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Sample records for isotopic equilibrium method

  1. The three-isotope method for equilibrium isotope fractionation factor determination: Unfounded optimism

    Science.gov (United States)

    Cao, X.; Hayles, J. A.; Bao, H.

    2015-12-01

    The equilibrium isotope fractionation factor α is a fundamental parameter in stable isotope geochemistry. Although equilibrium α can be determined by theoretical calculation or by measurement of natural samples, direct laboratory experiments are ultimately required to verify those results. The attainment of a true exchange equilibrium in experiments is often difficult, but three methods have been devised and used to ensure that an equilibrium α has been obtained in an isotope exchange experiment. These are the two-directional method, partial-exchange method, and three-isotope method. Of these, the three-isotope method is thought to be the most rigorous. Using water-water exchange as a basic unit, we have developed a set of complex exchange models to study when and why the three-isotope method may work well or not. We found that the method cannot promise to lead to an equilibrium α before the kinetic complexity of the specific exchange experiment is known. An equilibrium point in δ17O-δ18O space can be reached only when all of the isotope exchange pathways are fully reversible, i.e. there is no mass loss at any instant, and the forward and backward reactions share the same pathway. If the exchange pathways are not fully reversible, steady state may be reached, but a steady state α can be very different from the equilibrium α. Our results validated the earlier warning that the trajectory for three-isotope evolution in δ17O-δ18O space may be a distinctly curved line or contain more than one straight line due to the non-fully reversible isotope exchange reactions. The three-isotope method for equilibrium α determination is not as rigorous or as promising as it may seem. Instead, the trajectory of three-isotope evolution provides detailed insights into the kinetics of isotope exchange between compounds. If multiple components exist in the exchange system, the δ17O-δ18O evolving trajectory would be more complex.

  2. Determination of the Fe(II)aq-magnetite equilibrium iron isotope fractionation factor using the three-isotope method and a multi-direction approach to equilibrium

    Science.gov (United States)

    Frierdich, Andrew J.; Beard, Brian L.; Scherer, Michelle M.; Johnson, Clark M.

    2014-04-01

    Magnetite is ubiquitous in the Earth's crust and its presence in modern marine sediments has been taken as an indicator of biogeochemical Fe cycling. Magnetite is also the most abundant Fe oxide in banded iron formations (BIFs) that have not been subjected to ore-forming alteration. Magnetite is therefore an important target of stable Fe isotope studies, and yet interpretations are currently difficult because of large uncertainties in the equilibrium stable Fe isotope fractionation factors for magnetite relative to fluids and other minerals. In this study, we utilized the three-isotope method (57Fe-56Fe-54Fe) to explore isotopic exchange via an enriched-57Fe tracer, and natural mass-dependent fractionation using 56Fe/54Fe variations, during reaction of aqueous Fe(II) (Fe(II)aq) with magnetite. Importantly, we employed a multi-direction approach to equilibrium by reacting four 57Fe-enriched Fe(II) solutions that had distinct 56Fe/54Fe ratios, which identifies changes in the instantaneous Fe isotope fractionation factor and hence identifies kinetic isotope effects. We find that isotopic exchange can be described by two 56Fe/54Fe fractionations, where an initial rapid exchange (∼66% isotopic mixing within 1 day) involved a relatively small Fe(II)aq-magnetite 56Fe/54Fe fractionation, followed by slower exchange (∼25% isotopic mixing over 50 days) that was associated with a larger Fe(II)aq-magnetite 56Fe/54Fe fractionation; this later fractionation is interpreted to approach isotopic equilibrium between Fe(II)aq and the total magnetite. All four Fe(II) solutions extrapolate to the same final equilibrium 56Fe/54Fe fractionation for Fe(II)aq-magnetite of -1.56±0.20‰ (2σ) at 22 °C. Additional experiments that synthesized magnetite via conversion of ferrihydrite by reaction with aqueous Fe(II) yield final 56Fe/54Fe fractionations that are identical to those of the exchange experiments. Our experimental results agree well with calculated fractionation factors using

  3. Calculation of individual isotope equilibrium constants for geochemical reactions

    Science.gov (United States)

    Thorstenson, D.C.; Parkhurst, D.L.

    2004-01-01

    factors. The derivations can be extended to calculation of individual isotope equilibrium constants for ion pairs and equilibrium constants for isotopic species of other chemical elements. The individual isotope approach calculates the same phase isotopic compositions as existing methods, but also provides concentrations of individual species, which are needed in calculations of mass-dependent effects in transport processes. The equilibrium constants derived in this paper are used to calculate the example of gas-water equilibrium for CO2 in an acidic aqueous solution. ?? 2004 Elsevier Ltd.

  4. A Fast Numerical Method for the Calculation of the Equilibrium Isotopic Composition of a Transmutation System in an Advanced Fuel Cycle

    Directory of Open Access Journals (Sweden)

    F. Álvarez-Velarde

    2012-01-01

    Full Text Available A fast numerical method for the calculation in a zero-dimensional approach of the equilibrium isotopic composition of an iteratively used transmutation system in an advanced fuel cycle, based on the Banach fixed point theorem, is described in this paper. The method divides the fuel cycle in successive stages: fuel fabrication, storage, irradiation inside the transmutation system, cooling, reprocessing, and incorporation of the external material into the new fresh fuel. The change of the fuel isotopic composition, represented by an isotope vector, is described in a matrix formulation. The resulting matrix equations are solved using direct methods with arbitrary precision arithmetic. The method has been successfully applied to a double-strata fuel cycle with light water reactors and accelerator-driven subcritical systems. After comparison to the results of the EVOLCODE 2.0 burn-up code, the observed differences are about a few percents in the mass estimations of the main actinides.

  5. Theoretical prediction for several important equilibrium Ge isotope fractionation factors

    Science.gov (United States)

    Tang, M.; Li, X.; Liu, Y.

    2008-12-01

    As a newly emerging field, the stable isotope geochemistry of germanium (Ge) needs basic equilibrium fractionation factors to explore its unknown world. In this study, the Ge isotope fractionations between systems including the aqueous Ge(OH)4 and GeO(OH)3- which are the dominant Ge species in seawater, the Ge-bearing organic complexes (e.g. Ge-catechol, Ge-oxalic acid and Ge-citric acid), the quartz- (or opal- ), albite-, K-feldspar- and olivine- like mineral structures are studied. It is the first time that some geologically important equilibrium Ge isotope fractionation factors are reported. Surprisingly, up to 5 per mil large isotopic fractionations between these Ge isotope systems are found at 25 degree. These results suggest a potentially broad application for the Ge isotope geochemistry. Our theoretical calculations are based on the Urey model (or Bigeleisen-Mayer equation) and high level quantum chemistry calculations. The B3LYP/6-311+G(d,p) level quantum chemistry method and the explicit solvent model ("water droplet" method) are used. Many different conformers are also used for the aqueous complexes in order to reduce the possible errors coming from the differences of configurations in solution. The accuracy of our calculation of the Ge isotopic fractionations is estimated about 0.2 per mil. Our results show quartz-like or opal-like structure can enrich most heavy Ge isotopes. Relative to quartz (or opal), some Ge isotopic fractionations are (at 25 C): quartz-organic Ge = 4-5,quartz-Ge(OH)4 =0.9,quartz-GeO(OH)3- =1.5,quartz-albite=0.6,quartz-K-feldspar=0.4 and quartz-olivine=3.9 per mil. The large fractionations between inorganic Ge complexes and organic Ge ones could be used to distinguish the possible bio-involving processes. Our results suggest a good explanation to the experimental observations of Siebert et al. (2006) and Rouxel et al. (2006) and provide important constraints to the study of Ge cycle in ocean.

  6. Unbiased isotope equilibrium factors from partial isotope exchange experiments in 3-exchange site systems

    Science.gov (United States)

    Agrinier, Pierre; Javoy, Marc

    2016-09-01

    Two methods are available in order to evaluate the equilibrium isotope fractionation factors between exchange sites or phases from partial isotope exchange experiments. The first one developed by Northrop and Clayton (1966) is designed for isotope exchanges between two exchange sites (hereafter, the N&C method), the second one from Zheng et al. (1994) is a refinement of the first one to account for a third isotope exchanging site (hereafter, the Z method). In this paper, we use a simple model of isotope kinetic exchange for a 3-exchange site system (such as hydroxysilicates where oxygen occurs as OH and non-OH groups like in muscovite, chlorite, serpentine, or water or calcite) to explore the behavior of the N&C and Z methods. We show that these two methods lead to significant biases that cannot be detected with the usual graphical tests proposed by the authors. Our model shows that biases originate because isotopes are fractionated between all these exchanging sites. Actually, we point out that the variable mobility (or exchangeability) of isotopes in and between the exchange sites only controls the amplitude of the bias, but is not essential to the production of this bias as previously suggested. Setting a priori two of the three exchange sites at isotopic equilibrium remove the bias and thus is required for future partial exchange experiments to produce accurate and unbiased extrapolated equilibrium fractionation factors. Our modeling applied to published partial oxygen isotope exchange experiments for 3-exchange site systems (the muscovite-calcite (Chacko et al., 1996), the chlorite-water (Cole and Ripley, 1998) and the serpentine-water (Saccocia et al., 2009)) shows that the extrapolated equilibrium fractionation factors (reported as 1000 ln(α)) using either the N&C or the Z methods lead to bias that may reach several δ per mil in a few cases. These problematic cases, may be because experiments were conducted at low temperature and did not reach high

  7. ISOTOPE METHODS IN HOMOGENEOUS CATALYSIS.

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    BULLOCK,R.M.; BENDER,B.R.

    2000-12-01

    The use of isotope labels has had a fundamentally important role in the determination of mechanisms of homogeneously catalyzed reactions. Mechanistic data is valuable since it can assist in the design and rational improvement of homogeneous catalysts. There are several ways to use isotopes in mechanistic chemistry. Isotopes can be introduced into controlled experiments and followed where they go or don't go; in this way, Libby, Calvin, Taube and others used isotopes to elucidate mechanistic pathways for very different, yet important chemistries. Another important isotope method is the study of kinetic isotope effects (KIEs) and equilibrium isotope effect (EIEs). Here the mere observation of where a label winds up is no longer enough - what matters is how much slower (or faster) a labeled molecule reacts than the unlabeled material. The most careti studies essentially involve the measurement of isotope fractionation between a reference ground state and the transition state. Thus kinetic isotope effects provide unique data unavailable from other methods, since information about the transition state of a reaction is obtained. Because getting an experimental glimpse of transition states is really tantamount to understanding catalysis, kinetic isotope effects are very powerful.

  8. Assessment of surface reactivity of thorium oxide in conditions close to chemical equilibrium by isotope exchange {sup 229}Th/{sup 232}Th method

    Energy Technology Data Exchange (ETDEWEB)

    Suzuki-Muresan, Tomo; Perrigaud, Katy; Vandenborre, Johan; Ribet, Solange; Grambow, Bernd [Nantes Univ., CNRS/IN2P3 (France). SUBATECH Unite Mixte de Recherche 6457; Takamasa, Inai [TOKAI Univ., Kanagawa (Japan)

    2017-08-01

    This work aims to assess the solubility and the surface reactivity of crystallized thorium at pH 3.0 in presence of three types of solids: synthesized powder at 1300 C, crushed kernel, and intact kernel. In this study, the kernel is composed by the core solid from high temperature reactors (HTR) sphere particles. The originality of this work consisted in following in a sequential order the kinetic of dissolution, the surface reactivity in presence of isotope tracer {sup 229}Th, and its desorption process. Long time experiments (634 days) allowed to get deeper understanding on the behavior of the surface reactivity in contact with the solution. Solubility values are ranging from 0.3 x 10{sup -7} mol.L{sup -1} to 3 x 10{sup -7} mol.L{sup -1} with a dissolution rate of 10{sup -6}-10{sup -4} g.m{sup -2} day{sup -1}. PHREEQC modeling showed that crystallized ThO{sub 2}(cr, 20 nm) phase controls the equilibrium in solution. Isotope exchange between {sup 229}Th and {sup 232}Th indicated that well-crystallized phase exist as an inert surface regarding to the absence of exchange between surface solid and solution.

  9. The oxygen isotope equilibrium fractionation between sulfite species and water

    Science.gov (United States)

    Müller, Inigo A.; Brunner, Benjamin; Breuer, Christian; Coleman, Max; Bach, Wolfgang

    2013-11-01

    Sulfite is an important sulfoxy intermediate in oxidative and reductive sulfur cycling in the marine and terrestrial environment. Different aqueous sulfite species exist, such as dissolved sulfur dioxide (SO2), bisulfite (HSO3-), pyrosulfite (S2O52-) and sulfite sensu stricto (SO32-), whereas their relative abundance in solution depends on the concentration and the pH. Conversion of one species into another is rapid and involves in many cases incorporation of oxygen from, or release of oxygen to, water (e.g. SO2 + H2O ↔ HSO3- + H+), resulting in rapid oxygen isotope exchange between sulfite species and water. Consequently, the oxygen isotope composition of sulfite is strongly influenced by the oxygen isotope composition of water. Since sulfate does not exchange oxygen isotopes with water under most earth surface conditions, it can preserve the sulfite oxygen isotope signature that it inherits via oxidative and reductive sulfur cycling. Therefore, interpretation of δO values strongly hinges on the oxygen isotope equilibrium fractionation between sulfite and water which is poorly constrained. This is in large part due to technical difficulties in extraction of sulfite from solution for oxygen isotope analysis.

  10. Predicting equilibrium uranium isotope fractionation in crystals and solution

    Science.gov (United States)

    Schauble, E. A.

    2015-12-01

    Despite the rapidly growing interest in using 238U/235U measurements as a proxy for changes in oxygen abundance in surface and near-surface environments, the present theoretical understanding of uranium isotope fractionation is limited to a few simple gas-phase molecules and analogues of dissolved species (e.g., 1,2,3). Understanding uranium isotope fractionation behavior in more complicated species, such as crystals and adsorption complexes, will help in the design and interpretation of experiments and field studies, and may suggest other uses for 38U/235U measurements. In this study, a recently developed first-principles method for estimating the nuclear volume component of field shift fractionation in crystals and complex molecular species (4) is combined with mass-dependent fractionation theory to predict equilibrium 38U/235U fractionations in aqueous and crystalline uranium compounds, including uraninite (UO2). The nuclear field shift effect, caused by the interaction of electrons with the finite volume of the positive charge distribution in uranium nuclei, is estimated using Density Functional Theory and the Projector Augmented Wave method (DFT-PAW). Tests against relativistic electronic structure calculations and Mössbauer isomer shift data indicate that the DFT-PAW method is reasonably accurate, while being much better suited to models of complex and crystalline species. Initial results confirm previous predictions that the nuclear volume effect overwhelms mass depdendent fractionation in U(VI)-U(IV) exchange reactions, leading to higher 238U/235U in U(IV) species (i.e., for UO2 xtal vs. UO22+aq, ln αNV ≈ +1.8‰ , ln αMD ≈ -0.8‰, ln αTotal ≈ +1.0‰ at 25ºC). UO2 and U(H2O)94+, are within ~0.4‰ of each other, while U(VI) species appear to be more variable. This suggests that speciation is likely to significantly affect natural uranium isotope fractionations, in addition to oxidation state. Tentatively, it appears that uranyl-type (UO22

  11. Equilibrium clumped-isotope effects in doubly substituted isotopologues of ethane

    Science.gov (United States)

    Webb, Michael A.; Wang, Yimin; Braams, Bastiaan J.; Bowman, Joel M.; Miller, Thomas F.

    2017-01-01

    We combine path-integral Monte Carlo methods with a new intramolecular potential energy surface to quantify the equilibrium enrichment of doubly substituted ethane isotopologues due to clumped-isotope effects. Ethane represents the simplest molecule to simultaneously exhibit 13C-13C, 13C-D, and D-D clumped-isotope effects, and the analysis of corresponding signatures may provide useful geochemical and biogeochemical proxies of formation temperatures or reaction pathways. Utilizing path-integral statistical mechanics, we predict equilibrium fractionation factors that fully incorporate nuclear quantum effects, such as anharmonicity and rotational-vibrational coupling which are typically neglected by the widely used Urey model. The magnitude of the calculated fractionation factors for the doubly substituted ethane isotopologues indicates that isotopic clumping can be observed if rare-isotope substitutions are separated by up to three chemical bonds, but the diminishing strength of these effects suggests that enrichment at further separations will be negligible. The Urey model systematically underestimates enrichment due to 13C-D and D-D clumped-isotope effects in ethane, leading to small relative errors in the apparent equilibrium temperature, ranging from 5 K at 273.15 K to 30 K at 873.15 K. We additionally note that the rotameric dependence of isotopologue enrichment must be carefully considered when using the Urey model, whereas the path-integral calculations automatically account for such effects due to configurational sampling. These findings are of direct relevance to future clumped-isotope studies of ethane, as well as studies of 13C-13C, 13C-D, and D-D clumped-isotope effects in other hydrocarbons.

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

    Energy Technology Data Exchange (ETDEWEB)

    Roskosz, Mathieu; Sio, Corliss K. I.; Dauphas, Nicolas; Bi, Wenli; Tissot, Francois L. H.; Hu, Michael Y.; Zhao, Jiyong; Alp, Esen E.

    2015-11-15

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

  13. METHOD OF ISOTOPE CONCENTRATION

    Science.gov (United States)

    Spevack, J.S.

    1957-04-01

    An isotope concentration process is described which consists of exchanging, at two or more different temperature stages, two isotopes of an element between substances that are physically separate from each other and each of which is capable of containing either of the isotopes, and withdrawing from a point between at least two of the temperatare stages one of the substances containing an increased concentration of the desired isotope.

  14. EQUILIBRIUM AND KINETIC NITROGEN AND OXYGEN-ISOTOPE FRACTIONATIONS BETWEEN DISSOLVED AND GASEOUS N2O

    NARCIS (Netherlands)

    INOUE, HY; MOOK, WG

    1994-01-01

    Experiments were performed to determine the equilibrium as well as kinetic stable nitrogen and oxygen isotope fractionations between aqueous dissolved and gaseous N2O. The equilibrium fractionations, defined as the ratio of the isotopic abundance ratios (15R and 18R, respectively) of gaseous and

  15. First-principles models of equilibrium tellurium isotope fractionation

    Science.gov (United States)

    Haghnegahdar, M. A.; Schauble, E. A.; Fornadel, A. P.; Spry, P. G.

    2013-12-01

    In this study, equilibrium mass-dependent isotopic fractionation among representative Te-bearing species is estimated with first-principles thermodynamic calculations. Tellurium is a group 16 element (along with O, S, and Se) with eight stable isotopes ranging in mass from 120Te to 130Te, and six commonly-occurring oxidation states: -II, -I, 0, +II, +IV, and +VI. In its reduced form, Te(-II), tellurium has a unique crystal-chemical role as a bond partner for gold and silver in epithermal and orogenic gold deposits, which likely form when oxidized Te species (e.g., H2TeO3, TeO32-) or perhaps polytellurides (e.g., Te22-) interact with precious metals in hydrothermal solution. Te(IV) is the most common oxidation state at the Earth's surface, including surface outcrops of telluride ore deposits, where tellurite and tellurate minerals form by oxidation. In the ocean, dissolved tellurium tends to be scavenged by particulate matter. Te(VI) is more abundant than Te(IV) in the ocean water (1), even though it is thought to be less stable thermodynamically. This variety of valence states in natural systems and range of isotopic masses suggest that tellurium could exhibit geochemically useful isotope abundance variations. Tellurium isotope fractionations were determined for representative molecules and crystals of varying complexity and chemistry. Gas-phase calculations are combined with supermolecular cluster models of aqueous and solid species. These in turn are compared with plane-wave density functional theory calculations with periodic boundary conditions. In general, heavyTe/lightTe is predicted to be higher for more oxidized species, and lower for reduced species, with 130Te/125Te fractionations as large as 4‰ at 100οC between coexisting Te(IV) and Te(-II) or Te(0) compounds. This is a much larger fractionation than has been observed in naturally occurring redox pairs (i.e., Te (0) vs. Te(IV) species) so far, suggesting that disequilibrium processes may control

  16. Redefining the utility of the three-isotope method

    Science.gov (United States)

    Cao, Xiaobin; Bao, Huiming

    2017-09-01

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

  17. A new method for studying iodine metabolism; the isotopic equilibrium method - kinetic and quantitative aspects of measurements made on rats; Une nouvelle methode d'etude du metabolisme de l'iode: la methode d'equilibre isotopique - aspects cinetiques et quantitatifs obtenus chez le rat

    Energy Technology Data Exchange (ETDEWEB)

    Simon, C. [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1964-05-15

    The isotopic equilibrium method which has been developed in the case of the rat has made it possible to measure the absolute values of the principal parameters of iodine metabolism in this animal. The quantities and concentrations of iodine have been measured in the thyroid gland and in the plasma with a sensitivity of 0.001 {mu}g of {sup 127}I. This sensitivity has made it possible to measure pools as small as the iodide and the free iodotyrosines of the thyroid and to demonstrate the absence of free iodotyrosines in the plasma of the normal rat. In vivo, the isotopic equilibrium method has made it possible to measure the iodine content of the thyroid gland and to calculate the intensity of this gland's secretion without removing it. By double labelling with {sup 125}I and {sup 131}I the isotopic equilibrium method has made it possible to measure the flux, intensity of the intrathyroidal recycling as well as the turnover rates of all the iodine containing compounds of the thyroid gland. For this gland no precursor-product relationship has been found between The iodotyrosines (MIT and DIT) and the iodothyronines (T{sub 4} and T{sub 3}). The absence of this relationship is due to the heterogeneity of the thyroglobulin turnover. It has been shown furthermore that there exists in the plasma an organic fraction of the iodine which is different to thyroglobulin and which is renewed more rapidly than the circulating hormones T{sub 3} and T{sub 4}. The isotopic equilibrium method is very useful for series measurements of iodine. It makes it possible furthermore to improve the biochemical fractionations by adding carriers without affecting the subsequent {sup 127}I measurements. (author) [French] La methode d'equilibre isotopique, mise au point chez le rat, a permis de mesurer en valeur absolue les principaux parametres du metabolisme de l'iode chez cet animal. Les quantites ou les concentrations d'iode ont ete mesurees pour la thyroide et pour le

  18. Equilibrium Statistics: Monte Carlo Methods

    Science.gov (United States)

    Kröger, Martin

    Monte Carlo methods use random numbers, or ‘random’ sequences, to sample from a known shape of a distribution, or to extract distribution by other means. and, in the context of this book, to (i) generate representative equilibrated samples prior being subjected to external fields, or (ii) evaluate high-dimensional integrals. Recipes for both topics, and some more general methods, are summarized in this chapter. It is important to realize, that Monte Carlo should be as artificial as possible to be efficient and elegant. Advanced Monte Carlo ‘moves’, required to optimize the speed of algorithms for a particular problem at hand, are outside the scope of this brief introduction. One particular modern example is the wavelet-accelerated MC sampling of polymer chains [406].

  19. Methods of isotopic geochronology

    Science.gov (United States)

    Gorokhov, I. M.; Levchenkov, O. A.

    Papers are presented on such topics as the age of the chemical elements; the age of meteorites, the moon, and the earth; isotopic ages of the most ancient terrestrial formations; and the Archean evolution of Enderby Land in the Antarctic as evidenced by isotopic dating. Consideration is also given to a uranium-lead geochronology technique for investigating Precambrian ore deposits, a Pb-Pb technique of zircon dating, and the potentials and limitations of Sm-Nd geochronology.

  20. Prediction of equilibrium Li isotope fractionation between minerals and aqueous solutions at high P and T: an efficient ab initio approach

    CERN Document Server

    Kowalski, Piotr M

    2011-01-01

    The mass-dependent equilibrium stable isotope fractionation between different materials is an important geochemical process. Here we present an efficient method to compute the isotope fractionation between complex minerals and fluids at high pressure, P, and temperature, T, representative for the Earth's crust and mantle. The method is tested by computation of the equilibrium fractionation of lithium isotopes between aqueous fluids and various Li bearing minerals such as staurolite, spodumene and mica. We are able to correctly predict the direction of the isotope fractionation as observed in the experiments. On the quantitative level the computed fractionation factors agree within 1.0 permil with the experimental values indicating predictive power of ab initio methods. We show that with ab initio methods we are able to investigate the underlying mechanisms driving the equilibrium isotope fractionation process, such as coordination of the fractionating elements, their bond strengths to the neighboring atoms, c...

  1. Theoretical calculation of equilibrium copper (I) isotope fractionations in ore-forming fluid

    Science.gov (United States)

    Seo, J.; Lee, I.; Lee, S.

    2006-05-01

    Equilibrium isotope fractionation of Cu (I) complexes in hydrothermal ore-forming fluid is calculated. Ab-initio quantum calculation of molecular structures and vibrational frequencies is conducted by Density Functional Theory (DFT) and Hartree-Fock Self Consistent Field (HF-SCF) method. Cu isotope (65Cu, 63Cu) exchange is expressed as reduced partition function ratios, 103·ln(β65-63), for liquid phase complexes (copper chlorides, copper hydrosulfides), and vapor phase complexes (hydrated copper chloride). Isodensity Polarizable Continuum Model (IPCM) is applied to the liquid complexes, whereas the vapor complexes are calculated in vacuo. Large fractionation (more than 2‰ at 25°C) is predicted between coexisting phases without changing oxidation state. CuCl(H2O)2 (vapor phase) is enriched in 65Cu better than any other studied complexes, whereas [CuCl3]2- (liquid phase) is mostly depleted. Heavy copper isotope is favor to partition into vapor phase complexes than coexisting liquid phase complexes. In the sea-floor hydrothermal system, after separation of phases into vapor and brine, vapor phase (CuCl(H2O)2) and chlorine-rich brine ([CuCl3]2-) will show +0.418‰ and -0.688‰ deviation from [CuCl2]1- at 150°C, respectively. However, most of the dominant copper-bearing species in hydrothermal condition, [CuCl2]1- and [Cu(HS)2]1-, fractionate at almost the same degree. Possible ranges of copper isotope ratio, δ65Cu, can be constrained from the calculated equilibrium isotope fractionation. Changes of oxidation state in low-temperature (e.g. supergene formation) have been thought to trigger most copper isotope fractionations, so far. However, measurable Cu isotope fractionation (1.106‰ at 150°C and 0.615‰ at 300°C) in hydrothermal ore-forming fluid is predicted within +1 valence state by theoretical study. Molecular structures and vibrational frequencies are compared with measured data. However, there is no experimental or theoretical work of some molecules

  2. Group Contribution Methods for Phase Equilibrium Calculations.

    Science.gov (United States)

    Gmehling, Jürgen; Constantinescu, Dana; Schmid, Bastian

    2015-01-01

    The development and design of chemical processes are carried out by solving the balance equations of a mathematical model for sections of or the whole chemical plant with the help of process simulators. For process simulation, besides kinetic data for the chemical reaction, various pure component and mixture properties are required. Because of the great importance of separation processes for a chemical plant in particular, a reliable knowledge of the phase equilibrium behavior is required. The phase equilibrium behavior can be calculated with the help of modern equations of state or g(E)-models using only binary parameters. But unfortunately, only a very small part of the experimental data for fitting the required binary model parameters is available, so very often these models cannot be applied directly. To solve this problem, powerful predictive thermodynamic models have been developed. Group contribution methods allow the prediction of the required phase equilibrium data using only a limited number of group interaction parameters. A prerequisite for fitting the required group interaction parameters is a comprehensive database. That is why for the development of powerful group contribution methods almost all published pure component properties, phase equilibrium data, excess properties, etc., were stored in computerized form in the Dortmund Data Bank. In this review, the present status, weaknesses, advantages and disadvantages, possible applications, and typical results of the different group contribution methods for the calculation of phase equilibria are presented.

  3. Equilibrium and kinetic Si isotope fractionation factors and their implications on Si isotope distributions in the Earth's surface environments

    Science.gov (United States)

    Tang, M.; Zhang, S.; Liu, Y.

    2015-12-01

    Several important equilibrium Si isotope fractionation factors among minerals, organic molecules and the H4SiO4 solution are complemented to facilitate explanation of distributions of Si isotope in the Earth's surface environments. The results reveal that heavy Si isotopes will be significantly enriched in the secondary silicate minerals in comparison to aqueous H4SiO4. On the contrary, quadra-coordinated organosilicon complexes are enriched in light silicon isotope relative to the solution. The extent of 28Si-enrichment in hyper-coordinated organosilicon complexes is found the largest. In addition, the large kinetic isotope effect associated with the polymerization of monosilicic acid and dimer is calculated and the result supports previous statement that highly 28Si-enrichment in the formation of amorphous quartz precursor contributes to the discrepancy between theoretical calculations and field observations. With equilibrium Si isotope fractionation factors provided here, Si isotope distributions in many surface systems of the Earth can be explained. For example, the change of bulk soil δ30Si can be predicted as a concave pattern with respect to weathering degree, with the minimum value where allophane completely dissolves and the total amount of sesqui-oxides and poorly crystalline minerals reaches its maximum. When well-crystallized clays start to precipitate from pore solutions under equilibrium conditions, the bulk soil δ30Si will increase again and reach a constant value. Similarly, the precipitation of crystalline smectite and the dissolution of poorly crystalline kaolinite may explain δ30Si variations in the ground water profile. Equilibrium Si isotope fractionations among quadra-coordinated organosilicon complexes and the H4SiO4 solution may also shed the light on the Si isotope distributions in Si-accumulating plants.

  4. Theoretical prediction for several important equilibrium Ge isotope fractionation factors and geological implications

    Science.gov (United States)

    Li, Xuefang; Zhao, Hui; Tang, Mao; Liu, Yun

    2009-09-01

    This study estimates equilibrium fractionation factors in the Ge isotope system, including the dominant aqueous Ge(OH) 4 and GeO(OH) 3- species in seawater, Ge-bearing organic complexes (e.g. Ge-catechol, Ge-oxalic acid and Ge-citric acid), and Ge in quartz- (or opal-), albite-, K-feldspar-, olivine- and sphalerite-like structures. Estimations are based on Urey model (or Bigeleisen-Mayer equation) and high level quantum chemistry calculations. All calculations are made at B3LYP/6-311 + G(d,p) theory level. Solvation effects are treated by explicit solvent model ("water-droplet" method), and mineral structures are simulated using cluster models, in which the clusters are cut from the X-ray structures of those minerals. In addition, a number of different conformers are used for aqueous complexes in order to reduce the possible errors coming from the differences of configurations in solution. The "salt effect" on GeO(OH) 3-(aq) species is also carefully evaluated. We estimate the accuracy of these fractionation calculations at about ± 0.3‰. Excitedly, very large isotope fractionations are found between many Ge isotope systems. The Ge-containing sulfides (e.g. sphalerite) can extremely enrich light Ge isotopes (more than 10‰) compared with 4-coordinated Ge-O compounds (e.g. Ge(OH) 4(aq) or quartz). The fractionations between Ge(OH) 4(aq) and 6-coordinated Ge-bearing organic complexes can be also up to 4‰ at 25 °C. These results give a good explanation for the experimental observations of Rouxel et al. (2006). It also suggests a great potential for broad application of Ge isotope method in various geological systems.

  5. Barium isotope fractionation during witherite (BaCO3) dissolution, precipitation and at equilibrium

    Science.gov (United States)

    Mavromatis, Vasileios; van Zuilen, Kirsten; Purgstaller, Bettina; Baldermann, Andre; Nägler, Thomas F.; Dietzel, Martin

    2016-10-01

    This study examines the behavior of Ba isotope fractionation between witherite and fluid during mineral dissolution, precipitation and at chemical equilibrium. Experiments were performed in batch reactors at 25 °C in 10-2 M NaCl solution where the pH was adjusted by continuous bubbling of a water saturated gas phase of CO2 or atmospheric air. During witherite dissolution no Ba isotope fractionation was observed between solid and fluid. In contrast, during witherite precipitation, caused by a pH increase, a preferential uptake of the lighter 134Ba isotopomer in the solid phase was observed. In this case, the isotope fractionation factor αwitherite-fluid is calculated to be 0.99993 ± 0.00004 (or Δ137/134Bawitherite-fluid ≈ -0.07 ± 0.04‰, 2 sd). The most interesting feature of this study, however, is that after the attainment of chemical equilibrium, the Ba isotope composition of the aqueous phase is progressively becoming lighter, indicating a continuous exchange of Ba2+ ions between witherite and fluid. Mass balance calculations indicate that the detachment of Ba from the solid is not only restricted to the outer surface layer of the solid, but affects several (∼7 unit cells) subsurface layers of the crystal. This observation comes in excellent agreement with the concept of a dynamic system at chemical equilibrium in a mineral-fluid system, denoting that the time required for the achievement of isotopic equilibrium in the witherite-fluid system is longer compared to that observed for chemical equilibrium. Overall, these results indicate that the isotopic composition of Ba bearing carbonates in natural environments may be altered due to changes in fluid composition without a net dissolution/precipitation to be observed.

  6. Ice-vapor equilibrium fractionation factor of hydrogen and oxygen isotopes

    DEFF Research Database (Denmark)

    Ellehøj, Mads Dam; Steen-Larsen, Hans Christian; Johnsen, Sigfus Johann;

    2013-01-01

    RATIONALE: The equilibrium fractionation factors govern the relative change in the isotopic composition during phase transitions of water. The commonly used results, which were published more than 40 years ago, are limited to a minimum temperature of -33 degrees C. This limits the reliability...

  7. Isotopic Dilution Analysis and Secular Equilibrium Study: Two Complementary Radiochemistry Experiments.

    Science.gov (United States)

    Williams, Kathryn R.; Lipford, Levin C.

    1985-01-01

    Describes a complementary pair of radiochemistry experiments for instruction of isotopic dilution analysis and secular equilibrium. Both experiments use the readily available cesium-137 nuclide and the simple precipitation technique for cesium with the tetraphenylborate anion. Procedures used and typical results obtained are provided and…

  8. Measurement of fatty acid oxidation: validation of isotopic equilibrium extrapolation

    Energy Technology Data Exchange (ETDEWEB)

    Robin, A.P.; Jeevanandam, M.; Elwyn, D.H.; Askanazi, J.; Kinney, J.M.

    1989-01-01

    Measurement of whole body substrate oxidation requires prolonged isotope infusion to attain plateau specific activity (SA) of expired CO/sub 2/. We have investigated in 13 hospitalized patients a technique whereby plateau /sup 14/CO/sub 2/ SA is extrapolated using computer curve fitting based upon the early exponential rise. A primed-constant infusion of albumin-bound 1-/sup 14/C-palmitate was continued for 260 minutes with isotope priming of the secondary bicarbonate pool at 70 minutes. Plasma free fatty acid (FFA) SA reached steady state by 40 minutes and was 91% +/- 4% (SE) of values obtained at 190 to 260 minutes. At 70 minutes /sup 14/CO/sub 2/ SA reached only 44% +/- 1% of the 190 to 260 minute values, which were consistently at plateau. The predicted steady state /sup 14/CO/sub 2/ SA from the 40 to 70 minute curves and the FFA oxidation rates calculated from those values were 94% +/- 2% and 102% +/- 4%, respectively, of values measured at steady state (190 to 260 minutes). The relationship between predicted and measured values approximated the line of identity for /sup 14/CO/sub 2/ SA (y = 0.90x + 0.14, r = .98, P less than .001) and FFA oxidation (y = 1.02x, r = .98, P less than .001). The results suggest that FFA oxidation can be accurately calculated using a short infusion of labeled FFA without bicarbonate pool priming, thus avoiding overpriming or underpriming and possibly allowing multiple studies and diminished radioisotope exposure.

  9. Equilibrium simulations of Marine Isotope Stage 3 interstadial climate

    Science.gov (United States)

    Guo, Chuncheng; Nisancioglu, Kerim; Bentsen, Mats; Bethke, Ingo

    2017-04-01

    Marine Isotope Stage 3 (MIS3) was a period between approximately 60 ka to 30 ka BP that is characterised by abrupt climate transitions between cold, stadial and mild, interstadial climate conditions. The fluctuations are known as Dansgaard-Oeschger (D-O) events featured by a rapid warming from stadial to interstadial in a matter of a few decades, followed by a gradual cooling to stadial. We present fully coupled climate simulations of a pre-industrial control run and a MIS3 experiment at 38 ka, both integrated for 2000 years using the Norwegian Earth System Model (NorESM). With the recent model developments in the Bjerknes Centre for Climate Research (Norway), a new and efficient NorESM version (BCCR fast version) with 2 degrees atmosphere and 1 degree ocean is configured for paleo-modelling. BCCR fast version is capable of simulating Arctic sea ice and North Atlantic inflow well. We will present the large scale climate features in the MIS3 interstadial relative to today, such as the Atlantic Meridional Overturning Circulation, surface air temperature, etc. We also focus on the climate conditions in the Arctic and discuss the ocean circulations and sea ice conditions. In addition, sensitivity experiments with freshwater input into different regions (e.g., along the Norwegian coast, in the Nordic Seas, in the Labrador Sea, and in the region between 50 and 70 N) are performed; we will show the response of Arctic sea ice and Greenland temperature change from the freshwater perturbations and their implications for D-O events.

  10. Equilibrium magnesium isotope fractionation between aqueous Mg2+ and carbonate minerals: Insights from path integral molecular dynamics

    Science.gov (United States)

    Pinilla, Carlos; Blanchard, Marc; Balan, Etienne; Natarajan, Suresh K.; Vuilleumier, Rodolphe; Mauri, Francesco

    2015-08-01

    The theoretical determination of the isotopic fractionation between an aqueous solution and a mineral is of utmost importance in Earth sciences. While for crystals, it is well established that equilibrium isotopic fractionation factors can be calculated using a statistical thermodynamic approach based on the vibrational properties, several theoretical methods are currently used to model ions in aqueous solution. In this work, we present a systematic study to determine the reduced partition function ratio (β-factor) of aqueous Mg2+ using several levels of theory within the simulations. In particular, using an empirical force field, we compare and discuss the performance of the exact results obtained from path integral molecular dynamics (PIMD) simulations, with respect to the more traditional methods based on vibrational properties and the cluster approximation. The results show the importance of including configurational disorder for the estimation of the equilibrium isotope fractionation factor. We also show that using the vibrational frequencies computed from snapshots taken from equilibrated classical molecular dynamics represents a good approximation for the study of aqueous ions. Based on these conclusions, the β-factor of aqueous Mg2+ have been estimated from a Car-Parrinello molecular dynamics (CPMD) simulation with an ab initio force field, and combined with the β-factors of carbonate minerals (magnesite, dolomite, calcite and aragonite). Mg β-factor of Mg-bearing aragonite, calculated here for the first time, displays a lower value than the three other carbonate minerals. This is explained by a strong distortion of the cationic site leading to a decrease of the coordination number during Ca-Mg substitution. Overall, the equilibrium magnesium isotope fractionation factors between aqueous Mg2+ and carbonate minerals that derive from this methodological study support the previous theoretical results obtained from embedded cluster models.

  11. Equilibrium fractionation of H and O isotopes in water from path integral molecular dynamics

    Science.gov (United States)

    Pinilla, Carlos; Blanchard, Marc; Balan, Etienne; Ferlat, Guillaume; Vuilleumier, Rodolphe; Mauri, Francesco

    2014-06-01

    The equilibrium fractionation factor between two phases is of importance for the understanding of many planetary and environmental processes. Although thermodynamic equilibrium can be achieved between minerals at high temperature, many natural processes involve reactions between liquids or aqueous solutions and solids. For crystals, the fractionation factor α can be theoretically determined using a statistical thermodynamic approach based on the vibrational properties of the phases. These calculations are mostly performed in the harmonic approximation, using empirical or ab-initio force fields. In the case of aperiodic and dynamic systems such as liquids or solutions, similar calculations can be done using finite-size molecular clusters or snapshots obtained from molecular dynamics (MD) runs. It is however difficult to assess the effect of these approximate models on the isotopic fractionation properties. In this work we present a systematic study of the calculation of the D/H and 18O/16O equilibrium fractionation factors in water for the liquid/vapour and ice/vapour phases using several levels of theory within the simulations. Namely, we use a thermodynamic integration approach based on Path Integral MD calculations (PIMD) and an empirical potential model of water. Compared with standard MD, PIMD takes into account quantum effects in the thermodynamic modeling of systems and the exact fractionation factor for a given potential can be obtained. We compare these exact results with those of modeling strategies usually used, which involve the mapping of the quantum system on its harmonic counterpart. The results show the importance of including configurational disorder for the estimation of isotope fractionation in liquid phases. In addition, the convergence of the fractionation factor as a function of parameters such as the size of the simulated system and multiple isotope substitution is analyzed, showing that isotope fractionation is essentially a local effect in

  12. Chromatographic speciation of Cr(III)-species, inter-species equilibrium isotope fractionation and improved chemical purification strategies for high-precision isotope analysis.

    Science.gov (United States)

    Larsen, K K; Wielandt, D; Schiller, M; Bizzarro, M

    2016-04-22

    Chromatographic purification of chromium (Cr), which is required for high-precision isotope analysis, is complicated by the presence of multiple Cr-species with different effective charges in the acid digested sample aliquots. The differing ion exchange selectivity and sluggish reaction rates of these species can result in incomplete Cr recovery during chromatographic purification. Because of large mass-dependent inter-species isotope fractionation, incomplete recovery can affect the accuracy of high-precision Cr isotope analysis. Here, we demonstrate widely differing cation distribution coefficients of Cr(III)-species (Cr(3+), CrCl(2+) and CrCl2(+)) with equilibrium mass-dependent isotope fractionation spanning a range of ∼1‰/amu and consistent with theory. The heaviest isotopes partition into Cr(3+), intermediates in CrCl(2+) and the lightest in CrCl2(+)/CrCl3°. Thus, for a typical reported loss of ∼25% Cr (in the form of Cr(3+)) through chromatographic purification, this translates into 185 ppm/amu offset in the stable Cr isotope ratio of the residual sample. Depending on the validity of the mass-bias correction during isotope analysis, this further results in artificial mass-independent effects in the mass-bias corrected (53)Cr/(52)Cr (μ(53)Cr* of 5.2 ppm) and (54)Cr/(52)Cr (μ(54)Cr* of 13.5 ppm) components used to infer chronometric and nucleosynthetic information in meteorites. To mitigate these fractionation effects, we developed strategic chemical sample pre-treatment procedures that ensure high and reproducible Cr recovery. This is achieved either through 1) effective promotion of Cr(3+) by >5 days exposure to HNO3H2O2 solutions at room temperature, resulting in >∼98% Cr recovery for most types of sample matrices tested using a cationic chromatographic retention strategy, or 2) formation of Cr(III)-Cl complexes through exposure to concentrated HCl at high temperature (>120 °C) for several hours, resulting in >97.5% Cr recovery using a

  13. Neutron skin effect of some Mo isotopes in pre-equilibrium reactions

    Indian Academy of Sciences (India)

    M H Bölükdemir; E Tel; S Okuducu; N N Akti

    2011-03-01

    The neutron skin effect has been investigated for even isotopes of molybdenum at 25.6 MeV 94−100Mo(, ) reaction using the geometry-dependent hybrid model of pre-equilibrium nuclear reactions. Here the initial neutron/proton exciton numbers were calculated from the neutron/proton densities obtained from an effective nucleon–nucleon interaction of the Skyrme type. Initial exciton numbers from different radii of even Mo isotopes were used to obtain the corresponding neutron emission spectra. In this investigation the calculated results are compared with the experimental data as also with each other. The results using central densities in the geometry-dependent hybrid model are in better agreement with the experimental data.

  14. Isotopic equilibrium between precipitation and water vapor: evidence from continental rains in central Kenya

    Science.gov (United States)

    Soderberg, K.; Gerlein, C.; Kemeny, P. C.; Caylor, K. K.

    2013-12-01

    An accurate understanding of the relationships between the isotopic composition of liquid water and that of water vapor in the environment can help describe hydrologic processes across many scales. One such relationship is the isotopic equilibrium between falling raindrops and the surrounding vapor. The degree of equilibration is used to model the isotopic composition of precipitation in isotope-enable general circulation models and land-atmosphere exchange models. Although this equilibrium has been a topic of isotope hydrology research for more than four decades, few studies have included vapor measurements to validate modeling efforts. Recent advances in laser technology have allowed for in situ vapor measurements at high temporal resolution (e.g., >1 Hz). Here we present concomitant rain and vapor measurements for a series of 17 rain events during the 'Continental' rainy season (June through August) at Mpala Research Center in central Kenya. Rain samples (n=218) were collected at intervals of 2 to 35 minutes (median of 3 minutes) depending on the rain rate (0.4 to 10.5 mm/hr). The volume-weighted mean rain values for δ18O, δ2H and D-excess (δ2H - 8* δ18O) were 0.1 ‰, 10.7 ‰, and 10.1 ‰. These values are more enriched than the annual weighted means reported for the area (-2.2 ‰, -7.6 ‰, and 11.0 ‰, respectively). Vapor was measured continuously at ~2Hz (DLT-100, Los Gatos Research), with an inverted funnel intake 4m above the ground surface. The mean vapor isotopic composition during the rain events was -10.0 +/- 1.2 ‰ (1 σ) for δ18O and -73.9 +/- 7.0 ‰ for δ2H. The difference between the rain sample isotopic composition and that of liquid in isotopic equilibrium with the corresponding vapor at the ambient temperature was 0.8 +/- 2.2 ‰ for δ18O and 6.2 +/- 7.0 ‰ for δ2H. This disequilibrium was found to correlate with the natural log of rain rate (R2 of 0.26 for δ18O and 0.46 for δ2H), with lower rain rates having larger

  15. The early bird gets the shrimp: Confronting assumptions of isotopic equilibrium and homogeneity in a wild bird population

    Science.gov (United States)

    Wunder, Michael B.; Jehl, Joseph R.; Stricker, Craig A.

    2012-01-01

    1. Because stable isotope distributions in organic material vary systematically across energy gradients that exist in ecosystems, community and population structures, and in individual physiological systems, isotope values in animal tissues have helped address a broad range of questions in animal ecology. It follows that every tissue sample provides an isotopic profile that can be used to study dietary or movement histories of individual animals. Interpretations of these profiles depend on the assumption that metabolic pools are isotopically well mixed and in equilibrium with dietary resources prior to tissue synthesis, and they extend to the population level by assuming isotope profiles are identically distributed for animals using the same proximal dietary resource. As these assumptions are never fully met, studying structure in the variance of tissue isotope values from wild populations is informative. 2. We studied variation in δ13C, δ15N, δ2H and δ18O data for feathers from a population of eared grebes (Podiceps nigricollis) that migrate to Great Salt Lake each fall to moult feathers. During this time, they cannot fly and feed almost exclusively on superabundant brine shrimp (Artemia franciscana). The ecological simplicity of this situation minimized the usual spatial and trophic complexities often present in natural studies of feather isotope values. 3. Ranges and variances of isotope values for the feathers were larger than those from previously published studies that report feather isotopic variance, but they were bimodally distributed in all isotope dimensions. Isotope values for proximal dietary resources and local surface water show that some of the feathers we assumed to have been grown locally must have been grown before birds reached isotopic equilibrium with local diet or immediately prior to arrival at Great Salt Lake. 4. Our study provides novel insights about resource use strategies in eared grebes during migration. More generally, it

  16. Determination and application of the equilibrium oxygen isotope effect between water and sulfite

    Science.gov (United States)

    Wankel, Scott D.; Bradley, Alexander S.; Eldridge, Daniel L.; Johnston, David T.

    2014-01-01

    The information encoded by the two stable isotope systems in sulfate (δ34SSO4 and δ18OSO4) has been widely applied to aid reconstructions of both modern and ancient environments. Interpretation of δ18OSO4 records has been complicated by rapid oxygen isotope equilibration between sulfoxyanions and water. Specifically, the apparent relationship that develops between δ18OSO4 and δ18Owater during microbial sulfate reduction is thought to result from rapid oxygen isotope equilibrium between intracellular water and aqueous sulfite - a reactive intermediate of the sulfate reduction network that can back-react to produce sulfate. Here, we describe the oxygen equilibrium isotope effect between water and sulfite (referring to all the sum of all S(IV)-oxyanions including sulfite and both isomers and the dimer of bisulfite). Based on experiments conducted over a range of pH (4.5-9.8) and temperature (2-95 °C), where ε = 1000 * (α - 1), we find εSO3-H2O=13.61-0.299∗pH-0.081∗T °C. Thus, at a pH (7.0) and temperature (25 °C) typifying commonly used experimental conditions for sulfate reducing bacterial cultures, sulfite is enriched in 18O by 9.5‰ (±0.8‰) relative to ambient water. We examine the implication of these results in a sulfate reduction network that has been revised to reflect our understanding of the reactions involving oxygen. By evaluating previously published data within this new architecture, our results are consistent with previous suggestions of high reversibility of the sulfate reduction biochemical network. We also demonstrate that intracellular exchange rates between SO32- and water must be on average 1-3 orders of magnitude more rapid than intracellular fluxes of sulfate reduction intermediates and that kinetic isotope effects upstream of SO32- are required to explain previous laboratory and environmental studies of δ18OSO4 resulting as a consequence of sulfate reduction.

  17. Ab initio path-integral calculations of kinetic and equilibrium isotope effects on base-catalyzed RNA transphosphorylation models.

    Science.gov (United States)

    Wong, Kin-Yiu; Xu, Yuqing; York, Darrin M

    2014-06-30

    Detailed understandings of the reaction mechanisms of RNA catalysis in various environments can have profound importance for many applications, ranging from the design of new biotechnologies to the unraveling of the evolutionary origin of life. An integral step in the nucleolytic RNA catalysis is self-cleavage of RNA strands by 2'-O-transphosphorylation. Key to elucidating a reaction mechanism is determining the molecular structure and bonding characteristics of transition state. A direct and powerful probe of transition state is measuring isotope effects on biochemical reactions, particularly if we can reproduce isotope effect values from quantum calculations. This article significantly extends the scope of our previous joint experimental and theoretical work in examining isotope effects on enzymatic and nonenzymatic 2'-O-transphosphorylation reaction models that mimic reactions catalyzed by RNA enzymes (ribozymes), and protein enzymes such as ribonuclease A (RNase A). Native reactions are studied, as well as reactions with thio substitutions representing chemical modifications often used in experiments to probe mechanism. Here, we report and compare results from eight levels of electronic-structure calculations for constructing the potential energy surfaces in kinetic and equilibrium isotope effects (KIE and EIE) computations, including a "gold-standard" coupled-cluster level of theory [CCSD(T)]. In addition to the widely used Bigeleisen equation for estimating KIE and EIE values, internuclear anharmonicity and quantum tunneling effects were also computed using our recently developed ab initio path-integral method, that is, automated integration-free path-integral method. The results of this work establish an important set of benchmarks that serve to guide calculations of KIE and EIE for RNA catalysis. Copyright © 2014 Wiley Periodicals, Inc.

  18. Autoinduced catalysis and inverse equilibrium isotope effect in the frustrated Lewis pair catalyzed hydrogenation of imines.

    Science.gov (United States)

    Tussing, Sebastian; Greb, Lutz; Tamke, Sergej; Schirmer, Birgitta; Muhle-Goll, Claudia; Luy, Burkhard; Paradies, Jan

    2015-05-26

    The frustrated Lewis pair (FLP)-catalyzed hydrogenation and deuteration of N-benzylidene-tert-butylamine (2) was kinetically investigated by using the three boranes B(C6F5)3 (1), B(2,4,6-F3-C6H2)3 (4), and B(2,6-F2-C6H3)3 (5) and the free activation energies for the H2 activation by FLP were determined. Reactions catalyzed by the weaker Lewis acids 4 and 5 displayed autoinductive catalysis arising from a higher free activation energy (2 kcal mol(-1)) for the H2 activation by the imine compared to the amine. Surprisingly, the imine reduction using D2 proceeded with higher rates. This phenomenon is unprecedented for FLP and resulted from a primary inverse equilibrium isotope effect.

  19. Theoretical estimation for equilibrium Mo isotope fractionations between dissolved Mo species and the adsorbed complexes on (Fe,Mn)-oxyhydroxides

    Science.gov (United States)

    Tang, M.; Liu, Y.

    2009-12-01

    Although Mo isotopes have been increasingly used as a paleoredox proxy in the study of paleo-oceanographic condition changes (Barling et al., 2001; Siebert et al., 2003, 2005,2006; Arnold et al., 2004; Poulson et al., 2006), some very basic aspects of Mo isotopes geochemistry have not been obtained yet. First, although there are several previous studies on equilibrium Mo isotope fractionation factors(Tossell,2005; Weeks et al.,2007; Wasylenki et al.,2008), these studies were dealing with situations in vacuum and we find unfortunately the solvation effects for Ge species in solution cannot be ignored. Therefore, accurate Ge fractionation factors are actually not determined yet. Second, except the dominant dissolved Mo species in seawater which is known as molybdate ion (MoO42-), the forms of possible other minor species remain elusive. Third, the Mo removal mechanisms from seawater are only known for the anoxia and euxinic conditions (e.g. Helz et al., 1996; Zheng et al., 2000), the Mo removal mechanism under oxic condition are still arguing. Fourth, the adsorption effects on Mo isotope fractionation are almost completely unknown. Especially, without the adsorption fractionation knowledge, it is difficult to understand many distinct fractionations found in a number of geologic systems and it is difficult to explain the exceptionally long residence time of Mo in seawater. Urey model or Bigeleisen-Mayer equation based theoretical method and the super-molecule clusters are used to precisely evaluate the fractionation factors. The B3LYP/(6-311+G(2df,p),LANL2DZ) level method is used for frequencies calculation. 24 water molecules are used to form the supermolecues surrounding the Mo species. At least 4 different conformers for each supermolecule are used to prevent the errors from the diversity of configurations in solution. This study provides accurate equilibrium Mo isotope fractionation factors between possible dissolved Mo species and the adsorbed Mo species on the

  20. Investigation of Chemical Equilibrium Kinetics by the Electromigration Method

    CERN Document Server

    Bozhikov, G A; Bontchev, G D; Maslov, O D; Milanov, M V; Dmitriev, S N

    2002-01-01

    Measurement of the chemical reaction rates for complex formation as well as hydrolysis type reactions by the method of horizontal zone electrophoresis is outlined. The correlation between chemical equilibrium kinetics and electrodiffusion processes in a constant d.c. electric field is described. In model electromigration experiments the reaction rate constant of the complex formation of Hf(IV) and DTPA is determined.

