary for vapor-liquid isotopic equilibrium. The lack of vapor-liquid Ca isotope fractionation in our experiments is consistent with δ44Ca of mid-ocean ridge hydrothermal vent fluids that remain constant, regardless of chlorinity. Moreover, the narrow range of end member fluid δ44Ca, -0.98 to -1.13‰ (SW), is largely indistinguishable from MORB δ44Ca, suggesting that neither phase separation nor fluid-rock interactions at depth significantly fractionate Ca isotopes in modern high-temperature mid-ocean ridge hydrothermal systems.

Synchrotron based infrared imaging and spectroscopy via focal plane array on live fibroblasts in D2O enriched medium

DOE Office of Scientific and Technical Information (OSTI.GOV)

Quaroni, Luca; Zlateva, Theodora; Sarafimov, Blagoj

2014-03-26

We tested the viability of using synchrotron based infrared imaging to study biochemical processes inside living cells. As a model system, we studied fibroblast cells exposed to a medium highly enriched with D2O. We could show that the experimental technique allows us to reproduce at the cellular level measurements that are normally performed on purified biological molecules. We can obtain information about lipid conformation and distribution, kinetics of hydrogen/deuterium exchange, and the formation of concentration gradients of H and O isotopes in water that are associated with cell metabolism. The implementation of the full field technique in a sequential imagingmore » format gives a description of cellular biochemistry and biophysics that contains both spatial and temporal information.« less

Groundwater-quality data from the eastern Snake River Plain Aquifer, Jerome and Gooding Counties, south-central Idaho, 2017

USGS Publications Warehouse

Skinner, Kenneth D.

2018-05-11

Groundwater-quality samples and water-level data were collected from 36 wells in the Jerome/Gooding County area of the eastern Snake River Plain aquifer during June 2017. The wells included 30 wells sampled for the U.S. Geological Survey’s National Water-Quality Assessment project, plus an additional 6 wells were selected to increase spatial distribution. The data provide water managers with the ability for an improved understanding of groundwater quality and flow directions in the area. Groundwater-quality samples were analyzed for nutrients, major ions, trace elements, and stable isotopes of water. Quality-assurance and quality-control measures consisted of multiple blank samples and a sequential replicate sample. All data are available online at the USGS National Water Information System.

Experimental determination of the Mo isotope fractionation factor between metal and silicate liquids

NASA Astrophysics Data System (ADS)

Hin, R. C.; Burkhardt, C.; Schmidt, M. W.; Bourdon, B.

2011-12-01

The conditions and chemical consequences of core formation have mainly been reconstructed from experimentally determined element partition coefficients between metal and silicate liquids. However, first order questions such as the mode of core formation or the nature of the light element(s) in the Earth's core are still debated [1]. In addition, the geocentric design of most experimental studies leaves the conditions of core formation on other terrestrial planets and asteroids even more uncertain than for Earth. Through mass spectrometry, records of mass-dependent stable isotope fractionation during high-temperature processes such as metal-silicate segregation are detectable. Stable isotope fractionation may thus yield additional constrains on core formation conditions and its consequences for the chemical evolution of planetary objects. Experimental investigations of equilibrium mass-dependent stable isotope fractionation have shown that Si isotopes fractionate between metal and silicate liquids at temperatures of 1800°C and pressures of 1 GPa, while Fe isotopes leave no resolvable traces of core formation processes [2,3]. Molybdenum is a refractory and siderophile trace element in the Earth, and thus much less prone to complications arising from mass balancing core and mantle and from potential volatile behaviour than other elements. To determine equilibrium mass-dependent Mo isotope fractionation during metal-silicate segregation, we have designed piston cylinder experiments with a basaltic silicate composition and an iron based metal with ~8 wt% Mo, using both graphite and MgO capsules. Metal and silicate phases are completely segregated by the use of a centrifuging piston cylinder at ETH Zurich, thus preventing analysis of mixed metal and silicate signatures. Molybdenum isotope compositions were measured using a Nu Instruments 1700 MC-ICP-MS at ETH Zurich. To ensure an accurate correction of analytical mass fractionation a 100Mo-97Mo double spike was admixed before chemical purification. Initial results provide an equilibrium 98Mo/95Mo isotope fractionation factor between metal and silicate liquids of -0.18±0.10% (2σ) at 1400°C and 1 GPa. Although the relative mass difference of these Mo isotopes is smaller than for Fe isotopes, this result implies that metal-silicate segregation may have led to mass-dependent stable Mo isotope fractionation, as opposed to Fe isotopes. A possible explanation is that the bonding environment of Mo may counterbalance its relatively small mass separation. At reducing conditions, Mo occurs in 4+ valence state in silicates [4] and thus its bond strength difference between metal and silicate may be more similar to that of Si than Fe. Stable Mo isotopes may thus become an important tool for constraining the conditions of core formation in asteroids and terrestrial planets. [1] Rubie et al. (2011) EPSL 301, 31-42. [2] Shahar et al. (2009) EPSL 288, 228-234. [3] Poitrasson et al. (2009) EPSL 278, 376-385. [4] Farges et al. (2006) Can. Min. 44, 731-753.

Cell wall invertase as a regulator in determining sequential development of endosperm and embryo through glucose signaling early in seed development.

PubMed

Wang, Lu; Liao, Shengjin; Ruan, Yong-Ling

2013-01-01

Seed development depends on coordination among embryo, endosperm and seed coat. Endosperm undergoes nuclear division soon after fertilization, whereas embryo remains quiescent for a while. Such a developmental sequence is of great importance for proper seed development. However, the underlying mechanism remains unclear. Recent results on the cellular domain- and stage-specific expression of invertase genes in cotton and Arabidopsis revealed that cell wall invertase may positively and specifically regulate nuclear division of endosperm after fertilization, thereby playing a role in determining the sequential development of endosperm and embryo, probably through glucose signaling.

Weathering and vegetation controls on nickel isotope fractionation in surface ultramafic environments (Albania)

NASA Astrophysics Data System (ADS)

Estrade, Nicolas; Cloquet, Christophe; Echevarria, Guillaume; Sterckeman, Thibault; Deng, Tenghaobo; Tang, YeTao; Morel, Jean-Louis

2015-08-01

The dissolved nickel (Ni) isotopic composition of rivers and oceans presents an apparent paradox. Even though rivers represent a major source of Ni in the oceans, seawater is more enriched in the heavier isotopes than river-water. Additional sources or processes must therefore be invoked to account for the isotopic budget of dissolved Ni in seawater. Weathering of continental rocks is thought to play a major role in determining the magnitude and sign of isotopic fractionation of metals between a rock and the dissolved product. We present a study of Ni isotopes in the rock-soil-plant systems of several ultramafic environments. The results reveal key insights into the magnitude and the control of isotopic fractionation during the weathering of continental ultramafic rocks. This study introduces new constraints on the influence of vegetation during the weathering process, which should be taken into account in interpretations of the variability of Ni isotopes in rivers. The study area is located in a temperate climate zone within the ophiolitic belt area of Albania. The serpentinized peridotites sampled present a narrow range of heavy Ni isotopic compositions (δ60Ni = 0.25 ± 0.16 ‰, 2SD n = 2). At two locations, horizons within two soil profiles affected by different degrees of weathering all presented light isotopic compositions compared to the parent rock (Δ60Nisoil-rock up to - 0.63 ‰). This suggests that the soil pool takes up the light isotopes, while the heavier isotopes remain in the dissolved phase. By combining elemental and mineralogical analyses with the isotope compositions determined for the soils, the extent of fractionation was found to be controlled by the secondary minerals formed in the soil. The types of vegetation growing on ultramafic-derived soils are highly adapted and include both Ni-hyperaccumulating species, which can accumulate several percent per weight of Ni, and non-accumulating species. Whole-plant isotopic compositions were found to be isotopically heavier than the soil (Δ60Niwhole plant-soil up to 0.40‰). Fractions of Ni extracted by DTPA (diethylenetriaminepentaacetic acid) presented isotopically heavy compositions compared to the soil (Δ60NiDTPA-soil up to 0.89‰), supporting the hypothesis that the dissolved Ni fraction controlled by weathering has a heavy isotope signature. The non-hyperaccumulators (n = 2) were inclined to take up and translocate light Ni isotopes with a large degree of fractionation (Δ60Nileaves-roots up to - 0.60 ‰). For Ni-hyperaccumulators (n = 7), significant isotopic fractionation was observed in the plants in their early growth stages, while no fractionation occurred during later growth stages, when plants are fully loaded with Ni. This suggests that (i) the high-efficiency translocation process involved in hyperaccumulators does not fractionate Ni isotopes, and (ii) the root uptake process mainly controls the isotopic composition of the plant. In ultramafic contexts, vegetation composed of hyperaccumulators can significantly influence isotopic compositions through its remobilization in the upper soil horizon, thereby influencing the isotopic balance of Ni exported to rivers.

Trans-Atlantic slavery: isotopic evidence for forced migration to Barbados.

PubMed

Schroeder, Hannes; O'Connell, Tamsin C; Evans, Jane A; Shuler, Kristrina A; Hedges, Robert E M

2009-08-01

The question of the ultimate origin of African slaves is one of the most perplexing in the history of trans-Atlantic slavery. Here we present the results of a small, preliminary isotopic study that was conducted in order to determine the geographical origin of 25 enslaved Africans who were buried at the Newton plantation, Barbados, sometime between the late 17th and early 19th century. In order to gain a more nuanced understanding of the slaves' origin, we used a combination of carbon, nitrogen, oxygen, and strontium isotope analyses. Carbon and nitrogen isotope ratios were determined in bone and dentinal collagen; oxygen and strontium isotopes were measured in tooth enamel. Results suggest that the majority of individuals were born on the island, if not the estate itself. Seven individuals, however, yielded enamel oxygen and strontium ratios that are inconsistent with a Barbadian origin, which strongly suggests that we are dealing with first-generation captives who were brought to the island with the slave trade. This idea is also supported by the fact that their carbon and nitrogen stable isotope values differ markedly between their teeth and bones. These intra-skeletal shifts reflect major dietary changes that probably coincided with their enslavement and forced migration to Barbados. While it is impossible to determine their exact origins, the results clearly demonstrate that the slaves did not all grow up in the same part of Africa. Instead, the data seem to suggest that they originated from at least three different areas, possibly including the Gold Coast and the Senegambia.

Method for correcting for isotope burn-in effects in fission neutron dosimeters

DOEpatents

Gold, Raymond; McElroy, William N.

1988-01-01

A method is described for correcting for effect of isotope burn-in in fission neutron dosimeters. Two quantities are measured in order to quantify the "burn-in" contribution, namely P.sub.Z',A', the amount of (Z', A') isotope that is burned-in, and F.sub.Z', A', the fissions per unit volume produced in the (Z', A') isotope. To measure P.sub.Z', A', two solid state track recorder fission deposits are prepared from the very same material that comprises the fission neutron dosimeter, and the mass and mass density are measured. One of these deposits is exposed along with the fission neutron dosimeter, whereas the second deposit is subsequently used for observation of background. P.sub.Z', A' is then determined by conducting a second irradiation, wherein both the irradiated and unirradiated fission deposits are used in solid state track recorder dosimeters for observation of the absolute number of fissions per unit volume. The difference between the latter determines P.sub.Z', A' since the thermal neutron cross section is known. F.sub.Z', A' is obtained by using a fission neutron dosimeter for this specific isotope, which is exposed along with the original threshold fission neutron dosimeter to experience the same neutron flux-time history at the same location. In order to determine the fissions per unit volume produced in the isotope (Z', A') as it ingrows during the irradiation, B.sub.Z', A', from these observations, the neutron field must generally be either time independent or a separable function of time t and neutron energy E.

Isotope (δ13C, δ15N, δ2H) diet-tissue discrimination in African grey parrot Psittacus erithacus: implications for forensic studies.

PubMed

Symes, Craig; Skhosana, Felix; Butler, Mike; Gardner, Brett; Woodborne, Stephan

2017-12-01

Diet-tissue isotopic relationships established under controlled conditions are informative for determining the dietary sources and geographic provenance of organisms. We analysed δ 13 C, δ 15 N, and non-exchangeable δ 2 H values of captive African grey parrot Psittacus erithacus feathers grown on a fixed mixed-diet and borehole water. Diet-feather Δ 13 C and Δ 15 N discrimination values were +3.8 ± 0.3 ‰ and +6.3 ± 0.7 ‰ respectively; significantly greater than expected. Non-exchangeable δ 2 H feather values (-62.4 ± 6.4 ‰) were more negative than water (-26.1 ± 2.5 ‰) offered during feather growth. There was no positive relationship between the δ 13 C and δ 15 N values of the samples along each feather with the associated samples of food offered, or the feather non-exchangeable hydrogen isotope values with δ 2 H values of water, emphasising the complex processes involved in carbohydrate, protein, and income water routing to feather growth. Understanding the isotopic relationship between diet and feathers may provide greater clarity in the use of stable isotopes in feathers as a tool in determining origins of captive and wild-caught African grey parrots, a species that is widespread in aviculture and faces significant threats to wild populations. We suggest that these isotopic results, determined even in controlled laboratory conditions, be used with caution.

