Sample records for isotope dilution thermal

  1. Isotope dilution mass spectrometry

    NASA Astrophysics Data System (ADS)

    Heumann, Klaus G.

    1992-09-01

    In the past isotope dilution mass spectrometry (IDMS) has usually been applied using the formation of positive thermal ions of metals. Especially in calibrating other analytical methods and for the certification of standard reference materials this type of IDMS became a routine method. Today, the progress in this field lies in the determination of ultra trace amounts of elements, e.g. of heavy metals in Antarctic ice and in aerosols in remote areas down to the sub-pg g-1 and sub-pg m-3 levels respectively, in the analysis of uranium and thorium at concentrations of a few pg g-1 in sputter targets for the production of micro- electronic devices or in the determination of sub-picogram amounts of230Th in corals for geochemical age determinations and of226Ra in rock samples. During the last few years negative thermal ionization IDMS has become a frequently used method. The determination of very small amounts of selenium and technetium as well as of other transition metals such as vanadium, chromium, molybdenum and tungsten are important examples in this field. Also the measurement of silicon in connection with a re-determination of Avogadro's number and osmium analyses for geological age determinations by the Re/Os method are of special interest. Inductively-coupled plasma mass spectrometry is increasingly being used for multi-element analyses by the isotope dilution technique. Determinations of heavy metals in samples of marine origin are representative examples for this type of multi-element analysis by IDMS. Gas chromatography-mass spectrometry systems have also been successfully applied after chelation of metals (for example Pt determination in clinical samples) or for the determination of volatile element species in the environment, e.g. dimethyl sulfide. However, IDMS--specially at low concentration levels in the environment--seems likely to be one of the most powerful analytical methods for speciation in the future. This has been shown, up to now, for species of iodine, selenium and some heavy metals in aquatic systems.

  2. Determination of sulfur in fossil fuels by isotope dilution thermal ionization mass spectrometry

    SciTech Connect

    Kelly, W.R.; Paulsen, P.J.; Murphy, K.E.; Vocke, R.D. Jr.; Chen, L.T. (National Inst. of Standards and Technology, Gaithersburg, MD (United States))

    1994-08-01

    Total sulfur has been measured in 13 petroleum and 14 coal Standard Reference Materials (SRMs) by isotope dilution thermal ionization mass spectrometry. These materials are suitable as primary and quality control standards for determining the sulfur content of oils and coals by X-ray fluorescence and high-temperature combustion instrumentation. Samples were spiked with enriched stable [sup 34]S and combusted in sealed Carius tubes using nitric and hydrochloric acids. The oxidized sulfur was reduced to H[sub 2]S, precipitated as As[sub 2]S[sub 3], and then dissolved in an ammoniacal solution of As[sub 2]O[sub 3]. A portion of this solution, equivalent to 1.5 [mu]g of sulfur, was added to a single Re filament coated with silica gel. The amount of sulfur in the samples was determined from the [sup 32]S/[sup 34]S ratio by measuring the [sup 75]As[sup 32]S[sup +]/[sup 75]As[sup 34]S[sup +] molecular ions in a Faraday detector. A total of 158 sulfur procedural blanks covering a 10-year period show an approximate log-normal distribution with a grand mean of 0.26 [mu]g of sulfur. This is a negligible correction for most of the data reported here. The total uncertainty (95% confidence interval) for homogeneous materials such as oils is about 0.5%, and for less homogeneous materials such as coals is 1-4%. 30 refs., 4 figs., 4 tabs.

  3. Evaluation of Duluth Complex anorthositic series (AS3) zircon as a UPb geochronological standard: new high-precision isotope dilution thermal ionization mass spectrometry results

    Microsoft Academic Search

    Mark D Schmitz; Samuel A Bowring; Trevor R Ireland

    2003-01-01

    U-Pb zircon geochronology is increasingly called upon to achieve the resolution of absolute time at the 0.1% to 1% level for rocks of Phanerozoic to Hadean age. Doing so requires accurate calibration of the several methods (conventional isotope dilution thermal ionization mass spectrometry [ID-TIMS], Pb evaporation, high-resolution ion microprobe [e.g. SHRIMP], and laser ablation inductively coupled plasma mass spectrometry [LA-ICPMS])

  4. An algorithm for U-Pb isotope dilution data reduction and uncertainty propagation

    E-print Network

    McLean, Noah Morgan

    High-precision U-Pb geochronology by isotope dilution-thermal ionization mass spectrometry is integral to a variety of Earth science disciplines, but its ultimate resolving power is quantified by the uncertainties of ...

  5. Measurement of attogram quantities of 231Pa in dissolved and particulate fractions of seawater by isotope dilution thermal ionization mass spectroscopy.

    PubMed

    Shen, Chuan-Chou; Cheng, Hai; Edwards, R Lawrence; Moran, S Bradley; Edmonds, Henrietta N; Hoff, John A; Thomas, Rebecca B

    2003-03-01

    A technique has been developed to quantify ultratrace 231Pa (50-2000 ag; 1 ag = 10(-18) g) concentrations in seawater using isotope-dilution thermal ionization mass spectrometry (TIMS). The method is a modification of a process developed by Pickett et al. (Pickett, D. A.; Murrell, M. T.; Williams, R. W. Anal. Chem. 1994, 66, 1044-1049) and extends the technique to very low levels of protactinium. The procedural blank is 16 +/- 15 ag (2sigma), and the ionization efficiency (ions generated/atom loaded) approaches 0.5%. Measurement time is <1 h. The amount of 231Pa needed to produce 231Pa data with an uncertainty of +/-4-12% is 100-1000 ag (approximately 3 x 10(5) to 3 x 10(6) atoms). Replicate measurements made on known standards and seawater samples demonstrate that the analytical precision approximates that expected from counting statistics and that, based on detection limits of 38 and 49 ag, protactinium can be detected in a minimum sample size of surface seawater of approximately 2 L for suspended particulate matter and <0.1 L for filtered (<0.4 microm) seawater, respectively. The concentration of 231Pa (tens of attograms per liter) can be determined with an uncertainty of +/-5-10% (2sigma) for suspended particulate matter filtered from 5 to 10 L of seawater. For the dissolved fraction, 0.5-1 L of seawater yields 231Pa measurements with a precision of 1-10%. Sample size requirements are orders of magnitude less than traditional decay-counting techniques and significantly less than previously reported ICP-MS techniques. Our technique can also be applied to other environmental samples, including cave waters, rivers, and igneous rocks. PMID:12641225

  6. Fast and solvent-free quantitation of boar taint odorants in pig fat by stable isotope dilution analysis-dynamic headspace-thermal desorption-gas chromatography/time-of-flight mass spectrometry.

    PubMed

    Fischer, Jochen; Haas, Torsten; Leppert, Jan; Lammers, Peter Schulze; Horner, Gerhard; Wüst, Matthias; Boeker, Peter

    2014-09-01

    Boar taint is a specific off-odour of boar meat products, known to be caused by at least three unpleasant odorants, with very low odour thresholds. Androstenone is a boar pheromone produced in the testes, whereas skatole and indole originate from the microbial breakdown of tryptophan in the intestinal tract. A new procedure, applying stable isotope dilution analysis (SIDA) and dynamic headspace-thermal desorption-gas chromatography/time-of-flight mass spectrometry (dynHS-TD-GC/TOFMS) for the simultaneous quantitation of these boar taint compounds in pig fat was elaborated and validated in this paper. The new method is characterised by a simple and solvent-free dynamic headspace sampling. The deuterated compounds d3-androstenone, d3-skatole and d6-indole were used as internal standards to eliminate matrix effects. The method validation performed revealed low limits of detection (LOD) and quantitation (LOQ) with high accuracy and precision, thus confirming the feasibility of the new dynHS-TD-GC/TOFMS approach for routine analysis. PMID:24731353

  7. Determination of lead, cadmium, indium, thallium and silver in ancient ices from Antarctica by isotope dilution-thermal ionization mass spectrometry

    USGS Publications Warehouse

    Matsumoto, A.; Hinkley, T.K.

    1997-01-01

    The concentrations of five chalcophile elements (Pb, Cd, In, Tl and Ag) and the lead isotope rarios in ancient ices from the Taylor Dome near coastal Antarctica, have been determined by the isotope dilutionthermal ionization mass spectrometry (ID-TIMS), with ultra-clean laboratory techniques. The samples were selected from segments of cores, one of which included a visible ash layer. Electric conductivity measurement (ECM) or dielectric properties (DEP) gave distinctive sharp peaks for some of the samples c hosen. Exterior portions of the sample segments were trimmed away by methods described here. Samples w ere evaporated to dryness and later separated into fractions for the five elements using an HBr-HNO3 a nion exchange column method. The concentrations are in the range 2.62-36.7 pg Pb/g of ice, 0.413-2.83 pg Cd/g, 0.081-0.34 pg In/g, 0.096-2.8 pg Tl/g and 0.15-0.84 pg Ag/g. respectively. The dispersions in duplicate analyses are about ??1% for lead and cadmium, ??2% for indium. ??4% for thallium and ??6% for silver, respectively. The concentrations of lead obtained are commonly higher than those in the present-day Antarctic surface snows, but the isotope ratios are distinctively higher than those of the present-day snows and close to those of the other ancient ice collected from a different Antarctic area.

  8. Trace determination of zinc by substoichiometric isotope dilution analysis

    SciTech Connect

    Sandhya, D.; Priya, S.; Subramanian, M.O.S. [Indian Institute of Technology, Madras (India)

    1996-09-01

    A radiometric method based on substoichiometric isotope dilution analysis using 1,10-phenanthroline and a substoichiometric amount of eosin was developed for determining trace amounts of zinc. Evaluation of various metal ion interferences shows that as little as 0.2 {mu}g Zn could be determined in an aqueous-phase volume of 60 mL. The method has been successfully applied to the determination of Zn in city waste incineration ash, cadmium metal, Fourts-B tablets, Boro-plus ointment, and magnesium alloy samples. 12 refs., 3 figs., 3 tabs.

  9. Oxygen and hydrogen isotopes in thermal waters at Zunil, Guatemala

    SciTech Connect

    Fournier, R.O.; Hanshaw, B.B.; Urrutia Sole, J.F.

    1982-10-01

    Enthalpy-chloride relations suggest that a deep reservoir exists at Zunil with a temperature near 300/sup 0/C. Water from that reservoir moves to shallower and cooler local reservoirs, where it mixes with diluted water and then attains a new water-rock chemical equilibrium. This mixed water, in turn, generally is further diluted before being discharged from thermal springs. The stable-isotopic composition of the thermal water indicates that recharge for the deep water at Zunil comes mainly from local sources. The presence of measurable tritium, which suggests that the deep water has been underground about 20 to 30 years, also indicates a local source for the recharge.

  10. Application of Uranium Isotope Dilution Mass Spectrometry in the preparation of New Certified Reference Materials

    NASA Astrophysics Data System (ADS)

    Hasözbek, A.; Mathew, K. J.; Orlowicz, G.; Srinivasan, B.; Narayanan, U.

    2012-04-01

    Proven measurement techniques play a critical role in the preparation of Certified Reference Materials (CRMs) - those requiring high accuracy and precision in the measurement results. Isotope Dilution Mass Spectrometry (IDMS) is one such measurement method commonly used in the quantitative analysis of uranium in nuclear safeguards and isotope geology applications. In this project, we evaluated the possibility of using some of the uranium isotopic and assay CRMs made earlier by the New Brunswick laboratory as IDMS spikes to define the uranium mass fraction in future preparations of CRMs. Uranium solutions prepared from CRM 112-A (a highly pure uranium metal assay standard) and CRM 115 (a highly pure uranium oxide isotopic and assay standard) were used as spikes in the determination of uranium. Two different thermal ionization mass spectrometer instruments (MAT 261 and TRITON) were used for the isotopic measurements. Standard IDMS equation was used for data reduction to yield results for uranium mass fraction along with uncertainties, the latter calculated according to GUM. The results show that uranium mass fraction measurements can be made with the required accuracy and precision for defining the uranium concentration in new CRMs as well as in routine samples analyses.

  11. Quantitation of DNA adducts by stable isotope dilution mass spectrometry

    PubMed Central

    Tretyakova, Natalia; Goggin, Melissa; Janis, Gregory

    2012-01-01

    Exposure to endogenous and exogenous chemicals can lead to the formation of structurally modified DNA bases (DNA adducts). If not repaired, these nucleobase lesions can cause polymerase errors during DNA replication, leading to heritable mutations potentially contributing to the development of cancer. Due to their critical role in cancer initiation, DNA adducts represent mechanism-based biomarkers of carcinogen exposure, and their quantitation is particularly useful for cancer risk assessment. DNA adducts are also valuable in mechanistic studies linking tumorigenic effects of environmental and industrial carcinogens to specific electrophilic species generated from their metabolism. While multiple experimental methodologies have been developed for DNA adduct analysis in biological samples – including immunoassay, HPLC, and 32P-postlabeling – isotope dilution high performance liquid chromatography-electrospray ionization-tandem mass spectrometry (HPLC-ESI-MS/MS) generally has superior selectivity, sensitivity, accuracy, and reproducibility. As typical DNA adducts concentrations in biological samples are between 0.01 – 10 adducts per 108 normal nucleotides, ultrasensitive HPLC-ESI-MS/MS methodologies are required for their analysis. Recent developments in analytical separations and biological mass spectrometry – especially nanoflow HPLC, nanospray ionization MS, chip-MS, and high resolution MS – have pushed the limits of analytical HPLC-ESI-MS/MS methodologies for DNA adducts, allowing researchers to accurately measure their concentrations in biological samples from patients treated with DNA alkylating drugs and in populations exposed to carcinogens from urban air, drinking water, cooked food, alcohol, and cigarette smoke. PMID:22827593

  12. Quantitative Analysis by Isotopic Dilution Using Mass Spectroscopy: The Determination of Caffeine by GC-MS.

    ERIC Educational Resources Information Center

    Hill, Devon W.; And Others

    1988-01-01

    Describes a laboratory technique for quantitative analysis of caffeine by an isotopic dilution method for coupled gas chromatography-mass spectroscopy. Discusses caffeine analysis and experimental methodology. Lists sample caffeine concentrations found in common products. (MVL)

  13. Determination of Cyanide in Blood by Isotope Dilution Gas Chromatography-Mass Spectrometry

    Microsoft Academic Search

    Karen E. Murphy; Michele M. Schantz; Therese A. Butler; Bruce A. Benner; Laura J. Wood; Gregory C. Turk

    Background: Cyanide (CN) is a lethal toxin. Quantifi- cation in blood is necessary to indicate exposure from many sources, including food, combustion byproducts, and terrorist activity. We describe an automated proce- dure based on isotope-dilution gas chromatography- mass spectrometry (ID GC\\/MS) for the accurate and rapid determination of CN in whole blood. Methods: A known amount of isotopically labeled po-

  14. Thermal conductivity and sound attenuation in dilute atomic Fermi gases

    SciTech Connect

    Braby, Matt; Chao Jingyi; Schaefer, Thomas [Physics Department, North Carolina State University, Raleigh, North Carolina 27695 (United States)

    2010-09-15

    We compute the thermal conductivity and sound attenuation length of a dilute atomic Fermi gas in the framework of kinetic theory. Above the critical temperature for superfluidity, T{sub c}, the quasiparticles are fermions, whereas below T{sub c}, the dominant excitations are phonons. We calculate the thermal conductivity in both cases. We find that at unitarity the thermal conductivity {kappa} in the normal phase scales as {kappa}{proportional_to}T{sup 3/2}. In the superfluid phase we find {kappa}{proportional_to}T{sup 2}. At high temperature the Prandtl number, the ratio of the momentum and thermal diffusion constants, is 2/3. The ratio increases as the temperature is lowered. As a consequence we expect sound attenuation in the normal phase just above T{sub c} to be dominated by shear viscosity. We comment on the possibility of extracting the shear viscosity of the dilute Fermi gas at unitarity using measurements of the sound absorption length.

  15. Determination of Key Intermediates in Cholesterol and Bile Acid Biosynthesis by Stable Isotope Dilution Mass Spectrometry

    PubMed Central

    Yoshida, Tadashi; Honda, Akira; Miyazaki, Hiroshi; Matsuzaki, Yasushi

    2008-01-01

    For more than a decade, we have developed stable isotope dilution mass spectrometry methods to quantify key intermediates in cholesterol and bile acid biosynthesis, mevalonate and oxysterols, respectively. The methods are more sensitive and reproducible than conventional radioisotope (RI), gas-chromatography (GC) or high-performance liquid chromatography (HPLC) methods, so that they are applicable not only to samples from experimental animals but also to small amounts of human specimens. In this paper, we review the development of stable isotope dilution mass spectrometry for quantifying mevalonate and oxysterols in biological materials, and demonstrate the usefulness of this technique. PMID:19609389

  16. Isotope dilution spaces of mice injected simultaneously with deuterium, tritium and oxygen-18.

    PubMed

    Król, E; Speakman, J R

    1999-10-01

    The isotope dilution technique for measuring total body water (TBW), and the doubly labelled water (DLW) method for measuring energy expenditure, are both sensitive to small variations in the ratio of the hydrogen to oxygen-18 dilution space. Since the dilution space ratio varies between individuals, there has been much recent debate over what causes this variability (i.e. physiological differences between individuals or analytical error in the isotope determinations), and thus which values (individual or a population mean dilution space ratio) should be employed for TBW and DLW calculations. To distinguish between physiological and analytical variability, we injected 15 non-reproductive and 12 lactating mice (Mus musculus, outbred MF1) simultaneously with deuterium, tritium and oxygen-18. The two hydrogen labels were administered and analysed independently, therefore we expected a strong correlation between dilution space ratios based on deuterium and tritium if most of the variation in dilution spaces was physiological, but only a weak correlation if most of the variation was analytical. Dilution spaces were significantly influenced by reproductive status. Dilution spaces expressed as a percentage of body mass averaged 15.7 % greater in lactating mice than in non-reproductive mice. In addition, the hydrogen tracer employed had a significant effect (deuterium spaces were 2.0 % larger than tritium spaces). Deuterium and tritium dilution spaces, expressed as a percentage of body mass, were highly correlated. Dilution space ratios ranged from 0.952 to 1. 146 when using deuterium, and from 0.930 to 1.103 when using tritium. Dilution space ratios based on deuterium and tritium were also highly correlated. Comparison of standard deviations of the dilution space ratio based on deuterium in vivo and in vitro indicated that only 4.5 % of the variation in the dilution space ratios observed in the mice could be accounted for by analytical variation in the deuterium and oxygen-18 analyses. Although our results include data which were outside the limits previously regarded as biologically possible, the correlations that we detected strongly suggest that variation in the observed dilution space ratio was mostly physiological rather than analytical. PMID:10504320

  17. DETERMINATION OF NIACIN IN FOOD MATERIALS BY ISOTOPE DILUTION MASS SPECTROMETRY

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The availability of deuterium-labeled nicotinic acid makes stable isotope dilution mass spectrometry (SIDMS) coupled with liquid chromatography (LC) an attractive option for the determination of the water-soluble B-vitamin, niacin, in food samples. We present a method based on acid digestion, solid ...

  18. Measurement of dissolved neon by isotope dilution using a quadrupole mass spectrometer

    E-print Network

    Emerson, Steven R.

    Measurement of dissolved neon by isotope dilution using a quadrupole mass spectrometer Roberta C with improved precision for measuring the concentration of neon dissolved in water. Measurements were calibrated in the estimate of the Ne concentration of air. D 2004 Elsevier B.V. All rights reserved. Keywords: Neon

  19. Quantification of ferritin bound iron in human serum using species-specific isotope dilution mass spectrometry.

    PubMed

    Ren, Yao; Walczyk, Thomas

    2014-09-01

    Ferritin is a hollow sphere protein composed of 24 subunits that can store up to 4500 iron atoms in its inner cavity. It is mainly found in the liver and spleen but also in serum at trace levels. Serum ferritin is considered as the best single indicator in assessing body iron stores except liver or bone marrow biopsy. However, it is confounded by other disease conditions. Ferritin bound iron (FBI) and ferritin saturation have been suggested as more robust biomarkers. The current techniques for FBI determination are limited by low antibody specificity, low instrument sensitivity and possible analyte losses during sample preparation. The need for a highly sensitive and reliable method is widely recognized. Here we describe a novel technique to detect serum FBI using species-specific isotope dilution mass spectrometry (SS-IDMS). [(57)Fe]-ferritin was produced by biosynthesis and in vitro labeling with the (57)Fe spike in the form of [(57)Fe]-citrate after cell lysis and heat treatment. [(57)Fe]-ferritin for sample spiking was further purified by fast liquid protein chromatography. Serum ferritin and added [(57)Fe]-ferritin were separated from other iron species by ultrafiltration followed by isotopic analysis of FBI using negative thermal ionization mass spectrometry. Repeatability of our assay is 8% with an absolute detection limit of 18 ng FBI in the sample. As compared to other speciation techniques, SS-IDMS offers maximum control over sample losses and species conversion during analysis. The described technique may therefore serve as a reference technique for clinical applications of FBI as a new biomarker for assessing body iron status. PMID:25008269

  20. An isotope effect on the comparative quantification of flavonoids by means of methylation-based stable isotope dilution coupled with capillary liquid chromatography/mass spectrometry.

    PubMed

    Fukusaki, Ei'ichiro; Harada, Kazuo; Bamba, Takeshi; Kobayashi, Akio

    2005-01-01

    Ionization suppression is a serious problem in liquid chromatography/mass spectrometry-based metabolomics, and stable isotope dilution-based comparative quantification is one of the most important methods of overcoming this problem. Herein, the use of [(13)C]-methylation-based stable isotope dilution for comparative quantification of flavonoids is demonstrated. This is in contrast to the equivalent deuterium labeling methylation method, which has an adverse isotope effect on reverse phase chromatography. PMID:16233758

  1. Cadmium fixation in soils measured by isotopic dilution

    SciTech Connect

    Smolders, E.; Brans, K.; Foeldi, A.; Merckx, R. [K.U. Leuven, Heverlee (Belgium). Lab. of Soil Fertility and Soil Biology

    1999-01-01

    There is conflicting evidence on the effect of time of contact between soil and Cd on Cd availability to plants. If Cd can be fixed in soil by aging, higher soil contamination may be tolerated. Fixation of Cd by soil can be studied by adding small quantities of {sup 109}Cd to the indigenous soil Cd. The ratio of {sup 109}Cd to indigenous Cd in soil extracts or in plants gives information on the lability of Cd in soil. This isotope exchange technique was used to measure the labile and fixed Cd fractions in 10 Belgian agricultural soils (Soils A--I) with both background and elevated Cd content. The isotopically exchangeable Cd pool (E value) was measured after equilibrating {sup 109}Cd spiked soil suspensions in CaCl{sub 2} 0.01 M for 7 d. The %E values (the E value relative to aqua regia soluble Cd) ranged from 62 to 90% in the eight soils where %E values could be detected. The plant labile Cd pool, relative to aqua regia soluble Cd (%L value) was measured from the specific activities in wheat (Triticum aestivum L.) seedlings grown for 16 to 21 d on soils spiked with {sup 109}Cd. The Cd %L value varied from 55 to 109% (mean: 82%) with five soils having a significant (P < 0.05) fixed Cd fraction. Varying the soil incubation procedure after soil spiking and before plant growth marginally affected the specific activity of Cd in plants. The %L values always exceeded the respective %E value between 1.05- and 1.4-fold. It is concluded that Cd fixation, where found, is not very pronounced.

  2. Development of stable isotope dilution assays for the quantitation of Amadori compounds in foods.

    PubMed

    Meitinger, Michael; Hartmann, Sandra; Schieberle, Peter

    2014-06-01

    During thermal processing of foods, reducing carbohydrates and amino acids may form 1-amino-1-desoxyketoses named Amadori rearrangement products after the Italian chemist Mario Amadori. Although these compounds are transient intermediates of the Maillard reaction, they are often used as suitable markers to measure the extent of a thermal food processing, such as for spray-dried milk or dried fruits. Several methods are already available in the literature for their quantitation, but measurements are often done with external calibration without addressing losses during the workup procedure. To cope with this challenge, stable isotope dilution assays in combination with LC-MS/MS were developed for the glucose-derived Amadori products of the seven amino acids valine, leucine, isoleucine, phenylalanine, tyrosine, methionine, and histidine using the respective synthesized [(13)C6]-labeled isotopologues as internal standards. The quantitation of the analytes added to a model matrix showed a very good sensitivity with the lowest limits of detection for the Amadori compound of phenylalanine of 0.1 ?g/kg starch and 0.2 ?g/kg oil, respectively. Also, the standard deviation measured in, for example, wheat beer was only ±2% for this analyte. Application of the method to several foods showed the highest concentrations of the Amadori product of valine in unroasted cocoa (342 mg/kg) as well as in dried bell pepper (3460 mg/kg). In agreement with literature data, drying of foods led to the formation of Amadori products, whereas they were degraded during roasting of, for example, coffee or cocoa. The study presents for the first time results on concentrations of the Amadori compounds of tyrosine and histidine in foods. PMID:24865106

  3. Standard test method for uranium and plutonium concentrations and isotopic abundances by thermal ionization mass spectrometry

    E-print Network

    American Society for Testing and Materials. Philadelphia

    2005-01-01

    1.1 This test method covers the determination of the concentration and isotopic composition of uranium and plutonium in solutions. The purified uranium or plutonium from samples ranging from nuclear materials to environmental or bioassay matrices is loaded onto a mass spectrometric filament. The isotopic ratio is determined by thermal ionization mass spectrometry, the concentration is determined by isotope dilution. 1.2 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish safety and health practices and determine the applicability of regulatory limitations prior to use.

  4. Determination of perchlorate in infant formula by isotope dilution ion chromatography/tandem mass spectrometry

    PubMed Central

    Wang, Z.; Lau, B.P.-Y.; Tague, B.; Sparling, M.; Forsyth, D.

    2011-01-01

    A sensitive and selective isotope dilution ion chromatography/tandem mass spectrometry (ID IC-MS/MS) method was developed and validated for the determination of perchlorate in infant formula. The perchlorate was extracted from infant formula by using 20 ml of methanol and 5 ml of 1% acetic acid. All samples were spiked with 18O4 isotope-labelled perchlorate internal standard prior to extraction. After purification on a graphitised carbon solid-phase extraction column, the extracts were injected into an ion chromatography system equipped with an Ionpac AS20 column for separation of perchlorate from other anions. The presence of perchlorate in samples was quantified by isotope dilution mass spectrometry. Analysis of both perchlorate and its isotope-labelled internal standard was carried out on a Waters Quattro Ultima triple quadrupole mass spectrometer operating in a multiple reaction monitoring (MRM) negative ionisation mode. The method was validated for linearity and range, accuracy, precision, sensitivity, and matrix effects. The limit of quantification (LOQ) was 0.4 ?g 1?1 for liquid infant formula and 0.95 ?g kg?1 for powdered infant formula. The recovery ranged from 94% to 110% with an average of 98%. This method was used to analyse 39 infant formula, and perchlorate concentrations ranging from

  5. A stable isotope dilution method for measuring bioavailability of organic contaminants

    PubMed Central

    Delgado-Moreno, Laura; Gan, Jay

    2014-01-01

    Methods for determining bioavailability of organic contaminants suffer various operational limitations. We explored the use of stable isotope labeled references in developing an isotope dilution method (IDM) to measure the exchangeable pool (E) of pyrene and bifenthrin as an approximation of their bioavailability in sediments. The exchange of deuterated bifenthrin or pyrene with its native counterpart was completed within 48 h. The derived E was 38–82% for pyrene and 28–59% for bifenthrin. Regression between E and the sum of rapid and slow desorption fractions obtained from sequential desorption showed a slope close to 1.0. The ability of IDM to predict bioavailability was further shown from a strong relationship (r2 > 0.93) between E and bioaccumulation into Chironomus tentans. Given the abundance of stable isotope labeled references and their relatively easy analysis, the IDM has the potential to become a readily adoptable tool for estimating organic contaminants bioaccessibility in various matrices. PMID:23434573

  6. Determination of chloride ion in aqueous samples by isotope-dilution Fouriertransform flame infrared emission (ID-FIRE) spectrometry

    Microsoft Academic Search

    Kenneth W. Busch; Arvie J. Kuehn; Marianna A. Busch; Sandra Yescas; Ilse Y. Guzman Jimenez; Christine M. Algozo

    1998-01-01

    An isotope dilution method for the determination of chloride ion in aqueous samples is described. The method makes use of the isotopic shift in the rotational lines of the 1–0 band of HCl emitted in the near infrared region of the spectrum by vibrationally excited HCl molecules present in a hydrogen\\/entrained air flame. Chloride ion in the sample is converted

  7. Plutonium and americium determination in mosses by laser ablation ICP-MS combined with isotope dilution technique

    Microsoft Academic Search

    Sergei F. Boulyga; Donatella Desideri; Maria Assunta Meli; Corrado Testa; J. Sabine Becker

    2003-01-01

    Environmental contamination by artificial radionuclides and the evaluation of their sources requires precise isotopic analysis and accurate determination of transuranium elements, above all plutonium and americium. This can be achieved by alpha spectrometry or by inductively coupled plasma mass spectrometry (ICP-MS) after chemical separation of actinides. In the present work, laser ablation (LA) ICP-MS was combined with isotope dilution for

  8. Assessment of vitamin A status in rats by isotope dilution: A simplified model

    SciTech Connect

    Furr, H.C.; Cooper, D.A.; Olson, J.A. (Iowa State Univ., Ames (United States))

    1990-02-26

    Isotope-dilution analysis of vitamin A status requires giving a known quantity of labeled vitamin A to the subject and measuring the ratio of labeled to unlabeled retinol in the blood after a period for equilibration. To calculate total body stores from the isotopic ratio of plasma retinol, several assumptions must be made. In considering new ways of better calculating liver vitamin A stores from isotope-dilution data, the authors used the data of Green et al. to estimate loss of vitamin A tracer as a function of time and of vitamin A status. This correction markedly improves the correlation between calculated and analyzed liver vitamin A stores and also quantitively explains the hyperbolic relationship between fraction of tracer dose recovered in liver and mass of liver vitamin A stores. Agreement of this model with experimental data suggests that efficiency of absorption and storage of vitamin A is not affected by vitamin A status. This model can be used to estimate both the amount of tracer needed for a given lower limit of detection and an optimum sampling time.

  9. Use of isotope dilution method to predict bioavailability of organic pollutants in historically contaminated sediments.

    PubMed

    Jia, Fang; Bao, Lian-Jun; Crago, Jordan; Schlenk, Daniel; Gan, Jay

    2014-07-15

    Many cases of severe environmental contamination arise from historical episodes, where recalcitrant contaminants have resided in the environment for a prolonged time, leading to potentially decreased bioavailability. Use of bioavailable concentrations over bulk chemical levels improves risk assessment and may play a critical role in determining the need for remediation or assessing the effectiveness of risk mitigation operations. In this study, we applied the principle of isotope dilution to quantify bioaccessibility of legacy contaminants DDT and PCBs in marine sediments from a Superfund site. After addition of 13C or deuterated analogues to a sediment sample, the isotope dilution reached a steady state within 24 h of mixing. At the steady state, the accessible fraction (E) derived by the isotope dilution method (IDM) ranged from 0.28 to 0.89 and was substantially smaller than 1 for most compounds, indicating reduced availability of the extensively aged residues. A strong linear relationship (R2=0.86) was found between E and the sum of rapid (Fr) and slow (Fs) desorption fractions determined by sequential Tenax desorption. The IDM-derived accessible concentration (Ce) was further shown to correlate closely with tissue residue in the marine benthic polychaete Neanthes arenaceodentata exposed in the same sediments. As shown in this study, the IDM approach involves only a few simple steps and may be readily adopted in laboratories equipped with mass spectrometers. This novel method is expected to be especially useful for historically contaminated sediments or soils, for which contaminant bioavailability may have changed significantly due to aging and other sequestration processes. PMID:24946234

  10. Solar thermal energy storage using heat of dilution - Analysis of heat generation in multistage mixing column

    Microsoft Academic Search

    T. Tanaka; K. Sakuta; M. Kamimoto; T. Tani; S. Sawata; T. Horigome

    1978-01-01

    Heat recovery obtained after storage of solar energy in the form of heat of dilution is studied by analyzing the mixing of two liquids (H2SO4 and H2O) in two multistage mixing column systems. The thermal analysis shows that heat at various temperatures can be produced by heat of dilution in a manner useful for various energy supply systems. Enthalpy balances

  11. Column chromatographic boron isotope separation at 5 and 17 MPa with diluted boric acid solution.

    PubMed

    Musashi, Masaaki; Oi, Takao; Matsuo, Motoyuki; Nomura, Masao

    2008-08-01

    Boron isotopic fractionation factor (S) between boron taken up in strongly basic anion exchange resin and boron in aqueous solution was determined by breakthrough column chromatography at 5 and 17 MPa at 25 degrees C, using 0.1 mM boric acid solution as feed solution. The S values obtained were 1.018 and 1.012, respectively, which were smaller than the value reported by using the same chromatographic method at the atmospheric pressure at 25 degrees C with the boron concentration of 10mM, but were larger than the values under the same condition with much higher concentration of 100 and 501 mM. Calculations based on the theory of isotope distribution between two phases estimated that 21% (5 MPa) and 47% (17 MPa) of boron taken up in the resin phase was in the three-coordinated B(OH)(3)-form, instead of in the four-coordinated B(OH)(4)-form, at high pressures even with a very diluted boric acid solution. We discussed the present results by introducing (1) hydration and (2) a partial molar volume difference between isotopic molecules. Borate may have been partially dehydrated upon transfer from the solution phase to the resin phase at high pressures, which resulted in smaller S values compared with those at the atmospheric pressure. Instead, it may be possible that the difference in the isotopic partial molar volume difference between B(OH)(3) and B(OH)(4)(-) caused the S value to decrease with increasing pressure. PMID:18585727

  12. Determination of Selected B-complex Vitamins in the NIST Multivitamin Reference Standard Material by Stable Isotope Dilution Mass Spectrometry (Experimental Biology, April, 2007, Washington, D.C.)

    Technology Transfer Automated Retrieval System (TEKTRAN)

    There is increased interest in accurately assessing the total dietary intake of vitamins from all sources, including foods and dietary supplements. Isotope dilution can be a definitive analytical method for very accurate concentration determinations. Thus, a liquid chromatographic (LC) isotope dilut...

  13. Quantification of four artificial sweeteners in Finnish surface waters with isotope-dilution mass spectrometry.

    PubMed

    Perkola, Noora; Sainio, Pirjo

    2014-01-01

    The artificial sweeteners sucralose (SCL), acesulfame (ACS), saccharin (SAC), and cyclamate (CYC) have been detected in environmental waters in Europe and North America. Higher environmental levels are expected in view of the increasing consumption of these food additives. In this study, an isotope-dilution mass spectrometry (IDMS) LC-MS/MS method was developed and validated for quantifying the four artificial sweeteners in boreal lakes (n = 3) and rivers (n = 12). The highest concentrations of ACS, SAC, CYC and SCL were 9,600, 490, 210 and 1000 ng/L, respectively. ACS and SAC were detected in all studied samples, and CYC and SCL in 98% and 56% of the samples. Seasonal trends of ACS and SAC were observed in some rivers. ACS and SCL concentrations in rivers correlated linearly with population equivalents of the wastewater treatment plants in the catchment areas, whereas SAC and CYC concentrations depend more on the source. PMID:24100049

  14. Determination of Cholesterol Oxidation Products in Human Plasma by Isotope Dilution-Mass Spectrometry

    Microsoft Academic Search

    S. Dzeletovic; O. Breuer; E. Lund; U. Diczfalusy

    1995-01-01

    A method based on isotope dilution-mass spectrometry was developed for the determination of nine cholesterol oxidation products in human plasma. The cholesterol oxidation products determined were cholest-5-ene-3 ?,7 ?-diol, cholest-5-ene-3 ?,7?-diol (7?- and 7?-hydroxycholesterol, respectively), 3?-hydroxycholest-5-en-7-one (7-oxocholesterol), 5,6?-epoxy-5?-cholestan-3?-ol (cholesterol-5?,6?-epoxide), 5,6?-epoxy- 5?-cholestan-3?-ol (cholesterol-5?,6?-epoxide), cholestane-3?,5?,6?-triol, cholest-5-ene-3?,24-diol (24-hydroxycholesterol), cholest-5-ene-3?,25-diol (25-hydroxycholesterol), and cholest-5-ene-3?,27-diol (27-hydroxycholesterol). A corresponding deuterium-labeled internal standard, containing 3 to 6 deuterium

  15. Adenosine 3',5'-monophosphate waves in dictyostelium discoideum: a demonstration by isotope dilution-fluorography

    SciTech Connect

    Tomchik, K.J.; Devreotes, P.N.

    1981-04-24

    The distribution of adenosine 3',5'-monophosphate (cyclic AMP) in fields of aggregating amoebae of Dictyostelium discoidenum was examined by a novel isotope dilution-fluorographic technique. Cellular cyclic AMP was visualized by its competition with exogenous /sup 3/H-labeled cyclic AMP for high-affinity binding sites on protein kinase immobilized on a Millipore filter used to blot the monolayer. The cyclic AMP was distributed in spiral or concentric circular wave patterns which centered on the foci of the aggregations. These patterns were correlated with those of cell shape change that propagate through the monolayers. These observations support the hypothesis that the aggregation process in Dictyostelium is mediated by the periodic relay of cyclic AMP signals and suggest a simple scheme for the dynamics of the aggregation process.

  16. Isotope dilution assay in peptide quantification: the challenge of microheterogeneity of internal standard.

    PubMed

    Stoyanov, Alexander V; Rogatsky, Eduard; Stein, Daniel; Connolly, Shawn; Rohlfing, Curt L; Little, Randie R

    2013-12-01

    Isotope dilution analysis allows quantitation of elements and different compounds in complex mixtures. The quantitation is based on a known amount of reference material (internal standard, IS) added to a sample that makes the result critically dependent on the value assigned to the standard. In the case of peptides, IS concentration is determined by nitrogen and amino acid analysis while purity is normally assessed by methods such as chromatography or electrophoresis that might not be able to detect many possible amino acid modifications, either naturally occurring or chemically induced. Microheterogeneity of the IS, if it is not accounted for when assigning a reference value to the standard, results in highly overestimated values in target analyte quantitation. In this viewpoint article, we illustrate the problem of internal standard microheterogeneity by analyzing synthetic human C-peptide labeled analogs. PMID:23983084

  17. Screening of dimethoate in food by isotope dilution and electrospray ionization tandem mass spectrometry.

    PubMed

    Mazzotti, Fabio; Di Donna, Leonardo; Macchione, Barbara; Maiuolo, Loredana; Perri, Enzo; Sindona, Giovanni

    2009-05-01

    Crop control is an important issue in both developed and developing countries. An environmentally friendly approach is represented by the so-called Integrated Pest Management (IPM), whereby synthetic pesticides are only applied as a last resort, under the strict control of suitable experts. European and US regulatory authorities, such as the US EPA, are constantly assessing the risks of exposure to the organophosphate (OP) class of pesticides and, among these, specifically dimethoate. The use of dimethoate is still allowed in many crops, including olives, which once was based in the Mediterranean area but now is expanding rapidly throughout the world. An important aspect of IPM protocols is represented by the availability of reliable and sensitive methods to detect pesticides residues. This paper describes an isotope dilution dimethoate assay based on the application of electrospray ionization tandem mass spectrometry (ESI-MS/MS) by means of a deuterium-labeled internal standard. PMID:19370544

  18. Simultaneous quantification of several cholesterol autoxidation and monohydroxylation products by isotope-dilution mass spectrometry

    SciTech Connect

    Breuer, O.; Bjoerkhem, I. (Huddinge Univ. Hospital (Sweden))

    1990-04-01

    An assay based on isotope-dilution mass spectrometry with deuterium-labeled internal standards was developed for simultaneous quantification of cholest-5-ene-3 beta,7 alpha-diol (7 alpha-hydroxycholesterol), cholest-5 beta,6 beta-epoxy-3 beta-ol (cholesterol-5 beta,6 beta-epoxide), cholest-5 alpha,6 alpha-epoxy-3 beta-ol (cholesterol-5 alpha,6 alpha-epoxide), cholest-5-en-7-one-3 beta-ol (7-oxocholesterol), cholestane-3 beta,5 alpha,6 beta-triol, cholest-5-ene-3 beta,25-diol (25-hydroxycholesterol), and cholest-5-ene-3 beta,26-diol (26-hydroxycholesterol) in one single serum sample. Recovery experiments and replicate analyses showed that the assay was sufficiently sensitive, accurate, and precise. The concentrations of the listed compounds in sera from 19 healthy subjects were determined and are presented.

  19. Low level mercury speciation in freshwaters by isotope dilution GC-ICP-MS

    PubMed Central

    Jackson, Brian; Taylor, Vivien; Baker, R. Arthur; Miller, Eric

    2009-01-01

    Atmospheric deposition of anthropogenic Hg has led to increased Hg concentrations in many ecosystems. Modeling is an effective method for predicting the complex dynamics of Hg fate and transport in watersheds; such models require accurate concentrations for water column methylmercury, CH3Hg+, as input parameters, yet these concentrations are very difficult to measure precisely as they are so low. We developed a method for aqueous CH3Hg+ quantification in Lake Champlain VT, where ambient CH3Hg+ concentrations are < 0.04 ng l-1. The analysis utilized species specific isotope dilution, purge and trap, gas chromatography ICP-MS and provided instrument detection limits of ca 0.2 fM (0.04 pg l-1) and method detection limits of 15 fM (0.003 ng l-1) for CH3Hg+ which are amongst the lowest reported. Artifactual methylation of inorganic Hg2+ was shown to be minor and the precision of the isotope dilution method was generally < 5% relative standard deviation; much lower than would have been the case for an external calibration approach. The method is accurate even at low concentrations of ca. 0.025 ng l-1. This combination of precision, accuracy and low detection allow for quantification of significant differences in CH3Hg+ concentration between bays and over time within bays of Lake Champlain where mean CH3Hg+ concentrations differ by only 0.006 ng l-1 at concentrations as low as 0.014 ng l-1. PMID:19452902

  20. Low-level mercury speciation in freshwaters by isotope dilution GC-ICP-MS.

    PubMed

    Jackson, Brian; Taylor, Vivien; Baker, R Arthur; Miller, Eric

    2009-04-01

    Atmospheric deposition of anthropogenic Hg has led to increased Hg concentrations in many ecosystems. Modeling is an effective method for predicting the complex dynamics of Hg transport in watersheds. Such models require accurate concentrations of water column methylmercury, CH3Hg+, for input parameters, yet these concentrations are very difficult to measure precisely because they are so low. We developed a method for aqueous CH3Hg+ quantification in Lake Champlain, VT, where ambient CH3Hg+ concentrations are < 0.04 ng L(-1). The analysis utilized species-specific isotope dilution, purge and trap gas chromatography inductively coupled plasma mass spectrometry and provided instrument detection limits of about 0.3 fM (0.06 pg L(-1)) and method detection limits of 15 fM (0.003 ng L(-1)) for CH3Hg+, which are among the lowest reported. Artifactual methylation of inorganic Hg(2+) was shown to be minor, and the precision of the isotope dilution method was generally <5% relative standard deviation, which is much lower than would have been the case for an external calibration approach. The method is accurate even at low concentrations of 0.025 ng L(-1). This combination of precision, accuracy, and low detection allows for quantification of significant differences in CH3Hg+ concentration between bays and over time within bays of Lake Champlain, where mean CH3Hg+ concentrations differ by only 0.006 ng L(-1) at concentrations as low as 0.014 ng L(-1). PMID:19452902

  1. An isotope-dilution standard GC/MS/MS method for steroid hormones in water

    USGS Publications Warehouse

    Foreman, William T.; Gray, James L.; ReVello, Rhiannon C.; Lindley, Chris E.; Losche, Scott A.

    2013-01-01

    An isotope-dilution quantification method was developed for 20 natural and synthetic steroid hormones and additional compounds in filtered and unfiltered water. Deuterium- or carbon-13-labeled isotope-dilution standards (IDSs) are added to the water sample, which is passed through an octadecylsilyl solid-phase extraction (SPE) disk. Following extract cleanup using Florisil SPE, method compounds are converted to trimethylsilyl derivatives and analyzed by gas chromatography with tandem mass spectrometry. Validation matrices included reagent water, wastewater-affected surface water, and primary (no biological treatment) and secondary wastewater effluent. Overall method recovery for all analytes in these matrices averaged 100%; with overall relative standard deviation of 28%. Mean recoveries of the 20 individual analytes for spiked reagent-water samples prepared along with field samples analyzed in 2009–2010 ranged from 84–104%, with relative standard deviations of 6–36%. Detection levels estimated using ASTM International’s D6091–07 procedure range from 0.4 to 4 ng/L for 17 analytes. Higher censoring levels of 100 ng/L for bisphenol A and 200 ng/L for cholesterol and 3-beta-coprostanol are used to prevent bias and false positives associated with the presence of these analytes in blanks. Absolute method recoveries of the IDSs provide sample-specific performance information and guide data reporting. Careful selection of labeled compounds for use as IDSs is important because both inexact IDS-analyte matches and deuterium label loss affect an IDS’s ability to emulate analyte performance. Six IDS compounds initially tested and applied in this method exhibited deuterium loss and are not used in the final method.

  2. Facile preparation of deuterium-labeled N-acylhomoserine lactones as internal standards for isotope dilution mass spectrometry.

    PubMed

    Kai, Kenji; Tani, Ayaka; Hayashi, Hideo

    2010-06-01

    N-Acylhomoserine lactones (AHLs) are widely conserved signal molecules that mediate quorum sensing in Gram-negative bacteria. In this study, deuterium-labeled AHLs were prepared for use as internal standards for isotope dilution mass spectrometry. Their utility in the sensitive and precise quantification of AHLs in culture supernatants of bacteria by GC/MS was demonstrated. PMID:20471840

  3. STATISTICAL ESTIMATES OF VARIANCE FOR 15N ISOTOPE DILUTION MEASUREMENTS OF GROSS RATES OF NITROGEN CYCLE PROCESSES

    EPA Science Inventory

    It has been fifty years since Kirkham and Bartholmew (1954) presented the conceptual framework and derived the mathematical equations that formed the basis of the now commonly employed method of 15N isotope dilution. Although many advances in methodology and analysis have been ma...

  4. Evaluation of online carbon isotope dilution mass spectrometry for the purity assessment of synthetic peptide standards.

    PubMed

    Cueto Díaz, Sergio; Ruiz Encinar, Jorge; García Alonso, J Ignacio

    2014-09-24

    We present a novel method for the purity assessment of peptide standards which is applicable to any water soluble peptide. The method is based on the online (13)C isotope dilution approach in which the peptide is separated from its related impurities by liquid chromatography (LC) and the eluent is mixed post-column with a continuous flow of (13)C-enriched sodium bicarbonate. An online oxidation step using sodium persulfate in acidic media at 99°C provides quantitative oxidation to (12)CO2 and (13)CO2 respectively which is extracted to a gaseous phase with the help of a gas permeable membrane. The measurement of the isotope ratio 44/45 in the mass spectrometer allows the construction of the mass flow chromatogram. As the only species that is finally measured in the mass spectrometer is CO2, the peptide content in the standard can be quantified, on the base of its carbon content, using a generic primary standard such as potassium hydrogen phthalate. The approach was validated by the analysis of a reference material (NIST 8327), and applied to the quantification of two commercial synthetic peptide standards. In that case, the results obtained were compared with those obtained using alternative methods, such as amino acid analysis and ICP-MS. The results obtained proved the value of the method for the fast, accurate and precise mass purity assignment of synthetic peptide standards. PMID:25172815

  5. Convenient synthesis of stable deuterium-labeled alkylpyrazines for use in stable isotope dilution assays.

    PubMed

    Fang, Mingchih; Cadwallader, Keith R

    2013-04-17

    Stable isotope dilution assays (SIDA) provide for accurate and precise quantitation of aroma components, such as alkylpyrazines, which are often present in low concentrations in complex food matrices. The unavailability of labeled standards is the main limitation to the widespread use of SIDA. This study describes the chlorination of several alkylpyrazines to form the corresponding chloroalkylpyrazine compounds, which are efficient starting materials for the synthesis of deuterium-labeled alkylpyrazines, namely [²H?]-2-methylpyrazine (d-1), [²H?]-2-ethylpyrazine (d-2), [²H?]-2,3(or 6)-dimethylpyrazine (d-3A, d-3B), [²H?]-2,[²H?]-6-dimethylpyrazine (d-3C), [²H?]-2,[²H?]-6-diethylpyrazine (d-4), [²H?]-2-ethyl-3(or 6)-methylpyrazine (d-5A, d-5B), 2,[²H?]-3,5-trimethylpyrazine (d-6), [²H?]-2-ethyl-3,6-dimethylpyrazine (d-7), [²H?]-2-ethyl-3,5-dimethylpyrazine (d-8), and 2,3-diethyl-[²H?]-5-methylpyrazine (d-9), which were obtained in good yields (57-100%) and high purities (86-98%). These stable isotopes were used as internal standards in SIDA to accurately and precisely determine selected alkylpyrazines in commercial peanut butter, cocoa powder, and instant coffee. 2,3-Diethyl-5-methylpyrazine (p-9) and 2-ethyl-3,5-dimethylpyrazine (p-8), despite their low abundance, had the highest odor-active values among the 13 pyrazines quantified in all products due to their very low odor thresholds. PMID:23528050

  6. [Determination of endogenous agmatine in rat plasma by isotope dilution-gas chromatography-mass spectrometry].

    PubMed

    Qiu, Zhongli; Lin, Ying; Xiong, Zhili; Xie, Jianwei

    2014-07-01

    A method for the determination of endogenous agmatine in rat plasma was developed by isotope dilution-gas chromatography-negative chemical ionization mass spectrometry (GC-NCI/MS). The plasma samples were analyzed after protein precipitation, evaporation, derivatization by hexafluoroacetone (HFAA), and clean-up on a Florisil SPE column. The GC-MS analysis utilized stable isotope d8-agmatine as internal standard. The samples after treatme were tested by negative chemical ionization with selected ion monitoring (SIM) which was set at m/z 492 (molecular ion of agmatine) and m/z 500 (molecular ion of internal standard). The limit of detection (LOD) of agmatine standard solution was 0.005 7 ng/mL. The calibration curve of the agmatine spiked in rat plasma showed a good linear relationship at the range of 1.14-57.0 ng/mL (r = 0.997). The recoveries of agmatine spiked in rat plasma ranged from 92.3% to 109.8%. Inter-day and intra-day precisions were less than 15%. The average concentration level of agmatine in rat plasma was (22 +/- 9) ng/mL, and there was no significant difference between male and female SD rats (p > 0.05). The method is high sensitive and specific, and can be used for the determination of endogenous agmatine in plasma. It provides a strong support for the subsequent research of agmatine. PMID:25255573

  7. Determination of Mercury Content in a Shallow Firn Core from Summit, Greenland by Isotope Dilution Inductively Coupled Plasma Mass Spectrometry

    NASA Technical Reports Server (NTRS)

    Mann, Jacqueline L.; Long, Stephen E.; Shuman, Christopher A.; Kelly, W. Robert

    2003-01-01

    The total mercury Hg content was determined in 6 cm sections of a near-surface 7 m firn core and in surrounding surface snow from Summit, Greenland (elevation: 3238 m, 72.58 N, 38.53 W) in May 2001 by isotope dilution cold-vapor inductively coupled plasma mass spectrometry (ID-CV-ICP-MS). The focus of this research was to evaluate the capability of the ID-CV-ICPMS technique for measuring trace levels of Hg typical of polar snow and firn. Highly enriched Hg-201 isotopic spike is added to approximately 10 ml melted core and thoroughly mixed. The Hg(+2) in the sample is reduced on line with tin (II) chloride (SnCl2) and the elemental Hg (Hg(0)) vapor pre-concentrated on to gold gauze using a commercial amalgam system. The Hg is then thermally desorbed and introduced into a quadrupole ICP-MS. The blank corrected Hg concentrations determined for all samples ranged from 0.25 ng/L to 1.74 ng/L (ppt) (average 0.59 ng/L plus or minus 0.28 ng/L) and fall within the range of those previously determined by Boutron et al., 1998 (less than or equal to 0.05 ng/L to 2.0 ng/L) for the Summit site. The average blank value was 0.19 ng/L plus or minus 0.045 ng/L (n=6). The Hg values specifically for the firn core range from 0.25 ng/L to 0.87 ng/L (average 0.51 ng/L plus or minus 0.13 ng/L) and show both values declining with time and larger variability in concentration in the top 1.8 m.

  8. Apolipoprotein A-I assayed in human serum by isotope dilution as a potential standard for immunoassay

    SciTech Connect

    Weech, P.K.; Jewer, D.; Marcel, Y.L.

    1988-01-01

    We measured the amount of apoA-I in serum by isotope dilution, finding 1.33 mg/ml (standard deviation 0.177) in six normolipidemic, healthy subjects. We developed this method by adapting published techniques to purify apoA-I from 3 ml of serum in two steps: density gradient ultracentrifugation and high performance liquid chromatography gel filtration. The 125I-labeled apoA-I tracer was first screened, by incubation with serum, to select labeled apoA-I which retained the ability to exchange with native apoA-I and bind to HDL. A known amount of 125I-labeled apoA-I-labeled HDL was added to unknown serum samples; apoA-I was reisolated from the serum and its specific radioactivity was used to calculate the dilution of the added, labeled apoA-I by the unlabeled apoA-I in the unknown serum. By not relying on immunochemical techniques, the isotope dilution assay provided results that are independent of the expression of individual apoA-I antigenic sites. Therefore, sera that have been assayed by isotope dilution can serve as standards to evaluate the accuracy of immunoassays for serum apoA-I and provide primary standards for such immunoassays.

  9. Adenosine 3',5'-Monophosphate Waves in Dictyostelium discoideum: A Demonstration by Isotope Dilution--Fluorography

    NASA Astrophysics Data System (ADS)

    Tomchik, K. J.; Devreotes, P. N.

    1981-04-01

    The distribution of adenosine 3',5'-monophosphate (cyclic AMP) in fields of aggregating amoebae of Dictyostelium discoideum was examined by a novel isotope dilution-fluorographic technique. Cellular cyclic AMP was visualized by its competition with exogenous 3H-labeled cyclic AMP for high-affinity binding sites on protein kinase immobilized on a Millipore filter used to blot the monolayer. The cyclic AMP was distributed in spiral or concentric circular wave patterns which centered on the foci of the aggregations. These patterns were correlated with those of cell shape change that propagate through the monolayers: cells in regions of high concentrations of cyclic AMP were elongated (presumably moving up a cyclic AMP gradient), whereas those in regions of low cyclic AMP concentrations were randomly directed. The highest cyclic AMP concentrations were about 10-6M. The widths of the regions of elevated cyclic AMP were about 0.3 to 1 millimeter which, assuming a wave velocity of 300 micrometers per minute, suggests that a cell signals for about 1 to 3 minutes. These observations support the hypothesis that the aggregation process in Dictyostelium is mediated by the periodic relay of cyclic AMP signals and suggest a simple scheme for the dynamics of the aggregation process.

  10. Precise determination of seawater calcium using isotope dilution inductively coupled plasma mass spectrometry.

    PubMed

    Liu, Hou-Chun; You, Chen-Feng; Cai, Wei-Jun; Chung, Chuan-Hsiung; Huang, Kuo-Fang; Chen, Bao-Shan; Li, Yen

    2014-02-21

    We describe a method for rapid, precise and accurate determination of calcium ion (Ca(2+)) concentration in seawater using isotope dilution inductively coupled plasma mass spectrometry (ID-ICP-MS). A 10 ?L aliquot of seawater was spiked with an appropriate (43)Ca enriched solution for (44)Ca/(43)Ca ID-ICP-MS analyses, using an Element XR (Thermo Fisher Scientific), operated at low resolution in E-scan acquisition mode. A standard-sample bracketing technique was applied to correct for potential mass discrimination and ratio drift at every 5 samples. A precision of better than 0.05% for within-run and 0.10% for duplicate measurements of the IAPSO seawater standard was achieved using 10 ?L solutions with a measuring time less than 3 minutes. Depth profiles of seawater samples collected from the Arctic Ocean basin were processed and compared with results obtained by the classic ethylene glycol tetra-acetic acid (EGTA) titration. Our new ID-ICP-MS data agreed closely with the conventional EGTA data, with the latter consistently displaying 1.5% excess Ca(2+) values, possibly due to a contribution of interference from Mg(2+) and Sr(2+) in the EGTA titration. The newly obtained Sr/Ca profiles reveal sensitive water mass mixing in the upper oceanic column to reflect ice melting in the Arctic region. This novel technique provides a tool for seawater Ca(2+) determination with small sample size, high throughput, excellent internal precision and external reproducibility. PMID:24434804

  11. Daily cortisol production rate in man determined by stable isotope dilution/mass spectrometry

    SciTech Connect

    Esteban, N.V.; Loughlin, T.; Yergey, A.L.; Zawadzki, J.K.; Booth, J.D.; Winterer, J.C.; Loriaux, D.L. (National Institute of Child Health and Human Development, Bethesda, MD (USA))

    1991-01-01

    Growth retardation as well as the development of Cushingoid features in adrenally insufficient patients treated with the currently accepted replacement dose of cortisol (33-41 mumol/day.m2; 12-15 mg/m2.day) prompted us to reevaluate the cortisol production rate (FPR) in normal subjects and patients with Cushing's syndrome, using a recently developed thermospray liquid chromatography-mass spectrometry method. The stable isotope (9,12,12-2H3)cortisol was infused continuously for 31 h at about 5% of the anticipated FPR. Blood samples were obtained at 20-min intervals for 24 h, spun, and pooled in 4-h groups. Tracer dilution in plasma was determined by liquid chromatography/mass spectrometry. The method was validated with controlled infusions in 6 patients with adrenal insufficiency. Results from 12 normal volunteers revealed a FPR of 27.3 +/- 7.5 mumol/day (9.9 +/- 2.7 mg/day) or 15.7 mumol/day.m2; 5.7 mg/m2. day. A previously unreported circadian variation in FPR was observed. Patients with Cushing's syndrome demonstrated unequivocal elevation of FPR and cortisol concentration correlated during each sample period in normal volunteers, indicating that cortisol secretion, rather than metabolism, is mainly responsible for changes in plasma cortisol. Our data suggest that the FPR in normal subjects may be lower than previously believed.

  12. Quantifying gross fluxes of nitrous oxide and dinitrogen gas using a novel isotope pool dilution technique

    NASA Astrophysics Data System (ADS)

    Arn Teh, Yit; Yang, Wendy; Silver, Whendee L.

    2010-05-01

    One of the existing challenges in trace gas biogeochemistry lies in understanding the environmental controls on the net and gross fluxes of soil-derived compounds. This is because gross production and consumption fluxes of these gases often occur simultaneously or in close spatial proximity, making it difficult to make inferences about the effects of environmental variables (e.g. temperature, soil water content, porosity, redox, etc.) on gross fluxes based on bulk concentration measurements alone. One novel approach for quantifying gross fluxes of N2O and N2 is 'stable isotope pool dilution;' a technique that has been successfully applied to study bidirectional fluxes of other biogenic compounds, such as CH4 and halocarbons. To evaluate the efficacy of this method for quantifying gross N2O and N2 fluxes, we conducted a combined field and laboratory test of the pool dilution technique along side conventional measures of nitrification and denitrification. Experiments were conducted in a N-rich managed peatland pasture in the Sacramento-San Joaquin Delta, California, USA. Field and laboratory measurements were performed in a broad range of microforms and microtopes spanning a range of hydrologic and environmental conditions. Field experiments focussed on gross fluxes of N2O and N2 in upper soil horizons; the soil layers that exchange most rapidly with the atmosphere. Laboratory experiments indicated that 15N pool dilution compares favourably with more conventional measures of N2O and N2 flux, such as acetylene inhibition or the 15NO3- pulse-trace approach. Gross N2O fluxes greatly exceeded N2 fluxes by as much as an order of magnitude or more, and averaged 6.1 ± 2.2 mg N m-2 d-1, with a range from 0.06 to 63.13 mg N m-2 d-1. N2O:N2 emissions ratios generally exceeded 1 except along slopes, with an overall range of 0.2 to 30.9. NH4+ concentrations and denitrifying enzyme activity were the best predictors of gross N2O fluxes in the field (r2 = 0.65). Net N2O production rates explained 53 percent of the variability in gross N2 fluxes, whereas N2O:N2 ratios were best predicted by the combination of water-filled pore space and mineral N concentration (r2 = 0.44). This research highlights the potential of the pool dilution approach for quantifying gross fluxes of N2O and N2 from surface soils under both field and laboratory conditions. Future experiments will couple these measures of soil surface fluxes with push-pull methods for determining gross N2O and N2 fluxes at depth, and natural abundance isotopomer measurements to determine sources of N2O.

  13. Microwave-assisted deuterium exchange: the convenient preparation of isotopically labelled analogues for stable isotope dilution analysis of volatile wine phenols.

    PubMed

    Crump, Anna M; Sefton, Mark A; Wilkinson, Kerry L

    2014-11-01

    This study reports the convenient, low cost, one-step synthesis of labelled analogues of six volatile phenols, guaiacol, 4-methylguaiacol, 4-ethylguaiacol, 4-ethylphenol, eugenol and vanillin, using microwave-assisted deuterium exchange, for use as internal standards for stable isotope dilution analysis. The current method improves on previous strategies in that it enables incorporation of deuterium atoms on the aromatic ring, thereby ensuring retention of the isotope label during mass spectrometry fragmentation. When used as standards for SIDA, these labelled volatile phenols will improve the accuracy and reproducibility of quantitative food and beverage analysis. PMID:24874385

  14. Sensitive isotope dilution liquid chromatography\\/electrospray ionization tandem mass spectrometry method for the determination of acrylamide in chocolate

    Microsoft Academic Search

    Yiping Ren; Yu Zhang; Jingjing Jiao; Zengxuan Cai; Ying Zhang

    2006-01-01

    Isotope dilution liquid chromatography coupled with electrospray ionization tandem mass spectrometry (LC-MS\\/MS) was applied to the quantification of acrylamide in chocolate matrixes (dark chocolate, milk chocolate, chocolate with nuts, chocolate with almonds, and chocolate with wheat best element). The method included defatting with petroleum ether, extracting with aqueous solution of 2?mol?l sodium chloride and clean-up by solid-phase (SPE) with OASIS

  15. Relative Quantification of Serum Proteins from Pancreatic Ductal Adenocarcinoma Patients by Stable Isotope Dilution Liquid Chromatography-Mass Spectrometry

    PubMed Central

    Wehr, Angela Y.; Hwang, Wei-Ting; Blair, Ian A.; Yu, Kenneth H.

    2012-01-01

    We report an innovative multiplexed liquid chromatography-multiple reaction monitoring/mass spectrometry (LC-MRM/MS)-based assay for rapidly measuring a large number of disease specific protein biomarkers in human serum. Furthermore, this approach uses stable isotope dilution methodology to reliably quantify candidate protein biomarkers. Human serum was diluted using a stable isotope labeled proteome (SILAP) standard prepared from the secretome of pancreatic cell lines, subjected to immunoaffinity removal of the most highly abundant proteins, trypsin digested, and analyzed by LC-MRM/MS. The method was found to be precise, linear, and specific for the relative quantification of 72 proteins when analyte response was normalized to the relevant internal standard (IS) from the SILAP. The method made it possible to determine statistically different concentrations for three proteins (cystatin M, IGF binding protein 7, and villin 2) in control and pancreatic cancer patient samples. This method proves the feasibility of using a SILAP standard in combination with stable isotope dilution LC-MRM/MS analysis of tryptic peptides to compare changes in the concentration of candidate protein biomarkers in human serum. PMID:22264027

  16. Chemical and isotopic composition of water from thermal springs and mineral springs of Washington

    USGS Publications Warehouse

    Mariner, R.H.; Presser, T.S.; Evans, William C.

    1982-01-01

    Water from thermal springs of Washington range in chemical composition from dilute NaHC03, to moderately saline C02-charged NaHC03-Cl waters. St. Martin 's Hot Spring which discharges a slightly saline NaCl water, is the notable exception. Mineral springs generally discharge a moderately saline C02-charged NaHC03-Cl water. The dilute Na-HC03 waters are generally associated with granite. The warm to hot waters charged with C02 issue on or near the large stratovolcanoes and many of the mineral springs also occur near the large volcanoes. The dilute waters have oxygen isotopic compositions which indicate relatively little water-rock exchange. The C02-charged waters are usually more enriched in oxygen-18 due to more extensive water-rock reaction. Carbon-13 in the C02-charged thermal waters is more depleted (-10 to -12 permil) than in the cold C02-charged soda springs (-2 to -8 permil) which are also scattered throughout the Cascades. The hot and cold C02-charged waters are supersaturated with respect to CaC03, but only the hot springs are actively depositing CaC03. Baker, Gamma, Sulphur , and Ohanapecosh seem to be associated with thermal aquifers of more than 100C. (USGS)

  17. Stable isotope dilution analysis of wine fermentation products by HS-SPME-GC-MS.

    PubMed

    Siebert, Tracey E; Smyth, Heather E; Capone, Dimitra L; Neuwöhner, Corinna; Pardon, Kevin H; Skouroumounis, George K; Herderich, Markus J; Sefton, Mark A; Pollnitz, Alan P

    2005-02-01

    The aim of this study was to quantify, in a single analysis, 31 volatile fermentation-derived products that contribute to the aroma of red and white wine. We developed a multi-component method based on headspace solid-phase microextraction coupled with gas chromatography mass spectrometry (HS-SPME-GC-MS). The 31 volatile compounds analysed include ethyl esters, acetates, acids and alcohols. Although these compounds have a range of functional groups, chemical properties, volatilities, affinities for the SPME fibre, and are found in wine at various concentrations, the accuracy of the analysis was achieved with the use of polydeuterated internal standards for stable isotope dilution analyses (SIDA). Nine of the labelled standards were commercially available, while 22 were synthesised. The method was validated by a series of duplicate spiked standard additions to model, white and red wine matrices over the concentration range relevant for each compound in wine. This demonstrated that the appropriate use of SIDA helped to account for matrix effects, for instance potential sources of variation such as the relative response to the MS detector, ionic strength, ethanol content and pH of different wine matrices. The resultant calibration functions had correlation coefficients (R(2)) ranging from 0.995 to 1.000. Each compound could be quantified at levels below its aroma threshold in wine. Relative standard deviations were all <5%. The method was optimised for the best compromise (over the 31 compounds) of wine dilution factor, level of sodium chloride addition, SPME fibre, SPME temperature, SPME time, GC column and MS conditions. Confirmation of identity was achieved by retention time and peak shape, and measurement of at least three ions for each analyte and internal standard with the MS operating in selected ion monitoring mode to facilitate more precise quantitation with a high sampling rate. The method is a valuable research tool with many relevant applications. A novel method for the combined chiral separation and SIDA quantification of 2- and 3-methylbutanoic acid is also demonstrated. PMID:15660221

  18. Simultaneous Determination of Selected B Vitamins in the NIST SRM 3280 Multivitamin/Multielement Tablets by Liquid Chromatography Isotope Dilution Mass Spectrometry

    Technology Transfer Automated Retrieval System (TEKTRAN)

    There is increased interest in accurately assessing the total dietary intake of vitamins from all sources, including foods and dietary supplements. Isotope dilution mass spectrometry (IDMS) can be a definitive analytical method for very accurate concentration determinations. A liquid chromatographic...

  19. Quantitative determination of free and total bisphenol A in human urine using labeled BPA glucuronide and isotope dilution mass spectrometry.

    PubMed

    Kubwabo, Cariton; Kosarac, Ivana; Lalonde, Kaela; Foster, Warren G

    2014-07-01

    Bisphenol A (BPA) is a widely used industrial chemical in the manufacturing of polycarbonate plastic bottles, food and beverage can linings, thermal receipts, and dental sealants. Animal and human studies suggest that BPA may disrupt normal hormonal function and hence, potentially, have negative effects on the human health. While total BPA is frequently reported, it is recognized that free BPA is the biologically active form and is rarely reported in the literature. The objective of this study was to develop a sensitive and improved method for the measurement of free and total BPA in human urine. Use of a labeled conjugated BPA (bisphenol A-d6 ?-D-glucuronide) allowed for the optimization of the enzymatic reaction and permitted an accurate determination of the conjugated BPA concentration in urine samples. In addition, a (13)C12-BPA internal standard was used to account for the analytical recoveries and performance of the isotope dilution method. Solid-phase extraction (SPE) combined with derivatization and analysis using a triple quadrupole GC-EI/MS/MS system achieved very low method detection limit of 0.027 ng/mL. BPA concentrations were measured in urine samples collected during the second and third trimesters of pregnancy in 36 Canadian women. Total maternal BPA concentrations in urine samples ranged from not detected to 9.40 ng/mL (median, 1.21 ng/mL), and free BPA concentrations ranged from not detected to 0.950 ng/mL (median, 0.185 ng/mL). Eighty-six percent of the women had detectable levels of conjugated BPA, whereas only 22 % had detectable levels of free BPA in their urine. BPA levels measured in this study agreed well with data reported internationally. PMID:24817354

  20. Cellular lipid extraction for targeted stable isotope dilution liquid chromatography-mass spectrometry analysis.

    PubMed

    Gelhaus, Stacy L; Mesaros, A Clementina; Blair, Ian A

    2011-01-01

    The metabolism of fatty acids, such as arachidonic acid (AA) and linoleic acid (LA), results in the formation of oxidized bioactive lipids, including numerous stereoisomers(1,2). These metabolites can be formed from free or esterified fatty acids. Many of these oxidized metabolites have biological activity and have been implicated in various diseases including cardiovascular and neurodegenerative diseases, asthma, and cancer(3-7). Oxidized bioactive lipids can be formed enzymatically or by reactive oxygen species (ROS). Enzymes that metabolize fatty acids include cyclooxygenase (COX), lipoxygenase (LO), and cytochromes P450 (CYPs)(1,8). Enzymatic metabolism results in enantioselective formation whereas ROS oxidation results in the racemic formation of products. While this protocol focuses primarily on the analysis of AA- and some LA-derived bioactive metabolites; it could be easily applied to metabolites of other fatty acids. Bioactive lipids are extracted from cell lysate or media using liquid-liquid (l-l) extraction. At the beginning of the l-l extraction process, stable isotope internal standards are added to account for errors during sample preparation. Stable isotope dilution (SID) also accounts for any differences, such as ion suppression, that metabolites may experience during the mass spectrometry (MS) analysis(9). After the extraction, derivatization with an electron capture (EC) reagent, pentafluorylbenzyl bromide (PFB) is employed to increase detection sensitivity(10,11). Multiple reaction monitoring (MRM) is used to increase the selectivity of the MS analysis. Before MS analysis, lipids are separated using chiral normal phase high performance liquid chromatography (HPLC). The HPLC conditions are optimized to separate the enantiomers and various stereoisomers of the monitored lipids(12). This specific LC-MS method monitors prostaglandins (PGs), isoprostanes (isoPs), hydroxyeicosatetraenoic acids (HETEs), hydroxyoctadecadienoic acids (HODEs), oxoeicosatetraenoic acids (oxoETEs) and oxooctadecadienoic acids (oxoODEs); however, the HPLC and MS parameters can be optimized to include any fatty acid metabolites(13). Most of the currently available bioanalytical methods do not take into account the separate quantification of enantiomers. This is extremely important when trying to deduce whether or not the metabolites were formed enzymatically or by ROS. Additionally, the ratios of the enantiomers may provide evidence for a specific enzymatic pathway of formation. The use of SID allows for accurate quantification of metabolites and accounts for any sample loss during preparation as well as the differences experienced during ionization. Using the PFB electron capture reagent increases the sensitivity of detection by two orders of magnitude over conventional APCI methods. Overall, this method, SID-LC-EC-atmospheric pressure chemical ionization APCI-MRM/MS, is one of the most sensitive, selective, and accurate methods of quantification for bioactive lipids. PMID:22127066

  1. Estimation of the blood flow through a peripheral organ (kidney) using the technique of isotope dilution after i.v. injection in animal experiments

    Microsoft Academic Search

    H.-D. Herrmann; H. Ludt; H. Palleske; G. Harbauer

    1973-01-01

    Summary Animal experiments were carried out to prove that it is possible to estimate the blood flow through peripheral organs with the isotope dilution technique after intravenous injection. It could be shown that the mathematical treatment of the dilution events in three mixing chambers in a row, presented in a foregoing paper, is valid also for the animal organism where

  2. Determination of trace level cadmium in SRM 3280 Multivitamin/Multielement Tablets via isotope dilution inductively coupled plasma mass spectrometry.

    PubMed

    Christopher, Steven J; Thompson, Robert Q

    2013-11-15

    Cadmium was quantified at 80.15±0.86 ng/g (mean±95% expanded uncertainty) in NIST SRM 3280 Multivitamin/Multielement Tablets, using isotope dilution mass spectrometry. The method described utilized various precipitation and solid-phase extraction separation methodologies to isolate Cd from Sn and Mo, present respectively, at 11.1±0.9 mg/kg and 70.7±4.5 mg/kg in the tablet matrix. This allowed for measurement of (111)Cd/(113)Cd and (111)Cd/(114)Cd isotope ratios using both quadrupole collision cell technology inductively coupled plasma mass spectrometry (Q-CCT-ICP-MS) and sector field (SF)-ICP-MS equipped with a desolvating nebulizer system to mitigate the MoO(+) and MoOH(+) molecular ion interferences that typically affect the envelope of Cd isotopes. PMID:24148367

  3. A crowding factor model for the thermal conductivity of particulate composites at non-dilute limit

    NASA Astrophysics Data System (ADS)

    Ordonez-Miranda, J.; Yang, Ronggui; Alvarado-Gil, J. J.

    2013-08-01

    The effective thermal conductivity models for particulate composites are usually restricted to the dilute limit, with volumetric concentrations of particles typically less than 15%. By considering the particle interactions through a crowding factor, in this work, a new formula is developed to describe the thermal conductivity of composites with a dielectric matrix, for volume fractions of particles up to their maximum packing fraction. The crowding factor model is then applied to analyze two particulate composites with dielectric or metallic particles, where the effects of both interfacial thermal resistance and the electron-phonon coupling are taken into account. It is shown that the predictions of the proposed crowding factor model are larger than the ones predicted by the dilute-limit models, for composites with high volume fractions of particles, due to the particle interactions. The proposed crowding factor model extends the applicability of various thermal conductivity models for composites reported in the literature and its predictions are in good agreement with published experimental data.