  1. Lattice Boltzmann method with the cell-population equilibrium

    Institute of Scientific and Technical Information of China (English)

    Zhou Xiao-Yang; Cheng Bing; Shi Bao-Chang

    2008-01-01

    The central problem of the lattice Boltzmann method (LBM) is to construct a discrete equilibrium.In this paper,a multi-speed 1D cell-model of Boltzmann equation is proposed,in which the cell-population equilibrium,a direct nonnegative approximation to the continuous Maxwellian distribution,plays an important part.By applying the explicit one-order Chapman-Enskog distribution,the model reduces the transportation and collision,two basic evolution steps in LBM,to the transportation of the non-equilibrium distribution.Furthermore,1D dam-break problem is performed and the numerical results agree well with the analytic solutions.

  2. Importance of a Fully Anharmonic Treatment of Equilibrium Isotope Fractionation Properties of Dissolved Ionic Species As Evidenced by Li(+)(aq).

    Science.gov (United States)

    Dupuis, Romain; Benoit, Magali; Tuckerman, Mark E; Méheut, Merlin

    2017-07-18

    Equilibrium fractionation of stable isotopes is critically important in fields ranging from chemistry, including medicinal chemistry, electrochemistry, geochemistry, and nuclear chemistry, to environmental science. The dearth of reliable estimates of equilibrium fractionation factors, from experiment or from natural observations, has created a need for accurate computational approaches. Because isotope fractionation is a purely quantum mechanical phenomenon, exact calculation of fractionation factors is nontrivial. Consequently, a severe approximation is often made, in which it is assumed that the system can be decomposed into a set of independent harmonic oscillators. Reliance on this often crude approximation is one of the primary reasons that theoretical prediction of isotope fractionation has lagged behind experiment. A class of problems for which one might expect the harmonic approximation to perform most poorly is the isotopic fractionation between solid and solution phases. In order to illustrate the errors associated with the harmonic approximation, we have considered the fractionation of Li isotopes between aqueous solution and phyllosilicate minerals, where we find that the harmonic approximation overestimates isotope fractionation factors by as much as 30% at 25 °C. Lithium is a particularly interesting species to examine, as natural lithium isotope signatures provide information about hydrothermal processes, carbon cycle, and regulation of the Earth's climate by continental alteration. Further, separation of lithium isotopes is of growing interest in the nuclear industry due to a need for pure (6)Li and (7)Li isotopes. Moving beyond the harmonic approximation entails performing exact quantum calculations, which can be achieved using the Feynman path integral formulation of quantum statistical mechanics. In the path integral approach, a system of quantum particles is represented as a set of classical-like ring-polymer chains, whose interparticle

  3. A Review of Mg Isotope Analytical Methods by MC-ICP-MS

    Institute of Scientific and Technical Information of China (English)

    Yajun An; Fang Huang

    2014-01-01

    Application of multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS) has led to big breakthrough of analytical methods for metal stable isotopes, resulting in rapid progresses in non-traditional stable isotope geochemistry. As a new geological tracer, Mg isotopes have been widely applied in studies of almost all important disciplines of geochemistry. High precision Mg isotope data measured by MC-ICP-MS are now available with precision about 0.05‰ amu-1 (2SD) or better. Because mass bias caused by chemical procedure and instrument can easily cause significant analytical error, it is still a challenge to obtain accurate Mg isotope data for natural samples. In this paper, we systematically review the development of analytical technique of Mg isotopes, with a detailed description of a series of important techniques used in the measurement process, including calibration of instrumental mass-bias, chemical purification process, matrix effect, and pitfalls for high precision isotope analyses. We compare standard data from different labs and establish a guideline for Mg iso-tope analysis procedure. Additionally, we briefly discuss the behaviors of Mg isotopes during geological processes including equilibrium and kinetic Mg isotope fractionations, such as magma differentiation, chemical and thermal diffusion, and continental weathering. Finally, we propose some future prospects for Mg isotope geochemistry in both high and low temperature geological processes.

  4. Hybrid Method for Tokamak MHD Equilibrium Configuration Reconstruction

    Institute of Scientific and Technical Information of China (English)

    HE Hong-Da; DONG Jia-Qi; ZHANG Jin-Hua; JIANG Hai-Bin

    2007-01-01

    A hybrid method for tokamak MHD equilibrium configuration reconstruction is proposed and employed in the modified EFIT code. This method uses the free boundary tokamak equilibrium configuration reconstruction algorithm with one boundary point fixed. The results show that the position of the fixed point has explicit effects on the reconstructed divertor configurations. In particular, the separatrix of the reconstructed divertor configuration precisely passes the required position when the hybrid method is used in the reconstruction. The profiles of plasma parameters such as pressure and safety factor for reconstructed HL-2A tokamak configurations with the hybrid and the free boundary methods are compared. The possibility for applications of the method to swing the separatrix strike point on the divertor target plate is discussed.

  5. Simplified method for calculation of equilibrium plasma composition

    Science.gov (United States)

    Rydalevskaya, Maria A.

    2017-06-01

    In this work, a simplified method for the evaluation of equilibrium composition of plasmas consisted of monoatomic species is proposed. Multicomponent gas systems resulting from thermal ionization of spatially uniform mixtures are assumed enough rarefied to be treated as ideal gases even after multiple ionization steps. The method developed for the calculation of equilibrium composition of these mixtures makes use of the fundamental principles of statistical physics. Equilibrium concentrations of mixture components are determined by integration of distribution functions over the space of momentum and summation over electronic energy levels. These functions correspond to the entropy maximum. To determine unknown parameters, the systems of equations corresponding to the normalization conditions are derived. It is shown that the systems may be reduced to one algebraic equation if the equilibrium temperature is known. Numeral method to solve this equation is proposed. Special attention is given to the ionized mixtures, generated from the atoms of a single chemical species and the situations, when in the gas only the first- or the first- and second-order ionization are possible.

  6. Precise calibration of equilibrium oxygen isotope fractionations between dissolved phosphate and water from 3 to 37 °C

    Science.gov (United States)

    Chang, Sae Jung; Blake, Ruth E.

    2015-02-01

    The stable oxygen isotope composition of orthophosphate (δ18OPO4) is a widely used (paleo)temperature indicator and more recently, a useful tracer of phosphorus-cycling. In natural aqueous systems (e.g., oceans, rivers, soil/ground water) the largest reactive phosphorus pool is dissolved inorganic phosphate. Here, we present a new experimentally-determined equation for thermodynamic equilibrium O-isotope fractionations between dissolved phosphate and water, catalyzed by the enzyme inorganic pyrophosphatase (PPase) between 3 and 37 °C;

  7. Slope stability analysis using limit equilibrium method in nonlinear criterion.

    Science.gov (United States)

    Lin, Hang; Zhong, Wenwen; Xiong, Wei; Tang, Wenyu

    2014-01-01

    In slope stability analysis, the limit equilibrium method is usually used to calculate the safety factor of slope based on Mohr-Coulomb criterion. However, Mohr-Coulomb criterion is restricted to the description of rock mass. To overcome its shortcomings, this paper combined Hoek-Brown criterion and limit equilibrium method and proposed an equation for calculating the safety factor of slope with limit equilibrium method in Hoek-Brown criterion through equivalent cohesive strength and the friction angle. Moreover, this paper investigates the impact of Hoek-Brown parameters on the safety factor of slope, which reveals that there is linear relation between equivalent cohesive strength and weakening factor D. However, there are nonlinear relations between equivalent cohesive strength and Geological Strength Index (GSI), the uniaxial compressive strength of intact rock σ ci , and the parameter of intact rock m i . There is nonlinear relation between the friction angle and all Hoek-Brown parameters. With the increase of D, the safety factor of slope F decreases linearly; with the increase of GSI, F increases nonlinearly; when σ ci is relatively small, the relation between F and σ ci is nonlinear, but when σ ci is relatively large, the relation is linear; with the increase of m i , F decreases first and then increases.

  8. Investigations on application of multigrid method to MHD equilibrium analysis

    Energy Technology Data Exchange (ETDEWEB)

    Ikuno, Soichiro [Faculty of Engineering Science, School of Engineering, Tokyo Univ. of Technology, Tokyo (Japan)

    2000-06-01

    The potentiality of application for Multi-grid method to MHD equilibrium analysis is investigated. The nonlinear eigenvalue problem often appears when the MHD equilibria are determined by solving the Grad-Shafranov equation numerically. After linearization of the equation, the problem is solved by use of the iterative method. Although the Red-Black SOR method or Gauss-Seidel method is often used for the solution of the linearized equation, it takes much CPU time to solve the problem. The Multi-grid method is compared with the SOR method for the Poisson Problem. The results of computations show that the CPU time required for the Multi-grid method is about 1000 times as small as that for the SOR method. (author)

  9. Theoretical calculation of oxygen equilibrium isotope fractionation factors involving various NOy molecules, radOH, and H2O and its implications for isotope variations in atmospheric nitrate

    Science.gov (United States)

    Walters, Wendell W.; Michalski, Greg

    2016-10-01

    The oxygen stable isotope composition (δ18O) of nitrogen oxides [NOx = nitric oxide (NO) + nitrogen dioxide (NO2)] and their oxidation products (NOy = NOx + nitric acid (HNO3) + particulate nitrate (p-NO3-) + nitrate radical (NO3) + dinitrogen pentoxide (N2O5) + nitrous acid (HONO) + …) have been shown to be a useful tool for inferring the proportion of NOx that is oxidized by ozone (O3). However, isotopic fractionation processes may have an influence on δ18O of various NOy molecules and other atmospheric O-bearing molecules pertinent to NOx oxidation chemistry. Here we have evaluated the impacts of O isotopic exchange involving NOy molecules, the hydroxyl radical (radOH), and water (H2O) using reduced partition function ratios (xβ) calculated by hybrid density functional theory. Assuming atmospheric isotopic equilibrium is achieved between NO and NO2 during the daytime, and NO2, NO3, and N2O5 during the nighttime, δ18O-δ15N compositions were predicted for the major atmospheric nitrate formation pathways using our calculated exchange fractionation factors and isotopic mass-balance. Our equilibrium model predicts that various atmospheric nitrate formation pathways, including NO2 + radOH → HNO3, N2O5 + H2O + surface → 2HNO3, and NO3 + R → HNO3 + Rrad will yield distinctive δ18O-δ15N compositions. Our calculated δ18O-δ15N compositions match well with previous atmospheric nitrate measurements, and will potentially help better understand the role oxidation chemistry plays on the N and O isotopic composition of atmospheric nitrate.

  10. The procedure and results of calculations of the equilibrium isotopic composition of a demonstration subcritical molten salt reactor

    Science.gov (United States)

    Nevinitsa, V. A.; Dudnikov, A. A.; Blandinskiy, V. Yu.; Balanin, A. L.; Alekseev, P. N.; Titarenko, Yu. E.; Batyaev, V. F.; Pavlov, K. V.; Titarenko, A. Yu.

    2015-12-01

    A subcritical molten salt reactor with an external neutron source is studied computationally as a facility for incineration and transmutation of minor actinides from spent nuclear fuel of reactors of VVER-1000 type and for producing 233U from 232Th. The reactor configuration is chosen, the requirements to be imposed on the external neutron source are formulated, and the equilibrium isotopic composition of heavy nuclides and the key parameters of the fuel cycle are calculated.

  11. The procedure and results of calculations of the equilibrium isotopic composition of a demonstration subcritical molten salt reactor

    Energy Technology Data Exchange (ETDEWEB)

    Nevinitsa, V. A., E-mail: Neviniza-VA@nrcki.ru; Dudnikov, A. A.; Blandinskiy, V. Yu.; Balanin, A. L.; Alekseev, P. N. [National Research Centre Kurchatov Institute (Russian Federation); Titarenko, Yu. E.; Batyaev, V. F.; Pavlov, K. V.; Titarenko, A. Yu., E-mail: yuri.titarenko@itep.ru [Institute for Theoretical and Experimental Physics (Russian Federation)

    2015-12-15

    A subcritical molten salt reactor with an external neutron source is studied computationally as a facility for incineration and transmutation of minor actinides from spent nuclear fuel of reactors of VVER-1000 type and for producing {sup 233}U from {sup 232}Th. The reactor configuration is chosen, the requirements to be imposed on the external neutron source are formulated, and the equilibrium isotopic composition of heavy nuclides and the key parameters of the fuel cycle are calculated.

  12. First-principles investigation of equilibrium isotopic fractionation of Si and O isotopes among quartz, albite, anthorite, orthoenstatite, clinoenstatite, olivine, and zircon

    Science.gov (United States)

    Qin, T.; Wu, F.; Huang, F.; Wu, Z.

    2013-12-01

    Silicon is one of the most abundant elements in the crust and mantle. Because of advance of high precision analytical technique, Si isotope geochemistry has been widely applied into studies of a variety of important processes including planetary formation, core-mantle segregation, magmatism, and weathering of the crust. In order to better understanding Si isotope data in high temperature rock and mineral samples, it is critical to obtain equilibrium fractionation factors of Si isotopes among silicate minerals. However, experimental studies on calibrating Si isotope fractionation factors are still no available in literature. Here we used first-principles calculation based on density functional theory to investigate Si isotope fractionation factors among silicate minerals commonly occurring in magmatism in crustal level. These minerals include quartz, albite, anthorite, orthoenstatite, clinoenstatite, olivine, and zircon. We also calculated oxygen isotope fractionation factors among these minerals. Our results indicate the 18O-enrichment order among these minerals follows sequence of quartz > albite > anorthite > enstatite> zircon > olivine, showing good agreement with the data from previous experiments or natural sample measurement. For Si isotopes, our work shows that the 30Si-enrichment order in these minerals follows sequence of quartz > albite > anorthite > olivine ~ zircon > enstatite > diopside. These results are consistent with previous calculation [1] and observation from natural minerals. For example, Δ30Sianorthite-olivine = 0.2‰ at 1000oC based on our calculation, well consistent with value from the study of Skaergaard Intrusion (Δ30Siplagioclase-olivine = 0.24-27‰) [2] at same temperature. Our calculation indicates that Si isotopes can be significantly fractionated among silicate minerals during high temperature geochemical processes. References: [1] M. Méheut et al (2007), GCA 71:3170-3180. [2] P. S. Savage et al (2011), GCA 75:6124-6139.

  13. Equilibrium Fe isotope fractionation between inorganic aqueous Fe(III) and the siderophore complex, Fe(III)-desferrioxamine B

    DEFF Research Database (Denmark)

    Dideriksen, Knud; Baker, Joel A.; Stipp, Susan Louise Svane

    2008-01-01

    be controlled by isotope fractionation between the free and complexed iron.We have determined the equilibrium Fe isotope fractionation induced by organic ligand activity in experiments with solutions having co-existing inorganic Fe(III) species and siderophore complexes, Fedesferrioxamine B (at pH 2). The two......In oxic oceans, most of the dissolved iron (Fe) exists as complexes with siderophore-like, strongly coordinating organic ligands. Thus, the isotope composition of the little amount of free inorganic Fe that is available for precipitation and preservation in the geological record may largely...... for the slower stage, indicating that approximately 40% reequilibration may take place during the separation of the two pools. To further test if the induced precipitation leads to experimental artefacts, the fractionation during precipitation of inorganic Fe was determined. Assuming a Rayleigh...

  14. Effect of parent body evolution on equilibrium and kinetic isotope fractionation: a combined Ni and Fe isotope study of iron and stony-iron meteorites

    Science.gov (United States)

    Chernonozhkin, Stepan M.; Goderis, Steven; Costas-Rodríguez, Marta; Claeys, Philippe; Vanhaecke, Frank

    2016-08-01

    resolvable differences, similar in magnitude but opposite in sign (Δ56/54Femet-oliv of +0.178 ± 0.092‰ and Δ60/58Nimet-oliv of -0.212 ± 0.082‰, 2SD). As such, the heavier Fe isotope ratios for the metal (δ56/54Fe = +0.023‰ to +0.247‰) and lighter values for the corresponding olivines (δ56/54Fe = -0.155‰ to -0.075‰) are interpreted to reflect later-stage Fe isotopic re-equilibration between these phases, rather than a pristine record of mantle-core differentiation. In the case of mesosiderites, the similarly lighter Ni and Fe isotopic signatures found for the silicate phase (-0.149‰ to +0.023‰ for δ60/58Ni, -0.214‰ to -0.149‰ for δ56/54Fe) compared to the metal phase (+0.168‰ to +0.191‰ for δ60/58Ni, +0.018‰ to +0.120‰ for δ56/54Fe) likely result from Fe and Ni diffusion. Overall, the Fe and Ni isotopic compositions of iron-rich meteorites reflect multiple, often superimposed, processes of equilibrium or kinetic nature, illustrating convoluted parent body histories and late-stage interaction between early-formed planetesimal reservoirs.

  15. Method for production of an isotopically enriched compound

    Science.gov (United States)

    Watrous, Matthew G.

    2012-12-11

    A method is presented for producing and isolating an isotopically enriched compound of a desired isotope from a parent radionuclide. The method includes forming, or placing, a precipitate containing a parent radionuclide of the desired daughter isotope in a first reaction zone and allowing sufficient time for the parent to decay into the desired gaseous daughter radioisotope. The method further contemplates collecting the desired daughter isotope as a solid in a second reaction zone through the application of temperatures below the freezing point of the desired isotope to a second reaction zone that is connected to the first reaction zone. Specifically, a method is presented for producing isotopically enriched compounds of xenon, including the radioactive isotope Xe-131m and the stable isotope Xe-131.

  16. A variational method in out-of-equilibrium physical systems.

    Science.gov (United States)

    Pinheiro, Mario J

    2013-12-09

    We propose a new variational principle for out-of-equilibrium dynamic systems that are fundamentally based on the method of Lagrange multipliers applied to the total entropy of an ensemble of particles. However, we use the fundamental equation of thermodynamics on differential forms, considering U and S as 0-forms. We obtain a set of two first order differential equations that reveal the same formal symplectic structure shared by classical mechanics, fluid mechanics and thermodynamics. From this approach, a topological torsion current emerges of the form , where Aj and ωk denote the components of the vector potential (gravitational and/or electromagnetic) and where ω denotes the angular velocity of the accelerated frame. We derive a special form of the Umov-Poynting theorem for rotating gravito-electromagnetic systems. The variational method is then applied to clarify the working mechanism of particular devices.

  17. New theory of superconductivity. Method of equilibrium density matrix

    CERN Document Server

    Bondarev, Boris

    2014-01-01

    A new variational method for studying the equilibrium states of an interacting particles system has been proposed. The statistical description of the system is realized by means of a density matrix. This method is used for description of conduction electrons in metals. An integral equation for the electron distribution function over wave vectors has been obtained. The solutions of this equation have been found for those cases where the single-particle Hamiltonian and the electron interaction Hamiltonian can be approximated by a quite simple expression. It is shown that the distribution function at temperatures below the critical value possesses previously unknown features which allow to explain the superconductivity of metals and presence of a gap in the energy spectrum of superconducting electrons.

  18. A Variational Method in Out of Equilibrium Physical Systems

    CERN Document Server

    Pinheiro, Mario J

    2012-01-01

    A variational principle is further developed for out of equilibrium dynamical systems by using the concept of maximum entropy. With this new formulation it is obtained a set of two first-order differential equations, revealing the same formal symplectic structure shared by classical mechanics, fluid mechanics and thermodynamics. In particular, it is obtained an extended equation of motion for a rotating dynamical system, from where it emerges a kind of topological torsion current of the form $\\epsilon_{ijk} A_j \\omega_k$, with $A_j$ and $\\omega_k$ denoting components of the vector potential (gravitational or/and electromagnetic) and $\\omega$ is the angular velocity of the accelerated frame. In addition, it is derived a special form of Umov-Poynting's theorem for rotating gravito-electromagnetic systems, and obtained a general condition of equilibrium for a rotating plasma. The variational method is then applied to clarify the working mechanism of some particular devices, such as the Bennett pinch and vacuum a...

  19. Minimizing the Free Energy: A Computer Method for Teaching Chemical Equilibrium Concepts.

    Science.gov (United States)

    Heald, Emerson F.

    1978-01-01

    Presents a computer method for teaching chemical equilibrium concepts using material balance conditions and the minimization of the free energy. Method for the calculation of chemical equilibrium, the computer program used to solve equilibrium problems and applications of the method are also included. (HM)

  20. Research and application of method of oxygen isotope of inorganic phosphate in Beijing agricultural soils.

    Science.gov (United States)

    Tian, Liyan; Guo, Qingjun; Zhu, Yongguan; He, Huijun; Lang, Yunchao; Hu, Jian; Zhang, Han; Wei, Rongfei; Han, Xiaokun; Peters, Marc; Yang, Junxing

    2016-12-01

    Phosphorus (P) in agricultural ecosystems is an essential and limited element for plants and microorganisms. However, environmental problems caused by P accumulation as well as by P loss have become more and more serious. Oxygen isotopes of phosphate can trace the sources, migration, and transformation of P in agricultural soils. In order to use the isotopes of phosphate oxygen, appropriate extraction and purification methods for inorganic phosphate from soils are necessary. Here, we combined two different methods to analyze the oxygen isotopic composition of inorganic phosphate (δ(18)OP) from chemical fertilizers and different fractions (Milli-Q water, 0.5 mol L(-1) NaHCO3 (pH = 8.5), 0.1 mol L(-1) NaOH and 1 mol L(-1) HCl) of agricultural soils from the Beijing area. The δ(18)OP results of the water extracts and NaHCO3 extracts in most samples were close to the calculated equilibrium value. These phenomena can be explained by rapid P cycling in soils and the influence of chemical fertilizers. The δ(18)OP value of the water extracts and NaHCO3 extracts in some soil samples below the equilibrium value may be caused by the hydrolysis of organic P fractions mediated by extracellular enzymes. The δ(18)OP values of the NaOH extracts were above the calculated equilibrium value reflecting the balance state between microbial uptake of phosphate and the release of intracellular phosphate back to the soil. The HCl extracts with the lowest δ(18)OP values and highest phosphate concentrations indicated that the HCl fraction was affected by microbial activity. Hence, these δ(18)Op values likely reflected the oxygen isotopic values of the parent materials. The results suggested that phosphate oxygen isotope analyses could be an effective tool in order to trace phosphate sources, transformation processes, and its utilization by microorganisms in agricultural soils.

  1. New theory of superfluidity. Method of equilibrium density matrix

    CERN Document Server

    Bondarev, Boris

    2014-01-01

    The variational theory of equilibrium boson system state to have been previously developed by the author under the density matrix formalism is applicable for researching equilibrium states and thermodynamic properties of the quantum Bose gas which consists of zero-spin particles. Particle pulse distribution function is obtained and duly employed for calculation of chemical potential, internal energy and gas capacity temperature dependences. It is found that specific phase transition, which is similar to transition of liquid helium to its superfluid state, occurs at the temperature exceeding that of the Bose condensation.

  2. On anharmonic and pressure corrections to the equilibrium isotopic constants for minerals

    Science.gov (United States)

    Polyakov, Veniamin B.

    1998-09-01

    Specifies of the calculations of the reduced isotopic partition function ratios (β-factor) of minerals are discussed. Comparative calculations in the framework of the fully harmonic, quasi-harmonic, and intrinsic anharmonic approximations show minor anharmonic corrections to the harmonic values of the β-factor. In the case of calcite, the difference between the fully harmonic and intrinsic anharmonic values of 10 3lnβ varies from 0.60 at 300 K to 0.37 at 1200 K and is close to typical values of the anharmonic correction in gas molecules. A new treatment for calculating isotopic effects in molar volumes of minerals and pressure effects on their β-factors is developed on the basis of the Mie-Grüneisen equation of state. There is no significant difference between the quasi-harmonic and intrinsic harmonic values of (∂lnβ/∂ P) T. For calcite, the pressure derivative of the β-factor is positive, decreases monotonically with temperature, and becomes small at T ˜ 1000 K (10 3(∂lnβ/ ∂P) T ≈ 0.1-0.15 GPa -1). These results contradict the large anharmonic and pressure effects to the β-factor of calcite calculated by Gillet et al. (1996) as well as their conclusion that the pressure correction to the β-factor of calcite is negative at higher temperatures and increases in its absolute value with increasing temperature.

  3. Temperature dependency of the triple isotope fractionation relationship for equilibrium processes

    Science.gov (United States)

    Hayles, J. A.; Cao, X.; Bao, H.

    2015-12-01

    The use of an approximation to the Bigeleisen-Mayer-Urey model for isotope fractionation has led to the concept of a constant, and later constrained, mass fractionation law for multiple isotopes of the same element. This concept has brought new insights to investigation in photochemistry, radical chemistry, or the contribution of quantum tunneling to chemical and biological processes. Despite previous work indicating that these mass fractionation laws can be highly variable, the concept of a constant relationship remains common in these fields. Using the diatomic case as a first-order approximation, we demonstrate generically that the mass fractionation exponent, θ, can take any value for small fractionations but is less variable for large fractionations. The predicted variability is larger than both theoretical and analytical precision. These deviations from the traditional range of mass-dependence exponents are the largest under cross-over scenarios, but can occur for any scenario with small fractionations. We advocate the use of ∆∆‡M or "change in cap-delta", defined strictly with a slope of at the high-temperature limit, as a necessary, more reliable and more useful descriptor of mass-dependent fractionation. This work can bring new insights and a conventional explanation to low temperature experiments yielding traditionally unusual mass fractionation laws.

  4. Quantum Chemical Study of the Fe(III)-Desferrioxamine B Siderophore Complex-Electronic Structure, Vibrational Frequencies, and Equilibrium Fe-Isotope Fractionation

    Science.gov (United States)

    2008-09-19

    Goldman S. D. et a ..., Geochim. Cosmochim. Acta (2008), doi:10.1016/j.gca.2008.09tions of Urey (1947). First, we predicted the equilibrium constants...11623–11627. Urey H. C. (1947) The thermodynamic properties of isotopic substances. J. Chem. Soc., 562–581. Walker J. C. G., Klein C., Schidlowski M

  5. A new iterative method for solving a system of generalized equilibrium problems, generalized mixed equilibrium problems and common fixed point problems in Hilbert spaces

    Directory of Open Access Journals (Sweden)

    Benjawan Rodjanadid

    2013-12-01

    Full Text Available In this paper, we introduce an iterative method for finding a common element of the set of solutions of a generalized mixed equilibrium problem (GMEP, the solutions of a general system of equilibrium problem and the set of common fixed points of a finite family of nonexpansive mappings in a real Hilbert space. Then, we prove that the sequence converges strongly to a common element of the above three sets. Furthermore, we apply our result to prove four new strong convergence theorems in fixed point problems, mixed equilibrium problems, generalized equilibrium problems , equilibrium problems and variational inequality.

  6. Nanosecond redox equilibrium method for determining oxidation potentials in organic media

    NARCIS (Netherlands)

    Guirado Lopez, G.; Fleming, C.N.; Lingenfelter, T.G.; Williams, M.L.; Zuilhof, H.; Dinnocenzo, J.P.

    2004-01-01

    A general, nanosecond equilibrium method is described for determining thermodynamically meaningful oxidation potentials in organic media for compounds that form highly reactive cation radicals upon one-electron oxidation. The method provides oxidation potentials with unusually high precision and

  7. A general method to study equilibrium partitioning of macromolecules

    DEFF Research Database (Denmark)

    The distribution of macromolecules between a confined microscopic solution and a macroscopic bulk solution plays an important role in understanding separation processes such as Size Exclusion Chromatography (SEC). In this study, we have developed an efficient computational algorithm for obtaining...... the equilibrium partition coefficient (pore-to-bulk concentration ratio) and the concentration profile inside the confining geometry. The algorithm involves two steps. First, certain characteristic structure properties of the studied macromolecule are obtained by sampling its configuration space, and second those...... data are used for the computation of partition coefficient and concentration profile for any confinement size. Our algorithm is versatile to the model and type of the macromolecule studied, and is capable of handling three types of confining geometries (slit, rectangular channel and rectangular box...

  8. [Progress in stable isotope labeled quantitative proteomics methods].

    Science.gov (United States)

    Zhou, Yuan; Shan, Yichu; Zhang, Lihua; Zhang, Yukui

    2013-06-01

    Quantitative proteomics is an important research field in post-genomics era. There are two strategies for proteome quantification: label-free methods and stable isotope labeling methods which have become the most important strategy for quantitative proteomics at present. In the past few years, a number of quantitative methods have been developed, which support the fast development in biology research. In this work, we discuss the progress in the stable isotope labeling methods for quantitative proteomics including relative and absolute quantitative proteomics, and then give our opinions on the outlook of proteome quantification methods.

  9. A New Approximation Scheme Combining the Viscosity Method with Extragradient Method for Mixed Equilibrium Problems

    Directory of Open Access Journals (Sweden)

    Wu Soon-Yi

    2009-01-01

    Full Text Available We introduce a new approximation scheme combining the viscosity method with extragradient method for finding a common element of the set of solutions of a mixed equilibrium problem and the set of fixed points of a finite family of nonexpansive mappings and the set of the variational inequality for a monotone, Lipschitz continuous mapping. We obtain a strong convergence theorem for the sequences generated by these processes in Hilbert spaces. Based on this result, we also get some new and interesting results. The results in this paper generalize, extend, and improve some well-known results in the literature.

  10. Predicting equilibrium vapour pressure isotope effects by using artificial neural networks or multi-linear regression - A quantitative structure property relationship approach.

    Science.gov (United States)

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

    2015-09-01

    We aim at predicting the effect of structure and isotopic substitutions on the equilibrium vapour pressure isotope effect of various organic compounds (alcohols, acids, alkanes, alkenes and aromatics) at intermediate temperatures. We attempt to explore quantitative structure property relationships by using artificial neural networks (ANN); the multi-layer perceptron (MLP) and compare the performances of it with multi-linear regression (MLR). These approaches are based on the relationship between the molecular structure (organic chain, polar functions, type of functions, type of isotope involved) of the organic compounds, and their equilibrium vapour pressure. A data set of 130 equilibrium vapour pressure isotope effects was used: 112 were used in the training set and the remaining 18 were used for the test/validation dataset. Two sets of descriptors were tested, a set with all the descriptors: number of(12)C, (13)C, (16)O, (18)O, (1)H, (2)H, OH functions, OD functions, CO functions, Connolly Solvent Accessible Surface Area (CSA) and temperature and a reduced set of descriptors. The dependent variable (the output) is the natural logarithm of the ratios of vapour pressures (ln R), expressed as light/heavy as in classical literature. Since the database is rather small, the leave-one-out procedure was used to validate both models. Considering higher determination coefficients and lower error values, it is concluded that the multi-layer perceptron provided better results compared to multi-linear regression. The stepwise regression procedure is a useful tool to reduce the number of descriptors. To our knowledge, a Quantitative Structure Property Relationship (QSPR) approach for isotopic studies is novel.

  11. a Proposal for a General Method for Determining Semi-Experimental Equilibrium Structures of Carbon Atom Backbones

    Science.gov (United States)

    Craig, Norman C.

    2010-06-01

    Semi-experimental equilibrium structures are determined from ground state rotational constants derived from the analysis of rotational transitions in high-resolution spectra and from the quantum chemical calculation of spectroscopic alphas. In the full application of this method, spectra of numerous isotopic species must be investigated. Most of these isotopic species require specialized synthesis. We now propose focusing on the carbon atoms, for which microwave spectroscopy routinely yields spectra for polar molecules with 13C substitution in natural abundance. Needed spectroscopic alphas can be computed with Gaussian software. Application of the Kraitchman substitution relationships gives Cartesian coordinates for the carbon atoms and thence bond parameters for the carbon backbone. This method will be evaluated with ethylene, 1,1-difluoroethylene, 1,1-difluorocyclopropane, propene, and butadiene. The method will then be applied to cis-hexatriene and the two conformers of glycidol. R. D. Suenram, B. H. Pate, A. Lessari, J. L. Neill, S. Shipman, R. A. Holmes, M. C. Leyden, and N. C. Craig, J. Phys. Chem. A 113, 1864-1868 (2009). A. R. Conrad, N. H. Teumelsan, P. E. Wang, and M. J. Tubergen, J. Phys. Chem. A 114, 336-342 (2010).

  12. First intense isotopic titanium-50 beam using MIVOC method

    Energy Technology Data Exchange (ETDEWEB)

    Rubert, J.; Piot, J. [Departement de Recherches Subatomiques, Institut Pluridisciplinaire Hubert Curien, UMR 7178, Universite de Strasbourg/CNRS-IN-2P-3, 23 rue du Loess, F-67037 Strasbourg (France); Asfari, Z. [Laboratoire d' Ingenierie Moleculaire Appliquee a l' Analyse (DSA), Institut Pluridisciplinaire Hubert Curien, UMR 7178, Universite de Strasbourg/CNRS-IN-2P-3, 23 rue du Loess, F-67037 Strasbourg (France); Gall, B.JP., E-mail: benoit.gall@iphc.cnrs.fr [Departement de Recherches Subatomiques, Institut Pluridisciplinaire Hubert Curien, UMR 7178, Universite de Strasbourg/CNRS-IN-2P-3, 23 rue du Loess, F-67037 Strasbourg (France); Aerje, J. [Department of Physics, University of Jyvaeskylae, P.O. Box 35 (YFL), Jyvaeskylae FI-40014 (Finland); Dorvaux, O. [Departement de Recherches Subatomiques, Institut Pluridisciplinaire Hubert Curien, UMR 7178, Universite de Strasbourg/CNRS-IN-2P-3, 23 rue du Loess, F-67037 Strasbourg (France); Greenlees, P.T.; Koivisto, H. [Department of Physics, University of Jyvaeskylae, P.O. Box 35 (YFL), Jyvaeskylae FI-40014 (Finland); and others

    2012-04-01

    An organometallic compound isotopically enriched in titanium-50 has been successfully used for the first time to produce intense ion beams with an ECR ion source by means of the MIVOC method. After some fruitful tests performed with compounds produced at IPHC Strasbourg with natural titanium, enriched organometallic titanium compound was produced successfully, beam extracted from ECR ion sources and accelerated through a K = 130 MeV cyclotron to an energy of 242 MeV. This isotopic {sup 50}Ti{sup 11{sup +}} beam was used for the first time in three week-experiment with typical MIVOC stable operating conditions. After optimization, up to 19.4 {mu}A of titanium-50 in charge state 11{sup +} could be extracted from the JYFL 14 GHz ECRIS2 ion source. This measurement has demonstrated the possible use of the MIVOC method for production of an intense highly charged isotopic titanium-50 ion beam with rather low material consumption.

  13. Impact of the carbon pore size and topology on the equilibrium quantum sieving of hydrogen isotopes at zero coverage and finite pressures.

    Science.gov (United States)

    Kowalczyk, Piotr; Gauden, Piotr A; Terzyk, Artur P; Furmaniak, Sylwester

    2009-04-08

    Carbonaceous slit-shaped and square-shaped pores efficiently differentiate adsorbed hydrogen isotopes at 77 and 33 K. Extensive path integral Monte Carlo simulations revealed that the square-shaped carbon pores enhanced the selectivity of deuterium over hydrogen in comparison to equivalent slit-shaped carbon pores at zero coverage as well as at finite pressures (i.e. quantum sieving of hydrogen isotopes is pore-topology-dependent). We show that this enhancement of the D(2)/H(2) equilibrium selectivity results from larger localization of hydrogen isotopes in square-shaped pores. The operating pressures for efficient quantum sieving of hydrogen isotopes are strongly dependent on the topology as well as on the size of the carbon pores. However, for both considered carbon pore topologies the highest D(2)/H(2) separation factor is observed at zero-coverage limit. Depending on carbon pore size and topology we predicted monotonic decreasing and non-monotonic shape of the D(2)/H(2) equilibrium selectivity at finite pressures. For both kinds of carbonaceous pores of molecular sizes we predict high compression of hydrogen isotopes at 77 and 33 K (for example, the pore density of compressed hydrogen isotopes at 77 K and 0.25 MPa in a square-shaped carbon pore of size 2.6 Å exceeds 60 mmol cm(-3); for comparison, the liquid density of para-H(2) at 30 K and 30 MPa is 42 mmol cm(-3)). Finally, by direct comparison of simulation results with experimental data it is explained why 'ordinary' carbonaceous materials are not efficient quantum sieves.

  14. A method for determining the nitrogen isotopic composition of porphyrins.

    Science.gov (United States)

    Higgins, Meytal B; Robinson, Rebecca S; Casciotti, Karen L; McIlvin, Matthew R; Pearson, Ann

    2009-01-01

    We describe a new method for analysis of the nitrogen isotopic composition of sedimentary porphyrins. This method involves separation and purification of geoporphyrins from sediment samples using liquid chromatography and HPLC, oxidation of the nitrogen within porphyrin-enriched fractions using a two-step process, and isotopic analysis of the resulting nitrate using the denitrifier method. By analysis of these degradation products of chlorophylls, we are able to measure an isotopic signature that reflects the nitrogen utilized by primary producers. The high sensitivity of the denitrifier method allows measurement of small samples that contain low concentrations of porphyrins. Extraction of only 50 nmol of nitrogen (nmol N) allows the following five analyses to be made (each on approximately 10 nmol N): nitrogen concentration, an assessment of potential contamination by nonporphyrin N, and three replicate isotopic measurements. The measured values of delta15N have an average analytical precision of +/-0.5 per thousand (1sigma) and an average contribution from Rayleigh fractionation of 0.7 per thousand from incomplete oxidation of porphyrin N to nitrate. The overall method will enable high-resolution records of delta15N values to be obtained for geological and ecological applications.

  15. Generator Coordinate Method Analysis of Xe and Ba Isotopes

    Science.gov (United States)

    Higashiyama, Koji; Yoshinaga, Naotaka; Teruya, Eri

    Nuclear structure of Xe and Ba isotopes is studied in terms of the quantum-number projected generator coordinate method (GCM). The GCM reproduces well the energy levels of high-spin states as well as low-lying states. The structure of the low-lying states is analyzed through the GCM wave functions.

  16. An Iterative Method for the Construction of Equilibrium N-Body Models for Stellar Disks

    CERN Document Server

    Rodionov, S A

    2006-01-01

    One widely used technique for the construction of equilibrium models of stellar disks is based on the Jeans equations and the moments of velocity distribution functions derived using these equations. Stellar disks constructed using this technique are shown to be "not entirely" in equilibrium. Our attempt to abandon the epicyclic approximation and the approximation of infinite isothermal layers, which are commonly adopted in this technique, failed to improve the situation substantially. We conclude that the main drawback of techniques based on the Jeans equations is that the system of equations employed is not closed, and therefore requires adopting an essentially ad hoc additional closure condition. A new iterative approach to constructing equilibrium N-body models with a given density distribution is proposed. The main idea behind this approach is that a model is first constructed using some approximation method, and is then allowed to adjust to an equilibrium state with the specified density and the require...

  17. The global equilibrium method and its hybrid implementation for identifying heterogeneous elastic material parameters

    KAUST Repository

    Lubineau, Gilles

    2011-04-01

    New identification strategies have to be developed in order to perform the identification quickly and at very-low cost. A popular class of approaches relies on full-field measurement obtained through digital image correlation. We propose here a global equilibrium approach. It is based on the virtual field method in case specific virtual fields are used. It can also be seen as a generalization of the equilibrium gap method. This approach is easy to implement and we prove that it provides better or comparable results to the constitutive equation gap method that is known to be a very accurate reference. © 2010 Elsevier B.V.

  18. A superlinear iteration method for calculation of finite length journal bearing's static equilibrium position

    Science.gov (United States)

    Zhou, Wenjie; Wei, Xuesong; Wang, Leqin; Wu, Guangkuan

    2017-05-01

    Solving the static equilibrium position is one of the most important parts of dynamic coefficients calculation and further coupled calculation of rotor system. The main contribution of this study is testing the superlinear iteration convergence method-twofold secant method, for the determination of the static equilibrium position of journal bearing with finite length. Essentially, the Reynolds equation for stable motion is solved by the finite difference method and the inner pressure is obtained by the successive over-relaxation iterative method reinforced by the compound Simpson quadrature formula. The accuracy and efficiency of the twofold secant method are higher in comparison with the secant method and dichotomy. The total number of iterative steps required for the twofold secant method are about one-third of the secant method and less than one-eighth of dichotomy for the same equilibrium position. The calculations for equilibrium position and pressure distribution for different bearing length, clearance and rotating speed were done. In the results, the eccentricity presents linear inverse proportional relationship to the attitude angle. The influence of the bearing length, clearance and bearing radius on the load-carrying capacity was also investigated. The results illustrate that larger bearing length, larger radius and smaller clearance are good for the load-carrying capacity of journal bearing. The application of the twofold secant method can greatly reduce the computational time for calculation of the dynamic coefficients and dynamic characteristics of rotor-bearing system with a journal bearing of finite length.

  19. A superlinear iteration method for calculation of finite length journal bearing's static equilibrium position.

    Science.gov (United States)

    Zhou, Wenjie; Wei, Xuesong; Wang, Leqin; Wu, Guangkuan

    2017-05-01

    Solving the static equilibrium position is one of the most important parts of dynamic coefficients calculation and further coupled calculation of rotor system. The main contribution of this study is testing the superlinear iteration convergence method-twofold secant method, for the determination of the static equilibrium position of journal bearing with finite length. Essentially, the Reynolds equation for stable motion is solved by the finite difference method and the inner pressure is obtained by the successive over-relaxation iterative method reinforced by the compound Simpson quadrature formula. The accuracy and efficiency of the twofold secant method are higher in comparison with the secant method and dichotomy. The total number of iterative steps required for the twofold secant method are about one-third of the secant method and less than one-eighth of dichotomy for the same equilibrium position. The calculations for equilibrium position and pressure distribution for different bearing length, clearance and rotating speed were done. In the results, the eccentricity presents linear inverse proportional relationship to the attitude angle. The influence of the bearing length, clearance and bearing radius on the load-carrying capacity was also investigated. The results illustrate that larger bearing length, larger radius and smaller clearance are good for the load-carrying capacity of journal bearing. The application of the twofold secant method can greatly reduce the computational time for calculation of the dynamic coefficients and dynamic characteristics of rotor-bearing system with a journal bearing of finite length.

  20. Distance, dialogue and reflection : Interpersonal reflective equilibrium as method for professional ethics education

    NARCIS (Netherlands)

    van den Hoven, Mariëtte; Kole, Jos

    2015-01-01

    The method of reflective equilibrium (RE) is well known within the domain of moral philosophy, but hardly discussed as a method in professional ethics education. We argue that an interpersonal version of RE is very promising for professional ethics education. We offer several arguments to support th

  1. A control volume based finite difference method for solving the equilibrium equations in terms of displacements

    DEFF Research Database (Denmark)

    Hattel, Jesper; Hansen, Preben

    1995-01-01

    This paper presents a novel control volume based FD method for solving the equilibrium equations in terms of displacements, i.e. the generalized Navier equations. The method is based on the widely used cv-FDM solution of heat conduction and fluid flow problems involving a staggered grid formulati...

  2. Distance, Dialogue and Reflection: Interpersonal Reflective Equilibrium as Method for Professional Ethics Education

    Science.gov (United States)

    van den Hoven, Mariëtte; Kole, Jos

    2015-01-01

    The method of reflective equilibrium (RE) is well known within the domain of moral philosophy, but hardly discussed as a method in professional ethics education. We argue that an interpersonal version of RE is very promising for professional ethics education. We offer several arguments to support this claim. The first group of arguments focus on a…

  3. A control volume based finite difference method for solving the equilibrium equations in terms of displacements

    DEFF Research Database (Denmark)

    Hattel, Jesper; Hansen, Preben

    1995-01-01

    This paper presents a novel control volume based FD method for solving the equilibrium equations in terms of displacements, i.e. the generalized Navier equations. The method is based on the widely used cv-FDM solution of heat conduction and fluid flow problems involving a staggered grid formulation...

  4. Study of plasma equilibrium in toroidal fusion devices using mesh-free numerical calculation method

    Science.gov (United States)

    Rasouli, C.; Abbasi Davani, F.; Rokrok, B.

    2016-08-01

    Plasma confinement using external magnetic field is one of the successful ways leading to the controlled nuclear fusion. Development and validation of the solution process for plasma equilibrium in the experimental toroidal fusion devices is the main subject of this work. Solution of the nonlinear 2D stationary problem as posed by the Grad-Shafranov equation gives quantitative information about plasma equilibrium inside the vacuum chamber of hot fusion devices. This study suggests solving plasma equilibrium equation which is essential in toroidal nuclear fusion devices, using a mesh-free method in a condition that the plasma boundary is unknown. The Grad-Shafranov equation has been solved numerically by the point interpolation collocation mesh-free method. Important features of this approach include truly mesh free, simple mathematical relationships between points and acceptable precision in comparison with the parametric results. The calculation process has been done by using the regular and irregular nodal distribution and support domains with different points. The relative error between numerical and analytical solution is discussed for several test examples such as small size Damavand tokamak, ITER-like equilibrium, NSTX-like equilibrium, and typical Spheromak.

  5. Computational methods for multiphase equilibrium and kinetics calculations for geochemical and reactive transport applications

    Science.gov (United States)

    Leal, Allan; Saar, Martin

    2016-04-01

    Computational methods for geochemical and reactive transport modeling are essential for the understanding of many natural and industrial processes. Most of these processes involve several phases and components, and quite often requires chemical equilibrium and kinetics calculations. We present an overview of novel methods for multiphase equilibrium calculations, based on both the Gibbs energy minimization (GEM) approach and on the solution of the law of mass-action (LMA) equations. We also employ kinetics calculations, assuming partial equilibrium (e.g., fluid species in equilibrium while minerals are in disequilibrium) using automatic time stepping to improve simulation efficiency and robustness. These methods are developed specifically for applications that are computationally expensive, such as reactive transport simulations. We show how efficient the new methods are, compared to other algorithms, and how easy it is to use them for geochemical modeling via a simple script language. All methods are available in Reaktoro, a unified open-source framework for modeling chemically reactive systems, which we also briefly describe.

  6. Solution-large molecules method for calculating the equilibrium composition of heterogeneous systems

    Energy Technology Data Exchange (ETDEWEB)

    Alemasov, V.E.; Gruzdeva, Z.KH.; Dregalin, A.A.; Dregalin, A.F.

    1985-01-01

    A refined method for calculating the equilibrium composition of heterogeneous systems is presented which combines the advantages of the large-molecule method and of the model of an ideal solution of condensed phases. It is shown that the new method provides better convergence and requires less computational effort than either of the above approaches. Results are presented for the combustion products of O2 + BeH2 fuel.

  7. Semiexperimental equilibrium structure of the lower energy conformer of glycidol by the mixed estimation method.

    Science.gov (United States)

    Demaison, Jean; Craig, Norman C; Conrad, Andrew R; Tubergen, Michael J; Rudolph, Heinz Dieter

    2012-09-13

    Rotational constants were determined for (18)O-substituted isotopologues of the lower energy conformer of glycidol, which has an intramolecular inner hydrogen bond from the hydroxyl group to the oxirane ring oxygen. Rotational constants were previously determined for the (13)C and the OD species. These rotational constants have been corrected with the rovibrational constants calculated from an ab initio cubic force field. The derived semiexperimental equilibrium rotational constants have been supplemented by carefully chosen structural parameters, including those for hydrogen atoms, from medium level ab initio calculations. The combined data have been used in a weighted least-squares fit to determine an equilibrium structure for the glycidol H-bond inner conformer. This work shows that the mixed estimation method allows us to determine a complete and reliable equilibrium structure for large molecules, even when the rotational constants of a number of isotopologues are unavailable.

  8. Analysis of Equilibrium and Kinetics of Chromium-Fluoride Complexation from Spectroscopic Data via Chemometrics Methods

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    The complexation of Cr3+ with F- undergoes a multistep reversible process. An approach to research the involved equilibria and kinetics using suitable chemometrics methods to the online measured UV-Vis spectra is proposed. By investigating the equilibrium spectra of the complexes at different molar ratios of M to L(metal to ligand) and 50 ℃, the result of Principal Component Analysis(PCA) shows that three complexes, ML, ML2 and ML3, can be formed under the research conditions. The spectrum of each complex was then analyzed and the accumulated equilibrium constants were calculated by applying Target Testing Factor Analysis(TTFA). Meanwhile, a reactive intermediate was observed before the formation of MLx during the specific kinetic study at 15 ℃. The equilibrium constant and spectrum of the intermediate as well as the rate constants were all resolved by using TTFA.

  9. A new method of tree xylem water extraction for isotopic analysis

    Science.gov (United States)

    Gierke, C.; Newton, B. T.

    2011-12-01

    waters (IW), allowing diffusive processes to proceed to equilibrium, measuring the composition of the resulting mixture or final water (FW) then, solving a simple mixing equation. To evaluate this method, we collected several twig samples from Douglas Firs in the Sacramento Mountains. Twig water was prepared for isotopic analysis both by cryogenic distillation and the mixing method. Soil in close proximity to these trees was also sampled and water was extracted by cryogenic distillation. Preliminary results show that the isotopic composition of distilled twig water and soil waters plot to the right of the local meteoric water line (LMWL) suggesting that trees are extracting shallow evaporated soil water. Twig water obtained from the mixing method plot near the LMWL within the range expected for local snow melt, suggesting a possibly deeper non-evaporated source. In general, distillation values are approximately 4% heavier with respect to delta 18O than waters obtained from the mixing method. It is possible that this difference is due to the contribution of the fractionated water of the twig phloem that is released during the distillation process. This difference is quite significant and can lead to very different interpretations. These results are being addressed with additional experiments.

  10. Stability Analysis of Anchored Soil Slope Based on Finite Element Limit Equilibrium Method

    Directory of Open Access Journals (Sweden)

    Rui Zhang

    2016-01-01

    Full Text Available Under the condition of the plane strain, finite element limit equilibrium method is used to study some key problems of stability analysis for anchored slope. The definition of safe factor in slices method is generalized into FEM. The “true” stress field in the whole structure can be obtained by elastic-plastic finite element analysis. Then, the optimal search for the most dangerous sliding surface with Hooke-Jeeves optimized searching method is introduced. Three cases of stability analysis of natural slope, anchored slope with seepage, and excavation anchored slope are conducted. The differences in safety factor quantity, shape and location of slip surface, anchoring effect among slices method, finite element strength reduction method (SRM, and finite element limit equilibrium method are comparatively analyzed. The results show that the safety factor given by the FEM is greater and the unfavorable slip surface is deeper than that by the slice method. The finite element limit equilibrium method has high calculation accuracy, and to some extent the slice method underestimates the effect of anchor, and the effect of anchor is overrated in the SRM.

  11. A new method for stable lead isotope extraction from seawater

    Energy Technology Data Exchange (ETDEWEB)

    Zurbrick, Cheryl M., E-mail: CZurbric@ucsc.edu [WIGS, Department of Microbiology and Environmental Toxicology, University of California Santa Cruz, 1156 High Street, Santa Cruz, CA 95064 (United States); Gallon, Céline [Institute of Marine Sciences, University of California Santa Cruz, 1156 High Street, Santa Cruz, CA 95064 (United States); Flegal, A. Russell [WIGS, Department of Microbiology and Environmental Toxicology, University of California Santa Cruz, 1156 High Street, Santa Cruz, CA 95064 (United States); Institute of Marine Sciences, University of California Santa Cruz, 1156 High Street, Santa Cruz, CA 95064 (United States)

    2013-10-24

    Graphical abstract: -- Highlights: •We present a relatively fast (2.5–6.5 h), semi-automated system to extract Pb from seawater. •Extraction requires few chemicals and has a relatively low blank (0.7 pmol kg{sup −1}). •We compare analyses of Pb isotopes by HR ICP-MS with those by MC-ICP-MS. -- Abstract: A new technique for stable lead (Pb) isotope extraction from seawater is established using Toyopearl AF-Chelate 650 M{sup ®} resin (Tosoh Bioscience LLC). This new method is advantageous because it is semi-automated and relatively fast; in addition it introduces a relatively low blank by minimizing the volume of chemicals used in the extraction. Subsequent analyses by HR ICP-MS have a good relative external precision (2σ) of 3.5‰ for {sup 206}Pb/{sup 207}Pb, while analyses by MC-ICP-MS have a better relative external precision of 0.6‰. However, Pb sample concentrations limit MC-ICP-MS analyses to {sup 206}Pb, {sup 207}Pb, and {sup 208}Pb. The method was validated by processing the common Pb isotope reference material NIST SRM-981 and several GEOTRACES intercalibration samples, followed by analyses by HR ICP-MS, all of which showed good agreement with previously reported values.