Detection of testosterone administration based on the carbon isotope ratio profiling of endogenous steroids: international reference populations of professional soccer players.

PubMed

Strahm, E; Emery, C; Saugy, M; Dvorak, J; Saudan, C

2009-12-01

The determination of the carbon isotope ratio in androgen metabolites has been previously shown to be a reliable, direct method to detect testosterone misuse in the context of antidoping testing. Here, the variability in the 13C/12C ratios in urinary steroids in a widely heterogeneous cohort of professional soccer players residing in different countries (Argentina, Italy, Japan, South Africa, Switzerland and Uganda) is examined. Carbon isotope ratios of selected androgens in urine specimens were determined using gas chromatography/combustion/isotope ratio mass spectrometry (GC-C-IRMS). Urinary steroids in Italian and Swiss populations were found to be enriched in 13C relative to other groups, reflecting higher consumption of C3 plants in these two countries. Importantly, detection criteria based on the difference in the carbon isotope ratio of androsterone and pregnanediol for each population were found to be well below the established threshold value for positive cases. The results obtained with the tested diet groups highlight the importance of adapting the criteria if one wishes to increase the sensitivity of exogenous testosterone detection. In addition, confirmatory tests might be rendered more efficient by combining isotope ratio mass spectrometry with refined interpretation criteria for positivity and subject-based profiling of steroids.

Fast chemical and isotopic exchange of nitrogen during reaction with hot molybdenum

NASA Astrophysics Data System (ADS)

Yokochi, Reika; Marty, Bernard

2006-07-01

Molybdenum crucibles are commonly used to extract nitrogen from geological samples by induction heating. Because nitrogen is known to be reactive with certain metals (e.g., Ti and Fe), we have tested the reactivity of gaseous nitrogen with a Mo crucible held at 1800°C. The consumption of nitrogen, determined by monitoring the N2/40Ar ratio of the gas phase, varied between 25 and 100%, depending on the reaction duration. Nitrogen of the reacted gas was found to be systematically enriched in 15N relative to 14N by 10‰ compared to the initial isotopic composition, without any correlation with nitrogen consumption. We propose that a rapid isotopic exchange occurs between nitrogen originally trapped in the crucible and nitrogen from the gas phase, which modifies the isotopic composition of the reacted gas. This process can significantly bias the isotopic determination of nitrogen in rocks and minerals when a Mo furnace is used for gas extraction. Meanwhile, the rate of N-Mo chemical bonding may be controlled by the formation of nitride (rather than solid solution), a process slower than the isotopic exchange. The use of a Mo furnace for the extraction of trace nitrogen from rocks and minerals should therefore be avoided.

Oxygen isotopes in nitrite: Analysis, calibration, and equilibration

USGS Publications Warehouse

Casciotti, K.L.; Böhlke, J.K.; McIlvin, M.R.; Mroczkowski, S.J.; Hannon, J.E.

2007-01-01

Nitrite is a central intermediate in the nitrogen cycle and can persist in significant concentrations in ocean waters, sediment pore waters, and terrestrial groundwaters. To fully interpret the effect of microbial processes on nitrate (NO3-), nitrite (NO2-), and nitrous oxide (N2O) cycling in these systems, the nitrite pool must be accessible to isotopic analysis. Furthermore, because nitrite interferes with most methods of nitrate isotopic analysis, accurate isotopic analysis of nitrite is essential for correct measurement of nitrate isotopes in a sample that contains nitrite. In this study, nitrite salts with varying oxygen isotopic compositions were prepared and calibrated and then used to test the denitrifier method for nitrite oxygen isotopic analysis. The oxygen isotopic fractionation during nitrite reduction to N2O by Pseudomonas aureofaciens was lower than for nitrate conversion to N2O, while oxygen isotopic exchange between nitrite and water during the reaction was similar. These results enable the extension of the denitrifier method to oxygen isotopic analysis of nitrite (in the absence of nitrate) and correction of nitrate isotopes for the presence of nitrite in “mixed” samples. We tested storage conditions for seawater and freshwater samples that contain nitrite and provide recommendations for accurate oxygen isotopic analysis of nitrite by any method. Finally, we report preliminary results on the equilibrium isotope effect between nitrite and water, which can play an important role in determining the oxygen isotopic value of nitrite where equilibration with water is significant.

Multi-isotope tracers to investigate processes in the Elbe, Weser and Ems river catchment using B, Mo, Sr, and Pb isotope ratios assessed by MC ICP-MS

NASA Astrophysics Data System (ADS)

Irrgeher, Johanna; Reese, Anna; Zimmermann, Tristan; Prohaska, Thomas; Retzmann, Anika; Wieser, Michael E.; Zitek, Andreas; Proefrock, Daniel

2017-04-01

Environmental monitoring of complex ecosystems requires reliable sensitive techniques based on sound analytical strategies to identify the source, fate and sink of elements and matter. Isotopic signatures can serve to trace pathways by making use of specific isotopic fingermarks or to distinguish between natural and anthropogenic sources. The presented work shows the potential of using the isotopic variation of Sr, Pb (as well-established isotopic systems), Mo and B (as novel isotopic system) assessed by MC ICP-MS in water and sediment samples to study aquatic ecosystem transport processes. The isotopic variation of Sr, Pb, Mo and B was determined in different marine and estuarine compartments covering the catchment of the German Wadden Sea and its main tributaries, the Elbe, Weser and Ems River. The varying elemental concentrations, the complex matrix and the expected small variations in the isotopic composition required the development and application of reliable analytical measurement approaches as well as suited metrological data evaluation strategies. Aquatic isoscapes were created using ArcGIS® by relating spatial isotopic data with geographical and geological maps. The elemental and isotopic distribution maps show large variation for different parameters and also reflect the numerous impact factors (e.g. geology, anthropogenic sources) influencing the catchment area.

New biotite and muscovite isotopic reference materials, USGS57 and USGS58, for δ2H measurements–A replacement for NBS 30

USGS Publications Warehouse

Qi, Haiping; Coplen, Tyler B.; Gehre, Matthias; Vennemann, Torsten W.; Brand, Willi A.; Geilmann, Heike; Olack, Gerard; Bindeman, Ilya N.; Palandri, Jim; Huang, Li; Longstaffe, Fred J.

2017-01-01

The advent of continuous-flow isotope-ratio mass spectrometry (CF-IRMS) coupled with a high temperature conversion (HTC) system enabled faster, more cost effective, and more precise δ2H analysis of hydrogen-bearing solids. Accurate hydrogen isotopic analysis by on-line or off-line techniques requires appropriate isotopic reference materials (RMs). A strategy of two-point calibrations spanning δ2H range of the unknowns using two RMs is recommended. Unfortunately, the supply of the previously widely used isotopic RM, NBS 30 biotite, is exhausted. In addition, recent measurements have shown that the determination of δ2H values of NBS 30 biotite on the VSMOW-SLAP isotope-delta scale by on-line HTC systems with CF-IRMS may be unreliable because hydrogen in this biotite may not be converted quantitatively to molecular hydrogen. The δ2HVSMOW-SLAP values of NBS 30 biotite analyzed by on-line HTC systems can be as much as 21 mUr (or ‰) too positive compared to the accepted value of − 65.7 mUr, determined by only a few conventional off-line measurements. To ensure accurate and traceable on-line hydrogen isotope-ratio determinations in mineral samples, we here propose two isotopically homogeneous, hydrous mineral RMs with well-characterized isotope-ratio values, which are urgently needed. The U.S. Geological Survey (USGS) has prepared two such RMs, USGS57 biotite and USGS58 muscovite. The δ2H values were determined by both glassy carbon-based on-line conversion and chromium-based on-line conversion, and results were confirmed by off-line conversion. The quantitative conversion of hydrogen from the two RMs using the on-line HTC method was carefully evaluated in this study. The isotopic compositions of these new RMs with 1-σ uncertainties and mass fractions of hydrogen are:USGS57 (biotite)δ2HVSMOW-SLAP = − 91.5 ± 2.4 mUr (n = 24)Mass fraction hydrogen = 0.416 ± 0.002% (n = 4)Mass fraction water = 3.74 ± 0.02% (n = 4)USGS58 (muscovite)δ2HVSMOW-SLAP = − 28.4 ± 1.6 mUr (n = 24)Mass fraction hydrogen = 0.448 ± 0.002% (n = 4)Mass fraction water = 4.03 ± 0.02% (n = 4).These δ2HVSMOW-SLAP values encompass typical ranges for solid unknowns of crustal and mantle origin and are available to users for recommended two-point calibration.

Reappraising Accretion to Vesta and the Angrite Parent Body Through Mineral-Scale Platinum Group Element and Os-Isotope Analyses

NASA Astrophysics Data System (ADS)

Riches, A. J. V.; Burton, K. W.; Nowell, G. M.; Dale, C. W.; Ottley, C. J.

2016-08-01

New methods presented here enable quantitative determination of mineral-scale PGE-abundances and Os-isotope compositions in meteorite materials thereby providing valuable new insight into planetary evolution.

Cr Isotopes in Allende Ca-Al-rich Inclusions

NASA Technical Reports Server (NTRS)

Bogdanovski, O.; Papanastassiou, D. A.; Wasserburg, G. J.

2002-01-01

We have determined Cr isotope compositions in minerals from Allende CAI in order to address the initial 53Mn (half-life 3.7 Ma) abundance in the solar system. Additional information is contained in the original extended abstract.

Isotope specific arbitrary material flow meter

DOEpatents

Barty, Christopher P. J.; Post, John C.; Jones, Edwin

2016-10-25

A laser-based mono-energetic gamma-ray source is used to provide non-destructive and non-intrusive, quantitative determination of the absolute amount of a specific isotope contained within pipe as part of a moving fluid or quasi-fluid material stream.

Using carbon isotope fractionation for an improved quantification of CH4 oxidation efficiency in Arctic peatlands

NASA Astrophysics Data System (ADS)

Preuss, I.; Knoblauch, C.; Gebert, J.; Pfeiffer, E.-M.

2012-04-01

Much research effort is focused on identifying global CH4 sources and sinks to estimate their current and potential strength in response to land-use change and global warming. Aerobic CH4 oxidation is regarded as the key process reducing the strength of CH4 emissions in wetlands, but is hitherto difficult to quantify. Recent studies quantify the efficiency of CH4 oxidation based on CH4 stable isotope signatures. The approach utilizes the fact that a significant isotope fractionation occurs when CH4 is oxidized. Moreover, it also considers isotope fractionation by diffusion. For field applications the 'open-system equation' is applied to determine the CH4 oxidation efficiency: fox = (δE - δP)/ (αox - αtrans) where fox is the fraction of CH4 oxidized; δE is δ13C of emitted CH4; δP is δ13C of produced CH4; αox is the isotopic fractionation factor of oxidation; αtrans is the isotopic fractionation factor of transport. We quantified CH4 oxidation in polygonal tundra soils of Russia's Lena River Delta analyzing depth profiles of CH4 concentrations and stable isotope signatures. Therefore, both fractionation factors αox and αtrans were determined for three polygon centers with differing water table positions and a polygon rim. While most previous studies on landfill cover soils have assumed a gas transport dominated by advection (αtrans = 1), other CH4 transport mechanisms as diffusion have to be considered in peatlands and αtrans exceeds a value of 1. At our study we determined αtrans = 1.013 ± 0.003 for CH4 when diffusion is the predominant transport mechanism. Furthermore, results showed that αox differs widely between sites and horizons (αox = 1.013 ± 0.012) and has to be determined for each case. The impact of both fractionation factors on the quantification of CH4 oxidation was estimated by considering both the potential diffusion rate at different water contents and potential oxidation rates. Calculations for a water saturated tundra soil indicated a CH4 oxidation efficiency of 88% in the upper horizon. Using carbon isotope fractionation improves the in situ quantification of CH4 oxidation in wetlands and thus the assessment of current and potential CH4 sources and sinks in these ecosystems.

Natural abundances of carbon isotopes in acetate from a coastal marine sediment

NASA Technical Reports Server (NTRS)

Blair, N. E.; Martens, C. S.; Des Marais, D. J.

1987-01-01

Measurements of the natural abundances of carbon isotopes were made in acetate samples isolated from the anoxic marine sediment of Cape Lookout Bight, North Carolina. The typical value of the total acetate carbon isotope ratio (delta 13C) was -16.1 +/- 0.2 per mil. The methyl and carboxyl groups were determined to be -26.4 +/- 0.3 and -6.0 +/- 0.3 per mil, respectively, for one sample. The isotopic composition of the acetate is thought to have resulted from isotopic discriminations that occurred during the cycling of that molecule. Measurements of this type, which have not been made previously in the natural environment, may provide information about the dominant microbial pathways in anoxic sediments as well as the processes that influence the carbon isotopic composition of biogenic methane from many sources.

Evaluation of UV-fs-LA-MC-ICP-MS for precise in situ copper isotopic microanalysis of cubanite.