  4. NUCLEAR ISOTOPIC DILUTION OF HIGHLY ENRICHED URANIUM BY DRY BLENDING VIA THE RM-2 MILL TECHNOLOGY

    SciTech Connect

    Raj K. Rajamani; Sanjeeva Latchireddi; Vikas Devrani; Harappan Sethi; Roger Henry; Nate Chipman

    2003-08-01

    DOE has initiated numerous activities to focus on identifying material management strategies to disposition various excess fissile materials. In particular the INEEL has stored 1,700 Kg of offspec HEU at INTEC in CPP-651 vault facility. Currently, the proposed strategies for dispositioning are (a) aqueous dissolution and down blending to LEU via facilities at SRS followed by shipment of the liquid LEU to NFS for fabrication into LWR fuel for the TVA reactors and (b) dilution of the HEU to 0.9% for discard as a waste stream that would no longer have a criticality or proliferation risk without being processed through some type of enrichment system. Dispositioning this inventory as a waste stream via aqueous processing at SRS has been determined to be too costly. Thus, dry blending is the only proposed disposal process for the uranium oxide materials in the CPP-651 vault. Isotopic dilution of HEU to typically less than 20% by dry blending is the key to solving the dispositioning issue (i.e., proliferation) posed by HEU stored at INEEL. RM-2 mill is a technology developed and successfully tested for producing ultra-fine particles by dry grinding. Grinding action in RM-2 mill produces a two million-fold increase in the number of particles being blended in a centrifugal field. In a previous study, the concept of achieving complete and adequate blending and mixing (i.e., no methods were identified to easily separate and concentrate one titanium compound from the other) in remarkably short processing times was successfully tested with surrogate materials (titanium dioxide and titanium mono-oxide) with different particle sizes, hardness and densities. In the current project, the RM-2 milling technology was thoroughly tested with mixtures of natural uranium oxide (NU) and depleted uranium oxide (DU) stock to prove its performance. The effects of mill operating and design variables on the blending of NU/DU oxides were evaluated. First, NU and DU both made of the same oxide, UO{sub 3}, was used in the testing. Next, NU made up of UO{sub 3} and DU made up of UO{sub 2} was used in the test work. In every test, the blend achieved was characterized by spatial sampling of the ground product and analyzing for {sup 235}U concentration. The test work proved that these uranium oxide materials can be blended successfully. The spatial concentration was found to be uniform. Next, sintered thorium oxide pellets were used as surrogate for light water breeder reactor pellets (LWBR). To simulate LWBR pellet dispositioning, the thorium oxide pellets were first ground to a powder form and then the powder was blended with NU. In these tests also the concentration of {sup 235}U and {sup 232}Th in blended products fell within established limits proving the success of RM-2 milling technology. RM-2 milling technology is applicable to any dry radioactive waste, especially brittle solids that can be ground up and mixed with the non-radioactive stock.

  5. Tungsten isotope ratio determinations by negative thermal ionization mass spectrometry

    Microsoft Academic Search

    Joachim Völkening; Manfred Köppe; Klaus G. Heumann

    1991-01-01

    A precise determination of the isotopic abundances of tungsten with natural isotopic composition is presented. WO-3 ions are generated by negative thermal ionization (NTI) in a double-filament ion source. La2O3 is used as a chemical substance to reduce the electron work function of the rhenium filament material. An ionization efficiency of 1% is obtained for sample loadings of 100 ng.

  6. Biosynthesis of 15N3-labeled enniatins and beauvericin and their application to stable isotope dilution assays.

    PubMed

    Hu, Ling; Rychlik, Michael

    2012-07-25

    The first stable isotope dilution assay for the determination of enniatins A, A1, B, and B1 and beauvericin was developed. The (15)N(3)-labeled enniatins and beauvericin were biosynthesized by feeding two Fusarium strains Na(15)NO(3) and subsequently isolated from the fungal culture. The chemical structures of the biosynthesized products were characterized by LC-MS/MS and (1)H NMR. Standard solutions of (15)N(3)-labeled beauvericin, enniatin A, and enniatin A1 were accurately quantitated by quantitative NMR. On the basis of the use of the labeled products as internal standards, stable isotope dilution assays were developed and applied to various food samples using LC-MS/MS. The sample extracts were directly injected without any tedious cleanup procedures. The limits of detection were 3.9, 2.6, 3.7, 1.9, and 4.4 ?g/kg for enniatins A, A1, B, and B1 and beauvericin, respectively. Limits of quantitation were 11.5 (enniatin A), 7.6 (enniatin A1), 10.9 (enniatin B), 5.8 (enniatin B1), and 13.1 ?g/kg (beauvericin). Recoveries were within the range between 90 and 120%, and good intraday and interday precisions with coefficients of variation between 1.35 and 8.61% were obtained. Thus, the stable isotope dilution assay presented here is similarly sensitive and precise but more accurate than assays reported before. Analyses of cereals and cereal products revealed frequent contaminations of barley, wheat, rye, and oats with enniatins B and B1, whereas beauvericin was not quantifiable. PMID:22734473

  7. Determination of lead, uranium, thorium, and thallium in silicate glass standard materials by isotope dilution mass spectrometry

    USGS Publications Warehouse

    Barnes, I.L.; Garner, E.L.; Gramlich, J.W.; Moore, L.J.; Murphy, T.J.; Machlan, L.A.; Shields, W.R.; Tatsumoto, M.; Knight, R.J.

    1973-01-01

    A set of four standard glasses has been prepared which have been doped with 61 different elements at the 500-, 50-, 1-, and 0.02-ppm level. The concentrations of lead, uranium, thorium, and thallium have been determined by isotope dilution mass spectrometry at a number of points in each of the glasses. The results obtained from independent determinations in two laboratories demonstrate the homogeneity of the samples and that precision of the order of 0.5% (95% L.E.) may be obtained by the method even at the 20-ppb level for these elements. The chemical and mass spectrometric procedures necessary are presented.

  8. High-precision measurements of seawater Pb isotope compositions by double spike thermal ionization mass spectrometry.

    PubMed

    Paul, Maxence; Bridgestock, Luke; Rehkämper, Mark; van DeFlierdt, Tina; Weiss, Dominik

    2015-03-10

    A new method for the determination of seawater Pb isotope compositions and concentrations was developed, which combines and optimizes previously published protocols for the separation and isotopic analysis of this element. For isotopic analysis, the procedure involves initial separation of Pb from 1 to 2L of seawater by co-precipitation with Mg hydroxide and further purification by a two stage anion exchange procedure. The Pb isotope measurements are subsequently carried out by thermal ionization mass spectrometry using a (207)Pb-(204)Pb double spike for correction of instrumental mass fractionation. These methods are associated with a total procedural Pb blank of 28±21pg (1sd) and typical Pb recoveries of 40-60%. The Pb concentrations are determined by isotope dilution (ID) on 50mL of seawater, using a simplified version of above methods. Analyses of multiple aliquots of six seawater samples yield a reproducibility of about ±1 to ±10% (1sd) for Pb concentrations of between 7 and 50pmol/kg, where precision was primarily limited by the uncertainty of the blank correction (12±4pg; 1sd). For the Pb isotope analyses, typical reproducibilities (±2sd) of 700-1500ppm and 1000-2000ppm were achieved for (207)Pb/(206)Pb, (208)Pb/(206)Pb and (206)Pb/(204)Pb, (207)Pb/(204)Pb, (208)Pb/(204)Pb, respectively. These results are superior to literature data that were obtained using plasma source mass spectrometry and they are at least a factor of five more precise for ratios involving the minor (204)Pb isotope. Both Pb concentration and isotope data, furthermore, show good agreement with published results for two seawater intercomparison samples of the GEOTRACES program. Finally, the new methods were applied to a seawater depth profile from the eastern South Atlantic. Both Pb contents and isotope compositions display a smooth evolution with depth, and no obvious outliers. Compared to previous Pb isotope data for seawater, the (206)Pb/(204)Pb ratios are well correlated with (207)Pb/(206)Pb, underlining the significant improvement achieved in the measurement of the minor (204)Pb isotope. PMID:25732313

  9. On-line double isotope dilution laser ablation inductively coupled plasma mass spectrometry for the quantitative analysis of solid materials.

    PubMed

    Fernández, Beatriz; Rodríguez-González, Pablo; García Alonso, J Ignacio; Malherbe, Julien; García-Fonseca, Sergio; Pereiro, Rosario; Sanz-Medel, Alfredo

    2014-12-01

    We report on the determination of trace elements in solid samples by the combination of on-line double isotope dilution and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). The proposed method requires the sequential analysis of the sample and a certified natural abundance standard by on-line IDMS using the same isotopically-enriched spike solution. In this way, the mass fraction of the analyte in the sample can be directly referred to the certified standard so the previous characterization of the spike solution is not required. To validate the procedure, Sr, Rb and Pb were determined in certified reference materials with different matrices, including silicate glasses (SRM 610, 612 and 614) and powdered samples (PACS-2, SRM 2710a, SRM 1944, SRM 2702 and SRM 2780). The analysis of powdered samples was carried out both by the preparation of pressed pellets and by lithium borate fusion. Experimental results for the analysis of powdered samples were in agreement with the certified values for all materials. Relative standard deviations in the range of 6-21% for pressed pellets and 3-21% for fused solids were obtained from n=3 independent measurements. Minimal sample preparation, data treatment and consumption of the isotopically-enriched isotopes are the main advantages of the method over previously reported approaches. PMID:25440666

  10. Isotopic analysis of rhenium from a thermal ionization source

    Microsoft Academic Search

    G H Riley

    1967-01-01

    A review of the problems associated with thermal ionization of elements of high ionization potential is given. The development and performance of a simple, economical control circuit for pulse counting ion beams in a commercial 12 in. 90° mass spectrometer is discussed and an assessment of the errors involved in this mode of analysis is made.Past measurements of the isotopic

  11. Stable isotope dilution gas chromatography-mass spectrometry for quantification of thymoquinone in black cumin seed oil.

    PubMed

    Johnson-Ajinwo, Okiemute Rosa; Li, Wen-Wu

    2014-06-18

    Black cumin seed (Nigella sativa L.) is a widely used spice and herb, where thymoquinone (2-isopropyl-5-methyl-1,4-benzoquinone) is the major bioactive compound. Here, a stable isotope dilution (SID) gas chromatography-mass spectrometry (GC-MS) technique was developed for the quantification of thymoquinone. A doubly deuterated thymoquinone ([(2)H2]-thymoquinone) was synthesized for the first time with more than 93% deuteration degree shown by mass spectrometry and proton nuclear magnetic resonance ((1)H NMR). This compound was used as an internal standard for the quantification of thymoquinone using a SID GC-MS method. The validation experiment showed a recovery rate of 99.1 ± 1.1% relative standard deviation (RSD). Standard addition and external calibration methods have also been used to quantify thymoquinone, which cross-validated the developed stable isotope dilution assay (SIDA). In comparison to external calibration and standard addition methods, the SIDA method is robust and accurate. The concentration of thymoquinone in five marketed black cumin seed oils ranged between 3.34 and 10.8 mg/mL by use of SID GC-MS. PMID:24871868

  12. Pantothenic acid quantification by a stable isotope dilution assay based on liquid chromatography-tandem mass spectrometry.

    PubMed

    Rychlik, Michael

    2003-07-01

    A stable isotope dilution assay for the quantification of free and total pantothenic acid has been developed by using [13C3,15N]-pantothenic acid as the internal standard. The three-dimensional specificity of liquid chromatography-tandem mass spectrometry enabled unequivocal determination of the vitamin. Due to the very simple extraction and clean-up procedure, free pantothenic acid could be analysed within 2 h, which is much faster than by microbiological or gas chromatographic assays. For quantification of total pantothenic acid, the vitamin was liberated from its conjugates by an overnight incubation with pigeon liver pantetheinase and alkaline phosphatase. In analyses of corn flour, the intra-assay coefficient of variation was 8.5% (n = 5) and 15.3% (n = 4) for free and total pantothenic acid, respectively. When pantothenic acid was added to corn starch at a level of 6 mg kg(-1), a recovery of 97.5% was found. Application of the stable isotope dilution assay to whole egg powder, hazel nuts and corn revealed similar data compared to those listed in nutrition data bases, whereas the content in mushrooms and porcine liver determined by the newly developed assay appeared to be lower and that of cocoa higher than reported in the literature. PMID:12894818

  13. Existing and emerging technologies for measuring stable isotope labelled retinol in biological samples: isotope dilution analysis of body retinol stores.

    PubMed

    Preston, Tom

    2014-01-01

    This paper discusses some of the recent improvements in instrumentation used for stable isotope tracer measurements in the context of measuring retinol stores, in vivo. Tracer costs, together with concerns that larger tracer doses may perturb the parameter under study, demand that ever more sensitive mass spectrometric techniques are developed. GCMS is the most widely used technique. It has high sensitivity in terms of sample amount and uses high resolution GC, yet its ability to detect low isotope ratios is limited by background noise. LCMSMS may become more accessible for tracer studies. Its ability to measure low level stable isotope tracers may prove superior to GCMS, but it is isotope ratio MS (IRMS) that has been designed specifically for low level stable isotope analysis through accurate analysis of tracer:tracee ratios (the tracee being the unlabelled species). Compound-specific isotope analysis, where GC is interfaced to IRMS, is gaining popularity. Here, individual 13C-labelled compounds are separated by GC, combusted to CO2 and transferred on-line for ratiometric analysis by IRMS at the ppm level. However, commercially-available 13C-labelled retinol tracers are 2 - 4 times more expensive than deuterated tracers. For 2H-labelled compounds, GC-pyrolysis-IRMS has now become more generally available as an operating mode on the same IRMS instrument. Here, individual compounds are separated by GC and pyrolysed to H2 at high temperature for analysis by IRMS. It is predicted that GC-pyrolysis-IRMS will facilitate low level tracer procedures to measure body retinol stores, as has been accomplished in the case of fatty acids and amino acids. Sample size requirements for GC-P-IRMS may exceed those of GCMS, but this paper discusses sample preparation procedures and predicts improvements, particularly in the efficiency of sample introduction. PMID:25537104

  14. Systematic studies on the determination of Hg-labelled proteins using laser ablation-ICPMS and isotope dilution analysis.

    PubMed

    Kutscher, Daniel J; Fricker, Mattias B; Hattendorf, Bodo; Bettmer, Jörg; Günther, Detlef

    2011-11-01

    A method was developed for the precise and accurate determination of ovalbumin labelled with p-hydroxy-mercuribenzoic acid (pHMB) using polyacrylamide gel electrophoresis with ns-laser ablation-inductively coupled plasma mass spectrometry. Following systematic optimisation of the ablation process in terms of detection sensitivity, two different quantification strategies were applied: external calibration using standards of the derivatized protein after (13)C(+) normalization and, as a proof of concept, label-specific isotope dilution analysis (IDA) using pHMB enriched in the isotope (199)Hg. Due to the inhomogeneous distribution of the protein within the gel bands, it could be demonstrated that the IDA approach was superior in terms of precision and accuracy. Furthermore, it permits a reliable quantification, if more complex separation protocols are applied, as typically occurring analyte loss and degradation can be compensated for as soon as complete mixture of spike and sample is achieved. The estimated limit of detection was 160 fmol in the case of ovalbumin. In contrast to earlier studies using metals naturally present in proteins, no loss of mercury was observed during separation under denaturing conditions and other sample preparation steps. Using label-specific IDA, the measured isotope ratios in the gel corresponded to recoveries between 95% and 103%. PMID:21773737

  15. Isotope dilution analysis of polychlorinated biphenyls (PCBs) in transformer oil and global commercial PCB formulations by high resolution gas chromatography–high resolution mass spectrometry

    Microsoft Academic Search

    Takumi Takasuga; Kurunthachalam Senthilkumar; Tohru Matsumura; Ken Shiozaki; Shin-ichi Sakai

    2006-01-01

    Special polychlorinated biphenyls (PCBs) standards (native and isotope labeled) were analyzed by isotope dilution method using HRGC–HRMS. Multiple analysis of special PCBs standards by three different laboratories produced the relative response factors (RRFs) and relative standard deviations (RSDs %) was in the average of 0.979 and 3.86, respectively. Additionally, inter-laboratory analysis of various forms of transformer oil revealed the PCBs

  16. Short communication: milk output in llamas (Lama glama) in relation to energy intake and water turnover measured by an isotope dilution technique.

    PubMed

    Riek, A; Klinkert, A; Gerken, M; Hummel, J; Moors, E; Südekum, K-H

    2013-03-01

    Despite the fact that llamas have become increasingly popular as companion and farm animals in both Europe and North America, scientific knowledge on their nutrient requirements is scarce. Compared with other livestock species, relatively little is known especially about the nutrient and energy requirements for lactating llamas. Therefore, we aimed to measure milk output in llama dams using an isotope dilution technique and relate it to energy intakes at different stages of lactation. We also validated the dilution technique by measuring total water turnover (TWT) directly and comparing it with values estimated by the isotope dilution technique. Our study involved 5 lactating llama dams and their suckling young. Milk output and TWT were measured at 4 stages of lactation (wk 3, 10, 18, and 26 postpartum). The method involved the application of the stable hydrogen isotope deuterium ((2)H) to the lactating dam. Drinking water intake and TWT decreased significantly with lactation stage, whether estimated by the isotope dilution technique or calculated from drinking water and water ingested from feeds. In contrast, lactation stage had no effect on dry matter intake, metabolizable energy (ME) intake, or the milk water fraction (i.e., the ratio between milk water excreted and TWT). The ratios between TWT measured and TWT estimated (by isotope dilution) did not differ with lactation stage and were close to 100% in all measurement weeks, indicating that the D(2)O dilution technique estimated TWT with high accuracy and only small variations. Calculating the required ME intakes for lactation from milk output data and gross energy content of milk revealed that, with increasing lactation stage, ME requirements per day for lactation decreased but remained constant per kilogram of milk output. Total measured ME intakes at different stages of lactation were similar to calculated ME intakes from published recommendation models for llamas. PMID:23332845

  17. Direct determination of trace elements in powdered samples by in-cell isotope dilution femtosecond laser ablation ICPMS.

    PubMed

    Fernández, Beatriz; Claverie, Fanny; Pécheyran, Christophe; Alexis, Joel; Donard, Olivier F X

    2008-09-15

    A method has been developed for the direct and simultaneous multielement determination of Cu, Zn, Sn, and Pb in soil and sediment samples using femtosecond laser ablation inductively coupled plasma mass spectrometry (fs-LA-ICPMS) in combination with isotope dilution mass spectrometry (IDMS). The in-cell isotope dilution fs-LA-ICPMS method proposed in this work was based on the quasi-simultaneous ablation of the natural abundance sample and the isotopically enriched solid spike, which was performed using a high repetition rate laser and a fast scanning beam device in a combined manner. Both the sample preparation procedure and the total analysis time have been drastically reduced, in comparison with previous approaches, since a unique multielement isotopically enriched solid spike was employed to analyze different powdered samples. Numerous experimental parameters were carefully selected (e.g., carrier gas flow rate, inlet diameter of the ablation cell, sample translation speed, scanner speed, etc.) in order to ensure the complete mixing between the sample and the solid spike aerosols. The proposed in-cell fs-LA-ICP-IDMS method was tested for the analysis of two soil (CRM 142R, GBW-07405) and two sediment (PACS-2, IAEA-405) reference materials, and the analysis of Cu, Zn, Sn, and Pb yielded good agreement of usually not more than 10% deviation from the certified values and precisions of less than 15% relative standard deviation. Furthermore, the concentrations were in agreement not only with the certified values but also with those obtained by ICP-IDMS after the microwave-assisted digestion of the solid samples, demonstrating therefore that in-cell fs-LA-ICP-IDMS opens the possibility for accurate and precise determinations of trace elements in powdered samples reducing the total sample preparation time to less than 5 min. Additionally, scanning electron microscope measurements showed that the aerosol generated by in-cell fs-LA-ICP-IDMS predominantly consisted of linear agglomerates of small particles (in the order of few tens of nanometers) and a few large spherical particles with diameters below 225 nm. PMID:18714966

  18. Rapid simultaneous determination of dexamethasone and betamethasone in milk by liquid chromatography tandem mass spectrometry with isotope dilution.

    PubMed

    Li, Cun; Wu, Yinliang; Yang, Ting; Zhang, Yan

    2010-01-15

    A simple, sensitive and reliable analytical method for the rapid simultaneous determination of dexamethasone and betamethasone in milk by high performance liquid chromatography-negative electrospray ionization tandem mass spectrometry (HPLC-NESI-MS/MS) with isotope dilution was developed. Samples were directly purified through C(18) cartridge. Then the eluate was dried under nitrogen and residues were dissolved in mobile phase. Samples were analyzed by HPLC-MS/MS on a Hypercarb graphite column with a mixture of acetonitrile-water-formic acid as mobile phase. The samples were quantified using dexamethasone-D(4) as an internal standard. The procedure was validated according to the European Union regulation 2002/657/EC determining specificity, decision limit (CCalpha), detection capability (CCbeta), trueness, precision, linearity and stability. The method is demonstrated to be suitable for the determination of dexamethasone and betamethasone in milk. The total time required for the analysis of one sample was about 35 min. PMID:20015503

  19. Screening multimycotoxins in food-grade gums by stable isotope dilution and liquid chromatography/tandem mass spectrometry.

    PubMed

    Zhang, Kai; Wong, Jon W; Jia, Zhengwei; Vaclavikova, Marta; Trucksess, Mary W; Begley, Timothy H

    2014-01-01

    Stable isotope dilution with LC/MSIMS was used to determine the following 11 mycotoxins in food grade gums: aflatoxins B1, B2, G1, and G2; deoxynivalenol; fumonisins B1, B2, and B3; ochratoxin A; T-2 toxin; and zearalenone. Samples were fortified with 11 [13C]-uniformly labeled internal standard ([13C]-IS) mycotoxins that corresponded to the 11 target mycotoxins and extracted by acetonitrile-water (4 + 1, v/v), followed by LC/MS/MS analysis. Mycotoxins were quantitated with the fortified [13C]-IS in each sample. The average recoveries of aflatoxins B1, B2, G1, and G2 (1, 5, and 25 microg/kg); deoxynivalenol and fumonisins B1, B2, and B3 (25, 100, and 500 microg/kg); and ochratoxin A, T-2 toxin, and zearalenone (10, 50, and 250 microg/kg) ranged from 84 to 117% with RSDs less than 20%. Method-dependent LOQs were from 0.1 (aflatoxin B1) to 25 microg/kg (fumonisin B3). Among 20 market samples, aflatoxin B1 (< LOQ) was detected in a Guar gum and a Tragacanth gum, and zearalenone (6 +/- 0.6 microg/kg) was detected in a Xanthan gum. The detected mycotoxins were further confirmed by comparing their enhanced product ion spectra to those of reference standards. The single laboratory validated stable isotope dilution and LC/MSIMS method provides sufficient selectivity, sensitivity, accuracy, and reproducibility with a simple sample preparation to screen the 11 mycotoxins in gums. PMID:25051639

  20. Method for measurement of glucose enrichment in serum using isotope dilution mass spectrometry and its application for measurement of glucose kinetics

    SciTech Connect

    Dan, P.; Clemons, P.M.; Sperling, M.I.; Gelfand, M.J.; Chen, I.W.; Sperling, M.A.; Norman, E.J.

    1983-01-01

    An isotope dilution mass spectrometric method has been developed for kinetic studies of D-glucose in humans, using 6,6-dideuteroglucose as the internal standard. Glucose in plasma samples was purified by anion and cation exchange column chromatography after deproteinization and derivatized to ..cap alpha..-D-glucofuranose cyclic 1,2:3,5-bis (butylboronate)-6-acetate.

  1. Measurement of Niacin in a Variety of Food Samples by High Performance Liquid Chromatography-Stable Isotope Dilution Mass Spectrometry (AOAC Annual Meeting, Minneapolis, MN, Sept. 2006)

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The availability of deuterium-labeled nicotinic acid makes stable isotope dilution mass spectrometry (SIDMS) coupled with liquid chromatography (LC) an attractive option for the determination of the water-soluble B-vitamin, niacin, in food samples. We have developed a method based on AOAC Peer-Verif...

  2. COMPARISON OF ISOTOPE DILUTION WITH BIOIMPEDNACE SPECTROSCOPY AND ANTHROPOMETRY FOR ASSESSMENT OF BODY COMPOSITION IN ASYMPTOMAIC HIV-UNINFECTED BREASTFEEDING MOTHERS

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The effect of breastfeeding on the nutrition of HIV-infected (HIV+) mothers is unknown. Simple, valid methods are needed for body composition assessment of HIV+ women. We compared the ability of bioimpedance spectroscopy (BIS) and anthropometry with that of isotope dilution (2H20) to measure fat-...

  3. In vivo isotope-fractionation factors and the measurement of deuterium- and oxygen-18-dilution spaces from plasma, urine, saliva, respiratory water vapor, and carbon dioxide

    SciTech Connect

    Wong, W.W.; Cochran, W.J.; Klish, W.J.; Smith, E.O.; Lee, L.S.; Klein, P.D.

    1988-01-01

    In vivo isotope-fractionation factors were determined for hydrogen and oxygen between plasma water samples and samples of urine, saliva, respiratory water vapor, and carbon dioxide in 20 normal adults. The isotope-fractionation factors ranged from 0.944 to 1.039 for /sup 2/H in breath water vapor and for /sup 18/O in breath CO/sub 2/, respectively. When corrected for isotope fractionation, the /sup 2/H- and /sup 18/O-dilution spaces determined from urine, saliva, respiratory water, and CO/sub 2/ were within -0.10 +/- 1.09 kg (mean +/- SD, n = 60) and 0.04 +/- 0.68 kg (n = 80), respectively, of the values determined from plasma. In the absence of these corrections, we observed a 6% overestimation of /sup 2/H-dilution space and a 1% overestimation of /sup 18/O-dilution space from the use of respiratory water values. A 4% underestimation of the /sup 18/O-dilution space was observed for breath CO/sub 2/ without correction for isotope fractionation.

  4. In vivo isotope-fractionation factors and the measurement of deuterium- and oxygen-18-dilution spaces from plasma, urine, saliva, respiratory water vapor, and carbon dioxide.

    PubMed

    Wong, W W; Cochran, W J; Klish, W J; Smith, E O; Lee, L S; Klein, P D

    1988-01-01

    In vivo isotope-fractionation factors were determined for hydrogen and oxygen between plasma water samples and samples of urine, saliva, respiratory water vapor, and carbon dioxide in 20 normal adults. The isotope-fractionation factors ranged from 0.944 to 1.039 for 2H in breath water vapor and for 18O in breath CO2, respectively. When corrected for isotope fractionation, the 2H- and 18O-dilution spaces determined from urine, saliva, respiratory water, and CO2 were within -0.10 +/- 1.09 kg (mean +/- SD, n = 60) and 0.04 +/- 0.68 kg (n = 80), respectively, of the values determined from plasma. In the absence of these corrections, we observed a 6% overestimation of 2H-dilution space and a 1% overestimation of 18O-dilution space from the use of respiratory water values. A 4% underestimation of the 18O-dilution space was observed for breath CO2 without correction for isotope fractionation. PMID:3122550

  5. Probing the Structure of Water Molecules at an Oil/Water Interface in the Presence of a Charged Soluble Surfactant through Isotopic Dilution Studies

    E-print Network

    Richmond, Geraldine L.

    Soluble Surfactant through Isotopic Dilution Studies D. E. Gragson and G. L. Richmond* Department spectra of water molecules at an oil/water interface in the presence of a charged, soluble surfactant molecules in the bulk aqueous phase. The presence of a charged surfactant enhances the SF response in the OH

  6. Use of 15 N isotope dilution for quantification of N 2 fixation associated with roots of kallar grass ( Leptochloa fusca (L.))

    Microsoft Academic Search

    K. A. Malik; Y. Zafar; R. Bilal; E. Azam

    1987-01-01

    Leptochloa fusca (L.) Kunth (kallar grass) has previously been found to exhibit high rates of nitrogen fixation. A series of experiments to determine the level of biological nitrogen fixation using 15N isotopic dilution were carried out in nutrient solution and saline soil. In the nutrient solution, E. coli inoculated plants were taken as non-nitrogen-fixing control. It was observed that nearly

  7. Research recommendations for applying vitamin A-labelled isotope dilution techniques to improve human vitamin A nutrition.

    PubMed

    Tanumihardjo, Sherry A; Kurpad, Anura V; Hunt, Janet R

    2014-01-01

    The current use of serum retinol concentrations as a measurement of subclinical vitamin A deficiency is unsatisfactory for many reasons. The best technique available for vitamin A status assessment in humans is the measurement of total body pool size. Pool size is measured by the administration of retinol labelled with stable isotopes of carbon or hydrogen that are safe for human subjects, with subsequent measurement of the dilution of the labelled retinol within the body pool. However, the isotope techniques are time-consuming, technically challenging, and relatively expensive. There is also a need to assess different types of tracers and doses, and to establish clear guidelines for the use and interpretation of this method in different populations. Field-friendly improvements are desirable to encourage the application of this technique in developing countries where the need is greatest for monitoring the risk of vitamin A deficiency, the effectiveness of public health interventions, and the potential of hypervitaminosis due to combined supplement and fortification programs. These techniques should be applied to validate other less technical methods of assessing vitamin A deficiency. Another area of public health relevance for this technique is to understand the bioconversion of ?-carotene to vitamin A, and its relation to existing vitamin A status, for future dietary diversification programs. PMID:25537106

  8. Column chromatographic boron isotope separation at 5 and 17 MPa with diluted boric acid solution

    Microsoft Academic Search

    Masaaki Musashi; Takao Oi; Motoyuki Matsuo; Masao Nomura

    2008-01-01

    Boron isotopic fractionation factor (S) between boron taken up in strongly basic anion exchange resin and boron in aqueous solution was determined by breakthrough column chromatography at 5 and 17MPa at 25°C, using 0.1mM boric acid solution as feed solution. The S values obtained were 1.018 and 1.012, respectively, which were smaller than the value reported by using the same

  9. Comparison of thermal ionization mass spectrometry and Multiple Collector Inductively Coupled Plasma Mass Spectrometry for cesium isotope ratio measurements

    NASA Astrophysics Data System (ADS)

    Isnard, H.; Granet, M.; Caussignac, C.; Ducarme, E.; Nonell, A.; Tran, B.; Chartier, F.

    2009-11-01

    In the nuclear domain, precise and accurate isotopic composition determination of elements in spent nuclear fuels is mandatory to validate neutron calculation codes and for nuclear waste disposal. The present study presents the results obtained on Cs isotope ratio by mass spectrometric measurements. Natural cesium is monoisotopic ( 133Cs) whereas cesium in spent fuels has 4 isotopes ( 133Cs, 134Cs, 135Cs, and 137Cs). As no standard reference material is available to evaluate the accuracy of Cs isotopic measurements, a comparison of cesium isotopic composition in spent nuclear fuels has been performed between Thermal Ionization Mass Spectrometry (TIMS) and a new method involving Multiple Collector Inductively Coupled Plasma Mass Spectrometry (MC-ICPMS) measurements. For TIMS measurements, isotopic fractionation has been evaluated by studying the behavior of cesium isotope ratios ( 133Cs/ 137Cs and 135Cs/ 137Cs) during the analyses. For MC-ICPMS measurements, the mass bias effects have been corrected with an external mass bias correction using elements (Eu and Sb) close to cesium masses. The results obtained by the two techniques show good agreement: relative difference on 133Cs/ 137Cs and 135Cs/ 137Cs ratios for two nuclear samples, analyzed after chemical separation, ranges from 0.2% to 0.5% depending on the choice of reference value for mass bias correction by MC-ICPMS. Finally the quantification of the 135Cs/ 238U ratio by the isotope dilution technique is presented in the case of a MOx (mixed oxide) spent fuel sample. Evaluation of the global uncertainties shows that this ratio could be defined at an uncertainty of 0.5% ( k = 2). The intercomparison between two independent mass spectrometric techniques is fundamental for the evaluation of uncertainty when no isotopic standard is available.

  10. Evaluation of matrix effect in isotope dilution mass spectrometry based on quantitative analysis of chloramphenicol residues in milk powder.

    PubMed

    Li, Xiu Qin; Yang, Zong; Zhang, Qing He; Li, Hong Mei

    2014-01-01

    In the present study, we developed a comprehensive strategy to evaluate matrix effect (ME) and its impact on the results of isotope dilution mass spectrometry (IDMS) in analysis of chloramphenicol (CAP) residues in milk powder. Stable isotope-labeled internal standards do not always compensate ME, which brings the variation of the ratio (the peak area of analyte/the peak area of isotope). In our investigation, impact factors of this variation were studied in the extraction solution of milk powder using three mass spectrometers coupled with different ion source designs, and deuterium-labeled chloramphenicol (D5-CAP) was used as the internal standard. ME from mobile phases, sample solvents, pre-treatment methods, sample origins and instruments was evaluated, and its impact on the results of IDMS was assessed using the IDMS correction factor (?). Our data showed that the impact of ME of mobile phase on the correction factor was significantly greater than that of sample solvent. Significant ion suppression and enhancement effects were observed in different pre-treated sample solutions. The IDMS correction factor in liquid-liquid extraction (LLE) and molecular imprinted polymer (MIP) extract with different instruments was greater or less 1.0, and the IDMS correction factor in hydrophilic lipophilic balance (HLB) and mix-mode cation exchange (MCX) extract with different instruments was all close to 1.0. To the instrument coupled with different ion source design, the impact of ME on IDMS quantitative results was significantly different, exhibiting a large deviation of 11.5%. Taken together, appropriate chromatographic conditions, pre-treatment methods and instruments were crucial to overcome ME and obtain reliable results, when IDMS methods were used in the quantitative analysis of trace target in complex sample matrix. PMID:24356223

  11. Thermal neutron capture cross sections of the palladium isotopes

    SciTech Connect

    Krticka, M. [Charles University in Prague, Faculty of Mathematics and Physics, V Holesovickach 2, CZ-180 00 Prague 8 (Czech Republic); North Carolina State University, Raleigh, NC 27695 (United States); Firestone, R. B. [Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States); McNabb, D. P.; Sleaford, B.; Agvaanluvsan, U. [Lawrence Livermore National Laboratory, L-414, 7000 East Avenue, Livermore, CA 94551 (United States); Belgya, T.; Revay, Z. S. [Institute of Isotope and Surface Chemistry, H-1525, Budapest (Hungary)

    2008-05-15

    Precise thermal neutron capture {gamma}-ray cross sections {sigma}{sub {gamma}} were measured for all elements with Z=1-83,90, and 92, for He and Pm, at the Budapest Reactor. These data were evaluated with additional information from the literature to generate the Evaluated Gamma-ray Activation File (EGAF). Isotopic radiative neutron cross sections can be deduced from the total transition cross section feeding the ground state, {sigma}{sub 0}={sigma}{sigma}{sub {gamma}}(GS) if the decay scheme is complete. The EGAF file contains partial {gamma}-ray cross sections for all stable palladium isotopes. None of these decay schemes are complete, although in each case transitions de-exciting low-lying levels are known. We have performed Monte Carlo simulations of the palladium thermal neutron capture decay schemes using the computer code DICEBOX. The simulated populations of low low-lying levels are normalized to the measured {sigma}{sub {gamma}} values from EGAF and the total radiative neutron cross section {sigma}{sub 0} is obtained. The {sigma}{sub 0} values derived for the palladium isotopes agree well with previous measurements and were in several cases more precise. Complementary use of {gamma}-ray cross-section data and Monte Carlo calculations has proven effective in determining both the palladium total radiative cross sections and new nuclear structure information.

  12. Validation of a gas chromatography-mass spectrometry isotope dilution method for the determination of 2-butoxyethanol and other common glycol ethers in consumer products.

    PubMed

    Tokarczyk, Ryszard; Jiang, Ying; Poole, Gary; Turle, Richard

    2010-10-29

    A gas chromatography-mass spectrometry isotope dilution (GC-MS ID) method was developed and tested for the determination of 14 common glycol ethers in consumer products. Stable isotope labelled standards, 2-methoxyethanol-D(7) and 2-butoxyethanol-(13)C(2) (CDN isotopes) were employed to enhance the accuracy and precision of the glycol ethers determination. A 1000-fold sample dilution with methanol was applied to avoid column overload and contamination. At this dilution matrix effects were in most cases negligible and did not interfere with the analysis. The instrument detection limit (IDL) for analysed compounds varied from 0.01 to 1 ?g/mL; while the estimated limit of quantification (LoQ) varied between different glycol ethers from 0.02 to 3.4 ?g/mL. Calibration was tested in the range of 0.1-200 ?g/mL and showed that the linear fit is upheld from 0.1 to 10 ?g/mL, and extends beyond this range for some of the analytes. Recoveries of glycol ethers from products with different matrices were similar. The recoveries varied from 87% to 116% between the analysed compounds, while measurements precision varied between 2% and 14%. The method is applicable to products with glycol ether concentrations above 0.002-0.2% (w/w). The concentration range can be extended below the specified limits by decreasing the dilution factor; however, with lower dilution the sample matrix effect is expected to be stronger. Products with very high concentrations of glycol ether (>20%) may need to be further diluted prior to injection to avoid column overload. The method can be used for testing liquid and aerosol products designed for household use, such as cleaners, paints, solvents and paint stripers, for compliance and enforcement of regulations which limit glycol ethers content. PMID:20855078

  13. Characterising the exchangeability of phenanthrene associated with naturally occurring soil colloids using an isotopic dilution technique.

    PubMed

    Tavakkoli, Ehsan; Juhasz, Albert; Donner, Erica; Lombi, Enzo

    2015-04-01

    The association of polycyclic aromatic hydrocarbons (PAHs) with inorganic and organic colloids is an important factor influencing their bioavailability, mobility and degradation in the environment. Despite this, our understanding of the exchangeability and potential bioavailability of PAHs associated with colloids is limited. The objective of this study was to use phenanthrene as a model PAH compound and develop a technique using (14)C phenanthrene to quantify the isotopically exchangeable and non-exchangeable forms of phenanthrene in filtered soil water or sodium tetraborate extracts. The study was also designed to investigate the exchangeability of colloidal phenanthrene as a function of particle size. Our findings suggest that the exchangeability of phenanthrene in sodium tetraborate is controlled by both inorganic and organic colloids, while in aqueous solutions inorganic colloids play the dominant role (even though coating of these by organic matter cannot be excluded). Filter pore size did not have a significant effect on phenanthrene exchangeability. PMID:25689461

  14. Assessment of the amount of body water in the Red Knot (Calidris canutus): an evaluation of the principle of isotope dilution with H, O, and O as measured with laser spectrometry and isotope ratio mass spectrometry

    Microsoft Academic Search

    Erik R. T. Kerstel; Theunis A. J. Piersma; G. Jim Gessaman; Anne Dekinga; Harro A. J. Meijer; G. Henk Visser

    2006-01-01

    We have used the isotope dilution technique to study changes in the body composition of a migratory shorebird species (Red Knot, Calidris canutus) through an assessment of the amount of body water in it. Birds were quantitatively injected with a dose of water with elevated concentrations of H, O, and O. Thereafter, blood samples were taken and distilled. The resulting

  15. An accurate and transferable protocol for reproducible quantification of organic pollutants in human serum using direct isotope dilution mass spectrometry.

    PubMed

    Boggess, Andrew J; Rahman, G M Mizanur; Pamukcu, Matt; Faber, Scott; Kingston, H M Skip

    2014-12-01

    A robust method has been developed for easy transfer between analytical laboratories to obtain highly accurate and reproducible quantification of persistent organic pollutants (POPs) in micro-volumes of serum. This method is suited for analysts researching the impact of environmental exposure on human health. When performed by highly trained analysts, existing methods can produce high quality data; however, complex sample preparation steps often cannot be consistently replicated by laboratories, leading to variance in extraction recovery and quantitation. By combining stir-bar sorptive extraction (SBSE) with direct isotope dilution (D-ID) mass spectrometry quantification, a new analytical method was developed. The D-ID quantification significantly improved accuracy, corrected sample-to-sample irreproducibility, and reduced sample preparation time. Independent production of statistically identical data then confirmed transfer of the validated operating protocol to an off-site laboratory with different instrument models. SBSE performance was compared with industry-accepted extraction techniques. D-ID quantification was compared with peer-reviewed relative isotopic response factor (RF) quantification methods. Holding other variables constant, D-ID improved accuracy by 250% and precision by 300% compared with RF; SBSE improved accuracy by 37% compared to industry-accepted extraction methods. Limits of quantification of the analytes ranged from 60 pg g(-1) to 1 ?g g(-1). Protocol transfer exhibited <7% mean between-laboratory error and <2% mean within-laboratory RSD. These results indicate that a transferable method has been developed for academic, government, commercial, and clinical laboratories seeking to maximize throughput and improve quantitative validity. This validated method was applied in a recent clinical study to assess non-communicable disease in children in Pennsylvania, USA. PMID:25302342

  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. Stable-isotope dilution LC-ESI-MS/MS techniques for the quantification of total homocysteine in human plasma.

    PubMed

    Tomaiuolo, Michela; Vecchione, Gennaro; Margaglione, Maurizio; Pisanelli, Daniela; Grandone, Elvira

    2009-10-15

    Homocysteine is an endogenous sulphydryl aminoacid irreversibly catabolized by transsulfuration to cysteine or remethylated to methionine. Increased plasma levels of homocysteine are an independent risk factor for atherosclerosis and cardiovascular disease. Accurate and reliable quantification of this amino acid in plasma samples is essential in clinical practice to explore the presence of a hyperhomocysteinemia, for instance after an ischemic event, or to control a possible adjunctive risk factor in patients at higher risk. In this review, LC-ESI-MS/MS methods are discussed and compared with other analytical methods for plasma homocysteine. LC-ESI-MS/MS is a technique combining the physicochemical separation of liquid chromatography with the analysis of mass spectrometry. It is based on stable-isotope dilution and possesses inherent accuracy and precision. Quantitative analysis is achieved by using commercially available homocystine-d(8) as an internal standard. Taking advantage of the high sensitivity and specificity, approaches involving LC-ESI-MS/MS require less laborious sample preparation, no derivatization and produce reliable results. PMID:19651543

  18. Quantitation of glutathione and its oxidation products in erythrocytes by multiple-label stable-isotope dilution.

    PubMed

    Reinbold, Julia; Koehler, Peter; Rychlik, Michael

    2014-01-15

    A multiple-label stable isotope dilution assay for quantifying glutathione (GSH), glutathione disulfide (GSSG), and glutathione sulfonic acid in erythrocytes was developed. As the internal standards, [(13)C3,(15)N]glutathione, [(13)C4,(15)N2]glutathione disulfide, and [(13)C3,(15)N]glutathione sulfonic acid were used. Analytes and internal standards were detected by LC-MS/MS after derivatization of GSH with iodoacetic acid and dansylation of all compounds under study. The calibration functions for all analytes relative to their respective isotopologic standards revealed slopes close to 1.0 and negligible intercepts. As various labelings of the standards for GSH and GSSG were used, their simultaneous quantitation was possible, although GSH was partly oxidized to its disulfide during analysis. The degree of this artifact formation of GSSG was calculated from the abundance of the mixed disulfide formed from unlabeled GSH and its respective standard. Thus, the detected GSSG amount could be corrected for the artifact amount. In this way, the amount of GSSG in erythrocytes was found to be less than 0.5% of the GSH concentration. Similar to GSSG, the detected amount of glutathione sulfonic acid was found to be formed at least in part during the analytical process, but the degree could not be quantified. PMID:24120409

  19. Parkinson’s-Dementia Complex and Development of a New Stable Isotope Dilution Assay for BMAA Detection in Tissue

    PubMed Central

    Snyder, Laura R.; Cruz-Aguado, Reyniel; Sadilek, Martin; Galasko, Douglas; Shaw, Christopher A.; Montine, Thomas J.

    2009-01-01

    ?-Methylamino-L-alanine (BMAA) has been proposed as a global contributor to neurodegenerative diseases, including Parkinson-dementia complex (PDC) of Guam and Alzheimer’s disease (AD). The literature on the effects of BMAA is conflicting with some but not all in vitro data supporting a neurotoxic action, and experimental animal data failing to replicate the pattern of neurodegeneration of these human diseases, even at very high exposures. Recently, BMAA has been reported in human brain from individuals afflicted with PDC or AD. Some of the BMAA in human tissue reportedly is freely extractable (free) while some is protein-associated and liberated by techniques that hydrolyze the peptide bond. The latter is especially intriguing since BMAA is a non-proteinogenic amino acid that has no known tRNA. We attempted to replicate these findings with techniques similar to those used by others; despite more than adequate sensitivity, we were unable to detect free BMAA. Recently, using a novel stable isotope dilution assay we again were unable to detect free or protein-associated BMAA in human cerebrum. Here we review the development of our new assay for tissue detection of BMAA and show that we are able to detect free BMAA in liver but not cerebrum, nor do we detect any protein-associated BMAA in mice fed this amino acid. These studies demonstrate the importance of a sensitive and specific assay for tissue BMAA and seriously challenge the proposal that BMAA is accumulating in human brain. PMID:19716838

  20. Reliable quantitation of ?-hydroxyethoxyacetic acid in human urine by an isotope-dilution GC-MS procedure.

    PubMed

    Eckert, Elisabeth; Gries, Wolfgang; Göen, Thomas; Leng, Gabriele

    2013-09-15

    An analytical method for the determination of ?-hydroxyethoxyacetic acid (HEAA), the main urinary metabolite of 1,4-dioxane was developed and validated. The presented method involves liquid-liquid extraction of HEAA from the urine samples, followed by silylation and subsequent analytical separation and detection using GC-MS. The method is characterized by its simple and fast sample preparation in combination with a robust chromatography. The use of isotope dilution analysis enables an efficient compensation of matrix related effects and analyte losses due to sample workup. The excellent reliability and reproducibility of the method is demonstrated by the good accuracy and precision data. Within-day precision and day-to-day precision ranged from 0.6 to 1.2% and 1.5 to 2.6%, respectively. The mean relative recovery of the method was found to be 98-101%. The LOD and LOQ of HEAA were determined to be 0.2mg/L and 0.6mg/L, respectively. In summary, the presented analytical method is well suited to be used for routine biomonitoring of occupational exposure to 1,4-dioxane. PMID:23954659

  1. Development of an isotope dilution GC-MS procedure for the routine determination of creatinine in complex serum samples.

    PubMed

    Fernández-Fernández, Mario; González-Antuña, Ana; Rodríguez-González, Pablo; Añón Álvarez, M Elena; Álvarez, Francisco V; García Alonso, J Ignacio

    2014-04-20

    The accurate determination of creatinine in serum is essential for the diagnosis and treatment of kidney diseases. The determination of serum creatinine in clinical laboratories is routinely carried out by the Jaffe method or by enzymatic methods that may suffer from interferences. So, the development of reliable, fast and interference-free routine methods for complex serum samples is required. A fast method using isotope dilution mass spectrometry (IDMS) and gas chromatography mass spectrometry (GC-MS) was developed using minimally (13)C labeled creatinine analogs, multiple linear regression and rapid derivatization of creatinine with acetylacetone in 2 min by using focused microwave technology. The proposed method was validated with the analyses of two Certified Reference Materials (ERM-DA252a and ERM-DA253a) and compared with the Jaffe and enzymatic methods when analyzing real serum samples containing variable levels of bilirubin The proposed method is capable of providing accurate serum creatinine concentrations in less than 45 min from sample arrival to full data treatment and can be an alternative routine procedure for creatinine determinations in complex serum samples. PMID:24508629

  2. Parkinson-dementia complex and development of a new stable isotope dilution assay for BMAA detection in tissue

    SciTech Connect

    Snyder, Laura R. [Department of Chemistry, University of Washington, Seattle, WA (United States); Cruz-Aguado, Reyniel [Department of Ophthalmology and Visual Sciences, University of British Columbia, Vancouver, BC (Canada); Sadilek, Martin [Department of Chemistry, University of Washington, Seattle, WA (United States); Galasko, Douglas [Department of Neurosciences, University of California at San Diego, San Diego, CA (United States); Shaw, Christopher A. [Department of Ophthalmology and Visual Sciences, University of British Columbia, Vancouver, BC (Canada); Montine, Thomas J. [Department of Pathology, University of Washington, Seattle, WA 98104 (United States)], E-mail: tmontine@u.washington.edu

    2009-10-15

    {beta}-Methylamino-L-alanine (BMAA) has been proposed as a global contributor to neurodegenerative diseases, including Parkinson-dementia complex (PDC) of Guam and Alzheimer's disease (AD). The literature on the effects of BMAA is conflicting with some but not all in vitro data supporting a neurotoxic action, and experimental animal data failing to replicate the pattern of neurodegeneration of these human diseases, even at very high exposures. Recently, BMAA has been reported in human brain from individuals afflicted with PDC or AD. Some of the BMAA in human tissue reportedly is freely extractable (free) while some is protein-associated and liberated by techniques that hydrolyze the peptide bond. The latter is especially intriguing since BMAA is a non-proteinogenic amino acid that has no known tRNA. We attempted to replicate these findings with techniques similar to those used by others; despite more than adequate sensitivity, we were unable to detect free BMAA. Recently, using a novel stable isotope dilution assay, we again were unable to detect free or protein-associated BMAA in human cerebrum. Here we review the development of our new assay for tissue detection of BMAA and show that we are able to detect free BMAA in liver but not cerebrum, nor do we detect any protein-associated BMAA in mice fed this amino acid. These studies demonstrate the importance of a sensitive and specific assay for tissue BMAA and seriously challenge the proposal that BMAA is accumulating in human brain.

  3. Measurement of total body water in human infants using deuterium isotope dilution and nuclear magnetic resonance spectroscopy

    SciTech Connect

    Rebouche, C.J.; Pearson, G.A.; Serfass, R.E.; Roth, C.W.; Finley, J.W.

    1986-03-01

    Total body water (TBW) provides a useful measure of fat-free body mass. Deuterium (D) oxide isotope dilution is a useful method to determine TBW. Various techniques, including density, infrared absorption, mass spectrometry and gas chromatography have been employed to determine D enrichment in body fluids. Each of these methods requires extensive sample preparation (sublimation or distillation of the body fluid). The authors have employed nuclear magnetic resonance (NMR) spectroscopy to measure D enrichment in saliva and urine of human infants. No sample preparation was necessary. A standard (dg-t-butanol) was added to 0.5 ml of sample and D enrichment was measured using a JEOL FX-900 NMR spectrometer. Signal acquisition time was 4.7 min. Working range of D enrichment was 0.04-0.32 atom % D (corresponding to an oral dose of approximately 0.25-2.0 g D/sub 2/O/kg body weight). Coefficients of variation (c.v.) for saliva samples at 0.20 and 0.06 atom % enrichment were 1.97% and 4.78%, respectively. Mean (+/-SD) of TBW determinations for 6 infants was 58.5 +/- 5.4% of body weight (range 53-66%). Repeat measurements (3) of TBW for each infant at weekly intervals yielded a mean c.v. of 4.1% (n = 6). This method provides precise measurement of TBW without the extensive sample preparation requirements of previously-described methods.

  4. Sensitive isotope dilution liquid chromatography/electrospray ionization tandem mass spectrometry method for the determination of acrylamide in chocolate.

    PubMed

    Ren, Yiping; Zhang, Yu; Jiao, Jingjing; Cai, Zengxuan; Zhang, Ying

    2006-03-01

    Isotope dilution liquid chromatography coupled with electrospray ionization tandem mass spectrometry (LC-MS/MS) was applied to the quantification of acrylamide in chocolate matrixes (dark chocolate, milk chocolate, chocolate with nuts, chocolate with almonds, and chocolate with wheat best element). The method included defatting with petroleum ether, extracting with aqueous solution of 2 mol l(-1) sodium chloride and clean-up by solid-phase (SPE) with OASIS HLB 6 cm3 cartridges. Acrylamide was detected with an Atlantis dC18 5 microm 210 x 1.5 mm column using 10% methanol/0.1% formic acid in water as the mobile phase. The analytical method was in-house validated and good results were obtained with respect to repeatability (RSD < 3.5%) and recovery (86-93%), which fulfilled the requirements defined by European Union legislation. The acrylamide levels in chocolate were 23-537 microg kg(-1). Therefore, the method was successfully used for the quantitative analysis of acrlyamide in various chocolate products. PMID:16517524

  5. Isotopic fractionation of the major elements of molten basalt by chemical and thermal diffusion

    E-print Network

    Watkins, Jim

    by chemical diffusion between a natural basalt and rhyolite. The thermal isotopic fractionations for isotopes of the same element. The iron isotopic mea- surements of the basalt­rhyolite diffusion couple by chemical diffusion between molten basalt and rhyolite (Richter et al., 2003) and large fractionations

  6. Measurement of Ruminal Volatile Fatty Acid Production from Alfalfa Hay or Corn Silage Rations Using a Continuous Infusion Isotope Dilution Technique[1] and [2

    Microsoft Academic Search

    W. J. Esdale; G. A. Broderick; L. D. Satter

    1968-01-01

    A continuous infusion isotope dilution technique was used to measure ruminal volatile fatty acid (¥FA) production in a nonlactating cow. Equal portions of the daily ration of alfalfa hay (tI) or corn silage (S) were fed every hour. Daily dry matter (DM) intake was 3.9 kg of silage or 3.5 kg of the hay. Following a priming dose of acetate-l-l~C,

  7. Isotope Dilution Gas Chromatographic-Mass Spectrometric Method for the Determination of Unconjugated Lignans and Isoflavonoids in Human Feces, with Preliminary Results in Omnivorous and Vegetarian Women

    Microsoft Academic Search

    H. Adlercreutz; T. Fotsis; M. S. Kurzer; K. Wahala; T. Makela; T. Hase

    1995-01-01

    We describe an isotope dilution gas chromatographic-mass spectrometric (GC\\/MS) method for the identification and quantitative determination of the lignans enterolactone, enterodiol, and matairesinol and the isoflavonoids daidzein, equol, O-desmethylangolensin, and genistein in feces. Following the addition of deuterated internal standards for all compounds, the feces samples are extracted and purified in several ion exchange chromatographic steps. Following formation of trimethylsilyl

  8. The role of root-associated Klebsiella pneumoniae in the nitrogen nutrition of Poa pratensis and Triticum aestivum as estimated by the method of 15 N isotope dilution

    Microsoft Academic Search

    Kielo Haahtela; Kirsti Kari

    1986-01-01

    Summary  The technique of15N isotope dilution was used to verify that nitrogen was fixed and transferred to the plant byKlebsiella pneumoniae strain Pp in association withPoa pratensis orTriticum aestivum. Surface sterilized, sprouting seeds were inoculated withK. pneumoniae and grown in sand in modified Leonard jars. Potassium nitrate enriched with15N was used to provide N concentrations ranging from 10–40 mg Nl–1 nutrient

  9. Geochemical behaviour of Radium isotopes and Radon in a coastal thermal system (Balaruc-les-Bains, South of France)

    NASA Astrophysics Data System (ADS)

    Condomines, Michel; Gourdin, Elian; Gataniou, Delphine; Seidel, Jean-Luc

    2012-12-01

    The behaviour of the four Ra isotopes (measured by gamma spectrometry) and 222Rn (measured with an AlphaGUARD ionisation chamber) has been investigated in NaCl-rich thermal waters of Balaruc-les-Bains on the Mediterranean coast (South of France). This study allows identification of the deep thermal water signature and reveals the influence of seawater or karst water inflows on Ra isotopes and 222Rn. The deep thermal water has 226Ra and 222Rn activities of 840 and 1900 mBq/l, respectively, a (228Ra/226Ra) activity ratio of 0.59, and low (224Ra/228Ra) and (223Ra/226Ra) ratios of 0.67 and 0.025, respectively. Several arguments suggest a dominant role of radioactive decay for short-lived Ra isotopes and Rn during the relatively rapid ascent of thermal water through wide open fractures and drains. The low (223Ra/226Ra) ratio constrains the maximum ascent velocity of thermal water to 8-10 m/h. Seawater inflow into the hydrothermal system results in an enrichment in short-lived Ra isotopes and 222Rn. The high (223Ra/226Ra) ratio (0.23) suggests that 223Ra, 224Ra and 222Rn produced by alpha-recoil in the upper-Jurassic limestone are entrained by seawater percolation through the coastal basement, due to active pumping in one of the near shore production well. This process would be enhanced by a low water/rock ratio (i.e. in a low-porosity, micro-fractured limestone). Mixing of this enriched seawater with thermal water induces barite precipitation with co-precipitation of a large fraction of Ra. Short-lived Ra isotopes may thus be useful tracers of seawater flux towards the continent. Conversely, the inflow and mixing of karst groundwater result in a general dilution of all dissolved elements, only a small enrichment in 224Ra and 223Ra, but a large enrichment in 222Rn (up to 26 Bq/l). The combination of Ra isotopes and 222Rn data provides a good way to trace the dynamics of different water masses along coastal areas.

  10. Isotope Effect on the Thermal Conductivity of Boron Nitride Nanotubes C. W. Chang,1,5

    E-print Network

    Zettl, Alex

    Isotope Effect on the Thermal Conductivity of Boron Nitride Nanotubes C. W. Chang,1,5 A. M-dependent thermal conductivity T of individual multiwall boron nitride nanotubes using a microfabricated test. T is exceptionally sensitive to isotopic substitution, with a 50% enhancement in T resulting for boron nitride

  11. Tuning the thermal conductivity of silicene with tensile strain and isotopic doping: A molecular dynamics study

    NASA Astrophysics Data System (ADS)

    Pei, Qing-Xiang; Zhang, Yong-Wei; Sha, Zhen-Dong; Shenoy, Vivek B.

    2013-07-01

    Silicene is a monolayer of silicon atoms arranged in honeycomb lattice similar to graphene. We study the thermal transport in silicene by using non-equilibrium molecular dynamics simulations. We focus on the effects of tensile strain and isotopic doping on the thermal conductivity, in order to tune the thermal conductivity of silicene. We find that the thermal conductivity of silicene, which is shown to be only about 20% of that of bulk silicon, increases at small tensile strains but decreases at large strains. We also find that isotopic doping of silicene results in a U-shaped change of the thermal conductivity for the isotope concentration varying from 0% to 100%. We further show that ordered doping (isotope superlattice) leads to a much larger reduction in thermal conductivity than random doping. Our findings are important for the thermal management in silicene-based electronic devices and for thermoelectric applications of silicene.

  12. Determination of Glyphosate, its Degradation Product Aminomethylphosphonic Acid, and Glufosinate, in Water by Isotope Dilution and Online Solid-Phase Extraction and Liquid Chromatography/Tandem Mass Spectrometry

    USGS Publications Warehouse

    Meyer, Michael T.; Loftin, Keith A.; Lee, Edward A.; Hinshaw, Gary H.; Dietze, Julie E.; Scribner, Elisabeth A.

    2009-01-01

    The U.S. Geological Survey method (0-2141-09) presented is approved for the determination of glyphosate, its degradation product aminomethylphosphonic acid (AMPA), and glufosinate in water. It was was validated to demonstrate the method detection levels (MDL), compare isotope dilution to standard addition, and evaluate method and compound stability. The original method USGS analytical method 0-2136-01 was developed using liquid chromatography/mass spectrometry and quantitation by standard addition. Lower method detection levels and increased specificity were achieved in the modified method, 0-2141-09, by using liquid chromatography/tandem mass spectrometry (LC/MS/MS). The use of isotope dilution for glyphosate and AMPA and pseudo isotope dilution of glufosinate in place of standard addition was evaluated. Stable-isotope labeled AMPA and glyphosate were used as the isotope dilution standards. In addition, the stability of glyphosate and AMPA was studied in raw filtered and derivatized water samples. The stable-isotope labeled glyphosate and AMPA standards were added to each water sample and the samples then derivatized with 9-fluorenylmethylchloroformate. After derivatization, samples were concentrated using automated online solid-phase extraction (SPE) followed by elution in-line with the LC mobile phase; the compounds separated and then were analyzed by LC/MS/MS using electrospray ionization in negative-ion mode with multiple-reaction monitoring. The deprotonated derivatized parent molecule and two daughter-ion transition pairs were identified and optimized for glyphosate, AMPA, glufosinate, and the glyphosate and AMPA stable-isotope labeled internal standards. Quantitative comparison between standard addition and isotope dilution was conducted using 473 samples analyzed between April 2004 and June 2006. The mean percent difference and relative standard deviation between the two quantitation methods was 7.6 plus or minus 6.30 (n = 179), AMPA 9.6 plus or minus 8.35 (n = 206), and glufosinate 9.3 plus or minus 9.16 (n = 16). The analytical variation of the method, comparison of quantitation by isotope dilution and multipoint linear regressed standard curves, and method detection levels were evaluated by analyzing six sets of distilled-water, groundwater, and surface-water samples spiked in duplicate at 0.0, 0.05, 0.10 and 0.50 microgram per liter and analyzed on 6 different days during 1 month. The grand means of the normalized concentration percentage recovery for glyphosate, AMPA, and glufosinate among all three matrices and spiked concentrations ranged from 99 to 114 plus or minus 2 to 7 percent of the expected spiked concentration. The grand mean of the percentage difference between concentrations calculated by standard addition and linear regressed multipoint standard curves ranged from 8 to 15 plus or minus 2 to 9 percent for the three compounds. The method reporting levels calculated from all the 0.05- microgram per liter spiked samples were 0.02 microgram per liter for all three compounds. Compound stability experiments were conducted on 10 samples derivatized four times for periods between 136 to 269 days. The glyphosate and AMPA concentrations remained relatively constant in samples held up to 136 days before derivatization. The half life of glyphosate varied from 169 to 223 days in the underivatized samples. Derivatized samples were analyzed the day after derivitization, and again 54 and 64 days after derivatization. The derivatized samples analyzed at days 52 and 64 were within 20 percent of the concentrations of the derivatized samples analyzed the day after derivatization.

  13. Sulphur Speciation and Turnover in Soils: Evidence from Sulphur K-Edge XANES Spectroscopy and Isotope Dilution Studies

    SciTech Connect

    Zhao,F.; Lehmann, J.; Solomon, D.; Fox, M.; McGrath, S.

    2005-01-01

    Sulphur K-edge X-ray absorption near edge structure (XANES) spectroscopy was used to quantify S species in humic substance extracts from ten soils from the UK, China and New Zealand, which differ in land use and agricultural management. XANES spectroscopy showed the presence of most reduced (sulphides, disulphides, thiols and thiophenes), intermediate (sulphoxides and sulphonates) and highly oxidised S (ester sulphates) forms, with the three groups representing 14-32%, 33-50% and 22-53% of the organic S in the humic substance extracts, respectively. Land use had a profound influence on the relative proportions of S species. Well-drained arable soils generally had a higher proportion of organic S present in the most oxidised form than the grassland soils collected nearby, whereas paddy soils showed a more reduced profile due to episodic flooding. In the Broadbalk Classical Experiment at Rothamsted, reversion of an arable system to grassland or woodland in the 1880s resulted in an increase of the most reduced and intermediate S species at the expense of the most oxidised S species. Long-term applications of farmyard manure to an arable plot also shifted S species from the most oxidised to the intermediate and the most reduced species. Sulphur immobilization and gross mineralization were determined in seven soils using the {sup 35}S isotope dilution method. Gross mineralization during a 53-day incubation correlated more closely with the amounts of the most reduced and intermediate S species than with the most oxidised S species, suggesting that the former (C-bonded S) were the main source of organic S for mineralization in the short-term.

  14. Sulphur Speciation and Turnover in Soils: Evidence from Sulfur K-Edge XANES Spectroscopy and Isotope Dilution Studies

    SciTech Connect

    Zhao,F.; Lehmann, J.; Solomon, D.; Fox, M.; McGrath, S.

    2006-01-01

    Sulphur K-edge X-ray absorption near edge structure (XANES) spectroscopy was used to quantify S species in humic substance extracts from ten soils from the UK, China and New Zealand, which differ in land use and agricultural management. XANES spectroscopy showed the presence of most reduced (sulphides, disulphides, thiols and thiophenes), intermediate (sulphoxides and sulphonates) and highly oxidised S (ester sulphates) forms, with the three groups representing 14-32%, 33-50% and 22-53% of the organic S in the humic substance extracts, respectively. Land use had a profound influence on the relative proportions of S species. Well-drained arable soils generally had a higher proportion of organic S present in the most oxidised form than the grassland soils collected nearby, whereas paddy soils showed a more reduced profile due to episodic flooding. In the Broadbalk Classical Experiment at Rothamsted, reversion of an arable system to grassland or woodland in the 1880s resulted in an increase of the most reduced and intermediate S species at the expense of the most oxidised S species. Long-term applications of farmyard manure to an arable plot also shifted S species from the most oxidised to the intermediate and the most reduced species. Sulphur immobilisation and gross mineralisation were determined in seven soils using the {sup 35}S isotope dilution method. Gross mineralisation during a 53-day incubation correlated more closely with the amounts of the most reduced and intermediate S species than with the most oxidised S species, suggesting that the former (C-bonded S) were the main source of organic S for mineralisation in the short-term.

  15. An Isotope Dilution Method for High-frequency Measurements of Dissolved Inorganic Carbon concentration in the Surface Ocean

    NASA Astrophysics Data System (ADS)

    Huang, K.; Bender, M. L.; Wanninkhof, R. H.; Cassar, N.

    2013-12-01

    Dissolved inorganic carbon (DIC) is one of the most important species in the ocean carbon system. An autonomous system using isotope dilution as its core method has been developed to obtain high-frequency measurements of dissolved inorganic carbon (DIC) concentrations in the surface ocean. This system accurately mixes a seawater sample and a 13C-labeled sodium bicarbonate solution (spike). The mixed solution is then acidified and sent through a gas permeable membrane contactor. CO2 derived from DIC in the mixture is extracted by a CO2-free gas stream, and is sent to a cavity ring-down spectrometer to analyze its 13C/12C ratio. [DIC] of the seawater can then be derived from the measured 13C/12C, the known mixing ratio and the [DI13C] of the spike. The method has been tested under a wide [DIC] range (1800-2800 ?mol/kg) in the laboratory. It has also been deployed on a cruise that surveyed ocean waters to the south of Florida. At a sampling resolution of 4 minutes (15 samples per hour), the relative standard deviation of DIC determined from the laboratory tests and the field deployment is ×0.07% and ×0.09%, respectively. The accuracy of the method is better than 0.1% except where [DIC] varies faster than 5 ?mol/kg per minute. Based on the laboratory and field evaluations, we conclude that this method can provide accurate underway [DIC] measurements at high resolution in most oceanic regions. Schematic illustration of the work flow.

  16. Studies of transport and collection characteristics of gaseous mercury in natural gases using amalgamation and isotope dilution analysis.

    PubMed

    Larsson, Tom; Frech, Wolfgang; Björn, Erik; Dybdahl, Björn

    2007-06-01

    Transport and collection characteristics were studied for gaseous elemental mercury (Hg(0)(g)) in natural gases using newly developed methodology based on amalgamation, isotope dilution with permeation tubes and inductively coupled plasma mass spectrometry. The study involved different Au-Pt collection tube designs, tubing materials and gaseous matrices, including air, natural and sales gas, as well as methane and sales gas to which hydrogen sulfide (H(2)S) had been added. The Hg(0)(g) capacity of the Au-Pt tubes was determined to 3.5 +/- 0.1 microg. Blanks and detection limits of gaseous mercury (Hg(g)) were 58 +/- 17 pg m(-3) and 50 pg m(-3), respectively, for a 60 L sample volume. For the gases tested, added Hg(0)(g) tracers could be collected with 90% or higher efficiency at flow rates and volumes of up to 10 L min(-1) and 100 L, respectively. The collection efficiency was found to be independent of the type of gas tested, even in the presence of H(2)S. However, for the gases containing H(2)S, the apparent transport efficiency of added Hg(0)(g) tracers through stainless steel tubing varied from 50 to 150% upon changing the temperature from 25 to 100 degrees C. The interaction of stainless steel with Hg(0)(g) leading to either a sink, or source of Hg, was not observed in the absence of H(2)S, nor was it observed for PTFE tubing in the presence of H(2)S. These observations raise questions about the applicability of currently used sampling procedures for determination of Hg(g) in H(2)S rich natural gases, including the 6978-2 ISO standard method, in which stainless steel is a prescribed material for tubing and valves of the sampling apparatus. PMID:17525816

  17. Characterization of candidate reference materials for bone lead via interlaboratory study and double isotope dilution mass spectrometry

    PubMed Central

    Bellis, David J.; Hetter, Katherine M.; Verostek, Mary Frances; Parsons, Patrick J.

    2012-01-01

    Summary Four candidate ground bone reference materials (NYS RMs 05-01 through 04), were produced from lead-dosed bovine and caprine sources, and characterized by interlaboratory study. The consensus value ( X ) and expanded standard uncertainty (UX ) were determined from the robust average and standard deviation of the participants’ data for each NYS RM 05-01 through 04. The values were 1.08 ±0.04, 15.3 ±0.5, 12.4 ±0.5, and 29.9 ±1.1 ?g g?1 Pb, respectively. Youden plots of z-scores showed a statistically significant correlation between the results for pairs of NYS RM 05-02 through 04, indicating common sources of between-laboratory variation affecting reproducibility. NYS RM 05-01 exhibited more random variability affecting repeatability at low concentration. Some participants using electrothermal atomic absorption spectrometry (ETAAS) exhibited a negative bias compared to the all-method consensus value. Other methods used included inductively coupled plasma mass spectrometry (ICP-MS), isotope dilution (ID-) ICP-MS, and ICP atomic (optical) emission spectroscopy (-OES). The NYS RMs 05-01 through 04 were subsequently re-analyzed in house using double ID-ICP-MS to assign certified reference values (C ) and expanded uncertainty (UC ) of 1.09 ± 0.03, 16.1 ± 0.3, 13.2 ± 0.3 and 31.5 ± 0.7, respectively, indicating a low bias in the interlaboratory data. SRM 1486 Bone Meal was analyzed for measurement quality assessment obtaining results in agreement with the certified values within the stated uncertainty. Analysis using a primary reference method based on ID-ICP-MS with full quantification of uncertainty calculated according to ISO guidelines provided traceability to SI units. PMID:23087531

  18. Application of the total evaporation technique to chromium isotope ratio measurement by thermal ionization mass spectrometry.

    PubMed

    Fujii, Toshiyuki; Suzuki, Daisuke; Watanabe, Kazuo; Yamana, Hajimu

    2006-03-15

    The total evaporation technique of thermal ionization mass spectrometry was applied to the isotopic analysis of chromium. High measurement reproducibility of the chromium isotope ratios was verified (2 S.E.<0.05% ((53)Cr/(52)Cr)), while a clear mass fractionation effect was observed by using conventional measurement technique. The chromium isotope ratios analyzed by the total evaporation method were not affected by the sample amount on the rhenium filament (50-500 ng Cr). The isotopic analysis under the coexistence of zinc was also performed, and its effect to the chromium isotope ratios was confirmed. PMID:18970527

  19. Effect of isotopic purity on thermal conductivity of boron nitride: A theoretical study

    NASA Astrophysics Data System (ADS)

    Barman, Saswati

    2011-10-01

    In this letter we report the theoretical study of the effect of isotopic purity on the temperature dependence of the lattice thermal conductivity of cubic BN single crystals. The maximum thermal conductivity of pure BN is very high (~105 W/m/K) and it is comparable to the thermal conductivity of the carbon nanotube. It is two orders of magnitude higher than that of BN with 50%10B. We find that the very high contribution (~ 95%) of the usually neglected N-drift scattering at the thermal conductivity peak is the reason for such an increase in thermal conductivity of pure BN, compared to that of natural BN. The thermal conductivity is nearly symmetric with respect to the isotopic composition of boron and it is minimum for 50%10B and 50%11B. The role of phonon scattering by boron isotopes present in BN, in controlling the temperature dependence of thermal conductivity has been accurately quantified.

  20. New method for caffeine quantification by planar chromatography coupled with electropray ionization mass spectrometry using stable isotope dilution analysis.

    PubMed

    Aranda, Mario; Morlock, Gertrud

    2007-01-01

    A new high-performance thin-layer chromatography/electrospray ionization mass spectrometry (HPTLC/ESI-MS) method for the quantification of caffeine in pharmaceutical and energy drink samples was developed using stable isotope dilution analysis (SIDA). After sample preparation, samples and caffeine standard were applied on silica gel 60 F254 HPTLC plates and over-spotted with caffeine-d3 used for correction of the plunger positioning. After chromatography, densitometric detection was performed by UV absorption at 274 nm. The bands were then eluted by means of a plunger-based extractor into the ESI interface of a single-quadrupole mass spectrometer. For quantification by MS the [M+H]+ ions of caffeine and caffeine-d3 were recorded in the positive ion single ion monitoring (SIM) mode at m/z 195 and 198, respectively. The calibration showed a linear regression with a determination coefficient (R2) of 0.9998. The repeatability (RSD, n=6) in matrix was

  1. Determination of cellular redox status by stable isotope dilution liquid chromatography/mass spectrometry analysis of glutathione and glutathione disulfide.