  12. Analysis of Tensegrity Structures with Redundancies, by Implementing a Comprehensive Equilibrium Equations Method with Force Densities

    Directory of Open Access Journals (Sweden)

    Miltiades Elliotis

    2016-01-01

    Full Text Available A general approach is presented to analyze tensegrity structures by examining their equilibrium. It belongs to the class of equilibrium equations methods with force densities. The redundancies are treated by employing Castigliano’s second theorem, which gives the additional required equations. The partial derivatives, which appear in the additional equations, are numerically replaced by statically acceptable internal forces which are applied on the structure. For both statically determinate and indeterminate tensegrity structures, the properties of the resulting linear system of equations give an indication about structural stability. This method requires a relatively small number of computations, it is direct (there is no iteration procedure and calculation of auxiliary parameters and is characterized by its simplicity. It is tested on both 2D and 3D tensegrity structures. Results obtained with the method compare favorably with those obtained by the Dynamic Relaxation Method or the Adaptive Force Density Method.

  13. COUPLING OF ASSUMED STRESS FINITE ELEMENT AND BOUNDARY ELEMENT METHODS WITH STRESS-TRACTION EQUILIBRIUM

    Institute of Scientific and Technical Information of China (English)

    GUZELBEY Ibrahim H.; KANBER Bahattin; AKPOLAT Abdullah

    2004-01-01

    In this study, the stress based finite element method is coupled with the boundary element method in two different ways. In the first one, the ordinary distribution matrix is used for coupling. In the second one, the stress traction equilibrium is used at the interface line of both regions as a new coupling process. This new coupling procedure is presented without a distribution matrix. Several case studies are solved for the validation of the developed coupling procedure. The results of case studies are compared with the distribution matrix coupling, displacement based finite element method, assumed stress finite element method, boundary element method, ANSYS and analytical results whenever possible. It is shown that the coupling of the stress traction equilibrium with assumed stress finite elements gives as accurate results as those by the distribution matrix coupling.

  14. Variations of oceanic oxygen isotopes at the present day and the LGM: equilibrium simulations with an oceanic general circulation model

    Directory of Open Access Journals (Sweden)

    X. Xu

    2012-10-01

    Full Text Available The isotope-enabled oceanic general circulation model, MPI-OM, is used to simulate the oxygen isotope compositions of sea waters in the oceans under preindustrial and last glacial maximum climate conditions. Simulated oceanic isotope distributions at the last glacial maximum (21 000 yr ago show features similar to the preindustrial in most basins but the Northern North Atlantic. With the exception of the ice sheet impact, the oxygen-18 content variations at sea surface during the last glacial maximum are mainly controlled by the changes in boundary isotopic fluxes in most regions, while the changes from subsurface to bottom waters are mostly due to the differences in the water mass circulations. The changes in topography at the northern high latitudes have a remarkable influence on the isotopic composition in the Arctic Ocean. The pre-industrial and the last glacial maximum calcite oxygen isotope compositions in the surface water and their difference are also calculated. These results are compared with the observed values from different foraminifera species and are in agreement with the observations in most regions.

  15. A numerical method for solving equilibrium problems of no-tension solids subject to thermal loads

    OpenAIRE

    Padovani, Cristina; Pasquinelli, Giuseppe; Zani, Nicola

    1996-01-01

    The paper starts out by recalling a constitutive equation of no-tension materiate that accounts for thermal dilatation and the temperature dependence of the material constants. Subsequently, a numerical method is presented for solving, via the finite element method, equilibrium problems of no-tension solids subjected to thermal loads. Finally, three examples are solved and discussed: a spherical container subjected to two uniform radiai pressures and a steady temperature distribution, a mason...

  16. Chromatographic speciation of Cr(III)-species, inter-species equilibrium isotope fractionation and improved chemical purification strategies for high-precision isotope analysis

    DEFF Research Database (Denmark)

    Larsen, Kirsten Kolbjørn; Wielandt, Daniel Kim Peel; Schiller, Martin;

    2016-01-01

    Chromatographic purification of chromium (Cr), which is required for high-precision isotope analysis, is complicated by the presence of multiple Cr-species with different effective charges in the acid digested sample aliquots. The differing ion exchange selectivity and sluggish reaction rates of ...

  17. Equilibrium Fe isotope fractionation between inorganic aqueous Fe(III) and the siderophore complex, Fe(III)-desferrioxamine B

    DEFF Research Database (Denmark)

    Dideriksen, Knud; Baker, Joel A.; Stipp, Susan Louise Svane

    2008-01-01

    In oxic oceans, most of the dissolved iron (Fe) exists as complexes with siderophore-like, strongly coordinating organic ligands. Thus, the isotope composition of the little amount of free inorganic Fe that is available for precipitation and preservation in the geological record may largely...... differently complexed Fe(III) pools were separated by addition of Na2CO3, which led to immediate precipitation of the inorganic Fe without causing significant dissociation of Fe-desferrioxamine complexes. Experiments using enriched 57Fe tracer showed that isotopic equilibration between the 57Fe......(III)-bearing environments, such as soils and rivers, and may, for example, largely control the Fe isotope composition of marine Fe–Mn crusts....

  18. New method for computing unstable equilibrium points of power systems with induction motors

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    The computation of the unstable equilibrium point(UEP) is a key step involved in stability region estimation of nonlinear dynamic systems.A new continuation-based method to compute the UEPs of a power system with induction motors is proposed.The mechanical torques of motors are changed to form a parameterized equation set.Then the solution curve of the equation set is traced by the continuation method from the stable equilibrium point to a UEP.The direction of mechanical torque change is varied to get multiple UEPs.The obtained UEPs are mostly type-1.Then fast assessment of induction motor stability is studied by approximating the stable manifolds of the UEPs.The method is tested in several systems and satisfactory results are obtained.

  19. METHOD FOR IN SITU DETERMINATION OF PCO2 IN SEA-AIR EQUILIBRIUM SYSTEM

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The method for determining PCO2 in the atmosphere and water by using gas chromatography was studied. For determination of PCO2 in the atmosphere, a sampling method was developed in which the chromatograph was connected to a 6-port valve with a sampling pipe opening to the atmosphere, so gas pressure in the sampling pipe was identical to that of the atmosphere. A semi-automatic seawater-atmosphere equilibrium system was designed to determine the PCO2 in seawater. The equilibrium chamber contained in situ seawater and the well-equilibrated gas was pushed into the sampling pipe by sample water, so pressure and temperature calibration could be avoided. This method has high accuracy for the determination of PCO2 in the air and seawater, and was used for in situ determination of PCO2 in the atmosphere and of the seawater sample in the JGOFS cruise in the East China Sea.

  20. METHOD FOR IN SITU DETERMINATION OF Pco2 IN SEA-AIR EQUILIBRIUM SYSTEM

    Institute of Scientific and Technical Information of China (English)

    崔鹤; 纪雷; 王军; 辛淑平; 张龙军; 陆贤昆

    2001-01-01

    The method for determining Pco2 in the atmosphere and water by using gas chroma-tography was studied. For determination of Pco2 in the atmosphere, a sampling method was developed in which the chromatograph was connected to a 6-port valve with a sampling pipe opening to the atmosphere, so gas pressure in the sampling pipe was identical to that of the atmoesphere. A semi-automatic seawater-atmosphere equilibrium system was designed to determine the Pco2 in seawater. The equilibrium chamber contained in situ seawater and the well-equilibrated gas was pushed into the sampling pipe by sample wa-ter, so pressure and temperature calibration could be avoided. This method has high accuracy for the de-termination of Pco2 in the air and seawater, and was used for in situ determination of Pco2 in the atmo-sphere and of the seawater sample in the JGOFS cruise in the East China Sea.

  1. A refined method for calculating paleotemperatures from linear correlations in bamboo coral carbon and oxygen isotopes

    Science.gov (United States)

    Saenger, Casey; Watkins, James M.

    2016-06-01

    Bamboo corals represent an emerging paleoclimate archive with the potential to record variability at intermediate depths throughout much of the global ocean. Realizing this potential has been complicated by biologically mediated vital effects, which are evident in linear correlations of skeletal carbon (δ13C) and oxygen (δ18O) isotope composition. Previous efforts to develop a bamboo coral δ18O paleothermometer by accounting for such vital effects have not been completely successful as they still rely on empirical calibrations that are offset from the temperature dependence of abiogenic experiments. Here we describe an approach that better corrects for bamboo coral vital effects and allows paleotemperatures to be calculated directly from the abiogenic temperature dependence. The success of the method lies in calculating apparent equilibrium carbon and oxygen isotope fractionation at the temperature, pH, and growth rate of each coral, as well as in the use of model II regressions. Rigorous propagation of uncertainty suggests typical errors of ±2-3°C, but in select cases errors as low as ±0.65°C can be achieved for densely sampled and strongly correlated data sets. This lower limit approaches the value attributed to uncertainty in pH and growth rate estimates alone, as predicted by a series of pseudoproxy experiments. The incorporation of isotopically light metabolic CO2 appears to be negligible in most Pacific corals, but may be significant in Atlantic specimens, potentially requiring an additional correction. The success of the method therefore hinges on how well complex environmental systems and biomineralization strategies are constrained, with the most reliable temperatures occurring when calcifying fluid pH, growth rate, and incorporation of metabolic carbon into skeletal calcite are constrained using multiple geochemical proxies.

  2. EC-FORC: A New Cyclic Voltammetry Based Method for Examining Phase Transitions and Predicting Equilibrium

    CERN Document Server

    Hamad, Ibrahim Abou; Novotny, Mark A; Rikvold, Per Arne

    2007-01-01

    We propose a new, cyclic-voltammetry based experimental technique that can not only differentiate between discontinuous and continuous phase transitions in an adsorbate layer, but also quite accurately recover equilibrium behavior from dynamic analysis of systems with a continuous phase transition. The Electrochemical first-order reversal curve (EC-FORC) diagram for a discontinuous phase transition (nucleation and growth), such as occurs in underpotential deposition, is characterized by a negative region, while such a region does not exist for a continuous phase transition, such as occurs in the electrosorption of Br on Ag(100). Moreover, for systems with a continuous phase transition, the minima of the individual EC-FORCs trace the equilibrium curve, even at very high scan rates. Since obtaining experimental data for the EC-FORC method would require only a simple reprogramming of the potentiostat used in conventional cyclic-voltammetry experiments, we believe that this method has significant potential for ea...

  3. Strong Convergence of an Iterative Method for Equilibrium Problems and Variational Inequality Problems

    Directory of Open Access Journals (Sweden)

    HongYu Li

    2009-01-01

    Full Text Available We introduce an iterative method for finding a common element of the set of solutions of equilibrium problems, the set of solutions of variational inequality problems, and the set of fixed points of finite many nonexpansive mappings. We prove strong convergence of the iterative sequence generated by the proposed iterative algorithm to the unique solution of a variational inequality, which is the optimality condition for the minimization problem.

  4. A New Method of Assessing the Extent of Topographic Equilibrium at Different Spatial Scales

    Science.gov (United States)

    Walcott, R.

    2013-12-01

    The Earth's surface represents the current resultant state of the interaction between forces working to lower topography and those working to resist this, or to raise topography. A diversity of processes generate these forces and in some cases coupled feedbacks allow a dynamic equilibrium to emerge at certain spatial and temporal scales. Dynamic equilibrium is typically expressed by distinctive geometries (e.g., regular catchment shapes, first order geometry of an orogen, constant thickness of a soil horizon over space). However, the presence of stochastic surface and tectonic processes also means that regular geometries are rarely observed at all scales. Determining the scale and temporal range over which topography can be considered to be in equilibrium can be difficult and expensive, requiring a large range of spatially distributed data, and/or data that spans significant time periods. Here we present a new morphometric method that focuses on the product of erosive competition between catchments, that is the geometry of drainage divide intersections. We use this method to show that stable areas, with minimal tectonic disturbance and homogeneous rock types have distinctive drainage divide geometry (e.g. Eastern USA) which differs from the geometry of drainage divide intersections in other environments (e.g. tectonically active regions such as the South Island of New Zealand). With a few caveats, this method could be used to predict areas prone to drainage divide migration and river network reconfiguration.

  5. Strong convergence theorems for equilibrium problems and fixed point problems: A new iterative method, some comments and applications

    Directory of Open Access Journals (Sweden)

    Du Wei-Shih

    2011-01-01

    Full Text Available Abstract In this paper, we introduce a new approach method to find a common element in the intersection of the set of the solutions of a finite family of equilibrium problems and the set of fixed points of a nonexpansive mapping in a real Hilbert space. Under appropriate conditions, some strong convergence theorems are established. The results obtained in this paper are new, and a few examples illustrating these results are given. Finally, we point out that some 'so-called' mixed equilibrium problems and generalized equilibrium problems in the literature are still usual equilibrium problems. 2010 Mathematics Subject Classification: 47H09; 47H10, 47J25.

  6. Method of preparing mercury with an arbitrary isotopic distribution

    Science.gov (United States)

    Grossman, M.W.; George, W.A.

    1986-12-16

    This invention provides for a process for preparing mercury with a predetermined, arbitrary, isotopic distribution. In one embodiment, different isotopic types of Hg[sub 2]Cl[sub 2], corresponding to the predetermined isotopic distribution of Hg desired, are placed in an electrolyte solution of HCl and H[sub 2]O. The resulting mercurous ions are then electrolytically plated onto a cathode wire producing mercury containing the predetermined isotopic distribution. In a similar fashion, Hg with a predetermined isotopic distribution is obtained from different isotopic types of HgO. In this embodiment, the HgO is dissolved in an electrolytic solution of glacial acetic acid and H[sub 2]O. The isotopic specific Hg is then electrolytically plated onto a cathode and then recovered. 1 fig.

  7. A statistical method for evaluation of the experimental phase equilibrium data of simple clathrate hydrates

    DEFF Research Database (Denmark)

    Eslamimanesh, Ali; Gharagheizi, Farhad; Mohammadi, Amir H.

    2012-01-01

    , and the residuals of a selected correlation results lead to define the probable outliers. This method not only contributes to outliers diagnostics but also identifies the range of applicability of the applied model and quality of the existing experimental data. The available correlation in the literature......We, herein, present a statistical method for diagnostics of the outliers in phase equilibrium data (dissociation data) of simple clathrate hydrates. The applied algorithm is performed on the basis of the Leverage mathematical approach, in which the statistical Hat matrix, Williams Plot...

  8. Methods and limitations of 'clumped' CO2 isotope (Delta47) analysis by gas-source isotope ratio mass spectrometry.

    Science.gov (United States)

    Huntington, K W; Eiler, J M; Affek, H P; Guo, W; Bonifacie, M; Yeung, L Y; Thiagarajan, N; Passey, B; Tripati, A; Daëron, M; Came, R

    2009-09-01

    The geochemistry of multiply substituted isotopologues ('clumped-isotope' geochemistry) examines the abundances in natural materials of molecules, formula units or moieties that contain more than one rare isotope (e.g. (13)C(18)O(16)O, (18)O(18)O, (15)N(2), (13)C(18)O(16)O(2) (2-)). Such species form the basis of carbonate clumped-isotope thermometry and undergo distinctive fractionations during a variety of natural processes, but initial reports have provided few details of their analysis. In this study, we present detailed data and arguments regarding the theoretical and practical limits of precision, methods of standardization, instrument linearity and related issues for clumped-isotope analysis by dual-inlet gas-source isotope ratio mass spectrometry (IRMS). We demonstrate long-term stability and subtenth per mil precision in 47/44 ratios for counting systems consisting of a Faraday cup registered through a 10(12) ohm resistor on three Thermo-Finnigan 253 IRMS systems. Based on the analyses of heated CO(2) gases, which have a stochastic distribution of isotopes among possible isotopologues, we document and correct for (1) isotopic exchange among analyte CO(2) molecules and (2) subtle nonlinearity in the relationship between actual and measured 47/44 ratios. External precisions of approximately 0.01 per thousand are routinely achieved for measurements of the mass-47 anomaly (a measure mostly of the abundance anomaly of (13)C-(18)O bonds) and follow counting statistics. The present technical limit to precision intrinsic to our methods and instrumentation is approximately 5 parts per million (ppm), whereas precisions of measurements of heterogeneous natural materials are more typically approximately 10 ppm (both 1 s.e.). These correspond to errors in carbonate clumped-isotope thermometry of +/-1.2 degrees C and +/-2.4 degrees C, respectively.

  9. Modified Limiting Equilibrium Method for Stability Analysis of Stratified Rock Slopes

    Directory of Open Access Journals (Sweden)

    Rui Yong

    2016-01-01

    Full Text Available The stratified rock of Jurassic strata is widely distributed in Three Gorges Reservoir Region. The limit equilibrium method is generally utilized in the stability analysis of rock slope with single failure plane. However, the stratified rock slope cannot be accurately estimated by this method because of different bedding planes and their variable shear strength parameters. Based on the idealized model of rock slope with bedding planes, a modified limiting equilibrium method is presented to determine the potential sliding surface and the factor of safety for the stratified rock slope. In this method, the S-curve model is established to define the spatial variations of the shear strength parameters c and  φ of bedding plane and the tensile strength of rock mass. This method was applied in the stability evaluation of typical stratified rock slope in Three Gorges Reservoir Region, China. The result shows that the factor of safety of the case study is 0.973, the critical sliding surface for the potential slip surface appears at bedding plane C, and the tension-controlled failure occurs at 10.5 m to the slope face.

  10. Thermodynamic equilibrium solubility measurements in simulated fluids by 96-well plate method in early drug discovery.

    Science.gov (United States)

    Bharate, Sonali S; Vishwakarma, Ram A

    2015-04-01

    An early prediction of solubility in physiological media (PBS, SGF and SIF) is useful to predict qualitatively bioavailability and absorption of lead candidates. Despite of the availability of multiple solubility estimation methods, none of the reported method involves simplified fixed protocol for diverse set of compounds. Therefore, a simple and medium-throughput solubility estimation protocol is highly desirable during lead optimization stage. The present work introduces a rapid method for assessment of thermodynamic equilibrium solubility of compounds in aqueous media using 96-well microplate. The developed protocol is straightforward to set up and takes advantage of the sensitivity of UV spectroscopy. The compound, in stock solution in methanol, is introduced in microgram quantities into microplate wells followed by drying at an ambient temperature. Microplates were shaken upon addition of test media and the supernatant was analyzed by UV method. A plot of absorbance versus concentration of a sample provides saturation point, which is thermodynamic equilibrium solubility of a sample. The established protocol was validated using a large panel of commercially available drugs and with conventional miniaturized shake flask method (r(2)>0.84). Additionally, the statistically significant QSPR models were established using experimental solubility values of 52 compounds.

  11. Convergence Theorems Concerning Hybrid Methods for Strict Pseudocontractions and Systems of Equilibrium Problems

    Directory of Open Access Journals (Sweden)

    Duan Peichao

    2010-01-01

    Full Text Available Let be strict pseudo-contractions defined on a closed and convex subset of a real Hilbert space . We consider the problem of finding a common element of fixed point set of these mappings and the solution set of a system of equilibrium problems by parallel and cyclic algorithms. In this paper, new iterative schemes are proposed for solving this problem. Furthermore, we prove that these schemes converge strongly by hybrid methods. The results presented in this paper improve and extend some well-known results in the literature.

  12. Traffic Network Equilibrium Problems with Capacity Constraints of Arcs and Linear Scalarization Methods

    Directory of Open Access Journals (Sweden)

    X. Q. Tian

    2012-01-01

    Full Text Available Traffic network equilibrium problems with capacity constraints of arcs are studied. A (weak vector equilibrium principle with vector-valued cost functions, which are different from the ones in the work of Lin (2010, and three kinds of parametric equilibrium flows are introduced. Some necessary and sufficient conditions for a (weak vector equilibrium flow to be a parametric equilibrium flow are derived. Relationships between a parametric equilibrium flow and a solution of a scalar variational inequality problem are also discussed. Some examples are given to illustrate our results.

  13. Particle Swarm Optimization Algorithm Coupled with Finite Element Limit Equilibrium Method for Geotechnical Practices

    Directory of Open Access Journals (Sweden)

    Hongjun Li

    2012-01-01

    Full Text Available This paper proposes a modified particle swarm optimization algorithm coupled with the finite element limit equilibrium method (FELEM for the minimum factor of safety and the location of associated noncircular critical failure surfaces for various geotechnical practices. During the search process, the stress compatibility constraints coupled with the geometrical and kinematical compatibility constraints are firstly established based on the features of slope geometry and stress distribution to guarantee realistic slip surfaces from being unreasonable. Furthermore, in the FELEM, based on rigorous theoretical analyses and derivation, it is noted that the physical meaning of the factor of safety can be formulated on the basis of strength reserving theory rather than the overloading theory. Consequently, compared with the limit equilibrium method (LEM and the shear strength reduction method (SSRM through several numerical examples, the FELEM in conjunction with the improved search strategy is proved to be an effective and efficient approach to routine analysis and design in geotechnical practices with a high level of confidence.

  14. Calculation of isotopic mass and energy production by a matrix operator method. [Volterra method of the multiplicative integral

    Energy Technology Data Exchange (ETDEWEB)

    Lee, C.E.

    1976-08-01

    The Volterra method of the multiplicative integral is used to determine the isotopic density, mass, and energy production in linear systems. The solution method, assumptions, and limitations are discussed. The method allows a rapid accurate calculation of the change in isotopic density, mass, and energy production independent of the magnitude of the time steps, production or decay rates, or flux levels.

  15. Theoretical estimates of equilibrium sulfur isotope effects in aqueous sulfur systems: Highlighting the role of isomers in the sulfite and sulfoxylate systems

    Science.gov (United States)

    Eldridge, D. L.; Guo, W.; Farquhar, J.

    2016-12-01

    We present theoretical calculations for all three isotope ratios of sulfur (33S/32S, 34S/32S, 36S/32S) at the B3LYP/6-31+G(d,p) level of theory for aqueous sulfur compounds modeled in 30-40H2O clusters spanning the range of sulfur oxidation state (Sn, n = -2 to +6) for estimating equilibrium fractionation factors in aqueous systems. Computed 34β values based on major isotope (34S/32S) reduced partition function ratios (RPFRs) scale to a first order with sulfur oxidation state and coordination, where 34β generally increase with higher oxidation state and increasing coordination of the sulfur atom. Exponents defining mass dependent relationships based on β values (x/34κ = ln(xβ)/ln(34β), x = 33 or 36) conform to tight ranges over a wide range of temperature for all aqueous compounds (33/34κ ≈ 0.5148-0.5159, 36/34κ ≈ 1.89-1.90 from T ⩾ 0 °C). The exponents converge near a singular value for all compounds at the high temperature limit (33/34κT→∞ = 0.51587 ± 0.00003 and 36/34κT→∞ = 1.8905 ± 0.0002; 1 s.d. of all computed compounds), and typically follow trends based on oxidation state and coordination similar to those seen in 34β values at lower temperatures. Theoretical equilibrium fractionation factors computed from these β-values are compared to experimental constraints for HSO3-T(aq)/SO2(g, aq), SO2(aq)/SO2(g), H2S(aq)/H2S(g), H2S(aq)/HS-(aq), SO42-(aq)/H2ST(aq), S2O32-(aq) (intramolecular), and S2O32-(aq)/H2ST(aq), and generally agree within a reasonable estimation of uncertainties. We make predictions of fractionation factors where other constraints are unavailable. Isotope partitioning of the isomers of protonated compounds in the sulfite and sulfoxylate systems depend strongly on whether protons are bound to either sulfur or oxygen atoms. The magnitude of the HSO3-T/SO32- major isotope (34S/32S) fractionation factor is predicted to increase with temperature from 0 to 70 °C due to the combined effects of the large magnitude (HS)O3

  16. Stable isotope methods in biological and ecological studies of arthropods

    NARCIS (Netherlands)

    Hood-Nowotny, R.C.; Knols, B.G.J.

    2007-01-01

    This is an eclectic review and analysis of contemporary and promising stable isotope methodologies to study the biology and ecology of arthropods. It is augmented with literature from other disciplines, indicative of the potential for knowledge transfer. It is demonstrated that stable isotopes can

  17. THE GENERALIZED MAXIMUM LIKELIHOOD METHOD APPLIED TO HIGH PRESSURE PHASE EQUILIBRIUM

    Directory of Open Access Journals (Sweden)

    Lúcio CARDOZO-FILHO

    1997-12-01

    Full Text Available The generalized maximum likelihood method was used to determine binary interaction parameters between carbon dioxide and components of orange essential oil. Vapor-liquid equilibrium was modeled with Peng-Robinson and Soave-Redlich-Kwong equations, using a methodology proposed in 1979 by Asselineau, Bogdanic and Vidal. Experimental vapor-liquid equilibrium data on binary mixtures formed with carbon dioxide and compounds usually found in orange essential oil were used to test the model. These systems were chosen to demonstrate that the maximum likelihood method produces binary interaction parameters for cubic equations of state capable of satisfactorily describing phase equilibrium, even for a binary such as ethanol/CO2. Results corroborate that the Peng-Robinson, as well as the Soave-Redlich-Kwong, equation can be used to describe phase equilibrium for the following systems: components of essential oil of orange/CO2.Foi empregado o método da máxima verossimilhança generalizado para determinação de parâmetros de interação binária entre os componentes do óleo essencial de laranja e dióxido de carbono. Foram usados dados experimentais de equilíbrio líquido-vapor de misturas binárias de dióxido de carbono e componentes do óleo essencial de laranja. O equilíbrio líquido-vapor foi modelado com as equações de Peng-Robinson e de Soave-Redlich-Kwong usando a metodologia proposta em 1979 por Asselineau, Bogdanic e Vidal. A escolha destes sistemas teve como objetivo demonstrar que o método da máxima verosimilhança produz parâmetros de interação binária, para equações cúbicas de estado capazes de descrever satisfatoriamente até mesmo o equilíbrio para o binário etanol/CO2. Os resultados comprovam que tanto a equação de Peng-Robinson quanto a de Soave-Redlich-Kwong podem ser empregadas para descrever o equilíbrio de fases para o sistemas: componentes do óleo essencial de laranja/CO2.

  18. Boron isotope method for study of seawater intrusion

    Institute of Scientific and Technical Information of China (English)

    肖应凯; 尹德忠; 刘卫国; 王庆忠; 魏海珍

    2001-01-01

    A distinct difference in boron isotopes between seawater and terrestrial water is emphasized by δ11B values reported for seawater and groundwater, with an average of 38.8‰ and in the range of -8.9‰ to 9.8‰, respectively. The isotopic composition of boron in groundwater can be used to quantify seawater intrusion and identify intrusion types, e.g. seawater or brine intrusions with different chemical and isotopic characteristics, by using the relation of δ11B and chloride concentration. The feasibility of utilizing boron isotope in groundwater for studying seawater intrusion in Laizhou Bay Region, China, is reported in this study, which shows that boron isotope is a useful and excellent tool for the study of seawater intrusion.

  19. Development of new deactivation method for simulation of fluid catalytic cracking equilibrium catalyst

    Indian Academy of Sciences (India)

    T Chiranjeevi; D T Gokak; V Ravikumar; P S Viswanathan

    2014-03-01

    Selection of a good catalyst is the easiest way to increase profitability of a fluid catalytic cracking (FCC) unit. During operation, these catalysts get deactivated due to operation at high temperatures, steam and deposition of metals on the catalyst. Developing a proper catalyst deactivation method is crucial for optimization of a good catalyst for FCC. Conventional laboratory deactivation procedures include direct metal impregnation method, cyclic deactivation method (CDM) and cyclic propylene steaming (CPS). Direct metal impregnation method gives higher coke and gas yields. CDM and CPS methods implementation is very difficult and time-consuming and there is a deviation in coke and gas yield. New rapid deactivation method has been developed to simulate plant equilibrium catalyst (E-Cat) by modifying metal impregnation, steaming and oxidation/reduction procedures. The E-Cat generated through a new deactivation method was characterized for physico-chemical properties using X ray diffraction (XRD), temperature-programmed reduction (TPR), and SEM-EDX and activity studies. XRD studies show that metals are dispersed well on catalyst samples. SEMEDX studies reveal that the morphology of simulated E-Cat and plant E-Cat catalyst particles appear to be same. E-Cat obtained by new deactivationmethod gives better coke and gas yields. Two E-Cats were also generated through CDM and direct metal impregnation method for comparing with the one generated through new method. New deactivation method also significantly reduces the evaluation time.

  20. An Iterative Algorithm Combining Viscosity Method with Parallel Method for a Generalized Equilibrium Problem and Strict Pseudocontractions

    Directory of Open Access Journals (Sweden)

    2009-03-01

    Full Text Available We introduce a new approximation scheme combining the viscosity method with parallel method for finding a common element of the set of solutions of a generalized equilibrium problem and the set of fixed points of a family of finitely strict pseudocontractions. We obtain a strong convergence theorem for the sequences generated by these processes in Hilbert spaces. Based on this result, we also get some new and interesting results. The results in this paper extend and improve some well-known results in the literature.

  1. Non-equilibrium simulation of CH4 production through the depressurization method from gas hydrate reservoirs

    Science.gov (United States)

    Qorbani, Khadijeh; Kvamme, Bjørn

    2016-04-01

    as non-equilibrium processes under local constraint of mass and heat fluxes. In this work, we have extended RCB by adding another route for dissociation or reformation of CH4-hydrate towards CH4 into the aqueous phase and water. CH4-hydrate formation and dissociation is resolved by looking at supersaturation and undersaturation with respect to thermodynamics variables. Hydrate instability due to undersaturation of CH4 in the contacting water phase is also considered. A complete non-equilibrium thermodynamic package, developed in-house, was combined with RCB to account for competing phase transitions by considering the minimization of Gibb's free energy. The energy differences were calculated from variations in chemical potentials of hydrate and hydrate formers. Mass transport, heat transport and non-equilibrium thermodynamic effects were implemented through classical nucleation theory to model the kinetic rate of hydrate phase transitions. To illustrate our implementations we ran simulations covering time-spans in the order of hundred years. CH4 production was modelled using the depressurization method, where we employed the Messoyakha field data. We discuss our implementations, as well as results obtained from simulations utilizing our modifications.

  2. Clinical value of isotope methods in adrenal morphology investigations

    Energy Technology Data Exchange (ETDEWEB)

    Jakubowski, W.; Feltynowski, T.; Graban, W. (Akademia Medyczna, Warsaw (Poland))

    1981-01-01

    In the years 1976-1980 in 105 patients 124 adrenal scintigrams were obtained, including 50 in patients with primary hyperaldosteronism syndrome, 27 with Cushings syndrome, 8 after bilateral total adrenalectomy, 4 with adrenal virilizing tumours, 6 with phaeochromocytoma, 10 with normal adrenal function. The results of scintigraphy were compared with those of arteriography, phlebography, computer tomography and postoperative findings. The clinical value of scintigraphy was found to be greatest in cases of adrenocortical disease. In cases of phaeochromocytoma isotope angioscintigraphy is a useful method for localizing the tumour since it makes possible demonstration of the vascular bed of the tumour. A close correlation was demonstrated between the results of scintigraphy and those of computer tomography. In the group of 27 patients treated surgically for adrenocortical disease in 87% of cases an agreement was found between the results of scintigraphy and the result of the operation. For different adrenocortical diseases this per cent was: 77% for Cushings syndrome, 91% for primary hyperaldosteronism, 100% for adrenal virilizing tumours. The study showed that adrenal scintigraphy is a very valuable diagnostic method of high clinical usefulness in adrenocortical diseases.

  3. The non-equilibrium Green's function method for nanoscale device simulation

    CERN Document Server

    Pourfath, Mahdi

    2014-01-01

    For modeling the transport of carriers in nanoscale devices, a Green-function formalism is the most accurate approach. Due to the complexity of the formalism, one should have a deep understanding of the underlying principles and use smart approximations and numerical methods for solving the kinetic equations at a reasonable computational time. In this book the required concepts from quantum and statistical mechanics and numerical methods for calculating Green functions are presented. The Green function is studied in detail for systems both under equilibrium and under nonequilibrium conditions. Because the formalism enables rigorous modeling of different scattering mechanisms in terms of self-energies, but an exact evaluation of self-energies for realistic systems is not possible, their approximation and inclusion in the quantum kinetic equations of the Green functions are elaborated. All the elements of the kinetic equations, which are the device Hamiltonian, contact self-energies, and scattering self-energie...

  4. A continuous flow isotope ratio mass spectrometry method for high precision determination of dissolved gas ratios and isotopic composition

    DEFF Research Database (Denmark)

    Charoenpong, C. N.; Bristow, L. A.; Altabet, M. A.

    2014-01-01

    Dissolved gas ratios and isotopic compositions provide essential information about the biological and physical mechanisms influencing N-2, O-2, and Ar in aquatic systems. Current methods available are either limited by overall cost, labor-intensive sample collection and analysis, or insufficient ...

  5. Determination of the thermodynamic properties of liquid Ag-Sb-Sn system by equilibrium saturation method

    Directory of Open Access Journals (Sweden)

    J. Romanowska

    2011-09-01

    Full Text Available Purpose: The interaction of lead-free solders with a copper substrate is an essential issue for the reliability of solder joints. In order to understand this interaction, the knowledge of thermodynamic and other physical properties of several ternary systems such as Ag-Sb-Sn system is necessary. The aim of this work was to determine the activities of all components in Ag-Sb-Sn alloy.Design/methodology/approach: The investigation of this system was carried out using the equilibrium saturation (ES method. The ES measurements were performed at 1273, 1373 and 1473 K. As the latter method is a comparative one, a Sn-Sb alloy was accepted as a reference alloy, where a formula for the Sb activity proposed by Jönsson and verified by Vassiliev was accepted.Findings: In the frame of the presented experiments the activity of Sb was determined by ES method.Research limitations/implications: The activity of Sb was obtained by ES and fitted to the Redlich-Kister-Muggianu (RKM model.Practical implications: A knowledge of multi-component phase equilibrium can provide the alloy developer with specific data enabling finding alloys that meet certain criteria. Phase diagrams are built on the basis of experimental data and the reliability of phase diagrams depends on the reliability of the experimental data used for the optimisation. Hence it is advantageous to use various source of data obtained by several methods and when the data of different source agree (like the ones presented in this paper it proves their reliability. Data presented in this paper will be used for Ag-Sb-Sn phase diagram optimisation in the frame of the COST Action MP0602.Originality/value: Sb activity values in Ag-Sb-Sn alloys obtained by ES and activity values of Sb, Ag and Sn calculated using the RKM model.

  6. Development, optimisation, and application of ICP-SFMS methods for the measurement of isotope ratios

    Energy Technology Data Exchange (ETDEWEB)

    Stuerup, S

    2000-07-01

    The measurement of isotopic composition and isotope ratios in biological and environmental samples requires sensitive, precise, and accurate analytical techniques. The analytical techniques used are traditionally based on mass spectrometry, among these techniques is the ICP-SFMS technique, which became commercially available in the mid 1990s. This technique is characterised by high sensitivity, low background, and the ability to separate analyte signals from spectral interferences. These features are beneficial for the measurement of isotope ratios and enable the measurement of isotope ratios of elements, which it has not previously been possible to measure due to either spectral interferences or poor sensitivity. The overall purpose of the project was to investigate the potential of the single detector ICP-SFMS technique for the measurement of isotope ratios in biological and environmental samples. One part of the work has focused on the fundamental aspects of the ICP-SFMS technique with special emphasize on the features important to the measurement of isotope ratios, while another part has focused on the development, optimisation and application of specific methods for the measurement of isotope ratios of elements of nutritional interest and radionuclides. The fundamental aspects of the ICP-SFMS technique were investigated theoretically and experimentally by the measurement of isotope ratios applying different experimental conditions. It was demonstrated that isotope ratios could be measured reliably using ICP-SFMS by educated choice of acquisition parameters, scanning mode, mass discrimination correction, and by eliminating the influence of detector dead time. Applying the knowledge gained through the fundamental study, ICP-SFMS methods for the measurement of isotope ratios of calcium, zinc, molybdenum and iron in human samples and a method for the measurement of plutonium isotope ratios and ultratrace levels of plutonium and neptunium in environmental samples

  7. Stable isotope utilization methodology; Methodologie de l`emploi des isotopes stables

    Energy Technology Data Exchange (ETDEWEB)

    Roth, E. [Conservatoire National des Arts et Metiers (CNAM), 75 - Paris (France)

    1994-12-31

    The various applications of stable isotope utilization are reviewed, as a function of their specific properties: poly-isotopic abundance modification is used for tracer applications; the accurate measurement of the stable isotope abundance may be applied to isotopic dilution for ultra-trace measurement, physical constant determination, fluid volume and concentration measurement; isotopic effects, such as reaction equilibrium differences are used for separation and identification of molecule active centers (pharmacology, paleoclimatology, hydrogeological studies) while reaction rate differences (competitive and non competitive methods) are used for the study of reaction mechanisms, such as enzymatic reactions. Analysis techniques (mass spectrometry, nuclear magnetic resonance, optical methods) are reviewed. 2 figs., 18 refs.

  8. Vertical equilibrium with sub-scale analytical methods for geological CO2 sequestration

    KAUST Repository

    Gasda, S. E.

    2009-04-23

    Large-scale implementation of geological CO2 sequestration requires quantification of risk and leakage potential. One potentially important leakage pathway for the injected CO2 involves existing oil and gas wells. Wells are particularly important in North America, where more than a century of drilling has created millions of oil and gas wells. Models of CO 2 injection and leakage will involve large uncertainties in parameters associated with wells, and therefore a probabilistic framework is required. These models must be able to capture both the large-scale CO 2 plume associated with the injection and the small-scale leakage problem associated with localized flow along wells. Within a typical simulation domain, many hundreds of wells may exist. One effective modeling strategy combines both numerical and analytical models with a specific set of simplifying assumptions to produce an efficient numerical-analytical hybrid model. The model solves a set of governing equations derived by vertical averaging with assumptions of a macroscopic sharp interface and vertical equilibrium. These equations are solved numerically on a relatively coarse grid, with an analytical model embedded to solve for wellbore flow occurring at the sub-gridblock scale. This vertical equilibrium with sub-scale analytical method (VESA) combines the flexibility of a numerical method, allowing for heterogeneous and geologically complex systems, with the efficiency and accuracy of an analytical method, thereby eliminating expensive grid refinement for sub-scale features. Through a series of benchmark problems, we show that VESA compares well with traditional numerical simulations and to a semi-analytical model which applies to appropriately simple systems. We believe that the VESA model provides the necessary accuracy and efficiency for applications of risk analysis in many CO2 sequestration problems. © 2009 Springer Science+Business Media B.V.

  9. Generalized non-equilibrium vertex correction method in coherent medium theory for quantum transport simulation of disordered nanoelectronics

    Science.gov (United States)

    Yan, Jiawei; Ke, Youqi

    In realistic nanoelectronics, disordered impurities/defects are inevitable and play important roles in electron transport. However, due to the lack of effective quantum transport method, the important effects of disorders remain poorly understood. Here, we report a generalized non-equilibrium vertex correction (NVC) method with coherent potential approximation to treat the disorder effects in quantum transport simulation. With this generalized NVC method, any averaged product of two single-particle Green's functions can be obtained by solving a set of simple linear equations. As a result, the averaged non-equilibrium density matrix and various important transport properties, including averaged current, disordered induced current fluctuation and the averaged shot noise, can all be efficiently computed in a unified scheme. Moreover, a generalized form of conditionally averaged non-equilibrium Green's function is derived to incorporate with density functional theory to enable first-principles simulation. We prove the non-equilibrium coherent potential equals the non-equilibrium vertex correction. Our approach provides a unified, efficient and self-consistent method for simulating non-equilibrium quantum transport through disorder nanoelectronics. Shanghaitech start-up fund.

  10. The invariant constrained equilibrium edge preimage curve method for the dimension reduction of chemical kinetics

    Science.gov (United States)

    Ren, Zhuyin; Pope, Stephen B.; Vladimirsky, Alexander; Guckenheimer, John M.

    2006-03-01

    This work addresses the construction and use of low-dimensional invariant manifolds to simplify complex chemical kinetics. Typically, chemical kinetic systems have a wide range of time scales. As a consequence, reaction trajectories rapidly approach a hierarchy of attracting manifolds of decreasing dimension in the full composition space. In previous research, several different methods have been proposed to identify these low-dimensional attracting manifolds. Here we propose a new method based on an invariant constrained equilibrium edge (ICE) manifold. This manifold (of dimension nr) is generated by the reaction trajectories emanating from its (nr-1)-dimensional edge, on which the composition is in a constrained equilibrium state. A reasonable choice of the nr represented variables (e.g., nr "major" species) ensures that there exists a unique point on the ICE manifold corresponding to each realizable value of the represented variables. The process of identifying this point is referred to as species reconstruction. A second contribution of this work is a local method of species reconstruction, called ICE-PIC, which is based on the ICE manifold and uses preimage curves (PICs). The ICE-PIC method is local in the sense that species reconstruction can be performed without generating the whole of the manifold (or a significant portion thereof). The ICE-PIC method is the first approach that locally determines points on a low-dimensional invariant manifold, and its application to high-dimensional chemical systems is straightforward. The "inputs" to the method are the detailed kinetic mechanism and the chosen reduced representation (e.g., some major species). The ICE-PIC method is illustrated and demonstrated using an idealized H2/O system with six chemical species. It is then tested and compared to three other dimension-reduction methods for the test case of a one-dimensional premixed laminar flame of stoichiometric hydrogen/air, which is described by a detailed mechanism

  11. Investigation of the Photochemical Method for Uranium Isotope Separation

    Science.gov (United States)

    Urey, H. C.

    1943-07-10

    To find a process for successful photochemical separation of isotopes several conditions have to be fulfilled. First, the different isotopes have to show some differences in the spectrum. Secondly, and equally important, this difference must be capable of being exploited in a photochemical process. Parts A and B outline the physical and chemical conditions, and the extent to which one might expect to find them fulfilled. Part C deals with the applicability of the process.

  12. A simple, universal theory and method for computer plotting of stable equilibrium phase diagrams of a multisystem SFM method

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    A new easy method has been presented to calculate the variable intervals corresponding to the stable univariant curves and to discriminate the stabilities of invariant points. This method and the one reported previously constitute a simple and universal theory for the computer-plotting of the equilibrium phase diagrams of a multisystem sign function matrix (SFM) discrimination method. Its main steps are: determining the stable univariant scheme according to the derivative (or difference) of ΔrGm; grouping the univariant curves by comparisons of the mutual relations among them; determining the existing intervals of the variables for the stable curves by comparisons of coordinate values of the curves about the invariant point; determining the stabilities of invariant points by comparisons of relations between the common curves and the invariant points. This method is suitable for any kind of phase diagram of closed or open systems in a phase diagram "space" with either 2 or more than 2 dimensions.

  13. Modified Block Iterative Method for Solving Convex Feasibility Problem, Equilibrium Problems and Variational Inequality Problems

    Institute of Scientific and Technical Information of China (English)

    Shi Sheng ZHANG; Chi Kin CHAN; H.W. JOSEPH LEE

    2012-01-01

    The purpose of this paper is by using the modified block iterative method to propose an algorithm for finding a common element in the intersection of the set of common fixed points of an infinite family of quasi-φ-asymptotically nonexpansive and the set of solutions to an equilibrium problem and the set of solutions to a variational inequality.Under suitable conditions some strong convergence theorems are established in 2-uniformly convex and uniformly smooth Banach spaces.As applications we utilize the results presented in the paper to solving the convex feasibility problem (CFP) and zero point problem of maximal monotone mappings in Banach spaces.The results presented in the paper improve and extend the corresponding results announced by many authors.

  14. Elemental composition method for computation and analysis of simultaneous chemical and phase equilibrium

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    An elemental composition method for computation and analysis of simultaneous chemical and phase equilibrium (CPE) of non-ideal mixtures is proposed. The concept of element is defined, the relationship between component composition and elemental composition is derived, and the concept of elemental potential and its physical meaning are further cleared from the view point of thermodynamics. The relationship between chemical potential and elemental potential is derived in the thermodynamic principles, and the computation equations for CPE problem are obtained based on elemental potential. A simple form of necessary and sufficient condition in terms of elemental composition for reactive azeotropes is derived, which takes the same functional form as the condition for azeotropes in non-reactive systems. The element in this note may be atoms, molecules or group radicals. The presented method is applicable to CPE problem of non-ideal mixtures, and the computation can be simplified by the dimension reducing method. The presented method was supplied to compute and analyze CPE problem of several examples and it is found that it is a robust and efficient method.

  15. New neutron-based isotopic analytical methods; An explorative study of resonance capture and incoherent scattering

    NARCIS (Netherlands)

    Perego, R.C.

    2004-01-01

    Two novel neutron-based analytical techniques have been treated in this thesis, Neutron Resonance Capture Analysis (NRCA), employing a pulsed neutron source, and Neutron Incoherent Scattering (NIS), making use of a cold neutron source. With the NRCA method isotopes are identified by the isotopic-spe

  16. Equilibrium Decision Method for Earthquake First-Aid Medicine Allocation Based on Demand Information Updating

    Directory of Open Access Journals (Sweden)

    Yong Ye

    2017-01-01

    Full Text Available The allocation of rescue resources after an earthquake has become a popular research topic in the field of emergency management. The allocation of first-aid medicine for earthquake rescue has stronger time sensitivity than that of general rescue materials. This study focuses on the problem of first-aid medicine allocation in earthquake response. First, we consider the incompleteness and renewal of decision information in an emergency environment, as well as the balance between the risk of decision error and delay. Second, we propose an equilibrium decision method for the allocation of first-aid medicine in earthquake rescue based on information update. This method attempts to realize a fair allocation to all disaster places and minimize total transport time loss. Third, a simulation analysis is performed in which the proposed method is applied to the first-aid medicine allocation problem in the Wenchuan earthquake response. Results show that the method can be used to create a good allocation plan in an earthquake rescue situation.

  17. The development of a continuous isothermal titration calorimetric method for equilibrium studies.

    Science.gov (United States)

    Markova, Natalia; Hallén, Dan

    2004-08-01

    A continuous isothermal titration calorimetry (cITC) method for microcalorimeters has been developed. The method is based on continuous slow injection of a titrant into the calorimetric vessel. The experimental time for a cITC binding experiment is 12-20 min and the number of data points obtained is on the order of 1000. This gives an advantage over classical isothermal titration calorimetry (ITC) binding experiments that need 60-180 min to generate 20-30 data points. The method was validated using two types of calorimeters, which differ in calorimetric principle, geometry, stirring, and way of delivering the titrant into the calorimetric vessel. Two different experimental systems were used to validate the method: the binding of Ba(2+) to 18-crown-6 and the binding of cytidine 2'-monophosphate to RNAse A. Both systems are used as standard test systems for titration calorimetry. Computer simulations show that the dynamic range for determination of equilibrium constants can be increased by three orders of magnitude compared to that of classical ITC, making it possible to determine high affinities. Simulations also show an improved possibility to elucidate the actual binding model from cITC data. The simulated data demonstrate that cITC makes it easier to discriminate between different thermodynamic binding models due to the higher density of data points obtained from one experiment.

  18. A moving mesh finite difference method for equilibrium radiation diffusion equations

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Xiaobo, E-mail: xwindyb@126.com [Department of Mathematics, College of Science, China University of Mining and Technology, Xuzhou, Jiangsu 221116 (China); Huang, Weizhang, E-mail: whuang@ku.edu [Department of Mathematics, University of Kansas, Lawrence, KS 66045 (United States); Qiu, Jianxian, E-mail: jxqiu@xmu.edu.cn [School of Mathematical Sciences and Fujian Provincial Key Laboratory of Mathematical Modeling and High-Performance Scientific Computing, Xiamen University, Xiamen, Fujian 361005 (China)

    2015-10-01

    An efficient moving mesh finite difference method is developed for the numerical solution of equilibrium radiation diffusion equations in two dimensions. The method is based on the moving mesh partial differential equation approach and moves the mesh continuously in time using a system of meshing partial differential equations. The mesh adaptation is controlled through a Hessian-based monitor function and the so-called equidistribution and alignment principles. Several challenging issues in the numerical solution are addressed. Particularly, the radiation diffusion coefficient depends on the energy density highly nonlinearly. This nonlinearity is treated using a predictor–corrector and lagged diffusion strategy. Moreover, the nonnegativity of the energy density is maintained using a cutoff method which has been known in literature to retain the accuracy and convergence order of finite difference approximation for parabolic equations. Numerical examples with multi-material, multiple spot concentration situations are presented. Numerical results show that the method works well for radiation diffusion equations and can produce numerical solutions of good accuracy. It is also shown that a two-level mesh movement strategy can significantly improve the efficiency of the computation.

  19. Reflective equilibrium

    NARCIS (Netherlands)

    van der Burg, W.; van Willigenburg, T.

    1998-01-01

    The basic idea of reflective equilibrium, as a method for theory construction and decision making in ethics, is that we should bring together a broad variety of moral and non-moral beliefs and, through a process of critical scrutiny and mutual adjustment, combine these into one coherent belief syste

  20. Reflective equilibrium

    NARCIS (Netherlands)

    van der Burg, W.; van Willigenburg, T.

    1998-01-01

    The basic idea of reflective equilibrium, as a method for theory construction and decision making in ethics, is that we should bring together a broad variety of moral and non-moral beliefs and, through a process of critical scrutiny and mutual adjustment, combine these into one coherent belief syste

  1. Simple, rapid method for the preparation of isotopically labeled formaldehyde

    Energy Technology Data Exchange (ETDEWEB)

    Hooker, Jacob Matthew [Port Jefferson, NY; Schonberger, Matthias [Mains, DE; Schieferstein, Hanno [Aabergen, DE; Fowler, Joanna S [Bellport, NY

    2011-10-04

    Isotopically labeled formaldehyde (*C.sup..sctn.H.sub.2O) is prepared from labeled methyl iodide (*C.sup..sctn.H.sub.3I) by reaction with an oxygen nucleophile having a pendant leaving group. The mild and efficient reaction conditions result in good yields of *C.sup..sctn.H.sub.2O with little or no *C isotopic dilution. The simple, efficient production of .sup.11CH.sub.2O is described. The use of the .sup.11CH.sub.2O for the formation of positron emission tomography tracer compounds is described. The reaction can be incorporated into automated equipment available to radiochemistry laboratories. The isotopically labeled formaldehyde can be used in a variety of reactions to provide radiotracer compounds for imaging studies as well as for scintillation counting and autoradiography.

  2. Equilibrium and dynamic methods when comparing an English text and its Esperanto translation

    Science.gov (United States)

    Ausloos, M.

    2008-11-01

    A comparison of two English texts written by Lewis Carroll, one (Alice in Wonderland), also translated into Esperanto, the other (Through the Looking Glass) are discussed in order to observe whether natural and artificial languages significantly differ from each other. One dimensional time series like signals are constructed using only word frequencies (FTS) or word lengths (LTS). The data is studied through (i) a Zipf method for sorting out correlations in the FTS and (ii) a Grassberger-Procaccia (GP) technique based method for finding correlations in LTS. The methods correspond to an equilibrium and a dynamic approach respectively to human texts features. There are quantitative statistical differences between the original English text and its Esperanto translation, but the qualitative differences are very minutes. However different power laws are observed with characteristic exponents for the ranking properties, and the phase space attractor dimensionality. The Zipf exponent can take values much less than unity (∼0.50 or 0.30) depending on how a sentence is defined. This variety in exponents can be conjectured to be an intrinsic measure of the book style or purpose, rather than the language or author vocabulary richness, since a similar exponent is obtained whatever the text. Moreover the attractor dimension r is a simple function of the so called phase space dimension n, i.e., r=nλ, with λ=0.79. Such an exponent could also be conjectured to be a measure of the author style versatility, - here well preserved in the translation.

  3. Apparatus and method for monitoring of gas having stable isotopes

    Science.gov (United States)

    Clegg, Samuel M; Fessenden-Rahn, Julianna E

    2013-03-05

    Gas having stable isotopes is monitored continuously by using a system that sends a modulated laser beam to the gas and collects and transmits the light not absorbed by the gas to a detector. Gas from geological storage, or from the atmosphere can be monitored continuously without collecting samples and transporting them to a lab.

  4. COMBINING SOURCES IN STABLE ISOTOPE MIXING MODELS: ALTERNATIVE METHODS

    Science.gov (United States)

    Stable isotope mixing models are often used to quantify source contributions to a mixture. Examples include pollution source identification; trophic web studies; analysis of water sources for soils, plants, or water bodies; and many others. A common problem is having too many s...

  5. Apparatus and method for monitoring of gas having stable isotopes

    Energy Technology Data Exchange (ETDEWEB)

    Clegg, Samuel M; Fessenden-Rahn, Julianna E

    2013-03-05

    Gas having stable isotopes is monitored continuously by using a system that sends a modulated laser beam to the gas and collects and transmits the light not absorbed by the gas to a detector. Gas from geological storage, or from the atmosphere can be monitored continuously without collecting samples and transporting them to a lab.

