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Sample records for isotopic imaging study

  1. Identification of isotopically primitive interplanetary dust particles: A NanoSIMS isotopic imaging study

    SciTech Connect

    Floss, C; Stadermann, F J; Bradley, J P; Dai, Z R; Bajt, S; Graham, G; Lea, A S

    2005-09-02

    We have carried out a comprehensive survey of the isotopic compositions (H, B, C, N, O, S) of a suite of interplanetary dust particles (IDPs), including both cluster and individual particles. Isotopic imaging with the NanoSIMS shows the presence of numerous discrete hotspots that are strongly enriched in {sup 15}N, including the largest {sup 15}N enrichments ({approx}1300 {per_thousand}) observed in IDPs to date. A number of the IDPs also contain larger regions with more modest enrichments in {sup 15}N, leading to average bulk N isotopic compositions that are {sup 15}N-enriched in these IDPs. Although C isotopic compositions are normal in most of the IDPs, two {sup 15}N-rich N-hotspots have correlated {sup 13}C anomalies. CN{sup -}/C{sup -} ratios suggest that most of the {sup 15}N-rich hotspots are associated with relatively N-poor carbonaceous matter, although specific carriers have not been determined. H isotopic distributions are similar to those of N: D anomalies are present both as distinct very D-rich hotspots and as larger regions with more modest enrichments. Nevertheless, H and N isotopic anomalies are not directly correlated, consistent with results from previous studies. Oxygen isotopic imaging shows the presence of abundant presolar silicate grains in the IDPs. The O isotopic compositions of the grains are similar to those found in presolar oxide and silicate grains from primitive meteorites. Most of the silicate grains in the IDPs have isotopic ratios consistent with meteoritic Group 1 oxide grains, indicating origins in oxygen-rich red giant and asymptotic giant branch stars, but several presolar silicates exhibit the {sup 17}O and {sup 18}O enrichments of Group 4 oxide grains, whose origin is less well understood. Based on their N isotopic compositions, the IDPs studied here can be divided into two groups. One group is characterized as being ''isotopically primitive'' and consists of those IDPs that have anomalous bulk N isotopic compositions. These

  2. Three-dimensional imaging of the myocardium with isotopes

    NASA Technical Reports Server (NTRS)

    Budinger, T. F.

    1975-01-01

    Three methods of imaging the three-dimensional distribution of isotopes in the myocardium are discussed. Three-dimensional imaging was examined using multiple Anger-camera views. Longitudinal tomographic images with compensation for blurring were studied. Transverse-section reconstruction using coincidence detection of annihilation gammas from positron emitting isotopes was investigated.

  3. Quantitative imaging of subcellular metabolism with stable isotopes and multi-isotope imaging mass spectrometry

    PubMed Central

    Steinhauser, Matthew L.; Lechene, Claude P.

    2014-01-01

    Multi-isotope imaging mass spectrometry (MIMS) is the quantitative imaging of stable isotope labels in cells with a new type of secondary ion mass spectrometer (NanoSIMS). The power of the methodology is attributable to (i) the immense advantage of using non-toxic stable isotope labels, (ii) high resolution imaging that approaches the resolution of usual transmission electron microscopy and (iii) the precise quantification of label down to 1 part-per-million and spanning several orders of magnitude. Here we review the basic elements of MIMS and describe new applications of MIMS to the quantitative study of metabolic processes including protein and nucleic acid synthesis in model organisms ranging from microbes to humans. PMID:23660233

  4. Considerations for imaging Re-188 and Re-186 isotopes

    SciTech Connect

    Eary, J.F.; Durack, L.; Williams, D.; Vanderheyden, J.L. )

    1990-12-01

    Re-186 and Re-188 have been suggested for radioimmunotherapy because of their energetic beta particles, imageable gamma photons, and chemical properties similar to technetium. Because of this potential, these isotopes were evaluated before in vivo imaging was attempted. It was found that low-abundance, high-energy gamma photons present in these rhenium isotopes require a medium-energy collimator to yield optimal image resolution and count rate, which are critical factors in the performance of preliminary imaging studies on patients for antibody imaging and therapy.

  5. Stable isotope studies

    SciTech Connect

    Ishida, T.

    1992-01-01

    The research has been in four general areas: (1) correlation of isotope effects with molecular forces and molecular structures, (2) correlation of zero-point energy and its isotope effects with molecular structure and molecular forces, (3) vapor pressure isotope effects, and (4) fractionation of stable isotopes. 73 refs, 38 figs, 29 tabs.

  6. Evaluation of simultaneous 201Tl/99mTc dual-isotope cardiac SPECT imaging with model-based crosstalk compensation using canine studies

    PubMed Central

    Du, Y.; Links, J. M.; Becker, L.; DiPaula, A. F.; Frank, T.; Schuleri, K. H.; Lardo, A. C.; Frey, E. C.

    2014-01-01

    Background Simultaneous 201Tl/99mTc-Sestamibi dual-isotope myocardial perfusion SPECT imaging can reduce imaging time and produce perfectly registered rest/stress images. However, crosstalk from 99mTc into 201Tl images can significantly reduce 201Tl image quality. We have developed a model-based compensation (MBC) method to compensate for this crosstalk. The method has previously been validated with phantom and simulation studies. In this study, we evaluated the MBC method using a canine model. Methods Left anterior descending or left circumflex coronary artery stenoses were created in 50 adult mongrel dogs weighing 20–30 kg. The dogs were injected with 111 MBq (3 mCi) of 201Tl at rest, and a SPECT study acquired. Stress was induced by administering adenosine to the dog, followed by injection of 740 MBq (20 mCi) of 99mTc-Sestamibi at peak stress. A second SPECT study was performed with data acquired in both 201Tl and 99mTc energy windows to provide simultaneous dual-isotope projection data. The images were reconstructed using the ordered subsets-expectation maximization (OS-EM) reconstruction algorithm with compensation for attenuation, scatter and detector response. For simultaneously acquired 201Tl data, we also applied the MBC method to compensate for crosstalk contamination from 99mTc. Results Without compensation, 99mTc crosstalk increased the estimated 201Tl activity concentration in the rest images and reduced defect contrast. After MBC, the 201Tl images were in good agreement with the registered single isotope images and ex vivo count data. The ischemic (IS) to non-ischemic (NIS) region 201Tl activity concentration ratios were computed for single isotope and dual isotope studies. The correlation with ex vivo IS-NIS ratios was 0.815 after MBC, compared to the 0.495 from data without compensation. In addition, the regression line for the IS-NIS ratios with MBC was almost parallel to the line of identity with a slope of 0.93, compared to a slope of 0

  7. A preliminary feasibility study of simultaneous dual-isotope imaging with a solid-state dedicated cardiac camera for evaluating myocardial perfusion and fatty acid metabolism.

    PubMed

    Ko, Toshiyuki; Utanohara, Yuko; Suzuki, Yasuhiro; Kurihara, Makiko; Iguchi, Nobuo; Umemura, Jun; Sumiyoshi, Tetsuya; Tomoike, Hitonobu

    2016-01-01

    Simultaneous dual-isotope SPECT imaging with 201Tl and (123)I-β-methyl-p-iodophenylpentadecanoic acid (BMIPP) is used to study the perfusion-metabolism mismatch. It predicts post-ischemic functional recovery by detecting stunned myocardium. On the other hand, (99m)Tc-MIBI is another radioisotope widely used in myocardial perfusion imaging because of its better image quality and lower radiation exposure than 201Tl. However, since the photopeak energies of (99m)Tc and (123)I are very similar, crosstalk hampers the simultaneous use of these two radioisotopes. To overcome this problem, we conducted simultaneous dual-isotope imaging study using the D-SPECT scanner (Spectrum-Dynamics, Israel) which has a novel detector design and excellent energy resolution. We first conducted a basic experiment using cardiac phantom to simulate the condition of normal perfusion and impaired fatty acid metabolism. Subsequently, we prospectively recruited 30 consecutive patients who underwent successful percutaneous coronary intervention for acute myocardial infarction, and performed (99m)Tc-MIBI/(123)I-BMIPP dual-isotope imaging within 5 days after reperfusion. Images were interpreted by two experienced cardiovascular radiologists to identify the infarcted and stunned areas based on the coronary artery territories. As a result, cardiac phantom experiment revealed no significant crosstalk between (99m)Tc and (123)I. In the subsequent clinical study, (99m)Tc-MIBI/(123)I-BMIPP dual-isotope imaging in all participant yielded excellent image quality and detected infarcted and stunned areas correctly when compared with coronary angiographic findings. Furthermore, we were able to reduce radiation exposure to significantly approximately one-eighth. In conclusion, we successfully demonstrated the practical application of simultaneous assessment of myocardial perfusion and fatty acid metabolism by (99m)Tc-MIBI and (123)I-BMIPP using a D-SPECT cardiac scanner. Compared with conventional (201)Tl

  8. Brain stem cell division and maintenance studied using multi-isotope imaging mass spectrometry (MIMS)

    PubMed Central

    Enikolopov, G.; Guillermier, C.; Wang, M.; Trakimas, L.; Steinhauser, M.; Lechene, C.

    2015-01-01

    New neurons are continuously produced from neural stem cells in specific regions of the adult brain of animals and humans. In the hippocampus, a region crucial for cognitive function, neurogenesis responds to a multitude of extrinsic stimuli; emerging evidence indicates that it may be important for behavior, pathophysiology, brain repair, and response to drugs. We have developed an approach to identify and quantify the cellular targets of pro- and anti-neurogenic stimuli, based on reporter transgenic mouse lines in which neural stem and progenitor cells or their progeny are marked by fluorescent proteins. Here, we demonstrate the feasibility of using MIMS for studying adult neurogenesis. PMID:26379335

  9. Oxygen isotope studies and compilation of isotopic dates from Antarctica

    SciTech Connect

    Grootes, P.M.; Stuiver, M.

    1986-01-01

    The Quaternary Isotope Laboratory, alone or in collaboration with other investigators, is currently involved in a number of oxygen-isotope studies mainly in Antarctica. Studies of a drill core from the South Pole, seasonal oxygen-18 signals preserved in the Dominion Range, isotope dating of the Ross Ice Shelf, oxygen-18 profiles of the Siple Coast, McMurdo Ice Shelf sampling, and a data compilation of radiometric dates from Antarctica are discussed.

  10. Quantitative image reconstruction for dual-isotope parathyroid SPECT/CT: phantom experiments and sample patient studies

    NASA Astrophysics Data System (ADS)

    Shcherbinin, S.; Chamoiseau, S.; Celler, A.

    2012-08-01

    We investigated the quantitative accuracy of the model-based dual-isotope single-photon emission computed tomography (DI-SPECT) reconstructions that use Klein-Nishina expressions to estimate the scattered photon contributions to the projection data. Our objective was to examine the ability of the method to recover the absolute activities pertaining to both radiotracers: Tc-99m and I-123. We validated our method through a series of phantom experiments performed using a clinical hybrid SPECT/CT camera (Infinia Hawkeye, GE Healthcare). Different activity ratios and different attenuating media were used in these experiments to create cross-talk effects of varying severity, which can occur in clinical studies. Accurate model-based corrections for scatter and cross-talk with CT attenuation maps allowed for the recovery of the absolute activities from DI-SPECT/CT scans with errors that ranged 0-10% for both radiotracers. The unfavorable activity ratios increased the computational burden but practically did not affect the resulting accuracy. The visual analysis of parathyroid patient data demonstrated that our model-based processing improved adenoma/background contrast and enhanced localization of small or faint adenomas.

  11. Cerenkov luminescence imaging of medical isotopes

    PubMed Central

    Ruggiero, Alessandro; Holland, Jason P.; Lewis, Jason S.; Grimm, Jan

    2011-01-01

    The development of novel multimodality imaging agents and techniques represents the current frontier of research in the field of medical imaging science. However, the combination of nuclear tomography with optical techniques has yet to be established. Here, we report the use of the inherent optical emissions from the decay of radiopharmaceuticals for Cerenkov luminescence imaging (CLI) of tumors in vivo and correlate the results with those obtained from concordant immuno-PET studies. Methods In vitro phantom studies were used to validate the visible light emission observed from a range of radionuclides including the positron emitters 18F, 64Cu, 89Zr, and 124I; β-emitter 131I; and α-particle emitter 225Ac for potential use in CLI. The novel radiolabeled monoclonal antibody 89Zr-desferrioxamine B-[DFO-J591 for immuno-PET of prostate-specific membrane antigen (PSMA) expression was used to coregister and correlate the CLI signal observed with the immuno-PET images and biodistribution studies. Results Phantom studies confirmed that Cerenkov radiation can be observed from a range of positron-,β-, and α-emitting radionuclides using standard optical imaging devices. The change in light emission intensity versus time was concordant with radionuclide decay and was also found to correlate linearly with both the activity concentration and the measured PET signal (percentage injected dose per gram). In vivo studies conducted in male severe combined immune deficient mice bearing PSMA-positive, subcutaneous LNCaP tumors demonstrated that tumor-specific uptake of 89Zr-DFO-J591 could be visualized by both immuno-PET and CLI. Optical and immuno-PET signal intensities were found to increase over time from 24 to 96 h, and biodistribution studies were found to correlate well with both imaging modalities. Conclusion These studies represent the first, to our knowledge, quantitative assessment of CLI for measuring radiotracer uptake in vivo. Many radionuclides common to both nuclear

  12. Ion microscopic imaging of calcium transport in the intestinal tissue of vitamin D-deficient and vitamin D-replete chickens: A sup 44 Ca stable isotope study

    SciTech Connect

    Chandra, S.; Fullmer, C.S.; Smith, C.A.; Wasserman, R.H.; Morrison, G.H. )

    1990-08-01

    The intestinal absorption of calcium includes at least three definable steps; transfer across the microvillar membrane, movement through the cytosolic compartment, and energy-dependent extrusion into the lamina propria, Tracing the movement of calcium through the epithelium has been hampered by lack of suitable techniques and, in this study, advantage was taken of ion microscopy in conjunction with cryosectioning and use of the stable isotope 44Ca to visualize calcium in transit during the absorptive process. The effect of vitamin D, required for optimal calcium absorption, was investigated. Twenty millimolar 44Ca was injected into the duodenal lumen in situ of vitamin D-deficient and vitamin D-replete chickens. At 2.5, 5.0, and 20.0 min after injection, duodenal tissue was obtained and processed for ion microscopic imaging. At 2.5 min. 44Ca was seen to be concentrated in the region subjacent to the microvillar membrane in tissue from both groups. At 5.0 and 20.0 min, a similar pattern of localization was evident in D-deficient tissues. In D-replete tissues, the distribution of 44Ca became more homogenous, indicating that vitamin D increased the rate of transfer of Ca2+ from the apical to the basolateral membrane, a function previously ascribed to the vitamin D-induced calcium-binding protein (28-kDa calbindin-D). Quantitative aspects of the calcium absorptive process were determined in parallel experiments with the radionuclide 47Ca. Complementary information on the localization of the naturally occurring isotopes of calcium (40Ca) and potassium (39K) is also described.

  13. Production and in vivo imaging of (203)Pb as a surrogate isotope for in vivo (212)Pb internal absorbed dose studies.

    PubMed

    Máthé, Domokos; Szigeti, Krisztián; Hegedűs, Nikolett; Horváth, Ildikó; Veres, Dániel S; Kovács, Béla; Szűcs, Zoltán

    2016-08-01

    (212)Pb is a clinically relevant therapeutic alpha emitter isotope. A surrogate, (203)Pb, if prepared with sufficiently high specific activity could be used to estimate (212)Pb in vivo absorbed doses. An improved production procedure of (203)Pb with a simple, new separation method and high specific radioactivity for imaging is reported. We determined the in-vivo biodistribution of (203)Pb in mice by SPECT/CT. This highlights application possibilities of (203)Pb for further in vivo and clinical uses (radiolabeled (212)Pb-peptide co-injection, dosimetry calculation). PMID:27156049

  14. Isotopic studies in returned lunar samples

    NASA Technical Reports Server (NTRS)

    Alexander, E. C., Jr.

    1971-01-01

    Analysis of lunar soil samples returned by Apollo 11 and 12 flights are discussed. Isotopic studies of the rare gases from Apollo 11 flight lunar samples are presented. The lunar soil analyses indicated the following: (1) high concentrations of solar wind rare gases, (2) isotopic match between solar wind gases and gas components in gas-rich meteorites, and (3) rare gases attributable to spallation reactions induced in heavier nuclides by cosmic ray particles.

  15. Isotope specific resolution recovery image reconstruction in high resolution PET imaging

    SciTech Connect

    Kotasidis, Fotis A.; Angelis, Georgios I.; Anton-Rodriguez, Jose; Matthews, Julian C.; Reader, Andrew J.; Zaidi, Habib

    2014-05-15

    Purpose: Measuring and incorporating a scanner-specific point spread function (PSF) within image reconstruction has been shown to improve spatial resolution in PET. However, due to the short half-life of clinically used isotopes, other long-lived isotopes not used in clinical practice are used to perform the PSF measurements. As such, non-optimal PSF models that do not correspond to those needed for the data to be reconstructed are used within resolution modeling (RM) image reconstruction, usually underestimating the true PSF owing to the difference in positron range. In high resolution brain and preclinical imaging, this effect is of particular importance since the PSFs become more positron range limited and isotope-specific PSFs can help maximize the performance benefit from using resolution recovery image reconstruction algorithms. Methods: In this work, the authors used a printing technique to simultaneously measure multiple point sources on the High Resolution Research Tomograph (HRRT), and the authors demonstrated the feasibility of deriving isotope-dependent system matrices from fluorine-18 and carbon-11 point sources. Furthermore, the authors evaluated the impact of incorporating them within RM image reconstruction, using carbon-11 phantom and clinical datasets on the HRRT. Results: The results obtained using these two isotopes illustrate that even small differences in positron range can result in different PSF maps, leading to further improvements in contrast recovery when used in image reconstruction. The difference is more pronounced in the centre of the field-of-view where the full width at half maximum (FWHM) from the positron range has a larger contribution to the overall FWHM compared to the edge where the parallax error dominates the overall FWHM. Conclusions: Based on the proposed methodology, measured isotope-specific and spatially variant PSFs can be reliably derived and used for improved spatial resolution and variance performance in resolution

  16. The new frontiers of multimodality and multi-isotope imaging

    NASA Astrophysics Data System (ADS)

    Behnam Azad, Babak; Nimmagadda, Sridhar

    2014-06-01

    Technological advances in imaging systems and the development of target specific imaging tracers has been rapidly growing over the past two decades. Recent progress in "all-in-one" imaging systems that allow for automated image coregistration has significantly added to the growth of this field. These developments include ultra high resolution PET and SPECT scanners that can be integrated with CT or MR resulting in PET/CT, SPECT/CT, SPECT/PET and PET/MRI scanners for simultaneous high resolution high sensitivity anatomical and functional imaging. These technological developments have also resulted in drastic enhancements in image quality and acquisition time while eliminating cross compatibility issues between modalities. Furthermore, the most cutting edge technology, though mostly preclinical, also allows for simultaneous multimodality multi-isotope image acquisition and image reconstruction based on radioisotope decay characteristics. These scientific advances, in conjunction with the explosion in the development of highly specific multimodality molecular imaging agents, may aid in realizing simultaneous imaging of multiple biological processes and pave the way towards more efficient diagnosis and improved patient care.

  17. High-resolution quantitative imaging of mammalian and bacterial cells using stable isotope mass spectrometry

    PubMed Central

    Lechene, Claude; Hillion, Francois; McMahon, Greg; Benson, Douglas; Kleinfeld, Alan M; Kampf, J Patrick; Distel, Daniel; Luyten, Yvette; Bonventre, Joseph; Hentschel, Dirk; Park, Kwon Moo; Ito, Susumu; Schwartz, Martin; Benichou, Gilles; Slodzian, Georges

    2006-01-01

    Background Secondary-ion mass spectrometry (SIMS) is an important tool for investigating isotopic composition in the chemical and materials sciences, but its use in biology has been limited by technical considerations. Multi-isotope imaging mass spectrometry (MIMS), which combines a new generation of SIMS instrument with sophisticated ion optics, labeling with stable isotopes, and quantitative image-analysis software, was developed to study biological materials. Results The new instrument allows the production of mass images of high lateral resolution (down to 33 nm), as well as the counting or imaging of several isotopes simultaneously. As MIMS can distinguish between ions of very similar mass, such as 12C15N- and 13C14N-, it enables the precise and reproducible measurement of isotope ratios, and thus of the levels of enrichment in specific isotopic labels, within volumes of less than a cubic micrometer. The sensitivity of MIMS is at least 1,000 times that of 14C autoradiography. The depth resolution can be smaller than 1 nm because only a few atomic layers are needed to create an atomic mass image. We illustrate the use of MIMS to image unlabeled mammalian cultured cells and tissue sections; to analyze fatty-acid transport in adipocyte lipid droplets using 13C-oleic acid; to examine nitrogen fixation in bacteria using 15N gaseous nitrogen; to measure levels of protein renewal in the cochlea and in post-ischemic kidney cells using 15N-leucine; to study DNA and RNA co-distribution and uridine incorporation in the nucleolus using 15N-uridine and 81Br of bromodeoxyuridine or 14C-thymidine; to reveal domains in cultured endothelial cells using the native isotopes 12C, 16O, 14N and 31P; and to track a few 15N-labeled donor spleen cells in the lymph nodes of the host mouse. Conclusion MIMS makes it possible for the first time to both image and quantify molecules labeled with stable or radioactive isotopes within subcellular compartments. PMID:17010211

  18. Advanced diffusion studies with isotopically controlled materials

    SciTech Connect

    Bracht, Hartmut A.; Silvestri, Hughes H.; Haller, Eugene E.

    2004-11-14

    The use of enriched stable isotopes combined with modern epitaxial deposition and depth profiling techniques enables the preparation of material heterostructures, highly appropriate for self- and foreign-atom diffusion experiments. Over the past decade we have performed diffusion studies with isotopically enriched elemental and compound semiconductors. In the present paper we highlight our recent results and demonstrate that the use of isotopically enriched materials ushered in a new era in the study of diffusion in solids which yields greater insight into the properties of native defects and their roles in diffusion. Our approach of studying atomic diffusion is not limited to semiconductors and can be applied also to other material systems. Current areas of our research concern the diffusion in the silicon-germanium alloys and glassy materials such as silicon dioxide and ion conducting silicate glasses.

  19. Regularized Image Reconstruction Algorithms for Dual-Isotope Myocardial Perfusion SPECT (MPS) Imaging Using a Cross-Tracer Prior

    PubMed Central

    He, Xin; Cheng, Lishui; Fessler, Jeffrey A.

    2011-01-01

    In simultaneous dual-isotope myocardial perfusion SPECT (MPS) imaging, data are simultaneously acquired to determine the distributions of two radioactive isotopes. The goal of this work was to develop penalized maximum likelihood (PML) algorithms for a novel cross-tracer prior that exploits the fact that the two images reconstructed from simultaneous dual-isotope MPS projection data are perfectly registered in space. We first formulated the simultaneous dual-isotope MPS reconstruction problem as a joint estimation problem. A cross-tracer prior that couples voxel values on both images was then proposed. We developed an iterative algorithm to reconstruct the MPS images that converges to the maximum a posteriori solution for this prior based on separable surrogate functions. To accelerate the convergence, we developed a fast algorithm for the cross-tracer prior based on the complete data OS-EM (COSEM) framework. The proposed algorithm was compared qualitatively and quantitatively to a single-tracer version of the prior that did not include the cross-tracer term. Quantitative evaluations included comparisons of mean and standard deviation images as well as assessment of image fidelity using the mean square error. We also evaluated the cross tracer prior using a three-class observer study with respect to the three-class MPS diagnostic task, i.e., classifying patients as having either no defect, reversible defect, or fixed defects. For this study, a comparison with conventional ordered subsets-expectation maximization (OS-EM) reconstruction with postfiltering was performed. The comparisons to the single-tracer prior demonstrated similar resolution for areas of the image with large intensity changes and reduced noise in uniform regions. The cross-tracer prior was also superior to the single-tracer version in terms of restoring image fidelity. Results of the three-class observer study showed that the proposed cross-tracer prior and the convergent algorithms improved the

  20. Isotopic Study of Silicon Carbide in Semarkona

    NASA Astrophysics Data System (ADS)

    Smith, J. B.; Huss, G. R.

    2002-03-01

    We have measured Si and C isotopes for individual SiC grains from Semarkona. Our results are compared with those of previous studies on SiC from Murchison and Orgueil. Metamorphism and grain-size distribution can affect these comparisons.

  1. STABLE ISOTOPES IN ECOLOGICAL STUDIES: NEW DEVELOPMENTS IN MIXING MODELS

    EPA Science Inventory

    Stable isotopes are increasingly being used as tracers in ecological studies. One application uses isotopic ratios to quantify the proportional contributions of multiple sources to a mixture. Examples include food sources for animals, water sources for plants, pollution sources...

  2. Microturbulence study of the isotope effect

    SciTech Connect

    Bustos, A.; Bañón Navarro, A.; Görler, T.; Jenko, F.

    2015-01-15

    The influence of the ion mass on the dynamics of magnetized plasmas is an important challenge in fusion research. The discrepancies between the improvement of the magnetic confinement with the ion mass in tokamak experiments and diffusive turbulent transport predictions have remained unexplained for several decades. We refer to this phenomenon as the isotope effect. In this paper, we study this effect with gyrokinetic theory using the GENE code. We find several sets of plasma parameters that correspond to low wavenumber turbulence for which the isotope effect is present, although the intensity is smaller than the experimental observations. We also relate these results to the zonal flow intensity of the system, which is characterized by the average shear flow rate.

  3. In vivo characterization of the novel CD44v6-targeting Fab fragment AbD15179 for molecular imaging of squamous cell carcinoma: a dual-isotope study

    PubMed Central

    2014-01-01

    Background Patients with squamous cell carcinoma in the head and neck region (HNSCC) offer a diagnostic challenge due to difficulties to detect small tumours and metastases. Imaging methods available are not sufficient, and radio-immunodiagnostics could increase specificity and sensitivity of diagnostics. The objective of this study was to evaluate, for the first time, the in vivo properties of the radiolabelled CD44v6-targeting fragment AbD15179 and to assess its utility as a targeting agent for radio-immunodiagnostics of CD44v6-expressing tumours. Methods The fully human CD44v6-targeting Fab fragment AbD15179 was labelled with 111In or 125I, as models for radionuclides suitable for imaging with SPECT or PET. Species specificity, antigen specificity and internalization properties were first assessed in vitro. In vivo specificity and biodistribution were then evaluated in tumour-bearing mice using a dual-tumour and dual-isotope setup. Results Both species-specific and antigen-specific binding of the conjugates were demonstrated in vitro, with no detectable internalization. The in vivo studies demonstrated specific tumour binding and favourable tumour targeting properties for both conjugates, albeit with higher tumour uptake, slower tumour dissociation, higher tumour-to-blood ratio and higher CD44v6 sensitivity for the 111In-labelled fragment. In contrast, the 125I-Fab demonstrated more favourable tumour-to-organ ratios for liver, spleen and kidneys. Conclusions We conclude that AbD15179 efficiently targets CD44v6-expressing squamous cell carcinoma xenografts, and particularly, the 111In-Fab displayed high and specific tumour uptake. CD44v6 emerges as a suitable target for radio-immunodiagnostics, and a fully human antibody fragment such as AbD15179 can enable further clinical imaging studies. PMID:24598405

  4. NMR studies of isotopically labeled RNA

    SciTech Connect

    Pardi, A.

    1994-12-01

    In summary, the ability to generate NMR quantities of {sup 15}N and {sup 13}C-labeled RNAs has led to the development of heteronuclear multi-dimensional NMR techniques for simplifying the resonance assignment and structure determination of RNAs. These methods for synthesizing isotopically labeled RNAs are only several years old, and thus there are still relatively few applications of heteronuclear multi-dimensional NMR techniques to RNA. However, given the critical role that RNAs play in cellular function, one can expect to see an increasing number of NMR structural studies of biologically active RNAs.

  5. Isotope Labeling Study of Retinal Chromophore Fragmentation.

    PubMed

    Musbat, Lihi; Nihamkin, Maria; Ytzhak, Shany; Hirshfeld, Amiram; Friedman, Noga; Dilger, Jonathan M; Sheves, Mordechai; Toker, Yoni

    2016-04-28

    Previous studies have shown that the gas-phase fragmentation of the retinal chromophore after S0-S1 photoexcitation results in a prominent fragment of mass 248 which cannot be explained by the cleavage of any single bond along the polyene chain. It was therefore theorized that the fragmentation mechanism involves a series of isomerizations and cyclization processes, and two mechanisms for these processes were suggested. Here we used isotope labeling MS-MS to provide conclusive support for the fragmentation mechanism suggested by Coughlan et al. (J. Phys. Chem. Lett. 2014, 5, 3195). PMID:27046667

  6. Isotope pattern deconvolution as rising tool for isotope tracer studies in environmental research

    NASA Astrophysics Data System (ADS)

    Irrgeher, Johanna; Zitek, Andreas; Prohaska, Thomas

    2014-05-01

    During the last decade stable isotope tracers have emerged as versatile tool in ecological research. Besides 'intrinsic' isotope tracers caused by the natural variation of isotopes, the intentional introduction of 'extrinsic' enriched stable isotope tracers into biological systems has gained significant interest. Hereby the induced change in the natural isotopic composition of an element allows amongst others for studying the fate and fluxes of metals, trace elements and species in organisms or provides an intrinsic marker or tag of particular biological samples. Due to the shoreless potential of this methodology, the number of publications dealing with applications of isotope (double) spikes as tracers to address research questions in 'real world systems' is constantly increasing. However, some isotope systems like the natural Sr isotopic system, although potentially very powerful for this type of application, are still rarely used, mainly because their adequate measurement/determination poses major analytical challenges; as e.g. Sr is available in significant amounts in natural samples. In addition, biological systems underlie complex processes such as metabolism, adsorption/desorption or oxidation/reduction. As a consequence, classic evaluation approaches such as the isotope dilution mass spectrometry equation are often not applicable because of the unknown amount of tracer finally present in the sample. Isotope pattern deconvolution (IPD), based on multiple linear regression, serves as simplified alternative data processing strategy to double spike isotope dilution calculations. The outstanding advantage of this mathematical tool lies in the possibility of deconvolving the isotope pattern in a spiked sample without knowing the quantities of enriched isotope tracer being incorporated into the natural sample matrix as well as the degree of impurities and species-interconversion (e.g. from sample preparation). Here, the potential of IPD for environmental tracer

  7. Dual isotope brain SPECT imaging for monitoring cognitive activation: physical considerations.

    PubMed

    Madsen, M T; O'Leary, D S; Andreasen, N C; Kirchner, P T

    1993-05-01

    The physical considerations of using dual isotope brain SPECT imaging to monitor blood flow changes during cognitive activation studies were investigated. These factors included field uniformity, spatial resolution and crosstalk. Serial dual isotope single photon emission computed tomographic (SPECT) studies of a test tube phantom and an anthropomorphic brain phantom filled with 99Tcm and 123I were made over a 10 h period. The reconstructed counts in the 99Tcm and 123I windows were corrected for crosstalk and were plotted as a function of time. The plotted data from each window decreased over time with a half-life characteristic of each radionuclide. The relative difference between true 123I and 99Tcm region counts has to be of the order of 10% to be statistically significant at the P < 0.05 level. PMID:8510880

  8. Chemical imaging of biological materials by NanoSIMS using isotopic and elemental labels

    SciTech Connect

    Weber, P K; Fallon, S J; Pett-Ridge, J; Ghosal, S; Hutcheon, I D

    2006-04-10

    The NanoSIMS 50 combines unprecedented spatial resolution (as good as 50 nm) with ultra-high sensitivity (minimum detection limit of {approx}200 atoms). The NanoSIMS 50 incorporates an array of detectors, enabling simultaneous collection of 5 species originating from the same sputtered volume of a sample. The primary ion beam (Cs{sup +} or O{sup -}) can be scanned across the sample to produce quantitative secondary ion images. This capability for multiple isotope imaging with high spatial resolution provides a novel new approach to the study of biological materials. Studies can be made of sub-regions of tissues, mammalian cells, and bacteria. Major, minor and trace element distributions can be mapped on a submicron scale, growth and metabolism can be tracked using stable isotope labels, and biogenic origin can be determined based on composition. We have applied this technique extensively to mammalian and prokaryotic cells and bacterial spores. The NanoSIMS technology enables the researcher to interrogate the fate of molecules of interest within cells and organs through elemental and isotopic labeling. Biological applications at LLNL will be discussed.

  9. Chemical Imaging and Stable Isotope Analysis of Atmospheric Particles by NanoSIMS (Invited)

    NASA Astrophysics Data System (ADS)

    Sinha, B.; Harris, E. J.; Pöhlker, C.; Wiedemann, K. T.; van Pinxteren, D.; Tilgner, A.; Fomba, K. W.; Schneider, J.; Roth, A.; Gnauk, T.; Fahlbusch, B.; Mertes, S.; Lee, T.; Collett, J. L.; Shiraiwa, M.; Gunthe, S. S.; Smith, M.; Artaxo, P. P.; Gilles, M.; Kilcoyne, A. L.; Moffet, R.; Weigand, M.; Martin, S. T.; Poeschl, U.; Andreae, M. O.; Hoppe, P.; Herrmann, H.; Borrmann, S.

    2013-12-01

    Chemical imaging analysis of the internal distribution of chemical compounds by a combination of SEM-EDX, and NanoSIMS allows investigating the physico-chemical properties and isotopic composition of individual aerosol particles. Stable sulphur isotope analysis provides insight into the sources, sinks and oxidation pathways of SO2 in the environment. Oxidation by OH radicals, O3 and H2O2 enriches the heavier isotope in the product sulphate, whereas oxidation by transition metal ions (TMI), hypohalites and hypohalous acids depletes the heavier isotope in the product sulphate. The isotope fractionation during SO2 oxidation by stabilized Criegee Intermediate radicals is unknown. We studied the relationship between aerosol chemical composition and predominant sulphate formation pathways in continental clouds in Central Europe and during the wet season in the Amazon rain forest. Sulphate formation in continental clouds in Central Europe was studied during HCCT-2010, a lagrangian-type field experiment, during which an orographic cloud was used as a natural flow-through reactor to study in-cloud aerosol processing (Harris et al. 2013). Sulphur isotopic compositions in SO2 and H2SO4 gas and particulate sulphate were measured and changes in the sulphur isotope composition of SO2 between the upwind and downwind measurement sites were used to determine the dominant SO2 chemical removal process occurring in the cloud. Changes in the isotopic composition of particulate sulphate revealed that transition metal catalysis pathway was the dominant SO2 oxidation pathway. This reaction occurred primarily on coarse mineral dust particles. Thus, sulphate produced due to in-cloud SO2 oxidation is removed relatively quickly from the atmosphere and has a minor climatic effect. The aerosol samples from the Amazonian rainforest, a pristine tropical environment, were collected during the rainy season. The samples were found to be dominated by SOA particles in the fine mode and primary

  10. High Spatial Resolution Isotope Ratio Imaging and 3D Reconstruction of Presolar SiC Grains

    NASA Astrophysics Data System (ADS)

    Lyon, I. C.; Henkel, T.; Clarke, A.

    2015-07-01

    Presolar SiC grains have been analysed with a new NanoSIMS for isotope ratio measurements of C, N and Si. High spatial resolution imaging suggests that nitrogen isotope heterogeneity within the grains may lead to anomalous results in the literature.

  11. Lead isotope studies of mare basalt 70017

    NASA Technical Reports Server (NTRS)

    Mattinson, J. M.; Tilton, G. R.; Todt, W.; Chen, J. H.

    1977-01-01

    Uranium, thorium, and isotopic lead data for components of basalt 70017 are reported, and it is found that the whole rock, pyroxene, and ilmenite points in a concordia diagram plot along a chord intersecting the curve at 3.7 and 4.33 eons. The plagioclase data do not seem to lie on this line. The data for 70017 appear to plot along a distinctly different chord in a concordia diagram than do the data for 75055 and 75035, two other Apollo 17 mare basalts. The lead data are in accord with Sm-Nd results. A 3.7 eon crystallization age for 70017 would be consistent with the same kind of parentless lead that is indicated by previous studies of soils and soil breccias from stations at Taurus-Littrow. The Th/U ratio in ilmenite is 2.2, and the concentrations of these two elements are approximately twice those in pyroxene.

  12. Studies of enzyme mechanism using isotopic probes

    SciTech Connect

    Chen, C.

    1987-01-01

    The isotope partitioning studies of the Ascaris suum NAD-malic enzyme reaction were examined with five transitory complexes including E:NAD, E:NAD:Mg, E:malate, E:Mg:malate, and E:NAD:malate. Three productive complexes, E:NAD, E:NAD:Mg, and E:Mg:malate, were obtained, suggesting a steady-state random mechanism. Data for trapping with E:/sup 14/C-NAD indicate a rapid equilibrium addition of Mg/sup 2 +/ prior to the addition of malate. Trapping with /sup 14/C-malate could only be obtained from the E:Mg/sup 2 +/:/sup 14/C-malate complex, while no trapping from E:/sup 14/C-malate was obtained under feasible experimental conditions. The equations for the isotope partitioning studies varying two substrates in the chase solution in an ordered terreactant reaction were derived, allowing a determination of the relative rates of substrate dissociation to the catalytic reaction for each of the productive transitory complexes. NAD and malate are released from the central complex at an identical rate, equal to the catalytic rate. The release of NAD from E:NAD and E:NAD:Mg complexes is 2- to 4-fold and 5- to 9-fold V/sub max//E/sub t/, respectively. The release of malate from the E:Mg:malate complex is 0.1- to 0.3-fold of V/sub max//E/sub t/. The individual rate constants for association and dissociation of the substrates, NAD and malate have been estimated.

  13. Isotope ratio and trace element imaging of pyrite grains in gold ores

    NASA Astrophysics Data System (ADS)

    Fleming, Ronald H.; Bekken, Barbara M.

    1995-05-01

    Secondary ion mass spectrometry techniques for imaging measurements of 34S/32S isotope ratios and quantitative trace element concentrations in pyrite mineral grains have been demonstrated. Test samples show that the 34S/32S isotope ratios are constant within Poisson error, independent of image position. Variable 34S/32S isotope ratios have been found within a a single pyrite grain in a sample of gold ore from the Carlin mine in the Carlin District of Nevada. The locations of trace gold concentrations in this ore sample correlate with relative 34S enrichment. Imaging has the inherent problem of spreading already limited minor isotope signals among many pixels. This problem can be overcome with improved analysis methodology including new electron multiplier circuitry to accommodate more intense secondary ion signals, stable data collection over relatively long time periods, and improved software. High mass resolution imaging and careful neutralization of ion beam induced sample charging are also required.

  14. Stable Chlorine Isotope Study: Application to Early Solar System Materials

    NASA Technical Reports Server (NTRS)

    Mala,ira. M/; Nyquist, L. E.; Reese, Y.; Shih, C-Y; Fujitani, T.; Okano, O.

    2010-01-01

    A significantly large mass fractionation between two stable chlorine isotopes is expected during planetary processes In addition, in view of the isotopic heterogeneity of other light elements, the chlorine isotopes can potentially be used as a tracer for the origins and evolutionary processes of early solar system materials. Due to analytical difficulties, however, current chlorine isotope studies on planetary materials are quite controversial among IRMS (gas source mass spectrometry) and/or TIMS (Thermal Ionization Mass Spectrometry) groups [i.e. 1-3]. Although a cross-calibration of IRMS and TIMS indicates that both techniques are sufficiently consistent with each other [4], some authors have claimed that the Cl-37/Cl-35 ratio of geological samples obtained by TIMS technique are, in general, misleadingly too high and variable compared to those of IRMS [3]. For example, almost no differences of Cl isotope composition were observed among mantle materials and carbonaceous meteorites by [3]. On the other hand, according to more recent IRMS work [2], significant Cl isotope variations are confirmed for mantle materials. Therefore, additional careful investigation of Cl isotope analyses are now required to confirm real chlorine isotope variations for planetary materials including carbonaceous chondrites [5]. A significantly large mass fractionation between two stable chlorine isotopes is expected during planetary processes In addition, in view of the isotopic heterogeneity of other light elements, the chlorine isotopes can potentially be used as a tracer for the origins and evolutionary processes of early solar system materials. Due to analytical difficulties, however, current chlorine isotope studies on planetary materials are quite controversial among IRMS (gas source mass spectrometry) and/or TIMS (Thermal Ionization Mass Spectrometry) groups [i.e. 1-3]. Although a cross-calibration of IRMS and TIMS indicates that both techniques are sufficiently consistent with each

  15. Dual isotope notch observer for isotope identification, assay and imaging with mono-energetic gamma-ray sources

    SciTech Connect

    Barty, Christopher P.J.

    2013-02-05

    A dual isotope notch observer for isotope identification, assay and imaging with mono-energetic gamma-ray sources includes a detector arrangement consists of three detectors downstream from the object under observation. The latter detector, which operates as a beam monitor, is an integrating detector that monitors the total beam power arriving at its surface. The first detector and the middle detector each include an integrating detector surrounding a foil. The foils of these two detectors are made of the same atomic material, but each foil is a different isotope, e.g., the first foil may comprise U235 and second foil may comprise U238. The integrating detectors surrounding these pieces of foil measure the total power scattered from the foil and can be similar in composition to the final beam monitor. Non-resonant photons will, after calibration, scatter equally from both foils.

  16. Organic Analysis in the Miller Range 090657 CR2 Chondrite: Part 3 C and N Isotopic Imaging

    NASA Technical Reports Server (NTRS)

    Messenger, S.; Nakamura-Messenger, K.; Elsila, J. E.; Berger, E. L.; Burton, A. S.; Clemett, S. J.; Cao, T.

    2016-01-01

    Primitive carbonaceous chondrites contain a wide variety of organic material, ranging from soluble discrete molecules to insoluble nanoglobules of macro-molecular carbon. The relationship between the soluble organic molecules, macromolecular organic material, and host minerals are poorly understood. Large H, C and N isotopic anomalies suggest some organic components formed in low-T interstellar or outer Solar System environments. The highest isotope anomalies occur in m-scale inclusions in the most primitive materials, such as cometary dust and the least altered carbonaceous chondrites. Often, the hosts of these isotopically anomalous 'hotspots' are discrete organic nanoglobules that probably formed in the outermost reaches of the protosolar disk or cold molecular cloud. Molecular and isotopic studies of meteoritic organic matter are aimed at identifying the chemical properties and formation processes of interstellar organic materials and the subsequent chemical evolutionary pathways in various Solar System environments. The combination of soluble and insoluble analyses with in situ and bulk studies provides powerful constraints on the origin and evolution of organic matter in the Solar System. Using macroscale extraction and analysis techniques as well as microscale in situ observations we have been studying both insoluble and soluble organic material in primitive astromaterial samples. Here, we present results of bulk C and N isotopic measurements and coordinated in situ C and N isotopic imaging and mineralogical and textural studies of carbonaceous materials in a Cr2 carbonaceous chondrite. In accompanying abstracts we discuss the morphology and distribution of carbonaceous components and soluble organic species of this meteorite.

  17. High-precision γ -ray spectroscopy of the cardiac PET imaging isotope 82Rb and its impact on dosimetry

    NASA Astrophysics Data System (ADS)

    Nino, M. N.; McCutchan, E. A.; Smith, S. V.; Lister, C. J.; Greene, J. P.; Carpenter, M. P.; Muench, L.; Sonzogni, A. A.; Zhu, S.

    2016-02-01

    82Rb is a positron-emitting isotope used in cardiac positron emission tomography (PET) imaging which has been reported to deliver a significantly lower effective radiation dose than analogous imaging isotopes like 201Tl and 99 mTc sestamibi. High-quality β -decay data are essential to accurately appraise the total dose received by the patients. A source of 82Sr was produced at the Brookhaven Linac Isotope Producer (BLIP), transported to Argonne National Laboratory, and studied with the Gammasphere facility. Significant revisions have been made to the level scheme of 82Kr including 12 new levels, 50 new γ -ray transitions, and the determination of many new spin assignments through angular correlations. These new high-quality data allow a precise reappraisal of the β -decay strength function and thus the consequent dose received by patients.

  18. Oxygen isotope studies of ordinary chondrites

    NASA Technical Reports Server (NTRS)

    Clayton, Robert N.; Mayeda, Toshiko K.; Olsen, Edward J.; Goswami, J. N.

    1991-01-01

    Several stages in the evolution of ordinary chondritic meteorites are recorded in the oxygen isotopic composition of the meteorites and their separable components (chondrules, fragments, clasts, and matrix). The whole-rock isotopic compositions reflect the iron-group of the meteorite (H, L, or LL). Isotopic uniformity of H3 to H6 and L3 to L6 are consistent with closed-system metamorphism within each parent body. LL3 chondrites differ slightly from LL4 to LL6, implying a small degree of open-system aqueous alteration and carbon reduction. On the scale of individual chondrules, the meteorites are isotopically heterogeneous, allowing recognition of the solar-nebular processes of chondrule formation. Chondrules for all classes of ordinary chondrites are derived from a common population, which was separate from the population of chondrules in carbonaceous or enstatite chondrites. Chondrules define an isotopic mixing line dominated by exchange between (O - 16)-rich and (O - 16)-poor reservoirs. The oxygen isotopic compositions of chondrites serve as 'fingerprints' for identification of genetic association with other meteorite types (achondrites and iron) and for recognition of source materials in meteoritic breccias.

  19. Li Isotope Studies of Olivine in Mantle Xenoliths by SIMS

    NASA Technical Reports Server (NTRS)

    Bell, D. R.; Hervig, R. L.; Buseck, P. R.

    2005-01-01

    Variations in the ratio of the stable isotopes of Li are a potentially powerful tracer of processes in planetary and nebular environments [1]. Large differences in the 7Li/6Li ratio between the terrestrial upper mantle and various crustal materials make Li isotope composition a potentially powerful tracer of crustal recycling processes on Earth [2]. Recent SIMS studies of terrestrial mantle and Martian meteorite samples report intra-mineral Li isotope zoning [3-5]. Substantial Li isotope heterogeneity also exists within and between the components of chondritic meteorites [6,7]. Experimental studies of Li diffusion suggest the potential for rapid isotope exchange at elevated temperatures [8]. Large variations in 7Li, exceeding the range of unaltered basalts, occur in terrestrial mantle-derived xenoliths from individual localities [9]. The origins of these variations are not fully understood.

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

    NASA Astrophysics Data System (ADS)

    Ni, Yunyan; Ma, Qisheng; Ellis, Geoffrey S.; Dai, Jinxing; Katz, Barry; Zhang, Shuichang; Tang, Yongchun

    2011-05-01

    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 280.2 cal/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 δD values in ethane from several basins in the world are in close agreement with similar predictions based on the δ 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 δD 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 δD values in ethane might be more suitable for modeling than comparable values in methane and propane.

  1. 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.

  2. Shape-Controlled Synthesis of Isotopic Yttrium-90-Labeled Rare Earth Fluoride Nanocrystals for Multimodal Imaging.

    PubMed

    Paik, Taejong; Chacko, Ann-Marie; Mikitsh, John L; Friedberg, Joseph S; Pryma, Daniel A; Murray, Christopher B

    2015-09-22

    Isotopically labeled nanomaterials have recently attracted much attention in biomedical research, environmental health studies, and clinical medicine because radioactive probes allow the elucidation of in vitro and in vivo cellular transport mechanisms, as well as the unambiguous distribution and localization of nanomaterials in vivo. In addition, nanocrystal-based inorganic materials have a unique capability of customizing size, shape, and composition; with the potential to be designed as multimodal imaging probes. Size and shape of nanocrystals can directly influence interactions with biological systems, hence it is important to develop synthetic methods to design radiolabeled nanocrystals with precise control of size and shape. Here, we report size- and shape-controlled synthesis of rare earth fluoride nanocrystals doped with the β-emitting radioisotope yttrium-90 ((90)Y). Size and shape of nanocrystals are tailored via tight control of reaction parameters and the type of rare earth hosts (e.g., Gd or Y) employed. Radiolabeled nanocrystals are synthesized in high radiochemical yield and purity as well as excellent radiolabel stability in the face of surface modification with different polymeric ligands. We demonstrate the Cerenkov radioluminescence imaging and magnetic resonance imaging capabilities of (90)Y-doped GdF3 nanoplates, which offer unique opportunities as a promising platform for multimodal imaging and targeted therapy. PMID:26257288

  3. Embryotoxicity of stable isotopes and use of stable isotopes in studies of teratogenetic mechanisms

    SciTech Connect

    Spielmann, H.; Nau, H.

    1986-07-01

    Experiments on teratogenic effects of stable isotopes from our own and other laboratories are evaluated. In the first series of investigations, the enrichment of the stable isotope /sup 13/C derived from U-/sup 13/C-glucose was studied in mouse embryos at various stages of development, including limb buds in organ culture. Preimplantation mouse embryos incubated in vitro in /sup 13/C-enriched medium for 48 hours showed normal development during subsequent differentiation in vitro and also in vivo after embryo transfer to faster mothers. These embryos were 15% to 20% enriched in /sup 13/C. Administration of U-13-C-glucose to pregnant mice during organogenesis led to an increase of the absolute /sup 13/C content of the embryo for several days after the end of isotope administration, whereas the enrichment in maternal tissue decreased. No alterations of embryonic development were detected due to stable isotope enrichment. Development of cultured mouse limb buds was unaffected by incubation with 82 mol% U-/sup 13/C-glucose as judged from morphologic and biochemical criteria. The second part of the article describes the value of deuterium-labeled drugs as probes into the mechanism of activation of teratogenic metabolites. A comparison of the pharmacokinetics as well as the teratogenicity between cyclophosphamide and some specific deuterium-labeled analogues showed that the isotope effect observed can be related to a particular metabolic pathway crucial for teratogenic activation by this drug.

  4. Preliminary study: isotopic safeguards techniques (IST) LMFBR fuel cycles

    SciTech Connect

    Persiani, P. J.; Kroc, T. K.

    1980-06-01

    This memorandum presents the preliminary results of the effort to investigate the applicability of isotope correlation techniques (ICT), formulated for the LWR system, to the LMFBR fuel cycle. The detailed isotopic compositional changes with burnup developed for the CRBR was utilized as the reference case. This differs from the usual LMFBR design studies in that the core uranium is natural uranium rather than depleted. Nevertheless, the general isotopic behavior should not differ significantly and does allow an initial insight into the expected behavior of isotopic correlations for the LMFBR power systems such as: the U.K. PFR and reprocessing plant; the French Phenix and Superphenix; and the US reference conceptual design studies (CDS) of homogeneous and heterogeneous LMFBR systems as they are developed.

  5. An isotope identification injection study with GammaTracker

    NASA Astrophysics Data System (ADS)

    Batdorf, Michael T.; Erikson, Luke E.; Seifert, Carolyn E.; Myjak, Mitchell J.; Kirihara, Leslie J.

    2011-10-01

    GammaTracker is a portable handheld radioisotope identifier using position sensitive CdZnTe detectors. High confidence isotope identification is possible on GammaTracker owing to the system's relatively high energy resolution and count rate sensitivity. A study was undertaken to evaluate the isotope identification performance of a prototype unit. Background and source spectra for various nuclides were measured and then randomly sampled to simulate various integration times and source intensities. The resulting spectral data sets were then run through the isotope identification algorithm to determine the probability of detection and the false alarm rate for each nuclide. The process was repeated for various isotope identification input parameters until an optimized set was achieved. This paper presents results from the injection study.

  6. 44Sc: An Attractive Isotope for Peptide-Based PET Imaging

    PubMed Central

    2015-01-01

    The overexpression of integrin αvβ3 has been linked to tumor aggressiveness and metastasis in several cancer types. Because of its high affinity, peptides containing the arginine–glycine–aspartic acid (RGD) motif have been proven valuable vectors for noninvasive imaging of integrin αvβ3 expression and for targeted radionuclide therapy. In this study, we aim to develop a 44Sc-labeled RGD-based peptide for in vivo positron emission tomography (PET) imaging of integrin αvβ3 expression in a preclinical cancer model. High quality 44Sc (t1/2, 3.97 h; β+ branching ratio, 94.3%) was produced inexpensively in a cyclotron, via proton irradiation of natural Ca metal targets, and separated by extraction chromatography. A dimeric cyclic-RGD peptide, (cRGD)2, was conjugated to 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) and radiolabeled with 44Sc in high yield (>90%) and specific activity (7.4 MBq/nmol). Serial PET imaging of mice bearing U87MG tumor xenografts showed elevated 44Sc-DOTA-(cRGD)2 uptake in the tumor tissue of 3.93 ± 1.19, 3.07 ± 1.17, and 3.00 ± 1.25 %ID/g at 0.5, 2, and 4 h postinjection, respectively (n = 3), which were validated by ex vivo biodistribution experiments. The integrin αvβ3 specificity of the tracer was corroborated, both in vitro and in vivo, by competitive cell binding and receptor blocking assays. These results parallel previously reported studies showing similar tumor targeting and pharmacokinetic profiles for dimeric cRGD peptides labeled with 64Cu or 68Ga. Our findings, together with the advantageous radionuclidic properties of 44Sc, capitalize on the relevance of this isotope as an attractive alternative isotope to more established radiometals for small molecule-based PET imaging, and as imaging surrogate of 47Sc in theranostic applications. PMID:25054618

  7. Rapid sample throughput for biomedical stable isotope tracer studies.

    PubMed

    Preston, T; McMillan, D C

    1988-10-01

    Typical 13C or 15N tracer studies generate large numbers of samples. Instrumentation capable of rapid automated analysis is therefore of importance as a practical alternative to conventional isotope methodology. Although biomedical sample nature is diverse, experimenters often require analysis of substrates and products of particular biochemical pathways. Clearly, reaction products can contain considerably less isotope tracer than precursors. Analytical techniques thus need to accommodate samples of widely varying nature, size and isotope enrichment. In the clinical field, where stable isotopes are increasingly used to study protein, carbohydrate and fat metabolism, analysis of the isotope ratio of a substrate infused into the plasma and a product of its metabolism is often required. Conventional analytical approaches demand access to two mass spectrometers: isotope ratio mass spectrometry (IRMS) for isotope analysis of the relatively large concentrations of low-enrichment metabolic product, and gas chromatography/mass spectrometry (GC/MS) for analysis of the infused substrate often present at high enrichment but low concentration offers a practical alternative to the conventional approaches that is rapid and automatic. In addition to providing a considerably less complex and costly alternative to conventional instrumentation, a single CF-IRMS instrument can also analyse small quantities of low-enrichment metabolites with superior performance than either of the alternative approaches. CF-IRMS is illustrated using results from constant-infusion studies in human protein and fat metabolism which require measurement of the isotope enrichment in submicromolar quantities of plasma substrates together with analysis of larger quantities of their oxidation products, urinary nitrogen and breath CO2. PMID:3149535

  8. Imaging studies in hypercalcemia.

    PubMed

    Cecchin, D; Motta, R; Zucchetta, P; Bui, F; Basso, S M M; Lumachi, F

    2011-01-01

    Hypercalcemia is a relatively common clinical problem, mainly (>90%) related to primary hyperparathyroidism (HPT) and malignancies. The anatomical and functional imaging techniques available for locating enlarged parathyroid glands include ultrasound (US), computed tomography (CT), magnetic resonance imaging (MRI), and nuclear medicine imaging techniques. The most commonly employed are US and parathyroid scintigraphy, while CT, MRI, positron emission tomography (PET)/CT, and selective venous sampling are generally used in patients with persistent or recurrent HPT, or when findings of non-invasive studies are negative or conflicting. The reported accuracy is 57-93%, 54-93%, and up to 95% for US, (99m)Tc-sestamibi scintigraphy, and the two modalities combined, respectively. A multimodality approach (x-ray, whole-body scintigraphy, CT, MRI, and PET) is usually recommended for whole body assessment in cases of cancer-induced hypercalcemia (CIH). Imaging studies should evaluate each organ (i.e. breast, kidney, prostate, parathyroid) potentially involved in the pathogenesis of hypercalcemia in patients with CIH. In cases of skeletal metastases, when findings on plain x-ray or bone scans are uncertain, any unexplained region of abnormal uptake should be examined by MRI and/or ¹⁸F-fluoro-2- deoxyglucose (FDG)-PET/CT, which has proved more accurate than classical bone scintigraphy, especially for dealing with hematologic malignancies. A number of radionuclide tracers, other than ¹⁸F-FDG, are available for use in selected cases to locate specific tumors (i.e. ⁶⁸Ga for neuroendocrine tumors). This is a review of recently published information on the imaging techniques currently available for patients with hypercalcemia. PMID:21756234

  9. Stable Isotope Applications in Hydrologic Studies

    NASA Astrophysics Data System (ADS)

    Kendall, C.; Doctor, D. H.

    2003-12-01

    The topic of stream flow generation has received considerable attention over the last two decades, first in response to concern about "acid rain" and more recently in response to the increasingly serious contamination of surface and shallow groundwaters by anthropogenic contaminants. Many sensitive, low-alkalinity streams in North America and Europe are already acidified (see Chapter 9.10). Still more streams that are not yet chronically acidic may undergo acidic episodes in response to large rainstorms and/or spring snowmelt. These acidic events can seriously damage local ecosystems. Future climate changes may exacerbate the situation by affecting biogeochemical controls on the transport of water, nutrients, and other materials from land to freshwater ecosystems.New awareness of the potential danger to water supplies posed by the use of agricultural chemicals and urban industrial development has also focused attention on the nature of rainfall-runoff and recharge processes and the mobility of various solutes, especially nitrate and pesticides, in shallow systems. Dumping and spills of other potentially toxic materials are also of concern because these chemicals may eventually reach streams and other public water supplies. A better understanding of hydrologic flow paths and solute sources is required to determine the potential impact of contaminants on water supplies, develop management practices to preserve water quality, and devise remediation plans for sites that are already polluted.Isotope tracers have been extremely useful in providing new insights into hydrologic processes, because they integrate small-scale variability to give an effective indication of catchment-scale processes. The main purpose of this chapter is to provide an overview of recent research into the use of naturally occurring stable isotopes to track the movement of water and solutes in hydrological systems where the waters are relatively fresh: soils, surface waters, and shallow

  10. Nitrogen and Oxygen Isotopic Studies of the Marine Nitrogen Cycle

    NASA Astrophysics Data System (ADS)

    Casciotti, Karen L.

    2016-01-01

    The marine nitrogen cycle is a complex web of microbially mediated reactions that control the inventory, distribution, and speciation of nitrogen in the marine environment. Because nitrogen is a major nutrient that is required by all life, its availability can control biological productivity and ecosystem structure in both surface and deep-ocean communities. Stable isotopes of nitrogen and oxygen in nitrate and nitrite have provided new insights into the rates and distributions of marine nitrogen cycle processes, especially when analyzed in combination with numerical simulations of ocean circulation and biogeochemistry. This review highlights the insights gained from dual-isotope studies applied at regional to global scales and their incorporation into oceanic biogeochemical models. These studies represent significant new advances in the use of isotopic measurements to understand the modern nitrogen cycle, with implications for the study of past ocean productivity, oxygenation, and nutrient status.

  11. Nitrogen and Oxygen Isotopic Studies of the Marine Nitrogen Cycle.

    PubMed

    Casciotti, Karen L

    2016-01-01

    The marine nitrogen cycle is a complex web of microbially mediated reactions that control the inventory, distribution, and speciation of nitrogen in the marine environment. Because nitrogen is a major nutrient that is required by all life, its availability can control biological productivity and ecosystem structure in both surface and deep-ocean communities. Stable isotopes of nitrogen and oxygen in nitrate and nitrite have provided new insights into the rates and distributions of marine nitrogen cycle processes, especially when analyzed in combination with numerical simulations of ocean circulation and biogeochemistry. This review highlights the insights gained from dual-isotope studies applied at regional to global scales and their incorporation into oceanic biogeochemical models. These studies represent significant new advances in the use of isotopic measurements to understand the modern nitrogen cycle, with implications for the study of past ocean productivity, oxygenation, and nutrient status. PMID:26747521

  12. Imaging of Isotopically Enhanced Molecular Targeting Agents Final Report

    SciTech Connect

    Quong, J N

    2004-02-19

    The goal of this project is to develop experimental and computational protocols to use SIMS to image the chemical composition of biological samples, focusing on optimizing sample preparation protocols and developing multivariate data analysis methods. Our results on sample preparation, molecular imaging, and multivariate analysis have been presented at several meeting abstracts (UCRL151797ABS, UCRL151797ABSREV1, UCRL151426ABS, UCRL201277, UCRL154757). A refereed paper describing our results for sample preparation and molecular imaging of various endogenous biomolecules as well as the mutagen PhIP has been accepted for publication (UCRL-JC-151797). We are also preparing two additional papers describing our multivariate analysis methods to analyze spectral data. As these papers have not been submitted, their content is included in this final report.

  13. Ammonium transport and reaction in contaminated groundwater: Application of isotope tracers and isotope fractionation studies

    USGS Publications Warehouse

    Böhlke, J.K.; Smith, R.L.; Miller, D.N.

    2006-01-01

    Ammonium (NH4+) is a major constituent of many contaminated groundwaters, but its movement through aquifers is complex and poorly documented. In this study, processes affecting NH4+ movement in a treated wastewater plume were studied by a combination of techniques including large-scale monitoring of NH4+ distribution; isotopic analyses of coexisting aqueous NH4+, NO3-, N2, and sorbed NH 4+; and in situ natural gradient 15NH 4+ tracer tests with numerical simulations of 15NH4+, 15NO3-, and 15N2 breakthrough data. Combined results indicate that the main mass of NH4+ was moving downgradient at a rate about 0.25 times the groundwater velocity. Retardation factors and groundwater ages indicate that much of the NH4+ in the plume was recharged early in the history of the wastewater disposal. NO3- and excess N2 gas, which were related to each other by denitrification near the plume source, were moving downgradient more rapidly and were largely unrelated to coexisting NH 4+. The ??15N data indicate areas of the plume affected by nitrification (substantial isotope fractionation) and sorption (no isotope fractionation). There was no conclusive evidence for NH 4+-consuming reactions (nitrification or anammox) in the anoxic core of the plume. Nitrification occurred along the upper boundary of the plume but was limited by a low rate of transverse dispersive mixing of wastewater NH4+ and O2 from overlying uncontaminated groundwater. Without induced vertical mixing or displacement of plume water with oxic groundwater from upgradient sources, the main mass of NH4+ could reach a discharge area without substantial reaction long after the more mobile wastewater constituents are gone. Multiple approaches including in situ isotopic tracers and fractionation studies provided critical information about processes affecting NH4+ movement and N speciation.

  14. Cerenkov Radiation Energy Transfer (CRET) Imaging: A Novel Method for Optical Imaging of PET Isotopes in Biological Systems

    PubMed Central

    Dothager, Robin S.; Goiffon, Reece J.; Jackson, Erin; Harpstrite, Scott; Piwnica-Worms, David

    2010-01-01

    Background Positron emission tomography (PET) allows sensitive, non-invasive analysis of the distribution of radiopharmaceutical tracers labeled with positron (β+)-emitting radionuclides in small animals and humans. Upon β+ decay, the initial velocity of high-energy β+ particles can momentarily exceed the speed of light in tissue, producing Cerenkov radiation that is detectable by optical imaging, but is highly absorbed in living organisms. Principal Findings To improve optical imaging of Cerenkov radiation in biological systems, we demonstrate that Cerenkov radiation from decay of the PET isotopes 64Cu and 18F can be spectrally coupled by energy transfer to high Stokes-shift quantum nanoparticles (Qtracker705) to produce highly red-shifted photonic emissions. Efficient energy transfer was not detected with 99mTc, a predominantly γ-emitting isotope. Similar to bioluminescence resonance energy transfer (BRET) and fluorescence resonance energy transfer (FRET), herein we define the Cerenkov radiation energy transfer (CRET) ratio as the normalized quotient of light detected within a spectral window centered on the fluorophore emission divided by light detected within a spectral window of the Cerenkov radiation emission to quantify imaging signals. Optical images of solutions containing Qtracker705 nanoparticles and [18F]FDG showed CRET ratios in vitro as high as 8.8±1.1, while images of mice with subcutaneous pseudotumors impregnated with Qtracker705 following intravenous injection of [18F]FDG showed CRET ratios in vivo as high as 3.5±0.3. Conclusions Quantitative CRET imaging may afford a variety of novel optical imaging applications and activation strategies for PET radiopharmaceuticals and other isotopes in biomaterials, tissues and live animals. PMID:20949021

  15. Groundwater surface water interaction study using natural isotopes tracer

    NASA Astrophysics Data System (ADS)

    Yoon, Yoon Yeol; Kim, Yong Chul; Cho, Soo Young; Lee, Kil Yong

    2015-04-01

    Tritium and stable isotopes are a component of the water molecule, they are the most conservative tracer for groundwater study. And also, radon is natural radioactive nuclide and well dissolved in groundwater. Therefore, these isotopes are used natural tracer for the study of surface water and groundwater interaction of water curtain greenhouse area. The study area used groundwater as a water curtain for warming tool of greenhouse during the winter, and is associated with issues of groundwater shortage while being subject to groundwater-river water interaction. During the winter time, these interactions were studied by using Rn-222, stable isotopes and H-3. These interaction was monitored in multi depth well and linear direction well of groundwater flow. And dam effect was also compared. Samples were collected monthly from October 2013 to April 2014. Radon and tritium were analyzed using Quantulus low background liquid scintillation counter and stable isotopes were analyzed using an IRIS (Isotope Ratio Infrared Spectroscopy ; L2120-i, Picarro). During the winter time, radon concentration was varied from 0.07 Bq/L to 8.9 Bq/L and different interaction was showed between dam. Surface water intrusion was severe at February and restored April when greenhouse warming was ended. The stable isotope results showed different trend with depth and ranged from -9.16 ‰ to -7.24 ‰ for δ 18O value, while the δD value was ranged from -57.86 ‰ to -50.98 ‰. The groundwater age as dated by H-3 was ranged 0.23 Bq/L - 0.59 Bq/L with an average value of 0.37 Bq/L.

  16. Oxygen isotope fractionation between analcime and water - An experimental study

    NASA Technical Reports Server (NTRS)

    Karlsson, Haraldur R.; Clayton, Robert N.

    1990-01-01

    The oxygen isotope fractionation between analcime and water is studied to test the feasibility of using zeolites as low-temperature thermometers. The fractionation of oxygen isotopes between natural analcime and water is determined at 300, 350, and 400 C, and at fluid pressures ranging from 1.5 to 5.0 kbar. Also, isotope ratios for the analcime framework, the channel water, and bulk water are obtained. The results suggest that the channel water is depleted in O-18 relative to bulk water by a constant value of about 5 percent, nearly independent of temperature. The analcime-water fractionation curve is presented, showing that the exchange has little effect on grain morphology and does not involve recrystallization. The exchange is faster than any other observed for a silicate. The exchange rates suggest that zeolites in active high-temperature geothermal areas are in oxygen isotopic equilibrium with ambient fluids. It is concluded that calibrated zeolites may be excellent low-temperature oxygen isotope geothermometers.

  17. Contaminant source apportionment by PIMMS lead isotope analysis and SEM-image analysis.

    PubMed

    McGill, R A; Pearce, J M; Fortey, N J; Watt, J; Ault, L; Parrish, R R

    2003-03-01

    By combining scanning electron microscopy (SEM) image analysis and laser ablation plasma ionisation multi-collector mass spectrometry (LA-PIMMS), high precision lead isotope analyses can be obtained from individual metal-rich particles. Soils from Wolverhampton and Nottingham were sampled on the basis of high Pb concentrations or brownfield location. Pressed powder pellets of each were rastered by LA-PIMMS to obtain a bulk Pb-isotope signature. The results plot along an apparent mixing line between the major sources of lead contamination in the UK, that is UK ore deposits and alkyl-lead from petrol additives (Australian ore). Two particularly lead-rich soils were chosen to investigate the lead distribution and isotope variability between size and density fractions. The fine-grained and low-density fractions contained most of the lead and have Pb-isotope ratios comparable with the bulk soils. By contrast, the small, lead-enriched denser fractions contained only a minor proportion of the total lead but Pb-isotope signatures indicating relative enrichment in one or other of the end-members from the mixing line. Further characterisation of individual Pb-rich grains is in progress. PMID:12901075

  18. Study of the mechanism of diatom cell division by means of 29Si isotope tracing

    NASA Astrophysics Data System (ADS)

    Audinot, J.-N.; Guignard, C.; Migeon, H.-N.; Hoffmann, L.

    2006-07-01

    Diatoms are delicate unicellular organisms enclosed in a silica frustule, that is made up of two valves. Multiplication of the diatoms occurs by ordinary mitotic cell division. During cell division each cell produces two daughter cells, each of them keeping one of the two valves of the mother cell and producing a new valve by absorbing the silicon present in the environment. The NanoSIMS 50 allows ion imaging to be performed on diatoms in order to determine the site of fixation of silicon. The aim of this study was to observe and compare the mechanism of the construction of the new valve after cell division. To this end, different types of diatoms have been transferred in a culture medium enriched with 29Si and after several days, the distribution of the different isotopes of silicon has been determined by NanoSIMS50 imaging. The construction of new valves has been observed and the isotopic ratio has been determined.

  19. The Enriched Background Isotope Study (EBIS)

    SciTech Connect

    Hanson, Paul J.; Trumbore, Susan; Swanston, Chris; Torn, Margaret; Jastrow, Julie; Parton, William A; Post, Wilfred M.; Froberg, Mats J; Hainsworth, Laura J; Kleber, Markus; Kramer, Christiane; Matamala-Paradeda, Roser; Garten, Jr, Charles T.

    2007-02-05

    A unique, large release of radiocarbon occurred near the Oak Ridge Reservation (ORR), Oak Ridge, TN in July/August 1999. Measurements of 14C in tree ring cellulose throughout the ORR area demonstrate that the 1999 release was unprecedented in its uptake by vegetation. We are taking advantage of the whole-ecosystem isotopic label generated by this release to address five outstanding issues in the terrestrial carbon cycle: (1) partitioning of soil respiration between autotrophic and heterotrophic sources, and quantification of that partitioning seasonally and inter-annually, (2) partitioning of heterotrophic respiration sources between above-ground litter decomposition and below-ground root detritus decomposition, (3) identification of pathways leading from leaf and root detritus to long-term stabilization of soil organic matter, including the role of soil fauna, (4) the role of dissolved organic carbon (DOC) transport in distributing carbon within the soil profile, and, (5) the longevity and turnover time of fine roots. The first four issues are being addressed through a reciprocal litter transplant experiment set up at four sites on the ORR encompassing two soil types and two levels of 14C exposure in 1999. The fifth issue, longevity and turnover of fine roots, is being addressed by tracing the radiocarbon label through the fine root pool over time. With a combination of incubation, soil surface chamber and soil CO2 profiles, and continuous measurements of soil temperature and moisture controls, we are tracking changes in soil respiration partitioning over several years. The nature and source of organic matter pools that reside in soils for years to decades are being tracked with differently labeled root and surface litter, and experiments to exclude soil fauna have been initiated to elucidate their role in vertical transport. Periodic sampling of soils and soil solutions and the use of inert tracers, allow us to investigate the chemical nature and form of DOC and

  20. ISOTOPIC STUDY OF THE INHALATION TOXICOLOGY OF OXIDANTS

    EPA Science Inventory

    The purpose of these studies was to develop novel methods to investigate the biological fate of inhaled ozone and other oxygen-containing pollutants in animal and human tissues using the heavy isotope of oxygen, oxygen-18 (18O). Methods were developed which facilitated the conver...

  1. Thyroid imaging studies

    SciTech Connect

    Drew, H.H.; LaFrance, N.D.; Chen, J.J.S.

    1987-06-01

    This is the second in a series of Continuing Education articles related to functional/quantitative imaging techniques. After reading this article, the reader should be able to: 1) discuss the clinical applications of thyroid imaging; 2) understand the relationship of related thyroid tests; and 3) recognize the pitfalls and problems associated with this procedure.

  2. Subcutaneous infusion and capillary "finger stick" sampling of stable isotope tracer in metabolic studies

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Metabolic studies utilizing stable isotope tracer in humans have typically used intravenous tracer infusions and venous blood sampling. These studies explore subcutaneous infusion of isotope and "finger stick" capillary blood sampling to measure glucose turnover. Five subjects received simultaneous ...

  3. Sulfur and oxygen isotope studies of sulfate reduction

    NASA Astrophysics Data System (ADS)

    Farquhar, J.; Canfield, D. E.; Bao, H.; Masterson, A.; Johnston, D. T.; Wing, B. A.

    2007-12-01

    I will discuss insights into sulfur and oxygen isotope fractionations of dissimilatory sulfate reduction and specifically insight provided by experiments with natural populations of sulfate-reducing bacteria from Faellestrand, Denmark. The experiments yielded relatively large magnitude sulfur isotope fractionations for dissimilatory sulfate reduction (up to approximately 45 ‰ for 34S/32S), with higher δ18O accompanying higher δ34S, similar to that observed in previous studies. The seawater used in the experiments was spiked by addition of 17O-labelled water and the 17O content of residual sulfate was found to depend on the fraction of sulfate reduced in the experiments. The 17O data provides evidence for recycling of sulfur from metabolic intermediates and for an 18O/16O fractionation of ~25-30 ‰ for dissimilatory sulfate reduction, a magnitude that is consistent with isotopic exchange between a sulfite species and cell water. The molar ratio of oxygen exchange to sulfate reduction was found to be about 2.5. Using recent models of sulfur isotope fractionations we find that our combined sulfur and oxygen isotopic data places constraints on the proportion of sulfate recycled to the medium (78-96 %), the proportion of sulfur intermediate sulfite that was recycled by way of APS to sulfate and released back to the external sulfate pool (~70%) and also that a fraction of the sulfur intermediates between sulfite and sulfide were recycled to sulfate. These parameters can be constrained because of the independent information provided by δ18O, δ34S, 17O labels, and Δ33S.

  4. Isotopically modified nanoparticles for enhanced detection in bioaccumulation studies.

    PubMed

    Misra, Superb K; Dybowska, Agnieszka; Berhanu, Deborah; Croteau, Marie Noële; Luoma, Samuel N; Boccaccini, Aldo R; Valsami-Jones, Eugenia

    2012-01-17

    This work presents results on synthesis of isotopically enriched (99% (65)Cu) copper oxide nanoparticles and its application in ecotoxicological studies. (65)CuO nanoparticles were synthesized as spheres (7 nm) and rods (7 × 40 nm). Significant differences were observed between the reactivity and dissolution of spherical and rod shaped nanoparticles. The extreme sensitivity of the stable isotope tracing technique developed in this study allowed determining Cu uptake at exposure concentrations equivalent to background Cu concentrations in freshwater systems (0.2-30 μg/L). Without a tracer, detection of newly accumulated Cu was impossible, even at exposure concentrations surpassing some of the most contaminated water systems (>1 mg/L). PMID:22148182

  5. Isotopically modified nanoparticles for enhanced detection in bioaccumulation studies

    USGS Publications Warehouse

    Misra, S.K.; Dybowska, A.; Berhanu, D.; Croteau, M.-N.; Luoma, S.N.; Boccaccini, A.R.; Valsami-Jones, E.

    2012-01-01

    This work presents results on synthesis of isotopically enriched (99% 65Cu) copper oxide nanoparticles and its application in ecotoxicological studies. 65CuO nanoparticles were synthesized as spheres (7 nm) and rods (7 ?? 40 nm). Significant differences were observed between the reactivity and dissolution of spherical and rod shaped nanoparticles. The extreme sensitivity of the stable isotope tracing technique developed in this study allowed determining Cu uptake at exposure concentrations equivalent to background Cu concentrations in freshwater systems (0.2-30 ??g/L). Without a tracer, detection of newly accumulated Cu was impossible, even at exposure concentrations surpassing some of the most contaminated water systems (>1 mg/L). ?? 2011 American Chemical Society.

  6. Mars Molecular and Isotopic Analysis Research Study

    NASA Technical Reports Server (NTRS)

    Manning, Heidi L. K.

    1998-01-01

    Recently, the Martian atmosphere and surface constituents have become of great interest. The Viking in situ gas chromatograph mass spectrometer experiment contributed greatly to our knowledge of the composition of the Martian atmosphere. However, important questions remain such as the abundance of water on Mars. The Viking experiment employed solid reagents to enhance their carbon measurements. Techniques of chemical conversion using simple solid reagents have advanced considerably in the past 20 years. In this investigation we researched the advancements in techniques to reversibly adsorb and desorb water and focused on the techniques potentially useful for the temperatures and pressures on the Martian surface. During the granting period from June 15, 1998 to August 14, 1998, a literature study of the material appropriate for use in a chemical conversion device and the availability of these materials were undertaken. The focus of this investigation was searching for methods and materials potentially useful in enhancing the measurements of water. Three different methods were considered for the means to extract water from a given gas sample. These methods included adsorption in a desiccant, adsorption on a clean metal surface, and adsorption in a carbon molecular sieve or zeolite. Each method was evaluated with feasibility and reversibility in mind. By far the simplest and perhaps cheapest way to remove water from a gaseous sample is by means of a bulk desiccant. Desiccants are commercially available from many companies including those that supply chemicals. The main feature of a desiccant is its ability to rapidly bind or absorb water from the atmosphere. Calcium chloride, for example, is frequently incorporated into drying tubes by organic chemists when reactions require the absence of water. Other desiccants include sodium hydroxide, calcium hydride, and commercial products such as Drierite, available from Aldrich Chemical. The disadvantage to most desiccants is

  7. Fluid inclusion stable isotopes and clumped isotopes thermometry study of Eastern Mediterranean paleoclimate

    NASA Astrophysics Data System (ADS)

    Matthews, A.; Bar-Matthews, M.; Affek, H. P.; Ayalon, A.; Vonhof, H. B.; Zaarur, S.; Burstyn, Y.