    PubMed

    Zhu, Peijuan; Oe, Tomoyuki; Blair, Ian A

    2008-01-01

    Oxidation of glutathione (GSH) to glutathione disulfide (GSSG) occurs during cellular oxidative stress. The redox potential of the 2GSH/GSSG couple, which is determined by the Nernst equation, provides a means to assess cellular redox status. It is difficult to accurately quantify GSH and GSSG due to the ease with which GSH is oxidized to GSSG during sample preparation. To overcome this problem, a stable isotope dilution liquid chromatography/multiple reaction monitoring mass spectrometry (LC/MRM-MS) method has been developed using 4-fluoro-7-sulfamoylbenzofurazan (ABD-F) derivatization. ABD-F derivatization of the GSH thiol group was rapid, quantitative, and occurred at room temperature. The LC/MRM-MS method, which requires no sample clean-up, was validated within the calibration ranges of 5 to 400 nmol/mL in cell lysates for GSH and 0.5 to 40 nmol/mL in cell lysates for GSSG. Calibration curves prepared by adding known concentrations of GSH and GSSG to cell lysates were parallel to the standard curve prepared in buffers. GSH and GSSG concentrations were determined in two monocyte/macrophage RAW 267.4 cell lines with or without 15-LOX-1 expression (R15LO and RMock cells, respectively) after treatment with the bifunctional electrophile 4-oxo-2(E)-nonenal (ONE). R15LO cells synthesized much higher concentrations of the lipid hydroperoxide, 15(S)-hydroperoxyeicosatetraenoic acid (15-HPETE), which undergoes homolytic decomposition to ONE. GSH was depleted by ONE treatment in both RMock and R15LO cells, leading to significant increases in their redox potentials. However, R15LO cells had higher GSH concentrations (most likely through increased GSH biosynthesis) and had increased resistance to ONE-mediated GSH depletion than RMock cells. Consequently, R15LO cells had lower reduction potentials at all concentrations of ONE. GSSG concentrations were higher in R15LO cells after ONE treatment when compared with the ONE-treated RMock cells. This suggests that increased expression of 15(S)-HPETE modulates the activity of cellular GSH reductases or the transporters involved in removal of GSSG. PMID:18215009

  2. Isotopic Characteristics of Thermal Fluids from Mexican Subduction Zone

    NASA Astrophysics Data System (ADS)

    Taran, Y.; Inguaggiato, S.

    2007-05-01

    Chemical (major and trace elements) and isotopic (H,O,N,C,He) composition of waters and gases from thermal springs and geothermal wells of Mexican subduction zone have been measured. Three main geochemical profiles have been realized: (1) along the frontal Trans-Mexican Volcanic Belt (TMVB) zone through high- temperature Acoculco, Los Humeros, Los Azufres and La Primavera hydrothermal systems, Colima and Ceboruco volcanoes; (2) along the for-arc region of Pacific coast (12 groups of hot springs); (3) across the zone, from Pacific coast to TMVB, through the Jalisco Block. Fluids from El Chichon volcano in Chiapanecan arc system and Tacana volcano from the Central America Volcanic Arc have also been sampled. The frontal zone of TMVB is characterized by high 3He/4He ratios, from 7.2Ra in Ceboruco fumaroles to 7.6Ra in gases from Acoculco and Los Humeros calderas (Ra is atmospheric value of 1.4x10-6). These values are significantly higher than those published earlier in 80-s (up to 6.8Ra). Gases from coastal springs are low in 3He, usually < 1Ra with a minimum value of 0.2Ra in the northernmost submarine Punta Mita hot springs and a maximum value of 2.4Ra in La Tuna springs at the southern board of the Colima graben. An important feature of the TMVB thermal fluids is the absence of excess nitrogen in gases and, as a consequence, close to zero d15N values. In contrast, some coastal for-arc gases and gases from the Jalisco Block have high N2/Ar ratios and d15N up to +5 permil. Isotopic composition of carbon of CO2 along TMVB is close to typical "magmatic" values from -3 permil to -5 permil, but d13C of methane varies significantly indicating multiple sources of CH4 in geothermal fluids and a partial temperature control. High 3He/4He ratios and pure atmospheric nitrogen may indicate a low contribution of subducted sediments into the TMVB magmas and magmatic fluids. In contrast, El Chichon and Tacana fluids show some excess nitrogen (N2/Ar up to 500) and variable d15N, but quite different 3He/4He (up to 8.1Ra at El Chichon and <6.5Ra at Tacana). The data obtained are discussed in terms of the volatile budget of Mexican subduction zone and the local water-rock interaction.

  3. New commercial method for the enzymatic determination of creatinine in serum and urine evaluated: Comparison with a kinetic Jaffe method and isotope dilution-mass spectrometry

    SciTech Connect

    Lindbaeck, B.B.; Bergman, A.

    1989-05-01

    We evaluated a new, simple, enzymatic kinetic method from Wako Chemicals GmbH in comparison with a kinetic Jaffe method by using isotope dilution-mass spectrometry (ID-MS) as a reference method. An ID-MS-calibrated serum standard was used. Both the enzymatic and the Jaffe method correlated well with ID-MS, except for sera with high concentrations of bilirubin. Ethyl acetoacetate, acetone, and glucose in serum interfered somewhat with the Jaffe method but not with the enzymatic method. We conclude that the present enzymatic method has merit as compared with a Jaffe method for routine work, but is more expensive.

  4. Liquid-phase thermal diffusion isotope separation apparatus and method having tapered column

    DOEpatents

    Rutherford, William M. (Dayton, OH)

    1988-05-24

    A thermal diffusion counterflow method and apparatus for separating isotopes in solution in which the solution is confined in a long, narrow, vertical slit which tapers from bottom to top. The variation in the width of the slit permits maintenance of a stable concentration distribution with relatively long columns, thus permitting isotopic separation superior to that obtainable in the prior art.

  5. Elemental analyses of soil and sediment fused with lithium borate using isotope dilution laser ablation-inductively coupled plasma-mass spectrometry.

    PubMed

    Malherbe, Julien; Claverie, Fanny; Alvarez, Aitor; Fernandez, Beatriz; Pereiro, Rosario; Molloy, John L

    2013-09-01

    Quantitative analysis using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) remains challenging primarily due to the lack of appropriate reference materials available for the wide variety of samples of interest and to elemental fractionation effects. Isotopic dilution mass spectrometry (IDMS) is becoming the methodology of choice to address these issues because the different isotopes of an element represent near-perfect internal standards. In this work, we investigated the lithium borate fusion of powdered solid samples, including soils, sediments, rock mine waste and a meteorite, as a strategy to homogenously distribute, i.e. equilibrate the elements and the added isotopically enriched standards. A comparison of this methodology using two pulsed laser ablation systems (ArF* excimer and Nd:YAG) with different wavelengths as well as two ICP-MS instruments (quadrupole and double-focusing sector field) was performed. Emphasis was put on using standard equipment to show the potential of the proposed strategy for its application in routine laboratories. Cr, Zn, Ba, Sr and Pb were successfully determined by LA-ICP-IDMS in six Standard Reference Materials (SRMs) representing different matrices of environmental interest. Experimental results showed the SRM fused glasses exhibited a low level of heterogeneity (intra- and inter-sample) for both natural abundance and isotopically enriched samples (RSD <3%, n=3, 1?). A good agreement between experimental results and the certified values was also observed. PMID:23953208

  6. Determination of the alkylpyrazine composition of coffee using stable isotope dilution-gas chromatography-mass spectrometry (SIDA-GC-MS).

    PubMed

    Pickard, Stephanie; Becker, Irina; Merz, Karl-Heinz; Richling, Elke

    2013-07-01

    A stable isotope dilution analysis based on gas chromatography-mass spectrometry analysis (SIDA-GC-MS) was developed for the quantitative analysis of 12 alkylpyrazines found in commercially available coffee samples. These compounds contribute to coffee flavor. The accuracy of this method was tested by analyzing model mixtures of alkylpyrazines. Comparisons of alkylpyrazine-concentrations suggested that water as extraction solvent was superior to dichloromethane. The distribution patterns of alkylpyrazines in different roasted coffees were quite similar. The most abundant alkylpyrazine in each coffee sample was 2-methylpyrazine, followed by 2,6-dimethylpyrazine, 2,5-dimethylpyrazine, 2-ethylpyrazine, 2-ethyl-6-methylpyrazine, 2-ethyl-5-methylpyrazine, and 2,3,5-trimethylpyrazine, respectively. Among the alkylpyrazines tested, 2,3-dimethylpyrazine, 2-ethyl-3-methylpyrazine, 2-ethyl-3,6-dimethylpyrazine, and 2-ethyl-3,5-dimethylpyrazine revealed the lowest concentrations in roasted coffee. By the use of isotope dilution analysis, the total concentrations of alkylpyrazines in commercially available ground coffee ranged between 82.1 and 211.6 mg/kg, respectively. Decaffeinated coffee samples were found to contain lower amounts of alkylpyrazines than regular coffee samples by a factor of 0.3-0.7, which might be a result of the decaffeination procedure. PMID:23745606

  7. Determination of trace sulfur in biodiesel and diesel standard reference materials by isotope dilution sector field inductively coupled plasma mass spectrometry.

    PubMed

    Amais, Renata S; Long, Stephen E; Nóbrega, Joaquim A; Christopher, Steven J

    2014-01-01

    A method is described for quantification of sulfur at low concentrations on the order of mgkg(-1) in biodiesel and diesel fuels using isotope dilution and sector field inductively coupled plasma mass spectrometry (ID-SF-ICP-MS). Closed vessel microwave-assisted digestion was employed using a diluted nitric acid and hydrogen peroxide decomposition medium to reduce sample dilution volumes. Medium resolution mode was employed to eliminate isobaric interferences at (32)S and (34)S related to polyatomic phosphorus and oxygen species, and sulfur hydride species. The method outlined yielded respective limits of detection (LOD) and limits of quantification (LOQ) of 0.7 mg kg(-1) S and 2.5 mg kg(-1) S (in the sample). The LOD was constrained by instrument background counts at (32)S but was sufficient to facilitate value assignment of total S mass fraction in NIST SRM 2723b Sulfur in Diesel Fuel Oil at 9.06±0.13 mg kg(-1). No statistically significant difference at a 95% confidence level was observed between the measured and certified values for certified reference materials NIST SRM 2773 B100 Biodiesel (Animal-Based), CENAM DRM 272b and NIST SRM 2723a Sulfur in Diesel Fuel Oil, validating method accuracy. PMID:24331043

  8. Thermal neutron capture cross sections of the potassium isotopes

    NASA Astrophysics Data System (ADS)

    Firestone, R. B.; Krti?ka, M.; Révay, Zs.; Szentmiklosi, L.; Belgya, T.

    2013-02-01

    Precise thermal neutron capture ?-ray cross sections ?? for 39,40,41K were measured on a natural potassium target with the guided neutron beam at the Budapest Reactor. The cross sections were internally standardized using a stoichiometric KCl target with well-known 35Cl(n,?) ?-ray cross sections [Révay and Molnár, Radiochimica ActaRAACAP0033-823010.1524/ract.91.6.361.20027 91, 361 (2003); Molnár, Révay, and Belgya, Nucl. Instrum. Meth. Phys. Res. BNIMBEU0168-583X10.1016/S0168-583X(03)01529-5 213, 32 (2004)]. These data were combined with ?-ray intensities from von Egidy [von Egidy, Daniel, Hungerford, Schmidt, Lieb, Krusche, Kerr, Barreau, Borner, Brissot , J. Phys. G. Nucl. Phys.JPHGBM0305-461610.1088/0305-4616/10/2/013 10, 221 (1984)] and Krusche [Krusche, Lieb, Ziegler, Daniel, von Egidy, Rascher, Barreau, Borner, and Warner, Nucl. Phys. ANUPABL0375-947410.1016/0375-9474(84)90506-2 417, 231 (1984); Krusche, Winter, Lieb, Hungerford, Schmidt, von Egidy, Scheerer, Kerr, and Borner, Nucl. Phys. ANUPABL0375-947410.1016/0375-9474(85)90429-4 439, 219 (1985)] to generate nearly complete capture ?-ray level schemes. Total radiative neutron cross sections were deduced from the total ?-ray cross section feeding the ground state, ?0=???(GS) after correction for unobserved statistical ?-ray feeding from levels near the neutron capture energy. The corrections were performed with Monte Carlo simulations of the potassium thermal neutron capture decay schemes using the computer code dicebox where the simulated populations of low-lying levels are normalized to the measured cross section depopulating those levels. Comparisons of the simulated and experimental level feeding intensities have led to proposed new spins and parities for selected levels in the potassium isotopes where direct reactions are not a significant contribution. We determined the total radiative neutron cross sections ?0(39K)=2.28±0.04 b, ?0(40K)=90±7 b, and ?0(41K)=1.62±0.03 b from the prompt ?-ray data and the ?-ray transition probability P?(1524.66)=0.164(4) in the ?- decay of 42K in a low-background counting experiment.

  9. Non-thermal plasma processing for environmental protection: decomposition of dilute VOCs in air

    Microsoft Academic Search

    T. Oda

    2003-01-01

    Non-thermal plasma processing is one of the most hopeful air-cleaning technologies to remove toxic gas contaminants in air. The historical background of the non-thermal plasma related with the electrostatics is described and the fundamental experimental system including the reactor designs and their power supplies is introduced. Some experimental results suggested the high potential of the plasma processing to decompose those

  10. A novel sample decomposition technique at atmospheric pressure for the determination of Os abundances in iron meteorites using isotope dilution inductively coupled plasma-mass spectrometry.

    PubMed

    Hattori, M; Hirata, T

    2001-06-01

    A safe and reliable analytical technique for the determination of Os abundances in ten iron meteorites of various chemical groups was developed using isotope dilution inductively coupled plasma-mass spectrometry coupled with a sample decomposition technique. A major advantage of the sample decomposition technique developed here is that the pressure inside the reaction flask is not increased through the decomposition reaction because the flask is a fully opened system, obviating the risk of explosion of the glass apparatus. Another advantage is that there is no restriction in the sample size being decomposed. In this study, about 2 g of metallic sample were decomposed safely, and this sample size, > 10 times larger than that typically used for the Carius tube technique, allows one to obtain more reliable Os data for heterogeneous samples. The metallic samples were decomposed in a glass flask purged with Ar. Since the O2 was purged from the reaction flask, Os was not oxidised to volatile OsO4, thereby preventing significant evaporation loss of Os. The typical recovery of Os throughout the sample decomposition and separation processes was > 80%, and the total Os blank through the decomposition of a 1 g amount of sample was less than 20 pg. Os abundances were determined by means of stable isotope dilution mass spectrometry using a 190Os-enriched isotopic tracer. Except for Sikhote-Alin, the measured Os abundances in almost all the iron meteorites exhibited a good agreement with the previously published Os abundance data, within the analytical uncertainty achieved in this study (2-5%). For the Sikhote-Alin meteorite, on the basis of a better correlation between Os and Ir abundances, we believe that our Os abundance data should be more reliable. The Os abundance data obtained in this work clearly demonstrated the suitability of the newly developed sample decomposition procedure for low level Os determinations. PMID:11445949

  11. 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.

  12. Zn isotope compositions of the thermal spring waters of La Soufrière volcano, Guadeloupe Island

    NASA Astrophysics Data System (ADS)

    Chen, Jiu-Bin; Gaillardet, Jérôme; Dessert, Céline; Villemant, Benoit; Louvat, Pascale; Crispi, Olivier; Birck, Jean-Louis; Wang, Yi-Na

    2014-02-01

    To trace the sources and pathways of Zn in hydrothermal systems, the Zn isotope compositions of seventeen water samples from eight thermal springs and six gas samples from two fumaroles from La Soufrière, an active volcano on Guadeloupe Island (French West Indies, FWI), were analyzed using a method adapted for purifying Zn from Fe- and SO4-enriched thermal solutions. The fumaroles are enriched in Zn 100 to 8000 times compared to the local bedrock and have isotopic compositions (?66Zn values from +0.21‰ to +0.35‰) similar to or slightly higher than fresh andesite (+0.21‰). The enrichment of Zn in the thermal springs compared with the surface waters shows that Zn behaves as a soluble element during hydrothermal alteration but is significantly less mobile than Na. The ?66Zn values of most of the spring waters are relatively constant (approximately 0.70‰), indicating that the thermal springs from La Soufrière are enriched in heavy isotopes (i.e., 66Zn) compared to the host rocks (from -0.14‰ to +0.42‰). Only three thermal springs have lower ?66Zn values (as low as -0.43%). While the Zn in the fumaroles is essentially derived from magma degassing, which is consistent with a previous study on Merapi volcano (Toutain et al., 2008), we show that the Zn in the thermal springs is mainly derived from water-rock interactions. The 66Zn-enriched isotopic signature in most of the spring waters can be explained qualitatively by the precipitation at depth of sulfide minerals that preferentially incorporate the light isotopes. This agrees with the isotopic fractionation that was recently calculated for aqueous complexes of Zn. The few thermal springs with lower ?66Zn values also have low Zn concentrations, indicating the preferential scavenging of heavy Zn isotopes in the hydrothermal conduits. This study shows that unlike chemical weathering under surface conditions, hydrothermal alteration at high temperatures significantly fractionates Zn isotopes and enriches thermal waters in heavy Zn isotopes (e.g., 66Zn). Continental hydrothermal systems therefore constitute a source of heavy Zn isotopes to the oceans; this should be taken into account in the global oceanic budget of Zn.

  13. Thermally-driven isotope separation across nanoporous graphene

    NASA Astrophysics Data System (ADS)

    Schrier, Joshua; McClain, James

    2012-01-01

    Quantum tunneling contributes to the transmission of atoms through nanoporous graphene barriers, even at room temperature. In a temperature gradient, the mass-dependence of tunneling leads to isotope separation, in contrast to the classical transmission case where no separation can occur. Using transition state theory, we show that zero-point and tunneling contributions enrich the isotopes in opposite directions with respect to the temperature gradient. Zero-point energy differences dominate around room temperature.

  14. Hydrochemical and isotopic evidence of origin of thermal karst water at Taiyuan, northern China

    Microsoft Academic Search

    Teng Ma; Yanxin Wang; Qinghai Guo; Chunmiao Yan; Rui Ma; Zheng Huang

    2009-01-01

    Thermal karst groundwaters with temperatures ranging from 32.8 to 62.5 °C were found at Taiyuan (??) City, the capital of\\u000a Shanxi (??) Province. To identify the origin of the thermal groundwater, the following tracers were used in this study: ?D, ?\\u000a 18O, 4He, 3He\\/4He, and major chemical constituents in water. Hydrochemical and isotopic data indicate that the thermal groundwaters in

  15. Assessment of the amount of body water in the Red Knot (Calidris canutus): an evaluation of the principle of isotope dilution with 2H, (17)O, and (18)O as measured with laser spectrometry and isotope ratio mass spectrometry.

    PubMed

    Kerstel, Erik R T; Piersma, Theunis; Piersma, Theunis A J; Gessaman, James A; Gessaman, G Jim; Dekinga, Anne; Meijer, Harro A J; Visser, G Henk

    2006-03-01

    We have used the isotope dilution technique to study changes in the body composition of a migratory shorebird species (Red Knot, Calidris canutus) through an assessment of the amount of body water in it. Birds were quantitatively injected with a dose of water with elevated concentrations of 2H, (17)O, and (18)O. Thereafter, blood samples were taken and distilled. The resulting water samples were analysed using an isotope ratio mass spectrometry (for 2H and (18)O only) and a stable isotope ratio infrared laser spectrometry (2H, (17)O, and (18)O) to yield estimates of the amount of body water in the birds, which in turn could be correlated to the amount of body fat. Here, we validate laser spectrometry against mass spectrometry and show that all three isotopes may be used for body water determinations. This opens the way to the extension of the doubly labelled water method, used for the determination of energy expenditure, to a triply labelled water method, incorporating an evaporative water loss correction on a subject-by-subject basis or, alternatively, the reduction of the analytical errors by statistically combining the (17)O and (18)O measurements. PMID:16500750

  16. Isotope dilution mass spectrometry for quantitative elemental analysis of powdered samples by radiofrequency pulsed glow discharge time of flight mass spectrometry.

    PubMed

    Alvarez-Toral, Aitor; Fernandez, Beatriz; Malherbe, Julien; Claverie, Fanny; Molloy, John L; Pereiro, Rosario; Sanz-Medel, Alfredo

    2013-10-15

    In recent years particular effort is being devoted to the development of pulsed glow discharges (PGDs) for mass spectrometry because this powering operation mode could offer important ionization analytical advantages. However, the capabilities of radiofrequency (RF) PGD coupled to a time of flight mass spectrometry (ToFMS) for accurate isotope ratio measurements have not been demonstrated yet. This work is focused on investigating different time positions along the pulse profile for the accurate measurement of isotope ratios. As a result, a method has been developed for the direct and simultaneous multielement determination of trace elements in powdered geological samples by RF-PGD-ToFMS in combination with isotope dilution mass spectrometry (IDMS) as an absolute measurement method directly traceable to the International System of Units. Optimized operating conditions were 70 W of applied radiofrequency power, 250 Pa of pressure, 2 ms of pulse width and 4 ms of pulse period, being argon the plasma gas used. To homogeneously distribute the added isotopically-enriched standards, lithium borate fusion of powdered solid samples was used as sample preparation approach. In this way, Cu, Zn, Ba and Pb were successfully determined by RF-PGD-ToF(IDMS) in two NIST Standard Reference Materials (SRM 2586 and SRM 2780) representing two different matrices of geological interest (soil and rock samples). Cu, Zn, Ba and Pb concentrations determined by RF-PGD-ToF(IDMS) were well in agreement with the certified values at 95% confidence interval and precisions below 12% relative standard deviation were observed for three independent analyses. Elemental concentrations investigated were in the range of 81-5770 mg/kg, demonstrating the potential of RF-PGD-ToF(IDMS) for a sensitive, accurate and robust analysis of powdered samples. PMID:24054645

  17. A Stable-Isotope Dilution GC-MS Approach for the Analysis of DFRC (Derivatization Followed by Reductive Cleavage) Monomers from Low-Lignin Plant Materials.

    PubMed

    Schäfer, Judith; Urbat, Felix; Rund, Katharina; Bunzel, Mirko

    2015-03-18

    The derivatization followed by reductive cleavage (DFRC) method is a well-established tool to characterize the lignin composition of plant materials. However, the application of the original procedure, especially the chromatographic determination of the DFRC monomers, is problematic for low-lignin foods. To overcome these problems a modified sample cleanup and a stable-isotope dilution approach were developed and validated. To quantitate the diacetylated DFRC monomers, their corresponding hexadeuterated analogs were synthesized and used as internal standards. By using the selected-ion monitoring mode, matrix-associated interferences can be minimized resulting in higher selectivity and sensitivity. The modified method was applied to four low-lignin samples. Lignin from carrot fibers was classified as guaiacyl-rich whereas the lignins from radish, pear, and asparagus fibers where classified as balanced lignins (guaiacyl/syringyl ratio=1-2). PMID:25727138

  18. Ultrasonication extraction and gel permeation chromatography clean-up for the determination of polycyclic aromatic hydrocarbons in edible oil by an isotope dilution gas chromatography–mass spectrometry.

    PubMed

    Wang, Jian-Hua; Guo, Cui

    2010-07-01

    An analytical method for the determination of US EPA priority pollutant 16 polycyclic aromatic hydrocarbons (PAHs) in edible oil was developed by an isotope dilution gas chromatography-mass spectrometry (GC-MS). Extraction was performed with ultrasonication mode using acetonitrile as solvent, and subsequent clean-up was applied using narrow gel permeation chromatographic column. Three deuterated PAHs surrogate standards were used as internal standards for quantification and analytical quality control. The limits of quantification (LOQs) were globally below 0.5 ng/g, the recoveries were in the range of 81-96%, and the relative standard deviations (RSDs) were lower than 20%. Further trueness assessment of the method was also verified through participation in international cocoa butter proficiency test (T0638) organised by the FAPAS with excellent results in 2008. The results obtained with the described method were satisfying (z ? 2). The method has been applied to determine PAH in real edible oil samples. PMID:20627308

  19. Tracing the flow rate and mixing ratio of the Changjiang diluted water in the northwestern Pacific marginal seas using radium isotopes

    NASA Astrophysics Data System (ADS)

    Lee, Hojun; Kim, Guebuem; Kim, Jeonghyun; Park, Gwanserk; Song, Ki-Hoon

    2014-07-01

    We measured Ra isotopes (223Ra and 228Ra) in surface seawater of the northwestern Pacific marginal seas to trace the flow rate and mixing of the Changjiang diluted water (CDW) in the summer of 2012. Based on the horizontal distribution of 223Ra activities, the arrival time of CDW from the river mouth to 450 km offshore northeast was estimated to be 20-35 days, which is similar to that determined in previous studies. Moreover, we successfully calculated the relative contribution of CDW at each sampling station using a salinity and 228Ra diagram. Using this unique method, we found that the relative contribution of CDW was more than 30% in most surface seawaters of the northern East China Sea, the Yellow Sea, and the southern sea off Korea. Our results suggest that CDW is of high significance in the biogeochemistry of surface seawater of these northwestern Pacific marginal seas during the summer monsoon period.

  20. Development and validation of a high-throughput analysis of glutathione in grapes, musts and wines by Stable Isotope Dilution Assay and LC-MS/MS.

    PubMed

    Roland, Aurélie; Schneider, Rémi

    2015-06-15

    For the first time, we proposed a high-throughput method to quantify glutathione in grapes, musts and wines for all grape varieties using Stable Isotope Dilution Assay (SIDA). Indeed, the use of SIDA as a quantification method is essential to overcome the chemical instability of glutathione. In practice, glutathione was derivatized in-situ with N-ethylmaleimide to block the cysteine residue and to enhance its lipophilic properties. After quenching with acetic acid, samples were directly analyzed by LC-MS/MS (run of 13 min) in Multiple Reaction Monitoring mode using labeled glutathione as internal standard. The validation according to the International Organization of Vine and Wine recommendations demonstrated the high sensitivity (LOD=45 ?g L(-1)), accuracy (recovery=112%) and intermediate reproducibility (RSD=12%) of the method. This high-throughput method that requires only 1 mL of matrix, allowed us to analyze 70 samples per day for a moderate cost. PMID:25660871

  1. Significance of Isotopically Labile Organic Hydrogen in Thermal Maturation of Organic Matter

    SciTech Connect

    Arndt Schimmelmann; Maria Mastalerz

    2010-03-30

    Isotopically labile organic hydrogen in fossil fuels occupies chemical positions that participate in isotopic exchange and in chemical reactions during thermal maturation from kerogen to bitumen, oil and gas. Carbon-bound organic hydrogen is isotopically far less exchangeable than hydrogen bound to nitrogen, oxygen, or sulfur. We explore why organic hydrogen isotope ratios express a relationship with organic nitrogen isotope ratios in kerogen at low to moderate maturity. We develop and apply new techniques to utilize organic D/H ratios in organic matter fractions and on a molecular level as tools for exploration for fossil fuels and for paleoenvironmental research. The scope of our samples includes naturally and artificially matured substrates, such as coal, shale, oil and gas.

  2. Biosynthesis of seven carbon-13 labeled Alternaria toxins including altertoxins, alternariol, and alternariol methyl ether, and their application to a multiple stable isotope dilution assay.

    PubMed

    Liu, Yang; Rychlik, Michael

    2015-02-01

    An unprecedented stable isotope dilution assay for the genotoxic altertoxins along with exposure data of consumers is presented to enable a first risk assessment of these Alternaria toxins in foods. Altertoxins were produced as the most abundant Alternaria toxins in a modified Czapek-Dox medium with a low level of glucose as the carbon source and ammonium sulfate as the sole nitrogen source. Labeled altertoxins were synthesized in the same way using [(13)C6]glucose. Moreover, labeled alternariol, alternariol methyl ether, altenuene, and alternuisol were biosynthesized in another modified medium containing [(13)C6]glucose and sodium [(13)C2]acetate. A stable isotope dilution LC-MS/MS method was developed and used for food analysis. For altertoxin I, altertoxin II, alterperylenol, alternariol, and alternariol methyl ether, the limits of detection ranged from 0.09 to 0.53 ?g kg(-1). The inter-/intra-day (n?=?3?×?6) relative standard deviations of the method were below 13 %, and the recoveries ranged between 96 and 109 %. Among the various commercial food samples, some of the organic whole grains revealed low-level contamination with altertoxin I and alterperylenol, and paprika powder, which was heavily loaded with alternariol, alternariol methyl ether, and tentoxin, showed higher contamination level of altertoxin I and alterperylenol. Altertoxin II and III and stemphyltoxin III were not detectable. In addition, if the food was contaminated with altertoxins, it was likely to be co-contaminated with the other Alternaria toxins, but not necessarily vice versa. Maximum concentrations of altertoxin I and alterperylenol were detected in sorghum feed samples containing 43 and 58 ?g kg(-1), respectively. This was significantly higher than that in the measured food samples. PMID:25577349

  3. Determination of low methylmercury concentrations in peat soil samples by isotope dilution GC-ICP-MS using distillation and solvent extraction methods.

    PubMed

    Pietilä, Heidi; Perämäki, Paavo; Piispanen, Juha; Starr, Mike; Nieminen, Tiina; Kantola, Marjatta; Ukonmaanaho, Liisa

    2015-04-01

    Most often, only total mercury concentrations in soil samples are determined in environmental studies. However, the determination of extremely toxic methylmercury (MeHg) in addition to the total mercury is critical to understand the biogeochemistry of mercury in the environment. In this study, N2-assisted distillation and acidic KBr/CuSO4 solvent extraction methods were applied to isolate MeHg from wet peat soil samples collected from boreal forest catchments. Determination of MeHg was performed using a purge and trap GC-ICP-MS technique with a species-specific isotope dilution quantification. Distillation is known to be more prone to artificial MeHg formation compared to solvent extraction which may result in the erroneous MeHg results, especially with samples containing high amounts of inorganic mercury. However, methylation of inorganic mercury during the distillation step had no effect on the reliability of the final MeHg results when natural peat soil samples were distilled. MeHg concentrations determined in peat soil samples after distillation were compared to those determined after the solvent extraction method. MeHg concentrations in peat soil samples varied from 0.8 to 18 ?g kg(-1) (dry weight) and the results obtained with the two different methods did not differ significantly (p=0.05). The distillation method with an isotope dilution GC-ICP-MS was shown to be a reliable method for the determination of low MeHg concentrations in unpolluted soil samples. Furthermore, the distillation method is solvent-free and less time-consuming and labor-intensive when compared to the solvent extraction method. PMID:25434268

  4. Gas chromatography-combustion-mass spectrometry with postcolumn isotope dilution for compound-independent quantification: its potential to assess HS-SPME procedures.

    PubMed

    Cueto Díaz, Sergio; Ruiz Encinar, Jorge; Sanz-Medel, Alfredo; García Alonso, J Ignacio

    2010-08-15

    A quadrupole GC-MS instrument with an electron ionization (EI) source has been modified to enable application of postcolumn isotope dilution analysis for the standardless quantification of organic compounds injected in the gas chromatograph. Instrumental modifications included the quantitative conversion of the separated compounds into CO(2), using a postcolumn combustion furnace, and the subsequent mixing of the gas with a constant flow of (13)CO(2) diluted in helium. The online measurement of the (12)CO(2)/(13)CO(2) (44/45) ratio in the EI-MS allowed us to obtain quantitative data without resorting to compound-specific standards. Validation of the procedure involved the analysis of standard solutions containing different families of organic compounds (C(9)-C(20) linear hydrocarbons, BTEX and esters) obtaining satisfactory results in all cases in terms of absolute errors (<6%) and precision (<4% RSD). The developed procedure showed excellent linearity over the range assayed (2 orders of magnitude) and adequate detection limits for carbon containing compounds (0.8 pg C s(-1)). The generic value of this compound-independent calibration approach was assessed by studying the quantitative performance of Head Space-Solid Phase Microextraction (HS-SPME). The proposed compound-independent quantification by EI-MS permits comparison of the performance of different fibers by assessing analyte recoveries with extreme robustness, simplicity, and precision. PMID:20704376

  5. Inoculation of Bacillus sphaericus UPMB-10 to Young Oil Palm and Measurement of Its Uptake of Fixed Nitrogen Using the 15N Isotope Dilution Technique

    PubMed Central

    Zakry, Fitri Abdul Aziz; Shamsuddin, Zulkifli H.; Rahim, Khairuddin Abdul; Zakaria, Zin Zawawi; Rahim, Anuar Abdul

    2012-01-01

    There are increasing applications of diazotrophic rhizobacteria in the sustainable agriculture system. A field experiment on young immature oil palm was conducted to quantify the uptake of N derived from N2 fixation by the diazotroph Bacillus sphaericus strain UPMB-10, using the 15N isotope dilution method. Eight months after 15N application, young immature oil palms that received 67% of standard N fertilizer application together with B. sphaericus inoculation had significantly lower 15N enrichment than uninoculated palms that received similar N fertilizers. The dilution of labeled N served as a marker for the occurrence of biological N2 fixation. The proportion of N uptake that was derived from the atmosphere was estimated as 63% on the whole plant basis. The inoculation process increased the N and dry matter yields of the palm leaflets and rachis significantly. Field planting of young, immature oil palm in soil inoculated with B. sphaericus UPMB-10 might mitigate inorganic fertilizer-N application through supplementation by biological nitrogen fixation. This could be a new and important source of nitrogen biofertilizer in the early phase of oil palm cultivation in the field. PMID:22446306

  6. Inoculation of Bacillus sphaericus UPMB-10 to young oil palm and measurement of its uptake of fixed nitrogen using the ¹?N isotope dilution technique.

    PubMed

    Zakry, Fitri Abdul Aziz; Shamsuddin, Zulkifli H; Abdul Rahim, Khairuddin; Zawawi Zakaria, Zin; Abdul Rahim, Anuar

    2012-01-01

    There are increasing applications of diazotrophic rhizobacteria in the sustainable agriculture system. A field experiment on young immature oil palm was conducted to quantify the uptake of N derived from N? fixation by the diazotroph Bacillus sphaericus strain UPMB-10, using the ¹?N isotope dilution method. Eight months after ¹?N application, young immature oil palms that received 67% of standard N fertilizer application together with B. sphaericus inoculation had significantly lower ¹?N enrichment than uninoculated palms that received similar N fertilizers. The dilution of labeled N served as a marker for the occurrence of biological N? fixation. The proportion of N uptake that was derived from the atmosphere was estimated as 63% on the whole plant basis. The inoculation process increased the N and dry matter yields of the palm leaflets and rachis significantly. Field planting of young, immature oil palm in soil inoculated with B. sphaericus UPMB-10 might mitigate inorganic fertilizer-N application through supplementation by biological nitrogen fixation. This could be a new and important source of nitrogen biofertilizer in the early phase of oil palm cultivation in the field. PMID:22446306

  7. A study of thermal diffusion in dilute solutions of polystyrene in toluene

    E-print Network

    Herren, Cecil LeRoy

    1961-01-01

    '&n for se&r ra 1 ye q?s and &as &een s Iggested a s a means of f~act&onatin~ nulli?mrs snto bomogeneo?s samples, few +heori- tgcal or ex?erjmental stu+ies ha~!e been ~ade of thermal d1ffu- si?n in these samples. mhe theo~les attempting to describe t...~pa; ed to . he a?era(e temporat?re, 314 K and the change oI' tampa"ature with position should e nec ligihle. mhe~efore apprecIa~le error ah~?id not he introduced hy assum- Ing & and &m Independent of position, 0 If the motion of the molecules...

  8. Boron isotopic variations in fumarolic condensates and thermal waters from Vulcano Island, Italy: Implications for evolution of volcanic fluids

    Microsoft Academic Search

    W. P. Leeman; S. Tonarini; M. Pennisi; G. Ferrara

    2005-01-01

    Temporal variation in the isotopic composition of boron has been monitored in fumarolic condensates collected over an extended time period (1970–1996) from La Fossa crater, Volcano Island. We also report comparative boron isotopic data for representative Vulcano lavas and for shallow hydrologic samples (seawater, wells, thermal springs) from the north flank of La Fossa. Combined with concurrent chemical and isotopic

  9. Experimental investigation of sulphur isotope partitioning during outgassing of hydrogen sulphide from diluted aqueous solutions and seawater.

    PubMed

    Baune, Claudia; Bottcher, Michael E

    2010-12-01

    The diffusion of hydrogen sulphide across the sediment-water interface and subsequent liberation to the atmosphere may occur in iron-deficient coastal marine environments with enhanced microbial activity in surface sediments and corresponding accumulation of dissolved H2S in near-surface pore waters. The involvement of analogue processes in periods of global mass extinctions during Earth's history (e.g. at the Permian-Triassic boundary) is currently in discussion [L.R. Kump, A. Pavlov, and M. Arthur,Massive Release of Hydrogen Sulfide to the Surface Ocean and Atmosphere During Intervals of Oceanic Anoxia, Geology 33, 397 (2005)]. The outgassing of H?S is associated with a fractionation of the stable sulphur isotopes, which has so far only been investigated experimentally at selected acidic and neutral pH values, and no experiments with seawater had been carried out. In this communication, we report on sulphur isotope fractionation that takes place during the experimental degassing of H?S from aqueous solution by an inert gas (N?) at 21 °C. Experiments were conducted in the pH range between 2.6 and 10.8, corresponding to the dominance fields of dissolved hydrogen sulphide (H?S(aq)), bisulphide (HS-(aq)), and mixtures of both sulphide species. Overall isotope enrichment factors between -1.6 and +3.0‰ were observed, with the residual dissolved sulphide being enriched or depleted in ³?S compared to the liberated H?S at low and high pH values, respectively. The difference in the low and high pH isotope fractionation effects can be explained by isotope exchange between H?S(aq) and HS-(aq) [B. Fry, H. Gest, and J.M. Hayes, Sulfur Isotope Effects Associated with Protonation of HS- and Volatilization of H?S, Chem. Geol. (Isot. Geosci. Sec.) 58, 253 (1986); R. Geßler and K. von Gehlen, Investigation of Sulfur Isotope Fractionation Between H2S Gas and Aqueous Solutions, Fresenius J. Anal. Chem. 324, 130 (1986)] followed by the subsequent transfer of H?S(aq) to the gaseous phase. The assumption of pure physical outgassing of H?S(aq) at low pH values leads to an isotope enrichment factor of -0.9 ± 0.4‰ (n = 14) which is caused by the combined differences in dehydration and diffusion coefficients of H?³²S(aq) and H?³?S(aq). In the pH range of natural surface and shallow pore waters, ³?S will be equal to or enriched in the gaseous phase compared to the aqueous solution, therefore creating no or a slight enrichment of ³²S in the aqueous solution. Experiments in seawater solution showed no significant influence of increased ionic strength and changed corresponding aqueous speciation on sulphur isotope effects. PMID:21154004

  10. Chemical and isotopic data for water from thermal springs and wells of Oregon

    SciTech Connect

    Mariner, R.H.; Swanson, J.R.; Orris, G.J.; Presser, T.S.; Evans, W.C.

    1981-01-01

    The thermal springs of Oregon range in composition from dilute NaHCO/sub 3/ waters to moderately saline CO/sub 2/-charged NaCl-NaHCO/sub 3/ waters. Most of the thermal springs are located in southeastern or southcentral Oregon, with a few in northeastern Oregon and near the contact of the Western Cascades with the High Cascades. Thermal springs in the central and northern parts of the Cascades generally issue moderately saline NaCl waters. Farther south in the Cascades, the thermal waters are high in CO/sub 2/ as well as chloride. Most thermal springs in northeastern Oregon issue dilute NaHCO/sub 3/ waters of high pH (>8.5). These waters are similar to the thermal waters which issue from the Idaho batholith, farther east. Most of the remaining thermal waters are Na mixed-anion waters. Based on the chemical geothermometers, Mickey Srpings, Hot Borax Lake, Alvord Hot Springs, Neal Hot Springs, Vale Hot Springs, Crump Well, Hunters (Lakeview) Hot Springs, and perhaps some of the springs in the Cascades are associated with the highest temperature systems (>150/sup 0/C).

  11. Lead and strontium isotope data for thermal waters of the regional geothermal system in the Twin Falls and Oakley areas, South-Central Idaho

    SciTech Connect

    Mariner, R.H. [Geological Survey, Menlo Park, CA (United States); Young, H.W. [Geological Survey, Boise, ID (United States)

    1995-12-31

    Thermal fluids obviously related to aquifers in both rhyolite and limestone occur in the Twin Falls-Oakley area of south-central Idaho. Limestone-related waters (high calcium with low silica and fluoride) occur in the middle and upper (southern) parts of the area. Rhyolite-related waters (low calcium but high in silica and fluoride) occur in the lower (northern) part of the area. The relation of thermal fluids in Paleozoic limestone to thermal fluids in Tertiary rhyolite is unknown. Thermal fluids from limestone are dilute, so water-rock reaction in rhyolite could obliterate chemical evidence of fluid residence in a limestone. However, isotopic tracers such as {sup 206}Pb/{sup 204}Pb, {sup 207}Pb/{sup 204}Pb, {sup 208}Pb/{sup 204}Pb, and {sup 87}Sr/{sup 86}Sr might preserve evidence of fluid residence in limestone. Systematic relations between these isotopes and dissolved constituents in the water demonstrate the presence of limestone beneath most if not all of the study area and that aquifers in the limestone and rhyolite are hydrologically connected.

  12. Rapid and Precise Measurement of Serum Branched-Chain and Aromatic Amino Acids by Isotope Dilution Liquid Chromatography Tandem Mass Spectrometry

    PubMed Central

    Yang, Ruiyue; Dong, Jun; Guo, Hanbang; Li, Hongxia; Wang, Shu; Zhao, Haijian; Zhou, Weiyan; Yu, Songlin; Wang, Mo; Chen, Wenxiang

    2013-01-01

    Background Serum branched-chain and aromatic amino acids (BCAAs and AAAs) have emerged as predictors for the future development of diabetes and may aid in diabetes risk assessment. However, the current methods for the analysis of such amino acids in biological samples are time consuming. Methods An isotope dilution liquid chromatography tandem mass spectrometry (ID-LC/MS/MS) method for serum BCAAs and AAAs was developed. The serum was mixed with isotope-labeled BCAA and AAA internal standards and the amino acids were extracted with acetonitrile, followed by analysis using LC/MS/MS. The LC separation was performed on a reversed-phase C18 column, and the MS/MS detection was performed via the positive electronic spray ionization in multiple reaction monitoring mode. Results Specific analysis of the amino acids was achieved within 2 min. Intra-run and total CVs for the amino acids were less than 2% and 4%, respectively, and the analytical recoveries ranged from 99.6 to 103.6%. Conclusion A rapid and precise method for the measurement of serum BCAAs and AAAs was developed and may serve as a quick tool for screening serum BCAAs and AAAs in studies assessing diabetes risk. PMID:24339906

  13. Accurate quantification of polycyclic aromatic hydrocarbons in dust samples using microwave-assisted solvent extraction combined with isotope-dilution mass spectrometry.

    PubMed

    Itoh, Nobuyasu; Fushimi, Akihiro; Yarita, Takashi; Aoyagi, Yoshie; Numata, Masahiko

    2011-08-01

    For accurate quantification of polycyclic aromatic hydrocarbons (PAHs) in dust samples, we investigated the use of microwave-assisted solvent extraction (MAE) combined with isotope-dilution mass spectrometry (IDMS) using deuterium-labelled PAHs (D-PAHs). Although MAE with a methanol/toluene mixture (1:3 by volume) at 160°C for 40 min was best for extracting PAHs from tunnel dust among examined, the recovery yields of D-PAHs decreased with increasing molecular weight (<40% for MW?264; that of deuterium-labelled indeno[123-cd]pyrene (D-IcdP) was only 7.1%). Although the residues were extracted a second time, the observed concentrations did not change dramatically (<5%), and the recovery yields of heavier D-PAHs (i.e., MW?264) were approximately half of those of the first extract, including D-IcdP (3.4%). These results suggest that both partitioning and isotopic equilibria of PAHs and D-PAHs between sample and solvent were achieved for extractable heavier PAHs under the condition. Thus, the observed concentrations of PAHs obtained by MAE-IDMS were reasonable, even though recovery yields of D-PAHs were <50%. From the results of carbon analyses and extractable contents, lower recovery yields of D-PAHs from the tunnel dust were due to a large content of char with low extractable contents. PMID:21704757

  14. [Determination of urinary cotinine of children exposed to passive smoking by stable isotope dilution gas chromatography-triple quadrupole mass spectrometry].

    PubMed

    Wang, Yun; Huang, Zhiqiang; Ye, Ying; Zhang, Ying; Xiao, Shuiyuan

    2014-06-01

    An analytical method for the determination of urinary cotinine of children exposed to passive smoking was established based on stable isotope dilution by gas chromatography-triple quadrupole mass spectrometry (GC-MS/MS). The samples were extracted and purified with chloroform. The extracts were determined by GC-MS/MS in multiple reaction monitoring (MRM) mode. The cotinine-d3 as an isotope internal standard was applied to quantify and confirm the urinary cotinine of children exposed to passive smoking. The method had a good linearity from 0.1 microg/L to 10 microg/L with the correlation coefficient (r) > 0.998. The recoveries of the cotinine in blank urine were from 79.2% to 112.8% at spiked levels of 0.1, 1.0 and 10 microg/ L, with relative standard deviations (RSDs) from 2.1% to 5. 8%. The limit of quantification ( LOQ) of the method was 0.1 microg/L. The developed method is accurate, sensitive, rapid and can be applied to detect urinary cotinine of children exposed to passive smoking at home. PMID:25269267

  15. Simultaneous analysis of phthalates, adipate and polycyclic aromatic hydrocarbons in edible oils using isotope dilution-gas chromatography-mass spectrometry.

    PubMed

    Oh, Min-Seok; Lee, Seon-Hwa; Moon, Myeong Hee; Lee, Dong Soo; Park, Hyun-Mee

    2014-01-01

    A method for simultaneous determination of 12 priority phthalates, adipate and polycyclic aromatic hydrocarbons (PAHs) in edible oils by isotope dilution-gas chromatography-mass spectrometry (ID-GC-MS) was developed for fast, accurate and trace analysis. The extraction and clean-up procedures were optimised, and using stable isotope-labelled internal standards for each analyte, relative standard deviations (RSDs) of 0.92-10.6% and spiked sample recoveries of 80.6-97.8% were obtained. Limits of detection for PAHs were in the range of 0.15-0.77 µg/kg and those for phthalates were in the range of 4.6-10.0 µg/kg. The calibration curves exhibited good linearities with regression coefficients of R(2) ? 0.99. Twelve edible oils were examined to evaluate the efficiency of this method. Among the 12 analytes, dibutyl phthalates (DBP), diethylhexyl phthalates (DEHP), diethylhexyl adipate (DEHA), benzo[a]anthracene (B[a]A), chrysene (Chry) and benzo[b]fluoranthene (B[b]F) were detected in the range of 1.17-806 µg/kg. PMID:25029399

  16. Quantitation of S-methylmethionine in raw vegetables and green malt by a stable isotope dilution assay using LC-MS/MS: comparison with dimethyl sulfide formation after heat treatment.

    PubMed

    Scherb, Julia; Kreissl, Johanna; Haupt, Sonja; Schieberle, Peter

    2009-10-14

    The potent odorant dimethyl sulfide (1), showing a low odor threshold of 0.12 microg/L in water, is known to contribute to the aromas of various foods. Its cabbage-like odor plays an important role, particularly, in cooked vegetables, such as cabbage, celery, or asparagus. On the other hand, in fruit juices or beer, 1 may generate off-flavors. S-Methylmethionine (2) has previously been characterized as precursor of 1 during thermal processing, and several methods for its quantitation have been proposed. Using deuterium-labeled 2 as the internal standard, a stable isotope dilution assay (SIDA) using LC-MS/MS was developed for the fast quantitation of 2 in vegetables and malt. Application of the method to different foods revealed amounts between 2.8 mg (fresh tomatoes) and 176 mg (celery) of 2 per kilogram. To correlate the amount of 1 formed upon processing with the amounts of 2 present in the raw material, 1 was quantified before and after a thermal treatment of the same raw materials by a SIDA. Concentrations between 1.1 mg/kg (fresh tomatoes) and 26 mg/kg (celery) were determined in the processed samples. The quantitation of 2 during steeping, germination, and malting of barley, and a correlation of the data with the amounts of 1 formed after thermal treatment of the malt, resulted in yields between 24 and 27 mol % calculated on the basis of the amounts of 2. The results suggested that the extent of the formation of 1 can be predicted, for example, in plant materials, from the amount of 2 present in the raw foods. PMID:19754146

  17. Effect of dilution on the kinetics of cross-linking thermal polymerization of dental composite matrix resins

    Microsoft Academic Search

    H. K SHOBHA; M SANKARAPANDIAN; Y SUN; S KALACHANDRA; J. E McGRATH; D. F TAYLOR

    1997-01-01

    The effect of dilution of 2,2-bis-(4-(2-hydroxy-3-methacryloxyprop-1oxy) phenyl) propane (bis-GMA) with trethyleae glycol demethacrylate (TEGDMA) on the extent of polymerization, Ep, has been studied using differential scanning calorimetry. The isothermal and dynamic measurements indicate that the Ep is affected dramatically by dilution. The residual polymerization was also found to be strongly influenced by dilution. However, the apparent activation energy, Eapp, was

  18. Thermally-driven Isotope Separation Across Nanoporous Graphene

    NASA Astrophysics Data System (ADS)

    Schrier, Joshua

    2012-02-01

    Experiment and theory indicate that a single graphene sheet is impermeable to gases even as small as helium; pores are required for transmission of atoms and molecules. Nanoporous forms of graphene, such as two-dimensional polyphenylene (2D-PP), consist of a regular array of sub-nanometer pores which can be used for separating atoms and molecules by size. Because the nanoporous graphene barrier is only an atom-thick, quantum tunneling plays a role in the the transmission of atoms through the nanoporous barrier, even at room temperature. This talk describes how the mass-dependence of the tunneling, combined with a temperature gradient, can be used to separate isotope mixtures under conditions where classical transmission cannot. Using transition state theory, we show that the zero-point and tunneling contributions lead to isotopic separations in opposite directions with respect to the temperature gradient. We examine the separation of ^3He/^4He across a 2D-PP membrane under modest temperature and pressure conditions. We will also describe 2D-PP bilayer structures that yield resonant tunneling of helium atoms, and new nanoporous graphene structures suitable for separating heavier noble-gas isotopes.

  19. Reduced thermal conductivity of isotope substituted carbon nanomaterials: Nanotube versus graphene nanoribbon

    NASA Astrophysics Data System (ADS)

    Ray, Upamanyu; Balasubramanian, Ganesh

    2014-04-01

    Non-equilibrium molecular dynamics (MD) simulations of isotopically impure carbon nanotubes (CNTs) and graphene nanoribbons (GNRs) of varying lengths reveal that the relative decrease in thermal conductivity (k) in both the nanostructures are similar for constant isotope substitution. We find that the delocalized transverse modes in CNTs and the out-of-plane flexural modes in GNRs exert a substantial contribution to the thermal transport whereas the influence of isotope substitution on the phonon density of states (DOS) is similar in all directions. The vibrational spectra for different length scales consistently show that the energy modes shift to lower wave numbers reflecting the strong influence of mass disorder that reduces the energy transport through these nanomaterials, consequently lowering k.

  20. A theoretical model of isotopic fractionation by thermal diffusion and its implementation on silicate melts

    NASA Astrophysics Data System (ADS)

    Li, Xuefang; Liu, Yun

    2015-04-01

    When a homogeneous system is placed under a temperature gradient for a sufficient time, both its chemical and isotopic compositions will differentiate between the hot and the cold ends. Molecular-level knowledge of this process is of critical importance to understanding concentration and isotopic distributions in many geologic systems. Recently, different theoretical models have been proposed to explain isotopic fractionations observed in laboratory experiments under high temperatures, but there is still a lot of debating. Here we provide a unified theory based on local thermodynamic equilibrium approach to evaluating thermal isotope fractionations under a wide range of temperatures. For high temperature silicate melts, our theory offers a simple equation for calculating isotopic fractionations of all isotope systems: ?XM = -(3/2)ln(m?/m)ln(T/T0). The results from this equation agree with observed data for the most of network modifiers and resolve existing discrepancies among different interpretations. It can also explain O and Si isotope results if consider their diffusing species not as a single ion but a larger unit (e.g., [SiO3] or [SiO4]). The simplicity of the equation support a classical mechanical collision model for high-temperature diffusing particles in silica melts.

  1. Stable isotope fractionation by thermal diffusion through partially molten wet and dry silicate rocks

    E-print Network

    Bindeman, Ilya N.

    Stable isotope fractionation by thermal diffusion through partially molten wet and dry silicate rocks I.N. Bindeman a,n , C.C. Lundstrom b , C. Bopp b , F. Huang b,c a Department of Geological Article history: Received 12 January 2012 Received in revised form 26 December 2012 Accepted 27 December

  2. Accurate determination of selected pesticides in soya beans by liquid chromatography coupled to isotope dilution mass spectrometry.

    PubMed

    Huertas Pérez, J F; Sejerøe-Olsen, B; Fernández Alba, A R; Schimmel, H; Dabrio, M

    2015-05-01

    A sensitive, accurate and simple liquid chromatography coupled with mass spectrometry method for the determination of 10 selected pesticides in soya beans has been developed and validated. The method is intended for use during the characterization of selected pesticides in a reference material. In this process, high accuracy and appropriate uncertainty levels associated to the analytical measurements are of utmost importance. The analytical procedure is based on sample extraction by the use of a modified QuEChERS (quick, easy, cheap, effective, rugged, safe) extraction and subsequent clean-up of the extract with C18, PSA and Florisil. Analytes were separated on a C18 column using gradient elution with water-methanol/2.5mM ammonium acetate mobile phase, and finally identified and quantified by triple quadrupole mass spectrometry in the multiple reaction monitoring mode (MRM). Reliable and accurate quantification of the analytes was achieved by means of stable isotope-labelled analogues employed as internal standards (IS) and calibration with pure substance solutions containing both, the isotopically labelled and native compounds. Exceptions were made for thiodicarb and malaoxon where the isotopically labelled congeners were not commercially available at the time of analysis. For the quantification of those compounds methomyl-(13)C2(15)N and malathion-D10 were used respectively. The method was validated according to the general principles covered by DG SANCO guidelines. However, validation criteria were set more stringently. Mean recoveries were in the range of 86-103% with RSDs lower than 8.1%. Repeatability and intermediate precision were in the range of 3.9-7.6% and 1.9-8.7% respectively. LODs were theoretically estimated and experimentally confirmed to be in the range 0.001-0.005mgkg(-1) in the matrix, while LOQs established as the lowest spiking mass fractionation level were in the range 0.01-0.05mgkg(-1). The method reliably identifies and quantifies the selected pesticides in soya beans at appropriate uncertainty levels, making it suitable for the characterization of candidate reference materials. PMID:25770614

  3. Airborne measurements of sulfur dioxide, dimethyl sulfide, carbon disulfide, and carbonyl sulfide by isotope dilution gas chromatography/mass spectrometry

    NASA Technical Reports Server (NTRS)

    Bandy, Alan R.; Thornton, Donald C.; Driedger, Arthur R., III

    1993-01-01

    A gas chromatograph/mass spectrometer is described for determining atmospheric sulfur dioxide, carbon disulfide, dimethyl sulfide, and carbonyl sulfide from aircraft and ship platforms. Isotopically labelled variants of each analyte were used as internal standards to achieve high precision. The lower limit of detection for each species for an integration time of 3 min was 1 pptv for sulfur dioxide and dimethyl sulfide and 0.2 pptv for carbon disulfide and carbonyl sulfide. All four species were simultaneously determined with a sample frequency of one sample per 6 min or greater. When only one or two species were determined, a frequency of one sample per 4 min was achieved. Because a calibration is included in each sample, no separate calibration sequence was needed. Instrument warmup was only a few minutes. The instrument was very robust in field deployments, requiring little maintenance.

  4. Quantitation of orotic acid in urine using isotope dilution-selected ion gas chromatography-mass spectrometry.

    PubMed

    Chen, Jie; Bennett, Michael J

    2010-01-01

    The measurement of urinary orotic acid excretion is an important test for establishing a diagnosis of hereditary orotic aciduria, a genetic defect of pyrimidine biosynthesis. Measurement of secondary urinary orotic acid elevation is also an important clinical test for the differential diagnosis of hyperammonemia due to some of the primary disorders of the urea cycle including ornithine transcarbamylase (OTC) deficiency, and the hyperornithinemia-hyperammonemia-homocitrullinemia (HHH) syndrome. Low levels of orotic acid are observed in carbamylphosphate synthetase (CPS) defects. This method utilizes a stable-isotope labeled internal standard (1, 3-(15)N-orotic acid), which is added to the standards, controls, and patient samples prior to extraction. Interference from urea is removed by incubation of samples with urease and the orotic acid is derivatized by trimethylsilylation. Quantitation is made against an eight-point standard curve using specific selected ions from both the labeled and unlabeled orotic acid. PMID:20077096

  5. Thin-layer chromatography/direct analysis in real time time-of-flight mass spectrometry and isotope dilution to analyze organophosphorus insecticides in fatty foods.

    PubMed

    Kiguchi, Osamu; Oka, Kazuko; Tamada, Masafumi; Kobayashi, Takashi; Onodera, Jun

    2014-11-28

    To assess food safety emergencies caused by highly hazardous chemical-tainted foods, simultaneous analysis of organophosphorus insecticides in fatty foods such as precooked foods was conducted using thin-layer chromatography/direct analysis in real time time-of-flight mass spectrometry (TLC/DART-TOFMS) and isotope dilution technique. Polar (methamidophos and acephate) and nonpolar organophosphorus insecticides (fenitrothion, diazinon, and EPN) were studied. Experiments to ascertain chromatographic patterns using TLC/DART-TOFMS reveal that it was more useful than GC/MS or GC/MS/MS for the simultaneous analyses of polar and nonpolar pesticides, while obviating the addition of a protective agent for tailing effects of polar pesticides. Lower helium gas temperature (260°C) for DART-TOFMS was suitable for the simultaneous analysis of target pesticides. Linearities were achieved respectively at a lower standard concentration range (0.05-5 ?g) for diazinon and EPN and at a higher standard concentration range (2.5-25 ?g) for methamidophos, acephate, and fenitrothion. Their respective coefficients of determination were ? 0.9989 and ? 0.9959. A few higher repeatabilities (RSDs) for diazinon and EPN were found (>20%), although isotope dilution technique was used. Application to the HPTLC plate without an automatic TLC sampler might be inferred as a cause of their higher RSDs. Detection limits were estimated in the higher picogram range for diazinon and EPN, and in the lower nanogram range for methamidophos, acephate, and fenitrothion. Aside from methamidophos, recovery results (n=3) obtained using a highly insecticide-tainted fatty food (dumpling) and raw food (grapefruit) samples (10mg/kg) using TLC/DART-TOFMS with both complex and simpler cleanups were not as susceptible to matrix effects (95-121%; RSD, 1.3-14%) as those using GC/MS/MS (102-117%; RSD, 0.4-8.5%), although dumpling samples using GC/MS were remarkably susceptible to matrix effects. The coupled method of TLC with simpler cleanup and DART-TOFMS can be regarded as the same analytical tool as GC/MS/MS, which is useful to assess food safety emergencies caused by highly hazardous chemical-tainted foods. PMID:25454149

  6. An Update on the Non-Mass-Dependent Isotope Fractionation under Thermal Gradient

    NASA Technical Reports Server (NTRS)

    Sun, Tao; Niles, Paul; Bao, Huiming; Socki, Richard; Liu, Yun

    2013-01-01

    Mass flow and compositional gradient (elemental and isotope separation) occurs when flu-id(s) or gas(es) in an enclosure is subjected to a thermal gradient, and the phenomenon is named thermal diffusion. Gas phase thermal diffusion has been theoretically and experimentally studied for more than a century, although there has not been a satisfactory theory to date. Nevertheless, for isotopic system, the Chapman-Enskog theory predicts that the mass difference is the only term in the thermal diffusion separation factors that differs one isotope pair to another,with the assumptions that the molecules are spherical and systematic (monoatomic-like structure) and the particle collision is elastic. Our previous report indicates factors may be playing a role because the Non-Mass Dependent (NMD) effect is found for both symmetric and asymmetric, linear and spherical polyatomic molecules over a wide range of temperature (-196C to +237C). The observed NMD phenomenon in the simple thermal-diffusion experiments demands quantitative validation and theoretical explanation. Besides the pressure and temperature dependency illustrated in our previous reports, efforts are made in this study to address issues such as the role of convection or molecular structure and whether it is a transient, non-equilibrium effect only.

  7. Simultaneous Determination of Creatinine and Creatine in Human Serum by Double-Spike Isotope Dilution Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS) and Gas Chromatography-Mass Spectrometry (GC-MS).

    PubMed

    Fernández-Fernández, Mario; Rodríguez-González, Pablo; Añón Álvarez, M Elena; Rodríguez, Felix; Menéndez, Francisco V Álvarez; Alonso, J Ignacio García

    2015-04-01

    This work describes the first multiple spiking isotope dilution procedure for organic compounds using (13)C labeling. A double-spiking isotope dilution method capable of correcting and quantifying the creatine-creatinine interconversion occurring during the analytical determination of both compounds in human serum is presented. The determination of serum creatinine may be affected by the interconversion between creatine and creatinine during sample preparation or by inefficient chemical separation of those compounds by solid phase extraction (SPE). The methodology is based on the use differently labeled (13)C analogues ((13)C1-creatinine and (13)C2-creatine), the measurement of the isotopic distribution of creatine and creatinine by liquid chromatography-tandem mass spectrometry (LC-MS/MS) and the application of multiple linear regression. Five different lyophilized serum-based controls and two certified human serum reference materials (ERM-DA252a and ERM-DA253a) were analyzed to evaluate the accuracy and precision of the proposed double-spike LC-MS/MS method. The methodology was applied to study the creatine-creatinine interconversion during LC-MS/MS and gas chromatography-mass spectrometry (GC-MS) analyses and the separation efficiency of the SPE step required in the traditional gas chromatography-isotope dilution mass spectrometry (GC-IDMS) reference methods employed for the determination of serum creatinine. The analysis of real serum samples by GC-MS showed that creatine-creatinine separation by SPE can be a nonquantitative step that may induce creatinine overestimations up to 28% in samples containing high amounts of creatine. Also, a detectable conversion of creatine into creatinine was observed during sample preparation for LC-MS/MS. The developed double-spike LC-MS/MS improves the current state of the art for the determination of creatinine in human serum by isotope dilution mass spectrometry (IDMS), because corrections are made for all the possible errors derived from the sample preparation step. PMID:25751287

  8. Groundwater dilution and residence times, and constraints on chloride source, in the Mokai Geothermal System, New Zealand, from chemical, stable isotope, tritium, and 36Cl data

    NASA Astrophysics Data System (ADS)

    Hedenquist, Jeffrey W.; Goff, Fraser; Phillips, Fred M.; Elmore, David; Stewart, Michael K.

    1990-11-01

    The Mokai geothermal system, New Zealand, is located within a volcanic collapse structure comprised of flat-lying silicic rocks. The deep chloride fluid rises in the south, inside the caldera margin; near the surface the fluid flows laterally more than 12 km to the north, because of the hydraulic gradient caused by 300 m of relief. The maximum measured temperature of the production wells is near 323°C at 2500 m depth, whereas temperatures in two wells on the northern margin of the upflow are <200°C, with thermal inversions at 350 and 1000 m indicating lateral flow. These two marginal wells have about 50% of the chloride of the deep fluid, indicating dilution by cold ground water. Chloride-bearing springs discharge 6 km north of the zone of upflow and are even further diluted by cold groundwater than the wells on the margin of the system. The tritium data in this hydrologically rather simple system indicate that there is a mean residence time of greater than 100 years for the groundwater diluent; also, older water is mixed with <25% of young (thermonuclear, post-1955) water before the mixture dilutes outflowing chloride fluid from the deep system. The deep chloride fluid has a 36Cl/Cl ratio of 2.6×10-15 and a 36Cl concentration of 106 atoms per 10-6 kg. This fluid has a lower ratio (by a factor of 90) and a higher absolute concentration (by a factor of 7) than present-day stream water. However, the marginal wells have been diluted by groundwater with at least 500 36Cl atoms per 10-6 kg, 30 times richer in 36Cl than present-day stream waters. This spike is most likely due to circulation of precipitation formed during thermonuclear testing to depths of 1000 m (though the component with the 36Cl spike only makes a moderate, <25%, contribution to the groundwater diluent; most of the diluent is much older, pre-1955). The amount of 36Cl in the deep fluid at Mokai is 5-10 times less than that predicted from a calculation of the neutron fluxes in the silicic reservoir and underlying greywacke basement rocks. This indicates that the chloride was not derived from host rock leaching in the upper 3 km; rather, the fluids have interacted with more primitive rocks below the drilled depths of the Taupo Volcanic Zone, with the chloride possibly derived from a magmatic brine.

  9. Isotope dilution analysis of polychlorinated biphenyls (PCBs) in transformer oil and global commercial PCB formulations by high resolution gas chromatography-high resolution mass spectrometry.

    PubMed

    Takasuga, Takumi; Senthilkumar, Kurunthachalam; Matsumura, Tohru; Shiozaki, Ken; Sakai, Shin-ichi

    2006-01-01

    Special polychlorinated biphenyls (PCBs) standards (native and isotope labeled) were analyzed by isotope dilution method using HRGC-HRMS. Multiple analysis of special PCBs standards by three different laboratories produced the relative response factors (RRFs) and relative standard deviations (RSDs %) was in the average of 0.979 and 3.86, respectively. Additionally, inter-laboratory analysis of various forms of transformer oil revealed the PCBs concentrations were in the following order; PCBs fortified transformer oil (940-1300 ng/g)>PCB polluted transformer oil (490-680 ng/g)>chemically degraded-transformer oil (480-490 ng/g) and PCBs free oil (ND-17 ng/g). Chemical degradation resulted in an order of magnitude decrease in the PCB concentrations. Specifically, higher chlorinated PCBs degraded into lower chlorinated PCBs. Also, composition of PCBs have been determined in PCB formulations from Japan (Kanechlor), Germany (Clophen), USA (Aroclor), Russia (Sovol) and Poland (Chlorofen). Major PCBs (24-PCB congeners) contributed 54-67%, 55-68%, 16-69%, 71% and 72% in Kanechlor, Clophen, Aroclor, Sovol and Chlorofen, respectively to total PCBs. The homologue pattern of Kanechlor, Aroclor and Clophen in technical fromulation was similar (e.g., Kanechlor-300 resembled to those of Clophen A-30 and Aroclor-1242). Furthermore, congener-specific distributions of major PCBs/dioxin-like PCBs and toxic equivalency quantities (TEQ) were calculated. Based on our tentative assumption calculations, cumulative production of five different technical PCB formulations, WHO-TEQ emission was estimated to be approximately 16.05 tons. PMID:15946725

  10. Measurement of progesterone in human serum by isotope dilution liquid chromatography-tandem mass spectrometry and comparison with the commercial chemiluminescence immunoassay.

    PubMed

    Lee, Hwashim; Park, Chang Joon; Lee, Gaeho

    2010-03-01

    Progesterone is one of the steroid hormones. The hormone is especially important in preparing the uterus for the implantation of the blastocyst and in maintaining pregnancy. Its concentration in serum is measured to determine ovarian function and to predict early pregnancy. The progesterone concentration is also important for in-vitro fertilization and embryo-transfer outcomes. We have established isotope dilution liquid chromatography-tandem mass spectrometry as a primary method for the measurement of progesterone in human serum. Progesterone and its isotopic analogue, progesterone-(13)C(2), in serum were monitored at mass transitions of m/z 315.2/109.2 and 317.2/111.2 respectively in multiple-reaction monitoring (MRM) mode with electrospray positive ionization. For validation of the method, progesterone in a National Institute of Standards and Technology standard reference material (NIST SRM) was measured, and the measured results were in good agreement with the reference values within the uncertainty. On the basis of the established method, progesterone certified reference material (CRM) was developed in this work. The certified value was (1.41?±?0.036) ?g kg(-1). The repeatability of 1.1% and reproducibility of 0.14% showed that ID LC-MS-MS is a reliable and reproducible method. The expanded uncertainty for the measurement of progesterone in the CRM was approximately 2.6% within 95% confidence limits. The detection limit of progesterone was approximately 0.6 ?g kg(-1). The progesterone CRMs were distributed to representative clinical laboratories in the Republic of Korea for comparison with the chemiluminescence immunoassay (CLIA), which is the most sensitive immunoassay method. The results from the comparison showed quite a large bias among the participating laboratories. This implies that the CRM is a very important material for establishment of traceability to its practical use. PMID:20107773

  11. Body composition in Nepalese children using isotope dilution: the production of ethnic-specific calibration equations and an exploration of methodological issues

    PubMed Central

    Grijalva-Eternod, Carlos S.; Roberts, Sebastian; Chaube, Shiva Shankar; Saville, Naomi M.; Manandhar, Dharma S.; Costello, Anthony; Osrin, David; Wells, Jonathan C.K.

    2015-01-01

    Background. Body composition is important as a marker of both current and future health. Bioelectrical impedance (BIA) is a simple and accurate method for estimating body composition, but requires population-specific calibration equations. Objectives. (1) To generate population specific calibration equations to predict lean mass (LM) from BIA in Nepalese children aged 7–9 years. (2) To explore methodological changes that may extend the range and improve accuracy. Methods. BIA measurements were obtained from 102 Nepalese children (52 girls) using the Tanita BC-418. Isotope dilution with deuterium oxide was used to measure total body water and to estimate LM. Prediction equations for estimating LM from BIA data were developed using linear regression, and estimates were compared with those obtained from the Tanita system. We assessed the effects of flexing the arms of children to extend the range of coverage towards lower weights. We also estimated potential error if the number of children included in the study was reduced. Findings. Prediction equations were generated, incorporating height, impedance index, weight and sex as predictors (R2 93%). The Tanita system tended to under-estimate LM, with a mean error of 2.2%, but extending up to 25.8%. Flexing the arms to 90° increased the lower weight range, but produced a small error that was not significant when applied to children <16 kg (p 0.42). Reducing the number of children increased the error at the tails of the weight distribution. Conclusions. Population-specific isotope calibration of BIA for Nepalese children has high accuracy. Arm position is important and can be used to extend the range of low weight covered. Smaller samples reduce resource requirements, but leads to large errors at the tails of the weight distribution. PMID:25780755

  12. Structural, thermal, and safety analyses of isotope heat source and integrated heat exchangers for 6-kWe dynamic isotope power system (DIPS)

    Microsoft Academic Search

    Alfred Schock

    1992-01-01

    The design of a 30-kWt isotope heat source integrated with a Rankine boiler and a Brayton gas heater was subjected to structural, thermal, and safety analyses. Detailed structural analyses of the heat source integrated with the boiler and gas heater showed positive safety margins at all locations during launch. Detailed thermal analyses during assembly, transfer, and orbital operations showed acceptable

  13. A novel approach for high sensitive determination of sulfur mustard by derivatization and isotope-dilution LC-MS/MS analysis.

    PubMed

    Xu, Bin; Zong, Cheng; Nie, Zhiyong; Guo, Lei; Xie, Jianwei

    2015-01-01

    A new isotope-dilution liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for determination of sulfur mustard (SM) has been developed using a direct chemical derivatization method by nucleophile potassium thioacetate (PTA) in aqueous solution. The reaction conditions for derivatization, such as reaction temperature, time, solvent and concentration of PTA, were optimized for high performance. Reversed phase liquid chromatography was suitable for analysis of such a PTA derivatized SM in complex environmental samples. Compared with other conventional gas chromatography or gas chromatography-mass spectrometry methods for direct detection on SM, better sensitivity and selectivity were achieved by this direct derivatization and LC-MS/MS method, where SM can be detected as low as 0.05 ng/mL in acetonitrile. The linear range was from 0.1 to 1000 ng/mL. The relative standard deviation (RSD) of the intra-day precision was less than 11.8%, and RSD of the inter-day precision was less than 12.3%. The whole procedure for both derivatization and analysis was quick and simple, and the total time was less than 1h. This established method has been successfully employed for determination of spiking samples both in water and soil. A detection limit of 0.1 ng/mL was achieved for river water, while the SM in soil sample could be detected at 0.1 ng/g. PMID:25476305

  14. Analysis of permethrin isomers in composite diet samples by molecularly imprinted solid-phase extraction and isotope dilution gas chromatography-ion trap mass spectrometry.

    PubMed

    Vonderheide, Anne P; Boyd, Brian; Ryberg, Anna; Yilmaz, Ecevit; Hieber, Thomas E; Kauffman, Peter E; Garris, Sherry T; Morgan, Jeffrey N

    2009-05-29

    Determination of an individual's aggregate dietary ingestion of pesticides entails analysis of a difficult sample matrix. Permethrin-specific molecularly imprinted polymer (MIP) solid-phase extraction cartridges were developed for use as a sample preparation technique for a composite food matrix. Vortexing with acetonitrile and centrifugation were found to provide optimal extraction of the permethrin isomers from the composite foods. The acetonitrile (with 1% acetic acid) was mostly evaporated and the analytes reconstituted in 90:10 water/acetonitrile in preparation for molecularly imprinted solid-phase extraction. Permethrin elution was accomplished with acetonitrile and sample extracts were analyzed by isotope dilution gas chromatography-ion trap mass spectrometry. Quantitation of product ions provided definitive identification of the pesticide isomers. The final method parameters were tested with fortified composite food samples of varying fat content (1%, 5%, and 10%) and recoveries ranged from 99.3% to 126%. Vegetable samples with incurred pesticide levels were also analyzed with the given method and recoveries were acceptable (81.0-95.7%). Method detection limits were demonstrated in the low ppb range. Finally, the applicability of the MIP stationary phase to extract other pyrethroids, specifically cyfluthrin and cypermethrin, was also investigated. PMID:19393156

  15. Proficiency testing for determination of pesticide residues in soybean: comparison of assigned values from participants' results and isotope-dilution mass spectrometric determination.

    PubMed

    Yarita, Takashi; Otake, Takamitsu; Aoyagi, Yoshie; Kuroiwa, Takayoshi; Numata, Masahiko; Takatsu, Akiko

    2015-01-01

    Proficiency testing (PT) for the determination of pesticide residues in soybean samples was organized by the National Metrology Institute of Japan (NMIJ). The candidate certified reference material, NMIJ CRM 7509-a, that was prepared from the raw soybeans containing target pesticides (diazinon, fenitrothion, chlorpyrifos, and permethrin) was used as the test sample. Forty participants submitted two sets of analytical results along with the details of the analytical method and conditions they applied. Two types of assigned values were established for each target pesticide: one was derived from the analytical results of the participants, and the other was provided from the analytical results by isotope-dilution mass spectrometry (IDMS). The latter values were 7.4-16% higher than the former values, plausibly because the analytical values from the IDMS measurements were not affected by the recovery ratio of the target pesticides during the analytical process. Thus, two kinds of z-scores were calculated for individual participants using the corresponding assigned values: one (z1-score) showed the relative performance score for the present PT and the other (z2-score) could be used for evaluation of the trueness of their analytical methods. PMID:25476308

  16. Quantification of 13 priority polycyclic aromatic hydrocarbons in human urine by headspace solid-phase microextraction gas chromatography-isotope dilution mass spectrometry.