  6. A liquid chromatography - mass spectrometry method to measure ¹³C-isotope enrichment for DNA stable-isotope probing.

    Science.gov (United States)

    Auclair, Julie; Lépine, François; Villemur, Richard

    2012-03-01

    DNA stable-isotope probing (DNA-SIP) is a cultivation-independent technique that makes it possible to associate metabolic function and taxonomic identity in a wide range of terrestrial and aquatic environments. In DNA-SIP, DNA is labeled via the assimilation of a labeled growth substrate that is subsequently used to identify microorganisms involved in assimilation of the substrate. However, the labeling time has to be sufficient to obtain labeled DNA but not so long such that cross-feeding of ¹³C-labeled metabolites from the primary consumers to nontarget species can occur. Confirmation that the DNA is isotopically labeled in DNA-SIP assays can be achieved using an isotope ratio mass spectrometer. In this study, we describe the development of a method using liquid chromatography (HPLC) coupled to a quadrupole mass spectrometer (QMS) to measure the ¹³C enrichment of thymine incorporated into DNA in Escherichia coli cultures fed with [¹³C]acetate. The method involved the hydrolysis of DNA extracted from the cultures that released the nucleotides, followed by the separation of the thymine by HPLC on a reverse-phase C₈ column in isocratic elution mode and the detection and quantification of ¹³C-labeled thymine by QMS. To mimic a DNA-SIP assay, a DNA mixture was made using ¹³C-labeled E. coli DNA with DNA extracted from five bacterial species. The HPLC-MS method was able to measure the correct proportion of ¹³C-DNA in the mix. This method can then be used as an alternative to the use of isotope ratio mass spectrometry in DNA-SIP assays.

  7. The evaluation of the equilibrium partitioning method using sensitivity distributions of species in water and soil or sediment

    NARCIS (Netherlands)

    Beelen P van; Verbruggen EMJ; Peijnenburg WJGM; ECO

    2002-01-01

    The equilibrium partitioning method (EqP-method) can be used to derive environmental quality standards (like the Maximum Permissible Concentration or the intervention value) for soil or sediment, from aquatic toxicity data and a soil/water or sediment/water partitioning coefficient. The validity of

  8. Vapor-Liquid Equilibrium of Carbon Dioxide + Ethanol: Experimental Measurements with Acoustic Method and Thermodynamic Modeling

    Directory of Open Access Journals (Sweden)

    Ana Mehl

    2011-01-01

    Full Text Available Phase behavior of systems composed by supercritical carbon dioxide and ethanol is of great interest, especially in the processes involving supercritical extraction in which ethanol is used as a cosolvent. The development of an apparatus, which is able to perform the measurements of vapor-liquid equilibrium (VLE at high pressure using a combination of the visual and the acoustic methods, was successful and was proven to be suited for determining the isothermal VLE data of this system. The acoustic method, based on the variation of the amplitude of an ultra-sound signal passing through a mixture during a phase transition, was applied to investigate the phase equilibria of the system carbon dioxide + ethanol at temperatures ranging from 298.2 K to 323.2 K and pressures from 3.0 MPa to 9.0 MPa. The VLE data were correlated with Peng-Robinson equation of state combined with two different mixing rules and the SAFT equations of state as well. The compositions calculated with the models are in good agreement with the experimental data for the isotherms evaluated.

  9. A gas chromatograph/mass spectrometry method for determining isotopic distributions in organic compounds used in the chemical approach to stable isotope separation

    Energy Technology Data Exchange (ETDEWEB)

    Martinez, A.M.; Spall, W.D.; Smith, B.F.

    1990-01-01

    A variety of gas chromatograph/mass spectrometry (GC/MS) methods have been developed to resolve benzene, benzophenone, anthracene, fluorenone, and their respective stable isotope analogs from other components by gas chromatography. The ratio of stable isotope-labeled material to natural isotopic abundance compounds is determined from the mass spectra averaged across the chromatographic peak. Both total ion and selective ion chromatographic approaches were used for relative data and comparison. 9 refs., 11 tabs.

  10. Contribution of local thyroxine monodeiodination to intracellular 3,5, 3'-triiodothyronine in several tissues of hyperthyroid rats at isotopic equilibrium

    Energy Technology Data Exchange (ETDEWEB)

    van Doorn, J.; van der Heide, D.; Roelfsema, F.

    1984-07-01

    The local conversion of T4 as a source of intracellular T3 in several organs of both hypothyroid and euthyroid rats has recently been recognized to be an important phenomenon. In the present study the source and quantity of T3 in various peripheral tissues of hyperthyroid rats were investigated. Athyreotic rats received a continuous iv infusion of T4 over a prolonged period in order to attain hyperthyroid conditions. At the same time, the animals also received a continuous iv infusion of (/sup 125/I)T4 and (/sup 131/I)T3 until isotopic equilibrium was achieved. After the animals were bled and perfused, the source and quantity of T3 in various tissue homogenates and subcellular preparations of liver, kidney, and the anterior pituitary gland were analyzed. In spite of the elevated plasma T3 and T4 levels, the concentration of T3 in the cerebral cortex and cerebellum was within the normal range. The contribution of T3 derived from local T4 to T3 conversion (Lc T3(T4)) was rather low in both parts of the brain when compared with values previously determined for euthyroid rats. Whereas previous studies revealed that Lc T3(T4) contributes significantly to the T3 in the pituitary glands of both hypothyroid and euthyroid rats, this was not the case for the hyperthyroid animals; virtually all T3 was derived from plasma. It was found that the T3 in muscle was derived exclusively from plasma. Both the liver and kidney showed high concentrations of T3. Whereas Lc T3(T4) was the main source of T3 in the liver, it contributed only a minor fraction of the total T3 content in the kidney.

  11. Extension of Characteristic Equation Method to Stability Analysis of Equilibrium Points for Closed—Loop PWM Power Switching Converters8

    Institute of Scientific and Technical Information of China (English)

    YanfengCHEN; ShuishengQIU; 等

    1999-01-01

    An extension of characteristic equation analysis method to the stability analysis of equilibrium points for closed-loop PWM power switching converters is introduced based on equivalent small parameter method.The basic principle of the method is described in detail.The provided example shows that the method,incorporating with the system's state-plane trajectories,offers the advantages of both simplicity and practicality.

  12. Study on the Seismic Active Earth Pressure by Variational Limit Equilibrium Method

    Directory of Open Access Journals (Sweden)

    Jiangong Chen

    2016-01-01

    Full Text Available In the framework of limit equilibrium theory, the isoperimetric model of functional extremum regarding the seismic active earth pressure is deduced according to the variational method. On this basis, Lagrange multipliers are introduced to convert the problem of seismic active earth pressure into the problem on the functional extremum of two undetermined function arguments. Based on the necessary conditions required for the existence of functional extremum, the function of the slip surface and the normal stress distribution on the slip surface is obtained, and the functional extremum problem is further converted into a function optimization problem with two undetermined Lagrange multipliers. The calculated results show that the slip surface is a plane and the seismic active earth pressure is minimal when the action point is at the lower limit position. As the action point moves upward, the slip surface becomes a logarithmic spiral and the corresponding value of seismic active earth pressure increases in a nonlinear manner. And the seismic active earth pressure is maximal at the upper limit position. The interval estimation constructed by the minimum and maximum values of seismic active earth pressure can provide a reference for the aseismic design of gravity retaining walls.

  13. Application of kinetic Monte Carlo method to equilibrium systems: vapour-liquid equilibria.

    Science.gov (United States)

    Ustinov, E A; Do, D D

    2012-01-15

    Kinetic Monte Carlo (kMC) simulations were carried out to describe the vapour-liquid equilibria of argon at various temperatures. This paper aims to demonstrate the potential of the kMC technique in the analysis of equilibrium systems and its advantages over the traditional Monte Carlo method, which is based on the Metropolis algorithm. The key feature of the kMC is the absence of discarded trial moves of molecules, which ensures larger number of configurations that are collected for time averaging. Consequently, the kMC technique results in significantly fewer errors for the same number of Monte Carlo steps, especially when the fluid is rarefied. An additional advantage of the kMC is that the relative displacement probability of molecules is significantly larger in rarefied regions, which results in a more efficient sampling. This provides a more reliable determination of the vapour phase pressure and density in case of non-uniform density distributions, such as the vapour-liquid interface or a fluid adsorbed on an open surface. We performed kMC simulations in a canonical ensemble, with a liquid slab in the middle of the simulation box to model two vapour-liquid interfaces. A number of thermodynamic properties such as the pressure, density, heat of evaporation and the surface tension were reliably determined as time averages. Copyright © 2011 Elsevier Inc. All rights reserved.

  14. The Computation of Nash Equilibrium in Fashion Games via Semi-Tensor Product Method

    Institute of Scientific and Technical Information of China (English)

    GUO Peilian; WANG Yuzhen

    2016-01-01

    Using the semi-tensor product of matrices,this paper investigates the computation of pure-strategy Nash equilibrium (PNE) for fashion games,and presents several new results.First,a formal fashion game model on a social network is given.Second,the utility function of each player is converted into an algebraic form via the semi-tensor product of matrices,based on which the case of two-strategy fashion game is studied and two methods are obtained for the case to verify the existence of PNE.Third,the multi-strategy fashion game model is investigated and an algorithm is established to find all the PNEs for the general case.Finally,two kinds of optimization problems,that is,the so-called social welfare and normalized satisfaction degree optimization problems are investigated and two useful results are given.The study of several illustrative examples shows that the new results obtained in this paper are effective.

  15. Equilibrium isotherms of methane onto activated carbons using a static volumetric method.

    Science.gov (United States)

    Kavitha, T; Kaliappan, S

    2009-07-01

    The aim of this research is to develop a technology for the storage of biogas. The present work pertains to the measurement of the adsorption capacity of methane onto activated carbons at room temperature at pressure range varying from 1 atm to 10 atm. The results were obtained with a static volumetric method. Adsorption isotherms for methane on Sorbonorit 4, Norit SX Plus, Sorbonorit B3, Norit PAC 200 XC were plotted. The equilibrium pressure data were analysed using Langmuir, Dubinin-Astakhov's (DA) and Dubinin-Radushkevich (DR) equations. The DA equation described the isotherm behavior better with the exponent n equals to 1.0 for Sorbonorit 4, Sorbonorit B3, Norit PAC 200 XC and 1.7 for Norit SX Plus than the other equations. The order of the adsorption capacity is as follows: Sorbonorit 4 (4.6 mmol/g) > Norit PAC 200 XC (3.81 mmol/g) > Sorbonorit B3 (3.52 mmol/g) > Norit SX Plus (3.51 mmol/g).

  16. The quantum and mechanical justification of intensification by magnetic field of amalgam isotope separation method

    Directory of Open Access Journals (Sweden)

    Myshkin V. F.

    2015-09-01

    Full Text Available The steady increase in demand for isotopes requires the development of methods to increase the efficiency of isotope separation technologies. Methods of isotope separation based on thermodynamic differences of isotopic forms of the molecules don't require significant investment, but characterized by a low rate of exchange. It's known that the magnetic effect leads to a change the vibrational frequency of the molecules, and therefore their thermodynamic parameters. The change increases the thermodynamic parameters, including the exchange rate. The results of the experimental determination of the thermal effect of dissolving the salts of NaCl, KCl, CuSO4, sodium amalgam decomposition by distillate in a magnetic field and without field were shown. Magnetic interference can have a significant effect on the amalgam exchange method which was shown by quantum and mechanical analysis of the results

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

    CERN Document Server

    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.

  18. Non-Equilibrium Liouville and Wigner Equations: Moment Methods and Long-Time Approximations

    Directory of Open Access Journals (Sweden)

    Ramon F. Álvarez-Estrada

    2014-03-01

    Full Text Available We treat the non-equilibrium evolution of an open one-particle statistical system, subject to a potential and to an external “heat bath” (hb with negligible dissipation. For the classical equilibrium Boltzmann distribution, Wc,eq, a non-equilibrium three-term hierarchy for moments fulfills Hermiticity, which allows one to justify an approximate long-time thermalization. That gives partial dynamical support to Boltzmann’s Wc,eq, out of the set of classical stationary distributions, Wc;st, also investigated here, for which neither Hermiticity nor that thermalization hold, in general. For closed classical many-particle systems without hb (by using Wc,eq, the long-time approximate thermalization for three-term hierarchies is justified and yields an approximate Lyapunov function and an arrow of time. The largest part of the work treats an open quantum one-particle system through the non-equilibrium Wigner function, W. Weq for a repulsive finite square well is reported. W’s (< 0 in various cases are assumed to be quasi-definite functionals regarding their dependences on momentum (q. That yields orthogonal polynomials, HQ,n(q, for Weq (and for stationary Wst, non-equilibrium moments, Wn, of W and hierarchies. For the first excited state of the harmonic oscillator, its stationary Wst is a quasi-definite functional, and the orthogonal polynomials and three-term hierarchy are studied. In general, the non-equilibrium quantum hierarchies (associated with Weq for the Wn’s are not three-term ones. As an illustration, we outline a non-equilibrium four-term hierarchy and its solution in terms of generalized operator continued fractions. Such structures also allow one to formulate long-time approximations, but make it more difficult to justify thermalization. For large thermal and de Broglie wavelengths, the dominant Weq and a non-equilibrium equation for W are reported: the non-equilibrium hierarchy could plausibly be a three-term one and possibly not

  19. Inverse methods for estimating primary input signals from time-averaged isotope profiles

    Science.gov (United States)

    Passey, Benjamin H.; Cerling, Thure E.; Schuster, Gerard T.; Robinson, Todd F.; Roeder, Beverly L.; Krueger, Stephen K.

    2005-08-01

    Mammalian teeth are invaluable archives of ancient seasonality because they record along their growth axes an isotopic record of temporal change in environment, plant diet, and animal behavior. A major problem with the intra-tooth method is that intra-tooth isotope profiles can be extremely time-averaged compared to the actual pattern of isotopic variation experienced by the animal during tooth formation. This time-averaging is a result of the temporal and spatial characteristics of amelogenesis (tooth enamel formation), and also results from laboratory sampling. This paper develops and evaluates an inverse method for reconstructing original input signals from time-averaged intra-tooth isotope profiles. The method requires that the temporal and spatial patterns of amelogenesis are known for the specific tooth and uses a minimum length solution of the linear system Am = d, where d is the measured isotopic profile, A is a matrix describing temporal and spatial averaging during amelogenesis and sampling, and m is the input vector that is sought. Accuracy is dependent on several factors, including the total measurement error and the isotopic structure of the measured profile. The method is shown to accurately reconstruct known input signals for synthetic tooth enamel profiles and the known input signal for a rabbit that underwent controlled dietary changes. Application to carbon isotope profiles of modern hippopotamus canines reveals detailed dietary histories that are not apparent from the measured data alone. Inverse methods show promise as an effective means of dealing with the time-averaging problem in studies of intra-tooth isotopic variation.

  20. A versatile method for stable carbon isotope analysis of carbohydrates by high-performance liquid chromatography/isotope ratio mass spectrometry

    NARCIS (Netherlands)

    Boschker, H.T.S.; Moerdijk-Poortvliet, T.C.W.; Van Breugel, P.; Houtekamer, M.J.; Middelburg, J.J.

    2008-01-01

    We have developed a method to analyze stable carbon isotope (13C/12C) ratios in a variety of carbohydrates using high-performance liquid chromatography/isotope ratio mass spectrometry (HPLC/IRMS). The chromatography is based on strong anion-exchange columns with low strength NaOH eluents. An eluent

  1. Cryogenic separation of hydrogen isotopes in single-walled carbon and boron-nitride nanotubes: insight into the mechanism of equilibrium quantum sieving in quasi-one-dimensional pores.

    Science.gov (United States)

    Kowalczyk, Piotr; Gauden, Piotr A; Terzyk, Artur P

    2008-07-17

    Quasi-one-dimensional cylindrical pores of single-walled boron nitride and carbon nanotubes efficiently differentiate adsorbed hydrogen isotopes at 33 K. Extensive path integral Monte Carlo simulations revealed that the mechanisms of quantum sieving for both types of nanotubes are quantitatively similar; however, the stronger and heterogeneous external solid-fluid potential generated from single-walled boron nitride nanotubes enhanced the selectivity of deuterium over hydrogen both at zero coverage and at finite pressures. We showed that this enhancement of the D(2)/H(2) equilibrium selectivity results from larger localization of hydrogen isotopes in the interior space of single-walled boron nitride nanotubes in comparison to that of equivalent single-walled carbon nanotubes. The operating pressures for efficient quantum sieving of hydrogen isotopes are strongly depending on both the type as well as the size of the nanotube. For all investigated nanotubes, we predicted the occurrence of the minima of the D(2)/H(2) equilibrium selectivity at finite pressure. Moreover, we showed that those well-defined minima are gradually shifted upon increasing of the nanotube pore diameter. We related the nonmonotonic shape of the D(2)/H(2) equilibrium selectivity at finite pressures to the variation of the difference between the average kinetic energy computed from single-component adsorption isotherms of H(2) and D(2). In the interior space of both kinds of nanotubes hydrogen isotopes formed solid-like structures (plastic crystals) at 33 K and 10 Pa with densities above the compressed bulk para-hydrogen at 30 K and 30 MPa.

  2. A Stochastic Method for Estimating the Effect of Isotopic Uncertainties in Spent Nuclear Fuel

    Energy Technology Data Exchange (ETDEWEB)

    DeHart, M.D.

    2001-08-24

    This report describes a novel approach developed at the Oak Ridge National Laboratory (ORNL) for the estimation of the uncertainty in the prediction of the neutron multiplication factor for spent nuclear fuel. This technique focuses on burnup credit, where credit is taken in criticality safety analysis for the reduced reactivity of fuel irradiated in and discharged from a reactor. Validation methods for burnup credit have attempted to separate the uncertainty associated with isotopic prediction methods from that of criticality eigenvalue calculations. Biases and uncertainties obtained in each step are combined additively. This approach, while conservative, can be excessive because of a physical assumptions employed. This report describes a statistical approach based on Monte Carlo sampling to directly estimate the total uncertainty in eigenvalue calculations resulting from uncertainties in isotopic predictions. The results can also be used to demonstrate the relative conservatism and statistical confidence associated with the method of additively combining uncertainties. This report does not make definitive conclusions on the magnitude of biases and uncertainties associated with isotopic predictions in a burnup credit analysis. These terms will vary depending on system design and the set of isotopic measurements used as a basis for estimating isotopic variances. Instead, the report describes a method that can be applied with a given design and set of isotopic data for estimating design-specific biases and uncertainties.

  3. Important progress on the use of isotope techniques and methods in catchment hydrology

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    The use of isotope techniques and methods in catchment hydrology in the last 50 years has generated two major types of progress: (1) Assessment of the temporal variations of the major stocks and flows of water in catchments, from which the estimation of wa-ter residence times is introduced in this paper. (2) Assessment of catchment hydrologic processes, in which the interactions be-tween different waters, hydrographical separation, and bio-geochemical process are described by using isotopes tracers. Future progress on isotope techniques and methods in hydrology is toward the understanding of the hydrological process in large river basins. Much potential also waits realization in terms of how isotope information may be used to calibrate and test distributed rainfall-runoff models and regarding aid in the quantification of sustainable water resources management.

  4. Communication: A method to compute the transport coefficient of pure fluids diffusing through planar interfaces from equilibrium molecular dynamics simulations

    Science.gov (United States)

    Vermorel, Romain; Oulebsir, Fouad; Galliero, Guillaume

    2017-09-01

    The computation of diffusion coefficients in molecular systems ranks among the most useful applications of equilibrium molecular dynamics simulations. However, when dealing with the problem of fluid diffusion through vanishingly thin interfaces, classical techniques are not applicable. This is because the volume of space in which molecules diffuse is ill-defined. In such conditions, non-equilibrium techniques allow for the computation of transport coefficients per unit interface width, but their weak point lies in their inability to isolate the contribution of the different physical mechanisms prone to impact the flux of permeating molecules. In this work, we propose a simple and accurate method to compute the diffusional transport coefficient of a pure fluid through a planar interface from equilibrium molecular dynamics simulations, in the form of a diffusion coefficient per unit interface width. In order to demonstrate its validity and accuracy, we apply our method to the case study of a dilute gas diffusing through a smoothly repulsive single-layer porous solid. We believe this complementary technique can benefit to the interpretation of the results obtained on single-layer membranes by means of complex non-equilibrium methods.

  5. Two approaches to hydrograph separation of the glacial river runoff using isotopic methods

    Directory of Open Access Journals (Sweden)

    Yu. N. Chizhova

    2016-01-01

    Full Text Available Application of the stable isotope method in the balance equations used to calculate separation of the runoff hydrograph from the Djankuat Glacier basin is demonstrated. Simultaneous solution of equations of water, isotope and ion balances is applied to estimate contributions of different components and processes to formation of the Djankuat River runoff regime. For June 2014, we made calculations for the purpose to separate contributions of the spring (isotopically weighted snow and winter (isotopically depleted snow. Field works in the glacial basin Djankuat were performed during two ablation seasons, i.e. from June to September of 2013 and 2014. Two approaches were used when calculating separation of the runoff hydrograph by means of solution of systems of equations for isotopic and ion balances: 1 taking account of the isotope fractionation during snow melting, and 2 with no account for the fractionation. Separation of the hydrograph for June 2014 have shown that about 15–20% of the Djankuat River runoff is formed by spring snow melting, sometimes increasing up to 36%. Contribution of spring meltwater to the total runoff increases when the isotope fractionation during the snow melting is taken into account for the calculations. In this case, the contribution of spring snow changes from 30 to 50%.

  6. Development of a new method for hydrogen isotope analysis of trace hydrocarbons in natural gas samples

    Directory of Open Access Journals (Sweden)

    Xibin Wang

    2016-12-01

    Full Text Available A new method had been developed for the analysis of hydrogen isotopic composition of trace hydrocarbons in natural gas samples by using solid phase microextraction (SPME combined with gas chromatography-isotope ratio mass spectrometry (GC/IRMS. In this study, the SPME technique had been initially introduced to achieve the enrichment of trace content of hydrocarbons with low abundance and coupled to GC/IRMS for hydrogen isotopic analysis. The main parameters, including the equilibration time, extraction temperature, and the fiber type, were systematically optimized. The results not only demonstrated that high extraction yield was true but also shows that the hydrogen isotopic fractionation was not observed during the extraction process, when the SPME device fitted with polydimethylsiloxane/divinylbenzene/carbon molecular sieve (PDMS/DVB/CAR fiber. The applications of SPME-GC/IRMS method were evaluated by using natural gas samples collected from different sedimentary basins; the standard deviation (SD was better than 4‰ for reproducible measurements; and also, the hydrogen isotope values from C1 to C9 can be obtained with satisfying repeatability. The SPME-GC/IRMS method fitted with PDMS/DVB/CAR fiber is well suited for the preconcentration of trace hydrocarbons, and provides a reliable hydrogen isotopic analysis for trace hydrocarbons in natural gas samples.

  7. Novel methods for estimating 3D distributions of radioactive isotopes in materials

    Energy Technology Data Exchange (ETDEWEB)

    Iwamoto, Y., E-mail: y.iwamoto0805@ruri.waseda.jp [Research Institute for Science and Engineering, Waseda University, Shinjuku, Tokyo 169-8555 (Japan); Kataoka, J.; Kishimoto, A.; Nishiyama, T.; Taya, T.; Okochi, H.; Ogata, H. [Research Institute for Science and Engineering, Waseda University, Shinjuku, Tokyo 169-8555 (Japan); Yamamoto, S. [Nagoya University Graduate School of Medicine, 1-1-20, Daikominami, Higashi-ku, Nagoya-shi, Aichi 461-8673 (Japan)

    2016-09-21

    In recent years, various gamma-ray visualization techniques, or gamma cameras, have been proposed. These techniques are extremely effective for identifying “hot spots” or regions where radioactive isotopes are accumulated. Examples of such would be nuclear-disaster-affected areas such as Fukushima or the vicinity of nuclear reactors. However, the images acquired with a gamma camera do not include distance information between radioactive isotopes and the camera, and hence are “degenerated” in the direction of the isotopes. Moreover, depth information in the images is lost when the isotopes are embedded in materials, such as water, sand, and concrete. Here, we propose two methods of obtaining depth information of radioactive isotopes embedded in materials by comparing (1) their spectra and (2) images of incident gamma rays scattered by the materials and direct gamma rays. In the first method, the spectra of radioactive isotopes and the ratios of scattered to direct gamma rays are obtained. We verify experimentally that the ratio increases with increasing depth, as predicted by simulations. Although the method using energy spectra has been studied for a long time, an advantage of our method is the use of low-energy (50–150 keV) photons as scattered gamma rays. In the second method, the spatial extent of images obtained for direct and scattered gamma rays is compared. By performing detailed Monte Carlo simulations using Geant4, we verify that the spatial extent of the position where gamma rays are scattered increases with increasing depth. To demonstrate this, we are developing various gamma cameras to compare low-energy (scattered) gamma-ray images with fully photo-absorbed gamma-ray images. We also demonstrate that the 3D reconstruction of isotopes/hotspots is possible with our proposed methods. These methods have potential applications in the medical fields, and in severe environments such as the nuclear-disaster-affected areas in Fukushima.

  8. Novel methods for estimating 3D distributions of radioactive isotopes in materials

    Science.gov (United States)

    Iwamoto, Y.; Kataoka, J.; Kishimoto, A.; Nishiyama, T.; Taya, T.; Okochi, H.; Ogata, H.; Yamamoto, S.

    2016-09-01

    In recent years, various gamma-ray visualization techniques, or gamma cameras, have been proposed. These techniques are extremely effective for identifying ;hot spots; or regions where radioactive isotopes are accumulated. Examples of such would be nuclear-disaster-affected areas such as Fukushima or the vicinity of nuclear reactors. However, the images acquired with a gamma camera do not include distance information between radioactive isotopes and the camera, and hence are ;degenerated; in the direction of the isotopes. Moreover, depth information in the images is lost when the isotopes are embedded in materials, such as water, sand, and concrete. Here, we propose two methods of obtaining depth information of radioactive isotopes embedded in materials by comparing (1) their spectra and (2) images of incident gamma rays scattered by the materials and direct gamma rays. In the first method, the spectra of radioactive isotopes and the ratios of scattered to direct gamma rays are obtained. We verify experimentally that the ratio increases with increasing depth, as predicted by simulations. Although the method using energy spectra has been studied for a long time, an advantage of our method is the use of low-energy (50-150 keV) photons as scattered gamma rays. In the second method, the spatial extent of images obtained for direct and scattered gamma rays is compared. By performing detailed Monte Carlo simulations using Geant4, we verify that the spatial extent of the position where gamma rays are scattered increases with increasing depth. To demonstrate this, we are developing various gamma cameras to compare low-energy (scattered) gamma-ray images with fully photo-absorbed gamma-ray images. We also demonstrate that the 3D reconstruction of isotopes/hotspots is possible with our proposed methods. These methods have potential applications in the medical fields, and in severe environments such as the nuclear-disaster-affected areas in Fukushima.

  9. A new method of snowmelt sampling for water stable isotopes

    Science.gov (United States)

    Penna, D.; Ahmad, M.; Birks, S. J.; Bouchaou, L.; Brencic, M.; Butt, S.; Holko, L.; Jeelani, G.; Martinez, D. E.; Melikadze, G.; Shanley, J.B.; Sokratov, S. A.; Stadnyk, T.; Sugimoto, A.; Vreca, P.

    2014-01-01

    We modified a passive capillary sampler (PCS) to collect snowmelt water for isotopic analysis. Past applications of PCSs have been to sample soil water, but the novel aspect of this study was the placement of the PCSs at the ground-snowpack interface to collect snowmelt. We deployed arrays of PCSs at 11 sites in ten partner countries on five continents representing a range of climate and snow cover worldwide. The PCS reliably collected snowmelt at all sites and caused negligible evaporative fractionation effects in the samples. PCS is low-cost, easy to install, and collects a representative integrated snowmelt sample throughout the melt season or at the melt event scale. Unlike snow cores, the PCS collects the water that would actually infiltrate the soil; thus, its isotopic composition is appropriate to use for tracing snowmelt water through the hydrologic cycle. The purpose of this Briefing is to show the potential advantages of PCSs and recommend guidelines for constructing and installing them based on our preliminary results from two snowmelt seasons.

  10. An automated method for 'clumped-isotope' measurements on small carbonate samples.

    Science.gov (United States)

    Schmid, Thomas W; Bernasconi, Stefano M

    2010-07-30

    Clumped-isotope geochemistry deals with the state of ordering of rare isotopes in molecules, in particular with their tendency to form bonds with other rare isotopes rather than with the most abundant ones. Among its possible applications, carbonate clumped-isotope thermometry is the one that has gained most attention because of the wide potential of applications in many disciplines of earth sciences. Clumped-isotope thermometry allows reconstructing the temperature of formation of carbonate minerals without knowing the isotopic composition of the water from which they were formed. This feature enables new approaches in paleothermometry. The currently published method is, however, limited by sample weight requirements of 10-15 mg and because measurements are performed manually. In this paper we present a new method using an automated sample preparation device coupled to an isotope ratio mass spectrometer. The method is based on the repeated analysis (n = 6-8) of 200 microg aliquots of sample material and completely automated measurements. In addition, we propose to use precisely calibrated carbonates spanning a wide range in Delta(47) instead of heated gases to correct for isotope effects caused by the source of the mass spectrometer, following the principle of equal treatment of the samples and standards. We present data for international standards (NBS 19 and LSVEC) and different carbonates formed at temperatures exceeding 600 degrees C to show that precisions in the range of 10 to 15 ppm (1 SE) can be reached for repeated analyses of a single sample. Finally, we discuss and validate the correction procedure based on high-temperature carbonates instead of heated gases.

  11. A new particle-like method for high-speed flows with chemical non-equilibrium

    Directory of Open Access Journals (Sweden)

    Fábio Rodrigues Guzzo

    2010-04-01

    Full Text Available The present work is concerned with the numerical simulation of hypersonic blunt body flows with chemical non-equilibrium. New theoretical and numerical formulations for coupling the chemical reaction to the fluid dynamics are presented and validated. The fluid dynamics is defined for a stationary unstructured mesh and the chemical reaction process is defined for “finite quantities” moving through the stationary mesh. The fluid dynamics is modeled by the Euler equations and the chemical reaction rates by the Arrhenius law. Ideal gases are considered. The thermodynamical data are based on JANNAF tables and Burcat’s database. The algorithm proposed by Liou, known as AUSM+, is implemented in a cell-centered based finite volume method and in an unstructured mesh context. Multidimensional limited MUSCL interpolation method is used to perform property reconstructions and to achieve second-order accuracy in space. The minmod limiter is used. The second order accuracy, five stage, Runge-Kutta time-stepping scheme is employed to perform the time march for the fluid dynamics. The numerical code VODE, which is part of the CHEMKIN-II package, is adopted to perform the time integration for the chemical reaction equations. The freestream reacting fluid is composed of H2 and air at the stoichiometric ratio. The emphasis of the present paper is on the description of the new methodology for handling the coupling of chemical and fluid mechanic processes, and its validation by comparison with the standard time-splitting procedure. The configurations considered are the hypersonic flow over a wedge, in which the oblique detonation wave is induced by an oblique shock wave, and the hypersonic flow over a blunt body. Differences between the solutions obtained with each formulation are presented and discussed, including the effects of grid refinement in each case. The primary objective of such comparisons is the validation of the proposed methodology. Moreover, for

  12. Estimating groundwater exchange with lakes: 1. The stable isotope mass balance method

    Science.gov (United States)

    Krabbenhoft, David P.; Bowser, Carl J.; Anderson, Mary P.; Valley, John W.

    1990-01-01

    Groundwater inflow and outflow contributions to the hydrologic budget of lakes can be determined using a stable isotope (18O/16O) mass balance method. The stable isotope method provides a way of integrating the spatial and temporal complexities of the flow field around a lake, thereby offering an appealing alternative to the traditional time and labor intensive methods using seepage meters and an extensive piezometer network. In this paper the method is applied to a lake in northern Wisconsin, demonstrating that it can be successfully applied to lakes in the upper midwest where thousands of similar lakes exist. Inflow and outflow rates calculated for the Wisconsin lake using the isotope mass balance method are 29 and 54 cm/yr, respectively, which compare well to estimates, derived independently using a three-dimensional groundwater flow and solute transport model, of 20 and 50 cm/yr. Such a favorable comparison lends confidence to the use of the stable isotope method to estimate groundwater exchange with lakes. In addition, utilization of stable isotopes in studies of groundwater-lake systems lends insight into mixing processes occurring in the unsaturated zone and in the aquifer surrounding the lake and verifies assumed flow paths based on head measurements in piezometers.

  13. Comparison of the Green-Kubo and homogeneous non-equilibrium molecular dynamics methods for calculating thermal conductivity

    Science.gov (United States)

    Dongre, B.; Wang, T.; Madsen, G. K. H.

    2017-07-01

    Different molecular dynamics methods like the direct method, the Green-Kubo (GK) method and homogeneous non-equilibrium molecular dynamics (HNEMD) method have been widely used to calculate lattice thermal conductivity ({κ }{\\ell }). While the first two methods have been used and compared quite extensively, there is a lack of comparison of these methods with the HNEMD method. Focusing on the underlying computational parameters, we present a detailed comparison of the GK and HNEMD methods for both bulk and vacancy Si using the Stillinger-Weber potential. For the bulk calculations, we find both methods to perform well and yield {κ }{\\ell } within acceptable uncertainties. In case of the vacancy calculations, HNEMD method has a slight advantage over the GK method as it becomes computationally cheaper for lower {κ }{\\ell } values. This study could promote the application of HNEMD method in {κ }{\\ell } calculations involving other lattice defects like nanovoids, dislocations, interfaces.

  14. EC-FORC: A New Cyclic Voltammetry Based Method for Examining Phase Transitions and Predicting Equilibrium

    OpenAIRE

    2007-01-01

    We propose a new, cyclic-voltammetry based experimental technique that can not only differentiate between discontinuous and continuous phase transitions in an adsorbate layer, but also quite accurately recover equilibrium behavior from dynamic analysis of systems with a continuous phase transition. The Electrochemical first-order reversal curve (EC-FORC) diagram for a discontinuous phase transition (nucleation and growth), such as occurs in underpotential deposition, is characterized by a neg...

  15. Quick Link Selection Method by Using Pricing Strategy Based on User Equilibrium for Implementing an Effective Urban Travel Demand Management

    Directory of Open Access Journals (Sweden)

    Shahriar Afandizadeh Zargari

    2016-12-01

    Full Text Available This paper presents a two-stage model of optimization as a quick method to choose the best potential links for implementing urban travel demand management (UTDM strategy like road pricing. The model is optimized by minimizing the hidden cost of congestion based on user equilibrium (MHCCUE. It forecasts the exact amount of flows and tolls for links in user equilibrium condition to determine the hidden cost for each link to optimize the link selection based on the network congestion priority. The results show that not only the amount of total cost is decreased, but also the number of selected links for pricing is reduced as compared with the previous toll minimization methods. Moreover, as this model just uses the traffic assignment data for calculation, it could be considered as a quick and optimum solution for choosing the potential links.

  16. Viscosity-projection method for a family of general equilibrium problems and asymptotically strict pseudocontractions in the intermediate sense.

    Science.gov (United States)

    Wen, Dao-Jun

    2013-01-01

    In this paper, a Meir-Keeler contraction is introduced to propose a viscosity-projection approximation method for finding a common element of the set of solutions of a family of general equilibrium problems and the set of fixed points of asymptotically strict pseudocontractions in the intermediate sense. Strong convergence of the viscosity iterative sequences is obtained under some suitable conditions. Results presented in this paper extend and unify the previously known results announced by many other authors.

  17. Isobaric Molecular Dynamics Version of the Generalized Replica Exchange Method (gREM): Liquid-Vapor Equilibrium.

    Science.gov (United States)

    Małolepsza, Edyta; Secor, Maxim; Keyes, Tom

    2015-10-22

    A prescription for sampling isobaric generalized ensembles with molecular dynamics is presented and applied to the generalized replica exchange method (gREM), which was designed to simulate first-order phase transitions. The properties of the isobaric gREM ensemble are discussed, and a study is presented for the liquid-vapor equilibrium of the guest molecules given for gas hydrate formation with the mW water model. Phase diagrams, critical parameters, and a law of corresponding states are obtained.

  18. Computational methods for reactive transport modeling: An extended law of mass-action, xLMA, method for multiphase equilibrium calculations

    Science.gov (United States)

    Leal, Allan M. M.; Kulik, Dmitrii A.; Kosakowski, Georg; Saar, Martin O.

    2016-10-01

    We present an extended law of mass-action (xLMA) method for multiphase equilibrium calculations and apply it in the context of reactive transport modeling. This extended LMA formulation differs from its conventional counterpart in that (i) it is directly derived from the Gibbs energy minimization (GEM) problem (i.e., the fundamental problem that describes the state of equilibrium of a chemical system under constant temperature and pressure); and (ii) it extends the conventional mass-action equations with Lagrange multipliers from the Gibbs energy minimization problem, which can be interpreted as stability indices of the chemical species. Accounting for these multipliers enables the method to determine all stable phases without presuming their types (e.g., aqueous, gaseous) or their presence in the equilibrium state. Therefore, the here proposed xLMA method inherits traits of Gibbs energy minimization algorithms that allow it to naturally detect the phases present in equilibrium, which can be single-component phases (e.g., pure solids or liquids) or non-ideal multi-component phases (e.g., aqueous, melts, gaseous, solid solutions, adsorption, or ion exchange). Moreover, our xLMA method requires no technique that tentatively adds or removes reactions based on phase stability indices (e.g., saturation indices for minerals), since the extended mass-action equations are valid even when their corresponding reactions involve unstable species. We successfully apply the proposed method to a reactive transport modeling problem in which we use PHREEQC and GEMS as alternative backends for the calculation of thermodynamic properties such as equilibrium constants of reactions, standard chemical potentials of species, and activity coefficients. Our tests show that our algorithm is efficient and robust for demanding applications, such as reactive transport modeling, where it converges within 1-3 iterations in most cases. The proposed xLMA method is implemented in Reaktoro, a

  19. 几个重要Ge同位素平衡分馏参数的理论预测%THEORETICAL PREDICTION FOR SEVERAL IMPORTANT EQUILIBRIUM Ge ISOTOPE FRACTIONATION FACTORS

    Institute of Scientific and Technical Information of China (English)

    李雪芳; 唐茂; 刘耘

    2009-01-01

    This study provided a number of theoretical equilibrium isotope fractionations between several Ge species, including quartz- (or opal-), albite-, K-feldspar- and olivine-like structures, as well as the dominant Ge(OH)4 and GeO(OH)3- species in aqueous solutions. They are basic parameters for exploring the unknown application of Ge isotope in the field of geochemistry. Our method is based on the Urey model (or the Bigeleisen-Mayer equation) and quantum chemistry calculation. We estimated that the accuracy of the parameters could be around 0.3‰, with the calculations made at B3LYP/6-311+G(d,p) level. Solvent effect was handled using explicit solvent model ("water droplet" method), and the minerals were simulated by cluster model. Our results showed that quartz- or opal-like structure can enrich most heavy Ge isotopes, and at 25℃, the fractionations are around Δquartz-Ge(OH)4=0.9‰, ΔGe(OH)4-GeO(OH)3-=0.3‰ (in seawaters), Δquartz-albite=0.6‰, Δquartz-K-feldspar=0.4‰, Δolivine-Ge(OH)4=-1.2‰ and Δquartz-olivine=2.1‰. These data could give better explanations to the experimental observations of Siebert et al. (2006) and Rouxel et al. (2006), suggesting that our theoretical prediction is accurate and important for real geochemical problems.%本研究基于Urey模型(或称Bigeleisen和Mayer公式),结合量子化学计算的方法,在B3LYP/6-311+G(d, p)理论水平下,计算了Ge在类似石英(包括蛋白石)、钠长石、钾长石、橄榄石结构以及水溶液(包括海水)中Ge(OH)4和GeO(OH)3-之间的Ge同位素平衡分馏系数.其中,溶液效应用"水滴法"处理,矿物结构用簇合物方法模拟.结果显示这些基本分馏参数的精度约±0.3‰;类石英(或蛋白石)结构最可能富集重Ge同位素,在25 ℃,几个Ge同位素分馏系数分别约为:Δ石英-Ge(OH)4=0.9‰、ΔGe(OH)4-GeO(OH)3-=0.3‰(海水中)、Δ石英-钠长石=0.6‰、Δ石英-钾长石=0.4‰、Δ橄榄石-Ge(OH)4=-1.2‰.类石英与类橄榄

  20. Determine equilibrium dissociation constant of drug-membrane receptor affinity using the cell membrane chromatography relative standard method.

    Science.gov (United States)

    Ma, Weina; Yang, Liu; Lv, Yanni; Fu, Jia; Zhang, Yanmin; He, Langchong

    2017-06-23

    The equilibrium dissociation constant (KD) of drug-membrane receptor affinity is the basic parameter that reflects the strength of interaction. The cell membrane chromatography (CMC) method is an effective technique to study the characteristics of drug-membrane receptor affinity. In this study, the KD value of CMC relative standard method for the determination of drug-membrane receptor affinity was established to analyze the relative KD values of drugs binding to the membrane receptors (Epidermal growth factor receptor and angiotensin II receptor). The KD values obtained by the CMC relative standard method had a strong correlation with those obtained by the frontal analysis method. Additionally, the KD values obtained by CMC relative standard method correlated with pharmacological activity of the drug being evaluated. The CMC relative standard method is a convenient and effective method to evaluate drug-membrane receptor affinity. Copyright © 2017 Elsevier B.V. All rights reserved.

  1. Exogenous surfactant kinetics in infant respiratory distress syndrome : A novel method with stable isotopes

    NARCIS (Netherlands)

    Torresin, M; Zimmermann, LJI; Cogo, PE; Cavicchioli, P; Badon, T; Giordano, G; Zacchello, F; Sauer, PJJ; Carnielli, VP

    Little is known about surfactant metabolism in newborn infants, since radioactive isotopes cannot be used in humans. We describe here a new method for studying exogenous surfactant pharmacokinetics in vivo. We measured surfactant half-life, pool size, and turnover time in eight preterm infants

  2. New neutron-based isotopic analytical methods; An explorative study of resonance capture and incoherent scattering

    NARCIS (Netherlands)

    Perego, R.C.

    2004-01-01

    Two novel neutron-based analytical techniques have been treated in this thesis, Neutron Resonance Capture Analysis (NRCA), employing a pulsed neutron source, and Neutron Incoherent Scattering (NIS), making use of a cold neutron source. With the NRCA method isotopes are identified by the

  3. Isotope separation method for preparing novel semiconductors, and semiconductor junctions containing the novel semiconductor

    Energy Technology Data Exchange (ETDEWEB)

    Fanica, M.M.; Ivascu, M.; Ilas, G.; Dumitru, I.

    1997-02-20

    An isotope separation method for use in the field of semiconductors is provided. The method is an improvement to the invention disclosed in OSIM patent application no. 95-01302 of 13.07.1995. Specifically, a method is provided for processing a semiconductor element having a cubic, rhombic or hexagonal crystalline structure and containing at least two stable isotopes, to enable the concentration of the various isotopes to be altered. The method comprises exposing the element to a temperature adjacent to its diffusion temperature, simultaneously applying to the element a 1 Amp., 4-30 KV electric current proportional to the ionisation energy expressed in Kcal/g mol, arranging the element being processed in a gaseous medium containing at least one inert gas to prevent oxidation of the element, and continuing the process for around 2 hours. An antimony (Sb) element with an isotope ratio of Sb 121 (P1,P2):Sb 123 (P3) = 1.70 is also provided. (author) figs.

  4. Effect of deviation from local thermodynamic equilibrium on the Goldberg-Unno method. [turbulence effects on optical density in the solar photosphere

    Science.gov (United States)

    Troyan, V. I.

    1974-01-01

    The dependence of turbulent velocity on optical depth was studied by use of the Goldberg-Unno method, with allowance made for the influence of deviation from the local thermodynamic equilibrium. It was found that allowance for deviation from local thermodynamic equilibrium displaces the curve of dependence of turbulent velocity on optical depth along two axes.

  5. A simplified method for obtaining high-purity perchlorate from groundwater for isotope analyses.

    Energy Technology Data Exchange (ETDEWEB)

    vonKiparski, G; Hillegonds, D

    2011-04-04

    Investigations into the occurrence and origin of perchlorate (ClO{sub 4}{sup -}) found in groundwater from across North America have been sparse until recent years, and there is mounting evidence that natural formation mechanisms are important. New opportunities for identifying groundwater perchlorate and its origin have arisen with the utilization of improved detection methods and sampling techniques. Additionally, application of the forensic potential of isotopic measurements has begun to elucidate sources, potential formation mechanisms and natural attenuation processes. Procedures developed appear to be amenable to enable high precision stable isotopic analyses, as well as lower precision AMS analyses of {sup 36}Cl. Immediate work is in analyzing perchlorate isotope standards and developing full analytical accuracy and uncertainty expectations. Field samples have also been collected, and will be analyzed when final qa/qc samples are deemed acceptable.

  6. Application of a New Method to Study the Spin Equilibrium of Aql X–1: The Possibility of Gravitational Radiation

    Science.gov (United States)

    Bhattacharyya, Sudip

    2017-09-01

    Accretion via disks can make neutron stars in low-mass X-ray binaries (LMXBs) fast spinning, and some of these stars are detected as millisecond pulsars. Here we report a practical way to find out if a neutron star in a transient LMXB has reached the spin equilibrium by disk–magnetosphere interaction alone, and if not, to estimate this spin equilibrium frequency. These can be done using specific measurable source luminosities, such as the luminosity corresponding to the transition between the accretion and propeller phases, and the known stellar spin rate. Such a finding can be useful to test if the spin distribution of millisecond pulsars, as well as an observed upper cutoff of their spin rates, can be explained using disk–magnetosphere interaction alone, or additional spin-down mechanisms, such as gravitational radiation, are required. Applying our method, we find that the neutron star in the transient LMXB Aql X–1 has not yet reached the spin equilibrium by disk–magnetosphere interaction alone. We also perform numerical computations, with and without gravitational radiation, to study the spin evolution of Aql X–1 through a series of outbursts and to constrain its properties. While we find that the gravitational wave emission from Aql X–1 cannot be established with certainty, our numerical results show that the gravitational radiation from Aql X–1 is possible, with a 1.6× {10}37 g cm2 upper limit of the neutron star misaligned mass quadrupole moment.

  7. Application of an isotopic contrast method for the investigation of atomic dynamics of polyatomic compounds

    CERN Document Server

    Parshin, P P

    2002-01-01

    The method of isotopic contrast in inelastic neutron scattering is described. The analysis of capabilities of the method for researches of atomic dynamics of condensed matter is carried out. For an example of a binary oxide CuO the experimental implementation of this method is demonstrated. The researches of dynamic behavior of some chemical elements in HTSC cuprates and related compounds are discussed. (orig.)

  8. System and method of adjusting the equilibrium temperature of an inductively-heated susceptor

    Energy Technology Data Exchange (ETDEWEB)

    Matsen, Marc R; Negley, Mark A; Geren, William Preston

    2015-02-24

    A system for inductively heating a workpiece may include an induction coil, at least one susceptor face sheet, and a current controller coupled. The induction coil may be configured to conduct an alternating current and generate a magnetic field in response to the alternating current. The susceptor face sheet may be configured to have a workpiece positioned therewith. The susceptor face sheet may be formed of a ferromagnetic alloy having a Curie temperature and being inductively heatable to an equilibrium temperature approaching the Curie temperature in response to the magnetic field. The current controller may be coupled to the induction coil and may be configured to adjust the alternating current in a manner causing a change in at least one heating parameter of the susceptor face sheet.

  9. A new method of testing for Hardy–Weinberg equilibrium and ordering populations

    Indian Academy of Sciences (India)

    Nader Ebrahimi; Devrim Bilgili

    2007-01-01

    The assumption of Hardy–Weinberg equilibrium (HWE) among alleles in a nonevolving population is of fundamental importance in genetic studies. Deviation from HWE in a population usually indicates inbreeding, stratification and sometimes problems in genotyping. In populations of affected individuals, these deviations can also provide evidence for association. In this paper, we introduce a measure based on the Kullback–Leibler discrimination information function that quantifies the deviation from HWE in a population. We use this measure to order populations. We also propose a test for HWE based on an estimate of this measure. The test is a statistically consistent test of the null hypothesis for all alternatives and is very easy to implement. Our proposed test statistic is compared with an earlier, widely used, test. Finally, the use of the proposed new test is shown in an illustrative example.

  10. A General Iterative Method of Fixed Points for Mixed Equilibrium Problems and Variational Inclusion Problems

    Directory of Open Access Journals (Sweden)

    Phayap Katchang

    2010-01-01

    Full Text Available The purpose of this paper is to investigate the problem of finding a common element of the set of solutions for mixed equilibrium problems, the set of solutions of the variational inclusions with set-valued maximal monotone mappings and inverse-strongly monotone mappings, and the set of fixed points of a family of finitely nonexpansive mappings in the setting of Hilbert spaces. We propose a new iterative scheme for finding the common element of the above three sets. Our results improve and extend the corresponding results of the works by Zhang et al. (2008, Peng et al. (2008, Peng and Yao (2009, as well as Plubtieng and Sriprad (2009 and some well-known results in the literature.

  11. Design Considerations of Structural Parameters in Resonant Tunneling Diode by None-Equilibrium Green Function Method

    Directory of Open Access Journals (Sweden)

    M. Charmi

    2015-12-01

    Full Text Available This paper presents the effects of structural parameters like Quantum well width, barrier width, spacer width, contact width and contact doping, on performance of Resonant Tunneling Diode using full quantum simulation. The simulation is based on a self-consistent solution of the Poisson equation and Schrodinger equation with open boundary conditions, within the non-equilibrium Green’s function formalism. The effects of varying the structural parameters is investigated in terms of the output current, peak current, valley current, peak to valley current ratio and the voltage associated with the peak current. Simulation results illustrate that the device performance can be improved by proper selection of the structural parameters.

  12. Theoretical Methods in the Non-Equilibrium Quantum Mechanics of Many Bodies

    Science.gov (United States)

    2011-01-01

    function in real time GR (t) = ∫ dω 2π e−iωtGR (ω) ≈ e−it(ξα+ΣR)+tΣI (2.19) From here we see that the inclusion of many-body interactions renormalizes the...equilibrium with a bath at zero temperature. Following [63], we write the total Hamiltonian as Ĥ = Ĥ0 + V̂ where Ĥ0 is a “ bare ” Hamiltonian for...averaged over the known ground state |φ0〉 of the bare Hamiltonian. Gα,α′ (t, t ′) = −i〈Tâ † α (t) âα′ (t ′) Ŝ (∞,−∞)〉0 〈φ0|TŜ (∞,−∞) |φ0〉 (4.8) In

  13. GENERAL EQUILIBRIUM

    Directory of Open Access Journals (Sweden)

    Monique Florenzano

    2008-09-01

    Full Text Available General equilibrium is a central concept of economic theory. Unlike partial equilibrium analysis which study the equilibrium of a particular market under the clause “ceteris paribus” that revenues and prices on the other markets stay approximately unaffected, the ambition of a general equilibrium model is to analyze the simultaneous equilibrium in all markets of a competitive economy. Definition of the abstract model, some of its basic results and insights are presented. The important issues of uniqueness and local uniqueness of equilibrium are sketched; they are the condition for a predictive power of the theory and its ability to allow for statics comparisons. Finally, we review the main extensions of the general equilibrium model. Besides the natural extensions to infinitely many commodities and to a continuum of agents, some examples show how economic theory can accommodate the main ideas in order to study some contexts which were not thought of by the initial model

  14. Method for determination of stable carbon isotope ratio of methylnitrophenols in atmospheric PM

    Directory of Open Access Journals (Sweden)

    S. Moukhtar

    2011-05-01

    Full Text Available A technique for the measurement of the stable isotope ratio of methylnitrophenols in atmospheric particulate matter (PM is presented. It has been found in numerous laboratory studies that these compounds are photooxidation products of toluene in PM. Atmospheric samples from rural and suburban areas were collected for evaluation of the procedure. PM was collected on quartz fibre filters using dichotomous high volume air samplers for PM 2.5. Methylnitrophenols were extracted from the filters using acetonitrile. The sample was then purified using a combination of high-performance liquid chromatography (HPLC and solid phase extraction (SPE. The final solution was then divided into two aliquots. To one aliquot, a derivatising agent, Bis(trimethylsilyltrifluoroacetamide (BSTFA, was added to the solution for Gas Chromatography/Mass Spectroscopy (GC/MS analysis. The second half of the sample was stored at low temperature. When GC/MS analysis showed high enough concentrations the remaining sample was derivatized with BSTFA and analysed for stable isotope ratio using a Gas Chromatography/Isotope Ratio Mass Spectrometry (GC-IRMS.

    In all atmospheric PM samples analysed, 2-methyl-4-nitrophenol was found to be the most abundant methylnitrophenol. Nevertheless, due to low pollution levels occurring in the rural area, no samples had concentrations high enough to perform stable carbon isotope composition measurements of the methylnitrophenols. Samples collected in the suburban area could be analysed for carbon stable isotope ratio using GC-IRMS.

    The procedure described in this paper provides a very sensitive and selective method for the analysis of methylnitrophenols in atmospheric PM at concentrations as low as 1 pg m−3. For accurate (within ±0.5‰ stable isotope ratio analysis significantly higher concentrations in the range of 100 pg m−3 or more are required.

  15. In vitro interaction study of retinoic acid isomers with telmisartan and amlodipine by equilibrium dialysis method using UV spectroscopy

    Science.gov (United States)

    Varghese, Susheel John; Johny, Sojimol K.; Paul, David; Ravi, Thengungal Kochupappy

    2011-07-01

    The in vitro protein binding of retinoic acid isomers (isotretinoin and tretinoin) and the antihypertensive drugs (amlodipine and telmisartan) was studied by equilibrium dialysis method. In this study, free fraction of drugs and the % of binding of drugs in the mixture to bovine serum albumin (BSA) were calculated. The influence of retinoic acid isomers on the % of protein binding of telmisartan and amlodipine at physiological pH (7.4) and temperature (37 ± 0.5 °C) was also evaluated. The in vitro displacement interaction study of drugs telmisartan and amlodipine on retinoic acid isomers and also interaction of retinoic acid isomers on telmisartan and amlodipine were carried out.