    2012-04-01

    Fluid inclusion (FI) stable isotopes and clumped isotopes thermometry provide powerful tools for reconstructing paleoclimates using speleothems. Clumped isotopes thermometry is a unique tool for paleotemperature determination using the mass 47 anomaly (Δ47), but its application to speleothems is complicated by the occurrence of a kinetic isotope effect (KIE) that accompanies CO2 degassing during carbonate precipitation1. Experimental studies involving the surface precipitation of synthetic calcite2 provide a Δ47 thermometer calibration that takes KIE into account and allows its direct application to speleothems. Complementary, the δDw and δ18Ow values of speleothem FI provide an important proxy for cave water-rainfall paleo-hydrological conditions, together with the data required for construction of the meteoric water line (MWL) relationship. Until recently the main studied parameter is δDw, and the reliability of FI δ18Ow has been questioned because of the possibility of post-depositional isotope exchange with the surrounding calcite. When speleothem calcite δ18Occ is measured, Δ47 temperatures allow δ18Ow to be independently calculated using the calcite-water fractionation relationship. Methods for FI analysis using crushing in a helium stream, TC/EA and continuous flow mass spectrometry (Amsterdam system3) enable both δDw and δ18Ow to be determined, thus allowing measured δ18Ow values to be compared with those calculated from Δ47 temperatures and δ18Occ. We apply these methodologies to paleoclimate study in the Eastern Mediterranean (EM) region during the last 150 ky: in the Soreq Cave from the glacial stage 6 to the last interglacial stage 5e and the last glacial maximum (LGM) to the Holocene, and to the Alpine karst system of the Hermon mountain range (MS) cave4 during the last interglacial and brief warm intervals during the last glacial. Soreq Cave Δ47 data show temperature minima at the termination of stage 6 and the LGM, but the LGM

  8. Applications of C and N stable isotopes to ecological and environmental studies in seagrass ecosystems.

    PubMed

    Lepoint, Gilles; Dauby, Patrick; Gobert, Sylvie

    2004-12-01

    Stable isotopes of carbon and nitrogen are increasingly used in marine ecosystems, for ecological and environmental studies. Here, we examine some applications of stable isotopes as ecological integrators or tracers in seagrass ecosystem studies. We focus on both the use of natural isotope abundance as food web integrators or environmental tracers and on the use of stable isotopes as experimental tools. As ecosystem integrators, stable isotopes have helped to elucidate the general structure of trophic webs in temperate, Mediterranean and tropical seagrass ecosystems. As environmental tracers, stable isotopes have proven their utility in sewage impact measuring and mapping. However, to make such environmental studies more comprehensible, future works on understanding of basic reasons for variations of N and C stable isotopes in seagrasses should be encouraged. At least, as experimental tracers, stable isotopes allow the study of many aspects of N and C cycles at the scale of a plant or at the scale of the seagrass ecosystem. PMID:15556172

  9. STABLE ISOTOPES IN ECOLOGICAL STUDIES: NEW DEVELOPMENTS IN MIXING MODELS (BRAZIL)

    EPA Science Inventory

    Stable isotopes are increasingly being used as tracers in ecological studies. One application uses isotopic ratios to quantify the proportional contributions of multiple sources to a mixture. Examples include pollution sources for air or water bodies, food sources for animals, ...

  10. Theoretical study on isotope separation of an ytterbium atomic beam by laser deflection

    NASA Astrophysics Data System (ADS)

    Zhou, Min; Xu, Xin-Ye

    2014-01-01

    Isotope separation by laser deflecting an atomic beam is analyzed theoretically. Interacting with a tilted one-dimensional optical molasses, an ytterbium atomic beam is split into multi-beams with different isotopes like 172Yb,173Yb, and 174Yb. By using the numerical calculation, the dependences of the splitting angle on the molasses laser intensity and detuning are studied, and the optimal parameters for the isotope separation are also investigated. Furthermore, the isotope separation efficiency and purity are estimated. Finally a new scheme for the efficient isotope separation is proposed. These findings will give a guideline for simply obtaining pure isotopes of various elements.

  11. Isotopic Biogeochemistry

    NASA Technical Reports Server (NTRS)

    Hayes, J. M.

    1985-01-01

    An overview is provided of the biogeochemical research. The funding, productivity, personnel and facilities are reviewed. Some of the technical areas covered are: carbon isotopic records; isotopic studies of banded iron formations; isotope effects in microbial systems; studies of organic compounds in ancient sediments; and development in isotopic geochemistry and analysis.

  12. Strontium isotope study, Pine Barrens, Long Island, NY

    SciTech Connect

    Xin, Geng; Hanson, G.N. . Dept. of Earth and Space Sciences)

    1993-03-01

    Twenty-four samples representing precipitation, through-fall, soil water, ground water, vegetation and soil were analyzed for strontium concentration and the [sup 87]Sr/[sup 86]Sr ratio. The Pine Barrens, which consists of forests and dense vegetation, covers approximately 300 square miles of the coastal plain of Long Island, New York. This study estimates the relative importance of atmospheric and weathering inputs of Sr to vegetation in this ecosystem. The values of the [sup 87]Sr/[sup 86]Sr ratios and Sr concentration in the Pine Barrens are shown in the attached figure. Precipitation has Sr isotopic ratios that are close to that of sea water (0.7092). The Sr in through-fall is dominated by the Sr from the canopy foliage. The [sup 87]Sr/[sup 86]Sr ratios of soil water and ground water increase with depth. The Sr isotopic ratio for a composite sample of pine (0.71181) is a mixture of atmosphere Sr and soil or ground waters. The Sr isotopic ratios and concentrations in pine suggest that plants are a major reservoir of Sr in the system.

  13. s-process studies - Xenon and krypton isotopic abundances

    NASA Technical Reports Server (NTRS)

    Clayton, D. D.; Ward, R. A.

    1978-01-01

    We propose an analysis of the s-process contributions to the isotopes of xenon and krypton. The object is to aid studies of the possibility that meteorites may contain gas that was carried in presolar grains that were grown in stellar ejecta and that were not degassed prior to incorporation into parent bodies. That model suggests routine interstellar fractionation of s-isotopes from r-isotopes owing to differential incorporation into dust. We show that a deficiency of s-process nuclei cannot yield details of Xe-X, but the gross similarities are strong enough to lead one to think that such a deficiency may play a role in a more complicated explanation. We predict the existence of an s-rich complement somewhere if fractional separation of this type has played a role in Xe-X. We show that the analogous decomposition of krypton is more uncertain, and we call for measurements of neutron-capture cross sections to alleviate these uncertainties.

  14. Water isotopes and the Eocene. A tectonic sensitivity study

    NASA Astrophysics Data System (ADS)

    Legrande, A. N.; Roberts, C. D.; Tripati, A.; Schmidt, G. A.

    2009-04-01

    The early Eocene (54 Million years ago) is one of the warmest periods in the last 65 Million years. Its climate is postulated to have been the result of enhanced greenhouse gas concentration, with CO2 roughly 4 times pre-industrial and methane 7 times pre-industrial concentrations. One interesting feature of this period to emerge recently is the intermittent presence of fossilized Azolla, a type of freshwater fern, in the Arctic Ocean. Synchronous (within dating error) with this appearance were major changes in the restriction of the Arctic Ocean and the other global oceans. We investigate this time period using the Goddard Institute for Space Studies ModelE-R, a fully coupled atmosphere-ocean general circulation model that incorporates water isotopes throughout the hydrologic cycle, making it an ideal model to test hypotheses of past climate change and to compare to paleoclimate proxy data. We assess the impact of tectonic variability by using minimal and maximal levels of restriction for the Arctic Ocean seaways. We find that the modulation of connectivity of these basins dramatically alters global salinity distribution, leading to large changes in ocean circulation. Greater restriction of the Arctic Basin is associated with fresh and relatively warmer conditions. The same mechanisms responsible for this redistribution of salt also change the global distribution of water isotopes, and can alias (water isotope) proxy climate signals of warmth.

  15. Isotopic Analysis of Fingernails as a USGS Open House Demonstration of the Use of Stable Isotopes in Foodweb Studies

    NASA Astrophysics Data System (ADS)

    Silva, S. R.; Kendall, C.; Young, M. B.; Choy, D.

    2011-12-01

    The USGS Isotope Tracers Project uses stable isotopes and tritium to add a unique dimension of chemical information to a wide range of environmental investigations. The use and application of isotopes is usually an unfamiliar and even esoteric topic to the general public. Therefore during three USGS open house events, as a public outreach effort, we demonstrated the use of stable isotopes by analyzing nitrogen and carbon isotopes from very small fragments of fingernail from willing participants. We titled the exhibit "You Are What You Eat". The results from all participants were plotted on a graph indicating the general influence of different food groups on the composition of body tissues as represented by fingernails. All participants were assigned a number and no personal-identification information was collected. A subset of participants provided us with an estimate of the number of days a week various foods were eaten and if they were vegetarians, vegans or non-vegetarians. Volunteers from our research group were on hand to explain and discuss fundamental concepts such as how foods attain their isotopic composition, the difference between C3 and C4 plants, the effects of assimilation, trophic enrichment, and the various uses of stable isotopes in environmental studies. The results of the fingernail analyses showed the variation of the range of isotopic compositions among about 400 people at each event, the distinct influence of C4 plants (mainly corn and cane sugar) on our carbon isotopic composition, and the isotopic differences between vegetarians and non vegetarians among other details (http://wwwrcamnl.wr.usgs.gov/isoig/projects/fingernails/). A poll of visitors attending the open house event in 2006 indicated that "You Are What You Eat" was among the most popular exhibits. Following the first two open house events we were contacted by a group of researchers from Brazil who had completed a very similar study. Our collaboration resulted in a publication in

  16. Correlated optical and isotopic nanoscopy

    NASA Astrophysics Data System (ADS)

    Saka, Sinem K.; Vogts, Angela; Kröhnert, Katharina; Hillion, François; Rizzoli, Silvio O.; Wessels, Johannes T.

    2014-04-01

    The isotopic composition of different materials can be imaged by secondary ion mass spectrometry. In biology, this method is mainly used to study cellular metabolism and turnover, by pulsing the cells with marker molecules such as amino acids labelled with stable isotopes (15N, 13C). The incorporation of the markers is then imaged with a lateral resolution that can surpass 100 nm. However, secondary ion mass spectrometry cannot identify specific subcellular structures like organelles, and needs to be correlated with a second technique, such as fluorescence imaging. Here, we present a method based on stimulated emission depletion microscopy that provides correlated optical and isotopic nanoscopy (COIN) images. We use this approach to study the protein turnover in different organelles from cultured hippocampal neurons. Correlated optical and isotopic nanoscopy can be applied to a variety of biological samples, and should therefore enable the investigation of the isotopic composition of many organelles and subcellular structures.

  17. Isotope Cancer Treatment Research at LANL

    SciTech Connect

    Weidner, John; Nortier, Meiring

    2012-04-11

    Los Alamos National Laboratory has produced medical isotopes for diagnostic and imaging purposes for more than 30 years. Now LANL researchers have branched out into isotope cancer treatment studies. New results show that an accelerator-based approach can produce clinical trial quantities of actinium-225, an isotope that has promise as a way to kill tumors without damaging surrounding healthy cells.

  18. Isotope Cancer Treatment Research at LANL

    ScienceCinema

    Weidner, John; Nortier, Meiring

    2014-06-02

    Los Alamos National Laboratory has produced medical isotopes for diagnostic and imaging purposes for more than 30 years. Now LANL researchers have branched out into isotope cancer treatment studies. New results show that an accelerator-based approach can produce clinical trial quantities of actinium-225, an isotope that has promise as a way to kill tumors without damaging surrounding healthy cells.

  19. Elemental and isotopic imaging of biological samples using NanoSIMS.

    PubMed

    Kilburn, Matt R; Clode, Peta L

    2014-01-01

    With its low detection limits and the ability to analyze most of the elements in the periodic table, secondary ion mass spectrometry (SIMS) represents one of the most versatile in situ analytical techniques available, and recent developments have resulted in significant advantages for the use of imaging mass spectrometry in biological and biomedical research. Increases in spatial resolution and sensitivity allow detailed interrogation of samples at relevant scales and chemical concentrations. Advances in dynamic SIMS, specifically with the advent of NanoSIMS, now allow the tracking of stable isotopes within biological systems at subcellular length scales, while static SIMS combines subcellular imaging with molecular identification. In this chapter, we present an introduction to the SIMS technique, with particular reference to NanoSIMS, and discuss its application in biological and biomedical research. PMID:24357388

  20. Stable carbon isotopes and the study of prehistoric human diet.

    PubMed

    Boutton, T W; Lynott, M J; Bumsted, M P

    1991-01-01

    Mass spectrometric analysis of the stable carbon isotope composition (13C/12C or delta 13C) of bone collagen from human remains recovered at archaeological sites provides a direct chemical method for investigating dietary patterns of prehistoric human populations. This methodology is based on the facts that (1) different food items within the human diet have distinct delta 13C values, and (2) the delta 13C value of human bone collagen is determined by the delta 13C value of the diet. Studies of the development of subsistence patterns based on corn agriculture, one of the most significant developments in North American prehistory, can benefit from the use of stable carbon isotope techniques because corn has a high delta 13C value relative to other components of the human diet. Measurements of delta 13C of bone collagen from prehistoric human skeletal remains from southeastern Missouri and northeastern Arkansas indicate that intensive corn agriculture began in this region around A.D. 1000, that the incorporation of corn into the human diet was a rapid phenomenon, and that 35 to 77% of the human diet from A.D. 1000 to A.D. 1600 consisted of corn. Results from an isochronous population in southeastern South Dakota (A.D. 1400) suggest that 78 to 90% of the diet of this group consisted of corn, with no difference between males and females. Coupled with more traditional archaeological methods, stable carbon isotope analysis of bone collagen can significantly enhance reconstruction of dietary patterns of prehistoric humans. PMID:1910520

  1. Study of Urban environmental quality through Isotopes δ13C

    NASA Astrophysics Data System (ADS)

    González-Sosa, E.; Mastachi-Loza, C.; Becerril-Piña, R.; Ramos-Salinas, N. M.

    2012-04-01

    Usually, trees with similar pH values on their bark develop epiphytes of similar species, the acidity to be a factor for growth. The aim of the study was evaluate the air quality through isotope δ13C in order to define the levels of environmental quality in the city of Queretaro, Mexico. In this work were collected at least 4 epiphytes positioned in trees of the species Prosopis Laevigata at 25 sites of Queretaro City. The samples were analyzed for trace elements with an inductively coupled plasma atomic emission spectroscopy (ICP). The collecting took place during dry period, in May and early rain June 2011 period, and on four sectors to identify the spatial distribution of pollution, using isotopic analysis of concentration of δ 13C. According with the results there are significant differences among the species in each of the sampled areas. The 5 February Avenue presented greater diversity and richness of δ13C, followed by those who were surveyed in the proximity of the UAQ and finally in the middle-east area. An average value of δ13C-17.92%, followed by those surveyed in the vicinity of the UAQ that correspond to sector I and II with an concentration of δ13C-17.55% and δ13C-17.22%, and finally the samples collected in trees scattered in the East-Sector II and IV with a value of δ13C-17.02% and δ13C-15.62%, respectively. Also were observed differences between the dry and wet period. It is likely that these results of δ 13C in moist period reflect the drag of the isotopes due to rain events that could mark a trend in the dilution of this element, however there is a trend in terms of abundance and composition of finding more impact in those species sampled in dry period, in May and early June 2011.

  2. Inelastic proton scattering of Sn isotopes studied with GRETINA

    NASA Astrophysics Data System (ADS)

    Campbell, Christopher

    2014-03-01

    The chain of semi-magic Sn nuclei, with many stable isotopes, has been a fertile ground for experimental and theoretical studies. Encompassing a major neutron shell from N = 50 to 82, the properties and structure of these nuclei provided important data for the development of the pairing-plus-quadrupole model. Recent experimental information on B(E2) for 106,108,110,112Sn came as a surprise as it indicated a larger collectivity than the predicted parabolic trend of quadrupole collectivity. These data, instead, show an unexpectedly flat trend even as the number of valence particles is reduced from 12 to 6. To fully understand how collectivity is evolving in these isotopes, 108,110,112Sn have been studied using thick-target, inelastic proton scattering with GRETINA tagging inelastic scattering events by detecting gamma-rays from the prompt decay of states excited in the reaction. We will present the trend of 2 + excitation cross-sections, the deduced quadrupole deformation parameters, and observations of other low-lying collective states. Comparison of these (p,p') quadrupole deformation parameters with B(E2) data will provide new insights into the relative importance of proton and neutron contributions to collectivity in these nuclei. GRETINA was funded by the US DOE - Office of Science. Operation of the array at NSCL is supported by NSF under Cooperative Agreement PHY-1102511(NSCL) and DOE under grant DE-AC02-05CH11231(LBNL).

  3. Imaging study on acupuncture points

    NASA Astrophysics Data System (ADS)

    Yan, X. H.; Zhang, X. Y.; Liu, C. L.; Dang, R. S.; Ando, M.; Sugiyama, H.; Chen, H. S.; Ding, G. H.

    2009-09-01

    The topographic structures of acupuncture points were investigated by using the synchrotron radiation based Dark Field Image (DFI) method. Four following acupuncture points were studied: Sanyinjiao, Neiguan, Zusanli and Tianshu. We have found that at acupuncture point regions there exists the accumulation of micro-vessels. The images taken in the surrounding tissue out of the acupuncture points do not show such kind of structure. It is the first time to reveal directly the specific structure of acupuncture points by X-ray imaging.

  4. Community archiving of imaging studies

    NASA Astrophysics Data System (ADS)

    Fritz, Steven L.; Roys, Steven R.; Munjal, Sunita

    1996-05-01

    The quantity of image data created in a large radiology practice has long been a challenge for available archiving technology. Traditional methods ofarchiving the large quantity of films generated in radiology have relied on warehousing in remote sites, with courier delivery of film files for historical comparisons. A digital community archive, accessible via a wide area network, represents a feasible solution to the problem of archiving digital images from a busy practice. In addition, it affords a physician caring for a patient access to imaging studies performed at a variety ofhealthcare institutions without the need to repeat studies. Security problems include both network security issues in the WAN environment and access control for patient, physician and imaging center. The key obstacle to developing a community archive is currently political. Reluctance to participate in a community archive can be reduced by appropriate design of the access mechanisms.

  5. Concrete under sulphate attack: an isotope study on sulphur sources.

    PubMed

    Mittermayr, Florian; Bauer, Christoph; Klammer, Dietmar; Böttcher, Michael E; Leis, Albrecht; Escher, Peter; Dietzel, Martin

    2012-01-01

    The formation of secondary sulphate minerals such as thaumasite, ettringite and gypsum is a process causing severe damage to concrete constructions. A major key to understand the complex reactions, involving concrete deterioration is to decipher the cause of its appearance, including the sources of the involved elements. In the present study, sulphate attack on the concrete of two Austrian tunnels is investigated. The distribution of stable sulphur isotopes is successfully applied to decipher the source(s) of sulphur in the deteriorating sulphate-bearing minerals. Interestingly, δ(34)S values of sulphate in local groundwater and in the deteriorating minerals are mostly in the range from+14 to+27 ‰. These δ(34)S values match the isotope patterns of regional Permian and Triassic marine evaporites. Soot relicts from steam- and diesel-driven trains found in one of the tunnels show δ(34)S values from-3 to+5 ‰, and are therefore assumed to be of minor importance for sulphate attack on the concretes. In areas of pyrite-containing sedimentary rocks, the δ(34)S values of sulphate from damaged concrete range between-1 and+11 ‰. The latter range reflects the impact of sulphide oxidation on local groundwater sulphate. PMID:22321257

  6. Isotope studies of dolomite formation under sedimentary conditions

    USGS Publications Warehouse

    Clayton, R.N.; Jones, B.F.

    1968-01-01

    Measurements of stable isotope abundances of the carbonate portion of the sediment in Deep Springs Lake, California, indicate the presence of at least three phases: a magnesian calcite, a primary sedimentary dolomite, and a detrital dolomite. The former two have isotopic compositions consistent with precipitation at isotopic equilibrium from waters of the lake area. The measured isotopic fractionation factor between sedimentary dolomite and its interstitial water is 1.0351, which is outside the range possible for calcite-water. This indicates that the dolomite has formed by direct crystallization from solution and not from a caloite precursor without further isotope exchange. Isotopic and X-ray evidence does not support the contention of Peterson et al. (1966) that Deep Springs Lake dolomite crystals grow by means of a calcite-like surface layer. ?? 1968.

  7. Epilepsy Imaging Study Guideline Criteria

    PubMed Central

    Gaillard, William D; Cross, J Helen; Duncan, John S; Stefan, Hermann; Theodore, William H

    2011-01-01

    Recognition of limited economic resources, as well as potential adverse effects of ‘over testing,’ has increased interest in ‘evidence-based’ assessment of new medical technology. This creates a particular problem for evaluation and treatment of epilepsy, increasingly dependent on advanced imaging and electrophysiology, since there is a marked paucity of epilepsy diagnostic and prognostic studies that meet rigorous standards for evidence classification. The lack of high quality data reflects fundamental weaknesses in many imaging studies but also limitations in the assumptions underlying evidence classification schemes as they relate to epilepsy, and to the practicalities of conducting adequately powered studies of rapidly evolving technologies. We review the limitations of current guidelines and propose elements for imaging studies that can contribute meaningfully to the epilepsy literature. PMID:21740417

  8. Isotope labeling for NMR studies of macromolecular structure and interactions

    SciTech Connect

    Wright, P.E.

    1994-12-01

    Implementation of biosynthetic methods for uniform or specific isotope labeling of proteins, coupled with the recent development of powerful heteronuclear multidimensional NMR methods, has led to a dramatic increase in the size and complexity of macromolecular systems that are now amenable to NMR structural analysis. In recent years, a new technology has emerged that combines uniform {sup 13}C, {sup 15}N labeling with heteronuclear multidimensional NMR methods to allow NMR structural studies of systems approaching 25 to 30 kDa in molecular weight. In addition, with the introduction of specific {sup 13}C and {sup 15}N labels into ligands, meaningful NMR studies of complexes of even higher molecular weight have become feasible. These advances usher in a new era in which the earlier, rather stringent molecular weight limitations have been greatly surpassed and NMR can begin to address many central biological problems that involve macromolecular structure, dynamics, and interactions.

  9. Carbon and nitrogen isotope studies in an arctic ecosystem

    SciTech Connect

    Schell, D.M.

    1989-12-31

    This proposal requests funding for the completion of our current ecological studies at the MS-117 research site at Toolik Lake, Alaska. We have been using a mix of stable and radioisotope techniques to assess the fluxes of carbon and nitrogen within the ecosystem and the implications for long-term carbon storage or loss from the tundra. Several tentative conclusions have emerged from our study including: Tundra in the foothills is no longer accumulating carbon. Surficial radiocarbon abundances show little or no accumulation since 1000--2500 yrs BP. Coastal plain tundra is still accumulating carbon, but the rate of accumulation has dropped in the last few thousand years. Carbon export from watersheds in the Kuparuk and Imnavait Creek drainages are in excess of that expected from estimated primary productivity; and Nitrogen isotope abundances vary between species of plants and along hydrologic gradients.

  10. Carbon and nitrogen isotope studies in an arctic ecosystem

    SciTech Connect

    Schell, D.M.

    1989-01-01

    This proposal requests funding for the completion of our current ecological studies at the MS-117 research site at Toolik Lake, Alaska. We have been using a mix of stable and radioisotope techniques to assess the fluxes of carbon and nitrogen within the ecosystem and the implications for long-term carbon storage or loss from the tundra. Several tentative conclusions have emerged from our study including: Tundra in the foothills is no longer accumulating carbon. Surficial radiocarbon abundances show little or no accumulation since 1000--2500 yrs BP. Coastal plain tundra is still accumulating carbon, but the rate of accumulation has dropped in the last few thousand years. Carbon export from watersheds in the Kuparuk and Imnavait Creek drainages are in excess of that expected from estimated primary productivity; and Nitrogen isotope abundances vary between species of plants and along hydrologic gradients.

  11. SIMS imaging of gadolinium isotopes in tissue from Nephrogenic Systemic Fibrosis patients: Release of free Gd from magnetic resonance imaging (MRI) contrast agents

    NASA Astrophysics Data System (ADS)

    Abraham, Jerrold L.; Chandra, Subhash; Thakral, Charu; Abraham, Joshua M.

    2008-12-01

    Recently, Gd-based magnetic resonance imaging (MRI) contrast agents (GBMCA) have been linked to a new disease, Nephrogenic Systemic Fibrosis (NSF), with skin and systemic toxicity and death in certain patients with renal failure. Due to widespread use of GBMCA in diagnostic MRI, it is essential to study their excretion, metabolism, and target sites in cells and tissues. A CAMECA IMS-3f SIMS ion microscope and scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDS) were used for imaging Gd isotopes in relation to calcium distributions in histologic sections of human tissues. SIMS imaging revealed two types of Gd localization in skin biopsies of patients who received GBMCA. The Gd was present in micrometer size deposits in association with calcium, and in detectable amounts in a more diffuse cellular distribution. Only the Gd-containing deposits associated with Ca and P were detectable using SEM/EDS. As only insoluble deposits remain in the biopsy tissues after aqueous and organic solvent processing of the tissue, our observations support release of free Gd from the GBMCA and selective localization of insoluble Gd in the target tissue from patients with NSF. This study opens new novel applications of SIMS for characterization of the safety of GBMCA.

  12. Isotopic reconstruction of ancient human migrations: A comprehensive Sr isotope reference database for France and the first case study at Tumulus de Sables, south-western France

    NASA Astrophysics Data System (ADS)

    Willmes, M.; Boel, C.; Grün, R.; Armstrong, R.; Chancerel, A.; Maureille, B.; Courtaud, P.

    2012-04-01

    Strontium isotope ratios (87Sr/86Sr) can be used for the reconstruction of human and animal migrations across geologically different terrains. Sr isotope ratios in rocks are a product of age and composition and thus vary between geologic units. From the eroding environment Sr is transported into the soils, plants and rivers of a region. Humans and animals incorporate Sr from their diet into their bones and teeth, where it substitutes for calcium. Tooth enamel contains Sr isotope signatures acquired during childhood and is most resistant to weathering and overprinting, while the dentine is often diagenetically altered towards the local Sr signature. For the reconstruction of human and animal migrations the tooth enamel 87Sr/86Sr ratio is compared to the Sr isotope signature in the vicinity of the burial site and the surrounding area. This study focuses on the establishment of a comprehensive reference map of bioavailable 87Sr/86Sr ratios for France. In a next step we will compare human and animal teeth from key archaeological sites to this reference map to investigate mobility. So far, we have analysed plant and soil samples from ~200 locations across France including the Aquitaine basin, the western and northern parts of the Paris basin, as well as three transects through the Pyrenees Mountains. The isotope data, geologic background information (BRGM 1:1M), field images, and detailed method descriptions are available through our online database iRhum (http://rses.anu.edu.au/research/ee). This database can also be used in forensic studies and food sciences. As an archaeological case study teeth from 16 adult and 8 juvenile individuals were investigated from an early Bell Beaker (2500-2000 BC) site at Le Tumulus des Sables, south-west France (Gironde). The teeth were analysed for Sr isotope ratios using laser ablation ICP-MS. Four teeth were also analysed using solution ICP-MS, which showed a significant offset to the laser ablation results. This requires further

  13. Isotope-Resolved and Charge-Sensitive Force Imaging Using Scanned Single Molecules

    NASA Astrophysics Data System (ADS)

    Sun, Yan; Rastawicki, Dominik; Liu, Yang; Mar, Warren; Manoharan, Hari; Miglio, Anna; Melinte, Sorin; Charlier, Jean-Christophe; Rignanese, Gian-Marco; He, Lianhua; Liu, Fang; Zhou, Aihui

    Originally conceived as surface imaging instruments, the scanning tunnelling microscope (STM) and the atomic force microscope (AFM) were recently used to probe molecular chemical bonds with exquisite sensitivity. Remarkably, molecule-functionalized scanning tips can also provide direct access to the inelastic electron tunneling spectrum (IETS) of the terminal molecule. Here we report atomic manipulation experiments addressing carbon monoxide (CO) isotopes at low temperatures. The unique and quantifiable dependence of the CO vibrational modes offers insight into tip-controlled force and charge sensing of surface adsorbates, subsurface defects, and quantum nanostructures. The specific behavior of the monitored vibrational modes originates from the interplay of interaction forces between the top electrode--a scanned tip functionalized with a single molecule--and the atomic scale force field surrounding the target atomically-assembled nanostructure. We also present density functional theory (DFT) computations that have been performed in order to scrutinize and visualize the vibrational spectroscopic fingerprints and local force fields.

  14. Isotope Fractionation Studies in Prestellar Cores: The Case of Nitrogen

    NASA Technical Reports Server (NTRS)

    Milam, Stefanie N.; Charnley, Steven B.

    2011-01-01

    Isotopically fractionated material is found in many solar system objects, including meteorites and comets. It is considered, in some cases, to trace interstellar material that was incorporated into the solar system without undergoing significant processing, thus preserving the fractionation. In interstellar molecular clouds, ion-molecule chemistry continually cycles nitrogen between the two main reservoirs - N and N2 - leading to only minor N-15 enrichments. Charnley and Rodgers showed that depletion of CO removes oxygen from the gas and weakens this cycle such that significant N-15 fractionation can occur for N2 and other N-bearing species in such cores. Observations are being conducted at millimeter and submillimeter wavelengths employing various facilities in order to both spatially and spectrally, resolve emission from these cores. A preliminary study to obtain the N-14/N-15 ratio in nitriles (HCN and HNC) was conducted at the Arizona Radio Observatory's 12m telescope on Kitt Peak, AZ. Spectra were obtained at high resolution (0.08 km/s) in order to resolve dynamic properties of each source as well as to resolve hyperfine structure present in certain isotopologues. This study included four dark cloud cores, observed to have varying levels of molecular depletion: L1521E, L1498, L1544, and L1521F. Previous studies of the N-14/N-15 ratio towards LI544 were obtained with N2H+ and NIH3, yielding ratios of 446 and >700, respectively. The discrepancy observed in these two measurements suggests a strong chemical dependence on the fractionation of nitrogen. Ratios (C,N, and D) obtained from isotopologues for a particular molecule are likely tracing the same chemical heritage and are directly comparable within a given source. Results and comparisons between the protostellar evolutionary state and isomer isotope fractionation as well as between other N-bearing species will be presented.

  15. Iron-Isotopic Fractionation Studies Using Multiple Collector Inductively Coupled Plasma Mass Spectrometry

    NASA Technical Reports Server (NTRS)

    Anbar, A. D.; Zhang, C.; Barling, J.; Roe, J. E.; Nealson, K. H.

    1999-01-01

    The importance of Fe biogeochemistry has stimulated interest in Fe isotope fractionation. Recent studies using thermal ionization mass spectrometry (TIMS) and a "double spike" demonstrate the existence of biogenic Fe isotope effects. Here, we assess the utility of multiple-collector inductively-coupled plasma mass spectrometry(MC-ICP-MS) with a desolvating sample introduction system for Fe isotope studies, and present data on Fe biominerals produced by a thermophilic bacterium. Additional information is contained in the original extended abstract.

  16. Technical Note: A simple method for vaterite precipitation for isotopic studies: implications for bulk and clumped isotope analysis

    NASA Astrophysics Data System (ADS)

    Kluge, T.; John, C. M.

    2015-06-01

    Calcium carbonate (CaCO3) plays an important role in the natural environment as a major constituent of the skeleton and supporting structure of marine life and has high economic importance as an additive in food, chemicals and medical products. Anhydrous CaCO3 occurs in the three different polymorphs calcite, aragonite and vaterite, whereof calcite is the most abundant and best characterized mineral. In contrast, little is known about the rare polymorph vaterite, in particular with regard to the oxygen isotope fractionation between H2O and the mineral. Synthetic precipitation of vaterite in the laboratory typically involves rapid processes and isotopic non-equilibrium, which excludes isotope studies focused on the characterization of vaterite under equilibrium conditions. Here, we used a new experimental approach that enables vaterite mineral formation from an isotopically equilibrated solution. The solution consists of a ~0.007 mol L-1 CaCO3 solution that is saturated with NaCl at room temperature (up to 6.4 mol L-1). Vaterite precipitated as single phase or major phase (≥94%) in experiments performed between 23 and 91 °C. Only at 80 °C was vaterite a minor phase with a relative abundance of 27%. The high mineral yield per experiment of up to 235 mg relative to the initially dissolved CaCO3 amount of on average 360 mg enables an investigation of the oxygen isotope fractionation between the mineral and water, and the determination of clumped isotope values in vaterite.

  17. Isotopic and chemical studies of early crustal metasedimentary rocks

    NASA Technical Reports Server (NTRS)

    Jacobsen, Stein B.

    1988-01-01

    The aim, within the bounds of the Early Crustal Genesis Project, was the isotopic and chemical study of selected early crustal meta-sedimentary rocks. Western Australia was chosen as the first field area to examine, as the Yilgarn and Pilbara Blocks comprise one of the largest and most varied Precambrian terranes. Furthermore, the Western Gneiss Terrane (on the western flank of the Yilgarn Block) and the Pilbara Block are both non-greenstone in character; these types of terrane were relatively neglected, but are of great significance in the understanding of early crustal meta-sediments. The meta-sediments of aluminous or peraluminous character, commonly also enriched in Mg and/or Fe relative to the more common pelitic meta-sediments, and at many locations, deficient in one or more of the elements Ca, N, and K, were initially chosen.

  18. Decay studies of neutron deficient rare earth isotopes with OASIS

    SciTech Connect

    Gilat, J.; Nitschke, J.M.; Wilmarth, P.A.; Vierinen, K.; Firestone, R.B.

    1987-09-01

    We report results on the decay of /sup 124/Pr, /sup 124,125/Ce, /sup 124,125/La, /sup 134-136/Eu, /sup 134-136/Sm, /sup 134-136/Pm, /sup 144/Ho, /sup 141,142,144/Dy, /sup 140,141,142,144/Tb, /sup 140-142/Gd, and /sup 140-142/Eu, produced by /sup 92/Mo(H.I.,xpyn) reactions at the Berkeley SuperHILAC, and studied with the OASIS on-line mass separator facility. Half-lives, delayed proton branching ratios, ..gamma..-ray energies and intensities, partial decay schemes and several J/sup ..pi../ assignments are presented. Level systematics of the even mass Nd and Sm isotopes and of the nu h/sub 11/2/ - nu s/sub 1/2/ isomers for N = 77 are discussed.

  19. Culture Studies of Nitrogen and Oxygen Isotope Effects Associated with Nitrate Assimilation and Denitrification

    NASA Astrophysics Data System (ADS)

    Sigman, D. M.; Granger, J.; Lehmann, M. F.; Difiore, P. J.; Tortell, P. D.

    2007-12-01

    The isotope effects of nitrate-consuming reactions such as nitrate assimilation and denitrification are potential indicators of the physiological state of the organisms carrying out these reactions. Moreover, an understanding of these isotope effects is needed to use the stable isotopes to investigate the fluxes associated with these reactions in modern and ancient environments. We have used batch cultures to investigate the nitrogen (N) and oxygen (O) isotope effects of (1) nitrate assimilation by eukaryotic and prokaryotic algae and by heterotrophic bacteria, and (2) nitrate reduction by denitrifying bacteria. We observe intra- and inter-specific variation in isotope effect amplitudes and, in the case of denitrifiers, indications of isotope effect decreases during individual nitrate drawdown experiments. However, the measured N and O isotope effect ratio is close to 1 for all studied organisms, with the exception of an unusual denitrifier (Rhodobacter sphaeroides) that possesses only periplasmic (non-respiratory) nitrate reductase. This observation and other findings are consistent with nitrate reductase being the predominant source of isotope fractionation and with most isotope effect amplitude variability arising from variable degrees to which nitrate imported into the cell is reduced versus effluxed back into the environment; the more efflux, the more complete the expression of the fractionation imparted by nitrate reduction. If this is the case, then isotope effect amplitudes in the field should be related to physiological conditions in the environment, a prediction that, we argue, is supported by recent studies of (1) nitrate assimilation in the polar ocean and (2) denitrification in sediment porewaters.

  20. Petrologic and oxygen isotopic study of ALH 85085-like chondrites

    NASA Astrophysics Data System (ADS)

    Prinz, M.; Weisberg, M. K.; Clayton, R. N.; Mayeda, T. K.; Ebihara, M.

    1994-07-01

    Four meteorites (PAT 91546, PCA 91328, PCA 91452, PCA 91467) petrologically similar to ALH 85085 chondrite have now been found. Previous studies of ALH 85085 showed it be a new kind of CR-related microchondrule-bearing chondrite, although one called it a sub-chondrite. The purpose of this study is to learn more about ALH 85085-like meteorites and their relationship to CR and CR-related (LEW 85332, Acfer 182, Bencubbin) chondrites. The methods used included petrology, INA bulk chemical analysis (PAT 91546, PCA 91467), and O isotopic analyses of the whole rocks and separated chondrules and dark inclusions (DIs) from PAT 91546. Since microchondrules and fragments are approximately 20 microns it was necessary to analyze composite samples for O; one was of approximately 100 chondrules, and another was of 5 DIs. Petrologically, the four meteorites are similar to ALH 85085, and there is no basis for determining if all of them, or any combinations, are paired. Mineralogically, olivine and pyroxene are highly magnesian FeNi metal generally has 3-10% Ni, and has a positive Ni-Co correlation similar to that in CR and CR-related chondrites. Refractory inclusions are similar in size to the chondrules and have the following assemblages: (1) hibonite-perovskite, (2) melilite-fassaite-forsterite, (3) grossite (Ca-dialuminate)-melilite-perovskite, (4) spinel-melilite, and (5) spinel-pyroxene aggregates. Chemically, INA analyses indicate that PAT 91546 and PCA 91467 are generally similar to ALH 85085. Oxygen isotopic analyses of the four whole-rock compositions fall along the CR mixing line as does ALH 85085; they are also close to LEW 85332, Acfer 182, and Bencubbin. This supports the concept that these are all CR-related chondrites. Even stronger support is found in the compositions of the chondrules and DIs in PAT 91546, which also plot on or near the CR line.

  1. USE OF STABLE ISOTOPES IN ENVIRONMENTAL AND FORENSIC GEOCHEMISTRY STUDIES

    EPA Science Inventory

    Stable carbon and hydrogen isotopes have been used for many decades in the petroleum industry, but the development of combined gas chromatography-isotope ratio mass spectrometry (GCIRMS) has led to a virtual explosion in application of this technique not only in petroleum explora...

  2. Systematic AMD+GCM Study of Structure of Carbon Isotopes

    SciTech Connect

    Thiamova, G.; Itagaki, N.; Otsuka, T.; Ikeda, K.

    2004-02-27

    The structure of low-lying states of the carbon isotopes is investigated using the extended version of the Antisymmetrized Molecular Dynamics (AMD) Multi-Slater Determinant model. We can reproduce reasonably well many experimental data for carbon isotopes 12C-22C. A special approach is adopted for 15C to better describe the tail of the wave function.

  3. An improved pyrite pretreatment protocol for kinetic and isotopic studies

    NASA Astrophysics Data System (ADS)

    Mirzoyan, Natella; Kamyshny, Alexey; Halevy, Itay

    2014-05-01

    An improved pyrite pretreatment protocol for kinetic and isotopic studies Natella Mirzoyan1, Alexey Kamyshny Jr.2, Itay Halevy1 1Earth and Planetary Sciences, Weizmann Institute of Science, Rehovot 76100, Israel 2Geological and Environmental Sciences, Ben-Gurion University of the Negev, Beer Sheva 84105, Israel Pyrite is one of the most abundant and widespread of the sulfide minerals with a central role in biogeochemical cycles of iron and sulfur. Due to its diverse roles in the natural and anthropogenic sulfur cycle, pyrite has been extensively studied in various experimental investigations of the kinetics of its dissolution and oxidation, the isotopic fractionations associated with these reactions, and the microbiological processes involved. Pretreatment of pyrite for removal of oxidation impurities to prevent experimental artifacts and inaccuracies is often practiced. While numerous pyrite-cleaning methods have been used in experiments, a common pyrite pretreatment method, often used to investigate pyrite chemistry by the isotopic fractionations associated with it, includes several rinses by HCl, acetone and deionized water. Elemental sulfur (S0) is a common product of incomplete pyrite oxidation. Removal of S0 is desirable to avoid experimental biases associated with its participation in pyrite transformations, but is more complicated than the removal of sulfate. Although rinsing with an organic solvent is in part aimed at removing S0, to the best of our knowledge, the extraction efficiency of S0 in existing protocols has not been assessed. We have developed and tested a new protocol for elemental sulfur removal from the surface of pyrite by ultrasonication with warm acetone. Our data demonstrate the presence of large fractions of S0 on untreated pyrite particle surfaces, of which only approximately 60% was removed by the commonly used pretreatment method. The new protocol described here was found to be more efficient at S0 removal than the commonly used method

  4. An isotopic biogeochemical study of the Green River oil shale

    NASA Technical Reports Server (NTRS)

    Collister, J. W.; Summons, R. E.; Lichtfouse, E.; Hayes, J. M.

    1992-01-01

    Thirty-five different samples from three different sulfur cycles were examined in this stratigraphically oriented study of the Shell 22x-l well (U.S.G.S. C177 core) in the Piceance Basin, Colorado. Carbon isotopic compositions of constituents of Green River bitumens indicate mixing of three main components: products of primary photoautotrophs and their immediate consumers (delta approximately -30% vs PDB), products of methanotrophic bacteria (delta approximately -85%), and products of unknown bacteria (delta approximately -40%). For individual compounds synthesized by primary producers, delta-values ranged from -28 to -32%. 13C contents of individual primary products (beta-carotane, steranes, acyclic isoprenoids, tricyclic triterpenoids) were not closely correlated, suggesting diverse origins for these materials. 13C contents of numerous hopanoids were inversely related to sulfur abundance, indicating that they derived both from methanotrophs and from other bacteria, with abundances of methanotrophs depressed when sulfur was plentiful in the paleoenvironment. gamma-Cerane coeluted with 3 beta(CH3),17 alpha(H),21 beta(H)-hopane, but delta-values could be determined after deconvolution. gamma-Cerane (delta approximately -25%) probably derives from a eukaryotic heterotroph grazing on primary materials, the latter compound (delta approximately -90%) must derive from methanotrophic organisms. 13C contents of n-alkanes in bitumen differed markedly from those of paraffins generated pyrolytically. Isotopic and quantitative relationships suggest that alkanes released by pyrolysis derived from a resistant biopolymer of eukaryotic origin and that this was a dominant constituent of total organic carbon.

  5. An isotopic biogeochemical study of the Green River oil shale.

    PubMed

    Collister, J W; Summons, R E; Lichtfouse, E; Hayes, J M

    1992-12-01

    Thirty-five different samples from three different sulfur cycles were examined in this stratigraphically oriented study of the Shell 22x-l well (U.S.G.S. C177 core) in the Piceance Basin, Colorado. Carbon isotopic compositions of constituents of Green River bitumens indicate mixing of three main components: products of primary photoautotrophs and their immediate consumers (delta approximately -30% vs PDB), products of methanotrophic bacteria (delta approximately -85%), and products of unknown bacteria (delta approximately -40%). For individual compounds synthesized by primary producers, delta-values ranged from -28 to -32%. 13C contents of individual primary products (beta-carotane, steranes, acyclic isoprenoids, tricyclic triterpenoids) were not closely correlated, suggesting diverse origins for these materials. 13C contents of numerous hopanoids were inversely related to sulfur abundance, indicating that they derived both from methanotrophs and from other bacteria, with abundances of methanotrophs depressed when sulfur was plentiful in the paleoenvironment. gamma-Cerane coeluted with 3 beta(CH3),17 alpha(H),21 beta(H)-hopane, but delta-values could be determined after deconvolution. gamma-Cerane (delta approximately -25%) probably derives from a eukaryotic heterotroph grazing on primary materials, the latter compound (delta approximately -90%) must derive from methanotrophic organisms. 13C contents of n-alkanes in bitumen differed markedly from those of paraffins generated pyrolytically. Isotopic and quantitative relationships suggest that alkanes released by pyrolysis derived from a resistant biopolymer of eukaryotic origin and that this was a dominant constituent of total organic carbon. PMID:11540064

  6. Studies on image compression and image reconstruction

    NASA Technical Reports Server (NTRS)

    Sayood, Khalid; Nori, Sekhar; Araj, A.

    1994-01-01

    During this six month period our works concentrated on three, somewhat different areas. We looked at and developed a number of error concealment schemes for use in a variety of video coding environments. This work is described in an accompanying (draft) Masters thesis. In the thesis we describe application of this techniques to the MPEG video coding scheme. We felt that the unique frame ordering approach used in the MPEG scheme would be a challenge to any error concealment/error recovery technique. We continued with our work in the vector quantization area. We have also developed a new type of vector quantizer, which we call a scan predictive vector quantization. The scan predictive VQ was tested on data processed at Goddard to approximate Landsat 7 HRMSI resolution and compared favorably with existing VQ techniques. A paper describing this work is included. The third area is concerned more with reconstruction than compression. While there is a variety of efficient lossless image compression schemes, they all have a common property that they use past data to encode future data. This is done either via taking differences, context modeling, or by building dictionaries. When encoding large images, this common property becomes a common flaw. When the user wishes to decode just a portion of the image, the requirement that the past history be available forces the decoding of a significantly larger portion of the image than desired by the user. Even with intelligent partitioning of the image dataset, the number of pixels decoded may be four times the number of pixels requested. We have developed an adaptive scanning strategy which can be used with any lossless compression scheme and which lowers the additional number of pixels to be decoded to about 7 percent of the number of pixels requested! A paper describing these results is included.

  7. Isotopic studies of Yucca Mountain soil fluids and carbonate pedogenesis

    SciTech Connect

    McConnaughey, T.A.; Whelan, J.F.; Wickland, K.P.; Moscati, R.J.

    1994-12-31

    Secondary carbonates occurring within the soils, faults, and subsurface fractures of Yucca Mountain contain some of the best available records of paleoclimate and palehydrology for the potential radioactive waste repository site. This article discusses conceptual and analytical advances being made with regard to the interpretation of stable isotope data from pedogenic carbonates, specifically related to the {sup 13}C content of soil CO{sub 2}, CaCO{sub 3}, precipitation mechanisms, and isotopic fractionations between parent fluids and precipitating carbonates. The {sup 13}C content of soil carbon dioxide from Yucca Mountain and vicinity shows most of the usual patterns expected in such contexts: Decreasing {sup 13}C content with depth decreasing {sup 13}C with altitude and reduced {sup 13}C during spring. These patterns exist within the domain of a noisy data set; soil and vegetational heterogeneities, weather, and other factors apparently contribute to isotopic variability in the system. Several soil calcification mechanisms appear to be important, involving characteristic physical and chemical environments and isotopic fractionations. When CO{sub 2} loss from thin soil solutions is an important driving factor, carbonates may contain excess heavy isotopes, compared to equilibrium precipitation with soil fluids. When root calcification serves as a proton generator for plant absorption of soil nutrients, heavy isotope deficiencies are likely. Successive cycles of dissolution and reprecipitation mix and redistribute pedogenic carbonates, and tend to isotopically homogenize and equilibrate pedogenic carbonates with soil fluids.

  8. Surface studies of metals after interaction with hydrogen isotopes

    NASA Astrophysics Data System (ADS)

    Silver, David Samuel

    1998-12-01

    The objective of this research is to characterize surfaces of metals after interaction with hydrogen isotopes. Iron, which does not readily bond with hydrogen, and palladium, which strongly bonds with hydrogen, were studied. Observations of surfaces are used to determine the nature of their metamorphosis due to such exposures. An experimental study of pure iron foil (99.99%) exposed to a hot, dense hydrogen and argon gas mixture in a ballistic compressor yielded evidence for new structural and compositional changes of the metal due to the exposure. Atomic force microscope (AFM) studies demonstrated surfaces to be highly uneven, where height variations were often 2 mum for many micron-sized regions scanned. An iron foil exposed to argon gases alone revealed unique dendritic patterns but negligible height variations for micron-size scans. A cold rolled single crystal palladium cathode was electrolyzed in a solution of Dsb2O and 15% Hsb2SOsb4 by volume for 12 minutes. The cathode bent toward the anode during electrolysis. Examination of both concave and convex surfaces using the scanning electron microscope (SEM), scanning tunneling microscope (STM), and AFM revealed rimmed craters with faceted crystals inside and multi-textured surfaces. Also pairs of cold rolled polycrystalline palladium cathodes underwent electrolysis for six minutes or less, in Dsb2O and Hsb2O solutions, each solution containing 15% Hsb2SOsb4, by volume. Surface morphologies of the heavy water electrolyzed samples revealed asperities, craters, and nodules, and evidence of recrystallization and crystal planes. After 1.5 years, new AFM studies of the same Pd surfaces exposed to heavy water electrolyte exhibited loose, nanometer-sized particles. However, the surfaces of Pd cathodes exposed to light water electrolyte remained nearly identical to morphologies of foils not electrolyzed, and did not change with time. No surface asperities or loose grains were observed on the latter. Secondary ion mass

  9. Coordinated Isotopic and TEM Studies of Presolar Graphites from Murchison

    NASA Astrophysics Data System (ADS)

    Croat, T. K.; Stadermann, F. J.; Zinner, E.; Bernatowicz, T. J.

    2004-03-01

    TEM and NanoSIMS investigations of the same presolar Murchison KFC graphites revealed high Zr, Mo, and Ru content in refractory carbides within the graphites. Along with isotopically light carbon, these suggest a low-metallicity AGB source.

  10. [Isotope nephrographic studies during hormonal contraception using Depositon].

    PubMed

    Voigt, R; Klinger, G; Stoll, W; Arndt, J

    1978-01-01

    By means of isotope nephrograms of a total of 29 renally healthy women who had been taken for more than 1 year the drug Deposiston, the renal function is investigated. Checking is done by using the semiquantitative evaluation parameters according to Zum Winkel, Pabst and Hör and to own criteria. Our results show that the highly dosed application of estrogens does not induce significant changes of renal function in the isotope nephrogram. PMID:726732

  11. Study of the isotopic features of Swan bands in comets

    NASA Technical Reports Server (NTRS)

    Krishna Swamy, K. S.

    1987-01-01

    It is shown from a detailed statistical equilibrium calculation of the (C-12)(C-13) molecule that the interpretation of the observed intensities of Swan bands of the normal and the isotopic molecule of C2 in terms of the abundance ratio of C-12 and C-13 is a reasonable one. The synthetic profile of some isotopic features in the (0.0) Swan band is compared with the observed profiles for comet West.

  12. Live-cell vibrational imaging of choline metabolites by stimulated Raman scattering coupled with isotope-based metabolic labeling

    PubMed Central

    Hu, Fanghao; Wei, Lu; Zheng, Chaogu; Shen, Yihui

    2014-01-01

    Choline is a small molecule that occupies a key position in the biochemistry of all living organisms. Recent studies have strongly implicated choline metabolites in cancer, atherosclerosis and nervous system development. To detect choline and its metabolites, existing physical methods such as magnetic resonance spectroscopy and positron emission tomography, are often limited by the poor spatial resolution and substantial radiation dose. Fluorescence imaging, although with submicrometer resolution, requires introduction of bulky fluorophores and thus is difficult in labeling the small choline molecule. By combining the emerging bond-selective stimulated Raman scattering microscopy with metabolic incorporation of deuterated choline, herein we have achieved high resolution imaging of choline-containing metabolites in living mammalian cell lines, primary hippocampal neurons and multicellular organism C. elegans. Different subcellular distributions of choline metabolites are observed between cancer cells and non-cancer cells, which may reveal functional difference in the choline metabolism and lipid-mediated signaling events. In neurons, choline incorporation is visualized within both soma and neurites, where choline metabolites are more evenly distributed compared to the protein. Furthermore, choline localization is also observed in the pharynx region of C. elegans larvae, consistent with its organogenesis mechanism. These applications demonstrate the potential of isotope-based stimulated Raman scattering microscopy for future choline-related disease detection and development monitoring in vivo. PMID:24555181

  13. An isotope hydrology study of the Kilauea volcano area, Hawaii

    USGS Publications Warehouse

    Scholl, M.A.; Ingebritsen, S.E.; Janik, C.J.; Kauahikaua, J.P.

    1995-01-01

    Isotope tracer methods were used to determine flow paths, recharge areas, and relative age for ground water in the Kilauea volcano area on the Island of Hawaii. Stable isotopes in rainfall show three distinct isotopic gradients with elevation, which are correlated with trade-wind, rain shadow, and high-elevation climatological patterns. Temporal variations in isotopic composition of precipitation are controlled more by the frequency of large storms than b.y seasonal temperature fluctuations. Consistency in results between two separate areas with rainfall caused by tradewinds and thermally-driven upslope airflow suggests that isotopic gradients with elevation may be similar on other islands in the tradewind belt, especially the other Hawaiian Islands, which have similar climatology and temperature lapse rates. Areal contrasts in ground-water stable isotopes and tritium indicate that the volcanic ri~ zones compartmentalize the regional ground-water system. Tritium levels in ground water within and downgradient of Kilauea's ri~ zones indicate relatively long residence times. Part of Kilauea's Southwest Ri~ Zone appears to act as a conduit for water from higher elevation, but there is no evidence for extensive down-ri~ flow in the lower East Ri~ Zone.

  14. Coordinated Chemical and Isotopic Studies of GEMS in IDPS

    NASA Technical Reports Server (NTRS)

    Keller, L. P.; Messenger, S.

    2008-01-01

    Cometary IDPs contain a record of the building blocks of the solar system including presolar grains, molecular cloud material, and materials formed in the early solar nebula [1]. Following their accretion, these materials have remained relatively unaltered because of the lack of parent body hydrothermal alteration. We are using coordinated transmission electron microscope (TEM) and ion microprobe studies to establish the origins of the various components within cometary IDPs. Of particular interest is the nature and abundance of presolar silicates in these IDPs because astronomical observations suggest that crystalline and amorphous silicates are the dominant grain types produced in young main sequence stars and evolved O-rich stars [e.g. 2]. Amorphous silicates (in the form of GEMS grains) are a major component of cometary IDPs and so a major objective of this work is to elucidate their origins. In rare cases, GEMS grains have highly anomalous O isotopic compositions that establish their origins as circumstellar condensates [3]. Here we present data on a systematic study of the silicate components within a primitive IDP.

  15. 13 ENDOR studies of organic radicals in natural isotopic abundance

    NASA Astrophysics Data System (ADS)

    Kirste, Burkhard

    13C ENDOR studies of phenoxyls, galvinoxyls, triphenylmethyl radicals, nitroxides, and cyclosilane and semiquinone radical anions with natural isotopic distribution are reported. The method is described, and it is shown that 13C coupling constants can be measured precisely; in favorable cases even the determination of signs is possible by general TRIPLE resonance. Studies of the relaxation behavior of 13C ENDOR signals or measurements of hyperfine shifts in liquid-crystalline solutions yield information about dipolar hyperfine interactions and hence π spin populations which is of aid in assignments to molecular positions. Complete sets of 13C coupling constants have been determined for 2,4,6-tri- tert-butylphenoxyl and Coppinger's radical. For the central carbon atoms of tert-butyl groups, a Q parameter of Qτ-Bu C = -34 MHz is proposed, and for a 29Si atom in trimethylsilyl groups, QTMSSi = +49 MHz. Favorable conditions for natural-abundance 13C ENDOR experiments, e.g., small hyperfine anisotropies and use of deuterated compounds, and limitations of the method are discussed.

  16. Use of micrometeorological techniques to study the isotopic exchange in ecosystems

    NASA Astrophysics Data System (ADS)

    Santos, E.; Wagner-Riddle, C.; Brown, S. E.; Stropes, K.

    2015-12-01

    The combination of micrometeorological techniques with high frequency concentration measurements of stable isotopes are a powerful tool to study the temporal dynamics of isotope signatures at the ecosystem level. The objective of this study was to study the isotopic composition of the net CO2 exchange (NEE) above and with corn and tall grass canopies. Profiles of stable isotopes of CO2 (12C-CO2, 13C-CO2 and 18O-CO2) were measured using tunable diode laser trace gas analyzers and multiport sampling systems in corn (12C-CO2 and 13C-CO2, only) and tall grass canopies. These measurements were combined with the flux gradient method and Lagrangian dispersion analysis to estimate the isotopic signatures of the net CO2 flux. The use of a gradient of a concentration threshold to screen half hourly period improved the estimates of flux signatures by the isotope flux ratio approach. The Langrangian dispersion analysis and the isotope flux ratio method estimates showed good agreement above the corn canopy, indicating that the former method can be a viable alternative to study the isotopic exchange within plant canopies. The 13CO2 composition of NEE showed a downward trend near the end of the growing season, which may be related to a reduction of autotrophic respiration in the soil.

  17. Feasibility study of medical isotope production at Sandia National Laboratories

    SciTech Connect

    Massey, C.D.; Miller, D.L.; Carson, S.D.

    1995-12-01

    In late 1994, Sandia National Laboratories in Albuquerque, New Mexico, (SNL/NM), was instructed by the Department of Energy (DOE) Isotope Production and Distribution Program (IPDP) to examine the feasibility of producing medically useful radioisotopes using the Annular Core Research Reactor (ACRR) and the Hot Cell Facility (HCF). Los Alamos National Laboratory (LANL) would be expected to supply the targets to be irradiated in the ACRR. The intent of DOE would be to provide a capability to satisfy the North American health care system demand for {sup 99}Mo, the parent of {sup 99m}Tc, in the event of an interruption in the current Canadian supply. {sup 99m}Tc is used in 70 to 80% of all nuclear medicine procedures in the US. The goal of the SNL/NM study effort is to determine the physical plant capability, infrastructure, and staffing necessary to meet the North American need for {sup 99}Mo and to identify and examine all issues with potential for environmental impact.

  18. Isotopic study of oxygen diffusion in oxide coatings

    NASA Technical Reports Server (NTRS)

    Gulino, Daniel A.; Kren, Lawrence A.; Dever, Therese M.

    1989-01-01

    Diffusion of oxygen in thin films of silicon dioxide was studied using oxygen isotopically enriched in oxygen of atomic mass 18 (O-18). This subject is of interest because thin films of dielectrics such as SiO2 are proposed for use as a protective coatings for solar mirrors in low Earth orbit, which is a strongly oxidizing environment. Films of this material were prepared with a direct current magnetron using reactive sputtering techniques. To produce (O-18)- enriched SiO2, a standard 3.5-in.-diameter silicon wafer was reactively sputtered using (O-18)-enriched (95 percent) oxygen as the plasma feed gas. The films were characterized using Rutherford backscattering and Secondary Ion Mass Spectrometer (SIMS) to establish stoichiometry and purity. Subsequently, the films were exposed to an air-derived oxygen plasma in a standard laboratory plasma reactor for durations of up to 10 hr. The concentration ratio of O-16 as a function of depth was determined using SIMS profiling and compared to a baseline, nonplasma exposed sample. A value for the diffusivity of oxygen near the surface of these films was obtained and found to be about 10(-15)sq cm/sec.

  19. NMR studies of two spliced leader RNAs using isotope labeling

    SciTech Connect

    Lapham, J.; Crothers, D.M.

    1994-12-01

    Spliced leader RNAs are a class of RNA molecules (<200 nts) involved in the trans splicing of messenger RNA found in trypanosomes, nematodes, and other lower eukaryotes. The spliced leader RNA from the trypanosome Leptomonas Collosoma exists in two alternate structural forms with similar thermal stabilities. The 54 nucleotides on the 5{prime} end of the SL molecule is structurally independent from the 3{prime} half of the RNA, and displays the two structural forms. Furthermore, the favored of the two structures was shown to contain anomalous nuclease sensitivity and thermal stability features, which suggests that there may be tertiary interactions between the splice site and other nucleotides in the 5{prime} end. Multidimensional NMR studies are underway to elucidate the structural elements present in the SL RNAs that give rise to their physical properties. Two spliced leader sequences have been studied. The first, the 54 nucleotides on the 5{prime} end of the L. Collosoma sequence, was selected because of earlier studies in our laboratory. The second sequence is the 5{prime} end of the trypanosome Crithidia Fasciculata, which was chosen because of its greater sequence homology to other SL sequences. Given the complexity of the NMR spectra for RNA molecules of this size, we have incorporated {sup 15}N/{sup 13}C-labeled nucleotides into the RNA. One of the techniques we have developed to simplify the spectra of these RNA molecules is isotope labeling of specific regions of the RNA. This has been especially helpful in assigning the secondary structure of molecules that may be able to adopt multiple conformations. Using this technique one can examine a part of the molecule without spectral interference from the unlabeled portion. We hope this approach will promote an avenue for studying the structure of larger RNAs in their native surroundings.

  20. Isotope dilution study of exchangeable oxygen in premium coal samples

    SciTech Connect

    Finseth, D.

    1987-01-01

    A difficulty with improving the ability to quantitate water in coal is that truly independent methods do not always exist. The true value of any analytical parameter is always easier to determine if totally independent methods exist to determine that parameter. This paper describes the possibility of using a simple isotope dilution technique to determine the water content of coal and presents a comparison of these isotope dilution measurements with classical results for the set of Argonne coals from the premium coal sample program. Isotope dilution is a widely used analytical method and has been applied to the analysis of water in matrices as diverse as chicken fat, living humans, and coal. Virtually all of these applications involved the use of deuterium as the diluted isotope. This poses some problems if the sample contains a significant amount of exchangeable organic hydrogen and one is interested in discriminating exchangeable organic hydrogen from water. This is a potential problem in the coal system. To avoid this potential problem /sup 18/O was used as the diluted isotope in this work.

  1. Sr isotopic tracer study of the Samail ophiolite, Oman

    SciTech Connect

    Lanphere, M.A.; Coleman, R.G.; Hopson, C.A.

    1981-04-10

    We have measured Rb and Sr concentrations and Sr isotopic compositions in 41 whole-rock samples and 12 mineral separates from units of the Samail ophiolite, including peridotite, gabbro, plagiogranite diabase dikes, and gabbro and websterite dikes within the metamorphic peridotite. Ten samples of cummulate gabbro from the Wadir Kadir section and nine samples from the Wadi Khafifah section have mean /sup 87/Sr//sup 86/Sr ratios and standard deviations of 0.70314 +- 0.00030 and 0.70306 +- 0.00034, respectively. The dispersion in Sr isotopic composition may reflect real heterogeneities in the magma source region. The average Sr isotopic composition of cumulate gabbro falls in the range of isotopic compositions of modern midocean ridge basalt. The /sup 87/Sr//sup 86/Sr ratios of noncumulate gabbro, plagiogranite, and diabase dikes range from 0.7034 to 0.7047, 0.7038 to 0.7046, and 0.7037 to 0.7061, respectively. These higher /sup 87/Sr//sup 86/Sr ratios are due to alteration of initial magmatic compositions by hydrothermal exchange with seawater. Mineral separates from dikes that cut harzburgite tectonite have Sr isotopic compositions which agree with that of cumulate gabbro. These data indicate that the cumulate gabbro and the different dikes were derived from partial melting of source regions that had similar long-term histories and chemical compositions.

  2. Sr isotopic tracer study of the Samail ophiolite, Oman.

    USGS Publications Warehouse

    Lanphere, M.A.; Coleman, R.G.; Hopson, C.A.

    1981-01-01

    Rb and Sr concentrations and Sr-isotopic compositions were measured in 41 whole-rock samples and 12 mineral separates from units of the Samail ophiolite, including peridotite, gabbro, plagiogranite, diabase dykes, and gabbro and websterite dykes within the metamorphic peridotite. Ten samples of cumulate gabbro from the Wadir Kadir section and nine samples from the Wadi Khafifah section have 87Sr/86Sr ratios of 0.70314 + or - 0.00030 and 0.70306 + or - 0.00034, respectively. The dispersion in Sr- isotopic composition may reflect real heterogeneities in the magma source region. The average Sr-isotopic composition of cumulate gabbro falls in the range of isotopic compositions of modern MORB. The 87Sr/86Sr ratios of noncumulate gabbro, plagiogranite, and diabase dykes range 0.7034-0.7047, 0.7038-0.7046 and 0.7037- 0.7061, respectively. These higher 87Sr/86Sr ratios are due to alteration of initial magmatic compositions by hydrothermal exchange with sea-water. Mineral separates from dykes that cut harzburgite tectonite have Sr-isotopic compositions which agree with that of cumulate gabbro. These data indicate that the cumulate gabbro and the different dykes were derived from partial melting of source regions that had similar long-term histories and chemical compositions.-T.R.

  3. Oxygen and iron isotope studies of magnetite produced by magnetotactic bacteria

    PubMed

    Mandernack; Bazylinski; Shanks; Bullen

    1999-09-17

    A series of carefully controlled laboratory studies was carried out to investigate oxygen and iron isotope fractionation during the intracellular production of magnetite (Fe(3)O(4)) by two different species of magnetotactic bacteria at temperatures between 4 degrees and 35 degrees C under microaerobic and anaerobic conditions. No detectable fractionation of iron isotopes in the bacterial magnetites was observed. However, oxygen isotope measurements indicated a temperature-dependent fractionation for Fe(3)O(4) and water that is consistent with that observed for Fe(3)O(4) produced extracellularly by thermophilic Fe(3+)-reducing bacteria. These results contrast with established fractionation curves estimated from either high-temperature experiments or theoretical calculations. With the fractionation curve established in this report, oxygen-18 isotope values of bacterial Fe(3)O(4) may be useful in paleoenvironmental studies for determining the oxygen-18 isotope values of formation waters and for inferring paleotemperatures. PMID:10489363

  4. Oxygen and iron isotope studies of magnetite produced by magnetotactic bacteria

    USGS Publications Warehouse

    Mandernack, K.W.; Bazylinski, D.A.; Shanks, Wayne C., III; Bullen, T.D.

    1999-01-01

    A series of carefully controlled laboratory studies was carried out to investigate oxygen and iron isotope fractionation during the intracellular production of magnetite (Fe3O4) by two different species of magnetotactic bacteria at temperatures between 4??and 35??C under microaerobic and anaerobic conditions. No detectable fractionation of iron isotopes in the bacterial magnetites was observed. However, oxygen isotope measurements indicated a temperature-dependent fractionation for Fe3O4 and water that is consistent with that observed for Fe3O4 produced extracellularly by thermophilic Fe3+-reducing bacteria. These results contrast with established fractionation curves estimated from either high-temperature experiments or theoretical calculations. With the fractionation curve established in this report, oxygen-18 isotope values of bacterial Fe3O4 may be useful in paleoenvironmental studies for determining the oxygen-18 isotope values of formation waters and for inferring paleotemperatures.

  5. Isotopic imaging via nuclear resonance fluorescence with laser-based Thomson radiation

    DOEpatents

    Barty, Christopher P. J.; Hartemann, Frederic V.; McNabb, Dennis P.; Pruet, Jason A.

    2009-07-21

    The present invention utilizes novel laser-based, high-brightness, high-spatial-resolution, pencil-beam sources of spectrally pure hard x-ray and gamma-ray radiation to induce resonant scattering in specific nuclei, i.e., nuclear resonance fluorescence. By monitoring such fluorescence as a function of beam position, it is possible to image in either two dimensions or three dimensions, the position and concentration of individual isotopes in a specific material configuration. Such methods of the present invention material identification, spatial resolution of material location and ability to locate and identify materials shielded by other materials, such as, for example, behind a lead wall. The foundation of the present invention is the generation of quasimonochromatic high-energy x-ray (100's of keV) and gamma-ray (greater than about 1 MeV) radiation via the collision of intense laser pulses from relativistic electrons. Such a process as utilized herein, i.e., Thomson scattering or inverse-Compton scattering, produces beams having diameters from about 1 micron to about 100 microns of high-energy photons with a bandwidth of .DELTA.E/E of approximately 10E.sup.-3.

  6. Collectivity in the light xenon isotopes: A shell model study

    SciTech Connect

    Caurier, E.; Nowacki, F.; Sieja, K.; Poves, A.

    2010-12-15

    The lightest xenon isotopes are studied in the shell model framework, within a valence space that comprises all the orbits lying between the magic closures N=Z=50 and N=Z=82. The calculations produce collective deformed structures of triaxial nature that encompass nicely the known experimental data. Predictions are made for the (still unknown) N=Z nucleus {sup 108}Xe. The results are interpreted in terms of the competition between the quadrupole correlations enhanced by the pseudo-SU(3) structure of the positive parity orbits and the pairing correlations brought in by the 0h{sub 11/2} orbit. We also have studied the effect of the excitations from the {sup 100}Sn core on our predictions. We show that the backbending in this region is due to the alignment of two particles in the 0h{sub 11/2} orbit. In the N=Z case, one neutron and one proton align to J=11 and T=0. In {sup 110,112}Xe the alignment begins in the J=10, T=1 channel and it is dominantly of neutron-neutron type. Approaching the band termination the alignment of a neutron-proton pair to J=11 and T=0 takes over. In a more academic mood, we have studied the role of the isovector and isoscalar pairing correlations on the structure on the yrast bands of {sup 108,110}Xe and examined the possible existence of isovector and isoscalar pairing condensates in these N{approx}{approx}Z nuclei.

  7. Experimental stand for studies of hydrogen isotopes permeation

    SciTech Connect

    Brad, S.; Stefanescu, I.; Stefan, L.; Lazar, A.; Vijulie, M.; Sofilca, N.; Bornea, A.; Vasut, F.; Zamfirache, M.; Bidica, N.; Postolache, C.; Matei, L.

    2008-07-15

    As a result of the high probability of hydrogen isotope permeation through materials used in high-temperature reactor operations, the interaction of hydrogen isotopes with metallic structural materials proposed to be used for fusion reactor designing is of great importance for safety considerations. Determining the parameters of the interaction between hydrogen isotopes and different materials, is therefore essential to accurately calculate recycling, outgassing, loading, permeation and hydrogen embrittlement. The permeation tests were made in collaboration with IFIN Bucuresti inside of a special glove-box to avail their radioactive protection expertise. This investigation programme is ongoing. In this paper we describe the permeation stand facility and the preliminary tests carried out to date. (authors)

  8. Lead isotopic studies of the Samail ophiolite, Oman

    SciTech Connect

    Chen, J.H.; Pallister, J.S.

    1981-04-10

    The isotopic composition of Pb and the concentrations of U, Th, and Pb have been determined for samples from various lithologic units and massive sulfides of the Samail ophiolite. The observed /sup 206/Pb//sup 204/Pb ratios range from 17.90 to 19.06, /sup 207/Pb//sup 204/Pb ratios from 15.43 to 15.63, and /sup 208/Pb//sup 204/Pb from 37.66 to 38.78. In Pb isotopic evolution diagrams, the initial Pb isotopic compositions of most of the samples from the Samail ophiolite plot within the field of oceanic basalt, clearly distinct from island arc data, and define some of the least radiogenic Pb observed from oceanic rocks. Lead data from the Samail are compatible with a model involving magma generation from an oceanic mantle source and formation of the ophiolite at an oceanic spreading center. U--Th--Pb isotopic systematics demonstrate that vertical heterogeneity in the oceanic crust can be created through differential concentration of U, Th, and Pb during crystal fractionation and alteration at, or near, the spreading ridge. Calcite form amygdules in the ophiolite basalt has similar Pb isotopic composition to the igneous rocks, suggesting precipitation of the calcite from seawater which contained Pb derived mostly from the oceanic crust. Lead isotopic data on Fe--Cu sulfides are also similar to the results from the igneous suite suggesting that the source of the sulfides is predominently from the oceanic crust. Lead data from serpentinized peridotite and a galena sample from below the ophiolite suggest that part of the serpentinization process and the formation of galena could involve addition of radiogenic Pb from either a continental source or from oceanic sediments.

  9. Carbon isotopic studies of organic matter in Precambrian rocks.

    NASA Technical Reports Server (NTRS)

    Oehler, D. Z.; Schopf, J. W.; Kvenvolden, K. A.

    1972-01-01

    A survey has been undertaken of the carbon composition of the total organic fraction of a suite of Precambrian sediments to detect isotopic trends possibly correlative with early evolutionary events. Early Precambrian cherts of the Fig Tree and upper and middle Onverwacht groups of South Africa were examined for this purpose. Reduced carbon in these cherts was found to be isotopically similar to photosynthetically produced organic matter of younger geological age. Reduced carbon in lower Onverwacht cherts was found to be anomalously heavy; it is suggested that this discontinuity may reflect a major event in biological evolution.

  10. Imaging phased telescope array study

    NASA Technical Reports Server (NTRS)

    Harvey, James E.

    1989-01-01

    The problems encountered in obtaining a wide field-of-view with large, space-based direct imaging phased telescope arrays were considered. After defining some of the critical systems issues, previous relevant work in the literature was reviewed and summarized. An extensive list was made of potential error sources and the error sources were categorized in the form of an error budget tree including optical design errors, optical fabrication errors, assembly and alignment errors, and environmental errors. After choosing a top level image quality requirment as a goal, a preliminary tops-down error budget allocation was performed; then, based upon engineering experience, detailed analysis, or data from the literature, a bottoms-up error budget reallocation was performed in an attempt to achieve an equitable distribution of difficulty in satisfying the various allocations. This exercise provided a realistic allocation for residual off-axis optical design errors in the presence of state-of-the-art optical fabrication and alignment errors. Three different computational techniques were developed for computing the image degradation of phased telescope arrays due to aberrations of the individual telescopes. Parametric studies and sensitivity analyses were then performed for a variety of subaperture configurations and telescope design parameters in an attempt to determine how the off-axis performance of a phased telescope array varies as the telescopes are scaled up in size. The Air Force Weapons Laboratory (AFWL) multipurpose telescope testbed (MMTT) configuration was analyzed in detail with regard to image degradation due to field curvature and distortion of the individual telescopes as they are scaled up in size.

  11. Stable isotope variations in benthic primary producers along the Bosphorus (Turkey): A preliminary study.

    PubMed

    Calizza, Edoardo; Aktan, Yelda; Costantini, Maria Letizia; Rossi, Loreto

    2015-08-15

    The Bosphorus Strait is a dynamic and complex system. Recent evidences showed nitrogen and heavy metal concentrations to follow opposite patterns across the Strait, suggesting a complex spatial organisation of the anthropogenic disturbance in this system. Here, we provide isotopic information on the origin and transportation of dissolved nitrogen along the Bosphorus. C and N isotopic and elemental analyses were performed on specimens of Ulva lactuca and associated epiphytes sampled in five locations across the Strait. Variations in C and N isotopic signatures were observed in U. lactuca, pointing to a decrease in the availability of anthropogenic organic dissolved nitrogen along a north-south direction. Conversely, epiphytes did not show isotopic or elemental patterns across the Strait. These results suggest that preliminary stable isotope surveys in extended costal systems basing on U. lactuca can represent a valuable tool to focus meaningful targets and hypotheses for pollution studies in the Mediterranean region. PMID:25982821

  12. Isotopic Study ( 18O, 2H) of the Ground Water in the Bekaa's plain (Lebanon)

    NASA Astrophysics Data System (ADS)

    Awad, S.

    The stable isotopes of the water molecule (18O, 2H) give informations about the paleoclimate existing during the water seepage and about the recharge conditions of the groundwater. The effects of the Orography, the Continentality, and the origin of the masses of air have an effect on the isotopic abundance of the precipitations (rain + snow) in Lebanon. An evaporation of the recharge water exists in the atmosphere, with a mixing between the deep water and the shallow ones. The sea water has an isotopic abundance at 0 ‰ (SMOW: Standard Mean Ocean Water) for δ2H et δ18O, the Mediterranean Sea is at the origin of the rains which fall on the studied area, and which do not keep the isotopic abundances of the sea because the high mountains that they cross during their movement. This high altitude causes an impoverishment of the water of the rain on heavy isotope (18O).

  13. High flux isotope reactor cold source preconceptual design study report

    SciTech Connect

    Selby, D.L.; Bucholz, J.A.; Burnette, S.E.

    1995-12-01

    In February 1995, the deputy director of Oak Ridge National Laboratory (ORNL) formed a group to examine the need for upgrades to the High Flux Isotope Reactor (HFIR) system in light of the cancellation of the Advanced Neutron Source Project. One of the major findings of this study was that there was an immediate need for the installation of a cold neutron source facility in the HFIR complex. The anticipated cold source will consist of a cryogenic LH{sub 2} moderator plug, a cryogenic pump system, a refrigerator that uses helium gas as a refrigerant, a heat exchanger to interface the refrigerant with the hydrogen loop, liquid hydrogen transfer lines, a gas handling system that includes vacuum lines, and an instrumentation and control system to provide constant system status monitoring and to maintain system stability. The scope of this project includes the development, design, safety analysis, procurement/fabrication, testing, and installation of all of the components necessary to produce a working cold source within an existing HFIR beam tube. This project will also include those activities necessary to transport the cold neutron beam to the front face of the present HFIR beam room. The cold source project has been divided into four phases: (1) preconceptual, (2) conceptual design and research and development (R and D), (3) detailed design and procurement, and (4) installation and operation. This report marks the conclusion of the preconceptual phase and establishes the concept feasibility. The information presented includes the project scope, the preliminary design requirements, the preliminary cost and schedule, the preliminary performance data, and an outline of the various plans for completing the project.

  14. Development of a Laser Probe for Argon Isotope Studies.

    NASA Astrophysics Data System (ADS)

    McConville, Paul

    Available from UMI in association with The British Library. The first objective of this study was to develop a laser outgassing facility for argon isotope studies. Apart from the laser and construction of the laser sample port, existing vacuum and mass spectrometer systems were used. Laser performance and optimum operating conditions were investigated. The second objective was test and evaluate the laser extraction technique by studies of simple geological samples. Previous laser ^{40} Ar-^{39}Ar dating studies by other workers had not systematically established the basis or characteristics of the method. Results from laser and complementary stepped heating studies of the ^{40}Ar-^ {39}Ar dating standard hornblende, hb3gr; a phlogopite sample from the Palabora (Phalaborwa) Complex; and biotites in a thin section of the Hamlet Bjerg granite from East Greenland, verified that: (1) Laser extraction reproduced within experimental error the stepped heating ^{40}Ar-^ {39}Ar and K-Ar ages of simple samples. (2) The precision of the technique i.e. the amount of sample required to give reliable ages, was limited in the present experiments largely by the level of the blanks and backgrounds to 10-100 ug samples. (3) Sample outgassing appeared to be limited to the order of 10 um outside the physical size of the laser pit, consistent with other estimates of the spatial definition in the literature. This could be understood by thermal diffusion and the length of the laser pulse. (4) The efficiency of the laser pulse in melting and outgassing mineral samples was shown to be dependent on silicate latent heats and mineral absorption at the laser wavelength. In addition, the ^{40} Ar-^{39}Ar age of the geologically significant Palabora Complex was determined as (2053 +/- 5) Ma. Excess argon led to a discrepancy between the laser and stepped heating ages of biotite and muscovite, (405 +/- 5) Ma, and laser ages of feldspars (510 +/- 20) Ma in the Hamlet Bjerg granite. This illustrated

  15. Systematic study of (α ,γ ) reactions for stable nickel isotopes

    NASA Astrophysics Data System (ADS)

    Simon, A.; Beard, M.; Spyrou, A.; Quinn, S. J.; Bucher, B.; Couder, M.; DeYoung, P. A.; Dombos, A. C.; Görres, J.; Kontos, A.; Long, A.; Moran, M. T.; Paul, N.; Pereira, J.; Robertson, D.; Smith, K.; Stech, E.; Talwar, R.; Tan, W. P.; Wiescher, M.