PubMed

Ikehata, Kei; Hirata, Takafumi

2013-01-01

We evaluated the capabilities of an in situ method for measuring copper isotopes of cubanite using UV-fs-LA-MC-ICP-MS. A comparison of the UV-fs laser results with those obtained from the NIR-fs laser system shows that there is obviously an improvement in the precision (<0.10‰, 2SE) when using the UV-fs laser. In both wavelength modes, matrix-matched standards are required for reliable in situ copper isotope analysis of cubanite. This method was applied to determinations for copper isotopes of minute cubanite grains in a skarn ore. Copper isotopic ratios of cubanite grains near a weathered surface of the sample are lower than those of intact cubanite grains within the sample, suggesting that selective leaching of heavier copper isotope in primary minerals occurred during weathering.

Hunted gazelles evidence cooling, but not drying, during the Younger Dryas in the southern Levant

NASA Astrophysics Data System (ADS)

Hartman, Gideon; Bar-Yosef, Ofer; Brittingham, Alex; Grosman, Leore; Munro, Natalie D.

2016-04-01

The climatic downturn known globally as the Younger Dryas (YD; ∼12,900-11,500 BP) has frequently been cited as a prime mover of agricultural origins and has thus inspired enthusiastic debate over its local impact. This study presents seasonal climatic data from the southern Levant obtained from the sequential sampling of gazelle tooth carbonates from the Early and Late Natufian archaeological sites of Hayonim and Hilazon Tachtit Caves (western Galilee, Israel). Our results challenge the entrenched model that assumes that warm temperatures and high precipitation are synonymous with climatic amelioration and cold and wet conditions are combined in climatic downturns. Enamel carbon isotope values from teeth of human-hunted gazelle dating before and during the YD provide a proxy measure for water availability during plant growth. They reveal that although the YD was cooler, it was not drier than the preceding Bølling-Allerød. In addition, the magnitude of the seasonal curve constructed from oxygen isotopes is significantly dampened during the YD, indicating that cooling was most pronounced in the growing season. Cool temperatures likely affected the productivity of staple wild cereal resources. We hypothesize that human groups responded by shifting settlement strategies-increasing population mobility and perhaps moving to the warmer Jordan Valley where wild cereals were more productive and stable.

Expert system for online surveillance of nuclear reactor coolant pumps

DOEpatents

Gross, Kenny C.; Singer, Ralph M.; Humenik, Keith E.

1993-01-01

An expert system for online surveillance of nuclear reactor coolant pumps. This system provides a means for early detection of pump or sensor degradation. Degradation is determined through the use of a statistical analysis technique, sequential probability ratio test, applied to information from several sensors which are responsive to differing physical parameters. The results of sequential testing of the data provide the operator with an early warning of possible sensor or pump failure.

Determination of uranium and thorium in materials associated with real time electronic solar neutrino detectors

NASA Astrophysics Data System (ADS)

Fassett, J. D.; Kelly, W. R.

1992-07-01

The application of isotope dilution thermal ionization mass spectrometry to the determination of both uranium and thorium in four different target materials used or proposed for electronic neutrino detectors is described. Isotope dilution analysis is done using highly enriched 233U and 230Th separated isotopes. Sensitivity of the technique is such that sub-picogram amounts of material are readily measured. The overall limit to measurement is caused by contamination of these elements during the measurement process. Uranium is more easily measured than thorium because both the instrumental sensitivity is higher and contamination is better controlled. The materials analyzed were light and heavy water, pseudocumene, and mineral oil.

Microscale determination of the spectral characteristics and carbon-isotopic compositions of porphyrins

NASA Technical Reports Server (NTRS)

Popp, B. N.; Hayes, J. M.; Boreham, C. J.

1993-01-01

Molar extinction coefficients for band III of Ni porphyrins are calculated from results of spectrophotometric and manometric analyses of individual etioporphyrins, DPEP, cyclic, and diDPEP porphyrins known to initially be pure from mass spectrometry, 1H NMR, and analytical HPLC studies. A method for determining carbon-isotopic compositions and purity of micromolar quantities of individual porphyrins using combined spectrophotometric and manometric techniques is presented.

Measuring the radium quartet (228Ra, 226Ra, 224Ra, 223Ra) in seawater samples using gamma spectrometry.

PubMed

van Beek, P; Souhaut, M; Reyss, J-L

2010-07-01

Radium isotopes are widely used in marine studies (eg. to trace water masses, to quantify mixing processes or to study submarine groundwater discharge). While 228Ra and 226Ra are usually measured using gamma spectrometry, short-lived Ra isotopes (224Ra and 223Ra) are usually measured using a Radium Delayed Coincidence Counter (RaDeCC). Here we show that the four radium isotopes can be analyzed using gamma spectrometry. We report 226Ra, 228Ra, 224Ra, 223Ra activities measured using low-background gamma spectrometry in standard samples, in water samples collected in the vicinity of our laboratory (La Palme and Vaccarès lagoons, France) but also in seawater samples collected in the plume of the Amazon river, off French Guyana (AMANDES project). The 223Ra and 224Ra activities determined in these samples using gamma spectrometry were compared to the activities determined using RaDeCC. Activities determined using the two techniques are in good agreement. Uncertainties associated with the 224Ra activities are similar for the two techniques. RaDeCC is more sensitive for the detection of low 223Ra activities. Gamma spectrometry thus constitutes an alternate method for the determination of short-lived Ra isotopes. 2009 Elsevier Ltd. All rights reserved.

Determination of (187)Os in molybdenite by ICP-MS with neutron-induced (186)Os and (188)Os spikes.

PubMed

Qu, W; Du, A; Zhao, D

2001-10-31

The article describes a method for the determination of (187)Os in molybdenite by isotope dilution inductively coupled plasma-mass spectrometry (ID-ICP-MS) with neutron-induced (186)Os and (188)Os spike. The spike used in the present work was prepared in line with the principle by which artificial nuclides are produced in a nuclear reaction. The concentration and isotopic composition of osmium in the prepared spike were evaluated accurately with the isotope dilution method, using negative thermal ion mass spectrometry (N-TIMS). The advantage of this method is that using (186)Os and (188)Os double spikes can effectively compensate for the mass discrimination effects of ICP-MS. Thus, the common correction practice for mass bias in the isotope dilution method with a single spike is unnecessary. In addition, the method enables one to reduce the determined error arising from instrumental instability. The precision for the (187)Os/((186)Os+(188)Os) ratio was approximately 2% (2sigma, RSD), but in the case of (187)Os/(186)Os, (187)Os/(188)Os and (186)Os/(188)Os, precision ranged from 2.0 to 8% (2sigma, RSD). The results for (187)Os concentration in a molybdenite sample determined with this method showed good agreement with reference values.

Determining synthesis rates of individual proteins in zebrafish (Danio rerio) with low levels of a stable isotope labelled amino acid.

PubMed

Geary, Bethany; Magee, Kieran; Cash, Phillip; Young, Iain S; Whitfield, Phillip D; Doherty, Mary K

2016-05-01

The zebrafish is a powerful model organism for the analysis of human cardiovascular development and disease. Understanding these processes at the protein level not only requires changes in protein concentration to be determined but also the rate at which these changes occur on a protein-by-protein basis. The ability to measure protein synthesis and degradation rates on a proteome-wide scale, using stable isotope labelling in conjunction with mass spectrometry is now a well-established experimental approach. With the advent of more selective and sensitive mass spectrometers, it is possible to accurately measure lower levels of stable isotope incorporation, even when sample is limited. In order to challenge the sensitivity of this approach, we successfully determined the synthesis rates of over 600 proteins from the cardiac muscle of the zebrafish using a diet where either 30% or 50% of the L-leucine was replaced with a stable isotope labelled analogue ([(2) H7 ]L-leucine]. It was possible to extract sufficient protein from individual zebrafish hearts to determine the incorporation rate of the label into hundreds of proteins simultaneously, with the two labelling regimens showing a good correlation of synthesis rates. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Identification of volatile and semivolatile compounds in chemical ionization GC-MS using a mass-to-structure (MTS) Search Engine with integral isotope pattern ranking.

PubMed

Liao, Wenta; Draper, William M

2013-02-21

The mass-to-structure or MTS Search Engine is an Access 2010 database containing theoretical molecular mass information for 19,438 compounds assembled from common sources such as the Merck Index, pesticide and pharmaceutical compilations, and chemical catalogues. This database, which contains no experimental mass spectral data, was developed as an aid to identification of compounds in atmospheric pressure ionization (API)-LC-MS. This paper describes a powerful upgrade to this database, a fully integrated utility for filtering or ranking candidates based on isotope ratios and patterns. The new MTS Search Engine is applied here to the identification of volatile and semivolatile compounds including pesticides, nitrosoamines and other pollutants. Methane and isobutane chemical ionization (CI) GC-MS spectra were obtained from unit mass resolution mass spectrometers to determine MH(+) masses and isotope ratios. Isotopes were measured accurately with errors of <4% and <6%, respectively, for A + 1 and A + 2 peaks. Deconvolution of interfering isotope clusters (e.g., M(+) and [M - H](+)) was required for accurate determination of the A + 1 isotope in halogenated compounds. Integrating the isotope data greatly improved the speed and accuracy of the database identifications. The database accurately identified unknowns from isobutane CI spectra in 100% of cases where as many as 40 candidates satisfied the mass tolerance. The paper describes the development and basic operation of the new MTS Search Engine and details performance testing with over 50 model compounds.

GasBench/isotope ratio mass spectrometry: a carbon isotope approach to detect exogenous CO(2) in sparkling drinks.

PubMed

Cabañero, Ana I; San-Hipólito, Tamar; Rupérez, Mercedes

2007-01-01

A new procedure for the determination of carbon dioxide (CO(2)) (13)C/(12)C isotope ratios, using direct injection into a GasBench/isotope ratio mass spectrometry (GasBench/IRMS) system, has been developed to improve isotopic methods devoted to the study of the authenticity of sparkling drinks. Thirty-nine commercial sparkling drink samples from various origins were analyzed. Values of delta(13)C(cava) ranged from -20.30 per thousand to -23.63 per thousand, when C3 sugar addition was performed for a second alcoholic fermentation. Values of delta(13)C(water) ranged from -5.59 per thousand to -6.87 per thousand in the case of naturally carbonated water or water fortified with gas from the spring, and delta(13)C(water) ranged from -29.36 per thousand to -42.09 per thousand when industrial CO(2) was added. It has been demonstrated that the addition of C4 sugar to semi-sparkling wine (aguja) and industrial CO(2) addition to sparkling wine (cava) or water can be detected. The new procedure has advantages over existing methods in terms of analysis time and sample treatment. In addition, it is the first isotopic method developed that allows (13)C/(12)C determination directly from a liquid sample without previous CO(2) extraction. No significant isotopic fractionation was observed nor any influence by secondary compounds present in the liquid phase. Copyright (c) 2007 John Wiley & Sons, Ltd.

Limits and possibilities in the geolocation of humans using multiple isotope ratios (H, O, N, C) of hair from east coast cities of the USA.

PubMed

Reynard, Linda M; Burt, Nicole; Koon, Hannah E C; Tuross, Noreen

2016-01-01

We examined multiple natural abundance isotope ratios of human hair to assess biological variability within and between geographic locations and, further, to determine how well these isotope values predict location of origin. Sampling locations feature differing seasonality and mobile populations as a robust test of the method. Serially-sampled hair from Cambridge, MA, USA, shows lower δ(2)H and δ(18)O variability over a one-year time course than model-predicted precipitation isotope ratios, but exhibits considerable differences between individuals. Along a ∼13° north-south transect in the eastern USA (Brookline, MA, 42.3 ° N, College Park, MD, 39.0 ° N, and Gainesville, FL, 29.7 ° N) δ(18)O in human hair shows relatively greater differences and tracks changes in drinking water isotope ratios more sensitively than δ(2)H. Determining the domicile of humans using isotope ratios of hair can be confounded by differing variability in hair δ(18)O and δ(2)H between locations, differential incorporation of H and O into this protein and, in some cases, by tap water δ(18)O and δ(2)H that differ significantly from predicted precipitation values. With these caveats, randomly chosen people in Florida are separated from those in the two more northerly sites on the basis of the natural abundance isotopes of carbon, nitrogen, hydrogen, and oxygen.