  16. A method to extract soil water for stable isotope analysis

    Science.gov (United States)

    Revesz, K.; Woods, P.H.

    1990-01-01

    A method has been developed to extract soil water for determination of deuterium (D) and 18O content. The principle of this method is based on the observation that water and toluene form an azeotropic mixture at 84.1??C, but are completely immiscible at ambient temperature. In a specially designed distillation apparatus, the soil water is distilled at 84.1??C with toluene and is separated quantitatively in the collecting funnel at ambient temperature. Traces of toluene are removed and the sample can be analyzed by mass spectrometry. Kerosene may be substituted for toluene. The accuracy of this technique is ?? 2 and ?? 0.2???, respectively, for ??D and ??18O. Reduced accuracy is obtained at low water contents. ?? 1990.

  17. Intercomparison of Lab-Based Soil Water Extraction Methods for Stable Water Isotope Analysis

    Science.gov (United States)

    Pratt, D.; Orlowski, N.; McDonnell, J.

    2016-12-01

    The effect of pore water extraction technique on resultant isotopic signature is poorly understood. Here we present results of an intercomparison of five common lab-based soil water extraction techniques: high pressure mechanical squeezing, centrifugation, direct vapor equilibration, microwave extraction, and cryogenic extraction. We applied five extraction methods to two physicochemically different standard soil types (silty sand and clayey loam) that were oven-dried and rewetted with water of known isotopic composition at three different gravimetric water contents (8, 20, and 30%). We tested the null hypothisis that all extraction techniques would provide the same isotopic result independent from soil type and water content. Our results showed that the extraction technique had a significant effect on the soil water isotopic composition. Each method exhibited deviations from spiked reference water, with soil type and water content showing a secondary effect. Cryogenic extraction showed the largest deviations from the reference water, whereas mechanical squeezing and centrifugation provided the closest match to the reference water for both soil types. We also compared results for each extraction technique that produced liquid water on both an OA-ICOS and IRMS; differences between them were negligible.

  18. Toroidal figures of equilibrium from a second-order accurate, accelerated SCF method with subgrid approach

    Science.gov (United States)

    Huré, J.-M.; Hersant, F.

    2017-02-01

    We compute the structure of a self-gravitating torus with polytropic equation of state (EOS) rotating in an imposed centrifugal potential. The Poisson solver is based on isotropic multigrid with optimal covering factor (fluid section-to-grid area ratio). We work at second order in the grid resolution for both finite difference and quadrature schemes. For soft EOS (i.e. polytropic index n ≥ 1), the underlying second order is naturally recovered for boundary values and any other integrated quantity sensitive to the mass density (mass, angular momentum, volume, virial parameter, etc.), i.e. errors vary with the number N of nodes per direction as ˜1/N2. This is, however, not observed for purely geometrical quantities (surface area, meridional section area, volume), unless a subgrid approach is considered (i.e. boundary detection). Equilibrium sequences are also much better described, especially close to critical rotation. Yet another technical effort is required for hard EOS (n < 1), due to infinite mass density gradients at the fluid surface. We fix the problem by using kernel splitting. Finally, we propose an accelerated version of the self-consistent field (SCF) algorithm based on a node-by-node pre-conditioning of the mass density at each step. The computing time is reduced by a factor of 2 typically, regardless of the polytropic index. There is a priori no obstacle to applying these results and techniques to ellipsoidal configurations and even to 3D configurations.

  19. FEM-BEM coupling methods for Tokamak plasma axisymmetric free-boundary equilibrium computations in unbounded domains

    Science.gov (United States)

    Faugeras, Blaise; Heumann, Holger

    2017-08-01

    Incorporating boundary conditions at infinity into simulations on bounded computational domains is a repeatedly occurring problem in scientific computing. The combination of finite element methods (FEM) and boundary element methods (BEM) is the obvious instrument, and we adapt here for the first time the two standard FEM-BEM coupling approaches to the free-boundary equilibrium problem: the Johnson-Nédélec coupling and the Bielak-MacCamy coupling. We recall also the classical approach for fusion applications, dubbed according to its first appearance von-Hagenow-Lackner coupling and present the less used alternative introduced by Albanese, Blum and de Barbieri in [2]. We show that the von-Hagenow-Lackner coupling suffers from undesirable non-optimal convergence properties, that suggest that other coupling schemes, in particular Johnson-Nédélec or Albanese-Blum-de Barbieri are more appropriate for non-linear equilibrium problems. Moreover, we show that any of such coupling methods requires Newton-like iteration schemes for solving the corresponding non-linear discrete algebraic systems.

  20. Standard test method for isotopic analysis of uranium hexafluoride by double standard single-collector gas mass spectrometer method

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2010-01-01

    1.1 This is a quantitative test method applicable to determining the mass percent of uranium isotopes in uranium hexafluoride (UF6) samples with 235U concentrations between 0.1 and 5.0 mass %. 1.2 This test method may be applicable for the entire range of 235U concentrations for which adequate standards are available. 1.3 This test method is for analysis by a gas magnetic sector mass spectrometer with a single collector using interpolation to determine the isotopic concentration of an unknown sample between two characterized UF6 standards. 1.4 This test method is to replace the existing test method currently published in Test Methods C761 and is used in the nuclear fuel cycle for UF6 isotopic analyses. 1.5 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard. 1.6 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 appro...

  1. Seismic stability analysis of expanded MSW landfills using pseudo-static limit equilibrium method.

    Science.gov (United States)

    Choudhury, Deepankar; Savoikar, Purnanand

    2011-02-01

    Capacity expansion of existing landfills is the most economical alternative to constructing new landfills where cost of land is prohibitive. From the safety point of view, the stability analyses of existing landfills expanded either vertically and/or laterally are required for different stages of construction, operation and during closure of a landfill. In the present study, a pseudo-static limit equilibrium seismic stability analysis was performed for a typical side-hill type municipal solid waste (MSW) landfill expanded using an engineered berm. Seismic stability analyses were performed for the two critical cases, namely when the failure surface passes below the berm (under berm) and when the failure surface passes over the back slope of the berm (over berm). Close-form solutions were developed for the upper bound and lower bound factor of safety and the yield acceleration of such slopes under both failure conditions. From parametric analyses it was observed that as the height of the berm increased, the factor of safety for both the over-berm failure and the under-berm failure conditions also increased. The average factor of safety and yield acceleration coefficient were found and the under-berm failure condition became critical for a back slope steeper than 1.7H : 1V. The average factor of safety decreased as both horizontal and vertical seismic accelerations increased. Comparisons between the present results and those in the literature for the static case showed good agreement and the present results of the pseudo-static seismic case were found to be of particular importance.

  2. A method to predict the equilibrium solubility of drugs in solid polymers near room temperature using thermal analysis.

    Science.gov (United States)

    Bellantone, Robert A; Patel, Piyush; Sandhu, Harpreet; Choi, Duk Soon; Singhal, Dharmendra; Chokshi, H; Malick, A Waseem; Shah, Navnit

    2012-12-01

    A method is presented for determining the equilibrium solubility of a drug in a solid polymer at or near room temperature, which represents a typical storage temperature. The method is based on a thermodynamic model to calculate the Gibbs energy change ΔG(SS) associated with forming a binary drug-polymer solid solution from the unmixed polymer and solid drug. The model includes contributions from heat capacity differences between the solid solution and the corresponding unmixed components, breaking up of the solid drug structure, and drug-polymer mixing. Calculation of ΔG(SS) from thermal analysis data is demonstrated, and it is shown that minima of plots of ΔG(SS) versus the dissolved drug concentration represent the equilibrium drug solubility in the polymer. Solid solutions were produced for drug-polymer systems (griseofulvin, indomethacin, itraconazole; PVP K30, Eudragit L100, Eudragit E100) in drug weight fractions up to ∼25%. At 25°C, it was seen that heat capacity effects were important in determining the drug solubility. It was concluded that drug solubilities in solid polymers can be determined using thermal analysis, and must include heat capacity effects when evaluated near room temperature.

  3. Reviews and syntheses: Isotopic approaches to quantify root water uptake: a review and comparison of methods

    Science.gov (United States)

    Rothfuss, Youri; Javaux, Mathieu

    2017-05-01

    Plant root water uptake (RWU) has been documented for the past five decades from water stable isotopic analysis. By comparing the (hydrogen or oxygen) stable isotopic compositions of plant xylem water to those of potential contributive water sources (e.g., water from different soil layers, groundwater, water from recent precipitation or from a nearby stream), studies were able to determine the relative contributions of these water sources to RWU. In this paper, the different methods used for locating/quantifying relative contributions of water sources to RWU (i.e., graphical inference, statistical (e.g., Bayesian) multi-source linear mixing models) are reviewed with emphasis on their respective advantages and drawbacks. The graphical and statistical methods are tested against a physically based analytical RWU model during a series of virtual experiments differing in the depth of the groundwater table, the soil surface water status, and the plant transpiration rate value. The benchmarking of these methods illustrates the limitations of the graphical and statistical methods while it underlines the performance of one Bayesian mixing model. The simplest two-end-member mixing model is also successfully tested when all possible sources in the soil can be identified to define the two end-members and compute their isotopic compositions. Finally, the authors call for a development of approaches coupling physically based RWU models with controlled condition experimental setups.

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

    Science.gov (United States)

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

    2016-05-15

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

  5. A new method to track seed dispersal and recruitment using 15N isotope enrichment.

    Science.gov (United States)

    Carlo, Tomás A; Tewksbury, Joshua J; Martínez Del Río, Carlos

    2009-12-01

    Seed dispersal has a powerful influence on population dynamics, genetic structuring, evolutionary rates, and community ecology. Yet, patterns of seed dispersal are difficult to measure due to methodological shortcomings in tracking dispersed seeds from sources of interest. Here we introduce a new method to track seed dispersal: stable isotope enrichment. It consists of leaf-feeding plants with sprays of 15N-urea during the flowering stage such that seeds developed after applications are isotopically enriched. We conducted a greenhouse experiment with Solanum americanum and two field experiments with wild Capsicum annuum in southern Arizona, USA, to field-validate the method. First, we show that plants sprayed with 15N-urea reliably produce isotopically enriched progeny, and that delta 15N (i.e., the isotopic ratio) of seeds and seedlings is a linear function of the 15N-urea concentration sprayed on mothers. We demonstrate that three urea dosages can be used to distinctly enrich plants and unambiguously differentiate their offspring after seeds are dispersed by birds. We found that, with high urea dosages, the resulting delta 15N values in seedlings are 10(3) - 10(4) times higher than the delta 15N values of normal plants. This feature allows tracking not only where seeds arrive, but in locations where seeds germinate and recruit, because delta 15N enrichment is detectable in seedlings that have increased in mass by at least two orders of magnitude before fading to normal delta 15N values. Last, we tested a mixing model to analyze seed samples in bulk. We used the delta 15N values of batches (i.e., combined seedlings or seeds captured in seed traps) to estimate the number of enriched seeds coming from isotopically enriched plants in the field. We confirm that isotope enrichment, combined with batch-sampling, is a cheap, reliable, and user-friendly method for bulk-processing seeds and is thus excellent for the detection of rare dispersal events. This method could

  6. A rapid method for determination of the isotopic composition of uranium samples by alpha spectrometry

    Energy Technology Data Exchange (ETDEWEB)

    Martin Sanchez, A.; Tome, F.V.; Diaz Bejarano, J.; Jurado Vargas, M. (Dept. de Fisica, Univ. Extremadura, Badajoz (Spain))

    1992-03-01

    A simple method of analyzing alpha spectra from natural and enriched or depleted uranium samples is developed. The procedure is non-iterative, and takes into consideration low-energy tail and branching-ratio corrections to accurately calculate the area corresponding to each uranium isotope ({sup 234}U, {sup 235}U, {sup 236}U, {sup 238}U) in the spectrum, and then the isotopic composition of the sample. A BASIC computer program, called ENURA, has been developed to perform all the necessary calculations to give the results together with their uncertainties. Several samples were prepared with different uranium concentrations made from standard solutions with known compositions, and the method was checked against the experimental measurements from these samples. Other series of uranium spectra were theoretically constructed using a given line shape in order to cover the required range of enriched or depleted uranium. (orig.).

  7. Determination of the Galaxy age by the method of uranium-thorium-plutonium isotopic ratios

    Science.gov (United States)

    Panov, I. V.; Lutostansky, Yu. S.; Eichler, M.; Thielemann, F.-K.

    2017-07-01

    The dependence of the Galaxy age ( T G), as determined by the method of uranium-thorium isotopic ratios, on the parameters of the nucleosynthesis model is studied within the theory of galactic nucleosynthesis. It is shown that TG depends strongly both on the scenario of the production of nuclei in the r-process and those features of neutron-rich nuclei that are used in the respective analysis and on galactic-nucleosynthesis parameters. The effect of a sudden nucleosynthesis spike before the formation of a solar system on the Galaxy age is evaluated. The region of admissible values of the parameters of galacticnucleosynthesis theory is discussed. The method of uranium-thorium isotopic ratios is supplemented with the 244Pu/238U ratio for yet another cosmochronometer pair, and the Galaxy age is estimated on the basis of the model modified in this way.

  8. Trigonometric and hyperbolic functions method for constructing analytic solutions to nonlinear plane magnetohydrodynamics equilibrium equations

    Energy Technology Data Exchange (ETDEWEB)

    Moawad, S. M., E-mail: smmoawad@hotmail.com [Department of Mathematics, Faculty of Science, Beni-Suef University, Beni-Suef (Egypt)

    2015-02-15

    In this paper, we present a solution method for constructing exact analytic solutions to magnetohydrodynamics (MHD) equations. The method is constructed via all the trigonometric and hyperbolic functions. The method is applied to MHD equilibria with mass flow. Applications to a solar system concerned with the properties of coronal mass ejections that affect the heliosphere are presented. Some examples of the constructed solutions which describe magnetic structures of solar eruptions are investigated. Moreover, the constructed method can be applied to a variety classes of elliptic partial differential equations which arise in plasma physics.

  9. Aspect of human food ecology; Development of carbon and nitrogen isotope method

    Energy Technology Data Exchange (ETDEWEB)

    Minagawa, Masao (Hokkaido Univ., Sapporo (Japan))

    1994-01-01

    The isotopic dietary analysis was applied for some prehistoric human populations from East Asia, Latin America, and Oceania region. Most samples were from archeological sites from 1000 to 6000 year's bp. Some modern ethnological groups including Tibet, Kurud, Shelpa and Tlingit were also studied for evaluating prehistoric human food habit. Carbon and nitrogen isotope compositions of gelatin fractions have been analyzed for prehistoric bone samples. Analytical procedure for isotopes and data analyses for reconstructing dietary composition was developed and tested by a modern human food system. A stochastic method based on the Monte Carlo model was applied to estimate dependency of major food resources having unique isotope compositions in carbon and nitrogen, and has showed consistent results to the statistic food consumption record in Japan. Carbon and nitrogen isotope composition of human tissues showed distinct difference among human groups in both prehistoric and modern samples. These data were evaluated by difference of dietary patterns: contributions of marine food, terrestrial food, meat, C3 and C4 plant, which are characterized by the difference of [sup 13]C and [sup 15]N content. On the basis of the stochastic feeding simulation, dietary consumption patterns were estimated for Jomon fisher-hunter-gatherers, historic Ainu, prehistoric east Siberian, prehistoric Latin American farmers in Mexico and Peru, and prehistoric fisheres in Cook island. Results showed a remarkable relationship between animal protein dependence and marine food usage. This result will be discussed from following two possibilities; the human adaptation on marine resources would be one of the important direction to upgrade animal protein uptake, or marine food could be used as alternative protein source for terrestrial game animals. (author).

  10. Analytical Solutions for the Equilibrium states of a Swollen Hydrogel Shell and an Extended Method of Matched Asymptotics

    CERN Document Server

    Dai, Hui-Hui

    2011-01-01

    A polymer network can imbibe water, forming an aggregate called hydrogel, and undergo large and inhomogeneous deformation with external mechanical constraint. Due to the large deformation, nonlinearity plays a crucial role, which also causes the mathematical difficulty for obtaining analytical solutions. Based on an existing model for equilibrium states of a swollen hydrogel with a core-shell structure, this paper seeks analytical solutions of the deformations by perturbation methods for three cases, i.e. free-swelling, nearly free-swelling and general inhomogeneous swelling. Particularly for the general inhomogeneous swelling, we introduce an extended method of matched asymptotics to construct the analytical solution of the governing nonlinear second-order variable-coefficient differential equation. The analytical solution captures the boundary layer behavior of the deformation. Also, analytical formulas for the radial and hoop stretches and stresses are obtained at the two boundary surfaces of the shell, ma...

  11. 2D Quantum Simulation of MOSFET Using the Non Equilibrium Green's Function Method

    Science.gov (United States)

    Svizhenko, Alexel; Anantram, M. P.; Govindan, T. R.; Yan, Jerry (Technical Monitor)

    2000-01-01

    The objectives this viewgraph presentation summarizes include: (1) the development of a quantum mechanical simulator for ultra short channel MOSFET simulation, including theory, physical approximations, and computer code; (2) explore physics that is not accessible by semiclassical methods; (3) benchmarking of semiclassical and classical methods; and (4) study other two-dimensional devices and molecular structure, from discretized Hamiltonian to tight-binding Hamiltonian.

  12. Evolution of the South African mantle — A case study of garnet peridotites from the Finsch diamond mine (Kaapvaal craton); part 1: Inter-mineral trace element and isotopic equilibrium

    Science.gov (United States)

    Lazarov, Marina; Brey, Gerhard P.; Weyer, Stefan

    2012-12-01

    A thorough assessment of inter-mineral equilibrium is essential for the understanding of trace element partitioning and also for the interpretation of isotopic data. Here we investigated high temperature (~ 1200 °C and 6 GPa) garnet peridotite xenoliths from the Kaapvaal craton (Finsch mine, South Africa), with exceptionally well equilibrated mineral major element compositions, for their trace element and isotopic inter-mineral equilibrium. Trace element compositions for all major mineral phases, i.e. olivine, orthopyroxene (opx), clinopyroxene (cpx) and garnet, were analysed by laser ablation inductively coupled plasma mass spectrometry (ICP-MS). Garnet, cpx and opx of selected samples were analysed for their Sm-Nd and Lu-Hf isotope compositions by multi collector ICP-MS. Most important mineral characteristics include: a) olivines from most samples are enriched in high-field-strength elements relative to other incompatible trace elements. Their lithium content correlates negatively with Mg#, indicating a depletion signature; b) all other minerals are depleted in heavy and middle rare earth elements (H- and M-REE) and enriched in light REE and large ion lithophile elements. This implies a complex history of depletion and metasomatic overprint for the Finsch cratonic mantle; c) orthopyroxene has similarly shaped trace element patterns as cpx, with one to two orders of magnitude lower abundances; and d) both, garnet and cpx, display variable, mostly positive ɛHf coupled with moderate variations in ɛNd. Trace element partitioning between garnet/cpx, cpx/opx and garnet/opx, displays only a weak pressure and temperature dependency. However, equilibrium partitioning of most trace elements between garnet and cpx shows a strong compositional dependency, i.e. on the Cr- (and Ca-) content of the garnets. Garnet-cpx partition coefficients follow a second grade polynomial correlation with Cr2O3 of garnet, whereby high chromium garnets (Cr2O3 > 6 wt.%) have generally higher

  13. COMPUTATION METHOD OF CHEMICAL EQUILIBRIUM OF COMPLEX SYSTEM%复杂体系化学平衡组成计算方法

    Institute of Scientific and Technical Information of China (English)

    邓文生; 贾冬梅; 张青山; 李民丽

    2004-01-01

    The chaos-Monte Carlo algorithm (CMCA) was proposed for solving chemical equilibrium of complex system. By introducing random well-distributed points into the Monte Carlo algorithm, this new approach showed good convergent probability and high-speed. Equilibrium composition of some complex systems, such as methanol synthesis, ammonia oxidation, and Claus process were calculated. The results showed good agreement with Liu Xiaodi's and Xu Jinhuo's calculations. Compared with the gradient method, the genetic algorithm and the modified genetic algorithm, the CMCA is simple, general and insensitive to initial value. It is an efficient algorithm based on the theory of minimization of Gibbs free energy to solve chemical equilibrium of complex system.

  14. Isotope geochemistry. Biological signatures in clumped isotopes of O₂.

    Science.gov (United States)

    Yeung, Laurence Y; Ash, Jeanine L; Young, Edward D

    2015-04-24

    The abundances of molecules containing more than one rare isotope have been applied broadly to determine formation temperatures of natural materials. These applications of "clumped" isotopes rely on the assumption that isotope-exchange equilibrium is reached, or at least approached, during the formation of those materials. In a closed-system terrarium experiment, we demonstrate that biological oxygen (O2) cycling drives the clumped-isotope composition of O2 away from isotopic equilibrium. Our model of the system suggests that unique biological signatures are present in clumped isotopes of O2—and not formation temperatures. Photosynthetic O2 is depleted in (18)O(18)O and (17)O(18)O relative to a stochastic distribution of isotopes, unlike at equilibrium, where heavy-isotope pairs are enriched. Similar signatures may be widespread in nature, offering new tracers of biological and geochemical cycling.

  15. General method and thermodynamic tables for computation of equilibrium composition and temperature of chemical reactions

    Science.gov (United States)

    Huff, Vearl N; Gordon, Sanford; Morrell, Virginia E

    1951-01-01

    A rapidly convergent successive approximation process is described that simultaneously determines both composition and temperature resulting from a chemical reaction. This method is suitable for use with any set of reactants over the complete range of mixture ratios as long as the products of reaction are ideal gases. An approximate treatment of limited amounts of liquids and solids is also included. This method is particularly suited to problems having a large number of products of reaction and to problems that require determination of such properties as specific heat or velocity of sound of a dissociating mixture. The method presented is applicable to a wide variety of problems that include (1) combustion at constant pressure or volume; and (2) isentropic expansion to an assigned pressure, temperature, or Mach number. Tables of thermodynamic functions needed with this method are included for 42 substances for convenience in numerical computations.

  16. RAPID SEPARATION METHOD FOR 237NP AND PU ISOTOPES IN LARGE SOIL SAMPLES

    Energy Technology Data Exchange (ETDEWEB)

    Maxwell, S.; Culligan, B.; Noyes, G.

    2010-07-26

    A new rapid method for the determination of {sup 237}Np and Pu isotopes in soil and sediment samples has been developed at the Savannah River Site Environmental Lab (Aiken, SC, USA) that can be used for large soil samples. The new soil method utilizes an acid leaching method, iron/titanium hydroxide precipitation, a lanthanum fluoride soil matrix removal step, and a rapid column separation process with TEVA Resin. The large soil matrix is removed easily and rapidly using this two simple precipitations with high chemical recoveries and effective removal of interferences. Vacuum box technology and rapid flow rates are used to reduce analytical time.

  17. Investigation of recoil collection method for production of high specific activity nuclear medicine isotopes.

    Science.gov (United States)

    Cheng, K Y; Kunze, J F; Ehrhardt, G J

    1999-09-01

    High specific activity radiopharmaceuticals cannot readily be produced by (n, gamma) reactions in nuclear reactors, because the great abundance of parent atoms remaining have the same chemical characteristics as the produced isotope. We have investigated the effectiveness of using recoil atom collection methods for separating the produced radioisotope. Gold-198, produced from isotopically pure (natural) gold-197, was chosen for these experiments, which were run in the high flux (approximately 10(14) n/cm2 s thermal flux) of the reflector of the University of Missouri Research Reactor. Seven separate experiments were run, with a 2 mm separation between the emitter and the collector. Collection efficiencies were only a few percent of the radioisotope atoms produced in the top atomic layer of the emitter, instead of the 30% range anticipated. Furthermore, the collected radioisotope, instead of being nearly pure, contained a large quantity of the parent. Unless the reason for the "contamination" of product with the parent can be reduced by several orders of magnitude, this "surface hot atom recoil" method appears to offer no practical application for nuclear medicine isotope production.

  18. Simulation of cloud microphysical effects on water isotope fractionation in a frontal system

    Science.gov (United States)

    Chen, J. P.; Tsai, I. C.; Chen, W. Y.; Liang, M. C.

    2014-12-01

    The stable water isotopic composition changes due to fractionation during phase changes. This information is useful for understanding the water cycle, such as the water vapor source, transport and cloud microphysical processes. In conventional atmospheric models, the isotope exchange between liquid and gas phase is usually assumed to be in an equilibrium state, which is not sufficient to describe the highly kinetic phase transformation processes in clouds. In this study, a two-moment microphysical scheme incorporated into the NCAR Weather Research and Forecasting (WRF) model is modified to simulate the isotope fractionations. Experimentally determined stable water isotope thermal equilibrium data are converted into isotope saturation vapor pressure, which is then put into the two-stream Maxwellian kinetic equation to calculate the fractionation during vapor condensation/evaporation or deposition/sublimation. Isotope mass transfer between liquid- and ice-phase hydrometeors during freezing/melting are also considered explicitly. The simulation results were compared with rainwater isotope measurements and showed fairly good agreement. Sensitivity tests were also conducted to quantify the contribution of rainwater isotopic due to water vapor source and transport, condensation environment conditions, and cloud microphysical processes. The results show that isotopic water vapor source dominates the stable isotope concentration in rainwater but the cloud microphysical processes including the ice-phase processes are also quite important. The results also showed that the two-stream Maxwellian kinetic method would cause significantly more deuterium to be transported into higher altitudes during convection than the thermal equilibrium method.

  19. Equilibrium Modeling for Hydrogen Isotope Separation by Cryogenic Adsorption%氢同位素低温吸附分离的平衡吸附模型

    Institute of Scientific and Technical Information of China (English)

    张东辉; 周理; 苏伟; 孙艳

    2006-01-01

    The separation of hydrogen and deuterium by cryogenic adsorption was conducted, using the molecular sieve 5A as adsorbent, helium as the carrier gas in a fixed column. The breakthrough curves of hydrogen, deuterium and the mixture of two components in helium carrier gas were measured, a separation factor, approximately 2, for the hydrogen-deuterium binary mixture was obtained. The equilibrium model was built for simulation of the concentration distribution for single hydrogen, deuterium and their mixture with helium carrier in the fixed column, and the simulation compared well with the experimental results.

  20. Preservation Methods Alter Carbon and Nitrogen Stable Isotope Values in Crickets (Orthoptera: Grylloidea).

    Science.gov (United States)

    Jesus, Fabiene Maria; Pereira, Marcelo Ribeiro; Rosa, Cassiano Sousa; Moreira, Marcelo Zacharias; Sperber, Carlos Frankl

    2015-01-01

    Stable isotope analysis (SIA) is an important tool for investigation of animal dietary habits for determination of feeding niche. Ideally, fresh samples should be used for isotopic analysis, but logistics frequently demands preservation of organisms for analysis at a later time. The goal of this study was to establish the best methodology for preserving forest litter-dwelling crickets for later SIA analysis without altering results. We collected two cricket species, Phoremia sp. and Mellopsis doucasae, from which we prepared 70 samples per species, divided among seven treatments: (i) freshly processed (control); preserved in fuel ethanol for (ii) 15 and (iii) 60 days; preserved in commercial ethanol for (iv) 15 and (v) 60 days; fresh material frozen for (vi) 15 and (vii) 60 days. After oven drying, samples were analyzed for δ15N, δ13C values, N(%), C(%) and C/N atomic values using continuous flow isotope ratio mass spectrometry. All preservation methods tested, significantly impacted δ13C and δ15N and C/N atomic values. Chemical preservatives caused δ13C enrichment as great as 1.5‰, and δ15N enrichment as great as 0.9‰; the one exception was M. doucasae stored in ethanol for 15 days, which had δ15N depletion up to 1.8‰. Freezing depleted δ13C and δ15N by up to 0.7 and 2.2‰, respectively. C/N atomic values decreased when stored in ethanol, and increased when frozen for 60 days for both cricket species. Our results indicate that all preservation methods tested in this study altered at least one of the tested isotope values when compared to fresh material (controls). We conclude that only freshly processed material provides adequate SIA results for litter-dwelling crickets.

  1. Preservation Methods Alter Carbon and Nitrogen Stable Isotope Values in Crickets (Orthoptera: Grylloidea.

    Directory of Open Access Journals (Sweden)

    Fabiene Maria Jesus

    Full Text Available Stable isotope analysis (SIA is an important tool for investigation of animal dietary habits for determination of feeding niche. Ideally, fresh samples should be used for isotopic analysis, but logistics frequently demands preservation of organisms for analysis at a later time. The goal of this study was to establish the best methodology for preserving forest litter-dwelling crickets for later SIA analysis without altering results. We collected two cricket species, Phoremia sp. and Mellopsis doucasae, from which we prepared 70 samples per species, divided among seven treatments: (i freshly processed (control; preserved in fuel ethanol for (ii 15 and (iii 60 days; preserved in commercial ethanol for (iv 15 and (v 60 days; fresh material frozen for (vi 15 and (vii 60 days. After oven drying, samples were analyzed for δ15N, δ13C values, N(%, C(% and C/N atomic values using continuous flow isotope ratio mass spectrometry. All preservation methods tested, significantly impacted δ13C and δ15N and C/N atomic values. Chemical preservatives caused δ13C enrichment as great as 1.5‰, and δ15N enrichment as great as 0.9‰; the one exception was M. doucasae stored in ethanol for 15 days, which had δ15N depletion up to 1.8‰. Freezing depleted δ13C and δ15N by up to 0.7 and 2.2‰, respectively. C/N atomic values decreased when stored in ethanol, and increased when frozen for 60 days for both cricket species. Our results indicate that all preservation methods tested in this study altered at least one of the tested isotope values when compared to fresh material (controls. We conclude that only freshly processed material provides adequate SIA results for litter-dwelling crickets.

  2. Preservation Methods Alter Carbon and Nitrogen Stable Isotope Values in Crickets (Orthoptera: Grylloidea)

    Science.gov (United States)

    Jesus, Fabiene Maria; Pereira, Marcelo Ribeiro; Rosa, Cassiano Sousa; Moreira, Marcelo Zacharias; Sperber, Carlos Frankl

    2015-01-01

    Stable isotope analysis (SIA) is an important tool for investigation of animal dietary habits for determination of feeding niche. Ideally, fresh samples should be used for isotopic analysis, but logistics frequently demands preservation of organisms for analysis at a later time. The goal of this study was to establish the best methodology for preserving forest litter-dwelling crickets for later SIA analysis without altering results. We collected two cricket species, Phoremia sp. and Mellopsis doucasae, from which we prepared 70 samples per species, divided among seven treatments: (i) freshly processed (control); preserved in fuel ethanol for (ii) 15 and (iii) 60 days; preserved in commercial ethanol for (iv) 15 and (v) 60 days; fresh material frozen for (vi) 15 and (vii) 60 days. After oven drying, samples were analyzed for δ15N, δ13C values, N(%), C(%) and C/N atomic values using continuous flow isotope ratio mass spectrometry. All preservation methods tested, significantly impacted δ13C and δ15N and C/N atomic values. Chemical preservatives caused δ13C enrichment as great as 1.5‰, and δ15N enrichment as great as 0.9‰; the one exception was M. doucasae stored in ethanol for 15 days, which had δ15N depletion up to 1.8‰. Freezing depleted δ13C and δ15N by up to 0.7 and 2.2‰, respectively. C/N atomic values decreased when stored in ethanol, and increased when frozen for 60 days for both cricket species. Our results indicate that all preservation methods tested in this study altered at least one of the tested isotope values when compared to fresh material (controls). We conclude that only freshly processed material provides adequate SIA results for litter-dwelling crickets. PMID:26390400

  3. Employment of vapor pressure data in the description of vapor-liquid equilibrium with direct method

    Energy Technology Data Exchange (ETDEWEB)

    Morbidelli, M.; Carra, S.

    1981-07-01

    A general procedure for inserting vapor-pressure data of pure components into equations of state provides a straightforward scheme for the extension of direct methods to the study of phase equilibria of polar mixtures and of solutions containing nonvolatile electrolytes. It makes the equation of state applicable to all compounds and to the shole temperature range and more accurate in the prediction of both multicomponent and pure vapor-liquid equilibria.

  4. Finite-Temperature Non-equilibrium Quasicontinuum Method based on Langevin Dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Marian, J; Venturini, G; Hansen, B; Knap, J; Ortiz, M; Campbell, G

    2009-05-08

    The concurrent bridging of molecular dynamics and continuum thermodynamics presents a number of challenges, mostly associated with energy transmission and changes in the constitutive description of a material across domain boundaries. In this paper, we propose a framework for simulating coarse dynamic systems in the canonical ensemble using the Quasicontinuum method (QC). The equations of motion are expressed in reduced QC coordinates and are strictly derived from dissipative Lagrangian mechanics. The derivation naturally leads to a classical Langevin implementation where the timescale is governed by vibrations emanating from the finest length scale occurring in the computational cell. The equations of motion are integrated explicitly via Newmark's ({beta} = 0; {gamma} = 1/2) method, leading to a robust numerical behavior and energy conservation. In its current form, the method only allows for wave propagations supported by the less compliant of the two meshes across a heterogeneous boundary, which requires the use of overdamped dynamics to avoid spurious heating due to reflected vibrations. We have applied the method to two independent crystallographic systems characterized by different interatomic potentials (Al and Ta) and have measured thermal expansion in order to quantify the vibrational entropy loss due to homogenization. We rationalize the results in terms of system size, mesh coarseness, and nodal cluster diameter within the framework of the quasiharmonic approximation. For Al, we find that the entropy loss introduced by mesh coarsening varies linearly with the element size, and that volumetric effects are not critical in driving the anharmonic behavior of the simulated systems. In Ta, the anomalies of the interatomic potential employed result in negative and zero thermal expansion at low and high temperatures, respectively.

  5. Estimating the Isotope Ratio of Ecosystem Respiration Using the Keeling Plot and the Flux Ratio Method

    Science.gov (United States)

    Zhang, J.; Griffis, T. J.; Baker, J. M.

    2004-12-01

    Stable carbon isotope analyses have been used in identifying global carbon sources and sinks and in partitioning ecosystem CO2 exchange into component fluxes. The isotope ratio of ecosystem respiration (δ 13Cr) is a critical parameter in applying stable isotope techniques to carbon cycle problems. The commonly used Keeling plot method in estimating δ 13Cr has limitations related to: 1) insufficient range of CO2 mixing ratio; 2) high sensitivity to curve-fitting techniques; and 3) extrapolation of CO2 mixing ratio beyond observations. In this study, the Keeling plot method was examined and compared with the flux ratio approach using continuous measurements of the mixing ratios of 12CO2 and 13CO2 over an extensive corn canopy during the 2003 growing season. The seasonal variation of δ 13Cr estimated from both methods harmonized with the ecosystem phenology. The δ 13Cr started to increase (became more positive) from mid June and peaked in early August, followed by a decrease into October. The Keeling plot method agreed well with the flux ratio method in the seasonal pattern of δ 13Cr, but tended to give lower values (more negative). The discrepancy between the two approaches was significant in July and August (about 5 per mil) and relatively small in June and September (about 1 to 2 per mil). We examined this discrepancy with respect to wind direction/advection and measurement footprints. In addition, our analysis of high-frequency data (every two minutes) using the flux ratio method indicates that δ 13Cr may vary significantly at short time-scales (e.g., hourly), which could have significant implications for flux partitioning studies.

  6. Comparison of cellulose extraction methods for analysis of stable-isotope ratios of carbon and oxygen in plant material

    National Research Council Canada - National Science Library

    Cullen, Louise E; Macfarlane, Craig

    2005-01-01

    The Jayme-Wise and diglyme-HCl methods for extracting cellulose from plant material for stable-isotope analysis differ considerably in ease of use, with the latter requiring significantly less time...

  7. EPA Method EMSL-33: Isotopic Determination of Plutonium, Uranium, and Thorium in Water, Soil, Air, and Biological Tissue

    Science.gov (United States)

    SAM lists this method to provide for the analysis of isotopic plutonium, uranium and thorium, together or individually, in drinking water, aqueous/liquid, soil/sediment, surface wipe and/or air filter samples by alpha spectrometry.

  8. Continuous-flow isotope ratio mass spectrometry method for carbon and hydrogen isotope measurements on atmospheric methane

    NARCIS (Netherlands)

    Brass, M.; Roeckmann, T.

    2010-01-01

    We describe a continuous-flow isotope ratio mass spectrometry (CF-IRMS) technique for high-precision δD and δ13C measurements of atmospheric methane on 40 mL air samples. CH4 is separated from other air components by utilizing purely physical processes based on temperature, time and mechanical valve

  9. Beta-transition properties for neutron-rich Sn and Te isotopes by Pyatov method

    Indian Academy of Sciences (India)

    D I Salamov; S Unlu; N Cakmak

    2007-09-01

    Based on Pyatov's method, the low-lying Gamow–Teller (GT) 1+ state energies and log() values for 128,130,132Sb and 132,134,136I isotopes have been calculated. In this method, the strength parameter of the effective spin–isospin interaction is found by providing the commutativity of the GT operator with the central part of the nuclear Hamiltonian. The problem has been solved within the framework of RPA. The calculation results have been compared with the corresponding experimental data.

  10. Spectral - Lagrangian methods for Collisional Models of Non - Equilibrium Statistical States

    CERN Document Server

    Gamba, Irene M

    2007-01-01

    We propose a new spectral Lagrangian based deterministic solver for the non-linear Boltzmann Transport Equation for Variable Hard Potential (VHP) collision kernels with conservative or non-conservative binary interactions.The method is based on symmetries of the Fourier transform of the collision integral, where the complexity in its computing is reduced to a separate integral over the unit sphere $S^2$. In addition, the conservation of moments is enforced by Lagrangian constraints. The resulting scheme is very versatile and adjusts in a very simple manner, to several cases that involve energy dissipation due to local micro-reversibility (inelastic interactions) or elastic model of slowing down process. Our simulations are benchmarked with the available exact self-similar solutions, exact moment equations and analytical estimates for homogeneous Boltzmann equation for both elastic and inelastic VHP interactions. Benchmarking of the simulations involves the selection of a time self-similar rescaling of the num...

  11. A rapid method for the sampling of atmospheric water vapour for isotopic analysis.

    Science.gov (United States)

    Peters, Leon I; Yakir, Dan

    2010-01-01

    Analysis of the stable isotopic composition of atmospheric moisture is widely applied in the environmental sciences. Traditional methods for obtaining isotopic compositional data from ambient moisture have required complicated sampling procedures, expensive and sophisticated distillation lines, hazardous consumables, and lengthy treatments prior to analysis. Newer laser-based techniques are expensive and usually not suitable for large-scale field campaigns, especially in cases where access to mains power is not feasible or high spatial coverage is required. Here we outline the construction and usage of a novel vapour-sampling system based on a battery-operated Stirling cycle cooler, which is simple to operate, does not require any consumables, or post-collection distillation, and is light-weight and highly portable. We demonstrate the ability of this system to reproduce delta(18)O isotopic compositions of ambient water vapour, with samples taken simultaneously by a traditional cryogenic collection technique. Samples were collected over 1 h directly into autosampler vials and were analysed by mass spectrometry after pyrolysis of 1 microL aliquots to CO. This yielded an average error of system provides a rapid and reliable alternative to conventional cryogenic techniques, particularly in cases requiring high sample throughput or where access to distillation lines, slurry maintenance or mains power is not feasible.

  12. Method for determination of stable carbon isotope ratio of methylnitrophenols in atmospheric particulate matter

    Directory of Open Access Journals (Sweden)

    S. Moukhtar

    2011-11-01

    Full Text Available A technique for the measurement of the stable isotope ratio of methylnitrophenols in atmospheric particulate matter is presented. Atmospheric samples from rural and suburban areas were collected for evaluation of the procedure. Particulate matter was collected on quartz fibre filters using dichotomous high volume air samplers. Methylnitrophenols were extracted from the filters using acetonitrile. The sample was then purified using a combination of high-performance liquid chromatography and solid phase extraction. The final solution was then divided into two aliquots. To one aliquot, a derivatising agent, Bis(trimethylsilyltrifluoroacetamide, was added for Gas Chromatography-Mass Spectrometry analysis. The second half of the sample was stored in a refrigerator. For samples with concentrations exceeding 1 ng μl−1, the second half of the sample was used for measurement of stable carbon isotope ratios by Gas Chromatography-Isotope Ratio Mass Spectrometry.

    The procedure described in this paper provides a method for the analysis of methylnitrophenols in atmospheric particulate matter at concentrations as low as 0.3 pg m−3 and for stable isotope ratios with an accuracy of better than ±0.5‰ for concentrations exceeding 100 pg m−3.

    In all atmospheric particulate matter samples analysed, 2-methyl-4-nitrophenol was found to be the most abundant methylnitrophenol, with concentrations ranging from the low pg m−3 range in rural areas to more than 200 pg m−3 in some samples from a suburban location.

  13. Growth of 18O isotopically enriched ZnO nanorods by two novel VPT methods

    Science.gov (United States)

    Gray, Ciarán; Trefflich, Lukas; Röder, Robert; Ronning, Carsten; Henry, Martin O.; McGlynn, Enda

    2017-02-01

    We have developed two novel vapour phase transport methods to grow ZnO nanorod arrays isotopically enriched with 18O. Firstly, a three-step process used to grow natural and Zn-enriched ZnO nanorods has been further modified, by replacing the atmospheric O2 with enriched 18O2, in order to grow 18O-enriched ZnO nanorods using this vapour-solid method on chemical bath deposited buffer layers. In addition, 18O-enriched ZnO nanorods were successfully grown using 18O isotopically enriched ZnO source powders in a vapour-liquid-solid growth method. Scanning electron microscopy studies confirmed the success of both growth methods in terms of nanorod morphology, although in the case of the vapour-liquid-solid samples, the nanorods' c-axes were not vertically aligned due to the use of a non-epitaxial substrate. Raman and PL studies indicated clearly that O-enrichment was successful in both cases, although the results indicate that the enrichment is at a lower level in our samples compared to previous reports with the same nominal enrichment levels. The results of our studies also allow us to comment on both levels of enrichment achieved and on novel effects of the high temperature growth environment on the nanorod growth, as well as suggesting possible mechanisms for such effects. Very narrow photoluminescence line widths, far narrower than those reported previously in the literature for isotopically enriched bulk ZnO, are seen in both the vapour-solid and vapour-liquid-solid nanorod samples demonstrating their excellent optical quality and their potential for use in detailed optical studies of defects and impurities using low temperature photoluminescence.

  14. Accelerated radiation damping for increased spin equilibrium (ARISE): a new method for controlling the recovery of longitudinal magnetization.

    Science.gov (United States)

    Huang, Susie Y; Witzel, Thomas; Wald, Lawrence L

    2008-11-01

    Control of the longitudinal magnetization in fast gradient-echo (GRE) sequences is an important factor in enabling the high efficiency of balanced steady-state free precession (bSSFP) sequences. We introduce a new method for accelerating the return of the longitudinal magnetization to the +z-axis that is independent of externally applied RF pulses and shows improved off-resonance performance. The accelerated radiation damping for increased spin equilibrium (ARISE) method uses an external feedback circuit to strengthen the radiation damping (RD) field. The enhanced RD field rotates the magnetization back to the +z-axis at a rate faster than T(1) relaxation. The method is characterized in GRE phantom imaging at 3T as a function of feedback gain, phase, and duration, and compared with results from numerical simulations of the Bloch equations incorporating RD. A short period of feedback (10 ms) during a refocused interval of a crushed GRE sequence allowed greater than 99% recovery of the longitudinal magnetization when very little T(2) relaxation had time to occur. An appropriate application might be to improve navigated sequences. Unlike conventional flip-back schemes, the ARISE "flip-back" is generated by the spins themselves, thereby offering a potentially useful building block for enhancing GRE sequences.

  15. A moving mesh finite difference method for non-monotone solutions of non-equilibrium equations in porous media

    CERN Document Server

    Zhang, Hong

    2016-01-01

    An adaptive moving mesh finite difference method is presented to solve two types of equations with dynamic capillary pressure term in porous media. One is the non-equilibrium Richards Equation and the other is the modified Buckley-Leverett equation. The governing equations are discretized with an adaptive moving mesh finite difference method in the space direction and an implicit-explicit method in the time direction. In order to obtain high quality meshes, an adaptive time-dependent monitor function with directional control is applied to redistribute the mesh grid in every time step, and a diffusive mechanism is used to smooth the monitor function. The behaviors of the central difference flux, the standard local Lax-Friedrich flux and the local Lax-Friedrich flux with reconstruction are investigated by solving a 1D modified Buckley-Leverett equation. With the moving mesh technique, good mesh quality and high numerical accuracy are obtained. A collection of one-dimensional and two-dimensional numerical experi...

  16. On the progress in stable isotope separation

    Energy Technology Data Exchange (ETDEWEB)

    Prusakov, V.N. [Kurchatov Institute, Moscow (Russian Federation)

    1994-12-31

    The principles and process of centrifuge isotope separation are reviewed; the fundamental advantage of the centrifuge over gaseous diffusion arises from the fact that the primary isotope separation effect occurs at thermodynamic equilibrium; thus, gas centrifuge enrichment uses only about 1/20 to 1/30 of the electricity per SWU (separation work unit) consumed by gaseous diffusion. The various substances that can be used in centrifuge isotope separation are listed (fluorides, oxyfluorides, {pi}-complexes, boron hydrides, metal-organic compounds, halides...). The centrifuge method productivity is much greater than with the electromagnetic separation technique; examples of centrifuge stable and radioactive isotope separation are given; the method of the residue reduction is also presented with the example of separating radioactive krypton-85 out of a nuclear reactor krypton blend. 4 figs.

  17. Standard test method for radiochemical determination of uranium isotopes in soil by alpha spectrometry

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2011-01-01

    1.1 This test method covers the determination of alpha-emitting uranium isotopes in soil. This test method describes one acceptable approach to the determination of uranium isotopes in soil. 1.2 The test method is designed to analyze 10 g of soil; however, the sample size may be varied to 50 g depending on the activity level. This test method may not be able to completely dissolve all forms of uranium in the soil matrix. Studies have indicated that the use of hydrofluoric acid to dissolve soil has resulted in lower values than results using total dissolution by fusion. 1.3 The lower limit of detection is dependent on count time, sample size, detector, background, and tracer yield. The chemical yield averaged 78 % in a single laboratory evaluation, and 66 % in an interlaboratory collaborative study. 1.4 The values stated in SI units are to be regarded as standard. The values given in parentheses are for information only. 1.5 This standard does not purport to address all of the safety concerns, if any, ass...

  18. Application of the generator coordinate method to neutron-rich Se and Ge isotopes

    Science.gov (United States)

    Higashiyama, Koji; Yoshinaga, Naotaka

    2014-03-01

    The quantum-number projected generator coordinate method (GCM) is applied to the neutron-rich Se and Ge isotopes, where the monopole and quadrupole pairing plus quadrupole-quadrupole interaction is employed as an effective interaction. The energy spectra obtained by the GCM are compared to both the shell model results and the experimental data. The GCM reproduces well the energy levels of high-spin states as well as the low-lying states. The structure of the low-lying collective states is analyzed through the GCM wave functions.

  19. Application of the generator coordinate method to neutron-rich Se and Ge isotopes

    Directory of Open Access Journals (Sweden)

    Higashiyama Koji

    2014-03-01

    Full Text Available The quantum-number projected generator coordinate method (GCM is applied to the neutron-rich Se and Ge isotopes, where the monopole and quadrupole pairing plus quadrupole-quadrupole interaction is employed as an effective interaction. The energy spectra obtained by the GCM are compared to both the shell model results and the experimental data. The GCM reproduces well the energy levels of high-spin states as well as the low-lying states. The structure of the low-lying collective states is analyzed through the GCM wave functions.

  20. Integral Method for the Assessment of U-RANS Effectiveness in Non-Equilibrium Flows and Heat Transfer

    Science.gov (United States)

    Pond, Ian; Edabi, Alireza; Dubief, Yves; White, Christopher

    2015-11-01

    Reynolds Average Navier Stokes (RANS) modeling has established itself as a critical design tool in many engineering applications, thanks to its superior computational efficiency. The drawbacks of RANS models are well known, but not necessarily well understood: poor prediction of transition, non equilibrium flows, mixing and heat transfer, to name the ones relevant to our study. In the present study, we use a DNS of a reciprocating channel flow driven by an oscillating pressure gradient to test several low- and high-Reynolds RANS models. Temperature is introduced as a passive scalar to study heat transfer modeling. Low-Reynolds models manage to capture the overall physics of wall shear and heat flux well, yet with some phase discrepancies, whereas high Reynolds models fail. Under the microscope of the integral method for wall shear and wall heat flux, the qualitative agreement appears more serendipitous than driven by the ability of the models to capture the correct physics. The integral method is shown to be more insightful in the benchmarking of RANS models than the typical comparisons of statistical quantities. The authors acknowledges the support of NSF and DOE under grant NSF/DOE 1258697 (VT) and 1258702 (NH).

  1. Diffusivity and solubility of hydrogen in metallized polymer membranes measured by the non-equilibrium stripping potentiostatic method

    Energy Technology Data Exchange (ETDEWEB)

    Bucur, R.V.; Mecea, V.

    1986-07-15

    The diffusion and permeation rates of hydrogen through a metallized polymer membrane were measured by a non-equilibrium stripping potentiostatic method. A description of the gas membrane electrolyte permeation cell is given. The membrane was made of commercial polyethylene terephthalate (PET) (thickness, 7.3 x 10/sup -3/ cm) coated on the detection side with a thin palladium film (thickness, 800-1400 A). The membrane was first charged with hydrogen under a constant pressure at the entrance side until a linear concentration gradient was established across its thickness. Meanwhile, currents (stationary anodic current) were recorded corresponding to anodic removal of hydrogen from the detection side, while a constant anodic potential E/sub a/ was applied to the detection side. The E/sub a/ value corresponded to the potential of the palladium film free of hydrogen and was in the range 880 - 890 mV versus the reference hydrogen electrode in the same solution. Subsequently, hydrogen charging was ceased by replacing hydrogen with argon or air at the entrance side and the current corresponding to the stripping of hydrogen held within the membrane was recorded. The diffusion coefficient D was estimated from the stripping current-time curves, while the permeation coefficient P was estimated from the stationary anodic current within the range 283-333 K. The solubility coefficient S was calculated from the relation P=DS. Data on similar measurements carried out when hydrogen was electrolytically generated on Pd/PET/Pd membranes are also reported.

  2. Nonlinear Boltzmann equation for the homogeneous isotropic case: Some improvements to deterministic methods and applications to relaxation towards local equilibrium

    Science.gov (United States)

    Asinari, P.

    2011-03-01

    Boltzmann equation is one the most powerful paradigms for explaining transport phenomena in fluids. Since early fifties, it received a lot of attention due to aerodynamic requirements for high altitude vehicles, vacuum technology requirements and nowadays, micro-electro-mechanical systems (MEMs). Because of the intrinsic mathematical complexity of the problem, Boltzmann himself started his work by considering first the case when the distribution function does not depend on space (homogeneous case), but only on time and the magnitude of the molecular velocity (isotropic collisional integral). The interest with regards to the homogeneous isotropic Boltzmann equation goes beyond simple dilute gases. In the so-called econophysics, a Boltzmann type model is sometimes introduced for studying the distribution of wealth in a simple market. Another recent application of the homogeneous isotropic Boltzmann equation is given by opinion formation modeling in quantitative sociology, also called socio-dynamics or sociophysics. The present work [1] aims to improve the deterministic method for solving homogenous isotropic Boltzmann equation proposed by Aristov [2] by two ideas: (a) the homogeneous isotropic problem is reformulated first in terms of particle kinetic energy (this allows one to ensure exact particle number and energy conservation during microscopic collisions) and (b) a DVM-like correction (where DVM stands for Discrete Velocity Model) is adopted for improving the relaxation rates (this allows one to satisfy exactly the conservation laws at macroscopic level, which is particularly important for describing the late dynamics in the relaxation towards the equilibrium).

  3. Sorption of malachite green from aqueous solution by potato peel: Kinetics and equilibrium modeling using non-linear analysis method

    Directory of Open Access Journals (Sweden)

    El-Khamsa Guechi

    2016-09-01

    Full Text Available Potato peel (PP was used as a biosorbent to remove malachite green (MG from aqueous solution under various operating conditions. The effect of the experimental parameters such as initial dye concentration, biosorbent dose, initial pH, stirring speed, temperature, ionic strength and biosorbent particle size was investigated through a number of batch sorption experiments. The sorption kinetic uptake for MG by PP at various initial dye concentrations was analyzed by non-linear method using pseudo-first, pseudo-second and pseudo-nth order models. It was found that the pseudo-nth order kinetic model was the best applicable model to describe the sorption kinetic data and the order n of sorption reaction was calculated in the range from 0.71 to 2.71. Three sorption isotherms namely the Langmuir, Freundlich and Redlich–Peterson isotherms in their non-linear forms were applied to the biosorption equilibrium data. Both the Langmuir and Redlich–Peterson models were found to fit the sorption isotherm data well, but the Redlich–Peterson model was better. Thermodynamic parameters show that the sorption process of MG is endothermic and more effective process at high temperatures. The results revealed that PP is very effective for the biosorption of MG from aqueous solutions.