    2015-08-01

    A systematic measurement of the (α ,γ ) reaction for all the stable nickel isotopes has been performed using the γ -summing technique. For two of the isotopes, 60Ni and 61Ni, the α -capture cross sections have been experimentally measured for the first time. For 58,62,64Ni, the current measurement is in excellent agreement with earlier results found in the literature, and additionally extends the energy range of the measured cross sections up to 8.7 MeV. The data provided a tool for testing the cross section predictions of Hauser-Feshbach calculations. The experimental results were compared to the cross sections calculated with the talys 1.6 code and commonly used databases non-smoker and bruslib. For each of the investigated isotopes a combination of input parameter for talys was identified that best reproduces the experimental data, and recommended reaction rate has been calculated. Additionally, a set of inputs for Hauser-Feshbach calculations was given that, simultaneously for all the isotopes under consideration, reproduces the experimental data within the experimental uncertainties.

  16. A Gamma Ray Imaging Device for Small-Animal Studies

    NASA Astrophysics Data System (ADS)

    Saunders, Robert; Bradley, Eric; Majewski, Stan; Saha, Margaret S.; Weisenberger, Andrew G.; Welsh, Robert E.

    1999-11-01

    A novel, modular nuclear imaging device for in vivo imaging of small animals is described. A segmented scintillator is coupled to a position-sensitive photomultiplier. This combination is used to view the living system under study with a variety of collimators employed to limit the angular acceptance. A personal computer is coupled to a CAMAC electronic system for event-by-event data acquisition and subsequent selective data analysis. The system has been designed to exploit the availability of a wide range of ligands tagged with the isotope 125I. It has most recently been employed for a study of the transport of the cocaine analog, RTI-55, to the brain of a mouse. Results of studies to date and options for future expansion of the system will be described.

  17. Isotopic composition of Murchison organic compounds: Intramolecular carbon isotope fractionation of acetic acid. Simulation studies of cosmochemical organic syntheses

    NASA Technical Reports Server (NTRS)

    Yuen, G. U.; Cronin, J. R.; Blair, N. E.; Desmarais, D. J.; Chang, S.

    1991-01-01

    Recently, in our laboratories, samples of Murchison acetic acid were decarboxylated successfully and the carbon isotopic composition was measured for the methane released by this procedure. These analyses showed significant differences in C-13/C-12 ratios for the methyl and carboxyl carbons of the acetic acid molecule, strongly suggesting that more than one carbon source may be involved in the synthesis of the Murchison organic compounds. On the basis of this finding, laboratory model systems simulating cosmochemical synthesis are being studied, especially those processes capable of involving two or more starting carbon sources.

  18. Lead isotopic studies of the Samail ophiolite, Oman

    NASA Technical Reports Server (NTRS)

    Chen, J. H.; Pallister, J. S.

    1981-01-01

    The isotopic composition of Pb and the concentrations of U, Th, and Pb are determined for samples from massive sulfides and lithologic units of the Samail ophiolite. It is shown that the magma that formed the ophiolite was probably derived from a depleted mantle, similar in Pb isotopic composition to the source area of mid-ocean ridge basalt. The gross geochemical characteristics of the mantle sources have remained almost unchanged for the last 100 million years. It is also shown that the U-Th-Pb systematics of the Samail formation indicate that local vertical heterogeneity in the oceanic crust can result from crystal fractionation and metasomatism at, and near, an oceanic spreading center.

  19. Study of the charge radii of the stable lead isotopes

    SciTech Connect

    Borchert, G.L.; Schult, O.W.B.; Speth, J.; Hansen, P.G.; Jonson, B.; Ravn, H.; McGrory, J.B.

    1982-01-01

    Isotope shifts have been measured of the K/sub ..cap alpha..l/ x-ray lines emitted after photo ionization of /sup 204/Pb, /sup 206/Pb, /sup 207/Pb and /sup 208/Pb samples. The results are compared with theoretical values for delta < r/sup 2/> calculated with a microscopic model. The x-ray shift data are also compared with optical data and the nuclear parameters lambda derived from electron scattering results.

  20. Imaging Complex Protein Metabolism in Live Organisms by Stimulated Raman Scattering Microscopy with Isotope Labeling

    PubMed Central

    2016-01-01

    Protein metabolism, consisting of both synthesis and degradation, is highly complex, playing an indispensable regulatory role throughout physiological and pathological processes. Over recent decades, extensive efforts, using approaches such as autoradiography, mass spectrometry, and fluorescence microscopy, have been devoted to the study of protein metabolism. However, noninvasive and global visualization of protein metabolism has proven to be highly challenging, especially in live systems. Recently, stimulated Raman scattering (SRS) microscopy coupled with metabolic labeling of deuterated amino acids (D-AAs) was demonstrated for use in imaging newly synthesized proteins in cultured cell lines. Herein, we significantly generalize this notion to develop a comprehensive labeling and imaging platform for live visualization of complex protein metabolism, including synthesis, degradation, and pulse–chase analysis of two temporally defined populations. First, the deuterium labeling efficiency was optimized, allowing time-lapse imaging of protein synthesis dynamics within individual live cells with high spatial–temporal resolution. Second, by tracking the methyl group (CH3) distribution attributed to pre-existing proteins, this platform also enables us to map protein degradation inside live cells. Third, using two subsets of structurally and spectroscopically distinct D-AAs, we achieved two-color pulse–chase imaging, as demonstrated by observing aggregate formation of mutant hungtingtin proteins. Finally, going beyond simple cell lines, we demonstrated the imaging ability of protein synthesis in brain tissues, zebrafish, and mice in vivo. Hence, the presented labeling and imaging platform would be a valuable tool to study complex protein metabolism with high sensitivity, resolution, and biocompatibility for a broad spectrum of systems ranging from cells to model animals and possibly to humans. PMID:25560305

  1. Imaging complex protein metabolism in live organisms by stimulated Raman scattering microscopy with isotope labeling.

    PubMed

    Wei, Lu; Shen, Yihui; Xu, Fang; Hu, Fanghao; Harrington, Jamie K; Targoff, Kimara L; Min, Wei

    2015-03-20

    Protein metabolism, consisting of both synthesis and degradation, is highly complex, playing an indispensable regulatory role throughout physiological and pathological processes. Over recent decades, extensive efforts, using approaches such as autoradiography, mass spectrometry, and fluorescence microscopy, have been devoted to the study of protein metabolism. However, noninvasive and global visualization of protein metabolism has proven to be highly challenging, especially in live systems. Recently, stimulated Raman scattering (SRS) microscopy coupled with metabolic labeling of deuterated amino acids (D-AAs) was demonstrated for use in imaging newly synthesized proteins in cultured cell lines. Herein, we significantly generalize this notion to develop a comprehensive labeling and imaging platform for live visualization of complex protein metabolism, including synthesis, degradation, and pulse-chase analysis of two temporally defined populations. First, the deuterium labeling efficiency was optimized, allowing time-lapse imaging of protein synthesis dynamics within individual live cells with high spatial-temporal resolution. Second, by tracking the methyl group (CH3) distribution attributed to pre-existing proteins, this platform also enables us to map protein degradation inside live cells. Third, using two subsets of structurally and spectroscopically distinct D-AAs, we achieved two-color pulse-chase imaging, as demonstrated by observing aggregate formation of mutant hungtingtin proteins. Finally, going beyond simple cell lines, we demonstrated the imaging ability of protein synthesis in brain tissues, zebrafish, and mice in vivo. Hence, the presented labeling and imaging platform would be a valuable tool to study complex protein metabolism with high sensitivity, resolution, and biocompatibility for a broad spectrum of systems ranging from cells to model animals and possibly to humans. PMID:25560305

  2. Rare-isotope and kinetic studies of Pt/SnO2 catalysts

    NASA Technical Reports Server (NTRS)

    Upchurch, Billy T.; Wood, George M.; Schryer, David R.; Hess, Robert V.; Miller, Irvin M.; Kielin, Erik J.

    1990-01-01

    Closed-cycle pulsed CO2 laser operation requires the use of an efficient CO-O2 recombination catalyst for these dissociation products which otherwise would degrade the laser operation. The catalyst must not only operate at low temperatures but also must operate efficiently for long periods. In the case of the Laser Atmospheric Wind Sounder (LAWS) laser, an operational lifetime of 3 years is required. Additionally, in order to minimize atmospheric absorption and enhance aerosol scatter of laser radiation, the LAWS system will operate at 9.1 micrometers with an oxygen-18 isotope CO2 lasing medium. Consequently, the catalyst must not only operate at low temperatures but must also preserve the isotopic integrity of the rare-isotope composition in the recombination mode. Several years ago an investigation of commercially available and newly synthesized recombination catalysts for use in closed-cycle pulsed common and rare-isotope CO2 lasers was implemented at the NASA Langley Research Center. Since that time, mechanistic efforts utilizing both common and rare oxygen isotopes have been implemented and continue. Rare-isotope studies utilizing commercially available platinum-tin oxide catalyst have demonstrated that the catalyst contributes oxygen-16 to the product carbon dioxide thus rendering it unusable for rare-isotope applications. A technique has been developed for modification of the surface of the common-isotope catalyst to render it usable. Results of kinetic and isotope label studies using plug flow, recycle plug flow, and closed internal recycle plug flow reactor configuration modes are discussed.

  3. Multi-scale study of the isotope effect in ISTTOK

    NASA Astrophysics Data System (ADS)

    Liu, B.; Silva, C.; Figueiredo, H.; Pedrosa, M. A.; van Milligen, B. Ph.; Pereira, T.; Losada, U.; Hidalgo, C.

    2016-05-01

    The isotope effect, namely the isotope dependence of plasma confinement, is still one of the principal scientific conundrums facing the magnetic fusion community. We have investigated the impact of isotope mass on multi-scale mechanisms, including the characterization of radial correlation lengths (\\boldsymbol{L}{r} ) and long-range correlations (LRC) of plasma fluctuations using multi-array Langmuir probe system, in hydrogen (H) and deuterium (D) plasmas in the ISTTOK tokamak. We found that when changing plasma composition from the H dominated to D dominated, the LRC amplitude increased markedly (10–30%) and the \\boldsymbol{L}{r} increased slightly (~10%). The particle confinement also improved by about 50%. The changes of LRC and \\boldsymbol{L}{r} are congruent with previous findings in the TEXTOR tokamak (Xu et al 2013 Phys. Rev. Lett. 110 265005). In addition, using biorthogonal decomposition, both geodesic acoustic modes and very low frequency (<5 kHz) coherent modes were found to be contributing to LRC.

  4. Sm-Nd Isotopic Studies of Ureilite Novo Urei

    NASA Technical Reports Server (NTRS)

    Shih, C.-Y.; Nyquist, L. E.; Reese, Y.; Goodrich, C. A.

    2011-01-01

    Ureilites are ultramafic (harzburgitic) achondrites composed predominantly of olivine and pyroxenes, abundant carbon (graphites and shock-produced diamonds), some metal and sulfides. These rocks probably represent ultramafic mantles of differentiated parent asteroidal bodies. Age determinations of these rocks by Rb-Sr and Sm-Nd methods have been difficult because of their extremely low abundances of these parent-daughter elements. Nevertheless, Sm-Nd isochron ages were reported for Kenna, Goalpara, MET 78008 and PCA 82506 yielding ages of 3.74+/-0.02 Ga, approx.3.7 Ga, 4.09+/-0.08 Ga, 4.23+/-0.06 Ga, respectively [1-4]. These "young" Sm-Nd ages may represent secondary metasomatism events [1] related to impacts [5], as indicated by the similarly young Ar-39-Ar-40 degassing ages of 3.3-4.1 Ga for ureilites Kenna, Novo Urei and Havero [6]. Alternatively, it has been suggested that these rocks may have been contaminated with terrestrial crustal materials and the isochrons do not have any age significance [2,7]. Indications of old approx.4.56 Ga ages for ureilites were reported from the U-Pb and Sm-Nd model ages for MET 78008 [8]. More reliable evidences for old formation ages of ureilites were reported recently using the short-lived chronometers Hf-182-W-182, Al-26-Mg-26 and Mn-53-Cr-53. The deficits of 182W in ureilites suggest the metal-silicate segregation occurred very early, approx.1-2 Ma after CAI [9]. The Al-26-Mg-26 and Mn-53-Cr-53 studies for a feldspathic lithology [10] and the Mn-53-Cr-53 for olivine- and pyroxene-dominant lithologies [11] in ureilites revealed that they crystallized approx.5.4 Ma after CAI, i.e., at 4563.8+/-0.5 Ma relative to D.Orbigny. In this report, we present Sm-Nd isotopic data for a relatively fresh ureilite, Novo Urei, a rare ureilite fall (1886). We compare these data to Sm-Nd data for other ureilites, and discuss Novo Urei's petrogenesis

  5. Strontium isotope study of coal utilization by-products interacting with environmental waters.

    PubMed

    Spivak-Birndorf, Lev J; Stewart, Brian W; Capo, Rosemary C; Chapman, Elizabeth C; Schroeder, Karl T; Brubaker, Tonya M

    2012-01-01

    Sequential leaching experiments on coal utilization by-products (CUB) were coupled with chemical and strontium (Sr) isotopic analyses to better understand the influence of coal type and combustion processes on CUB properties and the release of elements during interaction with environmental waters during disposal. Class C fly ash tended to release the highest quantity of minor and trace elements-including alkaline earth elements, sodium, chromium, copper, manganese, lead, titanium, and zinc-during sequential extraction, with bottom ash yielding the lowest. Strontium isotope ratios ((87)Sr/(86)Sr) in bulk-CUB samples (total dissolution of CUB) are generally higher in class F ash than in class C ash. Bulk-CUB ratios appear to be controlled by the geologic source of the mineral matter in the feed coal, and by Sr added during desulfurization treatments. Leachates of the CUB generally have Sr isotope ratios that are different than the bulk value, demonstrating that Sr was not isotopically homogenized during combustion. Variations in the Sr isotopic composition of CUB leachates were correlated with mobility of several major and trace elements; the data suggest that arsenic and lead are held in phases that contain the more radiogenic (high-(87)Sr/(86)Sr) component. A changing Sr isotope ratio of CUB-interacting waters in a disposal environment could forecast the release of certain strongly bound elements of environmental concern. This study lays the groundwork for the application of Sr isotopes as an environmental tracer for CUB-water interaction. PMID:22218183

  6. A hydrogen gas-water equilibration method produces accurate and precise stable hydrogen isotope ratio measurements in nutrition studies

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Stable hydrogen isotope methodology is used in nutrition studies to measure growth, breast milk intake, and energy requirement. Isotope ratio MS is the best instrumentation to measure the stable hydrogen isotope ratios in physiological fluids. Conventional methods to convert physiological fluids to ...

  7. Frame Your Images: Making Digital Images Accessible for Study & Testing

    ERIC Educational Resources Information Center

    Gepner, Ivan

    2009-01-01

    Images, whether at the level of molecules, cells, organs, organisms, or environments, are at the core of many biological disciplines. Even with the contemporary emphasis on molecular analysis, biology has retained its traditional strong visual component. In courses that rely on the study of biological structure, the presentation of images for…

  8. Use of stable isotopes of selenium in human metabolic studies: development of analytical methodology

    SciTech Connect

    Janghorbani, M.; Ting, B.T.; Young, V.R.

    1981-12-01

    Use of stable isotopes of selenium in relation to enrichment of diets for studies of selenium absorption and metabolism in human subjects is discussed. A method based on radiochemical neutron activation analysis is described which allows accurate measurement of stable isotopes 74Se, 76Se, and 80Se in matrices (feces, plasma, red blood cells, and urine) of interest in metabolic studies. We show that these isotopes can routinely be measured with analytical precision and accuracy of 10% in samples of available size. This precision and accuracy is satisfactory for conduct of many nutritional experiments concerned with gastrointestinal absorption, plasma and red cell selenium turnover, and urinary excretion of the element, using an oral dose of 74Se. Original, experimental data are presented to illustrate the degree of enrichment of 74Se in feces, plasma, and urine after a single oral ingestion of 50 micrograms of the isotope with a breakfast meal in healthy young men.

  9. Study of dipole excitations and the single particle structure of neutron rich Ni isotopes

    NASA Astrophysics Data System (ADS)

    Mahata, K.; Paschalis, S.; Adrich, P.; Aksouh, F.; Aumann, T.; Babilon, M.; Behr, K.-H.; Benlliure, J.; Berg, T.; Boehmer, M.; Boretzky, K.; Brünle, A.; Casarejos, E.; Chartier, M.; Chatillon, A.; Cortina-Gil, D.; Pramanik, U. Datta; Deveaux, L.; Elvers, M.; Emling, H.; Fernandez-Dominguez, B.; Gorska, M.; Hüller, W.; Ickert, G.; Johansson, H.; Junghans, A.; Karagiannis, C.; Kern, L.; Kiselev, O.; Klimkiewicz, A.; Kurz, N.; Labiche, M.; Le Bleis, T.; Lemmon, R.; Lindenberg, K.; Litvinov, Y.; Maierbeck, P.; Müller, S.; Nilsson, T.; Nociforo, C.; Palit, R.; Prokopowicz, W.; Rossi, D.; Simon, H.; Sümmerer, K.; Wagner, A.; Walus, W.; Weick, H.; Winkler, M.

    2008-05-01

    An experiment was performed using the FRS-LAND setup at GSI to study the dipole strength distributions above neutron separation threshold for neutron-rich Ni isotopes. Measurements, using the same experimental setup, were also carried out to extract single particle occupancies via knockout reactions to investigate the structure and magicity of the neutron-rich Ni isotopes. The status of the data analysis and preliminary results are presented.

  10. Lead exchange in teeth and bone--a pilot study using stable lead isotopes.

    PubMed Central

    Gulson, B L; Gillings, B R

    1997-01-01

    Stable lead isotopes and lead concentrations were measured in the enamel and dentine of permanent (n = 37) and deciduous teeth (n = 14) from 47 European immigrants to Australia to determine whether lead exchange occurs in teeth and how it relates to lead exchange in bone. Enamel exhibits no exchange of its European-origin lead with lead from the Australian environment. In contrast, dentine lead exchanges with Australian lead to the extent of approximately 1% per year. In one subject, trabecular bone from the tooth socket exchanged almost all its European lead with Australian lead over a a 15-year period (turnover of approximately 6% per year), similar to the approximately 8% per year proposed for lead turnover in trabecular bone. The repository characteristics of intact circumpulpal dentine were investigated by analyses of four sets of contiguous slices from six teeth: 1) a set consisting of slices with intact circumpulpal dentine and cementum; 2) a set in which these areas were removed; 3) another set consisting of slices with intact circumpulpal dentine and cementum; and 4) a set without cementum. These analyses show relatively small differences in isotopic composition between contiguous slices except that circumpulpal dentine appears to be the dominant control on lead concentration. There is a significant correlation (R2 = 0.19, p = 0.01, n = 34) of dentine lead concentration and rate of exchange with residence time from the country of origin and Australian lead, but there is no such correlation with enamel lead concentration. Analyses of permanent and deciduous teeth of subjects from other countries who have resided in Australia for varying lengths of time should resolve some of the questions arising from this pilot study. Images Figure 1. PMID:9347897

  11. Phonon-isotope scattering and thermal conductivity in materials with a large isotope effect: A first-principles study

    NASA Astrophysics Data System (ADS)

    Lindsay, L.; Broido, D. A.; Reinecke, T. L.

    2013-10-01

    The interplay between phonon-isotope and phonon-phonon scattering in determining lattice thermal conductivities in semiconductors and insulators is examined using an ab initio Boltzmann transport equation approach. We identify materials with large enhancements to their thermal conductivities with isotopic purification, known as the isotope effect, and we focus in particular on results for beryllium-VI compounds and cubic germanium carbide. We find that germanium carbide and beryllium selenide have very large room temperature isotope effects of 450%, far larger than in any other material. Thus, isotopic purification in these materials gives surprisingly high intrinsic room temperature thermal conductivities, over 1500 Wm-1 K-1 for germanium carbide and over 600 Wm-1 K-1 for beryllium selenide, well above those of the best metals. In compound semiconductors, a large mass ratio of the constituent atoms and large isotope mixture for the heavier atom gives enhanced isotope scattering. A frequency gap between acoustic and optic phonons (also due to a large mass ratio) and bunching of the acoustic phonon branches give weak anharmonic scattering. Combined, weak anharmonic phonon scattering and strong isotope scattering give a large isotope effect in the materials examined here. The physical insights discussed in this work will help guide the efficient manipulation of thermal transport properties of compound semiconductors through isotopic modification.

  12. Landsat image data quality studies

    NASA Technical Reports Server (NTRS)

    Schueler, C. F.; Salomonson, V. V.

    1985-01-01

    Preliminary results of the Landsat-4 Image Data Quality Analysis (LIDQA) program to characterize the data obtained using the Thematic Mapper (TM) instrument on board the Landsat-4 and Landsat-5 satellites are reported. TM design specifications were compared to the obtained data with respect to four criteria, including spatial resolution; geometric fidelity; information content; and image relativity to Multispectral Scanner (MSS) data. The overall performance of the TM was rated excellent despite minor instabilities and radiometric anomalies in the data. Spatial performance of the TM exceeded design specifications in terms of both image sharpness and geometric accuracy, and the image utility of the TM data was at least twice as high as MSS data. The separability of alfalfa and sugar beet fields in a TM image is demonstrated.

  13. Coordinated Chemical and Isotopic Imaging of Bells (CM2) Meteorite Matrix

    NASA Technical Reports Server (NTRS)

    Clemett, S. J.; Messenger, S.; Naklamura-Messenger, K.; Thomas-Keprta, K. L.

    2014-01-01

    Meteoritic organic matter is a complex conglomeration of species formed in distinct environments and processes in circumstellar space, the interstellar medium, the Solar Nebula and asteroids. Consequently meteorites constitute a unique record of primordial organic chemical evolution. While bulk chemical analysis has provided a detailed description of the range and diversity of organic species present in carbonaceous chondrites, there is little information as to how these species are spatially distributed and their relationship to the host mineral matrix. The distribution of organic phases is nevertheless critical to understanding parent body processes. The CM and CI chondrites all display evidence of low temperature (< 350K) aqueous alteration that may have led to aqueous geochromatographic separation of organics and synthesis of new organics coupled to aqueous mineral alteration. Here we present the results of the first coordinated in situ isotopic and chemical mapping study of the Bells meteorite using a newly developed two-step laser mass spectrometer (mu-L(sup 2)MS) capable of measuring a broad range of organic compounds.

  14. The study of trace metal absoption using stable isotopes and mass spectrometry

    NASA Astrophysics Data System (ADS)

    Fennessey, P. V.; Lloyd-Kindstrand, L.; Hambidge, K. M.

    1991-12-01

    The absorption and excretion of zinc stable isotopes have been followed in more than 120 human subjects. The isotope enrichment determinations were made using a standard VG 7070E HF mass spectrometer. A fast atom gun (FAB) was used to form the ions from a dry residue on a pure silver probe tip. Isotope ratio measurements were found to have a precision of better than 2% (relative standard deviation) and required a sample size of 1-5 [mu]g. The average true absorption of zinc was found to be 73 ± 12% (2[sigma]) when the metal was taken in a fasting state. This absorption figure was corrected for tracer that had been absorbed and secreted into the gastrointestinal (GI) tract over the time course of the study. The average time for a majority of the stable isotope tracer to pass through the GI tract was 4.7 ± 1.9 (2[sigma]) days.

  15. X-Ray Imaging Study

    NASA Technical Reports Server (NTRS)

    OBrien, Susan K.; Workman, Gary L.

    1996-01-01

    The space environment in which the Space Station Freedom and other space platforms will orbit is truly a hostile environment. For example, the currently estimated integral fluence for electrons above 1 Mev at 2000 nautical miles is above 2 x 1O(exp 10) electrons/sq cm/day and the proton integral fluence is above 1 x 10(exp 9) protons/sq cm/day. At the 200 - 400 nautical miles, which is more representative of the altitude which will provide the environment for the Space Station, each of these fluences will be proportionally less; however, the data indicates that the radiation environment will obviously have an effect on structural materials exposed to the environment for long durations. The effects of this combined environment is the issue which needs to be understood for the long term exposure of structures in space. At the same time, there will be substantial potential for collisions between the space platforms and space debris. The current NASA catalogue contains over 4500 objects floating in space which are not considered payloads. This debris can have significant effects on collision with orbiting spacecraft. In order to better understand the effect of these hostile phenomena on spacecraft, several types of studies are being performed to simulate at some level the effect of the environment. In particular the study of debris clouds produced by hypervelocity impact on the various surfaces anticipated on the Space Station is very important at this point in time. The need to assess the threat of such debris clouds on space structures is an on-going activity. The Space Debris Impact facility in Building 4612 provides a test facility to monitor the types of damage produced with hypervelocity impact. These facilities are used to simulate space environmental effects from energetic particles. Flash radiography or x-ray imaging has traditionally provided such information and as such has been an important tool for recording damage in situ with the event. The proper

  16. Stable isotope methodology in the pharmacokinetic studies of androgenic steroids in humans

    SciTech Connect

    Shinohara, Y.; Baba, S. )

    1990-04-01

    The use of stable isotopically labeled steroids combined with gas chromatography/mass spectrometry (GC/MS) has found a broad application in pharmacologic studies. Initially, stable isotopically labeled steroids served as the ideal analytic internal standard for GC/MS analysis; however, their in vivo use has expanded and has proven to be a powerful pharmacokinetic tool. We have successfully used stable isotope methodology to study the pharmacokinetic/bioavailability of androgens. The primary advantage of the technique is that endogenous and exogenous steroids with the same basic structure can be differentiated by using stable isotopically labeled analogs. The method was used to examine the pharmacokinetics of testosterone and testosterone propionate, and to clarify the influence of endogenous testosterone. Another advantage of the isotope methods is that steroidal drugs can be administered concomitantly in two formulations (e.g., solution and solid dosage). A single set of blood samples serves to describe the time course of the formulations being compared. This stable isotope coadministration technique was used to estimate the relative bioavailability of 17 alpha-methyltestosterone. 35 references.

  17. 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

  18. Image Attributes: A Study of Scientific Diagrams.

    ERIC Educational Resources Information Center

    Brunskill, Jeff; Jorgensen, Corinne

    2002-01-01

    Discusses advancements in imaging technology and increased user access to digital images, as well as efforts to develop adequate indexing and retrieval methods for image databases. Describes preliminary results of a study of undergraduates that explored the attributes naive subjects use to describe scientific diagrams. (Author/LRW)

  19. Stable Isotope Resolved Metabolomics Studies in Ex Vivo TIssue Slices

    PubMed Central

    Fan, Teresa W-M.; Lane, Andrew N.; Higashi, Richard M.

    2016-01-01

    An important component of this methodology is to assess the role of the tumor microenvironment on tumor growth and survival. To tackle this problem, we have adapted the original approach of Warburg 1, by combining thin tissue slices with Stable Isotope Resolved Metabolomics (SIRM) to determine detailed metabolic activity of human tissues. SIRM enables the tracing of metabolic transformations of source molecules such as glucose or glutamine over defined time periods, and is a requirement for detailed pathway tracing and flux analysis. In our approach, we maintain freshly resected tissue slices (both cancerous and non- cancerous from the same organ of the same subject) in cell culture media, and treat with appropriate stable isotope-enriched nutrients, e.g. 13C6-glucose or 13C5, 15N2 -glutamine. These slices are viable for at least 24 h, and make it possible to eliminate systemic influence on the target tissue metabolism while maintaining the original 3D cellular architecture. It is therefore an excellent pre-clinical platform for assessing the effect of therapeutic agents on target tissue metabolism and their therapeutic efficacy on individual patients 2,3. PMID:27158639

  20. Experimental and computer modeling studies of isotopically selective two-step laser photodissociation of small molecules

    SciTech Connect

    Zittel, P.F.

    1992-03-25

    The approach to laser isotope separation taken in this study is based on isotopically selective, two-step, laser photodissociation of small molecules. A primary goal of this study is the measurement of fundamental molecular processes which control the two-step, photodissociative isotope enrichment process. This objective has led to experimental measurements of uv photodissociation cross sections for vibrationally excited states of several small molecules, including the first cross section reported for any neutral molecule in a specific, excited vibrational state. A second goal of this study has been the laboratory demonstration of isotope enrichment for isotopes of practical interest and for processes with a potential for larger scale production. Where possible, efforts have focussed on the separation of middle isotopes, such as {sup 17}O and {sup 33}S, which are expensive and difficult to separate using other techniques. Considerable success has been achieved in demonstrating the enrichment of isotopes of bromine, carbon, oxygen and a third goal of this study has been the application of computer modeling to the two-step enrichment process. Experimental measurements define as many as possible of the critical photophysical and chemical parameters required by an ab initio computer model of the enrichment process. Progress toward these goals has been documented in detail in a variety of journal articles and technical reports. It is not the objective of this final report to discuss each aspect of the work done under this contract/grant in detail. A general overview of the program, touches briefly on each of the problems addressed by the study and provides references to more detailed discussions. 19 refs.

  1. Study of the Photon Strength Functions for Gadolinium Isotopes with the DANCE Array

    SciTech Connect

    Dashdorj, D.; Mitchell, G. E.; Baramsai, B.; Chankova, R.; Chyzh, A.; Walker, C.; Agvaanluvsan, U.; Becker, J. A.; Parker, W.; Sleaford, B.; Wu, C. Y.; Bredeweg, T. A.; Couture, A.; Haight, R. C.; Jandel, M.; Rundberg, R. S.; Ullmann, J. L.; Vieira, D. J.; Wouters, J. M.; Krticka, M.

    2009-03-10

    The gadolinium isotopes are interesting for reactor applications as well as for medicine and astrophysics. The gadolinium isotopes have some of the largest neutron capture cross sections. As a consequence they are used in the control rod in reactor fuel assembly. From the basic science point of view, there are seven stable isotopes of gadolinium with varying degrees of deformation. Therefore they provide a good testing ground for the study of deformation dependent structure such as the scissors mode. Decay gamma rays following neutron capture on Gd isotopes are detected by the DANCE array, which is located at flight path 14 at the Lujan Neutron Scattering Center at Los Alamos National Laboratory. The high segmentation and close packing of the detector array enable gamma-ray multiplicity measurements. The calorimetric properties of the DANCE array coupled with the neutron time-of-flight technique enables one to gate on a specific resonance of a specific isotope in the time-of-flight spectrum and obtain the summed energy spectrum for that isotope. The singles gamma-ray spectrum for each multiplicity can be separated by their DANCE cluster multiplicity. Various photon strength function models are used for comparison with experimentally measured DANCE data and provide insight for understanding the statistical decay properties of deformed nuclei.

  2. Ammonium transport and reaction in contaminated groundwater: Application of isotope tracers and isotope fractionation studies

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Ammonium (NH4 +) is a major constituent of many contaminated groundwaters, but its movement through aquifers is complex and poorly documented. In this study, processes affecting NH4 + movement in a treated wastewater plume were studied by a combination of techniques including large-scale monitoring...

  3. Are Isotope Models of Tree Ring Cellulose Useful for Studies on Ecosystem and Climate Change?

    NASA Astrophysics Data System (ADS)

    Roden, J. S.

    2003-12-01

    For many years, the carbon, oxygen and hydrogen stable isotopes of tree ring cellulose have been used to infer environmental change at ecosystem and global scales. Most climate change studies have been based on empirical correlations with measured or inferred meteorological information. Recently, mechanistic models have been developed to interpret and predict the isotopic composition of cellulose. These models help clarify what environmental information might be contained in historic cellulose records. Although it is best to test and parameterize these models under controlled environmental conditions, field-testing is also critical since the tremendous variability of environmental factors in natural habitats could obscure important signals. However, field-testing these models can be problematic due to the large number of parameters that need to be estimated. Two studies will be presented that test a model that predicts the stable oxygen isotope content of cellulose under field conditions. The model adequately accounted for field observations of riparian zone trees at three sites in Arizona, Oregon and Utah that had contrasting isotopic and environmental inputs. Although the cellulose model underestimated the oxygen isotopic content of tree ring cellulose in a study along a transect of decreasing water status in Oregon, it did predict the greatly reduced range in oxygen isotope content over the transect. Both studies show that ambient humidity plays an important role in modifying the primary signal of meteoric water isotopic content in organic matter. Thus, tree ring records could provide important proxy information regarding changes in ecosystem humidity. However, teasing out humidity information may not be trivial due to the number of other factors involved. The use of dual isotope records (carbon and oxygen) allow for better interpretation of environmental information since each isotope provides different, though related, information regarding ecosystem water

  4. Isotope geochemistry and fluid inclusion study of skarns from Vesuvius

    USGS Publications Warehouse

    Gilg, H.A.; Lima, A.; Somma, R.; Belkin, H.E.; de Vivo, B.; Ayuso, R.A.

    2001-01-01

    We present new mineral chemistry, fluid inclusion, stable carbon and oxygen, as well as Pb, Sr, and Nd isotope data of Ca-Mg-silicate-rich ejecta (skarns) and associated cognate and xenolithic nodules from the Mt. Somma-Vesuvius volcanic complex, Italy. The typically zoned skarn ejecta consist mainly of diopsidic and hedenbergitic, sometimes "fassaitic" clinopyroxene, Mg-rich and Ti-poor phlogopite, F-bearing vesuvianite, wollastonite, gehlenite, meionite, forsterite, clinohumite, anorthite and Mg-poor calcite with accessory apatite, spinell, magnetite, perovskite, baddeleyite, and various REE-, U-, Th-, Zr- and Ti-rich minerals. Four major types of fluid inclusions were observed in wollastonite, vesuvianite, gehlenite, clinopyroxene and calcite: a) primary silicate melt inclusions (THOM = 1000-1050??C), b) CO2 ?? H2S-rich fluid inclusions (THOM = 20-31.3??C into the vapor phase), c) multiphase aqueous brine inclusions (THOM = 720-820??C) with mainly sylvite and halite daughter minerals, and d) complex chloride-carbonate-sulfate-fluoride-silicate-bearing saline-melt inclusions (THOM = 870-890??C). The last inclusion type shows evidence for immiscibility between several fluids (silicate melt - aqueous chloride-rich liquid - carbonate/sulfate melt?) during heating and cooling below 870??C. There is no evidence for fluid circulation below 700??C and participation of externally derived meteoric fluids in skarn formation. Skarns have considerably variable 206Pb/204Pb (19.047-19.202), 207Pb/204Pb (15.655-15.670), and 208Pb/204Pb (38.915-39.069) and relatively low 143Nd/144Nd (0.51211-0.51244) ratios. The carbon and oxygen isotope compositions of skarn calcites (??13CV-PDB = -5.4 to -1.1???; ??18OV-SMOW = 11.7 to 16.4???) indicate formation from a 18O- and 13C-enriched fluid. The isotope composition of skarns and the presence of silicate melt inclusion-bearing wollastonite nodules suggests assimilation of carbonate wall rocks by the alkaline magma at moderate depths (< 5

  5. Advances in optical imaging for pharmacological studies

    PubMed Central

    Arranz, Alicia; Ripoll, Jorge

    2015-01-01

    Imaging approaches are an essential tool for following up over time representative parameters of in vivo models, providing useful information in pharmacological studies. Main advantages of optical imaging approaches compared to other imaging methods are their safety, straight-forward use and cost-effectiveness. A main drawback, however, is having to deal with the presence of high scattering and high absorption in living tissues. Depending on how these issues are addressed, three different modalities can be differentiated: planar imaging (including fluorescence and bioluminescence in vivo imaging), optical tomography, and optoacoustic approaches. In this review we describe the latest advances in optical in vivo imaging with pharmacological applications, with special focus on the development of new optical imaging probes in order to overcome the strong absorption introduced by different tissue components, especially hemoglobin, and the development of multimodal imaging systems in order to overcome the resolution limitations imposed by scattering. PMID:26441646

  6. Hydrogen-isotope motion in scandium studied by ultrasonic measurements

    SciTech Connect

    Leisure, R.G. ); Schwarz, R.B.; Migliori, A. ); Torgeson, D.R. ); Svare, I. )

    1993-07-01

    Resonant ultrasound spectroscopy has been used to investigate ultrasonic attenuation in single crystals of Sc, ScH[sub 0.25], and ScD[sub 0.18] over the temperature range of 10--300 K for frequencies near 1 MHz. Ultrasonic-attenuation peaks were observed in the samples containing H or D with the maximum attenuation occurring near 25 K for ScH[sub 0.25] and near 50 K for ScD[sub 0.18]. The general features of the data suggest that the motion reflected in the ultrasonic attenuation is closely related to the low-temperature motion seen in nulcear-magnetic-resonance spin-lattice-relaxation measurements. The ultrasonic results were fit with a two-level-system (TLS) model involving tunneling between highly asymmetric sites. The relaxation of the TLS was found to consist of two parts: a weakly temperature-dependent part, probably due to coupling to electrons; and a much more strongly temperature-dependent part, attributed to multiple-phonon processes. The strongly temperature-dependent part was almost two orders of magnitude faster in ScH[sub 0.25] than in ScD[sub 0.18], in accordance with the idea that tunneling is involved in the motion. Surprisingly, the weakly temperature-dependent part was found to be about the same for the two isotopes. The asymmetries primarily responsible for coupling the TLS to the ultrasound are attributed to interactions between hydrogen ions that lie on adjacent [ital c] axes. The results are consistent with an isotope-independent strength for the coupling of the TLS to the ultrasound.

  7. Neodymium isotopic studies of Precambrian banded iron formations

    SciTech Connect

    Pimentel-Klose, M.R.

    1986-01-01

    The isotopic composition of Nd is reported for 11 different Precambrian BIFs and suggests a trend of increasingly positive epsilon/sub Nd/(T) values with age. This trend is interpreted to reflect isotopic variations in precambrian sea water. The Urucum and the Gunflint BIFs, both younger than 1.8 AE, yield negative epsilon/sub Nd/(T) values, between -4.6 and -1.1. The remaining BIFs, with ages between 1.85 and 3.4 AE, have predominantly positive values, between -0.7 and +4.0. The low UXSm/ UUNd ratio in BIFs is inconsistent with their REE being derived from rivers draining large proportions of greenstones. The positive, mantle-like values of BIFs older than 1.8 AE contrasts strongly with the negative, continental-like values of Phanerozoic sea water. Therefore, the REE budget of the oceans during most of the Precambrian was probably dominated by the hydrothermal circulation of sea water through MORBs and not by river waters, as today. A one order of magnitude higher hydrothermal contribution of Nd is suggested by the data for the Early Precambrian. This is most likely due to a higher hydrothermal water to river water flux ratio and/or a higher Nd concentration in hotter hydrothermal waters (>375 C) during this period. The large hydrothermal contribution of REE during the Early Precambrian can be explained best if the temperature of sea water fluxing through MORBs was higher than today. Experiments investigating the interaction between sea water and basalt have shown that the concentration of iron might have been about 20 times larger if the temperature of interaction was about 425 C. Such hot hydrothermal solutions could have been the most important source of iron in Precambrian BIFs.

  8. Study on nuclear structures of Te isotopes beyond N = 82 shell closure

    NASA Astrophysics Data System (ADS)

    Lee, Pilsoo; Lee, Chun Sik; Moon, Chang-Bum; Eurica Ribf-87 Collaboration Collaboration

    2016-03-01

    Tellurium which has two valence protons above the Z = 50 proton shell closure is well known for collective behavior in low-lying states. Therefore, Te isotopes are known to be a good test ground for studying nuclear collective modes but also the effect of neutron-proton interaction on the shell evolution with variation of neutron numbers owing to the valence protons above Z = 50 . For this reason Te isotopes always attract our attention, however, most available spectroscopic nuclear data of Te isotopes remains below N = 82 , and experimental data is severely limited above N = 82 . Meanwhile, recent study of 138Te by means of β- γ spectroscopy with fission fragments of 238U has provided us with new clues on excited states in 138Te, and the new experimental result has proposed new excited states that were unexpected in the previous theoretical studies. This study aims at understanding structural evolution in Te isotopes above N = 82 with respect to below N = 82 including the new data set available today. In this presentation we discuss the nuclear structures and effective interactions in Te isotopes above N = 82 based on the nuclear shell model and interacting boson approximations.

  9. Microwave Imaging of Human Forearms: Pilot Study and Image Enhancement

    PubMed Central

    Gilmore, Colin; Zakaria, Amer; Pistorius, Stephen; LoVetri, Joe

    2013-01-01

    We present a pilot study using a microwave tomography system in which we image the forearms of 5 adult male and female volunteers between the ages of 30 and 48. Microwave scattering data were collected at 0.8 to 1.2 GHz with 24 transmitting and receiving antennas located in a matching fluid of deionized water and table salt. Inversion of the microwave data was performed with a balanced version of the multiplicative-regularized contrast source inversion algorithm formulated using the finite-element method (FEM-CSI). T1-weighted MRI images of each volunteer's forearm were also collected in the same plane as the microwave scattering experiment. Initial “blind” imaging results from the utilized inversion algorithm show that the image quality is dependent on the thickness of the arm's peripheral adipose tissue layer; thicker layers of adipose tissue lead to poorer overall image quality. Due to the exible nature of the FEM-CSI algorithm used, prior information can be readily incorporated into the microwave imaging inversion process. We show that by introducing prior information into the FEM-CSI algorithm the internal anatomical features of all the arms are resolved, significantly improving the images. The prior information was estimated manually from the blind inversions using an ad hoc procedure. PMID:24023539

  10. Charge coupled device image sensor study

    NASA Technical Reports Server (NTRS)

    1974-01-01

    An evaluation of a charge-coupled device (CCD) image sensors for use in spacecraft-borne imaging systems was conducted. The study resulted in design recommendations for two sensors, an approximately 500 times 500 element imaging device and a 1 times 190 element linear imaging device with a 190 times 121 buffer store. Emphasis was placed on the higher resolution, area-imaging sensor. The objectives of the proposed sensors are listed, results of the experiments are analyzed, and estimates of the device performance are presented. A summary of the major technical recommendations is included.

  11. Coordinated Oxygen Isotopic and Petrologic Studies of CAIS Record Varying Composition of Protosolar

    NASA Technical Reports Server (NTRS)

    Simon, Justin I.; Matzel, J. E. P.; Simon, S. B.; Weber, P. K.; Grossman, L.; Ross, D. K.; Hutcheon, I. D.

    2012-01-01

    Ca-, Al-rich inclusions (CAIs) record the O-isotope composition of Solar nebular gas from which they grew [1]. High spatial resolution O-isotope measurements afforded by ion microprobe analysis across the rims and margin of CAIs reveal systematic variations in (Delta)O-17 and suggest formation from a diversity of nebular environments [2-4]. This heterogeneity has been explained by isotopic mixing between the O-16-rich Solar reservoir [6] and a second O-16-poor reservoir (probably nebular gas) with a "planetary-like" isotopic composition [e.g., 1, 6-7], but the mechanism and location(s) where these events occur within the protoplanetary disk remain uncertain. The orientation of large and systematic variations in (Delta)O-17 reported by [3] for a compact Type A CAI from the Efremovka reduced CV3 chondrite differs dramatically from reports by [4] of a similar CAI, A37 from the Allende oxidized CV3 chondrite. Both studies conclude that CAIs were exposed to distinct, nebular O-isotope reservoirs, implying the transfer of CAIs among different settings within the protoplanetary disk [4]. To test this hypothesis further and the extent of intra-CAI O-isotopic variation, a pristine compact Type A CAI, Ef-1 from Efremovka, and a Type B2 CAI, TS4 from Allende were studied. Our new results are equally intriguing because, collectively, O-isotopic zoning patterns in the CAIs indicate a progressive and cyclic record. The results imply that CAIs were commonly exposed to multiple environments of distinct gas during their formation. Numerical models help constrain conditions and duration of these events.

  12. Importance of the Lu-Hf isotopic system in studies of planetary chronology and chemical evolution

    NASA Technical Reports Server (NTRS)

    Patchett, P. J.

    1983-01-01

    The Lu-176-Hf-176 isotope method and its applications in earth sciences are discussed with regard to planetary-evolution studies. From new data on basalts from oceanic islands, Hf-176/Hf-177 and Nd-143/Nd-144 are found to display a single linear isotopic variation in the suboceanic mantle, whereas considerable divergences occur in Hf-176/Hf-177-Sr-87/Sr-86 and Nd-143/Nd-144-Sr87/Sr-86 diagrams. With the acquisition of further Hf-Sr-Nd isotopic data, these discordant Sr-87/Sr-86 relationships may allow a distinction between processes such as mantle metasomatism, influence of sea-water altered material in the magma source, or recycling of sediments into the mantle. The best quality Hf isotope data are obtained from granitoid or zircons, and are most suitable for studying ancient terrestrial Hf isotopic variations. Lu-Hf is shown to be a viable method for dating ancient terrestrial and extraterrestrial samples, but is unlikely to find wide application in pure chronological studies because it offers little advantage over existing methods.

  13. Nuclear shape coexistence in Po isotopes: An interacting boson model study

    NASA Astrophysics Data System (ADS)

    García-Ramos, J. E.; Heyde, K.

    2015-09-01

    Background: The lead region, Po, Pb, Hg, and Pt, shows up the presence of coexisting structures having different deformation and corresponding to different particle-hole configurations in the shell-model language. Purpose: We intend to study the importance of configuration mixing in the understanding of the nuclear structure of even-even Po isotopes, where the shape coexistence phenomena are not clear enough. Method: We study in detail a long chain of polonium isotopes, Po-208190, using the interacting boson model with configuration mixing (IBM-CM). We fix the parameters of the Hamiltonians through a least-squares fit to the known energies and absolute B (E 2 ) transition rates of states up to 3 MeV. Results: We obtained the IBM-CM Hamiltonians and we calculate excitation energies, B (E 2 ) 's, electric quadrupole moments, nuclear radii and isotopic shifts, quadrupole shape invariants, wave functions, and deformations. Conclusions: We obtain a good agreement with the experimental data for all the studied observables and we conclude that shape coexistence phenomenon is hidden in Po isotopes, very much as in the case of the Pt isotopes.

  14. Image dissector camera system study

    NASA Technical Reports Server (NTRS)

    Howell, L.

    1984-01-01

    Various aspects of a rendezvous and docking system using an image dissector detector as compared to a GaAs detector were discussed. Investigation into a gimbled scanning system is also covered and the measured video response curves from the image dissector camera are presented. Rendezvous will occur at ranges greater than 100 meters. The maximum range considered was 1000 meters. During docking, the range, range-rate, angle, and angle-rate to each reflector on the satellite must be measured. Docking range will be from 3 to 100 meters. The system consists of a CW laser diode transmitter and an image dissector receiver. The transmitter beam is amplitude modulated with three sine wave tones for ranging. The beam is coaxially combined with the receiver beam. Mechanical deflection of the transmitter beam, + or - 10 degrees in both X and Y, can be accomplished before or after it is combined with the receiver beam. The receiver will have a field-of-view (FOV) of 20 degrees and an instantaneous field-of-view (IFOV) of two milliradians (mrad) and will be electronically scanned in the image dissector. The increase in performance obtained from the GaAs photocathode is not needed to meet the present performance requirements.

  15. Methyl-specific isotopic labeling: a molecular tool box for solution NMR studies of large proteins.

    PubMed

    Kerfah, Rime; Plevin, Michael J; Sounier, Remy; Gans, Pierre; Boisbouvier, Jerome

    2015-06-01

    Nuclear magnetic resonance (NMR) spectroscopy is a uniquely powerful tool for studying the structure, dynamics and interactions of biomolecules at atomic resolution. In the past 15 years, the development of new isotopic labeling strategies has opened the possibility of exploiting NMR spectroscopy in the study of supra-molecular complexes with molecular weights of up to 1MDa. At the core of these isotopic labeling developments is the specific introduction of [(1)H,(13)C]-labeled methyl probes into perdeuterated proteins. Here, we describe the evolution of these approaches and discuss their impact on structural and biological studies. The relevant protocols are succinctly reviewed for single and combinatorial isotopic-labeling of methyl-containing residues, and examples of applications on challenging biological systems, including high molecular weight and membrane proteins, are presented. PMID:25881211

  16. Stable isotope-labeling studies in metabolomics: new insights into structure and dynamics of metabolic networks

    PubMed Central

    Chokkathukalam, Achuthanunni; Kim, Dong-Hyun; Barrett, Michael P; Breitling, Rainer; Creek, Darren J

    2014-01-01

    The rapid emergence of metabolomics has enabled system-wide measurements of metabolites in various organisms. However, advances in the mechanistic understanding of metabolic networks remain limited, as most metabolomics studies cannot routinely provide accurate metabolite identification, absolute quantification and flux measurement. Stable isotope labeling offers opportunities to overcome these limitations. Here we describe some current approaches to stable isotope-labeled metabolomics and provide examples of the significant impact that these studies have had on our understanding of cellular metabolism. Furthermore, we discuss recently developed software solutions for the analysis of stable isotope-labeled metabolomics data and propose the bioinformatics solutions that will pave the way for the broader application and optimal interpretation of system-scale labeling studies in metabolomics. PMID:24568354

  17. Tracing paleofluid circulations using iron isotopes: A study of hematite and goethite concretions from the Navajo Sandstone (Utah, USA)

    NASA Astrophysics Data System (ADS)

    Busigny, Vincent; Dauphas, Nicolas

    2007-02-01

    Iron concentrations and isotopic compositions were measured in spherical hematite and goethite concretions, together with associated red (Fe-oxide coated) and white (bleached) sandstones from the Jurassic Navajo formation, Utah (USA). Earlier studies showed that, in the Navajo Sandstone, reducing fluids (presumably rich in hydrocarbons) mobilized Fe present as Fe-oxide coatings on detrital quartz grains. Dissolved Fe then precipitated as spherical concretions by interaction with oxidizing groundwater. Despite being depleted in Fe by ˜ 50%, the bleached sandstones have Fe isotopic compositions similar to adjacent red sandstones (˜ 0‰/amu relative to IRMM-014). This shows that dissolution of Fe-oxide did not produce significant isotope fractionation, in agreement with previous experimental studies of abiotic Fe-oxide dissolution. In contrast, the concretions are depleted in the heavy isotopes of iron by - 0.07 to - 0.68‰/amu. This is opposite to the expected fractionation for partial Fe oxidation, which tends to enrich the precipitate in the heavy isotopes. Several scenarios are considered for explaining the measured Fe isotopic compositions. Although diffusion might be an important process in controlling the growth of spherical concretions, the associated isotopic fractionation is negligible compared to the observed variations. Kinetic isotope fractionation during precipitation can be ruled out as well because no isotopic zonation is seen within indurated concretions and Fe isotope evidence supports the occurrence of dissolution-reprecipitation reactions consistent with equilibrium growth conditions. The Fe isotopic compositions of the concretions are best explained by evolution of the fluid composition through precipitation and/or adsorption of isotopically heavy Fe during fluid flow through the sandstone. This scenario is supported by a regional trend in the isotopic composition of Fe, showing that this element was transported in fluids over several

  18. Small-scale studies of roasted ore waste reveal extreme ranges of stable mercury isotope signatures

    NASA Astrophysics Data System (ADS)

    Smith, Robin S.; Wiederhold, Jan G.; Jew, Adam D.; Brown, Gordon E.; Bourdon, Bernard; Kretzschmar, Ruben

    2014-07-01

    Active and closed Hg mines are significant sources of Hg contamination to the environment, mainly due to large volumes of mine waste material disposed of on-site. The application of Hg isotopes as source tracer from such contaminated sites requires knowledge of the Hg isotope signatures of different materials potentially released to the environment. Previous work has shown that calcine, the waste residue of the on-site ore roasting process, can exhibit distinct Hg isotope signatures compared with the primary ore. Here, we report results from a detailed small-scale study of Hg isotope variations in calcine collected from the closed New Idria Hg mine, San Benito County, CA, USA. The calcine samples exhibited different internal layering features which were investigated using optical microscopy, micro X-ray fluorescence, micro X-ray absorption spectroscopy (μ-XAS), and stable Hg isotope analysis. Significant Fe, S, and Hg concentration gradients were found across the different internal layers. Isotopic analyses revealed an extreme variation with pronounced isotopic gradients across the internal layered features. Overall, δ202Hg (±0.10‰, 2 SD) describing mass-dependent fractionation (MDF) ranged from -5.96 to 14.49‰, which is by far the largest range of δ202Hg values reported for any environmental sample. In addition, Δ199Hg (±0.06‰, 2 SD) describing mass-independent fractionation (MIF) ranged from -0.17 to 0.21‰. The μ-XAS analyses suggested that cinnabar and metacinnabar are the dominant Hg-bearing phases in the calcine. Our results demonstrate that the incomplete roasting of HgS ores in Hg mines can cause extreme mass-dependent Hg isotope fractionations at the scale of individual calcine pieces with enrichments in both light and heavy Hg isotopes relative to the primary ore signatures. This finding has important implications for the application of Hg isotopes as potential source tracers for Hg released to the environment from closed Hg mines and

  19. Can stable isotopes ride out the storms? The role of convection for water isotopes in models, records, and paleoaltimetry studies in the central Andes

    NASA Astrophysics Data System (ADS)

    Rohrmann, Alexander; Strecker, Manfred R.; Bookhagen, Bodo; Mulch, Andreas; Sachse, Dirk; Pingel, Heiko; Alonso, Ricardo N.; Schilgen, Taylor F.; Montero, Carolina

    2015-04-01

    Globally, changes in stable isotope ratios of oxygen and hydrogen (δ18O and δD) in the meteoric water cycle result from distillation and evaporation processes. Isotope fractionation occurs when air masses rise in elevation, cool, and reduce their water-vapor holding capacity with decreasing temperature. As such, d18O and dD values from a variety of sedimentary archives are often used to reconstruct changes in continental paleohydrology as well as paleoaltimetry of mountain ranges. Based on 234 stream-water samples, we demonstrate that areas experiencing deep convective storms in the eastern south-central Andes (22 - 28° S) do not show the commonly observed relationship between δ18O and δD with elevation. These convective storms arise from intermontane basins, where diurnal heating forces warm air masses upward, resulting in cloudbursts and raindrop evaporation. Especially at the boundary between the tropical and extra-tropical atmospheric circulation regimes where deep-convective storms are very common (~ 26° to 32° N and S), the impact of such storms may yield non-systematic stable isotope-elevation relationships as convection dominates over adiabatic lifting of air masses. Because convective storms can reduce or mask the depletion of heavy isotopes in precipitation as a function of elevation, linking modern or past topography to patterns of stable isotope proxy records can be compromised in mountainous regions, and atmospheric circulation models attempting to predict stable isotope patterns must have sufficiently high spatial resolution to capture the fractionation dynamics of convective cells. Rohrmann, A. et al. Can stable isotopes ride out the storms? The role of convection for water isotopes in models, records, and paleoaltimetry studies in the central Andes. Earth Planet. Sci. Lett. 407, 187-195 (2014).

  20. Mechanistic studies on the bovine liver mitochondrial dihydroorotate dehydrogenase using kinetic deuterium isotope effects

    SciTech Connect

    Hines, V.; Johnston, M. )

    1989-02-07

    Dihydroorotates deuteriated at both C{sub 5} and C{sub 6} have been prepared and used to probe the mechanism of the bovine liver mitochondrial dihydroorotate dehydrogenase. Primary deuterium isotope effects on k{sub cat} are observed with both (6RS)-(5(S)-{sup 2}H)- and (6RS)-(6-{sup 2}H)dihydroorotates ({bold 3} and {bold 6}, respectively); these effects are maximal at low pH. At pH 6.6, {sup D}V = 3.4 for the C{sub 5}-deuteriated dihydroorotate ({bold 3}), and {sup D}V = 2.3 for the C{sub 6}-deuteriated compound ({bold 6}). The isotope effects approach unity at pH 8.8. Analysis of the pH dependence of the isotope effects on k{sub cat} reveals a shift in the rate-determining step of the enzyme mechanism as a function of pH. Dihydroorotate oxidation appears to require general base catalysis; this step is completely rate-determining at low pH and isotopically sensitive. Reduction of the cosubstrate, coenzyme Q{sub 6}, is rate-limiting at high pH and is isotopically insensitive; this step appears to require general acid catalysis. The results of double isotope substitution studies and analysis for substrate isotope exchange with solvent point toward a concerted mechanism for oxidation of dihydroorotate. This finding serves to distinguish further the mammalian dehydrogenase from its parasitic cognate, which catalyzes a stepwise oxidation reaction.

  1. Isotopic and geochemical studies of fluid-rock interactions and the chemical evolution of the oceans

    SciTech Connect

    Derry, L.A.

    1989-01-01

    The isotopic compositions of Sr and Nd, and the abundances of rare earth elements (REE) are used to study various types of fluid-rock interactions in the Earth's crust. The isotopic compositions of Sr and Nd and REE patterns in marine chemical sediments of Precambrian age are used to estimate the relative importance of continental weathering versus submarine hydrothermal activity in determining the chemical mass balance of the Precambrian oceans. Major and trace element abundances and Sr and Nd isotopes are used to quantify the degree of interaction of a carbonatite fluid-magmatic system with felsic crust, and to constrain the isotopic characteristics of the mantle source region. The isotopic composition of Sr is reported from a well characterized sequence of Upper Proterozoic carbonates from Svalbard and east Greenland. A simple model of carbonate recycling and isotopic mass balance calculations illustrate that sedimentary recycling can have a strong influence on Sr in the oceans. REE patterns from Precambrian banded iron formations (BIFs) are very similar to modern metalliferous sediments, and imply that the overall REE pattern of Precambrian seawater was similar to today. The mantle-like {var epsilon}{sub Nd} values and positive Eu anomalies imply that the source of the REE in the BIFs was submarine hydrothermal activity. The implications of a large hydrothermal flux of reduced Fe on the redox controls of the Precambrian atmosphere are explored, and a testable hypothesis is developed. The mass balance of Eu in the oceans is affected by preferential scavenging at hydrothermal sites. Data from the Cherry Hill, CA mineralizing system imply a complex plumbing system and a long residence time for the water. Isotopic data from the Fen alkaline complex, Norway, define mixing trends between mantle derived magmas or magmatic fluids and old crust.

  2. Strontium Isotope Study of Coal Untilization By-products Interacting with Environmental Waters

    SciTech Connect

    Spivak-Birndorf, Lev J; Stewart, Brian W; Capo, Rosemary C; Chapman, Elizabeth C; Schroeder, Karl T; Brubaker, Tonya M

    2011-09-01

    Sequential leaching experiments on coal utilization by-products (CUB) were coupled with chemical and strontium (Sr) isotopic analyses to better understand the influence of coal type and combustion processes on CUB properties and the release of elements during interaction with environmental waters during disposal. Class C fly ash tended to release the highest quantity of minor and trace elements—including alkaline earth elements, sodium, chromium, copper, manganese, lead, titanium, and zinc—during sequential extraction, with bottom ash yielding the lowest. Strontium isotope ratios ({sup 87}Sr/{sup 86}Sr) in bulk-CUB samples (total dissolution of CUB) are generally higher in class F ash than in class C ash. Bulk-CUB ratios appear to be controlled by the geologic source of the mineral matter in the feed coal, and by Sr added during desulfurization treatments. Leachates of the CUB generally have Sr isotope ratios that are different than the bulk value, demonstrating that Sr was not isotopically homogenized during combustion. Variations in the Sr isotopic composition of CUB leachates were correlated with mobility of several major and trace elements; the data suggest that arsenic and lead are held in phases that contain the more radiogenic (high-{sup 87}Sr/{sup 86}Sr) component. A changing Sr isotope ratio of CUB-interacting waters in a disposal environment could forecast the release of certain strongly bound elements of environmental concern. This study lays the groundwork for the application of Sr isotopes as an environmental tracer for CUB–water interaction.

  3. Isotopomer Spectral Analysis: Utilizing Nonlinear Models in Isotopic Flux Studies.

    PubMed

    Kelleher, Joanne K; Nickol, Gary B

    2015-01-01

    We present the principles underlying the isotopomer spectral analysis (ISA) method for evaluating biosynthesis using stable isotopes. ISA addresses a classic conundrum encountered in the use of radioisotopes to estimate biosynthesis rates whereby the information available is insufficient to estimate biosynthesis. ISA overcomes this difficulty capitalizing on the additional information available from the mass isotopomer labeling profile of a polymer. ISA utilizes nonlinear regression to estimate the two unknown parameters of the model. A key parameter estimated by ISA represents the fractional contribution of the tracer to the precursor pool for the biosynthesis, D. By estimating D in cells synthesizing lipids, ISA quantifies the relative importance of two distinct pathways for flux of glutamine to lipid, reductive carboxylation, and glutaminolysis. ISA can also evaluate the competition between different metabolites, such as glucose and acetoacetate, as precursors for lipogenesis and thereby reveal regulatory properties of the biosynthesis pathway. The model is flexible and may be expanded to quantify sterol biosynthesis allowing tracer to enter the pathway at three different positions, acetyl CoA, acetoacetyl CoA, and mevalonate. The nonlinear properties of ISA provide a method of testing for the presence of gradients of precursor enrichment illustrated by in vivo sterol synthesis. A second ISA parameter provides the fraction of the polymer that is newly synthesized over the time course of the experiment. In summary, ISA is a flexible framework for developing models of polymerization biosynthesis providing insight into pools and pathway that are not easily quantified by other techniques. PMID:26358909

  4. Stable isotope studies of nicotine kinetics and bioavailability

    SciTech Connect

    Benowitz, N.L.; Jacob, P. 3d.; Denaro, C.; Jenkins, R. )

    1991-03-01

    The stable isotope-labeled compound 3',3'-dideuteronicotine was used to investigate the disposition kinetics of nicotine in smokers, the systemic absorption of nicotine from cigarette smoke, and the bioavailability of nicotine ingested as oral capsules. Blood levels of labeled nicotine could be measured for 9 hours after a 30-minute intravenous infusion. Analysis of disposition kinetics in 10 healthy men revealed a multiexponential decline after the end of an infusion, with an elimination half-life averaging 203 minutes. This half-life was longer than that previously reported, indicating the presence of a shallow elimination phase. Plasma clearance averaged 14.6 ml/min/kg. The average intake of nicotine per cigarette was 2.29 mg. A cigarette smoke-monitoring system that directly measured particulate matter in smoke was evaluated in these subjects. Total particulate matter, number of puffs on the cigarette, total puff volume, and time of puffing correlated with the intake of nicotine from smoking. The oral bioavailability of nicotine averaged 44%. This bioavailability is higher than expected based on the systemic clearance of nicotine and suggests that there may be significant extrahepatic metabolism of nicotine.

  5. Isotope geochemistry and the study of habitability and life on other planets (Invited)

    NASA Astrophysics Data System (ADS)

    Eiler, J.

    2010-12-01

    The question of life on other planets might be solved by a remarkable discovery — a martian coquina, or perhaps a tentacle print on a distant landscape. But, until this happens, evidence for life and, more generally, habitability will use indirect geochemical arguments such as isotope thermometers and biomarkers (molecular, isotopic, and elemental fingerprints of biology)., Understanding this evidence will also demand a quantitative planetary history based on isotopic dating. Laboratory study of samples derived from Mars or other solar-system bodies will be a focus of geochemical investigations aimed at such assessments. Examples of how this will be done can be found in studies of the Precambrian geologic record and Martian meteorites. Debates regarding environmental conditions and biogenicity of minerals and organic matter are common in the study of such materials. These controversies derive from simple but refractory problems with the geochemical principles we employ: Indicators of metabolism can be mimicked by abiologic reactions; paleo-environmental proxies generally require an understanding of related geochemical cycles (e.g., the isotopic budget of water); and, though many organic molecules are unambiguous biomarkers, diagenesis can transform them into compounds that resemble products of abiogenic organic synthesis. If planetary sample return is to produce definitive geochemical constraints on habitability and biology, we will require either luck or a new class of geochemical tools that explicitly address these problems. The spatial distribution of rare isotopes within molecular structures, including ‘clumping’ and position-specific isotope effects, offer new geochemical tools that could provide such solutions. For example, even a simple molecule like acetic acid (C2H4O2) has more than 200 distinct isotopic configurations when spatial distribution of isotopes is considered, and the proportions of these could reflect formation temperature, the nature of

  6. Isotope tracer studies of diffusion in silicates and of geological transport processes using actinide elements

    SciTech Connect

    Wasserburg, G.J.

    1992-01-01

    The following are reported: high abundance sensitivity mass spectrometer for U-Th studies; [sup 238]U-[sup 230]Th disequilibrium in recent lavas from Iceland; water-rock interaction from U-Th studies; resonance ionization mass spectrometry of Os and Ti isotopes; and self-diffusion of Mg.

  7. Molybdenum Isotopic Composition of the Archean Mantle As Inferred from Studies of Komatiites

    NASA Astrophysics Data System (ADS)

    Greber, N. D.; Puchtel, I. S.; Nagler, T. F.; Mezger, K.

    2014-12-01

    Molybdenum isotopic composition has been shown to be a powerful tool in studies of planetary processes, e.g. estimating core formation temperatures [1,2]. However, Mo isotope compositions of terrestrial reservoirs are not well constrained. In order to better constrain the Mo isotopic composition of the early Earth's mantle, komatiites from four locations were analyzed for their Mo concentrations and isotopic compositions. Komatiites are particularly appropriate for this type of study because they formed by high degrees of partial melting of the mantle leading to a complete base metal sulfide removal from the residual mantle and the production of sulfur-undersaturated melts and thus a quantitative removal of Mo from the source into the melt. All samples, except for two strongly altered specimens specifically chosen to study the effects of secondary alteration, are very fresh having preserved most of their primary mineralogy. The Mo concentrations in komatiites range from 10 to 120 ng/g. Fresh komatiites have lighter δ98Mo (NIST SRM 3134 = 0.25‰, [3]) than altered samples. The estimated primary Mo isotope compositions of the studied komatiite melts range from 0.02 ± 0.16‰ to 0.19 ± 0.14‰ and are therefore indistinguishable within analytical uncertainty (2SD) from published values for chondritic meteorites (0.09 ± 0.04 ‰; 2SD; [2]) and lighter than the proposed average for Earth's continental crust (0.3 to 0.4‰ [4]). All data combined, although overlapping in errors, show a consistent trend of lighter δ98Mo and lower Mo concentrations in more melt-depleted mantle sources, indicating incompatible behaviour of Mo and preferential mobilization of heavy Mo isotopes during mantle melting. [1] Hin et al. (2013) EPSL, 379 [2] Burkhardt et al. (2014) EPSL, 391 [3] Nägler, et al. (2014) GGR, 38. [4] Voegelin et al. (2014) Lithos, 190-191.

  8. Design study of an ultra-compact superconducting cyclotron for isotope production

    NASA Astrophysics Data System (ADS)

    Smirnov, V.; Vorozhtsov, S.; Vincent, J.

    2014-11-01

    A 12.5 MeV, 25 μA, proton compact superconducting cyclotron for medical isotope production has been designed and is currently in fabrication. The machine is initially aimed at producing 13N ammonia for Positron Emission Tomography (PET) cardiology applications. With an ultra-compact size and cost-effective price point, this system will offer clinicians unprecedented access to the preferred radiopharmaceutical isotope for cardiac PET imaging. A systems approach that carefully balanced the subsystem requirements coupled to precise beam dynamics calculations was followed. The system is designed to irradiate a liquid target internal to the cyclotron and to minimize the need for radiation shielding. The main parameters of the cyclotron, its design, and principal steps of the development work are presented here.

  9. Isotopic Studies of Contaminant Transport at the Hanford Site,WA

    SciTech Connect

    Christensen, J.N.; Conrad, M.E.; DePaolo, D.J.; Dresel, P.E.

    2006-11-01

    Processes of fluid flow and chemical transport through thevadose zone can be characterized through the isotopic systematics ofnatural soils, minerals, pore fluids and groundwater. In thiscontribution, we first review our research using measured isotopicvariations, due both to natural and site related processes, of theelements H, O, N, Sr and U, to study the interconnection between vadosezone and groundwater contamination at the Hanford Site in south-centralWashington. We follow this brief review with a presentation of new datapertaining to vadose zone and groundwater contamination in the WMAT-TX-TY vicinity. Uranium (U) isotopic data for the C3832 core (WMA TX)indicates the involvement of processed natural U fuel, and links theobserved U contamination to the nearby single shelled tank TX-104. Thedata also precludes contamination from an early 1970 s TX-107 leak. Inthe case of the C4104 core (WMA T), the U isotopic data indicates amixture of processed natural and enriched U fuels consistent with themajor leak from T-106 in 1973. Uranium and Strontium isotopic data forthe cores also provides direct evidence for chemical interaction betweenhigh-pH waste fluid and sediment. Isotopic data for groundwater nitratecontamination in the vicinity of WMA-T strongly suggests high-level tankwaste (most likely from T-106) as the source of very high 99Tcconcentrations recently observed at the NE corner of WMAT.

  10. Laboratory study of nitrate photolysis in Antarctic snow. II. Isotopic effects and wavelength dependence

    NASA Astrophysics Data System (ADS)

    Berhanu, Tesfaye A.; Meusinger, Carl; Erbland, Joseph; Jost, Rémy; Bhattacharya, S. K.; Johnson, Matthew S.; Savarino, Joël

    2014-06-01

    Atmospheric nitrate is preserved in Antarctic snow firn and ice. However, at low snow accumulation sites, post-depositional processes induced by sunlight obscure its interpretation. The goal of these studies (see also Paper I by Meusinger et al. ["Laboratory study of nitrate photolysis in Antarctic snow. I. Observed quantum yield, domain of photolysis, and secondary chemistry," J. Chem. Phys. 140, 244305 (2014)]) is to characterize nitrate photochemistry and improve the interpretation of the nitrate ice core record. Naturally occurring stable isotopes in nitrate (15N, 17O, and 18O) provide additional information concerning post-depositional processes. Here, we present results from studies of the wavelength-dependent isotope effects from photolysis of nitrate in a matrix of natural snow. Snow from Dome C, Antarctica was irradiated in selected wavelength regions using a Xe UV lamp and filters. The irradiated snow was sampled and analyzed for nitrate concentration and isotopic composition (δ15N, δ18O, and Δ17O). From these measurements an average photolytic isotopic fractionation of 15ɛ = (-15 ± 1.2)‰ was found for broadband Xe lamp photolysis. These results are due in part to excitation of the intense absorption band of nitrate around 200 nm in addition to the weaker band centered at 305 nm followed by photodissociation. An experiment with a filter blocking wavelengths shorter than 320 nm, approximating the actinic flux spectrum at Dome C, yielded a photolytic isotopic fractionation of 15ɛ = (-47.9 ± 6.8)‰, in good agreement with fractionations determined by previous studies for the East Antarctic Plateau which range from -40 to -74.3‰. We describe a new semi-empirical zero point energy shift model used to derive the absorption cross sections of 14NO3- and 15NO3- in snow at a chosen temperature. The nitrogen isotopic fractionations obtained by applying this model under the experimental temperature as well as considering the shift in width and center well

  11. Laboratory study of nitrate photolysis in Antarctic snow. II. Isotopic effects and wavelength dependence.

    PubMed

    Berhanu, Tesfaye A; Meusinger, Carl; Erbland, Joseph; Jost, Rémy; Bhattacharya, S K; Johnson, Matthew S; Savarino, Joël

    2014-06-28

    Atmospheric nitrate is preserved in Antarctic snow firn and ice. However, at low snow accumulation sites, post-depositional processes induced by sunlight obscure its interpretation. The goal of these studies (see also Paper I by Meusinger et al. ["Laboratory study of nitrate photolysis in Antarctic snow. I. Observed quantum yield, domain of photolysis, and secondary chemistry," J. Chem. Phys. 140, 244305 (2014)]) is to characterize nitrate photochemistry and improve the interpretation of the nitrate ice core record. Naturally occurring stable isotopes in nitrate ((15)N, (17)O, and (18)O) provide additional information concerning post-depositional processes. Here, we present results from studies of the wavelength-dependent isotope effects from photolysis of nitrate in a matrix of natural snow. Snow from Dome C, Antarctica was irradiated in selected wavelength regions using a Xe UV lamp and filters. The irradiated snow was sampled and analyzed for nitrate concentration and isotopic composition (δ(15)N, δ(18)O, and Δ(17)O). From these measurements an average photolytic isotopic fractionation of (15)ɛ = (-15 ± 1.2)‰ was found for broadband Xe lamp photolysis. These results are due in part to excitation of the intense absorption band of nitrate around 200 nm in addition to the weaker band centered at 305 nm followed by photodissociation. An experiment with a filter blocking wavelengths shorter than 320 nm, approximating the actinic flux spectrum at Dome C, yielded a photolytic isotopic fractionation of (15)ɛ = (-47.9 ± 6.8)‰, in good agreement with fractionations determined by previous studies for the East Antarctic Plateau which range from -40 to -74.3‰. We describe a new semi-empirical zero point energy shift model used to derive the absorption cross sections of (14)NO3 (-) and (15)NO3 (-) in snow at a chosen temperature. The nitrogen isotopic fractionations obtained by applying this model under the experimental temperature as well as considering the

  12. Laboratory study of nitrate photolysis in Antarctic snow. II. Isotopic effects and wavelength dependence

    SciTech Connect

    Berhanu, Tesfaye A.; Erbland, Joseph; Savarino, Joël; Meusinger, Carl; Johnson, Matthew S.; Jost, Rémy; Bhattacharya, S. K.

    2014-06-28

    Atmospheric nitrate is preserved in Antarctic snow firn and ice. However, at low snow accumulation sites, post-depositional processes induced by sunlight obscure its interpretation. The goal of these studies (see also Paper I by Meusinger et al. [“Laboratory study of nitrate photolysis in Antarctic snow. I. Observed quantum yield, domain of photolysis, and secondary chemistry,” J. Chem. Phys. 140, 244305 (2014)]) is to characterize nitrate photochemistry and improve the interpretation of the nitrate ice core record. Naturally occurring stable isotopes in nitrate ({sup 15}N, {sup 17}O, and {sup 18}O) provide additional information concerning post-depositional processes. Here, we present results from studies of the wavelength-dependent isotope effects from photolysis of nitrate in a matrix of natural snow. Snow from Dome C, Antarctica was irradiated in selected wavelength regions using a Xe UV lamp and filters. The irradiated snow was sampled and analyzed for nitrate concentration and isotopic composition (δ{sup 15}N, δ{sup 18}O, and Δ{sup 17}O). From these measurements an average photolytic isotopic fractionation of {sup 15}ε = (−15 ± 1.2)‰ was found for broadband Xe lamp photolysis. These results are due in part to excitation of the intense absorption band of nitrate around 200 nm in addition to the weaker band centered at 305 nm followed by photodissociation. An experiment with a filter blocking wavelengths shorter than 320 nm, approximating the actinic flux spectrum at Dome C, yielded a photolytic isotopic fractionation of {sup 15}ε = (−47.9 ± 6.8)‰, in good agreement with fractionations determined by previous studies for the East Antarctic Plateau which range from −40 to −74.3‰. We describe a new semi-empirical zero point energy shift model used to derive the absorption cross sections of {sup 14}NO{sub 3}{sup −} and {sup 15}NO{sub 3}{sup −} in snow at a chosen temperature. The nitrogen isotopic fractionations obtained by applying

  13. Isotopic Studies of O-O Bond Formation During Water Oxidation (SISGR)

    SciTech Connect

    Roth, Justine P.

    2015-03-03

    Isotopic Studies of O-O Bond Formation During Water Oxidation (SISGR) Research during the project period focused primarily on mechanisms of water oxidation by structurally defined transition metal complexes. Competitive oxygen isotope fractionation of water, mediated by oxidized precursors or reduced catalysts together with ceric, Ce(IV), ammonium nitrate in aqueous media, afforded oxygen-18 kinetic isotope effects (O-18 KIEs). Measurement, calculation, and interpretation of O-18 KIEs, described in the accompanying report has important ramifications for the production of electricity and solar hydrogen (as fuel). The catalysis division of BES has acknowledged that understanding mechanisms of transition metal catalyzed water oxidation has major ramifications, potentially leading to transformation of the global economy and natural environment in years to come. Yet, because of program restructuring and decreased availability of funds, it was recommended that the Solar Photochemistry sub-division of BES would be a more appropriate parent program for support of continued research.

  14. Study of 242‑248Cm isotopes in the projected shell model framework

    NASA Astrophysics Data System (ADS)

    Sadiq, Saiqa; Devi, Rani; Khosa, S. K.

    2016-04-01

    The projected shell model framework is employed to study the band spectra in 242‑248Cm isotopes. The present calculations reproduce the available experimental data on the yrast bands. Besides this, B(E2) transition probabilities of even-even Cm isotopes have also been calculated. The low spin states of yrast band are seen to arise purely from zero-quasi-particle (o-qp) intrinsic states whereas the high spin states have multi-quasi-particle structure. For the odd-neutron (odd-N) isotopes, the calculated results qualitatively reproduce the available data on ground and lowest excited state bands for 243,245Cm. However, for 247Cm the negative-parity ground state band is in reasonable agreement with the experimental data.

  15. Isotopic studies of the late Archean plutonic rocks of the Wind River Range, Wyoming.

    USGS Publications Warehouse

    Stuckless, J.S.; Hedge, C.E.; Worl, R.G.; Simmons, K.R.; Nkomo, I.T.; Wenner, D.B.

    1985-01-01

    Two late Archaean intrusive events were documented in the Wind River Range by isotopic studies of the Rb-Sr and U-Th-Pb systems in whole-rock samples and the U-Pb systematics for zircon. An age of approx 2630(20) m.y. for the Louis Lake batholith and apparent ages of 2504(40) to 2575(50) m.y. for the Bear Ears pluton were obtained. Post-magmatic hydrothermal events approximately Tertiary in age, lowered delta 18O values and disturbed parent-daughter relationships in most of the isotopic systems investigated. The two intrusive units apparently were derived from different protoliths. Initial isotopic ratios and petrochemistry for the Louis Lake batholith are consistent with an early Archaean trondhjemitic to tonalitic source. The protolith for the Bear Ears pluton must have been subjected to high-grade metamorphism that caused loss of Rb and U prior to magma generation. -L.C.H.