    PubMed

    Campo, Laura; Mercadante, Rosa; Rossella, Federica; Fustinoni, Silvia

    2009-01-12

    Polycyclic aromatic hydrocarbons (PAHs) are common environmental pollutants in both living and working environments. The aim of this study was the development of a headspace solid-phase microextraction gas chromatography-isotope dilution mass spectrometry (HS-SPME/GC-IDMS) method for the simultaneous quantification of 13 PAHs in urine samples. Different parameters affecting PAHs extraction by HS-SPME were considered and optimized: type/thickness of fiber coatings, extraction temperature/time, desorption temperature/time, ionic strength and sample agitation. The stability of spiked PAHs solutions and of real urine samples stored up to 90 days in containers of different materials was evaluated. In the optimized method, analytes were absorbed for 60min at 80 degrees C in the sample headspace with a 100mum polydimethylsiloxane fiber. The method is very specific, with linear range from the limit of quantification to 8.67 x 10(3)ngL(-1), a within-run precision of <20% and a between-run precision of <20% for 2-, 3- and 4-ring compounds and of <30% for 5-ring compounds, trueness within 20% of the spiked concentration, and limit of quantification in the 2.28-2.28 x 10(1)ngL(-1) range. An application of the proposed method using 15 urine samples from subjects exposed to PAHs at different environmental levels is shown. PMID:19084626

  17. Regional water-quality analysis of 2,4-D and dicamba in river water using gas chromatography-isotope dilution mass spectrometry

    USGS Publications Warehouse

    Thurman, E.M.; Zimmerman, L.R.; Aga, D.S.; Gilliom, R.J.

    2001-01-01

    Gas chromatography with isotope dilution mass spectrometry (GC-MS) and enzyme-linked immunosorbent assay (ELISA) were used in regional National Water Quality Assessment studies of the herbicides, 2,4-D and dicamba, in river water across the United States. The GC-MS method involved solid-phase extraction, derivatized with deutemted 2,4-D, and analysis by selected ion monitoring. The ELISA method was applied after preconcentration with solid-phase extraction. The ELISA method was unreliable because of interference from humic substances that were also isolated by solid-phase extraction. Therefore, GC-MS was used to analyzed 80 samples from river water from 14 basins. The frequency of detection of dicamba (28%) was higher than that for 2,4-D (16%). Concentrations were higher for dicamba than for 2,4-D, ranging from less than the detection limit (<0.05 ??g/L) to 3.77 ??g/L, in spite of 5 times more annual use of 2,4-D as compared to dicamba. These results suggest that 2,4-D degrades more rapidly in the environment than dicamba.

  18. Simplified method for the determination of Ru, Pd, Re, Os, Ir and Pt in chromitites and other geological materials by isotope dilution ICP-MS and acid digestion.

    PubMed

    Meisel, T; Moser, J; Fellner, N; Wegscheider, W; Schoenberg, R

    2001-03-01

    A method for the determination of low Ru, Pd, Re, Os, Ir and Pt abundances in geological reference materials by isotope dilution inductively coupled plasma mass spectrometry (ICP-MS) after acid digestion in a high pressure asher (HPA-S) is presented. The digestion technique is similar to that using Carius tubes but easier to handle and reaches higher temperatures. Osmium can be determined as OsO4 with ICP-MS directly after digestion through a sparging technique. The remaining elements are preconcentrated by means of anion column chromatography. The resin is digested directly without elution leading to high yields but this causes problems if Zr is present at higher levels in the silicate rich materials. The analytical results for international platinum group element (PGE) reference materials, chromitite CHR-Bkg, basalt TDB-1 and gabbro WGB-1, are presented and compared with literature data, demonstrating the validity of the described method. Although higher in concentration, PGEs determined for reference material WGB-1 were worse than for TDB-1 indicating a more inhomogeneous distribution of the platinum group mineral phases. The low PGE abundance chromitite standard, CHR-Bkg, is likely to be homogeneous for Ru, Re, Os and Ir and is recommended as a reference material for the study of chromitites. Detection limits (3s x total procedure blank) range from 0.012 ng (Re and Os) to 0.77 ng (Pt), which could be further improved by applying higher quality acids. PMID:11284333

  19. Studies on the analysis of 25-hydroxyvitamin D3 by isotope-dilution liquid chromatography–tandem mass spectrometry using enzyme-assisted derivatisation

    PubMed Central

    Abdel-Khalik, Jonas; Crick, Peter J.; Carter, Graham D.; Makin, Hugh L.; Wang, Yuqin; Griffiths, William J.

    2014-01-01

    The total serum concentration of 25-hydroxyvitamins D (25-hydroxyvitamin D3 and 25-hydroxyvitamin D2) is currently used as an indicator of vitamins D status. Vitamins D insufficiency is claimed to be associated with multiple diseases, thus accurate and precise reference methods for the quantification of 25-hydroxyvitamins D are needed. Here we present a novel enzyme-assisted derivatisation method for the analysis of vitamins D metabolites in adult serum utilising 25-[26,26,26,27,27,27-2H6]hydroxyvitamin D3 as the internal standard. Extraction of 25-hydroxyvitamins D from serum is performed with acetonitrile, which is shown to be more efficient than ethanol. Cholesterol oxidase is used to oxidize the 3?-hydroxy group in the vitamins D metabolites followed by derivatisation of the newly formed 3-oxo group with Girard P reagent. 17?-Hydroxysteroid dehydrogenase type 10 is shown to oxidize selectively the 3?-hydroxy group in the 3?-hydroxy epimer of 25-hydroxyvitamin D3. Quantification is achieved by isotope-dilution liquid chromatography–tandem mass spectrometry. Recovery experiments for 25-hydroxyvitamin D3 performed on adult human serum give recovery of 102–106%. Furthermore in addition to 25-hydroxyvitamin D3, 24,25-dihydroxyvitamin D3 and other uncharacterised dihydroxy metabolites, were detected in adult human serum. PMID:24486315

  20. Double spike isotope dilution GC-ICP-MS for evaluation of mercury species transformation in real fish samples using ultrasound-assisted extraction.

    PubMed

    Esteban-Fernández, Diego; Mirat, Manuela; de la Hinojosa, M Ignacia Martín; Alonso, J Ignacio García

    2012-08-29

    Sample preparation continues being a key factor to obtain fast and reliable quantification of Hg species. Assisted procedures enhance the efficiency and reduce the extraction time; however, collateral species transformations have been observed. Moreover, differential interconversions have been observed even between similar matrixes, which introduce an important uncertainty for real sample analysis. Trying to minimize Hg species transformations, we have tested a soft ultrasound-assisted extraction procedure. Species quantification and transformations have been evaluated using double spike isotope dilution analysis (IDA) together with gas chromatography inductively coupled plasma mass spectrometry (GC-ICP-MS) for a CRM material (Tort-2) and shark and swordfish muscle samples. Optimum extraction solution and sonication time led to quantitative extraction and accurate determination of MeHg and IHg in a short time, although different behaviors regarding species preservation were observed depending on the sample. Negligible species transformations were observed in the analysis of the CRM, while a small but significant demethylation factor was observed in the case of real samples. In comparison with other extraction procedures, species transformations became smaller, and fewer differences between fish species were found. Similar results were obtained for fresh and lyophilized samples of both fish samples, which permit one to analyze the fresh sample directly and save time in the sample preparation step. The high grade of species preservation and the affordability of the extraction procedure allow one to obtain accurate determinations even for routine laboratories using quantification techniques, which do not estimate species transformations. PMID:22827829

  1. Measurement of (5'R)- and (5'S)-8,5'-cyclo-2'-deoxyadenosines in DNA in vivo by liquid chromatography/isotope-dilution tandem mass spectrometry

    SciTech Connect

    Jaruga, Pawel [Chemical Science and Technology Laboratory, National Institute of Standards and Technology, Gaithersburg, MD 20899 (United States) [Chemical Science and Technology Laboratory, National Institute of Standards and Technology, Gaithersburg, MD 20899 (United States); Department of Clinical Biochemistry, Collegium Medicum, Nicolaus Copernicus University, Bydgoszcz (Poland); Xiao, Yan; Nelson, Bryant C. [Chemical Science and Technology Laboratory, National Institute of Standards and Technology, Gaithersburg, MD 20899 (United States)] [Chemical Science and Technology Laboratory, National Institute of Standards and Technology, Gaithersburg, MD 20899 (United States); Dizdaroglu, Miral, E-mail: miral@nist.gov [Chemical Science and Technology Laboratory, National Institute of Standards and Technology, Gaithersburg, MD 20899 (United States)] [Chemical Science and Technology Laboratory, National Institute of Standards and Technology, Gaithersburg, MD 20899 (United States)

    2009-09-04

    Oxidatively induced DNA lesions (5'R)- and (5'S)-8,5'-cyclo-2'-deoxyadenosines (R-cdA and S-cdA) are detectable and accumulate in vivo due to disease states and defects in DNA repair. They block transcription and inhibit gene expression, and may play a role in disease processes. Accurate measurement of these lesions in DNA in vivo is necessary to understand their biological effects. We report on a methodology using liquid chromatography/isotope-dilution tandem mass spectrometry to measure R-cdA and S-cdA in DNA. This methodology permitted the detection of these compounds at a level of 0.1 fmol on-column. Levels of R-cdA and S-cdA in mouse liver DNA amounted to 0.133 {+-} 0.024 and 0.498 {+-} 0.065 molecules/10{sup 7} DNA 2'-deoxynucleosides, respectively. The successful measurement of R-cdA and S-cdA in DNA in vivo suggests that this methodology will be used for understanding of their repair and biological consequences, and that these compounds may be used as putative biomarkers for disease states.

  2. Measurement of 2-carboxyarabinitol 1-phosphate in plant leaves by isotope dilution. [Spinacea oleracea; Triticum aestivum; Arabidopsis thaliana; Maize; Phaseolus vulgaris; Petunia hybrida

    SciTech Connect

    Moore, B.D.; Kobza, J.; Seemann, J.R. (Univ. of Nevada, Reno (United States))

    1991-05-01

    The level of 2-carboxyarabinitol 1-phosphate (CA1P) in leaves of 12 species was determined by an isotope dilution assay. {sup 14}C-labeled standard was synthesized from (2-{sup 14}C)carboxyarabinitol 1,5-bisphosphate using acid phosphatase, and was added at the initial point of leaf extraction. Leaf CA1P was purified and its specific activity determined. CA1P was found in dark-treated leaves of all species examined, including spinach (Spinacea oleracea), wheat (Triticum aestivum), Arabidopsis thaliana, and maize (Zea mays). The highest amounts were found in bean (Phaseolus vulgaris) and petunia (Petunia hybrida), which had 1.5 to 1.8 moles CA1P per mole ribulose 1,5-bisphosphate carboxylase catalytic sites. Most species had intermediate amounts of CA1P (0.2 to 0.8 mole CA1P per mole catalytic sites). Such intermediate to high levels of CA1P support the hypothesis that CA1P functions in many species as a light-dependent regulator of ribulose 1,5-bisphosphate carboxylase activity and whole leaf photosynthetic CO{sub 2} assimilation. However, CA1P levels in spinach, wheat, and A. thaliana were particularly low (less than 0.09 mole CA1P per mole catalytic sites). In such species, CA1P does not likely have a significant role in regulating ribulose 1,5-bisphosphate carboxylase activity, but could have a different physiological role.

  3. A Sr-isotopic comparison between thermal waters, rocks, and hydrothermal calcites, Long Valley caldera, California

    USGS Publications Warehouse

    Goff, F.; Wollenberg, H.A.; Brookins, D.C.; Kistler, R.W.

    1991-01-01

    The 87Sr/86Sr values of thermal waters and hydrothermal calcites of the Long Valley caldera geothermal system are more radiogenic than those of young intracaldera volcanic rocks. Five thermal waters display 87Sr/86Sr of 0.7081-0.7078 but show systematically lighter values from west to east in the direction of lateral flow. We believe the decrease in ratio from west to east signifies increased interaction of deeply circulating thermal water with relatively fresh volcanic rocks filling the caldera depression. All types of pre-, syn-, and post-caldera volcanic rocks in the west and central caldera have (87Sr/86Sr)m between about 0.7060 and 0.7072 and values for Sierra Nevada granodiorites adjacent to the caldera are similar. Sierran pre-intrusive metavolcanic and metasedimentary rocks can have considerably higher Sr-isotope ratios (0.7061-0.7246 and 0.7090-0.7250, respectively). Hydrothermally altered volcanic rocks inside the caldera have (87Sr/86Sr)m slightly heavier than their fresh volcanic equivalents and hydrothermal calcites (0.7068-0.7105) occupy a midrange of values between the volcanic/plutonic rocks and the Sierran metamorphic rocks. These data indicate that the Long Valley geothermal reservoir is first equilibrated in a basement complex that contains at least some metasedimentary rocks. Reequilibration of Sr-isotope ratios to lower values occurs in thermal waters as convecting geothermal fluids flow through the isotopically lighter volcanic rocks of the caldera fill. ?? 1991.

  4. Estradiol-17 beta quantified in serum by isotope dilution-gas chromatography-mass spectrometry: reversed-phase C18 high-performance liquid chromatography compared with immuno-affinity chromatography for sample pretreatment.

    PubMed

    Thienpont, L M; Verhaeghe, P G; Van Brussel, K A; De Leenheer, A P

    1988-10-01

    Here, isotope dilution-gas chromatography-mass spectometry is used as a reference technique for determining the concentration of estradiol-17 beta in candidate human serum Reference Material. The accuracy of assigned concentrations in biologic materials is not only determined by instrumental performance, it also depends greatly on the selectivity of the procedure for isolating the analyte from the biological matrix, an issue which we consider insufficiently addressed in the literature. We introduced reversed-phase C18 high-performance liquid chromatography as a fractionation procedure in addition to the commonly used solvent extraction and column chromatography on Sephadex LH-20. The validity of this approach as part of a Reference Method for measurement of estradiol-17 beta by isotope dilution-gas chromatography-mass spectrometry was investigated by comparison with immuno-affinity chromatography, which on theoretical grounds is generally considered as highly selective. PMID:3168218

  5. Analysis of non-fat soybean powder for the mass fractions of three elements: Copper and zinc by isotope dilution ICP–MS and calcium by ICP–AES

    Microsoft Academic Search

    Yiu-chung Yip; Kam-kit Chan; Ping-yuk Cheung; Kwok-wai Poon; Wing-cheong Sham

    2009-01-01

    Isotope dilution inductively coupled plasma–mass spectrometry with “approximate match” approach was developed for the measurement of mass fractions of Cu and Zn. An “approximate match” (within 10%) was made between calibration and sample blends. The method was validated against two certified reference materials, namely NIST SRM 1515 (Apple Leaves) and IAEA-359 (Cabbage). Inductively coupled plasma-atomic emission spectrometry with bracketing technique

  6. Fission yields of In isotopes in the thermal neutron fission of 235 U

    Microsoft Academic Search

    M. Shmid; G. Engler

    1983-01-01

    Fission yields of124–132In in the thermal neutron fission of235U were determined for the first time. Charge displacements?Z=Zp-ZUCD were calculated for the corresponding mass chains. Both fission yields and charge displacement values were compared with those obtained by systematics by Wahl et al. and Wolfsberg. It was found that the fission yields of the In isotopes obey the gaussian distribution. The

  7. Independent yields of Rb and Cs isotopes from thermal-neutron induced fission of 235U

    Microsoft Academic Search

    S. J. Balestrini; R. Decker; H. Wollnik; K. D. Wuensch; G. Jung; E. Koglin; G. Siegert

    1979-01-01

    The relative yields of Rb and Cs isotopes from thermal-neutron fission of 235U have been redetermined using the mass separator OSTIS, on-line at a neutron guide of the High-Flux Beam Reactor at the Institut Laue-Langevin, Grenoble, France. The separator ion source was a hot oven containing 235U in a graphite matrix. The neutron beam was pulsed. Alkali fission products diffused

  8. New Measurement of the Thermal-capture Cross Section for the Minor Isotope 180W

    NASA Astrophysics Data System (ADS)

    Hurst, A. M.; Firestone, R. B.; Szentmiklósi, L.; Révay, Zs.; Basunia, M. S.; Belgya, T.; Escher, J. E.; Krti?ka, M.; Summers, N. C.; Sleaford, B. W.

    2014-05-01

    Tungsten occurs naturally in five isotopic forms; four of them, 182,183,184,186W, contribute significantly to the overall elemental abundance (with each contribution between 14 and 30 %), whereas 180W only occurs at the 0.12 % level and is a minor isotope. Given its very low abundance, a precise measurement of the thermal neutron-capture cross section is extremely challenging. This work reports a new value of the thermal neutron-capture cross section from a direct 180W(n,?) measurement using a guided-thermal beam at the Budapest Research Reactor, incident upon an 11.35 % enriched sample to induce prompt ?-ray activation within the sample. The thermal-capture cross section was determined as the sum of experimentally observed partial neutron-capture ?-ray cross sections feeding the ground state directly, and, the modeled contribution from the (unobserved) ground-state feeding predicted from statistical-model calculations using the Monte Carlo program DICEBOX. The preliminary value of the 180W(n,?) thermal neutron-capture cross section is 20.5(42) b.

  9. High-precision determination of osmium and rhenium isotope ratios by in situ oxygen isotope ratio correction using negative thermal ionization mass spectrometry

    Microsoft Academic Search

    Yongzhong Liu; Min Huang; Akimasa Masuda; Masao Inoue

    1998-01-01

    The Os and Re isotope ratios were determined from the measurements of OsO3 and ReO4? ions by negative thermal ionization mass spectrometry. It was found that the oxygen isotope ratios of OsO3? and ReO4 ions vary to a large extent by the fluctuations in oxygen pressure in the ion source of the mass spectrometer and that the stability of oxygen

  10. Essentials of iron, chromium, and calcium isotope analysis of natural materials by thermal ionization mass spectrometry

    USGS Publications Warehouse

    Fantle, M.S.; Bullen, T.D.

    2009-01-01

    The use of isotopes to understand the behavior of metals in geological, hydrological, and biological systems has rapidly expanded in recent years. One of the mass spectrometric techniques used to analyze metal isotopes is thermal ionization mass spectrometry, or TIMS. While TIMS has been a useful analytical technique for the measurement of isotopic composition for decades and TIMS instruments are widely distributed, there are significant difficulties associated with using TIMS to analyze isotopes of the lighter alkaline earth elements and transition metals. Overcoming these difficulties to produce relatively long-lived and stable ion beams from microgram-sized samples is a non-trivial task. We focus here on TIMS analysis of three geologically and environmentally important elements (Fe, Cr, and Ca) and present an in-depth look at several key aspects that we feel have the greatest potential to trouble new users. Our discussion includes accessible descriptions of different analytical approaches and issues, including filament loading procedures, collector cup configurations, peak shapes and interferences, and the use of isotopic double spikes and related error estimation. Building on previous work, we present quantitative simulations, applied specifically in this study to Fe and Ca, that explore the effects of (1) time-variable evaporation of isotopically homogeneous spots from a filament and (2) interferences on the isotope ratios derived from a double spike subtraction routine. We discuss how and to what extent interferences at spike masses, as well as at other measured masses, affect the double spike-subtracted isotope ratio of interest (44Ca/40Ca in the case presented, though a similar analysis can be used to evaluate 56Fe/54Fe and 53Cr/52Cr). The conclusions of these simulations are neither intuitive nor immediately obvious, making this examination useful for those who are developing new methodologies. While all simulations are carried out in the context of a specific isotope system, it should be noted that the same methods can be used to evaluate any isotope system of interest. ?? 2008 Elsevier B.V.

  11. Fission yields in the symmetric region: Yields of the stable isotopes of tin and cadmium in the thermal neutron fission of 235U and 239Pu

    Microsoft Academic Search

    C. K. Mathews

    1977-01-01

    The relative isotopic abundances of five isotopes of cadmium (111, 112, 113, 114, and 116) and eight isotopes of tin (117, 118, 119, 120, 21, 122, 124, and 126) have been measured in the thermal neutron fission of 235U and 239Pu. Samples of 235U and 239Pu were irradiated in a reactor; the elements were chemically separated and the isotopic abundances

  12. Simultaneous determination of four sulfur mustard-DNA adducts in rabbit urine after dermal exposure by isotope-dilution liquid chromatography-tandem mass spectrometry.

    PubMed

    Zhang, Yajiao; Yue, Lijun; Nie, Zhiyong; Chen, Jia; Guo, Lei; Wu, Bidong; Feng, Jianlin; Liu, Qin; Xie, Jianwei

    2014-06-15

    Sulfur mustard (SM) is a classic vesicant agent, which has been greatly employed in several wars or military conflicts. The most lesion mechanism is its strong alkylation of DNAs in vivo. Until now there are four specific DNA adducts of SM identified for further retrospective detection, i.e., N(7)-(2-hydroxyethylthioethyl)-2'-guanine (N(7)-HETEG), bis(2-ethyl-N(7)-guanine)thioether (Bis-G), N(3)-(2-hydroxyethylthioethyl)-2'-adenine (N(3)-HETEA) and O(6)-(2-hydroxyethylthioethyl)-2'-guanine (O(6)-HETEG), respectively. Here, a novel and sensitive method of isotope-dilution ultrahigh performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) combining with solid phase extraction was reported for the simultaneous determination of four SM-DNA adducts. A lower limit of detection of 2-5ngL(-1), and a lower limit of quantitation of 5-10ngL(-1) were achieved, respectively, and the recoveries ranged from 87% to 116%. We applied this method in the determination of four SM-DNA adducts in rabbit urine after dermal exposure by SM in three dose levels (2, 5, 15mgkg(-1)), so as to investigate the related metabolic behavior in vivo. For the first time, in SM exposed rabbit urine, our results revealed the relative accumulation abundance of four SM-DNA adducts, i.e., 67.4% for N(7)-HETEG, 22.7% for Bis-G, 9.8% for N(3)-HETEA, 0.1% for O(6)-HETEG, and significant dose and time dependent responses of these SM-DNA adducts. The four adducts were detectable after 8h, afterwards, their contents continuously increased, achieved maximum in the first two or three days and then gradually decreased till the end of one month. Meanwhile, the amounts of SM-DNA adducts were positively correlated with the exposure doses. PMID:24858262

  13. Quantification of key red blood cell folates from subjects with defined MTHFR 677C>T genotypes using stable isotope dilution liquid chromatography/mass spectrometry

    PubMed Central

    Huang, Yuehua; Khartulyari, Stefanie; Morales, Megan E.; Stanislawska-Sachadyn, Anna; Von Feldt, Joan M.; Whitehead, Alexander S.; Blair, Ian A.

    2014-01-01

    Red blood cell (RBC) folate levels are established at the time of erythropoiesis and therefore provide a surrogate biomarker for the average folate status of an individual over the preceding four months. Folates are present as folylpolyglutamates, highly polar molecules that cannot be secreted from the RBCs, and must be converted into their monoglutamate forms prior to analysis. This was accomplished using an individual’s plasma pteroylpolyglutamate hydrolase by lysing the RBCs in whole blood at pH 5 in the presence of ascorbic acid. Quantitative conversion of formylated tetrahydrofolate derivatives into the stable 5,10-methenyltetrahydrofolate (5,10-MTHF) form was conducted at pH 1.5 in the presence of [13C5]-5-formyltetrahydrofolate. The resulting [13C5]-5,10-MTHF was then used as an internal standard for the formylated forms of tetrahydrofolate that had been converted into 5,10-MTHF as well any 5,10-MTHF that had been present in the original sample. A stable isotope dilution liquid chromatography-multiple reaction monitoring/mass spectrometry method was validated and then used for the accurate and precise quantification of RBC folic acid, 5-methyltetrahydrofolate (5-MTHF), tetrahydrofolate (THF), and 5,10-MTHF. The method was sensitive and robust and was used to assess the relationship between different methylenetetrahydrofolate reductase (MTHFR) 677C>T genotypes and RBC folate phenotypes. Four distinct RBC folate phenotypes could be identified. These were classified according to the relative amounts of individual RBC folates as type I (5-MTHF >95%; THF <5%; 5,10-MTHF <5%), type II (5-MTHF <95%; THF 5% to 20%; 5,10-MTHF <5%), type III (5-MTHF >55%; THF >20%; 5,10-MTHF >5%), and type IV (5-MTHF <55%; THF >20%; 5,10-MTHF >5%). PMID:18634122

  14. Quantitative analysis of penicillins in porcine tissues, milk and animal feed using derivatisation with piperidine and stable isotope dilution liquid chromatography tandem mass spectrometry.

    PubMed

    van Holthoon, Frédérique; Mulder, Patrick P J; van Bennekom, Eric O; Heskamp, Henri; Zuidema, Tina; van Rhijn, Hans J A

    2010-04-01

    Penicillins are used universally in both human and veterinary medicine. The European Union (EU) has established maximum residue levels (MRLs) for most ss-lactam antibiotics in milk and animal tissues and included them in the National Residue Monitoring Programs. In this study, a novel method is described for the determination and confirmation of eight penicillins in porcine tissues, milk and animal feed by liquid chromatography-tandem mass spectrometry (LC-MS/MS). To prevent degradation of penicillin residues during workup, a derivatisation procedure was developed, by which penicillins were converted to stable piperidine derivatives. Deuterated piperidine derivatives were synthesised for all relevant penicillins, enabling the use of isotope dilution for accurate quantification. Penicillin residues were derivatised in the crude extract with piperidine and isolated using solid-phase extraction. The penicillin piperidine derivatives were determined by LC-MS/MS. The method was validated at the current MRLs, which range from 25-300 microg kg(-1) in muscle and kidney to 4-30 microg kg(-1) in milk as well as at the target value of 100 microg kg(-1) chosen for animal feed, according to the EU requirements for a quantitative confirmatory method. Accuracy ranged from 94-113% (muscle), 83-111% (kidney) and 87-103% (milk) to 88-116% (animal feed). Intra-day precision (relative standard deviation (RSD)(r)) ranged from 5-13% (muscle, n = 18), 4-17% (kidney, n = 7) and 5-18% (milk, n = 7) to 11-32% (animal feed, n = 18). Inter-day precision (RSD(RL), n = 18) ranged from 6-23% (muscle) to 11-36% (animal feed). From the results, it was concluded that the method was fit for purpose at the target MRLs in animal tissue and target levels for animal feed. PMID:20186537

  15. [Determination of mono- to tri-chlorinated dibenzo-p-dioxins and dibenzofurans in stack gas using isotope dilution high resolution gas chromatography-high resolution mass spectrometry].

    PubMed

    Tang, Chen; Liu, Qipeng; Tian, Zhenyu; Xie, Huiting; Wang, Mengjing; Liu, Wenbin

    2014-09-01

    A method for the determination of mono- to tri-chlorinated dibenzo-p-dioxins and dibenzofurans (mono- to tri-CDD/Fs) in stack gas using isotope dilution high resolution gas chromatography-high resolution mass spectrometry (HRGC-HRMS) was developed. The sam- ples were extracted by Soxhlet extraction, and then the extracts were concentrated and purified using a multilayer silica gel column and a basic alumina column. The analytes were separated by HRGC on a DB-5MS column (30 m x 0.25 mm x 0.25 ?m) and determined by HRMS. The identi- fication of mono- to tri-CDD/Fs was based on the retention times of 13C-labelled standard and the abundance ratios of the two exacted mass-to-charge ratios. The quantitative analysis was performed using the ratios of the integrated areas of the 13C-labelled standards. This method had the recoveries ranging from 66.6% to 112.5% and the relative standard deviations (RSD) ranging from 19.9% to 40.5% (n = 5). The limits of detection (LODs) of this method for the mono- to tri-CDD/Fs were ranging from 0.027 to 0.485 ?g/L. Three stack gas samples from waste incinerators were measured using this method, with the recoveries ranging from 85.7% to 137.0% and the concentrations ranging from 11.4 to 9,183 pg/Nm3. The results indicated that the method can be applied to the precise determination of mono- to tri-CDD/Fs at trace level in stack gas. PMID:25752087

  16. Development of a species-unspecific isotope dilution GC-ICPMS method for possible routine quantification of sulfur species in petroleum products.

    PubMed

    Heilmann, Jens; Heumann, Klaus G

    2008-03-15

    Inductively coupled plasma mass spectrometry (ICPMS) hyphenated with capillary gas chromatography was applied for sulfur multispecies determination in petroleum products by species-unspecific isotope dilution mass spectrometry (IDMS). To guarantee a stable and continuous addition of the spike into the GC-ICPMS system, a special dosing unit was designed and synthesis of a (34)S-labeled dimethyldisulfide spike from (34)S-enriched elemental sulfur in the milligram range was developed. The sample was mixed with an internal standard for spike mass flow calibration. From the mass flow chromatogram obtained by species-unspecific GC-ICP-IDMS, determination of all separated sulfur species and of the total sulfur content was possible without any matrix influence by coeluting hydrocarbons. The accuracy of the developed method was evaluated by determining reference material SRM-2296 certified for three sulfur species and by comparison of results obtained by species-specific GC-ICP-IDMS. The total sulfur concentration determined for all separated species agreed well with the sulfur content in the original samples which demonstrated that all sulfur species have been covered. Structural characterization of sulfur species was carried out by corresponding sulfur standards and by applying electron ionization ion trap mass spectrometry. The low detection limit of 9 ng sulfur per gram sample, independent of results on coeluting hydrocarbons, and the robust instrumental design of the continuous spike flow dosing unit qualifies this species-unspecific GC-ICP-IDMS method for accurate and sensitive sulfur multispecies determinations also on a routine basis. PMID:18284218

  17. Simultaneous analysis of oxybutynin and its active metabolite N-desethyl oxybutynin in human plasma by stable isotope dilution LC-MS/MS to support a bioequivalence study.

    PubMed

    Sharma, Primal; Patel, Daxesh P; Sanyal, Mallika; Berawala, Hiren; Guttikar, Swati; Shrivastav, Pranav S

    2013-10-01

    An isotope dilution high performance liquid chromatography-tandem mass spectrometry (LC-MS/MS) method has been developed for the simultaneous determination of oxybutynin and its pharmacologically active metabolite N-desethyl oxybutynin in human plasma. Extraction of oxybutynin, its metabolite and their deuterated analogs as internal standards (ISs) from 300 ?L human plasma was carried out by liquid-liquid extraction with methyl tert-butyl ether-ethyl acetate solvent mixture. Chromatographic separation of analytes was performed on Cosmosil C18 (150 mm × 4.6 mm, 5 ?m) column under isocratic conditions with acetonitrile-1.0mM ammonium acetate (90:10, v/v) as the mobile phase. Six endogenous plasma phospholipids (496.3/184.0, 524.3/184.0, 758.5/184.0, 786.5/184.0, 806.5/184.0 and 810.5/184.0) were monitored to determine the extraction efficiency under different extraction conditions. The precursor?product ion transition for both the analytes and ISs were monitored on a triple quadrupole mass spectrometer, operating in the multiple reaction monitoring and positive ionization mode. The method was validated over a concentration range of 0.050-10.0 ng/mL for oxybutynin and 0.500-100 ng/mL for N-desethyl oxybutynin. The mean extraction recovery for analytes (80.4%) and ISs (76.9%) was consistent across five QC levels. Bench top, wet and dry extract, freeze-thaw and long term stability was evaluated for both the analytes. The method was applied to support a bioequivalence study of 5mg tablet formulation in 74 healthy Indian subjects. Assay reproducibility was demonstrated by reanalysis of 344 incurred samples. PMID:23867086

  18. Determination of 17 illicit drugs in oral fluid using isotope dilution ultra-high performance liquid chromatography/tandem mass spectrometry with three atmospheric pressure ionizations.

    PubMed

    Wang, I-Ting; Feng, Yu-Ting; Chen, Chia-Yang

    2010-11-15

    The collection of oral fluid for drug testing is easy and non-invasive. This study developed a drug testing method using ultra-high performance liquid chromatography/tandem mass spectrometry (UHPLC-MS/MS) in selected-reaction monitoring (SRM) mode. We tested the method on the analysis of four opiates and their metabolites, five amphetamines, flunitrazepam and its two metabolites, and cocaine and its four metabolites in oral fluid. 100-?L samples of oral fluid were diluted with twice the amount of water then spiked with isotope-labeled internal standards. After the samples had undergone high-speed centrifugation for 20 min, we analyzed the supernatant. The recovery of the sample preparation ranged from 81 to 108%. We compared the performance of electrospray ionization (ESI), atmospheric pressure chemical ionization (APCI) and atmospheric pressure photoionization (APPI). The ion suppression of most analytes on ESI (28-78%) was lower than that of APCI and APPI. A post-column flow split (5:1) did not reduce the matrix effect on ESI. Direct APPI performed better than dopant-assisted APPI using toluene. ESI, APCI and APPI limits of quantitation mostly ranged from 0.11 to 1.9 ng/mL, 0.02 to 2.2 ng/mL and 0.02 to 2.1 ng/mL, respectively, but were much higher on amphetamine and ecgonine methyl ester (about 2.7-4.7 ng/mL, 8.7-14 ng/mL, and 10-19 ng/mL, respectively). Most of the bias percentages (accuracy) and relative standard deviations (precision) on spiked samples were below 15%. This method greatly simplifies the process of sample preparation and shortens the chromatographic time to only 7.5 min per run and is able to detect analytes at sub-ppb levels. PMID:20951654

  19. Development of three stable isotope dilution assays for the quantitation of (E)-2-butenal (crotonaldehyde) in heat-processed edible fats and oils as well as in food.

    PubMed

    Granvogl, Michael

    2014-02-12

    Three stable isotope dilution assays (SIDAs) were developed for the quantitation of (E)-2-butenal (crotonaldehyde) in heat-processed edible fats and oils as well as in food using synthesized [¹³C?]-crotonaldehyde as internal standard. First, a direct headspace GC-MS method, followed by two indirect methods on the basis of derivatization with either pentafluorophenylhydrazine (GC-MS) or 2,4-dinitrophenylhydrazine (LC-MS/MS), was developed. All methods are also suitable for the quantitation of acrolein using the standard [¹³C?]-acrolein. Applying these three methods on five different types of fats and oils varying in their fatty acid compositions revealed significantly varying crotonaldehyde concentrations for the different samples, but nearly identical quantitative data for all methods. Formed amounts of crotonaldehyde were dependent not only on the type of oil, e.g., 0.29-0.32 mg/kg of coconut oil or 33.9-34.4 mg/kg of linseed oil after heat-processing for 24 h at 180 °C, but also on the applied temperature and time. The results indicated that the concentration of formed crotonaldehyde seemed to be correlated with the amount of linolenic acid in the oils. Furthermore, the formation of crotonaldehyde was compared to that of its homologue acrolein, demonstrating that acrolein was always present in higher amounts in heat-processed oils, e.g., 12.3 mg of crotonaldehyde/kg of rapeseed oil in comparison to 23.4 mg of acrolein/kg after 24 h at 180 °C. Finally, crotonaldehyde was also quantitated in fried food, revealing concentrations from 12 to 25 ?g/kg for potato chips and from 8 to 19 ?g/kg for donuts, depending on the oil used. PMID:24428123

  20. Simultaneous speciation of selenoproteins and selenometabolites in plasma and serum by dual size exclusion-affinity chromatography with online isotope dilution inductively coupled plasma mass spectrometry.

    PubMed

    García-Sevillano, M A; García-Barrera, T; Gómez-Ariza, J L

    2014-04-01

    A method for the simultaneous speciation of selenoproteins and selenometabolites in mouse plasma has been developed based on in series two-dimensional size exclusion and affinity high-performance liquid chromatography (2D/SE-AF-HPLC), using two columns of each type, and hyphenation to inductively coupled plasma-(quadrupole) mass spectrometry (ICP-QMS). The method allows the quantitative determination of selenoprotein P (SeP), extracellular glutathione peroxidase (eGPx), selenoalbumin (SeAlb), and selenometabolites in mouse plasma using species-unspecific isotope dilution (SUID). The 2D chromatographic separation is proposed to remove typical spectral interferences in plasma from chloride and bromide on (77)Se ((40)Ar(37)Cl) and (82)Se ((81)Br(1)H). In addition, the approach increases chromatographic resolution allowing the separation of eGPx from Se metabolites of low molecular mass. The method is robust, reliable, and fast with a typical chromatographic runtime less than 20 min. Precision in terms of relative standard deviation (n?=?5) is in the order of 4 %, and detection limits are in the range of 0.2 to 1.0 ng Se g(-1). Method accuracy for determination of total protein bound to Se was assessed by analyzing human serum reference material (BCR-637) certified for total Se content, and latterly applied to mouse plasma (Mus musculus). In summary, a reliable speciation method for the analysis of eGPx, selenometabolites, SeP, and SeAlb in plasma/serum samples is proposed for the first time and is applicable to the evaluation of Se status in human in clinical studies and other mammals for environmental or toxicological assessment. PMID:24535684

  1. OXYGEN ISOTOPIC COMPOSITIONS OF THE ALLENDE TYPE C CAIs: EVIDENCE FOR ISOTOPIC EXCHANGE DURING NEBULAR MELTING AND ASTEROIDAL THERMAL METAMORPHISM

    SciTech Connect

    Krot, A N; Chaussidon, M; Yurimoto, H; Sakamoto, N; Nagashima, K; Hutcheon, I D; MacPherson, G J

    2008-02-21

    Based on the mineralogy and petrography, coarse-grained, igneous, anorthite-rich (Type C) calcium-aluminum-rich inclusions (CAIs) in the CV3 carbonaceous chondrite Allende have been recently divided into three groups: (i) CAIs with melilite and Al,Ti-diopside of massive and lacy textures (coarse grains with numerous rounded inclusions of anorthite) in a fine-grained anorthite groundmass (6-1-72, 100, 160), (ii) CAI CG5 with massive melilite, Al,Ti-diopside and anorthite, and (iii) CAIs associated with chondrule material: either containing chondrule fragments in their peripheries (ABC, TS26) or surrounded by chondrule-like, igneous rims (93) (Krot et al., 2007a,b). Here, we report in situ oxygen isotopic measurements of primary (melilite, spinel, Al,Ti-diopside, anorthite) and secondary (grossular, monticellite, forsterite) minerals in these CAIs. Spinel ({Delta}{sup 17}O = -25{per_thousand} to -20{per_thousand}), massive and lacy Al,Ti-diopside ({Delta}{sup 17}O = -20{per_thousand} to -5{per_thousand}) and fine-grained anorthite ({Delta}{sup 17}O = -15{per_thousand} to -2{per_thousand}) in 100, 160 and 6-1-72 are {sup 16}O-enriched relative spinel and coarse-grained Al,Ti-diopside and anorthite in ABC, 93 and TS26 ({Delta}{sup 17}O ranges from -20{per_thousand} to -15{per_thousand}, from -15{per_thousand} to -5{per_thousand}, and from -5{per_thousand} to 0{per_thousand}, respectively). In 6-1-72, massive and lacy Al,Ti-diopside grains are {sup 16}O-depleted ({Delta}{sup 17}O {approx} -13{per_thousand}) relative to spinel ({Delta}{sup 17}O = -23{per_thousand}). Melilite is the most {sup 16}O-depleted mineral in all Allende Type C CAIs. In CAI 100, melilite and secondary grossular, monticellite and forsterite (minerals replacing melilite) are similarly {sup 16}O-depleted, whereas grossular in CAI 160 is {sup 16}O-enriched ({Delta}{sup 17}O = -10{per_thousand} to -6{per_thousand}) relative to melilite ({Delta}{sup 17}O = -5{per_thousand} to -3{per_thousand}). We infer that CAIs 100, 160 and CG5 experienced melting in an {sup 16}O-rich ({Delta}{sup 17}O < -20{per_thousand}) nebular gas in the CAI-forming region. The Type C and Type-B-like portions of CAI 6-1-72 experienced melting in an {sup 16}O-depleted ({Delta}{sup 17}O {ge} -13{per_thousand}) nebular gas. CAIs ABC, TS26 and 93 experienced isotopic exchange during re-melting in the presence of an {sup 16}O-poor ({Delta}{sup 17}O {ge} -10{per_thousand}) nebular gas in the chondrule-forming region(s). Subsequently, Allende Type C CAIs experienced post-crystallization isotopic exchange with an {sup 16}O-poor reservoir that affected largely melilite and anorthite. Because pseudomorphic replacement of lacy melilite by grossular, monticellite and forsterite occurred during thermal metamorphism, some oxygen isotopic exchange of melilite and anorthite must have continued after formation of these secondary minerals. We suggest that some or all oxygen isotopic exchange in melilite and anorthite occurred during fluid-assisted thermal metamorphism on the CV parent asteroid. Similar processes may have also affected melilite and anorthite of CAIs in metamorphosed CO chondrites.

  2. Disturbance of isotope systematics in meteorites during shock and thermal metamorphism and implications for shergottite chronology

    SciTech Connect

    Gaffney, A M; Borg, L E; Asmerom, Y

    2008-12-10

    Shock and thermal metamorphism of meteorites from differentiated bodies such as the Moon and Mars have the potential to disturb chronometric information contained in these meteorites. In order to understand the impact-related mechanisms and extent of disturbance to isochrons, we undertook experiments to shock and heat samples of 10017, a 3.6 billion year old lunar basalt. One sub-sample was shocked to 55 GPa, a second subsample was heated to 1000 C for one week, and a third sub-sample was maintained as a control sample. Of the isotope systems analyzed, the Sm-Nd system was the least disturbed by shock or heat, followed by the Rb-Sr system. Ages represented by the {sup 238}U-{sup 206}Pb isotope system were degraded by shock and destroyed with heating. In no case did either shock or heating alone result in rotated or reset isochrons that represent a spurious age. In some cases the true crystallization age of the sample was preserved, and in other cases age information was degraded or destroyed. Although our results show that neither shock nor thermal metamorphism alone can account for the discordant ages represented by different isotope systems in martian meteorites, we postulate that shock metamorphism may render a meteorite more susceptible than unshocked material to subsequent disturbance during impact-related heating or aqueous alteration on Mars or Earth. The combination of these processes may result in the disparate chronometric information preserved in some meteorites.

  3. Release behavior of hydrogen isotopes thermally sorbed in Li2TiO3 single crystal

    NASA Astrophysics Data System (ADS)

    Zhu, Deqiong; Oda, Takuji; Shono, Yohei; Tanaka, Satoru

    2013-11-01

    Understanding of fundamental processes governing tritium release in tritium breeder materials is important for blanket design in fusion reactors. In this paper, the release behavior of hydrogen isotopes in Li2TiO3 single crystal samples with different sizes was studied by thermal desorption spectroscopy (TDS). It was indicated that with the size of single crystal samples decreasing to several ?m, the rate-controlling step in the release of hydrogen isotopes moves from bulk diffusion to surface processes. Regarding the amount of hydroxyl groups, the surface hydroxyl groups became predominant for the grains smaller than several tens of ?ms. The amount of surface hydroxyl groups was influenced by the specific surface area and surface conditions.

  4. A Transient Model of Induced Natural Circulation Thermal Cycling for Hydrogen Isotope Separation

    SciTech Connect

    SHADDAY, MARTIN

    2005-07-12

    The property of selective temperature dependence of adsorption and desorption of hydrogen isotopes by palladium is used for isotope separation. A proposal to use natural circulation of nitrogen to alternately heat and cool a packed bed of palladium coated beads is under active investigation, and a device consisting of two interlocking natural convection loops is being designed. A transient numerical model of the device has been developed to aid the design process. It is a one-dimensional finite-difference model, using the Boussinesq approximation. The thermal inertia of the pipe walls and other heat structures as well as the heater control logic is included in the model. Two system configurations were modeled and results are compared.

  5. Rayleigh's distillation law and linear hypothesis of isotope fractionation in thermal ionization mass spectrometry

    NASA Astrophysics Data System (ADS)

    Cavazzini, Giancarlo

    2009-12-01

    The relationship which exists between Rayleigh's distillation law and linear models of instrumental isotopic fractionation in thermal ionization mass spectrometry is shown. If the process of isotope fractionation in the mass spectrometer source occurs in terms of a Rayleigh's distillation, and, within the range of mass of isotopes of the element, the vapor/residue distribution coefficient is a linear function of mass with a slope which is sufficiently small in absolute value, then the linear hypothesis of isotope fractionation is fulfilled. The model shows that the fractionation factor per amu, defined as the instantaneous difference between the measured and true values of the isotope ratio, per unit of measured/true value and per unit of mass difference between the two isotopes which define the ratio, can be interpreted as a function of two parameters: the residual mass fraction of the sample on the filament, and the rate of change of the distribution coefficient with mass. These two parameters can be calculated and, in particular, the value of the residual mass fraction of the sample when the measured values of the isotopic ratios coincide with the actual values can be calculated as a function of the rate of change with mass of the distribution coefficient. A linear model of instrumental isotopic fractionation can be derived from the exponential hypothesis of fractionation, which can be also interpreted in terms of a Rayleigh's distillation process, but where mass is an exponential function of the distribution coefficient. Experimental results of instrumental isotopic fractionation (up to 1% amu-1) of strontium in NIST standard reference material 987, loaded as a nitrate on a single tungsten filament, can be interpreted in terms of the linear models of isotope fractionation (and therefore of Rayleigh's distillation law) within experimental error. They show: (i) changes in the vapor/residue distribution coefficient with mass in the range -0.006 to -0.004 amu-1; (ii) approximately constant rates of sample consumption in the range of residual mass fraction from ~1 to ~0.3-0.25, which are between 0.05 and 0.13% min-1; (iii) values of the residual mass fraction of the sample, when the measured values of the isotopic ratios coincide with the true ones, between 0.3668 and 0.3671, which correspond to sample consumption of 63.3%. Since the linear hypothesis of fractionation is fulfilled, the values of isotopic ratios of strontium in the standard material can be determined. The global weighted averages of the weighted averages of the results obtained in eleven runs in which 86Sr, 87Sr and 88Sr peaks were sampled are as follows: 86Sr/88Sr = 0.119445 +/- 0.000053, 87Sr/86Sr = 0.71016 +/- 0.00019, and 87Sr/88Sr = 0.084826 +/- 0.000040.

  6. Effect of thermal decarbonation on the stable isotope composition of carbonates

    SciTech Connect

    Durakiewicz, T. (Tomasz); Sharp, Z. D. (Zachary D.); Papike, J. J. (James Joseph),

    2001-01-01

    The unusual texture and stable isotope variability of carbonates in AH84001 have been used as evidence for early life on Mars (Romanek et al., 1994; McKay et al., 1996). Oxygen and carbon isotope variability is most commonly attributed to low-temperature processes, including Rayleigh-like fractionation associated with biological activity. Another possible explanation for the isotopic variability in meteoritic samples is thermal decarbonation. In this report, different carbonates were heated in a He-stream until decomposition temperatures were reached. The oxygen and carbon isotope ratios ({delta}{sup 18}O and {delta}{sup 13}C values) of the resulting gas were measured on a continuous flow isotope ratio mass spectrometer. The aim of this work is to evaluate the possibility that large isotopic variations can be generated on a small scale abiogenically, by the process of thermal decarbonation. Oxygen isotope fractionations of >4{per_thousand} have been measured during decarbonation of calcite at high temperatures (McCrea, 1950), and in excess of 6{per_thousand} for dolomite decarbonated between 500 and 600 C (Sharma and Clayton, 1965). Isotopic fractionations of this magnitude, coupled with Rayleigh-like distillation behavior could result in very large isotopic variations on a small scale. To test the idea, calcite, dolomite and siderite were heated in a quartz tube in a He-stream in excess of 1 atmosphere. Simultaneous determinations of {delta}{sup 13}C and {Delta}{sup 18}O values were obtained on 250 {micro}l aliquots of the CO{sub 2}-bearing He gas using an automated 6-way switching valve system (Finnigan MAT GasBench II) and a Finnigan MAT Delta Plus mass spectrometer. It was found that decarbonation of calcite in a He atmosphere begins at 720 C, but the rate significantly increases at temperatures of 820 C. After an initial light {delta}{sup 18}O value of -14.1{per_thousand} at 720 C associated with very early decarbonation, {delta}{sup 18}0 values increase to a constant -11.8{per_thousand}, close to the accepted value of -12.09{per_thousand} (PDB). After 10 minutes at 820 C, the {delta}{sup 18}O values and signal strength both begin to decrease linearly to a {delta}{sup 18}O value of -14.75 and very low amounts of CO{sub 2} (Fig. 1). In contrast, the {delta}{sup 13}C values are extremely constant (0.12 {+-} 0.25{per_thousand}) for all measurements, in very good agreement with accepted values of 0.33{per_thousand} (PDB). There is much less isotopic variability during dolomite decarbonation. CO{sub 2} is first detected at 600 C. The signal strength increases by an order of magnitude between 670 and 700 C and again at 760 C. Both {delta}{sup 13}C and {delta}{sup 18}O values are nearly constant over the entire temperature range and sample size. For oxygen, the measured {delta}{sup 18}O values averaged -20.9 {+-} 0.7{per_thousand} (n = 30). Including only samples over 700 C, the average is -21.2 {+-} 0.2{per_thousand} compared to the accepted value of -21{per_thousand}. Carbon is similarly constant. The average {delta}{sup 13}C value is -2.50{per_thousand} compared to the accepted value of -2.62{per_thousand}. Far more variability is seen during the decomposition of siderite. Two samples were analyzed. In both samples, the initial {delta}{sup 18}O values were far lower than expected.

  7. Gas and isotope chemistry of thermal features in Yellowstone National Park, Wyoming

    USGS Publications Warehouse

    Bergfeld, Deborah; Lowenstern, Jacob B.; Hunt, Andrew G.; Shanks, W.C. Pat, III; Evans, William

    2011-01-01

    This report presents 130 gas analyses and 31 related water analyses on samples collected from thermal features at Yellowstone between 2003 and 2009. An overview of previous studies of gas emissions at Yellowstone is also given. The analytical results from the present study include bulk chemistry of gases and waters and isotope values for water and steam (delta18O, dealtaD), carbon dioxide (delta13C only), methane (delta13C only), helium, neon, and argon. We include appendixes containing photos of sample sites, geographic information system (GIS) files including shape and kml formats, and analytical results in spreadsheets. In addition, we provide a lengthy discussion of previous work on gas chemistry at Yellowstone and a general discussion of the implications of our results. We demonstrate that gases collected from different thermal areas often have distinct chemical signatures, and that differences across the thermal areas are not a simple function of surface temperatures or the type of feature. Instead, gas chemistry and isotopic composition are linked to subsurface lithologies and varying contributions from magmatic, crustal, and meteoric sources.

  8. Two-dimensional heart-cut LC-LC improves accuracy of exact-matching double isotope dilution mass spectrometry measurements of aflatoxin B1 in cereal-based baby food, maize, and maize-based feed.

    PubMed

    Breidbach, Andreas; Ulberth, Franz

    2014-07-12

    Aflatoxins, mycotoxins of fungi of the Aspergillus sp., pose a risk to consumer health and are, therefore, regulated by more than 100 countries. To facilitate method development and validation as well as assessment of measurement capabilities, availability of certified reference materials and proficiency testing schemes is important. For these purposes, highly accurate determinations of the aflatoxin content in the materials used are necessary. We describe here the use of two-dimensional heart-cut LC-LC in combination with exact-matching double isotope dilution mass spectrometry to determine the content of aflatoxin B1 in three materials used in a proficiency testing scheme. The serious reduction in ionization suppression afforded by the two-dimensional heart-cut LC-LC had a positive effect on the precision of the measured isotope ratios of the exact-matching double isotope dilution mass spectrometry. This is evidenced by the expanded measurement uncertainty (k?=?2) of 0.017 ?g/kg or 8.9 % relative to a mass fraction of aflatoxin B1 in a cereal-based baby food of 0.197 ?g/kg. This value is in perfect agreement with the consensus value of this material from a proficiency test (PT) scheme for National Reference Laboratories executed by the European Reference Laboratory for Mycotoxins. The effort necessary to perform the described methodology precludes its frequent use but for specific applications we see it as a valuable tool. PMID:25015044

  9. Ammonium in thermal waters of Yellowstone National Park: processes affecting speciation and isotope fractionation

    USGS Publications Warehouse

    Holloway, J.M.; Nordstrom, D.K.; Böhlke, J.K.; McCleskey, R.B.; Ball, J.W.

    2011-01-01

    Dissolved inorganic nitrogen, largely in reduced form (NH4(T)?NH4(aq)++NH3(aq)o), has been documented in thermal waters throughout Yellowstone National Park, with concentrations ranging from a few micromolar along the Firehole River to millimolar concentrations at Washburn Hot Springs. Indirect evidence from rock nitrogen analyses and previous work on organic compounds associated with Washburn Hot Springs and the Mirror Plateau indicate multiple sources for thermal water NH4(T), including Mesozoic marine sedimentary rocks, Eocene lacustrine deposits, and glacial deposits. A positive correlation between NH4(T) concentration and ?18O of thermal water indicates that boiling is an important mechanism for increasing concentrations of NH4(T) and other solutes in some areas. The isotopic composition of dissolved NH4(T) is highly variable (?15N = ?6‰ to +30‰) and is positively correlated with pH values. In comparison to likely ?15N values of nitrogen source materials (+1‰ to +7‰), high ?15N values in hot springs with pH >5 are attributed to isotope fractionation associated with NH3(aq)o loss by volatilization. NH4(T) in springs with low pH typically is relatively unfractionated, except for some acid springs with negative ?15N values that are attributed to NH3(g)o condensation. NH4(T) concentration and isotopic variations were evident spatially (between springs) and temporally (in individual springs). These variations are likely to be reflected in biomass and sediments associated with the hot springs and outflows. Elevated NH4(T) concentrations can persist for 10s to 1000s of meters in surface waters draining hot spring areas before being completely assimilated or oxidized.

  10. Monitoring urinary metabolites resulting from sulfur mustard exposure in rabbits, using highly sensitive isotope-dilution gas chromatography-mass spectrometry.

    PubMed

    Nie, Zhiyong; Zhang, Yajiao; Chen, Jia; Lin, Ying; Wu, Bidong; Dong, Yuan; Feng, Jianlin; Liu, Qin; Xie, Jianwei

    2014-08-01

    A highly sensitive method for the determination of sulfur mustard (SM) metabolites thiodiglycol (TDG) and thiodiglycol sulfoxide (TDGO) in urine was established and validated using isotope-dilution negative-ion chemical ionization (NICI) gas chromatography-mass spectrometry (GC-MS). TDGO in the samples was reduced with TiCl3, and then determined together with TDG as a single analyte. The sample preparation procedures, including two solid-phase-extraction (SPE) clean-up steps, were optimized to improve the sensitivity of the method. The limits of detection (LOD) for both TDG and TDG plus TDGO (TDG + TDGO) were 0.1 ng mL(-1), and the limits of quantitation (LOQ) for both were 0.3 ng mL(-1). The method was used in a rabbit cutaneous SM exposure model. Domestic rabbits were exposed to neat liquid SM at three dosage levels (0.02, 0.05, and 0.15 LD50), and the urinary excretion of four species of hydrolysis metabolites, namely free TDG, free plus conjugated TDG (total TDG), free TDG + TDGO, and free plus conjugated TDG + TDGO (total TDG + TDGO), was evaluated to investigate the metabolic processes. The total urinary excretion profiles of the metabolites, including the peak time, time window, and dose-response and time-response relationships, were clarified. The results revealed that the concentrations of TDG and TDG + TDGO in the urine increased quickly and then decreased rapidly in the first two days after SM exposure. The cumulative amount of total TDG + TDGO excreted in urine during the first five days accounted for 0.5-1% of the applied dose of SM. It is also concluded that TDG and TDGO in urine existed mainly in free form, the levels of glucuronide and of sulfate conjugates of TDG or TDGO were very low, and most hydrolysis metabolites were present in the oxidized form (TDGO). The study indicates that the abnormal increase of TDG and TDGO excretion levels can be used as a diagnostic indicator and establishes a reference time-window for retrospective analysis and sampling after SM exposure. PMID:24924210

  11. Quantitation of Benzo[a]pyrene Metabolic Profiles in Human Bronchoalveolar H358) Cells by Stable Isotope Dilution Liquid Chromatography-Atmospheric Chemical Ionization Mass Spectrometry

    PubMed Central

    Lu, Ding; Harvey, Ronald G.; Blair, Ian A.; Penning, Trevor M.

    2013-01-01

    Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous environmental pollutants and are carcinogenic in multiple organs and species. Benzo[a]pyrene (B[a]P) is a representative PAH and has been studied extensively for its carcinogenicity and toxicity. B[a]P itself is chemically inert and requires metabolic activation to exhibit its toxicity and carcinogenicity. Three major metabolic pathways have been well documented. The signature metabolites generated from the radical cation (peroxidase or monooxygenase mediated) pathway are B[a]P-1,6-dione and B[a]P-3,6-dione, the signature metabolite generated from the diol-epoxide (P450 mediated) pathway is B[a]P-r-7,t-8,t-9,c-10-tetrahydrotetrol (B[a]P-tetrol-1) and the signature metabolite generated from the o-quinone (aldo-keto reductase mediated) pathway is B[a]P-7,8-dione. The contributions of these different metabolic pathways to cancer initiation and the exploitation of this information for cancer prevention are still under debate. With the availability of a library of [13C4]-labeled B[a]P metabolite internal standards, we developed a sensitive stable isotope dilution atmospheric pressure chemical ionization tandem mass spectrometry method to address this issue by quantitating B[a]P metabolites from each metabolic pathway in human lung cells. This analytical method represents a 500 fold increased sensitivity compared with a method using HPLC-radiometric detection. The limit of quantitation (LOQ) was determined to be 6 fmol on column for 3-hydroxybenzo[a]pyrene (3-OH-B[a]P), the generally accepted biomarker for B[a]P exposure. This high level of sensitivity and robustness of the method was demonstrated in a study of B[a]P metabolic profiles in human bronchoalveolar H358 cells induced or uninduced with the AhR ligand, 2,3,7,8-tetrachlorodibenzodioxin (TCDD). All the signature metabolites were detected and successfully quantitated. Our results suggest that all three metabolic pathways contribute equally in the overall metabolism of B[a]P in H358 cells with or without TCDD induction. The sensitivity of the method should permit the identification of cell-type differences in B[a]P activation and detoxication and could also be used for biomonitoring human exposure to PAH. PMID:21962213

  12. Selenium and Tellurium concentrations of ultradepleted peridotites determined by isotope dilution ICPMS: implications for Se-Te systematics of the Earth's mantle

    NASA Astrophysics Data System (ADS)

    König, S.; Luguet, A.; Lorand, J.-P.; Wombacher, F.; Lissner, M.

    2012-04-01

    As for highly siderophile elements, selenium and tellurium may constitute key tracers for planetary processes such as formation of the Earth's core and the Late Veneer composition, provided that their geochemical behaviour and abundances in the primitive upper mantle (PUM) are constrained. Within this scope, we have developed a high precision analytical method for the simultaneous determination of selenium and tellurium concentrations from a single sample aliquot and various rock matrices, including ultradepleted peridotites. The technique employs isotope dilution, thiol cotton fiber (TCF) separation and hydride generation MC-ICP-MS. A selection of international mafic and ultramafic rock reference materials BIR-1, BE-N, TDB-1, UB-N, FON B 93, BIR-1 and BHVO-2 with a range of 30 to 350 ppb Se and 0.7 to 12 ppb Te show external reproducibilities of 3 to 8% for Se and 0.4 to 11% for Te (2 relative standard deviations (r.s.d.)). We have applied this method to a suite of refractory mantle peridotites (Al2O3 <1.5 wt. %) from Lherz, previously shown to be strongly and uniformly depleted in Se, Te and incompatible elements by high degree of partial melting (20 ± 5%). In contrast to fertile lherzolites which remain at broadly chondritic values (Se/Te = 9), the ultradepleted harzburgites show highly fractionated and up to suprachondritic Se/Te (< 35) that correlate with decreasing Te concentrations. The fractionation is displayed by the depleted peridotites as well as multiple analysis of a single Lherz harzburgite sample (64-3). This shows 1) a strong sample heterogeneity effect for Te and 2) a more incompatible behaviour of Te compared to Se on the whole rock scale, once base metal sulfides are highly depleted and in some cases entirely consumed by partial melting. The marked differences in Se-Te systematics observed between fertile lherzolites and depleted harzburgites can be explained by the combined effect of i) different abundances and proportions of residual and metasomatic base metal sulfides ii) discrete micrometric platinum-group minerals. In addition to re-fertilized lherzolites, harzburgites therefore offer new insights into the behaviour of Se and Te during mantle depletion which is a prerequisite to further constrain the Se and Te abundances of the primitive upper mantle.

  13. On a thermal analysis of a second stripper for rare isotope accelerator.

    SciTech Connect

    Momozaki, Y.; Nolen, J.; Nuclear Engineering Division

    2008-08-04

    This memo summarizes simple calculations and results of the thermal analysis on the second stripper to be used in the driver linac of Rare Isotope Accelerator (RIA). Both liquid (Sodium) and solid (Titanium and Vanadium) stripper concepts were considered. These calculations were intended to provide basic information to evaluate the feasibility of liquid (thick film) and solid (rotating wheel) second strippers. Nuclear physics calculations to estimate the volumetric heat generation in the stripper material were performed by 'LISE for Excel'. In the thermal calculations, the strippers were modeled as a thin 2D plate with uniform heat generation within the beam spot. Then, temperature distributions were computed by assuming that the heat spreads conductively in the plate in radial direction without radiative heat losses to surroundings.

  14. Thermal conductivity of silicon bulk and nanowires: Effects of isotopic composition, phonon confinement, and surface roughness

    NASA Astrophysics Data System (ADS)

    Kazan, M.; Guisbiers, G.; Pereira, S.; Correia, M. R.; Masri, P.; Bruyant, A.; Volz, S.; Royer, P.

    2010-04-01

    We present a rigorous analysis of the thermal conductivity of bulk silicon (Si) and Si nanowires (Si NWs) which takes into account the exact physical nature of the various acoustic and optical phonon mechanisms. Following the Callaway solution for the Boltzmann equation, where resistive and nonresistive phonon mechanisms are discriminated, we derived formalism for the lattice thermal conductivity that takes into account the phonon incidence angles. The phonon scattering processes are represented by frequency-dependent relaxation time. In addition to the commonly considered acoustic three-phonon processes, a detailed analysis of the role of the optical phonon decay into acoustic phonons is performed. This optical phonon decay mechanism is considered to act as acoustic phonon generation rate partially counteracting the acoustic phonon scattering rates. We have derived the analytical expression describing this physical mechanism which should be included in the general formalism as a correction to the resistive phonon-point-defects and phonon-boundary scattering expressions. The phonon-boundary scattering mechanism is taken as a function of the phonon frequency, incidence angles, and surface roughness. The importance of all the mechanisms we have involved in the model is demonstrated clearly with reference to reported data regarding the isotopic composition effect in bulk Si and Si NW samples. Namely, our model accounts for previously unexplained experimental results regarding (i) the isotope composition effect on the thermal conductivity of bulk silicon reported by Ruf et al. [Solid State Commun. 115, 243 (2000)], (ii) the size effect on ?(T ) of individual Si NWs reported by Li et al. [Appl. Phys. Lett. 83, 2934 (2003)], and (iii) the dramatic decrease in the thermal conductivity for rough Si NWs reported by Hochbaum et al. [Nature (London) 451, 163 (2008)].

  15. Low blank rhenium isotope ratio determinations by V2O5 coated nickel filaments using negative thermal ionization mass spectrometry

    Microsoft Academic Search

    Thomas Walczyk; Erhard H. Hebeda; Klaus G. Heumann

    1994-01-01

    Thenium isotope ratio determinations are, in principle, possible by negative thermal ionization mass spectrometry (NTI-MS). Relatively high rhenium blanks from the commonly-used filament materials prevent accurate isotope ratio determinations, especially for small rhenium sample amounts which are of importance, for example, in geochronology in connection with the Re\\/Os dating method. Platinum and nickel filaments were tested by different preparation techniques

  16. Radium isotope geochemistry of thermal waters, Yellowstone National Park, Wyoming, USA

    NASA Astrophysics Data System (ADS)

    Sturchio, N. C.; Bohlke, J. K.; Markun, F. J.

    1993-03-01

    Radium isotope activities ( 226Ra, 228Ra, and 224Ra), chemical compositions, and sulfur isotope ratios in sulfate were determined for water samples from thermal areas in Yellowstone National Park, Wyoming. Activities of 226Ra in these waters range from <0.2 to 37.9 dpm/kg. Activity ratios of 228Ra /226Ra range from 0.26 to 14.2, and those of 224Ra /228Ra range from 0.73 to 3.1. Radium concentrations are inversely correlated with aquifer equilibration temperatures (estimated from dissolved silica concentrations), while[ Ra/Ba] aq and 228Ra /226Ra activity ratios depend upon U/Ba and Th/U ratios in aquifer rocks. Major controls on Ra concentration in Yellowstone thermal waters are inferred to be (1) barite saturation (at Morris Geyser Basin, Mammoth Hot Springs, and other northern areas) and (2) zeolitewater ion exchange (at Upper Geyser Basin). The data are consistent with a model in which (1) radium and barium are supplied to water by bulk dissolution of aquifer rock, and (2) chemical equilibration of water with rock is rapid relative to the 1602 year half-life of 226Ra. The 228Ra /226Ra activity ratios of the waters may in some cases reflect surface enrichments of 232Th and/or may indicate that ?-recoil input of 228Ra is rapid relative to water-rock chemical equilibration. Activity ratios of 224Ra /228Ra indicate a nearly ubiquitous 224Ra excess that generally increases with decreasing pH. Near-surface (?100 m) thermal water flow velocities at Mammoth Hot Springs are estimated from 224Ra /228Ra variation to be ? 1 m h -1.

  17. Radium isotope geochemistry of thermal waters, Yellowstone National Park, Wyoming, USA

    SciTech Connect

    Sturchio, N.C.; Bohlke, J.K.; Markun, F.J. (Argonne National Lab., IL (United States))

    1993-03-01

    Radium isotope activities ([sup 226]Ra, [sup 228]Ra, and [sup 224]Ra), chemical compositions, and sulfur isotope ratios in sulfate were determined for water samples from thermal areas in Yellowstone National Park, Wyoming. Activities of [sup 226]Ra in these waters range from <0.2 to 37.9 dpm/kg. Activity ratios of [sup 228]Ra/[sup 226]Ra range from 0.26 to 14.2, and those of [sup 224]Ra/[sup 228]Ra range from 0.73 to 3.1. Radium concentrations are inversely correlated with aquifer equilibration temperatures (estimated from dissolved silica concentrations), while [Ra/Ba][sub aq] and [sup 228]Ra/[sup 226]Ra activity ratios depend upon U/Ba and Th/U ratios in aquifer rocks. Major controls on Ra concentration in Yellowstone thermal waters are inferred to be (1) barite saturation (at Norris Geyser Basin, Mammoth Hot Springs, and other northern areas) and (2) zeolite-water ion exchange (at Upper Geyser Basin). The data are consistent with a model in which (1) radium and barium are supplied to water by bulk dissolution of aquifer rock, and (2) chemical equilibration of water with rock is rapid relative to the 1602 year half-life of [sup 226]Ra. The [sup 228]Ra/[sup 226]Ra activity ratios of the waters may in some cases reflect surface enrichments of [sup 232]Th and/or may indicate that [alpha]-recoil input of [sup 228]Ra is rapid relative to water-rock chemical equilibration. Activity ratios of [sup 224]Ra/[sup 228]Ra indicate a nearly ubiquitous [sup 224]Ra excess that generally increases with decreasing pH. Near-surface ([le]100 m) thermal water flow velocities at Mammoth Hot Springs are estimated from [sup 224]Ra/[sup 228]Ra variation to be [ge]1 m h[sup [minus]1]. 73 refs., 4 figs., 4 tabs.

  18. The cumulative fission yields of light mass fragments in the thermal neutron fission of Pu239

    Microsoft Academic Search

    H. R. Fickel; R. H. Tomlinson

    1959-01-01

    The relative cumulative yields of 19 light mass fragments or rubidium, ; strontium, yttrium, zirconium. molybdenum, and ruthenium formed in the thermal ; neutron fission of Pu²³⁹ have been determined with a mass spectrometer ; using the isotope dilution technique. The yields of the fission product isotopes ; of these elements, together with the previously published relative yields of ;

  19. Mineralogical and isotopic constraints on chondrule formation from shock wave thermal histories

    NASA Astrophysics Data System (ADS)

    Fedkin, Alexei V.; Grossman, Lawrence; Ciesla, Fred J.; Simon, Steven B.

    2012-06-01

    When a shock wave passes through a nebular gas, increasing water enrichment leads to higher temperatures and post-shock P, but lower cooling rates. A kinetic evaporation model is developed for tracking the chemical and isotopic changes that would occur in a clump of chondrule precursor dust surrounded by nebular gas in a closed system traversed by a nebular shock wave, taking into account effects of non-equilibrium melting and fractional crystallization on the liquid composition and the temperature difference between the gas and the droplet. A range of shock wave temperature-pressure histories computed for systems enriched relative to solar composition by factors of 550 in water, to achieve the redox state of chondrules, and 600 in dust, to retard evaporation, are employed, and redox changes are assumed to occur on the time-scale of heating and cooling in each. Two different system compositions are assumed, with the mean Fe/Si ratios of Types I and II chondrules. Two different textural outcomes are modeled, PO, in which nuclei are preserved and olivine crystallization begins immediately upon reaching saturation, and BO, in which no nuclei are preserved and olivine crystallization begins only after 300-400 K of supersaturation. In all cases, all iron evaporates, regardless of its oxidation state, as well as alkalis and smaller fractions of Mg and Si. In most cases, recondensation occurs on the time-scale of cooling, resulting in droplets whose bulk compositions have small isotopic anomalies in Mg, Si and Fe, comparable to those seen in bulk chondrules. Because fractional crystallization of olivine occurs before recondensation is complete, however, large isotopic variations, especially for iron, would have been recorded both within olivine crystals and between olivine and glass within these objects. Even after diffusive relaxation during crystal growth and cooling, variations in ?25Mg of several tenths of a ‰ to several ‰, in ?29Si of 0.1‰ to several ‰ and in ?56Fe of several ‰ would be measurable within large grains that grew throughout the olivine crystallization interval in many cases, and olivine-glass differences of ?several tenths of a ‰ in ?29Si, and of several ‰ in ?56Fe would be preserved. Such internal isotopic heterogeneities have not yet been observed in chondrules, suggesting that the latter did not form in these shock wave thermal histories. Suppression of production of internal isotopic variations requires heating times that are shorter by a factor of 100, combined with dust enrichments ? 6 × 104 and/or P?10-2 bar. Together with relatively high f, these constraints suggest that chondrules formed in clouds of liquid and vapor generated by impact on ice-rich planetesimals.

  20. Chlorine isotopes of thermal springs in arc volcanoes for tracing shallow magmatic activity

    NASA Astrophysics Data System (ADS)

    Li, Long; Bonifacie, Magali; Aubaud, Cyril; Crispi, Olivier; Dessert, Céline; Agrinier, Pierre

    2015-03-01

    The evaluation of the status of shallow magma body (i.e., from the final intrusion stage, to quiescence, and back to activity), one of the key parameters that trigger and sustain volcanic eruptions, has been challenging in modern volcanology. Among volatile tracers, chlorine (Cl) uniquely exsolves at shallow depths and is highly hydrophilic. Consequently, Cl enrichment in volcanic gases and thermal springs has been proposed as a sign for shallow magmatic activities. However, such enrichment could also result from numerous other processes (e.g., water evaporation, dissolution of old chloride mineral deposits, seawater contamination) that are unrelated to magmatic activity. Here, based on stable isotope compositions of chloride and dissolved inorganic carbon, as well as previous published 3He/4He data obtained in thermal springs from two recently erupted volcanoes (La Soufrière in Guadeloupe and Montagne Pelée in Martinique) in the Lesser Antilles Arc, we show that the magmatic Cl efficiently trapped in thermal springs displays negative ?37Cl values (? - 0.65 ‰), consistent with a slab-derived origin but distinct from the isotope compositions of chloride in surface reservoirs (e.g. seawater, local meteoric waters, rivers and cold springs) displaying common ?37Cl values of around 0‰. Using this ?37Cl difference as an index of magmatic Cl, we further examined thermal spring samples including a 30-year archive from two thermal springs in Guadeloupe covering samples from its last eruption in 1976-1977 to 2008 and an island-wide sampling event in Martinique in 2008 to trace the evolution of magmatic Cl in the volcanic hydrothermal systems over time. The results show that magmatic Cl can be rapidly flushed out of the hydrothermal systems within <30 to 80 years after the eruption, much quicker than other volatile tracers such as CO2 and noble gases, which can exsolve at greater depths and constantly migrate to the surface. Because arc volcanoes often have well developed hydrothermal systems where magmatic Cl is easily transferred to the surface following its exsolution from shallow magma body, we suggest that ?37Cl has great potential to be a unique proxy to monitor the cessation and revival of infrequent arc volcanoes, particularly at centennial time scales.

  1. Chemical, isotopic, and gas compositions of selected thermal springs in Arizona, New Mexico, and Utah

    USGS Publications Warehouse

    Mariner, R.H.; Presser, T.S.; Evans, William C.

    1977-01-01

    Twenty-seven thermal springs in Arizona, New Mexico, and Utah were sampled for detailed chemical and isotopic analysis. The springs issue sodium chloride, sodium bicarbonate, or sodium mixed-anion waters of near neutral (6.2) to alkaline (9.2) pH. High concentrations of fluoride, more than 8 milligrams per liter, occur in Arizona in waters from Gillard Hot Springs, Castle Hot Springs, and the unnamed spring of Eagle Creek, and in New Mexico from springs along the Gila River. Deuterium compositions of the thermal waters cover the same range as those expected for meteoric waters in the respective areas. The chemical compositions of the thermal waters indicate that Thermo Hot Springs in Utah and Gillard Hot Springs in Arizona represent hydrothermal systems which are at temperatures higher than 125 deg C. Estimates of subsurface temperature based on the quartz and Na-K-Ca geothermometer differ by up to 60 deg C for Monroe, Joseph, Red Hill, and Crater hot springs in Utah. Similar conflicting estimates of aquifer temperature occur for Verde Hot Springs, the springs near Clifton and Coolidge Dam, in Arizona; and the warm springs near San Ysidro, Radium Hot Springs, and San Francisco Hot Springs, in New Mexico. Such disparities could result from mixing, precipitation of calcium carbonate, or perhaps appreciable concentrations of magnesium. (Woodard-USGS)

  2. Isotopes of deuterium and oxygen-18 in thermal groundwater in China

    NASA Astrophysics Data System (ADS)

    Xun, Zhou; Bin, Fang; Haiyan, Zhou; Juan, Li; Ying, Wang

    2009-06-01

    Compositions of deuterium and 18O isotopes of 90 representative samples indicate that thermal groundwater in most parts of China is meteoric in origin. Latitude, altitude, and continent effects have significant bearing on the values of ?D and ?18O of the hot water samples. Oxygen-18 shift is not significant in most of the thermal groundwater, especially the hot water of low-to-moderate temperature. Slight oxygen-18 shift is only found in some hot springs of high temperature in Tibet and western Yunnan and in thermal groundwater of low-to-moderate temperature in the deep-seated carbonate aquifers in the northern North China Plain (including the Tianjin area). Near-surface boiling may causes the shift of the former and the latter may be attributed to exchange of oxygen-18 between water and carbonates in the geothermal systems of taphrogenic basin-type. Hot springs in Tibet and western Sichuan have very low contents of ?D and ?18O, possibly due to recharge of precipitation and snow-melting water of extremely depleted ?D and ?18O values at high latitudes of several thousands of meters.