  4. Integrated use of soil physical and water isotope methods for ecohydrological characterization of desertified areas

    Science.gov (United States)

    Külls, Christoph; Nunes, Alice; Köbel-Batista, Melanie; Branquinho, Cristina; Bianconi, Nadja; Costantini, Eduardo

    2014-05-01

    marked decrease in water permeability at 0.04, 0.20, or 0.40 m depth. Soil isotope profiles indicated that percolation beneath the root zone and groundwater recharge ranges from 21.7 mm/y to 29.7 mm/y. The recharge rate was positively related to mean annual rainfall and soil organic matter, and interestingly, increased with aridity and desertification. The difference between mean annual rainfall and percolation was positively related to plant cover and in inverse proportion to the aridity index. Our results highlight the importance of combining different methods of site characterization by soil physics, soil water isotopes and soil water chemistry (chloride) with vegetation data, providing a more specific analysis of ecohydrological conditions and their relation to ecosystem functioning and recovery potential. The field protocol applied can provide relevant information for guiding restoration strategies. Costantini, E. A. C., Urbano, F., Aramini, G., Barbetti, R., Bellino, F., Bocci, M., & Tascone, F. (2009). Rationale and methods for compiling an atlas of desertification in Italy. Land Degradation & Development, 20(3), 261-276. Garvelmann, J., Külls, C., & Weiler, M. (2012). A porewater-based stable isotope approach for the investigation of subsurface hydrological processes. Hydrology and Earth System Sciences, 16(2), 631-640.

  5. A Robust and Fully-Automated Chromatographic Method for the Quantitative Purification of Ca and Sr for Isotopic Analysis

    Science.gov (United States)

    Smith, H. B.; Kim, H.; Romaniello, S. J.; Field, P.; Anbar, A. D.

    2014-12-01

    High throughput methods for sample purification are required to effectively exploit new opportunities in the study of non-traditional stable isotopes. Many geochemical isotopic studies would benefit from larger data sets, but these are often impractical with manual drip chromatography techniques, which can be time-consuming and demand the attention of skilled laboratory staff. Here we present a new, fully-automated single-column method suitable for the purification of both Ca and Sr for stable and radiogenic isotopic analysis. The method can accommodate a wide variety of sample types, including carbonates, bones, and teeth; silicate rocks and sediments; fresh and marine waters; and biological samples such as blood and urine. Protocols for these isotopic analyses are being developed for use on the new prepFAST-MCTM system from Elemental Scientific (ESI). The system is highly adaptable and processes up to 24-60 samples per day by reusing a single chromatographic column. Efficient column cleaning between samples and an all Teflon flow path ensures that sample carryover is maintained at the level of background laboratory blanks typical for manual drip chromatography. This method is part of a family of new fully-automated chromatographic methods being developed to address many different isotopic systems including B, Ca, Fe, Cu, Zn, Sr, Cd, Pb, and U. These methods are designed to be rugged and transferrable, and to allow the preparation of large, diverse sample sets via a highly repeatable process with minimal effort.

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

    Science.gov (United States)

    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.

  7. Mercury speciation analysis in seafood by species-specific isotope dilution: method validation and occurrence data

    Energy Technology Data Exchange (ETDEWEB)

    Clemens, Stephanie; Guerin, Thierry [Agence Nationale de Securite Sanitaire de l' Alimentation, Laboratoire de Securite des Aliments de Maisons-Alfort, Unite des Contaminants Inorganiques et Mineraux de l' Environnement, ANSES, Maisons-Alfort (France); Monperrus, Mathilde; Donard, Olivier F.X.; Amouroux, David [IPREM UMR 5254 CNRS - Universite de Pau et des Pays de l' Adour, Laboratoire de Chimie Analytique Bio-Inorganique et Environnement, Institut des Sciences Analytiques et de Physico-chimie pour l' Environnement et les Materiaux, Pau Cedex (France)

    2011-11-15

    Methylmercury (MeHg) and total mercury (THg) in seafood were determined using species-specific isotope dilution analysis and gas chromatography combined with inductively coupled plasma mass spectrometry. Sample preparation methods (extraction and derivation step) were evaluated on certified reference materials using isotopically enriched Hg species. Solid-liquid extraction, derivation by propylation and automated agitation gave excellent accuracy and precision results. Satisfactory figures of merit for the selected method were obtained in terms of limit of quantification (1.2 {mu}g Hg kg{sup -1} for MeHg and 1.4 {mu}g Hg kg{sup -1} for THg), repeatability (1.3-1.7%), intermediate precision reproducibility (1.5% for MeHg and 2.2% for THg) and trueness (bias error less than 7%). By means of a recent strategy based on accuracy profiles ({beta}-expectation tolerance intervals), the selected method was successfully validated in the range of approximately 0.15-5.1 mg kg{sup -1} for MeHg and 0.27-5.2 mg kg{sup -1} for THg. Probability {beta} was set to 95% and the acceptability limits to {+-}15%. The method was then applied to 62 seafood samples representative of consumption in the French population. The MeHg concentrations were generally low (1.9-588 {mu}g kg{sup -1}), and the percentage of MeHg varied from 28% to 98% in shellfish and from 84% to 97% in fish. For all real samples tested, methylation and demethylation reactions were not significant, except in one oyster sample. The method presented here could be used for monitoring food contamination by MeHg and inorganic Hg in the future to more accurately assess human exposure. (orig.)

  8. Sweatshop Equilibrium

    OpenAIRE

    Chau, Nancy H.

    2009-01-01

    This paper presents a capability-augmented model of on the job search, in which sweatshop conditions stifle the capability of the working poor to search for a job while on the job. The augmented setting unveils a sweatshop equilibrium in an otherwise archetypal Burdett-Mortensen economy, and reconciles a number of oft noted yet perplexing features of sweatshop economies. We demonstrate existence of multiple rational expectation equilibria, graduation pathways out of sweatshops in complete abs...

  9. Assay of tyrosol and hydroxytyrosol in olive oil by tandem mass spectrometry and isotope dilution method.

    Science.gov (United States)

    Mazzotti, Fabio; Benabdelkamel, Hicham; Di Donna, Leonardo; Maiuolo, Loredana; Napoli, Anna; Sindona, Giovanni

    2012-12-01

    Hydroxytyrosol and tyrosol, the strong antioxidant present in large amount in virgin olive oil have been assayed by LC-MS/MS under MRM condition and isotope dilution method, using d(2)-labelled internal standards obtained by simple synthetic procedures. The assay has been performed under MRM condition monitoring two transitions for each analyte to improve the specificity. This paper deals with a modern approach for assaying the content of this polyphenols in virgin olive oil down to a limit of a few hundreds of parts per billion. Tyrosol and hydroxytyrosol ranged from 10 to 47ppm and from 5 to 25ppm in commercial olive oil, respectively. The accuracy (98-107%) and analytical parameters values confirm the reliability of the proposed approach. The method can be extended to any natural matrices, including mill wastes, after a simple step of sample preparation.

  10. The equilibrium shape of fluid-fluid interfaces : Derivation and a new numerical method for Young's and Young-Laplace equations

    NARCIS (Netherlands)

    Soligno, Giuseppe; Dijkstra, Marjolein; van Roij, Rene

    2014-01-01

    Many physical problems require explicit knowledge of the equilibrium shape of the interface between two fluid phases. Here, we present a new numerical method which is simply implementable and easily adaptable for a wide range of problems involving capillary deformations of fluid-fluid interfaces. We

  11. A method for in situ monitoring of the isotope composition of tree xylem water using laser spectroscopy.

    Science.gov (United States)

    Volkmann, Till H M; Kühnhammer, Kathrin; Herbstritt, Barbara; Gessler, Arthur; Weiler, Markus

    2016-09-01

    Field studies analyzing the stable isotope composition of xylem water are providing important information on ecosystem water relations. However, the capacity of stable isotopes to characterize the functioning of plants in their environment has not been fully explored because of methodological constraints on the extent and resolution at which samples could be collected and analysed. Here, we introduce an in situ method offering the potential to continuously monitor the stable isotope composition of tree xylem water via its vapour phase using a commercial laser-based isotope analyser and compact microporous probes installed into the xylem. Our technique enables efficient high-frequency measurement with intervals of only a few minutes per sample while eliminating the need for costly and cumbersome destructive collection of plant material and laboratory-based processing. We present field observations of xylem water hydrogen and oxygen isotope compositions obtained over several days including a labelled irrigation event and compare them against results from concurrent destructive sampling with cryogenic distillation and mass spectrometric analysis. The data demonstrate that temporal changes as well as spatial patterns of integration in xylem water isotope composition can be resolved through direct measurement. The new technique can therefore present a valuable tool to study the hydraulic architecture and water utilization of trees.

  12. Tooth enamel maturation reequilibrates oxygen isotope compositions and supports simple sampling methods

    Science.gov (United States)

    Trayler, Robin B.; Kohn, Matthew J.

    2017-02-01

    Oxygen isotope and major element zoning patterns of several disparate ungulate teeth were collected to evaluate the timing and geometry of enamel formation, records of isotope zoning, and tooth enamel sampling strategies. Isotopic zoning in mammalian tooth enamel encodes a sub-annual time series of isotopic variation of an animal's body water composition, with a damping factor that depends on the specifics of how enamel mineralizes. Enamel formation comprises two stages: precipitation of appositional enamel with a high CO3:PO4 ratio, followed by precipitation of maturational enamel with a lower CO3:PO4. If appositional and maturational enamel both contribute to isotope compositions (but with different CO3:PO4), and if isotope compositions vary seasonally, paired δ18O values from CO3 and PO4 profiles should show a spatial separation. CO3 isotope patterns should be shifted earlier seasonally than PO4 isotope patterns. Such paired profiles for new and published data show no resolvable shifts, i.e. CO3 and PO4 δ18O profiles show coincident maxima and minima. This coincidence suggests that enamel maturation reequilibrates appositional isotope compositions. If enamel maturation establishes enamel isotope compositions, the geometry of maturation, not apposition, should be considered when devising sampling protocols. X-ray maps of Ca zoning show that the majority of enamel (inner and middle layers) mineralizes heavily at a high angle to the external tooth surface and the enamel-dentine junction over length scales of 2-4 mm, while the outer enamel surface mineralizes more slowly. These data suggest that isotopic sampling strategies should parallel maturational geometry and focus on interior enamel to improve data fidelity. The magnitude of isotopic damping is also smaller than implied in previous studies, so tooth enamel zoning more closely reflects original body water isotopic variations than previously assumed.

  13. A coupled-enzyme equilibrium method for measuring urea in serum: optimization and evaluation of the AACC study group on urea candidate reference method.

    Science.gov (United States)

    Sampson, E J; Baird, M A; Burtis, C A; Smith, E M; Witte, D L; Bayse, D D

    1980-06-01

    We describe a coupled-enzyme equilibrium method for measuring urea in serum, which is performed on supernates prepared by treating each specimen with Ba(OH)2 and ZnSO4 (Somogyi reagent). Analytical recovery of [14C]urea added to a variety of matrices was essentially complete (mean, 100.6%) for the supernates after precipitation. Nine variables were univariately examined in arriving at the reaction conditions for the method: glutamate dehydrogenase, urease, 2-oxoglutarate, ADP, Tris . HCI, NADH, EDTA, pH, and temperature. The reagent is stable for at least 48 days at--20 degrees C and for 23 days at 4 degrees C. Mean analytical recovery of urea (14 mmol/L) added to seven different specimens (three different matrices) was 100.8%. The analytical linear range of the method extends to 30 mmol of urea per liter. Of 22 potential interferents, only bilirubin at 1 mmol/L (580 mg/L), hemoglobin at 10 g/L, and hydroxyurea at 6 mmol/L showed more than 2% interference. We discuss precision and effects of specimen dilution, and compare results for 100 human serum specimens with those measured for the same specimens with four other urea methods. We examined the effects of measuring a blank, consisting of sample and reagent without urease, with each specimen.

  14. Structure of Krypton isotopes calculated with symmetry conserving configuration mixing methods

    CERN Document Server

    Rodríguez, Tomás R

    2014-01-01

    Shape transitions and shape coexistence in the $^{70-98}$Kr region are studied in a unified view with state-of-the-art beyond self-consistent mean field methods based on the Gogny D1S interaction. Beyond mean field effects are taken into account through the exact angular momentum and particle number restoration and the possibility of axial and non-axial shape mixing. The results of the low-lying properties of these isotopes are in good agreement with the experimental data when the triaxial degree of freedom is included. Shape transitions from axial-oblate ($^{70-72}$Kr) to triaxial-prolate ($^{74-78}$Kr) and from spherical-triaxial ($^{86-92}$Kr) to axial-oblate ($^{94-98}$Kr) ground states are obtained. Additionally, low-lying $0^{+}$ excited states and quasi-gamma bands are found showing the richness of the collective structure in this region.

  15. Standard test method for 238Pu isotopic abundance by alpha spectrometry

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2001-01-01

    1.1 This test method covers the use of alpha spectrometry for determining the 238Pu isotopic abundance in plutonium samples. It is particularly useful for samples in which the 238Pu content is less than 1 % of the total plutonium content. For such samples, mass spectrometric results are less reliable than those from alpha spectrometry because of interference from any 238U isobar remaining after ion exchange. 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 appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

  16. Using isotope methods to study alpine headwater regions in the Northern Caucasus and Tien Shan

    Science.gov (United States)

    Rets, Ekaterina; Chizhova, Julia N.; Loshakova, Nadezhda; Tokarev, Igor; Kireeva, Maria B.; Budantseva, Nadine A.; Vasil'chuk, Yurij K.; Frolova, Natalia; Popovnin, Viktor; Toropov, Pavel; Terskaya, Elena; Smirnov, Andrew M.; Belozerov, Egor; Karashova, Maria

    2017-09-01

    High mountain areas provide water resources for a large share of the world's population. The ongoing deglaciation of these areas is resulting in great instability of mountainous headwater regions, which could significantly affect water supply and intensify dangerous hydrological processes. The hydrological processes in mountains are still poorly understood due to the complexity of the natural conditions, great spatial variation and a lack of observation. A knowledge of flow-forming processes in alpine areas is essential to predict future possible trends in hydrological conditions and to calculate river runoff characteristics. The goal of this study is to gain detailed field data on various components of natural hydrological processes in the alpine areas of the North Caucasus and Central Tien Shan, and to investigate the possibility that the isotopic method can reveal important regularities of river flow formation in these regions. The study is based on field observations in representative alpine river basins in the North Caucasus (the Dzhankuat river basin) and the Central Tien Shan (the Chon-Kyzyl-Suu river basin) during 2013-2015. A mixing-model approach was used to conduct river hydrograph separation. Isotope methods were used to estimate the contribution of different nourishment sources in total runoff and its regime. d18O, dD and mineralization were used as indicators. Two equation systems for the study sites were derived: in terms of water routing and runoff genesis. The Dzhankuat and Chon-Kyzyl-Suu river hydrographs were separated into 4 components: liquid precipitation/meltwaters, surface routed/subsurface routed waters.

  17. Equilibrium thermodynamics

    CERN Document Server

    de Oliveira, Mário J

    2017-01-01

    This textbook provides an exposition of equilibrium thermodynamics and its applications to several areas of physics with particular attention to phase transitions and critical phenomena. The applications include several areas of condensed matter physics and include also a chapter on thermochemistry. Phase transitions and critical phenomena are treated according to the modern development of the field, based on the ideas of universality and on the Widom scaling theory. For each topic, a mean-field or Landau theory is presented to describe qualitatively the phase transitions. These theories include the van der Waals theory of the liquid-vapor transition, the Hildebrand-Heitler theory of regular mixtures, the Griffiths-Landau theory for multicritical points in multicomponent systems, the Bragg-Williams theory of order-disorder in alloys, the Weiss theory of ferromagnetism, the Néel theory of antiferromagnetism, the Devonshire theory for ferroelectrics and Landau-de Gennes theory of liquid crystals. This new edit...

  18. Equilibrium thermodynamics

    CERN Document Server

    Oliveira, Mário J

    2013-01-01

    This textbook provides an exposition of equilibrium thermodynamics and its applications to several areas of physics with particular attention to phase transitions and critical phenomena. The applications include several areas of condensed matter physics and include also a chapter on thermochemistry. Phase transitions and critical phenomena are treated according to the modern development of the field, based on the ideas of universality and on the Widom scaling theory. For each topic, a mean-field or Landau theory is presented to describe qualitatively the phase transitions.  These theories include the van der Waals theory of the liquid-vapor transition, the Hildebrand-Heitler theory of regular mixtures, the Griffiths-Landau theory for multicritical points in multicomponent systems, the Bragg-Williams theory of order-disorder in alloys, the Weiss theory of ferromagnetism, the Néel theory of antiferromagnetism, the Devonshire theory for ferroelectrics and Landau-de Gennes theory of liquid crystals. This textbo...

  19. Fe, Zn, and Cd stable isotopes from the eastern tropical South Pacific from GEOTRACES cruise GP16 - Methods and data

    Science.gov (United States)

    Helgoe, J. M.; Townsend, E.; John, S.

    2014-12-01

    A new method has been developed for the rapid analysis of metal concentrations and stable isotope ratios using a prepFAST automated sample processing robot. Although concentrations and isotopes are processed separately, similar methods are used for both. Initially all seawater is acidified to pH 2. Then Nobias resin with EDTA/IDA functional groups is added to either 10mL of sample for concentrations or ~1L samples for isotopes. Fe binds to the resin at low pH, and the pH is subsequently raised to allow Zn and Cd to bind. For concentration analyses, all subsequent chemistry is automated on the prepFAST including removal of seawater, rinsing of resin, and elution of resin into acid. For isotope samples these extraction techniques are performed manually, but the subsequent purification of Fe, Zn, and Cd by anion exchange chromatography is automated using the prepFAST. With these new methods, samples from the US GEOTRACES cruise GP16, in the eastern tropical South Pacific, are being analyzed. High concentrations of dissolved Fe are observed near the continental shelf and near submarine hydrothermal vents. Interestingly, isotope data show that dissolved Fe near the continental shelf generally has a δ56Fe close to 0 ‰. This δ56 Fe signature is suggestive of a non-reductive dissolution source for Fe, as Fe(II) released by reductive dissolution is typically closer to -2 ‰. Preliminary data show nutrient-type profiles for Zn and Cd, with Zn matching Si and Cd having a similar distribution to P. An increase in dissolved Zn near hydrothermal vents suggests a possible hydrothermal zinc source to the deep ocean. Continuing analysis of isotope data will reveal more about the source and biogeochemical cycling of these three chemically and biologically important trace metals throughout the eastern tropical Pacific Ocean.

  20. Stable isotope ratio method for the characterisation of the poultry house environment.

    Science.gov (United States)

    Skipitytė, Raminta; Mašalaitė, Agnė; Garbaras, Andrius; Mickienė, Rūta; Ragažinskienė, Ona; Baliukonienė, Violeta; Bakutis, Bronius; Šiugždaitė, Jūratė; Petkevičius, Saulius; Maruška, Audrius Sigitas; Remeikis, Vidmantas

    2017-06-01

    Stable isotope analysis was applied to describe the poultry house environment. The poultry house indoor environment was selected for this study due to the relevant health problems in animals and their caretakers. Air quality parameters including temperature, relative humidity, airflow rate, NH3, CO2 and total suspended particles, as well as mean levels of total airborne bacteria and fungi count, were measured. Carbon isotope ratios ((13)C/(12)C) were obtained in size-segregated aerosol particles. The carbon ((13)C/(12)C) and nitrogen ((15)N/(14)N) isotope ratios were measured in feed, litter, scrapings from the ventilation system, feathers and eggs. Additionally, the distribution of δ(13)C and δ(15)N values in different tissues of the chicken was examined. The airborne bacteria and fungi extracted from the air filters collected from poultry farms were grown in the laboratory in media with known isotope values and measured for stable isotope ratios. Analysis of isotope fractionation between microorganisms and their media indicated the applicability of stable isotope analysis in bulk samples for the identification of source material. The analysed examples imply that stable isotope analysis can be used to examine the indoor environment along with its biology and ecology, and serve as an informative bioanalytical tool.

  1. Uranium isotopes quantitatively determined by modified method of atomic absorption spectrophotometry

    Science.gov (United States)

    Lee, G. H.

    1967-01-01

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

  2. High-Throughput Method for Strontium Isotope Analysis by Multi-Collector-Inductively Coupled Plasma-Mass Spectrometer

    Energy Technology Data Exchange (ETDEWEB)

    Hakala, Jacqueline Alexandra [National Energy Technology Lab. (NETL), Morgantown, WV (United States)

    2016-11-22

    This technical report presents the details of the Sr column configuration and the high-throughput Sr separation protocol. Data showing the performance of the method as well as the best practices for optimizing Sr isotope analysis by MC-ICP-MS is presented. Lastly, this report offers tools for data handling and data reduction of Sr isotope results from the Thermo Scientific Neptune software to assist in data quality assurance, which help avoid issues of data glut associated with high sample throughput rapid analysis.

  3. High-Throughput Method for Strontium Isotope Analysis by Multi-Collector-Inductively Coupled Plasma-Mass Spectrometer

    Energy Technology Data Exchange (ETDEWEB)

    Wall, Andrew J. [National Energy Technology Lab. (NETL), Pittsburgh, PA, (United States); Capo, Rosemary C. [Univ. of Pittsburgh, PA (United States); Stewart, Brian W. [Univ. of Pittsburgh, PA (United States); Phan, Thai T. [Univ. of Pittsburgh, PA (United States); Jain, Jinesh C. [National Energy Technology Lab. (NETL), Pittsburgh, PA, (United States); Hakala, Alexandra [National Energy Technology Lab. (NETL), Pittsburgh, PA, (United States); Guthrie, George D. [National Energy Technology Lab. (NETL), Pittsburgh, PA, (United States)

    2016-09-22

    This technical report presents the details of the Sr column configuration and the high-throughput Sr separation protocol. Data showing the performance of the method as well as the best practices for optimizing Sr isotope analysis by MC-ICP-MS is presented. Lastly, this report offers tools for data handling and data reduction of Sr isotope results from the Thermo Scientific Neptune software to assist in data quality assurance, which help avoid issues of data glut associated with high sample throughput rapid analysis.

  4. Multi-mycotoxin stable isotope dilution LC-MS/MS method for Fusarium toxins in beer.

    Science.gov (United States)

    Habler, Katharina; Gotthardt, Marina; Schüler, Jan; Rychlik, Michael

    2017-03-01

    A stable isotope dilution LC-MS/MS multi-mycotoxin method was developed for 12 different Fusarium toxins including modified mycotoxins in beer (deoxynivalenol-3-glucoside, deoxynivalenol, 3-acetyldeoxynivalenol, 15-acetyl-deoxynivalenol, HT2-toxin, T2-toxin, enniatin B, B1, A1, A, beauvericin and zearalenone). As sample preparation and purification of beer a combined solid phase extraction for trichothecenes, enniatins, beauvericin and zearalenone was firstly developed. The validation of the new method gave satisfying results: intra-day and inter-day precision and recoveries were 1-5%, 2-8% and 72-117%, respectively. In total, 61 different organic and conventional beer samples from Germany and all over the world were analyzed by using the newly developed multi-mycotoxin method. In summary, deoxynivalenol, deoxynivalenol-3-glucoside, 3-acetyldeoxynivaleneol and enniatin B were quantified in rather low contents in the investigated beer samples. None of the other monitored Fusarium toxins like 15-acetyldeoxynivalenol, HT2- and T2-toxin, zearalenone, enniatin B1, A1, A or beauvericin were detectable.

  5. Online induction heating for determination of isotope composition of woody stem water with laser spectrometry: a methods assessment.

    Science.gov (United States)

    Lazarus, Brynne E; Germino, Matthew J; Vander Veen, Jessica L

    2016-06-01

    Application of stable isotopes of water to studies of plant-soil interactions often requires a substantial preparatory step of extracting water from samples without fractionating isotopes. Online heating is an emerging approach for this need, but is relatively untested and major questions of how to best deliver standards and assess interference by organics have not been evaluated. We examined these issues in our application of measuring woody stem xylem of sagebrush using a Picarro laser spectrometer with online induction heating. We determined (1) effects of cryogenic compared to induction-heating extraction, (2) effects of delivery of standards on filter media compared to on woody stem sections, and (3) spectral interference from organic compounds for these approaches (and developed a technique to do so). Our results suggest that matching sample and standard media improves accuracy, but that isotopic values differ with the extraction method in ways that are not due to spectral interference from organics.

  6. Online induction heating for determination of isotope composition of woody stem water with laser spectrometry: A methods assessment

    Science.gov (United States)

    Lazarus, Brynne E.; Germino, Matthew; Vander Veen, Jessica L.

    2016-01-01

    Application of stable isotopes of water to studies of plant–soil interactions often requires a substantial preparatory step of extracting water from samples without fractionating isotopes. Online heating is an emerging approach for this need, but is relatively untested and major questions of how to best deliver standards and assess interference by organics have not been evaluated. We examined these issues in our application of measuring woody stem xylem of sagebrush using a Picarro laser spectrometer with online induction heating. We determined (1) effects of cryogenic compared to induction-heating extraction, (2) effects of delivery of standards on filter media compared to on woody stem sections, and (3) spectral interference from organic compounds for these approaches (and developed a technique to do so). Our results suggest that matching sample and standard media improves accuracy, but that isotopic values differ with the extraction method in ways that are not due to spectral interference from organics.

  7. Quantitation of changes in protein phosphorylation: A simple method based on stable isotope labeling and mass spectrometry

    OpenAIRE

    Bonenfant, Débora; Schmelzle, Tobias; Jacinto, Estela; Crespo, José L; Mini, Thierry; Hall, Michael N.; Jenoe, Paul

    2003-01-01

    Reversible protein phosphorylation plays an important role in many cellular processes. However, a simple and reliable method to measure changes in the extent of phosphorylation is lacking. Here, we present a method to quantitate the changes in phosphorylation occurring in a protein in response to a stimulus. The method consists of three steps: (i) enzymatic digestion in H216O or isotopically enriched H218O to label individual pools of differentially phosphorylated proteins; (ii) affinity sele...

  8. Strong convergence theorems by hybrid projection methods for equilibrium problems and fixed point problems of the asymptotically quasi-ϕ-nonexpansive mappings

    Directory of Open Access Journals (Sweden)

    Kim Jong

    2011-01-01

    Full Text Available Abstract We consider a hybrid projection method for finding a common element in the fixed point set of an asymptotically quasi-ϕ-nonexpansive mapping and in the solution set of an equilibrium problem. Strong convergence theorems of common elements are established in a uniformly smooth and strictly convex Banach space which has the Kadec-Klee property. 2000 Mathematics subject classification: 47H05, 47H09, 47H10, 47J25

  9. Simulação do equilíbrio: o método de Monte Carlo Equilibrium simulation: Monte Carlo method

    Directory of Open Access Journals (Sweden)

    Alejandro López-Castillo

    2007-01-01

    Full Text Available We make several simulations using the Monte Carlo method in order to obtain the chemical equilibrium for several first-order reactions and one second-order reaction. We study several direct, reverse and consecutive reactions. These simulations show the fluctuations and relaxation time and help to understand the solution of the corresponding differential equations of chemical kinetics. This work was done in an undergraduate physical chemistry course at UNIFIEO.

  10. Discovery of the Cobalt Isotopes

    OpenAIRE

    Szymanski, T.; Thoennessen, M.

    2009-01-01

    Twenty-six cobalt isotopes have so far been observed; the discovery of these isotopes is discussed. For each isotope a brief summary of the first refereed publication, including the production and identification method, is presented.

  11. Discovery of the Arsenic Isotopes

    CERN Document Server

    Shore, A; Heim, M; Schuh, A; Thoennessen, M

    2009-01-01

    Twenty-nine arsenic isotopes have so far been observed; the discovery of these isotopes is discussed. For each isotope a brief summary of the first refereed publication, including the production and identification method, is presented.

  12. Equilibrium models and variational inequalities

    CERN Document Server

    Konnov, Igor

    2007-01-01

    The concept of equilibrium plays a central role in various applied sciences, such as physics (especially, mechanics), economics, engineering, transportation, sociology, chemistry, biology and other fields. If one can formulate the equilibrium problem in the form of a mathematical model, solutions of the corresponding problem can be used for forecasting the future behavior of very complex systems and, also, for correcting the the current state of the system under control. This book presents a unifying look on different equilibrium concepts in economics, including several models from related sciences.- Presents a unifying look on different equilibrium concepts and also the present state of investigations in this field- Describes static and dynamic input-output models, Walras, Cassel-Wald, spatial price, auction market, oligopolistic equilibrium models, transportation and migration equilibrium models- Covers the basics of theory and solution methods both for the complementarity and variational inequality probl...

  13. Development of an Isotope-Dilution Liquid Chromatography/Mass Spectrometric Method for the Accurate Determination of Acetaminophen in Tablets

    Energy Technology Data Exchange (ETDEWEB)

    Shin, Hyun Ju; Kim, Byung Joo; Lee, Joon Hee; Hwang, Eui Jin [Korea Research Institute of Standards and Science, Daejeon (Korea, Republic of)

    2010-12-15

    Acetaminophen (N-acetyl-p-aminophenol) is one of the most popular analgesic and antipyretic drugs. An isotope dilution mass spectrometric method based on LC/MS was developed as a candidate reference method for the accurate determination of acetaminophen in pharmaceutical product. After spiking an isotope labeled acetaminophen (acetyl-{sup 13}C{sub 2}, {sup 15}Nacetaminophen) as an internal standard, tablet extracts were analyzed by LC/MS in a selected reaction monitoring (SRM) mode to detect ions at m/z 152→110 and m/z 155→111 for acetaminophen and acetyl-{sup 13}C{sub 2}, {sup 15}N-acetaminophen, respectively. The repeatability and reproducibility of the developed ID/LC-MS method were tested for the validation and assessment of metrological quality of the method.

  14. Standard test method for determination of uranium or plutonium isotopic composition or concentration by the total evaporation method using a thermal ionization mass spectrometer

    CERN Document Server

    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...

  15. Hybrid Proximal-Point Methods for Zeros of Maximal Monotone Operators, Variational Inequalities and Mixed Equilibrium Problems

    Directory of Open Access Journals (Sweden)

    Kriengsak Wattanawitoon

    2011-01-01

    Full Text Available We prove strong and weak convergence theorems of modified hybrid proximal-point algorithms for finding a common element of the zero point of a maximal monotone operator, the set of solutions of equilibrium problems, and the set of solution of the variational inequality operators of an inverse strongly monotone in a Banach space under different conditions. Moreover, applications to complementarity problems are given. Our results modify and improve the recently announced ones by Li and Song (2008 and many authors.

  16. Determination of Uranium and Plutonium Concentration in 1AF by Isotopic Dilution Mass Spectrometry Methods

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    <正>It is important data to measure uranium and plutonium concentration for the reprocessing plant control analysis. The determination of uranium and plutonium concentration in 1AF by isotopic dilution mass

  17. Isotope-dilution TurboFlow-LC-MS/MS method for simultaneous quantification of ten steroid metabolites in serum

    DEFF Research Database (Denmark)

    Søeborg, Tue; Frederiksen, Hanne; Johannsen, Trine Holm

    2017-01-01

    An isotope-dilution TurboFlow-LC-MS/MS method for simultaneous quantification of the ten steroid metabolites dehydroepiandrosterone sulfate (DHEAS), progesterone, 17α-hydroxyprogesterone (17-OHP), Δ4-androstenedione (Adione), corticosterone, 11-deoxycortisol, cortisol, cortisone, testosterone (T)...... possible only to include some of these analytes for specific diagnostic purposes which make the new method an extremely useful tool in the clinical laboratory....

  18. Fast methods for determination of antropogenic actinides and U/Th-series isotopes in aqueous samples.

    Science.gov (United States)

    Eikenberg, J; Bajo, S; Beer, H; Hitz, J; Ruethi, M; Zumsteg, I; Letessier, P

    2004-01-01

    Rapid and simple methods are applied at the PSI radioanalytical laboratory for determining anthropogenic actinides in waste and nuclear reactor waters (U, Pu, Am, Cm) as well as for analysis of naturally occurring alpha-emitters in continental river and ground water. Anion exchange chromatography followed by alpha-spectrometry as well as alpha/beta-LSC is applied for the reactor coolant waters. To avoid alpha-spectrum interference between 238Pu and 241Am at 5.5 MeV, the Pu-fraction is purified using anion exchange resin. Prior to the separation of the Pu-fraction, all actinides (U, Pu, Am, Cm) are adsorbed batch-wise under stirring onto Actinide Resin and subsequent decomposition of the reagent. The residue is then re-dissolved in a sulfate buffer solution for electrolytic deposition. In tabular water samples isotopes of Ra and Po are analyzed additionally via sorption onto manganese coated discs (Ra) and deposition on silver discs (Po). For counting times of 1 day and use of 0.1-1l sample aliquots, detection limits of a few mBql(-1) can be obtained easily.

  19. Study on animals‘ femur blood flow alteration under inadequate decompression with 133Xe isotope washout method

    Institute of Scientific and Technical Information of China (English)

    YuShao-Ning; TiaoWu-Xun; 等

    1998-01-01

    Animals' regional femur blood(F) alteration was studied under an inadequate decompression by using the inhaled isotope 133Xe washout method.Results showed that the average F on left and right side of minipigs' femur decreased from 15.4±1.8 and 16.9±2.0mg/(100g.min)(before exposure)to 10±1.8and 11.1±1.6mg(100mg.min)(after expposure for 1.5h under the pressure of 0.5 MPa and then decompression to normal with the rate of 0.03-0.04MPa/min)respectively;the blood flow of hematopoietic marrow tissues(f1) on both sides also decreased from 19.3±2.0 and 22.1±1.9ml(100mg.min)to 13.9±1.4 and 13.8±1.0ml(100mg.min).The exact same alteration also happened in the experiment on New Zealand rabbits.It indicates that inadequate decompression in hyperbaric exposure can give rise to decrease animals' one blood flow and insufficient bone blood supply serves as one of the reasons for causing decompressive osteonecrosis.

  20. A comparison of pretreatment methods for the analysis of phosphate oxygen isotope ratios in bioapatite.

    Science.gov (United States)

    Grimes, Vaughan; Pellegrini, Maura

    2013-02-15

    The integrity of the biological phosphate oxygen isotope (δ(18)O(p) ) signal is thought to be contingent upon the complete removal of competing sources of oxygen such as associated organic matter. A range of pretreatment methods to purify phosphate material from competing sources of oxygen has been reported, with contradictory evidence on the usefulness and efficiency of one or another. Yet, a systematic comparison of these techniques for bioapatite phosphate has not been conducted. Chemical and thermal pretreatment techniques were tested for their effectiveness at removing organic matter and the likelihood that they modify original δ(18)O values. The test was performed in inorganic (synthetic apatite and a phosphorite rock) and organic (bone and tooth tissues) phosphate materials for which we had an expectation of the actual original δ(18)O(p) value. Analysis of nitrogen content (wt.%), scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectroscopy were employed. We detected variable efficiency at removing organic matter between pretreatment methods with no correlation to any specific structural change. The δ(18)O(p) results showed considerable variation between samples pretreated with the different methods and the untreated samples, with a compositional range of up to 4.5 ‰ in the bone samples. Variations of the δ(18)O(p) values within error were found for tooth enamel, phosphorite rock and inorganic apatite. We recommend a cautious approach when interpreting and comparing δ(18)O(p) data from bone samples treated with different pretreatment protocols. In general, the untreated samples seem to show δ(18)O(p) values closer to the expected ones. According to our results, pretreatment is completely unnecessary in highly mineralized tissues. Copyright © 2012 John Wiley & Sons, Ltd.

  1. A new method for the investigation of mercury redox chemistry in natural waters utilizing deflatable Teflon[reg] bags and additions of isotopically labeled mercury

    Energy Technology Data Exchange (ETDEWEB)

    Whalin, Lindsay M. [Chesapeake Biological Laboratory, University of Maryland, Solomons, MD 20688 (United States); Mason, Robert P. [Chesapeake Biological Laboratory, University of Maryland, Solomons, MD 20688 (United States)]. E-mail: robert.mason@uconn.edu

    2006-02-03

    The toxicity and behavior of mercury (Hg) varies greatly between its chemical species, yet the mechanisms which control the redox chemistry of Hg in natural waters are still poorly understood. Previous studies have identified these processes and compared the Hg redox chemistry between water types but have been hampered by errors associated primarily with the type of reaction vessels utilized, and the inability of the methods to simultaneously measure oxidation and reduction. Presented here are the results of experiments which demonstrate the validity of a new method that addresses both these issues through the design and use of a new reaction vessel, a 5 L PFA Teflon[reg] incubation bag, and by the addition of isotopically labeled inorganic Hg species (both Hg{sup II} and Hg{sup 0}). The method development showed that mm thick FEP Teflon[reg] is permeable to Hg{sup 0}, and therefore unsuitable. Application of this method showed that both oxidation and reduction occurred simultaneously in natural waters exposed to ambient sunlight and that the rate of these transformations were of similar order (10{sup -3} to 10{sup -4} s{sup -1}). Given such reaction rates, the characteristic time to equilibrium is rapid, on the order of hours. The method is applicable for tracer studies, and the method was able to quantify rate constants of greater than 10{sup -5} s{sup -1}. Overall, this study suggests that the rates of reaction are faster than previously predicted primarily because previous studies did not account for the fact that both reactions are occurring simultaneously in natural waters.

  2. A Shrinking Projection Method for Generalized Mixed Equilibrium Problems, Variational Inclusion Problems and a Finite Family of Quasi-Nonexpansive Mappings

    Directory of Open Access Journals (Sweden)

    Wiyada Kumam

    2010-01-01

    Full Text Available The purpose of this paper is to consider a shrinking projection method for finding a common element of the set of solutions of generalized mixed equilibrium problems, the set of fixed points of a finite family of quasi-nonexpansive mappings, and the set of solutions of variational inclusion problems. Then, we prove a strong convergence theorem of the iterative sequence generated by the shrinking projection method under some suitable conditions in a real Hilbert space. Our results improve and extend recent results announced by Peng et al. (2008, Takahashi et al. (2008, S.Takahashi and W. Takahashi (2008, and many others.

  3. New online method for water isotope analysis of speleothem fluid inclusions using laser absorption spectroscopy (WS-CRDS)

    Science.gov (United States)

    Affolter, S.; Fleitmann, D.; Leuenberger, M.

    2014-07-01

    A new online method to analyse water isotopes of speleothem fluid inclusions using a wavelength scanned cavity ring down spectroscopy (WS-CRDS) instrument is presented. This novel technique allows us simultaneously to measure hydrogen and oxygen isotopes for a released aliquot of water. To do so, we designed a new simple line that allows the online water extraction and isotope analysis of speleothem samples. The specificity of the method lies in the fact that fluid inclusions release is made on a standard water background, which mainly improves the δ D robustness. To saturate the line, a peristaltic pump continuously injects standard water into the line that is permanently heated to 140 °C and flushed with dry nitrogen gas. This permits instantaneous and complete vaporisation of the standard water, resulting in an artificial water background with well-known δ D and δ18O values. The speleothem sample is placed in a copper tube, attached to the line, and after system stabilisation it is crushed using a simple hydraulic device to liberate speleothem fluid inclusions water. The released water is carried by the nitrogen/standard water gas stream directly to a Picarro L1102-i for isotope determination. To test the accuracy and reproducibility of the line and to measure standard water during speleothem measurements, a syringe injection unit was added to the line. Peak evaluation is done similarly as in gas chromatography to obtain &delta D; and δ18O isotopic compositions of measured water aliquots. Precision is better than 1.5 ‰ for δ D and 0.4 ‰ for δ18O for water measurements for an extended range (-210 to 0 ‰ for δ D and -27 to 0 ‰ for δ18O) primarily dependent on the amount of water released from speleothem fluid inclusions and secondarily on the isotopic composition of the sample. The results show that WS-CRDS technology is suitable for speleothem fluid inclusion measurements and gives results that are comparable to the isotope ratio mass

  4. New on-line method for water isotope analysis of speleothem fluid inclusions using laser absorption spectroscopy (WS-CRDS)

    Science.gov (United States)

    Affolter, S.; Fleitmann, D.; Leuenberger, M.

    2014-01-01

    A new online method to analyse water isotopes of speleothem fluid inclusions using a wavelength scanned cavity ring down spectroscopy (WS-CRDS) instrument is presented. This novel technique allows us to simultaneously measure hydrogen and oxygen isotopes for a released aliquot of water. To do so, we designed a new simple line that allows the on-line water extraction and isotope analysis of speleothem samples. The specificity of the method lies in the fact that fluid inclusions release is made on a standard water background, which mainly improves the δD reliability. To saturate the line, a peristaltic pump continuously injects standard water into the line that is permanently heated to 140 °C and flushed with dry nitrogen gas. This permits instantaneous and complete vaporisation of the standard water resulting in an artificial water background with well-known δD and δ18O values. The speleothem sample is placed into a copper tube, attached to the line and after system stabilisation is crushed using a simple hydraulic device to liberate speleothem fluid inclusions water. The released water is carried by the nitrogen/standard water gas stream directly to a Picarro L1102-i for isotope determination. To test the accuracy and reproducibility of the line and to measure standard water during speleothem measurements a syringe injection unit was added to the line. Peak evaluation is done similarly as in gas chromatography to obtain δD and δ18O isotopic composition of measured water aliquots. Precision is better than 1.5‰ for δD and 0.4‰ for δ18O for water measurement for an extended range (-210 to 0‰ for δD and -27 to 0‰ for δ18O) primarily dependent on the amount of water released from speleothem fluid inclusions and secondarily on the isotopic composition of the sample. The results show that WS-CRDS technology is suitable for speleothem fluid inclusion measurements and gives results that are comparable to Isotope Ratio Mass Spectrometry (IRMS) technique.

  5. Determining origin in a migratory marine vertebrate: a novel method to integrate stable isotopes and satellite tracking

    Science.gov (United States)

    Vander Zanden, Hannah B.; Tucker, Anton D.; Hart, Kristen M.; Lamont, Margaret M.; Fujisaki, Ikuko; Addison, David S.; Mansfield, Katherine L.; Phillips, Katrina F.; Wunder, Michael B.; Bowen, Gabriel J.; Pajuelo, Mariela; Bolten, Alan B.; Bjorndal, Karen A.

    2015-01-01

    Stable isotope analysis is a useful tool to track animal movements in both terrestrial and marine environments. These intrinsic markers are assimilated through the diet and may exhibit spatial gradients as a result of biogeochemical processes at the base of the food web. In the marine environment, maps to predict the spatial distribution of stable isotopes are limited, and thus determining geographic origin has been reliant upon integrating satellite telemetry and stable isotope data. Migratory sea turtles regularly move between foraging and reproductive areas. Whereas most nesting populations can be easily accessed and regularly monitored, little is known about the demographic trends in foraging populations. The purpose of the present study was to examine migration patterns of loggerhead nesting aggregations in the Gulf of Mexico (GoM), where sea turtles have been historically understudied. Two methods of geographic assignment using stable isotope values in known-origin samples from satellite telemetry were compared: 1) a nominal approach through discriminant analysis and 2) a novel continuous-surface approach using bivariate carbon and nitrogen isoscapes (isotopic landscapes) developed for this study. Tissue samples for stable isotope analysis were obtained from 60 satellite-tracked individuals at five nesting beaches within the GoM. Both methodological approaches for assignment resulted in high accuracy of foraging area determination, though each has advantages and disadvantages. The nominal approach is more appropriate when defined boundaries are necessary, but up to 42% of the individuals could not be considered in this approach. All individuals can be included in the continuous-surface approach, and individual results can be aggregated to identify geographic hotspots of foraging area use, though the accuracy rate was lower than nominal assignment. The methodological validation provides a foundation for future sea turtle studies in the region to inexpensively

  6. Equilibrium CO bond lengths

    Science.gov (United States)

    Demaison, Jean; Császár, Attila G.

    2012-09-01

    Based on a sample of 38 molecules, 47 accurate equilibrium CO bond lengths have been collected and analyzed. These ultimate experimental (reEX), semiexperimental (reSE), and Born-Oppenheimer (reBO) equilibrium structures are compared to reBO estimates from two lower-level techniques of electronic structure theory, MP2(FC)/cc-pVQZ and B3LYP/6-311+G(3df,2pd). A linear relationship is found between the best equilibrium bond lengths and their MP2 or B3LYP estimates. These (and similar) linear relationships permit to estimate the CO bond length with an accuracy of 0.002 Å within the full range of 1.10-1.43 Å, corresponding to single, double, and triple CO bonds, for a large number of molecules. The variation of the CO bond length is qualitatively explained using the Atoms in Molecules method. In particular, a nice correlation is found between the CO bond length and the bond critical point density and it appears that the CO bond is at the same time covalent and ionic. Conditions which permit the computation of an accurate ab initio Born-Oppenheimer equilibrium structure are discussed. In particular, the core-core and core-valence correlation is investigated and it is shown to roughly increase with the bond length.

  7. Bird migration and avian influenza: a comparison of hydrogen stable isotopes and satellite tracking methods

    Science.gov (United States)

    Bridge, Eli S.; Kelly, Jeffrey F.; Xiao, Xiangming; Takekawa, John Y.; Hill, Nichola J.; Yamage, Mat; Haque, Enam Ul; Islam, Mohammad Anwarul; Mundkur, Taej; Yavuz, Kiraz Erciyas; Leader, Paul; Leung, Connie Y.H.; Smith, Bena; Spragens, Kyle A.; Vandegrift, Kurt J.; Hosseini, Parviez R.; Saif, Samia; Mohsanin, Samiul; Mikolon, Andrea; Islam, Ausrafal; George, Acty; Sivananinthaperumal, Balachandran; Daszak, Peter; Newman, Scott H.

    2014-01-01

    Satellite-based tracking of migratory waterfowl is an important tool for understanding the potential role of wild birds in the long-distance transmission of highly pathogenic avian influenza. However, employing this technique on a continental scale is prohibitively expensive. This study explores the utility of stable isotope ratios in feathers in examining both the distances traveled by migratory birds and variation in migration behavior. We compared the satellite-derived movement data of 22 ducks from 8 species captured at wintering areas in Bangladesh, Turkey, and Hong Kong with deuterium ratios (δD) in the feathers of these and other individuals captured at the same locations. We derived likely molting locations from the satellite tracking data and generated expected isotope ratios based on an interpolated map of δD in rainwater. Although δD was correlated with the distance between wintering and molting locations, surprisingly, measured δD values were not correlated with either expected values or latitudes of molting sites. However, population-level parameters derived from the satellite-tracking data, such as mean distance between wintering and molting locations and variation in migration distance, were reflected by means and variation of the stable isotope values. Our findings call into question the relevance of the rainfall isotope map for Asia for linking feather isotopes to molting locations, and underscore the need for extensive ground truthing in the form of feather-based isoscapes. Nevertheless, stable isotopes from feathers could inform disease models by characterizing the degree to which regional breeding populations interact at common wintering locations. Feather isotopes also could aid in surveying wintering locations to determine where high-resolution tracking techniques (e.g. satellite tracking) could most effectively be employed. Moreover, intrinsic markers such as stable isotopes offer the only means of inferring movement information from

  8. Standard test method for isotopic analysis of hydrolyzed uranium hexafluoride and uranyl nitrate solutions by thermal ionization mass spectrometry

    CERN Document Server

    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...

  9. Uniform deposition of uranium hexafluoride (UF6): Standardized mass deposits and controlled isotopic ratios using a thermal fluorination method.

    Science.gov (United States)

    McNamara, Bruce K; O'Hara, Matthew J; Casella, Andrew M; Carter, Jennifer C; Addleman, R Shane; MacFarlan, Paul J

    2016-07-01

    We report a convenient method for the generation of volatile uranium hexafluoride (UF6) from solid uranium oxides and other U compounds, followed by uniform deposition of low levels of UF6 onto sampling coupons. Under laminar flow conditions, UF6 is shown to interact with surfaces within a fixed reactor geometry to a highly predictable degree. We demonstrate the preparation of U deposits that range between approximately 0.01 and 500ngcm(-2). The data suggest the method can be extended to creating depositions at the sub-picogramcm(-2) level. The isotopic composition of the deposits can be customized by selection of the U source materials and we demonstrate a layering technique whereby two U solids, each with a different isotopic composition, are employed to form successive layers of UF6 on a surface. The result is an ultra-thin deposit that bears an isotopic signature that is a composite of the two U sources. The reported deposition method has direct application to the development of unique analytical standards for nuclear safeguards and forensics. Further, the method allows access to very low atomic or molecular coverages of surfaces.

  10. Application of isotopic and hydro-geochemical methods in identifying sources of mine inrushing water

    Institute of Scientific and Technical Information of China (English)

    Dou Huiping; Ma Zhiyuan; Cao Haidong; Liu Feng; Hu Weiwei; Li Ting

    2011-01-01

    Isotopic and hydro-geochemical surveys were carried out to identify the source of mine inrushing water at the #73003 face in the Laohutai Mine.Based on the analysis of isotopes and hydro-chemical features of surface water,groundwater from different levels and the inrushing water,a special relationship between water at the #73003 face and cretaceous water has been found.The results show that the isotopic and hydro-chemical features of the inrushing water are completely different from those of other groundwater bodies,except for the cretaceous water.The isotopic and hydrochemical characteristics of cretaceous water are similar to the inrushing water of the #73003 face,which aided with obtaining the evidence for the possible source of the inrushing water at the #73003 face.The isotope calculations show that the inrushing water at the #73003 face is a mixture of cretaceous water and Quaternary water,water from the cretaceous conglomerate is the main source,accounting for 67% of the inrushing water,while the Quaternary water accounts for 33%.The conclusion is also supported by a study of inrushing-water channels and an active fault near the inrushing-water plot on the #73003 face.

  11. A method of calculating of the thermodynamic properties and the composition of the explosion products of hydrocarbons and air under partial chemical equilibrium

    Science.gov (United States)

    Shargatov, V. A.

    2016-11-01

    We examined the approximate method to calculate composition and thermodynamic parameters of hydrocarbons-air nonequilibrium explosion products based on the assumption of the existence of a partial chemical equilibrium. With excellent accuracy of calculating thermodynamic properties and species mass fraction the respective stiff system of detailed kinetics differential equations can be replaced by the one differential equation or the two differential equations and a system of algebraic equations. This method is always consistent with the detailed kinetic mechanism. The constituent equations of the method were derived and the respective computer code written. We examine the applicability of the method by solving the test problem. The proposed method simulation results are in excellent agreement with the detailed kinetics model results corresponding the stiff ordinary differential equation solver including NO time histories.

  12. DNA-based stable isotope probing coupled with cultivation methods implicates Methylophaga in hydrocarbon degradation.

    Directory of Open Access Journals (Sweden)

    Sara eMishamandani

    2014-02-01

    Full Text Available Marine hydrocarbon-degrading bacteria perform a fundamental role in the oxidation and ultimate removal of crude oil and its petrochemical derivatives in coastal and open ocean environments. Those with an almost exclusive ability to utilize hydrocarbons as a sole carbon and energy source have been found confined to just a few genera. Here we used stable isotope probing (SIP, a valuable tool to link the phylogeny and function of targeted microbial groups, to investigate hydrocarbon-degrading bacteria in coastal North Carolina sea water (Beaufort Inlet, USA with uniformly labeled [13C]n-hexadecane. The dominant sequences in clone libraries constructed from 13C-enriched bacterial DNA (from n-hexadecane enrichments were identified to belong to the genus Alcanivorax, with ≤98% sequence identity to the closest type strain – thus representing a putative novel phylogenetic taxon within this genus. Unexpectedly, we also identified 13C-enriched sequences in heavy DNA fractions that were affiliated to the genus Methylophaga. This is a contentious group since, though some of its members have been proposed to degrade hydrocarbons, substantive evidence has not previously confirmed this. We used quantitative PCR primers targeting the 16S rRNA gene of the SIP-identified Alcanivorax and Methylophaga to determine their abundance in incubations amended with unlabeled n-hexadecane. Both showed substantial increases in gene copy number during the experiments. Subsequently, we isolated a strain representing the SIP-identified Methylophaga sequences (99.9% 16S rRNA gene sequence identity and used it to show, for the first time, direct evidence of hydrocarbon degradation by a cultured Methylophaga sp. This study demonstrates the value of coupling SIP with cultivation methods to identify and expand on the known diversity of hydrocarbon-degrading bacteria in the marine environment.

  13. GEOCHRONOMETRY ISOTOPE GEOLOGY

    Institute of Scientific and Technical Information of China (English)

    2004-01-01

    <正>20040631 Chen Jiangfeng (School of Earth and Space Sciences, University of Science and Technology of China, Hefei, Anhui) ; Xie Zhi Relationships Between Rb-Sr, Ar - Ar Geochronometers and Oxygen Isotopic Equilibrium of Intrusions from Eastern Anhui Province, China (Geological Journal of China Universities, ISSN 1006 - 7493, CN 32 -

  14. New method for the measurement of osmium isotopes applied to a New Zealand Cretaceous/Tertiary boundary shale

    Science.gov (United States)

    Lichte, F.E.; Wilson, S.M.; Brooks, R.R.; Reeves, R.D.; Holzbecher, J.; Ryan, D.E.