Thermal equilibration of iron meteorite and pallasite parent bodies recorded at the mineral scale by Fe and Ni isotope systematics

NASA Astrophysics Data System (ADS)

Chernonozhkin, Stepan M.; Weyrauch, Mona; Goderis, Steven; Oeser, Martin; McKibbin, Seann J.; Horn, Ingo; Hecht, Lutz; Weyer, Stefan; Claeys, Philippe; Vanhaecke, Frank

2017-11-01

In this work, a femtosecond laser ablation (LA) system coupled to a multi-collector inductively coupled plasma-mass spectrometer (fs-LA-MC-ICP-MS) was used to obtain laterally resolved (30-80 μm), high-precision combined Ni and Fe stable isotope ratio data for a variety of mineral phases (olivine, kamacite, taenite, schreibersite and troilite) composing main group pallasites (PMG) and iron meteorites. The stable isotopic signatures of Fe and Ni at the mineral scale, in combination with the factors governing the kinetic or equilibrium isotope fractionation processes, are used to interpret the thermal histories of small differentiated asteroidal bodies. As Fe isotopic zoning is only barely resolvable within the internal precision level of the isotope ratio measurements within a single olivine in Esquel PMG, the isotopically lighter olivine core relative to the rim (Δ56/54Ferim-core = 0.059‰) suggests that the olivines were largely thermally equilibrated. The observed hint of an isotopic and concentration gradient for Fe of crudely similar width is interpreted here to reflect Fe loss from olivine in the process of partial reduction of the olivine rim. The ranges of the determined Fe and Ni isotopic signatures of troilite (δ56/54Fe of -0.66 to -0.09‰) and schreibersite (δ56/54Fe of -0.48 to -0.09‰, and δ62/60Ni of -0.64 to +0.29‰) may result from thermal equilibration. Schreibersite and troilite likely remained in equilibrium with their enclosing metal to temperatures significantly below their point of crystallization. The Ni isotopic signatures of bulk metal and schreibersite correlate negatively, with isotopically lighter Ni in the metal of PMGs and isotopically heavier Ni in the metal of the iron meteorites analyzed. As such, the light Ni isotopic signatures previously observed in PMG metal relative to chondrites may not result from heterogeneity in the Solar Nebula, but rather reflect fractionation in the metal-schreibersite system. Comparison between the isotope ratio profiles of Fe and Ni determined across kamacite-taenite interfaces (Δ56/54Fekam-tae = -0.51 to -0.69‰ and Δ62/60Nikam-tae = +1.59 to +2.50‰) and theoretical taenite sub-solidus diffusive isotopic zoning broadly constrain the cooling rates of Esquel, CMS 04071 PMGs and Udei Station IAB to between ∼25 and 500 °C/Myr.

Ultrasensitive surveillance of sensors and processes

DOEpatents

Wegerich, Stephan W.; Jarman, Kristin K.; Gross, Kenneth C.

2001-01-01

A method and apparatus for monitoring a source of data for determining an operating state of a working system. The method includes determining a sensor (or source of data) arrangement associated with monitoring the source of data for a system, activating a method for performing a sequential probability ratio test if the data source includes a single data (sensor) source, activating a second method for performing a regression sequential possibility ratio testing procedure if the arrangement includes a pair of sensors (data sources) with signals which are linearly or non-linearly related; activating a third method for performing a bounded angle ratio test procedure if the sensor arrangement includes multiple sensors and utilizing at least one of the first, second and third methods to accumulate sensor signals and determining the operating state of the system.

Ultrasensitive surveillance of sensors and processes

DOEpatents

Wegerich, Stephan W.; Jarman, Kristin K.; Gross, Kenneth C.

1999-01-01

A method and apparatus for monitoring a source of data for determining an operating state of a working system. The method includes determining a sensor (or source of data) arrangement associated with monitoring the source of data for a system, activating a method for performing a sequential probability ratio test if the data source includes a single data (sensor) source, activating a second method for performing a regression sequential possibility ratio testing procedure if the arrangement includes a pair of sensors (data sources) with signals which are linearly or non-linearly related; activating a third method for performing a bounded angle ratio test procedure if the sensor arrangement includes multiple sensors and utilizing at least one of the first, second and third methods to accumulate sensor signals and determining the operating state of the system.

Diffusion of multi-isotopic chemical species in molten silicates

NASA Astrophysics Data System (ADS)

Watkins, James M.; Liang, Yan; Richter, Frank; Ryerson, Frederick J.; DePaolo, Donald J.

2014-08-01

Diffusion experiments in a simplified Na2O-CaO-SiO2 liquid system are used to develop a general formulation for the fractionation of Ca isotopes during liquid-phase diffusion. Although chemical diffusion is a well-studied process, the mathematical description of the effects of diffusion on the separate isotopes of a chemical element is surprisingly underdeveloped and uncertain. Kinetic theory predicts a mass dependence on isotopic mobility, but it is unknown how this translates into a mass dependence on effective binary diffusion coefficients, or more generally, the chemical diffusion coefficients that are housed in a multicomponent diffusion matrix. Our experiments are designed to measure Ca mobility, effective binary diffusion coefficients, the multicomponent diffusion matrix, and the effects of chemical diffusion on Ca isotopes in a liquid of single composition. We carried out two chemical diffusion experiments and one self-diffusion experiment, all at 1250 °C and 0.7 GPa and using a bulk composition for which other information is available from the literature. The self-diffusion experiment is used to determine the mobility of Ca in the absence of diffusive fluxes of other liquid components. The chemical diffusion experiments are designed to determine the effect on Ca isotope fractionation of changing the counter-diffusing component from fast-diffusing Na2O to slow-diffusing SiO2. When Na2O is the main counter-diffusing species, CaO diffusion is fast and larger Ca isotopic effects are generated. When SiO2 is the main counter-diffusing species, CaO diffusion is slow and smaller Ca isotopic effects are observed. In both experiments, the liquid is initially isotopically homogeneous, and during the experiment Ca isotopes become fractionated by diffusion. The results are used as a test of a new general expression for the diffusion of isotopes in a multicomponent liquid system that accounts for both self diffusion and the effects of counter-diffusing species. Our results show that (1) diffusive isotopic fractionations depend on the direction of diffusion in composition space, (2) diffusive isotopic fractionations scale with effective binary diffusion coefficient, as previously noted by Watkins et al. (2011), (3) self-diffusion is not decoupled from chemical diffusion, (4) self diffusion can be faster than or slower than chemical diffusion and (5) off-diagonal terms in the chemical diffusion matrix have isotopic mass-dependence. The results imply that relatively large isotopic fractionations can be generated by multicomponent diffusion even in the absence of large concentration gradients of the diffusing element. The new formulations for isotope diffusion can be tested with further experimentation and provide an improved framework for interpreting mass-dependent isotopic variations in natural liquids.

Paleoclimate Reconstruction at Lamanai, Belize Using Oxygen-Isotope Tropical Dendrochronology

NASA Astrophysics Data System (ADS)

Prentice, A.; Webb, E. A.; White, C. D.; Graham, E.

2009-05-01

Tropical dendrochronology can be complicated because many trees growing in these areas lack distinct visible annual rings. However, the oxygen-isotope composition of wood growing in tropical regions can provide a record of seasonal fluctuations in the amount of precipitation even when visible rings are absent. Variations in the oxygen-isotope compositions of cellulose as the trees grow can be related to the relative timing of wet and dry seasons and used to identify periods of drought. In this study, the oxygen-isotope composition was determined for cellulose extracted from living trees at the site of Lamanai, Belize to assess the variation in oxygen-isotope values that result from heterogeneity within individual tree rings and seasonal fluctuations in amount of precipitation. In temperate regions, the latewood rings that form during periods of reduced growth are traditionally selected for oxygen-isotope analysis of cellulose because their oxygen-isotope compositions are more directly influenced by climate and precipitation during the growing season. However, in tropical isotope dendrochronology, when visible rings are present, detailed sampling of both the light coloured earlywood and the denser latewood is required. At Lamanai, a seasonal signal was evident in the oxygen- isotope composition of the cellulose when tree rings were sectioned in very small increments (approximately every mm), sub-sampling both earlywood and latewood. However, the visible rings did not always correspond with minimum or maximum oxygen-isotope values. As a result, the amplitude of the oxygen-isotope signal obtained by considering only latewood samples is smaller than that obtained from fine-increment sampling. Hence, the oxygen-isotope values of latewood samples alone did not provide accurate data for climate reconstruction. Multiple series of latewood samples extracted from different cross-sections of the same tree did not consistently show the same trends in oxygen isotope values, which can differ by up to 2 permil around the circumference of the same ring. This indicates that even when visible rings are present in tropical trees, the rings may not be annual or continuous. However, the amplitude of variation in the oxygen-isotope values of cellulose from both early and latewood can be related to seasonal signals across the modern tree rings. These signals will be compared to the oxygen-isotope composition of tree ring cellulose extracted from a wood sample excavated from an ancient tomb at the site of Lamanai to assess the preservation of the cellulose- isotope signal in this artefact. If similar oxygen-isotope patterns are preserved in ancient cellulose they can be used as a proxy to determine past climate conditions, such as those experienced by the ancient Maya populations in Belize.

Cerium and Neodymium Isotope Fractionation in Geochemical Samples

NASA Astrophysics Data System (ADS)

Ohno, T.; Ishibashi, T.

2014-12-01

The study of naturally occurring isotopic variations of rare earth elements (REE) has a potentially significant influence in geochemical research fields with other traditional studies of REE. One of the key features of REE are their chemical similarities and gradual changes of ionic radius, which may make the isotopic variation of REE a potential tool to understand the mechanisms of isotopic fractionation in nature. Among the REE, geochemical and physicochemical features of Ce could be anomalous, because Ce could be present as the tetravalent (+IV) state as well as the common trivalent (+III) state of other REE. Since the oxidation state of Ce can change by reflecting the redox conditions of the environment, the measured differences in the degree of isotopic fractionation between Ce and other REE can provide unique information about the redox conditions. In this study, we developed a new analytical method to determine the mass-dependent isotopic fractionations of Ce and Nd in geochemical samples. The reproducibility of the isotopic ratio measurements on 142Ce/140Ce, 146Nd/144Nd and 148Nd/144Nd were 0.08‰ (2SD, n=25), 0.06‰ (2SD, n=39) and 0.12‰ (2SD, n=39), respectively. The present technique was applied to determine the variations of the Ce and Nd isotopic ratios for five geochemical reference materials (igneous rocks, JB-1a and JA-2; sedimentary rocks, JMn-1, JCh-1 and JDo-1). The resulting ratios for two igneous rocks (JB-1a and JA-2) and two sedimentary rocks (JMn-1 and JCh-1) did not vary significantly among the samples, whereas the Ce and Nd isotope ratios for the carbonate samples (JDo-1) were significantly higher than those for igneous and sedimentary rock samples. The 1:1 simple correlation between δ142Ce and δ146Nd indicates that there were no significant difference in the degree of isotopic fractionation between the Ce and Nd. This suggests that the isotopic fractionation for Ce found in the JDo-1 could be induced by physicochemical processes without changing the oxidation status of Ce, since the redox-reaction can produce larger isotopic fractionation than the reactions without changing the oxidation state. The variations in the Ce and Nd isotope ratios for geochemical samples could provide new information concerning the physico-chemical processes of the sample formation.

The subtyping of primary aldosteronism by adrenal vein sampling: sequential blood sampling causes factitious lateralization.

PubMed

Rossitto, Giacomo; Battistel, Michele; Barbiero, Giulio; Bisogni, Valeria; Maiolino, Giuseppe; Diego, Miotto; Seccia, Teresa M; Rossi, Gian Paolo

2018-02-01

The pulsatile secretion of adrenocortical hormones and a stress reaction occurring when starting adrenal vein sampling (AVS) can affect the selectivity and also the assessment of lateralization when sequential blood sampling is used. We therefore tested the hypothesis that a simulated sequential blood sampling could decrease the diagnostic accuracy of lateralization index for identification of aldosterone-producing adenoma (APA), as compared with bilaterally simultaneous AVS. In 138 consecutive patients who underwent subtyping of primary aldosteronism, we compared the results obtained simultaneously bilaterally when starting AVS (t-15) and 15 min after (t0), with those gained with a simulated sequential right-to-left AVS technique (R ⇒ L) created by combining hormonal values obtained at t-15 and at t0. The concordance between simultaneously obtained values at t-15 and t0, and between simultaneously obtained values and values gained with a sequential R ⇒ L technique, was also assessed. We found a marked interindividual variability of lateralization index values in the patients with bilaterally selective AVS at both time point. However, overall the lateralization index simultaneously determined at t0 provided a more accurate identification of APA than the simulated sequential lateralization indexR ⇒ L (P = 0.001). Moreover, regardless of which side was sampled first, the sequential AVS technique induced a sequence-dependent overestimation of lateralization index. While in APA patients the concordance between simultaneous AVS at t0 and t-15 and between simultaneous t0 and sequential technique was moderate-to-good (K = 0.55 and 0.66, respectively), in non-APA patients, it was poor (K = 0.12 and 0.13, respectively). Sequential AVS generates factitious between-sides gradients, which lower its diagnostic accuracy, likely because of the stress reaction arising upon starting AVS.

The relation between isotopic composition of argon and carbon in natural gases

NASA Technical Reports Server (NTRS)

Gavrilov, Y. Y.; Zhurov, Y. A.; Teplinskiy, G. I.

1977-01-01

The methods and results of determination of the argon and carbon isotope compositions of hydrocarbon gases of Mezozoic complexes of Western Siberia are presented. Based on the Ar-36, Ar-40, C-12, C-13 content of the various deposits and on the presumed mechanisms of entry of these isotopes into the deposits, it is concluded that formation of natural gas in some deposits included vertical migration from a lower complex.