  3. A case for a comet impact trigger for the Paleocene\\/Eocene thermal maximum and carbon isotope excursion

    Microsoft Academic Search

    D. V. Kent; B. S. Cramer; L. Lanci; D. Wang; J. D. Wright; R. van der Voo

    2003-01-01

    We hypothesize that the rapid onset of the carbon isotope excursion (CIE) at the Paleocene\\/Eocene boundary (?55 Ma) may have resulted from the accretion of a significant amount of 12C-enriched carbon from the impact of a ?10 km comet, an event that would also trigger greenhouse warming leading to the Paleocene\\/Eocene thermal maximum and, possibly, thermal dissociation of seafloor methane

  4. COMSOL Simulations for Steady State Thermal Hydraulics Analyses of ORNL s High Flux Isotope Reactor

    SciTech Connect

    Khane, Vaibhav B [ORNL] [ORNL; Jain, Prashant K [ORNL] [ORNL; Freels, James D [ORNL] [ORNL

    2012-01-01

    Simulation models for steady state thermal hydraulics analyses of Oak Ridge National Laboratory s High Flux Isotope Reactor (HFIR) have been developed using the COMSOL Multiphysics simulation software. A single fuel plate and coolant channel of each type of HFIR fuel element was modeled in three dimensions; coupling to adjacent plates and channels was accounted for by using periodic boundary conditions. The standard k- turbulence model was used in simulating turbulent flow with conjugate heat transfer. The COMSOL models were developed to be fully parameterized to allow assessing impacts of fuel fabrication tolerances and uncertainties related to low enriched uranium (LEU) fuel design and reactor operating parameters. Heat source input for the simulations was obtained from separate Monte Carlo N Particle calculations for the axially non-contoured LEU fuel designs at the beginning of the reactor cycle. Mesh refinement studies have been performed to calibrate the models against the pressure drop measured across the HFIR core.

  5. Isotopically exchangeable organic hydrogen in coal relates to thermal maturity and maceral composition

    USGS Publications Warehouse

    Mastalerz, Maria; Schimmelmann, A.

    2002-01-01

    Hydrogen isotopic exchangeability (Hex) and ??Dn values of non-exchangeable organic hydrogen were investigated in coal kerogens ranging in rank from lignite to graphite. The relative abundance of Hex is highest in lignite with about 18% of total hydrogen being exchangeable, and decreases to around 2.5% in coals with Ro of 1.7 to ca. 5.7%. At Still higher rank (Ro > 6%), Hex increases slightly, although the abundance of total hydrogen decreases. ??Dn is influenced by original biochemical D/H ratios and by thermal maturation in contact with water. Therefore, ??Dn does not show an overall consistent trend with maturity. ?? 2002 Elsevier Science Ltd. All rights reserved.

  6. Precise determination of 235 U\\/ 238 U isotope ratio in soil samples by using thermal ionisation mass spectrometry

    Microsoft Academic Search

    S. K. Sahoo; H. Isobe; T. Sato; K. Fujimoto; Y. Nakamura

    2002-01-01

    A rapid method based on extraction chromatography was developed for the separation of uranium from soil samples for TIMS. The isotope ratios were measured on three standards using a VG 54-30 thermal ionisation mass spectrometer in static mode with Faraday cup and Daly ion counting system. The use of a WARP (Wide Aperture Retardation Potential) energy filter improves abundance sensitivity

  7. Chemical, multi-isotopic (Li-B-Sr-U-H-O) and thermal characterization of Triassic formation waters from the Paris Basin

    E-print Network

    Boyer, Edmond

    were collected at the edge of the Basin near the recharge zone (dilute waters). The saline waters reported in the present work for Li and B isotopes could be used as a reference for future studies limestones. Both include oil accumulations associated with occurrences of saline groundwaters

  8. Isotope geochemistry of thermal and nonthermal waters in the Valles Caldera, Jemez Mountains, Northern New Mexico

    NASA Astrophysics Data System (ADS)

    Vuataz, FrançOis D.; Goff, Fraser

    1986-02-01

    Over 100 stable isotope and 45 tritium analyses from thermal and nonthermal waters of the Jemez Mountains region, New Mexico, have been used to define the hydrodynamics of the Valles caldera (Baca) geothermal system and related geothermal fluids of the region. Evaluation of 36 cold meteoric waters yields an equation for the Jemez Mountains meteoric water line of ?D = 8?18O + 12, while further evaluation of nine cold meteoric waters yields an equation relating recharge elevation to deuterium content of E(meters) = -44.9 (?D) - 1154. Based on the deuterium content of five Baca well waters (223°-294°C), the average recharge elevation of the Valles geothermal system ranges from 2530 to 2890 m. This range of elevations falls between the elevations of the lowest point of the caldera floor (2400 m) and the summit of the resurgent dome inside the caldera (3430 m). Thus stable isotopes indicate that the caldera depression probably serves as a recharge basin for the deep geothermal system. Although cold spring waters of the Jemez Mountains region consist of meteoric water, tritium analyses show that most of them contain water between 20 and 75 years old. The two major streams draining the Valles moat zone, San Antonio Creek and East Fork Jemez River, may contain more than 50% of this relatively old groundwater depending on the season. In contrast, streams draining the central resurgent dome of the caldera contain present-day meteoric water. Using piston flow and homogeneously mixed reservoir models as end-member cases, the tritium contents of the Baca fluids (0.18-1.10 tritium units (TU)) indicate that the mean residence time of water in the reservoir is between 60 and 10,000 years old. Deep geothermal fluids display a positive oxygen 18 shift of not less than 2‰ because of rock-water isotopic exchange at 220°-300°C. The Valles geothermal system is capped by a vapor zone that is roughly 600 m thick and best developed at Sulphur Springs. Fumarolic steam at Sulphur Springs is unusually depleted in oxygen 18, suggesting that it is probably derived by boiling of near-surface groundwater at 200°C. Surface acid-sulfate waters are mixtures of condensed steam and surficial groundwaters that display the isotopic processes of evaporation and exchange between H2O and CO2. A lateral outflow plume discharges from the Valles geothermal system down the Jemez fault zone and feeds two sets of thermal springs in San Diego Canyon. Isotopic evidence shows that these springs consist of three components: (1) deep geothermal fluid, (2) surficial and/or near-surface groundwater, and (3) relatively old, but cold, mineralized water. This latter component presumably circulates in Paleozoic strata underlying the western caldera flank. Hot, Precambrian, pore fluid brine occurs beneath the main Valles caldera hydrothermal system and may be generated by metamorphic processes in the relatively impermeable conductive regime above the magmatic heat source of the caldera.

  9. Solar Carbon Monoxide, Thermal Profiling, and the Abundances of C, O, and their Isotopes

    E-print Network

    Thomas R. Ayres; Claude Plymate; Christoph U. Keller

    2006-06-07

    A solar photospheric "thermal profiling" analysis is presented, exploiting the infrared rovibrational bands of carbon monoxide (CO) as observed with the McMath-Pierce Fourier transform spectrometer (FTS) at Kitt Peak, and from above the Earth's atmosphere by the Shuttle-borne ATMOS experiment. Visible continuum intensities and center-limb behavior constrained the temperature profile of the deep photosphere, while CO center-limb behavior defined the thermal structure at higher altitudes. The oxygen abundance was self consistently determined from weak CO absorptions. Our analysis was meant to complement recent studies based on 3-D convection models which, among other things, have revised the historical solar oxygen (and carbon) abundance downward by a factor of nearly two; although in fact our conclusions do not support such a revision. Based on various considerations, an oxygen abundance of 700+/-100 ppm (parts per million relative to hydrogen) is recommended; the large uncertainty reflects the model sensitivity of CO. New solar isotopic ratios also are reported for 13C, 17O, and 18O.

  10. Production Rates of Dihydrotestosterone in Healthy Men and Women and in Men with Male Pattern Baldness: Determination by Stable Isotope\\/Dilution and Mass Spectrometry

    Microsoft Academic Search

    H. Vierhapper; P. NOWOTNY; H. MAIER; W. WALDHAUSL

    2001-01-01

    Production rates of dihydrotestosterone (DHT) were deter- mined in healthy men (n 8), in healthy women during the follicular phase of their menstrual cycle (n 7), and in young men with male pattern baldness (n 8) using the stable iso- tope dilution technique and mass spectrometry. (2,3,4- 13 C)DHT was infused for 10 h at doses of 15 g\\/h (men)

  11. Mass Dependency of Isotope Fractionation of Gases Under Thermal Gradient and Its Possible Implications for Planetary Atmosphere Escaping Process

    NASA Technical Reports Server (NTRS)

    Sun, Tao; Niles, Paul; Bao, Huiming; Socki, Richard

    2014-01-01

    Physical processes that unmix elements/isotopes of gas molecules involve phase changes, diffusion (chemical or thermal), effusion and gravitational settling. Some of those play significant roles for the evolution of chemical and isotopic compositions of gases in planetary bodies which lead to better understanding of surface paleoclimatic conditions, e.g. gas bubbles in Antarctic ice, and planetary evolution, e.g. the solar-wind erosion induced gas escaping from exosphere on terrestrial planets.. A mass dependent relationship is always expected for the kinetic isotope fractionations during these simple physical processes, according to the kinetic theory of gases by Chapman, Enskog and others [3-5]. For O-bearing (O16, -O17, -O18) molecules the alpha O-17/ alpha O-18 is expected at 0.5 to 0.515, and for S-bearing (S32,-S33. -S34, -S36) molecules, the alpha S-33/ alpha S-34 is expected at 0.5 to 0.508, where alpha is the isotope fractionation factor associated with unmixing processes. Thus, one isotope pair is generally proxied to yield all the information for the physical history of the gases. However, we recently] reported the violation of mass law for isotope fractionation among isotope pairs of multiple isotope system during gas diffusion or convection under thermal gradient (Thermal Gradient Induced Non-Mass Dependent effect, TGI-NMD). The mechanism(s) that is responsible to such striking observation remains unanswered. In our past studies, we investigated polyatomic molecules, O2 and SF6, and we suggested that nuclear spin effect could be responsible to the observed NMD effect in a way of changing diffusion coefficients of certain molecules, owing to the fact of negligible delta S-36 anomaly for SF6.. On the other hand, our results also showed that for both diffusion and convection under thermal gradient, this NMD effect is increased by lower gas pressure, bigger temperature gradient and lower average temperature, which indicate that the nuclear spin effect may not be the significant contributor as the energies involved in the hyperfine effect are much smaller than those with molecular collisions, especially under convective conditions.

  12. Analysis of nitrosamines in water by automated SPE and isotope dilution GC/HRMS Occurrence in the different steps of a drinking water treatment plant, and in chlorinated samples from a reservoir and a sewage treatment plant effluent.

    PubMed

    Planas, Carles; Palacios, Oscar; Ventura, Francesc; Rivera, Josep; Caixach, Josep

    2008-08-15

    A method based on automated solid-phase extraction (SPE) and isotope dilution gas chromatography/high resolution mass spectrometry (GC/HRMS) has been developed for the analysis of nine nitrosamines in water samples. The combination of automated SPE and GC/HRMS for the analysis of nitrosamines has not been reported previously. The method shows as advantages the selectivity and sensitivity of GC/HRMS analysis and the high efficiency of automated SPE with coconut charcoal EPA 521 cartridges. Low method detection limits (MDLs) were achieved, along with a greater facility of the procedure and less dependence on the operator with regard to the methods based on manual SPE. Quality requirements for isotope dilution-based methods were accomplished for most analysed nitrosamines, regarding to trueness (80-120%), method precision (<15%) and MDLs (0.08-1.7 ng/L). Nineteen water samples (16 samples from a drinking water treatment plant {DWTP}, 2 chlorinated samples from a sewage treatment plant {STP} effluent, and 1 chlorinated sample from a reservoir) were analysed. Concentrations of nitrosamines in the STP effluent were 309.4 and 730.2 ng/L, being higher when higher doses of chlorine were applied. N-Nitrosodimethylamine (NDMA) and N-nitrosodiethylamine (NDEA) were the main compounds identified in the STP effluent, and NDEA was detected above 200 ng/L, regulatory level for NDMA in effluents stated in Ontario (Canada). Lower concentrations of nitrosamines were found in the reservoir (20.3 ng/L) and in the DWTP samples (n.d. -28.6 ng/L). NDMA and NDEA were respectively found in the reservoir and in treated and highly chlorinated DWTP samples at concentrations above 10 ng/L (guide value established in different countries). The highest concentrations of nitrosamines were found after chlorination and ozonation processes (ozonated, treated and highly chlorinated water) in DWTP samples. PMID:18656677

  13. A structural evaluation of the tungsten isotopes via thermal neutron capture

    E-print Network

    A. M. Hurst; R. B. Firestone; B. W. Sleaford; N. C. Summers; Zs. Revay; L. Szentmiklosi; M. S. Basunia; T. Belgya; J. E. Escher; M. Krticka

    2014-01-10

    Total radiative thermal neutron-capture $\\gamma$-ray cross sections for the $^{182,183,184,186}$W isotopes were measured using guided neutron beams from the Budapest Research Reactor to induce prompt and delayed $\\gamma$ rays from elemental and isotopically-enriched tungsten targets. These cross sections were determined from the sum of measured $\\gamma$-ray cross sections feeding the ground state from low-lying levels below a cutoff energy, E$_{\\rm crit}$, where the level scheme is completely known, and continuum $\\gamma$ rays from levels above E$_{\\rm crit}$, calculated using the Monte Carlo statistical-decay code DICEBOX. The new cross sections determined in this work for the tungsten nuclides are: $\\sigma_{0}(^{182}{\\rm W}) = 20.5(14)$ b and $\\sigma_{11/2^{+}}(^{183}{\\rm W}^{m}, 5.2 {\\rm s}) = 0.177(18)$ b; $\\sigma_{0}(^{183}{\\rm W}) = 9.37(38)$ b and $\\sigma_{5^{-}}(^{184}{\\rm W}^{m}, 8.33 \\mu{\\rm s}) = 0.0247(55)$ b; $\\sigma_{0}(^{184}{\\rm W}) = 1.43(10)$ b and $\\sigma_{11/2^{+}}(^{185}{\\rm W}^{m}, 1.67 {\\rm min}) = 0.0062(16)$ b; and, $\\sigma_{0}(^{186}{\\rm W}) = 33.33(62)$ b and $\\sigma_{9/2^{+}}(^{187}{\\rm W}^{m}, 1.38 \\mu{\\rm s}) = 0.400(16)$ b. These results are consistent with earlier measurements in the literature. The $^{186}$W cross section was also independently confirmed from an activation measurement, following the decay of $^{187}$W, yielding values for $\\sigma_{0}(^{186}{\\rm W})$ that are consistent with our prompt $\\gamma$-ray measurement. The cross-section measurements were found to be insensitive to choice of level density or photon strength model, and only weakly dependent on E$_{\\rm crit}$. Total radiative-capture widths calculated with DICEBOX showed much greater model dependence, however, the recommended values could be reproduced with selected model choices. The decay schemes for all tungsten isotopes were improved in these analyses.

  14. Isotope loss from exhaled moisture and correlation of multifrequency bioelectrical impedance to body fluid compartments measured by intravenous deuterium oxide and sodium bromide dilution in dogs

    E-print Network

    Witten, Tiffani Tipton

    2000-01-01

    for this route of isotope loss was necessary. Sodium bromide concentrations at 90 minutes and 180 minutes were tested for statistical equivalency to determine if NaBr had equilibrated by 90 minutes. Finally, impedance measured with electrodes separated by 2...

  15. Isotope and chemical compositions of meteoric and thermal waters and snow from the greater Yellowstone National Park region

    USGS Publications Warehouse

    Kharaka, Yousif K.; Thordsen, James J.; White, Lloyd D.

    2002-01-01

    An intensive hydrogeologic investigation, mandated by U.S. Congress and centered on the Norris-Mammoth corridor was conducted by USGS and other scientists during 1988-90 to determine the effects of using thermal water from a private well located in the Corwin Springs Known Geothermal Resources Area, Montana, on the thermal springs of Yellowstone National Park (YNP), especially Mammoth Hot Springs. As part of this investigation, we carried out a detailed study of the isotopic and chemical compositions of meteoric water from cold springs and wells, of thermal water, especially from the Norris-Mammoth corridor and of snow. Additional sampling of meteoric and thermal waters from YNP and surrounding region in northwest Wyoming, southwest Montana and southeast Idaho was carried out in 1991-92 to characterize the distribution of water isotopes in this mountainous region and to determine the origin and possible recharge locations of thermal waters in and adjacent to the Park. The D and 18O values for 40 snow samples range from ?88 to ?178? and ?12.5 to ?23.9?, respectively, and define a well constrained line given by D = 8.2 18O + 14.7 (r2 = 0.99) that is nearly identical to the Global Meteoric Water Line. The D and 18O values of 173 cold water samples range from ?115 to ?153? and ?15.2 to ?20.2?, respectively, and exhibit a similar relationship although with more scatter and with some shift to heavier isotopes, most likely due to evaporation effects. The spatial distribution of cold-water isotopes shows a roughly circular pattern with isotopically lightest waters centered on the mountains and high plateau in the northwest corner of Yellowstone National Park and becoming heavier in all directions. The temperature effect due to altitude is the dominant control on stable water isotopes throughout the region; however, this effect is obscured in narrow 'canyons' and areas of high topographic relief. The effects due to distance (i.e. 'continental') and latitude on water isotopes probably are relatively minor and difficult to resolve from the major controls. The data indicate that the groundwater are derived predominantly from cold, isotopically light winter precipitation, and that the isotope values of groundwater from elevations above about 2.5-3.0 km in the Gallatin and northern Absaroka Ranges are light enough (The D ?149?) to be the presumed recharge water for the hydrothermal system in the Park. However, estimation of the present-day volume of this recharged, isotopically light water indicates that it is not adequate to supply the high (3-4 m3/s) thermal water discharges from YNP, and cooler temperatures at the time of recharge would be required. The volume of meteoric water with D values lighter than ?145? may be adequate for recharging the hydrothermal system, and this may be a more plausible value than the ?149? originally calculated from data that are subject to moderate uncertainties.

  16. Independent Yields of Krypton and Xenon Isotopes in Thermal-Neutron Fission of 235U. Observation of an Odd-Even Effect in the Element Yield Distribution

    Microsoft Academic Search

    B. Ehrenberg; S. Amiel

    1972-01-01

    The fractional and independent fission yields of krypton isotopes (masses 87 to 94) and xenon isotopes (masses 137-143) produced in thermal-neutron fission of 235U were measured using a mass separator operating in an on-line mode with a fission source exposed to time-controlled neutron fluxes. The noble-gas isotopes were collected simultaneously at given times and each mass was measured separately. The

  17. Quantum and thermal ionic motion, oxygen isotope effect, and superexchange distribution in La2CuO4

    NASA Astrophysics Data System (ADS)

    Häfliger, P. S.; Gerber, S.; Pramod, R.; Schnells, V. I.; Piazza, B. dalla; Chati, R.; Pomjakushin, V.; Conder, K.; Pomjakushina, E.; Le Dreau, L.; Christensen, N. B.; Syljuâsen, O. F.; Normand, B.; Rønnow, H. M.

    2014-02-01

    We study the zero-point and thermal ionic motion in La2CuO4 by means of high-resolution neutron-diffraction experiments. Our results demonstrate anisotropic motion of O and, to a lesser extent, Cu ions, both consistent with the structure of coupled CuO6 octahedra, and quantify the relative effects of zero-point and thermal contributions to ionic motion. By substitution of O18, we find that the oxygen isotope effect on the lattice dimensions is small and negative (-0.01%), while the isotope effect on the ionic displacement parameters is significant (-6 to 50%). We use our results as input for theoretical estimates of the distribution of magnetic interaction parameters, J, in an effective one-band model for the cuprate plane. We find that ionic motion causes only small (1%) effects on the average value , which vary with temperature and O isotope, but results in dramatic (10-20%) fluctuations in J values that are subject to significant (8-12%) isotope effects. We demonstrate that this motional broadening of J can have substantial effects on certain electronic and magnetic properties in cuprates.

  18. Simultaneous determination of thiophanate-methyl and its metabolite carbendazim in tea using isotope dilution ultra performance liquid chromatography-tandem mass spectrometry.

    PubMed

    Chen, Hongping; Liu, Xin; Wang, Chuanpi; Wang, Qinghua; Jiang, Ying; Yin, Peng; Zhu, Li

    2014-01-01

    A rapid method has been developed for the determination of thiophanate methyl and its metabolite carbendazim in tea samples using ultra-high-performance liquid chromatography tandem mass. Dispersive solid-phase extraction was optimized and employed as a sample preparation technique without concentration and solvent exchange. Degradation of thiophanate methyl and its isotope were observed and they declined at the similar rate during sample preparation. The results showed that calibration by isotope internal standards was reliable to correct the degradation. With the extraction solvent at pH range of 2.3-10.3, difference for thiophanate methyl degradation was not much significant due to the buffer action of tea matrix solution. Matrix effects were dependent on the nature of the analytes and tea categories, but calibrated effectively by isotope internal standards. Recoveries ranged 97.2-110.6%, and relative standard deviations were <25.0%. The limit of quantification was both 0.010 mg kg(-1) for thiophanate methyl and carbendazim. The developed method was utilized to measure concentrations of thiophanate methyl and carbendazim in tea samples from seven provinces of China, as well as to investigate the degradation of thiophanate methyl in tea crop. PMID:24256946

  19. Fission-product formation in the thermal-neutron-induced fission of odd Cm isotopes

    NASA Astrophysics Data System (ADS)

    Tsekhanovich, I.; Varapai, N.; Rubchenya, V.; Rochman, D.; Simpson, G. S.; Sokolov, V.; Fioni, G.; Mahamid, Ilham Al

    2004-10-01

    Thermal-neutron-induced fission of 243Cm was studied at the Lohengrin mass separator. The light-mass peak of the fission-yield curve was investigated, and yields of masses from A=72 to A=120 were obtained. Independent-product yields were determined for nuclear charges Z=28 37 . The yield of masses in the superasymmetric region was found to be identical to other fission reactions studied at Lohengrin. The multimodal approach to fission and the macroscopic-microscopic method for the calculation of charge-distribution parameters in isobaric chains were used to analyze experimental results from the fission of 243Cm and 245Cm . A systematics on fission modes was derived from the analysis and extended to the 247Cm case. The weight of the 132Sn mode was found to decrease in 243Cm , relative to the 245Cm nucleus. A prediction of the 78Ni yield in the fission of Cm isotopes was made. The feasibility of the study of 78Ni at Lohengrin has been demonstrated.

  20. Estimation of the isotope effect on the lattice thermal conductivity of group IV and group III-V semiconductors

    Microsoft Academic Search

    D. T. Morelli; J. P. Heremans; G. A. Slack

    2002-01-01

    The isotope effect on the lattice thermal conductivity for group IV and group III-V semiconductors is calculated using the Debye-Callaway model modified to include both transverse and longitudinal phonon modes explicitly. The frequency and temperature dependences of the normal and umklapp phonon-scattering rates are kept the same for all compounds. The model requires as adjustable parameters only the longitudinal and

  1. Evidence for rapid climate change in North America during the latest Paleocene thermal maximum: oxygen isotope compositions of biogenic phosphate from the Bighorn Basin (Wyoming)

    Microsoft Academic Search

    Henry C. Frickea; William C. Clyde; James R. O'Neil; Philip D. Gingerich

    1998-01-01

    Oxygen isotope records of Cenozoic sea water temperatures indicate that a rapid warming event known as the Latest Paleocene Thermal Maximum (LPTM) occurred during the otherwise gradual increase in world temperatures during the Late Paleocene and Early Eocene. Oxygen isotope analysis of the carbonate and phosphate components of hydroxyapatite found in mammalian tooth enamel and body scales of river-dwelling fish

  2. Decay properties of short-lived neutron-rich halogen isotopes and their yields obtained in the thermal neutron fission of uranium

    Microsoft Academic Search

    Kratz

    1972-01-01

    Thesis. The present paper reports data on the nuclear charge ; distribution of halogen isotopes in the 50- and 82-neutron shell range resulting ; from thermal neutron fission of ²³⁵U. A fully automated rapid gas-; chromatographic system has been developed which allows the isolation of short-; lived bromine and iodine isotopes by volatilization of their methyl compounds ; within a

  3. Measurement of the stable carbon isotope ratio of atmospheric volatile organic compounds using chromatography, combustion, and isotope ratio mass spectrometry coupled with thermal desorption

    NASA Astrophysics Data System (ADS)

    Kawashima, Hiroto; Murakami, Mai

    2014-06-01

    The isotopic analysis of atmospheric volatile organic compounds (VOCs), and in particular of their stable carbon isotope ratio (?13C), could potentially be used as an effective tool for identifying the sources of VOCs. However, to date, there have been very few such analyses. In this work, we analyze the ?13C values of VOCs using thermal desorption coupled with chromatography, combustion, and isotope ratio mass spectrometry (TD-GC/C/IRMS). The measured peak shapes were of high quality and 36 compounds in a standard gas containing 58 VOCs (C5-C11) were detected. The measured ?13C varied widely, from -49.7‰ to -22.9‰, while the standard deviation of the ?13C values varied from 0.07‰ to 0.85‰ (n = 5). We then measured samples from two passenger cars in hot and cold modes, three gas stations, roadside air, and ambient air. In comparison with existing studies, the analytical precision for the 36 compounds in this study was reasonable. By comparing the ?13C values obtained from the cars and gas stations, we could identify some degree of the sources of VOCs in the roadside and ambient air samples.

  4. Influence of longitudinal isotope substitution on the thermal conductivity of carbon nanotubes: Results of nonequilibrium molecular dynamics and local density functional calculations

    SciTech Connect

    Leroy, Frédéric, E-mail: f.leroy@theo.chemie.tu-darmstadt.de; Böhm, Michael C., E-mail: boehm@theo.chemie.tu-darmstadt.de [Eduard-Zintl-Institut für Anorganische und Physikalische Chemie, Technische Universität Darmstadt, D-64287 Darmstadt (Germany); Schulte, Joachim [Bruker Biospin GmbH, Silberstreifen, D-76287 Rheinstetten (Germany)] [Bruker Biospin GmbH, Silberstreifen, D-76287 Rheinstetten (Germany); Balasubramanian, Ganesh [Department of Mechanical Engineering, Iowa State University, Ames, Iowa 50011 (United States)] [Department of Mechanical Engineering, Iowa State University, Ames, Iowa 50011 (United States)

    2014-04-14

    We report reverse nonequilibrium molecular dynamics calculations of the thermal conductivity of isotope substituted (10,10) carbon nanotubes (CNTs) at 300 K. {sup 12}C and {sup 14}C isotopes both at 50% content were arranged either randomly, in bands running parallel to the main axis of the CNTs or in bands perpendicular to this axis. It is found that the systems with randomly distributed isotopes yield significantly reduced thermal conductivity. In contrast, the systems where the isotopes are organized in patterns parallel to the CNTs axis feature no reduction in thermal conductivity when compared with the pure {sup 14}C system. Moreover, a reduction of approximately 30% is observed in the system with the bands of isotopes running perpendicular to the CNT axis. The computation of phonon dispersion curves in the local density approximation and classical densities of vibrational states reveal that the phonon structure of carbon nanotubes is conserved in the isotope substituted systems with the ordered patterns, yielding high thermal conductivities in spite of the mass heterogeneity. In order to complement our conclusions on the {sup 12}C-{sup 14}C mixtures, we computed the thermal conductivity of systems where the {sup 14}C isotope was turned into pseudo-atoms of 20 and 40 atomic mass units.

  5. Influence of longitudinal isotope substitution on the thermal conductivity of carbon nanotubes: Results of nonequilibrium molecular dynamics and local density functional calculations

    NASA Astrophysics Data System (ADS)

    Leroy, Frédéric; Schulte, Joachim; Balasubramanian, Ganesh; Böhm, Michael C.

    2014-04-01

    We report reverse nonequilibrium molecular dynamics calculations of the thermal conductivity of isotope substituted (10,10) carbon nanotubes (CNTs) at 300 K. 12C and 14C isotopes both at 50% content were arranged either randomly, in bands running parallel to the main axis of the CNTs or in bands perpendicular to this axis. It is found that the systems with randomly distributed isotopes yield significantly reduced thermal conductivity. In contrast, the systems where the isotopes are organized in patterns parallel to the CNTs axis feature no reduction in thermal conductivity when compared with the pure 14C system. Moreover, a reduction of approximately 30% is observed in the system with the bands of isotopes running perpendicular to the CNT axis. The computation of phonon dispersion curves in the local density approximation and classical densities of vibrational states reveal that the phonon structure of carbon nanotubes is conserved in the isotope substituted systems with the ordered patterns, yielding high thermal conductivities in spite of the mass heterogeneity. In order to complement our conclusions on the 12C-14C mixtures, we computed the thermal conductivity of systems where the 14C isotope was turned into pseudo-atoms of 20 and 40 atomic mass units.

  6. The isotopic composition of waters from the El Tatio geothermal field, Northern Chile

    Microsoft Academic Search

    Werner F. Giggenbach

    1978-01-01

    On the basis of isotopic and chemical analyses of 45 spring, well and meteoric water samples from the El Tatio geothermal field in Northern Chile, four main processes giving rise to the formation of a wide range of thermal discharges can be distinguished. (1) Deep dilution of a predominant, primary high chloride (5500 mg\\/l, 260°) supply water derived from precipitation

  7. Lattice thermal conductivity of crystalline and amorphous silicon with and without isotopic effects from the ballistic to diffusive thermal transport regime

    SciTech Connect

    Park, Minkyu; Lee, In-Ho; Kim, Yong-Sung, E-mail: yongsung.kim@kriss.re.kr [Korea Research Institute of Standards and Science, Daejeon 305-340 (Korea, Republic of); Department of Nano Science, Korea University of Science and Technology, Daejeon 305-350 (Korea, Republic of)

    2014-07-28

    Thermal conductivity of a material is an important physical parameter in electronic and thermal devices, and as the device size shrinks down, its length-dependence becomes unable to be neglected. Even in micrometer scale devices, materials having a long mean free path of phonons, such as crystalline silicon (Si), exhibit a strong length dependence of the thermal conductivities that spans from the ballistic to diffusive thermal transport regime. In this work, through non-equilibrium molecular-dynamics (NEMD) simulations up to 17??m in length, the lattice thermal conductivities are explicitly calculated for crystalline Si and up to 2??m for amorphous Si. The Boltzmann transport equation (BTE) is solved within a frequency-dependent relaxation time approximation, and the calculated lattice thermal conductivities in the BTE are found to be in good agreement with the values obtained in the NEMD. The isotopic effects on the length-dependent lattice thermal conductivities are also investigated both in the crystalline and amorphous Si.

  8. The Precambrian Biogeochemical Carbon Isotopic Record: Contributions of Thermal Versus Biological Processes

    NASA Technical Reports Server (NTRS)

    DesMarais, David J.; DeVincenzi, Donald L. (Technical Monitor)

    2000-01-01

    Superplumes offer a new approach for understanding global C cycles. Isotopes help to discern the impacts of geological, environmental and biological processes ujpun the evolution of these cycles. For example, C-13/C-12 values of coeval sedimentary organics and carbonates give global estimates of the fraction of C buried as organics (Forg), which today lies near 0.2. Before Oxygenic photosynthesis arose, our biosphere obtained reducing power for biosynthesis solely from thermal volatiles and rock alteration. Thus Forg was dominated by the mantle redox state, which has remained remarkably constant for greater than Gy. Recent data confirm that the long-term change in Forg had been small, indicating that the mantle redox buffer remains important even today. Oxygenic photosynthesis enabled life to obtain additional reducing power by splitting the water molecule. Accordingly, biological organic production rose above the level constrained by the mantle-derived flux of reduced species. For example, today, chemoautotrophs harvesting energy from hydrothermal emanations can synthesize at most between 0.2 x 10(exp 12) and 2x 10(exp 12) mol C yr-1 of organic C globally. In contrast, global photosynthetic productivity is estimated at 9000 x 10(exp 12) mol C yr-1. Occasionally photosynthetic productivity did contribute to dramatically -elevated Forg values (to 0.4 or more) as evidenced by very high carbonate C-13/C-12. The interplay between biological, tectonic and other environmental factors is illustrated by the mid-Archean to mid-Proterozoic isotopic record. The relatively constant C-13/C-12 values of Archean carbonates support the view that photosynthetically-driven Forg increases were not yet possible. In contrast, major excursions in C-13/C-12, and thus also in Forg, during the early Proterozoic confirmed the global importance of oxygenic photosynthesis by that time. Remarkably, the superplume event at 1.9 Ga did not trigger another major Forg increase, despite the favorable conditions for organic burial that were evidenced by elevated sea levels and higher black shale abundances. Perhaps those superplume-rated processes that favored enhanced organic burial were offset by the ability of mantle-derived redox buffering, which was enhanced during the superplume event, to limit excursions in Forg.

  9. Carbon isotope evidence for increased levels of multiple greenhouse gasses during the initial Eocene thermal maximum

    NASA Astrophysics Data System (ADS)

    Bowen, G. J.; Beerling, D. J.; Koch, P. L.

    2003-12-01

    Nearly a decade ago, it was shown that the abrupt, negative shift in marine and terrestrial carbon isotope ratios at the Paleocene/Eocene boundary provides indirect evidence for an abnormally large release of methane, probably from gas hydrates, to the ocean/atmosphere system. This release coincides with a dramatic, transient, warming event now termed the initial Eocene thermal maximum (IETM), inspiring obvious questions about the causal links between methane hydrate dissociation and climate warming during this event. However, uncertainties regarding the amount of methane which might have escaped to the atmosphere, and the short residence time of methane in the modern atmosphere, make direct and indirect radiative warming due to heightened atmospheric methane levels an imperfect explanation for IETM warming, which averaged ˜4-6° globally and persisted for ˜100 ky. Here, we provide evidence, based on a mechanistic examination of the divergence of marine and terrestrial ? 13C records during the IETM, for transient increases in atmospheric levels of CO2 and/or water vapor during this event. Exact quantification of these increases is not possible, but doubling of CO2 levels and/or relative humidity increases on the order of 20% are indicated. These changes in atmospheric chemistry appear to have been sustained for at least ˜80 ky, and likely contributed to climatic warming during the IETM. Further, elevated productivity of the terrestrial biosphere should have accompanied increased atmospheric CO2 and/or H2O levels, as indicted by the observed changes in terrestrial carbon isotope systems. Terrestrial biosphere fertilization might thus have accounted for a substantial carbon sink and a negative feedback on IETM climate warming by atmospheric carbon compounds. However, paleosol sections documenting this event show unchanged or decreased accumulation of organic matter, suggesting that organic matter turnover rates in soils increased and that the terrestrial carbon sink during the IETM was limited to the net increase in standing biomass, minus any reductions in soil carbon storage. Because standing biomass constitutes a transient carbon sink, long term carbon cycle recovery from the IETM must have occurred through other mechanisms, such as elevated silicate weathering or marine organic carbon burial.

  10. U-Pb dating of Plinian-eruption ashfalls by the isotope dilution method: A reliable and precise tool for time-scale calibration and biostratigraphic correlation

    SciTech Connect

    Tucker, R.D. (Washington Univ., St. Louis, MO (United States). Dept. of Earth and Planetary Sciences)

    1992-01-01

    Through a combination of low analytical blanks, clean Pb-205 enriched tracer-solution, and refined procedures of sample preparation, it is possible to isolate and measure minute quantities of radiogenic Pb in concordant zircon, thereby permitting accurate isotopic age determinations of small multigrain samples of Paleozoic zircon with 7--20 ppm radiogenic Pb. Refinement of these procedures, including reduction of laboratory blank, allows for analysis of single grains of Paleozoic zircon with greater than 25 ppm radiogenic Pb with an age precision of better than 1%. Mass spectrometric measurement of all Pb and U isotopes allows for the calculation of three isotopic ages from a single sample. Concordant multigrain and single-grain U-Pb zircon analyses from 13 biostratigraphically dated K-bentonites in Europe and North America define an internally consistent, absolute chronostratigraphy of Middle ordovician to Upper silurian stratotypes. As a test of trans-Atlantic stratigraphic correlation, a volcanic ash from Middle Ordovician (Rocklandian) strata of North America was found to be in excellent age agreement with Caradocian K-bentonites in Britain and Sweden, demonstrating age equivalence of sedimentary sequences lacking directly comparable fauna. In other case, precise dating of single zircons from three Caradocian K-bentonite in Sweden and Virginia was performed to test a hypothesis that a single ultraplinian volcanic eruption deposited airborne debris on both Larentia and Baltica. The ages of these presumed correlative ashes will be shown to provide quantitative information about the depositional rates of their enclosing strata, as well as tectonic events affecting the margins of Iapetus in Ordovician time.

  11. Low blank isotope ratio measurements of rhenium, osmium, and platinum using tantalum filaments with negative thermal ionization mass spectrometry.

    PubMed

    Hattori, K; Menagh, D P; Cole, T J

    1998-10-01

    Platinum is most commonly used as a filament for Re and Os isotopic measurements, but it contains impurities of Re and Os. Tantalum is low in platinum group elements (PGE) and in Re, but it is not used for negative thermal ionization mass spectrometry because of high electron emission and high reactivity with O(2). High thermal electron emission from Ta distorts the preoptimized ion source optics. In addition, Ta consumes O(2), leaving little for samples, but O(2) is essential for isotopic ratio measurements of PGE and Re as they are measured as negatively charged oxides, such as OsO(3)(-) and PtO(2)(-). These problems are solved by prebaking a filament to remove tantalum oxides before sample loading, keeping relatively high filament temperatures and high O(2) pressures (P(O)((2))) during the sample run, and lowering the potential difference between the filament and the draw-out plate. At P(O)((2)) of ?1 × 10(-)(5) Torr in the source, strong (>10 V) stable (>6 h) peaks of ReO(4)(-), OsO(3)(-), and PtO(2)(-) are obtained at 750 °C for Re, 850 °C for Pt, and over 900 °C for Os. Accurate isotopic ratio measurements of Re, Os, and Pt at picogram levels are possible using Ta filaments. PMID:21651247

  12. Structural, Thermal, and Safety Analysis of Isotope Heat Source and Integrated Heat Exchangers for 6-kWe Dynamic Isotope Power System (DIPS)

    SciTech Connect

    Schock, Alfred

    1989-01-01

    The design of the 30-kWt isotope heat source integrated with a Rankine boiler and a Brayton gas heater, which was described in the preceding paper in these proceedings, was subjected to structural, thermal, and safety analyses. The present paper describes and discusses the results of these analyses. Detailed structural analyses of the heat source integrated with the boiler and gas heater showed positive safety margins at all locations during the launch. Detailed thermal analyses showed acceptable temperatures at all locations, during assembly, transfer and orbital operations. Reentry thermal analyses showed that the clads have acceptable peak and impact temperatures. Loss-of-cooling analyses indicated the feasibility of a passive safety concept for preventing over temperatures. Static structural analysis showed positive safety margins at all locations, and dynamic analysis showed that there were no low-frequency resources. Continuum-mechanics code analyses of the effects of the impact of Solid Rocket Booster (SRB) fragments on the heat source and of the very unlikely impact of the full heat source on concrete indicated relatively modest fuel clad deformations and little or no fuel release.

  13. Measurement of urinary desmosine by isotope dilution and high performance liquid chromatography. Correlation between elastase-induced air-space enlargement in the hamster and elevation of urinary desmosine

    SciTech Connect

    Stone, P.J.; Bryan-Rhadfi, J.; Lucey, E.C.; Ciccolella, D.E.; Crombie, G.; Faris, B.; Snider, G.L.; Franzblau, C. (Department of Biochemistry, Boston University School of Medicine, MA (USA))

    1991-08-01

    The accuracy of methods employed to measure the elastin-specific crosslinks, desmosine (DES) and isodesmosine (IDES), has been called into question because contaminants in the urine may cause elevated values. In the present study urine samples were spiked with a known amount of (14C)DES and refluxed in 6 N HCl. Sephadex G-15 chromatography of the hydrolyzed urine employed to remove contaminants. DES and IDES were quantified by high performance liquid chromatography (HPLC) as well as by amino acid analysis. The amount of isotope recovered was used to determine losses during the overall procedure and the isotope dilution to calculate the amounts of endogenous DES and IDES originally present in the urine. Because similar values were obtained by both methods, the more rapid HPLC method was used for all succeeding analyses. In one experiment, the DES amounts in urine collected from hamsters for 3 days after intratracheal treatment with human neutrophil elastase (300 micrograms) or porcine pancreatic elastase (300 micrograms) were 0.212 {plus minus} 0.012 (mean {plus minus} SEM, two measurements on a single pool) and 0.816 {plus minus} 0.005 (two measurements) microgram per hamster per day, respectively. Urine from control hamsters had a mean value of 0.074 {plus minus} 0.008 (eight measurements) microgram per hamster per day. The HNE- and PPE-treated hamsters had mean linear intercept values of 119 and 159% of control values, respectively, giving a positive correlation between increase in airspace size and elevation of urinary DES.

  14. Optimisation of sample preparation protocols for measurement of PGE and Re-Os in organic-rich shales by isotope dilution ICP-MS

    NASA Astrophysics Data System (ADS)

    Rammensee, Philipp; Aulbach, Sonja; Gudelius, Dominik; Brey, Gerhard

    2013-04-01

    Platinum-group elements (PGE) and Re-Os isotopes, which are variably redox-sensitive and fluid-soluble, have potential as proxies for the oxygenation of the atmosphere and oceans (e.g. [1]). However, analysis of these elements in organic rich shales (ORS) is challenging due to abundances of <1 ng/g and the presence of interfering isotopes or molecules of matrix elements. Furthermore, PGE-ReOs systematics in detrital and hydrogenous components may vary, and the choice of digestion parameters (reagents, temperature and pressure) during decomposition of rock powder affects the ratio of digested components [2,3]. Additional treatment to remove the matrix and pre-concentrate PGE-Re by column chromatography is necessary to minimise the effects of interfering elements, but presents its own challenges. We are in the process of conducting variations of acid digestion and column chromatographic protocols on reference sample SDO-1 (Devonian Ohio Shale, USGS). We aim to identify the optimum protocol to investigate PGE-Re-Os systematics of ORS that were sampled as part of the Barberton Drilling Project BARB5 drill core, in order to constrain the changes in detrital and hydrogenous contributions to the sediment with time, to assess the extent of euxinity in the sedimentary basin and to look for evidence of transient "whiffs of oxygen" [1]. The following digestion methods were tested: (1) 4h acid digestion in High Pressure Asher (HPA) apparatus with reverse aqua regia at 300°C and 130 bar (only this digestion allows extraction of volatilised Os in CHCl3 followed by HBr); (2) 3h reverse aqua regia digestion in centrifuge vials on hotplate at 80°C; (3) 48h reverse aqua regia digestion in closed Teflon beakers on hotplate at 140°C followed by a HF/HNO3 digestion step; (4) 48h HF/HNO3 digestion of ashed sample powder in closed Teflon beaker at 140°C on hotplate followed by an aqua regia digestion step. Column chromatographic approaches to decrease the concentrations of interfering elements (Y, Zr, Mo, Cd, Hf, Hg) include the use of cation- and anion resins, and variations of the molarity and composition of the eluent. Preliminary results show that digestion method (1) leaves behind small amounts of presumably PGE-free silica gel; (2) yields consistently higher Re concentrations with an expectedly large amount of solid residue; (3) produces an insoluble sludge; (4) allows complete digestion, but precludes the collection of Os. Column calibrations show the best recovery of PGE-Re in cation resin using 0.2 mol/l HCl as eluent, but intolerably high ratios of interfering over elements of interest, whereas the best matrix separation is achieved using 0.05 mol/l HCl as eluent, but is accompanied by low PGE-Re yields presumably due to the instability of Cl complexes in this medium. They also show that U elutes separately from PGE-Re in 6 mol/l HCl and could be collected with a view to analysing U isotopes as an additional redox proxy. Further tests will be carried out using alternative high-pressure digestion systems. [1] Anbar, et al. (2007) Science 317:1903-1906; [2] Meisel et al. (2003) JAAS 18:720-726; [3] Xu et al. (2012) CG 324:132-147

  15. Isotope Variations in Terrestrial Carbonates and Thermal Springs as Biomarkers: Analogs for Martian Processes

    NASA Technical Reports Server (NTRS)

    Socki, Richard A.; Gibson, Everett K., Jr.; Bissada, K. K.

    2006-01-01

    Stable isotope measurements of carbonate minerals contained within ALH84001 [1] suggest that fluids were present at 3.9 Gy on Mars [2, 3, 4, 5]. Both oxygen and carbon isotopes provide independent means of deciphering paleoenvironmental conditions at the time of carbonate mineral precipitation. In terrestrial carbonate rocks oxygen isotopes not only indicate the paleotemperature of the precipitating fluid, but also provide clues to environmental conditions that affected the fluid chemistry. Carbon isotopes, on the other hand, can indicate the presence or absence of organic compounds during precipitation (i.e. biogenically vs. thermogenically-generated methane), thus serving as a potential biomarker. We have undertaken a study of micro scale stable isotope variations measured in some terrestrial carbonates and the influence of organic compounds associated with the formation of these carbonates. Preliminary results indicate that isotope variations occur within narrow and discrete intervals, providing clues to paleoenvironmental conditions that include both biological and non-biological activity. These results carry implications for deciphering Martian isotope data and therefore potential biological prospecting on the planet Mars. Recently, Fourier Transform Spectrometer observations have detected methane occurring in the Martian atmosphere [6] that could be attributed to a possible biogenic source. Indeed, Mars Express has detected the presence of methane in the Martian atmosphere [7], with evidence indicating that methane abundances are greatest above those basins with high water concentrations.

  16. Measuring environmental phenols and chlorinated organic chemicals in breast milk using automated on-line column-switching-high performance liquid chromatography-isotope dilution tandem mass spectrometry.

    PubMed

    Ye, Xiaoyun; Kuklenyik, Zsuzsanna; Needham, Larry L; Calafat, Antonia M

    2006-02-01

    Breast milk is one possible route of exposure to environmental chemicals, including phenols and chlorinated organic chemicals for breast-fed infants. We developed a highly sensitive method of analyzing breast milk for triclocarban (3,4,4'-trichlorocarbanilide) and eight phenolic compounds: bisphenol A (BPA), 4-tert-octylphenol (4-tOP), ortho-phenylphenol (OPP), 2,4-dichlorophenol, 2,5-dichlorophenol, 2,4,5-trichlorophenol, 2,4,6-trichlorophenol, and 2-hydroxy-4-metoxybenzophenone (BP-3). The method includes adding a solution containing a stable isotope of each chemical, enzymatic hydrolysis of the conjugated chemicals in the milk, and on-line solid-phase extraction coupled with high performance liquid chromatography-tandem mass spectrometry. It can also be used to measure the free (unconjugated) species by omitting the enzymatic deconjugation step. The method, validated using pooled breast milk samples, has inter-day coefficient of variations ranging from 4.8 to 18.9% for most analytes, and spiked recoveries generally about 100%. Detection limits for most analytes are below 1 ng/mL in 100 microL of breast milk. We tested the usefulness of the method by measuring concentrations of these nine compounds in 20 breast milk samples. BPA, OPP, and BP-3 were detected in more than 60% of the samples tested. The free species of these compounds appear to be most prevalent in milk. PMID:16377264

  17. Automated on-line column-switching high performance liquid chromatography isotope dilution tandem mass spectrometry method for the quantification of bisphenol A, bisphenol F, bisphenol S, and 11 other phenols in urine.

    PubMed

    Zhou, Xiaoliu; Kramer, Joshua P; Calafat, Antonia M; Ye, Xiaoyun

    2014-01-01

    Human exposure to bisphenol A (BPA) is widespread. However, in recent years, bisphenol analogs such as bisphenol S (BPS) and bisphenol F (BPF) are replacing BPA in the production of some consumer products. Because human exposure to these alternative bisphenols may occur, biomonitoring of these bisphenol analogs is warranted. In the present study, we developed and validated a sensitive and selective method that uses on-line solid phase extraction coupled to high performance liquid chromatography-isotope dilution tandem mass spectrometry with peak focusing to measure BPA, BPF, BPS, and 11 other environmental phenols in urine. The method required a small amount of sample (100?L) and minimal sample pretreatment. The limits of detection were 0.03ng/mL (BPS), 0.06ng/mL (BPF), 0.10ng/mL (BPA), and ranged from 0.1ng/mL to 1.0ng/mL for the other 11 phenols. In 100 urine samples collected in 2009-2012 from a convenience group of anonymous adults in the United States, of the three bisphenols, we detected BPA at the highest frequency and median concentrations (95%, 0.72ng/mL), followed by BPS (78%, 0.13ng/mL) and BPF (55%, 0.08ng/mL). This sensitive, rugged, and labor and cost-effective method could be used for the analysis of large number of samples for epidemiologic studies. PMID:24316527

  18. Development and application of a stable isotope dilution analysis for the quantitation of advanced glycation end products of creatinine in biofluids of type 2 diabetic patients and healthy volunteers.

    PubMed

    Kunert, Christof; Skurk, Thomas; Frank, Oliver; Lang, Roman; Hauner, Hans; Hofmann, Thomas

    2013-03-01

    N-(1-Methyl-4-oxoimidazolidin-2-ylidene) ?-amino acids were recently identified in roasted meat as so far unknown advanced glycation end products (AGEs) of creatinine. For the first time, this paper reports on the preparation of (13)C-labeled twin molecules of six N-(1-methyl-4-oxoimidazolidin-2-ylidene) ?-amino acids and the development of a stable isotope dilution analysis (SIDA) for their simultaneous quantitation in meat, plasma, and urine samples by means of HPLC-MS/MS. Method validation demonstrated good precision (<14% RSD) and accuracy (97-118%) for all analytes and a lower limit of quantitation of 1 pg injected onto the column. The SIDA was applied to monitor plasma appearance and urinary excretion of these AGEs in type 2 diabetes mellitus patients (DM, n = 7) and healthy controls (n = 10) prior to and after ingestion of a bolus of processed beef meat. Interestingly, the basal concentration of N-(1-methyl-4-oxoimidazolidin-2-ylidene) aminopropionic acid was elevated in plasma and urine of DM patients compared to healthy individuals. Further, ingestion of processed meat led to a significantly higher concentration of this AGE in biofluids from DM patients when compared to healthy controls. These findings suggest a favored in vivo formation, as demonstrated by physiological model incubations of creatinine and carbohydrates (37 °C, pH 7.4), or a more efficient dietary up-take of N-(1-methyl-4-oxoimidazolidin-2-ylidene) ?-amino acids in hyperglycemic diabetes patients. PMID:23379726

  19. Preparation, certification and validation of a stable solid spike of uranium and plutonium coated with a cellulose derivative for the measurement of uranium and plutonium content in dissolved nuclear fuel by isotope dilution mass spectrometry.

    PubMed

    Surugaya, Naoki; Hiyama, Toshiaki; Verbruggen, André; Wellum, Roger

    2008-02-01

    A stable solid spike for the measurement of uranium and plutonium content in nitric acid solutions of spent nuclear fuel by isotope dilution mass spectrometry has been prepared at the European Commission Institute for Reference Materials and Measurements in Belgium. The spike contains about 50 mg of uranium with a 19.838% (235)U enrichment and 2 mg of plutonium with a 97.766% (239)Pu abundance in each individual ampoule. The dried materials were covered with a thin film of cellulose acetate butyrate as a protective organic stabilizer to resist shocks encountered during transportation and to eliminate flaking-off during long-term storage. It was found that the cellulose acetate butyrate has good characteristics, maintaining a thin film for a long time, but readily dissolving on heating with nitric acid solution. The solid spike containing cellulose acetate butyrate was certified as a reference material with certified quantities: (235)U and (239)Pu amounts and uranium and plutonium amount ratios, and was validated by analyzing spent fuel dissolver solutions of the Tokai reprocessing plant in Japan. This paper describes the preparation, certification and validation of the solid spike coated with a cellulose derivative. PMID:18270417

  20. Quantification of Oxidative DNA Lesions in Tissues of Long-Evans Cinnamon Rats by Capillary High-performance Liquid Chromatography-Tandem Mass Spectrometry Coupled with Stable Isotope-dilution Method

    PubMed Central

    Wang, Jin; Yuan, Bifeng; Guerrero, Candace; Bahde, Ralf; Gupta, Sanjeev; Wang, Yinsheng

    2011-01-01

    The purpose of our study was to develop suitable methods to quantify oxidative DNA lesions in the setting of transition metal-related diseases. Transition metal-driven Fenton reactions constitute an important endogenous source of reactive oxygen species (ROS). In genetic diseases with accumulation of transition metal ions, excessive ROS production causes pathophysiological changes, including DNA damage. Wilson’s disease is an autosomal recessive disorder with copper toxicosis due to deficiency of ATP7B protein needed for excreting copper into bile. The Long-Evans Cinnamon (LEC) rat bears a deletion in Atp7b gene and serves as an excellent model for hepatic Wilson’s disease. We used a sensitive capillary LC-ESI-MS/MS/MS method in conjunction with stable-isotope dilution technique to quantify several types of oxidative DNA lesions in liver and brain of LEC rats. These lesions included 5-formyl-2?-deoxyuridine, 5-hydroxymethyl-2?-deoxyuridine, and the 5?R and 5?S diastereomers of 8,5?-cyclo-2?-deoxyguanosine and 8,5?-cyclo-2?-deoxyadenosine. Moreover, the levels of these DNA lesions in the liver and brain increased with age and correlated with age-dependent regulation of the expression of DNA repair genes in LEC rats. These results provide significant new knowledge for better understanding the implications of oxidative DNA lesions in transition metal-induced diseases, such as Wilson’s disease, as well as in ageing and ageing-related pathological conditions. PMID:21323344

  1. Chitin: 'Forgotten' Source of Nitrogen: From Modern Chitin to Thermally Mature Kerogen: Lessons from Nitrogen Isotope Ratios

    USGS Publications Warehouse

    Schimmelmann, A.; Wintsch, R.P.; Lewan, M.D.; DeNiro, M.J.

    1998-01-01

    Chitinous biomass represents a major pool of organic nitrogen in living biota and is likely to have contributed some of the fossil organic nitrogen in kerogen. We review the nitrogen isotope biogeochemistry of chitin and present preliminary results suggesting interaction between kerogen and ammonium during thermal maturation. Modern arthropod chitin may shift its nitrogen isotope ratio by a few per mil depending on the chemical method of chitin preparation, mostly because N-containing non-amino-sugar components in chemically complex chitin cannot be removed quantitatively. Acid hydrolysis of chemically complex chitin and subsequent ion-chromatographic purification of the "deacetylated chitin-monomer" D-glucosamine (in hydrochloride form) provides a chemically well-defined, pure amino-sugar substrate for reproducible, high-precision determination of ??15N values in chitin. ??15N values of chitin exhibited a variability of about one per mil within an individual's exoskeleton. The nitrogen isotope ratio differed between old and new exoskeletons by up to 4 per mil. A strong dietary influence on the ??15N value of chitin is indicated by the observation of increasing ??15N values of chitin from marine crustaceans with increasing trophic level. Partial biodegradation of exoskeletons does not significantly influence ??15N values of remaining, chemically preserved amino sugar in chitin. Diagenesis and increasing thermal maturity of sedimentary organic matter, including chitin-derived nitrogen-rich moieties, result in humic compounds much different from chitin and may significantly change bulk ??15N values. Hydrous pyrolysis of immature source rocks at 330??C in contact with 15N-enriched NH4Cl, under conditions of artificial oil generation, demonstrates the abiogenic incorporation of inorganic nitrogen into carbon-bound nitrogen in kerogen. Not all organic nitrogen in natural, thermally mature kerogen is therefore necessarily derived from original organic matter, but may partly result from reaction with ammonium-containing pore waters.

  2. Trace analysis of methylated and hydroxymethylated cytosines in DNA by isotope-dilution LC-MS/MS: first evidence of DNA methylation in Caenorhabditis elegans.

    PubMed

    Hu, Chiung-Wen; Chen, Jian-Lian; Hsu, Yu-Wen; Yen, Cheng-Chieh; Chao, Mu-Rong

    2015-01-01

    From 1986 to the present, the popular research model organism Caenorhabditis elegans has been thought to completely lack DNA methylation and seems to have lost DNA methylation enzymes from its genomes. In the present study, we report the development of a sensitive and selective assay based on LC-MS/MS to simultaneously measure 5-methyl-2'-deoxycytidine (5-mdC) and 5-hydroxymethyl-2'-deoxycytidine (5-hmdC) in DNA hydrolysates. With the use of isotope internal standards ([2H3]5-mdC and [2H3]5-hmdC) and online solid-phase extraction, the detection limits of 5-mdC and 5-hmdC were estimated to be 0.01 and 0.02 pg respectively, which correspond to a 0.000006% and 0.00001% methylation and hydroxymethylation level. This method was applied to investigate whether DNA methylation/hydroxymethylation exists in C. elegans. The present study for the first time demonstrates that 5-mdC is present in C. elegans genomic DNA (0.0019-0.0033% of cytosine methylated) using LC-MS/MS, whereas another epigenetic modification, 5-hmdC, is not detectable. Furthermore, we found that C. elegans DNA was hypo- or hyper-methylated in a dose-dependent manner by the DNA methyltransferase (DNMT)-inhibiting drug decitabine (5-aza-2'-deoxycytidine) or cadmium respectively. Our data support the possible existence of an active DNA-methylation mechanism in C. elegans, in which unidentified DNMTs could be involved. The present study highlights the importance of re-evaluating the evolutionary conservation of DNA-methylation machinery in nematodes which were traditionally considered to lack functional DNA methylation. PMID:25299492

  3. Simultaneous determination of albendazole and its metabolites in fish muscle tissue by stable isotope dilution ultra-performance liquid chromatography tandem mass spectrometry.

    PubMed

    Zhang, Xiaojun; Xu, Hanxiang; Zhang, Hong; Guo, Yuanming; Dai, Zhiyuan; Chen, Xuechang

    2011-08-01

    A rapid, specific, and sensitive method utilizing ultra-performance liquid chromatography tandem mass spectrometry was developed and validated to determine albendazole, albendazole sulfoxide, albendazole sulfone, and albendazole 2-aminosulfone in fish muscle tissue. The fish samples were extracted with ethyl acetate, then the organic phase was evaporated to dryness, and the residue was reconstituted in methanol-water solution and cleaned up by n-hexane. Reversed-phase separation of target compounds was achieved using a BEH C18 column and a gradient consisting of 0.2% (v/v) formic acid and methanol. Tandem mass spectrometry analyses were performed on a triple-quadrupole tandem mass spectrometer. In the whole procedure, the isotope-labeled internal standards were used to correct the matrix effect and variations associated with the analysis. The method was validated with respect to linearity, specificity, accuracy, and precision. The method exhibited a linear response from 0.1 to 20 ng mL(-1) (r(2)?>?0.9985). The limit of quantitation for albendazole (ABZ), albendazole sulfoxide (ABZSO), albendazole sulfone (ABZSO(2)), and albendazole 2-aminosulfone (ABZ-2-NH(2)SO(2)) was 0.1, 0.1, 0.1, and 0.2 ng g(-1), respectively. The mean recoveries of ABZ, ABZSO, ABZSO(2), and ABZ-2-NH(2)SO(2) spiked at a level of 0.2-5.0 ng g(-1) were 95.3-113.7%, and the relative standard deviations of intra- and inter-day measurements were less than 6.38%. The method was later successfully applied to the determination of albendazole and its three metabolites in 60 fish samples collected from local markets. PMID:21633840

  4. Antibody labeling and elemental mass spectrometry (inductively coupled plasma-mass spectrometry) using isotope dilution for highly sensitive ferritin determination and iron-ferritin ratio measurements.

    PubMed

    Konz, Tobias; Añón Alvarez, Elena; Montes-Bayon, Maria; Sanz-Medel, A

    2013-09-01

    Ferritin, an iron storage protein, is a sensitive clinical biomarker for iron metabolic disorders. It is mainly accumulated in the liver hepatocytes and is present in human plasma at trace levels (picomolar or nanograms per milliliter). Therefore, highly sensitive analytical methods are required to perform ferritin quantification in plasma with high precision and accuracy. For this purpose, we present a mass spectrometry-based analytical strategy (inductively coupled plasma-mass spectrometry, ICP-MS) combined with antibody labeling in a sandwich assay format for ferritin determination. The developed methodology involves two ferritin monoclonal antibodies, one of them biotinylated and the other one labeled with a ruthenium chelate [Ru(bpy)3](2+). The complex formed in solution between ferritin and the two antibodies is then captured using streptavidin-coated magnetic microparticles and directly introduced into ICP-MS for Ru monitoring. Since the Ru complex also allows one to obtain electrogenerated chemiluminescence (ECL), the combination of both sets of data (ICP-MS and ECL) will permit the establishment of the ferritin:Ru stoichiometry. This serves as a basis for further quantification studies using flow injection analysis with isotopically enriched (99)Ru as a carrier with ICP-MS detection. Such strategy permits absolute ferritin determination at a picomolar level with good precision (below 5%) and accuracy (85-109% recovery in the existing ferritin reference material, NIBSC code 94/572). Furthermore, the development of a new strategy to address ferritin:iron-ferritin ratios by ICP-MS opens the door also to address the potential of such ratios as a new clinical biomarker for Fe metabolic disorders. PMID:23889701

  5. Stable-isotope dilution LC-MS/MS measurement of nitrite in human plasma after its conversion to S-nitrosoglutathione.

    PubMed

    Hanff, Erik; Böhmer, Anke; Jordan, Jens; Tsikas, Dimitrios

    2014-11-01

    A specific, sensitive and fast LC-MS/MS method with positive electrospray ionization for the quantitative determination of nitrite in human plasma is reported. Added [(15)N]nitrite served as the internal standard (IS). Endogenous nitrite and IS were converted to their S-nitrosoglutathione (GSNO) derivatives, i.e., GS(14)NO and GS(15)NO, respectively, by using excess glutathione (GSH) and HCl. For plasmatic nitrite, fresh plasma (0.5 mL) was spiked with the IS (1000 nM) and ultrafiltered (cut-off 10 kDa). Ultrafiltrate aliquots (100 ?L) were treated with aqueous GSH at a final concentration of 1 mM and 1 ?L of 5M HCl for 5 min. After final sample dilution (1:1, v/v) with acetonitrile-water (70:30, v/v), 2 ?L aliquots were injected via a thermostated (4 °C) autosampler. The mobile phase was acetonitrile-water (70:30, v/v), contained 20mM ammonium formate, had a pH value of 7, and was pumped isocratically at 0.5 mL/min. A Nucleoshell column was used for LC separation. The retention time of GSNO was about 0.8 min and the total analysis time 5 min. Quantification was performed by selected-reaction monitoring the specific mass transition m/z337([M+H](+))?m/z 307([M+H-(14)NO](+·)) for GS(14)NO (i.e., for endogenous nitrite) and m/z338([M+H](+))?m/z307([M+H-(15)NO](+·)) for GS(15)NO (i.e., for the IS). The method was thoroughly validated in human plasma (range, 0-2000 nM). The LOD and LOQ values of the LC-MS/MS method were determined to be 1 fmol and 5 nM [(15)N]nitrite, respectively. The relative matrix-effect of about 21% was outweighed entirely by the IS. In freshly prepared plasma samples from heparinized blood donated by three healthy subjects, nitrite concentration was determined by LC-MS/MS to be 516, 199 and 369 nM. These concentrations were confirmed by using a previously reported GC-MS method and agree with those measured previously by HPLC-UV (334 nm) after nitrite conversion to S-nitroso-N-acetylcysteine (SNAC) by N-acetylcysteine (NAC). Measurement of nitrite by LC-MS/MS as GSNO is about 1000 times more sensitive than by HPLC-UV as SNAC. The applicability of the method to microdialysate, urine, and saliva samples from humans was demonstrated. The agreement of two orthogonal MS-based methods indicates that the concentration of nitrite in freshly prepared, non-frozen plasma from heparinized blood of fasted healthy humans is of the order of 400 nM. PMID:25237784

  6. Separation processes using expulsion from dilute supercritical solutions

    DOEpatents

    Cochran, H.D. Jr.

    1993-04-20

    A process is described for separating isotopes as well as other mixtures by utilizing the behavior of dilute repulsive or weakly attractive elements of the mixtures as the critical point of the solvent is approached.

  7. Separation processes using expulsion from dilute supercritical solutions

    DOEpatents

    Cochran, Jr., Henry D. (Oak Ridge, TN)

    1993-01-01

    A process for separating isotopes as well as other mixtures by utilizing the behavior of dilute repulsive or weakly attractive elements of the mixtures as the critical point of the solvent is approached.

  8. Irreversibility in diluted antiferromagnets

    SciTech Connect

    Soukoulis, C.M.; Grest, G.S.; Ro, C.; Levin, K.

    1985-04-15

    We compute the irreversibility phase diagram, and history-dependent magnetizations for diluted Ising antiferromagnets in three dimensions. We use an iterative mean-field technique which has proved quite successful for treating spin glasses. Motion of the domain walls as the magnetic field is varied at low temperature is also discussed. The onset of time-dependent long-range order and magnetization anomalies are predicted for certain regions of the H-T phase diagram from our studies of the free-energy surface. Our results are compared to those of the random field ferromagnet and spin glasses, which have the common feature that on the time scale of a physical measurement the system is trapped in a local minimum of the free-energy surface. Irreversibility then results primarily from the disappearance of a given minimum as the field or temperature are changed and not from tunneling or thermal activation processes.

  9. Identification of the new neutron-rich isotopes 70-74Ni and 74-77Cu in thermal neutron fission of 235U

    NASA Astrophysics Data System (ADS)

    Bernas, M.; Armbruster, P.; Bocquet, J. P.; Brissot, R.; Faust, H. R.; Roussel, P.

    1987-12-01

    The unknown isotopes 70-74Ni and 74-77Cu were identified in thermal neutron fission of 235U, using the recoil separator Lohengrin and ?E-E detection techniques. Isotopic yields for preselected values of ionic charge and kinetic energy of the fission fragments in the mass range A=70-80 were measured down to 10-9 frament/fission (f/f).

  10. Identification of the new neutron-rich isotopes 70-74Ni and 74-77Cu in thermal neutron fission of 235U

    Microsoft Academic Search

    P. Armbruster; M. Bernas; J. P. Bocquet; R. Brissot; H. R. Faust; P. Roussel

    1987-01-01

    The unknown isotopes 70-74Ni and 74-77Cu were identified in thermal neutron fission of 235U, using the recoil separator Lohengrin and ?E - E detection techniques. Isotopic yields, for preselected values of ionic charge and kinetic energy of the fission fragments in the mass range A = 70 ÷ 80, were measured down to 10-9 fragments\\/fission (f\\/f). Mass yields for the

  11. Identification of the new neutron-rich isotopes 70-74Ni and 74-77Cu in thermal neutron fission of 235U

    Microsoft Academic Search

    M. Bernas; P. Armbruster; J. P. Bocquet; R. Brissot; H. R. Faust; P. Roussel

    1987-01-01

    The unknown isotopes 70-74Ni and 74-77Cu were identified in thermal neutron fission of 235U, using the recoil separator Lohengrin and DeltaE-E detection techniques. Isotopic yields for preselected values of ionic charge and kinetic energy of the fission fragments in the mass range A=70-80 were measured down to 10-9 frament\\/fission (f\\/f).

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

    USGS Publications Warehouse

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

    1989-01-01

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

  13. Unusually large secondary deuterium isotope effect. Thermal trans-cis isomerization of trans-1-phenylcyclohexene

    SciTech Connect

    Caldwell, R.A.; Misawa, H.; Healy, E.F.; Dewar, M.J.S.

    1987-10-28

    The magnitudes of secondary deuterium isotope effects (SDIE) are generally in the range of 0.9 < k/sub H//k/sub D/ < 1.25, and are often satisfactorily rationalized by the zero-point energy (ZPE) change on going from reactant to transition state due to C-H rehybridization. They now report a far larger SDIE for the title reaction. Its rationalization on the basis of transition state theory suggests that it more closely resembles a primary isotope effect.

  14. Relative humidity across the Paleocene-Eocene Thermal Maximum via combined hydrogen-oxygen isotope paleohygrometry (Invited)

    NASA Astrophysics Data System (ADS)

    McInerney, F. A.; Bloch, J. I.; Secord, R.; Wing, S. L.; Kraus, M. J.; Boyer, D. M.

    2009-12-01

    The Paleocene-Eocene Thermal Maximum (PETM) presents an opportunity to characterize continental hydrologic changes during rapid and extreme global warming. The Bighorn Basin, Wyoming, USA, has long been recognized for the PETM sequences preserved there and sits in an ideal location for recording hydrologic changes in the interior of North America. The southeast Bighorn Basin is of particular interest because it contains not only alluvial paleosols and vertebrate fossils, but also macrofloral remains from the PETM. The carbon isotope excursion associated with this event is preserved in this part of the Basin in leaf wax lipids, tooth enamel, and bulk organic matter. To characterize the hydrologic changes that occurred during the PETM we are applying a suite of isotopic, paleobotanical and paleopedological approaches to sections in the southeast Bighorn Basin. Reported here are results from the combined hydrogen and oxygen isotope analysis aimed at reconstructing relative humidity. Oxygen isotope ratios (?18O) of biogenic apatite from mammalian tooth enamel and fish scales vary with environment, physiology and diet. Because mammals are homeothermic, they primarily track surface water values with predictable physiological offsets. Hydrogen isotope ratios (?D) of leaf-wax lipids (long-chain n-alkanes) reflect both meteoric water ?D values and additional D-enrichment caused by evapotranspiration. The enrichment factor between water ?D and n-alkane ?D can therefore be used as a proxy for relative humidity (RH). In this study, ?18O of surface water is estimated using the ?18O of Coryphodon tooth enamel. We use these ?18O values to estimate surface water ?D values using the Global Meteoric Water Line (?D = 8?18O + 10). We then calculate relative humidity from n-alkane ?D values using a Craig-Gordon type isotopic model for D-enrichment caused by transpiration from leaves. Results of the combined hydrogen-oxygen isotope paleohygrometer indicate a general rise in relative humidity during the first half of the PETM followed by a decline during the second half of the event. The rise is punctuated by at least one small drop in relative humidity. Other proxies for available soil moisture (soil weathering indices) and mean annual precipitation (leaf physiognomy) suggest an initial drying at the onset of the PETM followed by subsequent periods of wetter and dryer conditions in the southeastern Bighorn Basin. In contrast, the isotope results presented here suggest that the onset of the PETM was marked by an increase in relative humidity. This discrepancy might indicate increased seasonality during the PETM. Leaf wax hydrogen isotope values are likely biased to record primarily the growing season, which may have become more humid, while soil and plant proxies could reflect an overall decrease in available moisture as a result of increased seasonality of precipitation.

  15. The Absolute Isotopic Composition of Zn in Terrestrial Materials Determined Using Double Spike Thermal Ionization Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Ghidan, O. Y.; Loss, R. D.

    2008-12-01

    Although long suspected to be widespread in nature, until recently, little was known about the extent of the variation of the isotopic composition, or isotopic fractionation, of Zn in natural materials. During the last decade an increasing number of high precision Zn isotopic fractionation data have been reported using MC- ICP-MS (MARECHAL et al., 1999; PETIT et al., 2008; PICHAT et al., 2003), but none have been reported on an absolute scale which is essential for interlaboratory comparison of results. In this work we report sub- permil Zn fractionation in a range of natural materials relative to the internationally proposed absolute Zn isotopic reference material (? zero) (PONZEVERA et al., 2006)using the Thermal Ionization Mass Spectrometry double spike technique. Repeated double spike analysis of the laboratory standard relative to itself demonstrated a long term reproducibility of +0.006 ± 0.039 permil amu-1. The measured isotopic composition of Zn in minerals and igneous rocks SRMs was found to be the same as the proposed absolute (? zero) which makes it possible to consider the proposed absolute Zn isotopic standard as being representative of "bulk earth" Zn. A significant and consistent fractionation of ~+0.3 permil amu-1 was found in 5 sediments from a range of localities. The results obtained for metamorphic SRMs indicate that the fractionation of Zn in these rocks is the same as found in igneous rocks but are different from the Zn found in sedimentary rocks. A clay SRM sample TILL-3 appears to exhibit a consistently Zn fractionation of +0.12 ± 0.10 permil amu-1. The isotopic composition of Zn was also measured in two plant SRMs and one animal SRM sample. The fractionation of (-0.088 ± 0.070 permil amu-1) of Zn in the Rice (a C3 type plant material) sample suggested that Zn may be used to study Zn systematics in plants. The result obtained for MURST-ISS-A2 (Antarctic Krill) was +0.21 ± 0.11 permil amu-1 relative to the laboratory standard which is similar to the average Zn fractionation results of +0.281 ± 0.083 permil amu-1 obtained for marine sediments. The fractionation of Zn in seven ultra pure Zn standard materials was also measured relative to the laboratory standard and found to range from -5.11 ± 0.36 permil amu-1 for AE 10760 to +0.12 ± 0.16 permil amu-1 for Zn IRMM 10440 confirming that that significant care must be exercised in the selection of Zn isotope laboratory standards (TANIMIZU et al., 2002). A pilot study to determine the concentration and the isotopic composition of Zn in river and tap water, and a number of processed materials was also performed. The implications and applications of these results, such as on the atomic weight of Zn will be presented.