    1986-01-01

    The determination of osmium content and isotopic abundances in geological materials has received increasing attention in recent years following the proposal of Alvarez et al.1 that mass extinctions at the end of the Cretaceous period were caused by the impact of a large (???10km) meteorite which left anomalously high iridium levels as a geochemical signature in the boundary shales. Here we report a new and simple method for measuring osmium in geological materials, involving fusion of the sample with sodium peroxide, distillation of the osmium as the tetroxide using perchloric acid, extraction into chloroform, and absorption of the chloroform extract onto graphite powder before instrumental neutron activation analysis. In a variant of this technique, the chloroform extract is back-extracted into an aqueous phase and the osmium isotopes are determined by plasma-source mass spectrometry (ICPMS). We have used this method on the Woodside Creek (New Zealand) Cretaceous/Tertiary boundary clay and have obtained the first osmium content (6g ng g-1) for this material. The 187Os/186Os ratio is 1.12??0.16, showing a typical non-crustal signature. This combined distillation-extraction- ICPMS method will prove to be useful for measuring osmium isotopes in other geological materials. ?? 1986 Nature Publishing Group.

  15. A Novel Method for Analyzing Chlorine Isotope Fractionation for Source and Fate Assessment of Organochlorine Soil and Groundwater Pollutants

    Science.gov (United States)

    Aeppli, Christoph; Wiegert, Charline; Holmstrand, Henry; Andersson, Per; Gustafsson, Örjan

    2010-05-01

    We developed a simple and accurate analytical method for compound-specific determination of chlorine isotopic composition (δ37Cl) or organochlorines based on GC/MS analysis and standard isotope bracketing. Good accuracy (comparison with off-line thermal ionization mass spectrometry) and a precision comparable to other on-line δ37Cl-methods (0.6 permil vs SMOC) were achieved. We applied this method to assess biodegradation of polychlorinated phenols used for wood preservation at a former sawmill site in northern Sweden. To come up with a δ37Cl-based estimation of the importance of on-going aerobic microbial degradation, we analyzed 37Cl-enrichment during enzymatic dechlorination of polychlorinated phenols in laboratory experiments. We also investigated δ37Cl fingerprints of chloroperoxidase-mediated chlorinated phenols, which can be used for apportionment of natural and anthropogenic sources of chlorophenols in boreal soils. Furthermore, we investigated natural attenuation of chlorinated ethenes in a contaminated aquifer in the Czech Republic. At this site, the extent of naturally occurring reductive tetrachloroethene (PCE) dechlorination was estimated based on PCE-δ37Cl. Overall, our laboratory and field studies demonstrate the potential of using compound-specific chlorine isotope analysis for assessing the source and fate of organochlorine groundwater and soil contaminants.

  16. Uniform deposition of uranium hexafluoride (UF6): Standardized mass deposits and controlled isotopic ratios using a thermal fluorination method

    Energy Technology Data Exchange (ETDEWEB)

    McNamara, Bruce K.; O’Hara, Matthew J.; Casella, Andrew M.; Carter, Jennifer C.; Addleman, R. Shane; MacFarlan, Paul J.

    2016-07-01

    Abstract: We report a convenient method for the generation of volatile uranium hexafluoride (UF6) from solid uranium oxides and other uranium compounds, followed by uniform deposition of low levels of UF6 onto sampling coupons. Under laminar flow conditions, UF6 is shown to interact with surfaces within the chamber to a highly predictable degree. We demonstrate the preparation of uranium deposits that range between ~0.01 and 470±34 ng∙cm-2. The data suggest the method can be extended to creating depositions at the sub-picogram∙cm-2 level. Additionally, the isotopic composition of the deposits can be customized by selection of the uranium source materials. We demonstrate a layering technique whereby two uranium solids, each with a different isotopic composition, are employed to form successive layers of UF6 on a surface. The result is an ultra-thin deposit of UF6 that bears an isotopic signature that is a composite of the two uranium sources. The reported deposition method has direct application to the development of unique analytical standards for nuclear safeguards and forensics.

  17. Stable isotope analyses of oxygen (18O:17O:16O) and chlorine (37Cl:35Cl) in perchlorate: reference materials, calibrations, methods, and interferences

    Science.gov (United States)

    Böhlke, John Karl; Mroczkowski, Stanley J.; Sturchio, Neil C.; Heraty, Linnea J.; Richman, Kent W.; Sullivan, Donald B.; Griffith, Kris N.; Gu, Baohua; Hatzinger, Paul B.

    2017-01-01

    RationalePerchlorate (ClO4−) is a common trace constituent of water, soils, and plants; it has both natural and synthetic sources and is subject to biodegradation. The stable isotope ratios of Cl and O provide three independent quantities for ClO4− source attribution and natural attenuation studies: δ37Cl, δ18O, and δ17O (or Δ17O or 17Δ) values. Documented reference materials, calibration schemes, methods, and interferences will improve the reliability of such studies.MethodsThree large batches of KClO4 with contrasting isotopic compositions were synthesized and analyzed against VSMOW-SLAP, atmospheric O2, and international nitrate and chloride reference materials. Three analytical methods were tested for O isotopes: conversion of ClO4− to CO for continuous-flow IRMS (CO-CFIRMS), decomposition to O2 for dual-inlet IRMS (O2-DIIRMS), and decomposition to O2 with molecular-sieve trap (O2-DIIRMS+T). For Cl isotopes, KCl produced by thermal decomposition of KClO4 was reprecipitated as AgCl and converted into CH3Cl for DIIRMS.ResultsKClO4 isotopic reference materials (USGS37, USGS38, USGS39) represent a wide range of Cl and O isotopic compositions, including non-mass-dependent O isotopic variation. Isotopic fractionation and exchange can affect O isotope analyses of ClO4− depending on the decomposition method. Routine analyses can be adjusted for such effects by normalization, using reference materials prepared and analyzed as samples. Analytical errors caused by SO42−, NO3−, ReO42−, and C-bearing contaminants include isotope mixing and fractionation effects on CO and O2, plus direct interference from CO2 in the mass spectrometer. The results highlight the importance of effective purification of ClO4− from environmental samples.ConclusionsKClO4 reference materials are available for testing methods and calibrating isotopic data for ClO4− and other substances with widely varying Cl or O isotopic compositions. Current ClO4−extraction, purification

  18. A novel quantitative dual-isotope method for simultaneous ventilation and perfusion lung SPET

    Energy Technology Data Exchange (ETDEWEB)

    Sanchez-Crespo, Alejandro; Larsson, Stig A. [Section of Nuclear Medicine, Department of Hospital Physics, Karolinska Hospital, Stockholm (Sweden); Medical Radiation Physics, Department of Oncology-Pathology, Stockholm University and Karolinska Institute, Stockholm (Sweden); Petersson, Johan; Mure, Margareta; Lindahl, Sten G.E. [Department of Anaesthesiology and Intensive Care, Karolinska Hospital, Stockholm (Sweden); Nyren, Sven [Department of Radiology, Karolinska Hospital, Stockholm (Sweden); Glenny, Robb W. [University of Washington School of Medicine, Seattle (United States); Thorell, Jan-Olov [Karolinska Pharmacy, Stockholm (Sweden); Jacobsson, Hans [Section of Nuclear Medicine, Department of Hospital Physics, Karolinska Hospital, Stockholm (Sweden); Department of Radiology, Karolinska Hospital, Stockholm (Sweden)

    2002-07-01

    A quantitative dual-isotope single-photon emission tomography (SPET) technique for the assessment of lung ventilation (V) and perfusion (Q) using, respectively, technetium-99m labelled Technegas (140 keV) and indium-113m labelled macro-aggregated albumin (392 keV), is presented, validated and clinically tested in a healthy volunteer. In order to assess V, Q and V/Q distributions in quantitative terms, algorithms which correct for down scattering, photon scattering and attenuation, as well as an organ outline algorithm, were implemented. Scatter and down-scatter correction were made in the spatial domain by pixel-wise image subtraction of projection-dependent global scattering factors obtained from the energy domain. The attenuation correction was based on an iterative projection/back-projection method. All studies were made on a three-headed SPET system (Trionix) with medium-energy parallel-hole collimators. The set of input data for quantification was based on SPET acquisition of emission data in four separate energy windows, the associated cumulative energy spectra and transmission data. The attenuation correction routine as well as the edge detection algorithm utilized data from {sup 99m}Tc transmission tomography. Attenuation data for {sup 113m}In were obtained by linear scaling of the {sup 99m}Tc attenuation maps. The correction algorithms were experimentally validated with a stack phantom system and applied on a healthy volunteer. The mean difference between the corrected SPET data of the dense stack lung phantom and those obtained from the corresponding scatter- and attenuation-''free'' version was only 1.9% for {sup 99m}Tc and 0.9% for {sup 113m}In. The estimated fractional V/Q distribution in the 3-D lung phantom volume had its peak at V/Q=1, with a width (FWHM) of 0.31 due to noise, particularly in the {sup 113m}In images, and to partial volume effects. For a healthy volunteer, the corresponding values were 0.9 and 0.35, respectively

  19. Measurement of dinitrogen fixation by Biological soil crust (BSC) from the Sahelian zone: an isotopic method.

    Science.gov (United States)

    Ehrhardt, F.; Alavoine, G.; Bertrand, I.

    2012-04-01

    Amongst the described ecological roles of Biological Soil Crust, N fixation is of importance for soil fertility, especially in arid and semi-arid ecosystems with low inputs. In BSC, the quantification of N fixation fluxes using an indirect method is widespread, usually with the Acetylene Reduction Assay (ARA) which consists in measuring the nitrogenase activity through the process of acetylene reduction into ethylene. A converting factor, still discussed in the literature and greatly depending of the constitutive organisms of the BSC, is the tool used to convert the amount of reduced ethylene into quantitative fixed Nitrogen. The aim of this poster is to describe an isotopic direct method to quantify the atmospheric dinitrogen fixation fluxes in BSC, while minimizing the variability due to manipulations. Nine different BSC from the Sahelian zone were selected and placed in an incubation room at 28° C in dark and light conditions during three days, while moisture equivalent to pF=2 was regularly adjusted using the gravimetric method with needles and deionized water, in order to activate and reach a dynamic stability of their metabolisms. Subsequently, each crust was placed into a gas-tight glass vial for incubation with a reconstituted 15N2 enriched atmosphere (31.61 % atom 15N, while the proportion of each main gas present in the air was conserved, i.e. 78% N2, 21% O2 and 0.04% CO2). Principal difficulties are to guarantee the airtighness of the system, to avoid crust desiccation and to keep the crust metabolically active under stable conditions for six hours. Several tests were performed to determine the optimum time for 15N2 incubation. Three replicated control samples per crust were also stabilized for three days and then dried at 105° C, without any incubation with 15N2 enriched atmosphere. Total N and 15N were then measured in the grounded (80μm) and dried (105° C) crust, using a Flash EA elemental analyzer (Eurovector, Milan, Italy) coupled to a Delta

  20. An Iterative Method for Solving a System of Mixed Equilibrium Problems, System of Quasivariational Inclusions, and Fixed Point Problems of Nonexpansive Semigroups with Application to Optimization Problems

    Directory of Open Access Journals (Sweden)

    Pongsakorn Sunthrayuth

    2012-01-01

    Full Text Available We introduce a general implicit iterative scheme base on viscosity approximation method with a ϕ-strongly pseudocontractive mapping for finding a common element of the set of solutions for a system of mixed equilibrium problems, the set of common fixed point for a nonexpansive semigroup, and the set of solutions of system of variational inclusions with set-valued maximal monotone mapping and Lipschitzian relaxed cocoercive mappings in Hilbert spaces. Furthermore, we prove that the proposed iterative algorithm converges strongly to a common element of the above three sets, which is a solution of the optimization problem related to a strongly positive bounded linear operator.

  1. A versatile method for simultaneous stable carbon isotope analysis of DNA and RNA nucleotides by liquid chromatography/isotope ratio mass spectrometry

    NARCIS (Netherlands)

    Moerdijk-Poortvliet, T.C.W.; Brasser, J.; de Ruiter, G.; Houtekamer, M.; Bolhuis, H.; Stal, L.J.; Boschker, H.T.S.

    2014-01-01

    RATIONALE Liquid chromatography/isotope ratio mass spectrometry (LC/IRMS) is currently the most accurate and precise technique for the measurement of compound-specific stable carbon isotope ratios (13C/12C) in biological metabolites, at their natural abundance. However, until now this technique coul

  2. A versatile method for simultaneous stable carbon isotope analysis of DNA and RNA nucleotides by liquid chromatography/isotope ratio mass spectrometry

    NARCIS (Netherlands)

    Moerdijk-Poortvliet, T.C.W.; Brasser, J.; de Ruiter, G.; Houtekamer, M.; Bolhuis, H.; Stal, L.J.; Boschker, H.T.S.

    2014-01-01

    RATIONALELiquid chromatography/isotope ratio mass spectrometry (LC/IRMS) is currently the most accurate and precise technique for the measurement of compound-specific stable carbon isotope ratios (C-13/C-12) in biological metabolites, at their natural abundance. However, until now this technique cou

  3. Non-equilibrium phase transitions

    CERN Document Server

    Henkel, Malte; Lübeck, Sven

    2009-01-01

    This book describes two main classes of non-equilibrium phase-transitions: (a) static and dynamics of transitions into an absorbing state, and (b) dynamical scaling in far-from-equilibrium relaxation behaviour and ageing. The first volume begins with an introductory chapter which recalls the main concepts of phase-transitions, set for the convenience of the reader in an equilibrium context. The extension to non-equilibrium systems is made by using directed percolation as the main paradigm of absorbing phase transitions and in view of the richness of the known results an entire chapter is devoted to it, including a discussion of recent experimental results. Scaling theories and a large set of both numerical and analytical methods for the study of non-equilibrium phase transitions are thoroughly discussed. The techniques used for directed percolation are then extended to other universality classes and many important results on model parameters are provided for easy reference.

  4. An upwind, kinetic flux-vector splitting method for flows in chemical and thermal non-equilibrium

    Science.gov (United States)

    Eppard, W. M.; Grossman, B.

    1993-01-01

    We have developed new upwind kinetic difference schemes for flows with non-equilibrium thermodynamics and chemistry. These schemes are derived from the Boltzmann equation with the resulting Euler schemes developed as moments of the discretized Boltzmann scheme with a locally Maxwellian velocity distribution. Splitting the velocity distribution at the Boltzmann level is seen to result in a flux-split Euler scheme and is called Kinetic Flux Vector Splitting (KFVS). Extensions to flows with finite-rate chemistry and vibrational relaxation is accomplished utilizing nonequilibrium kinetic theory. Computational examples are presented comparing KFVS with the schemes of Van Leer and Roe for a quasi-one-dimensional flow through a supersonic diffuser, inviscid flow through two-dimensional inlet, and viscous flow over a cone at zero angle-of-attack. Calculations are also shown for the transonic flow over a bump in a channel and the transonic flow over an NACA 0012 airfoil. The results show that even though the KFVS scheme is a Riemann solver at the kinetic level, its behavior at the Euler level is more similar to the existing flux-vector splitting algorithms than to the flux-difference splitting scheme of Roe.

  5. Toroidal figures of equilibrium from a 2nd-order accurate, accelerated SCF-method with subgrid approach

    CERN Document Server

    Huré, J -M

    2016-01-01

    We compute the structure of a self-gravitating torus with polytropic equation-of-state (EOS) rotating in an imposed centrifugal potential. The Poisson-solver is based on isotropic multigrid with optimal covering factor (fluid section-to-grid area ratio). We work at $2$nd-order in the grid resolution for both finite difference and quadrature schemes. For soft EOS (i.e. polytropic index $n \\ge 1$), the underlying $2$nd-order is naturally recovered for Boundary Values (BVs) and any other integrated quantity sensitive to the mass density (mass, angular momentum, volume, Virial Parameter, etc.), i.e. errors vary with the number $N$ of nodes per direction as $\\sim 1/N^2$. This is, however, not observed for purely geometrical quantities (surface area, meridional section area, volume), unless a subgrid approach is considered (i.e. boundary detection). Equilibrium sequences are also much better described, especially close to critical rotation. Yet another technical effort is required for hard EOS ($n < 1$), due to ...

  6. An upwind, kinetic flux-vector splitting method for flows in chemical and thermal non-equilibrium

    Science.gov (United States)

    Eppard, W. M.; Grossman, B.

    1993-01-01

    We have developed new upwind kinetic difference schemes for flows with non-equilibrium thermodynamics and chemistry. These schemes are derived from the Boltzmann equation with the resulting Euler schemes developed as moments of the discretized Boltzmann scheme with a locally Maxwellian velocity distribution. Splitting the velocity distribution at the Boltzmann level is seen to result in a flux-split Euler scheme and is called Kinetic Flux Vector Splitting (KFVS). Extensions to flows with finite-rate chemistry and vibrational relaxation is accomplished utilizing nonequilibrium kinetic theory. Computational examples are presented comparing KFVS with the schemes of Van Leer and Roe for a quasi-one-dimensional flow through a supersonic diffuser, inviscid flow through two-dimensional inlet, and viscous flow over a cone at zero angle-of-attack. Calculations are also shown for the transonic flow over a bump in a channel and the transonic flow over an NACA 0012 airfoil. The results show that even though the KFVS scheme is a Riemann solver at the kinetic level, its behavior at the Euler level is more similar to the existing flux-vector splitting algorithms than to the flux-difference splitting scheme of Roe.

  7. Analysis Method of 241Pu Radioactivity by Isotope Dilution-Extraction Liquid Scintillation Spectrometer

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    <正>241Pu is the only pure β emitter with the maximum energy of 20.81 keV in plutonium isotopes of 238Pu, 239Pu, 240Pu and 242Pu, in which 241Pu is mostly specific radioactivity because its half-life is 14.29 a.

  8. Comparison of a Label-Free Quantitative Proteomic Method Based on Peptide Ion Current Area to the Isotope Coded Affinity Tag Method

    Directory of Open Access Journals (Sweden)

    Young Ah Goo

    2008-01-01

    Full Text Available Recently, several research groups have published methods for the determination of proteomic expression profiling by mass spectrometry without the use of exogenously added stable isotopes or stable isotope dilution theory. These so-called label-free, methods have the advantage of allowing data on each sample to be acquired independently from all other samples to which they can later be compared in silico for the purpose of measuring changes in protein expression between various biological states. We developed label free software based on direct measurement of peptide ion current area (PICA and compared it to two other methods, a simpler label free method known as spectral counting and the isotope coded affinity tag (ICAT method. Data analysis by these methods of a standard mixture containing proteins of known, but varying, concentrations showed that they performed similarly with a mean squared error of 0.09. Additionally, complex bacterial protein mixtures spiked with known concentrations of standard proteins were analyzed using the PICA label-free method. These results indicated that the PICA method detected all levels of standard spiked proteins at the 90% confidence level in this complex biological sample. This finding confirms that label-free methods, based on direct measurement of the area under a single ion current trace, performed as well as the standard ICAT method. Given the fact that the label-free methods provide ease in experimental design well beyond pair-wise comparison, label-free methods such as our PICA method are well suited for proteomic expression profiling of large numbers of samples as is needed in clinical analysis.

  9. Continuous flow stable isotope methods for study of δ13C fractionation during halomethane production and degradation

    Science.gov (United States)

    Kalin, Robert M.; Hamilton, John T.G.; Harper, David B.; Miller, Laurence G.; Lamb, Clare; Kennedy, James T.; Downey, Angela; McCauley, Sean; Goldstein, Allen H.

    2001-01-01

    Gas chromatography/mass spectrometry/isotope ratio mass spectrometry (GC/MS/IRMS) methods for δ13C measurement of the halomethanes CH3Cl, CH3Br, CH3I and methanethiol (CH3SH) during studies of their biological production, biological degradation, and abiotic reactions are presented. Optimisation of gas chromatographic parameters allowed the identification and quantification of CO2, O2, CH3Cl, CH3Br, CH3I and CH3SH from a single sample, and also the concurrent measurement of δ13C for each of the halomethanes and methanethiol. Precision of δ13C measurements for halomethane standards decreased (±0.3, ±0.5 and ±1.3‰) with increasing mass (CH3Cl, CH3Br, CH3I, respectively). Given that carbon isotope effects during biological production, biological degradation and some chemical (abiotic) reactions can be as much as 100‰, stable isotope analysis offers a precise method to study the global sources and sinks of these halogenated compounds that are of considerable importance to our understanding of stratospheric ozone destruction. 

  10. Method for the isolation of citric acid and malic acid in Japanese apricot liqueur for carbon stable isotope analysis.

    Science.gov (United States)

    Akamatsu, Fumikazu; Hashiguchi, Tomokazu; Hisatsune, Yuri; Oe, Takaaki; Kawao, Takafumi; Fujii, Tsutomu

    2017-02-15

    A method for detecting the undeclared addition of acidic ingredients is required to control the authenticity of Japanese apricot liqueur. We developed an analytical procedure that minimizes carbon isotope discrimination for measurement of the δ(13)C values of citric and malic acid isolated from Japanese apricot liqueur. Our results demonstrated that freeze-drying is preferable to nitrogen spray-drying, because it does not significantly affect the δ(13)C values of citric acid and results in smaller isotope discrimination for malic acid. Both 0.1% formic acid and 0.2% phosphoric acid are acceptable HPLC mobile phases for the isolation of citric and malic acid, although the δ(13)C values of malic acid exhibited relatively large variation compared with citric acid following isolation using either mobile phase. The developed procedure allows precise δ(13)C measurements of citric and malic acid isolated from Japanese apricot liqueur.

  11. Organic Tank Safety Project: development of a method to measure the equilibrium water content of Hanford organic tank wastes and demonstration of method on actual waste

    Energy Technology Data Exchange (ETDEWEB)

    Scheele, R.D.; Bredt, P.R.; Sell, R.L.

    1996-09-01

    Some of Hanford`s underground waste storage tanks contain Organic- bearing high level wastes that are high priority safety issues because of potentially hazardous chemical reactions of organics with inorganic oxidants in these wastes such as nitrates and nitrites. To ensure continued safe storage of these wastes, Westinghouse Hanford Company has placed affected tanks on the Organic Watch List and manages them under special rules. Because water content has been identified as the most efficient agent for preventing a propagating reaction and is an integral part of the criteria developed to ensure continued safe storage of Hanford`s organic-bearing radioactive tank wastes, as part of the Organic Tank Safety Program the Pacific Northwest National Laboratory developed and demonstrated a simple and easily implemented procedure to determine the equilibrium water content of these potentially reactive wastes exposed to the range of water vapor pressures that might be experienced during the wastes` future storage. This work focused on the equilibrium water content and did not investigate the various factors such as @ ventilation, tank surface area, and waste porosity that control the rate that the waste would come into equilibrium, with either the average Hanford water partial pressure 5.5 torr or other possible water partial pressures.

  12. Isotopes in heterogeneous catalysis

    CERN Document Server

    Hargreaves, Justin SJ

    2006-01-01

    The purpose of this book is to review the current, state-of-the-art application of isotopic methods to the field of heterogeneous catalysis. Isotopic studies are arguably the ultimate technique in in situ methods for heterogeneous catalysis. In this review volume, chapters have been contributed by experts in the field and the coverage includes both the application of specific isotopes - Deuterium, Tritium, Carbon-14, Sulfur-35 and Oxygen-18 - as well as isotopic techniques - determination of surface mobility, steady state transient isotope kinetic analysis, and positron emission profiling.

  13. Problems in equilibrium theory

    CERN Document Server

    Aliprantis, Charalambos D

    1996-01-01

    In studying General Equilibrium Theory the student must master first the theory and then apply it to solve problems. At the graduate level there is no book devoted exclusively to teaching problem solving. This book teaches for the first time the basic methods of proof and problem solving in General Equilibrium Theory. The problems cover the entire spectrum of difficulty; some are routine, some require a good grasp of the material involved, and some are exceptionally challenging. The book presents complete solutions to two hundred problems. In searching for the basic required techniques, the student will find a wealth of new material incorporated into the solutions. The student is challenged to produce solutions which are different from the ones presented in the book.

  14. Can a combination of the conformal thin-sandwich and puncture methods yield binary black hole solutions in quasi-equilibrium?

    CERN Document Server

    Hannam, M D; Cook, G B; Baumgarte, T W; Hannam, Mark D.; Evans, Charles R.; Cook, Gregory B.; Baumgarte, Thomas W.

    2003-01-01

    We consider combining two important methods for constructing quasi-equilibrium initial data for binary black holes: the conformal thin-sandwich formalism and the puncture method. The former seeks to enforce stationarity in the conformal three-metric and the latter attempts to avoid internal boundaries, like minimal surfaces or apparent horizons. We show that these two methods make partially conflicting requirements on the boundary conditions that determine the time slices. In particular, it does not seem possible to construct slices that are quasi-stationary and avoid physical singularities and simultaneously are connected by an everywhere positive lapse function, a condition which must obtain if internal boundaries are to be avoided. Some relaxation of these conflicting requirements may yield a soluble system, but some of the advantages that were sought in combining these approaches will be lost.

  15. Determination of (241)Pu by the method of disturbed radioactive equilibrium using 2πα-counting and precision gamma-spectrometry.

    Science.gov (United States)

    Alekseev, I; Kuzmina, T

    2016-04-01

    A simple technique is proposed for the determination of the content of (241)Pu, which is based on disturbance of radioactive equilibrium in the genetically related (237)U←(241)Pu→(241)Am decay chain of radionuclides, with the subsequent use of 2πα-counting and precision gamma-spectroscopy for monitoring the process of restoration of that equilibrium. It has been shown that the data on dynamics of accumulation of the daughter (241)Am, which were obtained from the results of measurements of α- and γ-spectra of the samples, correspond to the estimates calculated for the chain of two genetically related radionuclides, the differences in the estimates of (241)Pu radioactivity not exceeding 2%. Combining the different methods of registration (2πα-counting, semiconductor alpha- and gamma-spectrometry) enables the proposed method to be efficiently applied both for calibration of (241)Pu-sources (from several hundreds of kBq and higher) and for radioisotopic analysis of plutonium mixtures. In doing so, there is a deep purification of (241)Pu from its daughter decay products required due to unavailability of commercial detectors that could make it possible, based only on analysis of alpha-spectra, to conduct quantitative analysis of the content of (238)Pu and (241)Am.

  16. Influence analysis of slope stability based on limit equilibrium method%极限平衡法对边坡稳定性影响分析

    Institute of Scientific and Technical Information of China (English)

    隋来才

    2015-01-01

    EX3 examination of ACADS ( soft and weak interlayers slope) is analysed by limit equilibrium calculation software LIZHENG geotech-nical, GEO-Studios and Slide. While the stability coefficient of basically the same, the sliding surface is slightly different calculated by three kinds of software support various limit equilibrium method. The slope stability coefficient of circular-arc and polygonal sliding surface are different in soft and weak interlayers analysis, circular-arc slip surface is not recommended, the US army corps engineers and lowe-karafiath method also should be carefully used.%利用理正岩土,GEO-Studio,Slide三种极限平衡计算软件对ACADS的EX3考题(存在软弱夹层边坡)进行分析,指出对于三种软件支持的各种极限平衡法的稳定性系数基本相同,滑动面略有不同。在进行存在软弱滑动面边坡稳定性分析时,折线形滑动面与圆弧形滑动面稳定性系数相差较大,不适宜使用圆弧形滑动面,同时陆军工程师团法和罗厄法也应谨慎使用。

  17. Thermochemical parameters of minerals from oxygen-buffered hydrothermal equilibrium data: Method, application to annite and almandine

    Science.gov (United States)

    Zen, E.-A.

    1973-01-01

    Reversed univariant hydrothermal phase-equilibrium reactions, in which a redox reaction occurs and is controlled by oxygen buffers, can be used to extract thermochemical data on minerals. The dominant gaseous species present, even for relatively oxidizing buffers such as the QFM buffer, are H2O and H2; the main problem is to calculate the chemical potentials of these components in a binary mixture. The mixing of these two species in the gas phase was assumed by Eugster and Wones (1962) to be ideal; this assumption allows calculation of the chemical potentials of the two components in a binary gas mixture, using data in the literature. A simple-mixture model of nonideal mixing, such as that proposed by Shaw (1967), can also be combined with the equations of state for oxygen buffers to permit derivation of the chemical potentials of the two components. The two mixing models yield closely comparable results for the more oxidizing buffers such as the QFM buffer. For reducing buffers such as IQF, the nonideal-mixing correction can be significant and the Shaw model is better. The procedure of calculation of mineralogical thermochemical data, in reactions where hydrogen and H2O simultaneously appear, is applied to the experimental data on annite, given by Wones et al. (1971), and on almandine, given by Hsu (1968). For annite the results are: Standard entropy of formation from the elements, Sf0 (298, 1)=-283.35??2.2 gb/gf, S0 (298, 1) =+92.5 gb/gf. Gf0 (298, 1)=-1148.2??6 kcal, and Hf0 (298, 1)=-1232.7??7 kcal. For almandine, the calculation takes into account the mutual solution of FeAl2O4 (Hc) in magnetite and of Fe3O4 (Mt) in hercynite and the temperature dependence of this solid solution, as given by Turnock and Eugster (1962); the calculations assume a regular-solution model for this binary spinel system. The standard entropy of formation of almandine, Sf,A0 (298, 1) is -272.33??3 gb/gf. The third law entropy, S0 (298, 1) is +68.3??3 gb/gf, a value much less than the

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

    Science.gov (United States)

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

    2014-02-15

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

  19. Effects of preservation methods of muscle tissue from upper-trophic level reef fishes on stable isotope values (δ13C and δ15N

    Directory of Open Access Journals (Sweden)

    Christopher D. Stallings

    2015-03-01

    Full Text Available Research that uses stable isotope analysis often involves a delay between sample collection in the field and laboratory processing, therefore requiring preservation to prevent or reduce tissue degradation and associated isotopic compositions. Although there is a growing literature describing the effects of various preservation techniques, the results are often contextual, unpredictable and vary among taxa, suggesting the need to treat each species individually. We conducted a controlled experiment to test the effects of four preservation methods of muscle tissue from four species of upper trophic-level reef fish collected from the eastern Gulf of Mexico (Red Grouper Epinephelus morio, Gag Mycteroperca microlepis, Scamp Mycteroperca phenax, and Red Snapper Lutjanus campechanus. We used a paired design to measure the effects on isotopic values for carbon and nitrogen after storage using ice, 95% ethanol, and sodium chloride (table salt, against that in a liquid nitrogen control. Mean offsets for both δ13C and δ15N values from controls were lowest for samples preserved on ice, intermediate for those preserved with salt, and highest with ethanol. Within species, both salt and ethanol significantly enriched the δ15N values in nearly all comparisons. Ethanol also had strong effects on the δ13C values in all three groupers. Conversely, for samples preserved on ice, we did not detect a significant offset in either isotopic ratio for any of the focal species. Previous studies have addressed preservation-induced offsets in isotope values using a mass balance correction that accounts for changes in the isotope value to that in the C/N ratio. We tested the application of standard mass balance corrections for isotope values that were significantly affected by the preservation methods and found generally poor agreement between corrected and control values. The poor performance by the correction may have been due to preferential loss of lighter isotopes

  20. Effects of preservation methods of muscle tissue from upper-trophic level reef fishes on stable isotope values (δ13C and δ15N)

    Science.gov (United States)

    Nelson, James A.; Rozar, Katherine L.; Adams, Charles S.; Wall, Kara R.; Switzer, Theodore S.; Winner, Brent L.; Hollander, David J.

    2015-01-01

    Research that uses stable isotope analysis often involves a delay between sample collection in the field and laboratory processing, therefore requiring preservation to prevent or reduce tissue degradation and associated isotopic compositions. Although there is a growing literature describing the effects of various preservation techniques, the results are often contextual, unpredictable and vary among taxa, suggesting the need to treat each species individually. We conducted a controlled experiment to test the effects of four preservation methods of muscle tissue from four species of upper trophic-level reef fish collected from the eastern Gulf of Mexico (Red Grouper Epinephelus morio, Gag Mycteroperca microlepis, Scamp Mycteroperca phenax, and Red Snapper Lutjanus campechanus). We used a paired design to measure the effects on isotopic values for carbon and nitrogen after storage using ice, 95% ethanol, and sodium chloride (table salt), against that in a liquid nitrogen control. Mean offsets for both δ13C and δ15N values from controls were lowest for samples preserved on ice, intermediate for those preserved with salt, and highest with ethanol. Within species, both salt and ethanol significantly enriched the δ15N values in nearly all comparisons. Ethanol also had strong effects on the δ13C values in all three groupers. Conversely, for samples preserved on ice, we did not detect a significant offset in either isotopic ratio for any of the focal species. Previous studies have addressed preservation-induced offsets in isotope values using a mass balance correction that accounts for changes in the isotope value to that in the C/N ratio. We tested the application of standard mass balance corrections for isotope values that were significantly affected by the preservation methods and found generally poor agreement between corrected and control values. The poor performance by the correction may have been due to preferential loss of lighter isotopes and corresponding

  1. Effects of preservation methods of muscle tissue from upper-trophic level reef fishes on stable isotope values (δ (13)C and δ (15)N).

    Science.gov (United States)

    Stallings, Christopher D; Nelson, James A; Rozar, Katherine L; Adams, Charles S; Wall, Kara R; Switzer, Theodore S; Winner, Brent L; Hollander, David J

    2015-01-01

    Research that uses stable isotope analysis often involves a delay between sample collection in the field and laboratory processing, therefore requiring preservation to prevent or reduce tissue degradation and associated isotopic compositions. Although there is a growing literature describing the effects of various preservation techniques, the results are often contextual, unpredictable and vary among taxa, suggesting the need to treat each species individually. We conducted a controlled experiment to test the effects of four preservation methods of muscle tissue from four species of upper trophic-level reef fish collected from the eastern Gulf of Mexico (Red Grouper Epinephelus morio, Gag Mycteroperca microlepis, Scamp Mycteroperca phenax, and Red Snapper Lutjanus campechanus). We used a paired design to measure the effects on isotopic values for carbon and nitrogen after storage using ice, 95% ethanol, and sodium chloride (table salt), against that in a liquid nitrogen control. Mean offsets for both δ (13)C and δ (15)N values from controls were lowest for samples preserved on ice, intermediate for those preserved with salt, and highest with ethanol. Within species, both salt and ethanol significantly enriched the δ (15)N values in nearly all comparisons. Ethanol also had strong effects on the δ (13)C values in all three groupers. Conversely, for samples preserved on ice, we did not detect a significant offset in either isotopic ratio for any of the focal species. Previous studies have addressed preservation-induced offsets in isotope values using a mass balance correction that accounts for changes in the isotope value to that in the C/N ratio. We tested the application of standard mass balance corrections for isotope values that were significantly affected by the preservation methods and found generally poor agreement between corrected and control values. The poor performance by the correction may have been due to preferential loss of lighter isotopes and

  2. A Viscosity Hybrid Steepest Descent Method for Equilibrium Problems, Variational Inequality Problems, and Fixed Point Problems of Infinite Family of Strictly Pseudocontractive Mappings and Nonexpansive Semigroup

    Directory of Open Access Journals (Sweden)

    Haitao Che

    2013-01-01

    Full Text Available In this paper, modifying the set of variational inequality and extending the nonexpansive mapping of hybrid steepest descent method to nonexpansive semigroups, we introduce a new iterative scheme by using the viscosity hybrid steepest descent method for finding a common element of the set of solutions of a system of equilibrium problems, the set of fixed points of an infinite family of strictly pseudocontractive mappings, the set of solutions of fixed points for nonexpansive semigroups, and the sets of solutions of variational inequality problems with relaxed cocoercive mapping in a real Hilbert space. We prove that the sequence converges strongly to a common element of the above sets under some mild conditions. The results shown in this paper improve and extend the recent ones announced by many others.

  3. Capture and isotopic exchange method for water and hydrogen isotopes on zeolite catalysts up to technical scale for pre-study of processing highly tritiated water

    Energy Technology Data Exchange (ETDEWEB)

    Michling, R.; Braun, A.; Cristescu, I.; Dittrich, H.; Gramlich, N.; Lohr, N. [Karlsruhe Institute of Technology, Eggenstein-Leopoldshafen (Germany); Glugla, M.; Shu, W.; Willms, S. [ITER Organization, Saint-Paul-lez-Durance (France)

    2015-03-15

    Highly tritiated water (HTW) may be generated at ITER by various processes and, due to the excessive radio toxicity, the self-radiolysis and the exceedingly corrosive property of HTW, a potential hazard is associated with its storage and process. Therefore, the capture and exchange method for HTW utilizing Molecular Sieve Beds (MSB) was investigated in view of adsorption capacity, isotopic exchange performance and process parameters. For the MSB, different types of zeolite were selected. All zeolite materials were additionally coated with platinum. The following work comprised the selection of the most efficient zeolite candidate based on detailed parametric studies during the H{sub 2}/D{sub 2}O laboratory scale exchange experiments (about 25 g zeolite per bed) at the Tritium Laboratory Karlsruhe (TLK). For the zeolite, characterization analytical techniques such as Infrared Spectroscopy, Thermogravimetry and online mass spectrometry were implemented. Followed by further investigation of the selected zeolite catalyst under full technical operation, a MSB (about 22 kg zeolite) was processed with hydrogen flow rates up to 60 mol*h{sup -1} and deuterated water loads up to 1.6 kg in view of later ITER processing of arising HTW. (authors)

  4. 广义平衡与不动点问题的黏性逼近%Viscosity Approximation Method for Generallized Equilibrium Problems and Fixed Point Problems

    Institute of Scientific and Technical Information of China (English)

    赵良才; 张石生

    2012-01-01

    本文的目的是在Hilbert空间中引入和研究了一种新的迭代序列,用以寻求具逆-强单调映象的广义平衡问题的解集与无限簇非扩张映象的不动点集的公共元.在适当的条件下,用黏性逼近法证明了逼近于这一公共元的强收敛定理.应用该结论,我们证明了逼近于平衡问题和变分不等式问题的强收敛定理.所得结果改进和推广了文献的相应结果.%The purpose of this paper is to introduce a new iterative scheme for finding a common element of the set of solutions of a generalized equilibrium problem with inverse-strongly monotone mapping and the set of common fixed point for a family of infinite nonexpansive mappings in Hilbert space. It is shown that under suitable conditions by the viscosity approximation methods, some strong convergence theorems for approximating to this common elements are proved. Using this result, we prove two new strong convergence theorems in equilibrium problems and variational inequalities. The results presented in the paper extend and improve some recent results.

  5. Linear and Nonlinear Regression Methods for Equilibrium Modelling of p-Nitrophenol Biosorption by Rhizopus oryzae: Comparison of Error Analysis Criteria

    Directory of Open Access Journals (Sweden)

    Zvezdelina Lyubenova Yaneva

    2013-01-01

    Full Text Available The study assessed the applicability of Rhizopus oryzae dead fungi as a biosorbent medium for p-nitrophenol (p-NP removal from aqueous phase. The extent of biosorption was measured through five equilibrium sorption isotherms represented by the Langmuir, Freundlich, Redlich-Peterson, multilayer and Fritz-Schlunder models. Linear and nonlinear regression methods were compared to determine the best-fitting equilibrium model to the experimental data. A detailed error analysis was undertaken to investigate the effect of applying seven error criteria for the determination of the single-component isotherm parameters. According to the comparison of the error functions and to the estimation of the corrected Akaike information criterion (, the Freundlich equation was ranked as the first and the Fritz-Schlunder as the second best-fitting models describing the experimental data. The present investigations proved the high efficiency (94% of Rhizopus Oryzae as an alternative adsorbent for p-NP removal from aqueous phase and revealed the mechanism of the separation process.

  6. New treatment method for boron in aqueous solutions using Mg–Al layered double hydroxide: Kinetics and equilibrium studies

    Energy Technology Data Exchange (ETDEWEB)

    Kameda, Tomohito, E-mail: kameda@env.che.tohoku.ac.jp; Oba, Jumpei; Yoshioka, Toshiaki

    2015-08-15

    Highlights: • NO{sub 3}·Mg–Al LDHs and Cl·Mg–Al LDHs could take up boron from aqueous solutions. • Boron was removed by anion exchange of B(OH){sub 4}{sup −} with intercalated NO{sub 3}{sup −} and Cl{sup −}. • The residual concentration of B was less than the effluent standards in Japan. • The removal of B was well described by a pseudo second-order kinetic equation. • The adsorption of B followed a Langmuir-type adsorption. - Abstract: Mg–Al layered double hydroxides (LDHs) intercalated with NO{sub 3}{sup −} (NO{sub 3}·Mg–Al LDHs) and with Cl{sup −} (Cl·Mg–Al LDHs) were found to take up boron from aqueous solutions. Boron was removed by anion exchange of B(OH){sub 4}{sup −} in solution with NO{sub 3}{sup −} and Cl{sup −} intercalated in the interlayer of the LDH. Using three times the stoichiometric quantity of NO{sub 3}·Mg–Al LDH, the residual concentration of B decreased from 100 to 1.9 mg L{sup −1} in 120 min. Using five times the stoichiometric quantity of Cl·Mg–Al LDH, the residual concentration of B decreased from 100 to 5.6 mg L{sup −1} in 120 min. It must be emphasized that, in both cases, the residual concentration of B was less than the effluent standards in Japan (10 mg L{sup −1}). The rate-determining step of B removal by the NO{sub 3}·Mg–Al and Cl·Mg–Al LDHs was found to be chemical adsorption involving anion exchange of B(OH){sub 4}{sup −} with intercalated NO{sub 3}{sup −} and Cl{sup −}. The removal of B was well described by a pseudo second-order kinetic equation. The adsorption of B by NO{sub 3}·Mg–Al LDH and Cl·Mg–Al LDH followed a Langmuir-type adsorption. The values of the maximum adsorption and the equilibrium adsorption constant were 3.6 mmol g{sup −1} and 1.7, respectively, for NO{sub 3}·Mg–Al LDH, and 3.8 mmol g{sup −1} and 0.7, respectively, for Cl·Mg–Al LDH. The B(OH){sub 4}{sup −} in B(OH){sub 4}·Mg–Al LDH produced by removal of B was found to undergo

  7. Concurrent fractional and equilibrium crystallisation

    Science.gov (United States)

    Sha, Lian-Kun

    2012-06-01

    This paper proposes the concept of concurrent fractional and equilibrium crystallisation (CFEC) in a multi-phase magmatic system in light of experimental results on diffusivities of elements and other species in minerals and melts. A group of equations are presented to describe how the concentrations of an element or isotope change in fractionated solid, equilibrated solid, melt, liquid, and gas phases, as well as in magma, as a function of distribution coefficients and mass fractions during the CFEC process. CFEC model is a generalised and unified formulation that is valid, not only for pure fractional crystallisation (FC) and perfect equilibrium crystallisation (EC) singly, as two of its limiting end-member cases, but also for the geologically more important process of concurrent fractional and equilibrium crystallisation. The concept that both fractional and equilibrium crystallisation can operate concurrently in a magmatic system, for a given element, among different minerals, and even within different-sized crystal grains of the very same mineral phase, is of fundamental importance in deepening our current understanding of magmatic differentiation processes. CFEC probably occurs more frequently in the natural world than either pure fractional or perfect equilibrium crystallisation alone, as a result of the interplay of varying diffusivities of elements under diverse physicochemical conditions, different residence time and growth rates of mineral phases in magmas, and varying grain sizes within each phase and among different phases. The marked systematic variations in trace element concentrations in the melts of the Bishop Tuff have long been perplexing and difficult to reconcile with existing models of differentiation. CFEC, which is able to better explain the scatter trends in a systematic way than fractional crystallisation, is considered to be the cause.

  8. N-methylputrescine oxidation during cocaine biosynthesis: study of prochiral methylene hydrogen discrimination using the remote isotope method.

    Science.gov (United States)

    Hoye, T R; Bjorklund, J A; Koltun, D O; Renner, M K

    2000-01-01

    [structure: see text] The stereoselectivity of N-methylputrescine (3) oxidation to pyrrolinium ion 4 in Erythroxylum coca during cocaine (1) biosynthesis was studied. The remote isotope method was used to advantage. Each enantiomer of 4-monodeuterated N-methylputrescine served as a precursor for plant feeding. To facilitate mass-spectrometric analysis of products, a 2H3 13C-methyl group was also incorporated into the 4-deuterio-N-methylputrescines. Oxidative deamination of N-methylputrescine was found to be stereoselective; the pro-S hydrogen atom is removed with 6-10:1 selectivity.

  9. Stable isotope phenotyping via cluster analysis of NanoSIMS data as a method for characterizing distinct microbial ecophysiologies and sulfur-cycling in the environment

    Directory of Open Access Journals (Sweden)

    Katherine S Dawson

    2016-05-01

    Full Text Available Stable isotope probing (SIP is a valuable tool for gaining insights into ecophysiology and biogeochemical cycling of environmental microbial communities by tracking isotopically labeled compounds into cellular macromolecules as well as into byproducts of respiration. SIP, in conjunction with nanoscale secondary ion mass spectrometry (NanoSIMS, allows for the visualization of isotope incorporation at the single cell level. In this manner, both active cells within a diverse population as well as heterogeneity in metabolism within a homogeneous population can be observed. The ecophysiological implications of these single cell stable isotope measurements are often limited to the taxonomic resolution of paired fluorescence in situ hybridization (FISH microscopy. Here we introduce a taxonomy-independent method using multi-isotope SIP and NanoSIMS for identifying and grouping phenotypically similar microbial cells by their chemical and isotopic fingerprint. This method was applied to SIP experiments in a sulfur-cycling biofilm collected from sulfidic intertidal vents amended with 13C-acetate, 15N-ammonium, and 33S-sulfate. Using a cluster analysis technique based on fuzzy c-means to group cells according to their isotope (13C/12C, 15N/14N, and 33S/32S and elemental ratio (C/CN and S/CN profiles, our analysis partitioned ~2200 cellular regions of interest (ROIs into 5 distinct groups. These isotope phenotype groupings are reflective of the variation in labeled substrate uptake by cells in a multispecies metabolic network dominated by Gamma- and Deltaproteobacteria. Populations independently grouped by isotope phenotype were subsequently compared with paired FISH data, demonstrating a single coherent deltaproteobacterial cluster and multiple gammaproteobacterial groups, highlighting the distinct ecophysiologies of spatially-associated microbes within the sulfur-cycling biofilm from White Point Beach, CA.

  10. Stable isotope phenotyping via cluster analysis of NanoSIMS data as a method for characterizing distinct microbial ecophysiologies and sulfur-cycling in the environment

    Science.gov (United States)

    Dawson, K.; Scheller, S.; Dillon, J. G.; Orphan, V. J.

    2016-12-01

    Stable isotope probing (SIP) is a valuable tool for gaining insights into ecophysiology and biogeochemical cycling of environmental microbial communities by tracking isotopically labeled compounds into cellular macromolecules as well as into byproducts of respiration. SIP, in conjunction with nanoscale secondary ion mass spectrometry (NanoSIMS), allows for the visualization of isotope incorporation at the single cell level. In this manner, both active cells within a diverse population as well as heterogeneity in metabolism within a homogeneous population can be observed. The ecophysiological implications of these single cell stable isotope measurements are often limited to the taxonomic resolution of paired fluorescence in situ hybridization (FISH) microscopy. Here we introduce a taxonomy-independent method using multi-isotope SIP and NanoSIMS for identifying and grouping phenotypically similar microbial cells by their chemical and isotopic fingerprint. This method was applied to SIP experiments in a sulfur-cycling biofilm collected from sulfidic intertidal vents amended with 13C-acetate, 15N-ammonium, and 33S-sulfate. Using a cluster analysis technique based on fuzzy c-means to group cells according to their isotope (13C/12C, 15N/14N, and 33S/32S) and elemental ratio (C/CN and S/CN) profiles, our analysis partitioned 2200 cellular regions of interest (ROIs) into 5 distinct groups. These isotope phenotype groupings are reflective of the variation in labeled substrate uptake by cells in a multispecies metabolic network dominated by Gamma- and Deltaproteobacteria. Populations independently grouped by isotope phenotype were subsequently compared with paired FISH data, demonstrating a single coherent deltaproteobacterial cluster and multiple gammaproteobacterial groups, highlighting the distinct ecophysiologies of spatially-associated microbes within the sulfur-cycling biofilm from White Point Beach, CA.

  11. 1-D EQUILIBRIUM DISCRETE DIFFUSION MONTE CARLO

    Energy Technology Data Exchange (ETDEWEB)

    T. EVANS; ET AL

    2000-08-01

    We present a new hybrid Monte Carlo method for 1-D equilibrium diffusion problems in which the radiation field coexists with matter in local thermodynamic equilibrium. This method, the Equilibrium Discrete Diffusion Monte Carlo (EqDDMC) method, combines Monte Carlo particles with spatially discrete diffusion solutions. We verify the EqDDMC method with computational results from three slab problems. The EqDDMC method represents an incremental step toward applying this hybrid methodology to non-equilibrium diffusion, where it could be simultaneously coupled to Monte Carlo transport.

  12. Linear Algebra Aspects in the Equilibrium-Based Implementation of Finite/Boundary Element Methods for FGMs

    Science.gov (United States)

    Dumont, Ney Augusto

    2008-02-01

    The paper briefly outlines the conventional and three variational implementations of the boundary element method, pointing out the conceptual imbrications of their constituent matrices. The nature of fundamental solutions is investigated in terms of the resulting matrix spectral properties, as applied to multiply-connected domains, reentering corners and FGMs.

  13. Lifetimes in neutron-rich Nd isotopes measured by Doppler profile method

    Energy Technology Data Exchange (ETDEWEB)

    Ahmad, I.; Lister, C.J.; Morss, L.R. [and others

    1995-08-01

    Lifetimes of the rotational levels in neutron-rich even-even Nd isotopes were deduced from the analysis of the Doppler broadened line shapes. The experiment was performed at Daresbury with the Eurogam array, which at that time consisted of 45 Compton-suppressed Ge detectors and 5 Low-Energy Photon Spectrometers. The source was in the form of a 7-mm pellet which was prepared by mixing 5-mg; {sup 248}Cm and 65-mg KCl and pressing it under high pressure. Events for which three or more detectors fired were used to construct a cubic data array whose axes represented the {gamma}-ray energies and the contents of each channel the number of events with that particular combination of {gamma}-ray energies. From this cubic array, one-dimensional spectra were generated by placing gates on peaks on the other two axes. Gamma-ray spectra of even-even Nd isotopes were obtained by gating on the transitions in the complimentary Kr fragments. The gamma peaks de-exciting states with I {>=} 12 h were found to be broader than the instrumental line width due to the Doppler effect. The line shapes of they-ray peaks were fitted separately with a simple model for the feeding of the states and assuming a rotational band with constant intrinsic quadruple moment and these are shown in Fig. I-27. The quadrupole moments thus determined were found to be in good agreement with the quadrupole moments measured previously for lower spin states. Because of the success of this technique for the Nd isotopes, we intend to apply this technique to the new larger data set collected with the Eurogam II array. The results of this study were published.

  14. On the Use of Biomineral Oxygen Isotope Data to Identify Human Migrants in the Archaeological Record: Intra-Sample Variation, Statistical Methods and Geographical Considerations.

    Directory of Open Access Journals (Sweden)

    Emma Lightfoot

    Full Text Available Oxygen isotope analysis of archaeological skeletal remains is an increasingly popular tool to study past human migrations. It is based on the assumption that human body chemistry preserves the δ18O of precipitation in such a way as to be a useful technique for identifying migrants and, potentially, their homelands. In this study, the first such global survey, we draw on published human tooth enamel and bone bioapatite data to explore the validity of using oxygen isotope analyses to identify migrants in the archaeological record. We use human δ18O results to show that there are large variations in human oxygen isotope values within a population sample. This may relate to physiological factors influencing the preservation of the primary isotope signal, or due to human activities (such as brewing, boiling, stewing, differential access to water sources and so on causing variation in ingested water and food isotope values. We compare the number of outliers identified using various statistical methods. We determine that the most appropriate method for identifying migrants is dependent on the data but is likely to be the IQR or median absolute deviation from the median under most archaeological circumstances. Finally, through a spatial assessment of the dataset, we show that the degree of overlap in human isotope values from different locations across Europe is such that identifying individuals' homelands on the basis of oxygen isotope analysis alone is not possible for the regions analysed to date. Oxygen isotope analysis is a valid method for identifying first-generation migrants from an archaeological site when used appropriately, however it is difficult to identify migrants using statistical methods for a sample size of less than c. 25 individuals. In the absence of local previous analyses, each sample should be treated as an individual dataset and statistical techniques can be used to identify migrants, but in most cases pinpointing a specific

  15. Determination of low isotopic enrichment of L-[1-C-13]valine by gas chromatography combustion isotope ratio mass spectrometry : a robust method for measuring protein fractional synthetic rates in vivo

    NARCIS (Netherlands)

    Reijngoud, DJ; Hellstern, G; Elzinga, H; de Sain-van der Velden, MG; Okken, A; Stellaard, F

    1998-01-01

    A method was developed for measuring protein fractional synthetic rates using the N-methoxycarbonylmethyl ester (MCM) derivative of L-[1-C-13]valine and on-line gas chromatography/combustion/isotope ratio mass spectrometry (GC/C/IRMS). The derivatization procedure can be performed rapidly and GC sep

  16. Determination of low isotopic enrichment of L-[1-C-13]valine by gas chromatography combustion isotope ratio mass spectrometry : a robust method for measuring protein fractional synthetic rates in vivo

    NARCIS (Netherlands)

    Reijngoud, DJ; Hellstern, G; Elzinga, H; de Sain-van der Velden, MG; Okken, A; Stellaard, F

    A method was developed for measuring protein fractional synthetic rates using the N-methoxycarbonylmethyl ester (MCM) derivative of L-[1-C-13]valine and on-line gas chromatography/combustion/isotope ratio mass spectrometry (GC/C/IRMS). The derivatization procedure can be performed rapidly and GC

  17. A new method for collection of nitrate from fresh water and the analysis of nitrogen and oxygen isotope ratios

    Science.gov (United States)

    Silva, S. R.; Kendall, C.; Wilkison, D. H.; Ziegler, A. C.; Chang, C. C. Y.; Avanzino, R. J.