Sulfate and sulfide sulfur isotopes (δ34S and δ33S) measured by solution and laser ablation MC-ICP-MS: An enhanced approach using external correction

USGS Publications Warehouse

Pribil, Michael; Ridley, William I.; Emsbo, Poul

2015-01-01

Isotope ratio measurements using a multi-collector inductively coupled plasma mass spectrometer (MC-ICP-MS) commonly use standard-sample bracketing with a single isotope standard for mass bias correction for elements with narrow-range isotope systems measured by MC-ICP-MS, e.g. Cu, Fe, Zn, and Hg. However, sulfur (S) isotopic composition (δ34S) in nature can range from at least − 40 to + 40‰, potentially exceeding the ability of standard-sample bracketing using a single sulfur isotope standard to accurately correct for mass bias. Isotopic fractionation via solution and laser ablation introduction was determined during sulfate sulfur (Ssulfate) isotope measurements. An external isotope calibration curve was constructed using in-house and National Institute of Standards and Technology (NIST) Ssulfate isotope reference materials (RM) in an attempt to correct for the difference. The ability of external isotope correction for Ssulfate isotope measurements was evaluated by analyzing NIST and United States Geological Survey (USGS) Ssulfate isotope reference materials as unknowns. Differences in δ34Ssulfate between standard-sample bracketing and standard-sample bracketing with external isotope correction for sulfate samples ranged from 0.72‰ to 2.35‰ over a δ34S range of 1.40‰ to 21.17‰. No isotopic differences were observed when analyzing Ssulfide reference materials over a δ34Ssulfide range of − 32.1‰ to 17.3‰ and a δ33S range of − 16.5‰ to 8.9‰ via laser ablation (LA)-MC-ICP-MS. Here, we identify a possible plasma induced fractionation for Ssulfate and describe a new method using external isotope calibration corrections using solution and LA-MC-ICP-MS.

Calcium isotope analysis by mass spectrometry.

PubMed

Boulyga, Sergei F

2010-01-01

The variations in the isotopic composition of calcium caused by fractionation in heterogeneous systems and by nuclear reactions can provide insight into numerous biological, geological, and cosmic processes, and therefore isotopic analysis finds a wide spectrum of applications in cosmo- and geochemistry, paleoclimatic, nutritional, and biomedical studies. The measurement of calcium isotopic abundances in natural samples has challenged the analysts for more than three decades. Practically all Ca isotopes suffer from significant isobaric interferences, whereas low-abundant isotopes can be particularly affected by neighboring major isotopes. The extent of natural variations of stable isotopes appears to be relatively limited, and highly precise techniques are required to resolve isotopic effects. Isotope fractionation during sample preparation and measurements and instrumental mass bias can significantly exceed small isotope abundance variations in samples, which have to be investigated. Not surprisingly, a TIMS procedure developed by Russell et al. (Russell et al., 1978. Geochim Cosmochim Acta 42: 1075-1090) for Ca isotope measurements was considered as revolutionary for isotopic measurements in general, and that approach is used nowadays (with small modifications) for practically all isotopic systems and with different mass spectrometric techniques. Nevertheless, despite several decades of calcium research and corresponding development of mass spectrometers, the available precision and accuracy is still not always sufficient to achieve the challenging goals. The present article discusses figures of merits of presently used analytical methods and instrumentation, and attempts to critically assess their limitations. In Sections 2 and 3, mass spectrometric methods applied to precise stable isotope analysis and to the determination of (41)Ca are described. Section 4 contains a short summary of selected applications, and includes tracer experiments and the potential use of biological isotope fractionation in medical studies, paleoclimatic and paleoceanographic, and other terrestrial as well as extraterrestrial investigations. 2009 Wiley Periodicals, Inc.

Electron Scattering from MERCURY-198 and Mercury -204.

NASA Astrophysics Data System (ADS)

Laksanaboonsong, Jarungsaeng

This experiment is the first electron scattering study on mercury isotopes. Electron scattering from ^{198}Hg and ^{204 }Hg has been performed at the NIKHEF-K Medium Energy Accelerator. Measured cross sections cover an effective momentum transfer range from 0.4 to 2.9 fm^ {-1}. Elastic cross sections were determined for scattering from both isotopes. Cross section for inelastic excitations in ^{198}Hg below 3 MeV were also determined. Measured cross sections were fit using DWBA phase shift codes to determine coefficients for Fourier-Bessel expansions of ground state and transition charge densities. Differences between the ground state charge densities of the two isotopes reveal the effect of the polarization of the proton core in response to the addition of neutrons. Spin and parity of several excited states of ^{198}Hg were determined. Extracted transition densities of these states show their predominantly collective nature. Charge densities for members of the ground state rotational band were compared with axially symmetric Hartree-Fock and geometrical model predictions.

Improved solution accuracy for Landsat-4 (TDRSS-user) orbit determination

NASA Technical Reports Server (NTRS)

Oza, D. H.; Niklewski, D. J.; Doll, C. E.; Mistretta, G. D.; Hart, R. C.

1994-01-01

This paper presents the results of a study to compare the orbit determination accuracy for a Tracking and Data Relay Satellite System (TDRSS) user spacecraft, Landsat-4, obtained using a Prototype Filter Smoother (PFS), with the accuracy of an established batch-least-squares system, the Goddard Trajectory Determination System (GTDS). The results of Landsat-4 orbit determination will provide useful experience for the Earth Observing System (EOS) series of satellites. The Landsat-4 ephemerides were estimated for the January 17-23, 1991, timeframe, during which intensive TDRSS tracking data for Landsat-4 were available. Independent assessments were made of the consistencies (overlap comparisons for the batch case and convariances for the sequential case) of solutions produced by the batch and sequential methods. The filtered and smoothed PFS orbit solutions were compared with the definitive GTDS orbit solutions for Landsat-4; the solution differences were generally less than 15 meters.

DANCEing with the Stars: Measuring Neutron Capture on Unstable Isotopes with DANCE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Couture, A.; Bond, E.; Bredeweg, T. A.

2009-03-10

Isotopes heavier than iron are known to be produced in stars through neutron capture processes. Two major processes, the slow (s) and rapid (r) processes are each responsible for 50% of the abundances of the heavy isotopes. The neutron capture cross sections of the isotopes on the s process path reveal information about the expected abundances of the elements as well as stellar conditions and dynamics. Until recently, measurements on unstable isotopes, which are most important for determining stellar temperatures and reaction flow, have not been experimentally feasible. The Detector for Advance Neutron Capture Experiments (DANCE) located at the Losmore » Alamos Neutron Science Center (LANSCE) was designed to perform time-of-flight neutron capture measurements on unstable isotopes for nuclear astrophysics, stockpile stewardship, and reactor development. DANCE is a 4-{pi}BaF{sub 2} scintillator array which can perform measurements on sub-milligram samples of isotopes with half-lives as short as a few hundred days. These cross sections are critical for advancing our understanding of the production of the heavy isotopes.« less

Optimization of a novel sequential alkalic and metal salt pretreatment for enhanced delignification and enzymatic saccharification of corn cobs.

PubMed

Sewsynker-Sukai, Yeshona; Gueguim Kana, E B

2017-11-01

This study presents a sequential sodium phosphate dodecahydrate (Na 3 PO 4 ·12H 2 O) and zinc chloride (ZnCl 2 ) pretreatment to enhance delignification and enzymatic saccharification of corn cobs. The effects of process parameters of Na 3 PO 4 ·12H 2 O concentration (5-15%), ZnCl 2 concentration (1-5%) and solid to liquid ratio (5-15%) on reducing sugar yield from corn cobs were investigated. The sequential pretreatment model was developed and optimized with a high coefficient of determination value (0.94). Maximum reducing sugar yield of 1.10±0.01g/g was obtained with 14.02% Na 3 PO 4 ·12H 2 O, 3.65% ZnCl 2 and 5% solid to liquid ratio. Scanning electron microscopy (SEM) and Fourier Transform Infrared analysis (FTIR) showed major lignocellulosic structural changes after the optimized sequential pretreatment with 63.61% delignification. In addition, a 10-fold increase in the sugar yield was observed compared to previous reports on the same substrate. This sequential pretreatment strategy was efficient for enhancing enzymatic saccharification of corn cobs. Copyright © 2017 Elsevier Ltd. All rights reserved.

Classification and Sequential Pattern Analysis for Improving Managerial Efficiency and Providing Better Medical Service in Public Healthcare Centers

PubMed Central

Chung, Sukhoon; Rhee, Hyunsill; Suh, Yongmoo

2010-01-01

Objectives This study sought to find answers to the following questions: 1) Can we predict whether a patient will revisit a healthcare center? 2) Can we anticipate diseases of patients who revisit the center? Methods For the first question, we applied 5 classification algorithms (decision tree, artificial neural network, logistic regression, Bayesian networks, and Naïve Bayes) and the stacking-bagging method for building classification models. To solve the second question, we performed sequential pattern analysis. Results We determined: 1) In general, the most influential variables which impact whether a patient of a public healthcare center will revisit it or not are personal burden, insurance bill, period of prescription, age, systolic pressure, name of disease, and postal code. 2) The best plain classification model is dependent on the dataset. 3) Based on average of classification accuracy, the proposed stacking-bagging method outperformed all traditional classification models and our sequential pattern analysis revealed 16 sequential patterns. Conclusions Classification models and sequential patterns can help public healthcare centers plan and implement healthcare service programs and businesses that are more appropriate to local residents, encouraging them to revisit public health centers. PMID:21818426

[Sequential sampling plans to Orthezia praelonga Douglas (Hemiptera: Sternorrhyncha, Ortheziidae) in citrus].

PubMed

Costa, Marilia G; Barbosa, José C; Yamamoto, Pedro T

2007-01-01

The sequential sampling is characterized by using samples of variable sizes, and has the advantage of reducing sampling time and costs if compared to fixed-size sampling. To introduce an adequate management for orthezia, sequential sampling plans were developed for orchards under low and high infestation. Data were collected in Matão, SP, in commercial stands of the orange variety 'Pêra Rio', at five, nine and 15 years of age. Twenty samplings were performed in the whole area of each stand by observing the presence or absence of scales on plants, being plots comprised of ten plants. After observing that in all of the three stands the scale population was distributed according to the contagious model, fitting the Negative Binomial Distribution in most samplings, two sequential sampling plans were constructed according to the Sequential Likelihood Ratio Test (SLRT). To construct these plans an economic threshold of 2% was adopted and the type I and II error probabilities were fixed in alpha = beta = 0.10. Results showed that the maximum numbers of samples expected to determine control need were 172 and 76 samples for stands with low and high infestation, respectively.

Better together: reduced compliance after sequential versus simultaneous bilateral hearing aids fitting.

PubMed

Lavie, Limor; Banai, Karen; Attias, Joseph; Karni, Avi

2014-03-01

The purpose of this study was to determine the effects of sequential versus simultaneous bilateral hearing aids fitting on patient compliance. Thirty-six older adults with hearing impairment participated in this study. Twelve were fitted with bilateral hearing aids simultaneously. The remaining participants were fitted sequentially: One hearing aid (to the left or to the right ear) was used initially; 1 month later, the other ear was also fitted with a hearing aid for bilateral use. Self-reports on usefulness and compliance were elicited after the first and second months of hearing aid use. In addition, the number of hours the hearing aids were used was extracted from the data loggings of each device. Simultaneous fitting resulted in high levels of compliance and consistent usage throughout the study period. Sequential fitting resulted in abrupt reduction in compliance and hours of use once the second hearing aid was added, both in the clinical scoring and in the data loggings. Simultaneous fitting of bilateral hearing aids results in better compliance compared with sequential fitting. The addition of a second hearing aid after a relatively short period of monaural use may lead to inconsistent use of both hearing aids.

Comparison of TOPEX/Poseidon orbit determination solutions obtained by the Goddard Space Flight Center Flight Dynamics Division and Precision Orbit Determination Teams

NASA Technical Reports Server (NTRS)

Doll, C.; Mistretta, G.; Hart, R.; Oza, D.; Cox, C.; Nemesure, M.; Bolvin, D.; Samii, Mina V.

1993-01-01

Orbit determination results are obtained by the Goddard Space Flight Center (GSFC) Flight Dynamics Division (FDD) using the Goddard Trajectory Determination System (GTDS) and a real-time extended Kalman filter estimation system to process Tracking Data and Relay Satellite (TDRS) System (TDRSS) measurements in support of the Ocean Topography Experiment (TOPEX)/Poseidon spacecraft navigation and health and safety operations. GTDS is the operational orbit determination system used by the FDD, and the extended Kalman fliter was implemented in an analysis prototype system, the Real-Time Orbit Determination System/Enhanced (RTOD/E). The Precision Orbit Determination (POD) team within the GSFC Space Geodesy Branch generates an independent set of high-accuracy trajectories to support the TOPEX/Poseidon scientific data. These latter solutions use the Geodynamics (GEODYN) orbit determination system with laser ranging tracking data. The TOPEX/Poseidon trajectories were estimated for the October 22 - November 1, 1992, timeframe, for which the latest preliminary POD results were available. Independent assessments were made of the consistencies of solutions produced by the batch and sequential methods. The batch cases were assessed using overlap comparisons, while the sequential cases were assessed with covariances and the first measurement residuals. The batch least-squares and forward-filtered RTOD/E orbit solutions were compared with the definitive POD orbit solutions. The solution differences were generally less than 10 meters (m) for the batch least squares and less than 18 m for the sequential estimation solutions. The differences among the POD, GTDS, and RTOD/E solutions can be traced to differences in modeling and tracking data types, which are being analyzed in detail.