  16. Discontinuity in Isotopic Mass Dispersion in Thermal-Neutron-Induced Fission of U235

    Microsoft Academic Search

    M. Talât-Erben

    1970-01-01

    The isotopic mass dispersion curves have been calculated by using a universal isobaric-charge dispersion function and the revised fission yield data for individual nuclides reported by Wahl et al. The mass dispersion curves are discontinuous at the most probable fragment mass value, so that a different dispersion curve applies on either side of the most probable mass, both branches being

  17. Development of an accurate, sensitive, and robust isotope dilution laser ablation ICP-MS method for simultaneous multi-element analysis (chlorine, sulfur, and heavy metals) in coal samples.

    PubMed

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

    2007-10-01

    A method for the direct multi-element determination of Cl, S, Hg, Pb, Cd, U, Br, Cr, Cu, Fe, and Zn in powdered coal samples has been developed by applying inductively coupled plasma isotope dilution mass spectrometry (ICP-IDMS) with laser-assisted introduction into the plasma. A sector-field ICP-MS with a mass resolution of 4,000 and a high-ablation rate laser ablation system provided significantly better sensitivity, detection limits, and accuracy compared to a conventional laser ablation system coupled with a quadrupole ICP-MS. The sensitivity ranges from about 590 cps for (35)Cl+ to more than 6 x 10(5) cps for (238)U+ for 1 microg of trace element per gram of coal sample. Detection limits vary from 450 ng g(-1) for chlorine and 18 ng g(-1) for sulfur to 9.5 pg g(-1) for mercury and 0.3 pg g(-1) for uranium. Analyses of minor and trace elements in four certified reference materials (BCR-180 Gas Coal, BCR-331 Steam Coal, SRM 1632c Trace Elements in Coal, SRM 1635 Trace Elements in Coal) yielded good agreement of usually not more than 5% deviation from the certified values and precisions of less than 10% relative standard deviation for most elements. Higher relative standard deviations were found for particular elements such as Hg and Cd caused by inhomogeneities due to associations of these elements within micro-inclusions in coal which was demonstrated for Hg in SRM 1635, SRM 1632c, and another standard reference material (SRM 2682b, Sulfur and Mercury in Coal). The developed LA-ICP-IDMS method with its simple sample pretreatment opens the possibility for accurate, fast, and highly sensitive determinations of environmentally critical contaminants in coal as well as of trace impurities in similar sample materials like graphite powder and activated charcoal on a routine basis. PMID:17653533

  18. S1 certification of alpha-endosulfan, beta-endosulfan, and endosulfan sulfate in a candidate certified reference material (organochlorine pesticides in tea) by isotope dilution gas chromatography-mass spectrometry.

    PubMed

    Sin, Della Wai-Mei; Wong, Yee-Lok; Cheng, Eddie Chung-Chin; Lo, Man-Fung; Ho, Clare; Mok, Chuen-Shing; Wong, Siu-Kay

    2015-04-01

    This paper presents the certification of alpha-endosulfan, beta-endosulfan, and endosulfan sulfate in a candidate tea certified reference material (code: GLHK-11-03) according to the requirements of the ISO Guide 30 series. Certification of GLHK-11-03 was based on an analytical method purposely developed for the accurate measurement of the mass fraction of the target analytes in the material. An isotope dilution mass spectrometry (IDMS) method involving determination by (i) gas chromatography-negative chemical ionization-mass spectrometry (GC-NCI-MS) and (ii) gas chromatography-electron ionization-high-resolution mass spectrometry (GC-EI-HRMS) techniques was employed. The performance of the described method was demonstrated through participation in the key comparison CCQM-K95 "Mid-Polarity Analytes in Food Matrix: Mid-Polarity Pesticides in Tea" organized by the Consultative Committee for Amount of Substance-Metrology in Chemistry in 2012, where the study material was the same as the certified reference material (CRM). The values reported by using the developed method were in good agreement with the key comparison reference value (KCRV) assigned for beta-endosulfan (727?±?14 ?g kg(-1)) and endosulfan sulfate (505?±?11 ?g kg(-1)), where the degree of equivalence (DoE) values were 0.41 and 0.40, respectively. The certified values of alpha-endosulfan, beta-endosulfan, and endosulfan sulfate in dry mass fraction in GLHK-11-03 were 350, 730, and 502 ?g kg(-1), respectively, and the respective expanded uncertainties, due to sample inhomogeneity, long-term and short-term stability, and variability in the characterization procedure, were 27 ?g kg(-1) (7.8 %), 48 ?g kg(-1) (6.6 %), and 33 ?g kg(-1) (6.6 %). PMID:25619984

  19. Fission yields in the symmetric region: Yields of the stable isotopes of tin and cadmium in the thermal neutron fission of ²³⁵U and ²³⁹Pu

    Microsoft Academic Search

    1977-01-01

    The relative isotopic abundances of five isotopes of cadmium (111, 112, 113, 114, and 116) and eight isotopes of tin (117, 118, 119, 120, 121, 122, 124, and 126) have been measured in the thermal neutron fission of ²³⁵U and ²³⁹Pu. Samples of ²³⁵U and ²³⁹Pu were irradiated in a reactor; the elements were chemically separated and the isotopic abundances

  20. Isotope and thermal effects in chemiosmotic coupling to the flagellar motor of Streptococcus

    SciTech Connect

    Khan, S.; Berg, H.C.

    1983-03-01

    The torque generated by the flagellar motor of Streptococcus strain V4051 has been determined from rates of rotation of cells tethered by a single flagellum in media of different isotopic composition and temperature. Starved cells were energized artificially with either a potassium diffusion potential or a pH gradient. The torque increased linearly with protonmotive force. Identical results were obtained in media made with D2O or H2O; there was no solvent isotope effect. At a fixed protonmotive force, the torque was approximately constant over a temperature range of 4 degrees -38 degrees C. In cells chemotactically inert to changes in cytoplasmic pH, the motor turned counterclockwise when protons moved inward and clockwise when they moved outward. We conclude that the motor is a reversible engine driven by simple acid-base dissociation. A detailed model is discussed.

  1. Unusually large secondary deuterium isotope effect. Thermal trans-cis isomerization of trans-1-phenylcyclohexene

    SciTech Connect

    Caldwell, R.A.; Misawa, H.; Healy, E.F.; Dewar, M.J.

    1987-01-01

    The magnitudes of secondary deuterium isotope effects (SDIE) are generally in the range of 0.9 < kH/kD < 1.25, and are often satisfactorily rationalized by the zero-point energy (ZPE) change on going from reactant to transition state due to C-H rehybridization. We now report a far larger SDIE for the title reaction. Its rationalization on the basis of transition-state theory suggests that it more closely resembles a primary isotope effect. Laser flash photolysis of cis-1-phenylcyclohexene (direct, 266 nm, or sensitized by thioxanthone, 355 nm) affords its trans isomer which in heptane exclusively reverts to 1, k = 2.1 x 10/sup 5/ s at 300 K. Isotopically substituted 2-2-d1 or 2-2,6-6-d3 (generated similarly from the corresponding cis isomers5) both have rates of reversion longer than 2 itself by a factor of 2.0 at room temperature. No previously reported SDIE approaches this magnitude.

  2. Thermal decomposition of methanol in the sonolysis of methanol-water mixtures. Spin-trapping evidence for isotope exchange reactions

    SciTech Connect

    Krishna, C.M.; Lion, Y.; Kondo, T.; Riesz, P.

    1987-11-05

    The spin trap 3,5-dibromo-4-nitrosobenzenesulfonate was used to monitor the yield of free radicals produced during sonolysis of water-methanol mixtures. Methyl radicals and CH/sub 2/OH radicals were observed as well as the isotopically mixed radicals CH/sub 2/D and CHD/sub 2/ when CH/sub 3/OD:D/sub 2/O mixtures were studied. The results clearly show that thermal decomposition of methanol to methyl radicals occurs in the gas phase. The methyl radical yield rises sharply at very low concentrations of methanol, reaches a maximum at 5 mol dm/sup -3/ in water and decreases to a smaller value in methanol. The yield of methyl radicals as a function of methanol concentration is discussed in terms of the different factors influencing the sonochemistry.

  3. ?D and ?13C analyses of atmospheric volatile organic compounds by thermal desorption gas chromatography isotope ratio mass spectrometry.

    PubMed

    von Eckstaedt, Christiane Vitzthum; Grice, Kliti; Ioppolo-Armanios, Marisa; Chidlow, Geoff; Jones, Mark

    2011-09-16

    This paper describes the establishment of a robust method to determine compound specific ?D and ?(13)C values of volatile organic compounds (VOCs) in a standard mixture ranging between C(6) and C(10) and was applied to various complex emission samples, e.g. from biomass combustion and car exhaust. A thermal desorption (TD) unit was linked to a gas chromatography isotope ratio mass spectrometer (GC-irMS) to enable compound specific isotope analysis (CSIA) of gaseous samples. TenaxTA was used as an adsorbent material in stainless steel TD tubes. We determined instrument settings to achieve a minimal water background level for reliable ?D analysis and investigated the impact of storage time on ?D and ?(13)C values of collected VOCs (176 days and 40 days of storage, respectively). Most of the standard compounds investigated showed standard deviations (SD)<6‰ (?D) when stored for 148 days at 4 °C. However, benzene revealed occasionally D depleted values (21‰ SD) for unknown reasons. ?(13)C analysis demonstrated that storage of 40 days had no effect on VOCs investigated. We also showed that breakthrough (benzene and toluene, 37% and 7%, respectively) had only a negligible effect (0.7‰ and 0.4‰, respectively) on ?(13)C values of VOCs on the sample tube. We established that the sample portion collected at the split flow effluent of the TD unit can be used as a replicate sample for isotope analysis saving valuable sampling time and resources. We also applied TD-GC-irMS to different emission samples (biomass combustion, petrol and diesel car engines exhaust) and for the first time ?D values of atmospheric VOCs in the above range are reported. Significant differences in ?D of up to 130‰ were observed between VOCs in emissions from petrol car engine exhaust and biomass combustion (Karri tree). However, diesel car emissions showed a high content of highly complex unresolved mixtures thus a baseline separation of VOCs was not achieved for stable hydrogen isotope analysis. The ability to analyse ?D by TD-GC-irMS complements the characterisation of atmospheric VOCs and is maybe used for establishing further source(s). PMID:21807368

  4. Thermal history of the Mississippian-Pennsylvanian boundary at Arrow Canyon, NV, USA: Insights from carbonate clumped isotopes and fluid inclusion microthermometry

    NASA Astrophysics Data System (ADS)

    Shenton, B.; Grossman, E. L.; Passey, B. H.; Henkes, G. A.; Becker, S. P.; Pottorf, R. J.

    2013-12-01

    Constraining the temperature-time history of sedimentary basins is critical for understanding basin evolution and related problems, such as petroleum systems analysis and genesis of metallic ore deposits. The importance of burial history studies is confirmed by the abundance and diversity of techniques aimed at acquiring thermal history information. Often, multiple techniques are required to fully characterize sediment thermal histories because each tool targets different burial temperatures (e.g., maximum burial temperature, T-t points, or cooling rates) and different indicators may be limited by suitable study material or geologic setting. Therefore it is important to test new techniques, such as clumped isotopes, that may aid in reconstructing basin thermal histories. The potential utility of clumped isotopes as a thermal history tool is suggested by the observation of elevated clumped isotope temperatures in nominally well-preserved fossils, and also from recent laboratory heating experiments showing that C-O bonds can reorder in the solid-state during heating. While this phenomenon conceals primary paleoclimate information, it may record burial temperatures useful for constraining basin thermal histories. Here we present clumped isotope measurements from brachiopods, crinoids, diagenetic cements, and bulk matrix material collected from within ~ 50 m of the global stratotype section and point (GSSP) for the Mississippian-Pennsylvanian boundary along with new fluid inclusion microthermometry data. Preliminary clumped isotope temperatures range from ~100-165 °C and generally cluster based on component type. Secondary fluid inclusion assemblages in blocky calcite cement indicate that strata surrounding the GSSP experienced at least 175-180 °C during burial in the Antler foreland basin. The fact that clumped isotope temperatures in all carbonate components are lower than independently constrained peak temperature estimates from fluid inclusions suggests that clumped isotope compositions either (1) reordered extensively, but not completely, during heating or (2) equilibrated with ambient burial temperature during heating and now reflect ';closure temperatures' achieved during cooling. Our data also suggest that different carbonate components that experience the same T-t history can yield different clumped isotope temperatures.

  5. Microfluidic serial dilution ladder.

    PubMed

    Ahrar, Siavash; Hwang, Michelle; Duncan, Philip N; Hui, Elliot E

    2014-01-01

    Serial dilution is a fundamental procedure that is common to a large number of laboratory protocols. Automation of serial dilution is thus a valuable component for lab-on-a-chip systems. While a handful of different microfluidic strategies for serial dilution have been reported, approaches based on continuous flow mixing inherently consume larger amounts of sample volume and chip real estate. We employ valve-driven circulatory mixing to address these issues and also introduce a novel device structure to store each stage of the dilution process. The dilution strategy is based on sequentially mixing the rungs of a ladder structure. We demonstrate a 7-stage series of 1?:?1 dilutions with R(2) equal to 0.995 in an active device area of 1 cm(2). PMID:24231765

  6. Method to simultaneously determine the sphingosine 1-phosphate breakdown product (2E)-hexadecenal and its fatty acid derivatives using isotope-dilution HPLC-electrospray ionization-quadrupole/time-of-flight mass spectrometry.

    PubMed

    Neuber, Corinna; Schumacher, Fabian; Gulbins, Erich; Kleuser, Burkhard

    2014-09-16

    Sphingosine 1-phosphate (S1P), a bioactive lipid involved in various physiological processes, can be irreversibly degraded by the membrane-bound S1P lyase (S1PL) yielding (2E)-hexadecenal and phosphoethanolamine. It is discussed that (2E)-hexadecenal is further oxidized to (2E)-hexadecenoic acid by the long-chain fatty aldehyde dehydrogenase ALDH3A2 (also known as FALDH) prior to activation via coupling to coenzyme A (CoA). Inhibition or defects in these enzymes, S1PL or FALDH, result in severe immunological disorders or the Sjögren-Larsson syndrome, respectively. Hence, it is of enormous importance to simultaneously determine the S1P breakdown product (2E)-hexadecenal and its fatty acid metabolites in biological samples. However, no method is available so far. Here, we present a sensitive and selective isotope-dilution high performance liquid chromatography-electrospray ionization-quadrupole/time-of-flight mass spectrometry method for simultaneous quantification of (2E)-hexadecenal and its fatty acid metabolites following derivatization with 2-diphenylacetyl-1,3-indandione-1-hydrazone and 1-ethyl-3-(3-(dimethylamino)propyl)carbodiimide. Optimized conditions for sample derivatization, chromatographic separation, and MS/MS detection are presented as well as an extensive method validation. Finally, our method was successfully applied to biological samples. We found that (2E)-hexadecenal is almost quantitatively oxidized to (2E)-hexadecenoic acid, that is further activated as verified by cotreatment of HepG2 cell lysates with (2E)-hexadecenal and the acyl-CoA synthetase inhibitor triacsin C. Moreover, incubations of cell lysates with deuterated (2E)-hexadecenal revealed that no hexadecanoic acid is formed from the aldehyde. Thus, our method provides new insights into the sphingolipid metabolism and will be useful to investigate diseases known for abnormalities in long-chain fatty acid metabolism, e.g., the Sjögren-Larsson syndrome, in more detail. PMID:25137547

  7. Quantitative analysis of phosphoric acid esters in aqueous samples by isotope dilution stir-bar sorptive extraction combined with direct analysis in real time (DART)-Orbitrap mass spectrometry.

    PubMed

    Bridoux, Maxime C; Malandain, Hélène; Leprince, Françoise; Progent, Frédéric; Machuron-Mandard, Xavier

    2015-04-15

    A novel hyphenated technique, namely the combination of stir bar sorptive extraction (SBSE) with isotope dilution direct analysis in real time (DART) Orbitrap™ mass spectrometry (OT-MS) is presented for the extraction of phosphoric acid alkyl esters (tri- (TnBP), di- (HDBP), and mono-butyl phosphate (H2MBP)) from aqueous samples. First, SBSE of phosphate esters was performed using a Twister™ coated with 24?L of polydimethylsiloxane (PDMS) as the extracting phase. SBSE was optimized for extraction pH, phase ratio (PDMS volume/aqueous phase volume), stirring speed, extraction time and temperature. Then, coupling of SBSE to DART/Orbitrap-MS was achieved by placing the Twister™ in the middle of an open-ended glass tube between the DART and the Orbitrap™. The DART mass spectrometric response of phosphate esters was probed using commercially available and synthesized alkyl phosphate ester standards. The positive ion full scan spectra of alkyl phosphate triesters (TnBP) was characterized by the product of self-protonation [M+H](+) and, during collision-induced dissociation (CID), the major fragmentation ions corresponded to consecutive loss of alkyl chains. Negative ionization gave abundant [M-H](-) ions for both HDnBP and H2MnBP. Twisters™ coated with PDMS successfully extracted phosphate acid esters (tri-, di- and mono-esters) granted that the analytes are present in the aqueous solution in the neutral form. SBSE/DART/Orbitrap-MS results show a good linearity between the concentrations and relative peak areas for the analytes in the concentration range studied (0.1-750ngmL(-1)). Reproducibility of this SBSE/DART/Orbitrap-MS method was evaluated in terms of %RSD by extracting a sample of water fortified with the analytes. The %RSDs for TnBP, HDnBP and H2MnBP were 4, 3 and 3% (n=5) using the respective perdeuterated internal standards. Matrix effects were investigated by matrix matched calibration standards using underground water samples (UWS) and river water samples (RWS). Matrix effects were effectively compensated by the addition of the perdeuterated internal standards. The application of this new SBSE/DART/Orbitrap-MS method should be very valuable for on-site sampling/monitoring, limiting the transport of large volumes of water samples from the sampling site to the laboratory. PMID:25818134

  8. Abundance of four sulfur mustard-DNA adducts ex vivo and in vivo revealed by simultaneous quantification in stable isotope dilution-ultrahigh performance liquid chromatography-tandem mass spectrometry.

    PubMed

    Yue, Lijun; Wei, Yuxia; Chen, Jia; Shi, Huiqin; Liu, Qin; Zhang, Yajiao; He, Jun; Guo, Lei; Zhang, Tingfen; Xie, Jianwei; Peng, Shuangqing

    2014-04-21

    Sulfur mustard (SM) is a highly reactive alkylating vesicant and causes blisters upon contact with skin, eyes, and respiratory organs. It covalently links with DNAs by forming four mono- or cross-link adducts. In this article, the reference standards of SM-DNA adducts and deuterated analogues were first synthesized with simplified procedures containing only one or two steps and using less toxic chemical 2-(2-chloroethylthio)ethanol or nontoxic chemical thiodiglycol as starting materials. A sensitive and high-throughput simultaneous quantification method of N(7)-[2-[(2-hydroxyethyl)thio]-ethyl]guanine (N(7)-HETEG), O(6)-[2-[(2-hydroxyethyl)thio]-ethyl]guanine (O(6)-HETEG), N(3)-[2-[(2-hydroxyethyl)thio]-ethyl]adenine (N(3)-HETEA), and bis[2-(guanin-7-yl)ethyl]sulfide (Bis-G) in the Sprague-Dawley rat derma samples was developed by stable isotope dilution-ultrahigh performance liquid chromatography-tandem mass spectrometry (ID-UPLC-MS/MS) with the aim of revealing the real metabolic behaviors of four adducts. The method was validated, the limit of detection (S/N ratio greater than 10) was 0.01, 0.002, 0.04, and 0.11 fmol on column for N(7)-HETEG, O(6)-HETEG, Bis-G, and N(3)-HETEA, respectively, and the lower limit of quantification (S/N ratio greater than 20) was 0.04, 0.01, 0.12, and 0.33 fmol on column for N(7)-HETEG, O(6)-HETEG, Bis-G, and N(3)-HETEA, respectively. The accuracy of this method was determined to be 76% to 129% (n = 3), and both the interday (n = 6) and intraday (n = 7) precisions were less than 10%. The method was further applied for the quantifications of four adducts in the derma of adult male Sprague-Dawley rats exposed to SM ex vivo and in vivo, and all adducts had time- and dose-effect relationships. To the best of our knowledge, this is the first time that the real presented status of four DNA adducts was simultaneously revealed by the MS-based method, in which Bis-G showed much higher abundance than the result previously reported and N(3)-HETEA showed much less. It should be noted that since the interstrand cross-linked adduct is believed to stall DNA replication and finally induce a double-strand break, the higher abundance of Bis-G is a great indication of a more serious DNA lesion by SM alkylation. PMID:24467472

  9. The mathematics of dilution.

    PubMed

    Chatterjee, Barun Kumar

    2014-04-01

    The major objection to homeopathic medicine is that the doses of medicine prescribed in some cases are too dilute for any active ingredient to be present. The medicines would hence be rendered inactive, necessitating novel explanations for the action. A further examination of dilution in the light of the Langmuir equation shows that homeopathic medicines may not be as dilute as a simplistic application of Avogadro's Principle suggests, due to surface effects. PMID:24685420

  10. Investigations of an intrusive contact, northwest Nelson, New Zealand--I. Thermal, chronological and isotopic constraints

    Microsoft Academic Search

    T. Mark Harrison; Ian McDougall

    1980-01-01

    In the Nelson area of New Zealand, intrusion of the Separation Point Batholith 114 Ma ago caused thermal metamorphism in the adjacent Devonian Rameka Gabbro that allowed radiogenic 40 Ar to diffuse partially out of hornblendes in the gabbro. Comparison of mineral ages in the batholith (obtained by the K-Ar, 40 Ar \\/ 39 Ar , Rb-Sr, U-Pb and fission

  11. Stable Chlorine Isotopes and Elemental Chlorine by Thermal Ionization Mass Spectrometry and Ion Chromatography; Martian Meteorites, Carbonaceous Chondrites and Standard Rocks

    NASA Technical Reports Server (NTRS)

    Nakamura, N.; Nyquist, L. E.; Reese, Y.; Shih, C.-Y.; Fujitani, T.; Okano, O.

    2011-01-01

    Recently significantly large mass fractionation of stable chlorine isotopes has been reported for terrestrial and lunar samples [1,2]. In addition, in view of possible early solar system processes [3] and also potential perchlorate-related fluid/microbial activities on the Martian surface [4,5], a large chlorine isotopic fractionation might be expected for some types of planetary materials. Due to analytical difficulties of isotopic and elemental analyses, however, current chlorine analyses for planetary materials are controversial among different laboratories, particularly between IRMS (gas source mass spectrometry) and TIMS (Thermal Ionization Mass Spectrometry) groups [i.e. 1,6,7] for isotopic analyses, as well as between those doing pyrohydrolysis and other groups [i.e. 6,8]. Additional careful investigations of Cl isotope and elemental abundances are required to confirm real chlorine isotope and elemental variations for planetary materials. We have developed a TIMS technique combined with HF-leaching/ion chromatography at NASA JSC that is applicable to analysis of small amounts of meteoritic and planetary materials. We present here results for several standard rocks and meteorites, including Martian meteorites.

  12. Fission-product formation in the thermal-neutron-induced fission of odd Cm isotopes

    Microsoft Academic Search

    I. Tsekhanovich; N. Varapai; V. Rubchenya; D. Rochman; G. S. Simpson; V. Sokolov; G. Fioni; Ilham Al Mahamid

    2004-01-01

    Thermal-neutron-induced fission of 243Cm was studied at the Lohengrin mass separator. The light-mass peak of the fission-yield curve was investigated, and yields of masses from A=72 to A=120 were obtained. Independent-product yields were determined for nuclear charges Z=28 37 . The yield of masses in the superasymmetric region was found to be identical to other fission reactions studied at Lohengrin.

  13. Isotopic yield measurement in the heavy mass region for 239Pu thermal neutron induced fission

    NASA Astrophysics Data System (ADS)

    Bail, A.; Serot, O.; Mathieu, L.; Litaize, O.; Materna, T.; Köster, U.; Faust, H.; Letourneau, A.; Panebianco, S.

    2011-09-01

    Despite the huge number of fission yield data available in the different evaluated nuclear data libraries, such as JEFF-3.1.1, ENDF/B-VII.0, and JENDL-4.0, more accurate data are still needed both for nuclear energy applications and for our understanding of the fission process itself. It is within the framework of this that measurements on the recoil mass spectrometer Lohengrin (at the Institut Laue-Langevin, Grenoble, France) was undertaken, to determine isotopic yields for the heavy fission products from the 239Pu(nth,f) reaction. In order to do this, a new experimental method based on ?-ray spectrometry was developed and validated by comparing our results with those performed in the light mass region with completely different setups. Hence, about 65 fission product yields were measured with an uncertainty that has been reduced on average by a factor of 2 compared to that previously available in the nuclear data libraries. In addition, for some fission products, a strongly deformed ionic charge distribution compared to a normal Gaussian shape was found, which was interpreted as being caused by the presence of a nanosecond isomeric state. Finally, a nuclear charge polarization has been observed in agreement, with the one described on other close fissioning systems.

  14. Isotopic yield measurement in the heavy mass region for {sup 239}Pu thermal neutron induced fission

    SciTech Connect

    Bail, A.; Serot, O.; Mathieu, L.; Litaize, O.; Materna, T.; Koester, U.; Faust, H.; Letourneau, A.; Panebianco, S. [CEA, DEN-Cadarache, F-13108 Saint-Paul-lez-Durance (France); Institut Laue Langevin, 6 rue Jules Horowitz, B.P. 156, F-38042, Grenoble (France); CEA, DSM-Saclay, IRFU/SPhN, F-91191 Gif-sur-Yvette (France)

    2011-09-15

    Despite the huge number of fission yield data available in the different evaluated nuclear data libraries, such as JEFF-3.1.1, ENDF/B-VII.0, and JENDL-4.0, more accurate data are still needed both for nuclear energy applications and for our understanding of the fission process itself. It is within the framework of this that measurements on the recoil mass spectrometer Lohengrin (at the Institut Laue-Langevin, Grenoble, France) was undertaken, to determine isotopic yields for the heavy fission products from the {sup 239}Pu(n{sub th},f) reaction. In order to do this, a new experimental method based on {gamma}-ray spectrometry was developed and validated by comparing our results with those performed in the light mass region with completely different setups. Hence, about 65 fission product yields were measured with an uncertainty that has been reduced on average by a factor of 2 compared to that previously available in the nuclear data libraries. In addition, for some fission products, a strongly deformed ionic charge distribution compared to a normal Gaussian shape was found, which was interpreted as being caused by the presence of a nanosecond isomeric state. Finally, a nuclear charge polarization has been observed in agreement, with the one described on other close fissioning systems.

  15. MECHANICAL ALLOYING AND THERMAL TREATMENT FOR PRODUCTION OF ZIRCONIUM IRON HYDROGEN ISOTOPE GETTERS

    SciTech Connect

    Fox, K.

    2008-02-20

    The objective of this task was to demonstrate that metal hydrides could be produced by mechanical alloying in the quantities needed to support production-scale hydrogen isotope separations. Three starting compositions (ratios of elemental Zr and Fe powders) were selected and attritor milled under argon for times of 8 to 60 hours. In general, milling times of at least 24 hours were required to form the desired Zr{sub 2}Fe and Zr{sub 3}Fe phases, although a considerable amount of unalloyed Zr and Fe remained. Milling in liquid nitrogen does not appear to provide any advantages over milling in hexane, particularly due to the formation of ZrN after longer milling times. Carbides of Zr formed during some of the milling experiments in hexane. Elemental Zr was present in the as-milled material but not detected after annealing for milling times of 48 and 60 hours. It may be that after intimate mixing of the powders in the attritor mill the annealing temperature was sufficient to allow for the formation of a Zr-Fe alloy. Further investigation of this conversion is necessary, and could provide an opportunity for reducing the amount of unreacted metal powder after milling.

  16. Rhenium-osmium isotope systematics of ordinary chondrites and iron meteorites

    NASA Technical Reports Server (NTRS)

    Walker, R. J.; Morgan, J. W.; Horan, M. F.; Grossman, J. N.

    1993-01-01

    Using negative thermal ionization mass spectrometry, Re and Os abundances were determined by isotope dilution and Os-187/Os-186 measured in 11 ordinary chondrites, and also in 1 IIB and 3 IIIB irons. In addition, Os-186/Os-188 and Os-189/Os-188 ratios were precisely determined for 3 unspiked ordinary chondrites as a means of constraining the intensity of any neutron irradiation these meteorites may have experienced.

  17. Determination of isotope enrichments of magnesium in microwave-digested biological samples by thermal ionization mass spectrometry using a direct loading technique.

    PubMed

    Stegmann, W; Goldstein, S L; Georgieff, M

    1996-07-01

    The isotope ratios of magnesium were determined in isotopically normal and 26 Mg-enriched samples of human blood, blood plasma, urine and faeces and bovine muscle. The measurements were made with a magnetic sector, thermal ionization mass spectrometer (TIMS) equipped with a multiple ion collector system for simultaneous detection of the ion currents. The samples were decomposed using microwave digestion with HNO3 and HCI. Without further chemical treatment, the mineralized samples were deposited together with silica gel and boric acid on rhenium filaments, which served as thermal ionization source filaments. This method, called the direct loading technique (DLT), results in stable ion signals of the magnesium isotopes with isotope ratios indistinguishable from those of natural Mg standards within experimental error. Fractionation-corrected 26 Mg/24 Mg ratios of natural Mg standards were determined with a relative external precision of 0.02%. The magnesium recoveries for all of the analysed matrices were > or = 97%; 26 Mg was added to calibrated sample solutions to produce isotopic enrichments within a range typically appearing in samples of human tracer studies. Linear regression analysis of measured versus expected per 1000 (/1000) enrichments yields y = 0.998x + 0.79. The DLT described here is a simpler and quicker method than other methods reported hitherto. It has the advantage of avoiding magnesium separation and purification steps prior to TIMS analysis for all of the analysed biological samples and thus reduces contamination and guarantees optimum magnesium recovery. The reported method improves the applicability of stable isotopes of magnesium in human tracer studies. PMID:8757922

  18. Thermal stratification of Dilute Lakes. Evaluation of regulatory processes and biological effects before and after base addition: Effects on brook trout habitat and growth. Technical report series

    SciTech Connect

    Schofield, C.L.; Josephson, D.; Keleher, C.; Gloss, S.P.

    1993-04-01

    The authors address the significance of changes in summer thermal stratification patterns of Adirondack lakes affected by acidification to cold-water fish populations inhabiting these sensitive lakes. The brook trout (Salvelinus fontinalis) is the primary cold-water fish species indigenous to acid-sensitive lakes in the Adirondack region of northern New York State; the ability of these lakes to sustain this important sport species is highly dependent on the availability of adequate summer habitat, consisting of cool, well-oxygenated water. The authors hypothesized that acidification-induced reductions in the thermal stability of sensitive Adirondack lakes could lead to degradation of potential brook trout habitat. These hypotheses were addressed in the study by utilizing data available from previous lake liming studies in the Adirondack region, brook trout growth data from management studies in the region, and the extensive Adirondack Lake Survey Corporation (ALSC) data base. More than 70% of the small, shallow ALSC lakes were classified as predominantly weakly stratified systems that would be potentially sensitive to changes in thermal stratification status resulting from relatively small changes in color and transparency.

  19. Soret and Dilution Effects on Premixed Flames

    Microsoft Academic Search

    PEDRO GARCÍA-YBARRA; COLETTE NICOLI; PAUL CLAVIN

    1984-01-01

    The structure of a wrinkled premixed flame is analysed theoretically. By assuming the reactive mixture diluted in an inert gas and a weak cross-diffusion coupling between the heat and mass fluxes, the effect of the change by the reaction of the physical gas properties (thermal conductivity, specific heat, number of molecules) and Soret and Dufour diffusions have been investigated in

  20. Determination of the hydrogen isotopic compositions of organic materials and hydrous minerals using thermal combustion laser spectroscopy.

    PubMed

    Koehler, Geoff; Wassenaar, Leonard I

    2012-04-17

    Hydrogen isotopic compositions of hydrous minerals and organic materials were measured by combustion to water, followed by optical isotopic analysis of the water vapor by off-axis integrated cavity output spectroscopy. Hydrogen and oxygen isotopic compositions were calculated by numerical integration of the individual isotopologue concentrations measured by the optical spectrometer. Rapid oxygen isotope exchange occurs within the combustion reactor between water vapor and molecular oxygen so that only hydrogen isotope compositions may be determined. Over a wide range in sample sizes, precisions were ±3-4 per mil. This is comparable but worse than continuous flow-isotope ratio mass spectroscopy (CF-IRMS) methods owing to memory effects inherent in water vapor transfer. Nevertheless, the simplicity and reduced cost of this analysis compared to classical IRMS or CF-IRMS methods make this an attractive option to determine the hydrogen isotopic composition of organic materials where the utmost precision or small sample sizes are not needed. PMID:22432837

  1. Cool Bottom Processes on the Thermally Pulsing Asymptotic Giant Branch and the Isotopic Composition of Circumstellar Dust Grains

    NASA Astrophysics Data System (ADS)

    Nollett, Kenneth M.; Busso, M.; Wasserburg, G. J.

    2003-01-01

    We examine the effects of cool bottom processing (CBP) on the isotopic ratios 18O/16O, 17O/16O, 14N/15N, 26Al/27Al, C/O, and N/O in the convective envelope during the thermally pulsing asymptotic giant branch (TP-AGB) phase of evolution in a 1.5 Msolar initial mass star of solar initial composition. We use a parametric model that treats extra mixing by introducing mass flow between the convective envelope and the underlying radiative zone. The parameters of this model are the mass circulation rate (M) and the maximum temperature (TP) experienced by the circulating material. The effects of nuclear reactions in the flowing matter were calculated using a set of static structures of the radiative zone selected from particular times in a complete stellar evolution calculation. The compositions of the flowing material were obtained, and the resulting changes in the envelope determined. No major shifts in the star's energy budget occur from the imposed CBP if logTP<7.73. Using structures from several times on the TP-AGB, it was found that the results for all species except 26Al were essentially independent of the time chosen if logTP>7.6. Abundant 26Al was produced by CBP for logTP>7.65. While 26Al/27Al depends on TP, the other isotopic ratios depend dominantly on the circulation rate. The relationship is shown between models of CBP as parameterized by a diffusion formalism within the stellar evolution model and those using the mass-flow formalism employed here. They are shown to be effectively equivalent. In general, the CBP treatment readily permits calculation of envelope compositions as affected by different degrees of extra mixing, based on stellar structures computed by normal stellar evolution models. Using these results, the isotopic ratios under conditions of C/O<1 and C/O>1 are compared with the data on circumstellar dust grains. It is found that the 18O/16O, 17O/16O, and 26Al/27Al observed for oxide grains formed at C/O<1 are reasonably well understood. However, the 15N/14N, 12C/13C, and 26Al/27Al in carbide grains (C/O>1) require that many of their stellar sources must have had 14N/15N at least a factor of 4 lower than the solar value. This allows a self-consistent description of all these isotopes in most SiC grains. The rare grains with 12C/13C<10 cannot be produced by any red giant or AGB source, nor are they reconcilable with novae sources.

  2. Thermal decomposition of barium sulfate-vanadium pentaoxide-silica glass mixtures for preparation of sulfur dioxide in sulfur isotope ratio measurements

    Microsoft Academic Search

    F. Yanaglsawa; Hitoshi. Sakai

    1983-01-01

    A previously reported procedure for the thermal decomposition of BaSOâ-VâOâ-SiOâ for the preparation of SOâ in sulfur isotope ratio measurements has been studied in detail, certain portions of the procedure have been modified, and certain aspects of the reaction mechanism have been defined. It was determined that the ¹⁸O\\/¹⁶O ratio of SOâ must be kept constant in order to apply

  3. NUCLEAR-CHARGE DISTRIBUTION IN FISSION: CUMULATIVE YIELDS OF SHORT-LIVED KRYPTON AND XENON ISOTOPES FROM THERMAL-NEUTRON FISSION OF ²³⁵U

    Microsoft Academic Search

    A Wahl

    1958-01-01

    Experiments are described in which use was nnade of the very large ; emanating powers of barium stearate and uranyl stearate for determination of ; cumulative yields for a number of krypton and xenon isotopes formed in the ; thermal-neutron fission of U²³⁵. The results, expressed as the fraction of ; the total chain yield, are: Kr⁸⁹ 0.960 plus or

  4. Coupled variations in helium isotopes and fluid chemistry: Shoshone Geyser Basin, Yellowstone National Park

    SciTech Connect

    Hearn, E.H.; Kennedy, B.M. (Univ. of California, Berkeley (USA)); Truesdell, A.H. (Geological Survey, Menlo Park, CA (USA))

    1990-11-01

    Early studies of {sup 3}He/{sup 4}He variations in geothermal systems have generally attributed these fluctuations to either differences in the source of the magmatic {sup 3}He-rich helium or to local differences in the deep flux of magmatic {sup 3}He-rich helium. Kennedy et al, however, show that near-surface processes such as boiling and dilution may also drastically affect {sup 3}He/{sup 4}He ratios of geothermal vapors. Helium isotope ratios were determined for several hot springs at Shoshone Geyser Basin of Yellowstone National Park for this study, along with other noble gas data. Stable isotope data and water and gas chemistry data for each spring were also compiled. The water chemistry indicates that there is one deep, hot thermal water in the area which is mixing with dilute meteoric water that has entered the system at depth. Spring HCO{sub 3}{sup {minus}} concentrations correlate with {sup 3}He/{sup 4}He values, as in nearby Lower Geyser Basin. This correlation is attributed to variable amounts of deep dilution of thermal waters with a relatively cool water that inhibits boiling at depth, thus preventing the loss of CO{sub 2} and magmatic He in the most diluted samples. Oxygen and hydrogen isotope data also support a boiling and dilution model, but to produce the observed fractionations, the boiling event would have to be extensive, with steam loss at the surface, whereas the boiling that affected the helium isotope ratios was probably a small scale event with steam loss at depth. It is possible that deep boiling occurred in the basin and that small amounts of steam escaped along fractures at about 500 m below the surface while all subsequently produced steam was lost near or at the surface.

  5. Coupled variations in helium isotopes and fluid chemistry: Shoshone Geyser Basin, Yellowstone National Park

    USGS Publications Warehouse

    Hearn, E.H.; Kennedy, B.M.; Truesdell, A.H.

    1990-01-01

    Early studies of 3He/4He variations in geothermal systems have generally attributed these fluctuations to either differences in the source of the magmatic 3He-rich helium or to local differences in the deep flux of magmatic 3He-rich helium. Kennedy et al. (1987), however, show that near-surface processes such as boiling and dilution may also drastically affect 3He 4He ratios of geothermal vapors. Helium isotope ratios were determined for several hot springs at Shoshone Geyser Basin of Yellowstone National Park for this study, along with other noble gas data. Stable isotope data and water and gas chemistry data for each spring were also compiled. The water chemistry indicates that there is one deep, hot thermal water in the area which is mixing with dilute meteoric water that has entered the system at depth. Spring HCO3- concentrations correlate with 3He 4He values, as in nearby Lower Geyser Basin. This correlation is attributed to variable amounts of deep dilution of thermal waters with a relatively cool water that inhibits boiling at depth, thus preventing the loss of CO2 (and therefore HCO3-) and magmatic He in the most diluted samples. Oxygen and hydrogen isotope data also support a boiling and dilution model, but to produce the observed fractionations, the boiling event would have to be extensive, with steam loss at the surface, whereas the boiling that affected the helium isotope ratios was probably a small scale event with steam loss at depth. It is possible that deep boiling occurred in the basin and that small amounts of steam escaped along fractures at about 500 m below the surface while all subsequently produced steam was lost near or at the surface. ?? 1990.

  6. Osmium Isotope Constraints on the Origin of Highly Siderophile Elements in the Earth's Primitive Upper Mantle

    NASA Astrophysics Data System (ADS)

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

    1996-03-01

    Using negative thermal ionization mass spectrometry (NTIMS), Re and Os abundances were determined by isotope dilution, and 187Os/188Os ratios were measured in a variety of terrestrial upper mantle xenoliths, and also ordinary, enstatite and carbonceous chondrites. Our objective is to precisely constrain the Os isotopic composition of the Earth's primitive upper mantle (PUM) and compare it with the Re-Os systematics of the different chondrite classes. Ultimately, these results should provide us with a better understanding of the relative abundances of highly siderophile elements added to the Earth by late accretion, and how their abundances were modified by subsequent processes.

  7. Characterization of volatile nylon 6.6 thermal-oxidative degradation products by selective isotopic labeling and cryo-GC/MS.

    PubMed

    Smith, Jonell N; White, Gregory V; White, Michael I; Bernstein, Robert; Hochrein, James M

    2012-09-01

    Aged materials, such as polymers, can exhibit modifications to their chemical structure and physical properties, which may render the material ineffective for its intended purpose. Isotopic labeling was used to characterize low-molecular weight volatile thermal-oxidative degradation products of nylon 6.6 in an effort to better understand and predict changes in the aged polymer. Headspace gas from aged (up to 243 d at 138 °C) nylon 6.6 monomers (adipic acid and 1,6-hexanediamine) and polymer were preconcentrated, separated, and detected using cryofocusing gas chromatography mass spectrometry (cryo-GC/MS). Observations regarding the relative concentrations observed in each chromatographic peak with respect to aging time were used in conjunction with mass spectra for samples aged under ambient air to determine the presence and identity of 18 degradation products. A comparison of the National Institute of Standards and Technology (NIST) library, unlabeled, and isotopically labeled mass spectra (C-13 or N-15) and expected fragmentation pathways of each degradation product were used to identify the location of isotopically labeled atoms within the product's chemical structure, which can later be used to determine the exact origin of the species. In addition, observations for unlabeled nylon 6.6 aged in an O-18 enriched atmosphere were used to determine if the source of oxygen in the applicable degradation products was from the gaseous environment or the polymer. Approximations for relative isotopic ratios of unlabeled to labeled products are reported, where appropriate. PMID:22711515

  8. Standard test method for determination of uranium or plutonium isotopic composition or concentration by the total evaporation method using a thermal ionization mass spectrometer

    E-print Network

    American Society for Testing and Materials. Philadelphia

    2007-01-01

    1.1 This method describes the determination of the isotopic composition and/or the concentration of uranium and plutonium as nitrate solutions by the thermal ionization mass spectrometric (TIMS) total evaporation method. Purified uranium or plutonium nitrate solutions are loaded onto a degassed metal filament and placed in the mass spectrometer. Under computer control, ion currents are generated by heating of the filament(s). The ion beams are continually measured until the sample is exhausted. The measured ion currents are integrated over the course of the run, and normalized to a reference isotope ion current to yield isotopic ratios. 1.2 In principle, the total evaporation method should yield isotopic ratios that do not require mass bias correction. In practice, some samples may require this bias correction. When compared to the conventional TIMS method, the total evaporation method is approximately two times faster, improves precision from two to four fold, and utilizes smaller sample sizes. 1.3 The tot...

  9. Assessment of groundwater pollution from ash ponds using stable and unstable isotopes around the Koradi and Khaperkheda thermal power plants (Maharashtra, India).

    PubMed

    Voltaggio, M; Spadoni, M; Sacchi, E; Sanam, R; Pujari, P R; Labhasetwar, P K

    2015-06-15

    The impact on local water resources due to fly ash produced in the Koradi and Khaperkheda thermal power plants (district of Nagpur, Maharashtra - India) and disposed in large ponds at the surface was assessed through the study of environmental variation of ratios of stable and unstable isotopes. Analyses of oxygen and hydrogen isotopes suggest scarce interaction between the water temporarily stored in the ponds and the groundwater in the study area. Data also highlight that the high salinity of groundwater measured in the polluted wells is not due to evaporation, but to subsequent infiltration of stream waters draining from the ponds to the local aquifer. (87)Sr/(86)Sr values, when associated with Sr/Ca ratios, demonstrate the dominant role of waste waters coming from tens of brick kilns surrounding the pond sulfate pollution. Uranium isotopic analyses clearly show evidence of the interaction between groundwater and aquifer rocks, and confirm again the low influence of ash ponds. A new conceptual model based on the study of the isotopes of radium is also proposed and used to estimate residence times of groundwater in the area. This model highlights that high salinity cannot be in any case attributed to a prolonged water-rock interaction, but is due to the influence of untreated waste water of domestic or brick kiln origin on the shallow and vulnerable aquifers. PMID:25783943

  10. Characterization of Volatile Nylon 6.6 Thermal-Oxidative Degradation Products by Selective Isotopic Labeling and Cryo-GC/MS

    NASA Astrophysics Data System (ADS)

    Smith, Jonell N.; V. White, Gregory; White, Michael I.; Bernstein, Robert; Hochrein, James M.

    2012-09-01

    Aged materials, such as polymers, can exhibit modifications to their chemical structure and physical properties, which may render the material ineffective for its intended purpose. Isotopic labeling was used to characterize low-molecular weight volatile thermal-oxidative degradation products of nylon 6.6 in an effort to better understand and predict changes in the aged polymer. Headspace gas from aged (up to 243 d at 138 °C) nylon 6.6 monomers (adipic acid and 1,6-hexanediamine) and polymer were preconcentrated, separated, and detected using cryofocusing gas chromatography mass spectrometry (cryo-GC/MS). Observations regarding the relative concentrations observed in each chromatographic peak with respect to aging time were used in conjunction with mass spectra for samples aged under ambient air to determine the presence and identity of 18 degradation products. A comparison of the National Institute of Standards and Technology (NIST) library, unlabeled, and isotopically labeled mass spectra (C-13 or N-15) and expected fragmentation pathways of each degradation product were used to identify the location of isotopically labeled atoms within the product's chemical structure, which can later be used to determine the exact origin of the species. In addition, observations for unlabeled nylon 6.6 aged in an O-18 enriched atmosphere were used to determine if the source of oxygen in the applicable degradation products was from the gaseous environment or the polymer. Approximations for relative isotopic ratios of unlabeled to labeled products are reported, where appropriate.

  11. Thermal unobtainiums? The perfect thermal conductor and

    E-print Network

    Braun, Paul

    Thermal unobtainiums? The perfect thermal conductor and the perfect thermal insulator David G condensate of magnons #12;Outline--toward perfect thermal insulators · Einstein and minimum thermal contribute to thermal resistance · Isotopically pure diamond has highest thermal conductivity of any material

  12. Direct isotope ratio analysis of individual uranium-plutonium mixed particles with various U/Pu ratios by thermal ionization mass spectrometry.

    PubMed

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

    2015-02-01

    Uranium and plutonium isotope ratios in individual uranium-plutonium (U-Pu) mixed particles with various U/Pu atomic ratios were analyzed without prior chemical separation by thermal ionization mass spectrometry (TIMS). Prior to measurement, micron-sized particles with U/Pu ratios of 1, 5, 10, 18, and 70 were produced from uranium and plutonium certified reference materials. In the TIMS analysis, the peaks of americium, plutonium, and uranium ion signals were successfully separated by continuously increasing the evaporation filament current. Consequently, the uranium and plutonium isotope ratios, except the (238)Pu/(239)Pu ratio, were successfully determined for the particles at all U/Pu ratios. This indicates that TIMS direct analysis allows for the measurement of individual U-Pu mixed particles without prior chemical separation. PMID:25479434

  13. RNB production with thermal neutrons

    NASA Astrophysics Data System (ADS)

    Kester, O.; Habs, D.; Groß, M.; Maier, H. J.; Thirolf, P. G.; Sieber, T.; Faestermann, T.; von Egidy, T.; Köster, U.

    2002-04-01

    Thermal neutron induced nuclear fission is the most suitable method to produce neutron-rich isotopes (70? A?160) due to the large fission cross section and the high thermal neutron fluxes in modern reactors. Intensities of mass separated neutron rich nuclei of some 10 11 ions/s are expected, e.g. for 91Kr, 132Sn or 144Cs from 235U diluted in a porous graphite target. Several front runners with low-energy fission-fragment beams exist like OSIRIS in Studsvik. In order to get beams of neutron-rich nuclei at the Coulomb barrier, the PIAFE project worked out a first concept of production and mass separation of high-intensity beams of fission fragments. At the new Munich high-flux reactor FRMII, the Munich Accelerator for Fission Fragments (MAFF) is under development to make use of post accelerated beams of neutron rich isotopes for experiments in many different fields of nuclear physics, solid state physics and medicine. One key experiment will be the production and the study of very heavy elements. An overview of the production method of neutron-rich isotopes by thermal neutron induced fission, and of the expected yields will be given and the development of target-ion-sources and of the fission targets for MAFF will be characterized.

  14. Dilution, Concentration, and Flotation

    ERIC Educational Resources Information Center

    Liang, Ling; Schmuckler, Joseph S.

    2004-01-01

    As both classroom teaching practice and literature show, many students have difficulties learning science concepts such as density. Here are some investigations that identify the relationship between density and floating through experimenting with successive dilution of a liquid, or the systematic change of concentration of a saltwater solution.…

  15. Helium dilution refrigeration system

    DOEpatents

    Roach, P.R.; Gray, K.E.

    1988-09-13

    A helium dilution refrigeration system operable over a limited time period, and recyclable for a next period of operation is disclosed. The refrigeration system is compact with a self-contained pumping system and heaters for operation of the system. A mixing chamber contains [sup 3]He and [sup 4]He liquids which are precooled by a coupled container containing [sup 3]He liquid, enabling the phase separation of a [sup 3]He rich liquid phase from a dilute [sup 3]He-[sup 4]He liquid phase which leads to the final stage of a dilution cooling process for obtaining low temperatures. The mixing chamber and a still are coupled by a fluid line and are maintained at substantially the same level with the still cross sectional area being smaller than that of the mixing chamber. This configuration provides maximum cooling power and efficiency by the cooling period ending when the [sup 3]He liquid is depleted from the mixing chamber with the mixing chamber nearly empty of liquid helium, thus avoiding unnecessary and inefficient cooling of a large amount of the dilute [sup 3]He-[sup 4]He liquid phase. 2 figs.

  16. High precision Hf isotope measurements of MORB and OIB by thermal ionisation mass spectrometry: insights into the depleted mantle

    Microsoft Academic Search

    G. M. Nowell; P. D. Kempton; S. R. Noble; J. G. Fitton; A. D. Saunders; J. J. Mahoney; R. N. Taylor

    1998-01-01

    The existing Hf isotope database for mid-ocean ridge basalts (MORB) is limited in both quantity and precision. Nevertheless, in Hf–Nd isotope space, MORBs show a wide variation in 176Hf\\/177Hf over a relatively restricted range in 143Nd\\/144Nd. The highest 176Hf\\/177Hf ratios (?0.283355) within the MORB range are restricted to just four samples (<6.5% of total). Of these high 176Hf\\/177Hf MORBs, three

  17. Identification of the new neutron-rich isotopes ⁷°⁻⁻⁷⁴Ni and ⁷⁴⁻⁻⁷⁷Cu in thermal neutron fission of ²³⁵U

    Microsoft Academic Search

    M. Bernas; P. Armbruster; J. P. Bocquet; R. Brissot; H. R. Faust; P. Roussel

    1987-01-01

    The unknown isotopes ⁷°⁻⁻⁷⁴Ni and ⁷⁴⁻⁻⁷⁷Cu were identified in thermal neutron fission of ²³⁵U, using the recoil separator Lohengrin and ..delta..E-E detection techniques. Isotopic yields for preselected values of ionic charge and kinetic energy of the fission fragments in the mass range A = 70--80 were measured down to 10⁻⁹ frament\\/fission (f\\/f).

  18. Mass-dependent and Mass-independent Sulphur Isotope Fractionation Accompanying Thermal- and Photo-chemical Decomposition of Sulphur Bearing Organic Compounds

    NASA Astrophysics Data System (ADS)

    Oduro, Harry; Izon, Gareth; Ono, Shuhei

    2014-05-01

    The bimodal S-isotope record, specifically the transition from mass independent (MIF) to mass dependent fractionation (MDF), is perhaps the most widely cited line of evidence for an irreversible rise in atmospheric oxygen at ca. 2.4Ga. The production and preservation of S-MIF, manifested in both ?33S and ?36S, within the geological record are linked to atmospheric O2 via a number of arguments. However, to date, the only mechanism capable of generating S-MIF consistent with the Archaean sedimentary records involves gas-phase ultraviolet irradiation of SO21 photolysis. More recently, ?33S S-MIF trends have been reported from en vitro thermochemical sulphate reduction (TSR) experiments, prompting authors to question the importance of S-MIF as a proxy for Earth oxidation2. Importantly, whilst emerging TSR experiments3,4 affirm the reported ?33S trends2, these experiments fail to identify correlated S-MIF between ?33S and ?36S values3,4. Realization that S-MIF is confined to ?33S during TSR, precludes TSR as a mechanism responsible for the origin of the Archaean S-MIF record but strongly suggests the effect originating from a magnetic isotope effect (MIE) associated with 33S nucleus3,4. Clearly, photochemical and thermochemical processes impart different ?36S/?33S trends with significant variation in ?34S; however, a complete experimental elucidation of mechanisms responsible for the S-MIF and S-MIE signatures is lacking. Interestingly, a complete understanding of the S-isotope chemistry during thermal- and photo-chemical decomposition may reveal wavelength and thermal dependence archived in the sedimentary record. Here we extend the experimental database to explore the magnitude and sign of ?36S/?33S and ?34S produced during both photo- and thermochemical processes. Here the organic sulphur compounds (OSC) utilized in these experiments carries diagnostic ?36S/?33S patterns that differ from those reported from photolysis experiment SO2 and from the Archaean sedimentary record. Further thermal decomposition of several sulphur containing compounds with; 1) an aliphatic-S (e.g., diphenyl disulphide), 2) tri-substituted aromatic-S (trithiane), and S-amino acids (e.g., cysteine, methionine, taurine, and glutathionine) were tested for four S-isotope fractionation under vacuum. Among these, aromatic trithiane produced anomalous 33S up to 1.3‰, indicating thermal decomposition through radical chemistry, producing S-MIE. While taurine with sulphonic acid (R-SO2OH) functional groups yielded S-MDF up to 15‰ (between the AVS and the residual OSC), which is consistent with estimated zero-point energy shifts for thiol (R-SH), and thiyl (R-S-CH3) groups of cysteine and methionine, respectively. These results suggest that OSC might undergo either thermal or photochemical decomposition and the S-MIF, S-MDF, and S-MIE signatures may be archived in the geologic record. The emerging mechanisms responsible for these isotope signals and their implications will be discussed in more detail. Ultimately this work offers a framework where these signals can be used as a diagnostic marker to distinguish between thermo- and photochemical processes. References: 1. Farquhar et al., Science 2000 2. Watanabe et al., Science 2010; 3. Oduro et al., PNAS 2011; 4. Kopf and Ono, GCA 2012.

  19. Sequential separation of light rare-earth elements, thorium and uranium by miniaturized extraction chromatography: Application to isotopic analyses of silicate rocks

    Microsoft Academic Search

    Christian Pin; JoséFrancisco Santos Zalduegui

    1997-01-01

    A new method for the concomitant separation of the light rare-earth elements (LREEs), thorium and uranium is described, and applied to the determination of 143Nd144Nd ratios, and concentrations of Sm, Nd, Th and U in silicate rocks, using isotope dilution and thermal ionization mass spectrometry. The proposed scheme is based on two recently introduced extraction chromatographic materials, referred to as

  20. Geothermal reservoir temperatures estimated from the oxygen isotope compositions of dissolved sulfate and water from hot springs and shallow drillholes

    USGS Publications Warehouse

    McKenzie, W.F.; Truesdell, A.H.

    1977-01-01

    The oxygen isotope compositions of dissolved sulfate and water from hot springs and shallow drillholes have been tested as a geothermometer in three areas of the western United States. Limited analyses of spring and borehole fluids and existing experimental rate studies suggest that dissolved sulfate and water are probably in isotopic equilibrium in all reservoirs of significant size with temperatures above ca. 140??C and that little re-equilibration occurs during ascent to the surface. The geothermometer is, however, affected by changes in ??18O of water due to subsurface boiling and dilution and by addition of sulfate of nearsurface origin. Methods are described to calculate the effects of boiling and dilution. The geothermometer, is applied to thermal systems of Yellowstone Park, Wyoming, Long Valley, California, and Raft River, Idaho to estimate deep reservoir temperatures of 360, 240, and 142??C, respectively. ?? 1976.

  1. Determination of femtogram quantities of protactinium in geologic samples by thermal ionization mass spectrometry

    SciTech Connect

    Pickett, D.A.; Murrell, M.T.; Williams, R.W. (Los Alamos National Lab., NM (United States))

    1994-04-01

    We describe a procedure for measurement of [sup 231]Pa in geologic samples by isotope dilution thermal ionization mass spectrometry, using [sup 233]Pa as a spike isotope, which provides marked improvements in precision and sample size relative to established decay counting techniques. This method allows determination of as little as a few tens of femtograms of [sup 231]Pa (approximately 10[sup 3] atoms) with a conservative estimated uncertainty of [+-]1% (95% confidence level). Applications of [sup 231]Pa-[sup 235]U systematics to uranium-series geochemistry and geochronology should be greatly enhanced by this approach. 31 refs., 4 figs., 1 tab.

  2. He dilution refrigerator

    NASA Astrophysics Data System (ADS)

    Jessen, F.; Knufinke, M.; Bell, S. C.; Vergien, P.; Hattermann, H.; Weiss, P.; Rudolph, M.; Reinschmidt, M.; Meyer, K.; Gaber, T.; Cano, D.; Günther, A.; Bernon, S.; Koelle, D.; Kleiner, R.; Fortágh, J.

    2014-09-01

    We describe the preparation of ultracold atomic clouds in a dilution refrigerator. The closed-cycle 3He/4He cryostat was custom made to provide optical access for laser cooling, optical manipulation and detection of atoms. We show that the cryostat meets the requirements for cold atom experiments, specifically in terms of operating a magneto-optical trap, magnetic traps and magnetic transport under ultrahigh vacuum conditions. The presented system is a step toward the creation of a quantum hybrid system combining ultracold atoms and solid-state quantum devices.

  3. Dispersion serial dilution methods using the gradient diluter device.

    PubMed

    Walling, Leslie; Schulz, Craig; Johnson, Michael

    2012-12-01

    A solute aspirated into a prefilled tube of diluent undergoes a dilution effect known as dispersion. Traditionally the effects of dispersion have been considered a negative consequence of using liquid-filled fixed-tip liquid handlers. We present a novel device and technique that utilizes the effects of dispersion to the benefit of making dilutions. The device known as the Gradient Diluter extends the dilution range of practical serial dilutions to six orders of magnitude in final volumes as low as 10??L. Presented are the device, dispersion methods, and validation tests using fluorescence detection of sulforhodamine and the high-performance liquid chromatography/ultraviolet detection of furosemide. In addition, a T-cell inhibition assay of a relevant downstream protein is used to demonstrate IC(50) curves made with the Gradient Diluter compare favorably with those generated by hand. PMID:22364546

  4. Standard test method for isotopic analysis of hydrolyzed uranium hexafluoride and uranyl nitrate solutions by thermal ionization mass spectrometry

    E-print Network

    American Society for Testing and Materials. Philadelphia

    2005-01-01

    1.1 This method applies to the determination of isotopic composition in hydrolyzed nuclear grade uranium hexafluoride. It covers isotopic abundance of 235U between 0.1 and 5.0 % mass fraction, abundance of 234U between 0.0055 and 0.05 % mass fraction, and abundance of 236U between 0.0003 and 0.5 % mass fraction. This test method may be applicable to other isotopic abundance providing that corresponding standards are available. 1.2 This test method can apply to uranyl nitrate solutions. This can be achieved either by transforming the uranyl nitrate solution to a uranyl fluoride solution prior to the deposition on the filaments or directly by depositing the uranyl nitrate solution on the filaments. In the latter case, a calibration with uranyl nitrate standards must be performed. 1.3 This test method can also apply to other nuclear grade matrices (for example, uranium oxides) by providing a chemical transformation to uranyl fluoride or uranyl nitrate solution. 1.4 This standard does not purport to address al...

  5. Structure of the carbon isotope excursion in a high-resolution lacustrine Paleocene-Eocene Thermal Maximum record from central China

    NASA Astrophysics Data System (ADS)

    Chen, Zuoling; Wang, Xu; Hu, Jianfang; Yang, Shiling; Zhu, Min; Dong, Xinxin; Tang, Zihua; Peng, Ping'an; Ding, Zhongli

    2014-12-01

    The carbon isotope excursion (CIE) associated with the Paleocene-Eocene Thermal Maximum (PETM) has been recognized for the first time in the micritic carbonate, total organic carbon (TOC) and black carbon (BC) contained within the lacustrine sediments from the Nanyang Basin, central China. The remarkably large excursion (? - 6 ‰) in the ?13CTOC and ?13CBC values is possibly attributable to increased humidity and elevated pCO2 concentration. The ? - 4 ‰ CIE recorded in the ?13Ccalcite, reflecting the average isotope change of the watershed system, is consistent with that observed in planktonic foraminifera. This correspondence suggests that the true magnitude of the carbon isotope excursion in the ocean-atmosphere system is likely close to - 4 ‰. The ?10 m excursion onset in our multi-proxy ?13C records demonstrates that the large input of 13C-depleted carbon into the ocean-atmosphere system was not geologically instantaneous. Despite difference and somewhat smoothness in detailed pattern of the CIE due to localized controls on different substrates, inorganic and organic ?13C data generally depict a gradual excursion onset at least over timescales of thousands of years. In addition, continental temperature reconstruction, based on the distribution of membrane lipids of bacteria, suggests a warming of ?4 °C prior to the PETM and ?7 °C increase in temperature during the PETM. The temperature data are overall similar in pattern and trend to the ?13C change across the PETM. These observations, combined with pre-CIE warming, are in line with the idea that 13C-depleted carbon release operated as a positive feedback to temperature, suggesting supply from one or more large organic carbon reservoirs on Earth's surface.

  6. Dilute magnetic topological semiconductors

    NASA Astrophysics Data System (ADS)

    Kim, Kyoung-Min; Jho, Yong-Soo; Kim, Ki-Seok

    2015-03-01

    Replacing semiconductors with topological insulators, we propose the problem of dilute magnetic topological semiconductors. Performing the renormalization group analysis for an effective field theory, where doped magnetic impurities give rise to a spatially modulated random axion term, we find a novel insulator-metal transition from either a topological or band insulating phase to an inhomogeneously distributed Weyl metallic state with such insulating islands, where extremely broad distributions of ferromagnetic clusters combined with strong spin-orbit interactions are responsible for the emergence of randomly distributed Weyl metallic islands. Since electromagnetic properties in a Weyl metal are described by axion electrodynamics, the role of random axion electrodynamics in transport phenomena casts an interesting problem beyond the physics of percolation in conventional disorder-driven metal-insulator transitions.

  7. Standard dilution analysis.

    PubMed

    Jones, Willis B; Donati, George L; Calloway, Clifton P; Jones, Bradley T

    2015-02-17

    Standard dilution analysis (SDA) is a novel calibration method that may be applied to most instrumental techniques that will accept liquid samples and are capable of monitoring two wavelengths simultaneously. It combines the traditional methods of standard additions and internal standards. Therefore, it simultaneously corrects for matrix effects and for fluctuations due to changes in sample size, orientation, or instrumental parameters. SDA requires only 200 s per sample with inductively coupled plasma optical emission spectrometry (ICP OES). Neither the preparation of a series of standard solutions nor the construction of a universal calibration graph is required. The analysis is performed by combining two solutions in a single container: the first containing 50% sample and 50% standard mixture; the second containing 50% sample and 50% solvent. Data are collected in real time as the first solution is diluted by the second one. The results are used to prepare a plot of the analyte-to-internal standard signal ratio on the y-axis versus the inverse of the internal standard concentration on the x-axis. The analyte concentration in the sample is determined from the ratio of the slope and intercept of that plot. The method has been applied to the determination of FD&C dye Blue No. 1 in mouthwash by molecular absorption spectrometry and to the determination of eight metals in mouthwash, wine, cola, nitric acid, and water by ICP OES. Both the accuracy and precision for SDA are better than those observed for the external calibration, standard additions, and internal standard methods using ICP OES. PMID:25599250

  8. Uranium-lead Isotope Evidence in the Shelyabinsk LL5 Chondrite Meteorite for Ancient and Recent Thermal Events

    NASA Technical Reports Server (NTRS)

    Lapen, T. J.; Kring, D. A.; Zolensky, M. E.; Andreasen, R.; Righter, M.; Swindle, T. D.; Beard, S. P.; Swindle, T. D.

    2014-01-01

    The impact histories on chondrite parent bodies can be deduced from thermochronologic analyses of materials and isotope systems with distinct apparent closure temperatures. It is especially critical to better understand the geological histories and physical properties of potenally hazardous near-Earth asteroids. Chelyabinsk is an LL5 chondrite meteorite that was dispersed over a wide area tens of kilometers south of the town of Chelyabinsk, Russia by an explosion at an altitude of 27 km at 3:22 UT on 15 Feb 2013 [1,2]. The explosion resulted in significant damage to surrounding areas and over 1500 injuries along with meteorite fragments being spread over a wide area [1].

  9. Quantification of Thiazolidine-4-carboxylic Acid in Toxicant-Exposed Cells by Isotope-Dilution Liquid Chromatography-Mass Spectrometry Reveals an Intrinsic Antagonistic Response to Oxidative Stress-Induced Toxicity.

    PubMed

    Liu, Jingjing; Chan, Wan

    2015-03-16

    Carcinogenic formaldehyde is produced by endogenous protein oxidation and various exogenous sources. With formaldehyde being both ubiquitous in the ambient environment and one of the most common reactive carbonyls produced from endogenous metabolism, quantifying formaldehyde exposure is an essential step in risk assessments. We present in this study an approach to assess the risk of exposure to oxidative stress by quantifying thiazolidine-4-carboxylic acid (TA), a cysteine-conjugated metabolite of formaldehyde in toxicant-exposed Escherichia coli. The method entails TA derivatization with ethyl chloroformate, addition of isotope-labeled TA derivatives as internal standards, solid-phase extraction of the derivatives, and quantification by liquid chromatography-mass spectrometry (LC-MS). After validating for accuracy and precision, the developed method was used to detect TA in oxidizing agent-exposed E. coli samples. Dose-dependent TA formation was observed in E. coli exposed to hydroxyl radical mediators Fe(2+)-EDTA, H2O2, and NaOCl, indicating the potential use of TA as a biomarker of exposure to oxidative stress and disease risk. PMID:25325739

  10. Automated headspace-solid-phase micro extraction-retention time locked-isotope dilution gas chromatography-mass spectrometry for the analysis of organotin compounds in water and sediment samples.

    PubMed

    Devosa, Christophe; Vliegen, Maarten; Willaert, Bart; David, Frank; Moens, Luc; Sandra, Pat

    2005-06-24

    An automated method for the simultaneous determination of six important organotin compounds namely monobutyltin (MBT), dibutyltin (DBT), tributyltin (TBT), monophenyltin (MPhT), diphenyltin (DPhT) and triphenyltin (TPhT) in water and sediment samples is described. The method is based on derivatization with sodium tetraethylborate followed by automated headspace-solid-phase micro extraction (SPME) combined with GC-MS under retention time locked (RTL) conditions. Home-synthesized deuterated organotin analogues were used as internal standards. Two high abundant fragment ions corresponding to the main tin isotopes Sn118 and Sn120 were chosen; one for quantification and one as qualifier ion. The method was validated and excellent figures of merit were obtained. Limits of quantification (LOQs) are from 1.3 to 15 ng l(-1) (ppt) for water samples and from 1.0 to 6.3 microg kg(-1) (ppb) for sediment samples. Accuracy for sediment samples was tested on spiked real-life sediment samples and on a reference PACS-2 marine harbor sediment. The developed method was used in a case-study at the harbor of Antwerp where sediment samples in different areas were taken and subsequently screened for TBT contamination. Concentrations ranged from 15 microg kg(-1) in the port of Antwerp up to 43 mg kg(-1) near a ship repair unit. PMID:16038329

  11. A field survey of metal binding to metallothionein and other cytosolic ligands in liver of eels using an on-line isotope dilution method in combination with size exclusion (SE) high pressure liquid chromatography (HPLC) coupled to Inductively Coupled Plasma time-of-flight Mass Spectrometry (ICP-TOFMS).

    PubMed

    Van Campenhout, Karen; Goenaga Infante, Heidi; Goemans, Geert; Belpaire, Claude; Adams, Freddy; Blust, Ronny; Bervoets, Lieven

    2008-05-15

    The effect of metal exposure on the accumulation and cytosolic speciation of metals in livers of wild populations of European eel with special emphasis on metallothioneins (MT) was studied. Four sampling sites in Flanders showing different degrees of heavy metal contamination were selected for this purpose. An on-line isotope dilution method in combination with size exclusion (SE) high pressure liquid chromatography (HPLC) coupled to Inductively Coupled Plasma time-of-flight Mass Spectrometry (ICP-TOFMS) was used to study the cytosolic speciation of the metals. The distribution of the metals Cd, Cu, Ni, Pb and Zn among cytosolic fractions displayed strong differences. The cytosolic concentration of Cd, Ni and Pb increased proportionally with the total liver levels. However, the cytosolic concentrations of Cu and Zn only increased above a certain liver tissue threshold level. Cd, Cu and Zn, but not Pb and Ni, were largely associated with the MT pool in correspondence with the environmental exposure and liver tissue concentrations. Most of the Pb and Ni and a considerable fraction of Cu and Zn, but not Cd, were associated to High Molecular Weight (HMW) fractions. The relative importance of the Cu and Zn in the HMW fraction decreased with increasing contamination levels while the MT pool became progressively more important. The close relationship between the cytosolic metal load and the total MT levels or the metals bound on the MT pool indicates that the metals, rather than other stress factors, are the major factor determining MT induction. PMID:18302969

  12. Bicosomes: Bicelles in Dilute Systems

    Microsoft Academic Search

    Gelen Rodríguez; Guadalupe Soria; Elisenda Coll; Laia Rubio; Lucyanna Barbosa-Barros; Carmen López-Iglesias; Anna M. Planas; Joan Estelrich; Alfons de la Maza; Olga López

    2010-01-01

    Bicelles are discoidal phospholipid nanostructures at high lipid concentrations. Under dilute conditions, bicelles become larger and adopt a variety of morphologies. This work proposes a strategy to preserve the discoidal morphology of bicelles in environments with high water content. Bicelles were formed in concentrated conditions and subsequently encapsulated in liposomes. Later dilution of these new structures, called bicosomes, demonstrated that

  13. Improved 206Pb\\/ 238U microprobe geochronology by the monitoring of a trace-element-related matrix effect; SHRIMP, ID–TIMS, ELA–ICP–MS and oxygen isotope documentation for a series of zircon standards

    Microsoft Academic Search

    Lance P. Black; Sandra L. Kamo; Charlotte M. Allen; Donald W. Davis; John N. Aleinikoff; John W. Valley; Roland Mundil; Ian H. Campbell; Russell J. Korsch; Ian S. Williams; Chris Foudoulis

    2004-01-01

    Precise isotope dilution–thermal ionisation mass spectrometry (ID–TIMS) documentation is given for two new Palaeozoic zircon standards (TEMORA 2 and R33). These data, in combination with results for previously documented standards (AS3, SL13, QGNG and TEMORA 1), provide the basis for a detailed investigation of inconsistencies in 206Pb\\/238U ages measured by microprobe. Although these ages are normally consistent between any two

  14. Simultaneous determination of N7-alkylguanines in DNA by isotope-dilution LC-tandem MS coupled with automated solid-phase extraction and its application to a small fish model.

    PubMed

    Chao, Mu-Rong; Wang, Chien-Jen; Yen, Cheng-Chieh; Yang, Hsi-Hsien; Lu, Yao-Cheng; Chang, Louis W; Hu, Chiung-Wen

    2007-03-15

    In the present study, we report the development of a sensitive and selective assay based on LC (liquid chromatography)-MS/MS (tandem MS) to simultaneously measure N7-MeG (N7-methylguanine) and N7-EtG (N7-ethylguanine) in DNA hydrolysates. With the use of isotope internal standards (15N5-N7-MeG and 15N5-N7-EtG) and on-line SPE (solid-phase extraction), the detection limit of this method was estimated as 0.42 fmol and 0.17 fmol for N7-MeG and N7-EtG respectively. The high sensitivity achieved here makes this method applicable to small experimental animals. This method was applied to measure N7-alkylguanines in liver DNA from mosquito fish (Gambusia affinis) that were exposed to NDMA (N-nitrosodimethylamine) and NDEA (N-nitrosodiethylamine) alone or their combination over a wide range of concentrations (1-100 mg/l). Results showed that the background level of N7-MeG in liver of control fish was 7.89+/-1.38 mmol/mol of guanine, while N7-EtG was detectable in most of the control fish with a range of 0.05-0.19 mmol/mol of guanine. N7-MeG and N7-EtG were significantly induced by NDMA and NDEA respectively, at a concentration as low as 1 mg/l and increased in a dose-dependent manner. Taken together, this LC-MS/MS assay provides the sensitivity and high throughput required to evaluate the extent of alkylated DNA lesions in small animal models of cancer induced by alkylating agents. PMID:17134374

  15. Hydrogen isotope inventory in the graphite divertor tiles of ASDEX Upgrade as measured by thermal desorption spectroscopy

    Microsoft Academic Search

    P. Franzen; R. Behrisch; C. Garcia-Rosales; D. Schleussner; D. Rosler; J. Becker; W. Knapp; C. Edelmann

    1997-01-01

    The hydrogen and deuterium inventories of the ASDEX Upgrade divertor tiles were measured after the experimental period from December 1994 to July 1995 by thermal desorption spectroscopy (TDS) of samples cut out of the divertor tiles. The samples were heated by electron bombardment up to 2100 K; the released gases were measured by means of a calibrated quadrupole mass spectrometer.

  16. Stress in dilute suspensions

    NASA Technical Reports Server (NTRS)

    Passman, Stephen L.