  16. Feasibility study of plutonium isotopic analysis of resin beads by nondestructive gamma-ray spectroscopy

    SciTech Connect

    Li, T.K.

    1985-01-01

    We have initiated a feasibility study on the use of nondestructive low-energy gamma-ray spectroscopy for plutonium isotopic analysis on resin beads. Seven resin bead samples were measured, with each sample containing an average of 9 ..mu..g of plutonium; the isotopic compositions of the samples varied over a wide range. The gamma-ray spectroscopy results, obtained from 4-h counting-time measurements, were compared with mass spectrometry results. The average ratios of gamma-ray spectroscopy to mass spectrometry were 1.014 +- 0.025 for /sup 238/Pu//sup 239/Pu, 0.996 +- 0.018 for /sup 240/Pu//sup 239/Pu, and 0.980 +- 0.038 for /sup 241/Pu//sup 239/Pu. The rapid, automated, and accurate nondestructive isotopic analysis of resin beads may be very useful to process technicians and International Atomic Energy Agency inspectors. 3 refs., 1 fig., 3 tabs.

  17. Syntrophic interactions and mechanisms underpinning anaerobic methane oxidation: targeted metaproteogenomics, single-cell protein detection and quantitative isotope imaging of microbial consortia

    SciTech Connect

    Orphan, Victoria Jeanne

    2014-11-26

    Syntrophy and mutualism play a central role in carbon and nutrient cycling by microorganisms. Yet, our ability to effectively study symbionts in culture has been hindered by the inherent interdependence of syntrophic associations, their dynamic behavior, and their frequent existence at thermodynamic limits. Now solutions to these challenges are emerging in the form of new methodologies. Developing strategies that establish links between the identity of microorganisms and their metabolic potential, as well as techniques that can probe metabolic networks on a scale that captures individual molecule exchange and processing, is at the forefront of microbial ecology. Understanding the interactions between microorganisms on this level, at a resolution previously intractable, will lead to our greater understanding of carbon turnover and microbial community resilience to environmental perturbations. In this project, we studied an enigmatic syntrophic association between uncultured methane-oxidizing archaea and sulfate-reducing bacteria. This environmental archaeal-bacterial partnership represents a globally important sink for methane in anoxic environments. The specific goals of this project were organized into 3 major tasks designed to address questions relating to the ecophysiology of these syntrophic organisms under changing environmental conditions (e.g. different electron acceptors and nutrients), primarily through the development of microanalytical imaging methods which enable the visualization of the spatial distribution of the partners within aggregates, consumption and exchange of isotopically labeled substrates, and expression of targeted proteins identified via metaproteomics. The advanced tool set developed here to collect, correlate, and analyze these high resolution image and isotope-based datasets from methane-oxidizing consortia has the potential to be widely applicable for studying and modeling patterns of activity and interactions across a broad range of

  18. Study of shape transitions in N{approx}90 isotopes with beyond mean field calculations

    SciTech Connect

    Rodriguez, Tomas R.; Egido, J. L.

    2009-01-28

    We study the spherical to prolate-deformed shape transition in {sup 144-158}Sm and {sup 146-160}Gd isotopes with modern calculations beyond the mean field with the Gogny D1S force. We compare the results with the shape-phase transition predicted by the collective Hamiltonian model and with the experimental data. Our calculations do not support the existence of a first order phase transition in these isotopic chains in the viewpoint of the Bohr Hamiltonian neither the interpretation of the nuclei N = 90 as critical points.

  19. Study of asymmetric fission yield behavior from neutron-deficient Hg isotope

    SciTech Connect

    Perkasa, Y. S.; Waris, A. Kurniadi, R. Su'ud, Z.

    2014-09-30

    A study of asymmetric fission yield behavior from a neutron-deficient Hg isotope has been conducted. The fission yield calculation of the neutron-deficient Hg isotope using Brownian Metropolis shape had showed unusual result at decreasing energy. In this paper, this interesting feature will be validated by using nine degree of scission shapes parameterization from Brosa model that had been implemented in TALYS nuclear reaction code. This validation is intended to show agreement between both model and the experiment result. The expected result from these models considered to be different due to dynamical properties that implemented in both models.

  20. Rare isotope studies involving catalytic oxidation of CO over platinum-tin oxide

    NASA Technical Reports Server (NTRS)

    Upchurch, Billy T.; Wood, George M., Jr.; Hess, Robert V.; Hoyt, Ronald F.

    1987-01-01

    Results of studies utilizing normal and rare oxygen isotopes in the catalytic oxidation of carbon monoxide over a platinum-tin oxide catalyst substrate are presented. Chemisorption of labeled carbon monoxide on the catalyst followed by thermal desorption yielded a carbon dioxide product with an oxygen-18 composition consistent with the formation of a carbonate-like intermediate in the chemisorption process. The efficacy of a method developed for the oxygen-18 labeling of the platinum-tin oxide catalyst surface for use in closed cycle pulsed care isotope carbon dioxide lasers is demonstrated for the equivalent of 10 to the 6th power pulses at 10 pulses per second.

  1. Penn State's Visual Image User Study

    ERIC Educational Resources Information Center

    Pisciotta, Henry A.; Dooris, Michael J.; Frost, James; Halm, Michael

    2005-01-01

    The Visual Image User Study (VIUS), an extensive needs assessment project at Penn State University, describes academic users of pictures and their perceptions. These findings outline the potential market for digital images and list the likely determinates of whether or not a system will be used. They also explain some key user requirements for…

  2. Kinetic and metabolic isotope effects in coral skeletal carbon isotopes: A re-evaluation using experimental coral bleaching as a case study

    NASA Astrophysics Data System (ADS)

    Schoepf, Verena; Levas, Stephen J.; Rodrigues, Lisa J.; McBride, Michael O.; Aschaffenburg, Matthew D.; Matsui, Yohei; Warner, Mark E.; Hughes, Adam D.; Grottoli, Andréa G.

    2014-12-01

    Coral skeletal δ13C can be a paleo-climate proxy for light levels (i.e., cloud cover and seasonality) and for photosynthesis to respiration (P/R) ratios. The usefulness of coral δ13C as a proxy depends on metabolic isotope effects (related to changes in photosynthesis) being the dominant influence on skeletal δ13C. However, it is also influenced by kinetic isotope effects (related to calcification rate) which can overpower metabolic isotope effects and thus compromise the use of coral skeletal δ13C as a proxy. Heikoop et al. (2000) proposed a simple data correction to remove kinetic isotope effects from coral skeletal δ13C, as well as an equation to calculate P/R ratios from coral isotopes. However, despite having been used by other researchers, the data correction has never been directly tested, and isotope-based P/R ratios have never been compared to P/R ratios measured using respirometry. Experimental coral bleaching represents a unique environmental scenario to test this because bleaching produces large physiological responses that influence both metabolic and kinetic isotope effects in corals. Here, we tested the δ13C correction and the P/R calculation using three Pacific and three Caribbean coral species from controlled temperature-induced bleaching experiments where both the stable isotopes and the physiological variables that cause isotopic fractionation (i.e., photosynthesis, respiration, and calcification) were simultaneously measured. We show for the first time that the data correction proposed by Heikoop et al. (2000) does not effectively remove kinetic effects in the coral species studied here, and did not improve the metabolic signal of bleached and non-bleached corals. In addition, isotope-based P/R ratios were in poor agreement with measured P/R ratios, even when the data correction was applied. This suggests that additional factors influence δ13C and δ18O, which are not accounted for by the data correction. We therefore recommend that the

  3. An experimental study of the isotopic enrichment in Ar, Kr, and Xe when trapped in water ice

    NASA Technical Reports Server (NTRS)

    Notesco, G.; Laufer, D.; Bar-Nun, A.; Owen, T.

    1999-01-01

    The isotopic enrichment of argon, krypton, and xenon, when trapped in water ice, was studied experimentally. The isotopes were found to be enriched according to their (m1/m2)1/2 ratio. These enrichment factors could be useful for comparison among the uncertain cosmic or solar isotopic ratios, the hopeful in situ cometary ratio, and those in Earth's atmosphere, in the context of cometary delivery of volatiles to Earth.

  4. A Mass Spectrometry Study of Isotope Separation in the Laser Plume

    NASA Astrophysics Data System (ADS)

    Suen, Timothy Wu

    Accurate quantification of isotope ratios is critical for both preventing the development of illicit weapons programs in nuclear safeguards and identifying the source of smuggled material in nuclear forensics. While isotope analysis has traditionally been performed by mass spectrometry, the need for in situ measurements has prompted the development of optical techniques, such as laser-induced breakdown spectroscopy (LIBS) and laser ablation molecular isotopic spectrometry (LAMIS). These optical measurements rely on laser ablation for direct solid sampling, but several past studies have suggested that the distribution of isotopes in the ablation plume is not uniform. This study seeks to characterize isotope separation in the laser plume through the use of orthogonal-acceleration time-of-flight mass spectrometry. A silver foil was ablated with a Nd:YAG at 355 nm at an energy of 50 muJ with a spot size of 71 mum, for a fluence of 1.3 J/cm2 and an irradiance of 250 MW/cm2. Flat-plate repellers were used to sample the plume, and a temporal profile of the ions was obtained by varying the time delay on the high-voltage pulse. A spatial profile along the axis of the plume was generated by changing the position of the sample, which yielded snapshots of the isotopic composition with time. In addition, the reflectron time-of-flight system was used as an energy filter in conjunction with the repellers to sample slices of the laser plasma orthogonal to the plume axis. Mass spectrometry of the plume revealed a fast ion distribution and a slow ion distribution. Measurements taken across the entire plume showed the fast 109Ag ions slightly ahead in both space and time, causing the 107Ag fraction to drop to 0.34 at 3 mus, 4 mm from the sample surface. Although measurements centered on the near side of the plume did not show isotope separation, the slow ions on the far side of the plume included much more 109Ag than 107Ag. In addition to examining the isotope content of the ablation

  5. DETERMINING CARBON ISOTOPE SIGNATURES FROM MICROMETEOROLOGICAL MEASUREMENTS: IMPLICATIONS FOR STUDYING BIOSPHERE-ATMOSPHERE EXCHANGE PROCESSES

    Technology Transfer Automated Retrieval System (TEKTRAN)

    In recent years considerable effort has been focused on combining micrometeorological and stable isotope techniques to elucidate and study biosphere-atmosphere exchange processes. At the ecosystem scale, these methods are increasingly being used to address a number of challenging problems, including...

  6. Three-dimensional oxygen isotope imaging of convective fluid flow around the Big Bonanza, Comstock lode mining district, Nevada

    USGS Publications Warehouse

    Criss, R.E.; Singleton, M.J.; Champion, D.E.

    2000-01-01

    Oxygen isotope analyses of propylitized andesites from the Con Virginia and California mines allow construction of a detailed, three-dimensional image of the isotopic surfaces produced by the convective fluid flows that deposited the famous Big Bonanza orebody. On a set of intersecting maps and sections, the δ18O isopleths clearly show the intricate and conformable relationship of the orebody to a deep, ~500 m gyre of meteoric-hydrothermal fluid that circulated along and above the Comstock fault, near the contact of the Davidson Granodiorite. The core of this gyre (δ18O = 0 to 3.8‰) encompasses the bonanza and is almost totally surrounded by rocks having much lower δ18O values (–1.0 to –4.4‰). This deep gyre may represent a convective longitudinal roll superimposed on a large unicellular meteoric-hydrothermal system, producing a complex flow field with both radial and longitudinal components that is consistent with experimentally observed patterns of fluid convection in permeable media.

  7. Evaporation from the shallow Lake Massaciuccoli (Tuscany, Italy) studied using stable isotopes and evaporation pan data

    NASA Astrophysics Data System (ADS)

    Baneschi, I.; Gonfiantini, R.; Guidi, M.

    2009-04-01

    Oxygen and hydrogen isotope variations monitored in Lake Massaciuccoli (7 km2, 2 m deep, seasonally variable water level) during summer 2008, were compared with those observed in a Class A evaporation pan (diameter 120.6 cm, depth 25.4 cm) placed on the lake eastern shore. Air temperature, pressure, relative humidity, wind speed and direction, solar radiation, water temperature in the lake and the pan were also measured. The pluviometer indicated that no precipitation occurred during the study period. The pan was initially filled with groundwater up to the level of 19.2 cm (219 L), depleted in heavy isotopes with respect to tha lake water. Sodium chloride was added up to the concentration of 1 g×L-1, which is assumed do not affect significantly the evaporation rate till the water volume is reduced to less than 10 %. The Cl- concentration was used to provide an estimation of the evaporated water fraction, in addition to the micrometer measuring the water level variations. The pan water was sampled every 2-3 days and Cl- and stable isotopes determined. The set of stable isotope and evaporation data enabled us to compute the parameters governing the evaporation process and the isotopic exchanges with the atmospheric moisture, according to the procedure proposed by Gonfiantini (1986). The values were applied to test three working hypotheses of water balance of Lake Massaciuccoli: (i) surface inflow and outflow of liquid water are negligible and only evaporation is important; (ii) the inflow is negligible and outflow and evaporation are both significant; (iii) the three terms of balance are all important but the losses by evaporation and outflow exceed inflow (as the lake water level was decreasing). Water exchanges with groundwater are considered negligible. The best agreement between lake and pan data was obtained with the second hypothesis, for which the fraction of water removed by evaporation was estimated to be about 40 % ot he total water losses. This residual

  8. Bronze Age volcanic event recorded in stalagmites by combined isotope and trace element studies.

    PubMed

    Siklósy, Zoltán; Demény, Attila; Vennemann, Torsten W; Pilet, Sebastien; Kramers, Jan; Leél-Ossy, Szabolcs; Bondár, Mária; Shen, Chuan-Chou; Hegner, Ernst

    2009-03-01

    Stable isotope analyses of speleothems (carbonate deposits formed in caves) have been widely used to reconstruct paleoenvironmental conditions. Recent improvements in geochemical techniques have enabled us to analyze climate-influenced deposits at high temporal resolution so that hitherto unrecognized environmental conditions may be identified. Stable H, C and O isotope analyses on carbonate and inclusion water have been combined with multicollector inductively coupled plasma mass spectrometry (MC-ICP-MS) age dating and laser-ablation ICP-MS trace element analyses on a stalagmite from southern Hungary. The study reveals significant changes in chemical and isotopic compositions of the speleothem between approx. 3800 and 3500 years BP ('Before Present') indicating coupled changes in the temperature and precipitation regime under which the speleothem formed. Stable isotopic and trace element correlations within this time period correlate with similar studies of stalagmites of comparable age from the Alpine-Mediterranean region. Our studies suggest that traces of deposition of volcanic dust, possibly related to the Thera eruption of Santorini (Greece) ca. 1650 BC (approximately 3650 BP), and environmental changes can be detected at a distance of several thousand kilometers. PMID:19219896

  9. Automated data extraction from in situ protein-stable isotope probing studies.

    PubMed

    Slysz, Gordon W; Steinke, Laurey; Ward, David M; Klatt, Christian G; Clauss, Therese R W; Purvine, Samuel O; Payne, Samuel H; Anderson, Gordon A; Smith, Richard D; Lipton, Mary S

    2014-03-01

    Protein-stable isotope probing (protein-SIP) has strong potential for revealing key metabolizing taxa in complex microbial communities. While most protein-SIP work to date has been performed under controlled laboratory conditions to allow extensive isotope labeling of the target organism(s), a key application will be in situ studies of microbial communities for short periods of time under natural conditions that result in small degrees of partial labeling. One hurdle restricting large-scale in situ protein-SIP studies is the lack of algorithms and software for automated data processing of the massive data sets resulting from such studies. In response, we developed Stable Isotope Probing Protein Extraction Resources software (SIPPER) and applied it for large-scale extraction and visualization of data from short-term (3 h) protein-SIP experiments performed in situ on phototrophic bacterial mats isolated from Yellowstone National Park. Several metrics incorporated into the software allow it to support exhaustive analysis of the complex composite isotopic envelope observed as a result of low amounts of partial label incorporation. SIPPER also enables the detection of labeled molecular species without the need for any prior identification. PMID:24467184

  10. Automated data extraction from in situ protein stable isotope probing studies

    SciTech Connect

    Slysz, Gordon W.; Steinke, Laurey A.; Ward, David M.; Klatt, Christian G.; Clauss, Therese RW; Purvine, Samuel O.; Payne, Samuel H.; Anderson, Gordon A.; Smith, Richard D.; Lipton, Mary S.

    2014-01-27

    Protein stable isotope probing (protein-SIP) has strong potential for revealing key metabolizing taxa in complex microbial communities. While most protein-SIP work to date has been performed under controlled laboratory conditions to allow extensive isotope labeling of the target organism, a key application will be in situ studies of microbial communities under conditions that result in small degrees of partial labeling. One hurdle restricting large scale in situ protein-SIP studies is the lack of algorithms and software for automated data processing of the massive data sets resulting from such studies. In response, we developed Stable Isotope Probing Protein Extraction Resources software (SIPPER) and applied it for large scale extraction and visualization of data from short term (3 h) protein-SIP experiments performed in situ on Yellowstone phototrophic bacterial mats. Several metrics incorporated into the software allow it to support exhaustive analysis of the complex composite isotopic envelope observed as a result of low amounts of partial label incorporation. SIPPER also enables the detection of labeled molecular species without the need for any prior identification.

  11. Pb isotopic study on soils from Domizio-Flegreo Littoral area, Napoli, Italy

    NASA Astrophysics Data System (ADS)

    Grezzi, G.; Ayuso, R. A.; Lima, A.; Albanese, S.; de Vivo, B.

    2009-04-01

    The Domizio - Flegreo Littoral area, together with the Agro Aversano area, are part of a Site of National Interest for pollution assessment. This area is located along the north coastal zone of the Campania region (Italy) and has an extension of about 855 Km2. We analyzed soils for heavy metal content in order to study and discriminate the impact of natural and anthropogenic sources. We collected 292 soil surface samples (5-15 cm depth) and produced maps showing the distribution of heavy metals in the soils. On the basis of the geographic distribution of heavy metals, 9 soil profiles were also collected for detailed examination (1 meter from surface). From each soil profile, we collected 10 soil samples (1/10 cm) in the urban and suburban areas of the littoral area. Also, we collected 8 groundwater samples likely associated with the soils. Pb isotope compositions of these soils and waters help to constrain the impact of anthropogenic and natural components on the soil profiles. Possible anthropogenic end-members include pesticides used in the area. Lead isotope compositions of soils known to contain anomalously high values of heavy metals were measured in order to determine the sources of the Pb and, by inference, sources of other metals that are likely to share similar geochemical behaviour in the surface environment (e.g., As). Acid-leach compositions of the soils represent Pb that is adsorbed to mineral surfaces, whereas residue compositions may reflect bedrock. Labile Pb (acid-leach fractions) from the soils shows a range in compositions of 207Pb/206Pb = 0.8275 to 0.8486, and 208Pb/206Pb = 2.0488 to 2.0873. The isotope values vary and decrease with depth. The Pb isotope ratios obtained on groundwater samples range from about 207Pb/206Pb = 0.8516 to 0.8636, 208Pb/206Pb = 2.0706 to 2.1064. The Pb isotope ratios in the soil profiles and groundwater are generally consistent with multiple sources that include anthropogenic Pb. Surface soil samples from Giugliano

  12. A Combined He and Os Isotopic Study of the HSDP-2 Core from Mauna Kea, Hawaii

    NASA Astrophysics Data System (ADS)

    Ireland, T. J.; Walker, R. J.; Depaolo, D. J.; Kurz, M. D.

    2004-12-01

    Combined osmium and helium isotope systematics of hotspot lavas have the potential to reveal information about the deep Earth. A high 3He/4He ratio may represent an undegassed reservoir, generally associated with the lower mantle. There are two Os isotopes that can be studied to help to further elucidate the problem. The decay of 187Re to 187Os is the more frequently cited system; however, in terms of lower mantle processes, the decay of 190Pt to 186Os may be extremely useful. Both of these Os isotopes are enriched in the core relative to chondritic values. In a previous study, Brandon et al. (1999) examined several Hawaiian volcanoes for both He and Os isotopes. A correlation was noted between the 3He/4He, 187Os/188Os and 186Os/188Os ratios. In terms of 3He/4He and 187Os/188Os space, the three commonly cited Hawaiian end-members (Kea, Koolau and Loihi members) were clearly defined. A strong positive correlation was also observed for 186Os/188Os versus 3He/4He. These correlations were interpreted as a possible signature of core-mantle interaction. There were some limitations to previous studies. Only 2-3 samples from each volcano were studied, with these samples generally being subaerially erupted. The He data utilized were often not for the same samples for which the Os data were collected (volcano averages for He were used on some samples). With the introduction of data from the Hawaiian Scientific Drilling Project (HSDP-2), which drilled 2.84 km into the Mauna Kea volcanics (DePaolo et al., 2000), an extensive history of a single volcano can be observed (from the early submarine stages to the later subaerial rocks). In the current study a detailed Os isotopic analysis of several samples that span a large depth range of the HSDP-2 core, in conjunction with previously collected He isotopic data (Kurz et al., 2004), was conducted. The samples define a relatively narrow range of slightly suprachondritic 187Os/188Os ratios (0.12865-0.13056), despite having a large

  13. Online analysis of chlorine stable isotopes in chlorinated ethylenes: an inter-laboratory study

    NASA Astrophysics Data System (ADS)

    Bernstein, Anat; Shouakar-Stash, Orfan; Hunkeler, Daniel; Sakaguchi-Söder, Kaori; Laskov, Christine; Aravena, Ramon; Elsner, Martin

    2010-05-01

    In the last decade, compound-specific stable isotopes analysis of groundwater pollutants became an important tool to identify different sources of the same pollutant and for tracking natural attenuating processes in the sub-surface. It has been shown that trends in the isotopic composition of the target compounds can shed light on in-situ processes that are otherwise difficult to track. Analytical methods of carbon, nitrogen and hydrogen were established and are by now frequently used for a variety of organic pollutants. Yet, the motivation of introducing analytical methods for new isotopes is emerging. This motivation is further enhanced, as advantages of using two or more stable isotopes for gaining better insight on degradation pathways are well accepted. One important element which demands the development of appropriate analytical methods is chlorine, which is found in various groups of organic pollutants, among them the chlorinated ethylenes. Chlorinated ethylenes are considered as high priority environmental pollutants, and the development of suitable chlorine isotope methods for this group of pollutants is highly desired. Ideally, stable isotope techniques should have the capability to determine the isotopic composition of and individual target compound in a non-pure mixture, without the requirement of a laborious off-line treatment. Indeed, in the last years two different concepts for on-line chlorine isotope analysis methods were introduced, by using either a standard quadrapole GC/MS (Sakaguchi-Söder et al., 2007) or by using a GC/IRMS (Shouakar-Stash et al., 2006). We present a comparison of the performances of two concepts, carried out in five different laboratories: Waterloo (GC/IRMS), Neuchâtel (GC/MS), Darmstadt (GC/MS), Tübingen (GC/MS) and Munich (GC/IRMS). This comparison was performed on pure trichloroethylene and dichloroethylene products of different manufactures, as well as trichloroethylene and dichloroethylene samples that were exposed to

  14. Image processing of angiograms: A pilot study

    NASA Technical Reports Server (NTRS)

    Larsen, L. E.; Evans, R. A.; Roehm, J. O., Jr.

    1974-01-01

    The technology transfer application this report describes is the result of a pilot study of image-processing methods applied to the image enhancement, coding, and analysis of arteriograms. Angiography is a subspecialty of radiology that employs the introduction of media with high X-ray absorption into arteries in order to study vessel pathology as well as to infer disease of the organs supplied by the vessel in question.

  15. Isotope studies of hydrogen and oxygen in ground ice-experiences with the equilibration technique.

    PubMed

    Meyer, H; Schönicke, L; Wand, U; Hubberten, H W; Friedrichsen, H

    2000-01-01

    Equilibration technique suitable for a large amount of samples is described for hydrogen and oxygen isotope analyses of ground ice, especially ice wedges, including the sampling strategy and the analytical procedure as well as the calibration of the Finnigan MAT Delta-S mass spectrometer in June, 1999. Since for future analyses of ice wedges, a higher sampling resolution with limited sample volume is required, the limit of the equilibration technique for small water sample sizes of between 0.05 and 5 ml was checked. For water samples smaller than 1 ml, corresponding to a molar ratio [H2O]/[H2] of smaller than 0.994, a balance correction has to be applied. The experimental errors due to partial evaporation during evacuation, the balance calculation of the isotope equilibration process, the linearity as well as memory effects of the mass spectrometer for samples with large differences in delta18O and deltaD are tackled in this paper. In the polar regions of Northern Siberia without Late Pleistocene and Holocene glaciation, ground ice is used as an archive for paleoclimate studies. First results of stable isotope measurements on ice wedges clearly show a shift towards heavier isotopes and thus warmer winter temperatures as well as a change in the source of the precipitation between Late Pleistocene and Holocene. These results indicate the high potential of ground ice for paleoclimate studies. PMID:11077928

  16. Preliminary isotopic studies of fluids from the Cerro Prieto geothermal field

    USGS Publications Warehouse

    Truesdell, A.H.; Rye, R.O.; Pearson, F.J., Jr.; Olson, E.R.; Nehring, N.L.; Whelan, J.F.; Huebner, M.A.; Coplen, T.B.

    1979-01-01

    Preliminary isotopic studies of Cerro Prieto geothermal fluids and earlier studies of Mexicali Valley ground waters suggest local recharge of the geothermal system from the area immediately to the west. Oxygen isotope exchange of water with reservoir rock minerals at temperatures increasing with depth has produced fluids with oxygen-18 contents increasing with depth, and pressure drawdown in the southeastern part of the field has allowed lower oxygen-18 fluids to invade the production aquifer from above. The contents of tritium and carbon-14 in the fluid suggest only that the age of the fluid is between 50 and 10,000 years. The isotopic compositions of carbon and sulfur are consistent with a magmatic origin of these elements but a mixed sedimentary-organic origin appears more likely for carbon and is also possible for sulfur. Investigations of the isotopic compositions of geothermal and cold ground waters continue and are being expanded as fluids become available and as separation and analysis methods are improved. ?? 1979.

  17. Neonatal Respiratory Diseases in the Newborn Infant: Novel Insights from Stable Isotope Tracer Studies.

    PubMed

    Carnielli, Virgilio P; Giorgetti, Chiara; Simonato, Manuela; Vedovelli, Luca; Cogo, Paola

    2016-01-01

    Respiratory distress syndrome is a common problem in preterm infants and the etiology is multifactorial. Lung underdevelopment, lung hypoplasia, abnormal lung water metabolism, inflammation, and pulmonary surfactant deficiency or disfunction play a variable role in the pathogenesis of respiratory distress syndrome. High-quality exogenous surfactant replacement studies and studies on surfactant metabolism are available; however, the contribution of surfactant deficiency, alteration or dysfunction in selected neonatal lung conditions is not fully understood. In this article, we describe a series of studies made by applying stable isotope tracers to the study of surfactant metabolism and lung water. In a first set of studies, which we call 'endogenous studies', using stable isotope-labelled intravenous surfactant precursors, we showed the feasibility of measuring surfactant synthesis and kinetics in infants using several metabolic precursors including plasma glucose, plasma fatty acids and body water. In a second set of studies, named 'exogenous studies', using stable isotope-labelled phosphatidylcholine tracer given endotracheally, we could estimate surfactant disaturated phosphatidylcholine pool size and half-life. Very recent studies are focusing on lung water and on the endogenous biosynthesis of the surfactant-specific proteins. Information obtained from these studies in infants will help to better tailor exogenous surfactant treatment in neonatal lung diseases. PMID:27251153

  18. Ischemic "memory image" in acute myocardial infarction of 123I-BMIPP after reperfusion therapy: a comparison with 99mTc-pyrophosphate and 201Tl dual-isotope SPECT.

    PubMed

    Mochizuki, Teruhito; Murase, Kenya; Higashino, Hiroshi; Miyagawa, Masao; Sugawara, Yoshifumi; Kikuchi, Takanori; Ikezoe, Junpei

    2002-12-01

    Ischemic "memory image" is a phenomenon of 123I-15-(p-iodophenyl)-3-(R,S)-methylpentadecanoic acid (BMIPP) in which an area at risk of acute myocardial infarction (AMI), could be detected as a defect in a couple of weeks even after successful reperfusion therapy. The purpose of this study was to clarify the incidence of the ischemic "memory image" of 123I-BMIPP in patients with AMI by comparing 99mTc-PYP and 201Tl dual-isotope SPECT. Materials consisted of 14 patients with successfully reperfused AMI and 20 patients with old myocardial infarction (OMI). All AMI patients underwent PYP/Tl dual-isotope SPECT within 1 week after the onset of AMI, and BMIPP SPECT was performed within 1 week after the PYP/Tl dual-isotope SPECT. The extent and severity of the defect of BMIPP and Tl were visually scored into four grades: 0 = no defect to 3 = large or severe defect. These scores were compared. PYP positive AMI lesions were concordant with BMIPP defects (13/14). In AMI, both the extent and severity scores of BMIPP were higher than 201Tl (p < 0.001). Differences (BMIPP - Tl) of extent and severity scores were greater in AMI than in OMI (p < 0.001). In conclusion, the ischemic "memory image" obtained by means of the BMIPP is a common phenomenon (13/14) in AMI, and helpful in evaluating the area at risk. PMID:12593422

  19. Medical applications of NMR imaging and NMR spectroscopy with stable isotopes. Summary

    SciTech Connect

    Matwiyoff, N.A.

    1983-01-01

    The current status of NMR imaging and NMR spectroscopy are summarized. For the most part examples from the March 1983 Puerto Rico symposium are used to illustrate the utility of NMR in medicine. 18 refs., 5 figs.

  20. Carbon allocation in plants and ecosystems - insights from stable isotope studies

    NASA Astrophysics Data System (ADS)

    Gessler, Arthur

    2014-05-01

    Trees are large global stores of carbon (C) that will be impacted by increased carbon dioxide levels and climate change. However, at present we cannot properly predict the carbon balance of forests in future as we lack knowledge on how plant physiological processes, the transfer of carbon within the plant, carbon storage, and remobilization in the plant tissues as well as the release of carbon from the roots to the soil interact with environmental drivers and ecosystem-scale processes. This paper will summarise how stable isotope techniques can give new insights in the fate of newly assimilated C in plants and ecosystems on time scales from hours to seasons and it will include studies either characterizing temporal and spatial variation in the natural abundance of carbon and oxygen isotopes or applying isotopically enriched tracers. It comprises the assessment of the mechanisms of C partitioning among specific metabolic pathways, between plant organs and into various ecosystem C pools with different residence times. Moreover stable isotopes are highly suitable tools to characterise the role of the phloem, which is the central long-distance conveyer distributing C from source to sinks and thus plays a central role in linking sites and structures of storage, growth and other metabolic activities. A deeper understanding of these processes and their interaction with environmental drivers is critical for predicting how trees and ecosystems will respond to coming global environmental changes, including increased temperature, altered precipitation, and elevated carbon dioxide concentrations.

  1. In situ NRA study of hydrogen isotope exchange in self-ion damaged tungsten exposed to neutral atoms

    NASA Astrophysics Data System (ADS)

    Markelj, S.; Založnik, A.; Schwarz-Selinger, T.; Ogorodnikova, O. V.; Vavpetič, P.; Pelicon, P.; Čadež, I.

    2016-02-01

    Isotope exchange was studied in-situ by Nuclear Reaction Analysis in the bulk of self-ion damaged tungsten at 600 K. Both variations of isotope exchange of H by D and of D by H were measured. The deuterium isothermal desorption was also studied and evaluated in order to be able to resolve the self-desorption from the isotope exchange at 600 K. The isotope exchange was also studied on the surface by Elastic Recoil Detection Analysis at 480 K and 380 K. The exchange mechanism was effective both on the surface and in the bulk of damaged tungsten. A simple model was introduced to describe the exchange efficiency on the surface and in the bulk obtaining the exchange cross sections on the surface and in bulk. In both cases an isotope effect was observed, where the exchange of H atoms by D atoms was more efficient than for the reverse sequence.

  2. Geochemical and isotopic study of soils and waters from an Italian contaminated site: Agro Aversano (Campania)

    USGS Publications Warehouse

    Bove, M.A.; Ayuso, R.A.; de Vivo, B.; Lima, A.; Albanese, S.

    2011-01-01

    Lead isotope applications have been widely used in recent years in environmental studies conducted on different kinds of sampled media. In the present paper, Pb isotope ratios have been used to determine the sources of metal pollution in soils and waters in the Agro Aversano area. During three different sampling phases, a total of 113 surface soils (5-20. cm), 20 samples from 2 soil profiles (0-1. m), 11 stream waters and 4 groundwaters were collected. Major element concentrations in sampled media have been analyzed by the ICP-MS technique. Surface soils (20 samples), all soil profiles and all waters have been also analyzed for Pb isotope compositions by thermal ionization (TIMS). The geochemical data were assessed using statistic methods and cartographically elaborated in order to have a clear picture of the level of disturbance of the area. Pb isotopic data were studied to discriminate between anthropogenic and geologic sources. Our results show that As (5.6-25.6. mg/kg), Cu (9-677. mg/kg), Pb (22-193. mg/kg), Tl (0.53-3.62. mg/kg), V (26-142. mg/kg) and Zn (34-215. mg//kg) contents in analyzed soils, exceed the intervention limits fixed by the Italian Environmental Law for residential areas in some of the sampled sites, while intervention limit for industrial areas is exceeded only for Cu concentrations. Lead isotopic data, show that there is a high similarity between the ratios measured in the leached soil samples and those deriving from anthropic activities. This similarity with anthropogenic Pb is also evident in the ratios measured in both groundwater and stream water samples. ?? 2010 Elsevier B.V.

  3. Carbon and nitrogen isotope studies in an arctic aquatic ecosystem

    SciTech Connect

    Schell, D.M.

    1989-01-01

    The Phase II studies of the R4D Program on stream and watershed ecology reflect the accomplishments and accumulation of baseline information obtained during the past studies. Although our rough estimates indicate that nitrogen inputs to the watershed ba lance losses, the carbon fluxes suggest that they are not in equilibrium and that there is a net loss of carbon from the tundra ecosystem through respiration and transport out of the watershed via the stream system. Radiocarbon profiles of soil sections coupled with mass transport calculations revealed that peat accumulation has essentially ceased in the R4D watershed and appears to be in ablative loss. Thus the carbon flux measurements provide validation tests for the PLANTGRO and GAS-HYDRO models of the PHASE II studies. These findings are also important in the context of global CO[sub 2] increases from positive feedback mechanisms in peatlands associated with climatic warming in the subarctic regions.

  4. Carbon and nitrogen isotope studies in an arctic aquatic ecosystem

    SciTech Connect

    Schell, D.M.

    1989-12-31

    The Phase II studies of the R4D Program on stream and watershed ecology reflect the accomplishments and accumulation of baseline information obtained during the past studies. Although our rough estimates indicate that nitrogen inputs to the watershed ba lance losses, the carbon fluxes suggest that they are not in equilibrium and that there is a net loss of carbon from the tundra ecosystem through respiration and transport out of the watershed via the stream system. Radiocarbon profiles of soil sections coupled with mass transport calculations revealed that peat accumulation has essentially ceased in the R4D watershed and appears to be in ablative loss. Thus the carbon flux measurements provide validation tests for the PLANTGRO and GAS-HYDRO models of the PHASE II studies. These findings are also important in the context of global CO{sub 2} increases from positive feedback mechanisms in peatlands associated with climatic warming in the subarctic regions.

  5. Study of thermochemical sulfate reduction mechanism using compound specific sulfur isotope analysis

    NASA Astrophysics Data System (ADS)

    Meshoulam, Alexander; Ellis, Geoffrey S.; Said Ahmad, Ward; Deev, Andrei; Sessions, Alex L.; Tang, Yongchun; Adkins, Jess F.; Liu, Jinzhong; Gilhooly, William P.; Aizenshtat, Zeev; Amrani, Alon

    2016-09-01

    The sulfur isotopic fractionation associated with the formation of organic sulfur compounds (OSCs) during thermochemical sulfate reduction (TSR) was studied using gold-tube pyrolysis experiments to simulate TSR. The reactants used included n-hexadecane (n-C16) as a model organic compound with sulfate, sulfite, or elemental sulfur as the sulfur source. At the end of each experiment, the S-isotopic composition and concentration of remaining sulfate, H2S, benzothiophene, dibenzothiophene, and 2-phenylthiophene (PT) were measured. The observed S-isotopic fractionations between sulfate and BT, DBT, and H2S in experimental simulations of TSR correlate well with a multi-stage model of the overall TSR process. Large kinetic isotope fractionations occur during the first, uncatalyzed stage of TSR, 12.4‰ for H2S and as much as 22.2‰ for BT. The fractionations decrease as the H2S concentration increases and the reaction enters the second, catalyzed stage. Once all of the oxidizable hydrocarbons have been consumed, sulfate reduction ceases and equilibrium partitioning then dictates the fractionation between H2S and sulfate (∼17‰). Experiments involving sparingly soluble CaSO4 show that during the second catalytic phase of TSR the rate of sulfate reduction exceeds that of sulfate dissolution. In this case, there is no apparent isotopic fractionation between source sulfate and generated H2S, as all of the available sulfate is effectively reduced at all reaction times. When CaSO4 is replaced with fully soluble Na2SO4, sulfate dissolution is no longer rate limiting and significant S-isotopic fractionation is observed. This supports the notion that CaSO4 dissolution can lead to the apparent lack of fractionation between H2S and sulfate produced by TSR in nature. The S-isotopic composition of individual OSCs record information related to geochemical reactions that cannot be discerned from the δ34S values obtained from bulk phases such as H2S, oil, and sulfate minerals, and

  6. Stable isotopes and Digital Elevation Models to study nutrient inputs in high-Arctic lakes

    NASA Astrophysics Data System (ADS)

    Calizza, Edoardo; Rossi, David; Costantini, Maria Letizia; Careddu, Giulio; Rossi, Loreto

    2016-04-01

    Ice cover, run-off from the watershed, aquatic and terrestrial primary productivity, guano deposition from birds are key factors controlling nutrient and organic matter inputs in high-Arctic lakes. All these factors are expected to be significantly affected by climate change. Quantifying these controls is a key baseline step to understand what combination of factors subtends the biological productivity in Arctic lakes and will drive their ecological response to environmental change. Basing on Digital Elevation Models, drainage maps, and C and N elemental content and stable isotope analysis in sediments, aquatic vegetation and a dominant macroinvertebrate species (Lepidurus arcticus Pallas 1973) belonging to Tvillingvatnet, Storvatnet and Kolhamna, three lakes located in North Spitsbergen (Svalbard), we propose an integrated approach for the analysis of (i) nutrient and organic matter inputs in lakes; (ii) the role of catchment hydro-geomorphology in determining inter-lake differences in the isotopic composition of sediments; (iii) effects of diverse nutrient inputs on the isotopic niche of Lepidurus arcticus. Given its high run-off and large catchment, organic deposits in Tvillingvatnet where dominated by terrestrial inputs, whereas inputs were mainly of aquatic origin in Storvatnet, a lowland lake with low potential run-off. In Kolhamna, organic deposits seem to be dominated by inputs from birds, which actually colonise the area. Isotopic signatures were similar between samples within each lake, representing precise tracers for studies on the effect of climate change on biogeochemical cycles in lakes. The isotopic niche of L. aricticus reflected differences in sediments between lakes, suggesting a bottom-up effect of hydro-geomorphology characterizing each lake on nutrients assimilated by this species. The presented approach proven to be an effective research pathway for the identification of factors subtending to nutrient and organic matter inputs and transfer

  7. A Study of Imaging Interferometer Simulators

    NASA Technical Reports Server (NTRS)

    Allen, Ronald J.

    2002-01-01

    Several new space science mission concepts under development at NASA-GSFC for astronomy are intended to carry out synthetic imaging using Michelson interferometers or direct (Fizeau) imaging with sparse apertures. Examples of these mission concepts include the Stellar Imager (SI), the Space Infrared Interferometric Telescope (SPIRIT), the Submillimeter Probe of the Evolution of Cosmic Structure (SPECS), and the Fourier-Kelvin Stellar Interferometer (FKSI). We have been developing computer-based simulators for these missions. These simulators are aimed at providing a quantitative evaluation of the imaging capabilities of the mission by modelling the performance on different realistic targets in terms of sensitivity, angular resolution, and dynamic range. Both Fizeau and Michelson modes of operation can be considered. Our work is based on adapting a computer simulator called imSIM, which was initially written for the Space Interferometer Mission in order to simulate the imaging mode of new missions such as those listed. In a recent GSFC-funded study we have successfully written a preliminary version of a simulator SISIM for the Stellar Imager and carried out some preliminary studies with it. In a separately funded study we have also been applying these methods to SPECS/SPIRIT.

  8. An isotopic study of fiber-water interactions

    NASA Astrophysics Data System (ADS)

    Walsh, Frances Luella

    A new technique for measuring the water content of fiber is presented. Tritiated water is added to a pulp/water suspension whereupon the tritium partitions between the bulk water and the pulp. Through this technique a fiber:water partition coefficient is developed, Kpw. This thesis will cover the development of the Kpw procedure and three different case studies. The first study involves comparing Kpw to traditional methods of fiber water content. The procedure provides a value of ten percent for the tightly bound water content of unrefined hardwood or softwood kraft fiber, either bleached or unbleached. If this water is assumed to cover the fiber surface as a monolayer, then an estimate of the wet surface area of fiber can be obtained. This estimate compares well to independent measurements of surface area. Kpw has also been found to be valuable in furthering the understanding of refining. Based on the study, it is proposed that refining occurs in three discrete stages. First, refining removes the primary cell wall and S1 layer while beginning to swell the S2 layer. Next, internal delamination occurs within the S2 layer. Finally, fiber destruction occurs at high refining levels. By using Kpw, the three stages of refining are clearly recognized. Lastly, Kpw is used to study the effect of hornification on bleached softwood kraft fiber. The recycling effects at three refining levels were characterized by Kpw and followed closely the findings of the refining study. At low and high refining levels, the impact of recycling was minimal according to Kpw results, but at 400 mL csf the impact of recycling was much more pronounced. This could be attributed to the closing of internal delaminations within the fiber.

  9. Studies on stable isotopic composition of daily rainfall from Kozhikode, Kerala, India.

    PubMed

    Unnikrishnan Warrier, C; Praveen Babu, M; Sudheesh, M; Deshpande, Rajendrakumar D

    2016-06-01

    The stable isotopic compositions of all major daily rain fall samples (n = 113) collected from Kozhikode station in Kerala, India, for the year 2010 representing the pre-monsoon, southwest and northeast monsoon seasons are examined. The isotopic variations δ(18)O, δ(2)H and d-excess in daily rainfall ranged from δ(18)O: -4.4 to 2 ‰, δ(2)H: -25.3 to 13.8 ‰, and d-excess: -2.4 to 15.3 ‰; δ(18)O: -9.7 to -0.6 ‰, δ(2)H: -61.7 to 5.3 ‰, and d-excess 5.8 to 17.4 ‰; δ(18)O -11.3 to -1.4 ‰, δ(2)H: -75.3 to 0.9 ‰, and d-excess: 8.8 to 21.3 ‰ during the pre-, southwest and northeast monsoon periods, respectively. Thus, daily rainfall events during two monsoon periods had a distinct range of isotopic variations. The daily rain events within the two monsoon seasons also exhibited periodic variations. The isotopic composition of rain events during pre-monsoon and a few low-intensity events during the southwest monsoon period had imprints of secondary evaporation. This study analysing the stable isotopic characteristics of individual rain events in southern India, which is influenced by dual monsoon rainfall, will aid in a better understanding of its mechanism. PMID:26617222

  10. Hydrogeological and isotopic study of surface water and groundwater in the Eastern Haouz Plain. Western Morocco

    NASA Astrophysics Data System (ADS)

    El Mandour, Abdennabi; Rochdane, Samia; Reddy, Venkat; Himi, Mahjoub; Casas, Albert

    2014-05-01

    The Eastern Haouz area, characterized by a semi-arid climate, is part of the Haouz plain. The basin is built over a broad synclinal between the High Atlas and the Jebilets mountains. The compilation of geological, geophysical and hydrogeological data shows that this area is straddling two major basins of western Morocco. Map of the river system and the piezometric map show the same division line of surface water and groundwater. This division line oriented NNW-SSE is evidenced by the rise of the basement constituted by Paleozoic schists that outcrop near Tamelalt. Thus we can distinguish two main directions of groundwater flow feeding two watersheds (Tensift and Oum Rabiaa rivers) and two large reservoirs in the region of Marrakech. As a contribution to solve the water supply problem in the area, a hydrochemical study has been conducted, involving 40 groundwater samples for major ions and 20 stable isotope analyses. Hydrochemical results show the geological control on water quality. Samples from Paleozoic schists and Triassic sediments are relatively highly mineralisation and unsuitable for drinking as well as for irrigation. Conversely, groundwater from the alluvial plains is relatively less mineralised than other older geological formations; however, many of the samples are also non-potable. Apart of salinity problem, about 25% of the samples have higher nitrate content than the drinking water permissible limit. Stable isotope analysis show that groundwater recharge to the phreatic aquifer is controlled by local conditions. The small difference in the isotopic content of river water and a group of groundwater samples is interpreted as the evaporation effect during the recharge. On the other hand, the group of samples with relatively depleted stable isotopic content shows faster recharge conditions and less water-rock interaction. Finally, another group of samples is relatively enriched in stable isotope content and confirm an increase during the recharge

  11. An Experimental Study of Lithium Isotope Partitioning Among Quartz, Muscovite, and Fluid

    NASA Astrophysics Data System (ADS)

    Lynton, S. J.; Walker, R. J.; Candela, P. A.

    2002-05-01

    Preliminary results from an experimental study suggest that lithium isotopes may serve as an indicator of magmatic hydrothermal processes in felsic environments, such as granitic pegmatites and porphyry-type ore deposits. The experiments were carried out with natural (pegmatitic) specimens of quartz and muscovite and with a chloride-bearing aqueous fluid at 400-500° C and 50-100 MPa. Lithium was introduced into the experimental charges through the fluid, which also contains KCl and HCl (K/Li/H = 100/10/1) and is 1M in total chloride. Two other phases (K-feldspar and phlogopite) were included in the charges to permit coupled substitutions by Li + Al and by Li + Mg into Qz and Ms. In contrast with experiments in other isotope systems (eg., O), Li partitioning experiments require allowance for coupled substitutions because some crystallographic sites only become available to Li through coupled substitutions and because the chemical potentials of components necessary for coupled substitutions must be fixed to define fully the thermodynamic conditions of Li partitioning. In two of the experiments a 6Li spike was used to prepare the fluid to magnify the shifts in Li isotopic compositions among run products. The experiments were conducted for 15-60 days under argon pressure with Pt capsules, which were loaded into Inconel 625 cold seal vessels. The experimental design permits simultaneous determination of isotopic fractionation and elemental partitioning by Li among quartz, muscovite and the fluid. Lithium isotopic compositions were determined by thermal ionization mass spectrometry with a triple-filament technique, in which samples are evaporated from side filaments as a phosphate and Li ions are measured directly by the peak-jumping method. Replicate analyses and duplicate experiments indicate reproduceability within approximately +/-1-2‰ . Li concentrations were determined by isotope dilution. For the 500° C runs, the preliminary results provide some indications

  12. Theoretical studies on the alpha decay of 178-220Pb isotopes

    NASA Astrophysics Data System (ADS)

    Santhosh, K. P.; Sukumaran, Indu; Priyanka, B.

    2015-03-01

    The α decay half lives for the isotopes of Pb (Z = 82) nuclei in the range 178 ≤ A ≤ 220 have been studied systematically within the Coulomb and proximity potential model (CPPM) and also within CPPM with modified deformation dependent assault frequency. The half-lives have been evaluated using the experimental Q values. The computed half-lives are compared with the experimental data and also with the existing theoretical models and are found in good agreement. Using our model we could also demonstrate the influence of the neutron shell closure (N = 126) in the alpha decay half lives through the Geiger-Nuttall (GN) plots of ln ⁡ λ vs. ZE - 1 / 2, log10 ⁡T1/2 vs. Q - 1 / 2 and - ln ⁡ P vs. ZQ - 1 / 2. We have also studied the Universal curve of log10 ⁡T1/2 vs. - ln ⁡ P, where all the alpha transitions could be plotted as a single line. The study on the various forms of GN plots, with various variables, enabled us in developing a new, simple relation for the alpha decay half lives of the Pb isotopes and our study also revealed that CPPM and CPPM with the modified assault frequency are appropriate for the alpha decay studies of Pb isotopes and thus can be successfully applied to other alpha emitter nuclides.

  13. Importance of the Lu-Hf isotopic system in studies of planetary chronology and chemical evolution

    USGS Publications Warehouse

    Patchett, P.J.

    1983-01-01

    The 176Lu-176Hf isotope method and its applications in earth sciences are discussed. Greater fractionation of Lu/Hf than Sm/Nd in planetary magmatic processes makes 176Hf 177Hf a powerful geochemical tracer. In general, proportional variations of 176Hf 177Hf exceed those of 143Nd l44Nd by factors of 1.5-3 in terrestrial and lunar materials. Lu-Hf studies therefore have a major contribution to make in understanding of terrestrial and other planetary evolution through time, and this is the principal importance of Lu-Hf. New data on basalts from oceanic islands show unequivocally that whereas considerable divergences occur in 176Hf 177Hf- 87Sr 86Sr and 143Nd l44Nd- 87Sr 86Sr diagrams, 176Hf 177Hf and 143Nd 144Nd display a single, linear isotopic variation in the suboceanic mantle. These discordant 87Sr 86Sr relationships may allow, with the acquisition of further Hf-Nd-Sr isotopic data, a distinction between processes such as mantle metasomatism, influence of seawater-altered material in the magma source, or recycling of sediments into the mantle. In order to evaluate the Hf-Nd isotopic correlation in terms of mantle fractionation history, there is a need for measurements of Hf distribution coefficients between silicate minerals and liquids, and specifically for a knowledge of Hf behavior in relation to rareearth elements. For studying ancient terrestrial Hf isotopic variations, the best quality Hf isotope data are obtained from granitoid rocks or zircons. New data show that very U-Pb discordant zircons may have upwardly-biased 176Hf 177Hf, but that at least concordant to slightly discordant zircons appear to be reliable carriers of initial 176Hf 177Hf. Until the controls on addition of radiogenic Hf to zircon are understood, combined zircon-whole rock studies are recommended. Lu-Hf has been demonstrated as a viable tool for dating of ancient terrestrial and extraterrestrial samples, but because it offers little advantage over existing methods, is unlikely to find

  14. The suitability of the dual isotope approach (δ13C and δ18O) in tree ring studies

    NASA Astrophysics Data System (ADS)

    Siegwolf, Rolf; Saurer, Matthias

    2016-04-01

    The use of stable isotopes, complementary to tree ring width data in tree ring research has proven to be a powerful tool in studying the impact of environmental parameters on tree physiology and growth. These three proxies are thus instrumental for climate reconstruction and improve the understanding of underlying causes of growth changes. In various cases, however, their use suggests non-plausible interpretations. Often the use of one isotope alone does not allow the detection of such "erroneous isotope responses". A careful analysis of these deviating results shows that either the validity of the carbon isotope discrimination concept is no longer true (Farquhar et al. 1982) or the assumptions for the leaf water enrichment model (Cernusak et al., 2003) are violated and thus both fractionation models are not applicable. In this presentation we discuss such cases when the known fractionation concepts fail and do not allow a correct interpretation of the isotope data. With the help of the dual isotope approach (Scheidegger et al.; 2000) it is demonstrated, how to detect and uncover the causes for such anomalous isotope data. The fractionation concepts and their combinations before the background of CO2 and H2O gas exchange are briefly explained and the specific use of the dual isotope approach for tree ring data analyses and interpretations are demonstrated. References: Cernusak, L. A., Arthur, D. J., Pate, J. S. and Farquhar, G. D.: Water relations link carbon and oxygen isotope discrimination to phloem sap sugar concentration in Eucalyptus globules, Plant Physiol., 131, 1544-1554, 2003. Farquhar, G. D., O'Leary, M. H. and Berry, J. A.: On the relationship between carbon isotope discrimination and the intercellular carbon dioxide concentration in leaves, Aust. J. Plant Physiol., 9, 121-137, 1982. Scheidegger, Y., Saurer, M., Bahn, M. and Siegwolf, R.: Linking stable oxygen and carbon isotopes with stomatal conductance and photosynthetic capacity: A conceptual model

  15. Beam Loss Studies for Rare Isotope Driver Linacs Final Report

    SciTech Connect

    Wangler, T P; Kurennoy, S S; Billen, J H; Crandall, K R; Qiang, J; Ryne, R D; Mustapha, B; Ostroumov, P; Zhao, Q; York, and R. C.

    2008-03-26

    The Fortran 90 RIAPMTQ/IMPACT code package is a pair of linked beam-dynamics simulation codes that have been developed for end-to-end computer simulations of multiple-charge-state heavy-ion linacs for future exotic-beam facilities. These codes have multiple charge-state capability, and include space-charge forces. The simulations can extend from the low-energy beam-transport line after an ECR ion source to the end of the linac. The work has been performed by a collaboration including LANL, LBNL, ANL, and MSU. The code RIAPMTQ simulates the linac front-end beam dynamics including the LEBT, RFQ, and MEBT. The code IMPACT simulates the beam dynamics of the main superconducting linac. The codes have been benchmarked for rms beam properties against previously existing codes at ANL and MSU. The codes allow high-statistics runs on parallel supercomputing platforms, particularly at NERSC at LBNL, for studies of beam losses. The codes also run on desktop PC computers for low-statistics work. The code package is described in more detail in a recent publication [1] in the Proceedings of PAC07 (2007 US Particle Accelerator Conference). In this report we describe the main activities for the FY07 beam-loss studies project using this code package.

  16. A preliminary study of iron isotope fractionation in marine invertebrates (chitons, Mollusca) in near-shore environments

    NASA Astrophysics Data System (ADS)

    Emmanuel, S.; Schuessler, J. A.; Vinther, J.; Matthews, A.; von Blanckenburg, F.

    2014-10-01

    Chitons (Mollusca) are marine invertebrates that produce radulae (teeth or rasping tongues) containing high concentrations of biomineralized magnetite and other iron-bearing minerals. As Fe isotope signatures are influenced by redox processes and biological fractionation, Fe isotopes in chiton radulae might be expected to provide an effective tracer of ambient oceanic conditions and biogeochemical cycling. Here, in a pilot study to measure Fe isotopes in marine invertebrates, we examine Fe isotopes in modern marine chiton radulae collected from different locations in the Atlantic and Pacific oceans to assess the range of isotopic values, and to test whether or not the isotopic signatures reflect seawater values. Values of δ56Fe (relative to IRMM-014) in chiton teeth range from -1.90 to 0.00 ‰ (±0.05‰ (2σ) uncertainty in δ56Fe), probably reflecting a combination of geographical control and biological fractionation processes. Comparison with published local surface seawater Fe isotope data shows a consistent negative offset of chiton teeth Fe isotope compositions relative to seawater. Strikingly, two different species from the same locality in the North Pacific (Puget Sound, Washington, USA) have distinct isotopic signatures. Tonicella lineata, which feeds on red algae in the sublittoral zone, has a mean δ56Fe of -0.65 ± 0.26‰ (2σ, 3 specimens), while Mopalia muscosa, which feeds on both green and red algae in the eulittoral zone, shows lighter isotopic values with a mean δ56Fe of -1.47 ± 0.98‰ (2σ, 5 specimens). Three possible pathways are proposed to account for the different isotopic signatures: (i) physiologically controlled processes within the chitons that lead to species-dependent fractionation; (ii) diet-controlled variability due to different Fe isotope fractionation in the red and green algal food sources; and (iii) environmentally controlled fractionation that causes variation in the isotopic signatures of bioavailable Fe in the different

  17. Decay studies of the highly neutron-deficient indium isotopes

    SciTech Connect

    Wouters, J.M.

    1982-02-01

    An extension of the experimentally known nuclidic mass surface to nuclei far from the region of beta-stability is of fundamental interest in providing a better determination of the input parameters for the various nuclear mass formulae, allowing a more accurate prediction of the ultimate limits of nuclear stability. In addition, a study of the shape of the mass surface in the vicinity of the doubly-closed nuclide /sup 100/Sn provides initial information on the behavior of the shell closure to be expected when Z = N = 50. Experiments measuring the decay energies of /sup 103/ /sup 105/In by ..beta..-endpoint measurements are described with special attention focused on the development of a plastic scintillator ..beta..-telescope coupled to the on-line mass separator RAMA (Recoil Atom Mass Analyzer). An attempt to measure the ..beta..-endpoint energy of /sup 102/In is also briefly described. The experimentally determined decay energies and derived masses for /sup 103/ /sup 105/In are compared with the predictions of different mass models to identify which models are more successful in this region. Furthermore, the inclusion in these comparisons of the available data on the neutron-rich indium nuclei permits a systematic study of their ground state mass behavior as a function of the neutron number between the shell closures at N = 50 and N = 82. These analyses indicate that the binding energy of /sup 103/In is 1 MeV larger than predicted by the majority of the mass models. An examination of the Q/sub EC/ surface and the single- and two-neutron separation energies in the vicinity of /sup 103/ /sup 105/In is also performed to investigate further the deviation and other possible systematic variations in the mass surface in a model-independent way.

  18. A carbon and nitrogen isotope study of carbonaceous vein material in ureilite meteorites

    NASA Technical Reports Server (NTRS)

    Russell, S. S.; Arden, J. W.; Franchi, I. A.; Pillinger, C. T.

    1993-01-01

    The ureilite meteorite group is known to be rich in carbon in the form of graphite/diamond veins that are associated with planetary type noble gases. This paper reports preliminary data from a systematic study of the carbon and nitrogen isotopic composition of this carbonaceous vein material. A previous study focused on the whole rock signatures and reported that the carbon inventory appeared to be dominated by the graphitic/diamond intergrowths, whereas the nitrogen was clearly composed of several distinct components including one that was isotopically light, possibly associated with the carbonaceous material. Recent studies have demonstrated that diamonds in the solar system formed in many different environments. C and N measurements from ureilitic diamond made in a similar way would be a useful addition to this overall study. The methods used for isolating diamonds of possible presolar origin from primitive meteorites are equally applicable to the processing of carbon bearing components in the ureilite group so that their stable isotopic composition can be determined. Herein we discuss conjoint C and N stepped combustion measurements made on crushed whole rock ureilite samples that have been treated with 1M HCl/9M HF to dissolve silicate and free metal. In addition, two samples have been further treated with oxidizing acids to leave a diamond rich residue.

  19. Stable Isotope Biogeochemistry of Seabird Guano Fertilization: Results from Growth Chamber Studies with Maize (Zea Mays)

    PubMed Central

    Szpak, Paul; Longstaffe, Fred J.; Millaire, Jean-François; White, Christine D.

    2012-01-01

    Background Stable isotope analysis is being utilized with increasing regularity to examine a wide range of issues (diet, habitat use, migration) in ecology, geology, archaeology, and related disciplines. A crucial component to these studies is a thorough understanding of the range and causes of baseline isotopic variation, which is relatively poorly understood for nitrogen (δ15N). Animal excrement is known to impact plant δ15N values, but the effects of seabird guano have not been systematically studied from an agricultural or horticultural standpoint. Methodology/Principal Findings This paper presents isotopic (δ13C and δ15N) and vital data for maize (Zea mays) fertilized with Peruvian seabird guano under controlled conditions. The level of 15N enrichment in fertilized plants is very large, with δ15N values ranging between 25.5 and 44.7‰ depending on the tissue and amount of fertilizer applied; comparatively, control plant δ15N values ranged between −0.3 and 5.7‰. Intraplant and temporal variability in δ15N values were large, particularly for the guano-fertilized plants, which can be attributed to changes in the availability of guano-derived N over time, and the reliance of stored vs. absorbed N. Plant δ13C values were not significantly impacted by guano fertilization. High concentrations of seabird guano inhibited maize germination and maize growth. Moreover, high levels of seabird guano greatly impacted the N metabolism of the plants, resulting in significantly higher tissue N content, particularly in the stalk. Conclusions/Significance The results presented in this study demonstrate the very large impact of seabird guano on maize δ15N values. The use of seabird guano as a fertilizer can thus be traced using stable isotope analysis in food chemistry applications (certification of organic inputs). Furthermore, the fertilization of maize with seabird guano creates an isotopic signature very similar to a high-trophic level marine resource, which must

  20. Biometric study using hyperspectral imaging during stress

    NASA Astrophysics Data System (ADS)

    Nagaraj, Sheela; Quoraishee, Shafik; Chan, Gabriel; Short, Kenneth R.

    2010-04-01

    To the casual observer, transient stress results in a variety of physiological changes that can be seen in the face. Although the conditions can be seen visibly, the conditions affect the emissivity and absorption properties of the skin, which imaging spectrometers, commonly referred to as Hyperspectral (HS) cameras, can quantify at every image pixel. The study reported on in this paper, using Hyperspectral cameras, provides a basis for continued study of HS imaging to eventually quantify biometric stress. This study was limited to the visible to near infrared (VNIR) spectral range. Signal processing tools and algorithms have been developed and are described for using HS face data from human subjects. The subjects were placed in psychologically stressful situations and the camera data were analyzed to detect stress through changes in dermal reflectance and emissivity. Results indicate that hyperspectral imaging may potentially serve as a non-invasive tool to measure changes in skin emissivity indicative of a stressful incident. Particular narrow spectral bands in the near-infrared region of the electromagnetic spectrum seem especially important. Further studies need to be performed to determine the optimal spectral bands and to generalize the conclusions. The enormous information available in hyperspectral imaging needs further analysis and more spectral regions need to be exploited. Non-invasive stress detection is a prominent area of research with countless applications for both military and commercial use including border patrol, stand-off interrogation, access control, surveillance, and non-invasive and un-attended patient monitoring.

  1. Imaging study of the painful heel syndrome

    SciTech Connect

    Williams, P.L.; Smibert, J.G.; Cox, R.; Mitchell, R.; Klenerman, L.

    1987-06-01

    A total of 45 patients with the painful heel syndrome without evidence of an associated inflammatory arthritis, seven of whom had pain in both heels, were studied using technetium-99 isotope bone scans and lateral and 45 degrees medial oblique radiographs of both feet. Of the 52 painful heels 31 (59.6%) showed increased uptake of tracer at the calcaneum. Patients with scans showing increased uptake tended to have more severe heel pain and responded more frequently to a local hydrocortisone injection. On plain x-ray, 39 of 52 painful heels (75%) and 24 of the 38 opposite nonpainful heels (63%) showed plantar spurs, compared with five of 63 (7.9%) heels in 59 age- and sex-matched controls. No evidence of stress fractures was seen.

  2. Lunar Crustal History from Isotopic Studies of Lunar Anorthosites

    NASA Technical Reports Server (NTRS)

    Nyquist, Laurence E.; Shih, C.-Y.; Bogard, D. D.; Yamaguchi, A.

    2010-01-01

    Anorthosites occur ubiquitously within the lunar crust at depths of approx.3-30 km in apparent confirmation of the Lunar Magma Ocean (LMO) hypothesis. [1]. We will present recent chronological studies of anorthosites [2] that are relevant both to the LMO hypothesis and also to the lunar cataclysm hypothesis. Old (approx.4.4 Ga) Sm-Nd ages have been determined for some Apollo 16 anorthosites, and primitive initial Sr-87/Sr-86 ratios have been measured for several, but well-defined Rb-Sr ages concordant with the Sm-Nd ages have not been determined until now. Lunar anorthosite 67075, a Feldspathic Fragmental Breccia (FFB) collected near the rim of North Ray Crater, has concordant Sm-Nd and Rb-Sr ages of 4.47+/-0.07 Ga and 4.49+/-0.07 Ga, respectively. Initial Nd-143/Nd-144 determined from the Sm-Nd isochron corresponds to E(sub Nd,CHUR) = 0.3+/-0.5 compared to a Chondritic Uniform Reservoir, or E(sub Nd,HEDPB) = -0.6+/-0.5 compared to the initial Nd-143/Nd-144 of the HED Parent Body [3]. Lunar anorthosites tend to have E(sub Nd) > 0 when compared to CHUR, apparently inconsistent with derivation from a single lunar magma ocean. Although E(sub Nd) < 0 for some anorthosites, if lunar initial Nd-143/Nd-144 is taken equal to HEDR for the HED parent body [3], enough variability remains among the anorthosite data alone to suggest that lunar anorthosites do not derive from a single source, i.e., they are not all products of the LMO. An anorthositic clast from desert meteorite Dhofar 908 has an Ar-39-Ar-40 age of 4.42+/-0.04 Ga, the same as the 4.36-4.41+/-0.035 Ga Ar-39-Ar-40 age of anorthositic clast Y-86032,116 in Antarctic meteorite Yamato- 86032 [3,4]. Conclusions: (i) Lunar anorthosites come from diverse sources. Orbital geochemical studies confirm variability in lunar crustal composition [1, 5]. We suggest that the variability extends to anorthosites alone as shown by the Sm-Nd data (Fig. 2) and the existence of magnesian anorthosites (MAN, [6]) and "An93 anorthosites

  3. Fundamental Symmetries and Interactions Studied with Radioactive Isotopes in Atom Traps

    SciTech Connect

    Wilschut, H.W.

    2005-11-21

    The structure of certain nuclei and atoms allow one to study fundamental symmetries and interactions. In this review we consider the search for Time-Reversal invariance Violation (TRV). We consider two options: TRV in {beta} decay or the search for the forbidden Electric Dipole Moment (EDM). In both cases atomic trapping can be an appropriate tool. For {beta} decay radioactive isotopes are necessary, but also for EDM searches they appear to be useful.

  4. Stable isotope studies. Final report, March 1, 1972--February 29, 1992

    SciTech Connect

    Ishida, T.

    1992-10-01

    The research has been in four general areas: (1) correlation of isotope effects with molecular forces and molecular structures, (2) correlation of zero-point energy and its isotope effects with molecular structure and molecular forces, (3) vapor pressure isotope effects, and (4) fractionation of stable isotopes. 73 refs, 38 figs, 29 tabs.

  5. Study of medical isotope production facility stack emissions and noble gas isotopic signature using automatic gamma-spectra analysis platform

    NASA Astrophysics Data System (ADS)

    Zhang, Weihua; Hoffmann, Emmy; Ungar, Kurt; Dolinar, George; Miley, Harry; Mekarski, Pawel; Schrom, Brian; Hoffman, Ian; Lawrie, Ryan; Loosz, Tom

    2013-04-01

    The nuclear industry emissions of the four CTBT (Comprehensive Nuclear-Test-Ban Treaty) relevant radioxenon isotopes are unavoidably detected by the IMS along with possible treaty violations. Another civil source of radioxenon emissions which contributes to the global background is radiopharmaceutical production companies. To better understand the source terms of these background emissions, a joint project between HC, ANSTO, PNNL and CRL was formed to install real-time detection systems to support 135Xe, 133Xe, 131mXe and 133mXe measurements at the ANSTO and CRL 99Mo production facility stacks as well as the CANDU (CANada Deuterium Uranium) primary coolant monitoring system at CRL. At each site, high resolution gamma spectra were collected every 15 minutes using a HPGe detector to continuously monitor a bypass feed from the stack or CANDU primary coolant system as it passed through a sampling cell. HC also conducted atmospheric monitoring for radioxenon at approximately 200 km distant from CRL. A program was written to transfer each spectrum into a text file format suitable for the automatic gamma-spectra analysis platform and then email the file to a server. Once the email was received by the server, it was automatically analysed with the gamma-spectrum software UniSampo/Shaman to perform radionuclide identification and activity calculation for a large number of gamma-spectra in a short period of time (less than 10 seconds per spectrum). The results of nuclide activity together with other spectrum parameters were saved into the Linssi database. This database contains a large amount of radionuclide information which is a valuable resource for the analysis of radionuclide distribution within the noble gas fission product emissions. The results could be useful to identify the specific mechanisms of the activity release. The isotopic signatures of the various radioxenon species can be determined as a function of release time. Comparison of 133mXe and 133Xe activity

  6. Feasibility study on the medical isotopes production with solution target using OSTR: (99)Mo and related isotopes

    NASA Astrophysics Data System (ADS)

    Baik, Seung-Hyuk

    1999-11-01

    Molybdenum-99 (99Mo) is the parent nuclide of Technetium-99m (99mTc), a radioisotope which is widely used in nuclear medicine. 99Mo is produced from the fission of 235U or the irradiation of 98Mo. This study shows the feasibility of the using an 'aqueous homogeneous uranium solution target' for the production of a medical isotope, 99Mo. Some of the advantages that the solution target has over a solid target include the inherent reactor safety features offered by large negative temperature and power reactivity coefficients, the fabrication convenience, the straightforward extraction process, and a low volume of waste generated. To evaluate the core configuration and the production rate of 99Mo, a three-dimensional model of the Oregon State University TRIGA Reactor (OSTR) core was developed for use with the Monte Carlo N-Particle Transport Code (MCNP) and then verified by comparing with the measured values. Two values are in good agreement within one percent in the keffective values calculated. Two types of solution targets are analyzed for the OSTR. The first one has the same outer-dimensions as an OSTR fuel element but is filled with a uranium solution. The other is the continuous flow target system (CFTS) like solution fuel reactors. Uranyl nitrate and uranyl sulfate solutions enriched to 20% or 93% are investigated as a target material without raising any safety concern to the OSTR operation. A seven-day irradiation of ten tube-type-93% enriched uranyl nitrate solution targets would produce 43% of the 99Mo required in the US for one week. The CFTS would generate 31% of the required 99Mo in a 7-day cycle. The conceptual chemical extraction processes for irradiated solution targets are developed. This work also includes an analysis of nuclear safety issues such as the radiolytic gas, thermal hydraulics, the waste, and the radiological impacts of an accident. The production of 99Mo in the OSTR with the uranium solution is technically feasible as demonstrated in this

  7. Isotopic study of mercury sources and transfer between a freshwater lake and adjacent forest food web.

    PubMed

    Kwon, Sae Yun; Blum, Joel D; Nadelhoffer, Knute J; Timothy Dvonch, J; Tsui, Martin Tsz-Ki

    2015-11-01

    Studies of monomethylmercury (MMHg) sources and biogeochemical pathways have been extensive in aquatic ecosystems, but limited in forest ecosystems. Increasing evidence suggests that there is significant mercury (Hg) exchange between aquatic and forest ecosystems. We use Hg stable isotope ratios (δ(202)Hg and Δ(199)Hg) to investigate the relative importance of MMHg sources and assess Hg transfer pathways between Douglas Lake and adjacent forests located at the University of Michigan Biological Station, USA. We characterize Hg isotopic compositions of basal resources and use linear regression of % MMHg versus δ(202)Hg and Δ(199)Hg to estimate Hg isotope values for inorganic mercury (IHg) and MMHg in the aquatic and adjacent forest food webs. In the aquatic ecosystem, we found that lake sediment represents a mixture of IHg pools deposited via watershed runoff and precipitation. The δ(202)Hg and Δ(199)Hg values estimated for IHg are consistent with other studies that measured forest floor in temperate forests. The Δ(199)Hg value estimated for MMHg in the aquatic food web indicates that MMHg is subjected to ~20% photochemical degradation prior to bioaccumulation. In the forest ecosystem, we found a significant negative relationship between total Hg and δ(202)Hg and Δ(199)Hg of soil collected at multiple distances from the lakeshore and lake sediment. This suggests that IHg input from watershed runoff provides an important Hg transfer pathway between the forest and aquatic ecosystems. We measured Δ(199)Hg values for high trophic level insects and compared these insects at multiple distances perpendicular to the lake shoreline. The Δ(199)Hg values correspond to the % canopy cover suggesting that forest MMHg is subjected to varying extents of photochemical degradation and the extent may be controlled by sunlight. Our study demonstrates that the use of Hg isotopes adds important new insight into the relative importance of MMHg sources and complex Hg transfer

  8. Insights into iron sources and pathways in the Amazon River provided by isotopic and spectroscopic studies

    NASA Astrophysics Data System (ADS)

    Mulholland, Daniel Santos; Poitrasson, Franck; Boaventura, Geraldo Resende; Allard, Thierry; Vieira, Lucieth Cruz; Santos, Roberto Ventura; Mancini, Luiz; Seyler, Patrick

    2015-02-01

    The present study investigated the weathering and transport mechanisms of Fe in the Amazon River. A particular emphasis was placed on Fe partitioning, speciation, and isotopic fractionation in the contrasting waters of the Solimões and Negro rivers and their mixing zone at the beginning of the Amazon River. Samples collected in the end-member rivers and thirteen sites distributed throughout the mixing zone were processed through frontal vacuum filtration and tangential-flow ultrafiltration to separate the different suspended solid fractions, i.e., particulate (P > 0.45 μm and P > 0.22 μm), colloidal (0.22 μm > C > 5 kDa) and truly dissolved elements (TD < 5 kDa). The Fe isotopic composition and electron paramagnetic resonance (EPR) species were measured on these different pore-sized fractions. The acidic and organo-Fe-rich waters of the Negro River displayed dissolved and colloidal fractions enriched in heavy isotopes (∼1.2‰, in δ57Fe values relative to IRMM-14), while the particulate fractions yielded light isotopic compositions of -0.344‰ for P > 0.22 μm and -0.104‰ for P > 0.45 μm fractions). The mineral particulate-rich waters of the Solimões River had dissolved and colloidal fractions with light isotopic composition (-0.532‰ and -0.176‰, respectively), whereas the particulate fractions yielded δ57Fe values close to those of the continental crust (i.e., -0.029‰ for P > 0.22 μm and 0.028‰ for P > 0.45 μm). Ten kilometers downstream from the Negro and Solimões junction, the concentrations of colloidal and dissolved Fe species deviate markedly from conservative mixing. A maximum Fe loss of 43 μg/L (i.e., 50% of the dissolved and colloidal Fe) is observed 110 km downstream from the rivers junction. The contrasting Negro and Solimões Rivers isotopic compositions along the pore-sized water fractions is attributable to the biogeochemical processes involving different types of upland soils and parental materials. For instance, the isotopic

  9. Isotopic effects of nitrate photochemistry in snow: A field study at Dome C, Antarctica

    NASA Astrophysics Data System (ADS)

    Berhanu, T. A.; Erbland, J.; Savarino, J. P.

    2012-12-01

    Nitrate (NO3-) is the end product of NOx (NO+NO2) oxidation in the atmosphere and one of the most abundant anions present in the Antarctic snow pack. The comprehensive isotopic composition of nitrate (δ18O, Δ17O and δ15N) obtained from deep ice-cores may provide valuable information regarding the oxidative capacity of the atmosphere and could provide constraints on the global NOx budget. Nitrogen stable isotope ratios are typically thought to trace NOx sources while oxygen isotope ratios convey quantitative information regarding the oxidation pathways leading to nitrate formation. However, nitrate deposited at low accumulation sites in Polar Regions such as Dome C, Antarctica, is exposed to post depositional processes that modify its original isotopic composition. Among these processes, photolysis has been identified as the most significant mechanism leading to large nitrate mass loss and isotopic fractionation. Emission of NOx and OH from photolysis of nitrate, as well as formation of by-products such as HONO, can have a significant impact on the overlying boundary layer chemistry of polar regions. The quantitative effect of photolysis on the isotopic signature of nitrate is presently not well constrained and previous experimental and modelling studies have resulted in differing conclusions regarding the role of photolysis in the post processing of nitrate deposited to snow. In order to quantify the effect of photolysis on the isotopic composition of nitrate in snow, we have conducted a field study at Dome C, Antarctica. In this study, two snow sampling fields (1m wide, 2m long and 0.5m deep) within close proximity of each other were studied for the effect of UV light using a plexi glass filter experiment. The two fields were filled with wind blown snow at the beginning of December 2011 and then covered with plexi glass sheets. One of these sheets was equipped with a UV filter. Sampling was conducted every 10 days at a 2-5 cm depth resolution during the period

  10. Isotope-edited proton NMR study on the structure of a pepsin/inhibitor complex

    SciTech Connect

    Fesik, S.W.; Luly, J.R.; Erickson, J.W.; Abad-Zapatero, C.

    1988-11-01

    A general approach is illustrated for providing detailed structural information on large enzyme/inhibitor complexes using NMR spectroscopy. The method involves the use of isotopically labeled ligands to simplify two-dimensional NOE spectra of large molecular complexes by isotope-editing techniques. With this approach, the backbone and side-chain conformations (at the P/sub 2/ and P/sub 3/ sites) of a tightly bound inhibitor of porcine pepsin have bene determined. In addition, structural information on the active site of pepsin has been obtained. Due to the sequence homology between porcine pepsin and human renin, this structural information may prove useful for modeling renin/inhibitor complexes with the ultimate goal of designing more effective renin inhibitors. Moreover, this general approach can be applied to study other biological systems of interest such as other enzyme/inhibitor complexes, ligands bound to soluble receptors, and enzyme/substrate interactions.

  11. Study of nuclear structure of 76-86Sr isotopes in the pn interacting boson model

    NASA Astrophysics Data System (ADS)

    Saxena, M.; Gupta, J. B.; Mandal, S.

    2015-08-01

    The proton neutron interacting boson model (IBM-2) has been used to make a systematic study of Strontium isotopes in this mass region of A ˜ 80 with 38 ≤slant N ≤slant 48 and Z = 38. The three-term Talmi-Otsuka general Hamiltonian in the framework of the neutron proton version of the Interaction boson model was used to perform the calculations. The yrast levels energy are reproduced. The beta and gamma band energy levels also matched well. The reduced transition probabilities were also calculated and were found to be in agreement with the experimental values. In addition, g-factor for the {2}1+ state was evaluated. Possible candidates for mixed symmetry states were also predicted for several nuclei in this isotopic chain.

  12. A radiogenic isotope tracer study of transatlantic dust transport from Africa to the Caribbean

    USGS Publications Warehouse

    Kumar, A.; Abouchami, W.; Galer, S.J.G.; Garrison, V.H.; Williams, E.; Andreae, M.O.