The biogeochemical iron cycle and astrobiology

NASA Astrophysics Data System (ADS)

Schröder, Christian; Köhler, Inga; Muller, Francois L. L.; Chumakov, Aleksandr I.; Kupenko, Ilya; Rüffer, Rudolf; Kappler, Andreas

2016-12-01

Biogeochemistry investigates chemical cycles which influence or are influenced by biological activity. Astrobiology studies the origin, evolution and distribution of life in the universe. The biogeochemical Fe cycle has controlled major nutrient cycles such as the C cycle throughout geological time. Iron sulfide minerals may have provided energy and surfaces for the first pioneer organisms on Earth. Banded iron formations document the evolution of oxygenic photosynthesis. To assess the potential habitability of planets other than Earth one looks for water, an energy source and a C source. On Mars, for example, Fe minerals have provided evidence for the past presence of liquid water on its surface and would provide a viable energy source. Here we present Mössbauer spectroscopy investigations of Fe and C cycle interactions in both ancient and modern environments. Experiments to simulate the diagenesis of banded iron formations indicate that the formation of ferrous minerals depends on the amount of biomass buried with ferric precursors rather than on the atmospheric composition at the time of deposition. Mössbauer spectra further reveal the mutual stabilisation of Fe-organic matter complexes against mineral transformation and decay of organic matter into CO2. This corresponds to observations of a `rusty carbon sink' in modern sediments. The stabilisation of Fe-organic matter complexes may also aid transport of particulate Fe in the water column while having an adverse effect on the bioavailability of Fe. In the modern oxic ocean, Fe is insoluble and particulate Fe represents an important source. Collecting that particulate Fe yields small sample sizes that would pose a challenge for conventional Mössbauer experiments. We demonstrate that the unique properties of the beam used in synchrotron-based Mössbauer applications can be utilized for studying such samples effectively. Reactive Fe species often occur in amorphous or nanoparticulate form in the environment and are therefore difficult to study with standard mineralogical tools. Sequential extraction techniques are commonly used as proxies. We provide an example where Mössbauer spectroscopy can replace sequential extraction techniques where mineralogical information is sought. Where mineral separation is needed, for example in the investigation of Fe or S isotope fractionation, Mössbauer spectroscopy can help to optimize sequential extraction procedures. This can be employed in a large number of investigations of soils and sediments, potentially even for mineral separation to study Fe and S isotope fractionation in samples returned from Mars, which might reveal signatures of biological activity. When looking for the possibility of life outside Earth, Jupiter's icy moon Europa is one of the most exciting places. It may be just in reach for a Mössbauer spectrometer deployed by a future lander to study the red streak mineral deposits on its surface to look for clues about the composition of the ocean hidden under the moon's icy surface.

Enzymatic Kinetic Isotope Effects from First-Principles Path Sampling Calculations.

PubMed

Varga, Matthew J; Schwartz, Steven D

2016-04-12

In this study, we develop and test a method to determine the rate of particle transfer and kinetic isotope effects in enzymatic reactions, specifically yeast alcohol dehydrogenase (YADH), from first-principles. Transition path sampling (TPS) and normal mode centroid dynamics (CMD) are used to simulate these enzymatic reactions without knowledge of their reaction coordinates and with the inclusion of quantum effects, such as zero-point energy and tunneling, on the transferring particle. Though previous studies have used TPS to calculate reaction rate constants in various model and real systems, it has not been applied to a system as large as YADH. The calculated primary H/D kinetic isotope effect agrees with previously reported experimental results, within experimental error. The kinetic isotope effects calculated with this method correspond to the kinetic isotope effect of the transfer event itself. The results reported here show that the kinetic isotope effects calculated from first-principles, purely for barrier passage, can be used to predict experimental kinetic isotope effects in enzymatic systems.

Marine sulfur cycle constrained from isotope analysis of different forms of sulfur in the 3.2 Ga black shale (DXCL-DP) from Pilbara, Australia

NASA Astrophysics Data System (ADS)

Kobayashi, Y.; Yamaguchi, K. E.; Sakamoto, R.; Naraoka, H.; Kiyokawa, S.; Ikehara, M.; Ito, T.

2012-12-01

Co-evolution of early life and surface environment has been one of the most important events on Earth. Rise of atmospheric oxygen, or as known as GOE (Great Oxidation Event: e.g., Holland, 1994), has been widely believed to have occurred at around 2.4 billion years ago. But geological and geochemical evidence suggest possibility of much earlier (by hundreds of millions of years) existence of oxic atmosphere and oceans. In order to further investigate the mystery of biological and environmental evolution, we conducted continental drilling in northwestern Pilbara, Western. Australia, to obtain 3.2 billion-years-old least-metamorphosed drillcore black shale samples (DXCL-DP:Dixon Island - Cleaverville Drilling Project; Yamaguchi et al., 2009). Preliminary stable isotope analyses using these samples suggested that photosynthetic organisms produced organic matter (Hosoi et al., 2011), nitrogen fixing bacteria were intermittently active (Yamada et al., 2011), and sulfate-reducing bacteria were active in environment with a limited supply of sulfate (Sakamoto et al., 2011) in the 3.2 Ga ocean. Bulk S isotope compositions could only provide limited information on the biogeochemical cycling of sedimentary S, because it is normally present as different facies (acid-volatile sulfur: AVS, pyrite: FeS2, sulfate, organic sulfur: Sorg, and elemental sulfur: S0) that depend on physicochemical and biological conditions. Therefore, abundance and isotope ratios of these species possess very useful information on oceanic and diagenetic conditions such as redox state and microbiological activity. In order to constrain biogeochemical cycling of S in the 3.2 Ga ocean, we conducted sequential extraction analysis using the DXCL-DP black shales to obtain different S-bearing species and S isotopic analysis. Average S contents for each form of S-bearing species were: ΣS = 2.56 wt.%, AVS = 0.02 wt.%, pyrite = 1.61 wt.%, and sulfate = 0.57 wt%. Relationship between amounts of pyrite-S and organic C suggest presence of syngenetic pyrite (formed in water column) as well as diagenetic pyrite. Average S isotope compositions are: pyrite = 12.3±6.3 ‰, sulfate = 17.3 ± 7.1 ‰, and difference between them are up to as high as 16.8 ‰. These results show that depositional environment was probably close to the modern Black Sea, where sulfate-reducing bacteria are active in anaerobic water mass in semi-closed deep basin, with a limited supply of sulfate from the oxic surface ocean.

A fast and accurate online sequential learning algorithm for feedforward networks.

PubMed

Liang, Nan-Ying; Huang, Guang-Bin; Saratchandran, P; Sundararajan, N

2006-11-01

In this paper, we develop an online sequential learning algorithm for single hidden layer feedforward networks (SLFNs) with additive or radial basis function (RBF) hidden nodes in a unified framework. The algorithm is referred to as online sequential extreme learning machine (OS-ELM) and can learn data one-by-one or chunk-by-chunk (a block of data) with fixed or varying chunk size. The activation functions for additive nodes in OS-ELM can be any bounded nonconstant piecewise continuous functions and the activation functions for RBF nodes can be any integrable piecewise continuous functions. In OS-ELM, the parameters of hidden nodes (the input weights and biases of additive nodes or the centers and impact factors of RBF nodes) are randomly selected and the output weights are analytically determined based on the sequentially arriving data. The algorithm uses the ideas of ELM of Huang et al. developed for batch learning which has been shown to be extremely fast with generalization performance better than other batch training methods. Apart from selecting the number of hidden nodes, no other control parameters have to be manually chosen. Detailed performance comparison of OS-ELM is done with other popular sequential learning algorithms on benchmark problems drawn from the regression, classification and time series prediction areas. The results show that the OS-ELM is faster than the other sequential algorithms and produces better generalization performance.

Reaction Intermediates of Quinol Oxidation in a Photoactivatable System that Mimics Electron Transfer in the Cytochrome bc1 Complex

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cape, Jonathan L.; Bowman, Michael K.; Kramer, David M.

2005-03-30

Current competing models for the two-electron oxidation of quinol (QH{sub 2}) at the cytochrome bc{sub 1} complex and related complexes have different requirements for the reaction intermediate. At present, the intermediate species of the enzymatic oxidation process have not been observed or characterized, probably due to their transient nature. Here, we use a biomimetic oxidant, Ru(bpy){sub 2}(pbim)(PF6)2 (bpy = 2,2'-dipyridyl, pbim = 2-(2-benzimidazolate)pyridine) in an aprotic medium to probe the oxidation of the ubiquinol analogue, 2,3-dimethoxy-5-methyl-1,4-benzoquinol (UQH{sub 2}-0), an the plastoquinol analogue, trimethyl-1,4-benzoquinol (TMQH{sub 2}-0), using time-resolved and steady state spectroscopic techniques. This system qualitatively reproduces key features observed duringmore » ubiquinol oxidation by the mitochondrial cytochrome bc1 complex. Comparison of isotope dependent activation properties in the native and synthetic systems, as well as, analysis of the time-resolved direct-detection electron para magnetic resonance signals in the synthetic system allows us to conclude that: (1) the initial and rate-limiting step in quinol oxidation, both in the biological and biomimetic systems, involves electron and proton transfer, probably via a proton coupled electron transfer mechanism; (2) a neutral semiquinone intermediate is formed in the biomimetic system; and (3) oxidation of the QH*/QH{sub 2} couple for UQH{sub 2}-0, but not TMQH{sub 2}-0, exhibits a non-classical primary deuterium kinetic isotope effect on its Arrhenius activation energy ({Delta}G{sup TS}), where {Delta}G{sup TS} for the protiated form is larger than for the deuterated form. The same behavior is observed during steady state turnover of the cyt bc{sub 1} complex using ubiquinol, but not plastoquinol, as a substrate, leading to the conclusion that similar chemical pathways are involved in both systems. The synthetic system is an unambiguous n=1 electron acceptor and it is thus inferred that sequential oxidation of ubiquinol (by two sequential n=1 processes) is more rapid than a truly concerted (n=2) oxidation in the cyt bc{sub 1} complex.« less

Isotopic homogeneity of iron in the early solar nebula.

PubMed

Zhu, X K; Guo, Y; O'Nions, R K; Young, E D; Ash, R D

2001-07-19

The chemical and isotopic homogeneity of the early solar nebula, and the processes producing fractionation during its evolution, are central issues of cosmochemistry. Studies of the relative abundance variations of three or more isotopes of an element can in principle determine if the initial reservoir of material was a homogeneous mixture or if it contained several distinct sources of precursor material. For example, widespread anomalies observed in the oxygen isotopes of meteorites have been interpreted as resulting from the mixing of a solid phase that was enriched in 16O with a gas phase in which 16O was depleted, or as an isotopic 'memory' of Galactic evolution. In either case, these anomalies are regarded as strong evidence that the early solar nebula was not initially homogeneous. Here we present measurements of the relative abundances of three iron isotopes in meteoritic and terrestrial samples. We show that significant variations of iron isotopes exist in both terrestrial and extraterrestrial materials. But when plotted in a three-isotope diagram, all of the data for these Solar System materials fall on a single mass-fractionation line, showing that homogenization of iron isotopes occurred in the solar nebula before both planetesimal accretion and chondrule formation.

Selenium isotope fractionation during reduction by Fe(II)-Fe(III) hydroxide-sulfate (green rust)

USGS Publications Warehouse

Johnson, T.M.; Bullen, T.D.

2003-01-01

We have determined the extent of Se isotope fractionation induced by reduction of selenate by sulfate interlayered green rust (GRSO4), a Fe(II)-Fe(III) hydroxide-sulfate. This compound is known to reduce selenate to Se(0), and it is the only naturally relevant abiotic selenate reduction pathway documented to date. Se reduction reactions, when they occur in nature, greatly reduce Se mobility and bioavailability. Se stable isotope analysis shows promise as an indicator of Se reduction, and Se isotope fractionation by various Se reactions must be known in order to refine this tool. We measured the increase in the 80Se/76Se ratio of dissolved selenate as lighter isotopes were preferentially consumed during reduction by GRSO4. Six different experiments that used GRSO4 made by two methods, with varying solution compositions and pH, yielded identical isotopic fractionations. Regression of all the data yielded an instantaneous isotope fractionation of 7.36 ?? 0.24???. Selenate reduction by GRSO4 induces much greater isotopic fractionation than does bacterial selenate reduction. If selenate reduction by GRSO4 occurs in nature, it may be identifiable on the basis of its relatively large isotopic fractionation. ?? 2003 Elsevier Science Ltd.