    1989-01-01

    Generally, two types of theory are used to describe the field equations for suspensions. The so-called postulated equations are based on the kinetic theory of mixtures, which logically should give reasonable equations for solutions. The basis for the use of such theory for suspensions is tenuous, though it at least gives a logical path for mathematical arguments. It has the disadvantage that it leads to a system of equations which is underdetermined, in a sense that can be made precise. On the other hand, the so-called averaging theory starts with a determined system, but the very process of averaging renders the resulting system underdetermined. A third type of theory is proposed in which the kinetic theory of gases is used to motivate continuum equations for the suspended particles. This entails an interpretation of the stress in the particles that is different from the usual one. Classical theory is used to describe the motion of the suspending medium. The result is a determined system for a dilute suspension. Extension of the theory to more concentrated systems is discussed.

  17. 40 CFR 1065.240 - Dilution air and diluted exhaust flow meters.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 2014-07-01 false Dilution air and diluted exhaust flow meters...ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR POLLUTION CONTROLS ENGINE-TESTING PROCEDURES...Measurements § 1065.240 Dilution air and diluted exhaust flow...

  18. 40 CFR 1065.240 - Dilution air and diluted exhaust flow meters.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 2010-07-01 false Dilution air and diluted exhaust flow meters...ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR POLLUTION CONTROLS ENGINE-TESTING PROCEDURES...Measurements § 1065.240 Dilution air and diluted exhaust flow...

  19. 40 CFR 1065.240 - Dilution air and diluted exhaust flow meters.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 2013-07-01 false Dilution air and diluted exhaust flow meters...ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR POLLUTION CONTROLS ENGINE-TESTING PROCEDURES...Measurements § 1065.240 Dilution air and diluted exhaust flow...

  20. 40 CFR 1065.240 - Dilution air and diluted exhaust flow meters.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 2012-07-01 false Dilution air and diluted exhaust flow meters...ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR POLLUTION CONTROLS ENGINE-TESTING PROCEDURES...Measurements § 1065.240 Dilution air and diluted exhaust flow...

  1. 40 CFR 1065.240 - Dilution air and diluted exhaust flow meters.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 2011-07-01 false Dilution air and diluted exhaust flow meters...ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR POLLUTION CONTROLS ENGINE-TESTING PROCEDURES...Measurements § 1065.240 Dilution air and diluted exhaust flow...

  2. Ca isotope variations in Allende

    NASA Technical Reports Server (NTRS)

    Jungck, M. H. A.; Shimamura, T.; Lugmair, G. W.

    1984-01-01

    Ca-isotope measurements of Allende Ca-Al-rich inclusions (CAIs), together with those on an apatite-enriched fraction from Orgueil, indicate the existence of widespread excesses on the neutron-rich isotope Ca-48. Isotopic anomalies are noted in 7 out of 11 CAIs analyzed. This abundance of isotopic excesses places Ca alongside Ti and O, although no clear correlation has yet been found between Ca-48 and Ti-50, which are thought to be coproduced by neutron-rich nucleosynthetic processes within stars. It is suggested that the higher volatility of Ca, by comparison with Ti compounds, led to a variable dilution with isotopically normal Ca in vaporization and recondensation processes in stellar envelopes, the interstellar medium, and/or the solar nebula.

  3. Dilution refrigeration for space applications

    NASA Technical Reports Server (NTRS)

    Israelsson, U. E.; Petrac, D.

    1990-01-01

    Dilution refrigerators are presently used routinely in ground based applications where temperatures below 0.3 K are required. The operation of a conventional dilution refrigerator depends critically on the presence of gravity. To operate a dilution refrigerator in space many technical difficulties must be overcome. Some of the anticipated difficulties are identified in this paper and possible solutions are described. A single cycle refrigerator is described conceptually that uses forces other than gravity to function and the stringent constraints imposed on the design by requiring the refrigerator to function on the earth without using gravity are elaborated upon.

  4. Origins of large-volume, compositionally zoned volcanic eruptions: New constraints from U-series isotopes and numerical thermal modeling for the 1912 Katmai-Novarupta eruption

    USGS Publications Warehouse

    Turner, Simon; Sandiford, Mike; Reagan, Mark; Hawkesworth, Chris; Hildreth, Wes

    2010-01-01

    We present the results of a combined U-series isotope and numerical modeling study of the 1912 Katmai-Novarupta eruption in Alaska. A stratigraphically constrained set of samples have compositions that range from basalt through basaltic andesite, andesite, dacite, and rhyolite. The major and trace element range can be modeled by 80–90% closed-system crystal fractionation over a temperature interval from 1279°C to 719°C at 100 MPa, with an implied volume of parental basalt of ?65 km3. Numerical models suggest, for wall rock temperatures appropriate to this depth, that 90% of this volume of magma would cool and crystallize over this temperature interval within a few tens of kiloyears. However, the range in 87Sr/86Sr, (230Th/238U), and (226Ra/230Th) requires open-system processes. Assimilation of the host sediments can replicate the range of Sr isotopes. The variation of (226Ra/230Th) ratios in the basalt to andesite compositional range requires that these were generated less than several thousand years before eruption. Residence times for dacites are close to 8000 years, whereas the rhyolites appear to be 50–200 kyr old. Thus, the magmas that erupted within only 60 h had a wide range of crustal residence times. Nevertheless, they were emplaced in the same thermal regime and evolved along similar liquid lines of descent from parental magmas with similar compositions. The system was built progressively with multiple inputs providing both mass and heat, some of which led to thawing of older silicic material that provided much of the rhyolite.

  5. DYNAMIC STRESSES IN THE LHC TCDS DILUTER FROM 7 TEV BEAM LOADING

    Microsoft Academic Search

    B. Goddard; A. Presland; W. Weterings; L. Massidda

    2006-01-01

    In the event of an unsynchronised beam abort, the MSD extraction septum of the LHC beam dumping system is protected from damage by the TCDS diluter. The simultaneous constraints of obtaining sufficient beam dilution while ensuring the survival of the TCDS make the design difficult, with high thermally induced dynamic stresses occurring in the material needed to attenuate the particle

  6. Physics with isotopically controlled semiconductors

    SciTech Connect

    Haller, E.E.

    1994-08-01

    Control of the isotopic composition of semiconductors offers a wide range of new scientific opportunities. In this paper a number of recent results obtained with isotopically pure as well as deliberately mixed diamond and Ge bulk single crystals and Ge isotope superlattices will be reviewed. Isotopic composition affects several properties such as phonon energies, bandstructure and lattice constant in subtle but theoretically well understood ways. Large effects are observed for thermal conductivity, local vibrational modes of impurities and after neutron transmutation doping (NTD). Several experiments which could profit greatly from isotope control are proposed.

  7. Sea Urchin Embryology: Sperm Dilution

    NSDL National Science Digital Library

    PhD David Epel (Stanford U. Hopkins Marine Station)

    2007-04-20

    Lab directions for up to two 50 min periods and the last of the dilution labs. Includes set up information, materials, procedure, experimental design, things to observe, math possibilities, thought-provoking questions and an assessment.

  8. Sea Urchin Embryology: Simple Dilutions

    NSDL National Science Digital Library

    PhD David Epel (Stanford U. Hopkins Marine Station)

    2006-12-20

    Starting from a known concentration students learn to use dilutions to determine the concentration of an unknown. The following skills are used in this lesson: 1. making dilutions 2. reading the meter on a simple homemade spectrophotometer 3. keeping careful laboratory records 4. graphing on linear graph paper 5. determining an unknown concentration from known 6. using a colored filter to enhance contrast and sensitivity

  9. Evidence of magnetic isotope effects during thermochemical sulfate reduction

    E-print Network

    Oduro, Harry D.

    Thermochemical sulfate reduction experiments with simple amino acid and dilute concentrations of sulfate reveal significant degrees of mass-independent sulfur isotope fractionation. Enrichments of up to 13‰ for [superscript ...

  10. Effects of self-heating and phase change on the thermal profile of hydrogen isotopes in confined geometries

    SciTech Connect

    Baxamusa, S., E-mail: baxamusa1@llnl.gov; Field, J.; Dylla-Spears, R.; Kozioziemski, B.; Suratwala, T.; Sater, J. [Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, California 94550 (United States)

    2014-03-28

    Growth of high-quality single-crystal hydrogen in confined geometries relies on the in situ formation of seed crystals. Generation of deuterium-tritium seed crystals in a confined geometry is governed by three effects: self-heating due to tritium decay, external thermal environment, and latent heat of phase change at the boundary between hydrogen liquid and vapor. A detailed computation of the temperature profile for liquid hydrogen inside a hollow shell, as is found in inertial confinement fusion research, shows that seeds are likely to form at the equatorial plane of the shell. Radioactive decay of tritium to helium slowly alters the composition of the hydrogen vapor, resulting in a modified temperature profile that encourages seed formation at the top of the shell. We show that the computed temperature profile is consistent with a variety of experimental observations.

  11. Reliability in estimates of body composition of birds: oxygen-18 versus deuterium dilution.

    PubMed

    Mata, Astolfo J; Caloin, Michel; Robin, Jean-Patrice; Le Maho, Yvon

    2006-01-01

    Body composition in birds was evaluated indirectly by 18O and 2H dilution. Body composition was determined by whole-body chemical analysis of eight adult roosters (Gallus gallus). In vivo measurements of total body water (TBW) were carried out using doubly labeled water (2H2 18O). Estimated dilution spaces using both the plateau and intercept approaches were compared with the results obtained by carcass lyophilization. Both 18O and 2H slightly overestimated TBW compared with the results obtained by lyophilization, by 2.2%+/-1.9% and 5.7%+/-0.2%, respectively; both differences were statistically significant (P<0.01). The difference between these isotope estimations was significant (P<0.001). However, isotope dilution spaces and TBW were highly correlated. There was a strong inverse relationship between total body fat and TBW percentages (r2=0.98, P<0.0001). The relation between TBW and body protein was significant. Water content in lean body mass (72.8%) obtained in our study was very close to that reported in mammals, demonstrating no fundamental difference in tissue water content between birds and mammals. Estimated body fat and protein values from isotopic dilution did not significantly differ from values obtained by direct chemical analysis (P>0.05), except for body fat in the Pace and Rathbun approach (Table 3). Although estimation of TBW and body composition by isotope dilution is time consuming and expensive, deuterium offers a reliable and low-cost alternative compared with 18O. The advantage of in vivo estimation of TBW with isotopic dilution in combination with the regression approach is that it permits repeated measurements of body composition on the same birds under laboratory and free-living conditions. PMID:16380942

  12. 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.

  13. Chromatographic hydrogen isotope separation

    DOEpatents

    Aldridge, Frederick T. (Livermore, CA)

    1981-01-01

    Intermetallic compounds with the CaCu.sub.5 type of crystal structure, particularly LaNiCo.sub.4 and CaNi.sub.5, exhibit high separation factors and fast equilibrium times and therefore are useful for packing a chromatographic hydrogen isotope separation colum. The addition of an inert metal to dilute the hydride improves performance of the column. A large scale mutli-stage chromatographic separation process run as a secondary process off a hydrogen feedstream from an industrial plant which uses large volumes of hydrogen can produce large quantities of heavy water at an effective cost for use in heavy water reactors.

  14. Isotopic dilution and solvent effect studies using raman difference spectroscopy

    E-print Network

    Johnson, Andrew Norman

    1984-01-01

    =C bond stretching vibrations in isobutylene and C=O stretches in acetone. Introductor Theor The line shape caused by liquid induced frequency changes is given by the Fourier transform of t Q(o)Q(t) = Re exp(tw t) exp[i dt'n(t')] (39) 0 where w... involving the 2 atoms defining the bond. 30 Previous A lications Schweizer and Chandler applied their model to the C-C and C=C symmetric stretches of isobutylene and C=O stretch in acetone. Both 11, 12 of these molecules had previously been studied...

  15. Quantification of neptunium by isotope dilution mass spectrometry

    SciTech Connect

    Efurd, D.W.; Drake, J.; Roensch, F.R.; Cappis, J.H.; Perrin, R.E.

    1986-05-01

    A surface ionization-diffusion-type ionization source that uses a rhenium filament overplated with platinum has been developed and optimized for 0.1-ng neptunium samples. This source is capable of measuring the neptunium content of nuclear-test-debris samples to 0.15% precision at the 95% confidence level. 14 refs., 3 figs., 3 tabs.

  16. Quantification of americium by isotope dilution mass spectrometry

    SciTech Connect

    Efurd, D.W.; Drake, J.; Roensch, F.R.; Miller, G.G.; Cappis, J.H.; Perrin, R.E.

    1987-08-01

    A surface ionization-diffusion-type ionization source that uses a rhenium filament overplated with platinum has been developed and optimized for 0.01-ng americium samples. This source is capable of measuring the americium content of nuclear-test-debris samples to 0.20% precision at the 95% confidence level.

  17. Strontium isotope composition of Rotorua geothermal waters

    SciTech Connect

    Graham, I.J. (DSIR Physical Sciences, Nuclear Sciences Group, P.O. Box 31-312, Lower Hutt (NZ))

    1992-04-01

    This paper reports that strontium isotope compositions of Rotorua geothermal waters, taken in conjunction with chemical and stable isotope data, are broadly consistent with existing hydrogeologic models, and provide new insights into complex water-rock interactions and fluid-fluid mixing processes. Primary alkali chloride water upwelling in the eastern part of the field have {sup 87}Sr/{sup 86}Sr ratios higher than their presumed aquifer wall rocks, implying a component of more radiogenic strontium from metasedimentary basement. Secondary waters, in contrast, have relatively low {sup 87}Sr/{sup 86}Sr ratios consistent with interaction of primary fluids (variably diluted by deep groundwaters) with rhyolite country rock, followed by shallow dilution by young groundwater. Although complicated by the non-conservative behavior of strontium, the strontium isotope data require significant water-rock interaction in the central and western parts of the Rotorua geothermal field, a feature not made obvious by other chemical or isotope studies.

  18. Chemical and isotopic compositions of thermal springs, fumaroles and bubbling gases at Tacaná Volcano (Mexico-Guatemala): implications for volcanic surveillance

    NASA Astrophysics Data System (ADS)

    Rouwet, Dmitri; Inguaggiato, Salvatore; Taran, Yuri; Varley, Nicholas; Santiago S., José A.

    2009-04-01

    This study presents baseline data for future geochemical monitoring of the active Tacaná volcano-hydrothermal system (Mexico-Guatemala). Seven groups of thermal springs, related to a NW/SE-oriented fault scarp cutting the summit area (4,100m a.s.l.), discharge at the northwest foot of the volcano (1,500-2,000m a.s.l.); another one on the southern ends of Tacaná (La Calera). The near-neutral (pH from 5.8 to 6.9) thermal ( T from 25.7°C to 63.0°C) HCO3-SO4 waters are thought to have formed by the absorption of a H2S/SO2-CO2-enriched steam into a Cl-rich geothermal aquifer, afterwards mixed by Na/HCO3-enriched meteoric waters originating from the higher elevations of the volcano as stated by the isotopic composition (?D and ?18O) of meteoric and spring waters. Boiling temperature fumaroles (89°C at ~3,600m a.s.l. NW of the summit), formed after the May 1986 phreatic explosion, emit isotopically light vapour (?D and ?18O as low as -128 and -19.9‰, respectively) resulting from steam separation from the summit aquifer. Fumarolic as well as bubbling gases at five springs are CO2-dominated. The ?13CCO2 for all gases show typical magmatic values of -3.6 ± 1.3‰ vs V-PDB. The large range in 3He/4He ratios for bubbling, dissolved and fumarolic gases [from 1.3 to 6.9 atmospheric 3He/4He ratio ( R A)] is ascribed to a different degree of near-surface boiling processes inside a heterogeneous aquifer at the contact between the volcanic edifice and the crystalline basement (4He source). Tacaná volcano offers a unique opportunity to give insight into shallow hydrothermal and deep magmatic processes affecting the CO2/3He ratio of gases: bubbling springs with lower gas/water ratios show higher 3He/4He ratios and consequently lower CO2/3He ratios (e.g. Zarco spring). Typical Central American CO2/3He and 3He/4He ratios are found for the fumarolic Agua Caliente and Zarco gases (3.1 ± 1.6 × 1010 and 6.0 ± 0.9 R A, respectively). The L/ S (5.9 ± 0.5) and ( L + S)/ M ratios (9.2 ± 0.7) for the same gases are almost identical to the ones calculated for gases in El Salvador, suggesting an enhanced slab contribution as far as the northern extreme of the Central American Volcanic Arc, Tacaná.

  19. Isotopically controlled semiconductors

    SciTech Connect

    Haller, E.E.

    2004-11-15

    A review of recent research involving isotopically controlled semiconductors is presented. Studies with isotopically enriched semiconductor structures experienced a dramatic expansion at the end of the Cold War when significant quantities of enriched isotopes of elements forming semiconductors became available for worldwide collaborations. Isotopes of an element differ in nuclear mass, may have different nuclear spins and undergo different nuclear reactions. Among the latter, the capture of thermal neutrons which can lead to neutron transmutation doping, can be considered the most important one for semiconductors. Experimental and theoretical research exploiting the differences in all the properties has been conducted and will be illustrated with selected examples. Manuel Cardona, the longtime editor-in-chief of Solid State Communications has been and continues to be one of the major contributors to this field of solid state physics and it is a great pleasure to dedicate this review to him.

  20. Measuring oxygen yields of a thermal conversion/elemental analyzer-isotope ratio mass spectrometer for organic and inorganic materials through injection of CO.

    PubMed

    Yin, Xijie; Chen, Zhigang

    2014-12-01

    The thermal conversion/elemental analyzer-isotope ratio mass spectrometer (TC/EA-IRMS) is widely used to measure the ?(18) O value of various substances. A premise for accurate ?(18) O measurement is that the oxygen in the sample can be converted into carbon monoxide (CO) quantitatively or at least proportionally. Therefore, a precise method to determine the oxygen yield of TC/EA-IRMS measurements is needed. Most studies have used the CO peak area obtained from a known amount of a solid reference material (for example, benzoic acid) to calibrate the oxygen yield of the sample. Although it was assumed that the oxygen yield of the solid reference material is 100%, no direct evidence has been provided. As CO is the analyte gas for ?(18) O measurement by IRMS, in this study, we use a six-port valve to inject CO gas into the TC/EA. The CO is carried to the IRMS by the He carrier gas and the CO peak area is measured by the IRMS. The CO peak area thus obtained from a known amount of the injected CO is used to calibrate the oxygen yield of the sample. The oxygen yields of commonly used organic and inorganic reference materials such as benzoic acid (C6 H5 COOH), silver phosphate (Ag3 PO4 ), calcium carbonate (CaCO3 ) and silicon dioxide (SiO2 ) are investigated at different reactor temperatures and sample sizes. We obtained excellent linear correlation between the peak area for the injected CO and its oxygen atom amount. C6 H5 COOH has the highest oxygen yield, followed by Ag3 PO4 , CaCO3 and SiO2 . The oxygen yields of TC/EA-IRMS are less than 100% for both organic and inorganic substances, but the yields are relatively stable at the specified reactor temperature and for a given quantity of sample. PMID:25476948

  1. Chemical, isotopic, and dissolved gas compositions of the hot springs of the Owyhee Uplands, Malheur County, Oregon

    USGS Publications Warehouse

    Mariner, R.H.; Young, H.W.; Evans, William C.

    1994-01-01

    Hot springs along the Owyhee River in southeastern Oregon between Three Forks and Lake Owyhee could be part of a north flowing regional system or a series of small separate geothermal systems Heat for the waters could be from a very young (Holocene) volcanic activity (basalt flows) of the Owyhee Uplands or the regional heat flow. The springs discharge warm to hot, dilute, slightly alkaline, sodium bicarbonate water. Chemically they are similar to the dilute thermal water at Bruneau Grand View and Twin Falls, Idaho. Maximum aquifer temperatures in the Owyhee Uplands, estimated from chemical geothermometry, are about 100°C. Dissolved helium concentrations, carbon 14 activity, and chemical and isotope data are examined fro systematic trends which would indicate a geothermal system of regional extent.

  2. Dilution and the elusive baseline.

    PubMed

    Likens, Gene E; Buso, Donald C

    2012-04-17

    Knowledge of baseline conditions is critical for evaluating quantitatively the effect of human activities on environmental conditions, such as the impact of acid deposition. Efforts to restore ecosystems to prior, "pristine" condition require restoration targets, often based on some presumed or unknown baseline condition. Here, we show that rapid and relentless dilution of surface water chemistry is occurring in the White Mountains of New Hampshire, following decades of acid deposition. Extrapolating measured linear trends using a unique data set of up to 47 years, suggest that both precipitation and streamwater chemistry (r(2) >0.84 since 1985) in the Hubbard Brook Experimental Forest (HBEF) will approximate demineralized water within one to three decades. Because such dilute chemistry is unrealistic for surface waters, theoretical baseline compositions have been calculated for precipitation and streamwater: electrical conductivity of 3 and 5 ?S/cm, base cation concentrations of 7 and 39 ?eq/liter, acid-neutralizing capacity values of <1 and 14 ?eq/liter, respectively; and pH 5.5 for both. Significantly large and rapid dilution of surface waters to values even more dilute than proposed for Pre-Industrial Revolution (PIR) conditions has important ecological, biogeochemical and water resource management implications, such as for the success of early reproductive stages of aquatic organisms. PMID:22455659

  3. Isotopic distributions.

    PubMed

    Rockwood, Alan L; Palmblad, Magnus

    2013-01-01

    Isotopic information determined by mass spectrometry can be used in a wide variety of applications. Broadly speaking these could be classified as "passive" applications, meaning that they use naturally occurring isotopic information, and "active" applications, meaning that the isotopic distributions are manipulated in some way. The classic passive application is the determination of chemical composition by comparing observed isotopic patterns of molecules to theoretically calculated isotopic patterns. Active applications include isotope exchange experiments of a variety of types, as well as isotope labeling in tracing studies and to provide references for quantitation. Regardless of the type of application considered, the problem of theoretical calculation of isotopic patterns almost invariably arises. This paper reviews a number of application examples and computational approaches for isotopic studies in mass spectrometry. PMID:23666722

  4. Investigations on the effect of O(6)-benzylguanine on the formation of dG-dC interstrand cross-links induced by chloroethylnitrosoureas in human glioma cells using stable isotope dilution high-performance liquid chromatography electrospray ionization tandem mass spectrometry.

    PubMed

    Sun, Guohui; Zhao, Lijiao; Fan, Tengjiao; Li, Sisi; Zhong, Rugang

    2014-07-21

    Chloroethylnitrosoureas (CENUs) are bifunctional alkylating agents widely used for the clinical treatment of cancer. They exert anticancer activity by inducing DNA interstrand cross-links (ICLs) within GC base pairs to form dG-dC cross-links. This lesion inhibits DNA double strand separation during replication and transcription and results in the apoptosis of cancer cells. However, O(6)-alkylguanine DNA alkyltransferase (AGT) repairs the DNA ICLs by removing the alkyl group at the O(6) position of either O(6)-(2-chloroethyl)deoxyguanosine (O(6)-ClEtdGuo) or N1,O(6)-ethanodeoxyguanosine (N1,O(6)-EtdGuo), which are intermediates in the formation of dG-dC cross-links. The action of AGT leads to drug resistance against CENUs. O(6)-Benzylguanine (O(6)-BG) was identified as an effective AGT inhibitor that enhances the antitumor effects of CENUs. In this study, the effect of O(6)-BG on the formation of dG-dC cross-links was investigated by treating human brain glioma SF767 cells with 1-[(4-amino-2-methyl-5-pyrimidinyl)methyl]-3-(2-chloroethyl)-3-nitrosourea (ACNU). The levels of dG-dC cross-link were determined using stable isotope dilution high-performance liquid chromatography electrospray ionization tandem mass spectrometry (HPLC-ESI-MS/MS). The results indicated that ACNU induced higher levels of dG-dC cross-link in SF767 cells pretreated with O(6)-BG compared to cells without O(6)-BG pretreatment. The highest dG-dC cross-linking levels were generally observed at 12 h for all drug concentration groups, a result which was consistent with cytotoxicity assay. These results provided direct evidence for the enhancement of dG-dC cross-linking levels caused by the inhibition of AGT by O(6)-BG. These data indicate that dG-dC cross-links may be developed as a biomarker for evaluating the activity of novel O(6)-BG analogues as AGT inhibitors for combination therapy with CENUs. PMID:24914620

  5. QUANTITATIVE ASSESSMENT OF TOTAL-BODY STORES OF VITAMIN A IN ADULTS BY A THREE-DAY DEUTERATED-RETINOL-DILUTION (3D-DRD) PROCEDURE

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The isotope-dilution technique is useful for assessing vitamin A status. Up to now, the conventional deuterated-retinol-dilution (DRD) procedure is the only measure that provides a quantitative estimate of the total-body stores of vitamin A; the procedure has been validated twice in two independent...

  6. Measurement of Sulfur Isotopic Composition (?34S) by Multiple-Collector Thermal Ionization Mass Spectrometry (MC-TIMS) Using a 33S/36S Double Spike

    NASA Astrophysics Data System (ADS)

    Mann, J. L.; Kelly, W. R.

    2006-05-01

    A new analytical technique for the determination of ?34S will be described. The technique is based on the production of singularly charged arsenic sulfide molecular ions (AsS+) by thermal ionization using silica gel as an emitter and combines multiple-collector thermal ionization mass spectrometry (MC-TIMS) with a 33S/36S double spike to correct instrumental fractionation. Because the double spike is added to the sample before chemical processing, both the isotopic composition and sulfur concentration are measured simultaneously. The accuracy and precision of the double spike technique is comparable to or better than modern gas source mass spectrometry, but requires about a factor of 10 less sample. ?33S effects can be determined directly in an unspiked sample without any assumptions about the value of k (mass dependent fractionation factor) which is currently required by gas source mass spectrometry. Three international sulfur standards (IAEA-S-1, IAEA-S-2, and IAEA-S-3) were measured to evaluate the precision and accuracy of the new technique and to evaluate the consensus values for these standards. Two different double spike preparations were used. The ?34S values (reported relative to Vienna Canyon Diablo Troilite (VCDT), (?34S (‰) = 34S/32S)sample/(34S/32S)VCDT - 1) x 1000]), 34S/32SVCDT = 0.0441626) determined were -0.32‰ ± 0.04‰ (1?, n=4) and -0.31‰ ± 0.13‰ (1?, n=8) for IAEA-S-1, 22.65‰ ± 0.04‰ (1?, n=7) and 22.60‰ ± 0.06‰ (1?, n=5) for IAEA- S-2, and -32.47‰ ± 0.07‰ (1?, n=8) for IAEA-S-3. The amount of natural sample used for these analyses ranged from 0.40 ?moles to 2.35 ?moles. Each standard showed less than 0.5‰ variability (IAEA-S-1 < 0.4‰, IAEA-S-2 < 0.2‰, and IAEA-S-3 < 0.2‰). Our values for S-1 and S-2 are in excellent agreement with the consensus values and the values reported by other laboratories using both SF6 and SO2. Our value for S-3 differs statistically from the Institute for Reference Materials and Measurement (IRMM) value and is slightly lower than the currently accepted consensus value (-32.3). Because the technique is based on thermal ionization of AsS+, and As is mononuclidic, corrections for interferences or for scale contraction/expansion are not required. The availability of MC-TIMS instruments in laboratories around the world makes this technique immediately available to a much larger scientific community who require highly accurate and precise measurements of sulfur.

  7. Sea Urchin Embryology: Simple Dilutions 2

    NSDL National Science Digital Library

    PhD David Epel (Stanford U. Hopkins Marine Station)

    2006-12-20

    SUMMARY: Building on what was learned in SIMPLE DILUTION, students will determine the best dilution strategy to solve a dilution problem. 1. Students are given an unknown dye solution and asked to determine its concentration by comparing it with standards they create. 2. Repeated "serial" dilutions will be necessary to determine accurate concentration readings. 3. Varying the color of the filters and the path length will aid in seeing lower concentrations.

  8. Botulinum toxin: dosing and dilution.

    PubMed

    Francisco, Gerard E

    2004-10-01

    In the United States, the popularity of botulinum toxins as agents to treat muscle hypertonia has grown significantly over the last decade, despite lack of approval from the Food and Drug Administration for the indication of spasticity. Botox (botulinum toxin type A) and Myobloc (botulinum toxin type B) are Food and Drug Administration-approved for other indications, such as cervical dystonia. Another commercial preparation of type A, Dysport, has yet to reach the United States market as of this writing. Although botulinum toxin's efficacy in influencing spastic hypertonia is well accepted, the impact of certain clinical issues, such as dosing and dilution, on treatment outcome is not well established by published studies. This article will review important articles and selected abstracts on the use of botulinum toxin, specifically for spastic hypertonia in adults, with emphasis on current clinical practices as they relate to dosing and dilution. PMID:15448575

  9. BASIC RESEARCH ON HIGH DILUTION EFFECTS

    Microsoft Academic Search

    MADELEINE BASTIDE

    Basic research on high dilution effects started with homeopathic therapy. So many models have been tested that we have tried to classify them according to the general concept of regulation. Firstly, succussed dilutions must be separated from unsuccussed very low doses from a physical point of view. This leads us to discuss the validity of the controls in high dilution

  10. Science Notes: Dilution of a Weak Acid

    ERIC Educational Resources Information Center

    Talbot, Christopher; Wai, Chooi Khee

    2014-01-01

    This "Science note" arose out of practical work involving the dilution of ethanoic acid, the measurement of the pH of the diluted solutions and calculation of the acid dissociation constant, K[subscript a], for each diluted solution. The students expected the calculated values of K[subscript a] to be constant but they found that the…

  11. Cryogen-free dilution refrigerators

    NASA Astrophysics Data System (ADS)

    Uhlig, K.

    2012-12-01

    We review briefly our first cryogen-free dilution refrigerator (CF-DR) which was precooled by a GM cryocooler. We then show how today's dry DRs with pulse tube precooling have developed. A few examples of commercial DRs are explained and noteworthy features pointed out. Thereby we describe the general advantages of cryogen-free DRs, but also show where improvements are still desirable. At present, our dry DR has a base temperature of 10 mK and a cooling capacity of 700 ?W at a mixing chamber temperature of 100 mK. In our cryostat, in most recent work, an additional refrigeration loop was added to the dilution circuit. This 4He circuit has a lowest temperature of about 1 K and a refrigeration capacity of up to 100 mW at temperatures slightly above 1 K; the dilution circuit and the 4He circuit can be run separately or together. The purpose of this additional loop is to increase the cooling capacity for experiments where the cooling power of the still of the DR is not sufficient to cool cold amplifiers and cables, e.g. in studies on superconducting quantum circuits or astrophysical applications.

  12. Dispersion of Sound in Dilute Suspensions with Nonlinear Particle Relaxation

    NASA Technical Reports Server (NTRS)

    Kandula, Max

    2010-01-01

    The theory accounting for nonlinear particle relaxation (viscous and thermal) has been applied to the prediction of dispersion of sound in dilute suspensions. The results suggest that significant deviations exist for sound dispersion between the linear and nonlinear theories at large values of Omega(Tau)(sub d), where Omega is the circular frequency, and Tau(sub d) is the Stokesian particle relaxation time. It is revealed that the nonlinear effect on the dispersion coefficient due to viscous contribution is larger relative to that of thermal conduction

  13. Geothermal investigation in Idaho. Part 14. Geochemical and isotopic investigations of thermal water occurrences of the Boise Front Area, Ada County, Idaho

    SciTech Connect

    Mayo, A.L.; Muller, A.B.; Mitchell, J.C.

    1984-12-01

    A limited chemical and isotopic investigation was undertaken and geological, geophysical, and hydrological data in the literature were reviewed to evaluate the geothermal potential of the Boise area. 68 refs., 12 figs., 4 tabs. (ACR)

  14. Total body water and lean body mass estimated by ethanol dilution

    NASA Technical Reports Server (NTRS)

    Loeppky, J. A.; Myhre, L. G.; Venters, M. D.; Luft, U. C.

    1977-01-01

    A method for estimating total body water (TBW) using breath analyses of blood ethanol content is described. Regression analysis of ethanol concentration curves permits determination of a theoretical concentration that would have existed if complete equilibration had taken place immediately upon ingestion of the ethanol; the water fraction of normal blood may then be used to calculate TBW. The ethanol dilution method is applied to 35 subjects, and comparison with a tritium dilution method of determining TBW indicates that the correlation between the two procedures is highly significant. Lean body mass and fat fraction were determined by hydrostatic weighing, and these data also prove compatible with results obtained from the ethanol dilution method. In contrast to the radioactive tritium dilution method, the ethanol dilution method can be repeated daily with its applicability ranging from diseased individuals to individuals subjected to thermal stress, strenuous exercise, water immersion, or the weightless conditions of space flights.

  15. Certification of a 41Ca dose material for use in human studies (IRMM-3703) and a corresponding set of isotope reference materials for 41Ca measurements (IRMM-3701)

    NASA Astrophysics Data System (ADS)

    Hennessy, Carmel; Berglund, Michael; Ostermann, Markus; Walczyk, Thomas; Synal, Hans-Arno; Geppert, Christopher; Wendt, Klaus; Taylor, Philip D. P.

    2005-03-01

    The long-living radioisotope 41Ca could overcome current limitations in assessing the impact of interventions on bone health in controlled human studies. Changes in bone Ca metabolism can be identified directly via the induced changes in 41Ca excretion from 41Ca-labelled bones via the n( 41Ca)/ n( 40Ca) ratio in urine. A 41Ca dose material (IRMM-3703), for use in human studies, was produced by IRMM within the EC funded project OSTEODIET. The 41Ca base material was purified and the purified solution is certified for both isotopic composition and amount content by isotope dilution mass spectrometry. The 44Ca-enriched isotope reference material, IM-6009, was used as spike and the natural Ca reference material, IM-6008, was used for correction of procedural bias. Isotope ratio measurements were performed using thermal ionisation mass spectrometry (TIMS). The certified n( 41Ca)/ n( 40Ca) ratio in IRMM-3703 is 0.012789 (58). A set of synthetic isotope mixtures, IRMM-3701, was prepared from IRMM-3703. It enables comparability of 41Ca measurement results in different laboratories and by different techniques. The IRMM-3701 series is derived from gravimetric mixing of IRMM-3703 and a Ca solution of natural isotopic composition. It covers n( 41Ca)/ n( 40Ca) ratios in the range of 1.0114(68) × 10 -6 to 1.0524(71) × 10 -13.

  16. Dilute Acid and Autohydrolysis Pretreatment

    NASA Astrophysics Data System (ADS)

    Yang, Bin; Wyman, Charles E.

    Exposure of cellulosic biomass to temperatures of about 120-210°C can remove most of the hemicellulose and produce cellulose-rich solids from which high glucose yields are possible with cellulase enzymes. Furthermore, the use of dilute sulfuric acid in this pretreatment operation can increase recovery of hemicellulose sugars substantially to about 85-95% of the maximum possible versus only about 65% if no acid is employed. The use of small-diameter tubes makes it possible to employ high solids concentrations similar to those preferred for commercial operations, with rapid heat-up, good temperature control, and accurate closure of material balances. Mixed reactors can be employed to pretreat larger amounts of biomass than possible in such small-diameter tubes, but solids concentrations are limited to about 15% or less to provide uniform temperatures. Pretreatment of large amounts of biomass at high solids concentrations is best carried out using direct steam injection and rapid pressure release, but closure of material balances in such “steam gun” devices is more difficult. Although flow of water alone or containing dilute acid is not practical commercially, such flow-through configurations provide valuable insight into biomass deconstruction kinetics not possible in the batch tubes, mixed reactors, or steam gun systems.

  17. A Microgravity Helium Dilution Cooler

    NASA Technical Reports Server (NTRS)

    Roach, Pat R.; Sperans, Joel (Technical Monitor)

    1994-01-01

    We are developing a He-3-He-4 dilution cooler to operate in microgravity. It uses charcoal adsorption pumps and heaters for its operation; it has no moving parts. It currently operates cyclically to well below 0.1 K and we have designed a version to operate continuously. We expect that the continuous version will be able to provide the long-duration cooling that many experiments need at temperatures down to 0.040 K. More importantly, such a dilution cooler could provide the precooling that enables the use of adiabatic demagnetization techniques that can reach temperatures below 0.001 K. At temperatures below 0.002 K many fascinating microgravity experiments on superfluid He-3 become possible. Among the possibilities are: research into a superfluid He-3 gyroscope, study of the nucleation of the B-phase of superfluid He-3 when the sample is floating out of contact with walls, study of the anisotropy of the surface tension of the B-phase, and NMR experiments on tiny free-floating clusters of superfluid He-3 atoms that should model the shell structure of nuclei.

  18. Studies on the isotopic analysis of boron by thermal ionisation mass spectrometry using NaCl for the formation of Na2BO2+ species

    NASA Astrophysics Data System (ADS)

    Rao, R. M.; Parab, A. R.; Sasibhushan, K.; Aggarwal, S. K.

    2008-06-01

    Studies were carried out on the use of NaCl instead of sodium carbonate or sodium hydroxide for the formation of Na2BO2+ ion used for the determination of isotopic composition of boron by TIMS. The addition of mannitol which forms an anionic complex with boron was found to be essential when using NaCl. The investigations show that when NaCl is used, B/Na molar concentration ratio need not be critically adjusted to 1 as required in case of sodium carbonate or sodium hydroxide. The 10B/11B ratio was found to be independent of B/Na molar concentration ratio in the range of 25-0.05. This aspect is extremely useful in carrying out isotopic analysis of B in unknown samples solutions. NIST boron isotopic standard SRM-951 having 10B/11B isotopic ratio of 0.2473 ± 0.0002 was used in these studies and a value of 0.24742 ± 0.00006 (1[sigma]) was obtained.

  19. DILUTE SURFACTANT METHODS FOR CARBONATE FORMATIONS

    SciTech Connect

    Kishore K. Mohanty

    2005-07-01

    There are many carbonate reservoirs in US (and the world) with light oil and fracture pressure below its minimum miscibility pressure (or reservoir may be naturally fractured). Many carbonate reservoirs are naturally fractured. Waterflooding is effective in fractured reservoirs, if the formation is water-wet. Many fractured carbonate reservoirs, however, are mixed-wet and recoveries with conventional methods are low (less than 10%). Thermal and miscible tertiary recovery techniques are not effective in these reservoirs. Surfactant flooding (or huff-n-puff) is the only hope, yet it was developed for sandstone reservoirs in the past. The goal of this research is to evaluate dilute (hence relatively inexpensive) surfactant methods for carbonate formations and identify conditions under which they can be effective. Laboratory imbibition tests show that imbibition rate is not very sensitive to the surfactant concentration (in the range of 0.05-0.2 wt%) and small amounts of trapped gas saturation. It is however very sensitive to oil permeability and water-oil-ratio. Less than 0.5 M Na2CO3 is needed for in situ soap generation and low adsorption; NaCl can be added to reach the necessary total salinity. The simulation result matches the laboratory imbibition experimental data. Small fracture spacing and high permeability would be needed for high rate of recovery.

  20. Dilute Surfactant Methods for Carbonate Formations

    SciTech Connect

    Kishore K. Mohanty

    2005-10-01

    There are many carbonate reservoirs in US (and the world) with light oil and fracture pressure below its minimum miscibility pressure (or reservoir may be naturally fractured). Many carbonate reservoirs are naturally fractured. Waterflooding is effective in fractured reservoirs, if the formation is water-wet. Many fractured carbonate reservoirs, however, are mixed-wet and recoveries with conventional methods are low (less than 10%). Thermal and miscible tertiary recovery techniques are not effective in these reservoirs. Surfactant flooding (or huff-n-puff) is the best hope, yet it was developed for sandstone reservoirs in the past. The goal of this research is to evaluate dilute (hence relatively inexpensive) surfactant methods for carbonate formations and identify conditions under which they can be effective. Laboratory-scale surfactant brine imbibition experiments give high oil recovery (35-62% OOIP) for initially oil-wet cores through wettability alteration and IFT reduction. Core-scale simulation results match those of the experiments. Initial capillarity-driven imbibition gives way to a final gravity-driven process. As the matrix block height increases, surfactant alters wettability to a lesser degree, or permeability decreases, oil production rate decreases. The scale-up to field scale will be further studied in the next quarter.

  1. DILUTE SURFACTANT METHODS FOR CARBONATE FORMATIONS

    SciTech Connect

    Kishore K. Mohanty

    2004-10-01

    There are many carbonate reservoirs in US (and the world) with light oil and fracture pressure below its minimum miscibility pressure (or reservoir may be naturally fractured). Many carbonate reservoirs are naturally fractured. Waterflooding is effective in fractured reservoirs, if the formation is water-wet. Many fractured carbonate reservoirs, however, are mixed-wet and recoveries with conventional methods are low (less than 10%). Thermal and miscible tertiary recovery techniques are not effective in these reservoirs. Surfactant flooding (or huff-n-puff) is the only hope, yet it was developed for sandstone reservoirs in the past. The goal of this research is to evaluate dilute (hence relatively inexpensive) surfactant methods for carbonate formations and identify conditions under which they can be effective. Simulation studies indicate that both wettability alteration and gravity-driven flow play significant role in oil recovery from fractured carbonates. Anionic surfactants (Alfoterra 35, 38) recover about 55% of the oil in about 150 days by imbibition driven by wettability alteration and low tension in the core-scale. Anionic surfactant, Alfoterra-68, recovers about 40% of the oil by lower tension aided gravity-driven imbibition in the core-scale. Cationic surfactant, DTAB recovers about 35% of the oil. Plans for the next quarter include conducting simulation and imbibition studies.

  2. DILUTE SURFACTANT METHODS FOR CARBONATE FORMATIONS

    SciTech Connect

    Kishore K. Mohanty

    2005-01-01

    There are many carbonate reservoirs in US (and the world) with light oil and fracture pressure below its minimum miscibility pressure (or reservoir may be naturally fractured). Many carbonate reservoirs are naturally fractured. Waterflooding is effective in fractured reservoirs, if the formation is water-wet. Many fractured carbonate reservoirs, however, are mixed-wet and recoveries with conventional methods are low (less than 10%). Thermal and miscible tertiary recovery techniques are not effective in these reservoirs. Surfactant flooding (or huff-n-puff) is the only hope, yet it was developed for sandstone reservoirs in the past. The goal of this research is to evaluate dilute (hence relatively inexpensive) surfactant methods for carbonate formations and identify conditions under which they can be effective. Imbibition in an originally oil-wet 2D capillary is the fastest in the case of Alf-38 and slowest in the case of DTAB (among the surfactants studied). Force of adhesion studies and contact angle measurements show that greater wettability alteration is possible with these anionic surfactants than the cationic surfactant studied. The water imbibition rate does not increase monotonically with an increase in the surfactant concentration. A numerical model has been developed that fits the rate of imbibition. Plans for the next quarter include conducting simulation and imbibition studies.

  3. DILUTE SURFACTANT METHODS FOR CARBONATE FORMATIONS

    SciTech Connect

    Kishore K. Mohanty

    2004-01-01

    There are many carbonate reservoirs in US (and the world) with light oil and fracture pressure below its minimum miscibility pressure (or reservoir may be naturally fractured). Many carbonate reservoirs are naturally fractured. Waterflooding is effective in fractured reservoirs, if the formation is water-wet. Many fractured carbonate reservoirs, however, are mixed-wet and recoveries with conventional methods are low (less than 10%). Thermal and miscible tertiary recovery techniques are not effective in these reservoirs. Surfactant flooding (or huff-n-puff) is the only hope, yet it was developed for sandstone reservoirs in the past. The goal of this research is to evaluate dilute (hence relatively inexpensive) surfactant methods for carbonate formations and identify conditions under which they can be effective. Anionic surfactants (SS-6656, Alfoterra 35, 38, 63,65,68) have been identified which can change the wettability of the calcite surface to intermediate/water-wet condition as well or better than the cationic surfactant DTAB with a West Texas crude oil in the presence of Na{sub 2}CO{sub 3}. All the carbonate surfaces (Lithographic Limestone, Marble, Dolomite and Calcite) show similar behavior with respect to wettability alteration with surfactant 4-22. Anionic surfactants (5-166, Alfoterra-33 and Alfoterra-38 and Alfoterra-68), which lower the interfacial tension with a West Texas crude oil to very low values (<10{sup -2} nM/m), have also been identified. Plans for the next quarter include conducting wettability, mobilization, and imbibition studies.

  4. DILUTE SURFACTANT METHODS FOR CARBONATE FORMATIONS

    SciTech Connect

    Kishore K. Mohanty

    2003-07-01

    There are many carbonate reservoirs in US (and the world) with light oil and fracture pressure below its minimum miscibility pressure (or reservoir may be naturally fractured). Many carbonate reservoirs are naturally fractured. Waterflooding is effective in fractured reservoirs, if the formation is water-wet. Many fractured carbonate reservoirs, however, are mixed-wet and recoveries with conventional methods are low (less than 10%). Thermal and miscible tertiary recovery techniques are not effective in these reservoirs. Surfactant flooding (or huff-n-puff) is the only hope, yet it was developed for sandstone reservoirs in the past. The goal of this research is to evaluate dilute (hence relatively inexpensive) surfactant methods for carbonate formations and identify conditions under which they can be effective. We have conducted adsorption, phase behavior, interfacial tension (IFT) and wettability studies. Addition of Na{sub 2}CO{sub 3} decreases IFT with a minimum at about 0.2 M. Addition of surfactant decreases IFT further. In the absence of surfactant the minerals are oil-wet after aging with crude oil. Addition of surfactant solution decreases the contact angle to intermediate-wet for many surfactants and water-wet for one surfactant. Addition of Na{sub 2}CO{sub 3} decreases anionic surfactant adsorption on calcite surface. Plans for the next quarter include conducting core adsorption, phase behavior, wettability and mobilization studies.

  5. DILUTE SURFACTANT METHODS FOR CARBONATE FORMATIONS

    SciTech Connect

    Kishore K. Mohanty

    2003-10-01

    There are many carbonate reservoirs in US (and the world) with light oil and fracture pressure below its minimum miscibility pressure (or reservoir may be naturally fractured). Many carbonate reservoirs are naturally fractured. Waterflooding is effective in fractured reservoirs, if the formation is water-wet. Many fractured carbonate reservoirs, however, are mixed-wet and recoveries with conventional methods are low (less than 10%). Thermal and miscible tertiary recovery techniques are not effective in these reservoirs. Surfactant flooding (or huff-n-puff) is the only hope, yet it was developed for sandstone reservoirs in the past. The goal of this research is to evaluate dilute (hence relatively inexpensive) surfactant methods for carbonate formations and identify conditions under which they can be effective. We have conducted adsorption, phase behavior, interfacial tension (IFT) and wettability studies. Alfoterra-38 (0.05 wt%), Alfoterra-35 (0.05 wt%), SS-6656 (0.05 wt%), and DTAB (1 wt%) altered the wettability of the initially oil-wet calcite plate to an intermediate/water-wet state. Low IFT ({approx}10{sup -3} dynes/cm) is obtained with surfactants 5-166, Alfoterra-33 and Alfoterra-38. Plans for the next quarter include conducting wettability and mobilization studies.

  6. DILUTE SURFACTANT METHODS FOR CARBONATE FORMATIONS

    SciTech Connect

    Kishore K. Mohanty

    2003-07-01

    There are many carbonate reservoirs in US (and the world) with light oil and fracture pressure below its minimum miscibility pressure (or reservoir may be naturally fractured). Many carbonate reservoirs are naturally fractured. Waterflooding is effective in fractured reservoirs, if the formation is water-wet. Many fractured carbonate reservoirs, however, are mixed-wet and recoveries with conventional methods are low (less than 10%). Thermal and miscible tertiary recovery techniques are not effective in these reservoirs. Surfactant flooding (or huff-n-puff) is the only hope, yet it was developed for sandstone reservoirs in the past. The goal of this research is to evaluate dilute (hence relatively inexpensive) surfactant methods for carbonate formations and identify conditions under which they can be effective. We have conducted adsorption, phase behavior and wettability studies. Addition of Na{sub 2}CO{sub 3} decreases IFT with a minimum at about 0.2 M. Addition of surfactant decreases IFT further. In the absence of surfactant the minerals are oil wet after aging with crude oil. Addition of surfactant solution decreases the contact angle to intermediate wettability. Addition of Na{sub 2}CO{sub 3} decreases anionic surfactant adsorption on calcite surface. Plans for the next quarter include conducting adsorption, phase behavior and wettability studies.

  7. RADIATIVE AND DYNAMIC STABILITY OF A DILUTE PLASMA

    SciTech Connect

    Balbus, Steven A. [Laboratoire de Radioastronomie, Ecole Normale Superieure, 24 rue Lhomond, 75231 Paris Cedex 05 (France); Reynolds, Christopher S., E-mail: steven.balbus@lra.ens.f [Department of Astronomy, University of Maryland, College Park, MD 20742 (United States)

    2010-09-01

    We analyze the linear stability of a dilute, hot plasma, taking into account the effects of stratification and anisotropic thermal conduction. The work is motivated by attempts to understand the dynamics of the intracluster medium in galaxy clusters. We show that magnetic field configurations that nominally stabilize either the heat-flux driven buoyancy instability (associated with a positive thermal gradient) or the magnetothermal instability (negative thermal gradient) can lead to previously unrecognized g-mode overstabilities. The driving source of the overstability is either radiative cooling (positive temperature gradient) or the heat flux itself (negative temperature gradient). While the implications of these overstabilities have yet to be explored, we speculate that the cold fronts observed in many relaxed galaxy clusters may be related to their nonlinear evolution.

  8. A compact rotating dilution refrigerator

    E-print Network

    Fear, M J; Chorlton, D A; Zmeev, D E; Gillott, S J; Sellers, M C; Richardson, P P; Agrawal, H; Batey, G; Golov, A I

    2013-01-01

    We describe the design and performance of a new rotating dilution refrigerator that will primarily be used for investigating the dynamics of quantized vortices in superfluid 4He. All equipment required to operate the refrigerator and perform experimental measurements is mounted on two synchronously driven, but mechanically decoupled, rotating carousels. The design allows for relative simplicity of operation and maintenance and occupies a minimal amount of space in the laboratory. Only two connections between the laboratory and rotating frames are required for the transmission of electrical power and helium gas recovery. Measurements on the stability of rotation show that rotation is smooth to around 0.001 rad/s up to angular velocities in excess of 2.5 rad/s. The behavior of a high-Q mechanical resonator during rapid changes in rotation has also been investigated.

  9. Desynchronization in diluted neural networks

    SciTech Connect

    Zillmer, Ruediger [INFN Sezione Firenze, via Sansone 1, I-50019 Sesto Fiorentino (Italy); Livi, Roberto [Dipartimento di Fisica, Universita di Firenze, via Sansone 1, I-50019 Sesto Fiorentino (Italy); Sezione INFN, Unita' INFM e Centro Interdipartimentale per lo Studio delle Dinamiche Complesse, via Sansone 1, I-50019 Sesto Fiorentino (Italy); Politi, Antonio; Torcini, Alessandro [Istituto dei Sistemi Complessi, CNR, CNR, via Madonna del Piano 10, I-50019 Sesto Fiorentino (Italy); Centro Interdipartimentale per lo Studio delle Dinamiche Complesse, via Sansone 1, I-50019 Sesto Fiorentino (Italy)

    2006-09-15

    The dynamical behavior of a weakly diluted fully inhibitory network of pulse-coupled spiking neurons is investigated. Upon increasing the coupling strength, a transition from regular to stochasticlike regime is observed. In the weak-coupling phase, a periodic dynamics is rapidly approached, with all neurons firing with the same rate and mutually phase locked. The strong-coupling phase is characterized by an irregular pattern, even though the maximum Lyapunov exponent is negative. The paradox is solved by drawing an analogy with the phenomenon of 'stable chaos', i.e., by observing that the stochasticlike behavior is 'limited' to an exponentially long (with the system size) transient. Remarkably, the transient dynamics turns out to be stationary.

  10. Precise determination of the absolute isotopic abundance ratio and the atomic weight of chlorine in three international reference materials by the positive thermal ionization mass spectrometer-Cs2Cl+-graphite method.

    PubMed

    Wei, Hai-Zhen; Jiang, Shao-Yong; Xiao, Ying-Kai; Wang, Jun; Lu, Hai; Wu, Bin; Wu, He-Pin; Li, Qing; Luo, Chong-Guang

    2012-12-01

    Because the variation in chlorine isotopic abundances of naturally occurring chlorine bearing substances is significant, the IUPAC Inorganic Chemistry Division, Commission on Isotopic Abundances and Atomic Weights (CIAAW-IUPAC) decided that the uncertainty of atomic weight of chlorine (A(r)(Cl)) should be increased so that the implied range was related to terrestrial variability in 1999 (Coplen, T. B. Atomic weights of the elements 1999 (IUPAC Technical Report), Pure Appl. Chem.2001, 73(4), 667-683; and then, it emphasized that the standard atomic weights of ten elements including chlorine were not constants of nature but depend upon the physical, chemical, and nuclear history of the materials in 2009 (Wieser, M. E.; Coplen, T. B. Pure Appl. Chem.2011, 83(2), 359-396). According to the agreement by CIAAW that an atomic weight could be defined for one specified sample of terrestrial origin (Wieser, M. E.; Coplen, T. B. Pure Appl. Chem.2011, 83(2), 359-396), the absolute isotope ratios and atomic weight of chlorine in standard reference materials (NIST 975, NIST 975a, ISL 354) were accurately determined using the high-precision positive thermal ionization mass spectrometer (PTIMS)-Cs(2)Cl(+)-graphite method. After eliminating the weighing error caused from evaporation by designing a special weighing container and accurately determining the chlorine contents in two highly enriched Na(37)Cl and Na(35)Cl salts by the current constant coulometric titration, one series of gravimetric synthetic mixtures prepared from two highly enriched Na(37)Cl and Na(35)Cl salts was used to calibrate two thermal ionization mass spectrometers in two individual laboratories. The correction factors (i.e., K(37/35) = R(37/35meas)/R(37/35calc)) were obtained from five cycles of iterative calculations on the basis of calculated and determined R((37)Cl/(35)Cl) values in gravimetric synthetic mixtures. The absolute R((37)Cl/(35)Cl) ratios for NIST SRM 975, NIST 975a, and ISL 354 by the precise calibrated isotopic composition measurements are 0.319876 ± 0.000067, 0.319768 ± 0.000187, and 0.319549 ± 0.000044, respectively. As a result, the atomic weights of chlorine in NIST 975, NIST 975a, and ISL 354 are derived as 35.45284(8), 35.45272(21), and 35.45252(2) individually, which are consistent with the issued values of 35.453(2) by IUPAC in 1999. PMID:23088631

  11. Evidence of magnetic isotope effects during thermochemical sulfate reduction

    PubMed Central

    Oduro, Harry; Harms, Brian; Sintim, Herman O.; Kaufman, Alan J.; Cody, George; Farquhar, James

    2011-01-01

    Thermochemical sulfate reduction experiments with simple amino acid and dilute concentrations of sulfate reveal significant degrees of mass-independent sulfur isotope fractionation. Enrichments of up to 13‰ for 33S are attributed to a magnetic isotope effect (MIE) associated with the formation of thiol-disulfide, ion-radical pairs. Observed 36S depletions in products are explained here by classical (mass-dependent) isotope effects and mixing processes. The experimental data contrasts strongly with multiple sulfur isotope trends in Archean samples, which exhibit significant 36S anomalies. These results support an origin other than thermochemical sulfate reduction for the mass-independent signals observed for early Earth samples. PMID:21997216

  12. Resonance ionization mass spectrometry (RIMS) for the measurement of multi-element concentrations and Re-OS isotopes in crustal rocks

    SciTech Connect

    Walker, R.J.; Moore, L.J.

    1985-01-01

    Resonance ionization mass spectrometry (RIMS) has been demonstrated to be a viable means of selectively ionizing a variety of elements for isotope ratio measurement with better than 1% precision. With RIMS atomic ions are produced by resonance ionization using a tunable dye laser, from a cloud of neutral atoms formed in a modified conventional thermal ionization filament source. At least 47 elements are amenable to resonance ionization using a simple two-photon process with a Nd:YAG pumped dye laser system. Many of these elements are of geologic interest. The advantages of this system over conventional mass spectrometry include the elimination of isobaric interferences, high sensitivity and the ability to ionize many elements not amenable to thermal ionization. Current research centers on the development of RIMS to precisely measure by isotope dilution a number of elements of interest to geochemists including Hf, Zr, Re, Os, W, Mo and the rare earth elements using minimal chemical separation procedures. Resonance ionization of these elements has been demonstrated. Techniques are being developed to utilize RIMS in the measurement of Os isotope ratios in crustal rocks, requiring picogram sensitivity. Isotope ratio measurement of nanogram quantities of Os have already been achieved.

  13. Diluted Magnetic Manganese Germanide for Nanostructure Devices

    NASA Astrophysics Data System (ADS)

    Yin, Wenjing

    Diluted magnetic semiconductor (DMS) materials have great potential when applied to spin-based devices, which integrate the electron charge and spin degrees of freedom. By appropriately controlling the magnetism in the semiconductor, a spin exchange switch can realize spin flipping with switching energy far less than what is needed in conventional complementary metal-oxide-semiconductor (CMOS) devices. Mn-doped Ge is a very promising candidate for such an application due to its theoretically predicted room temperature ferromagnetism and the compatibility with current CMOS technology. This thesis work mainly focuses on optimizing the material properties of MnxGe1-x thin films to achieve strong magnetization, high Curie temperature, and good film conductivity. Both ion implantation and molecular beam epitaxy (MBE)* have been used to synthesize diluted Mn xGe1-x thin films. Rapid thermal annealing was found to enhance the magnetism by incorporating more Mn ions into substitutional lattice sites. Transmission electron microscopy showed that Mn ions were highly mobile in the Ge matrix, and tended to form nanoscale clusters. MnxGe 1-x also exhibited very interesting magnetotransport properties, indicating that the ferromagnetism is closely correlated with carriers. The underlying fundamental mechanisms for the magnetism in MnxGe 1-x and its relation with microstructures will also be discussed. In order to study the carrier-mediated ferromagnetism in MnxGe 1-x, two experimental approaches were carried out: (1) B, P, and C atoms were codoped in MnxGe1-x thin films to investigate the impact of electronic dopants on ferromagnetism and electrical transport; (2) Mg and Au metal capping layers were deposited on MnxGe 1-x thin films to deplete / inject hole carriers through the metal-semiconductor interface. Both results suggested that ferromagnetism is effectively modulated by changing the hole concentration in MnxGe1-x. Additionally, a molecular dynamics (MD) simulation has been carried out for the Mn ion implantation into a Ge crystalline lattice. The dynamic change of the microstructure during the ion implantation is demonstrated, which will lead to a better understanding of how the material becomes amorphous, how the defects form and how the Mn distributes in the Ge matrix. * In collaboration with Prof. Jerrold Floro's group.

  14. Hydrogen abstraction reactions by atomic fluorine. III. Temperature dependence of the intermolecular kinetic isotope effect for the thermal F+H$sub 2$ reaction

    SciTech Connect

    Grant, E.R.; Root, J.W.

    1975-10-01

    The intermolecular kinetic isotope effect for the title reaction has been investigated using a moderated nuclear recoil technique. The following Arrhenius temperature dependence was obtained: k)2/k)2 = (1.04plus-or- minus0.06)exp(382plus-or-minus35)/RT. This result is in quantitative agreement with an independent study based upon a discharge flow reactor method. The advantages and limitations of the nuclear recoil procedure are considered, and relevant literature results are critically reviewed.

  15. Origins of large-volume, compositionally zoned volcanic eruptions: New constraints from U-series isotopes and numerical thermal modeling for the 1912 Katmai-Novarupta eruption

    Microsoft Academic Search

    Simon Turner; Mike Sandiford; Mark Reagan; Chris Hawkesworth; Wes Hildreth

    2010-01-01

    We present the results of a combined U-series isotope and numerical modeling study of the 1912 Katmai-Novarupta eruption in Alaska. A stratigraphically constrained set of samples have compositions that range from basalt through basaltic andesite, andesite, dacite, and rhyolite. The major and trace element range can be modeled by 80–90% closed-system crystal fractionation over a temperature interval from 1279°C to

  16. À propos des dilutions homéopathiques des vaccins

    Microsoft Academic Search

    Marie-Noëlle Domalain; Florence Peyrefitte; Bernard Poitevin

    2010-01-01

    Vaccine dilutions are used in homeopathy for different purposes, for example to limit the side effects of vaccines or to prevent diseases in certain cases. However, in the absence of any scientific information on how they work, vaccine dilutions prepared using homeopathic methods can in no circumstances be used in place of legal vaccination.

  17. 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.

  18. 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 studies is critically discussed, where special emphasis is set on evaluating different data processing strategies on the example of enriched stable Sr isotopes.1 The analytical key parameters such as blank (Kr, Sr and Rb), variation of the natural Sr isotopic composition in the sample, mass bias, interferences (Rb) and total combined uncertainty are considered. A full metrological protocol for data processing using IPD is presented based on data gained during two transgenerational marking studies of fish, where the transfer of a Sr isotope double spike (84Sr and 86Sr) from female spawners of common carp (Cyprinus carpio L.) and brown trout (Salmo trutta f.f.)2 to the centre of the otoliths of their offspring was studied by (LA)-MC-ICP-MS. 1J. Irrgeher, A. Zitek, M. Cervicek and T. Prohaska, J. Anal. At. Spectrom., 2014, 29, 193-200. 2A. Zitek, J. Irrgeher, M. Kletzl, T. Weismann and T. Prohaska, Fish. Manage. Ecol., 2013, 20, 654-361.

  19. Chemical characteristics of the major thermal springs of Montana

    USGS Publications Warehouse

    Mariner, R.H.; Presser, T.S.; Evans, William C.

    1976-01-01

    Twenty-one thermal springs in western Montana were sampled for chemical, isotope, and gas compositions. Most of the springs issue dilute to slightly saline sodium-bicarbonate waters of neutral to slightly alkaline pH. A few of the springs issue sodium-mixed anion waters of near neutral pH. Fluoride concentrations are high in most of the thermal waters, up to 18 milligramsper litre, while F/Cl ratios range from 3/1 in the dilute waters to 1/10 in the slightly saline waters. Most of the springs are theoretically in thermodynamic equilibrium with respect to calcite and fluorite. Nitrogen is the major gas escaping from most of the hot springs; however, Hunters Hot Springs issue principally methane. The deuterium content of the hot spring waters is typical of meteoric water in western Montana. Geothermal calculations based on silica concentrations and Na-K-Ca ratios indicate that most of the springs are associated with low temperature aquifers (less than 100?C). Chalcedony may be controlling the silica concentrations in these low temperature aquifers even in 'granitic' terranes.

  20. Hydrogen Isotopic (D/H) Composition of Organic Matter

    E-print Network

    Sessions, Alex L.

    Hydrogen Isotopic (D/H) Composition of Organic Matter During Diagenesis and Thermal Maturation/05/06.Forpersonaluseonly. #12;1. INTRODUCTION: STABLE ISOTOPES OF HYDROGEN IN ORGANIC MATTER Exploration for fossil fuels) and fossil fuels, and is usually the most abundant element. Yet studies of stable hydrogen isotopes in SOM

  1. Isotope spectroscopy

    NASA Astrophysics Data System (ADS)

    Caffau, E.; Steffen, M.; Bonifacio, P.; Ludwig, H.-G.; Monaco, L.; Lo Curto, G.; Kamp, I.

    2014-01-01

    The measurement of isotopic ratios provides a privileged insight both into nucleosynthesis and into the mechanisms operating in stellar envelopes, such as gravitational settling. In this article, we give a few examples of how isotopic ratios can be determined from high-resolution, high-quality stellar spectra. We consider examples of the lightest elements, H and He, for which the isotopic shifts are very large and easily measurable, and examples of heavier elements for which the determination of isotopic ratios is more difficult. The presence of 6Li in the stellar atmospheres causes a subtle extra depression in the red wing of the 7Li 670.7 nm doublet which can only be detected in spectra of the highest quality. But even with the best spectra, the derived 6Li abundance can only be as good as the synthetic spectra used for their interpretation. It is now known that 3D non-LTE modelling of the lithium spectral line profiles is necessary to account properly for the intrinsic line asymmetry, which is produced by convective flows in the atmospheres of cool stars, and can mimic the presence of 6Li. We also discuss briefly the case of the carbon isotopic ratio in metal-poor stars, and provide a new determination of the nickel isotopic ratios in the solar atmosphere.

  2. Ionic liquids behave as dilute electrolyte solutions.

    PubMed

    Gebbie, Matthew A; Valtiner, Markus; Banquy, Xavier; Fox, Eric T; Henderson, Wesley A; Israelachvili, Jacob N

    2013-06-11

    We combine direct surface force measurements with thermodynamic arguments to demonstrate that pure ionic liquids are expected to behave as dilute weak electrolyte solutions, with typical effective dissociated ion concentrations of less than 0.1% at room temperature. We performed equilibrium force-distance measurements across the common ionic liquid 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([C4mim][NTf2]) using a surface forces apparatus with in situ electrochemical control and quantitatively modeled these measurements using the van der Waals and electrostatic double-layer forces of the Derjaguin-Landau-Verwey-Overbeek theory with an additive repulsive steric (entropic) ion-surface binding force. Our results indicate that ionic liquids screen charged surfaces through the formation of both bound (Stern) and diffuse electric double layers, where the diffuse double layer is comprised of effectively dissociated ionic liquid ions. Additionally, we used the energetics of thermally dissociating ions in a dielectric medium to quantitatively predict the equilibrium for the effective dissociation reaction of [C4mim][NTf2] ions, in excellent agreement with the measured Debye length. Our results clearly demonstrate that, outside of the bound double layer, most of the ions in [C4mim][NTf2] are not effectively dissociated and thus do not contribute to electrostatic screening. We also provide a general, molecular-scale framework for designing ionic liquids with significantly increased dissociated charge densities via judiciously balancing ion pair interactions with bulk dielectric properties. Our results clear up several inconsistencies that have hampered scientific progress in this important area and guide the rational design of unique, high-free-ion density ionic liquids and ionic liquid blends. PMID:23716690

  3. Physics with isotopically controlled semiconductors

    SciTech Connect

    Haller, E. E., E-mail: eehaller@lbl.gov [University of California at Berkeley, Department of Materials Science and Engineering (United States)

    2010-07-15

    This paper is based on a tutorial presentation at the International Conference on Defects in Semiconductors (ICDS-25) held in Saint Petersburg, Russia in July 2009. The tutorial focused on a review of recent research involving isotopically controlled semiconductors. Studies with isotopically enriched semiconductor structures experienced a dramatic expansion at the end of the Cold War when significant quantities of enriched isotopes of elements forming semiconductors became available for worldwide collaborations. Isotopes of an element differ in nuclear mass, may have different nuclear spins and undergo different nuclear reactions. Among the latter, the capture of thermal neutrons which can lead to neutron transmutation doping, is the most prominent effect for semiconductors. Experimental and theoretical research exploiting the differences in all the properties has been conducted and will be illustrated with selected examples.

  4. Helium isotopes: Lower geyser basin, Yellowstone National Park

    SciTech Connect

    Kennedy, B.M.; Reynolds, J.H.; Smith, S.P.; Truesdell, A.H.

    1987-11-10

    High /sup 3/He//sup 4/He ratios associated with the Yellowstone caldera reflect the presence of a magmatic helium component. This component is ultimately derived from a mantle plume capped by a cooling batholith underlying the caldera. In surface hot springs, fumaroles, etc., the /sup 3/He//sup 4/He ratio varies from approx.1 to 16 tims the air ratio. The variations are produced by varying degrees of dilution of the magmatic component with radiogenic helium. The radiogenic helium is crustal-derived and is thought to be scavenged from aquifers in which the hydrothermal fluids circulate. We determined the helium iosotopic composition in 12 different springs from the Lower Geyser Basin, a large hydrothermal basin with the caldera. The /sup 3/He//sup 4/He ratio was found to vary from approx.2.7 to 7.7 times the air ratio. The variations correlate with variations in water chemistry. Specifically, the /sup 3/He//sup 4/He ratio increased with total bicarbonate concentration. The dissolved bicarbonate is from gas-water-rock interactions involving CO/sub 2/ and Na silicates. The concentration of bicarbonate is a function of the availability of dissolved CO/sub 2/, which, in turn, is a function of deep boiling with phase separation prior to CO/sub 2/-bicarbonate conversion. The correlation of high /sup 3/He//sup 4/He ratios with high bicarbonate is interpreted as the result of deep dilution of a single thermal fluid with cooler water during ascent to the surface. The dilution and cooling deters deep boiling, and therefore both CO/sub 2/ and /sup 3/He are retained in the rising fluid. Fluids that are not diluted with boil to a greater extent, losing a large proportion of /sup 3/He, as well as CO/sub 2/, leaving a helium-poor residual fluid in which the isotopic composition of helium will be strongly affected by the addition of radiogenic helium.

  5. 21 CFR 864.5240 - Automated blood cell diluting apparatus.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ...2013-04-01 false Automated blood cell diluting apparatus. 864.5240 Section...Devices § 864.5240 Automated blood cell diluting apparatus. (a) Identification. An automated blood cell diluting apparatus is a fully...

  6. 21 CFR 864.5240 - Automated blood cell diluting apparatus.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ...2012-04-01 false Automated blood cell diluting apparatus. 864.5240 Section...Devices § 864.5240 Automated blood cell diluting apparatus. (a) Identification. An automated blood cell diluting apparatus is a fully...

  7. 21 CFR 864.5240 - Automated blood cell diluting apparatus.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ...2014-04-01 false Automated blood cell diluting apparatus. 864.5240 Section...Devices § 864.5240 Automated blood cell diluting apparatus. (a) Identification. An automated blood cell diluting apparatus is a fully...

  8. 21 CFR 864.5240 - Automated blood cell diluting apparatus.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ...2011-04-01 false Automated blood cell diluting apparatus. 864.5240 Section...Devices § 864.5240 Automated blood cell diluting apparatus. (a) Identification. An automated blood cell diluting apparatus is a fully...

  9. 21 CFR 864.5240 - Automated blood cell diluting apparatus.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ...2010-04-01 false Automated blood cell diluting apparatus. 864.5240 Section...Devices § 864.5240 Automated blood cell diluting apparatus. (a) Identification. An automated blood cell diluting apparatus is a fully...

  10. Sound Absorption and Dispersion in Dilute Polyatomic Gases: A Generalized Kinetic Approach

    E-print Network

    Fischer, Sebastian

    2013-01-01

    A generalized kinetic model equation which takes into account the frequency depence of the thermal conductivity is used to analyze the problem of sound propagation in dilute polyatomic gases. By comparing the theoretical results with some available experimental data we infer that our model equation provides a precise transition between low and high-frequency limits.

  11. Stability of a Planar Interface During Solidification of a Dilute Binary Alloy

    Microsoft Academic Search

    W. W. Mullins; R. F. Sekerka

    1964-01-01

    The stability of the shape of a moving planar liquid-solid interface during the unidirectional freezing of a dilute binary alloy is theoretically investigated by calculating the time dependence of the amplitude of a sinusoidal perturbation of infinitesimal amplitude introduced into the planar shape. The calculation is accomplished by using gradients of the steady-state thermal and diffusion fields satisfying the perturbed

  12. SOME RECENT APPLICATIONS OF ISOTOPES IN RESEARCH AND CONTROL IN INDUSTRY

    Microsoft Academic Search

    Spinks; J. W. T

    1959-01-01

    The application of radioisotopes in research and control in industry ; depends on the detection of the radiations emitted when the isotope decays. The ; radiations can be used for analysis, both qualitative and quantitative, and in ; the unique analytical method of isotope dilution. They can also be used to trace ; materials or things of interest to industry

  13. Long-Range Interactions Dilute Granular Systems

    E-print Network

    Luding, Stefan

    in General . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 1.2 Intermolecular Forces algorithm for MD methods is developed that handles long-range forces in a computationally efficient between dissipation at contact and long-range repulsive/attractive forces in homogeneous dilute particle

  14. Isotopically pure magnesium isotope-24 is prepared from magnesium-24 oxide

    NASA Technical Reports Server (NTRS)

    Chellew, N. R.; Schilb, J. D.; Steunenberg, R. K.

    1968-01-01

    Apparatus is used to prepare isotopically pure magnesium isotope-24, suitable for use in neutron scattering and polarization experiments. The apparatus permits thermal reduction of magnesium-24 oxide with aluminum and calcium oxide, and subsequent vaporization of the product metal in vacuum. It uses a resistance-heated furnace tube and cap assembly.

  15. Comparison of microtiter broth dilution and agar dilution methods for susceptibility testing of Eikenella corrodens.

    PubMed

    Goldstein, E J; Cherubin, C E; Shulman, M

    1983-01-01

    Eikenella corrodens is a slow-growing, capnophilic, gram-negative rod which often grows poorly in liquid media. Consequently, the agar dilution technique is the method of choice for susceptibility testing of E. corrodens. We report a new microtiter broth dilution method for susceptibility testing of E. corrodens which compared favorably with results obtained by the agar dilution technique. Minimal bactericidal concentrations correlated well with minimal inhibitory concentrations. PMID:6338819

  16. Evaluation of the deuterium dilution technique against the test-weighing procedure for the determination of breast milk intake

    SciTech Connect

    Butte, N.F.; Garza, C.; Smith, E.O.; Nichols, B.L.

    1983-06-01

    A noninvasive isotopic method for the determination of milk intake in breast-fed infants was evaluated against the conventional method of test-weighing. In experiment 1, 48-h breast milk intake was estimated concurrently by the test-weighing procedure and by the deuterium dilution technique. In experiment 2, the isotopic method, modified to minimize fluctuations in water flux, was evaluated against a 24-h test-weighing. In experiment 1, the mean 48-h milk intake estimated by the isotopic method (1616 +/- 353 ml) was significantly higher than that measured by the test-weighing procedure (1449 +/- 234 ml) (p less than 0.01). In experiment 2, 24-h milk intake as determined by test-weighing and deuterium dilution averaged 878.0 +/- 188.1 and 690.7 +/- 141.4 ml/day, respectively, and differed significantly (p less than 0.001). The ability of the deuterium dilution method to predict values obtained by the test-weighing procedure was unsatisfactory for individual estimations. These experiments indicate that the deuterium dilution technique is unacceptable for the determination of breast-milk intake in individuals, but may be satisfactory for a population estimation.

  17. Dilute Oxygen Combustion Phase 2 Final Report

    SciTech Connect

    Ryan, H.M.; Riley, M.F.; Kobayashi, H.