    2014-01-01

    Many studies have suggested that long-range transport of African desert dusts across the Atlantic Ocean occurs, delivering key nutrients and contributing to fertilization of the Amazon rainforest. Here we utilize radiogenic isotope tracers – Sr, Nd and Pb – to derive the provenance, local or remote, and pathways of dust transport from Africa to the Caribbean. Atmospheric total suspended particulate (TSP) matter was collected in 2008 on quartz fibre filters, from both sides of the Atlantic Ocean at three different locations: in Mali (12.6°N, 8.0°W; 555 m a.s.l.), Tobago (11.3°N, 60.5°W; 329 m a.s.l.) and the U.S. Virgin Islands (17.7°N, 64.6°W; 27 m a.s.l.). Both the labile phase, representative of the anthropogenic signal, and the refractory detrital silicate fraction were analysed. Dust deposits and soils from around the sampling sites were measured as well to assess the potential contribution from local sources to the mineral dust collected. The contribution from anthropogenic sources of Pb was predominant in the labile, leachate phase. The overall similarity in Pb isotope signatures found in the leachates is attributed to a common African source of anthropogenic Pb, with minor inputs from other sources, such as from Central and South America. The Pb, Sr and Nd isotopic compositions in the silicate fraction were found to be systematically more radiogenic than those in the corresponding labile phases. In contrast, Nd and Sr isotopic compositions from Mali, Tobago, and the Virgin Islands are virtually identical in both leachates and residues. Comparison with existing literature data on Saharan and Sahelian sources constrains the origin of summer dust transported to the Caribbean to mainly originate from the Sahel region, with some contribution from northern Saharan sources. The source regions derived from the isotope data are consistent with 7-day back-trajectory analyses, demonstrating the usefulness of radiogenic isotopes in tracing dust provenance and

  13. Isotope effect studies of the chemical mechanism of pig heart NADP isocitrate dehydrogenase

    SciTech Connect

    Grissom, C.B.; Cleland, W.W.

    1988-04-19

    The catalytic mechanism of porcine heart NADP isocitrate dehydrogenase has been investigated by use of the variation of deuterium and /sup 13/C kinetic isotope effects with pH. The observed /sup 13/C isotope effect on VK for isocitrate increases from 1.0038 at neutral pH to a limiting value of 1.040 at low pH. The limiting /sup 13/C isotope effect with deuteriated isocitrate at low pH is 1.016. This decrease in /sup 13/(VK/sub Ic/) upon deuteriation indicates a stepwise mechanism for the oxidation and decarboxylation of isocitrate. This predicts a deuterium isotope effect on VK of 2.9, but /sup D/(VK) at low pH only increases to a maximum of 1.08. The pK seen in the /sup 13/(VK/sub Ic/) pH profile for isocitrate if 4.5. This pK is displaced 1.2 pH units from the true pK of the acidbase functionality of 5.7 seen in the pK/sub i/ profile for oxalylglycine. From this displacement, catalysis is estimated to be 16 times faster than substrate dissociation. By use of the pH-dependent partitioning ratio of the reaction intermediate oxalosuccinate between decarboxylation to 2-ketoglutarate and reduction to isocitrate, the forward commitment to catalysis for decarboxylation was determined to be 7.3 at pH 5.4 and 3.2 at pH 5.0. This gives in intrinsic /sup 13/C isotope effect for decarboxylation of 1.050. The product of oxidative decarboxylation of 3-hydroxyisocitrate by NADP isocitrate dehydrogenase is 2-hydroxy-3-ketoglutarate. This results from enzymatic protonation of the cis-enediol intermediate at C/sub 2/ rather than C/sub 3/ (as seen with isocitrate and 3-fluoroisocitrate). 2-Hydroxy-3-ketoglutarate further decarboxylates in solution to 2-hydroxy-3-ketobutyrate, which further decarboxylates to acetol. This makes 3-hydroxyisocitrate unsuitable for /sup 13/C isotope effect studies.

  14. Quantum Dynamics Study of the Isotopic Effect on Capture Reactions: HD, D2 + CH3

    NASA Technical Reports Server (NTRS)

    Wang, Dunyou; Kwak, Dochan (Technical Monitor)

    2002-01-01

    Time-dependent wave-packet-propagation calculations are reported for the isotopic reactions, HD + CH3 and D2 + CH3, in six degrees of freedom and for zero total angular momentum. Initial state selected reaction probabilities for different initial rotational-vibrational states are presented in this study. This study shows that excitations of the HD(D2) enhances the reactivities; whereas the excitations of the CH3 umbrella mode have the opposite effects. This is consistent with the reaction of H2 + CH3. The comparison of these three isotopic reactions also shows the isotopic effects in the initial-state-selected reaction probabilities. The cumulative reaction probabilities (CRP) are obtained by summing over initial-state-selected reaction probabilities. The energy-shift approximation to account for the contribution of degrees of freedom missing in the six dimensionality calculation is employed to obtain approximate full-dimensional CRPs. The rate constant comparison shows H2 + CH3 reaction has the biggest reactivity, then HD + CH3, and D2 + CH3 has the smallest.

  15. A study of stable isotopic variations of Antarctic snow by albedo differences

    NASA Astrophysics Data System (ADS)

    Lee, Jeonghoon; Han, Yeongcheol; Ham, Ji-Young; Kim, Young-Hee; Kim, Songyi; Kim, Hyerin; Na, Un-Sung

    2015-04-01

    Snow's albedo can be decreased if there are any impurities on the snow surface other than snow itself. Due to the decrease of albedo of snow, melting rates of surface snow can be enhanced, which is very crucial in climate change and hydrogeology in many parts of the world. Anthropogenic black carbons caused by the incomplete combustion of fossil fuel affect on snow and tephra particles generated by geologic volcanic activities reduce snow albedo. In this study, we investigated isotopic compositions between snow covered by tephra particles and clean snow. Isotopic compositions of snow with tephra statistically shows more enriched than those of clean snow (p<0.02). This can be explained by the fact that snow becomes enriched in 18O or D relative to meltwater as melting rates are increased. In addition, the slopes of the linear regression between oxygen and hydrogen for snow with tephra and clean snow are 6.7 and 8, respectively, and the latter is similar to that of the global meteoric water line of 8. Therefore, we can conclude that snow impurities control the isotopic compositions of snow, which is very crucial in the study of climate change and hydrogeology. To quantitatively explain these observations, melting experiments and numerical approaches are required.

  16. Final Progress Report: Isotope Identification Algorithm for Rapid and Accurate Determination of Radioisotopes Feasibility Study

    SciTech Connect

    Rawool-Sullivan, Mohini; Bounds, John Alan; Brumby, Steven P.; Prasad, Lakshman; Sullivan, John P.

    2012-04-30

    This is the final report of the project titled, 'Isotope Identification Algorithm for Rapid and Accurate Determination of Radioisotopes,' PMIS project number LA10-HUMANID-PD03. The goal of the work was to demonstrate principles of emulating a human analysis approach towards the data collected using radiation isotope identification devices (RIIDs). It summarizes work performed over the FY10 time period. The goal of the work was to demonstrate principles of emulating a human analysis approach towards the data collected using radiation isotope identification devices (RIIDs). Human analysts begin analyzing a spectrum based on features in the spectrum - lines and shapes that are present in a given spectrum. The proposed work was to carry out a feasibility study that will pick out all gamma ray peaks and other features such as Compton edges, bremsstrahlung, presence/absence of shielding and presence of neutrons and escape peaks. Ultimately success of this feasibility study will allow us to collectively explain identified features and form a realistic scenario that produced a given spectrum in the future. We wanted to develop and demonstrate machine learning algorithms that will qualitatively enhance the automated identification capabilities of portable radiological sensors that are currently being used in the field.

  17. Studying the Permian cross-section (Volga region) using chemical and isotopic investigations

    NASA Astrophysics Data System (ADS)

    Gareev, Bulat; Georgii, Batalin; Nurgaliev, Danis; Nurgalieva, Nuriya

    2016-04-01

    This paper presents a study of international important site: the cross-section of Permian system's Urzhumian Stage in the ravine "Pechischy". Outcrop is located on the right bank of the Volga River (about 10 km West of Kazan). It has local, regional and planetary correlation features and also footprints of different geographical scale events. The main objective in the research is the deep study of sediments using chemical and isotopic investigations. XRF spectrometer was used for chemical investigations of samples. Chemistry of carbonates and clastic rocks includes the analysis of chemical elements, compounds, petrochemical (lithogeochemical) modules for the interpretation of the genesis of lithotypes. For the review of the geochemistry of stable isotopes of carbon (oxygen) we used IRMS. The main objective is the nature of the isotope fractionation issues, to addressing the issues of stratigraphy and paleogeography. The measurements have shown the variability of chemical parameters in cross-section. It gives us opportunity to see small changes in sedimentation and recognize the factors that influence to the process. The work was carried out according to the Russian Government's Program of Competitive Growth of Kazan Federal University, supported by the grant provided to the Kazan State University for performing the state program in the field of scientific research.

  18. Study of Density and Structure of Oxygen Isotopes with the Cluster-Orbital Shell Model Approach

    NASA Astrophysics Data System (ADS)

    Masui, Hiroshi; Kato, Kiyoshi; Ikeda, Kiyomi

    2009-10-01

    We study structure of oxygen isotopes through the analysis of the density and the s-wave contribution. From experiments, the r.m.s.radius of oxygen isotopes has an abrupt increase at ^23O from the empirical A^1/3-low. However, as we have shown with the calculation by using our m-scheme cluster-orbital shell model (COSM) approach, such the abrupt increase can hardly be reproduced only by considering the valence nucleon degree of freedom. In our COSM approach, we construct the core-N Hamiltonian using a semi-microscopic approach by taking into account the Pauli principle for the nucleons in the core. As the nucleon-nucleon potential, we use Volkov No.2 potential. The parameters of the potential are adjusted so as to reproduce the ^16O+2n threshold. Using the potential model described above, however, we obtain the over bound nature as the number of valence nucleon increase. Hence, we perform calculations using slightly weaker potential strength for the valence neutrons so as to reproduce the drip-line at ^24O. In this study, we discuss the density distributions of the isotopes and the contributions of partial waves especially the s-wave.

  19. Stable isotope study of fluid inclusions in fluorite from Idaho: implications for continental climates during the Eocene

    USGS Publications Warehouse

    Seal, R.R., II; Rye, R.O.

    1993-01-01

    Isotopic studies of fluid inclusions from meteoric water-dominated epithermal ore deposits offer a unique opportunity to study paleoclimates because the fluids can provide direct samples of ancient waters. Fluorite-hosted fluid inclusions from the Eocene (51-50 Ma) epithermal deposits of the Bayhorse mining district, have low salinities and low to moderate homogenization temperatures indicating meteoric origins for the fluids. Oxygen and hydrogen isotope data on inclusion fluids are almost identical to those of modern meteoric waters in the area. The equivalence of the isotope composition of the Eocene inclusion fluids and modern meteoric waters indicates that the Eocene climatic conditions were similar to those today. -from Authors

  20. Sr isotopic characteristics in two small watersheds draining typical silicate and carbonate rocks: implication for the studies on seawater Sr isotopic evolution

    NASA Astrophysics Data System (ADS)

    Wu, W. H.; Zheng, H. B.; Yang, J. D.

    2013-06-01

    We systematically investigated Sr isotopic characteristics of small silicate watershed - the tributary Xishui River of the Yangtze River, and small carbonate watershed - the tributary Guijiang River of the Pearl River. The results show that the Xishui River has relatively high Sr concentrations (0.468-1.70 μmol L-1 in summer and 1.30-3.17 μmol L-1 in winter, respectively) and low 87Sr/86Sr ratios (0.708686-0.709148 in summer and 0.708515-0.709305 in winter), which is similar to the characteristics of carbonate weathering. The Guijiang River has low Sr concentrations (0.124-1.098 μmol L-1) and high 87Sr/86Sr ratios (0.710558-0.724605), being characterized by silicate weathering. In the Xishui River catchment, chemical weathering rates in summer are far higher than those in winter, indicating significant influence of climate regime. However, slight differences of 87Sr/86Sr ratios between summer and winter show that influence of climate on Sr isotope is uncertainty owing to very similar Sr isotope values in silicate and carbonate bedrocks. As 87Sr/86Sr ratios in the Xishui River are lower than those in seawater, they will decrease 87Sr/86Sr ratio of seawater after transported into oceans. Previous studies also showed that some basaltic watersheds with extremely high chemical weathering rates reduced the seawater Sr isotope ratios. In other words, river catchments with high silicate weathering rates do not certainly transport highly radiogenic Sr into oceans. Therefore, it may be questionable that using the variations of seawater 87Sr/86Sr ratio to indicate the continental silicate weathering intensity. In the Guijiang River catchment, 87Sr/86Sr ratios of carbonate rocks and other sources (rainwater, domestic and industrial waste water, and agricultural fertilizer) are lower than 0.71. In comparison, some non-carbonate components, such as, sand rocks, mud rocks, shales, have relatively high Sr isotopic compositions. Moreover, granites accounted for only 5% of the

  1. Inductively coupled plasma mass spectrometry for stable isotope metabolic tracer studies of living systems

    SciTech Connect

    Luong, E.

    1999-05-10

    This dissertation focuses on the development of methods for stable isotope metabolic tracer studies in living systems using inductively coupled plasma single and dual quadrupole mass spectrometers. Sub-nanogram per gram levels of molybdenum (Mo) from human blood plasma are isolated by the use of anion exchange alumina microcolumns. Million-fold more concentrated spectral and matrix interferences such as sodium, chloride, sulfate, phosphate, etc. in the blood constituents are removed from the analyte. The recovery of Mo from the alumina column is 82 {+-} 5% (n = 5). Isotope dilution inductively coupled plasma mass spectrometry (ID-ICP-MS) is utilized for the quantitative ultra-trace concentration determination of Mo in bovine and human blood samples. The average Mo concentration in reference bovine serum determined by this method is 10.2 {+-} 0.4 ng/g, while the certified value is 11.5 {+-} 1.1 ng/g (95% confidence interval). The Mo concentration of one pool of human blood plasma from two healthy male donors is 0.5 {+-} 0.1 ng/g. The inductively coupled plasma twin quadrupole mass spectrometer (ICP-TQMS) is used to measure the carbon isotope ratio from non-volatile organic compounds and bio-organic molecules to assess the ability as an alternative analytical method to gas chromatography combustion isotope ratio mass spectrometry (GC-combustion-IRMS). Trytophan, myoglobin, and {beta}-cyclodextrin are chosen for the study, initial observation of spectral interference of {sup 13}C{sup +} with {sup 12}C{sup 1}H{sup +} comes from the incomplete dissociation of myoglobin and/or {beta}-cyclodextrin.

  2. Bibliography of geologic studies using imaging radar

    NASA Technical Reports Server (NTRS)

    Bryan, M. L.

    1979-01-01

    Articles concerning imaging studies on the geomorphology, mineralogy, and topology of various landforms are reported. One hundred and ninety citations are listed and an index by National Technical Information service citation number is included. Several illustrations of L-band radar imagery are presented.

  3. Laboratory Study of Nitrate Photolysis in Antarctic Snow: Quantum Yield and Isotope Effects

    NASA Astrophysics Data System (ADS)

    Meusinger, C.; Berhanu, T. A.; Erbland, J.; Jost, R.; Bhattacharya, S. K.; Savarino, J. P.; Johnson, M. S.

    2013-12-01

    Post-depositional processes alter the nitrate concentration and its isotopic composition in the top layers of snow at low snow accumulation sites, such as Dome C, Antarctica. Available nitrate ice core records can provide input for studying past atmospheres and climate if such processes are understood. Photolysis of nitrate in the snowpack was shown to be the major nitrate loss mechanism from the snowpack. Here a laboratory study is presented that uses snow from Dome C and minimizes effects of desorption by flushing the snow with pure N2 at 100 % humidity during irradiation with UV light from a Xenon lamp. A selection of UV filters allowed examination of the 200 and 300 nm absorption bands of nitrate and to emulate actinic fluxes similar to those in Dome C. Irradiated snow was sampled in 1 cm sections and analyzed for nitrate concentration and isotopic composition (δ15N, δ18O and Δ17O); the actinic flux was measured at similar sections in the snow. The quantum yield was observed to decrease from 0.44 to 0.05 within what corresponds to weeks of UV exposure in Antarctica. The superposition of photolysis in two photochemical domains of nitrate in snow is proposed: one of photolabile nitrate and one of trapped or buried nitrate. The difference lies in the ability of reaction products to escape the snow crystal, versus undergoing secondary (recombination) chemistry. Modeled NOx emissions may be increased significantly due to the observed quantum yield in this study influencing predicted boundary layer chemistry including ozone concentrations. An average photolytic isotopic fractionation of 15ɛ = -15×1.2 ‰ was found for the experiments without a wavelength filter. These results are ascribed to excitation of the 200 nm nitrate absorption band. Blocking wavelengths shorter than 320 nm, approximating the actinic flux spectrum at Dome C, showed a photolytic fractionation constant of 15ɛ = -47.9 × 6.8 ‰ which lies within the fractionation determined in the field

  4. Magnetic source imaging studies of dyslexia interventions.

    PubMed

    Simos, Panagiotis G; Fletcher, Jack M; Denton, Carolyn; Sarkari, Shirin; Billingsley-Marshall, Rebecca; Papanicolaou, Andrew C

    2006-01-01

    Rapidly accumulating evidence from functional brain imaging studies indicates that developmental reading disability is associated with a functional disruption of the brain circuits that normally develop to support reading-related processes. This article briefly overviews recent advances in methods that capture the anatomical outline and temporal (dynamic) features of regional brain activation during performance of reading tasks. One of these methods, magnetoencephalography (MEG) or magnetic sources imaging (MSI) is described in more detail in the context of investigations of changes in spatiotemporal patterns of brain activity associated with improvement in reading skills in response to various types of educational interventions. PMID:16925476

  5. Estimating niche width using stable isotopes in the face of habitat variability: a modelling case study in the marine environment.

    PubMed

    Cummings, David O; Buhl, Jerome; Lee, Raymond W; Simpson, Stephen J; Holmes, Sebastian P

    2012-01-01

    Distributions of stable isotopes have been used to infer an organism's trophic niche width, the 'isotopic niche', and examine resource partitioning. Spatial variation in the isotopic composition of prey may however confound the interpretation of isotopic signatures especially when foragers exploit resources across numerous locations. In this study the isotopic compositions from marine assemblages are modelled to determine the role of variation in the signature of prey items and the effect of dietary breadth and foraging strategies on predator signatures. Outputs from the models reveal that isotopic niche widths can be greater for populations of dietary specialists rather than for generalists, which contravenes what is generally accepted in the literature. When a range of different mixing models are applied to determine if the conversion from δ to p-space can be used to improve model accuracy, predator signature variation is increased rather than model precision. Furthermore the mixing models applied failed to correctly identify dietary specialists and/or to accurately estimate diet contributions that may identify resource partitioning. The results presented illustrate the need to collect sufficiently large sample sizes, in excess of what is collected under most current studies, across the complete distribution of a species and its prey, before attempts to use stable isotopes to make inferences about niche width can be made. PMID:22876280

  6. Image spectroscopy and stable isotopes elucidate functional dissimilarity between native and nonnative plant species in the aquatic environment.

    PubMed

    Santos, Maria J; Hestir, Erin L; Khanna, Shruti; Ustin, Susan L

    2012-02-01

    • Nonnative species may change ecosystem functionality at the expense of native species. Here, we examine the similarity of functional traits of native and nonnative submersed aquatic plants (SAP) in an aquatic ecosystem. • We used field and airborne imaging spectroscopy and isotope ratios of SAP species in the Sacramento-San Joaquin Delta, California (USA) to assess species identification, chlorophyll (Chl) concentration, and differences in photosynthetic efficiency. • Spectral separability between species occurs primarily in the visible and near-infrared spectral regions, which is associated with morphological and physiological differences. Nonnatives had significantly higher Chl, carotene, and anthocyanin concentrations than natives and had significantly higher photochemical reflectance index (PRI) and δ(13) C values. • Results show nonnative SAPs are functionally dissimilar to native SAPs, having wider leaf blades and greater leaf area, dense and evenly distributed vertical canopies, and higher pigment concentrations. Results suggest that nonnatives also use a facultative C(4) -like photosynthetic pathway, allowing efficient photosynthesis in high-light and low-light environments. Differences in plant functionality indicate that nonnative SAPs have a competitive advantage over native SAPs as a result of growth form and greater light-use efficiency that promotes growth under different light conditions, traits affecting system-wide species distributions and community composition. PMID:22126662

  7. LaBr3:Ce small FOV gamma camera with excellent energy resolution for multi-isotope imaging

    NASA Astrophysics Data System (ADS)

    Pani, R.; Fabbri, A.; Cinti, M. N.; Orlandi, C.; Pellegrini, R.; Scafè, R.; Artibani, M.

    2015-06-01

    The simultaneous administration of radiopharmaceuticals labeled with more than one radioisotope is becoming of increasing interest in clinical practice. Because the photon energies of the utilized radioisotopes could be very close (less than 15% difference), a gamma camera with adequate energy resolution is required. The availability of scintillation crystals with high light yield, as lanthanum tri-bromide (LaBr3:Ce), is particularly appealing for these applications. In this work, a new small field of view gamma camera prototype is presented, based on a planar LaBr3:Ce scintillation crystal with surfaces treatment typical of spectrometric devices, in order to enhance energy resolution performances. The crystal has round shape and has been optically coupled with a position sensitive photomultiplier tube with high quantum efficiency. The presented gamma camera shows outstanding energy resolution results in the investigated energy range (32-662 keV). These relevant performances have been obtained through the application of uniformity correction on the raw data, necessary due to the presence of position sensitive phototube, characterized by a spread of anodic gain values. In spite of position linearity degradation at crystal edges, due to reflective treatment of surfaces, intrinsic spatial resolution values are satisfactory on the useful field of view.The characterization of the presented gamma camera, based on a continuous LaBr3:Ce scintillation crystal with reflective surfaces, indicates good performances in multi-isotope imaging due to the excellent energy resolution results, also in comparison with similar detectors.

  8. Isotopic studies of mariposite-bearing rocks from the south- central Mother Lode, California.

    USGS Publications Warehouse

    Kistler, R.W.; Dodge, F.C.W.; Silberman, M.L.

    1983-01-01

    Gold-bearing vein formation in the Mother Lode belt of the study area apparently occurred during the Early Cretaceous between 127 and 108 m.y. B.P. The hydrothermal fluids that carried the gold precipitated quartz and mariposite at approx 320oC, similar to the T of precipitation of gold-bearing quartz veins in the Allegheny district. The O- and H-isotopic composition calculated for the fluid indicate that it was similar to formation water or was metamorphic in origin. If the carbonate in the veins was in isotopic equilibrium with this same fluid, it apparently precipitated at a higher T of approx 400oC. The Sr in the carbonate is much less radiogenic than that in any known marine carbonate, but is similar in isotopic composition to that in metamorphosed mafic volcanic rocks of the general region. These mafic rocks could have been the source for the Sr in the hydrothermal veins. This observation supports the contention that the gold-mariposite-quartz-carbonate rocks were formed as an alteration product of serpentinite and other mafic igneous rocks.-A.P.

  9. A molecular and isotopic study of the organic matter from the Paris Basin, France

    NASA Technical Reports Server (NTRS)

    Lichtfouse, E.; Albrecht, P.; Behar, F.; Hayes, J. M.

    1994-01-01

    Thirteen Liassic sedimentary rocks of increasing depth and three petroleums from the Paris Basin were studied for 13C/12C isotopic compositions and biological markers, including steranes, sterenes, methylphenanthrenes, methylanthracenes, and triaromatic steroids. The isotopic compositions of n-alkanes from mature sedimentary rocks and petroleums fall in a narrow range (2%), except for the deepest Hettangian rock and the Trias petroleum, for which the short-chain n-alkanes are enriched and depleted in 13C, respectively. Most of the molecular parameters increase over the 2000-2500 m depth range, reflecting the transformation of the organic matter at the onset of petroleum generation. In this zone, carbonate content and carbon isotopic composition of carbonates, as well as molecular parameters, are distinct for the Toarcian and Hettangian source rocks and suggest a migration of organic matter from these two formations. Two novel molecular parameters were defined for this task: one using methyltriaromatic steroids from organic extracts; the other using 1-methylphenanthrene and 2-methylanthracene from kerogen pyrolysates. The anomalous high maturity of the Dogger petroleum relative to the maturity-depth trend of the source rocks is used to estimate the minimal vertical distance of migration of the organic matter from the source rock to the reservoir.

  10. DoE optimization of a mercury isotope ratio determination method for environmental studies.

    PubMed

    Berni, Alex; Baschieri, Carlo; Covelli, Stefano; Emili, Andrea; Marchetti, Andrea; Manzini, Daniela; Berto, Daniela; Rampazzo, Federico

    2016-05-15

    By using the experimental design (DoE) technique, we optimized an analytical method for the determination of mercury isotope ratios by means of cold-vapor multicollector ICP-MS (CV-MC-ICP-MS) to provide absolute Hg isotopic ratio measurements with a suitable internal precision. By running 32 experiments, the influence of mercury and thallium internal standard concentrations, total measuring time and sample flow rate was evaluated. Method was optimized varying Hg concentration between 2 and 20ngg(-1). The model finds out some correlations within the parameters affect the measurements precision and predicts suitable sample measurement precisions for Hg concentrations from 5ngg(-1) Hg upwards. The method was successfully applied to samples of Manila clams (Ruditapes philippinarum) coming from the Marano and Grado lagoon (NE Italy), a coastal environment affected by long term mercury contamination mainly due to mining activity. Results show different extents of both mass dependent fractionation (MDF) and mass independent fractionation (MIF) phenomena in clams according to their size and sampling sites in the lagoon. The method is fit for determinations on real samples, allowing for the use of Hg isotopic ratios to study mercury biogeochemical cycles in complex ecosystems. PMID:26992509

  11. Isotopic Evidence for Microbial Activity in Crystalline Bedrock Fractures - a Case Study from Olkiluoto, SW Finland

    NASA Astrophysics Data System (ADS)

    Sahlstedt, E. K.; Karhu, J.; Pitkänen, P.

    2015-12-01

    Changes in the geochemical environment in crystalline bedrock fractures were investigated using the stable isotopes of C, O and S in fracture filling minerals as tracers. Of special interest were the possible changes which may occur in the subsurface at low temperatures. Especially, the influence of microbial activity was recognized as a catalyst for inducing changes in the geochemical environment. The study site is the Olkiluoto island located on the western coast of Finland, planned to host a geological repository for nuclear waste. Fracture surfaces were investigated to recognize the latest mineralizations at the site. These fillings were comprised of thin plates or small euhedral crystals of calcite and pyrite. The carbon and sulfur isotope compositions of calcite and pyrite were measured from bulk material by conventional IRMS, and in situ by secondary ion mass spectrometry. A notable feature of the late-stage fillings was high variabilities in the δ13C values of calcite and the δ34S values of pyrite, which ranged from -53.8 ‰ to +31.6 ‰ and from -50.4 ‰ to +77.7 ‰, respectively. Based on the isotopic compositions of the fillings, several features in the past hydrogeochemical environment could be recognized. The isotopic composition of the fracture fillings indicate an environment which was stratified with respect to depth. Characteristic features include bacterial sulfate reduction (BSR) occurring at depths <111 m (bsl), and a methanogenetic environment at depths >50 m. It appears that methanic conditions were replaced by sulfate reduction at depths >50 m likely due to infiltration of SO42--rich brackish waters. Sulfate reducing bacteria used mainly surface derived organic carbon as electron donors. Some indication of minor methanotrophic activity was recognized in anomalously low δ13C values of calcite, down to -53.8 ‰, at the depth range of 34-54 m. This methanotrophic activity may have been related to bacteria using CH4 as an electron donor in

  12. Hydroponic isotope labelling of entire plants (HILEP) for quantitative plant proteomics; an oxidative stress case study.

    PubMed

    Bindschedler, Laurence V; Palmblad, Magnus; Cramer, Rainer

    2008-07-01

    Hydroponic isotope labelling of entire plants (HILEP) is a cost-effective method enabling metabolic labelling of whole and mature plants with a stable isotope such as (15)N. By utilising hydroponic media that contain (15)N inorganic salts as the sole nitrogen source, near to 100% (15)N-labelling of proteins can be achieved. In this study, it is shown that HILEP, in combination with mass spectrometry, is suitable for relative protein quantitation of seven week-old Arabidopsis plants submitted to oxidative stress. Protein extracts from pooled (14)N- and (15)N-hydroponically grown plants were fractionated by SDS-PAGE, digested and analysed by liquid chromatography electrospray ionisation tandem mass spectrometry (LC-ESI-MS/MS). Proteins were identified and the spectra of (14)N/(15)N peptide pairs were extracted using their m/z chromatographic retention time, isotopic distributions, and the m/z difference between the (14)N and (15)N peptides. Relative amounts were calculated as the ratio of the sum of the peak areas of the two distinct (14)N and (15)N peptide isotope envelopes. Using Mascot and the open source trans-proteomic pipeline (TPP), the data processing was automated for global proteome quantitation down to the isoform level by extracting isoform specific peptides. With this combination of metabolic labelling and mass spectrometry it was possible to show differential protein expression in the apoplast of plants submitted to oxidative stress. Moreover, it was possible to discriminate between differentially expressed isoforms belonging to the same protein family, such as isoforms of xylanases and pathogen-related glucanases (PR 2). PMID:18538804

  13. The CG-1D neutron imaging beamline at the Oak Ridge National Laboratory High Flux Isotope Reactor

    SciTech Connect

    Santodonato, Louis J; Bilheux, Hassina Z; Bailey, William Barton; Bilheux, Jean-Christophe; Nguyen, Phong T; Tremsin, Anton S; Selby, Douglas L; Walker, Lakeisha MH

    2015-01-01

    The Oak Ridge National Laboratory Neutron Sciences Directorate has installed a neutron imaging beamline at the High Flux Isotope Reactor (HFIR) cold guide hall. CG-1D is one of the three instruments that make up the CG1 instrument suite. The beamline optics and detector have recently been upgraded to meet the needs of the neutron imaging community (better smoothing of guide system artifacts, higher flux or spatial resolution). These upgrades comprise a new diffuser/aperture system, two new detectors, a He-filled flight tube and silicon (Si) windows. Shielding inside the flight tube, beam scrapers and a beam stop ensure that biological dose is less than 50 Sv/hr outside of the radiation boundary. A set of diffusers and apertures (pinhole geometry) has been installed at the exit of the guide system to allow motorized L/D variation. Samples sit on a translation/rotation stage for alignment and tomography purposes. Detectors for the CG-1D beamline are (1) an ANDOR DW936 charge coupled device (CCD) camera with a field of view of approximately 7 cm x 7 cm and ~ 80 microns spatial resolution and 1 frame per second time resolution, (2) a new Micro-Channel Plate (MCP) detector with a 2.8 cm x 2.8 cm field of view and 55 microns spatial resolution, and 5 s timing capability. 6LiF/ZnS scintillators of thickness varying from 50 to 200 microns are being used at this facility. An overview of the beamline upgrade and preliminary data is presented here.

  14. The CG-1D Neutron Imaging Beamline at the Oak Ridge National Laboratory High Flux Isotope Reactor

    NASA Astrophysics Data System (ADS)

    Santodonato, Lou; Bilheux, Hassina; Bailey, Barton; Bilheux, Jean; Nguyen, Phong; Tremsin, Anton; Selby, Doug; Walker, Lakeisha

    The Oak Ridge National Laboratory Neutron Sciences Directorate has installed a neutron imaging beamline at the High Flux Isotope Reactor (HFIR) cold guide hall. CG-1D is one of the three instruments that make up the CG1 instrument suite. The beamline optics and detector have recently been upgraded to meet the needs of the neutron imaging community (better "smoothing" of guide system artifacts, higher flux or spatial resolution). These upgrades comprise a new diffuser/aperture system, two new detectors, a He-filled flight tube and silicon (Si) windows. Shielding inside the flight tube, beam scrapers and a beam stop ensure that biological dose is less than 50 μSv/hr outside of the radiation boundary. A set of diffusers and apertures (pinhole geometry) has been installed at the exit of the guide system to allow motorized L/D variation. Samples sit on a translation/rotation stage for alignment and tomography purposes. Detectors for the CG-1D beamline are (1) an ANDOR DW936 charge coupled device (CCD) camera with a field of view of approximately 7 cm x 7 cm and ∼ 80 microns spatial resolution and 1 frame per second time resolution, (2) a new Micro-Channel Plate (MCP) detector with a 2.8 cm x 2.8 cm field of view and 55 microns spatial resolution, and 5 μs timing capability. 6LiF/ZnS scintillators of thickness varying from 50 to 200 microns are being used at this facility. An overview of the beamline upgrade and preliminary data is presented here.

  15. Microwave imaging diagnostics for plasma fluctuation studies

    NASA Astrophysics Data System (ADS)

    Wang, Jian

    Electron Cyclotron Emission Imaging (ECEI) and Microwave Imaging Reflectometry (MIR) combined systems are being investigated by the UC Davis Plasma Diagnostic Group (PDG), in collaboration with Princeton Plasma Physics Laboratory (PPPL) researchers, Drs. E. Mazzucato, H.K. Park and T. Munsat, as well as researchers from the FOM-Instituut voor Plasmafysica Rijnhuizen,the Netherlands. The goal is to develop the plasma diagnostic systems based on the imaging technology developed in the UC Davis PDG group, for the study of plasma micro-turbulence, which is extremely important for the understanding of anomalous transport behavior of magnetically confined plasmas such as in tokamaks. This dissertation work provides the design of the optical systems, the design of the electronics, the testing of the antenna array and the data analysis of TEXTOR ECEI/MIR combined systems.

  16. Detail isotopic stratigraphy of snowpack - case study from Julian Alps (Slovenia)

    NASA Astrophysics Data System (ADS)

    Vreča, P.; Brenčič, M.; Sinjur, I.; Sokratov, S.

    2012-04-01

    In temperate humid catchments the storage of precipitation in snowpack, and the subsequent melting, both highly variable in space and time, substantially impacts the water cycle. Recent climate warming and changes in atmospheric circulation patterns have resulted in reductions in the duration of the snow cover season, the amount of water stored in the snowpack, as well as a widespread trend toward earlier melt. Comparison of water balance for periods 1961-90 and 1971-2000 showed that in Slovenia average precipitation amount remained the same in both periods while runoff decreased and the evaporation increased recently. The area of Julian Alps (NW Slovenia) represents the upper catchment area of river Sava. The area is locally characterised as one with the highest annual precipitation amount in Europe, rapid runoffs and low evaporation. Snow cover is regular, starts to accumulate in late autumn and lasts more than 100 days, at the upper tree line usually more than 150 days. Due to positive air temperature trend snow cover period is changing and consequently the discharge regime is affected. Spatial and temporal variability of snow, as well as snow cover contribution to the water balance in Julian Alps remains poorly investigated. Isotopes of O and H have been used to study snow deposition and the subsequent alteration of snowpack and its influence on runoff. Despite their potential, environmental isotopes were only rarely used in investigations of water cycle in mountain areas of Slovenia in the past. To improve the knowledge on snowpack isotope characteristics and processes in it, and consequently to enable better understanding of water balance with emphasize on recharge of important Slovene aquifers, in 2011 at selected site in the area of Triglav National Park (Planina Javornik) the first isotope research of snowpack has been started. We performed detail sampling of snowpack at two locations with different canopy structures (e.g. clearing and forest stand

  17. Carnivore specific bone bioapatite and collagen carbon isotope fractionations: Case studies of modern and fossil grey wolf populations

    NASA Astrophysics Data System (ADS)

    Fox-Dobbs, K.; Wheatley, P. V.; Koch, P. L.

    2006-12-01

    -tissue differences we measured for wolves are applicable to future isotopic studies of consumers with purely carnivorous diets. For example, we collected bone bioapatite and collagen carbon isotope data from late Pleistocene grey wolf fossils from eastern Beringia (Fairbanks, Alaska), and used the modern inter-tissue difference presented here to verify bioapatite preservation. We then compared the wolves to herbivores (horse and caribou) from the same locality, and found the difference in their bone bioapatite carbon isotope values corresponded to the modern carnivore-herbivore trophic spacing given above. We therefore were able to conclude that horse and caribou were part of Beringian wolf diet.

  18. Laser Spectroscopic Study on Oxygen Isotope Effects in Ozone Surface Decomposition

    NASA Astrophysics Data System (ADS)

    Minissale, Marco; Boursier, Corinne; Elandaloussi, Hadj; Te, Yao; Jeseck, Pascal; Rouille, Christian; Zanon-Willette, Thomas; Janssen, Christof

    2016-04-01

    The isotope kinetics of ozone formation in the Chapman reaction [1] O + O2 + M → O3 + M (1) provides the primary example for a chemically induced oxygen isotope anomaly and is associated with large [2] and mass independent [3] oxygen isotope enrichments in the product molecule, linked to a symmetry selection in the ozone formation kinetics [4-5]. The isotopic composition of ozone and its transfer to other molecules is a powerful tracer in the atmospheric and biogeochemical sciences [6] and serves as a primary model for a possible explanation of the oxygen isotopic heterogeneity in the Solar system [7-8]. Recently, the isotope fractionation in the photolytic decomposition process O3 + hν → O2 + O (2) using visible light has been studied in detail [9-10]. Much less is currently known about the isotope fractionation in the dry deposition or in the gas phase thermal decomposition of ozone O3 + M → O2 + O +M. (3) Here we report on first spectroscopic studies of non-photolytic ozone decomposition using a cw-quantum cascade laser at 9.5 μm. The concentration of individual ozone isotopomers (16O3,16O16O17O, and 16O17O16O) in a teflon coated reaction cell is followed in real time at temperatures between 25 and 150 °C. Observed ozone decay rates depend on homogeneous (reaction (3)) processes in the gas phase and on heterogeneous reactions on the wall. A preliminary analysis reveals agreement with currently recommended ozone decay rates in the gas phase and the absence of a large symmetry selection in the surface decomposition process, indicating the absence of a mass independent fractionation effect. This result is in agreement with previous mass spectrometer (MS) studies on heterogeneous ozone formation on pyrex [11], but contradicts an earlier MS study [12] on ozone surface decomposition on pyrex and quartz. Implications for atmospheric chemistry will be discussed. [1] Morton, J., Barnes, J., Schueler, B. and Mauersberger, K. J. Geophys. Res. 95, 901 - 907 (1990

  19. A combined radio- and stable-isotopic study of a California coastal aquifer system

    USGS Publications Warehouse

    Swarzenski, Peter W.; Baskaran, Mark; Rosenbauer, Robert J.; Edwards, Brian D.; Land, Michael

    2013-01-01

    Stable and radioactive tracers were utilized in concert to characterize geochemical processes in a complex coastal groundwater system and to provide constraints on the kinetics of rock/water interactions. Groundwater samples from wells within the Dominguez Gap region of Los Angeles County, California were analyzed for a suite of major cations (Na+, K+, Mg2+, Ca2+) and anions (Cl−, SO42−), silica, alkalinity, select trace elements (Ba, B, Sr), dissolved oxygen, stable isotopes of hydrogen (δD), oxygen (δ18O), dissolved inorganic carbon (δ13CDIC), and radioactive isotopes (3H, 222Rn and 223,224,226,228Ra). In the study area, groundwater may consist of a complex mixture of native groundwater, intruded seawater, non-native injected water, and oil-field brine water. In some wells, Cl− concentrations attained seawater-like values and in conjunction with isotopically heavier δ18O values, these tracers provide information on the extent of seawater intrusion and/or mixing with oil-field brines. Groundwater 3H above 1 tritium unit (TU) was observed only in a few select wells close to the Dominguez Gap area and most other well groundwater was aged pre-1952. Based on an initial 14C value for the study site of 90 percent modern carbon (pmc), groundwater age estimates likely extend beyond 20 kyr before present and confirm deep circulation of some native groundwater through multiple aquifers. Enriched values of groundwater δ13CDIC in the absence of SO42− imply enhanced anaerobic microbial methanogenesis. While secular equilibrium was observed for 234U/238U (activity ratios ~1) in host matrices, strong isotopic fractionation in these groundwater samples can be used to obtain information of adsorption/desorption kinetics. Calculated Ra residence times are short, and the associated desorption rate constant is about three orders of magnitude slower than that of the adsorption rate constant. Combined stable- and radio-isotopic results provide unique insights into aquifer

  20. The mechanism of oxygen isotopic fractionation during fungal denitrification - A pure culture study

    NASA Astrophysics Data System (ADS)

    Wrage-Moennig, Nicole; Rohe, Lena; Anderson, Traute-Heidi; Braker, Gesche; Flessa, Heinz; Giesemann, Annette; Lewicka-Szczebak, Dominika; Well, Reinhard

    2014-05-01

    Nitrous oxide (N2O) from soil denitrification originates from bacteria and - to an unknown extent - also from fungi. During fungal denitrification, oxygen (O) exchange takes place between H2O and intermediates of the denitrification process as in bacterial exchange[1,2]. However, information about enzymes involved in fungal O exchanges and the associated fractionation effects is lacking. The objectives of this study were to estimate the O fractionation and O exchange during the fungal denitrifying steps using a conceptual model[2] adapted from concepts for bacterial denitrification[3], implementing controls of O exchange proposed by Aerssens, et al.[4] and using fractionation models by Snider et al.[5] Six different pure fungal cultures (five Hypocreales, one Sordariales) known to be capable of denitrification were incubated under anaerobic conditions, either with nitrite or nitrate. Gas samples were analyzed for N2O concentration and its isotopic signatures (SP, average δ15N, δ18O). To investigate O exchange, both treatments were also established with 18O-labelled water as a tracer in the medium. The Hypocreales strains showed O exchange mainly at NO2- reductase (Nir) with NO2- as electron acceptor and no additional O exchange at NO3- reductase (Nar) with NO3- as electron acceptor. The only Hypocreales species having higher O exchange with NO3- than with NO2- also showed O exchange at Nar. The Sordariales species tested seems capable of O exchange at NO reductase (Nor) additionally to O exchange at Nir with NO2-. The data will help to better interpret stable isotope values of N2O from soils. .[1] D. M. Kool, N. Wrage, O. Oenema, J. Dolfing, J. W. Van Groenigen. Oxygen exchange between (de)nitrification intermediates and H2O and its implications for source determination of NO?3- and N2O: a review. Rapid Commun. Mass Spec. 2007, 21, 3569. [2] L. Rohe, T.-H. Anderson, B. Braker, H. Flessa, A. Giesemann, N. Wrage-Mönnig, R. Well. Fungal Oxygen Exchange between

  1. Stable isotope distribution in precipitation in Romania and its relevance for palaeoclimatic studies

    NASA Astrophysics Data System (ADS)

    Perşoiu, Aurel; Nagavciuc, Viorica; Bădăluţă, Carmen

    2014-05-01

    A surge of recent studies in Romania have targeted various aspects of palaeoclimate (based on stable isotopes in ice, speleothems, tree rings), mineral water origin, wine and other juices provenance. However, while much needed, these studies lack a stable isotope in precipitation background, with only two LMWL's being published so far. In this paper we discuss the links between the stable isotopic composition of precipitation (δ18O and δ2H), climate (air temperature, precipitation amount and large scale circulation) and their relevance for the palaeocllimatic interpretation of stable isotope values in cave ice, cryogenic calcite and tree rings from different sites in Romania. Most of the precipitation in Romania is delivered by the Westerlies, bringing moisture from the North Atlantic; however, their influence is greatly reduced in the eastern half of the country where local evaporative sources play an important role in the precipitation balance. The SW is dominated by water masses from the Mediterranean Sea, while the SE corner clearly draws most of the moisture from the Black Sea and strongly depleted North Atlantic vapor masses. In 2012, Romania experienced the worst draught in 60 years, possibly due to a northward shift of the jest stream associated to blocking conditions in summer, which led to a more northern penetration of the Mediterranean-derived air masses, as well increased precipitation of re-evaporated waters. We have further analyzed cave drip water (δ18O and δ2H), cryogenic cave calcite (δ18O and δ13C) and tree rings (δ18O and δ13C) from selected sites across NW Romania, where the water isotopes in precipitation showed the best (and easiest to understand, given the climatic conditions in 2012) correlation with climatic parameters. Our results that 1) δ18O and δ2H in cave ice are a good proxy for late summer through early winter air temperature; 2) δ13C in cryogenic cave calcite are possible indicators of soil humidity and 3) δ18O in pine

  2. Isotope Tracer Studies of Diffusion in Sillicates and of Geological Transport Processes Using Actinide Elements

    SciTech Connect

    Wasserburg, Gerald J

    2008-07-31

    The objectives were directed toward understanding the transport of chemical species in nature, with particular emphasis on aqueous transport in solution, in colloids, and on particles. Major improvements in measuring ultra-low concentrations of rare elements were achieved. We focused on two areas of studies: (1) Field, laboratory, and theoretical studies of the transport and deposition of U, Th isotopes and their daughter products in natural systems; and (2) Study of calcium isotope fractionation effects in marine carbonates and in carbonates precipitated in the laboratory, under controlled temperature, pH, and rates of precipitation. A major study of isotopic fractionation of Ca during calcite growth from solution has been completed and published. It was found that the isotopic shifts widely reported in the literature and attributed to biological processes are in fact due to a small equilibrium fractionation factor that is suppressed by supersaturation of the solution. These effects were demonstrated in the laboratory and with consideration of the solution conditions in natural systems, where [Ca{sup 2+}] >> [CO{sub 3}{sup 2-}] + [HCO{sub 3}{sup -}]. The controlling rate is not the diffusion of Ca, as was earlier proposed, but rather the rate of supply of [CO{sub 3}{sup 2-}] ions to the interface. This now opens the issues of isotopic fractionation of many elements to a more physical-chemical approach. The isotopic composition of Ca {Delta}({sup 44}Ca/{sup 40}Ca) in calcite crystals has been determined relative to that in the parent solutions by TIMS using a double spike. Solutions were exposed to an atmosphere of NH{sub 3} and CO{sub 2}, provided by the decomposition of (NH4)2CO3. Alkalinity, pH, and concentrations of CO{sub 3}{sup 2-}, HCO{sub 3}{sup -}, and CO{sub 2} in solution were determined. The procedures permitted us to determine {Delta}({sup 44}Ca/{sup 40}Ca) over a range of pH conditions, with the associated ranges of alkalinity. Two solutions with

  3. Biochemical and physiological bases for the use of carbon and nitrogen isotopes in environmental and ecological studies

    NASA Astrophysics Data System (ADS)

    Ohkouchi, Naohiko; Ogawa, Nanako O.; Chikaraishi, Yoshito; Tanaka, Hiroyuki; Wada, Eitaro

    2015-12-01

    We review the biochemical and physiological bases of the use of carbon and nitrogen isotopic compositions as an approach for environmental and ecological studies. Biochemical processes commonly observed in the biosphere, including the decarboxylation and deamination of amino acids, are the key factors in this isotopic approach. The principles drawn from the isotopic distributions disentangle the complex dynamics of the biosphere and allow the interactions between the geosphere and biosphere to be analyzed in detail. We also summarize two recently examined topics with new datasets: the isotopic compositions of individual biosynthetic products (chlorophylls and amino acids) and those of animal organs for further pursuing the basis of the methodology. As a tool for investigating complex systems, compound-specific isotopic analysis compensates the intrinsic disadvantages of bulk isotopic signatures. Chlorophylls provide information about the particular processes of various photoautotrophs, whereas amino acids provide a precise measure of the trophic positions of heterotrophs. The isotopic distributions of carbon and nitrogen in a single organism as well as in the whole biosphere are strongly regulated, so that their major components such as amino acids are coordinated appropriately rather than controlled separately.

  4. Deformation in the neutron-deficient rare earth isotopes: Radioactive decay scheme studies in the neodymium, promethium, and samarium isotopes

    SciTech Connect

    Breitenbach, J.B.

    1993-12-31

    Several experiments were performed at the UNISOR isotope separator facility at HHIRF at the Oak Ridge National Laboratory on the {beta}{sup +}/EC decay of neutron-deficient rare earth isotopes. Data for the decay chain {sup 133}Sm {yields} {sup 133}Pm {yields} {sup 133}Nd was obtained, consisting of multiscaled spectra of {gamma} rays, X rays, and conversion electrons, as well as {gamma}{gamma}t, X{gamma}t, e{gamma}t and eXt coincidences. Gamma rays associated with the decay of {sup 133}Sm and {sup 133}Pm were observed for the first time. The decay of a new low-spin (1/2) isomeric state, with a half life of about 70 sec was established for {sup 133}Nd. The level schemes for {sup 133}Nd and {sup 133}Pr were constructed. An M3 and two E1 isomers are established in {sup 133}Nd and an E3 isomer is confirmed in {sup 133}Pr. The energy level systematics for the nuclear region bounded by Z {ge} 58 and N {le} 78 is discussed. Theoretical interpretations are based on the particle-plus-triaxial rotor model calculations. In the framework of these calculations, the {beta}{sub 2} deformation is moderate for these nuclei ({beta}{sub 2} {approx} 0.20-0.25). A sudden onset of strong deformation is not observed, in contrast with the theoretical predictions by Leander and Moeller [Lea82].

  5. Distribution of carbon isotopes in amino acids of protein fraction of micro-organisms as a means of studying the mechanisms of their biosynthesis in the cell

    SciTech Connect

    Ivlev, A.A.

    1986-04-10

    The intramolecular distribution of carbon isotopes in the amino acids of the protein fraction of a number of photosynthesizing microorganisms was analyzed using the previously proposed model of carbon isotope fractionation in the cell. A correlation was found between the distributions of the isotopes in the amino acids and the pathways and sequence of their synthesis in the cell cycle. The feasibility of using the isotopic distributions of metabolites for a study of the temporal organization of metabolism in the cell is illustrated.

  6. Study of SGD along the French Mediterranean coastline using airborne TIR images and in situ analyses

    NASA Astrophysics Data System (ADS)

    van Beek, Pieter; Stieglitz, Thomas; Souhaut, Marc

    2015-04-01

    Although submarine groundwater discharge (SGD) has been investigated in many places of the world, very few studies were conducted along the French coastline of the Mediterranean Sea. Almost no information is available on the fluxes of water and chemical elements associated with these SGD and on their potential impact on the geochemical cycling and ecosystems of the coastal zones. In this work, we combined the use of airborne thermal infrared (TIR) images with in situ analyses of salinity, temperature, radon and radium isotopes to study SGD at various sites along the French Mediterranean coastline and in coastal lagoons. These analyses allowed us to detect SGD sites and to quantify SGD fluxes (that include both the fluxes of fresh groundwater and recirculated seawater). In particular, we will show how the Ra isotopes determined in the La Palme lagoon were used to estimate i) the residence time of waters in the lagoon and ii) SGD fluxes.

  7. Effects of sample preparation on stable isotope ratios of carbon and nitrogen in marine invertebrates: implications for food web studies using stable isotopes.

    PubMed

    Mateo, Miguel A; Serrano, Oscar; Serrano, Laura; Michener, Robert H

    2008-08-01

    Trophic ecology has benefitted from the use of stable isotopes for the last three decades. However, during the last 10 years, there has been a growing awareness of the isotopic biases associated with some pre-analytical procedures that can seriously hamper the interpretation of food webs. We have assessed the extent of such biases by: (1) reviewing the literature on the topic, and (2) compiling C and N isotopic values of marine invertebrates reported in the literature with the associated sample preparation protocols. The factors considered were: acid-washing, distilled water rinsing (DWR), sample type (whole individuals or pieces of soft tissues), lipid content, and gut contents. Two-level ANOVA revealed overall large and highly significant effects of acidification for both delta(13)C values (up to 0.9 per thousand decrease) and delta(15) N values (up to 2.1 per thousand decrease in whole individual samples, and up to 1.1 per thousand increase in tissue samples). DWR showed a weak overall effect with delta(13)C increments of 0.6 per thousand (for the entire data set) or decrements of 0.7 per thousand in delta(15) N values (for tissue samples). Gut contents showed no overall significant effect, whereas lipid extraction resulted in the greatest biases in both isotopic signatures (delta(13)C, up to -2.0 per thousand in whole individuals; delta(15)N, up to +4.3 per thousand in tissue samples). The study analyzed separately the effects of the various factors in different taxonomic groups and revealed a very high diversity in the extent and direction of the effects. Maxillopoda, Gastropoda, and Polychaeta were the classes that showed the largest isotopic shifts associated with sample preparation. Guidelines for the standardization of sample preparation protocols for isotopic analysis are proposed both for large and small marine invertebrates. Broadly, these guidelines recommend: (1) avoiding both acid washing and DWR, and (2) performing lipid extraction and gut

  8. A stable carbon isotope and biological marker study of Polish bituminous coals and carbonaceous shales

    USGS Publications Warehouse

    Kotarba, M.J.; Clayton, J.L.

    2003-01-01

    Biological marker and carbon isotopic compositions of coals and carbonaceous shales from the Upper Carboniferous strata of the Upper Silesian (USCB), Lower Silesian (LSCB), and Lublin (LCB) coal basins were determined to assess depositional conditions and sources of the organic matter. n-Alkane, sterane, and isoprenoid distribution, and carbon isotope ratios are consistent with an origin from higher plants. In some cases, pristane/phytane (Pr/Ph) ratios of carbonaceous shales (roof and floor shales) are < 1.0, while the associated coals have high ratios (??? 1.0). This suggests that reducing conditions prevailed during deposition of the shales, but a period of oxidizing conditions accompanied deposition of the coals. Steranes present in coal extracts are dominated by the 14??(H)17??(H)20R C29 stereoisomers, typical, but not conclusive, of higher plant origin. Carbonaceous shales exhibit a wider range of sterane composition, suggesting local, significant input of algal organic matter. Significant amounts of benzohopanes and gammacerane are present in some coals. Although benzohopanes are present at least in small amounts in samples from many different environments, they have been reported to occur most commonly in marine environments. The present study seems to provide the first example where benzohopanes have been reported in significant amounts in terrestrial organic matter. Gammacerane is abundant in rocks or sediments deposited in carbonate or highly saline marine environments. The finding of high gammacerane concentrations in the coals expands the depositional settings in which it has been observed and questions its utility as an independent indicator of hypersaline carbonate environments. Stable carbon isotope composition of coals, and type III kerogen in carbonaceous shales as well as correlation of stable carbon isotope composition of saturated and aromatic hydrocarbons in carbonaceous shales from both the USCB and the LSCB indicate terrigenous origin

  9. Digital Image Distribution: A Study of Costs and Uses.

    ERIC Educational Resources Information Center

    Besser, Howard

    1999-01-01

    Describes a study that examined an experimental multi-site image distribution scheme among museums and universities in California, The Museum Educational Site Licensing Project, whose content was primarily digital images and metadata. Discusses barriers to using digital images; digital image distribution; comparing digital images to analog slide…

  10. Stable isotope and hydrogeochemical studies of Beaver Lake and Radok Lake, MacRobertson Land, East Antarctica.

    PubMed

    Wand, Ulrich; Hermichen, Wolf-Dieter; Brüggemann, Erika; Zierath, Reinhard; Klokov, Valerii Dmitrievich

    2011-12-01

    Beaver Lake and Radok Lake, the largest known epishelf lake and the deepest freshwater lake on the Antarctic continent, respectively, were isotopically (δ(2)H, δ(18)O) and hydrogeochemically studied. Radok Lake is an isothermal and non-stratified, i.e. homogeneous water body, while Beaver Lake is stratified with respect to temperature, salinity, and isotopic composition. The results for the latter attest to freshwater (derived from snow and glacier melt) overlying seawater. PMID:22092172

  11. Scatterometry or imaging overlay: a comparative study

    NASA Astrophysics Data System (ADS)

    Hsu, Simon C. C.; Pai, Yuan Chi; Chen, Charlie; Yu, Chun Chi; Hsing, Henry; Wu, Hsing-Chien; Kuo, Kelly T. L.; Amir, Nuriel

    2015-03-01

    Most fabrication facilities today use imaging overlay measurement methods, as it has been the industry's reliable workhorse for decades. In the last few years, third-generation Scatterometry Overlay (SCOL™) or Diffraction Based Overlay (DBO-1) technology was developed, along another DBO technology (DBO-2). This development led to the question of where the DBO technology should be implemented for overlay measurements. Scatterometry has been adopted for high volume production in only few cases, always with imaging as a backup, but scatterometry overlay is considered by many as the technology of the future. In this paper we compare imaging overlay and DBO technologies by means of measurements and simulations. We outline issues and sensitivities for both technologies, providing guidelines for the best implementation of each. For several of the presented cases, data from two different DBO technologies are compared as well, the first with Pupil data access (DBO-1) and the other without pupil data access (DBO-2). Key indicators of overlay measurement quality include: layer coverage, accuracy, TMU, process robustness and robustness to process changes. Measurement data from real cases across the industry are compared and the conclusions are also backed by simulations. Accuracy is benchmarked with reference OVL, and self-consistency, showing good results for Imaging and DBO-1 technology. Process sensitivity and metrology robustness are mostly simulated with MTD (Metrology Target Designer) comparing the same process variations for both technologies. The experimental data presented in this study was done on ten advanced node layers and three production node layers, for all phases of the IC fabrication process (FEOL, MEOL and BEOL). The metrology tool used for most of the study is KLA-Tencor's Archer 500LCM system (scatterometry-based and imaging-based measurement technologies on the same tool) another type of tool is used for DBO-2 measurements. Finally, we conclude that

  12. Cosmic ray isotopes

    NASA Technical Reports Server (NTRS)

    Stone, E. C.

    1973-01-01

    The isotopic composition of cosmic rays is studied in order to develop the relationship between cosmic rays and stellar processes. Cross section and model calculations are reported on isotopes of H, He, Be, Al and Fe. Satellite instrument measuring techniques separate only the isotopes of the lighter elements.

  13. Archeological contributions to the use of stable isotopes in paleoclimate studies

    SciTech Connect

    Cormie, A.B. . Dept. of Earth Sciences); Schwarcz, H.P. . Dept. of Geology)

    1992-01-01

    Determining paleoclimates in the terrestrial environment is difficult yet of increasing interest in many disciplines. Earth scientists have examined the hydrogen isotope ratios delta D of materials that record the delta D of rain which, in turn is dependent on local temperature. These include glacier ice, cave speleothem fluid inclusions, tree wood or peat bog plant cellulose and insect chitin. Bone has long been examined by the archaeologists for the information it can provide about the past. The carbon and nitrogen stable isotope ratios of bone collagen have been used by archaeologists in the reconstruction human paleodiets. The authors expanded on previous studies and measured the delta D values of bone collagen in an effort to provide climatic information pertinent to archeological interpretations. It was found that the delta D and delta N-15 of herbivore bone collagen can be used together to accurately estimate the delta D of local rain from which temperature can then be evaluated. Furthermore, the delta D and delta N-15 of bone collagen along with the delta O-18 of bone phosphate can be used to estimate humidity. The use of bone to evaluate paleoclimate is advantageous in that it can be dated by C-14, it is a widespread, well preserved material in the terrestrial environment and is commonly found in direct association with cultural, paleontological or ecological events of interest. Thus by studying the isotopic signatures of a material that is primarily identified, collected and studied by archaeologists the authors are able to contribute significantly to the problem of determining paleoclimates.

  14. ForCent Model Development and Testing using the Enriched Background Isotope Study (EBIS) Experiment

    SciTech Connect

    Parton, William; Hanson, Paul J; Swanston, Chris; Torn, Margaret S.; Trumbore, Susan E.; Riley, William J.; Kelly, Robin

    2010-01-01

    The ForCent forest ecosystem model was developed by making major revisions to the DayCent model including: (1) adding a humus organic pool, (2) incorporating a detailed root growth model, and (3) including plant phenological growth patterns. Observed plant production and soil respiration data from 1993 to 2000 were used to demonstrate that the ForCent model could accurately simulate ecosystem carbon dynamics for the Oak Ridge National Laboratory deciduous forest. A comparison of ForCent versus observed soil pool 14C signature (? 14C) data from the Enriched Background Isotope Study 14C experiment (1999-2006) shows that the model correctly simulates the temporal dynamics of the 14C label as it moved from the surface litter and roots into the mineral soil organic matter pools. ForCent model validation was performed by comparing the observed Enriched Background Isotope Study experimental data with simulated live and dead root biomass ? 14C data, and with soil respiration ? 14C (mineral soil, humus layer, leaf litter layer, and total soil respiration) data. Results show that the model correctly simulates the impact of the Enriched Background Isotope Study 14C experimental treatments on soil respiration ? 14C values for the different soil organic matter pools. Model results suggest that a two-pool root growth model correctly represents root carbon dynamics and inputs to the soil. The model fitting process and sensitivity analysis exposed uncertainty in our estimates of the fraction of mineral soil in the slow and passive pools, dissolved organic carbon flux out of the litter layer into the mineral soil, and mixing of the humus layer into the mineral soil layer.

  15. ForCent model development and testing using the Enriched Background Isotope Study experiment

    SciTech Connect

    Parton, W.J.; Hanson, P. J.; Swanston, C.; Torn, M.; Trumbore, S. E.; Riley, W.; Kelly, R.

    2010-10-01

    The ForCent forest ecosystem model was developed by making major revisions to the DayCent model including: (1) adding a humus organic pool, (2) incorporating a detailed root growth model, and (3) including plant phenological growth patterns. Observed plant production and soil respiration data from 1993 to 2000 were used to demonstrate that the ForCent model could accurately simulate ecosystem carbon dynamics for the Oak Ridge National Laboratory deciduous forest. A comparison of ForCent versus observed soil pool {sup 14}C signature ({Delta} {sup 14}C) data from the Enriched Background Isotope Study {sup 14}C experiment (1999-2006) shows that the model correctly simulates the temporal dynamics of the {sup 14}C label as it moved from the surface litter and roots into the mineral soil organic matter pools. ForCent model validation was performed by comparing the observed Enriched Background Isotope Study experimental data with simulated live and dead root biomass {Delta} {sup 14}C data, and with soil respiration {Delta} {sup 14}C (mineral soil, humus layer, leaf litter layer, and total soil respiration) data. Results show that the model correctly simulates the impact of the Enriched Background Isotope Study {sup 14}C experimental treatments on soil respiration {Delta} {sup 14}C values for the different soil organic matter pools. Model results suggest that a two-pool root growth model correctly represents root carbon dynamics and inputs to the soil. The model fitting process and sensitivity analysis exposed uncertainty in our estimates of the fraction of mineral soil in the slow and passive pools, dissolved organic carbon flux out of the litter layer into the mineral soil, and mixing of the humus layer into the mineral soil layer.

  16. Performance of human mass balance studies with stable isotope-labeled drug and continuous flow-isotope ratio mass spectrometry: a progress report.

    PubMed

    Browne, T R; Szabo, G K; Ajami, A; Browne, D G

    1998-04-01

    We propose performing human mass balance studies by administering stable isotope labeled (13C or 15N) drug and quantitating excess (above background) 13C or 15N in urine, serum, and feces by continuous flow-isotope ratio mass spectrometry (CF-IRMS). Theoretical calculations and empirical data (dynamic range, linearity, sensitivity, precision, accuracy) are presented to establish that commercially available CF-IRMS instruments can quantitate stable isotope labeled (one or two 15N or 13C labels) drug concentrations of 1.0 microg/mL or greater in urine, serum (15N), or feces. More than two 13C labels may be necessary to quantitate 1.0 microg/mL of drug in serum. Three volunteers received 650 mg of 15N13C2-acetaminophen, and urine was collected for 72 hours. Percent of administered label recovered in urine from the three subjects was 97.4, 78.9, and 95.4 for 13C and 90.3, 77.0, and 90.6 for 15N. Fecal recovery of label for one subject was 0.9% (13C2) and 1.1% (15N). Serum pharmacokinetic values obtained by counting 13C or 15N in one subject were as expected for acetaminophen. This method appears to be promising, and further validation is ongoing. PMID:9590457

  17. Trap-assisted studies of odd, neutron-rich isotopes from Tc to Pd

    NASA Astrophysics Data System (ADS)

    Kurpeta, J.; Jokinen, A.; Penttilä, H.; Płochocki, A.; Rissanen, J.; Urban, W.; Äystö, J.

    2014-01-01

    We review the present and future of trap-assisted structure studies of odd, neutron-rich Tc, Ru, Rh and Pd isotopes at the limits of present experimental techniques. These nuclei of refractory elements are produced in light-particle induced fission and filtered by their mass number with the IGISOL mass separator. Further mass separation with the JYFLTRAP Penning trap system provides a clean, monoisotopic beam perfectly suited for precise nuclear spectroscopy. Connecting the IGISOL and the JYFLTRAP facilities to the recently installed MCC30/15 cyclotron opens new prospects for post-trap spectroscopy of very exotic, neutron-rich nuclei.

  18. Study of hydrogen isotopes behavior in tungsten by a multi trapping macroscopic rate equation model

    NASA Astrophysics Data System (ADS)

    Hodille, E. A.; Ferro, Y.; Fernandez, N.; Becquart, C. S.; Angot, T.; Layet, J. M.; Bisson, R.; Grisolia, C.

    2016-02-01

    Density functional theory (DFT) studies show that in tungsten a mono vacancy can contain up to six hydrogen isotopes (HIs) at 300 K with detrapping energies varying with the number of HIs in the vacancy. Using these predictions, a multi trapping rate equation model has been built and used to model thermal desorption spectrometry (TDS) experiments performed on single crystal tungsten after deuterium ions implantation. Detrapping energies obtained from the model to adjust temperature of TDS spectrum observed experimentally are in good agreement with DFT values within a deviation below 10%. The desorption spectrum as well as the diffusion of deuterium in the bulk are rationalized in light of the model results.

  19. 2H Stable Isotope Analysis of Tooth Enamel: A Pilot Study

    NASA Astrophysics Data System (ADS)

    Holobinko, Anastasia; Kemp, Helen; Meier-Augenstein, Wolfram; Prowse, Tracy; Ford, Susan

    2010-05-01

    Stable isotope analysis of biogenic tissues such as tooth enamel and bone mineral has become a well recognized and increasingly important method for determining provenance of human remains, and has been used successfully in bioarchaeological studies as well as forensic investigations (Lee-Thorp, 2008; Meier-Augenstein and Fraser, 2008). Particularly, 18O and 2H stable isotopes are well established proxies as environmental indicators of climate (temperature) and source water and are therefore considered as indicators of geographic life trajectories of animals and humans (Hobson et al., 2004; Schwarcz and Walker, 2006). While methodology for 2H analysis of human hair, fingernails, and bone collagen is currently used to determine geographic origin and identify possible migration patterns, studies involving the analysis of 2H in tooth enamel appear to be nonexistent in the scientific literature. The apparent lack of research in this area is believed to have two main reasons. (1) Compared to the mineral calcium hydroxylapatite Ca10(PO4)6(OH)2, in tooth enamel forming bio-apatite carbonate ions replace some of the hydroxyl ions at a rate of one CO32 replacing two OH, yet published figures for the degree of substitution vary (Wopenka and Pasteris, 2005). (2) Most probably due to the aforementioned no published protocols exist for sample preparation and analytical method to obtain δ2H-values from the hydroxyl fraction of tooth enamel. This dilemma has been addressed through a pilot study to establish feasibility of 2H stable isotope analysis of ground tooth enamel by continuous-flow isotope ratio mass spectrometry (IRMS) coupled on-line to a high-temperature conversion elemental analyzer (TC/EA). An array of archaeological and modern teeth has been analyzed under different experimental conditions, and results from this pilot study are being presented. References: Lee-Thorp, J.A. (2008) Archaeometry, 50, 925-950 Meier-Augenstein, W. and Fraser, I. (2008) Science & Justice

  20. Uranium isotope fractionation in Saanich Inlet: A modern analog study of a paleoredox tracer

    NASA Astrophysics Data System (ADS)

    Holmden, C.; Amini, M.; Francois, R.

    2015-03-01

    Uranium isotope fractionation was studied in the sediment and water of Saanich Inlet, a seasonally anoxic fjord on the east coast of Vancouver Island. The concentration of dissolved U is the same above and below the redoxcline at ˜120 m depth, with an average δ238U value of -0.45 ± 0.06‰ (2 s.e.), which is indistinguishable from seawater values reported in other studies. This finding is consistent with water renewal times for the inlet that are roughly seasonal in frequency, thus hiding the impact of the U losses to the anoxic sediment of the inlet. Complete digests of the anoxic sediment yielded higher δ238U values than seawater (-0.21 ± 0.11‰ (2 s.e.)). By contrast, complete digests of the sediment trap samples yielded lower δ238U values than seawater (-0.52 ± 0.10‰ (2 s.e.)), and marine plankton from the inlet yielded the lowest δ238U value of -1.24 ± 0.17‰ (2σ). Cross-plots of δ238U and δ234U vs. Th/U reveal strong correlations indicative of two-component mixing when the data from traps and anoxic inlet sediment are combined. One mixing end-member is fractionated uranium of seawater origin, with a δ238U value of 0.17 ± 0.14‰ (2σ). The other is detrital uranium with a δ238U value of -0.83 ± 0.12‰ (2σ). The detrital end-member is lower than the range of δ238U values reported in the literature for granitoid igneous rocks (-0.44‰ to -0.17‰, 2σ) (Telus et al., 2012), suggesting that continental weathering fractionates uranium isotopes, with preferential release of 238U. Development and application of U isotopes as a paleoredox proxy has its basis in the nuclear volume fractionation. The data from Saanich Inlet meets this expectation, with a positive fractionation factor (Δaq(VI)sed(IV)) of 0.62 ± 0.17‰ (2σ) calculated as the difference in δ238U between authigenic U in anoxic sediments and sediment traps (+0.17‰) and U dissolved in seawater (-0.45‰). However, it is widely believed that U(VI) reduction in the marine

  1. Isotope Trace Studies of Diffusion in Silicates and of Geological Transport Processes Using Actinide Elements

    SciTech Connect

    Prof. G. J. Wasserburg

    2001-01-19

    Over the past year we have competed two studies of Os concentration and isotopic composition in rivers from the Himalayan uplift and in hydrothermal fluids from the Juan de Fuca Ridge. Both of these studies have been published. We have completed a study of paleo-climate in Soreq Cave, Israel, and have expanded our studies of the transport of U-Th through riverine and estuarine environments. We are completing two studies of weathering and transport in the vadose in two very different environments--one a tropical regime with a deep laterite profile and the other a northern arboreal forest with only a thin weathering zone. We have begun a new study of U-Th in aquifers with low water velocity.

  2. The Yanaurcu volcano (Western Cordillera, Ecuador): A field, petrographic, geochemical, isotopic and geochronological study

    NASA Astrophysics Data System (ADS)

    Béguelin, Paul; Chiaradia, Massimo; Beate, Bernardo; Spikings, Richard

    2015-03-01

    The Yanaurcu volcanic center in the Ecuadorian frontal arc is characterized by several epochs of activity from the Early Pliocene to approx. 61 ka, with important changes in geochemistry and isotope ratio values throughout its history. Most of its units have high Sr/Y and La/Yb signatures. We present a comprehensive study of this volcano involving morphological and stratigraphical observations, sampling, petrography, whole rock and in situ geochemistry, whole rock radiogenic isotope analysis and 40Ar/39Ar geochronology. We identify three magmatic series: (1) Early Pliocene andesitic and dacitic volcanics, (2) Pliocene andesitic flows (~ 3.6 Ma), and (3) two Pleistocene andesitic domes (~ 172 ka and ~ 61 ka). Radiogenic isotope data suggest an increasing amount of basement assimilation through the evolution of Yanaurcu, as well as lower rates of ascent and increasing recharge at upper crustal levels, with the Pleistocene domes representing a thermally more mature state of the crust (deep and mid-crust becoming warmer with time when fluxed by a continuous magmatic supply). We also investigate the deep and mid-crustal magma evolution of Yanaurcu by modeling REE + Sr + Y with the Monte Carlo approach in order to get constraints on the fractionating assemblage. We highlight the importance of fractionating garnet in the development of high Sr/Y and La/Yb signatures, and propose a changing regional stress to modify the depth of magma evolution, and therefore the stability of garnet in the fractionating assemblage. Switches from transtensional to compressional regimes in Ecuador have been highlighted by various studies based on tectonic and thermochronological evidences. We conclude that (1) Yanaurcu high Sr/Y and La/Yb ratios can be fully explained by crustal processes and do not need an enriched mantle source nor slab melting, and (2) local thermal maturation of the crust is responsible for an enrichment of incompatible elements through time via recharge processes

  3. Isotopic tracer studies of Fischer-Tropsch Synthesis over Ru/TiO sub 2 catalysts

    SciTech Connect

    Krishna, K.R.

    1992-01-01

    Fischer-Tropsch synthesis is a process in which CO and H{sub 2} react to give predominantly liquid hydrocarbons. The reaction can be considered a special type of polymerization in which the monomer is produced in situ, and chain growth occurs by a sequence of independently repeated additions of the monomer to the growing chain. A investigation has been conducted to study the CO hydrogenation reaction in order to better understand catalyst deactivation and the elementary surface processes involved in chain growth. Isotopic tracers are used in conjunction with transient-response techniques in this study of Fischer-Tropsch synthesis over Ru/TiO{sub 2} catalysts. Experiments are conducted at a total pressure of 1 atmosphere, reaction temperatures of 453--498 K and D{sub 2}/CO (or H{sub 2}/CO) ratios of 2--5. Synthesis products are analyzed by gas chromatography or isotope-ratio gas chromatography-mass spectrometry. Rate constants for chain initiation, propagation and termination are evaluated under steady-state reaction conditions by using transients in isotopic composition. The activation energy for chain termination is much higher than that for propagation, accounting for the observed decrease in the chain growth parameter are also estimated. Coverages by reaction intermediates are also estimated. When small amounts of {sup 12}C-labelled ethylene are added to {sup 13}CO/H{sub 2} synthesis gas, ethylene acts as the sole chain initiator. Ethylene-derived carbon also accounts for 45% of the C{sub 1} monomer pool. 102 refs., 29 figs., 11 tabs.

  4. Isotopic tracer studies of Fischer-Tropsch Synthesis over Ru/TiO{sub 2} catalysts

    SciTech Connect

    Krishna, K.R.

    1992-01-01

    Fischer-Tropsch synthesis is a process in which CO and H{sub 2} react to give predominantly liquid hydrocarbons. The reaction can be considered a special type of polymerization in which the monomer is produced in situ, and chain growth occurs by a sequence of independently repeated additions of the monomer to the growing chain. A investigation has been conducted to study the CO hydrogenation reaction in order to better understand catalyst deactivation and the elementary surface processes involved in chain growth. Isotopic tracers are used in conjunction with transient-response techniques in this study of Fischer-Tropsch synthesis over Ru/TiO{sub 2} catalysts. Experiments are conducted at a total pressure of 1 atmosphere, reaction temperatures of 453--498 K and D{sub 2}/CO (or H{sub 2}/CO) ratios of 2--5. Synthesis products are analyzed by gas chromatography or isotope-ratio gas chromatography-mass spectrometry. Rate constants for chain initiation, propagation and termination are evaluated under steady-state reaction conditions by using transients in isotopic composition. The activation energy for chain termination is much higher than that for propagation, accounting for the observed decrease in the chain growth parameter are also estimated. Coverages by reaction intermediates are also estimated. When small amounts of {sup 12}C-labelled ethylene are added to {sup 13}CO/H{sub 2} synthesis gas, ethylene acts as the sole chain initiator. Ethylene-derived carbon also accounts for 45% of the C{sub 1} monomer pool. 102 refs., 29 figs., 11 tabs.

  5. Isotopic study of soils in chronological sequences of alluvial deposits, Providence Mountains, California

    SciTech Connect

    Wang, Y.; Amundson, R.; McDonald, E.; McFadden, L.; Chadwick, O.

    1996-04-01

    The carbon ({sup 14}C and {sup 13}C) and oxygen isotopic composition of pedogenic carbonate was determined for two soil chronosequences on limestone and granitic alluvium in the Providence Mountains area in the Mojave Desert, California. The measured {sup 14}C ages of pedogenic carbonate coating on clasts were interpreted in the light of a diffusion-reaction model developed in our recent studies. Model ages of soil formation calculated from the measured {sup 14}C ages of pedogenic carbonate are in correct relative order as determined by geomorphic evidence, and are also consistent with model ages from the measured {sup 14}C ages of soil organic matter. {sup 14}C model ages suggest that the order geomorphic surfaces we studied are of late Pleistocene age (ca. 47-17 ka) and the younger surfaces formed during the Holocene (ca. 11-4 ka). These age estimates of the geomorphic surfaces are older than the previously assigned ages based on a combination of soil development, geomorphic relationships, and several infrared-stimulated luminescence dates, but they are within a few thousand years of these other age estimates. Stable carbon isotopic composition of the soil carbonate indicates either a slight increase in C{sub 4} or CAM (crassulacean acid metabolism) plants or a decrease in plant density in this area during the Holocene. Both the carbon and oxygen isotopic composition of soil carbonates suggests that the climate in the eastern Mojave Desert has, in general, become warmer and drier during the Holocene. 57 refs., 9 figs., 5 tabs.

  6. Self-diffusion of polycrystalline ice Ih under confining pressure: Hydrogen isotope analysis using 2-D Raman imaging

    NASA Astrophysics Data System (ADS)

    Noguchi, Naoki; Kubo, Tomoaki; Durham, William B.; Kagi, Hiroyuki; Shimizu, Ichiko

    2016-08-01

    We have developed a high-resolution technique based on micro Raman spectroscopy to measure hydrogen isotope diffusion profiles in ice Ih. The calibration curve for quantitative analysis of deuterium in ice Ih was constructed using micro Raman spectroscopy. Diffusion experiments using diffusion couples composed of dense polycrystalline H2O and D2O ice were carried out under a gas confining pressure of 100 MPa (to suppress micro-fracturing and pore formation) at temperatures from 235 K to 245 K and diffusion times from 0.2 to 94 hours. Two-dimensional deuterium profiles across the diffusion couples were determined by Raman imaging. The location of small spots of frost from room air could be detected from the shapes of the Raman bands of OH and OD stretching modes, which change because of the effect of the molar ratio of deuterium on the molecular coupling interaction. We emphasize the validity for screening the impurities utilizing the coupling interaction. Some recrystallization and grain boundary migration occurred in recovered diffusion couples, but analysis of two-dimensional diffusion profiles of regions not affected by grain boundary migration allowed us to measure a volume diffusivity for ice at 100 MPa of (2.8 ± 0.4) ×10-3exp[ -57.0±15.4kJ/mol/RT ] m2 /s (R is the gas constant, T is temperature). Based on ambient pressure diffusivity measurements by others, this value indicates a high (negative) activation volume for volume diffusivity of -29.5 cm3/mol or more. We can also constrain the value of grain boundary diffusivity in ice at 100 MPa to be <104 that of volume diffusivity.

  7. Stable isotope study of fluid inclusions in fluorite from Idaho: Implications for continental climates during the Eocene

    NASA Astrophysics Data System (ADS)

    Seal, Robert R., II; Rye, Robert O.