Nitrogen isotopes suggest a change in nitrogen dynamics between the Late Pleistocene and modern time in Yukon, Canada

PubMed Central

Longstaffe, Fred J.; Zazula, Grant

2018-01-01

A magnificent repository of Late Pleistocene terrestrial megafauna fossils is contained in ice-rich loess deposits of Alaska and Yukon, collectively eastern Beringia. The stable carbon (δ13C) and nitrogen (δ15N) isotope compositions of bone collagen from these fossils are routinely used to determine paleodiet and reconstruct the paleoecosystem. This approach requires consideration of changes in C- and N-isotope dynamics over time and their effects on the terrestrial vegetation isotopic baseline. To test for such changes between the Late Pleistocene and modern time, we compared δ13C and δ15N for vegetation and bone collagen and structural carbonate of some modern, Yukon, arctic ground squirrels with vegetation and bones from Late Pleistocene fossil arctic ground squirrel nests preserved in Yukon loess deposits. The isotopic discrimination between arctic ground squirrel bone collagen and their diet was measured using modern samples, as were isotopic changes during plant decomposition; Over-wintering decomposition of typical vegetation following senescence resulted in a minor change (~0–1 ‰) in δ13C of modern Yukon grasses. A major change (~2–10 ‰) in δ15N was measured for decomposing Yukon grasses thinly covered by loess. As expected, the collagen-diet C-isotope discrimination measured for modern samples confirms that modern vegetation δ13C is a suitable proxy for the Late Pleistocene vegetation in Yukon Territory, after correction for the Suess effect. The N-isotope composition of vegetation from the fossil arctic ground squirrel nests, however, is determined to be ~2.8 ‰ higher than modern grasslands in the region, after correction for decomposition effects. This result suggests a change in N dynamics in this region between the Late Pleistocene and modern time. PMID:29447202

Carbon isotope analyses of n-alkanes released from rapid pyrolysis of oil asphaltenes in a closed system.

PubMed

Chen, Shasha; Jia, Wanglu; Peng, Ping'an

2016-08-15

Carbon isotope analysis of n-alkanes produced by the pyrolysis of oil asphaltenes is a useful tool for characterizing and correlating oil sources. Low-temperature (320-350°C) pyrolysis lasting 2-3 days is usually employed in such studies. Establishing a rapid pyrolysis method is necessary to reduce the time taken for the pretreatment process in isotope analyses. One asphaltene sample was pyrolyzed in sealed ampoules for different durations (60-120 s) at 610°C. The δ(13) C values of the pyrolysates were determined by gas chromatography/combustion/isotope ratio mass spectrometry (GC/C/IRMS). The molecular characteristics and isotopic signatures of the pyrolysates were investigated for the different pyrolysis durations and compared with results obtained using the normal pyrolysis method, to determine the optimum time interval. Several asphaltene samples derived from various sources were analyzed using this method. The asphaltene pyrolysates of each sample were similar to those obtained by the flash pyrolysis method on similar samples. However, the molecular characteristics of the pyrolysates obtained over durations longer than 90 s showed intensified secondary reactions. The carbon isotopic signatures of individual compounds obtained at pyrolysis durations less than 90 s were consistent with those obtained from typical low-temperature pyrolysis. Several asphaltene samples from various sources released n-alkanes with distinct carbon isotopic signatures. This easy-to-use pyrolysis method, combined with a subsequent purification procedure, can be used to rapidly obtain clean n-alkanes from oil asphaltenes. Carbon isotopic signatures of n-alkanes released from oil asphaltenes from different sources demonstrate the potential application of this method in 'oil-oil' and 'oil-source' correlations. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

Nitrogen isotopes suggest a change in nitrogen dynamics between the Late Pleistocene and modern time in Yukon, Canada.

PubMed

Tahmasebi, Farnoush; Longstaffe, Fred J; Zazula, Grant

2018-01-01

A magnificent repository of Late Pleistocene terrestrial megafauna fossils is contained in ice-rich loess deposits of Alaska and Yukon, collectively eastern Beringia. The stable carbon (δ13C) and nitrogen (δ15N) isotope compositions of bone collagen from these fossils are routinely used to determine paleodiet and reconstruct the paleoecosystem. This approach requires consideration of changes in C- and N-isotope dynamics over time and their effects on the terrestrial vegetation isotopic baseline. To test for such changes between the Late Pleistocene and modern time, we compared δ13C and δ15N for vegetation and bone collagen and structural carbonate of some modern, Yukon, arctic ground squirrels with vegetation and bones from Late Pleistocene fossil arctic ground squirrel nests preserved in Yukon loess deposits. The isotopic discrimination between arctic ground squirrel bone collagen and their diet was measured using modern samples, as were isotopic changes during plant decomposition; Over-wintering decomposition of typical vegetation following senescence resulted in a minor change (~0-1 ‰) in δ13C of modern Yukon grasses. A major change (~2-10 ‰) in δ15N was measured for decomposing Yukon grasses thinly covered by loess. As expected, the collagen-diet C-isotope discrimination measured for modern samples confirms that modern vegetation δ13C is a suitable proxy for the Late Pleistocene vegetation in Yukon Territory, after correction for the Suess effect. The N-isotope composition of vegetation from the fossil arctic ground squirrel nests, however, is determined to be ~2.8 ‰ higher than modern grasslands in the region, after correction for decomposition effects. This result suggests a change in N dynamics in this region between the Late Pleistocene and modern time.

Ultrahigh thermal conductivity of isotopically enriched silicon

NASA Astrophysics Data System (ADS)

Inyushkin, Alexander V.; Taldenkov, Alexander N.; Ager, Joel W.; Haller, Eugene E.; Riemann, Helge; Abrosimov, Nikolay V.; Pohl, Hans-Joachim; Becker, Peter

2018-03-01

Most of the stable elements have two and more stable isotopes. The physical properties of materials composed of such elements depend on the isotopic abundance to some extent. A remarkably strong isotope effect is observed in the phonon thermal conductivity, the principal mechanism of heat conduction in nonmetallic crystals. An isotopic disorder due to random distribution of the isotopes in the crystal lattice sites results in a rather strong phonon scattering and, consequently, in a reduction of thermal conductivity. In this paper, we present new results of accurate and precise measurements of thermal conductivity κ(T) for silicon single crystals having three different isotopic compositions at temperatures T from 2.4 to 420 K. The highly enriched crystal containing 99.995% of 28Si, which is one of the most perfect crystals ever synthesized, demonstrates a thermal conductivity of about 450 ± 10 W cm-1 K-1 at 24 K, the highest measured value among bulk dielectrics, which is ten times greater than the one for its counterpart natSi with the natural isotopic constitution. For highly enriched crystal 28Si and crystal natSi, the measurements were performed for two orientations [001] and [011], a magnitude of the phonon focusing effect on thermal conductivity was determined accurately at low temperatures. The anisotropy of thermal conductivity disappears above 31 K. The influence of the boundary scattering on thermal conductivity persists sizable up to much higher temperatures (˜80 K). The κ(T) measured in this work gives the most accurate approximation of the intrinsic thermal conductivity of single crystal silicon which is determined solely by the anharmonic phonon processes and diffusive boundary scattering over a wide temperature range.

Stable Isotope Characteristics of Jarosite: The Acidic Aqueous History of Mars

NASA Technical Reports Server (NTRS)

Earl, Lyndsey D.

2005-01-01

The Mars Rover Opportunity found jarosite (Na(+) or K(+))Fe3SO4(OH)6 at the Meridiani Planum site. This mineral forms from the evaporation of an aqueous acidic sulfate brine. Oxygen isotope compositions may characterize formation conditions but subsequent isotope exchange may have occurred between the sulfate and hydroxide of jarosite and water. The rate of oxygen isotope exchange depends on the acidity and temperature of the brine, but it has not been investigated in detail. We performed laboratory experiments to determine the rate of oxygen isotope exchange under varying acidities and temperatures to learn more about this process. Barium sulfate samples were precipitated weekly from acidic sodium sulfate brines. The oxygen isotope composition of the precipitated sulfate was obtained using a Finnigan MAT253 Isotope Ratio Mass-Spectrometer. The results show that water was trapped in barium sulfate during precipitation. Trapped water may exchange with sulfate when exposed to high temperatures, thus changing the isotope composition of sulfate and the observed fractionation factor of oxygen isotope exchange between sulfate and water. The results of our research will contribute to the understanding of oxygen isotope exchange rates between water and sulfate under acidic conditions and provide experimental knowledge for the dehydration of barium sulfate samples.

Intramolecular carbon and nitrogen isotope analysis by quantitative dry fragmentation of the phenylurea herbicide isoproturon in a combined injector/capillary reactor prior to GC separation.

PubMed

Penning, Holger; Elsner, Martin

2007-11-01

Potentially, compound-specific isotope analysis may provide unique information on source and fate of pesticides in natural systems. Yet for isotope analysis, LC-based methods that are based on the use of organic solvents often cannot be used and GC-based analysis is frequently not possible due to thermolability of the analyte. A typical example of a compound with such properties is isoproturon (3-(4-isopropylphenyl)-1,1-dimethylurea), belonging to the worldwide extensively used phenylurea herbicides. To make isoproturon accessible to carbon and nitrogen isotope analysis, we developed a GC-based method during which isoproturon was quantitatively fragmented to dimethylamine and 4-isopropylphenylisocyanate. Fragmentation occurred only partially in the injector but was mainly achieved on a heated capillary column. The fragments were then chromatographically separated and individually measured by isotope ratio mass spectrometry. The reliability of the method was tested in hydrolysis experiments with three isotopically different batches of isoproturon. For all three products, the same isotope fractionation factors were observed during conversion and the difference in isotope composition between the batches was preserved. This study demonstrates that fragmentation of phenylurea herbicides does not only make them accessible to isotope analysis but even enables determination of intramolecular isotope fractionation.

Precipitation isotopes link regional climate patterns to water supply in a tropical mountain forest, eastern Puerto Rico

USGS Publications Warehouse

Scholl, Martha A.; Murphy, Sheila F.

2014-01-01

Like many mountainous areas in the tropics, watersheds in the Luquillo Mountains of eastern Puerto Rico have abundant rainfall and stream discharge and provide much of the water supply for the densely populated metropolitan areas nearby. Projected changes in regional temperature and atmospheric dynamics as a result of global warming suggest that water availability will be affected by changes in rainfall patterns. It is essential to understand the relative importance of different weather systems to water supply to determine how changes in rainfall patterns, interacting with geology and vegetation, will affect the water balance. To help determine the links between climate and water availability, stable isotope signatures of precipitation from different weather systems were established to identify those that are most important in maintaining streamflow and groundwater recharge. Precipitation stable isotope values in the Luquillo Mountains had a large range, from fog/cloud water with δ2H, δ18O values as high as +12 ‰, −0.73 ‰ to tropical storm rain with values as low as −127 ‰, −16.8 ‰. Temporal isotope values exhibit a reverse seasonality from those observed in higher latitude continental watersheds, with higher isotopic values in the winter and lower values in the summer. Despite the higher volume of convective and low-pressure system rainfall, stable isotope analyses indicated that under the current rainfall regime, frequent trade -wind orographic showers contribute much of the groundwater recharge and stream base flow. Analysis of rain events using 20 years of 15 -minute resolution data at a mountain station (643 m) showed an increasing trend in rainfall amount, in agreement with increased precipitable water in the atmosphere, but differing from climate model projections of drying in the region. The mean intensity of rain events also showed an increasing trend. The determination of recharge sources from stable isotope tracers indicates that water supply will be affected if regional atmospheric dynamics change trade- wind orographic rainfall patterns in the Caribbean.

Nuclear applications of inorganic mass spectrometry.

PubMed

De Laeter, John

2010-01-01

There are several basic characteristics of mass spectrometry that are not always fully appreciated by the science community. These characteristics include the distinction between relative and absolute isotope abundances, and the influence of isotope fractionation on the accuracy of isotopic measurements. These characteristics can be illustrated in the field of nuclear physics with reference to the measurement of nuclear parameters, which involve the use of enriched isotopes, and to test models of s-, r-, and p-process nucleosynthesis. The power of isotope-dilution mass spectrometry (IDMS) to measure trace elements in primitive meteorites to produce accurate Solar System abundances has been essential to the development of nuclear astrophysics. The variety of mass spectrometric instrumentation used to measure the isotopic composition of elements has sometimes been accompanied by a lack of implementation of basic mass spectrometric protocols which are applicable to all instruments. These metrological protocols are especially important in atomic weight determinations, but must also be carefully observed in cases where the anomalies might be very small, such as in studies of the daughter products of extinct radionuclides to decipher events in the early history of the Solar System. There are occasions in which misleading conclusions have been drawn from isotopic data derived from mass spectrometers where such protocols have been ignored. It is important to choose the mass spectrometer instrument most appropriate to the proposed experiment. The importance of the integrative nature of mass spectrometric measurements has been demonstrated by experiments in which long, double beta decay and geochronological decay half-lives have been measured as an alternative to costly radioactive-counting experiments. This characteristic is also illustrated in the measurement of spontaneous fission yields, which have accumulated over long periods of time. Mass spectrometry is also a valuable tool in the determination of neutron capture cross-section measurements and the application of such determinations in Planetary Science. 2009 Wiley Periodicals, Inc.

A review of lunar chronology revealing a preponderance of 4.34-4.37 Ga ages

DOE PAGES

Borg, Lars E.; Gaffney, Amy M.; Shearer, Charles K.