    2005-09-30

    A novel burner, in which fuel (natural gas) and oxidant (oxygen or air) are separately injected into a furnace, shows promise for achieving very low nitrogen oxide(s) (NOx) emissions for commercial furnace applications. The dilute oxygen combustion (DOC) burner achieves very low NOx through in-furnace dilution of the oxidant stream prior to combustion, resulting in low flame temperatures, thus inhibiting thermal NOx production. The results of a fundamental and applied research effort on the development of the DOC burner are presented. In addition, the results of a market survey detailing the potential commercial impact of the DOC system are disclosed. The fundamental aspects of the burner development project involved examining the flame characteristics of a natural gas turbulent jet in a high-temperature (~1366 K) oxidant (7-27% O2 vol. wet). Specifically, the mass entrainment rate, the flame lift-off height, the velocity field and major species field of the jet were evaluated as a function of surrounding-gas temperature and composition. The measured entrainment rate of the fuel jet decreased with increasing oxygen content in the surrounding high-temperature oxidant, and was well represented by the d+ scaling correlation found in the literature. The measured flame lift-off height decreased with increasing oxygen content and increasing temperature of the surrounding gas. An increase in surrounding-gas oxygen content and/or temperature inhibited the velocity decay within the jet periphery as a function of axial distance as compared to isothermal turbulent jets. However, the velocity measurements were only broadly represented by the d+ scaling correlation. Several DOC burner configurations were tested in a laboratory-scale furnace at a nominal firing rate of 185 kW (~0.63 MMBtu/h). The flue gas composition was recorded as a function of furnace nitrogen content, furnace temperature, burner geometric arrangement, firing rate, and fuel injection velocity. NOx emissions increased with increasing furnace nitrogen content and furnace temperature, but remained relatively insensitive to variations in fuel injection velocity and firing rate. NOx emissions below 5-10-3 g/MJ (10 ppm-air equivalent at 3% O2 dry) were obtained for furnace temperatures below 1533 K (2300?F) and furnace nitrogen levels between 1 and 40%. CO emissions were typically low (<35 ppm). Detailed in-furnace species measurements revealed the importance of the interior furnace circulation patterns, as influenced by fuel and oxidant injection schemes, on pollutant emissions. The combustion stability traits of several DOC burner arrangements were ascertained through furnace pressure measurements, wit6h increased stability occurring as furnace temperature increased and as the separation distance between fuel and oxidant inputs decreased. Based on current market conditions, oxy-fuel conversion of batch steel reheat furnaces with a DOC burner is justified on the basis of lower utility costs alone. However, conversion of continuous steel reheat furnaces, which are responsible for most steel production, required additional economic incentives, such as further fuel savings, increased furnace productivity, or emission credits.

  18. Dilute Oxygen Combustion Phase I Final Report

    SciTech Connect

    Ryan, H.M.; Riley, M.F.; Kobayashi, H.

    1997-10-31

    A novel burner, in which fuel (natural gas) and oxidant (oxygen or air) are separately injected into a furnace, shows promise for achieving very low nitrogen oxide(s) (NOx) emissions for commercial furnace applications. The dilute oxygen combustion (DOC) burner achieves very low NOx through in-furnace dilution of the oxidant stream prior to combustion, resulting in low flame temperatures, thus inhibiting thermal NOx production. The results of a fundamental and applied research effort on the development of the DOC burner are presented. In addition, the results of a market survey detailing the potential commercial impact of the DOC system are disclosed. The fundamental aspects of the burner development project involved examining the flame characteristics of a natural gas turbulent jet in a high-temperature (~1366 K) oxidant (7-27% O2 vol. wet). Specifically, the mass entrainment rate, the flame lift-off height, the velocity field and major species field of the jet were evaluated as a function of surrounding-gas temperature and composition. The measured entrainment rate of the fuel jet decreased with increasing oxygen content in the surrounding high-temperature oxidant, and was well represented by the d+ scaling correlation found in the literature. The measured flame lift-off height decreased with increasing oxygen content and increasing temperature of the surrounding gas. An increase in surrounding-gas oxygen content and/or temperature inhibited the velocity decay within the jet periphery as a function of axial distance as compared to isothermal turbulent jets. However, the velocity measurements were only broadly represented by the d+ scaling correlation. Several DOC burner configurations were tested in a laboratory-scale furnace at a nominal firing rate of 185 kW (~0.63 MMBtu/h). The flue gas composition was recorded as a function of furnace nitrogen content, furnace temperature, burner geometric arrangement, firing rate, and fuel injection velocity. NOx emissions increased with increasing furnace nitrogen content and furnace temperature, but remained relatively insensitive to variations in fuel injection velocity and firing rate. NOx emissions below 5-10-3 g/MJ (10 ppm-air equivalent at 3% O2 dry) were obtained for furnace temperatures below 1533 K (2300°F) and furnace nitrogen levels between 1 and 40%. CO emissions were typically low (<35 ppm). Detailed in-furnace species measurements revealed the importance of the interior furnace circulation patterns, as influenced by fuel and oxidant injection schemes, on pollutant emissions. The combustion stability traits of several DOC burner arrangements were ascertained through furnace pressure measurements, wit6h increased stability occurring as furnace temperature increased and as the separation distance between fuel and oxidant inputs decreased. Based on current market conditions, oxy-fuel conversion of batch steel reheat furnaces with a DOC burner is justified on the basis of lower utility costs alone. However, conversion of continuous steel reheat furnaces, which are responsible for most steel production, required additional economic incentives, such as further fuel savings, increased furnace productivity, or emission credits.

  19. Dilute oxygen combustion. Phase I report

    SciTech Connect

    NONE

    1997-10-01

    A novel burner, in which fuel (natural gas) and oxidant (oxygen or air) are separately injected into a furnace, shows promise for achieving very low nitrogen oxide(s) (NO{sub x}) emissions for commercial furnace applications. The dilute oxygen combustion (DOC) burner achieves very low NO{sub x} through in-furnace dilution of the oxidant stream prior to combustion, resulting in low flame temperatures, thus inhibiting thermal NO{sub x} production. The results of a fundamental and applied research effort on the development of the DOC burner are presented. In addition, the results of a market survey detailing the potential commercial impact of the DOC system are disclosed. The fundamental aspects of the burner development project involved examining the flame characteristics of a natural gas turbulent jet in a high-temperature ({approximately}1366 K) oxidant (7-27% O{sub 2} vol. wet). Specifically, the mass entrainment rate, the flame lift-off height, the velocity field and major species field of the jet were evaluated as a function of surrounding-gas temperature and composition. The measured entrainment rate of the fuel jet decreased with increasing oxygen content in the surrounding high-temperature oxidant, and was well represented by the d{sup +} scaling correlation found in the literature. The measured flame lift-off height decreased with increasing oxygen content and increasing temperature of the surrounding gas. An increase in surrounding-gas oxygen content and/or temperature inhibited the velocity decay within the jet periphery as a function of axial distance as compared to isothermal turbulent jets. However, the velocity measurements were only broadly represented by the d{sup +} scaling correlation. Several DOC burner configurations were tested in a laboratory-scale furnace at a nominal firing rate of 185 kW ({approximately}0.63 MMBtu/h). The flue gas composition was recorded as a function of furnace nitrogen content, furnace temperature, burner geometric arrangement, firing rate, and fuel injection velocity. NO{sub x} emissions increased with increasing furnace nitrogen content and furnace temperature, but remained relatively insensitive to variations in fuel injection velocity and firing rate. NO{sub x} emissions below 5{times}10{sup -3} g/MJ (10 ppm-air equivalent at 3% O{sub 2} dry) were obtained for furnace temperatures below 1533 K (2300{degree}F) and furnace nitrogen levels between 1 and 40%. CO emissions were typically low (<35 ppm). Detailed in- furnace species measurements revealed the importance of the interior furnace circulation patterns, as influenced by fuel and oxidant injection schemes, on pollutant emissions. The combustion stability traits of several DOC burner arrangements were ascertained through furnace pressure measurements, with increased stability occurring as furnace temperature increased and as the separation distance between fuel and oxidant inputs decreased. Based on current market conditions, oxy-fuel conversion of batch steel reheat furnaces with a DOC burner is justified on the basis of utility costs alone. However, conversion of continuous steel reheat furnaces, which are responsible for most steel production, requires additional economic incentives, such as further fuel savings, increased furnace productivity, or emission credits.

  20. Fragment shell effect in low energy fission: Independent yields of technetium isotopes in the thermal-neutron-induced fission of 239Pu

    Microsoft Academic Search

    Alok Srivastava; A. Goswami; B. K. Srivastava; A. G. C. Nair; S. B. Manohar; Satya Prakash; M. V. Ramaniah

    1986-01-01

    The independent yields of 101Tc, 103Tc, 104Tc, and 105Tc have been determined in the thermal-neutron-induced fission of 239Pu using fast radiochemical separation techniques followed by gamma-ray spectrometry. The most probable fragment mass A'p and mass dispersion sigma'A are obtained from the measured independent yields as 108.35+\\/-0.45 and 1.80+\\/-0.25 mass units, respectively. A comparison of the elemental yield (Yz) of technetium

  1. Looking at catchments in colors: combining thermal IR imagery with geochemical and isotopic tracers to document spatio-temporal dynamics of water source and flowpaths in the hillslope-riparian zone-stream system

    NASA Astrophysics Data System (ADS)

    Pfister, L.; Martínez-Carreras, N.; Wetzel, C.; Ector, L.; Hissler, C.; Hoffmann, L.; Frentress, J. J.; McDonnell, J. J.

    2012-04-01

    At present, our conceptual understanding of catchment-scale water mixing, source apportionment and hydrological connectivity is thwarted by measurement limitations. For instance, the measurement and documentation of HRS connectivity is a major impediment to better process understanding. In recent literature, there have been repeatedly calls for interdisciplinary approaches to expand the frontier of hydrological theory and eventually overcome the well-known limitations that are inherent to conventional techniques used for tracing water source, flowpaths and residence times. The 2010 edition of the EGU Leonardo Topical Conference Series on the hydrological cycle had concluded that a major challenge for hydrology in the near future will be to apply more often multidisciplinary approaches, so to find creative solutions that will eventually allow us to move away from 'monochrome pictures of reality', and 'see the catchments in colors'. Here, we demonstrate the potential for thermal infrared imagery to both determine adequate water sampling sites and validate the identification of water source and connectivity through conventional tracers. Until recently, the use of heat as a ground water tracer had been largely restricted to the hydrogeological literature. Thermal remote sensing of riparian and water surface temperatures has been of interest in aquatic management issues, as well as for the assessment of spatial heterogeneities. Our proof-of-concept study in the Weierbach experimental watershed further extended the potential for infrared thermography via hand-held cameras to hydrological processes studies across various hydrological response units (HRU). Infrared thermography of surface water dynamics stemming either from infiltration excess overland flow or saturation excess overland flow was mapped throughout a complete rainfall-runoff event. In order to grasp the spatial and temporal variability of geochemical and isotopic signatures, during and after a storm event, we have combined thermal IR imagery with grab sampling of water inside the hillslope-riparian zone-stream system. While relying on IR thermography, we also used simultaneous optical image capture to aid in classifying the incoming IR signal and differentiating between substances of different temperature. The distinction between flowing water, saturated zones, soil, wooden branches, pebbles or leaves is extremely difficult when observing the optical image alone. The IR thermography interprets the heat signal from the same source and provides a much better view for identifying both areas where water is flowing and areas where water is either seeping from the soil, flowing as surface runoff or accumulating temporarily in micro-depressions during a rainfall event. This approach has revealed how crucial the location of the grab sampling can be within extremely small geographical zones (a few square meters) due to incomplete mixing, as well as it has helped to map the dynamics of geochemical and isotopic signatures in the area of interest. To date, our investigations have revealed: (a) the potential for infrared thermography to identify, discriminate and observe the spatio-temporal dynamics of hydrological processes, namely infiltration excess overland flow, saturation excess overland flow and subsurface return flow; and (b) the complementarity of information gained from conventional tracers (geochemicals and stable isotopes) and remote sensing (infrared thermography). Our next step will consist in assessing the individual and combined potential of these techniques for reducing uncertainties in hydrological process identification and quantification (especially with respect to hydrograph separation).

  2. The Isotopes Project Home Page

    NSDL National Science Digital Library

    Lawrence Berkeley National Laboratory provides the Isotopes Project Home Page. The goal of this project is to "compile, evaluate, and disseminate nuclear structure and radioactive decay data for basic and applied research." The project evaluates nuclear structure data for 43 mass chains (A=167-194), "nuclei far-from-stability with the Atomic Mass Data Center (Orsay), neutron capture gamma-ray data with the Institute of Isotope and Surface Chemistry (Budapest), and spontaneous fission data with the GANDS collaboration (LBNL, LLNL, INEL, Vanderbilt, UCB)." Site sections include Exploring the Isotopes; Glossary of Nuclear Science Terms; WWW Table of the Isotope, a database; Isotope Explorer, a tool that accesses and displays nuclear data, and searches for literature references; Nuclear Science Reference Search, searchable by keyword, data type, and topic; Table of Superdeformed Nuclear Bands and Fission Isomers (HTML, .pdf, .ps); Nuclear Astrophysics, a database; Thermal Neutron Capture; Fission, a section that provides Gamma-Ray and Nuclear Structure Data; Atomic Masses (.ps, .pdf); Table of Radioactive Isotopes (mentioned in the April 29, 1998 Scout Report for Science & Engineering Report); and Gamquest, a computer program to identify gamma rays.

  3. Evaluation of the deuterium dilution technique against the test-weighing procedure for the determ ination of breast milk intake1

    Microsoft Academic Search

    C Garza; BL Nichols

    A noninvasive isotopic method for the determination of milk intake in breast-fed infants was evaluated against the conventional method of test-weighing. In experiment 1, 48-h breast milk intake was estimated concurrently by the test-weighing procedure and by the deuterium dilution technique. In experiment 2, the isotopic method, modified to minimize fluctuations in water flux, was evaluated against a 24-h test-weighing.

  4. Sulfur isotope analysis of bitumen and pyrite associated with thermal sulfate reduction in reservoir carbonates at the Big Piney-La Barge production complex

    NASA Astrophysics Data System (ADS)

    King, Hubert E.; Walters, Clifford C.; Horn, William C.; Zimmer, Mindy; Heines, Maureen M.; Lamberti, William A.; Kliewer, Christine; Pottorf, Robert J.; Macleod, Gordon

    2014-06-01

    Sulfur isotopes of solid bitumen and associated pyrite from the Madison Limestone in the Big Piney-La Barge production complex were measured using a Secondary Ion Mass Spectrometry (SIMS) method. The solid bitumens, a product of thermochemical sulfate reduction, yielded ?34S values of +18.9 ± 3.9 that are consistent with inferred values for native Mississippian sulfate. In contrast, coarse and fine grain pyrite grains were found to be 34S depleted, with values similar to that of the produced H2S (?34S ? +10‰). We interpret these results to indicate that two different sources of sulfate were involved with TSR within the Madison Limestone-autochthonous anhydrite, which is now completely replaced with calcite, and Permian age sulfate dissolved in the aquifer. While checking for inclusions within the bitumen that could lead to erroneous measurement, we found the bitumen possesses a ?5 ?m rim and internal “worm-like” features enriched in organic sulfur. We hypothesize that the rim is the result of back reaction of the late forming H2S with the solid bitumen and that the <1 ?m diameter wormy features may result from liquid-liquid immiscibility occurring at the high temperatures of formation.

  5. Thermal repair of tryptophan synthase mutations in a regulatory intersubunit salt bridge. Evidence from arrhenius plots, absorption spectra, and primary kinetic isotope effects.

    PubMed

    Fan, Y X; McPhie, P; Miles, E W

    2000-07-01

    This work is aimed at understanding how protein structure and conformation regulate activity and allosteric communication in the tryptophan synthase alpha(2)beta(2) complex from Salmonella typhimurium. Previous crystallographic and kinetic results suggest that both monovalent cations and a salt bridge between alpha subunit Asp(56) and beta subunit Lys(167) play allosteric roles. Here we show that mutation of either of these salt bridging residues produced deleterious effects that could be repaired by increased temperature in combination with CsCl or with NaCl plus an alpha subunit ligand, alpha-glycerol 3-phosphate. Arrhenius plots of the activity data under these conditions were nonlinear. The same conditions yielded temperature-dependent changes in the equilibrium distribution of enzyme-substrate intermediates and in primary kinetic isotope effects. We correlate the results with a model in which the mutant enzymes are converted by increased temperature from a low activity, "open" conformation to a high activity, "closed" conformation under certain conditions. The allosteric ligand and different monovalent cations affected the equilibrium between the open and closed forms. The results suggest that alpha subunit Asp(56) and beta subunit Lys(167) are not essential for catalysis and for allosteric communication between the alpha and beta subunits but that their mutual interaction is important in stabilization of the active, closed form of the alpha(2)beta(2) complex. PMID:10801803

  6. Chemical and isotopic compositions of thermal springs, fumaroles and bubbling gases at Tacaná Volcano (Mexico–Guatemala): implications for volcanic surveillance

    Microsoft Academic Search

    Dmitri Rouwet; Salvatore Inguaggiato; Yuri Taran; Nicholas Varley

    2009-01-01

    This study presents baseline data for future geochemical monitoring of the active Tacaná volcano–hydrothermal system (Mexico–Guatemala).\\u000a Seven groups of thermal springs, related to a NW\\/SE-oriented fault scarp cutting the summit area (4,100m a.s.l.), discharge\\u000a at the northwest foot of the volcano (1,500–2,000m a.s.l.); another one on the southern ends of Tacaná (La Calera). The near-neutral\\u000a (pH from 5.8 to 6.9)

  7. Carbon isotopes of hydrocarbons and carbon dioxide in natural gases in China

    NASA Astrophysics Data System (ADS)

    Sheng, Xu; Nakai, Shun'ichi; Wakita, Hiroshi; Yongchang, Xu; Wang, Xianbin

    1997-02-01

    130 natural gases in the continent of China were determined for the abundance and carbon isotopes of hydrocarbons and carbon dioxide. The ?13C (PDB) values of methane range from -68 to - 24.4%, and the largest isotopic variability for hydrocarbons is of ?13C 1 < ?13C; < ?13C; < ?13C 4 < ?13C 5. These characteristics suggest that the gaseous hydrocarbons originated principally from thermal and or microbial decomposition of organic matter. The wide variations of ?13C 0 distribution patterns (n = 1, 2, 3, 4 and 5) can be explained by (1) extensive mixture between thermogenic and microbial gases, or between thermogenic gases produced during different thermal stage, and or (2) preferential microbial oxidation. There is no direct evidence for the presence of abiogenic hydrocarbon in natural gases in China. One sample from Songliao basin shows a heavier ?13C 1 ( - 24‰) and reverse isotopic distribution pattern ( ?13C 1 > ?13C 2 > ?13C 3). Concerning the occurrence of mantle-derived He, Ne, Ar and Xe in the south Songliao basin, we propose that the methane mantle derived and heavy hydrocarbons (ethane, propane, butane, etc.) formed from polymerization of the mantle-derived methane. The ?13C values for carbon dioxide range from - 13.9 to + 13.5‰ suggesting the multiple origins. Gases with CO 2 concentrations greater than 10% have a narrow range of ?13C values, from - 8 to - 2‰, and show higher 1He 4He ratios ( > 0.1 times the atmospheric value), suggesting that a mantle-derived component is diluted by CO 2 derived from carbonate and or organic matter. Positive ?13C values ( + 4 - + 14‰) indicate CO 2 reduction to CH 2, CO 2 with trace concentration in CH 4-rich gases can be attributed to microbial decomposition of organic matter in sedimentary rocks.

  8. Fragment shell effect in low energy fission: Independent yields of technetium isotopes in the thermal-neutron-induced fission of 239Pu

    NASA Astrophysics Data System (ADS)

    Srivastava, Alok; Goswami, A.; Srivastava, B. K.; Nair, A. G. C.; Manohar, S. B.; Prakash, Satya; Ramaniah, M. V.

    1986-03-01

    The independent yields of 101Tc, 103Tc, 104Tc, and 105Tc have been determined in the thermal-neutron-induced fission of 239Pu using fast radiochemical separation techniques followed by gamma-ray spectrometry. The most probable fragment mass A'p and mass dispersion ?'A are obtained from the measured independent yields as 108.35+/-0.45 and 1.80+/-0.25 mass units, respectively. A comparison of the elemental yield (Yz) of technetium obtained from the present work and the literature for the thermal-neutron-induced fission of 235U and 239Pu and the spontaneous fission of 252Cf shows that the Yz of technetium in the case of fission of 240Pu and 252Cf is very high compared to that of 236U. The enhancement of the yields in the case of 240Pu and 252Cf is attributed to the proximity of spherical-deformed neutron shells 82-88 in the complementary fragments antimony and cesium, respectively.

  9. Mossbauer effect in dilute iron alloys

    NASA Technical Reports Server (NTRS)

    Singh, J. J.

    1975-01-01

    The effects of variable concentration, x, of Aluminum, Germanium, and Lanthanum atoms in Iron lattice on various Mossbauer parameters was studied. Dilute binary alloys of (Fe-Al), (Fe-Ge), (Fe-Al) containing up to x = 2 a/o of the dilute constituent were prepared in the form of ingots and rolled to a thickness of 0.001 in. Mossbauer spectra of these targets were then studied in transmission geometry to measure changes in the hyperfine field, peak widths isomer shifts as well as the ratio of the intensities of peaks (1,6) to the intensities of peaks (2,5). It was shown that the concept of effective hyperfine structure field in very dilute alloys provides a useful means of studying the effects of progressively increasing the solute concentration on host lattice properties.

  10. Molybdenum Isotopic Composition of Iron Meteorites, Chondrites and Refractory Inclusions

    NASA Technical Reports Server (NTRS)

    Becker, H.; Walker, R. J.

    2003-01-01

    Recent Mo isotopic studies of meteorites reported evidence for differences in isotopic compositions for whole rocks of some primitive and differentiated meteorites relative to terrestrial materials. Enrichments of r- and p-process isotopes of up to 3-4 units (e unit = parts in 10(exp 4) over s-process dominated isotopes are the most prominent features. Certain types of presolar grains show large enrichments in s-process isotopes, however, it was concluded on grounds of mass balance that incomplete digestion of such grains cannot explain the enrichments of r- and p-process isotopes in whole rocks of primitive chondrites. If the reported variability in r- and p-process isotope enrichments reflects the true isotopic characteristics of the whole rocks, the implications are quite profound. It would suggest the presence of large scale Mo isotopic heterogeneity within the solar accretion disk with likely collateral effects for other elements. However, such effects were not found for Ru isotopes, nor for Zr isotopes. Another recent Mo isotopic study by multi collector ICP-MS could not confirm the reported deviations in Allende, Murchison or iron meteorites. Here, we present new results for the Mo isotopic composition of iron meteorites, chondrites and CAIs obtained by negative thermal ionization mass spectrometry (NTIMS). We discuss analytical aspects and the homogeneity of Mo isotopic compositions in solar system materials.

  11. Diluted magnetic semiconductor nanowires exhibiting magnetoresistance

    DOEpatents

    Yang, Peidong (El Cerrito, CA); Choi, Heonjin (Seoul, KR); Lee, Sangkwon (Daejeon, KR); He, Rongrui (Albany, CA); Zhang, Yanfeng (El Cerrito, CA); Kuykendal, Tevye (Berkeley, CA); Pauzauskie, Peter (Berkeley, CA)

    2011-08-23

    A method for is disclosed for fabricating diluted magnetic semiconductor (DMS) nanowires by providing a catalyst-coated substrate and subjecting at least a portion of the substrate to a semiconductor, and dopant via chloride-based vapor transport to synthesize the nanowires. Using this novel chloride-based chemical vapor transport process, single crystalline diluted magnetic semiconductor nanowires Ga.sub.1-xMn.sub.xN (x=0.07) were synthesized. The nanowires, which have diameters of .about.10 nm to 100 nm and lengths of up to tens of micrometers, show ferromagnetism with Curie temperature above room temperature, and magnetoresistance up to 250 Kelvin.

  12. Standard test method for analysis of isotopic composition of uranium in nuclear-grade fuel material by quadrupole inductively coupled plasma-mass spectrometry

    E-print Network

    American Society for Testing and Materials. Philadelphia

    2000-01-01

    1.1 This test method is applicable to the determination of the isotopic composition of uranium (U) in nuclear-grade fuel material. The following isotopic weight percentages are determined using a quadrupole inductively coupled plasma-mass spectrometer (Q-ICP-MS): 233U, 234U, 235U, 236U, and 238U. The analysis can be performed on various material matrices after acid dissolution and sample dilution into water or dilute nitric (HNO3) acid. These materials include: fuel product, uranium oxide, uranium oxide alloys, uranyl nitrate (UNH) crystals, and solutions. The sample preparation discussed in this test method focuses on fuel product material but may be used for uranium oxide or a uranium oxide alloy. Other preparation techniques may be used and some references are given. Purification of the uranium by anion-exchange extraction is not required for this test method, as it is required by other test methods such as radiochemistry and thermal ionization mass spectroscopy (TIMS). This test method is also described i...

  13. Method of enhancing selective isotope desorption from metals

    DOEpatents

    Knize, Randall J. (Plainsboro, NJ); Cecchi, Joseph L. (Lawrenceville, NJ)

    1984-01-01

    A method of enhancing the thermal desorption of a first isotope of a diatomic gas from a metal comprises the steps of (a) establishing a partial pressure of a second isotope of the diatomic gas in vicinity of the metal; heating the metal to a temperature such that the first isotope is desorbed from the metal; and reducing the partial pressure of the desorbed first isotope while maintaining the partial pressure of the second isotope substantially constant. The method is especially useful for enhancing the desorption of tritium from the Zr-Al getter in a plasma confinement device.

  14. Lithium 7 Isotope (Li) Desorption from a Degraded Amberlite IRN 217 Lithiated Mixed-Bed Ion-Exchange Resin

    Microsoft Academic Search

    M. Basitere; S. K. O. Ntwampe; M. S. Sheldon

    2012-01-01

    This study investigated the possibility of desorpting the lithium isotope (Li) from the cation part of an Amberlite IRN 217 lithiated mixed-bed resin that had been deemed unsuitable for use as a result of anion degradation and the release of organically bound impurities. The desorption of the isotope from the cation part of the mixed-bed resin was studied using dilute

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

    USGS Publications Warehouse

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

    1989-01-01

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

  16. AN INITIAL DILUTION ZONE IMPACT ASSESSMENT

    E-print Network

    of the Fraser River Estuary Monitoring Program (FREMP) Environmental Monitoring Program. The study consisted River. A reference site was established near the FREMP water quality monitoring station at Mission#12;AN INITIAL DILUTION ZONE IMPACT ASSESSMENT OF SELECTED INDUSTRIES IN THE FRASER RIVER ESTUARY

  17. Zinc oxide based diluted magnetic semiconductors

    Microsoft Academic Search

    Shivaraman Ramachandran

    2007-01-01

    During my graduate research I have synthesized materials known as diluted magnetic semiconductors (DMS) as epitaxial thin film structures using the process of pulsed laser deposition (PLD). These materials are envisioned to be of importance in the emerging field of spintronics where the charge as well as the spin of the charge carriers can be combined to yield unique functionalities

  18. Resistance Minimum in Dilute Magnetic Alloys

    Microsoft Academic Search

    Jun Kondo

    1964-01-01

    Based on the s-d interaction model for dilute magnetic alloys we have calculated the scattering probability of the conduction electrons to the second Born approximation. Because of the dynamical character of the localized spin system, the Pauli principle should be taken into account in the intermediate states of the second order terms. Thus the effect of the Fermi sphere is

  19. Irradiated gases transferred without contamination or dilution

    NASA Technical Reports Server (NTRS)

    Bonn, J. L.; Kern, W.

    1967-01-01

    Vacuum chamber apparatus opens sealed canisters of irradiated gases and transfers the contents without contaminating the surrounding area, and without diluting or polluting the contained gases. The apparatus consists of the chamber, a valved piping manifold, and a special drill and sealed drilling access.

  20. Sulfuric Acid and Water: Paradoxes of Dilution

    ERIC Educational Resources Information Center

    Leenson, I. A.

    2004-01-01

    On equilibrium properties of aqueous solutions of sulfuric acid, Julius Thomsen has marked that the heat evolved on diluting liquid sulfuric acid with water is a continuous function of the water used, and excluded absolutely the acceptance of definite hydrates as existing in the solution. Information about thermochemical measurement, a discussion…

  1. Magnetic properties of diluted magnetic semiconductors

    NASA Astrophysics Data System (ADS)

    de Jonge, W. J. M.; Swagten, H. J. M.

    1991-11-01

    A review will be given of the magnetic characteristics of diluted magnetic semiconductors and the relation with the driving exchange mechanisms. II-VI as well as IV-VI compounds will be considered. The relevance of the long-range interaction and the role of the carrier concentration will be emphasized.

  2. 1. Isotope Definitions and terms a) Isotopes and isotope ratios.

    E-print Network

    Saleska, Scott

    discrimination in C3 plants b) C3 vs C4 photosynthesis and the distinction in isotopes c) Measuring isotopic and fixation at night Why C4 plants? Problems with C3 photosynthesis Increase in photorespiration - in hot dry fractionation c) Simple illustration with the water cycle 2. CO2 isotopes in photosynthesis a) Photosynthetic

  3. Deciphering the iron isotope message of the human body

    NASA Astrophysics Data System (ADS)

    Walczyk, Thomas; von Blanckenburg, Friedhelm

    2005-04-01

    Mass-dependent variations in isotopic composition are known since decades for the light elements such as hydrogen, carbon or oxygen. Multicollector-inductively coupled plasma mass spectrometry (MC-ICP-MS) and double-spike thermal ionization mass spectrometry (TIMS) permit us now to resolve small variations in isotopic composition even for the heavier elements such as iron. Recent studies on the iron isotopic composition of human blood and dietary iron sources have shown that lighter iron isotopes are enriched along the food chain and that each individual bears a certain iron isotopic signature in blood. To make use of this finding in biomedical research, underlying mechanisms of isotope fractionation by the human body need to be understood. In this paper available iron isotope data for biological samples are discussed within the context of isotope fractionation concepts and fundamental aspects of human iron metabolism. This includes evaluation of new data for body tissues which show that blood and muscle tissue have a similar iron isotopic composition while heavier iron isotopes are concentrated in the liver. This new observation is in agreement with our earlier hypothesis of a preferential absorption of lighter iron isotopes by the human body. Possible mechanisms for inducing an iron isotope effect at the cellular and molecular level during iron uptake are presented and the potential of iron isotope effects in human blood as a long-term measure of dietary iron absorption is discussed.

  4. An oxide-diluted magnetic semiconductor: Mn-doped ZnO

    Microsoft Academic Search

    T. Fukumura; Zhengwu Jin; A. Ohtomo; H. Koinuma; M. Kawasaki

    1999-01-01

    Epitaxial thin films of an oxide-diluted magnetic semiconductor, Mn-doped ZnO, were fabricated by pulsed-laser deposition technique. Solubility of Mn into ZnO exceeds thermal equilibrium limit as a result of nonequilibrium film growth process. As Mn content is increased, the lattice constants of both a and c axes of wurtzite Zn1-xMnxO films (x<0.35) increase and the band gap expands although considerable

  5. Isotope Shifts

    NASA Astrophysics Data System (ADS)

    Zamick, Larry

    2010-11-01

    A three parameter formula (3P) for isotope shifts r^2(n)= n C +n)n-1)/2A+[n/2]B is related to he staggering parameter G= 2 [r^2(n+1)-r^2(n)]/[r^(n+2)-r^2(n)] If A+B=0 then G=1 (no staggering). If A=0 there is no n dependence to the staggering.One can get G to almost be plus or minus infinity for certain n,but this does not necessarily mean that there are major changes in the nuclear structure. We consider Potassium and Argon isotopes. We also consider quadrupole and monopole core polarization with a delta interaction. We vary the oscillator length parameter of the valence particle but keep the core values fixed. We find for both modes the amount of core polarization decreases as we increase the radius of the valence particle relative to that of the core (for small deviations from the case where the core and valence length parameters are the same).

  6. 40 CFR 1065.667 - Dilution air background emission correction.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 2010-07-01 false Dilution air background emission correction...ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR POLLUTION CONTROLS ENGINE-TESTING PROCEDURES...Requirements § 1065.667 Dilution air background emission...

  7. 40 CFR 1065.667 - Dilution air background emission correction.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 2014-07-01 false Dilution air background emission correction...ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR POLLUTION CONTROLS ENGINE-TESTING PROCEDURES...Requirements § 1065.667 Dilution air background emission...

  8. 40 CFR 1065.667 - Dilution air background emission correction.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 2012-07-01 false Dilution air background emission correction...ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR POLLUTION CONTROLS ENGINE-TESTING PROCEDURES...Requirements § 1065.667 Dilution air background emission...

  9. 40 CFR 1065.667 - Dilution air background emission correction.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 2013-07-01 false Dilution air background emission correction...ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR POLLUTION CONTROLS ENGINE-TESTING PROCEDURES...Requirements § 1065.667 Dilution air background emission...

  10. 40 CFR 1066.610 - Dilution air background correction.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 2014-07-01 false Dilution air background correction. 1066.610...ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR POLLUTION CONTROLS VEHICLE-TESTING PROCEDURES...Calculations § 1066.610 Dilution air background correction....

  11. 40 CFR 1065.667 - Dilution air background emission correction.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 2011-07-01 false Dilution air background emission correction...ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR POLLUTION CONTROLS ENGINE-TESTING PROCEDURES...Requirements § 1065.667 Dilution air background emission...

  12. Dilution jet mixing program, supplementary report

    NASA Technical Reports Server (NTRS)

    Srinivasan, R.; White, C.

    1986-01-01

    The velocity and temperature distributions predicted by a 3-D numerical model and experimental measurements are compared. Empirical correlations for the jet velocity trajectory developed are presented. The measured velocity distributions for all test cases of phase through phase 3 are presented in the form of contour and oblique plots. quantification of the effects of the following on the jet mixing characteristics with a confined crossflow are: (1) orifice geometry momentum flux ratio and density ratio; (2) nonuniform mainstream temperature and velocity profiles upstream of dilution orifices; (3) cold versus hot jet injection; (4) cross-stream flow are a convergence as encountered in practical dilution zone geometries; (5) 2-D slot versus circular orifices; (6) discrete noncirculcer orifices; (7) single-sided versus opposed jets; (8) single row of jets.

  13. Polarized neutron reflectivity of dilute magnetic semiconductors

    Microsoft Academic Search

    Amitesh Paul; Heiko Braak; Daniel E. Bürgler; Reinert Schreiber; Diana Rata; Peter Grünberg; Claus M. Schneider; Thomas Brückel

    2007-01-01

    We report on a polarized neutron reflectivity investigation of the magnetization in Ge-based dilute magnetic semiconductors. We could observe a net magnetization from the splitting of the non-spin flip reflectivity patterns, which measure the magnetic moment parallel and antiparallel to the applied field. This contrast is visible at 50K, at remanence and it is pronounced at higher fields even at

  14. Transversal inhomogeneities in dilute vibrofluidized granular fluids

    E-print Network

    J. Javier Brey; M. J. Ruiz-Montero; F. Moreno; R. Garcia-Rojo

    2002-01-24

    The spontaneous symmetry breaking taking place in the direction perpendicular to the energy flux in a dilute vibrofluidized granular system is investigated, using both a hydrodynamic description and simulation methods. The latter include molecular dynamics and direct Monte Carlo simulation of the Boltzmann equation. A marginal stability analysis of the hydrodynamic equations, carried out in the WKB approximation, is shown to be in good agreement with the simulation results. The shape of the hydrodynamic profiles beyond the bifurcation is discussed.

  15. Thermoluminescence in ultra-high dilution research

    Microsoft Academic Search

    R. van Wijk; S. Bosman; E. P. A. van Wijk

    Objective Thermoluminescence of homeopathically prepared ultra-high dilutions of lithium chloride in D2O (10 -30 g cm-3 ; C15 LiCl in D2O) and similarly pre- pared D2O (C15 D2O) was compared in three experiments varying a) time between preparation of substance and time of experimentation, and b) time between irradiation and thermoluminescence recording. Data were also compared with a normal solution

  16. Preservative activity in diluted corticosteroid creams.

    PubMed

    Hugo, W B; Denyer, S P; York, H L; Tucker, J D

    1984-09-01

    The preservative efficacy of both 'Betnovate' and 'Synalar' creams diluted 1:1 with 'Unguentum Merck' was investigated. Each formulation was challenged with Escherichia coli, Staphylococcus aureus and Pseudomonas aeruginosa at an initial inoculum level of approximately 1 X 10(6) viable organisms per gram of cream. All formulations tested were found to be effectively preserved against the organisms used and no viable bacteria were detected 7 days after inoculation. PMID:6208253

  17. A dilution refrigerator insert for standard ILL cryostats K. Neumaier

    E-print Network

    Paris-Sud XI, Université de

    773 A dilution refrigerator insert for standard ILL cryostats K. Neumaier WMI Garching, F.R.G. A-1.2 K) the sample stick was replaced by a dilution refrigerator insert with a minimum no temperatures, we replaced the sample stick by a dilution refrigerator insert (Fig. 1). The large cooling power

  18. Dilution and microsegregation in dissimilar metal welds between super austenitic

    E-print Network

    DuPont, John N.

    Dilution and microsegregation in dissimilar metal welds between super austenitic stainless steel. An important aspect of this processing is the weld metal dilution level, which will control the composition. Since the Fe content of the weld is controlled by dilution, which in turn is controlled by the welding

  19. Theory of linear viscoelasticity of semiflexible rods in dilute solution

    E-print Network

    Natelson, Douglas

    Theory of linear viscoelasticity of semiflexible rods in dilute solution V. Shankar, Matteo received 19 June 2002) Synopsis We present a theory of the linear viscoelasticity of dilute solutions semiflexible rods for lengths up to L Lp , and with linear viscoelastic data for dilute solutions of poly

  20. Effective Viscosity Properties of Dilute Suspensions of Arbitrarily Shaped Particles

    E-print Network

    Ammari, Habib

    Effective Viscosity Properties of Dilute Suspensions of Arbitrarily Shaped Particles Habib Ammari. Mathematics subject classifications (MSC2000): 35B30. Keywords: effective viscosity, dilute suspension and the intrinsic viscosities of the suspension in the dilute limit in terms of the volume fraction occupied

  1. Dilution of brackish waters in irrigation networks —An analytic approach

    Microsoft Academic Search

    G. Sinai; E. Koch; M. Farbman

    1985-01-01

    Rational method of improving poor water by the admixture of good-quality water for irrigation purposes is proposed and demonstrated. The principles of the dilution process, carried out in dilution junctions, are explained. Continuity equations for water and for the mass of relevant substances present in the water are derived for a dilution junction. These equations characterize the suitability of the

  2. Number-conserving master equation theory for a dilute Bose-Einstein condensate

    SciTech Connect

    Schelle, Alexej [Physikalisches Institut der Albert-Ludwigs Universitaet Freiburg, Hermann-Herder Str. 3, D-79104 Freiburg (Germany); Laboratoire Kastler-Brossel, Universite Pierre et Marie Curie-Paris 6, ENS, CNRS, 4 Place Jussieu, F-75005 Paris (France); Wellens, Thomas; Buchleitner, Andreas [Physikalisches Institut der Albert-Ludwigs Universitaet Freiburg, Hermann-Herder Str. 3, D-79104 Freiburg (Germany); Delande, Dominique [Laboratoire Kastler-Brossel, Universite Pierre et Marie Curie-Paris 6, ENS, CNRS, 4 Place Jussieu, F-75005 Paris (France)

    2011-01-15

    We describe the transition of N weakly interacting atoms into a Bose-Einstein condensate within a number-conserving quantum master equation theory. Based on the separation of time scales for condensate formation and noncondensate thermalization, we derive a master equation for the condensate subsystem in the presence of the noncondensate environment under the inclusion of all two-body interaction processes. We numerically monitor the condensate particle number distribution during condensate formation, and derive a condition under which the unique equilibrium steady state of a dilute, weakly interacting Bose-Einstein condensate is given by a Gibbs-Boltzmann thermal state of N noninteracting atoms.

  3. A superior process for forming titanium hydrogen isotopic films

    NASA Technical Reports Server (NTRS)

    Steinberg, R.; Alger, D. L.; Cooper, D. W.

    1975-01-01

    Process forms stoichiometric, continuous, strongly bonded titanium hydrogen isotopic films. Films have thermal and electrical conductivities approximately the same as bulk pure titanium, ten times greater than those of usual thin films.

  4. Helium isotopes in hydrothermal volcanic fluids of the Azores archipelago

    NASA Astrophysics Data System (ADS)

    Jean-Baptiste, P.; Allard, P.; Coutinho, R.; Ferreira, T.; Fourré, E.; Queiroz, G.; Gaspar, J. L.

    2009-04-01

    We present the first helium isotope data for thermal waters and gas emissions on the islands of Terceira, Graciosa, Faial, Pico and Flores, as well as new data for Sao Miguel. The results allow us to track current mantle degassing associated with the Azores hot spot, to delineate its spatial distribution and to discuss its possible origin. As a general rule, we find that free gases tend to display somewhat higher 3He/ 4He ratio than groundwaters. We argue that this difference is likely due to radiogenic helium inputs to aquifers during water-rock interactions and, therefore, that gas phases are the fluid carriers with the most representative of mantle source signature. The measured 3He/ 4He ratios (normalized to the air ratio, Ra) range from lower-than-MORB values (5.23-6.07 Ra) on central Sao Miguel, to MORB values on Faial (8.53 Ra) and Flores (8.04 Ra) - located on either side of the Mid-Atlantic Ridge - and to plume-type values on Graciosa (11.2 Ra) and Terceira (13.5 Ra) where free gases also display ten times higher-than-MORB CO 2/ 3He ratios (1.8-2.6 × 10 10). Such a wide He isotopic range and its spatial distribution corroborate with available data for volcanic rocks, indicating that plume's head presently underlies the central part of the archipelago. The plume-type 3He/ 4He ratios on Terceira and Graciosa agree with geochemical and seismic evidence of a deep-rooted mantle plume feeding the Azores hot spot. Our finding that high 3He/ 4He ratios correspond to low 3He concentrations and high (arc-type) CO 2/ 3He values exclude a simple plume supply of 3He-rich primitive mantle. Instead, the simultaneity of both elevated CO 2/ 3He and 3He/ 4He ratios is best explained by a 3He-rich contribution from the lower mantle diluted in a CO 2-rich feeding plume that contains a recycled altered oceanic plate component. The alternative possibility of an enhanced time-integrated 3He/(U + Th) ratio in the Azores plume due to a greater compatibility of helium relative to U and Th during melting events is difficult to reconcile with the enriched pattern of volcanic rocks from the central islands. In any case, the Azores plume should derive from a mantle reservoir that could escape convective homogenization for a very long period of time, in agreement with sub-chondritic osmium isotopic ratios in volcanic rocks from the central islands of the archipelago.

  5. Laser isotope separation

    Microsoft Academic Search

    M. Yamashita; H. Kashiwagi

    1976-01-01

    The present state of the art is reviewed and developments on the horizon are sketched. Major chapter headings are: isotope shift and optical spectrum; present state of the art in laser isotope separation (LIS); future trends in research on laser isotope separation. Isotope shift data on nuclides and molecules of interest are tabulated. Published LIS methods are reviewed (LIS of

  6. 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.

  7. Isotopic composition and concentration of sulfur in carbonaceous chondrites

    NASA Technical Reports Server (NTRS)

    Gao, Xia; Thiemens, Mark H.

    1993-01-01

    New sulfur isotopic ratio measurements are reported for seven carbonaceous chondrites. Newly developed procedures permit measurement of delta S-33, delta S-34, and delta S-36 at precisions significantly greater than previously reported. A search for S-36 nucleosynthetic anomalies coproduced with anomalies in, for example, Ti-50 and Ca-48 was negative. The high endemic sulfur concentration probably dilutes any S-36 anomaly, and separation of individual sulfur phases may be needed to identify S-36 carrier phases. Large internal isotopic variations are observed, deriving from parent body and possibly nebular processes. Chondrule separates from Allende demonstrate isotopic compositions which vary as a function of diameter. High-temperature gas-solid exchange and a two-component mixing model may account for the observations. High-resolution isotopic data and structural information are reported for organic sulfur compounds separated by chemical extractions. The insoluble organics appear to be of either aliphatic or alicyclic structure and are dominant phases.

  8. 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 that equilibrium was approached, such as lack of variance with run duration or with approach from higher as compared with lower temperature. The preliminary results, particularly those from the spiked runs, suggest that quartz and muscovite are susceptible to appreciable changes in Li isotopic composition within short times through diffusion by interaction with a Li-bearing fluid at 500° C. At that temperature, the quartz run products were enriched in 7Li by approximately 9‰ compared with the fluid run products but were depleted in 7Li by approximately 10‰ compared with the muscovite run products. The results also suggest that the Li isotopic composition of the two minerals is likely influenced by temperature, though not measurably by pressure. The results may provide a way to model the Li isotopic composition of hydrothermal fluids that have interacted with felsic rocks. For example, if the quartz starting specimen used in the experiments were assumed hypothetically to have crystallized in a pegmatite body that interacted with a Li-bearing fluid at 500° C, the Li isotopic composition of the starting specimen (? 7Li = +28) would imply a model ? 7Li value of +19 for the fluid (? Quartz-Fluid = 9).

  9. Isotope impurity doping in graphene

    NASA Astrophysics Data System (ADS)

    Rodriguez-Nieva, Joaquin

    2012-02-01

    Isotope impurities provide a powerful technique to study phonon related properties of graphene. The advantage of this approach is that phonon frequencies or thermal properties can be modified so that we can identify the origin of the interaction in the unknown optical spectra without changing either the electrical or chemical properties. In the presence of a ^13C isotope impurity in a normally ^12C lattice, the phonon wavefunction of graphene becomes localized. When we discuss the electron-phonon interaction of graphene, we treat phonons in terms of a delocalized wavefunction. However, in real graphene, we know that 2% of the atoms are ^13C and thus phonons have a finite lifetime, which results in a natural width in the Raman spectra. Many experimental results were obtained recently related to isotopic doping of graphene and carbon nanotubes and its effect on Raman spectra. In this work, we calculate the localization length of the phonons as well as the power law dependence for this effect. At the same time, we calculate the phonon lifetime of the different phonon modes within first order perturbation theory to elucidate the physical mechanisms behind isotope doping and to provide further insight into the experimental results.

  10. Inhibition of oil plume dilution in Langmuir ocean circulation

    NASA Astrophysics Data System (ADS)

    Yang, Di; Chamecki, Marcelo; Meneveau, Charles

    2014-03-01

    Oil spills from deep-water blowouts rise through and interact with the ocean mixed layer and Langmuir turbulence, leading to considerable diversity of oil slick dilution patterns observed on the ocean surface. Certain conditions can drive oil droplet plumes to organize into distinct bands called windrows, inhibiting oil dilution. Observations of blurred or even diffused plumes are also common, but conditions under which these various dilution regimes emerge are not well understood. Here we use large eddy simulations to explain and quantify the dilution patterns and their dependence on relevant physical parameters. Two mechanisms, the downwelling and dilution due to Langmuir cells and the inhibition of dilution due to buoyancy of oil droplets, compete. This competition can be characterized by the ratio of Stokes drift to droplet rise velocity—the drift-to-buoyancy parameter, Db. We find that plume appearance and quantitative measures of relative dilution depend mainly on Db.

  11. Global NOx Measurements in Turbulent Nitrogen-Diluted Hydrogen Jet Flames

    SciTech Connect

    Weiland, N.T.; Strakey, P.A.

    2007-03-01

    Turbulent hydrogen diffusion flames diluted with nitrogen are currently being studied to assess their ability to achieve the DOE Turbine Program’s aggressive emissions goal of 2 ppm NOx in a hydrogen-fueled IGCC gas turbine combustor. Since the unstrained adiabatic flame temperatures of these diluted flames are not low enough to eliminate thermal NOx formation the focus of the current work is to study how the effects of flame residence time and global flame strain can be used to help achieve the stated NOx emissions goal. Dry NOx measurements are presented as a function of jet diameter nitrogen dilution and jet velocity for a turbulent hydrogen/nitrogen jet issuing from a thin-lipped tube in an atmospheric pressure combustor. The NOx emission indices from these experiments are normalized by the flame residence time to ascertain the effects of global flame strain and fuel Lewis Number on the NOx emissions. In addition dilute hydrogen diffusion flame experiments were performed in a high-pressure combustor at 2 4 and 8 atm. The NOx emission data from these experiments are discussed as well as the results from a Computational Fluid Dynamics modeling effort currently underway to help explain the experimental data.

  12. 40 CFR 1065.546 - Validation of minimum dilution ratio for PM batch sampling.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ...diluted flow), dilution air flow, and dilute exhaust...based on the measured intake air molar flow rate and the...flow rate based on intake air, fuel rate measurements, and...Determine minimum dilution ratio based on tracer gas...

  13. 40 CFR 1065.546 - Validation of minimum dilution ratio for PM batch sampling.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ...diluted flow), dilution air flow, and dilute exhaust...based on the measured intake air molar flow rate and the...flow rate based on intake air, fuel rate measurements, and...Determine minimum dilution ratio based on tracer gas...

  14. Hydrologic Cycle Response to the Paleocene-Eocene Thermal Maximum at Austral, High-Latitude Site 690 as Revealed by In Situ Measurements of Foraminiferal Oxygen Isotope and Mg/Ca Ratios

    NASA Astrophysics Data System (ADS)

    Kozdon, R.; Kelly, D.; Fournelle, J.; Valley, J. W.

    2012-12-01

    Earth surface temperatures warmed by ~5°C during an ancient (~55.5 Ma) global warming event termed the Paleocene-Eocene thermal maximum (PETM). This transient (~200 ka) "hyperthermal" climate state had profound consequences for the planet's surficial processes and biosphere, and is widely touted as being an ancient analog for climate change driven by human activities. Hallmarks of the PETM are pervasive carbonate dissolution in the ocean basins and a negative carbon isotope excursion (CIE) recorded in variety of substrates including soil and marine carbonates. Together these lines of evidence signal the rapid (?30 ka) release of massive quantities (?2000 Gt) of 13C-depleted carbon into the exogenic carbon cycle. Paleoenvironmental reconstructions based on pedogenic features in paleosols, clay mineralogy and sedimentology of coastal and continental deposits, and land-plant communities indicate that PETM warmth was accompanied by a major perturbation to the hydrologic cycle. Micropaleontological evidence and n-alkane hydrogen isotope records indicate that increased poleward moisture transport reduced sea-surface salinities (SSSs) in the central Arctic Ocean during the PETM. Such findings are broadly consistent with predictions of climate model simulations. Here we reassess a well-studied PETM record from the Southern Ocean (ODP Site 690) in light of new ?18O and Mg/Ca data obtained from planktic foraminiferal shells by secondary ion mass spectrometry (SIMS) and electron microprobe analysis (EMPA), respectively. The unparalleled spatial resolution of these in situ techniques permits extraction of more reliable ?18O and Mg/Ca data by targeting of minute (?10 ?m spots), biogenic domains within individual planktic foraminifera that retain the original shell chemistry (Kozdon et al. 2011, Paleocean.). In general, the stratigraphic profile and magnitude of the ?18O decrease (~2.2‰) delimiting PETM warming in our SIMS-generated record are similar to those of published whole-shell ?18O records for this site; however, the mean baseline of the SIMS ?18O record is consistently ~1-2‰ lower than that of the published records. We attribute this ?18O offset to post-depositional diagenesis, which added 18O-enriched secondary calcite to planktic shells biasing conventional measurements. In the SIMS ?18O record, a minimum value of -4.4‰ is attained ~43 ka after the CIE onset. This ?18O minimum coincides with both the minimum ?13C value of the CIE and an abundance peak in warm-water immigrant taxa (morozovellids) of planktic foraminifera. Congruence of these two datasets reflects warming of sea-surface temperatures (SSTs), but the magnitude of the SST anomaly captured by complementary Mg/Ca data (~5°C) cannot account for the full magnitude of the ?18O decrease. This discrepancy is reconciled by lowering seawater ?18O to a value (-2‰) well below that computed for an ice-free world (-1.2‰). We therefore conclude that, much like in the Arctic, increased poleward moisture transport enhanced Antarctic continental runoff and reduced SSSs in the Weddell Sea region during the PETM.

  15. Recovering chemical products from dilute fermentation broths

    SciTech Connect

    Busche, R.M.

    1983-01-01

    Resurgence of interest in the fermentation of renewable biomass to produce oxychemical feedstocks and specialty chemicals has suggested the corollary need for new energy-efficient processes to recover products from dilute aqueous broths. Of the commercially demonstrated processes, distillation appears most suitable for low boilers, while solvent extraction appears to be the method of choice for high boilers. A number of new approaches such as supercritical extraction, molecular sieve adsorption, and membrane separation hold promise for further development. In any event, the concomitant development of both new fermentation systems and recovery processes appears critical to the growth of a revitalized fermentation industry. 47 references, 14 figures, 5 tables.

  16. Dilution jet mixing program, phase 3

    NASA Technical Reports Server (NTRS)

    Srinivasan, R.; Coleman, E.; Myers, G.; White, C.

    1985-01-01

    The main objectives for the NASA Jet Mixing Phase 3 program were: extension of the data base on the mixing of single sided rows of jets in a confined cross flow to discrete slots, including streamlined, bluff, and angled injections; quantification of the effects of geometrical and flow parameters on penetration and mixing of multiple rows of jets into a confined flow; investigation of in-line, staggered, and dissimilar hole configurations; and development of empirical correlations for predicting temperature distributions for discrete slots and multiple rows of dilution holes.

  17. Theory of diluted magnetic semiconductor ferromagnetism

    PubMed

    Konig; Lin; MacDonald

    2000-06-12

    We present a theory of carrier-induced ferromagnetism in diluted magnetic semiconductors ( III1-xMnxV) which allows for arbitrary itinerant-carrier spin polarization and dynamic correlations. Both ingredients are essential in identifying the system's elementary excitations and describing their properties. We find a branch of collective modes, in addition to the spin waves and Stoner continuum which occur in metallic ferromagnets, and predict that the low-temperature spin stiffness is independent of the strength of the exchange coupling between magnetic ions and itinerant carriers. We discuss the temperature dependence of the magnetization and the heat capacity. PMID:10991011

  18. Three-dimensional structure of dilute pyroclastic density currents

    NASA Astrophysics Data System (ADS)

    Andrews, B. J.

    2013-12-01

    Unconfined experimental density currents dynamically similar to pyroclastic density currents (PDCs) suggest that cross-stream motions of the currents and air entrainment through currents' lateral margins strongly affects PDC behavior. Experiments are conducted within an air-filled tank 8.5 m long by 6.1 m wide by 2.6 m tall. Currents are generated by feeding heated powders down a chute into the tank at controlled rates to form dilute, particle-laden, turbulent gravity currents that are fed for 30 to 600 seconds. Powders include 5 ?m aluminum oxide, 25 ?m talc, 27 ?m walnut, 76 ?m glass beads and mixtures thereof. Experiments are scaled such that Froude, densimetric and thermal Richardson, particle Stokes and Settling numbers, and thermal to kinetic energy densities are all in agreement with dilute PDCs; experiments have lower Reynolds numbers that natural currents, but the experiments are fully turbulent, thus the large scale structures should be similar. The experiments are illuminated with 3 orthogonal laser sheets (650, 532, and 450 nm wavelengths) and recorded with an array of HD video cameras and a high speed camera (up to 3000 fps); this system provides synchronous observation of a vertical streamwise and cross-stream planes, and a horizontal plane. Ambient temperature currents tend to spread out radially from the source and have long run out distances, whereas warmer currents tend to focus along narrow sectors and have shorter run outs. In addition, when warm currents lift off to form buoyant plumes, lateral spreading ceases. The behavior of short duration currents are dominated by the current head; as eruption duration increases, current transport direction tends to oscillate back and forth (this is particularly true for ambient temperature currents). Turbulent structures in the horizontal plane show air entrainment and advection downstream. Eddies illuminated by the vertical cross-stream laser sheet often show vigorous mixing along the current margins, particularly after the current head has passed. In some currents, the head can persist as a large, vertically oriented vortex long after the bulk of the current has lifted off to form a coignimbrite plume. These unconfined experiments show that three-dimensional structures can affect PDC behavior and suggest that our typical cross-sectional or 'cartoon' understanding of PDCs misses what may be very important parts of PDC dynamics.

  19. Stoichiometric controls of mercury dilution by growth

    PubMed Central

    Karimi, Roxanne; Chen, Celia Y.; Pickhardt, Paul C.; Fisher, Nicholas S.; Folt, Carol L.

    2007-01-01

    Rapid growth could significantly reduce methylmercury (MeHg) concentrations in aquatic organisms by causing a greater than proportional gain in biomass relative to MeHg (somatic growth dilution). We hypothesized that rapid growth from the consumption of high-quality algae, defined by algal nutrient stoichiometry, reduces MeHg concentrations in zooplankton, a major source of MeHg for lake fish. Using a MeHg radiotracer, we measured changes in MeHg concentrations, growth and ingestion rates in juvenile Daphnia pulex fed either high (C:P = 139) or low-quality (C:P = 1317) algae (Ankistrodesmus falcatus) for 5 d. We estimated Daphnia steady-state MeHg concentrations, using a biokinetic model parameterized with experimental rates. Daphnia MeHg assimilation efficiencies (?95%) and release rates (0.04 d?1) were unaffected by algal nutrient quality. However, Daphnia growth rate was 3.5 times greater when fed high-quality algae, resulting in pronounced somatic growth dilution. Steady-state MeHg concentrations in Daphnia that consumed high-quality algae were one-third those of Daphnia that consumed low-quality algae due to higher growth and slightly lower ingestion rates. Our findings show that rapid growth from high-quality food consumption can significantly reduce the accumulation and trophic transfer of MeHg in freshwater food webs. PMID:17456601

  20. Stoichiometric controls of mercury dilution by growth.

    PubMed

    Karimi, Roxanne; Chen, Celia Y; Pickhardt, Paul C; Fisher, Nicholas S; Folt, Carol L

    2007-05-01

    Rapid growth could significantly reduce methylmercury (MeHg) concentrations in aquatic organisms by causing a greater than proportional gain in biomass relative to MeHg (somatic growth dilution). We hypothesized that rapid growth from the consumption of high-quality algae, defined by algal nutrient stoichiometry, reduces MeHg concentrations in zooplankton, a major source of MeHg for lake fish. Using a MeHg radiotracer, we measured changes in MeHg concentrations, growth and ingestion rates in juvenile Daphnia pulex fed either high (C:P = 139) or low-quality (C:P = 1317) algae (Ankistrodesmus falcatus) for 5 d. We estimated Daphnia steady-state MeHg concentrations, using a biokinetic model parameterized with experimental rates. Daphnia MeHg assimilation efficiencies (approximately 95%) and release rates (0.04 d(-1)) were unaffected by algal nutrient quality. However, Daphnia growth rate was 3.5 times greater when fed high-quality algae, resulting in pronounced somatic growth dilution. Steady-state MeHg concentrations in Daphnia that consumed high-quality algae were one-third those of Daphnia that consumed low-quality algae due to higher growth and slightly lower ingestion rates. Our findings show that rapid growth from high-quality food consumption can significantly reduce the accumulation and trophic transfer of MeHg in freshwater food webs. PMID:17456601

  1. The Statistical Mechanics of Dilute, Disordered Systems

    NASA Astrophysics Data System (ADS)

    Blackburn, Roger Michael

    Available from UMI in association with The British Library. Requires signed TDF. A graph partitioning problem with variable inter -partition costs is studied by exploiting its mapping on to the Ashkin-Teller spin glass. The cavity method is used to derive the TAP equations and free energy for both extensively connected and dilute systems. Unlike Ising and Potts spin glasses, the self-consistent equation for the distribution of effective fields does not have a solution solely made up of delta functions. Numerical integration is used to find the stable solution, from which the ground state energy is calculated. Simulated annealing is used to test the results. The retrieving activity distribution for networks of boolean functions trained as associative memories for optimal capacity is derived. For infinite networks, outputs are shown to be frozen, in contrast to dilute asymmetric networks trained with the Hebb rule. For finite networks, a steady leaking to the non-retrieving attractor is demonstrated. Simulations of quenched networks are reported which show a departure from this picture: some configurations remain frozen for all time, while others follow cycles of small periods. An estimate of the critical capacity from the simulations is found to be in broad agreement with recent analytical results. The existing theory is extended to include noise on recall, and the behaviour is found to be robust to noise up to order 1/c^2 for networks with connectivity c.

  2. ANALYSIS OF BORON DILUTION TRANSIENTS IN PWRS.

    SciTech Connect

    DIAMOND,D.J.BROMLEY,B.P.ARONSON,A.L.

    2004-02-04

    A study has been carried out with PARCS/RELAP5 to understand the consequences of hypothetical boron dilution events in pressurized water reactors. The scenarios of concern start with a small-break loss-of-coolant accident. If the event leads to boiling in the core and then the loss of natural circulation, a boron-free condensate can accumulate in the cold leg. The dilution event happens when natural circulation is re-established or a reactor coolant pump (RCP) is restarted in violation of operating procedures. This event is of particular concern in B&W reactors with a lowered-loop design and is a Generic Safety Issue for the U.S. Nuclear Regulatory Commission. The results of calculations with the reestablishment of natural circulation show that there is no unacceptable fuel damage. This is determined by calculating the maximum fuel pellet enthalpy, based on the three-dimensional model, and comparing it with the criterion for damage. The calculation is based on a model of a B&W reactor at beginning of the fuel cycle. If an RCP is restarted, unacceptable fuel damage may be possible in plants with sufficiently large volumes of boron-free condensate in the cold leg.

  3. EDITORIAL: Focus on Dilute Magnetic Semiconductors FOCUS ON DILUTE MAGNETIC SEMICONDUCTORS

    Microsoft Academic Search

    Scott A. Chambers; Bryan Gallagher

    2008-01-01

    This focus issue of New Journal of Physics is devoted to the materials science of dilute magnetic semiconductors (DMS). A DMS is traditionally defined as a diamagnetic semiconductor doped with a few to several atomic per cent of some transition metal with unpaired d electrons. Several kinds of dopant dopant interactions can in principle couple the dopant spins leading to

  4. Thermal springs in Lake Baikal

    USGS Publications Warehouse

    Shanks, Wayne C., III; Callender, E.

    1992-01-01

    The ??18O values of pore wqters range from -15.2??? to -16.7???, and ??D values range from -119??? to -126??? (both isotopes determined relative to standard mean ocean water [SMOW]). Bottom water in Lake Baikal has a ??18O value of -5.6??? and a ??D value of -120???. Pore waters in the vent area are significantly enriched in Mg, K, Ca, and especially Na and have the lowest ??D and ??18O values; these pore waters are isotopically and chemically distinct from pore waters in other, more typical parts of the lake. The pore-water isotopic data fall on a local meteoric water line, and covariations in water isotopes and chemistry are not consistent with evaporation or hydrothermal water-rock interaction. The thermal springs represent discharging meteoric waters that have been gently heated during subsurface circulation and are largely unaltered isotopically. Chemical variations are most likely due to dissolution of subsurface evaporites. -from Authors

  5. Dynamic Stresses in the LHC TCDS Diluter from 7 TeV Beam Loading

    E-print Network

    Goddard, B; Presland, A; Weterings, W

    2006-01-01

    In the event of an unsynchronised beam abort, the MSD extraction septum of the LHC beam dumping system is protected from damage by the TCDS diluter. The simultaneous constraints of obtaining sufficient beam dilution while ensuring the survival of the TCDS make the design difficult, with high thermally induced dynamic stresses occurring in the material needed to attenuate the particle showers induced by the primary beam impact. In this paper, full 3D simulations are described where the worst-case beam loading has been used to generate the local temperature rise and to follow the resulting time evolution of the mechanical stresses. The results and the accompanying design changes for the TCDS, to provide an adequate performance margin, are detailed.

  6. Spectroscopic studies of GTA welding plasmas. Temperature calculation and dilution measurement

    NASA Astrophysics Data System (ADS)

    Lacroix, D.; Boudot, C.; Jeandel, G.

    1999-10-01

    A spectroscopic study of the GTAW plasma-plume created during the welding of stainless steel and other materials (iron, nickel and chromium) has been carried out. The spectra of these plasmas have been studied for several welding parameters. Temperature calculations are based on the observation of relative intensities and shapes of the emission peaks. We assume that the plasma is in local thermal equilibrium. The temperature is calculated with the Boltzmann plot method from twelve iron emission lines (in the range 368 385 nm): it varies between 9650 and 12 100 K. Dilution experiments have been carried out. We checked the mixing of metals: during welding of two different metallic plates and during welding with an Inconel wire. Dilution is monitored following the intensity of some characteristic emission lines (chromium and nickel). Comparison of spectroscopic results and metallographic ones is made.

  7. Modeling Sucrose Hydrolysis in Dilute Sulfuric Acid Solutions at Pretreatment Conditions for Lignocellulosic Biomass

    SciTech Connect

    Bower, S.; Wickramasinghe, R.; Nagle, N. J.; Schell, D. J.

    2008-01-01

    Agricultural and herbaceous feedstocks may contain appreciable levels of sucrose. The goal of this study was to evaluate the survivability of sucrose and its hydrolysis products, fructose and glucose, during dilute sulfuric acid processing at conditions typically used to pretreat lignocellulose biomass. Solutions containing 25 g/l sucrose with 0.1-2.0% (w/w) sulfuric acid concentrations were treated at temperatures of 160-200 C for 3-12 min. Sucrose was observed to completely hydrolyze at all treatment conditions. However, appreciable concentrations of fructose and glucose were detected and glucose was found to be significantly more stable than fructose. Different mathematical approaches were used to fit the kinetic parameters for acid-catalyzed thermal degradation of these sugars. Since both sugars may survive dilute acid pretreatment, they could provide an additional carbon source for production of ethanol and other bio-based products.

  8. The preparation and calibration of calcium synthetic isotope mixtures

    NASA Astrophysics Data System (ADS)

    Berglund, M.; Hennessy, C.; Richter, S.; Fortunato, G.; Wunderli, S.

    2010-12-01

    Calcium is one of the most-abundant elements but still there is no calibrated measurement of its isotopic composition. In this work a set of six mixtures were gravimetrically prepared from highly enriched calcium isotopes. The purification of the enriched calcium material was done by vacuum distillation. Solutions of the now highly enriched metallic 40Ca, 42Ca, 44Ca and 48Ca where prepared in an inert atmosphere. Mixtures were then made gravimetrically with the isotope ratios in Table 1. The measurements of the mixtures were done by a total evaporation method for isotopic analysis by multi-collector thermal ionization mass spectrometry (TIMS). This work describes the preparation, measurement and the calibrated results of the mixtures and mother solutions.Table 1: Isotope ratios of calcium isotope mixtures

  9. 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 other [4], some authors have claimed that the 37Cl/35Cl ratio of geological samples obtained by TIMS technique are, in general, misleadingly too high and variable compared to those of IRMS [3]. For eample, 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]. In order to clarify the stable chlorine isotope features of early solar system materials, we have initiated development of the TIMS technique at NASA JSC applicable to analysis of small amounts of meteoritic and planetary materials. We report here the current status of chlorine isotope analysis at NASA JSC.

  10. Isotopes and Hydrology

    NSDL National Science Digital Library

    This program provides a clickable periodic table that links elements to additional information about their isotopic systems. Information is provided about the isotopes important to hydrology, their applications, how they are measured, and how much it costs for an analysis.

  11. ChemTeacher: Isotopes

    NSDL National Science Digital Library

    2011-01-01

    ChemTeacher compiles background information, videos, articles, demonstrations, worksheets and activities for high school teachers to use in their classrooms. The Isotopes page includes resources for teaching students about the structure and uses of isotopes.

  12. Fe and Si isotope variations at Cedar Butte volcano; insight into magmatic differentiation

    NASA Astrophysics Data System (ADS)

    Zambardi, Thomas; Lundstrom, Craig C.; Li, Xiaoxiao; McCurry, Michael

    2014-11-01

    This study presents the stable isotopic variations of both Si and Fe recorded in a single well-characterized magmatic suite from Cedar Butte volcano (ID, USA), as well as a sill with progressive compositional change within Finland granophyre (Duluth Complex, MN, USA). Both isotopic systems show a significant enrichment in heavy isotopes in the more differentiated materials, in agreement with previous studies. In addition, the Finland granophyre sill shows a strong dependence between the isotopic composition and the sampling depth, suggesting the isotopic compositions follow a temperature gradient in which the cold part systematically enriches in heavy isotopes. From these results it appears that at Cedar Butte, neither crystal fractionation, nor crustal contamination, nor late stage fluid exsolution can likely explain the isotopic variations we observe for both Fe and Si. We rather attribute these isotopic fractionations to a thermal migration process involving a top-down sill injection during which the isotopic distribution mostly follows a vertical temperature gradient.

  13. Enhanced diffusion of tracer particles in dilute bacterial suspensions.

    PubMed

    Morozov, Alexander; Marenduzzo, Davide

    2014-04-28

    Swimming bacteria create long-range velocity fields that stir a large volume of fluid and move around passive particles dispersed in the fluid. Recent experiments and simulations have shown that long-time mean-squared displacement of passive particles in a bath of swimming bacteria exhibits diffusive behaviour with an effective diffusion coefficient significantly larger than its thermal counterpart. A comprehensive theoretical prediction of this effective diffusion coefficient and the understanding of the enhancement mechanism remain a challenge. Here, we adapt the kinetic theory by Lin et al., J. Fluid Mech., 2011, 669, 167 developed for 'squirmers' to the bacterial case to quantitatively predict enhanced diffusivity of tracer particles in dilute two- and three-dimensional suspensions of swimming bacteria. We demonstrate that the effective diffusion coefficient is a product of the bacterial number density, their swimming speed, a geometric factor characterising the velocity field created by a single bacterium, and a numerical factor. We show that the numerical factor is, in fact, a rather strong function of the system parameters, most notably the run length of the bacteria, and that these dependencies have to be taken into account to quantitatively predict the enhanced diffusivity. We perform molecular-dynamics-type simulations to confirm the conclusions of the kinetic theory. Our results are in good agreement with the values of enhanced diffusivity measured in recent two- and three-dimensional experiments. PMID:24668266

  14. Characterization of the Dilute Ising Antiferromagnet

    SciTech Connect

    Wiener, T.

    2000-09-12

    A spin glass is a magnetic ground state in which ferromagnetic and antiferromagnetic exchange interactions compete, thereby creating frustration and a multidegenerate state with no long range order. An Ising system is a system where the spins are constrained to lie parallel or antiparallel to a primary axis. There has been much theoretical interest in the past ten years in the effects of applying a magnetic field transverse to the primary axis in an Ising spin glass at low temperatures and thus study phase transitions at the T=0 limit. The focus of this study is to search for and characterize a new Ising spin glass system. This is accomplished by site diluting yttrium for terbium in the crystalline material TbNi{sub 2}Ge{sub 2}. The first part of this work gives a brief overview of the physics of rare earth magnetism and an overview of experimental characteristics of spin glasses. This is followed by the methodology used to manufacture the large single crystals used in this study, as well as the measurement techniques used. Next, a summary of the results of magnetic measurements on across the dilution series from pure terbium to pure yttrium is presented. This is followed by detailed measurements on particular dilutions which demonstrate spin glass behavior. Pure TbNi{sub 2}Ge{sub 2} is an Ising antiferromagnet with a several distinct metamagnetic states below 17 K. As the terbium is alloyed with yttrium, these magnetic states are weakened in a consistent manner, as is seen in measurements of the transition temperatures and analysis of Curie-Weiss behavior at high temperature. At low concentrations of terbium, below 35%, long range order is no longer present and a spin-glass-like state emerges. This state is studied through various measurements, dc and ac susceptibility, resistivity, and specific heat. This magnetic behavior was then compared to that of other well characterized spin glasses. It is concluded that there is a region of concentration s for which a spin glass state is formed with the best spin glasses existing between the concentration of 25% and 30%.

  15. Dilute acid/metal salt hydrolysis of lignocellulosics

    DOEpatents

    Nguyen, Quang A. (Golden, CO); Tucker, Melvin P. (Lakewood, CO)

    2002-01-01

    A modified dilute acid method of hydrolyzing the cellulose and hemicellulose in lignocellulosic material under conditions to obtain higher overall fermentable sugar yields than is obtainable using dilute acid alone, comprising: impregnating a lignocellulosic feedstock with a mixture of an amount of aqueous solution of a dilute acid catalyst and a metal salt catalyst sufficient to provide higher overall fermentable sugar yields than is obtainable when hydrolyzing with dilute acid alone; loading the impregnated lignocellulosic feedstock into a reactor and heating for a sufficient period of time to hydrolyze substantially all of the hemicellulose and greater than 45% of the cellulose to water soluble sugars; and recovering the water soluble sugars.

  16. 21 CFR 866.2500 - Microtiter diluting and dispensing device.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ...ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES IMMUNOLOGY AND MICROBIOLOGY DEVICES Microbiology Devices § 866.2500 Microtiter diluting and dispensing device. (a) Identification....

  17. 21 CFR 866.2500 - Microtiter diluting and dispensing device.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ...ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES IMMUNOLOGY AND MICROBIOLOGY DEVICES Microbiology Devices § 866.2500 Microtiter diluting and dispensing device. (a) Identification....

  18. 21 CFR 866.2500 - Microtiter diluting and dispensing device.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ...ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES IMMUNOLOGY AND MICROBIOLOGY DEVICES Microbiology Devices § 866.2500 Microtiter diluting and dispensing device. (a) Identification....

  19. 21 CFR 866.2500 - Microtiter diluting and dispensing device.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ...ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES IMMUNOLOGY AND MICROBIOLOGY DEVICES Microbiology Devices § 866.2500 Microtiter diluting and dispensing device. (a) Identification....

  20. Formation of subsurface waters of oil and gas-bearing basins, according to isotopic data

    Microsoft Academic Search

    R. P. Gottikh

    1981-01-01

    The author examines certain aspects of the origin and formation of subsurface waters of oil- and gas-bearing basins. An investigation of the isotopic composition of the hydrogen of the waters revealed that the waters of these basins are of the sedimentation type, diluted with meteoric waters during periods in which ancient infiltration regimes were operative. Within the limits of the