    1993-03-01

    Isotopic studies of fluid inclusions from meteoric water-dominated epithermal ore deposits offer a unique opportunity to study paleoclimates because the fluids can provide direct samples of ancient waters. The oxygen and hydrogen isotope compositions of meteoric waters vary because of changes in climatic variables such as mean annual temperature of precipitation, relative humidity, origin and history of air masses, and the isotope composition of the oceans. Inclusion fluids found in fluorite (CaF2) are especially useful because their host is devoid of oxygen or hydrogen, thus precluding postentrapment isotope exchange. Fluorite-hosted fluid inclusions from the Eocene (51-50 Ma) epithermal deposits of the Bayhorse mining district, northeastern Idaho, have low salinities, most less than 0.6 equivalent wt% NaCl, and low to moderate homogenization temperatures (98 to 146 °C), indicating meteoric origins for the fluids. Oxygen and hydrogen isotope data on inclusion fluids are almost identical to those of modern meteoric waters in the area. The equivalence of the isotope composition of the Eocene inclusion fluids and modern meteoric waters indicates that the Eocene climatic conditions were similar to those today. This conclusion supports the climate modeling of Sloan and Barron, who suggested that the climates of continental interiors do not reflect the magnitude of warming preserved by the deep-ocean paleoclimate record during the Eocene.

  8. Oxygen and chlorine isotopic fractionation during perchlorate biodegradation: Laboratory results and implications for forensics and natural attenuation studies

    USGS Publications Warehouse

    Sturchio, N.C.; Böhlke, J.K.; Beloso, A.D., Jr.; Streger, S.H.; Heraty, L.J.; Hatzinger, P.B.

    2007-01-01

    Perchlorate is a widespread environmental contaminant having both anthropogenic and natural sources. Stable isotope ratios of O and Cl in a given sample of perchlorate may be used to distinguish its source(s). Isotopic ratios may also be useful for identifying the extent of biodegradation of perchlorate, which is critical for assessing natural attenuation of this contaminant in groundwater. For this approach to be useful, however, the kinetic isotopic fractionations of O and Cl during perchlorate biodegradation must first be determined as a function of environmental variables such as temperature and bacterial species. A laboratory study was performed in which the O and Cl isotope ratios of perchlorate were monitored as a function of degradation by two separate bacterial strains (Azospira suillum JPLRND and Dechlorospirillum sp. FBR2) at both 10??C and 22??C with acetate as the electron donor. Perchlorate was completely reduced by both strains within 280 h at 22??C and 615 h at 10??C. Measured values of isotopic fractionation factors were ??18O = -36.6 to -29.0??? and ??37Cl = -14.5 to -11.5???, and these showed no apparent systematic variation with either temperature or bacterial strain. An experiment using 18O-enriched water (??18O = +198???) gave results indistinguishable from those observed in the isotopically normal water (??18O = -8.1???) used in the other experiments, indicating negligible isotope exchange between perchlorate and water during biodegradation. The fractionation factor ratio ??18O/??37Cl was nearly invariant in all experiments at 2.50 ?? 0.04. These data indicate that isotope ratio analysis will be useful for documenting perchlorate biodegradation in soils and groundwater. The establishment of a microbial fractionation factor ratio (??18O/??37Cl) also has significant implications for forensic studies. ?? 2007 American Chemical Society.

  9. GEOTRACES: Studying the global marine biogeochemistry of trace elements and isotopes

    NASA Astrophysics Data System (ADS)

    Frank, Martin; Jeandel, Catherine; Anderson, Robert F.; Henderson, Gideon; Francois, Roger; Sharma, Mukul

    There is a growing international interest among geochemists and oceanographers in building a coordinated global study of the marine biogeochemical cycles of selected trace elements and isotopic tracers. This is reflected by the increasing numbers of contributions to corresponding special sessions at meetings such as the 2001 AGU Fall Meeting, the 2002 Goldschmidt Meeting, and the 2003 European Geophysical Union Annual Meeting. With support from the U.S. National Science Foundation's Chemical Oceanography program, the Centre National de Recherche Scientifique in France, the University Paul Sabatier, and the Observatoire Midi-Pyrénées, an international planning workshop was recently held to define the scientific goals for such a global study.Eighty-five scientists from 15 nations representing fields as diverse as physical oceanography, dynamic and biogeochemical ocean modeling, ocean geochemistry, and paleoceanography attended the workshop. There was a broad consensus recognizing the need for a coordinated research effort in the spirit of the 1970s Geochemical Ocean Sections Study (GEOSECS) program, which led to fundamental advances in the understanding of ocean circulation and biogeochemical cycles. Dramatic advances have been made in a nalytical techniques, chemical sensors, and modeling since the days of GEOSECS, but progress in understanding the global biogeochemical cycles of trace elements and their isotopes has been limited by the lack of a large-scale coordinated effort. Workshop participants enthusiastically endorsed the development of such a program, for which the name GEOTRACES was adopted.

  10. A Sr and Mg isotopic study of soil and stream waters along an erosional gradient, Sierra Nevada, California

    NASA Astrophysics Data System (ADS)

    Rosen, V. B.; Maher, K.; Kouba, C. M.; Weinman, B. A.; Yoo, K.; Mudd, S. M.

    2012-12-01

    Since chemical weathering rates are proposed to regulate atmospheric CO2 concentrations and by extension global temperature over geologic timescales, understanding the relationship between chemical weathering rates and physical erosion is crucial to accurately interpreting Earth's climate history. The rate of supply of fresh minerals to the weathering zone is known to be an important control on chemical weathering rates. However, the consequences of physical erosion on the isotopic composition of weathering-derived solutes are more difficult to assess. This study capitalizes on a series of granitic hillslope transects with different erosion rates but similar climate, vegetation, and bedrock, in order to assess the consequences of erosion on the Sr and Mg isotopic composition of solutes. Reactive transport model simulations of varying complexity have been used to complement the field measurements and to analyze the sensitivity of fluid isotopic compositions to changes in key parameters such as erosion rate, flow rate, and biological cycling. The three hillslopes in the Feather River Basin, California reflect different degrees of channel erosion at their bases—BRC is a hillslope with active channel incision (60% average slope, below the knickpoint), FTA is a hillslope reflecting the transition between the relict and modern-day incising areas (50% average slope, at the knickpoint), and POMD is a 30% average hillslope in the relict landscape above the knickpoint. We measured the major element compositions, as well as the Sr and Mg isotopic compositions of soil water leaches (deionized water leaches), lysimeters, stream waters, and groundwaters by multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS). The 87Sr/86Sr values of soil and stream waters show minimal variation (0.7042 to 0.7046) as a function of soil depth, erosion rate, or sampling season despite abundant radiogenic biotite in the profiles. These results agree with the reactive transport

  11. Isotopically controlled semiconductors

    SciTech Connect

    Haller, Eugene E.

    2001-12-21

    Semiconductor bulk crystals and multilayer structures with controlled isotopic composition have attracted much scientific and technical interest in the past few years. Isotopic composition affects a large number of physical properties, including phonon energies and lifetimes, bandgaps, the thermal conductivity and expansion coefficient and spin-related effects. Isotope superlattices are ideal media for self-diffusion studies. In combination with neutron transmutation doping, isotope control offers a novel approach to metal-insulator transition studies. Spintronics, quantum computing and nanoparticle science are emerging fields using isotope control.

  12. Cryogenic Carbonate Formation on Mars: Clues from Stable Isotope Variations Seen in Experimental Studies

    NASA Technical Reports Server (NTRS)

    Socki, Richard A.; Niles, Paul B.; Fu, Qi; Gibson, Everett K., Jr.

    2010-01-01

    Discoveries of large deposits of sedimentary materials on the planet Mars by landers and orbiters have confirmed the widely held hypothesis that water has played a crucial role in the development of the martian surface. Recent studies have indicated that both water ice and liquid water may have been present and in the case of water ice perhaps is still present on or near the surface of Mars. However, there remains much controversy about the prevailing atmospheric conditions and climate of Mars during its history and whether liquid water existed on the martian surface simply during discrete geological events or whether this water was present over relatively much longer geologic time periods. The recent identification of Ca-rich carbonate by the Phoenix lander as well as its measurement of the isotopic composition of atmospheric CO2 has shown the importance of understanding the carbonates on Mars as an important sink of atmospheric carbon. This work compliments that of our past experiments where we produced cryogenic calcite in open containers, as analogs for terrestrial aufeis formation, and as a means for evaluating the fractionation of C-13 in CO2 during bicarbonate freezing [13]. Unlike our previous experiments in which carbonates were grown in ambient laboratory condition in open containers (atmospheric pressure and composition), this work attempts to quantify the amount of delta C-13 enrichment possible in both fluids and secondary carbonates formed from freezing of bicarbonate fluids under martian-like atmospheric conditions. Morphologic textures of produced carbonates in these experiments are also examined under SEM in order to identify the effect that the cryogenic freezing process has on the mineral's mineralogy. Understanding the role of kinetic isotope fractionation during formation of carbonates under martian-like conditions will aid in our ability to quantify the isotopic composition of the carbonate sink furthering our ability to model the climate

  13. Experimental and computer modeling studies of isotopically selective two-step laser photodissociation of small molecules. Final report

    SciTech Connect

    Zittel, P.F.

    1992-03-25

    The approach to laser isotope separation taken in this study is based on isotopically selective, two-step, laser photodissociation of small molecules. A primary goal of this study is the measurement of fundamental molecular processes which control the two-step, photodissociative isotope enrichment process. This objective has led to experimental measurements of uv photodissociation cross sections for vibrationally excited states of several small molecules, including the first cross section reported for any neutral molecule in a specific, excited vibrational state. A second goal of this study has been the laboratory demonstration of isotope enrichment for isotopes of practical interest and for processes with a potential for larger scale production. Where possible, efforts have focussed on the separation of middle isotopes, such as {sup 17}O and {sup 33}S, which are expensive and difficult to separate using other techniques. Considerable success has been achieved in demonstrating the enrichment of isotopes of bromine, carbon, oxygen and a third goal of this study has been the application of computer modeling to the two-step enrichment process. Experimental measurements define as many as possible of the critical photophysical and chemical parameters required by an ab initio computer model of the enrichment process. Progress toward these goals has been documented in detail in a variety of journal articles and technical reports. It is not the objective of this final report to discuss each aspect of the work done under this contract/grant in detail. A general overview of the program, touches briefly on each of the problems addressed by the study and provides references to more detailed discussions. 19 refs.

  14. Infrared Imaging System for Studying Brain Function

    NASA Technical Reports Server (NTRS)

    Mintz, Frederick; Mintz, Frederick; Gunapala, Sarath

    2007-01-01

    A proposed special-purpose infrared imaging system would be a compact, portable, less-expensive alternative to functional magnetic resonance imaging (fMRI) systems heretofore used to study brain function. Whereas a typical fMRI system fills a large room, and must be magnetically isolated, this system would fit into a bicycle helmet. The system would include an assembly that would be mounted inside the padding in a modified bicycle helmet or other suitable headgear. The assembly would include newly designed infrared photodetectors and data-acquisition circuits on integrated-circuit chips on low-thermal-conductivity supports in evacuated housings (see figure) arranged in multiple rows and columns that would define image coordinates. Each housing would be spring-loaded against the wearer s head. The chips would be cooled by a small Stirling Engine mounted contiguous to, but thermally isolated from, the portions of the assembly in thermal contact with the wearer s head. Flexible wires or cables for transmitting data from the aforementioned chips would be routed to an integrated, multichannel transmitter and thence through the top of the assembly to a patch antenna on the outside of the helmet. The multiple streams of data from the infrared-detector chips would be sent to a remote site, where they would be processed, by software, into a three-dimensional display of evoked potentials that would represent firing neuronal bundles and thereby indicate locations of neuronal activity associated with mental or physical activity. The 3D images will be analogous to current fMRI images. The data would also be made available, in real-time, for comparison with data in local or internationally accessible relational databases that already exist in universities and research centers. Hence, this system could be used in research on, and for the diagnosis of response from the wearer s brain to physiological, psychological, and environmental changes in real time. The images would also be

  15. Nitrogen isotope tracers of high-temperature fluid-rock interactions: Case study of the Catalina Schist, California

    NASA Astrophysics Data System (ADS)

    Bebout, Gray E.

    1997-09-01

    Nitrogen isotope data for metasomatized rocks, veins, and pegmatites in the Catalina Schist subduction zone metamorphic complex allow futher characterization of complex, high-P/T metasomatic proceses and evaluation of the scales of isotopic equilibration and fluid transport during subduction-zone metamorphism. Throughout the Catalina Schist, N resides predominantly as NH 4+ in white mica, which occurs in nearly all bulk compositions (i.e., metasedimentary, metamafic and, to a lesser extent, metaultramafic mélange) at all grades. Within each metamorphic unit of the Catalina Schist (ranging in grade from lawsonite-albite to amphibolite facies), δ 15N values of mica in metasomatized metamafic and metaultramafic rocks are consistent with the metasomatic addition of N from nearby, devolatilizing metasedimentary rocks into the initially N-poor mafic and ultramafic rocks. Within each unit, uniformity of mica δ 15N in metasomatized rocks relative to the δ 15N of metasedimentary rocks in the same unit implies mixing of N from nearby, heterogeneous metasedimentary sources, perhaps producing fluids with unifrom δ 15N at up to the kilometer scale. However, the trend in δ 15N of metasedimentary sources, with increasing metamorphic grade is inconsistent with larger scale up-temperature transfer of fluid (in this case, N 2-bearing) in the Catalina Schist paleosubduction zone; such flow (at scales of up to tens of kilometers) has been inferred through previous oxygen isotope study. Nitrogen isotope compositions are instead believed to have been controlled at a more local scale than the O isotope systematics, due to the more rock-dominated fluid-rock mass balance for N. The δ 15N of muscovite in leucosomes and pegmatites in amphibolite-grade metasedimentary exposures matches that of muscovite in metasedimentary hosts, implying minimal N-isotope fractionation during migmatization processes and possible transfer of metasedimentary N-isotope signatures in silicate melts. These

  16. Developments towards in-gas-jet laser spectroscopy studies of actinium isotopes at LISOL

    NASA Astrophysics Data System (ADS)

    Raeder, S.; Bastin, B.; Block, M.; Creemers, P.; Delahaye, P.; Ferrer, R.; Fléchard, X.; Franchoo, S.; Ghys, L.; Gaffney, L. P.; Granados, C.; Heinke, R.; Hijazi, L.; Huyse, M.; Kron, T.; Kudryavtsev, Yu.; Laatiaoui, M.; Lecesne, N.; Luton, F.; Moore, I. D.; Martinez, Y.; Mogilevskiy, E.; Naubereit, P.; Piot, J.; Rothe, S.; Savajols, H.; Sels, S.; Sonnenschein, V.; Traykov, E.; Van Beveren, C.; Van den Bergh, P.; Van Duppen, P.; Wendt, K.; Zadvornaya, A.

    2016-06-01

    To study exotic nuclides at the borders of stability with laser ionization and spectroscopy techniques, highest efficiencies in combination with a high spectral resolution are required. These usually opposing requirements are reconciled by applying the in-gas-laser ionization and spectroscopy (IGLIS) technique in the supersonic gas jet produced by a de Laval nozzle installed at the exit of the stopping gas cell. Carrying out laser ionization in the low-temperature and low density supersonic gas jet eliminates pressure broadening, which will significantly improve the spectral resolution. This article presents the required modifications at the Leuven Isotope Separator On-Line (LISOL) facility that are needed for the first on-line studies of in-gas-jet laser spectroscopy. Different geometries for the gas outlet and extraction ion guides have been tested for their performance regarding the acceptance of laser ionized species as well as for their differential pumping capacities. The specifications and performance of the temporarily installed high repetition rate laser system, including a narrow bandwidth injection-locked Ti:sapphire laser, are discussed and first preliminary results on neutron-deficient actinium isotopes are presented indicating the high capability of this novel technique.

  17. Potential of Opuntia ficus-indica for air pollution biomonitoring: a lead isotopic study.

    PubMed

    El Hayek, Eliane; El Samrani, Antoine; Lartiges, Bruno; Kazpard, Veronique; Benoit, Mathieu; Munoz, Marguerite

    2015-11-01

    Opuntia ficus-indica (Ofi) is a long-domesticated cactus that is widespread throughout arid and semiarid regions. Ofi is grown for both its fruits and edible cladodes, which are flattened photosynthetic stems. Young cladodes develop from mother cladodes, thus forming series of cladodes of different ages. Therefore, successive cladodes may hold some potential for biomonitoring over several years the local atmospheric pollution. In this study, cladodes, roots, dust deposited onto the cladodes, and soil samples were collected in the vicinity of three heavily polluted sites, i.e., a fertilizer industry, the road side of a highway, and mine tailings. The lead content was analyzed using atomic absorption spectroscopy (AAS) and inductively coupled plasma-mass spectrometry (ICP-MS). Scanning electron microscopy coupled with energy dispersive X-ray spectroscopy (SEM-EDX) was used to characterize the cladode surfaces and the nature of dust deposit, and the lead isotopes were analyzed to identify the origin of Pb. The results show that (i) Ofi readily bioaccumulates Pb, (ii) the lead isotopic composition of cladodes evidences a foliar pathway of lead into Ofi and identifies the relative contributions of local Pb sources, and (iii) an evolution of air quality is recorded with successive cladodes, which makes Ofi a potential biomonitor to be used in environmental and health studies. PMID:26160126

  18. Hydrogeochemistry and isotope studies of groundwater in the Ga West Municipal Area, Ghana

    NASA Astrophysics Data System (ADS)

    Saka, David; Akiti, Tetteh T.; Osae, Shiloh; Appenteng, Michael K.; Gibrilla, Abass

    2013-09-01

    This paper assesses groundwater in the Ga West Municipal Area of Ghana using hydrogeochemistry and isotope approaches. High salinity groundwaters are obtained in the municipality which poses problems for current and future domestic water supply exploitation. The increase in salinity is related to the dissolution of minerals in the host rocks and the evaporative concentration of solutes. The dominant groundwater composition in both shallow and deep wells sampled is Na-Cl. The concentration of the Na-Cl was observed to increase substantially with well depths. The mixing of freshwater of the shallow hand dug wells with that of saline water of the deep boreholes was noted in the shift from Ca-HCO3 facies to Ca-Cl facies. Schoeller diagram showed that groundwater in the study area is recharged from a similar source. The Schoeller diagram also showed the gradual increase in concentration of the major ions with depth. This leads to salinization in the deep boreholes. The oxygen and hydrogen isotope compositions in the groundwater samples suggest that groundwater recharge is of meteoric origin with few samples showing evidence of evaporation. An average deuterium excess of rainfall of 14.2 ‰ was observed, which indicates the significance of kinetic evaporation due to low humidity conditions prevalent in the study area. The d-excess also indicates modern recharge along the foothills of the Akwapim-Togo Ranges.

  19. Initial rate and isotope exchange studies of rat skeletal muscle hexokinase

    SciTech Connect

    Ganson, N.J.; Fromm, H.J.

    1985-10-05

    The kinetic mechanism of rat skeletal muscle hexokinase (hexokinase II) was investigated in light of a proposal by Cornish-Bowden and his co-workers. The authors investigated the mechanism of action of hexokinase II by studying initial rate kinetics in the nonphysiological direction and by isotope exchange at chemical equilibrium. The former experiments were carried out in the absence of inhibitors and then with AMP, which is a competitive inhibitor of ADP, and with glucose 1,6-bisphosphate, a competitive inhibitor of glucose-6-P. The findings from these experiments suggest that the kinetic mechanism is rapid equilibrium Random Bi Bi. Isotope exchange at equilibrium studies also supports the random nature of the muscle hexokinase reaction; however, they also suggest that the mechanism is partially ordered, i.e. there is a preferred pathway associated with the branched mechanism. Approximately two-thirds of the flux through the hexokinase reaction involves the glucose on first glucose-6-P off last branch of the Random Bi Bi mechanism. These results imply that the kinetic mechanism is steady state Random Bi Bi. There is some evidence to suggest that glucose-6-P binds to an allosteric site on muscle hexokinase, but none to suppose that ATP binds allosterically.

  20. Reconnaissance isotopic and hydrochemical study of Cuatro Ciénegas groundwater, Coahuila, México

    NASA Astrophysics Data System (ADS)

    Johannesson, Karen H.; Cortés, Alejandra; Kilroy, Kathryn C.

    2004-10-01

    The springs of the Cuatro Ciénegas bolson (Four Marshes basin), Coahuila, México, support more than 70 endemic species of biota. The specifics of the groundwater flow regime, however, remain a mystery. Water samples were collected from a series of springs and pools and one canal in the Cuatro Ciénegas bolson and analyzed for field parameters (temperature, pH, conductivity, alkalinity) and stable oxygen and hydrogen isotopes in an attempt to begin a systematic study of the hydrogeology of the region. Groundwaters discharging directly along a fault-controlled spring line in Cretaceous carbonate rocks of the Cupido-Aurora aquifer are the most dilute (lowest conductivities) and warmest of those sampled. Cuatro Ciénegas waters are characterized by circumneutral pH (6.9-7.7) and reasonably low alkalinity (160-215 mg/kg as HCO 3). The δ18O values of Cuatro Ciénegas waters range from -8.2 to -5.7‰, with a mean of -6.5±0.82‰, whereas δD ranges from -52 to -43‰, with a mean of -46.6±3.2‰. The majority of the water samples plot subparallel and beneath the local meteoric water line; those samples collected farthest from the spring line exhibit the most enriched δ18O and δD values. The stable isotope data indicate that isotopic enrichment of groundwaters by evaporation following discharge and subsequent surface flow is an important process within the Cuatro Ciénegas bolson. The isotope data also suggest that a fraction of Cuatro Ciénegas groundwater originates with local recharge in mountains surrounding the bolson. Those springs that issue from the western base of the Sierra de San Marcos mountain range are recharged in part in these mountains, whereas groundwaters discharging from Laguna Anteojo in the northern part of the bolson are more likely recharged in the higher San de la Madera mountain range. An estimate of the water balance suggests that interbasin flow also may contribute to the considerable groundwater discharge.

  1. Study on Over-Sampling for Imager

    NASA Technical Reports Server (NTRS)

    Kigawa, Seiichiro; Sullivan, Pamela C.

    1998-01-01

    This report describes the potential improvement of the effective ground resolution of MTSAT (Multi-functional Transport Satellite) Imager. The IFOV (Instantaneous Field of View) of MTSAT Imager is 4 km for infrared and 1 km visible. A combination of some images acquired by the MTSAT Imager could generate 2 km-latticed infrared images. Furthermore, it is possible to generate an effective 2 km IFOV image by the enhancement of the 2 km-latticed image using Digital Signal Processing. This report also mentions the on-orbit demonstration of this concept.

  2. He-Ne-Ar isotope studies of mafic volcanic rocks and mantle xenoliths from the East African Rift System - contrasting isotope signals in different rift branches

    NASA Astrophysics Data System (ADS)

    Halldorsson, S. A.; Hilton, D. R.; Scarsi, P.; Abebe, T.; Massi, K. M.; Barry, P. H.; Fischer, T. P.; de Moor, J.; Rudnick, R. L.

    2010-12-01

    Helium isotope studies of the East African Rift System (EARS) suggest the involvement of a deep mantle plume(s) beneath the northern (Ethiopian) segment [1-3]. The highest 3He/4He (RA) signatures found to date show a close association with the greatest magma volumes erupted since the Early Cenozoic in the region. While the helium isotope characteristics are well established in the Ethiopia-Afar region, Ne and Ar systematics remain poorly constrained. Using a combined He-Ne-Ar isotope approach, our aim is to determine the regional extent of the influence of the Afar plume and to distinguish between subcontinental lithospheric mantle (SCLM) and/or a possible second mantle plume sources located to the south of the Turkana Depression. Xenoliths and mafic lavas from N-Tanzania display a limited range in He isotopes (5-7 RA) with exceptions at Arusha (7.8RA) and Labait (8.7RA), through 7.1-8.7 RA in N-Kenya and S-Ethiopia, to 14.3 RA in the Main Ethiopian Rift and Afar, spanning nearly the entire range of previously reported values. The mean 3He/4He ratio from of lavas and xenoliths from N-Tanzania is remarkably close to the global average of 6.1±0.9 (RA) for continental xenoliths and basalts, thought to represent the SCLM [4]. Thus far, only MORB-like values of 7.3-8.3 RA have been found in volcanics of the Western rift. Initial Ne isotope data reveal the presence of a solar-like Ne component in xenoliths from the Ethiopia-Afar region, with extrapolated 21Ne/22Neex ratios of 0.0365 (assuming Ne-B = 12.5). This trend overlaps that of the Loihi-Kilauea line (L-K). Interestingly, a xenolith from N-Tanzania has a 21Ne/22Neex ratio of 0.0415, falling on a trajectory intermediate between MORB and L-K. The highest 40Ar/36Ar ratio obtained on phenocrysts/xenoliths to date is 1510. The generally low 3He/4He ratios of N-Tanzania likely result from different mixing proportions of asthenospheric sources with lithospheric material, the latter having developed lower 3He/4He ratios

  3. Tracing amino acid exchange during host-pathogen interaction by combined stable-isotope time-resolved Raman spectral imaging

    NASA Astrophysics Data System (ADS)

    Naemat, Abida; Elsheikha, Hany M.; Boitor, Radu A.; Notingher, Ioan

    2016-02-01

    This study investigates the temporal and spatial interchange of the aromatic amino acid phenylalanine (Phe) between human retinal pigment epithelial cell line (ARPE-19) and tachyzoites of the apicomplexan protozoan parasite Toxoplasma gondii (T. gondii). Stable isotope labelling by amino acids in cell culture (SILAC) is combined with Raman micro-spectroscopy to selectively monitor the incorporation of deuterium-labelled Phe into proteins in individual live tachyzoites. Our results show a very rapid uptake of L-Phe(D8) by the intracellular growing parasite. T. gondii tachyzoites are capable of extracting L-Phe(D8) from host cells as soon as it invades the cell. L-Phe(D8) from the host cell completely replaces the L-Phe within T. gondii tachyzoites 7-9 hours after infection. A quantitative model based on Raman spectra allowed an estimation of the exchange rate of Phe as 0.5-1.6 × 104 molecules/s. On the other hand, extracellular tachyzoites were not able to consume L-Phe(D8) after 24 hours of infection. These findings further our understanding of the amino acid trafficking between host cells and this strictly intracellular parasite. In particular, this study highlights new aspects of the metabolism of amino acid Phe operative during the interaction between T. gondii and its host cell.

  4. Tracing amino acid exchange during host-pathogen interaction by combined stable-isotope time-resolved Raman spectral imaging

    PubMed Central

    Naemat, Abida; Elsheikha, Hany M.; Boitor, Radu A.; Notingher, Ioan

    2016-01-01

    This study investigates the temporal and spatial interchange of the aromatic amino acid phenylalanine (Phe) between human retinal pigment epithelial cell line (ARPE-19) and tachyzoites of the apicomplexan protozoan parasite Toxoplasma gondii (T. gondii). Stable isotope labelling by amino acids in cell culture (SILAC) is combined with Raman micro-spectroscopy to selectively monitor the incorporation of deuterium-labelled Phe into proteins in individual live tachyzoites. Our results show a very rapid uptake of l-Phe(D8) by the intracellular growing parasite. T. gondii tachyzoites are capable of extracting l-Phe(D8) from host cells as soon as it invades the cell. l-Phe(D8) from the host cell completely replaces the l-Phe within T. gondii tachyzoites 7–9 hours after infection. A quantitative model based on Raman spectra allowed an estimation of the exchange rate of Phe as 0.5–1.6 × 104 molecules/s. On the other hand, extracellular tachyzoites were not able to consume l-Phe(D8) after 24 hours of infection. These findings further our understanding of the amino acid trafficking between host cells and this strictly intracellular parasite. In particular, this study highlights new aspects of the metabolism of amino acid Phe operative during the interaction between T. gondii and its host cell. PMID:26857158

  5. Charge-coupled device image sensor study

    NASA Technical Reports Server (NTRS)

    1973-01-01

    The design specifications and predicted performance characteristics of a Charge-Coupled Device Area Imager and a Charge-Coupled Device Linear Imager are presented. The Imagers recommended are intended for use in space-borne imaging systems and therefore would meet the requirements for the intended application. A unique overlapping metal electrode structure and a buried channel structure are described. Reasons for the particular imager designs are discussed.

  6. A neutronic feasibility study for LEU conversion of the high flux isotope reactor (HFIR).

    SciTech Connect

    Mo, S. C.

    1998-01-14

    A neutronic feasibility study was performed to determine the uranium densities that would be required to convert the High Flux Isotope Reactor (HFIR) at the Oak Ridge National Laboratory (ORNL) from HEU (93%) to LEU (<20%)fuel. The LEU core that was studied is the same as the current HEU core, except for potential changes in the design of the fuel plates. The study concludes that conversion of HFIR from HEU to LEU fuel would require an advanced fuel with a uranium density of 6-7 gU/cm{sup 3} in the inner fuel element and 9-10 gU/cm{sup 3} in the outer fuel element to match the cycle length of the HEU core. LEU fuel with uranium density up to 4.8 gU/cm{sup 3} is currently qualified for research reactor use. Modifications in fuel grading and burnable poison distribution are needed to produce an acceptable power distribution.

  7. Environmental isotopic and hydrochemical study of groundwater in the Ejina Basin, northwest China

    NASA Astrophysics Data System (ADS)

    Su, Y. H.; Zhu, G. F.; Feng, Q.; Li, Z. Z.; Zhang, F. P.

    2009-08-01

    The study investigates the groundwater evolution and its residence time in the Ejina Basin, northwest China according to isotope and hydrochemical analyses results. The groundwater chemistry is mainly controlled by the dissolution of halite, Glauber’s salt, gypsum, dolomite and calcite, also influenced by other processes such as evaporation, ion exchange, and deposition. Based on tritium content in atmospheric precipitation and by adopting a model with exponential time distribution function, the mean residence time of the unconfined aquifer groundwater with fairly high tritium activities (21-49 TU) is evaluated. The results show that these groundwaters have low residence time (5-120 years) and are renewable. In contrast, the deep confined groundwaters are tritium-free and radiocarbon values range from 18.3 to 26.7 pmc. According to the most commonly used 14C correction models, the radiocarbon groundwater ages were calculated which yield ages of approximately 4,087-9,364 years BP. Isotopic signatures indicate formation of deep confined groundwaters in a colder and wetter climate during the late Pleistocene and Holocene. It is suggested that long-term, rational water usage guide should be set up for the Heihe River Basin as a whole to permit a considerable discharge to the Ejina Basin.

  8. Inferences of paleoenvironment from petrographic, chemical and stable-isotope studies of calcretes and fracture calcites

    SciTech Connect

    Vaniman, D.T.; Whelan, J.F.

    1994-03-01

    Past research has indicated a genetic connection between calcite formed in calcretes at the surface of Yucca Mountain, Nevada, and calcites deposited in underlying fractures of the unsaturated zone. This common genesis suggests that paleoenvironmental information, as well as the timing and pathways of past recharge episodes, might be obtained from studies of the deposits in both the calcretes and the unsaturated fractures. Chemical and isotopic modification of calcite-precipitating fluids appears to begin at the surface, largely under the influence of plant roots and their decay products. Chemical characteristics of the deeper calcites are either initiated or largely defined within the first few meters of fluid migration into the unsaturated tuffs beneath the calcretes. However, petrographic and isotopic data indicate a very unique low-{delta}{sup 13}C microenvironment that is localized at the upper surfaces of the calcretes. These surfaces form an interface in the soil horizon where infiltration may pond above the underlying carbonate ``plug.`` In order to decipher the chemistry and petrology of past recharge events, it is important to first understand microenvironments such as this that contribute to mineral precipitation/dissolution events in the pedogenic environment.

  9. Imaging studies in patients with spinal pain

    PubMed Central

    Ferrari, Robert

    2016-01-01

    Abstract Objective To evaluate an a priori threshold for advanced imaging in patients with spinal pain. Design Patients with spinal pain in any region for 6 to 52 weeks were assessed to determine if radiologic studies beyond x-ray scans were indicated, including magnetic resonance imaging (MRI), computed tomography (CT), and radionuclide bone scans. An a priori threshold was set before MRI, CT, or bone scans would be considered. Those who did not have MRI, CT, or bone scans ordered were followed for at least 1 year to determine if any of them went on to be diagnosed with a more serious spinal disorder (eg, infection, fracture, spondylitis, tumour, neurologic compression). Setting Four large primary care clinics in Edmonton, Alta. Participants A total of 1003 consecutively presenting patients with symptoms suspected to be related to the spine (for a duration of generally 6 to 52 weeks) who had not already undergone advanced imaging and did not have a diagnosis of nonbenign back pain. Main outcome measures Number of cases of nonbenign spinal disorder in participants who underwent advanced imaging and participants who did not undergo advanced imaging (ie, did not have any red flags). Results There were 399 women (39.8%) and 604 men (60.2%). The mean (SD) age of the group was 47.2 (14.6) years. The mean (SD) duration of symptoms was 15.1 (8.6) weeks. Of the 1003 participants, 110 met an a priori threshold for undergoing at least 1 of MRI, CT, or bone scan. In these 110 participants, there were newly diagnosed cases of radiculopathy (n = 12), including a case of cauda equina syndrome; spondyloarthropathy (n = 6); occult fracture (n = 2); solitary metastasis (n = 1); epidural lipomatosis (n = 1); osteomyelitis (n = 1), and retroperitoneal hematoma (n = 1), each of which was considered likely to be the cause of the patient’s spinal symptoms. The remaining 893 participants were followed for at least 1 year and none showed evidence of a nonbenign cause of his or her

  10. Image quality and dose efficiency of high energy phase sensitive x-ray imaging: Phantom studies

    PubMed Central

    Wong, Molly Donovan; Wu, Xizeng; Liu, Hong

    2014-01-01

    The goal of this preliminary study was to perform an image quality comparison of high energy phase sensitive imaging with low energy conventional imaging at similar radiation doses. The comparison was performed with the following phantoms: American College of Radiology (ACR), contrast-detail (CD), acrylic edge and tissue-equivalent. Visual comparison of the phantom images indicated comparable or improved image quality for all phantoms. Quantitative comparisons were performed through ACR and CD observer studies, both of which indicated higher image quality in the high energy phase sensitive images. The results of this study demonstrate the ability of high energy phase sensitive imaging to overcome existing challenges with the clinical implementation of phase contrast imaging and improve the image quality for a similar radiation dose as compared to conventional imaging near typical mammography energies. In addition, the results illustrate the capability of phase sensitive imaging to sustain the image quality improvement at high x-ray energies and for – breast – simulating phantoms, both of which indicate the potential to benefit fields such as mammography. Future studies will continue to investigate the potential for dose reduction and image quality improvement provided by high energy phase sensitive contrast imaging. PMID:24865208

  11. APQ-102 imaging radar digital image quality study

    NASA Astrophysics Data System (ADS)

    Griffin, C. R.; Estes, J. M.

    1982-11-01

    A modified APQ-102 sidelooking radar collected synthetic aperture radar (SAR) data which was digitized and recorded on wideband magnetic tape. These tapes were then ground processed into computer compatible tapes (CCT's). The CCT's may then be processed into high resolution radar images by software on the CYBER computer.

  12. APQ-102 imaging radar digital image quality study

    NASA Technical Reports Server (NTRS)

    Griffin, C. R.; Estes, J. M.

    1982-01-01

    A modified APQ-102 sidelooking radar collected synthetic aperture radar (SAR) data which was digitized and recorded on wideband magnetic tape. These tapes were then ground processed into computer compatible tapes (CCT's). The CCT's may then be processed into high resolution radar images by software on the CYBER computer.

  13. An isotopic study of biogeochemical relationships between carbonates and organic carbon in the Greenhorn Formation

    NASA Technical Reports Server (NTRS)

    Hayes, J. M.; Popp, Brian N.; Takigiku, Ray; Johnson, Marcus W.

    1989-01-01

    Carbon-isotopic compositions of total carbonate, inoceramid carbonate, micritic carbonate, secondary cements, total organic carbon, and geoporphyrins have been measured in 76 different beds within a 17-m interval of a core through the Greenhorn Formation, an interbedded limestone and calcareous shale unit of Cretaceous age from the Western Interior Seaway of North America. Results are considered in terms of variations in the processes of primary production and in secondary processes. It is shown that the porphyrin isotopic record reflects primary isotopic variations more closely than the TOC isotopic record and that, in these sediments, TOC is enriched in C-13 relative to its primary precursor by 0.6 to 2.8 percent. This enrichment is attributed to isotope effects within the consumer foodweb and is associated with respiratory heterotrophy. Variation in this secondary enrichment are correlated with variations in the isotopic composition of marine carbonate.

  14. Sulfur isotope study of the Velardeña skarn (Zn-Pb), Durango, Mexico

    NASA Astrophysics Data System (ADS)

    Jimenez, A.

    2012-04-01

    Sulfur isotope study of the Velardeña skarn (Zn-Pb), Durango, Mexico Abigail Jimenez-Franco1*, Pura Alfonso Abella2, Carles Canet3, Eduardo González-Partida4 1 Posgrado en Ciencias de la Tierra, Universidad Nacional Autónoma de México, Ciudad Universitaria, Delegación Coyoacán, 04510 México D.F., Mexico 2 Departament d'Enginyeria Minera i Recursos Naturals, Universitat Politècnica de Catalunya, Av de Les Bases de Manresa 61-73, 08242 Manresa. 3Instituto de Geofísica, Universidad Nacional Autónoma de México, Ciudad Universitaria, Delegación Coyoacán, 04510 México D.F., Mexico 4Centro de Geociencias, Universidad Nacional Autónoma de México, Campus Juriquilla, Boulevard Juriquilla 3001, 76230 Santiago de Querétaro, Qro., Mexico The Velardeña mining district is located in north-eastern part of the state of Durango, in northern of Mexico. The ore deposit is a lead-zinc, garnet-rich skarn developed at the contact between granite porphyry dikes (Eocene) and well-laminated limestones with interbedded chert (Albian-Cenomanian). A study of sulfur isotopes has been carried out in various sulfide minerals of the ores of Velardeña, in order to: (a) constrain the possible sources of sulfur and, therefore, better understand the sulfide mineralizing processes, and (b) to estimate the temperature of the ore-forming stage of the skarn. Sulfur isotope analyses were performed in 21 pure fractions of sulfide minerals of the ore mineralization (pyrite, chalcopyrite, sphalerite and galena). The mineral separation was performed using a series of sieves, and the purity of the samples was verified under a binocular microscope. Isotopic analyses were done on a Finnigan MAT Delta C flow elemental analyzer coupled to a TC-EA, according with the method of Giesemann et al. (1974). The δ34S values of the analyzed sulfides range mostly between -0.6 and +2.6 ‰ (relative to the CDT standard). These values are indicative of a magmatic source of sulfur. A single analysis falls

  15. Carbon Isotopic Studies of Assimilated and Ecosystem Respired CO2 in a Southeastern Pine Forest. Final Report and Conference Proceedings

    SciTech Connect

    Conte, Maureen H

    2008-04-10

    Carbon dioxide is the major “greenhouse” gas responsible for global warming. Southeastern pine forests appear to be among the largest terrestrial sinks of carbon dioxide in the US. This collaborative study specifically addressed the isotopic signatures of the large fluxes of carbon taken up by photosynthesis and given off by respiration in this ecosystem. By measuring these isotopic signatures at the ecosystem level, we have provided data that will help to more accurately quantify the magnitude of carbon fluxes on the regional scale and how these fluxes vary in response to climatic parameters such as rainfall and air temperature. The focus of the MBL subcontract was to evaluate how processes operating at the physiological and ecosystem scales affects the resultant isotopic signature of plant waxes that are emitted as aerosols into the convective boundary layer. These wax aerosols provide a large-spatial scale integrative signal of isotopic discrimination of atmospheric carbon dioxide by terrestrial photosynthesis (Conte and Weber 2002). The ecosystem studies have greatly expanded of knowledge of wax biosynthetic controls on their isootpic signature The wax aerosol data products produced under this grant are directly applicable as input for global carbon modeling studies that use variations in the concentration and carbon isotopic composition of atmospheric carbon dioxide to quantify the magnitude and spatial and temporal patterns of carbon uptake on the global scale.

  16. The Magnetosphere Imager Mission Concept Definition Study

    NASA Technical Reports Server (NTRS)

    Johnson, L.; Herrmann, M.; Alexander, Reggie; Beabout, Brent; Blevins, Harold; Bridge, Scott; Burruss, Glenda; Buzbee, Tom; Carrington, Connie; Chandler, Holly; Chu, Phillip; Chubb, Steve; Cushman, Paul; DeSanctis, Carmine; Edge, Ted; Freestone, Todd; French, Ray; Gallagher, Dennis; Hajos, Greg; Herr, Joel

    1997-01-01

    For three decades, magnetospheric field and plasma measurements have been made by diverse instruments flown on spacecraft in many different orbits, widely separated in space and time, and under various solar and magnetospheric conditions. Scientists have used this information to piece together an intricate, yet incomplete view of the magnetosphere. A simultaneous global view, using various light wavelengths and energetic neutral atoms, could reveal exciting new data and help explain complex magnetospheric processes, thus providing us with a clear picture of this region of space. The George C. Marshall Space Flight Center (MSFC) is responsible for defining the Magnetosphere Imager mission which will study this region of space. A core instrument complement of three imagers (with the potential addition of one or more mission enhancing instrument) will fly in an elliptical polar Earth orbit with an apogee of 44,600 kilometers and a perigee of 4,800 km. This report will address the mission objectives, spacecraft design concepts, and the results of the MSFC concept definition study.

  17. Isotope studies to determine dry deposition of sulfate to deciduous and coniferous trees: Final draft

    SciTech Connect

    Garten, C.T. Jr.

    1988-01-01

    Experiments have been conducted at two locations near Oak Ridge, Tennessee, with radioactive /sup 35/S (87 day half-life) to examine the cycling behavior of sulfur in yellow poplar (Liriodendron tulipifera), red maple (Acer rubrum), and loblolly pine (Pinus taeda) trees. Some findings pertain to methods development for estimating dry deposition of sulfur to forest canopies and the magnitude of sulfur emissions from natural sources (Task II). We will determine through field studies, the internal cycling, storage, and biogenic emission of sulfur, as traced by /sup 35/SO/sub 4//sup 2 -/, in environments impacted by atmospheric sulfate deposition; and will determine through isotope dilution studies, the contribution of foliar leaching and dry deposition to net throughfall (NTF) sulfate concentrations beneath deciduous and coniferous trees in such environments. 3 refs., 2 figs., 1 tab.

  18. Helium isotope study of geothermal features in Chile with field and laboratory data

    DOE Data Explorer

    Dobson, Patrick

    2013-02-11

    Helium isotope and stable isotope data from the El Tatio, Tinginguirica, Chillan, and Tolhuaca geothermal systems, Chile. Data from this submission are discussed in: Dobson, P.F., Kennedy, B.M., Reich, M., Sanchez, P., and Morata, D. (2013) Effects of volcanism, crustal thickness, and large scale faulting on the He isotope signatures of geothermal systems in Chile. Proceedings, 38th Workshop on Geothermal Reservoir Engineering, Stanford University, Feb. 11-13, 2013

  19. Animal imaging studies of potential brain damage

    NASA Astrophysics Data System (ADS)

    Gatley, S. J.; Vazquez, M. E.; Rice, O.

    To date, animal studies have not been able to predict the likelihood of problems in human neurological health due to HZE particle exposure during space missions outside the Earth's magnetosphere. In ongoing studies in mice, we have demonstrated that cocaine stimulated locomotor activity is reduced by a moderate dose (120 cGy) of 1 GeV 56Fe particles. We postulate that imaging experiments in animals may provide more sensitive and earlier indicators of damage due to HZE particles than behavioral tests. Since the small size of the mouse brain is not well suited to the spatial resolution offered by microPET, we are now repeating some of our studies in a rat model. We anticipate that this will enable us to identify imaging correlates of behavioral endpoints. A specific hypothesis of our studies is that changes in the metabolic rate for glucose in striatum of animals will be correlated with alterations in locomotor activity. We will also evaluate whether the neuroprotective drug L-deprenyl reduces the effect of radiation on locomotor activity. In addition, we will conduct microPET studies of brain monoamine oxidase A and monoamine oxidase B in rats before and at various times after irradiation with HZE particles. The hypothesis is that monoamine oxidase A, which is located in nerve terminals, will be unchanged or decreased after irradiation, while monoamine oxidase B, which is located in glial cells, will be increased after irradiation. Neurochemical effects that could be measured using PET could in principle be applied in astronauts, in terms of detecting and monitoring subtle neurological damage that might have occurred during long space missions. More speculative uses of PET are in screening candidates for prolonged space missions (for example, for adequate reserve in critical brain circuits) and in optimizing medications to treat impairments after missions.

  20. The isotope composition of water vapour: A powerful tool to study transport and chemistry of middle atmospheric water vapour

    NASA Astrophysics Data System (ADS)

    Bechtel, Ch.; Zahn, A.

    2003-07-01

    A one-dimensional chemistry model is applied to study the stable hydrogen (D) and stable oxygen isotope (17O, 18O) composition of water vapour in stratosphere and mesosphere. The stable isotope ratios of tropospheric H2O are determined by "physical'' fractionation effects, i.e. phase changes, diffusion processes, and mixing of air masses. Due to these processes water vapour entering the stratosphere (i) is mass-dependently fractionated (MDF), i.e. shifts in the isotope ratio 17O/16O are ~0.52 times of those of 18O/16O and (ii) shows isotope shifts in D/H, which are ~5 times of those in 18O/16O. In stratosphere and mesosphere "chemical'' fractionation, that are the oxidation of methane, re-cycling of H2O via the HOx family, and isotope exchange reactions are shown to considerably enhance the isotope ratios in the imported tropospheric H2O. Enrichments relative to the isotope ratios at the tropopause are used to derive the partitioning of tropospheric (unmodified), re-cycled and in situ generated H2O. The model reasonably predicts overall increases of the stable isotope ratios in H2O by ~23% for D/H, ~8.5% for 17O/16O, and ~14% for 18O/16O. The17O/16O and 18O/16O ratios in H2O are shown to be a measure of the partitioning of HOx that receives its O atom either from the reservoirs O2 or O3. In the entire middle atmosphere, MDF O2 is the major donator of oxygen atoms incorporated in OH and HO2 and thus in H2O. It is demonstrated that in the stratosphere mass-independent fractionation (MIF) in O3 in a first step is transferred to the NOx family and only in a second step to HOx and H2O. In contrast to CO2, O(1D) only plays a minor role in this MIF transfer. The major uncertainty in our calculation arises from the many badly quantified isotope exchange reactions and kinetic isotope fractionation factors.

  1. Changes in the lead isotopic composition of blood, diet and air in Australia over a decade: Globalization and implications for future isotopic studies

    SciTech Connect

    Gulson, Brian . E-mail: bgulson@gse.mq.edu.au; Mizon, Karen; Korsch, Michael; Taylor, Alan

    2006-01-15

    Source apportionment in biological or environmental samples using the lead isotope method, where there are diverse sources of lead, relies on a significant difference between the isotopic composition in the target media and the sources. Because of the unique isotopic composition of Australian lead, source apportionment has been relatively successful in the past. Over the period of a decade, the {sup 206}Pb/{sup 204}Pb ratio for Australian (mainly female) adults has shown an increase from a geometric mean of 16.8-17.3. Associated with this increase, there has been a decrease in mean blood lead concentration from 4.7 to 2.3 {mu}g/dL, or about 5% per year, similar to that observed in other countries. Lead in air, which up until 2000 was derived largely from the continued use of leaded gasoline, showed an overall increase in the {sup 206}Pb/{sup 204}Pb ratio during 1993-2000 from 16.5 to 17.2. Since 1998 the levels of lead in air were less than 0.2 {mu}g/m{sup 3} and would contribute negligibly to blood lead. Over the 10-year period, the {sup 206}Pb/{sup 204}Pb ratio in diet, based mainly on quarterly 6-day duplicate diets, increased from 16.9 to 18.3. The lead concentration in diet showed a small decrease from 8.7 to 6.4 {mu}g Pb/kg although the daily intake increased markedly from 7.4 to 13.9 {mu}g Pb/day during the latter part of the decade probably reflecting differences in demographics. The changes in blood lead from sources such as lead in bone or soil or dust is not dominant because of the low {sup 206}Pb/{sup 204}Pb ratios in these media. Unless there are other sources not identified and analysed for these adults, it would appear that in spite of our earlier conclusions to the contrary, diet does make an overall contribution to blood lead, and this is certainly the case for specific individuals. Certain population groups from south Asia, south-east Asia, the Middle East and Europe (e.g. UK) are unsuitable for some studies as their isotopic ratios in blood are

  2. First principles study of lattice thermal conductivity and large isotope effect in materials

    NASA Astrophysics Data System (ADS)

    Broido, David; Lindsay, Lucas; Reinecke, Tom

    2014-03-01

    The isotope effect--the percent enhancement to a material's lattice thermal conductivity, k, with isotopic purification--depends on the interplay between phonon-isotope and phonon-phonon scattering. Diamond is known to have the largest measured room temperature (RT) isotope effect of any bulk crystal, achieving a k enhancement of 50%. Using an ab initioBoltzmann transport equation approach, we have identified several other materials with far larger RT isotope effects. In particular, we find that germanium carbide (GeC) and beryllium selenide (BeSe) have RT isotope effects of 450%, almost an order of magnitude higher than that in diamond. Isotopic purification in these materials gives surprisingly high intrinsic RT k values, over 1500 Wm-1K-1 for GeC and over 600 Wm-1 K-1 for BeSe, well above those of the best metals. These large values stem from fundamental material properties that give both enhanced phonon scattering by isotopes and weak anharmonic phonon-phonon scattering. The physical insights discussed in this work provide guidance for efficient manipulation of thermal transport properties of compound semiconductors through isotopic modification. This work was supported by ONR, DARPA and NSF.

  3. Interstellar SiC: Extended Studies of C, N, and SI Isotopes in Small Single Grains

    NASA Astrophysics Data System (ADS)

    Hoppe, P.; Strebel, R.; Eberhardt, P.; Amari, S.; Lewis, R. S.

    1993-07-01

    In search of grain-size dependent characteristics of interstellar SiC, we have measured the C, N, and Si isotopes in 596 single grains from Murchison separate KJE (average size 1.14 micrometers) [1]. So far, extended studies of single SiC grains from the Murchison K-series were made on separates KJG (average size 3.02 micrometers) and KJH (average size 4.57 micrometers) [2] and a limited dataset was also obtained for separate KJF (average size 1.86 micrometers) [2,3]. As it is the case for the larger grains, most grains from KJE have heavy carbon and light nitrogen. ^12C/^13C ratios vary between 2.3 and 270. The distribution of ^12C/^13C ratios is almost identical to those observed for the larger-grain separates, with most grains having ^12C/^13C ~40-100 (Fig. 1a-c). ^14N/^15N ratios vary between 48 and >10,000. The distribution of ^14N/^15N ratios clearly differs from those observed for the larger-grain separates (Fig. 1d-f). Grains from separate KJE, on the average, have much higher ^14N/^15N ratios. The median value is 2800 compared to 1250 for KJG and 550 for KJH [2]. As is evident from these numbers, there is a clear trend with the typical ^14N/^15N ratio increasing with decreasing grain size. In close agreement with the larger grains, most grains from KJE have delta^29Si ~ -50 to 200 per mil and delta^30Si ~ 0 to 160 per mil, in a three-isotope-plot lying along a line with slope ~1.1. However, there are 12 grains clearly off this line with 10 of them being depleted in ^29Si and enriched in ^30Si. Nine grains were identified as grains X [4], being charaterized by light C, heavy N, and light Si. Five of them, in addition, show a very high nitrogen content, ~5x higher than that of a typical grain from KJE. Furthermore, one grain has the Si-isotopic signature of grains X, but heavy C. While the observed C-isotopic ratios for the majority of the grains can be explained by standard stellar evolution models for AGB-stars [5], the ^14N/^15N ratios > ~2000, as it is

  4. Evaluation of a Stable Isotope Method to Mark Naturally-Breeding Larval Mosquitoes for Adult Dispersal Studies

    PubMed Central

    HAMER, GABRIEL L.; DONOVAN, DANIELLE J.; HOOD-NOWOTNY, REBECCA; KAUFMAN, MICHAEL G.; GOLDBERG, TONY L.; WALKER, EDWARD D.

    2014-01-01

    Understanding mosquito dispersal is critically important for vector-borne disease control and prevention. Mark–release–recapture methods using various marking techniques have made substantial contributions to the study of mosquito biology. However, the ability to mark naturally breeding mosquitoes noninvasively and with life-long retention has remained problematic. Here, we describe a method to mark naturally breeding mosquitoes with stable isotopes. Culexpipiens f. molestus mosquitoes were provisioned as larvae in laboratory experiments with 15N-labeled potassium nitrate and 13C-labeled glucose. Larval enrichment was sufficient to differentiate marked adult mosquitoes from unmarked control mosquitoes and the natural source population from Chicago Illinois, using either δ15N or δ13C. Isotopic retention lasted for at least 55 d for adult male and females mosquitoes. There were no consistent effects of isotopic enrichment on immature mosquito survival or adult mosquito body size. We then applied this marking technique to naturally breeding Culex pipiens mosquitoes in suburban Chicago, IL, and for the first time, report successful isotopic enrichment of mosquitoes in the field. This stable isotope marking technique will facilitate studies of mosquito dispersal. PMID:22308772

  5. Identification of sources of lead exposure in French children by lead isotope analysis: a cross-sectional study

    PubMed Central

    2011-01-01

    Background The amount of lead in the environment has decreased significantly in recent years, and so did exposure. However, there is no known safe exposure level and, therefore, the exposure of children to lead, although low, remains a major public health issue. With the lower levels of exposure, it is becoming more difficult to identify lead sources and new approaches may be required for preventive action. This study assessed the usefulness of lead isotope ratios for identifying sources of lead using data from a nationwide sample of French children aged from six months to six years with blood lead levels ≥25 μg/L. Methods Blood samples were taken from 125 children, representing about 600,000 French children; environmental samples were taken from their homes and personal information was collected. Lead isotope ratios were determined using quadrupole ICP-MS (inductively coupled plasma - mass spectrometry) and the isotopic signatures of potential sources of exposure were matched with those of blood in order to identify the most likely sources. Results In addition to the interpretation of lead concentrations, lead isotope ratios were potentially of use for 57% of children aged from six months to six years with blood lead level ≥ 25 μg/L (7% of overall children in France, about 332,000 children), with at least one potential source of lead and sufficiently well discriminated lead isotope ratios. Lead isotope ratios revealed a single suspected source of exposure for 32% of the subjects and were able to eliminate at least one unlikely source of exposure for 30% of the children. Conclusions In France, lead isotope ratios could provide valuable additional information in about a third of routine environmental investigations. PMID:21871122

  6. Sulfur and oxygen isotope study of sulfate reduction in experiments with natural populations from Fællestrand, Denmark

    NASA Astrophysics Data System (ADS)

    Farquhar, James; Canfield, Don E.; Masterson, Andrew; Bao, Huiming; Johnston, David

    2008-06-01

    This study investigates the sulfur and oxygen isotope fractionations of dissimilatory sulfate reduction and works to reconcile the relationships between the oxygen and sulfur isotopic and elemental systems. We report results of experiments with natural populations of sulfate-reducing bacteria using sediment and seawater from a marine lagoon at Fællestrand on the northern shore of the island of Fyn, Denmark. The experiments yielded relatively large magnitude sulfur isotope fractionations for dissimilatory sulfate reduction (up to approximately 45‰ for 34S/32S) with higher δ18O accompanying higher δ34S, similar to that observed in previous studies. The seawater used in the experiments was spiked by addition of 17O-labeled water and the 17O content of residual sulfate was found to depend on the fraction of sulfate reduced in the experiments. The 17O data provides evidence for recycling of sulfur from metabolic intermediates and for an 18O/16O fractionation of ∼25-30‰ for dissimilatory sulfate reduction. The close correlation between the 17O data and the sulfur isotope data suggests that isotopic exchange between cell water and external water (reactor water) was rapid under experimental conditions. The molar ratio of oxygen exchange to sulfate reduction was found to be about 2.5. This value is slightly lower than observed in studies of natural ecosystems [e.g., Wortmann U. G., Chernyavsky B., Bernasconi S. M., Brunner B., Böttcher M. E. and Swart P. K. (2007) Oxygen isotope biogeochemistry of pore water sulfate in the deep biosphere: dominance of isotope exchange reactions with ambient water during microbial sulfate reduction (ODP Site 1130). Geochim. Cosmochim. Acta71, 4221-4232]. Using recent models of sulfur isotope fractionations we find that our combined sulfur and oxygen isotopic data places constraints on the proportion of sulfate recycled to the medium (78-96%), the proportion of sulfur intermediate sulfite that was recycled by way of APS to sulfate

  7. Fully integrated surface-subsurface flow modelling of groundwater-lake interaction in an esker aquifer: Model verification with stable isotopes and airborne thermal imaging

    NASA Astrophysics Data System (ADS)

    Ala-aho, Pertti; Rossi, Pekka M.; Isokangas, Elina; Kløve, Bjørn

    2015-03-01

    Water resources management is moving towards integration, where groundwater (GW), surface water (SW) and related aquatic ecosystems are considered one management unit. Because of this paradigm shift, more information and new tools are needed to understand the ecologically relevant fluxes (water, heat, solutes) at the GW-SW interface. This study estimated the magnitude, temporal variability and spatial distribution of water fluxes at the GW-SW interface using a fully integrated hydrological modelling code (HydroGeoSphere). The model domain comprised a hydrologically complex esker aquifer in Northern Finland with interconnected lakes, streams and wetlands. The model was calibrated in steady state for soil hydraulic conductivity and anisotropy and it reproduced the hydraulic head and stream baseflow distribution throughout the aquifer in both transient and steady state modes. In a novel analysis, model outputs were compared with the locations and magnitude of GW discharge to lakes estimated using field techniques. Spatial occurrence of GW-lake interaction was interpreted from airborne thermal infrared imaging. The observed GW inflow locations coincided well with model nodes showing positive exchange flux between surface and subsurface domains. Order of magnitude of simulated GW inflow to lakes showed good agreement with flux values calculated with a stable water isotope technique. Finally, time series of GW inflow, extracted as model output, showed moderate annual variability and demonstrated different interannual inflow changes in seepage and drainage lakes of the aquifer. Overall, this study demonstrated the ability of a fully integrated numerical model to reproduce observed GW-SW exchange processes in a complex unconfined aquifer system. The model-based estimates obtained for GW influx magnitude and spatial distribution, along with information on GW quality can be used to estimate ecologically relevant fluxes in future water resources management.

  8. Quantitative study of coherent pairing modes with two-neutron transfer: Sn isotopes

    NASA Astrophysics Data System (ADS)

    Potel, G.; Idini, A.; Barranco, F.; Vigezzi, E.; Broglia, R. A.

    2013-05-01

    Pairing rotations and pairing vibrations are collective modes associated with a field, the pair field, which changes the number of particles by two. Consequently, they can be studied at profit with the help of two-particle transfer reactions in superfluid and in normal nuclei, respectively. The advent of exotic beams has opened, for the first time, the possibility to carry out such studies in medium heavy nuclei, within the same isotopic chain. The case studied in the present paper is that of the Sn isotopes [essentially from closed (Z=N=50) to closed (Z=50, N=82) shells]. The static and dynamic off-diagonal, long-range order phase coherence in gauge space displayed by pairing rotations and vibrations, respectively, leads to coherent states which behave almost classically. Consequently, these modes are amenable to an accurate nuclear structure description in terms of simple models containing the right physics, in particular, BCS plus quasiparticle random-phase approximation and Hartree-Fock mean field plus random-phase approximation, respectively. The associated two-nucleon transfer spectroscopic amplitudes predicted by such model calculations can thus be viewed as essentially “exact.” This fact, together with the availability of optical potentials for the different real and virtual channels involved in the reactions considered, namely A+2Sn+p, A+1Sn+d, and ASn+t, allows for the calculation of the associated absolute cross sections without, arguably, free parameters. The numerical predictions of the absolute differential cross sections, obtained making use of the above-mentioned nuclear structure and optical potential inputs, within the framework of second-order distorted-wave Born approximation, taking into account simultaneous, successive, and nonorthogonality contributions, provide, within experimental errors in general, and below 10% uncertainty in particular, an overall account of the experimental findings for all of the measured A+2Sn

  9. Recent advances in human viruses imaging studies.

    PubMed

    Florian, Paula Ecaterina; Rouillé, Yves; Ruta, Simona; Nichita, Norica; Roseanu, Anca

    2016-06-01

    Microscopy techniques are often exploited by virologists to investigate molecular details of critical steps in viruses' life cycles such as host cell recognition and entry, genome replication, intracellular trafficking, and release of mature virions. Fluorescence microscopy is the most attractive tool employed to detect intracellular localizations of various stages of the viral infection and monitor the pathogen-host interactions associated with them. Super-resolution microscopy techniques have overcome the technical limitations of conventional microscopy and offered new exciting insights into the formation and trafficking of human viruses. In addition, the development of state-of-the art electron microscopy techniques has become particularly important in studying virus morphogenesis by revealing ground-braking ultrastructural details of this process. This review provides recent advances in human viruses imaging in both, in vitro cell culture systems and in vivo, in the animal models recently developed. The newly available imaging technologies bring a major contribution to our understanding of virus pathogenesis and will become an important tool in early diagnosis of viral infection and the development of novel therapeutics to combat the disease. PMID:27059598

  10. Lunar Science Conference, 6th, Houston, Tex., March 17-21, 1975, Proceedings. Volume 2 - Chemical and isotopic studies

    NASA Technical Reports Server (NTRS)

    Merrill, R. B.

    1975-01-01

    The chemical compositions of lunar rocks and soils are examined, taking into account sulfur abundances and distributions in mare basalts and their source magmas, lithophile trace and major elements in Apollo 16 and 17 lunar samples, the role of vaporization processes in lunar rock formation, chemical studies of the lunar regolith with emphasis on zirconium and hafnium, a model for the lunar anorthositic gabbro, and trace-element chemistry and reducing capacity of size fractions from the Apollo 16 regolith. Other topics considered are related to lunar chronology, volatile meteoritic elements, isotopic studies, light element geochemistry, and agglutinates and regolith processes. Attention is given to meteoritic material in four terrestrial meteorite craters, the state of meteoritic material on the moon, volatile elements in Allende inclusions, oxygen isotope fractionation in Apollo 17 rocks, cosmogenic isotope production in Apollo deep-core samples, and the effects of exposure conditions on cosmic-ray records in lunar rocks.

  11. Study of water mixing in the coastal waters of the western Taiwan Strait based on radium isotopes.

    PubMed

    Men, Wu; Jiang, Yuwu; Liu, Guangshan; Wang, Fenfen; Zhang, Yusheng

    2016-02-01

    Radium is considered to be a useful tracer for studying the physical processes of seawater. In this work, three naturally occurring radium isotopes, (224)Raex, (226)Ra and (228)Ra, were measured in the coastal zone of the western Taiwan Strait during the summer seasons. Based on the distributions of the three radium isotopes and the salinity, we conclude that the water mixing pattern in the study area in summer consists of diluted water flowing from the Jiulong River to the open sea towards the east and southeast, and open sea seawater flowing inward from south to north. The submarine ground water discharges in the estuarine region, as suggested by the radium and salinity data. The residence times of the Jiulong River estuary, ranging from 7 to 49 d, were estimated using the radium isotope pairs (224)Raex and (226)Ra. PMID:26630036

  12. Isotope tracer studies of diffusion in silicates and of geological transport processes using actinide elements. Progress report

    SciTech Connect

    Wasserburg, G.J.

    1992-12-31

    The following are reported: high abundance sensitivity mass spectrometer for U-Th studies; {sup 238}U-{sup 230}Th disequilibrium in recent lavas from Iceland; water-rock interaction from U-Th studies; resonance ionization mass spectrometry of Os and Ti isotopes; and self-diffusion of Mg.

  13. PET IMAGING STUDIES IN DRUG ABUSE RESEARCH.

    SciTech Connect

    Fowler, J.S.; Volkow, N.D.; Ding, Y.S.; Logan, J.; Wang, G.J.

    2001-01-29

    . This will be followed by highlights of PET studies of the acute effects of the psychostimulant drugs cocaine and methylphenidate (ritalin) and studies of the chronic effects of cocaine and of tobacco smoke on the human brain. This chapter concludes with the description of a study which uses brain imaging coupled with a specific pharmacological challenge to address the age-old question of why some people who experiment with drugs become addicted while others do not.

  14. Preliminary design study of an alternate heat source assembly for a Brayton isotope power system

    NASA Technical Reports Server (NTRS)

    Strumpf, H. J.

    1978-01-01

    Results are presented for a study of the preliminary design of an alternate heat source assembly (HSA) intended for use in the Brayton isotope power system (BIPS). The BIPS converts thermal energy emitted by a radioactive heat source into electrical energy by means of a closed Brayton cycle. A heat source heat exchanger configuration was selected and optimized. The design consists of a 10 turn helically wound Hastelloy X tube. Thermal analyses were performed for various operating conditions to ensure that post impact containment shell (PICS) temperatures remain within specified limits. These limits are essentially satisfied for all modes of operation except for the emergency cooling system for which the PICS temperatures are too high. Neon was found to be the best choice for a fill gas for auxiliary cooling system operation. Low cycle fatigue life, natural frequency, and dynamic loading requirements can be met with minor modifications to the existing HSA.

  15. CO2 production by impact in carbonates? An ATEM and stable isotope (C,O) study

    NASA Technical Reports Server (NTRS)

    Martinez, I.; Agrinier, P.; Guyot, F.; Ildefonse, PH.; Javoy, M.; Schaerer, U.; Hornemann, U.; Deutsch, A.

    1993-01-01

    Carbonates may have been a common target for large impacts on the Earth and possible related CO2 outgassing would have important consequences for the composition of the atmosphere. To estimate volatile release during such impacts, isotopic ratios (C-13/C-12 and O-18/O-16) were determined on highly shocked carbonate samples in combination with SEM and analytical transmission electron microscopy (ATEM) investigations. The study was performed on both naturally and experimentally shocked rocks, i.e. 50-60 GPa shocked limestone-dolomite fragments from the Haughton impact crater (Canada), and carbonates shocked in shock recovery experiments. For the experiments, unshocked carbonates consisting of mixture of dolomite and calcite from the Haughton area were used. Naturally shocked samples were collected in the polymict breccia near the center of the Haughton crater.

  16. The Dengli (H3.8) Complex Breccia: Petrological and Isotopic Studies

    NASA Astrophysics Data System (ADS)

    Ivanova, M. A.; Assonov, S. S.; Kononkova, N. N.; Shukolyukov, Yu. A.

    1993-07-01

    The Dengli meteorite was found in the Karakum desert in July 1976. Previous studies [1] have shown that the meteorite is a complex chondritic breccia containing unusual components of achondritic affinity. In order to understand the origin of the breccia, we studied its mineralogy, petrology, and isotopic composition of noble gases. In addition, in cooperation with Dr. J. N. Goswami, we are now studying minerals in achondritic clasts using an ion microprobe. The Dengli meteorite has a distinct chondritic texture and consists of chondrules and chondrule fragments embedded into a fine-grained matrix. Equilibrated and unequilibrated populations were found among the chondrules, the latter of which are characterized by normal or inverse Mg-Fe zoning. Olivine (Fa19.6, N = 52, C.V. = 19.3) and pyroxene (Fs18.2, N = 27, C.V. = 17.0) displays large compositional variations. Based on textural and chemical characteristics, Dengli can be classified as an H3.8 chondrite. Two objects with unique compositions were identified. One has a round shape and consists of silica, orthopyroxene (Fs18.1 Wo6.2), clinopyroxene (Fs17.6 Wo27.6), and feldspar (An76.2 Ab23.2). The other object is an angular clast, which is composed of olivine (Fa17.2), Al-rich clinopyroxene (Fs6.3 Wo46.8), and feldspar (An44.7 Ab54.7). The presence of clinopyroxene and Ca-rich feldspar in these objects indicates their similarity with an achondritic material. The Ar, Kr, and Xe contents measured in Dengli are very close to those in other ordinary chondrites of petrological types 3 through 5 [2]. The Xe and Kr isotopic compositions at any temperature step differ from those of solar Xe and Kr. High ^38Ar concentrations were found. The exposure age was estimated to be 7.6 Ma, which is close to the average (6.3 +/- 0.2 Ma) exposure age of 350 H chondrites. The Dengli K/Ar age, 3.73 +/- 0.10 Ga, is close to K/Ar ages of the majority of H chondrites. Thus, Dengli is depleted in noble gases as compared to regolith

  17. Systematic study of excited 0+ states in the Er isotopes populated in the (p , t) reaction

    NASA Astrophysics Data System (ADS)

    Garrett, P. E.; Finlay, A.; Kisliuk, D.; Chagnon-Lessard, S.; Diaz Varela, A.; Dunlop, R.; Jamieson, D. S.; Leach, K. G.; Svensson, C. E.; Ball, G. C.; Triambak, S.; Faestermann, T.; Hertenberger, R.; Wirth, H.-F.

    2014-09-01

    The nature of excited 0+ states in well-deformed nuclei continue to pose a challenge in nuclear structure. Often, even the nature of the first excited 0+ state, 02+, is unclear and interpretations involving β vibrations, pairing excitations, two-phonon γ vibrations, etc., have been advanced with different degrees of success. A major issue historically has been lack of data on excited 0+ states. In light of this, the study of the Er isotopes has been extended via the 162Er and 164Er (p , t) reactions. The experiments were performed at the Maier-Leibnitz Laboratory using 22 MeV proton beams on highly-enriched targets of 162,164Er, and the reaction products were analyzed with the Q3D spectrograph. Strong populations of the 02+ states have been observed. The systematics of the strong population of the 0+ states in the Er (p , t) reactions sheds light on the underlying nature of these levels.

  18. Gallium self-diffusion in gallium arsenide: A study using isotope heterostructures

    SciTech Connect

    Wang, Lei; Hsu, L.; Haller, E.E. |; Erickson, J.W.; Fischer, A.; Eberl, K.; Cardona, M.

    1996-09-01

    Ga self-diffusion was studied with secondary-ion mass spectroscopy in {sup 69}GaAs/{sup 71}GaAs isotope heterostructures grown by molecular beam epitaxy on GaAs substrates. Results show that the Ga self- diffusion coefficient in intrinsic GaAs can be described accurately with D = (43{+-}25 cm{sup 2}s{sup -1})exp(-4.24{+-}0.06 eV/k{sub B}T) over 6 orders of magnitude between 800 and 1225 C under As-rich condition. Experimental results combined with theoretical calculations strongly suggest Ga vacancy being the dominant native defect controlling the diffusion. No significant doping effects were observed in samples where the substrates were doped with Te up to 4x10{sup 17}cm{sup -3} or Zn up to 1x10{sup 19}cm{sup -3}.

  19. Lead isotopic studies of lunar soils - Their bearing on the time scale of agglutinate formation

    NASA Technical Reports Server (NTRS)

    Church, S. E.; Tilton, G. R.; Chen, J. H.

    1976-01-01

    Fines (smaller than 75 microns) and bulk soil were studied to analyze loss of volatile lead; losses of the order of 10% to 30% radiogenic lead during the production of agglutinates are assessed. Lead isotope data from fine-agglutinate pairs are analyzed for information on the time scale of micrometeorite bombardment, from the chords generated by the data in concordia diagrams. Resulting mean lead loss ages were compared to spallogenic gas exposure ages for all samples. Labile parentless radiogenic Pb residing preferentially on or in the fines is viewed as possibly responsible for aberrant lead loss ages. Bulk soils plot above the concordia curve (in a field of excess radiogenic Pb) for all samples with anomalous ages.

  20. Isotope labelling to study molecular fragmentation during the dielectric barrier discharge wet reforming of methane

    NASA Astrophysics Data System (ADS)

    Montoro-Damas, Antonio M.; Gómez-Ramírez, Ana; Gonzalez-Elipe, Agustín R.; Cotrino, José

    2016-09-01

    Isotope labelling is used to study the wet plasma reforming of methane in a dielectric barrier discharge reactor using D2O and CH4 as reactants. Besides the formation of CO and hydrogen as main products, different partitions of H and D atoms are found in the hydrogen (i.e., H2, HD, D2), methane (i.e., CH4, CH3D and CH2D2) and water (D2O, DHO) molecules detected by mass spectrometry as outlet gases of the plasma process. The effect of operating parameters such as applied current, residence time and the addition of oxygen to the reaction mixture is correlated with the H/D distribution in these molecules, the overall reaction yield and the energetic efficiency of the process. The results prove the plasma formation of intermediate excited species that rendering water and methane instead of CO and hydrogen greatly contribute to decrease the overall energy efficiency of the reforming process.

  1. Cold source moderator vessel development for the High Flux Isotope Reactor: Thermal-hydraulic studies

    SciTech Connect

    Williams, P.T.; Lucas, A.T.; Wendel, M.W.

    1998-07-01

    A project is underway at Oak Ridge National Laboratory (ORNL) to design, test, and install a cold neutron source facility in the High Flux Isotope Reactor (HFIR). This new cold source employs supercritical hydrogen at cryogenic temperatures both as the medium for neutron moderation and as the working fluid for removal of internally-generated nuclear heating. The competing design goals of minimizing moderator vessel mass and providing adequate structural integrity for the vessel motivated the requirement of detailed multidimensional thermal-hydraulic analyses of the moderator vessel as a critical design subtask. This paper provides a summary review of the HFIR cold source moderator vessel design and a description of the thermal-hydraulic studies that were carried out to support the vessel development.

  2. Study of evaluation of groundwater in Gadilam basin using hydrogeochemical and isotope data.

    PubMed

    Prasanna, Mohan Viswanathan; Chidambaram, S; Shahul Hameed, A; Srinivasamoorthy, K

    2010-09-01

    Gadilam river basin has gained its importance due to the presence of Neyveli Lignite open cast mines and other industrial complexes. It is also due to extensive depressurization of Cuddalore aquifer, and bore wells for New Veeranam Scheme are constructed downstream of the basin. Geochemical indicators of groundwater were used to identify the chemical processes that control hydrogeochemistry. Chemical parameters of groundwater such as pH, electrical conductivity, total dissolved solids, sodium (Na(+)), potassium (K(+)), calcium (Ca(+)), magnesium (Mg(+)), bicarbonate (HCO(-)(3)), sulfate (SO(-)(4)), phosphate (PO(-)(4)), and silica (H(4)SiO(4)) were determined. Interpretation of hydrogeochemical data suggests that leaching of ions followed by weathering and anthropogenic impact controls the chemistry of the groundwater. Isotopic study reveals that recharge from meteoric source in sedimentary terrain and rock-water interaction with significant evaporation prevails in hard rock region. PMID:19609693

  3. Study of oxygen isotopes and N=8 isotones with an extended cluster-orbital shell model

    NASA Astrophysics Data System (ADS)

    Masui, H.; Katō, K.; Ikeda, K.

    2006-03-01

    We attempt to obtain a unified description of the bound and unbound states of multivalence nucleons of a core system in the framework of the cluster-orbital shell model (COSM). In this framework, the interaction between the core and a valence nucleon (the core-N interaction) is treated microscopically, and the changes in both the core structure and the core-N interaction are discussed on the same basis. Furthermore, the center-of-mass motion of every nucleon is completely eliminated, and higher shell configurations, including unbound continuum components, are appropriately taken into account by applying a stochastic variational approach. To examine the reliability of this approach and to discuss how the dynamics of the core reflects to the total system, we study oxygen isotopes and N=8 isotones, which are described by O16 + Xn and O16 + Xp models, respectively.

  4. Study on multispectral imaging detection and recognition

    NASA Astrophysics Data System (ADS)

    Jun, Wang; Na, Ding; Gao, Jiaobo; Yu, Hu; Jun, Wu; Li, Junna; Zheng, Yawei; Fei, Gao; Sun, Kefeng

    2009-07-01

    Multispectral imaging detecting technology use target radiation character in spectral spatial distribution and relation between spectral and image to detect target and remote sensing measure. Its speciality is multi channel, narrow bandwidth, large amount of information, high accuracy. The ability of detecting target in environment of clutter, camouflage, concealment and beguilement is improved. At present, spectral imaging technology in the range of multispectral and hyperspectral develop greatly. The multispectral imaging equipment of unmanned aerial vehicle can be used in mine detection, information, surveillance and reconnaissance. Spectral imaging spectrometer operating in MWIR and LWIR has already been applied in the field of remote sensing and military in the advanced country. The paper presents the technology of multispectral imaging. It can enhance the reflectance, scatter and radiation character of the artificial targets among nature background. The targets among complex background and camouflage/stealth targets can be effectively identified. The experiment results and the data of spectral imaging is obtained.

  5. 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.

  6. Lead isotope systematics in Polytrichum formosum: An example from a biomonitoring field study with mosses

    SciTech Connect

    Kunert, M.; Friese, K.; Weckert, V.; Markert, B.

    1999-10-15

    With the aid of inductively coupled plasma mass spectrometry (ICP-MS), {sup 206/207}Pb isotope ratios were determined in 34 moss samples (Polytrichum formosum) taken from the Hoerner Bruch area near Osnabrueck (FRG) in the years 1987--1996. The goal was to distinguish different sources of atmospheric lead pollution by the investigation of lead isotope ratios. Reproducibility tests were carried out to ensure the reliability of analyzing Pb isotope ratios in moss samples by means of quadrupole ICP-MS. The reproducibility of the isotope ratios for one digested sample and the day-to-day reproducibility were determined. In all the moss samples analyzed, relative standard deviations of < 0.26% for five replicate measurements of one digested sample were achieved for the {sup 206/207}Pb isotope ratios. On the basis of the {sup 206/207}Pb isotope ratio, it was possible to establish that the sources of man-made atmospheric inputs of lead have changed over the 10-year period investigated. In the moss samples analyzed, the {sup 206/207}Pb isotope ratio was found to have risen significantly from 1.131 in 1987 to 1.154 in 1996. This increase in the {sup 206/207}Pb isotope ratio can be attributed to a reduction of atmospheric inputs of lead from petrol.

  7. A Combined Molecular and Isotopic Study of Anoxygenic Photosynthesis in Meromictic Lakes of the Northwestern United States

    NASA Astrophysics Data System (ADS)

    Harris, J. H., IV; Gilhooly, W., III; Crane, E. J., III; Steinman, B.; Shelton, M. R.