2014-11-24

In this study, data obtained from Sm-Nd and Rb-Sr isotopic measurements of lunar highlands’ samples are renormalized to common standard values and then used to define ages with a common isochron regression algorithm. The reliability of these ages is evaluated using five criteria that include whether: (1) the ages are defined by multiple isotopic systems, (2) the data demonstrate limited scatter outside uncertainty, (3) initial isotopic compositions are consistent with the petrogenesis of the samples, (4) the ages are defined by an isotopic system that is resistant to disturbance by impact metamorphism, and (5) the rare-earth element abundances determined bymore » isotope dilution of bulk of mineral fractions match those measured by in situ analyses. From this analysis, it is apparent that the oldest highlands’ rock ages are some of the least reliable, and that there is little support for crustal ages older than ~4.40 Ga. A model age for ur-KREEP formation calculated using the most reliable Mg-suite Sm-Nd isotopic systematics, in conjunction with Sm-Nd analyses of KREEP basalts, is 4389 ± 45 Ma. This age is a good match to the Lu-Hf model age of 4353 ± 37 Ma determined using a subset of this sample suite, the average model age of 4353 ± 25 Ma determined on mare basalts with the 146Sm- 142Nd isotopic system, with a peak in Pb-Pb ages observed in lunar zircons of ~4340 ± 20 Ma, and the oldest terrestrial zircon age of 4374 ± 6 Ma. The preponderance of ages between 4.34 and 4.37 Ga reflect either primordial solidification of a lunar magma ocean or a widespread secondary magmatic event on the lunar nearside. The first scenario is not consistent with the oldest ages reported for lunar zircons, whereas the second scenario does not account for concordance between ages of crustal rocks and mantle reservoirs.« less

Contribution of seawater recirculation to submarine groundwater discharge and related nutrient fluxes in two tropical bays

NASA Astrophysics Data System (ADS)

Vautier, Camille; Dulaiova, Henrietta

2017-04-01

Hawaiian coastal waters suffer from excess terrestrial nutrient loading, most of which comes from submarine groundwater discharge (SGD). This study quantifies and distinguishes the role of the fresh terrestrial and tidally pumped salt water components of SGD into the nearshore zone of two reefs on the island of Oahu: Maunalua Bay and Kāneohe Bay. The two components of SGD are characterized using isotopic techniques, and the study mainly focuses on the less understood recirculation component. A two-step approach is implemented: first, a conceptual model of groundwater circulation is established; second, nutrient fluxes associated with seawater recirculation are quantified. Groundwater circulation through the beach berm is quantified and characterized using 222Rn and 224Ra activity measurements. Nutrient fluxes are obtained by coupling nutrient concentration measurements and discharge estimates. The isotopic signatures inform us about the influence of the tidal cycle on groundwater circulation. 222Rn, 224Ra, and δ18O isotopes are used to derive apparent ages of the infiltrated seawater and allow us to quantify recirculation rates. The method is also complemented with the use of silicate concentration as tracers of the recirculation process. The trends in apparent ages observed in pore water in Maunalua match previously published conceptual groundwater circulation models and show a sequentially aging pore water circulation loop. However, the ages obtained in Kāneohe suggest a different tidal pumping dynamic that lacks a circulation loop, perhaps resulting from the absence of freshwater discharge. Derived nutrient fluxes show that the autochthonous production of inorganic nitrogen and phosphorus that occurs during seawater recirculation has a significant impact on nutrient cycles in the nearshore areas of the bays. This result suggests that seawater recirculation should be taken into account in biogeochemical studies of coastal areas.

Isotopically constrained lead sources in fugitive dust from unsurfaced roads in the southeast Missouri mining district.

PubMed

Witt, Emitt C; Pribil, Michael J; Hogan, John P; Wronkiewicz, David J

2016-09-01

The isotopic composition of lead (Pb) in fugitive dust suspended by a vehicle from 13 unsurfaced roads in Missouri was measured to identify the source of Pb within an established long-term mining area. A three end-member model using (207)Pb/(206)Pb and concentration as tracers resulted in fugitive dust samples plotting in the mixing field of well characterized heterogeneous end members. End members selected for this investigation include the (207)Pb/(206)Pb for 1) a Pb-mixture representing mine tailings, 2) aerosol Pb-impacted soils within close proximity to the Buick secondary recycling smelter, and 3) an average of soils, rock cores and drill cuttings representing the background conditions. Aqua regia total concentrations and (207)Pb/(206)Pb of mining area dust suggest that 35.4-84.3% of the source Pb in dust is associated with the mine tailings mixture, 9.1-52.7% is associated with the smelter mixture, and 0-21.6% is associated with background materials. Isotope ratios varied minimally within the operational phases of sequential extraction suggesting that mixing of all three Pb mixtures occurs throughout. Labile forms of Pb were attributed to all three end members. The extractable carbonate phase had as much as 96.6% of the total concentration associated with mine tailings, 51.8% associated with smelter deposition, and 34.2% with background. The next most labile geochemical phase (Fe + Mn Oxides) showed similar results with as much as 85.3% associated with mine tailings, 56.8% associated with smelter deposition, and 4.2% associated with the background soil. Published by Elsevier Ltd.

Thallium dispersal and contamination in surface sediments from South China and its source identification.

PubMed

Liu, Juan; Wang, Jin; Chen, Yongheng; Shen, Chuan-Chou; Jiang, Xiuyang; Xie, Xiaofan; Chen, Diyun; Lippold, Holger; Wang, Chunlin

2016-06-01

Thallium (Tl) is a non-essential element in humans and it is considered to be highly toxic. In this study, the contents, sources, and dispersal of Tl were investigated in surface sediments from a riverine system (the western Pearl River Basin, China), whose catchment has been contaminated by mining and roasting of Tl-bearing pyrite ores. The isotopic composition of Pb and total contents of Tl and other relevant metals (Pb, Zn, Cd, Co, and Ni) were measured in the pyrite ores, mining and roasting wastes, and the river sediments. Widespread contamination of Tl was observed in the sediments across the river, with the highest concentration of Tl (17.3 mg/kg) measured 4 km downstream from the pyrite industrial site. Application of a modified Institute for Reference Materials and Measurement (IRMM) sequential extraction scheme in representative sediments unveiled that 60-90% of Tl and Pb were present in the residual fraction of the sediments. The sediments contained generally lower (206)Pb/(207)Pb and higher (208)Pb/(206)Pb ratios compared with the natural Pb isotope signature (1.2008 and 2.0766 for (206)Pb/(207)Pb and (208)Pb/(206)Pb, respectively). These results suggested that a significant fraction of non-indigenous Pb could be attributed to the mining and roasting activities of pyrite ores, with low (206)Pb/(207)Pb (1.1539) and high (208)Pb/(206)Pb (2.1263). Results also showed that approximately 6-88% of Tl contamination in the sediments originated from the pyrite mining and roasting activities. This study highlights that Pb isotopic compositions could be used for quantitatively fingerprinting the sources of Tl contamination in sediments. Copyright © 2016 Elsevier Ltd. All rights reserved.

Sequential isotopic signature along gladius highlights contrasted individual foraging strategies of jumbo squid (Dosidicus gigas).

PubMed

Lorrain, Anne; Argüelles, Juan; Alegre, Ana; Bertrand, Arnaud; Munaron, Jean-Marie; Richard, Pierre; Cherel, Yves

2011-01-01

Cephalopods play a major role in marine ecosystems, but knowledge of their feeding ecology is limited. In particular, intra- and inter-individual variations in their use of resources has not been adequatly explored, although there is growing evidence that individual organisms can vary considerably in the way they use their habitats and resources. Using δ(13)C and δ(15)N values of serially sampled gladius (an archival tissue), we examined high resolution variations in the trophic niche of five large (>60 cm mantle length) jumbo squids (Dosidicus gigas) that were collected off the coast of Peru. We report the first evidence of large inter-individual differences in jumbo squid foraging strategies with no systematic increase of trophic level with size. Overall, gladius δ(13)C values indicated one or several migrations through the squid's lifetime (∼8-9 months), during which δ(15)N values also fluctuated (range: 1 to 5‰). One individual showed an unexpected terminal 4.6‰ δ(15)N decrease (more than one trophic level), thus indicating a shift from higher- to lower-trophic level prey at that time. The data illustrate the high diversity of prey types and foraging histories of this species at the individual level. The isotopic signature of gladii proved to be a powerful tool to depict high resolution and ontogenic variations in individual foraging strategies of squids, thus complementing traditional information offered by stomach content analysis and stable isotopes on metabolically active tissues. The observed differences in life history strategies highlight the high degree of plasticity of the jumbo squid and its high potential to adapt to environmental changes.

Sequential Isotopic Signature Along Gladius Highlights Contrasted Individual Foraging Strategies of Jumbo Squid (Dosidicus gigas)

PubMed Central

Lorrain, Anne; Argüelles, Juan; Alegre, Ana; Bertrand, Arnaud; Munaron, Jean-Marie; Richard, Pierre; Cherel, Yves

2011-01-01

Background Cephalopods play a major role in marine ecosystems, but knowledge of their feeding ecology is limited. In particular, intra- and inter-individual variations in their use of resources has not been adequatly explored, although there is growing evidence that individual organisms can vary considerably in the way they use their habitats and resources. Methodology/Principal Findings Using δ13C and δ15N values of serially sampled gladius (an archival tissue), we examined high resolution variations in the trophic niche of five large (>60 cm mantle length) jumbo squids (Dosidicus gigas) that were collected off the coast of Peru. We report the first evidence of large inter-individual differences in jumbo squid foraging strategies with no systematic increase of trophic level with size. Overall, gladius δ13C values indicated one or several migrations through the squid's lifetime (∼8–9 months), during which δ15N values also fluctuated (range: 1 to 5‰). One individual showed an unexpected terminal 4.6‰ δ15N decrease (more than one trophic level), thus indicating a shift from higher- to lower-trophic level prey at that time. The data illustrate the high diversity of prey types and foraging histories of this species at the individual level. Conclusions/Significance The isotopic signature of gladii proved to be a powerful tool to depict high resolution and ontogenic variations in individual foraging strategies of squids, thus complementing traditional information offered by stomach content analysis and stable isotopes on metabolically active tissues. The observed differences in life history strategies highlight the high degree of plasticity of the jumbo squid and its high potential to adapt to environmental changes. PMID:21779391

The chronology for the d18O record from Devils Hole, Nevada, extended into the Mid-Holocene

USGS Publications Warehouse

Landwehr, J.M.; Sharp, W.D.; Coplen, T.B.; Ludwig, K. R.; Winograd, I.J.

2011-01-01

This report presents the numeric values for the chronology of the paleoclimatically relevant mid-to-late Pleistocene record of the ratios of stable oxygen isotope (delta18O) in vein calcite from Devils Hole, Nev., which recently had been extended into the mid-Holocene. Dating was obtained using 230Th-234U-238U thermal ionization mass spectrometry. Devils Hole is a subaqueous cave of tectonic origin, which developed in the discharge zone of a regional aquifer in south-central Nevada. The primary groundwater recharge source area is the Spring Mountains, the highest mountain range in southern Nevada [altitude 3,630 meters (m)], approximately 80 kilometers to the east of the cavern. The walls of the open fault zone comprising the cave system are coated with dense vein calcite precipitated from the through-flowing groundwater. The calcite, up to 40 centimeters (cm) thick, contains a continuous record of the sequential variation of the composition of stable oxygen isotopes in the ground water over time. The vein calcite has also proven to be a suitable material for precise uranium-series dating via thermal ionization mass spectrometry utilizing the 230Th-234U-238U decay clock. Earlier work has presented data from the Devils Hole core DH-11, a 36-cm-long core of vein calcite recovered from a depth of about 30 m below the water table (about 45 m beneath the ground surface). The DH-11 core provided a continuous record of isotopic oxygen variation from 567,700 to 59,800 years before present. Recent work has extended this record up to 4,500 years before present, into the mid-Holocene epoch.

Isotopically constrained lead sources in fugitive dust from unsurfaced roads in the southeast Missouri mining district

USGS Publications Warehouse

Witt, Emitt C.; Pribil, Michael; Hogan, John P; Wronkiewicz, David

2016-01-01

The isotopic composition of lead (Pb) in fugitive dust suspended by a vehicle from 13 unsurfaced roads in Missouri was measured to identify the source of Pb within an established long-term mining area. A three end-member model using 207Pb/206Pb and concentration as tracers resulted in fugitive dust samples plotting in the mixing field of well characterized heterogeneous end members. End members selected for this investigation include the 207Pb/206Pb for 1) a Pb-mixture representing mine tailings, 2) aerosol Pb-impacted soils within close proximity to the Buick secondary recycling smelter, and 3) an average of soils, rock cores and drill cuttings representing the background conditions. Aqua regia total concentrations and 207Pb/206Pb of mining area dust suggest that 35.4–84.3% of the source Pb in dust is associated with the mine tailings mixture, 9.1–52.7% is associated with the smelter mixture, and 0–21.6% is associated with background materials. Isotope ratios varied minimally within the operational phases of sequential extraction suggesting that mixing of all three Pb mixtures occurs throughout. Labile forms of Pb were attributed to all three end members. The extractable carbonate phase had as much as 96.6% of the total concentration associated with mine tailings, 51.8% associated with smelter deposition, and 34.2% with background. The next most labile geochemical phase (Fe + Mn Oxides) showed similar results with as much as 85.3% associated with mine tailings, 56.8% associated with smelter deposition, and 4.2% associated with the background soil.