    2014-12-01

    Sulfur isotope fractionations within the chemocline can be an indication of green and purple sulfur photosynthetic activity. This isotopic signal is, however, small and variable, on the order of +2-6‰ (Zerkle et al. 2009). It is therefore advantageous to investigate the environmental and ecological effects on this signal so that these influences can be taken into account when estimating the contribution of anoxygenic phototrophs to the sulfur cycle in aquatic environments. This project aims to investigate the ways in which anoxygenic phototroph community structure and lake water geochemistry impact the sulfur isotope fractionation expressed during anoxygenic photosynthesis in meromictic lakes. During the summer of 2013, water column profile analysis of six lakes in the Pacific Northwest (located in eastern Washington and western Montana) were conducted to assess photosynthetically available radiation, salinity, pH, temperature, dissolved solids, and specific conductivity. Water column samples were obtained to determine the sulfur isotopic composition of dissolved sulfate and sulfide, major ion and sulfide concentrations. Microbial samples were also collected for genetic sequencing. Initial results found green (e.g., Chlorobiaceae sp.) and purple (e.g., Lamprocystis purpurea) bacteria at the same depth in one of the study lakes. These data, in addition to the same suite of samples collected in the summer of 2014, provide insight into relationships between the isotopic composition of sulfur (in H2S, S0, and SO4), lake water chemistry, and the presence or absence of green and purple sulfur bacteria.

  8. Li isotope geochemical study on weathering of granite in Longnan, Jiangxi Province, South China

    NASA Astrophysics Data System (ADS)

    Liu, W.; Xu, Z.; Zhao, T.; Yu, C.; Zhou, L.

    2015-12-01

    Li isotopes have been demonstrated to be a powerful tool in silicate weathering research from the continental scale to that of catchments and weathering profiles. In this study, we focus on Li isotopic behavior during granite weathering and pedogenic processes. Study profiles are developed on a granite intrusion in Longnan, South China, under a subtropical monsoon climate. Two soil profiles (JLN-S4 on the ridgetop and JLN-S3 on the midslope; both 120cm deep) and one weathering profiles (JLN-S1 on the toe slope; 1100cm deep) along a hill slope were selected to represent the granite weathering process in near surface condition. Bulk samples of these profiles were analyzed for major element and Li content, and δ7Li value. CIA (chemical index of alteration) values were determined. The uppermost soil profile (JLN-S4) samples have CIA values between 97.6 and 98.3, with δ7Li values from -2.50 to -3.90‰; JLN-S3 profile samples have lower CIA values varing from 94.4 to 96.1 and δ7Li values from -0.73‰ to -1.55‰. The weathering profile JLN-S1 at the toe slope has a generally increasing CIA values (in the range of 57.8~92.4) upward in the profile. The δ7Li values variation with CIA in JLN-S1, shows a two staged relationship: δ7Li increasing from -14.92‰ to 0.66‰ when CIA increases from 57.8 to 74.6 as the first stage (from the bottom to 370cm depth), and no obvious relationship between CIA andδ7Li(-4.74~3.62‰) was observed in the second stage (CIA higher than 74.6, 370cm depth above). Li contents in JLN-S4 vary between 3.84 and 15.03 μg/g, in JLN-S3 between 1.43~8.03 μg/g, and in JLN-S1 between 6.95~22.27μg/g. In the first stage defined by δ7Li and CIA relationship, Li contents decrease with increasing CIA. However, in the second stage, Li abundance decreases upward at the beginning and turns into an increacing tendency (at 175cm depth) to the surface. Two granite bedrock samples have δ7Li value of -0.23 and 0.39‰, and Li contents of 38.58 and 34

  9. Carbon Isotopes of Alkanes in Hydrothermal Abiotic Organic Synthesis Processes at High Temperatures and Pressures: An Experimental Study

    NASA Technical Reports Server (NTRS)

    Fu, Qi; Socki, Richard A.; Niles, Paul B.

    2010-01-01

    Observation of methane in the Martian atmosphere has been reported by different detection techniques [1-4]. With more evidence showing extensive water-rock interaction in Martian history [5-7], abiotic formation by Fischer-Tropsch Type (FTT) synthesis during serpentization reactions may be one possible process responsible for methane generation on Mars [8, 9]. While the experimental studies performed to date leave little doubt that chemical reactions exist for the abiotic synthesis of organic compounds by mineral surface-catalyzed reactions [10-12], little is known about the reaction pathways by which CO2 and/or CO are reduced under hydrothermal conditions. Carbon and hydrogen isotope measurements of alkanes have been used as an effective tool to constrain the origin and reaction pathways of hydrocarbon formation. Alkanes generated by thermal breakdown of high molecular weight organic compounds have carbon and hydrogen isotopic signatures completely distinct from those formed abiotically [13-15]. Recent experimental studies, however, showed that different abiogenic hydrocarbon formation processes (e.g., polymerization vs. depolymerization) may have different carbon and hydrogen isotopic patterns [16]. Results from previous experiments studying decomposition of higher molecular weight organic compounds (lignite) also suggested that pressure could be a crucial factor affecting fractionation of carbon isotopes [17]. Under high pressure conditions, no experimental data are available describing fractionation of carbon isotope during mineral catalyzed FTT synthesis. Thus, hydrothermal experiments present an excellent opportunity to provide the requisite carbon isotope data. Such data can also be used to identify reaction pathways of abiotic organic synthesis under experimental conditions.

  10. An image assessment study of image acceptability of the Galileo low gain antenna mission

    NASA Technical Reports Server (NTRS)

    Chuang, S. L.; Haines, R. F.; Grant, T.; Gold, Yaron; Cheung, Kar-Ming

    1994-01-01

    This paper describes a study conducted by NASA Ames Research Center (ARC) in collaboration with the Jet Propulsion Laboratory (JPL), Pasadena, California on the image acceptability of the Galileo Low Gain Antenna mission. The primary objective of the study is to determine the impact of the Integer Cosine Transform (ICT) compression algorithm on Galilean images of atmospheric bodies, moons, asteroids and Jupiter's rings. The approach involved fifteen volunteer subjects representing twelve institutions involved with the Galileo Solid State Imaging (SSI) experiment. Four different experiment specific quantization tables (q-table) and various compression stepsizes (q-factor) to achieve different compression ratios were used. It then determined the acceptability of the compressed monochromatic astronomical images as evaluated by Galileo SSI mission scientists. Fourteen different images were evaluated. Each observer viewed two versions of the same image side by side on a high resolution monitor, each was compressed using a different quantization stepsize. They were requested to select which image had the highest overall quality to support them in carrying out their visual evaluations of image content. Then they rated both images using a scale from one to five on its judged degree of usefulness. Up to four pre-selected types of images were presented with and without noise to each subject based upon results of a previously administered survey of their image preferences. Fourteen different images in seven image groups were studied. The results showed that: (1) acceptable compression ratios vary widely with the type of images; (2) noisy images detract greatly from image acceptability and acceptable compression ratios; and (3) atmospheric images of Jupiter seem to have higher compression ratios of 4 to 5 times that of some clear surface satellite images.

  11. A Dual Isotope Study of Nitrates in Aquifer and Surface Waters: Initial Results at the Watershed Scale

    NASA Astrophysics Data System (ADS)

    Savard, M. M.; Simpson, S.; Smirnoff, A.; Somers, G.; van Bochove, E.

    2004-12-01

    This dual isotope-nitrate study is aimed at contributing to the quantification of the annual N budget of the Wilmot River watershed on Prince-Edward Island (PEI, Canada). Aquifers constitute the only source of freshwater on PEI. In many areas, nitrate concentrations in groundwater (GW) have been increasing over time. It is assumed that mineral fertilization for potato cropping constitutes a major source of nitrates. However, a better understanding of the transfer dynamics of nitrates from soils to GW is required to reduce their detrimental effects. Here we report on N concentrations ([N-NO3-]), nitrate isotope analyses (N and O), and water isotope ratios (H and O) obtained after one year of seasonal sampling of surface water and groundwater (GW). The analyses of the nitrate isotopes were performed on silver nitrates using EA-CF- and Pyrolysis/EA-IRMS systems for N and O, respectively. Water isotopes were analysed with an equilibration system in continuous flow. Our 2003 summer and fall results indicate that 23% of the samples have N-NO3 concentrations above the threshold established for human health (10 mg/L), whereas 10% have concentrations within natural ranges (<1 mg/L). Combined nitrate and water isotope results suggest that during summer and fall most nitrates in the Wilmot River are derived from GW, and that about 75% of the GW samples contain nitrates from chemical fertilizers while the remaining 25% of nitrates are from natural soils, manures or septic wastes. Moreover, the N isotopes-nitrate concentration trend for GW departs significantly from the curve expected to result from microbial denitrification and corresponds better to natural attenuation due to dilution of nitrate-rich waters with water devoid of nitrates. The oxygen isotopes in GW nitrates indicate that summer rain and evaporated vadose water likely represent the O sources involved in soil nitrification. Future work will involve characterization of potential nitrate sources and of N

  12. Stratospheric ozone isotope enrichment studied by submillimeter-wave heterodyne radiometry

    NASA Astrophysics Data System (ADS)

    Kasai, Y.; Urban, J.; Takahashi, K.; JEM/SMILES Science-Team,

    2002-05-01

    Since the discovery of the heavy isotope enrichment of ozone formation in the stratosphere in 1981, considerable progress has been made in understanding the processes that control the isotope enrichment by using mass spectrometry, spectrometric techniques, laboratory measurements, and so on. The detection limit of the mass spectrometers is enough to discuss these isotope enrichments, but symmetric and asymmetric ozone isotopes cannot be distinguished. It is important to observe symmetric and asymmetric ozone isotopes separately with enough accuracy to understand the mechanism of the ozone isotope enrichment for the ozone formation chemistry. Measurements of the ozone isotopes using a new technology of he superconducting submillimeter-wave limb emission spectrometer (SMILES) have been proposed. The instrument is planned to be aboard the Japanese Experiment Module (JEM) at the International Space Station. The SMILES instrument is planned to be launched in 2006. The SMILES instrument measures thermal emissions from ozone isotopes as well as ozone-depletion-related molecules such as ClO, HCl, HO2, HNO3 and BrO in the frequency bands at 624.32-626.32 GHz and 649.12-650.32 GHz. Overview of this experiment, such as new techniques for a high-sensitive sounding, measurement coverage, measurement frequency, is described. The scientific objective of the SMILES experiment, including a brief review on the controversial problem of stratospheric ozone isotope anomaly, is presented. The error analysis of the SMILES measurement is evaluated by using the SMILES simulator for all 5 isotopes of normal ozone, asymmetric-17-ozone, asymmetric-18-ozone, symmetric-17-ozone, symmetric-18-ozone. The evaluation suggests that the global distributions of symmetric-17-ozone, asymmetric-18-ozone, symmetric-17-ozone, as well as normal ozone can be obtained from the single profile, with the errors of less than about 1 % between 20 and 40 km with the partial column about 5 km.

  13. Tracking amino acid's uptake into the protozoan Acanthamoeba castellanii by stable-isotope labelling and Raman spectral imaging

    NASA Astrophysics Data System (ADS)

    Naemat, Abida; Elsheikha, Hany M.; Notingher, Ioan

    2016-04-01

    The capacity of pathogens to acquire nutrients from their host cells is one of the most fundamental aspects of infection biology. Hence, measuring the patterns of nutrients' uptake by pathogens is essential for understanding the interactions of pathogens with eukaryotic host cells. In this study, we optimized a technique that allows fast and non-destructive measurement of the amino acid Phenylalanine (Phe) acquired by the trophozoite stage of the protozoan Acanthamoeba castellanii (A. castellanii) as they engage with individual human retinal pigment epithelial cells (ARPE-19). ARPE-19 host cells were pre-saturated with Deuterated Phe (L-Phe(D8)) to replace the native substrate Phe (L-Phe). The uptake of L-Phe(D8) by A. castellanii trophozoites was measured by Raman microspectroscopy. This approach allowed us to characterize the uptake patterns of this essential amino acid into A. castellanii trophozoites at a single cell level. At 24 hours post infection (PI) A. castellanii trophozoites are capable of salvaging L-Phe(D8) from host cells. The uptake pattern was time-dependent during the first 24 hours of infection and complete substitution with L-Phe(D8) in all parasites was detected at 48 hours PI. On the other hand, isolated A. castellanii trachyzoites (grown without host cells) did not show significant uptake for L-Phe(D8) from the media; only achieved an uptake ratio of 16-18% of L-Phe(D8) from the culture medium after 24 hours. These findings demonstrate the potential of combining Raman microspectroscopy and stable isotope labelling approaches to elucidate the role of metabolism in mediating A. castellanii interaction with host cells.

  14. You are not always what we think you eat. Selective assimilation across multiple whole-stream isotopic tracer studies

    SciTech Connect

    Dodds, W. K.; Collins, S. M.; Hamilton, S. K.; Tank, J. L.; Johnson, S.; Webster, J. R.; Simon, K. S.; Whiles, M. R.; Rantala, H. M.; McDowell, W. H.; Peterson, S. D.; Riis, T.; Crenshaw, C. L.; Thomas, S. A.; Kristensen, P. B.; Cheever, B. M.; Flecker, A. S.; Griffiths, N. A.; Crowl, T.; Rosi-Marshall, E. J.; El-Sabaawi, R.; Martí, E.

    2014-10-01

    Analyses of 21 15N stable isotope tracer experiments, designed to examine food web dynamics in streams around the world, indicated that the isotopic composition of food resources assimilated by primary consumers (mostly invertebrates) poorly reflected the presumed food sources. Modeling indicated that consumers assimilated only 33–50% of the N available in sampled food sources such as decomposing leaves, epilithon, and fine particulate detritus over feeding periods of weeks or more. Thus, common methods of sampling food sources consumed by animals in streams do not sufficiently reflect the pool of N they assimilate. Lastly, Isotope tracer studies, combined with modeling and food separation techniques, can improve estimation of N pools in food sources that are assimilated by consumers.

  15. You are not always what we think you eat. Selective assimilation across multiple whole-stream isotopic tracer studies

    DOE PAGESBeta

    Dodds, W. K.; Collins, S. M.; Hamilton, S. K.; Tank, J. L.; Johnson, S.; Webster, J. R.; Simon, K. S.; Whiles, M. R.; Rantala, H. M.; McDowell, W. H.; et al

    2014-10-01

    Analyses of 21 15N stable isotope tracer experiments, designed to examine food web dynamics in streams around the world, indicated that the isotopic composition of food resources assimilated by primary consumers (mostly invertebrates) poorly reflected the presumed food sources. Modeling indicated that consumers assimilated only 33–50% of the N available in sampled food sources such as decomposing leaves, epilithon, and fine particulate detritus over feeding periods of weeks or more. Thus, common methods of sampling food sources consumed by animals in streams do not sufficiently reflect the pool of N they assimilate. Lastly, Isotope tracer studies, combined with modeling andmore » food separation techniques, can improve estimation of N pools in food sources that are assimilated by consumers.« less

  16. Study on the improvement of overall optical image quality via digital image processing

    NASA Astrophysics Data System (ADS)

    Tsai, Cheng-Mu; Fang, Yi Chin; Lin, Yu Chin

    2008-12-01

    This paper studies the effects of improving overall optical image quality via Digital Image Processing (DIP) and compares the promoted optical image with the non-processed optical image. Seen from the optical system, the improvement of image quality has a great influence on chromatic aberration and monochromatic aberration. However, overall image capture systems-such as cellphones and digital cameras-include not only the basic optical system but also many other factors, such as the electronic circuit system, transducer system, and so forth, whose quality can directly affect the image quality of the whole picture. Therefore, in this thesis Digital Image Processing technology is utilized to improve the overall image. It is shown via experiments that system modulation transfer function (MTF) based on the proposed DIP technology and applied to a comparatively bad optical system can be comparable to, even possibly superior to, the system MTF derived from a good optical system.

  17. Collective vibrational effects in hydrogen bonded liquid amides and proteins studied by isotopic substitution

    NASA Astrophysics Data System (ADS)

    Nielsen, O. F.; Johansson, C.; Christensen, D. H.; Hvidt, S.; Flink, J.; Høime Hansen, S.; Poulsen, F.

    2000-09-01

    Raman spectroscopy is used to study the fast dynamics of simple liquid amides and proteins. Raman spectra in the visible region of liquid amides are obtained with a triple additive scanning monochromator, whereas FT-Raman technique is used in the near-IR region in order to avoid fluorescence from impurities in the proteins. Raman spectra are shown in the amide-I region of HCONHCH 3 ( N-methylformamide with all isotopes in their natural abundance), H 13CONHCH 3, HC 18ONHCH 3, human growth hormone, frog tropomyosin and chymotrypsin inhibitor 2 including C-13 and N-15 enriched samples of the latter. Resonance energy transfer (RET) between amide molecules gives rise to a non-coincidence effect of the anisotropic and the isotropic components of the amide-I band. This effect influences the band position in mixtures of liquid amide isotopomers. A further spectral feature caused by collective vibrational modes in the hydrogen bonded liquid amides is named coalescence of bands in mixtures of isotopomers (CBMI). The result of this effect is that only one band is found in mixtures of isotopomers where bands at different frequencies are observed for each of the isotopomers. A similar effect may account for the observation of protein amide-I bands with frequencies dependent only on the secondary structure of the protein and not on the amino acid residues. RET and CBMI are due to a collectivity of vibrational modes in different amide molecules. This collectivity may be related to a cooperativity of hydrogen bonds. A low-frequency band around 100 cm -1 is observed in hydrogen bonded liquid amides and proteins. Isotopic substitution shows that the mode corresponding to this band involves displacements of atoms in hydrogen bonds. This mode may drive a breaking of the hydrogen bond.

  18. Methodologies for extraction of dissolved inorganic carbon for stable carbon isotope studies : evaluation and alternatives

    USGS Publications Warehouse

    Hassan, Afifa Afifi

    1982-01-01

    The gas evolution and the strontium carbonate precipitation techniques to extract dissolved inorganic carbon (DIC) for stable carbon isotope analysis were investigated. Theoretical considerations, involving thermodynamic calculations and computer simulation pointed out several possible sources of error in delta carbon-13 measurements of the DIC and demonstrated the need for experimental evaluation of the magnitude of the error. An alternative analytical technique, equilibration with out-gassed vapor phase, is proposed. The experimental studies revealed that delta carbon-13 of the DIC extracted from a 0.01 molar NaHC03 solution by both techniques agreed within 0.1 per mil with the delta carbon-13 of the DIC extracted by the precipitation technique, and an increase of only 0.27 per mil in that extracted by the gas evolution technique. The efficiency of extraction of DIC decreased with sulfate concentration in the precipitation technique but was independent of sulfate concentration in the gas evolution technique. Both the precipitation and gas evolution technique were found to be satisfactory for extraction of DIC from different kinds of natural water for stable carbon isotope analysis, provided appropriate precautions are observed in handling the samples. For example, it was found that diffusion of atmospheric carbon dioxide does alter the delta carbon-13 of the samples contained in polyethylene bottles; filtration and drying in the air change the delta carbon-13 of the samples contained in polyethylene bottles; filtration and drying in the air change the delta carbon-13 of the precipitation technique; hot manganese dioxide purification changes the delta carbon-13 of carbon dioxide. (USGS)

  19. Laboratory studies of carbon kinetic isotope effects on the production mechanism of particulate phenolic compounds formed by toluene photooxidation: a tool to constrain reaction pathways.

    PubMed

    Irei, Satoshi; Rudolph, Jochen; Huang, Lin; Auld, Janeen; Collin, Fabrice; Hastie, Donald

    2015-01-01

    In this study, we examined compound-specific stable carbon isotope ratios for phenolic compounds in secondary organic aerosol (SOA) formed by photooxidation of isotope-label-free toluene. SOA generated by photooxidation of toluene using a continuous-flow reactor and an 8 m(3) indoor smog chamber was collected on filters, which were extracted with acetonitrile for compound-specific analysis. Eight phenolic compounds were identified in the extracts using a gas chromatograph coupled with a mass spectrometer, and their compound-specific stable carbon isotope ratios were determined using a gas chromatograph coupled with a combustion furnace followed by an isotope ratio mass spectrometer. The majority of products, including methylnitrophenols and methylnitrocatechols, were isotopically depleted by 5-6‰ compared to the initial isotope ratio of toluene, whereas the isotope ratio for 4-nitrophenol remained identical to that of toluene. On the basis of the reaction mechanisms proposed in previous reports, stable carbon isotope ratios of these products were calculated. By comparing the observed isotope ratios with the predicted isotope ratios, we explored possible production pathways for the particulate phenolic compounds. PMID:25490235

  20. Using multi-scale stable isotopes analyses to study the microbial processes of soil organic matter stabilization

    NASA Astrophysics Data System (ADS)

    Hatton, P.; Remusat, L.; Zeller, B.; Bode, S.; Brewer, E.; Boeckx, P. F.; Derrien, D.

    2012-12-01

    Soil microorganisms are increasingly recognized as important drivers for the stabilization of soil organic matter (OM) with soil assemblages, but the way they act remains not fully explored. Here, we used a multi-scale approach to investigate the attachment of microbial products with soil organo-mineral assemblages. A surface acidic Cambisol was amended with 13C15N labeled glycine and leaf fragments prior to sequential density separation of plant debris, aggregates and non-aggregates mineral grains with little OM attached. Labels were tracked using elemental analyzer coupled to isotope ratio mass spectrometry (EA-IRMS), liquid chromatography (LC) coupled to IRMS and nano-scale secondary ions MS (NanoSIMS). After 8h of glycine incubation, the comparison between γ-irradiated and non-sterile soils revealed that more than 90% and 85% of the stabilized glycine-derived 13C and 15N were found in microbial products, with a higher occurrence in aggregates than in plant debris and mineral grains. NanoSIMS images showed that these stabilized microbial products are principally not confined to the microbial cells, but evenly spread at the surface of the mineral-attached OM as extracellular products. After calibration, the comparison of their C/N ratios with the C/N ratios of the corresponding soil particles suggested that the microbial products are stabilized through physico-chemical interactions most likely mediated by the reactivity of the underlying minerals. Unlike NanoSIMS, LC-IRMS analyses allow the tracing of 13C tracers within microbial biomasses using amino sugars as biomarkers. After 3 months of incubation, freshly produced amino sugars deriving from the readily accessible glycine and finely ground leaf fragments clearly peaked in microbial aggregates and plant debris, respectively. Differences in distributions indicated that bacteria and fungi both grow where the resource is, but accumulate in microbial aggregates. These results suggested either a higher

  1. An imaging calorimeter for ACCESS concept study

    NASA Astrophysics Data System (ADS)

    Parnell, T. A.; Adams, J. H.; Binns, R. W.; Christl, M. J.; Derrickson, J. H.; Fountain, W. F.; Howell, L. W.; Gregory, J. C.; Hink, P. L.; Israel, M. H.; Kippen, R. M.; Lee, J.; Pendleton, G. N.; Takahashi, Y.; Watts, J. W.

    2001-08-01

    A mission concept study to define the "Advanced Cosmic-ray Composition Experiment for Space Station (ACCESS)" was sponsored by the National Aeronautics and Space Administration (NASA). The ACCESS instrument complement contains a transition radiation detector and an ionization calorimeter to measure the spectrum of protons, helium, and heavier nuclei up to ~1015 eV to search for the limit of S/N shock wave acceleration, or evidence for other explanations of the spectra. Several calorimeter configurations have been studied, including the "baseline" totally active bismuth germanate instrument and sampling calorimeters utilizing various detectors. The Imaging Calorimeter for ACCESS (ICA) concept comprises a carbon target and a calorimeter using a high atomic number absorber sampled approximately each radiation length (rl) by thin scintillating fiber (SCIFI) detectors. The main features and options of the ICA instrument configuration are described in this paper. Since direct calibration is not possible over most of the energy range, the best approach must be decided from simulations of calorimeter performance extrapolated from CERN calibrations at 0.375 TeV. This paper presents results from the ICA simulations study.

  2. Ultrasonic flow imaging system: A feasibility study

    SciTech Connect

    Sheen, S.H.; Lawrence, W.P.; Chien, H.T.; Raptis, A.C.

    1991-09-01

    This report examines the feasibility and potential problems in developing a real-time ultrasonic flow imaging instrument for on-line monitoring of mixed-phased flows such as coal slurries. State-of-the-art ultrasonic imaging techniques are assessed for this application. Reflection and diffraction tomographies are proposed for further development, including image-reconstruction algorithms and parallel processing systems. A conventional ultrasonic C-scan technique is used to demonstrate the feasibility of imaging the particle motion in a solid/water flow. 13 refs., 11 figs.

  3. Constraining dolomitization by Mg isotopes: A case study from partially dolomitized limestones of the middle Cambrian Xuzhuang Formation, North China

    NASA Astrophysics Data System (ADS)

    Peng, Yang; Shen, Bing; Lang, Xian-Guo; Huang, Kang-Jun; Chen, Ji-Tao; Yan, Zhen; Tang, Wen-bo; Ke, Shan; Ma, Hao-Ran; Li, Fang-Bing

    2016-03-01

    The "dolomite problem" refers to the rare dolomite formation in modern oceans that is in sharp contrast to the widespread ancient dolostone in rock record, as well as failure of laboratory inorganic dolomite precipitation at near Earth-surface temperature. Novel Mg isotope systematics provides a promising tool in resolving the "dolomite problem". Here, we develop a protocol to place constraints on the dolomitization process by using Mg isotopes. In this study, we measured Mg isotopic compositions (δ26Mg) of two batches of partially dolomitized limestone samples from the middle Cambrian Xuzhuang Formation in North China. δ26Mg varies between -0.55‰ and -3.18‰, and shows a negative linear correlation with 1>/[Mg>], suggesting that δ26Mg can be described by a binary mixing between the calcite and dolomite components. Mg isotopic composition of the dolomite component (δ26Mgdol) for the lower sample set that is collected from a 4 m stratigraphic interval containing three high-frequency ribbon rock-packstone cycles is -1.6‰, while δ26Mgdol for the upper sample set (from a thick sequence of ribbon rock) is significantly higher (-0.3‰). However, neither mineralogical and elemental compositions, carbon and oxygen isotopes, nor crystal morphologies of dolomite provides diagnostic criteria to differentiate these two batches of samples. δ26Mgdol of the Xuzhuang limestone is simulated by the Advective Flow (AF) and the Diffusion-Advection-Reaction (DAR) models. The AF model assumes that Mg is transported by advective fluid flows, while the DAR model simulates a contemporaneous seawater dolomitization process, in which Mg is delivered by diffusion. The AF modeling result indicates that δ26Mg of the dolomitization fluid is +0.4‰ and +1.7‰ for the lower and upper sample sets, respectively. These values are significantly higher than modern and Cenozoic seawater Mg isotopic composition, suggesting that the dolomitization fluid is not contemporaneous seawater. The

  4. Study on simulation of low light level images and photon images

    NASA Astrophysics Data System (ADS)

    Zhao, Lei; Yu, Xin; Chen, Yi-nan

    2008-03-01

    This paper concentrates on images formation simulation under low light level condition (10 -6images and system entire noise and simulate a deblurred image intensified by photon imaging system recently constructed under low light level condition. The influence of scene luminance and photon imaging system optical errors on the simulation is introduced. Then the system entire noise is appended to low light level images by a novel noise analysis and generation method based on experimental study method. The second part of this paper deals with simulation of photon images. Because of randomicity of photon images, roulette wheel selection is utilized to confirm the grey level of stochastic signal photon image and noise photon image is generated by poissson stochastic process pixel by pixel. The final photon image is acquired by synthesizing the two images. The simulation presented in this paper provides an economical and convenient method to investigate the detection ability of photon imaging system and image reconstruction algorithm under low light level condition and photon limited condition.

  5. USE OF THE COMPOSITION AND STABLE CARBON ISOTOPE RATIO OF MICROBIAL FATTY ACIDS TO STUDY CARBON CYCLING

    EPA Science Inventory

    We use measurements of the concentration and stable carbon isotopic ratio (Gamma 13C) of individual microbial phospholipid fatty acids (PLFAS) in soils and sediments as indicators of live microbial biomass levels and microbial carbon source. For studies of soil organic matter (SO...

  6. Cu isotopic signature in blood serum of liver transplant patients: a follow-up study

    NASA Astrophysics Data System (ADS)

    Lauwens, Sara; Costas-Rodríguez, Marta; van Vlierberghe, Hans; Vanhaecke, Frank

    2016-07-01

    End-stage liver disease (ESLD) is life-threatening and liver transplantation (LTx) is the definitive treatment with good outcomes. Given the essential role of hepatocytes in Cu homeostasis, the potential of the serum Cu isotopic composition for monitoring a patient’s condition post-LTx was evaluated. For this purpose, high-precision Cu isotopic analysis of blood serum of ESLD patients pre- and post-LTx was accomplished via multi-collector ICP-mass spectrometry (MC-ICP-MS). The Cu isotopic composition of the ESLD patients was fractionated in favour of the lighter isotope (by about ‑0.50‰). Post-LTx, a generalized normalization of the Cu isotopic composition was observed for the patients with normal liver function, while it remained light when this condition was not reached. A strong decrease in the δ65Cu value a longer term post-LTx seems to indicate the recurrence of liver failure or cancer. The observed trend in favour of the heavier Cu isotopic composition post-LTx seems to be related with the restored biosynthetic capacity of the liver, the restored hepatic metabolism and/or the restored biliary secretion pathways. Thus, Cu isotopic analysis could be a valuable tool for the follow-up of liver transplant patients and for establishing the potential recurrence of liver failure.

  7. Cu isotopic signature in blood serum of liver transplant patients: a follow-up study

    PubMed Central

    Lauwens, Sara; Costas-Rodríguez, Marta; Van Vlierberghe, Hans; Vanhaecke, Frank

    2016-01-01

    End-stage liver disease (ESLD) is life-threatening and liver transplantation (LTx) is the definitive treatment with good outcomes. Given the essential role of hepatocytes in Cu homeostasis, the potential of the serum Cu isotopic composition for monitoring a patient’s condition post-LTx was evaluated. For this purpose, high-precision Cu isotopic analysis of blood serum of ESLD patients pre- and post-LTx was accomplished via multi-collector ICP-mass spectrometry (MC-ICP-MS). The Cu isotopic composition of the ESLD patients was fractionated in favour of the lighter isotope (by about −0.50‰). Post-LTx, a generalized normalization of the Cu isotopic composition was observed for the patients with normal liver function, while it remained light when this condition was not reached. A strong decrease in the δ65Cu value a longer term post-LTx seems to indicate the recurrence of liver failure or cancer. The observed trend in favour of the heavier Cu isotopic composition post-LTx seems to be related with the restored biosynthetic capacity of the liver, the restored hepatic metabolism and/or the restored biliary secretion pathways. Thus, Cu isotopic analysis could be a valuable tool for the follow-up of liver transplant patients and for establishing the potential recurrence of liver failure. PMID:27468898

  8. 15N Isotopic Crop Exchange Residue Studies Suggest that IPCC N Input Methodologies to Assess N2O-N Emissions Should be Reevaluated

    Technology Transfer Automated Retrieval System (TEKTRAN)

    It is difficult to quantify nitrogen (N) losses from agricultural systems to the environment, however we can use 15N isotopic techniques to conduct site specific studies to increase our knowledge about N management and fate. This manuscript synthesizes the review of two selected 15N isotopic studies...

  9. Application Of Stable Isotope Analysis To Study Temporal Changes In Foraging Ecology In A Highly Endangered Amphibian

    PubMed Central

    Gillespie, J. Hayley

    2013-01-01

    study illustrates the feasibility of stable isotope analysis in identifying preferred prey species that can be used to guide conservation management of both wild and captive food sources for endangered species. PMID:23341920

  10. Preliminary study of lead isotopes in the carbonate-silica veins of Trench 14, Yucca Mountain, Nevada

    SciTech Connect

    Zartman, R.E.; Kwak, L.M.

    1993-12-15

    The sub-vertical carbonate-silica veins filling the Bow Ridge Fault, where exposed in Trench 14 on the east side of Yucca Mountain, carry a lead isotopic signature that can be explained in terms of local sources. Two isotopically distinguishable--silicate and carbonate--fractions of lead are recognized within the vein system as well as in overlying surficial calcrete deposits. The acid-insoluble silicate fraction is contributed largely from the decomposing Miocene volcanic tuff, which forms the wall rock of the fault zone and is a ubiquitous component of the overlying soil. Lead contained in the silicate fraction approaches in isotopic composition that of the Miocene volcanic rocks of Yucca Mountain, but diverges from it in some samples by being more enriched in uranogenic isotopes. The carbonate fraction of lead in both vein and calcrete samples resides dominantly in the HCl- and CH{sub 3}COOH-soluble calcite. HCl evidently also attacks and removes lead from silicate phases, but the milder CH{sub 3}COOH dissolution procedure oftentimes identifies a significantly more radiogenic lead in the calcite. Wind-blown particulate matter brought to the area from Paleozoic and Late Proterozoic limestones in surrounding mountains may be the ultimate source of the calcite. Isotopically more uniform samples suggest that locally the basaltic ash and other volcanic rock have contributed most of the lead to both fractions of the vein system. An important finding of this study is that the data does not require the more exotic mechanisms or origins that have been proposed for the veins. Instead, the remarkably similar lead isotopic properties of the veins to those of the soil calcretes support their interpretation as a surficial, pedogenic phenomenon.

  11. An experimental study on isotope fractionation in a mesoporous silica-water system with implications for vadose-zone hydrology

    NASA Astrophysics Data System (ADS)

    Lin, Ying; Horita, Juske

    2016-07-01

    Soil water dynamics within a thick vadose (unsaturated) zone is a key component in the hydrologic cycle in arid regions. In isotopic studies of soil water, the isotopic composition of adsorbed/pore-condensed water within soils has been assumed to be identical to that of bulk liquid water. To test this critical assumption, we have conducted laboratory experiments on equilibrium isotope fractionation between adsorbed/condensed water in mesoporous silica (average pore diameter 15 nm) and the vapor at relative pressures p/po = 0.3-1.0 along the adsorption-desorption isotherm at 30 °C. The isotope fractionation factors between condensed water in the silica pores and the vapor, α(2H) and α(18O), are smaller than those between liquid and vapor of bulk water (1.074 and 1.0088, respectively, at 30 °C). The α(2H) and α(18O) values progressively decrease from 1.064 and 1.0083 at p/po = 1 to 1.024 and 1.0044 at p/po = 0.27 for hydrogen and oxygen isotopes, respectively, establishing trends very similar to the isotherm curves. Empirical formulas relating α(2H) and α(18O) to the proportions of filled pores (f) are developed. Our experimental results challenge the long-held assumption that the equilibrium isotope fractionation factors for the soil water-vapor are identical to those of liquid water-vapor system with potential implications for arid-zone and global water cycles, including paleoclimate proxies in arid regions.

  12. Isotopic studies of Mg, Fe, Mo, RU and W in Fremdlinge from Allende refractory inclusions

    NASA Astrophysics Data System (ADS)

    Hutcheon, I. D.; Armstrong, J. T.; Wasserburg, G. J.

    1987-12-01

    This paper presents the first isotopic measurements, made with an ion microprobe, of Mg, Fe, Mo, Ru, and W in Fremdlinge and refractory metal nuggets from Allende meteorite. No non-mass-dependent deviations exceeding 1 percent from normal solar isotopic abundances were found for any of the elements analyzed, despite the unusual mineralogy of Fremdlinge and the extreme enrichment in refractory siderophile elements. It is concluded that the chemical, petrologic, and isotopic data on Fremdlinge are most plausibly interpreted in terms of the origin of Fremdlinge within the solar nebula.

  13. Mass spectrometric study of the mercury isotopes in the Allende meteorite

    NASA Technical Reports Server (NTRS)

    Nier, A. O.; Schlutter, D. J.

    1986-01-01

    Isotopic abundance ratios for mercury were determined by mass spectrometry in six samples of bulk material and in one sample of chondrules from the Allende meteorite. A primary purpose of the work was to attempt to verify the anomalous ratios reported for Hg-196/Hg-202 by neutron activation. Measurements were made on the mercury released at temperatures of 250, 450, 600 C, and in some cases, higher temperatures. The precision of the measurements was such that if an anomaly of the magnitude reported exists, it should have been seen. The isotopic abundance ratios for the other mercury isotopes were also measured. Within the errors of measurement these agreed with normal terrestrial values.

  14. Cenozoic marine geochemistry of thallium deduced from isotopic studies of ferromanganese crusts and pelagic sediments

    USGS Publications Warehouse

    Rehkamper, M.; Frank, M.; Hein, J.R.; Halliday, A.

    2004-01-01

    Cenozoic records of Tl isotope compositions recorded by ferromanganese (Fe-Mn) crusts have been obtained. Such records are of interest because recent growth surfaces of Fe-Mn crusts display a nearly constant Tl isotope fractionation relative to seawater. The time-series data are complemented by results for bulk samples and leachates of various marine sediments. Oxic pelagic sediments and anoxic marine deposits can be distinguished by their Tl isotope compositions. Both pelagic clays and biogenic oozes are typically characterized by ??205Tl greater than +2.5, whereas anoxic sediments have ??205Tl of less than -1.5 (??205Tl is the deviation of the 205Tl/203Tl isotope ratio of a sample from NIST SRM 997 Tl in parts per 104). Leaching experiments indicate that the high ??205Tl values of oxic sediments probably reflect authigenic Fe-Mn oxyhydroxides. Time-resolved Tl isotope compositions were obtained from six Fe-Mn crusts from the Atlantic, Indian, and Pacific oceans and a number of observations indicate that these records were not biased by diagenetic alteration. Over the last 25 Myr, the data do not show isotopic variations that significantly exceed the range of Tl isotope compositions observed for surface layers of Fe-Mn crusts distributed globally (??205 Tl=+12.8??1.2). This indicates that variations in deep-ocean temperature were not recorded by Tl isotopes. The results most likely reflect a constant Tl isotope composition for seawater. The growth layers of three Fe-Mn crusts that are older than 25 Ma show a systematic increase of ??205Tl with decreasing age, from about +6 at 60-50 Ma to about +12 at 25 Ma. These trends are thought to be due to variations in the Tl isotope composition of seawater, which requires that the oceans of the early Cenozoic either had smaller output fluxes or received larger input fluxes of Tl with low ??205Tl. Larger inputs of isotopically light Tl may have been supplied by benthic fluxes from reducing sediments, rivers, and/or volcanic

  15. Study of hydrogen isotopes super permeation through vanadium membrane on 'Prometheus' setup

    SciTech Connect

    Musyaev, R. K.; Yukhimchuk, A. A.; Lebedev, B. S.; Busnyuk, A. O.; Notkin, M. E.; Samartsev, A. A.; Livshits, A. I.

    2008-07-15

    To develop the membrane pumping technology by means of superpermeable membranes at RFNC-VNIIEF in the 'Prometheus' setup, the experiments on superpermeation of hydrogen isotopes through metal membranes were carried out. The experimental results on superpermeation of thermal atoms of hydrogen isotopes including tritium through a cylindrical vanadium membrane are presented. The possibility of effective pumping, compression and recuperation of hydrogen isotopes by means of superpermeable membrane was demonstrated. The evaluation of membrane pumping rates and asymmetry degree of pure vanadium membrane was given. The work was performed under the ISTC-2854 project. (authors)

  16. Application of isotope dilution mass spectrometry: determination of ochratoxin A in the Canadian Total Diet Study

    PubMed Central

    Tam, J.; Pantazopoulos, P.; Scott, P.M.; Moisey, J.; Dabeka, R.W.; Richard, I.D.K.

    2011-01-01

    Analytical methods are generally developed and optimized for specific commodities. Total Diet Studies, representing typical food products ‘as consumed’, pose an analytical challenge since every food product is different. In order to address this technical challenge, a selective and sensitive analytical method was developed suitable for the quantitation of ochratoxin A (OTA) in Canadian Total Diet Study composites. The method uses an acidified solvent extraction, an immunoaffinity column (IAC) for clean-up, liquid chromatography-tandem mass spectrometry (LC-MS/MS) for identification and quantification, and a uniformly stable isotope-labelled OTA (U-[13C20]-OTA) as an internal recovery standard. Results are corrected for this standard. The method is accurate (101% average recovery) and precise (5.5% relative standard deviation (RSD)) based on 17 duplicate analysis of various food products over 2 years. A total of 140 diet composites were analysed for OTA as part of the Canadian Total Diet Study. Samples were collected at retail level from two Canadian cities, Quebec City and Calgary, in 2008 and 2009, respectively. The results indicate that 73% (102/140) of the samples had detectable levels of OTA, with some of the highest levels of OTA contamination found in the Canadian bread supply. PMID:21623499

  17. Flickr's Potential as an Academic Image Resource: An Exploratory Study

    ERIC Educational Resources Information Center

    Angus, Emma; Stuart, David; Thelwall, Mike

    2010-01-01

    Many web 2.0 sites are extremely popular and contain vast amounts of content, but how much of this content is useful in academia? This exploratory paper investigates the potential use of the popular web 2.0 image site Flickr as an academic image resource. The study identified images tagged with any one of 12 subject names derived from recognized…

  18. Lessons learned from 25+ years of piggybacking environmental isotope studies onto large-scale federal and state water quality monitoring programs (Invited)

    NASA Astrophysics Data System (ADS)

    Kendall, C.; Silva, S. R.; Young, M. B.

    2010-12-01

    Isotopes are a potentially powerful component of monitoring and assessment programs aimed at quantifying and mitigating alterations to environments from human activities. Locations exhibiting unusually high rates of biogeochemical cycling or elevated pollution levels usually have distinctive isotopic compositions that are suggestive or diagnostic of the reactions and pollution sources. Isotopes can be more effective at identifying hot spots and hot moments than concentrations alone because isotopic ratios may change even when concentrations do not. Hence, isotopes facilitate the identification of hot spots and moments that otherwise would not be apparent, thereby providing a valuable addition to standard chemical and hydrological mass balance methods. In addition, isotopic techniques have proved useful for tracing sources and sinks of various pollutants in large river basins, wetlands, and airsheds. Many of these studies have been conducted at the regional to national scale by building on existing large-scale water, air, and ecological monitoring programs managed by federal and state agencies, and demonstrate the usefulness of isotopes as a complement to standard chemical and hydrological mass balance methods. This presentation presents an overview of how a multi-isotope approach can be used to interpret spatial patterns and temporal changes in pollution sources, biogeochemical processes, and ecosystem function in large watersheds, at the regional to national scale. Examples from several of our recent and ongoing studies in the San Joaquin, Sacramento, and Mississippi Rivers are presented. From the insights developed using (1) a multi-isotope approach (emphasizing nitrate, seston, and water isotopes) used in conjunction with detailed hydrologic and chemical data collected from both mainstem and tributary sites as part of annual or multi-year studies; (2) varied sampling strategies including fixed site, synoptic, Lagrangian, and diel approaches; (3) different types

  19. Spectroscopy of actinium-215 and (p,t) studies of the stable palladium isotopes

    NASA Astrophysics Data System (ADS)

    Winkler, Ryan

    2009-12-01

    The study of both the microscopic and macroscopic structural evolution of the atomic nucleus is presented in this work. The excited states of the N = 126 isotone 215Ac were investigated at WNSL using the gas-filled recoil separator SASSYER. Recoil-decay tagging of the gamma rays corresponding to the decay of 215Ac after production via a fusion-evaporation reaction was made possible by using the redesigned SASSYER focal plane apparatus, including the addition of a pair of DSSDs and the multi-wire avalanche counter MACY. A number of transitions feeding the 29/2+ isomeric state corresponding to the ( ph49/2 )⊗(pii13/2) configuration were observed and tentatively assigned as decays from the high-spin 35/2 +, 39/2+, and 41/2+ states. Additionally, the decay from the low-lying 13/2+ state, corresponding to a pii13/2 quasiparticle excitation, was observed at 859 keV. This excitation energy is consistent with the systematics of the lighter N = 126 isotones suggesting a decrease in the energy gap between the pih9/2 and pi i13/2 orbitals. High-resolution (p,t) spectroscopy of the stable, even-even Palladium isotopes was performed in the search for signatures of quantum phase transitional behavior. A total of 54 previously unidentified 0+, 2 +, and 4+ states below an excitation energy of 3.5 MeV were discovered in this experiment. No enhancement of the 0+ level density, a signature of first-order phase transitions in nuclei, was observed in the studied isotopes. A theoretical description of the population strengths of excited 0+ states in two-nucleon transfer reactions was investigated within the framework of the IBM. These studies reveal that an enhanced population strength is not exclusive to regions of shape-coexistence but rather is a measure of the magnitude of the "change of structure" from the initial to residual nucleus.

  20. Binding modes of DL-2-haloacid dehalogenase revealed by crystallography, modeling and isotope effects studies.

    PubMed

    Siwek, Agata; Omi, Rie; Hirotsu, Ken; Jitsumori, Keiji; Esaki, Nobuyoshi; Kurihara, Tatsuo; Paneth, Piotr

    2013-12-01

    Several pathways of biotic dechlorination can be found in enzymes, each characterized by different chlorine isotopic fractionation, which can thus serve as a signature of a particular mechanism. Unlike other dehalogenases, DL-2-haloacid dehalogenase, DL-DEX, converts both enantiomers of the substrate. Chlorine isotope effects for this enzyme are larger than in the case of other dehalogenases. Recently, the 3D structure of this enzyme became available and enabled us to model these isotope effects and seek their origin. We show that the elevated values of the chlorine kinetic isotope effects originate in part in the processes of binding and migration within the enzyme active site that precede the dehalogenation step. PMID:24071515

  1. Stable Isotopes of Carbon Monoxide in an Urban Environment: A Study at Indianapolis, IN as part of the INFLUX Campaign

    NASA Astrophysics Data System (ADS)

    Vimont, I.; Petrenko, V. V.; Turnbull, J. C.; Place, P.; White, J. W. C.; Karion, A.

    2015-12-01

    We have developed a new system capable of measuring stable isotopes of carbon monoxide (CO) in small atmospheric samples. Measurements at 3 tall tower sites in Indianapolis, IN, USA have been ongoing since July 2013 as part of the INdianapolis FLUX (INFLUX) project. These three towers consist of an upwind, or background site, a site in the urban center, and a site on the downwind edge of the city. The tower collections are discrete, one hour integrated samples taken using NOAA's Portable Flask Package system. These sites have been measured for CO mole fraction, 13CO, and C18O approximately 6 times per month. We present a time series of data from these three sites, as well as a source analysis of the CO produced during the winter months (the winter data allow the use of several simplifying assumptions). We have identified mobile (vehicular) fossil fuel emissions as the only clearly significant wintertime source of CO, and quantified the stable isotopic signature of that source. We also present data from a traffic study done in March of 2015. A vehicle-based collection system was used for this study, and both continuous CO mole fraction and discrete CO mole fraction, 13CO, and C18O measurements were made. The results for CO stable isotopes are consistent with the vehicular emission CO isotopic signatures inferred from the tower samples.

  2. A Br Isotopic Study of Australian Arid Playa Lakes and halophyte vegetation as a monitor of Br transport

    NASA Astrophysics Data System (ADS)

    Schaefer, B. F.

    2014-12-01

    Bromine possesses a chemistry broadly comparable to that of Cl and F, however its heavier mass and lower abundance results in slightly different behaviours in geochemical cycling. For example it is disproportionately enriched in sea water with respect to Cl. Br can be considered to be a "hydrophile" element, and hence its behaviour is in governed by that of water. It possesses two isotopes 79Br (50.686%) and 81Br (49.314%). This study has developed new chemical extraction, and most significantly, new mass spectrometric protocols for Br isotopes on silicates, evaporites and waters using N-TIMS methodologies. Existing CF-IRMS methodologies offer internal precision of ~0.3‰ (1SD, [1]), whereas N-TIMS measurements of laboratory HBr and seawater standards produce external reproducibility of <0.07‰ (1SD) over an 18 month period with internal precision typically <0.06‰ (1SD) on single analyses. This study presents the first high precision, N-TIMS isotopic data on playa lake evaporites, recording a >5‰ variation in solar system 81Br/79Br. Also presented is data from the analysis of the halophylic saltbush (sp Atriplex) adjacent to the lakes to constrain biological fractionation of Br isotopes. Variations of ~4‰ are observed between the lakes with a comparable shift for the leaves of the saltbush. [1] Shouaker-Stash et al., Anal. Chem, 77; p4027-4033, 2005.

  3. A groundwater separation study in boreal wetland terrain: the WATFLOOD hydrological model compared with stable isotope tracers.

    PubMed

    Stadnyk, T; St Amour, N; Kouwen, N; Edwards, T W D; Pietroniro, A; Gibson, J J

    2005-03-01

    Monitoring of stable water isotopes (18O and 2H) in precipitation and surface waters in the Mackenzie River basin of northern Canada has created new opportunities for researchers to study the complex hydrology and hydroclimatology of this remote region. A number of prior studies have used stable isotope data to investigate aspects of the hydrological regime of the wetland-dominated terrain near Fort Simpson, Northwest Territories, Canada. The present paper compares estimates of groundwater contributions to streamflow derived using the WATFLOOD distributed hydrological model, equipped with a new water isotope tracer module, with the results of conventional isotope hydrograph separation for five wetland-dominated catchments along the lower Liard River. The comparison reveals highly promising agreement, verifying that the hydrological model is simulating groundwater flow contributions to total streamflow with reasonable fidelity, especially during the crucial snowmelt period. Sensitivity analysis of the WATFLOOD simulations also reveals intriguing features about runoff generation from channelized fens, which may contribute less to streamflow than previously thought. PMID:15823857

  4. Stabile Chlorine Isotope Study of Martian Shergottites and Nakhlites; Whole Rock and Acid Leachates and Residues

    NASA Technical Reports Server (NTRS)

    Nakamura, N.; Nyquist, L. E.; Reese, Y.; Shih, C-Y; Fujitani, T.; Okano, O.

    2011-01-01

    We have established a precise analytical technique for stable chlorine isotope measurements of tiny planetary materials by TIMS (Thermal Ionization Mass Spectrometry) [1], for which the results are basically consistent with the IRMS tech-nique (gas source mass spectrometry) [2,3,4]. We present here results for Martian shergottites and nakhlites; whole rocks, HNO3-leachates and residues, and discuss the chlorine isotope evolution of planetary Mars.

  5. Interannual variability in seagrass carbon and nitrogen stable isotopes from the Florida Keys National Marine Sanctuary, a preliminary study

    NASA Astrophysics Data System (ADS)

    Fourqurean, J. W.; Fourqurean, J. W.; Anderson, W. T.; Anderson, W. T.

    2001-12-01

    The shallow marine waters surrounding the southern tip of Florida provide an ideal environment for seagrasses, which are the most common benthic community in the region. Yet, these communities are susceptible to a variety of anthropogenic disturbances, especially changes in water quality caused by an increase the nutrient flux to the near shore environment. In order to better understand the carbon and nitrogen isotopic ratio in marine plants, an extensive times series analysis was constructed from quarterly sampling of Thalassia testudinum (the dominate species in the study area) from 1996 through 1998. Sites for study where selected from permanent stations within the Florida Keys National Marine Sanctuary (FKNMS), from both sides of the Florida Keys - two stations on the bay side and two stations on the reef side. These data will also help to constrain elements of the carbon and nitrogen cycles affecting this region. The data analyzed over the three year study period show unique cyclic trends associated with seasonal changes in primary productivity and potentially changes in the nitrogen and carbon pools. Additionally, the analysis of our time series indicates that isotope food web studies need to take into account spatial and temporal changes when evaluating trophic levels. The mean carbon and nitrogen isotope values of T. testudinum from all 4 stations vary respectively from -7.2 per mil to -10.41 and 1.1 per mil to 2.2 per mil (n = 48). However, certain stations displayed anonymously depleted nitrogen isotope values, values as low as -1.2 per mil. These values potentially indicated that biogeochmical processes like N fixation, ammonification and denitrification cause regional pattern in the isotopic composition of the source DIN. Both carbon and nitrogen isotopes displayed seasonal enrichment-depletion trends, with maximum enrichment occurring during the summer. The overall seasonal variation for carbon 13 from the different stations ranged from 1 per mil to

  6. {alpha} decay studies of very neutron-deficient francium and radium isotopes

    SciTech Connect

    Uusitalo, J.; Leino, M.; Enqvist, T.; Grahn, T.; Greenlees, P.T.; Jones, P.; Julin, R.; Juutinen, S.; Keenan, A.; Kettunen, H.; Koivisto, H.; Kuusiniemi, P.; Leppaenen, A.-P.; Nieminen, P.; Pakarinen, J.; Rahkila, P.; Scholey, C.; Eskola, K.

    2005-02-01

    Very neutron-deficient francium and radium isotopes have been produced in fusion evaporation reactions using {sup 63}Cu and {sup 65}Cu ions on {sup 141}Pr targets and {sup 36}Ar ions on {sup 170}Yb targets. The gas-filled recoil separator RITU was employed to collect the fusion products and to separate them from the scattered beam. The activities were implanted into a position-sensitive silicon detector after passing through a gas-counter system. The isotopes were identified using spatial and time correlations between the implants and decays. Two new {alpha} decaying radium isotopes, {sup 201}Ra and {sup 202}Ra, were identified. The {alpha} decay energy and half-life of {sup 203}Ra were measured with improved precision. The {alpha} decay properties measured for the francium isotopes {sup 201}Fr,{sup 202}Fr,{sup 203}Fr, and {sup 204}Fr were confirmed, in many cases with improved precision. For the first time, a ({pi}s{sub 1/2}{sup -1})1/2{sup +} proton intruder state was identified in francium isotopes, namely in {sup 201}Fr and tentatively in {sup 203}Fr. The measured decay properties for the neutron-deficient odd-mass Fr isotopes suggest an onset of substantial deformation at N=112.

  7. Isotope Fractionation of chlorine in Aqueous System: One Study on Anion-Exchange Chromatography.

    NASA Astrophysics Data System (ADS)

    Musashi, M.; Oi, T.; Eggenkamp, H.; Van Cappellen, P.

    2001-05-01

    Stable chlorine isotopes such as 37Cl and 35Cl have been paid attention as useful tool identifying the source, and monitoring the transport process and natural fate of chlorinated organic pollutants in air and groundwater. However, it is not established yet whether any isotope effects accompany biodegradation or reductive dehalogenation of the pollutants (Clark and Fritz, 1997). Here we first present an experimental determination of isotope fractionation factor of chlorine in aqueous system by using anion-exchange chromatographic technique. Into the Cl-free anion exchange resin (Muromac, OH- form) packed in a 30 cm long pyrex glass column and controlled temperature at 25 oC, hydrochloric solution was fed with controlling the flow rate constant. Effluent from the column was recovered by an automatic fraction collector and prepared for Cl isotope analysis. The Cl isotope ratio (δ 37Cl vs. SMOC) was measured by IR-MS at the Utrecht University with precision of 0.06 per-mil. Magnitude of the factor obtained was 1.00035 at 25 oC. The result indicates that the lighter isotope (35Cl) was preferably fractionated into the resin phase, while the heavier one (37Cl) was enriched into the aqueous phase. This trend suggests that molecular structure of hydrolysis with Cl in aqueous phase may be more stable than that of Cl ionically bonding with the resin. This result may offer physico-chemical insights into behavior and fate of the pollutants.

  8. Studies of superresolution range-Doppler imaging

    NASA Astrophysics Data System (ADS)

    Zhu, Zhaoda; Ye, Zhenru; Wu, Xiaoqing; Yin, Jun; She, Zhishun

    1993-02-01

    This paper presents three superresolution imaging methods, including the linear prediction data extrapolation DFT (LPDEDFT), the dynamic optimization linear least squares (DOLLS), and the Hopfield neural network nonlinear least squares (HNNNLS). Live data of a metalized scale model B-52 aircraft, mounted on a rotating platform in a microwave anechoic chamber, have in this way been processed, as has a flying Boeing-727 aircraft. The imaging results indicate that, compared to the conventional Fourier method, either higher resolution for the same effective bandwidth of transmitted signals and total rotation angle in imaging, or equal-quality images from smaller bandwidth and total rotation, angle may be obtained by these superresolution approaches. Moreover, these methods are compared in respect of their resolution capability and computational complexity.

  9. Isotopically coded cleavable cross-linker for studying protein-protein interaction and protein complexes.

    PubMed

    Petrotchenko, Evgeniy V; Olkhovik, Vyacheslav K; Borchers, Christoph H

    2005-08-01

    An emerging approach for studying protein-protein interaction in complexes is the combination of chemical cross-linking and mass spectrometric analysis of the cross-linked peptides (cross-links) obtained after proteolysis of the complex. This approach, however, has several challenges and limitations, including the difficulty of detecting the cross-links, the potential interference from non-informative "cross-linked peptides" (dead end and intrapeptide cross-links), and unambiguous identification of the cross-links by mass spectrometry. Thus, we have synthesized an isotopically coded ethylene glycol bis(succinimidylsuccinate) derivate (D12-EGS), which contains 12 deuterium atoms for easy detection of cross-links when applied in a 1:1 mixture with its H12 counterpart and is also cleavable for releasing the cross-linked peptides allowing unambiguous identification by MS sequencing. Moreover, hydrolytic cleavage permits rapid distinguishing between different types of cross-links. Cleavage of a dead end cross-link produces a doublet with peaks 4.03 Da apart, with the lower peak appearing at a molecular mass 162 Da lower than the mass of the H12 form of the original cross-linked peptide. Cleavage of an intrapeptide cross-link leads to a doublet 8.05 Da apart and 62 Da lower than the molecular mass of the H12 form of the original cross-linked peptide. Cleavage of an interpeptide cross-link forms a pair of 4.03-Da doublets, with the lower mass member of each pair each shifted up from its unmodified molecular weight by 82 Da because of the attached portion of the cross-linker. All of this information has been incorporated into a software algorithm allowing automatic screening and detection of cross-links and cross-link types in matrix-assisted laser desorption/ionization mass spectra. In summary, the ease of detection of these species through the use of an isotopically coded cleavable cross-linker and our software algorithm, followed by mass spectrometric sequencing of the

  10. Compound-specific chlorine isotope analysis: a comparison of gas chromatography/isotope ratio mass spectrometry and gas chromatography/quadrupole mass spectrometry methods in an interlaboratory study.

    PubMed

    Bernstein, Anat; Shouakar-Stash, Orfan; Ebert, Karin; Laskov, Christine; Hunkeler, Daniel; Jeannottat, Simon; Sakaguchi-Söder, Kaori; Laaks, Jens; Jochmann, Maik A; Cretnik, Stefan; Jager, Johannes; Haderlein, Stefan B; Schmidt, Torsten C; Aravena, Ramon; Elsner, Martin

    2011-10-15

    Chlorine isotope analysis of chlorinated hydrocarbons like trichloroethylene (TCE) is of emerging demand because these species are important environmental pollutants. Continuous flow analysis of noncombusted TCE molecules, either by gas chromatography/isotope ratio mass spectrometry (GC/IRMS) or by GC/quadrupole mass spectrometry (GC/qMS), was recently brought forward as innovative analytical solution. Despite early implementations, a benchmark for routine applications has been missing. This study systematically compared the performance of GC/qMS versus GC/IRMS in six laboratories involving eight different instruments (GC/IRMS, Isoprime and Thermo MAT-253; GC/qMS, Agilent 5973N, two Agilent 5975C, two Thermo DSQII, and one Thermo DSQI). Calibrations of (37)Cl/(35)Cl instrument data against the international SMOC scale (Standard Mean Ocean Chloride) deviated between instruments and over time. Therefore, at least two calibration standards are required to obtain true differences between samples. Amount dependency of δ(37)Cl was pronounced for some instruments, but could be eliminated by corrections, or by adjusting amplitudes of standards and samples. Precision decreased in the order GC/IRMS (1σ ≈ 0.1‰), to GC/qMS (1σ ≈ 0.2-0.5‰ for Agilent GC/qMS and 1σ ≈ 0.2-0.9‰ for Thermo GC/qMS). Nonetheless, δ(37)Cl values between laboratories showed good agreement when the same external standards were used. These results lend confidence to the methods and may serve as a benchmark for future applications. PMID:21851081

  11. Isotopic studies of rare gases in terrestrial samples and natural nucleosynthesis

    SciTech Connect

    Not Available

    1991-05-01

    This project is concerned with research in rare gas mass spectrometry. Using a two-pronged attack, we study fluids using a system (RARGA) designed for fluid analysis in bulk which is sometimes deployed in the field and a laser microprobe mass spectrometer for fluid inclusion studies. In 1991 the RARGA project continued monitoring helium isotope variations associated with renewed seismic activity in Long Valley Caldera and expanded our geothermal data base to include Lassen National Park. An important objective, continuing in 1992, is to understand better the reasons for somewhat elevated {sup 3}He/{sup 4}He ratios in regions where there is no contemporary volcanism which could produce the effect by addition of mantle helium. To this end, 1991 saw continued efforts to understand variations in composition between fluids and associated reservoir rocks and extended the data base to include fluids from the Gulf of Mexico. Our DOE work in calibrating a sensitive laser microprobe mass spectrometer for noble gases in fluid inclusions continues with successful returns particularly in calibrating neutron irradiated samples for tracing halogen ratios. In connection with observations of neutron-produced noble gas nuclides in granites, we have begun comparing measurements with calculations for both thermal and epithermal neutrons. We submitted a third paper on noble gases in diamonds, concentrating on observed effects of {sup 4}He, {sup 3}He, and fission xenon implantation from nuclear processes in adjacent material in the matrix rock. 16 refs., 1 tab.

  12. Isotopic studies of rare gases in terrestrial samples and natural nucleosynthesis. Progress report

    SciTech Connect

    Not Available

    1991-05-01

    This project is concerned with research in rare gas mass spectrometry. Using a two-pronged attack, we study fluids using a system (RARGA) designed for fluid analysis in bulk which is sometimes deployed in the field and a laser microprobe mass spectrometer for fluid inclusion studies. In 1991 the RARGA project continued monitoring helium isotope variations associated with renewed seismic activity in Long Valley Caldera and expanded our geothermal data base to include Lassen National Park. An important objective, continuing in 1992, is to understand better the reasons for somewhat elevated {sup 3}He/{sup 4}He ratios in regions where there is no contemporary volcanism which could produce the effect by addition of mantle helium. To this end, 1991 saw continued efforts to understand variations in composition between fluids and associated reservoir rocks and extended the data base to include fluids from the Gulf of Mexico. Our DOE work in calibrating a sensitive laser microprobe mass spectrometer for noble gases in fluid inclusions continues with successful returns particularly in calibrating neutron irradiated samples for tracing halogen ratios. In connection with observations of neutron-produced noble gas nuclides in granites, we have begun comparing measurements with calculations for both thermal and epithermal neutrons. We submitted a third paper on noble gases in diamonds, concentrating on observed effects of {sup 4}He, {sup 3}He, and fission xenon implantation from nuclear processes in adjacent material in the matrix rock. 16 refs., 1 tab.

  13. Stable isotopic studies of H,C,N,O and S in samples of Martian origin

    NASA Technical Reports Server (NTRS)

    Wright, I. P.; Pillinger, C. T.

    1988-01-01

    The present day geochemical cycles of volatile elements through the various reservoirs on Earth are largely understood within the context of the planet's standing as a geologically and biologically evolved body. In terrestrial studies stable isotope measurements of light elements (H, C, N, O and S) can be utilized to obtain insight into the conditions prevailing during formation of rocks of various types. Perhaps the most important problem which could be addressed by light element studies of the sorts of specimen likely to be available from remote automatic sampling, would be the role of volatiles during evolution. Of fundamental importance here is the question of whether Mars was volatile rich or volatile poor. The only way to fully comprehend the effects of volatile cycling through the mantle crust and regolith atmosphere polar cap system of Mars, is by analyses of appropriate returned samples. In order to interpret the record of geological activity in Martian samples it will be necessary to understand how the past, or present, surface environment may have acted to disturb the primary characteristics of the rocks.

  14. Terahertz pulsed imaging study of dental caries

    NASA Astrophysics Data System (ADS)

    Karagoz, Burcu; Altan, Hakan; Kamburoglu, Kıvanç

    2015-07-01

    Current diagnostic techniques in dentistry rely predominantly on X-rays to monitor dental caries. Terahertz Pulsed Imaging (TPI) has great potential for medical applications since it is a nondestructive imaging method. It does not cause any ionization hazard on biological samples due to low energy of THz radiation. Even though it is strongly absorbed by water which exhibits very unique chemical and physical properties that contribute to strong interaction with THz radiation, teeth can still be investigated in three dimensions. Recent investigations suggest that this method can be used in the early identification of dental diseases and imperfections in the tooth structure without the hazards of using techniques which rely on x-rays. We constructed a continuous wave (CW) and time-domain reflection mode raster scan THz imaging system that enables us to investigate various teeth samples in two or three dimensions. The samples comprised of either slices of individual tooth samples or rows of teeth embedded in wax, and the imaging was done by scanning the sample across the focus of the THz beam. 2D images were generated by acquiring the intensity of the THz radiation at each pixel, while 3D images were generated by collecting the amplitude of the reflected signal at each pixel. After analyzing the measurements in both the spatial and frequency domains, the results suggest that the THz pulse is sensitive to variations in the structure of the samples that suggest that this method can be useful in detecting the presence of caries.

  15. 'Body image is for girls': a qualitative study of boys' body image.

    PubMed

    Hargreaves, Duane A; Tiggemann, Marika

    2006-07-01

    Although a considerable and informative literature on boys' body image is beginning to emerge, this literature has been guided strongly by theorizing about female body image. The present study aimed to gain access to boys' own ideas and terminology regarding their body image. The participants (aged 14 to 16 years) said that they are satisfied with their appearance, but some conceded their physical appearance to be more important than they like to admit. Boys do not believe that the mass media influences their body image and said they do not talk about body image because it is a feminine or gay issue. PMID:16769736

  16. A lead isotopic study of the Stillwater Complex, Montana: constraints on crustal contamination and source regions

    USGS Publications Warehouse

    Wooden, J.L.; Czamanske, G.K.; Zientek, M.L.

    1991-01-01

    Analyses of the Pb isotopic compositions of plagioclase from 23 samples covering the stratigraphic thickness of the Stillwater Complex indicate a narrow range of apparent initial isotopic compositions (206Pb/ 204Pb=13.95; 207Pb/204Pb=14.95-15.01; 208Pb/204Pb=33.6). The uniformity of our data is in contrast to, but not necessarily contradictory to, other recent investigations which give indications that the complex formed by repeated injection of magmas with at least two distinct compositions that were presumably derived from different source regions. Samples from the Basal series of the complex have consistently higher 207Pb/204Pb ratios, suggesting either minor contamination from adjacent country rocks or a slight distinction between parental magmas. Apparent initial Pb isotopic compositions of the complex are very radiogenic compared to Late Archean model-mantle values, but are nearly identical to initial Pb isotopic compositions found for the the adjacent, slightly older (2.73-2.79 Ga), Late Archean crustal suite in the Beartooth Mountains. Contamination of magmas parental to the Stillwater Complex by the Late Archean crustal suite is rejected for two reasons: (1) Th and U concentrations in Stillwater rocks and plagioclase are very low (about 0.08 and 0.02 ppm respectively), yet Th/U ratios are uniform at about 4, in contrast to the highly variable (2-26) but often high Th/U ratios found for the Late Archean crustal complex; (2) it seems improbable that any contamination process would have adjusted the isotopic compositions of the diverse magmas entering the Stillwater chamber to near-identical values. The preferred hypothesis to explain the Pb isotopic data for the Stillwater Complex and the associated Late Archean crustal suite involves a major Late Archean crust-forming event that resulted in a compositionally complex crust/mantle system with relatively homogeneous and unusual Pb isotopic compositions. The parental magmas of the Stillwater Complex were

  17. Tree STEM Reconstruction Using Vertical Fisheye Images: a Preliminary Study

    NASA Astrophysics Data System (ADS)

    Berveglieri, A.; Tommaselli, A. M. G.

    2016-06-01

    A preliminary study was conducted to assess a tree stem reconstruction technique with panoramic images taken with fisheye lenses. The concept is similar to the Structure from Motion (SfM) technique, but the acquisition and data preparation rely on fisheye cameras to generate a vertical image sequence with height variations of the camera station. Each vertical image is rectified to four vertical planes, producing horizontal lateral views. The stems in the lateral view are rectified to the same scale in the image sequence to facilitate image matching. Using bundle adjustment, the stems are reconstructed, enabling later measurement and extraction of several attributes. The 3D reconstruction was performed with the proposed technique and compared with SfM. The preliminary results showed that the stems were correctly reconstructed by using the lateral virtual images generated from the vertical fisheye images and with the advantage of using fewer images and taken from one single station.

  18. Neodymium and strontium isotopic study of Australasian tektites - New constraints on the provenance and age of target materials

    NASA Technical Reports Server (NTRS)

    Blum, Joel D.; Papanastassiou, D. A.; Wasserburg, G. J.; Koeberl, C.

    1992-01-01

    The Nd and Sr isotopic compositions of Australasian tectites (including two flanged Australian tectites, two low-SiO2 Muong Nong-type tectites, and three high-SiO2 Muong Nong-type tectites) and the Nd, Sm, Sr, and Rb concentrations were investigated by isotope-dilution thermal ionization mass spectrometry, and the Sm-Nd and Rb-Sr isotope systematics were used to study the characteristics of the parental material. It is shown that the Nd and Sr isotopic data provide evidence that all Australasian tektites were derived from a single sedimentary formation with a narrow range of stratigraphic ages close to 170 Ma. It is suggested that all of the Australasian tektites were derived from a single impact event and that the australites represent the upper part of a melt sheet ejected at high velocity, whereas the indochinites represent melts formed at a lower level in the target material distributed closer to the area of the impact.

  19. Mercury Isotope Study of Sources and Exposure Pathways of Methylmercury in Estuarine Food Webs in the Northeastern U.S.

    PubMed Central

    2015-01-01

    We measured mercury (Hg) isotope ratios in sediments and various estuarine organisms (green crab, blue mussel, killifish, eider) to investigate methylmercury (MMHg) sources and exposure pathways in five Northeast coast (U.S.) estuaries. The mass independent Hg isotopic compositions (MIF; Δ199Hg) of the sediments were linearly correlated with the sediment 1/Hg concentrations (Δ199Hg: r2 = 0.77, p < 0.05), but the mass dependent isotope compositions (MDF; δ202Hg) were not (r2 = 0.26, p = 0.16), reflecting inputs of anthropogenic Hg sources with varying δ202Hg. The estuarine organisms all display positive Δ199Hg values (0.21 to 0.98 ‰) indicating that MMHg is photodegraded to varying degrees (5–12%) prior to entry into the food web. The δ202Hg and Δ199Hg values of most organisms can be explained by a mixture of MMHg and inorganic Hg from sediments. At one contaminated site mussels have anomalously high δ202Hg, indicating exposure to a second pool of MMHg, compared to sediment, crabs and fish. Eiders have similar Δ199Hg as killifish but much higher δ202Hg, suggesting that there is an internal fractionation of δ202Hg in birds. Our study shows that Hg isotopes can be used to identify multiple anthropogenic inorganic Hg and MMHg sources and determine the degree of photodegradation of MMHg in estuarine food webs. PMID:25116221

  20. S and O Isotope Studies of Microbial S Cycling in the Deep Biosphere of Marine Sediments: Eastern Equatorial Pacific Ocean

    NASA Astrophysics Data System (ADS)

    Blake, R. E.; Bottcher, M. E.; Surkov, A. V.; Ferdelman, T. G.; Jorgensen, B. B.

    2004-12-01

    We have determined the oxygen (18O/16O) and sulfur (34S/32S) isotope ratios of porewater sulfate to depths of over 400 mbsf in sediments from open-ocean and upwelling sites in the Eastern Equatorial Pacific ocean. Sulfate δ 18O ranges from near-normal seawater values (9.5 permil) at organic-poor open-ocean sites, to approximately 30 permil at sites with higher organic matter content and higher associated microbial activity. Depth-correlative trends of δ 18O, δ 34S, alkalinity, methane, ammonium and the presence of sulfide, indicate significant oxidation of sedimentary organic matter by sulfate-reducing microbial populations as well as anaerobic oxidation of methane. δ 18O-SO4 values at low-activity sites reveal the presence of significant microbial sulfur-cycling activity despite relatively flat sulfate concentration and δ 34S profiles. This activity may include contributions from several processes including: enzyme-catalyzed equilibration between oxygen in sulfate and water superimposed upon microbial sulfate reduction, sulfide oxidation, and bacterial disproportionation of sulfur intermediates. Large isotope enrichment factors observed at low-activity sites (40-80 permil) likely reflect concurrent processes of: kinetic isotope fractionation, equilibrium fractionation between sulfate and water, and sulfide oxidation at low rates of sulfate reduction. Results of this study indicate that coupled measurements of S and O isotope ratios of porewater sulfate are a powerful tool for tracing microbial activity and sulfur cycling in marine sediments.

  1. An intercomparison study of isotopic ozone profiles from the ACE-FTS, JEM-SMILES, and Odin-SMR instruments

    NASA Astrophysics Data System (ADS)

    Jones, A.; Walker, K. A.; Suzuki, M.; Kasai, Y.; Shiotani, M.; Urban, J.; Bernath, P. F.; Manney, G. L.

    2012-12-01

    Observations of various atmospheric isotopologue species are a valuable source of information, as they can improve our current understanding of the atmosphere. For example, isotopic signatures in atmospheric profiles can be used to investigate atmospheric dynamical processes, while differences in the isotopic composition of atmospheric trace gases can be traced to effects due to their sources and sinks. This study focuses on the intercomparison of three satellite missions that provide measurements of isotopic species. The Atmospheric Chemistry Experiment-Fourier Transform Spectrometer (ACE-FTS) aboard the Canadian satellite SCISAT (launched in August 2003) was designed to investigate the composition of the upper troposphere, stratosphere, and mesosphere. ACE-FTS utilizes solar occultation to measure temperature, pressure, and vertical profiles of over thirty chemical species, including isotopologue profiles for; O3, H2O, CH4, N2O, CO, CO2 and NO. Global coverage for each species is obtained approximately over one year and with a vertical resolution of typically 3-4 km. ACE-FTS O3 isotopologue volume mixing ratio profiles are firstly compared to data measured by the Superconducting Sub-Millimeter-wave Limb Emission Sounder (SMILES), onboard the Japanese Experiment Module (JEM) of the International Space Station (ISS), and the Sub-Millimetre Radiometer (SMR) aboard the Swedish Odin satellite. Secondly, we intercompare the isotopic fractionation profiles for each ozone isotopologue product measured by the three instruments to further ascertain a level of confidence in the measurements.

  2. Mercury isotope study of sources and exposure pathways of methylmercury in estuarine food webs in the Northeastern U.S.

    PubMed

    Kwon, Sae Yun; Blum, Joel D; Chen, Celia Y; Meattey, Dustin E; Mason, Robert P

    2014-09-01

    We measured mercury (Hg) isotope ratios in sediments and various estuarine organisms (green crab, blue mussel, killifish, eider) to investigate methylmercury (MMHg) sources and exposure pathways in five Northeast coast (U.S.) estuaries. The mass independent Hg isotopic compositions (MIF; Δ(199)Hg) of the sediments were linearly correlated with the sediment 1/Hg concentrations (Δ(199)Hg: r(2) = 0.77, p < 0.05), but the mass dependent isotope compositions (MDF; δ(202)Hg) were not (r(2) = 0.26, p = 0.16), reflecting inputs of anthropogenic Hg sources with varying δ(202)Hg. The estuarine organisms all display positive Δ(199)Hg values (0.21 to 0.98 ‰) indicating that MMHg is photodegraded to varying degrees (5-12%) prior to entry into the food web. The δ(202)Hg and Δ(199)Hg values of most organisms can be explained by a mixture of MMHg and inorganic Hg from sediments. At one contaminated site mussels have anomalously high δ(202)Hg, indicating exposure to a second pool of MMHg, compared to sediment, crabs and fish. Eiders have similar Δ(199)Hg as killifish but much higher δ(202)Hg, suggesting that there is an internal fractionation of δ(202)Hg in birds. Our study shows that Hg isotopes can be used to identify multiple anthropogenic inorganic Hg and MMHg sources and determine the degree of photodegradation of MMHg in estuarine food webs. PMID:25116221

  3. Effect of Soil Frost on Snow-melt runoff Generation: Stable Isotope Study in Drained Peatlands

    NASA Astrophysics Data System (ADS)

    Eskelinen, Riku; Ronkanen, Anna-Kaisa; Marttila, Hannu; Kløve, Bjørn

    2013-04-01

    In this study, we analysed stable isotopes and water quality of runoff water collected daily from two different peatland drainage areas with automated samplers from March 2012 to October 2012, located in Northern Finland. In addition we collected weekly snow samples for stable isotope analysis. Our primary aim was to find out how different land use types, i) peat extraction area and ii) peatland forestry, are affecting the flow paths and runoff water quality during the snow melt period. Results show that there is a clear difference in δO18 signal between these systems. The peatland forestry area is located at groundwater dominated area which can be seen as a flat line when δO18 values of all samples are plotted. Samples taken at the peat extraction area show a clear response to the snowmelt event. Most likely this difference is caused by different soil frost conditions. Quantity of the groundwater at the forestry area prevents the soil from freezing during winter, therefore water originating from melting snow is able to infiltrate to the peat soil and push pre-event water into the drainage system. This observation is also visible in water quality of runoff water as high peak in colour during the snow melt period. Contrary, the peat extraction area behaves in opposite way. Melting water from snow is not able to infiltrate to ditches but instead will rapidly move on the frozen soil surface as a Hortonian overland flow. Because the soil is frozen, moving water is not able to leach humic substances from soil layers or erode particulate matter from the soil surface. These observations can be used to develop water quality protection policies for drained peatland areas. In Northern areas, where freezing of soil during winter is common it is not crucial to emphasize water protection during spring snowmelt, as frozen soil helps to maintain the runoff water quality at reasonable levels. In the areas where ground frost is rarer the impact of purifying runoff water in spring

  4. Helium isotope studies in the Mojave Desert, California: Implications for groundwater chronology and regional seismicity

    USGS Publications Warehouse

    Kulongoski, J.T.; Hilton, David R.; Izbicki, J.A.

    2003-01-01

    We report helium isotope and concentration results for groundwaters from the western Mojave River Basin (MRB), 130 km east of Los Angeles, CA. The basin lies adjacent to the NW-SE trending San Andreas Fault (SAF) system. Samples were collected along two groundwater flowpaths that originate in the San Gabriel Mountains and discharge to the Mojave River located ???32 km to the northeast. Additional groundwater samples were collected from Mojave River Deposits underlying the Mojave River. The primary objective of this study is to identify and quantify crustal and mantle helium contributions to the regional groundwater system. A total of 27 groundwaters, sampled previously for chemistry and isotope systematics (including 14C activity) have measured helium concentrations that increase along flowpaths from 9.9??10-8 to 1.0??10-4 cm3 STP g-1 H2O. Concomitantly, 3He/4He ratios decrease from 0.84RA to 0.11RA (RA equals the 3He/4He ratio in air=1.4??10-6). We did not record 3He/4He ratios equivalent to crustal-production values (???0.02RA) in any sample. Dissolved helium concentrations were resolved into components associated with solubility equilibration, air entrainment, mantle-derivation, in-situ production within the aquifer, and extraneous crustal fluxes. All samples contained the first four components, but only older samples had the superimposed effects of helium derived from a crustal flux. The radiogenic He component has chronological significance, and good concordance between 4He and 14C ages for younger groundwaters (<25,000 year) demonstrates the integrity of the 4 He-chronometer in this setting. Helium-rich waters could also be dated with the 4He technique, but only by first isolating the whole crustal flux (3-10??10-6 cm3 STP cm-2 year-1). Mantle-derived 3He (3Hem) is present in all MRB samples irrespective of distance from the SAF. However, regional-aquifer groundwaters near the terminus of the flowpath have a significantly greater content of mantle-derived 3He

  5. Coupled U-Pb isotopic studies and synchrotron x-ray microbeam analysis of geologic systems

    NASA Astrophysics Data System (ADS)

    Lanzirotti, A.; Sutton, S.; Rasbury, T.; Becker, M.; Hanson, G. N.

    2001-12-01

    Analytical advances in thermal ionization mass spectrometry now allow for precise measurement of U and Pb abundance and Pb isotopic composition in minerals where U and Pb may only amount to a few picograms by weight. High precision analysis at such low levels means that a much wider variety of mineral species can be considered as potentially useful U-Pb geochronometers. However, evaluating the potential use of these minerals for high-precision dating requires understanding the environmental and crystal chemistry of the U and Pb being analyzed in these minerals. Advances in the production of microfocused synchrotron x-ray beams allow more unambiguous evaluation of uranium partitioning and speciation in these geochemical systems. The microbeam capabilities of these instruments, such as the X26A beamline at the NSLS, allow for near simultaneous evaluation of major and trace elements using synchrotron XRF, elemental speciation and coordination using x-ray absorption spectroscopy (XANES and EXAFS), and mineralogy using micro-XRD at resolutions of 10 microns or less. Additionally, the synchrotron hard x-ray microprobe allows for non-destructive analysis of the same hand specimens or thin sections from which samples are separated for isotopic analysis with a detection sensitivity often of 1 ppm or better. Some examples illustrate how these combined studies can help characterize the U and Pb geochemistry of the host environments in which these minerals formed. Andradite garnets from the Grand Canyon Supergroup (1178+/-26 Ma) are shown to be compositionally homogeneous in U abundance (10-25 ppm), with U as a 4+ species. Fossilized Jurassic fish coprolites from the Shuttle Meadow Fm. (ca. 200 Ma) show that although they are dominated by apatite the highest U abundance is consistent with adsorption onto organic C at the time of sedimentation. Examples of U analyzed from a number of terrestrial carbonates shows that U can be incorporated as both 4+ and 6+ species and may also

  6. Food web dynamics in the Scotia Sea in summer: A stable isotope study

    NASA Astrophysics Data System (ADS)

    Stowasser, G.; Atkinson, A.; McGill, R. A. R.; Phillips, R. A.; Collins, M. A.; Pond, D. W.

    2012-01-01

    The pelagic food web of the Scotia Sea was studied by analysing natural abundances of nitrogen and carbon stable isotopes of primary producers and pelagic consumers, sampled from the seasonal ice edge in the south to the Antarctic Polar Front in the north. The analysis covered, within a single mid-summer period, particulate organic matter (POM) and 38 taxa, ranging from suspension feeding copepods and salps to omnivorous euphausiids, pelagic fish and higher, land-based predators including fur seals, penguins and flying birds. Spatial variation in δ 15N of POM correlated well with nutrient availability and primary productivity. Latitudinal differences in δ 13C of POM were closely linked to variations in temperature, nutrients and productivity depending on the frontal region sampled. This translated to equivalent (although smaller) regional δ 13C differences among higher trophic levels. The trophic positions of species based on isotope values broadly agreed with previously published dietary data with three important exceptions. First, the carnivorous amphipod Themisto gaudichaudii had anomalously low δ 15N values. Second, Euphausia superba had δ 15N values that were also surprisingly low, considering the abundant literature suggesting its omnivory. Third, the copepod Rhincalanus gigas, considered a suspension feeder, had unexpectedly high δ 15N values rather more in keeping with omnivorous feeding. The consumer δ 15N values ranged from 1.2‰ (min.) measured in Salpa thompsoni (designated here as trophic level (TL) 2 across all regions) to 15.2‰ (max.) measured in white-chinned petrels ( Procellaria aequinoctialis, calculated as TL5 relative to the TL2 of salps). Excluding seabirds, the resulting food chain length of 3.7 TL (above POM at TL1) was lower than in most other Southern Ocean and temperate marine pelagic ecosystems. The majority (60%) of vertebrate predators occupied only 1-1.5 trophic levels above the herbivorous suspension feeders such as krill

  7. A Stable Isotope Study of Fluid-Rock Interactions in the Saddlebag Lake Roof Pendant, Sierra Nevada, California

    NASA Astrophysics Data System (ADS)

    Lojasiewicz, I.; Hartman, S. M.; Holk, G. J.; Paterson, S. R.

    2015-12-01

    The Saddlebag Lake Pendant (SLP) is a ~ 100 km2 zone of Ordovician-Cretaceous metasedimentary and metavolcanic rocks just east of the 95-85 Ma Tuolumne Intrusive Complex (TIC) in the Sierra Nevada of central California. Western SLP and adjacent parts of TIC are affected by the Steelhead Lake Shear Zone (SLSZ), with leucogranitic dikes, abundant qz-tm veins, ductile epidote-chlorite alteration, and massive qz veins. While TIC shows uniform stable isotope values, isotope studies of other Sierra Nevada pendants evidence diversity of fluid sources: Jurassic seawater, Cretaceous magmatic fluids, metamorphic fluids, and meteoric-hydrothermal fluids. We conducted a stable isotope study of 49 samples from units across the SLSZ, focusing on the shear zone. Unlike other pendants, both δ18 O and δD values from SLSZ showed great variability, and most samples were not in isotopic equilibrium. Overall, δ18 O mineral values ranged from -1.5‰(plag) to +15.8‰(bt); mineral δD values ranged from -140‰(tm) to -67‰(bt). TIC δ18 O was +7.8 to +10.0 (plag) and +4.8 to +9.2 (tm), normal magmatic values, and δD were -105 to -75. Paleozoic and Triassic metasedimentary units had most qz δ18 O from +11.3 to +15.8, so within metamorphic range, and δD from -100 to -72 (ep and tm). Jurassic metasedimentary units (Sawmill) and Triassic metavolcanics (Koip) had largest isotopic variability: δ18 O qz from +8.1 to +14.8, plag from -1.1 to +11.8, but ep and tm between +1.3 and +9.3 and δD between -108 and -81. All lower (submagmatic) isotopic values were from a wider, possibly transtensional, part of the SLSZ, transected by Sawmill Canyon. Although TIC and many of the Paleozoic units do not show isotopic evidence for alteration, the Koip and Sawmill units were likely infiltrated by later magmatic waters, and then subjected to very localized meteoric water infiltration in the area surrounding Sawmill Canyon.

  8. In-gas-cell laser ionization studies of plutonium isotopes at IGISOL

    NASA Astrophysics Data System (ADS)

    Pohjalainen, I.; Moore, I. D.; Kron, T.; Raeder, S.; Sonnenschein, V.; Tomita, H.; Trautmann, N.; Voss, A.; Wendt, K.

    2016-06-01

    In-gas-cell resonance laser ionization has been performed on long-lived isotopes of Pu at the IGISOL facility, Jyväskylä. This initiates a new programme of research towards high-resolution optical spectroscopy of heavy actinide elements which can be produced in sufficient quantities at research reactors and transported to facilities elsewhere. In this work a new gas cell has been constructed for fast extraction of laser-ionized elements. Samples of 238-240,242Pu and 244Pu have been evaporated from Ta filaments, laser ionized, mass separated and delivered to the collinear laser spectroscopy station. Here we report on the performance of the gas cell through studies of the mass spectra obtained in helium and argon, before and after the radiofrequency quadrupole cooler-buncher. This provides valuable insight into the gas phase chemistry exhibited by Pu, which has been additionally supported by measurements of ion time profiles. The resulting monoatomic yields are sufficient for collinear laser spectroscopy. A gamma-ray spectroscopic analysis of the Pu samples shows a good agreement with the assay provided by the Mainz Nuclear Chemistry department.

  9. Stable isotopic studies of n-alkane metabolism by a sulfate-reducing bacterial enrichment culture.

    PubMed

    Davidova, Irene A; Gieg, Lisa M; Nanny, Mark; Kropp, Kevin G; Suflita, Joseph M

    2005-12-01

    Gas chromatography-mass spectrometry and nuclear magnetic resonance spectroscopy were used to study the metabolism of deuterated n-alkanes (C6 to C12) and 1-13C-labeled n-hexane by a highly enriched sulfate-reducing bacterial culture. All substrates were activated via fumarate addition to form the corresponding alkylsuccinic acid derivatives as transient metabolites. Formation of d14-hexylsuccinic acid in cell extracts from exogenously added, fully deuterated n-hexane confirmed that this reaction was the initial step in anaerobic alkane metabolism. Analysis of resting cell suspensions amended with 1-13C-labeled n-hexane confirmed that addition of the fumarate occurred at the C-2 carbon of the parent substrate. Subsequent metabolism of hexylsuccinic acid resulted in the formation of 4-methyloctanoic acid, and 3-hydroxy-4-methyloctanoic acid was tentatively identified. We also found that 13C nuclei from 1-13C-labeled n-hexane became incorporated into the succinyl portion of the initial metabolite in a manner that indicated that 13C-labeled fumarate was formed and recycled during alkane metabolism. Collectively, the findings obtained with a sulfate-reducing culture using isotopically labeled alkanes augment and support the previously proposed pathway (H. Wilkes, R. Rabus, T. Fischer, A. Armstroff, A. Behrends, and F. Widdel, Arch. Microbiol. 177:235-243, 2002) for metabolism of deuterated n-hexane by a denitrifying bacterium. PMID:16332800

  10. Further study of α-decay in heavy isotopic chains considering the isospin effect

    NASA Astrophysics Data System (ADS)

    Qian, Yibin; Ren, Zhongzhou

    2016-06-01

    We have enhanced the deformed density-dependent cluster model to improve the quantitative description of α-decay in heavy even–even nuclei with 84≤slant Z≤slant 92. To preliminarily introduce the isospin effect into α-decay, the neutron excess term is added in the establishment of the crucial α-core potential. The proton and neutron density distributions are respectively considered in different parameterized formulas by combining them with available experimental data of both the charge radius and the neutron skin thickness. The calculated α-decay half-lives are found to be in somewhat better agreement with the experimental data as compared with our previous results. Strikingly, it is noted that the relatively large deviation between theory and experiment, along the tail of the isotopic chain, is obviously reduced and smoother. This may indicate the necessity of considering the isospin effect in α-decay, especially for extremely neutron-rich nuclei, which appears to be essential for the extended study of heaviest nuclei as well.

  11. Measurement of alpha-induced reaction cross sections on erbium isotopes for γ process studies

    NASA Astrophysics Data System (ADS)

    Kiss, G. G.; Szücs, T.; Török, Zs.; Fülöp, Zs.; Gyürky, Gy.; Halász, Z.; Somorjai, E.; Rauscher, T.

    2014-05-01

    The cross sections of the 162Er(α,γ)166Yb and 162,164,166Er(α,n)165,167,169Yb reactions have been measured at MTA Atomki. The radiative alpha capture reaction cross section was measured between Ec.m. = 11.21 MeV and Ec.m. = 16.09 MeV just above the astrophysically relevant energy region (which lies between 7.8 and 11.48 MeV at T9 = 3 GK). The 162Er(α,n)165Yb, 164Er(α,n)167Yb and 166Er(α,n)169Yb reactions were studied between Ec.m. = 12.19 and 16.09 MeV, Ec.m. = 13.17 and 16.59 MeV and Ec.m. = 12.68 and 17.08 MeV, respectively. The aim of this work is to provide experimental data for modeling the γ process which is thought to be responsible for the production of the proton-rich isotopes heavier than iron.

  12. A lead isotope distribution study in swine tissue using ICP-MS

    USGS Publications Warehouse

    May, T.W.; Wiedmeyer, R.H.; Brown, L.D.; Casteel, S.W.

    1999-01-01

    In the United States lead is an ubiquitous environmental pollutant that is a serious human health hazard, especially for women of childbearing age, developing fetuses, and young children. Information concerning the uptake and distribution of lead to maternal and fetal tissues during pregnancy is poorly documented. A study was designed using domestic swine and lead isotope enrichment methodology to focus on maternal absorption and distribution of lead into bone and soft tissues, including the fetal compartment, under varying conditions of oral lead exposure and during altered physiological states (pregnant vs unbred). Total lead levels and Pb207/Pb206 ratios in bone (femur and vertebra), blood, and soft tissues (liver, kidney, brain) were determined by ICP-MS. Lead in fetal tissues derived from maternal bone could be differentiated from that derived from exogenous dosing. Unbred swine absorbed much less lead than pregnant females receiving the same dose. The accuracy and precision of ICP-MS at the instrumental level and for the entire method (sample collection, digestion, and analysis) were evaluated for both Pb207/Pb206 ratios and total lead. Several changes were suggested in method design to improve both instrumental and total method precision.

  13. Carbon dioxide gasification of carbon black: isotope study of carbonate catalysis

    SciTech Connect

    Saber, J.M.; Falconer, J.L.; Brown, L.F.

    1984-11-01

    Temperature-programmed reaction was used with labeled isotopes (/sup 13/C and /sup 18/O) to study interactions between carbon black and potassium carbonate in pure He and 10% CO/sub 2//90% He atmospheres. Catalytic gasification precursor complexes were observed. Carbon and oxygen-bearing carbon surface groups interacted with the carbonate above 500 K to form surface complexes. Between 500 and 950 K, and in the presence of gaseous CO/sub 2/, the complexes participated in C and O exchange with the gas phase while oxygen atoms within the complexes also exchanged with those on the carbon surface. As the temperature rose, the complexes decomposed, with CO/sub 2/ the initial product. Decomposition started around 500 K in pure He, and around 950 K in CO/sub 2//He. Catalytic gasification began only after decomposition of significant portions of the complexes. Elemental potassium formed, and the active catalyst appears to alternate between being potassium metal and a potassium-oxygen-carbon complex. Potassium carbonate is not part of the catalytic cycle. 20 references, 10 figures.

  14. Measurement of alpha-induced reaction cross sections on erbium isotopes for γ process studies

    SciTech Connect

    Kiss, G. G.; Szücs, T.; Török, Zs.; Fülöp, Zs.; Gyürky, Gy.; Halász, Z.; Somorjai, E.; Rauscher, T.

    2014-05-02

    The cross sections of the {sup 162}Er(α,γ){sup 166}Yb and {sup 162,164,166}Er(α,n){sup 165,167,169}Yb reactions have been measured at MTA Atomki. The radiative alpha capture reaction cross section was measured between E{sub c.m.} = 11.21 MeV and E{sub c.m.} = 16.09 MeV just above the astrophysically relevant energy region (which lies between 7.8 and 11.48 MeV at T{sub 9} = 3 GK). The {sup 162}Er(α,n){sup 165}Yb, {sup 164}Er(α,n){sup 167}Yb and {sup 166}Er(α,n){sup 169}Yb reactions were studied between E{sub c.m.} = 12.19 and 16.09 MeV, E{sub c.m.} = 13.17 and 16.59 MeV and E{sub c.m.} = 12.68 and 17.08 MeV, respectively. The aim of this work is to provide experimental data for modeling the γ process which is thought to be responsible for the production of the proton-rich isotopes heavier than iron.

  15. Segmented images and 3D images for studying the anatomical structures in MRIs

    NASA Astrophysics Data System (ADS)

    Lee, Yong Sook; Chung, Min Suk; Cho, Jae Hyun

    2004-05-01

    For identifying the pathological findings in MRIs, the anatomical structures in MRIs should be identified in advance. For studying the anatomical structures in MRIs, an education al tool that includes the horizontal, coronal, sagittal MRIs of entire body, corresponding segmented images, 3D images, and browsing software is necessary. Such an educational tool, however, is hard to obtain. Therefore, in this research, such an educational tool which helps medical students and doctors study the anatomical structures in MRIs was made as follows. A healthy, young Korean male adult with standard body shape was selected. Six hundred thirteen horizontal MRIs of the entire body were scanned and inputted to the personal computer. Sixty anatomical structures in the horizontal MRIs were segmented to make horizontal segmented images. Coronal, sagittal MRIs and coronal, sagittal segmented images were made. 3D images of anatomical structures in the segmented images were reconstructed by surface rendering method. Browsing software of the MRIs, segmented images, and 3D images was composed. This educational tool that includes horizontal, coronal, sagittal MRIs of entire body, corresponding segmented images, 3D images, and browsing software is expected to help medical students and doctors study anatomical structures in MRIs.

  16. Biomedical studies by TOF-SIMS imaging.

    PubMed

    Bich, Claudia; Touboul, David; Brunelle, Alain

    2015-01-01

    Imaging by secondary ion mass spectrometry coupled to time-of-flight mass analysis (TOF-SIMS) is a method of which the applications have greatly increased since 10 years. Taking advantage of the development of cluster ion sources, TOF-SIMS offers images of molecular ions at a micrometer lateral resolution or slightly below and does not require complex sample preparation. Although TOF-SIMS has been primarily dedicated to surface analysis of inorganic or polymeric samples, several groups have successfully demonstrated that TOF-SIMS imaging is also perfectly suited for mapping organic compounds, such as drugs or lipids, directly on tissue sections from animals or from human biopsies. This minireview will enlighten some of these developments in the field of biomedical applications. PMID:25708628

  17. Enthesopathies and enthesitis. Part 2: Imaging studies.

    PubMed

    Sudoł-Szopińska, Iwona; Kwiatkowska, Brygida; Prochorec-Sobieszek, Monika; Pracoń, Grzegorz; Walentowska-Janowicz, Marta; Maśliński, Włodzimierz

    2015-06-01

    The pathologies of tendon and ligament attachments are called enthesopathies. Enthesitis is one of enthesopathies and it is considered a characteristic sign of rheumatic diseases from the spondyloarthritis group, including peripheral spondyloarthritis. Therefore, enthesitis has been included in a number of clinical classifications for diagnosing these diseases. Clinical diagnosis of enthesitis is based on rather non-specific clinical signs and results of laboratory tests. It is believed that imaging examinations might improve diagnosis, particularly because numerous papers prove that differentiating enthesitis from other enthesopathic processes is possible. On the other hand, a number of authors report the lack of specific signs in imaging as well as typical histological and immunological features that would enable confirmation of clinical diagnosis of enthesitis. The first part of the publication presented theories on the etiopathogenesis of enthesitis (inflammatory, mechanical, autoimmune and associated with the synovio-entheseal complex) as well as on the formation of enthesophytes (inflammatory, molecular and mechanical). This paper - the second part of the article, is a review of the state-of-the-art on the ability of imaging examinations to diagnose enthesitis. It turns out that none of the enthesitis criteria used in imaging examinations is specific for inflammation. As enthesitis may be the only symptom of early spondyloarthritis (particularly in patients with absent HLA-B27 antigen), the lack of its unambiguous picture in ultrasound and magnetic resonance imaging prompts the search for other signs characteristic of spondyloarthritis and more specific features in imaging in order to make a diagnosis as early as possible. PMID:26672488

  18. Enthesopathies and enthesitis. Part 2: Imaging studies

    PubMed Central

    Kwiatkowska, Brygida; Prochorec-Sobieszek, Monika; Pracoń, Grzegorz; Walentowska-Janowicz, Marta; Maśliński, Włodzimierz

    2015-01-01

    The pathologies of tendon and ligament attachments are called enthesopathies. Enthesitis is one of enthesopathies and it is considered a characteristic sign of rheumatic diseases from the spondyloarthritis group, including peripheral spondyloarthritis. Therefore, enthesitis has been included in a number of clinical classifications for diagnosing these diseases. Clinical diagnosis of enthesitis is based on rather non-specific clinical signs and results of laboratory tests. It is believed that imaging examinations might improve diagnosis, particularly because numerous papers prove that differentiating enthesitis from other enthesopathic processes is possible. On the other hand, a number of authors report the lack of specific signs in imaging as well as typical histological and immunological features that would enable confirmation of clinical diagnosis of enthesitis. The first part of the publication presented theories on the etiopathogenesis of enthesitis (inflammatory, mechanical, autoimmune and associated with the synovio-entheseal complex) as well as on the formation of enthesophytes (inflammatory, molecular and mechanical). This paper – the second part of the article, is a review of the state-of-the-art on the ability of imaging examinations to diagnose enthesitis. It turns out that none of the enthesitis criteria used in imaging examinations is specific for inflammation. As enthesitis may be the only symptom of early spondyloarthritis (particularly in patients with absent HLA-B27 antigen), the lack of its unambiguous picture in ultrasound and magnetic resonance imaging prompts the search for other signs characteristic of spondyloarthritis and more specific features in imaging in order to make a diagnosis as early as possible. PMID:26672488

  19. Effect of parent body evolution on equilibrium and kinetic isotope fractionation: a combined Ni and Fe isotope study of iron and stony-iron meteorites

    NASA Astrophysics Data System (ADS)

    Chernonozhkin, Stepan M.; Goderis, Steven; Costas-Rodríguez, Marta; Claeys, Philippe; Vanhaecke, Frank

    2016-08-01

    Various iron and stony-iron meteorites have been characterized for their Ni and Fe isotopic compositions using multi-collector inductively coupled plasma-mass spectrometry (MC-ICP-MS) after sample digestion and chromatographic separation of the target elements in an attempt to further constrain the planetary differentiation processes that shifted these isotope ratios and to shed light on the formational history and evolution of selected achondrite parent body asteroids. Emphasis was placed on spatially resolved isotopic analysis of iron meteorites, known to be inhomogeneous at the μm to mm scale, and on the isotopic characterization of adjacent metal and silicate phases in main group pallasites (PMG), mesosiderites, and the IIE and IAB complex silicate-bearing iron meteorites. In a 3-isotope plot of 60/58Ni versus62/58Ni, the slope of the best-fitting straight line through the laterally resolved Ni isotope ratio data for iron meteorites reveals kinetically controlled isotope fractionation (βexper = 1.981 ± 0.039, 1 SD), predominantly resulting from sub-solidus diffusion (with the fractionation exponent β connecting the isotope fractionation factors, as α62/58 =α60/58β). The observed relation between δ56/54Fe and Ir concentration in the metal fractions of PMGs and in IIIAB iron meteorites indicates a dependence of the bulk Fe isotopic composition on the fractional crystallization of an asteroidal metal core. No such fractional crystallization trends were found for the corresponding Ni isotope ratios or for other iron meteorite groups, such as the IIABs. In the case of the IIE and IAB silicate-bearing iron meteorites, the Fe and Ni isotopic signatures potentially reflect the influence of impact processes, as the degree of diffusion-controlled Ni isotope fractionation is closer to that of Fe compared to what is observed for magmatic iron meteorite types. Between the metal and olivine counterparts of pallasites, the Fe and Ni isotopic compositions show clearly

  20. EOS image data processing system definition study

    NASA Technical Reports Server (NTRS)

    Gilbert, J.; Honikman, T.; Mcmahon, E.; Miller, E.; Pietrzak, L.; Yorsz, W.

    1973-01-01

    The Image Processing System (IPS) requirements and configuration are defined for NASA-sponsored advanced technology Earth Observatory System (EOS). The scope included investigation and definition of IPS operational, functional, and product requirements considering overall system constraints and interfaces (sensor, etc.) The scope also included investigation of the technical feasibility and definition of a point design reflecting system requirements. The design phase required a survey of present and projected technology related to general and special-purpose processors, high-density digital tape recorders, and image recorders.

  1. Dynamics of a stepped carbon-isotope excursion: Ultra high-resolution study of Early Toarcian environmental change

    NASA Astrophysics Data System (ADS)

    Hermoso, Michaël; Minoletti, Fabrice; Rickaby, Rosalind E. M.; Hesselbo, Stephen P.; Baudin, François; Jenkyns, Hugh C.

    2012-02-01

    In the Toarcian (Early Jurassic; ~ 183 Myr ago), the ocean-atmosphere system was subject to one of the largest perturbations of the carbon cycle in the last 250 Myr known as the Toarcian Oceanic Anoxic Event (T-OAE). This event was accompanied by a - 6‰ negative carbon-isotope excursion (CIE) caused by massive injection of isotopically light carbon into the ocean-atmosphere system, possibly from destabilisation of gas hydrates. This study reveals the pacing and sequence of events leading up to the CIE and to widespread deposition of organic-rich sediments. The very high-resolution isotopic record from exceptionally well-preserved carbonate and organic matter from the Paris Basin enables recognition of increased CO2 levels ~ 130 kyr in advance of the major negative CIE. An accelerated increase in the pCO2 is registered ~ 25 kyr before the onset of this negative excursion and was so rapid and so intense that it led to a water column undersaturated with respect to calcium carbonate in the Paris Basin. Undersaturation is expressed as a dramatic drop in the accumulation of the biogenic calcite produced by the surface-dwelling calcifiers. These environmental perturbations, representing precursor phases of CO2 injection, predate the first step towards relatively light carbon isotopes in carbonate and organic matter and are tentatively attributed to Karoo-Ferrar magmatism. This negative shift was registered slightly earlier in terrestrial carbon than marine carbonate. Subsequent global warming is credited with liberating isotopically light carbon, and ultimately fostered anoxia in the Paris Basin: the response of these cumulative inputs of carbon to the Earth system. Isotopic and sedimentological evidence indicates continuously elevated phytoplanktonic productivity throughout the first step of the negative CIE, suggesting that the biological pump accelerated the drawdown of excess carbon leading to temporary recovery of carbonate sedimentation, ~ 45 kyr after the first

  2. Isotopically engineered semiconductors

    NASA Astrophysics Data System (ADS)

    Haller, E. E.

    1995-04-01

    Scientific interest, technological promise, and increased availability of highly enriched isotopes have led to a sharp rise in the number of experimental and theoretical studies with isotopically controlled semiconductor crystals. This review of mostly recent activities begins with an introduction to some past classical experiments which have been performed on isotopically controlled semiconductors. A review of the natural isotopic composition of the relevant elements follows. Some materials aspects resulting in part from the high costs of enriched isotopes are discussed next. Raman spectroscopy studies with a number of isotopically pure and deliberately mixed Ge bulk crystals show that the Brillouin-zone-center optical phonons are not localized. Their lifetime is almost independent of isotopic disorder, leading to homogeneous Raman line broadening. Studies with short period isotope superlattices consisting of alternating layers of n atomic planes of 70Ge and 74Ge reveal a host of zone-center phonons due to Brillouin-zone folding. At n≳40 one observes two phonon lines at frequencies corresponding to the bulk values of the two isotopes. In natural diamond, isotope scattering of the low-energy phonons, which are responsible for the thermal conductivity, is very strongly affected by small isotope disorder. Isotopically pure 12C diamond crystals exhibit thermal conductivities as high as 410 W cm-1 K-1 at 104 K, leading to projected values of over 2000 W cm-1 K-1 near 80 K. The changes in phonon properties with isotopic composition also weakly affect the electronic band structures and the lattice constants. The latter isotope dependence is most relevant for future standards of length based on crystal lattice constants. Capture of thermal neutrons by isotope nuclei followed by nuclear decay produces new elements, resulting in a very large number of possibilities for isotope selective doping of semiconductors. This neutron transmutation of isotope nuclei, already used

  3. Light stable isotope study of the Roosevelt Hot Springs thermal area, Southwestern Utah

    SciTech Connect

    Rohrs D.T.; Bowman, J.R.

    1980-05-01

    The isotopic composition of hydrogen, oxygen, and carbon has been determined for regional cold springs, thermal fluids, and rocks and minerals from the Roosevelt Hot Springs thermal area. The geothermal system has developed within plutonic granitic rocks and amphibolite facies gneiss, relying upon fracture-controlled permeability for the migration of the thermal fluids. Probably originating as meteoric waters in the upper elevations of the Mineral Mountains, the thermal waters sampled in the production wells display an oxygen isotopic shift of at least +1.2. Depletions of delta /sup 18/O in wole rock, K-feldspar, and biotite have a positive correlation with alteration intensity. W/R mass ratios, calculated from the isotopic shifts of rock and water, range up to 3.0 in a producing horizon of one well, although the K-feldspar has experienced only 30% exchange with the thermal waters. While veinlet quartz has equilibrated with the thermal waters, the /sup 18/O values of K-mica clay, an alteration product of plagioclase, mimic the isotopic composition of K-feldspar and whole rock. This suggests that locally small W/R ratios enable plagioclase to influence its alteration products by isotopic exchange.

  4. Stable oxyten and carbon isotope study of recent sediments and cements, Lee Stocking island, Bahamas: Organic vs. inorganic precipitation

    SciTech Connect

    Falls, W.F.; Williams, D.F.; Kendall, C.G.St.C.; Dill, R.F. )

    1990-05-01

    Stable isotope analyses of modern carbonates from the tidal inlet along the north end of Lee Stocking Island indicate a strong correlation of both carbon and oxygen isotope values with grain size. Carbonate samples used in this study include the soft, recently formed outer surface of several large columnar stromatolites, bedded muds from within the tidal channel, and marine hardgrounds from the shallow shoals adjacent to the channel. All samples are predominantly aragonite and were divided into mud-, silt-, and sand-size particles and bleached of organics prior to isotopic analysis. The range in isotopic values for all carbonate samples is 3.3 to 4.6 {per thousand} for {delta}{sup 13}C and {minus}0.3 to {minus}1.4{per thousand} for {delta}{sup 18}O. The {delta}{sup 18}O and {delta}{sup 13}C values of the mud-size aragonite from all of these samples are depleted relative to the silt- and sand-size ooids and peloids and have isotope values lighter than 1.4{per thousand} for {delta}{sup 13}C and 0.8{per thousand} for {delta}{sup 18}O. The {delta}{sup 13}C values for green calcerous algae from the restricted platform behind Lee Stocking are similar to values for the stromatolite mud. {delta}{sup 13}C values for the hardground and channel-based muds are intermediate between the {delta}{sup 13}C values for the calcareous algae, and coarse-grained sediment. These data suggest that the green calcareous algae which fluorish in the restricted platform, are a significant source of aragonite mud in and around the channel but are not the only source.

  5. Climatic Controls on the Stable Isotopic Composition of Precipitation in Northeast Asia : applicability to groundwater recharge study

    NASA Astrophysics Data System (ADS)

    Lee, K.; Wenner, D. B.; Grunstein, A. J.; Choi, M.; Woo, N.

    2001-05-01

    Based on the data available from the IAEA/WMO Global Network for Isotopes in Precipitation (GNIP), spatial and temporal variability of oxygen and hydrogen isotope composition of precipitation is reviewed for 9 selected sites in the Northeast Asia. These sites include Pohang (Korea), Tokyo and Ryori (Japan) and Shijiazhuang, Baotou, Tianjin, Wulumuqi, Zhangye and Qiqihar (China). The temperature is the main factor controlling the stable isotope composition of precipitation in the northwestern (inner continental) region of the study area, whereas the amount effect for summer rains is overshadowing the temperature effect in the southeastern (coastal) region. The IAEA/WMO data set reveals that many sites in Northeast Asia show a distinct winter-summer cyclic pattern in deuterium excess values that appears to reflect different climatic conditions. To further understand this pattern, stable isotopic data were obtained for individual rainfall events over a two-year period at Cheju Island, Korea. The d18- and dD- values of precipitation at Cheju Island are not dependent upon temperature. However, the deuterium excess values, which range from 3.0 to 40.6 per mil show a distinct seasonal variation with higher d-values in winter (> ~15 per mil) and lower values in summer (~10 permil). Such a seasonal variation appears to be closely related to different air masses affecting the island during different seasons: cold-dry continental polar air mass in winter and hot-humid maritime tropical air mass in summer. Such stable isotopic characteristics in Northeast Asia could potentially provide a means for evaluating the relative contribution of summer and winter precipitation to groundwater recharge.

  6. NanoSIMS studies of Ba isotopic compositions in single presolar silicon carbide grains from AGB stars and supernovae

    NASA Astrophysics Data System (ADS)

    Marhas, K. K.; Hoppe, P.; Ott, U.

    2007-08-01

    We have studied 74 single presolar silicon carbide grains with sizes between 0.2 and 2.6 μm from the Murchison and Murray meteorites for Ba isotopic compositions using NanoSIMS. We also analyzed 7 SiC particles either consisting of sub-micron-size SiC grains or representing a morphologically and isotopically distinct subgroup. Of the 55 (likely) mainstream grains, originating from asymptotic giant branch (AGB) stars, 32 had high enough Ba contents for isotopic analysis. For 26 of them, CsHx interferences were either negligible or could be corrected with confidence. They exhibit typical s-process Ba isotopic patterns with slightly higher than solar 134Ba/136Ba and lower than solar 135,137,138Ba/136Ba ratios. Results are generally well explained in the context of neutron capture nucleosynthesis in low mass (1-3 M⊙) AGB stars and provide constraints on AGB models, by reducing the needed 13C spread from factor of ˜20 down to 2. Out of the 19 supernova X grains, three had sufficient concentrations for isotopic analysis. They tend to exhibit higher than solar 134Ba/136Ba and 138Ba/136Ba ratios, close to solar 137Ba/136Ba, and 135Ba/136Ba lower than solar but higher than in mainstream grains. This signature could indicate a mixture of n-burst type Ba with either "normal Ba" more s-process-rich than solar, or normal Ba plus weak s-process Ba. In the n-burst component Cs may have to be separated from Ba at ˜10 years after the SN explosion. Depending on predictions for its composition, another possibility is early separation (at ˜1 year) coupled with addition of some unfractionated n-burst matter. Abundances of trace elements (Sr, Zr, Cs, La, and Ce) analyzed along with Ba signify that implantation may have been an important process for their introduction.

  7. Mechanism of O2 activation by cytochrome P450cam studied by isotope effects and transient state kinetics.

    PubMed

    Purdy, Matthew M; Koo, Laura S; de Montellano, Paul R Ortiz; Klinman, Judith P

    2006-12-26

    The early steps in dioxygen activation by the monooxygenase cytochrome P450cam (CYP101) include binding of O2 to ferrous P450cam to yield the ferric-superoxo form (oxyP450cam) followed by an irreversible, long-range electron transfer from putidaredoxin to reduce the oxyP450cam. The steady state kinetic parameter kcat/Km(O2) has been studied by a variety of probes that indicate a small D2O solvent isotope effect (1.21 +/- 0.08), a very small solvent viscosogen effect, and a 16O/18O isotope effect of 1.0147 +/- 0.0007. This latter value, which can be compared with the 16O/18O equilibrium isotope effect of 1.0048 +/- 0.0003 measured for oxyP450cam formation, is attributed to a primarily rate-limiting outer-sphere electron transfer from the heme iron center as O2 that has prebound to protein approaches the active site cofactor. The electron transfer from putidaredoxin to oxyP450cam was investigated by rapid mixing at 25 degrees C to complement previous lower-temperature measurements. A rate of 390 +/- 23 s-1 (and a near-unity solvent isotope effect) supports the view that the long-range electron transfer from reduced putidaredoxin to oxyP450cam is rapid relative to dissociation of O2 from the enzyme. P450cam represents the first enzymatic reaction of O2 in which both equilibrium and kinetic 16O/18O isotope effects have been measured. PMID:17176102

  8. A stable isotope study of fossil mammal remains from the Paglicci cave, Southern Italy. N and C as palaeoenvironmental indicators

    NASA Astrophysics Data System (ADS)

    Iacumin, P.; Bocherens, H.; Delgado Huertas, A.; Mariotti, A.; Longinelli, A.

    1997-04-01

    A set of 102 tooth and bone samples of Pleistocene age (32,600-13,300 yr BP) belonging to the species Cervus elaphus, Bos primigenius and Equus caballus and coming from the Paglicci cave (Southern Italy) was studied for the carbon (δ 13C) and nitrogen (δ 15N) isotopic composition of bone and dentine collage and for the carbon (δ 13C c) isotopic composition of tooth enamel carbonate. The amount of collagen extracted from bone and tooth samples (mg/g) was rather variable, representing approximately only 0.5-15% of the collagen present in a fresh bone. However, the loss of an important fraction of the original collagen during diagenesis did not change the in vivo isotopic composition. In general, when the δ 13C of both collagen and carbonate and the δ 15N of collagen obtained from each level for the three species are compared, wild ox shows the most increased values, deer the most decreased values and horse shows intermediate results. These differences are probably related to distinct diets or to differences in their physiological behaviour. However, the isotopic results suggest that the three species considered lived in an open environment with a diet based on C 3 plants. The stratigraphic sequence of light and heavy nitrogen isotope values between 19,000 and 15,000 may be related to shifts from arid to humid conditions, while the overall trend shown by δ 13C toward lighter values may be related to a progressive development of a forest habitat.

  9. Olympus Imaging Fraud Scandal: A Case Study

    ERIC Educational Resources Information Center

    Elam, Dennis; Madrigal, Marion; Jackson, Maura

    2014-01-01

    This case examines the two decade long tobashi scheme by Olympus Imaging Executives to hide $1.7 billion in losses. In the 1980s, a soaring yen and falling dollar caused bottom line income problems for many Japanese companies. Some companies sought to offset the declining revenue with zaiteku, a form of speculative investment. While early…

  10. Brain Imaging Studies of Developmental Stuttering.

    ERIC Educational Resources Information Center

    Ingham, Roger J.

    2001-01-01

    A review of research on brain imaging of developmental stuttering concludes that findings increasingly point to a failure of normal temporal lobe activation during speech that may either contribute to (or is the result of) a breakdown in the sequencing of processing among premotor regions implicated in phonologic planning. (Contains references.)…

  11. Phonon coherence in isotopic silicon superlattices

    SciTech Connect

    Frieling, R.; Radek, M.; Eon, S.; Bracht, H.; Wolf, D. E.

    2014-09-29

    Recent experimental and theoretical investigations have confirmed that a reduction in thermal conductivity of silicon is achieved by isotopic silicon superlattices. In the present study, non-equilibrium molecular dynamics simulations are performed to identify the isotope doping and isotope layer ordering with minimum thermal conductivity. Furthermore, the impact of isotopic intermixing at the superlattice interfaces on phonon transport is investigated. Our results reveal that the coherence of phonons in isotopic Si superlattices is prevented if interfacial mixing of isotopes is considered.

  12. Stable isotopic study of precipitation and spring discharge on the Nevada Test Site

    SciTech Connect

    Ingraham, N.L.; Jacobson, R.L.; Hess, J.W.; Lyles, B.F. . Water Resources Center Nevada Univ., Reno, NV . Water Resources Center)

    1990-07-01

    Precipitation was collected in southern Nevada (on the Nevada Test Site) on a semi-regular monthly basis at 41 locations for six years for stable isotopic analysis. The precipitation record shows two time-based regimes. For the first three years of collection, the precipitation was highly variable with several large events and several dry periods. During the last three years of collection, the precipitation was much more even with no large events. However, there is no correlation between the variability in the amount of precipitation and the stable isotopic composition of precipitation. In addition, the oxygen isotope composition and discharge of two springs, Whiterock Spring and Cane Spring, issuing from perched water tables, were monitored for five years in a similar time frame as for the precipitation. 17 refs., 42 figs., 3 tabs.

  13. Efficient and selective isotopic labeling of hemes to facilitate the study of multiheme proteins

    SciTech Connect

    Fonseca, Bruno M.; Tien, Ming; Rivera, Mario; Shi, Liang; Louro, Ricardo O.

    2012-04-02

    Specific isotopic labeling of hemes provides a unique opportunity to characterize the structure and function of heme-proteins. Unfortunately, present day methods do not allow efficient labeling in high yields of multiheme cytochromes c, which are of great biotechnological interest. Here, a method for production of recombinant multiheme cytochromes c in Escherichia coli with isotopically labeled hemes is reported. A small tetraheme cytochrome of 12 kDa from Shewanella oneidensis MR-1 was used to demonstrate the method, achieving a production of 4 mg of pure protein per liter. This method achieves, in a single step, efficient expression and incorporation of hemes isotopically labeled in specific atom positions adequate for spectroscopic characterization of these complex heme proteins. It is, furthermore, of general application to heme proteins opening new possibilities in the characterization of this important class of proteins.

  14. Isotope-Encoded Carboxyl Group Footprinting for Mass Spectrometry-Based Protein Conformational Studies

    NASA Astrophysics Data System (ADS)

    Zhang, Hao; Liu, Haijun; Blankenship, Robert E.; Gross, Michael L.

    2016-01-01

    We report an isotope-encoding method coupled with carboxyl-group footprinting to monitor protein conformational changes. The carboxyl groups of aspartic/glutamic acids and of the C-terminus of proteins can serve as reporters for protein conformational changes when labeled with glycine ethyl ester (GEE) mediated by carbodiimide. In the new development, isotope-encoded "heavy" and "light" GEE are used to label separately the two states of the orange carotenoid protein (OCP) from cyanobacteria. Two samples are mixed (1:1 ratio) and analyzed by a single LC-MS/MS experiment. The differences in labeling extent between the two states are represented by the ratio of the "heavy" and "light" peptides, providing information about protein conformational changes. Combining isotope-encoded MS quantitative analysis and carboxyl-group footprinting reduces the time of MS analysis and improves the sensitivity of GEE and other footprinting.

  15. Isotope-Encoded Carboxyl Group Footprinting for Mass Spectrometry-Based Protein Conformational Studies.

    PubMed

    Zhang, Hao; Liu, Haijun; Blankenship, Robert E; Gross, Michael L

    2016-01-01

    We report an isotope-encoding method coupled with carboxyl-group footprinting to monitor protein conformational changes. The carboxyl groups of aspartic/glutamic acids and of the C-terminus of proteins can serve as reporters for protein conformational changes when labeled with glycine ethyl ester (GEE) mediated by carbodiimide. In the new development, isotope-encoded "heavy" and "light" GEE are used to label separately the two states of the orange carotenoid protein (OCP) from cyanobacteria. Two samples are mixed (1:1 ratio) and analyzed by a single LC-MS/MS experiment. The differences in labeling extent between the two states are represented by the ratio of the "heavy" and "light" peptides, providing information about protein conformational changes. Combining isotope-encoded MS quantitative analysis and carboxyl-group footprinting reduces the time of MS analysis and improves the sensitivity of GEE and other footprinting. PMID:26384685

  16. Synthesis of ¹⁸O-labeled RNA for application to kinetic studies and imaging.

    PubMed

    Hamasaki, Tomohiro; Matsumoto, Takahiro; Sakamoto, Naoya; Shimahara, Akiko; Kato, Shiori; Yoshitake, Ayumi; Utsunomiya, Ayumi; Yurimoto, Hisayoshi; Gabazza, Esteban C; Ohgi, Tadaaki

    2013-07-01

    Radioisotopes and fluorescent compounds are frequently used for RNA labeling but are unsuitable for clinical studies of RNA drugs because of the risk from radiation exposure or the nonequivalence arising from covalently attached fluorophores. Here, we report a practical phosphoramidite solid-phase synthesis of (18)O-labeled RNA that avoids these disadvantages, and we demonstrate its application to quantification and imaging. The synthesis involves the introduction of a nonbridging (18)O atom into the phosphate group during the oxidation step of the synthetic cycle by using (18)O water as the oxygen donor. The (18)O label in the RNA was stable at pH 3-8.5, while the physicochemical and biological properties of labeled and unlabeled short interfering RNA were indistinguishable by circular dichroism, melting temperature and RNA-interference activity. The (18)O/(16)O ratio as measured by isotope ratio mass spectrometry increased linearly with the concentration of (18)O-labeled RNA, and this technique was used to determine the blood concentration of (18)O-labeled RNA after administration to mice. (18)O-labeled RNA transfected into human A549 cells was visualized by isotope microscopy. The RNA was observed in foci in the cytoplasm around the nucleus, presumably corresponding to endosomes. These methodologies may be useful for kinetic and cellular-localization studies of RNA in basic and pharmaceutical studies. PMID:23632164

  17. Application of stable carbon isotopes in long term mesocosm studies for carbon cycle investigation

    NASA Astrophysics Data System (ADS)

    Esposito, Mario

    2016-04-01

    Carbon dioxide (CO2) is an effective greenhouse gas. The Oceans absorb ca. 30% of the anthropogenic CO2 emissions and thereby partly attenuate deleterious climate effects. A consequence of the oceanic CO2 uptake is a decreased seawater pH and planktonic community shifts. The quantification of the anthropogenic perturbation was investigated through stable carbon isotope analysis in three "long term" mesocosm experiments (Sweden 2013, Gran Canaria 2014, Norway 2015) which reproduced near natural ecosystem conditions under both controlled and modified future CO2 level (up to 2000 ppm) scenarios. Parallel measurements of the stable isotope composition of dissolved inorganic carbon (δ13CDIC) dissolved organic carbon (δ13CDOC) and particulate carbon (δ13CTPC) both from the mesocosms water column and sediment traps showed similar trends in all the three experiments. A CO2 response was noticeable in the isotopic dataset, but increased CO2 levels had only a subtle effect on the concentrations of the dissolved and particulate organic carbon pool. Distinctive δ13C signatures of the particulate carbon pool both in the water column and the sediments were detectable for the different CO2 treatments and they were strongly correlated with the δ13CDIC signatures but not with the δ13CDOC pool. The validity of the isotopic data was verified by cross-analyses of multiple substances of known isotopic signatures on a GasBench, Elemental Analyser (EA) and on an in-house TOC-IRMS setup for the analysis of δ13CDIC, δ13CTPC and δ13CDOC, respectively. Results from these mesocosm experiments proved the stable carbon isotope approach to be an effective tool for quantifying the uptake and carbon transfer among the various compartments of the marine carbon system.

  18. Intracellular Cadmium Isotope Fractionation

    NASA Astrophysics Data System (ADS)

    Horner, T. J.; Lee, R. B.; Henderson, G. M.; Rickaby, R. E.

    2011-12-01

    Recent stable isotope studies into the biological utilization of transition metals (e.g. Cu, Fe, Zn, Cd) suggest several stepwise cellular processes can fractionate isotopes in both culture and nature. However, the determination of fractionation factors is often unsatisfactory, as significant variability can exist - even between different organisms with the same cellular functions. Thus, it has not been possible to adequately understand the source and mechanisms of metal isotopic fractionation. In order to address this problem, we investigated the biological fractionation of Cd isotopes within genetically-modified bacteria (E. coli). There is currently only one known biological use or requirement of Cd, a Cd/Zn carbonic anhydrase (CdCA, from the marine diatom T. weissfloggii), which we introduce into the E. coli genome. We have also developed a cleaning procedure that allows for the treating of bacteria so as to study the isotopic composition of different cellular components. We find that whole cells always exhibit a preference for uptake of the lighter isotopes of Cd. Notably, whole cells appear to have a similar Cd isotopic composition regardless of the expression of CdCA within the E. coli. However, isotopic fractionation can occur within the genetically modified E. coli during Cd use, such that Cd bound in CdCA can display a distinct isotopic composition compared to the cell as a whole. Thus, the externally observed fractionation is independent of the internal uses of Cd, with the largest Cd isotope fractionation occurring during cross-membrane transport. A general implication of these experiments is that trace metal isotopic fractionation most likely reflects metal transport into biological cells (either actively or passively), rather than relating to expression of specific physiological function and genetic expression of different metalloenzymes.

  19. Mineral-chemical and isotopic studies of Namaqualand granulites, South Africa: A grenville analogue

    NASA Astrophysics Data System (ADS)

    Clifford, Tom N.; Stumpfl, Eugen F.; Burger, Alwyn J.; McCarthy, Terence S.; Rex, David C.

    1981-10-01

    The northwestern part of South Africa and southern South-West Africa/Namibia is amongst the most extensive granulite terranes in Africa. This work reports the results of electron microprobe studies of minerals from two-pyroxene, cordieriteorthopyroxene (-gedrite) (-sapphirine) and garnet and/or cordierite parageneses from Namaqualand, in the N.W. Cape Province of South Africa. Determined PT conditions of prograde metamorphism based on thermodynamic calculations are 800°-900° C and ca. 6-7 Kb; and it is argued that rocks of unusual composition, notably cordierite-orthopyroxene rocks, are restites after the extraction of granitic liquid from former argillites. This interpretation is consistent with previously published data on similar rocks, and with McCarthy's (1976) suggestion of extensive partial melting in the quartzofeldspathic rocks in the area. U-Pb isotopic studies of some 50 zircon fractions have been carried out and confirm an age of 1,200 m.y. for the high-grade regional metamorphism; but certain zircon populations record inherited ages greater than 1,700 m.y. Garnet-sillimanite rocks that contain retrograde kyanite reflect PT conditions of 550°-650° C and ca. 7-8 Kb; and constituent biotite has yielded a K-Ar age of ca. 950 m.y. These data, the regional stratigraphy and structure, and the mineralisation are compared with data from the Grenville Province of Canada. Notable similarities are the possible basement-cover relationships, and the calendar of tectonothermal events, while differences include the important stratiform base-metal mineralisation in the supracrustal sequence in Namaqualand, and the Cu-mineralisation in hypersthenebearing intrusives, emplaced some 1,100 m.y. ago, that are areally, and believed to be genetically, related to the granulite facies metamorphic regime.

  20. Coupled-channels study of fine structure in the {alpha} decay of platinum isotopes

    SciTech Connect

    Ni Dongdong; Ren Zhongzhou

    2011-09-15

    The fine structure observed in the {alpha} decay of deformed platinum isotopes is investigated using the recently developed five-channel formalism, based on the coupled-channel Schroedinger equation with outgoing wave boundary conditions. The internal effect of daughter states is taken into account in dealing with the interaction matrix and the {alpha}-cluster formation. The available experimental data concerning {alpha}-decay half-lives and fine structures are reproduced. Some predictions are made especially for the {alpha} decay of neutron-rich isotopes, which could guide future experiments.

  1. Multiple Scattering Effects in de/dx-E Instruments for Isotopic Composition Studies

    NASA Technical Reports Server (NTRS)

    Wiedenbeck, M. E.

    1985-01-01

    The development of cosmic ray telescopes to separate individual isotopes of heavy elements using the dE/dx-vs.-E technique depends on the incorporation of precise trajectory sensing elements into these systems. In typical implementations the particle trajectory is derived from a set of position measurements made prior to a particle's entering the first energy loss detector. The use of the trajectory obtained in this way to correct energy loss signals for the actual pathlengths through the detectors depends on the assumption that the particle trajectory is a straight line. In order to resolve iron isotopes the angles of incidence, theta the particle track must be known rather accurately.

  2. Systematic study of Bh isotopes in a relativistic mean field formalism

    NASA Astrophysics Data System (ADS)

    Mehta, M. S.; Raj, B. K.; Patra, S. K.; Gupta, Raj K.

    2002-10-01

    The binding energy, charge radius, and quadrupole deformation parameter for the isotopic chain of the superheavy element bohrium (107Bh), from proton to neutron drip line, are calculated by using an axially deformed relativistic mean field model. The potential energy surfaces for some of the selected nuclei are plotted and the various possible shapes are investigated. The rms radii, density distributions, and two-neutron separation energies are also evaluated and the single-particle energies for some illustrative cases are analyzed to see the magic structures. Furthermore, the α-decay rates are calculated and compared with the available experimental data for the recently observed new isotopes 266,267Bh.

  3. Beryllium Isotope and Combined Be and U-series Isotope Studies of Volcanic Arcs: Implications for Fluid and Melt Transport Through the Mantle Wedge

    NASA Astrophysics Data System (ADS)

    Morris, J. D.; Ryan, J. G.

    2004-12-01

    Beryllium isotope and combined studies of 10Be/9Be and U-series isotopes in volcanic arcs can 1) map transport of demonstrably slab derived elements through the mantle wedge; 2) certify the relationship of U series isotopes to slab derivation; 3) identify multiple stages in subduction modification of the mantle and constrain their timescales; and 4) speak to element partitioning into fluids and melts from the slab. In the Kurile, Aleutian and Bismarck arcs, 10Be/9Be ratios for lavas from behind the volcanic front are often comparable to, and sometimes greater than, those at the volcanic front, despite the longer path to rear-arc locations, along which 10Be is decaying in transit. Be/Zr ratios show a similar pattern of across-arc increase, without increases in enrichments of Mo and Sn, species which would be mobilized with Be if F-bearing fluids were present. The simplest interpretation is that sediment melting, and its contribution to the mantle wedge, is greater behind the front than at the volcanic front. Despite evidence for an increasing sediment melt contribution behind the front, volcanoes from the Kuriles contain progressively less B, Pb, As and Sb with increasing depth to the slab, indicating that fluid processes updip of about 180 km (beginning in the shallow forearc) strip these elements nearly quantitatively from the sedimentary portion of the downgoing slab. For studies published to date (Aleutians, Central America, S. Chile, Bismarck, Mariana) 10Be/9Be ratios are generally highest for samples plotting furthest from the 238U-230Th equiline (i.e. highest 238U/232Th, 230Th/232Th, or both). In lavas from the Southern Volcanic Zone (SVZ) of S. Chile (Sigmarsson et al., EPSL 2002), U excess (Uxs), Ra excess (Raxs) and 10Be/9Be are strongly correlated (r2=0.81-0.94). This argues that U enrichment and in some cases Ra enrichment in arc lavas is related to slab processes that are capable of mobilizing 10Be out of the sediment column, rather than reflecting only

  4. Multiple stable oxygen isotopic studies of atmospheric sulfate: A new quantitative way to understand sulfate formation processes in the atmosphere

    NASA Astrophysics Data System (ADS)

    Lee, Charles Chi-Woo

    2000-11-01

    Sulfate is an important trace species in the Earth's atmosphere because of its roles in numerous atmospheric processes. In addition to its inherent light-scattering properties, sulfate can serve as cloud condensation nucleus (CCN), affecting cloud formation as well as microphysical properties of clouds. Consequently, atmospheric sulfate species influence the global radiative energy balance. Sulfate is known to increase acidity of rainwater with negative consequences in both natural and urban environments. In addition, aerosol sulfate (<=2.5 μm) is respirable and poses a threat to human health as a potential carrier of toxic pollutants through the respiratory tract. Despite intense investigative effort, uncertainty regarding the relative significance of gas and aqueous phase oxidation pathways still remains. Acquisition of such information is important because the lifetime and transport of S(IV) species and sulfate aerosols are influenced by the oxidative pathways. In addition, sulfate formation processes affect the aerosol size distribution, which ultimately influences radiative properties of atmospheric aerosols. Therefore, the budgetary information of the sulfur cycle, as well as the radiative effects of sulfate on global climate variation, can be attained from better quantitative understanding of in situ sulfate formation processes in the atmosphere. Multiple stable oxygen isotopic studies of atmospheric sulfate are presented as a new tool to better comprehend the atmospheric sulfate formation processes. Coupled with isotopic studies, 35S radioactivity measurements have been utilized to assess contribution of sulfate from high altitude air masses. Atmospheric sulfate (aerosols and rainwater) samples have been collected from diverse environments. Laboratory experiments of gas and aqueous phase S(IV) oxidation by various oxidants, as well as biomass burning experiments, have also been conducted. The main isotopic results from these studies are as follows: (1

  5. Experimental study of the Mg and Sr isotopic evolution of seawater interacting with basalt between 150 and 300 ° C.

    NASA Astrophysics Data System (ADS)

    Voigt, Martin; Pearce, Christopher R.; Oelkers, Eric H.

    2016-04-01

    The chemical exchange of material between seawater and the oceanic crust plays a major role in marine geochemical cycles [1]. Isotopic signatures provide an important means of tracing elemental transfer in hydrothermal environments, yet only a limited amount of experimental data on the extent of isotopic fractionation under these conditions is currently available. This study consequently investigated the extent of δ26/24Mg and 87Sr/86Sr isotopic variation during a seawater-basalt interaction experiments at 150, 250 and 290 ° C. A suite of closed system experiments were run for several months at each temperature under saturated water pressure, using either crystalline or glassy basalt as the starting material and a water/rock ratio of 10 or 25. Our results demonstrate that the dissolution of basaltic material in hydrothermal environments occurs at the same time as the precipitation of alteration minerals (mainly smectite and anhydrite), which is consistent with results from similar studies in the past (e.g. [2]). As expected, the rate of reaction using crystalline basalt was slower than with basaltic glass, and both sample types reacted faster at higher temperatures. The 87Sr/86Sr composition of the experimental fluids decreased from the initial seawater value (0.70916) towards the lower basaltic signature during the experiments (0.70317), demonstrating the progressive release of Sr during basalt dissolution. Magnesium was steadily removed from the fluid via the precipitation of clay minerals, with the residual fluids having progressively lighter δ26/24Mg compositions. The mean Mg isotope fractionation factor (αsolid‑solution) observed at 250 oC was 1.0005±0.0002, supporting low-temperature evidence that clay minerals preferentially incorporate isotopically heavy magnesium [3]. These experiments provide quantitative information on the extent of Mg isotopic fractionation between fluids and secondary silicate minerals in hydrothermal systems, and demonstrate

  6. Study protocol: the Whitehall II imaging sub-study

    PubMed Central

    2014-01-01

    Background The Whitehall II (WHII) study of British civil servants provides a unique source of longitudinal data to investigate key factors hypothesized to affect brain health and cognitive ageing. This paper introduces the multi-modal magnetic resonance imaging (MRI) protocol and cognitive assessment designed to investigate brain health in a random sample of 800 members of the WHII study. Methods/design A total of 6035 civil servants participated in the WHII Phase 11 clinical examination in 2012–2013. A random sample of these participants was included in a sub-study comprising an MRI brain scan, a detailed clinical and cognitive assessment, and collection of blood and buccal mucosal samples for the characterisation of immune function and associated measures. Data collection for this sub-study started in 2012 and will be completed by 2016. The participants, for whom social and health records have been collected since 1985, were between 60–85 years of age at the time the MRI study started. Here, we describe the pre-specified clinical and cognitive assessment protocols, the state-of-the-art MRI sequences and latest pipelines for analyses of this sub-study. Discussion The integration of cutting-edge MRI techniques, clinical and cognitive tests in combination with retrospective data on social, behavioural and biological variables during the preceding 25 years from a well-established longitudinal epidemiological study (WHII cohort) will provide a unique opportunity to examine brain structure and function in relation to age-related diseases and the modifiable and non-modifiable factors affecting resilience against and vulnerability to adverse brain changes. PMID:24885374

  7. Mass-dependent sulfur isotope fractionation during reoxidative sulfur cycling: A case study from Mangrove Lake, Bermuda

    NASA Astrophysics Data System (ADS)

    Pellerin, André; Bui, Thi Hao; Rough, Mikaella; Mucci, Alfonso; Canfield, Donald E.; Wing, Boswell A.

    2015-01-01

    The multiple sulfur isotope composition of porewater sulfate from the anoxic marine sapropel of Mangrove Lake, Bermuda was measured in order to establish how multiple sulfur isotopes are fractionated during reoxidative sulfur cycling. The porewater-sulfate δ34S and Δ33S dataset exhibits the distinct isotopic signatures of microbial sulfate reduction and sulfur reoxidation. We reproduced the measurements with a simple diagenetic model that yielded fractionation factors for net sulfate removal of between -29.2‰ and -32.5‰. A new approach to isotopic modeling of the sulfate profiles, informed by the chemistry of sulfur intermediate compounds in Mangrove Lake, reveals that sulfate reduction produces a relatively small intrinsic fractionation and that an active reoxidative sulfur cycle increases the fractionation of the measured values. Based on the model results, the reoxidative cycle of Mangrove Lake appears to include sulfide oxidation to elemental sulfur followed by the disproportionation of the elemental sulfur to sulfate and sulfide. This model also indicates that the reoxidative sulfur cycle of Mangrove Lake turns over from 50 to 80% of the sulfide produced by microbial sulfate reduction. The Mangrove Lake case study shows how sulfur isotope fractionations can be separated into three different "domains" in Δ33S-δ34S space based on their ability to resolve reductive and reoxidative sulfur transformations. The first domain that differentiates reductive and reoxidative sulfur cycling is well illustrated by previous studies and requires 34S-32S fractionations more negative than ≈-70‰, beyond the fractionation limit of microbial sulfate reduction at earth surface temperatures. The second domain that distinguishes reductive and reoxidative processes is between 34S-32S fractionations of -40‰ and 0‰, where the 33S-32S fractionations of sulfate reduction and reoxidation are significantly different. In the remaining domain (between 34S-32S fractionations

  8. Studies of Plutonium-238 Production at the High Flux Isotope Reactor

    SciTech Connect

    Lastres, Oscar; Chandler, David; Jarrell, Joshua J; Maldonado, G. Ivan

    2011-01-01

    facilities such as the High Flux Isotope Reactor at ORNL has been initiated by the US DOE and NASA for space exploration needs. Two Monte Carlo-based depletion codes, TRITON (ORNL) and VESTA (IRSN), were used to study the {sup 238}Pu production rates with varying target configurations in a typical HFIR fuel cycle. Preliminary studies have shown that approximately 11 grams and within 15 to 17 grams of {sup 238}Pu could be produced in the first irradiation cycle in one small and one large VXF facility, respectively, when irradiating fresh target arrays as those herein described. Important to note is that in this study we discovered that small differences in assumptions could affect the production rates of Pu-238 observed. The exact flux at a specific target location can have a significant impact upon production, so any differences in how the control elements are modeled as a function of exposure, will also cause differences in production rates. In fact, the surface plot of the large VXF target Pu-238 production shown in Figure 3 illustrates that the pins closest to the core can potentially have production rates as high as 3 times those of pins away from the core, thus implying that a cycle-to-cycle rotation of the targets may be well advised. A methodology for generating spatially-dependent, multi-group self-shielded cross sections and flux files with the KENO and CENTRM codes has been created so that standalone ORIGEN-S inputs can be quickly constructed to perform a variety of {sup 238}Pu production scenarios, i.e. combinations of the number of arrays loaded and the number of irradiation cycles. The studies herein shown with VESTA and TRITON/KENO will be used to benchmark the standalone ORIGEN.

  9. Visualization of microcalcifications using photoacoustic imaging: feasibility study

    NASA Astrophysics Data System (ADS)

    Hsiao, Tsai-Chu; Wang, Po-Hsun; Fan, Chih-Tai; Cheng, Yao-You; Li, Meng-Lin

    2011-03-01

    Recently, photoacoustic imaging has been intensively studied for blood vessel imaging, and shown its capability of revealing vascular features suggestive of malignancy of breast cancer. In this study, we explore the feasibility of visualization of micro-calcifications using photoacoustic imaging. Breast micro-calcification is also known as one of the most important indicators for early breast cancer detection. The non-ionizing radiation and speckle free nature of photoacoustic imaging overcomes the drawbacks of current diagnostic tools - X-ray mammography and ultrasound imaging, respectively. We employed a 10-MHz photoacoustic imaging system to verify our idea. A sliced chicken breast phantom with granulated calcium hydroxyapatite (HA) - major chemical composition of the breast calcification associated with malignant breast cancers - embedded was imaged. With the near infared (NIR) laser excitation, it is shown that the distribution of ~500 μm HAs can be clearly imaged. In addition, photoacoustic signals from HAs rivals those of blood given an optimal NIR wavelength. In summary, photoacoustic imaging shows its promise for breast micro-calcification detection. Moreover, fusion of the photoacoustic and ultrasound images can reveal the location and distribution of micro-calcifications within anatomical landmarks of the breast tissue, which is clinically useful for biopsy and diagnosis of breast cancer staging.

  10. A clinical image preference study comparing digital tomosynthesis with digital radiography for pediatric spinal imaging

    NASA Astrophysics Data System (ADS)

    King, Jenna M.; Elbakri, Idris A.; Reed, Martin; Wrogemann, Jens

    2011-03-01

    The purpose of this study was to evaluate the diagnostic quality of digital tomosynthesis (DT) images for pediatric imaging of the spine. We performed a phantom image rating study to assess the visibility of anatomical spinal structures in DT images relative to digital radiography (DR) and computed tomography (CT). We collected DT and DR images of the cervical, thoracic and lumbar spine using anthropomorphic phantoms. Four pediatric radiologists and two residents rated the visibility of structures on the DT image sets compared to DR using a four point scale (0 = not visible; 1 = visible; 2 = superior to DR; 3 = excellent, CT unnecessary). In general, the structures in the spine received ratings between 1 and 3 (cervical), or 2 and 3 (thoracic, lumbar), with a few mixed scores for structures that are usually difficult to see on diagnostic images, such as vertebrae near the cervical-thoracic joint and the apophyseal joints of the lumbar spine. The DT image sets allow most critical structures to be visualized as well or better than DR. When DR imaging is inconclusive, DT is a valuable tool to consider before sending a pediatric patient for a higher-dose CT exam.

  11. Microfacies Analyses and Carbon Isotope Studies on Lower Triassic Microbialites from Armenia

    NASA Astrophysics Data System (ADS)

    Friesenbichler, Evelyn; Baud, Aymon; Krystyn, Leopold; Sahakyan, Lilit; Richoz, Sylvain

    2016-04-01

    After the end-Permian mass extinction the upper Paleozoic skeletal carbonate factory was abruptly replaced by a non-skeletal carbonate factory and Permian-Triassic boundary microbialites (PTBMs) were flourishing. These PTBMs were abundant in low-latitude shallow-marine carbonate shelves in central Tethyan continents and were present during at least four events in the Lower Triassic. The investigated PTBMs from three different sites in southern Armenia were formed in a distal open marine setting on a pelagic carbonate ramp. They grew during two microbial growth phases in Griesbachian times, whereas the microbialites from the first microbial growth phase co-occur with calcium carbonate crystal fans (CCFs). The microbes formed predominantly thrombolites that vary in size between 5 cm to 1.5 m. The biggest thrombolite has a cone-shaped build-up geometry and an asymmetrical growth, which indicates the influence of a steady bottom current. It consists of numerous thrombolite domes with a top head diameter of up to 8 m width and a total height of up to 12 m. The microbialites are surrounded by a bioclastic wackestone that mainly contains ostracods, foraminifers, microgastropods, thin-shelled bivalves and sponges. Carbon isotope studies were performed on both the microbialites and the surrounding sediment. A comparison between the δ13C values of the microbialites and the surrounding sediment revealed that there is little difference (<0.4‰) between these values in the microbialites that formed during the second microbial growth phase. In contrast, the microbialites and CCFs from the first microbial growth phase show differences in the δ13C values of up to 2.3‰ , which could be due to microbial activity.

  12. Methylmercury effects on migratory behaviour in glass eels (Anguilla anguilla): an experimental study using isotopic tracers.

    PubMed

    Claveau, Julie; Monperrus, Mathilde; Jarry, Marc; Baudrimont, Magalie; Gonzalez, Patrice; Cavalheiro, Joana; Mesmer-Dudons, Nathalie; Bolliet, Valérie

    2015-05-01

    The effect of methylmercury (MeHg) on glass eels' propensity to migrate, mitochondrial activity and antioxidative defence systems was investigated. Marine glass eels were first sorted in an experimental flume according to their response to dusk. Fish responding to the decrease in light intensity by ascending in the water column and moving with or against the flow were considered as having a high propensity to migrate (migrant). Glass eels still sheltering at the end of the 24 h catching period were considered as having a low propensity to migrate and were called non-migrant. Migrant and non-migrant glass eels were then individually tagged and exposed to isotopically enriched (201)MeHg (50 ng L(-1)) for 11 days. The effect of contamination was studied on muscle fibre structure, and the expression level of genes involved in mitochondrial activity and antioxidative defence systems. To investigate the effect of MeHg on glass eel behaviour, migrant and non-migrant glass eels were sorted again and the bioaccumulation of (201)MeHg and its demethylation product ((201)Hg(II)) were determined for each individual. MeHg exposure increased activity in non-migrant glass eels but not migratory behaviour. Contamination affected mitochondrial structure and metabolism and suggests a higher oxidative stress and activation of antioxidative defence systems in non-migrant glass eels. Overall, our results suggest that exposure to MeHg might induce an increase in energy expenditure and a higher vulnerability to predation in non-migrant glass eels in the wild. PMID:25797033

  13. Nanosecond flash studies of reduction of benzophenone by aliphatic amines. Quantum yields and kinetic isotope effects

    SciTech Connect

    Inbar, S.; Linschitz, H.; Cohen, S.G.

    1981-03-11

    Nanosecond flash photolysis, steady irradiation, and deuterium substitution studies have been carried out on solutions of benzophenone with added reductants. Quantum yields (phi/sub ketyl/) for reduction in benzene of benzophenone triplet to ketyl radical, based on phi = 2 for benzhydrol (I), were approx. 1 for cyclohexane (II), tert-butylamine (III), 2-aminobutane (IV), cyclohexylamine (V), di-n-propylamine (VI), and triethylamine (VII), approx. 0.7 for 1,4-diazabicyclo(2.2.2)octane (VIII), and approx. 0 for tert-butyl alcohol (IX). Thus, quenching, without radical formation by H abstraction from N and/or ..cap alpha..-C, does not occur with common aliphatic amines but does with Dabco (VIII). The latter quenching is markedly increased by small additions of acetonitrile; the flash spectrum from this compound indicates formation of a triplet amine CT complex or radical ion pair. Triplet-reductant interaction rate constants, k/sur ir/, are high for the amines (approx. 10/sup 8/-10/sup 9/ M/sup -1/ s/sup -1/) but also show significant deuterium kinetic isotope effects: 1.9 with III-N-d/sub 2/; 1.4 with IV-N-d/sub 2/; 1.2-1.3 with IV-..cap alpha..-C-d. It is proposed that k/sub ir/ measures H atom abstraction, favored in the transition state by an initial charge-transfer interaction. Overall steady irradiation quantum yields of reduction by amines, phi/sub Red/, are much lower than phi/sub ketyl/. This is attributed to disproportionationreactions of ketyl and alkylaminyl radicals for primary and secondary amines, and, possibly, aminoalkyl radicals for tertiary amines. In the case of tert-butylamine, the rate constant for disproportionation is obtained from the decay kinetics of ketyl radical and leads to phi/sub Red/ in agreement with that directly measured.

  14. Hydrochemistry and environmental isotope study of the geothermal water around Beypazarı granitoids, Ankara, Turkey

    NASA Astrophysics Data System (ADS)

    Çelmen, Oktay; Çelik, Mehmet

    2009-10-01

    Hydrochemical analysis results suggest four different water types: bicarbonate dominant water (facies-I), sulfate dominant cold brine water (facies-II), sodium-bicarbonate dominant thermal water and thermal and mineralized water (facies-III), and sulfate-chloride dominant thermal and mineralized water (facies-IV). The mineral content/salinity of the water is related to the ions that these waters dissolve from the minerals on the rocks during infiltration and circulation in the saturated zone. Gypsum cover units that exist on the granitoids in the region is the main factor for the ion increase in the facies III geothermal water similar to the cold brine water (facies II). Isotopic analyses indicate that the thermal springs (Dutlu bath spring, Ayaş bath well, Çoban bath well and Kapullu bath spring) are of meteoric origin and receive recharge from precipitation in the Beypazarı granitoids and around gypseous formations with elevations of about 950-1,150 m. Karakaya bath well and Ilıca bath spring thermal water points are recharged from the Bilecik limestone hills, Tekke volcanics and İncedoruk Formations. Karakoca mineral spring of thermal and mineralized water is recharged from out of the study area. According to oxygen-18 (SO4 2-) and sulfur-34 (SO4 2-) contents, sulfate in water samples from Ayaş and Dutlu resorts as well as Çoban bath is derived from the gypsum of Kirmir Formation as the primary source. Sulfates of the Kapullu bath water and Karakoca mineral water originate from secondary sources such as pyrite oxidation and bacteriological reduction.

  15. Hydroperiod affects nutrient accumulation in tree islands of the Florida Everglades: a stable isotope study

    NASA Astrophysics Data System (ADS)

    Wang, X.; Sternberg, L. O.; Engel, V.; Ross, M. S.

    2009-12-01

    Tree islands are important and unique components of wetland ecosystems. In many cases they are the end product of self organizing vegetation systems, which are often characterized by uneven soil nutrient distributions. Tree islands in the Everglades are phosphorus rich in contrast to the phosphorus-poor surrounding vegetation matrix. Everglades tree islands occur in the ridge-slough habitat of Shark River Slough, which is characterized by deep organic soils, multi-year hydroperiods, and maximum water depths of ~ 1 m. Tree islands are also found in the drier marl prairie habitat of the Everglades, characterized by marl soils, shallow water (< 0.5 m) and short (< 180 day) hydroperiods. In this study we used stable isotopes to investigate dry season water limitation and soil and foliar nutrient status in upland hammock communities of 18 different tree islands located in the Shark River Slough and adjacent prairie landscapes. We observed that prairie tree islands suffer greater drought stress during the dry season than slough tree islands by examining shifts in foliar δ13C values. We also found that slough tree islands have higher soil total phosphorus concentration and lower foliar N/P ratio than prairie tree islands. Foliar δ15N values, which often increase with greater P availability, was also found to be higher in slough tree islands than in prairie tree islands. Both the elemental N and P and foliar δ15N results indicate that the upland hammock plant communities in slough tree islands have higher amount of P available than those in prairie tree islands. Our findings are consistent with the transpiration driven nutrient harvesting chemohydrodynamic model. Tree islands without drought stress hypothetically transpire more and harvest more P than tree islands that have drought stress during the dry season. These findings suggest that hydroperiod is important to nutrient accumulation of tree island habitats and to the self-organization of the Everglades landscape.

  16. A hydrogen isotope study of CO3 type carbonaceous chondrites; comparison with type 3 ordinary chondrites

    NASA Technical Reports Server (NTRS)

    Morse, A. D.; Newton, J.; Pillinger, C. T.

    1993-01-01

    Meteorites of the Ornans type 3 carbonaceous chondrites exhibit a range in degree of equilibration, attributed to differing amounts of thermal metamorphism. These differences have been used to split the CO3 chondrites into petrologic sub-types from 3.0, least equilibrated, to 3.7, being most equilibrated. This is similar to the system of assigning the type 3 ordinary chondrites into petrologic sub-types 3.0 to 3.9 based upon thermoluminescence (TL) and other properties; however, the actual range of thermal metamorphism experienced by CO3 chondrites is much less than that of the type 3 ordinary chondrites. The least equilibrated ordinary chondrites show evidence of aqueous alteration and have high D/H ratios possibly due to a deuterium-rich organic carrier. The aim of this study was to determine whether the CO3 chondrites, which have experienced similar secondary conditions to the type 3 ordinary chondrites, also contain a similar deuterium-rich carrier. To date a total of 5 CO3 meteorites, out of a set of 11 for which carbon and nitrogen isotopic data are available, have been analyzed. Ornans has not been analyzed yet, because it does not appear to fit in with the metamorphic sequence exhibited by the other CO3 chondrites; it also has an extremely high delta-D value of +2150 percent, unusual for such a comparatively equilibrated meteorite (type 3.4). Initial results indicate that the more equilibrated CO3's tend to have lower delta-D values, analogous to the higher petrologic type ordinary chondrites. However this is complicated by the effects of terrestrial weathering and the small data-set.

  17. Rb-Sr and Sm-Nd Isotopic Studies of Lunar Green and Orange Glasses

    NASA Technical Reports Server (NTRS)

    Shih, C.-Y.; Nyquist, L. E.; Reese, Y.

    2012-01-01

    Lunar volcanic glassy beads have been considered as quenched basaltic magmas derived directly from deep lunar mantle during fire-fountaining eruptions [1]. Since these sub-mm size glassy melt droplets were cooled in a hot gaseous medium during free flight [2], they have not been subject to mineral fractionations. Thus, they represent primary magmas and are the best samples for the investigation of the lunar mantle. Previously, we presented preliminary Rb- Sr and Sm-Nd isotopic results for green and orange glassy samples from green glass clod 15426,63 and orange soil 74220,44, respectively [3]. Using these isotopic data, initial Sr-87/Sr-86 and Nd ratios for these pristine mare glass sources can be calculated from their respective crystallization ages previously determined by other age-dating techniques. These isotopic data were used to evaluate the mineralogy of the mantle sources. In this report, we analyzed additional glassy samples in order to further characterize isotopic signatures of their source regions. Also, we'll postulate a relationship between these two major mare basalt source mineralogies in the context of lunar magma ocean dynamics.

  18. Stable isotopes of carbon and nitrogen in the study of organochlorine contaminants in albatrosses and petrels.

    PubMed

    Colabuono, Fernanda I; Barquete, Viviane; Taniguchi, Satie; Ryan, Peter G; Montone, Rosalinda C

    2014-06-15

    Carbon and nitrogen stable isotopes in albatrosses and petrels collected off southern Brazil were compared with concentrations of organochlorine contaminants (OCs). δ(13)C and δ(15)N values, as well as OCs concentrations, exhibited a high degree of variability among individuals and overlap among species. δ(13)C values reflected latitudinal differences among species, with lower values found in Wandering and Tristan Albatrosses and higher values found in Black-browed and Atlantic Yellow-nosed Albatrosses and White-chinned Petrels. Some relationships were found between OCs and stable isotopes, but in general a partial 'uncoupling' was observed between OCs concentrations and stable isotopes ratios (especially for δ(15)N). δ(13)C and δ(15)N values in Procellariiformes tissues during the non-breeding season appear to be a better indicator of foraging habitats than of trophic relationships, which may partially explain the high degree of variability between concentrations of OCs and stable isotopes ratios in birds with a diversified diet and wide foraging range. PMID:24766898

  19. AGGREGATING FOOD SOURCES IN STABLE ISOTOPE DIETARY STUDIES: LUMP IT OR LEAVE IT?

    EPA Science Inventory

    A common situation when stable isotope mixing models are used to estimate food source dietary contributions is that there are too many sources to allow a unique solution. To resolve this problem one option is to combine sources with similar signatures such that the number of sou...