    2000-02-01

    A new method for concentrating nitrate from fresh waters for δ15N and δ18O analysis has been developed and field-tested for four years. The benefits of the method are: (1) elimination of the need to transport large volumes of water to the laboratory for processing; (2) elimination of the need for hazardous preservatives; and (3) the ability to concentrate nitrate from fresh waters. Nitrate is collected by, passing the water-sample through pre-filled, disposable, anion exchanging resin columns in the field. The columns are subsequently transported to the laboratory where the nitrate is extracted, converted to AgNO 3 and analyzed for its isotope composition. Nitrate is eluted from the anion exchange columns with 15 ml of 3 M HCl. The nitrate-bearing acid eluant is neutralized with Ag 2O, filtered to remove the AgCl precipitate, then freeze-dried to obtain solid AgNO 3, which is then combusted to N 2 in sealed quartz tubes for δ15N analysis. For δ18O analysis, aliquots of the neutralized eluant are processed further to remove non-nitrate oxygen-bearing anions and dissolved organic matter. Barium chloride is added to precipitate sulfate and phosphate; the solution is then filtered, passed through a cation exchange column to remove excess Ba 2+, re-neutralized with Ag 2O, filtered, agitated with activated carbon to remove dissolved organic matter and freeze-dried. The resulting AgNO 3 is combusted with graphite in a closed tube to produce CO 2, which is cryogenically purified and analyzed for its oxygen isotope composition. The 1 σ analytical precisions for δ15N and δ18O are ±0.05‰ and ±0.5‰, respectively, for solutions of KNO 3 standard processed through the entire column procedure. High concentrations of anions in solution can interfere with nitrate adsorption on the anion exchange resins, which may result in isotope fractionation of nitrogen and oxygen (fractionation experiments were conducted for nitrogen only; however, fractionation for oxygen is

  18. A new method for collection of nitrate from fresh water and the analysis of nitrogen and oxygen isotope ratios

    Science.gov (United States)

    Silva, S.R.; Kendall, C.; Wilkison, D.H.; Ziegler, A.C.; Chang, Cecily C.Y.; Avanzino, R.J.

    2000-01-01

    A new method for concentrating nitrate from fresh waters for ??15N and ??18O analysis has been developed and field-tested for four years. The benefits of the method are: (1) elimination of the need to transport large volumes of water to the laboratory for processing; (2) elimination of the need for hazardous preservatives; and (3) the ability to concentrate nitrate from fresh waters. Nitrate is collected by, passing the water-sample through pre-filled, disposable, anion exchanging resin columns in the field. The columns are subsequently transported to the laboratory where the nitrate is extracted, converted to AgNO3 and analyzed for its isotope composition. Nitrate is eluted from the anion exchange columns with 15 ml of 3 M HCl. The nitrate-bearing acid eluant is neutralized with Ag2O, filtered to remove the AgCl precipitate, then freeze-dried to obtain solid AgNO3, which is then combusted to N2 in sealed quartz tubes for ?? 15N analysis. For ?? 18O analysis, aliquots of the neutralized eluant are processed further to remove non-nitrate oxygen-bearing anions and dissolved organic matter. Barium chloride is added to precipitate sulfate and phosphate; the solution is then filtered, passed through a cation exchange column to remove excess Ba2+, re-neutralized with Ag2O, filtered, agitated with activated carbon to remove dissolved organic matter and freeze-dried. The resulting AgNO3 is combusted with graphite in a closed tube to produce CO2, which is cryogenically purified and analyzed for its oxygen isotope composition. The 1?? analytical precisions for ??15N and ??18O are ?? 0.05%o and ??0.5???, respectively, for solutions of KNO3 standard processed through the entire column procedure. High concentrations of anions in solution can interfere with nitrate adsorption on the anion exchange resins, which may result in isotope fractionation of nitrogen and oxygen (fractionation experiments were conducted for nitrogen only; however, fractionation for oxygen is expected

  19. ASE extraction method for simultaneous carbon and nitrogen stable isotope analysis in soft tissues of aquatic organisms

    Energy Technology Data Exchange (ETDEWEB)

    Bodin, Nathalie [ISM/LPTC, UMR 5255 CNRS, Universite de Bordeaux 1, 351 Cours de la Liberation, 33405 Talence (France); CRH, UMR 212 EME, Institut de Recherche et de Developpement, Av Jean Monnet BP171, 34203 Sete (France); Budzinski, Helene, E-mail: h.budzinski@ism.u-bordeaux1.fr [ISM/LPTC, UMR 5255 CNRS, Universite de Bordeaux 1, 351 Cours de la Liberation, 33405 Talence (France); Le Menach, Karyn; Tapie, Nathalie [ISM/LPTC, UMR 5255 CNRS, Universite de Bordeaux 1, 351 Cours de la Liberation, 33405 Talence (France)

    2009-06-08

    Since lipids are depleted in {sup 13}C relative to proteins and carbohydrates, variations in lipid composition among species and within individuals significantly influence {delta}{sup 13}C and may result in misleading ecological interpretations. Whereas lipid extraction before IRMS analysis constitutes a way of stable isotope result lipid-normalisation, such a procedure was given up because of the un-controlled effects of the methods used (i.e., 'Bligh and Dyer', Soxhlet, etc.) on {delta}{sup 15}N. The aim of this work was to develop a simple, rapid and efficient lipid extraction method allowing for simultaneous C and N stable isotope analysis in the biological soft tissues of aquatic organisms. The goal was to be free from the lipid influence on {delta}{sup 13}C values without interfering with {delta}{sup 15}N values. For that purpose, the modern automated pressurized liquid extraction technique ASE (accelerated solvent extraction) was selected. Eel muscles representative of a broad range of fat contents were extracted via ASE by using different semi-polar solvents (100% dichloromethane and 80% n-hexane/20% acetone) and by operating at different temperature (ambient temperature and 100 deg. C) and pressure (750 and 1900 psi) conditions. The results were discussed in terms of lipid extraction efficiency as well as {delta}{sup 13}C and {delta}{sup 15}N variability.

  20. Standard test method for analysis of total and isotopic uranium and total thorium in soils by inductively coupled plasma-mass spectrometry

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2008-01-01

    1.1 This test method covers the measurement of total uranium (U) and thorium (Th) concentrations in soils, as well as the determination of the isotopic weight percentages of 234U, 235U, 236U, and 238U, thereby allowing for the calculation of individual isotopic uranium activity or total uranium activity. This inductively coupled plasma-mass spectroscopy (ICP-MS) method is intended as an alternative analysis to methods such as alpha spectroscopy or thermal ionization mass spectroscopy (TIMS). Also, while this test method covers only those isotopes listed above, the instrumental technique may be expanded to cover other long-lived radioisotopes since the preparation technique includes the preconcentration of the actinide series of elements. The resultant sample volume can be further reduced for introduction into the ICP-MS via an electrothermal vaporization (ETV) unit or other sample introduction device, even though the standard peristaltic pump introduction is applied for this test method. The sample preparatio...

  1. Ion exchange equilibrium constants

    CERN Document Server

    Marcus, Y

    2013-01-01

    Ion Exchange Equilibrium Constants focuses on the test-compilation of equilibrium constants for ion exchange reactions. The book first underscores the scope of the compilation, equilibrium constants, symbols used, and arrangement of the table. The manuscript then presents the table of equilibrium constants, including polystyrene sulfonate cation exchanger, polyacrylate cation exchanger, polymethacrylate cation exchanger, polysterene phosphate cation exchanger, and zirconium phosphate cation exchanger. The text highlights zirconium oxide anion exchanger, zeolite type 13Y cation exchanger, and

  2. Surface area dependence of calcium isotopic reequilibration in carbonates: Implications for isotopic signatures in the weathering zone

    Science.gov (United States)

    Fernandez, N. M.; Druhan, J. L.; Potrel, A.; Jacobson, A. D.

    2016-12-01

    The concept of dynamic equilibrium carries the implicit assumption of continued isotopic exchange between a mineral and the surrounding fluid. While this effect has received much attention in the marine paleoproxy literature, it has been relatively overlooked in application to the terrestrial environment. In weathering systems, a potential consequence is that rapid reequilibration may alter or erase isotopic signatures generated during secondary mineral formation. The extent and timescale over which isotopic signatures are reset in these hydrologic systems is unknown. Using reactive transport modeling, we show isotopic reequilibration under conditions reflecting terrestrial hydrologic settings to be significant and dependent on the reactive surface area of the solid. In particular, we suggest that the non-traditional stable isotopes commonly used in application to carbonates (e.g., Ca, Mg, Sr) are sensitive to these effects due to their rapid reaction rates. We aim to characterize the dependence of Ca isotopic reequilibration on surface area during calcite precipitation via batch experiments conducted at ambient temperature over 48-hour time periods. Calcite precipitation was performed in a closed batch reactor utilizing a controlled free-drift method. The batch reactors contained mixed supersaturated solutions of CaCl2 and NaHCO3 at an initial pH of 8.54. Precipitation was initiated by seed inoculation of calcite crystals with two distinct, pre-constrained surface areas. All experiments achieved the same final state of chemical equilibrium, but as expected, the fastest approach to equilibrium occurred for experiments employing calcite seeds with the highest surface area. This implies that differences in equilibrated Ca isotope ratios (δ44/40Ca) should reflect differences in surface area. This prediction is upheld by models of the experiments, indicating a measureable difference in δ44Ca during calcite precipitation where the higher surface area corresponds to

  3. Stable isotopes of authigenic minerals in variably-saturated fractured tuff

    Energy Technology Data Exchange (ETDEWEB)

    Weber, D.S.; Evans, D.D.

    1988-11-01

    Identifying stable isotope variation and mineralogical changes in fractured rock may help establish the history of climatic and geomorphological processes that might affect the isolation properties of a waste repository site. This study examines the use of the stable isotope ratios of oxygen ({sup 18}O/{sup 16}O) and carbon ({sup 13}C/{sup 12}C) in authigenic minerals as hydrogeochemical tools tracing low-temperature rock-water interaction in variably-saturated fractured stuff. Isotopic compositions of fracture-filling and rock matrix minerals in the Apache Leap tuff, near Superior, Arizona were concordant with geothermal temperatures and in equilibrium with water isotopically similar to present-day meteoric water and groundwater. Oxygen and carbon isotope ratios of fracture-filling, in unsaturated fractured tuff, displayed an isotopic gradient believed to result from near-surface isotopic enrichment due to evaporation rather than the effects of rock-water interaction. Oxygen isotope ratios of rock matrix opal samples exhibited an isotopic gradient believed to result from, leaching and reprecipitation of silica at depth. Methods and results can be used to further define primary flowpaths and the movement of water in variably-saturated fractured rock. 71 refs., 23 figs., 3 tabs.

  4. Method for ultra-trace cesium isotope ratio measurements from environmental samples using thermal ionization mass spectrometry

    Energy Technology Data Exchange (ETDEWEB)

    Snow, Mathew S. [Washington State Univ., Pullman, WA (United States). Dept. of Chemistry; Idaho National Lab. (INL), Idaho Falls, ID (United States); Snyder, Darin C. [Idaho National Lab. (INL), Idaho Falls, ID (United States); Mann, Nick R. [Idaho National Lab. (INL), Idaho Falls, ID (United States); White, Byron M. [Idaho National Lab. (INL), Idaho Falls, ID (United States)

    2015-05-01

    135Cs/137Cs isotope ratios can provide the age, origin and history of environmental Cs contamination. Relatively high precision 135Cs/137Cs isotope ratio measurements from samples containing femtogram quantities of 137Cs are needed to accurately track contamination resuspension and redistribution following environmental 137Cs releases; however, mass spectrometric analyses of environmental samples are limited by the large quantities of ionization inhibitors and isobaric interferences which are present at relatively high concentrations in the environment. We report a new approach for Cs purification from environmental samples. An initial ammonium molybdophosphate-polyacrylonitrile (AMP-PAN) column provides a robust method for extracting Cs under a wide variety of sample matrices and mass loads. Cation exchange separations using a second AMP-PAN column result in more than two orders of magnitude greater Cs/Rb separation factors than commercially available strong cation exchangers. Coupling an AMP-PAN cation exchanging step to a microcation column (AG50W resin) enables consistent 2-4% (2σ) measurement errors for samples containing 3-6,000 fg 137Cs, representing the highest precision 135Cs/137Cs ratio measurements currently reported for soil samples at the femtogram level.

  5. Solvent-based dissolution method to sample gas-phase volatile organic compounds for compound-specific isotope analysis.

    Science.gov (United States)

    Bouchard, Daniel; Hunkeler, Daniel

    2014-01-17

    An investigation was carried out to develop a simple and efficient method to collect vapour samples for compound specific isotope analysis (CSIA) by bubbling vapours through an organic solvent (methanol or ethanol). The compounds tested were benzene and trichloroethylene (TCE). The dissolution efficiency was tested for different air volume injections, using flow rates ranging from 25ml/min to 150ml/min and injection periods varying between 10 and 40min. Based on the results, complete mass recovery for benzene and TCE in both solvents was observed for the flow rates of 25 and 50ml/min. However, small mass loss was observed at increased flow rate. At 150ml/min, recovery was on average 80±17% for benzene and 84±10% for TCE, respectively in methanol and ethanol. The δ(13)C data measured for benzene and TCE dissolved in both solvents were reproducible and were stable independently of the volume of air injected (up to 6L) or the flow rate used. The stability of δ(13)C values hence underlines no isotopic fractionation due to compound-solvent interaction or mass loss. The development of a novel and simple field sampling technique undertaken in this study will facilitate the application of CSIA to diverse gas-phase volatile organic compound studies, such as atmospheric emissions, soil gas or vapour intrusion.

  6. The Sm-Nd isotopic method in the geochronology laboratory of the University of Brasília

    Directory of Open Access Journals (Sweden)

    S.M.C.L. GIOIA

    2000-06-01

    Full Text Available Nd isotopes represent one of the best tools to investigate the processes involved in the evolution of the continental crust and mantle. This is due mainly to the similar geochemical behaviour of Sm and Nd, both light rare earth elements, which inhibits their fractionation during most varied geological processes. In order to carry out crustal evolution studies in central Brazil, the Sm-Nd isotopic method was implanted at the Geochronology Laboratory of the University of Brasília. The Sm-Nd separation methodology is basically that described in Richard et al. (1976, with the addition of some improvements. In this study we describe in detail the methodology used in Brasília. Precision and accuracy were checked with the international standards such as JB-3, BCR-1, BHVO-1 and La Jolla, and the following results were found: JB-3 (Nd=15.74 ppm and Sm=4.28 ppm, BCR-1 (143Nd/144Nd=0.512647±8, Nd=28.73 ppm and Sm=6.66 ppm, BHVO-1 (Nd=24.83 ppm and Sm=6.2 ppm and La Jolla (143Nd/144Nd=0.511835±14.

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

    Science.gov (United States)

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

    2014-11-18

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

  8. Oxygen isotopes as a tracer of phosphate sources and cycling in aquatic systems (Invited)

    Science.gov (United States)

    Young, M. B.; Kendall, C.; Paytan, A.

    2013-12-01

    The oxygen isotopic composition of phosphate can provide valuable information about sources and processes affecting phosphorus as it moves through hydrologic systems. Applications of this technique in soil and water have become more common in recent years due to improvements in extraction methods and instrument capabilities, and studies in multiple aquatic environments have demonstrated that some phosphorus sources may have distinct isotopic compositions within a given system. Under normal environmental conditions, the oxygen-phosphorus bonds in dissolved inorganic phosphate (DIP) can only be broken by enzymatic activity. Biological cycling of DIP will bring the phosphate oxygen into a temperature-dependent equilibrium with the surrounding water, overprinting any existing isotopic source signals. However, studies conducted in a wide range of estuarine, freshwater, and groundwater systems have found that the phosphate oxygen is often out of biological equilibrium with the water, suggesting that it is common for at least a partial isotopic source signal to be retained in aquatic systems. Oxygen isotope analysis on various potential phosphate sources such as synthetic and organic fertilizers, animal waste, detergents, and septic/wastewater treatment plant effluents show that these sources span a wide range of isotopic compositions, and although there is considerable overlap between the source groups, sources may be isotopically distinct within a given study area. Recent soil studies have shown that isotopic analysis of phosphate oxygen is also useful for understanding microbial cycling across different phosphorus pools, and may provide insights into controls on phosphorus leaching. Combining stable isotope information from soil and water studies will greatly improve our understanding of complex phosphate cycling, and the increasing use of this isotopic technique across different environments will provide new information regarding anthropogenic phosphate inputs and

  9. Hybrid quantum and classical methods for computing kinetic isotope effects of chemical reactions in solutions and in enzymes.

    Science.gov (United States)

    Gao, Jiali; Major, Dan T; Fan, Yao; Lin, Yen-Lin; Ma, Shuhua; Wong, Kin-Yiu

    2008-01-01

    A method for incorporating quantum mechanics into enzyme kinetics modeling is presented. Three aspects are emphasized: 1) combined quantum mechanical and molecular mechanical methods are used to represent the potential energy surface for modeling bond forming and breaking processes, 2) instantaneous normal mode analyses are used to incorporate quantum vibrational free energies to the classical potential of mean force, and 3) multidimensional tunneling methods are used to estimate quantum effects on the reaction coordinate motion. Centroid path integral simulations are described to make quantum corrections to the classical potential of mean force. In this method, the nuclear quantum vibrational and tunneling contributions are not separable. An integrated centroid path integral-free energy perturbation and umbrella sampling (PI-FEP/UM) method along with a bisection sampling procedure was summarized, which provides an accurate, easily convergent method for computing kinetic isotope effects for chemical reactions in solution and in enzymes. In the ensemble-averaged variational transition state theory with multidimensional tunneling (EA-VTST/MT), these three aspects of quantum mechanical effects can be individually treated, providing useful insights into the mechanism of enzymatic reactions. These methods are illustrated by applications to a model process in the gas phase, the decarboxylation reaction of N-methyl picolinate in water, and the proton abstraction and reprotonation process catalyzed by alanine racemase. These examples show that the incorporation of quantum mechanical effects is essential for enzyme kinetics simulations.

  10. Computing Equilibrium Free Energies Using Non-Equilibrium Molecular Dynamics

    Directory of Open Access Journals (Sweden)

    Christoph Dellago

    2013-12-01

    Full Text Available As shown by Jarzynski, free energy differences between equilibrium states can be expressed in terms of the statistics of work carried out on a system during non-equilibrium transformations. This exact result, as well as the related Crooks fluctuation theorem, provide the basis for the computation of free energy differences from fast switching molecular dynamics simulations, in which an external parameter is changed at a finite rate, driving the system away from equilibrium. In this article, we first briefly review the Jarzynski identity and the Crooks fluctuation theorem and then survey various algorithms building on these relations. We pay particular attention to the statistical efficiency of these methods and discuss practical issues arising in their implementation and the analysis of the results.

  11. Calculation of liquid-vapor and liquid-liquid equilibrium in multicomponent systems using correlations of equilibrium data

    OpenAIRE

    Reyes Labarta, Juan Antonio; Olaya López, María del Mar; Gómez Siurana, Amparo; Marcilla Gomis, Antonio

    1999-01-01

    Póster presentado en el congreso EQUIFASE 99 (Vigo, del 20 al 24 de Junio de 1999). Resumen publicado en el libro de actas del Congreso An algebraic correlation method to calculate equilibrium data for ternary vapor-liquid equilibrium and quaternary liquid-liquid equilibrium has been proposed. The proposed method allows the calculation of the conjugated phase in equilibrium with a given phase, and the calculation of the two phases in equilibrium from the composition of a heterogeneous glob...

  12. Preliminary attempt to distinguish the domesticated pigs from wild boars by the methods of carbon and nitrogen stable isotope analysis

    Institute of Scientific and Technical Information of China (English)

    Michael; P.RICHARDS

    2009-01-01

    Despite great achievements in the origins of domestic pigs made by the methods of zooarchaeology and molecular biology,how to scientifically distinguish the domesticated pigs from wild boars during the early stage of pig domestication is still poorly understood.Compared to wild boar’s diets which come from the natural environment,the diets of domestic pigs are more easily influenced by human feeding activities.Therefore,in principle,exploration of the dietary differences among pigs and understanding the impact on pig diets fed by humans can have great potential to differentiate between wild boars and domesticated pigs.To reveal dietary differences among pigs and distinguish the domesticated pigs from wild boars based on comparison with the diets of humans and other animals,we analyzed the carbon and nitrogen stable isotopes of human bones from Xiaojingshan Site and animal bones from Yuezhuang Site,both of which belong to Houli Culture in Shandong Province and date to about 8500―7500 years ago.The mean δ 13C value((-17.8 ± 0.3)‰) and δ 15N value((9.0±0.6)‰) in human collagen indicate that although millet agriculture began it was not the main subsistence strategy as millets are typical of C4 plants and that humans made a living mainly by gathering,hunting or raising some domesticated animals.The δ 13C value(-16.1‰) and δ 15N value(6.9‰) in the bovine suggest that C3 plants were dominant in its diet with some C4 plants complemented.The fish has lower δ 13C value(-24.9‰) and higher δ 15N value(8.8‰) than the bovine,which is the characteristic of the isotopic values from Eurasian freshwater fish.Based on the differences in carbon and nitrogen isotope values,the pigs can be divided into three groups.A group,composed of two pigs,has low δ 13C values(-18.1‰,-20.0‰) and low δ 15N values(4.7‰,6.0‰).B group,only one pig,has the highest δ 13C value(-10.6‰) and mediate δ 15N value(6.4‰).As for the C group,also only one pig,low δ 13C

  13. Preliminary attempt to distinguish the domesticated pigs from wild boars by the methods of carbon and nitrogen stable isotope analysis

    Institute of Scientific and Technical Information of China (English)

    HU YaoWu; LUAN FengShi; WANG ShouGong; WANG ChangSui; Michael P. RICHARDS

    2009-01-01

    Despite great achievements in the origins of domestic pigs made by the methods of zooarchaeology and molecular biology, how to scientifically distinguish the domesticated pigs from wild boars during the early stage of pig domestication is still poorly understood. Compared to wild boar's diets which come from the natural environment, the diets of domestic pigs are more easily influenced by human feeding activities. Therefore, in principle, exploration of the dietary differences among pigs and under standing the impact on pig diets fed by humans can have great potential to differentiate between wild boars and domesticated pigs. To reveal dietary differences among pigs and distinguish the domesti cated pigs from wild boars based on comparison with the diets of humans and other animals, we ana lyzed the carbon and nitrogen stable isotopes of human bones from Xiaojingshan Site and animal bones from Yuezhuang Site, both of which belong to Houli Culture in Shandong Province and date to about 8500--7500 years ago. The mean б13C value ((-17.8 ± 0.3)%o) and б15N value ((9.0±0.6)%0) in human collagen indicate that although millet agriculture began it was not the main subsistence strategy as millets are typical of C4 plants and that humans made a living mainly by gathering, hunting or raisingsome domesticated animals. The б13C value (-16.1%.) and б15N value (6.9%.) in the bovine suggest that C3 plants were dominant in its diet with some C4 plants complemented. The fish has lower б13C value (-24.9%.) and higher б15N value (8.8%.) than the bovine, which is the characteristic of the isotopic val ues from Eurasian freshwater fish. Based on the differences in carbon and nitrogen isotope values, the pigs can be divided into three groups. A group, composed of two pigs, has low б13C values (-18.1%o,-20.0%o) and low б15N values (4.7%o, 6.0%.). B group, only one pig, has the highest б13C value (-10.6%o)and mediate б15N value (6.4%.). As for the C group, also only one pig

  14. Silicon Burning, Quasi-Equilibrium and the formation of the Iron Peak

    Science.gov (United States)

    Hix, William Raphael; Thielemann, Friedrich-Karl

    1994-12-01

    As the most tightly bound nuclei, the 'Iron Peak' nuclei result from Nuclear Statistical Equilibrium (NSE) and are the culmination of nuclear energy generation in astrophysical environments. Our re-examination of silicon burning, the mechanism by which the nuclei of the iron peak are produced, has revealed a number of potential improvements in the treatment of this ultimate stage of astrophysical nuclear energy generation. We will discuss results gleaned from simulation work done with a large nuclear network (300 nuclei and 3000 reactions) and from independent calculations of equilirium abundance distributions, which offer new insights into the quasi-equilibrium mechanism and the approach to NSE. We find that the degree to which the matter has been neutronized is of great importance, not only to the final products, but also to the rate of energy generation and the membership of the quasi-equilibrium groups. Furthermore, we find that, as a result of quasi-equilibrium, incomplete silicon burning results in neutron richness among the isotopes of the iron group much larger than the global neutronization would indicate. We will discuss methods which use this quasi-equilibrium mechanism to preserve the most important features of the large nuclear network calculations at a significant improvement in computational speed. Such improved methods are ideally suited for hydrodynamic calculations which involve the production of iron peak nuclei, where the larger network calculation proves unmanageable.

  15. A novel method for concurrent measurements of dissolved inorganic carbon concentration and its carbon isotope composition δ13C

    Science.gov (United States)

    Huang, K.; Cai, W. J.; Kim-Hak, D.; Jonsson, B. F.

    2016-02-01

    The concentration of dissolved inorganic carbon ([DIC]) and its stable carbon isotopic composition (δ13C) in the surface ocean are key to studying the important processes in the carbon cycle, e.g., photosynthesis and respiration, calcification, water mass mixing, and, in particularly, the Suess effect as well as the penetration of anthropogenic carbon into the surface ocean and the subsequent ocean acidification. Real-time, shipboard measurements of these properties are highly desired. Here we present a new method that concurrently measures [DIC] and δ13C of DIC in the surface ocean. The method couples sample acidification and delivery techniques (Apollo Scitech) with a cavity ring-down spectrometer (CRDS, Picarro), and works automatically to analyzer samples at the throughput of 8 minutes/sample. In each sampling cycle, a syringe pump withdraws a fixed volume of phosphoric acid and seawater sample, and injects them slowly into a reaction chamber where they were mixed. In the meantime, the CO2 evolved from the acidified sample is purged by a CO2-free gas flow into a CRDS carbon isotope analyzer for measurements of the CO2 concentration and δ13C-CO2. The concurrent injection, acidification, and purging yield a broad, flat peak of CO2 which is precisely and frequently measured by the CRDS analyzer. [DIC] and δ13C can then be calculated by integrating the concentration and δ13C of the CO2 peak. The precision of the [DIC] and δ13C is automated to run continuously onboard a research vessel as well as discrete samples in a lab environment.

  16. ON VECTOR NETWORK EQUILIBRIUM PROBLEMS

    Institute of Scientific and Technical Information of China (English)

    Guangya CHEN

    2005-01-01

    In this paper we define a concept of weak equilibrium for vector network equilibrium problems.We obtain sufficient conditions of weak equilibrium points and establish relation with vector network equilibrium problems and vector variational inequalities.

  17. Kinetic and equilibrium studies for the adsorption process of cadmium(II) and copper(II) onto Pseudomonas aeruginosa using square wave anodic stripping voltammetry method

    Energy Technology Data Exchange (ETDEWEB)

    Kong Bo; Tang Biyu; Liu Xiaoying; Zeng Xiandong; Duan Haiyan [State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Hunan, Changsha 410082 (China); Luo Shenglian, E-mail: kongbo2136@163.com [State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Hunan, Changsha 410082 (China); Wei Wanzhi [State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Hunan, Changsha 410082 (China)

    2009-08-15

    A novel method for the simultaneous determination of cadmium(II) and copper(II) during the adsorption process onto Pseudomonas aeruginosa was developed. The concentration of the free metal ions was successfully detected by square wave anodic stripping voltammetry (SWASV) on the mercaptoethane sulfonate (MES) modified gold electrode, while the P. aeruginosa was efficiently avoided approaching to the electrode surface by the MES monolayer. And the anodic stripping peaks of Cd{sup 2+} and Cu{sup 2+} appear at -0.13 and 0.34 V respectively, at the concentration range of 5-50 {mu}M, the peak currents of SWASV present linear relationships with the concentrations of cadmium and copper respectively. As the determination of Cd{sup 2+} and Cu{sup 2+} was in real time and without pretreatment, the kinetic characteristics of the adsorption process were studied and all the corresponding regression parameters were obtained by fitting the electrochemical experimental data to the pseudo-second-order kinetic model. Moreover, Langmuir and Freundlich models well described the biosorption isotherms. And there were some differences in the amount of metal ion adsorbed at equilibrium (q{sub e}) and other kinetics parameters when the two ions coexisted were compared with the unaccompanied condition, which were also discussed in this paper. The proposed electrode system provides excellent platform for the simultaneous determination of trace metals in complex biosorption process.

  18. Comprehensive analysis of slope stability and determination of stable slopes in the Chador-Malu iron ore mine using numerical and limit equilibrium methods

    Institute of Scientific and Technical Information of China (English)

    ATAEIM; BODAGHABADIS

    2008-01-01

    One of the critical aspects in mine design is slope stability analysis and the determination of stable slopes. In the Chador Malu iron ore mine, one of the most important iron ore mines in central Iran, it was considered vital to perform a comprehensive slope stability analysis. At first, we divided the existing rock hosting pit into six zones and a geotechnical map was prepared. Then,the value of MRMR (Mining Rock Mass Rating) was determined for each zone. Owing to the fact that the Chador-Malu iron ore mine is located in a highly tectonic area and the rock mass completely crushed, the Hock-Brown failure criterion was found suitable to estimate geo-mechanical parameters. After that, the value of cohesion (c) and friction angle (e) were calculated for different geotechnical zones and relative graphs and equations were derived as a function of slope height. The stability analyses using numerical and limit equilibrium methods showed that some instability problems might occur by increasing the slope height.Therefore, stable slopes for each geotechnical zone and prepared sections were calculated and presented as a function of slope height.

  19. Mathematical models and equilibrium in irreversible microeconomics

    Directory of Open Access Journals (Sweden)

    Anatoly M. Tsirlin

    2010-07-01

    Full Text Available A set of equilibrium states in a system consisting of economic agents, economic reservoirs, and firms is considered. Methods of irreversible microeconomics are used. We show that direct sale/purchase leads to an equilibrium state which depends upon the coefficients of supply/demand functions. To reach the unique equilibrium state it is necessary to add either monetary exchange or an intermediate firm.

  20. Total N difference method and 15N isotope dilution methode - A comparative study on N-fixation

    OpenAIRE

    2002-01-01

    In the study, the 15N fixation of a number of green manure crops were studied using either the 15N dilution technique, or the simple total N difference method. The results of the two methods were not very different, and the total N difference method seemed to give as good results as the more complicated and expencive 15N dillution method.

  1. Phase equilibrium engineering

    CERN Document Server

    Brignole, Esteban Alberto

    2013-01-01

    Traditionally, the teaching of phase equilibria emphasizes the relationships between the thermodynamic variables of each phase in equilibrium rather than its engineering applications. This book changes the focus from the use of thermodynamics relationships to compute phase equilibria to the design and control of the phase conditions that a process needs. Phase Equilibrium Engineering presents a systematic study and application of phase equilibrium tools to the development of chemical processes. The thermodynamic modeling of mixtures for process development, synthesis, simulation, design and

  2. 基于矢量和法的边坡三维极限平衡稳定分析法%Limit equilibrium analysis method based on vector sum method for 3D slope

    Institute of Scientific and Technical Information of China (English)

    叶秋红; 凌道盛

    2013-01-01

    对于具有复杂几何特征的边坡问题,用二维极限平衡理论难以得到与实际相应的分析结果.基于矢量和法安全系数定义,提出了能满足所有条柱3个力的平衡和滑坡体3个整体力矩平衡的严格通用极限平衡分析法.通过侧向剪力系数和侧向剪力分布函数对条间力进行假定,考虑所有条间剪力对安全系数的影响.利用滑体力的平衡条件和边界条件分别得到条柱各行和各列的安全系数,再利用滑体整体力矩平衡条件确定侧向剪力系数.将条柱底面剪力矢量和的反方向作为潜在滑动方向,通过抗滑力和滑动力在其上的投影之和之比确定整个坡体的矢量和安全系数.典型算例验证了方法的合理性,计算结果表明,完全考虑条间力作用将提高边坡的稳定安全系数.%The 2D limit equilibrium method is not suitable to analyze the stability of slope with complicated geometry.Based on the definition of vector sum factor of safety,a general limit equilibrium method,which satisfies the three force equilibriums for all columns and the three moment equilibriums for total failure mass,was proposed.The lateral shear factors and lateral shear distribution functions were introduced to simplify the interslice force distribution,and all interslice forces were taken into account in calculating the safety factor.The safety factors for each row and column were obtained by force equilibriums and boundary conditions for total failure mass,and the lateral shear factors were determined by solving the torque—equilibrium equations for total failure mass.The vector sum factor was determined according to the vector characteristics of forces against the tendency direction which is the opposite direction of the sum of the shears along the sliding surface.A classical example was adopted to validate the presented method.The numerical results showed that fully consideration of interslice forces improves the safe factor of 3D

  3. Continuous measurements of isotopic composition of water vapour on the East Antarctic Plateau

    Science.gov (United States)

    Casado, Mathieu; Landais, Amaelle; Masson-Delmotte, Valérie; Genthon, Christophe; Kerstel, Erik; Kassi, Samir; Arnaud, Laurent; Picard, Ghislain; Prie, Frederic; Cattani, Olivier; Steen-Larsen, Hans-Christian; Vignon, Etienne; Cermak, Peter

    2016-07-01

    Water stable isotopes in central Antarctic ice cores are critical to quantify past temperature changes. Accurate temperature reconstructions require one to understand the processes controlling surface snow isotopic composition. Isotopic fractionation processes occurring in the atmosphere and controlling snowfall isotopic composition are well understood theoretically and implemented in atmospheric models. However, post-deposition processes are poorly documented and understood. To quantitatively interpret the isotopic composition of water archived in ice cores, it is thus essential to study the continuum between surface water vapour, precipitation, surface snow and buried snow. Here, we target the isotopic composition of water vapour at Concordia Station, where the oldest EPICA Dome C ice cores have been retrieved. While snowfall and surface snow sampling is routinely performed, accurate measurements of surface water vapour are challenging in such cold and dry conditions. New developments in infrared spectroscopy enable now the measurement of isotopic composition in water vapour traces. Two infrared spectrometers have been deployed at Concordia, allowing continuous, in situ measurements for 1 month in December 2014-January 2015. Comparison of the results from infrared spectroscopy with laboratory measurements of discrete samples trapped using cryogenic sampling validates the relevance of the method to measure isotopic composition in dry conditions. We observe very large diurnal cycles in isotopic composition well correlated with temperature diurnal cycles. Identification of different behaviours of isotopic composition in the water vapour associated with turbulent or stratified regime indicates a strong impact of meteorological processes in local vapour/snow interaction. Even if the vapour isotopic composition seems to be, at least part of the time, at equilibrium with the local snow, the slope of δD against δ18O prevents us from identifying a unique origin leading

  4. A simple, universal theory and method for computer plotting of stable equilibrium phase diagrams of a multisystem——SFM method

    Institute of Scientific and Technical Information of China (English)

    胡家文; 殷辉安; 唐明林

    2000-01-01

    A new easy method has been presented to calculate the variable intervals corresponding to the stable univariant curves and to discriminate the stabilities of invariant points. This method and the one reported previously constitute a simple and universal theory for the computer-plotting of the equilibriumphase diagrams of a multisystem——sign function matrix (SFM) discrimination method. Its main steps are:determining the stable univariant scheme according to the derivative (or difference) of △rGm; grouping the univariant curves by comparisons of the mutual relations among them; determining the existing intervals of the variables for the stable curves by comparisons of coordinate values of the curves about the invariant point; determining the stabilities of invariant points by comparisons of relations between the common curves and the invariant points. This method is suitable for any kind of phase diagram of closed or open systems in a phase diagram "space" with either 2 or more than 2 dimensions.

  5. Physicochemical Perturbations of Phase Equilibriums

    CERN Document Server

    Dobruskin, Vladimir Kh

    2010-01-01

    The alternative approach to the displacement of gas/liquid equilibrium is developed on the basis of the Clapeyron equation. The phase transition in the system with well-established properties is taken as a reference process to search for the parameters of phase transition in the perturbed equilibrium system. The main equation, derived in the framework of both classical thermodynamics and statistical mechanics, establishes a correlation between variations of enthalpies of evaporation, \\Delta (\\Delta H), which is induced by perturbations, and the equilibrium vapor pressures. The dissolution of a solute, changing the surface shape, and the effect of the external field of adsorbents are considered as the perturbing actions on the liquid phase. The model provides the unified method for studying (1) solutions, (2) membrane separations (3) surface phenomena, and (4) effect of the adsorption field; it leads to the useful relations between \\Delta (\\Delta H), on the one hand, and the osmotic pressures, the Donnan poten...

  6. An Investigation Into the Molecular and Isotopic Composition of Diatom Frustule-Bound Organic Matter: Method Development for New Proxies

    Science.gov (United States)

    Bridoux, M. C.; Ingalls, A. E.

    2009-12-01

    Diatoms are single cell phytoplankton that are ubiquitous in marine ecosystems and are responsible for up to 40% of the carbon fixed annually in the ocean. Their intricately nanopatterned siliceous frustules are formed under the control of template organic molecules, some of which are incorporated into the frustule during growth. Several diatom frustule-based paleoproxies have been developed to exploit these microfossils because they are from a known phytoplankton source that is relatively unaltered from diagenesis. Among these proxies, diatom frustule-bound organic matter (OM) is recognized as a potentially important material for use in paleoreconstructions of past productivity (13C/12C), nutrient utilization (15N/14N) as well as to determine the radiocarbon age of sedimentary frustules (Δ14C). Despite numerous advances, diatom frustule-bound OM remains poorly characterized. Here we focus on the chemical characterization of diatom frustule-bound OM with the goal of developing molecular and compound-specific isotope methods to better reconstruct the past environments of diatom rich regions such as the Southern Ocean and the North Pacific. To do this, we 1) chemically cleaned diatom frustules, 2) dissolve them in HF to release organic compounds embedded in the frustules and 3) unambiguously characterized this organic matter by ion pairing reversed phase liquid chromatography coupled to diode array, electrospray ionization - ion trap mass spectrometry (ESI/IT-MSn) and accurate mass quadrupole time of flight mass spectrometry (Q-TOF). These analyses reveal the presence of low molecular weight, UV light absorbing compounds called mycosporine-like amino acids (MAAs) and a series of long chain polyamines (LCPAs) consisting of N-methylated derivatives of polypropyleneimine units attached to putrescine. LCPAs are known to direct silicification, while MAAs are thought to provide sunscreen to many marine organisms. The presence of these specific biomarkers in sediment

  7. Low-temperature, non-stoichiometric oxygen isotope exchange coupled to Fe(II)-goethite interactions

    Energy Technology Data Exchange (ETDEWEB)

    Frierdich, Andrew J. [Univ. of Wisconsin, Madison, WI (United States); Univ. of Iowa, Iowa City, IA (United States); Beard, Brian L. [Univ. of Wisconsin, Madison, WI (United States); Rosso, Kevin M. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Scherer, Michelle M. [Univ. of Iowa, Iowa City, IA (United States); Spicuzza, Michael J. [Univ. of Wisconsin, Madison, WI (United States); Valley, John W. [Univ. of Wisconsin, Madison, WI (United States); Johnson, Clark M. [Univ. of Wisconsin, Madison, WI (United States)

    2015-07-01

    The oxygen isotope composition of natural iron oxide minerals has been widely used as a paleoclimate proxy. Interpretation of their stable isotope compositions, however, requires accurate knowledge of isotopic fractionation factors and an understanding of their isotopic exchange kinetics, the latter of which informs us how diagenetic processes may alter their isotopic compositions. Prior work has demonstrated that crystalline iron oxides do not significantly exchange oxygen isotopes with pure water at low temperature, which has restricted studies of isotopic fractionation factors to precipitation experiments or theoretical calculations. Using a double three-isotope method (¹⁸O-¹⁷O-¹⁶O and ⁵⁷Fe-⁵⁶Fe-⁵⁴Fe) we compare O and Fe isotope exchange kinetics, and demonstrate, for the first time, that O isotope exchange between structural O in crystalline goethite and water occurs in the presence of aqueous Fe(II) (Fe(II)aq) at ambient temperature (i.e., 22–50 °C). The three-isotope method was used to extrapolate partial exchange results to infer the equilibrium, mass-dependent isotope fractionations between goethite and water. In addition, this was combined with a reversal approach to equilibrium by reacting goethite in two unique waters that vary in composition by about 16‰ in ¹⁸O/¹⁶O ratios. Our results show that interactions between Fe(II)aq and goethite catalyzes O isotope exchange between the mineral and bulk fluid; no exchange (within error) is observed when goethite is suspended in ¹⁷O-enriched water in the absence of Fe(II)aq. In contrast, Fe(II)-catalyzed O isotope exchange is accompanied by significant changes in ¹⁸O/¹⁶O ratios. Despite significant O exchange, however, we observed disproportionate amounts of Fe versus O exchange, where Fe isotope exchange in goethite was roughly three times that of O. This disparity provides novel insight into the reactivity of oxide minerals in aqueous

  8. Recoil distance transmission method: Measurement of interaction cross sections of excited states with fast rare-isotope beams

    Energy Technology Data Exchange (ETDEWEB)

    Kobayashi, N., E-mail: kobayashi@nscl.msu.edu [National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, MI 48824-1321 (United States); Whitmore, K.; Iwasaki, H. [National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, MI 48824-1321 (United States); Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824-1321 (United States)

    2016-09-11

    The possible appearance of nuclear halos in ground and excited states close to the particle-decay threshold is of great importance in the investigation of nuclear structure and few-body correlations at the limit of stability. In order to obtain direct evidence of the halo structure manifested in nuclear excited states, we have considered a new method to measure the interaction cross sections of excited states. The combination of the transmission method and the recoil distance Doppler-shift method with a plunger device enables us to measure the number of interactions of the excited states in a target. Formulae to determine the interaction cross section are derived, and key issues to realize measurements are discussed. Dominant sources of errors are uncertainties in the excited-state lifetimes and γ-ray yields. We examine prototype experiments and perform simulations to study the impact of each uncertainty on the final result. This method provides a novel opportunity to perform cross section measurements on the excited states of rare isotopes.

  9. Labile pools of Pb in vegetable-growing soils investigated by an isotope dilution method and its influence on soil pH.

    Science.gov (United States)

    Xie, Hong; Huang, Zhi-Yong; Cao, Ying-Lan; Cai, Chao; Zeng, Xiang-Cheng; Li, Jian

    2012-08-01

    Pollution of Pb in the surface of agricultural soils is of increasing concern due to its serious impact on the plant growth and the human health through the food chain. However, the mobility, activity and bioavailability of Pb rely mainly on its various chemical species in soils. In the present study, E and L values, the labile pools of isotopically exchangeable Pb, were estimated using the method of isotope dilution in three vegetable-growing soils. The experiments involved adding a stable enriched isotope ((206)Pb > 96%) to a soil suspension and to soils in which plants are subsequently grown, the labile pools of Pb were then estimated by measuring the isotopic composition of Pb in soil solutions and in the plant tissues, respectively. In addition, the correlation of E values and soil pH was investigated at the ranges of pH 4.5-7.0. The amount of labile Pb in soils was also estimated using different single chemical extractants and a modified BCR approach. The results showed that after spiking the enriched isotopes of (206)Pb (>96%) for 24 hours an equilibration of isotopic exchanges in soil suspensions was achieved, and the isotope ratios of (208)Pb/(206)Pb measured at that time was used for calculating the E(24 h) values. The labile pools of Pb by %E(24 h) values, ranging from 53.2% to 61.7% with an average 57%, were found to be significantly higher (p EDTA and the Σ(BCR) values extracted with the modified BCR approach are helpful to detect the labile pools of Pb in soils. In addition, the negative correlation between soil pH and the labile pools of Pb in soils may be useful for further remediation to reduce the bioavailability of Pb in contaminated soils.

  10. A method for combined Sr-Nd-Hf isotopic analysis of <10 mg dust samples: implication for ice core science

    Science.gov (United States)

    Ujvari, Gabor; Wegner, Wencke; Klötzli, Urs

    2017-04-01

    Aeolian mineral dust particles below the size of 10-20 μm often experience longer distance transport in the atmosphere, and thus Aeolian dust is considered an important tracer of large-scale atmospheric circulation. Since ice core dust is purely Aeolian in origin, discrimination of its potential source region(s) can contribute to a better understanding of past dust activity and climatic/environmental causes. Furthermore, ice core dust source information provides critical experimental constraints for model simulations of past atmospheric circulation patterns [1,2]. However, to identify dust sources in past dust archives such as ice cores, the mineralogy and geochemistry of the wind-blown dust material must be characterized. While the amount of dust in marine cores or common terrestrial archives is sufficient for different types of analyses and even for multiple repeat measurements, dust content in ice cores is usually extremely low even for the peak dusty periods such as the Last Glacial Maximum (LGM) (5-8 mg dust/kg ice; [3]). Since the most powerful dust fingerprinting methods, such as REE composition and Sr-Nd-Pb isotopic analyses are destructive there is a clear need to establish sequential separation techniques of Sr, Nd, Pb and other REEs to get the most information out of small (5-10 mg) dust samples recovered from ice cores. Although Hf isotopes have recently been added as a robust tool of aerosol/dust source discrimination (e.g. [4,5,6,7]), precise Hf isotopic measurements of small (Central Europe (NUS), China (BEI) and the US (JUD) were processed (all acetic acid treated for carbonate removal, i.e. aluminosilicate fractions were analysed). Sr isotopic compositions varied between the aliquots within a range of ˜0.00007 for the three samples. Comparison of these values with previously obtained 87Sr/86Sr isotopic ratios from the same samples (different acid/sample amounts) reveals that these values are very sensitive to the acetic acid treatment (acid

  11. Phenylalanine isotope pulse method to measure effect of sepsis on protein breakdown and membrane transport in the pig.

    Science.gov (United States)

    Ten Have, Gabriella A M; Engelen, Mariëlle P K J; Wolfe, Robert R; Deutz, Nicolaas E P

    2017-06-01

    The primed-continuous (PC) phenylalanine (Phe) stable isotope infusion methodology is often used as a proxy for measuring whole body protein breakdown (WbPB) in sepsis. It is unclear if WbPB data obtained by an easy-to-use single IV Phe isotope pulse administration (PULSE) are comparable to those by PC. Compartmental modeling with PULSE could provide us more insight in WbPB in sepsis. Therefore, in the present study, we compared PULSE with PC as proxy for WbPB in an instrumented pig model with Pseudomonas aeruginosa-induced severe sepsis (Healthy: n = 9; Sepsis: n = 13). Seventeen hours after sepsis induction, we compared the Wb rate of appearance (WbRa) of Phe obtained by PC (L-[ring-(13)C6]Phe) and PULSE (L-[(15)N]Phe) in arterial plasma using LC-MS/MS and (non)compartmental modeling. PULSE-WbRa was highly correlated with PC-WbRa (r = 0.732, P sepsis (Healthy: 3,378 ± 103; Sepsis: 4,333 ± 160 nmol·kg BW(-1)·min(-1), P = 0.0002). With PULSE, sepsis was characterized by an increase of the metabolic shunting (Healthy: 3,021 ± 347; Sepsis: 4,233 ± 344 nmol·kg BW(-1)·min(-1), P = 0.026). Membrane transport capacity was the same. Both PC and PULSE methods are able to assess changes in WbRa of plasma Phe reflecting WbPB changes with high sensitivity, independent of the (patho)physiological state. The easy-to-use (non)compartmental PULSE reflects better the real WbPB than PC. With PULSE compartmental analysis, we conclude that the membrane transport capacity for amino acids is not compromised in severe sepsis. Copyright © 2017 the American Physiological Society.

  12. Evaluating the fate of chlorinated ethenes in streambed sediments by combining stable isotope, geochemical and microbial methods

    Science.gov (United States)

    Abe, Yumiko; Aravena, Ramon; Zopfi, Jakob; Parker, Beth; Hunkeler, Daniel

    2009-06-01

    The occurrence of chlorinated ethene transformation in a streambed was investigated using concentration and carbon isotope data from water samples taken at different locations and depths within a 15 × 25 m study area across which a tetrachloroethene (PCE) plume discharges. Furthermore, it was evaluated how the degree of transformation is related to groundwater discharge rates, redox conditions, solid organic matter content (SOM) and microbial factors. Groundwater discharge rates were quantified based on streambed temperatures, and redox conditions using concentrations of dissolved redox-sensitive species. The degree of chlorinated ethene transformation was highly variable in space from no transformation to transformation beyond ethene. Complete reductive dechlorination to ethane and ethene occurred at locations with at least sulfate-reducing conditions and with a residence time in the samples streambed zone (80 cm depth) of at least 10 days. Among these locations, Dehalococcoides was detected using a PCR method where SOM contents were > 2% w/w and where transformation proceeded beyond ethene. However, it was not detected at locations with low SOM, which may cause an insufficient H 2 supply to sustain a detectably dense Dehalococcoides population. Additionally, it is possible that other organisms are responsible for the biodegradation. A microcosm study with streambed sediments demonstrated the potential of VC oxidation throughout the site even at locations without a pre-exposure to VC, consistent with the detection of the epoxyalkane:coenzyme M transferase (EaCoMT) gene involved in the degradation of chlorinated ethenes via epoxidation. In contrast, no aerobic transformation of cDCE in microcosms over a period of 1.5 years was observed. In summary, the study demonstrated that carbon isotope analysis is a sensitive tool to identify the degree of chlorinated ethene transformation even in hydrologically and geochemically complex streambed systems. In addition, it was

  13. Study of the control-equilibrium of control systems

    Institute of Scientific and Technical Information of China (English)

    Liu Qiaoge; Fu Mengyin; Sun Changsheng

    2008-01-01

    Not so much had been talked about equilibrium in control area.On the basis of the phenomenon of balance,the concept of control-equilibrium and control-equilibrium of a control system is proposed.According to this theory,a perfect control method should not only guarantee stability of the system,but also ensure the control-equilibrium of the system.To achieve the control-equilibrium,feed-forward control is required.

  14. Including the spatial variability of metal speciation in the effect factor in life cycle impact assessment: Limits of the equilibrium partitioning method.

    Science.gov (United States)

    Tromson, Clara; Bulle, Cécile; Deschênes, Louise

    2017-03-01

    In life cycle assessment (LCA), the potential terrestrial ecotoxicity effect of metals, calculated as the effect factor (EF), is usually extrapolated from aquatic ecotoxicological data using the equilibrium partitioning method (EqP) as it is more readily available than terrestrial data. However, when following the AMI recommendations (i.e. with at least enough species that represents three different phyla), there are not enough terrestrial data for which soil properties or metal speciation during ecotoxicological testing are specified to account for the influence of soil property variations on metal speciation when using this approach. Alternatively, the TBLM (Terrestrial Biotic Ligand Model) has been used to determine an EF that accounts for speciation, but is not available for metals; hence it cannot be consistently applied to metals in an LCA context. This paper proposes an approach to include metal speciation by regionalizing the EqP method for Cu, Ni and Zn with a geochemical speciation model (the Windermere Humic Aqueous Model 7.0), for 5213 soils selected from the Harmonized World Soil Database. Results obtained by this approach (EF(EqP)regionalized) are compared to the EFs calculated with the conventional EqP method, to the EFs based on available terrestrial data and to the EFs calculated with the TBLM (EF(TBLM)regionalized) when available. The spatial variability contribution of the EF to the overall spatial variability of the characterization factor (CF) has been analyzed. It was found that the EFs(EqP)regionalized show a significant spatial variability. The EFs calculated with the two non-regionalized methods (EqP and terrestrial data) fall within the range of the EFs(EqP)regionalized. The EFs(TBLM)regionalized cover a larger range of values than the EFs(EqP)regionalized but the two methods are not correlated. This paper highlights the importance of including speciation into the terrestrial EF and shows that using the regionalized EqP approach is not an

  15. Physical Equilibrium Evaluation in Parkinson Disease

    Directory of Open Access Journals (Sweden)

    Schmidt, Paula da Silva

    2011-04-01

    Full Text Available Introduction: The Parkinson disease can be among the multiple causes of alterations in the physical equilibrium. Accordingly, this study has the objective to evaluate Parkinson patients' physical equilibrium. Method: Potential study in which 12 Parkinson individuals were evaluated by way of tests of static and dynamic equilibrium, dynamic posturography and vectoelectronystagmograph. To compare the dynamic posturography results a group of gauged control was used. Results: Alterations in Romberg-Barré, Unterberger and Walk tests were found. The vestibular exam revealed 06 normal cases, 04 central vestibular syndrome and 02 cases of peripheral vestibular syndrome. In the dynamic posturography, an equilibrium alteration has been verified, when compared to the control group in all Sensorial Organization Tests, in average and in the utilization of vestibular system. Conclusion: Parkinson patients present a physical equilibrium alteration. The dynamic posturography was more sensitive to detect the equilibrium alterations than vectoelectronystagmograph.

  16. Equilibrium Solubility of CO2 in Alkanolamines

    DEFF Research Database (Denmark)

    Waseem Arshad, Muhammad; Fosbøl, Philip Loldrup; von Solms, Nicolas

    2014-01-01

    Equilibrium solubility of CO2 were measured in aqueous solutions of Monoethanolamine (MEA) and N,N-diethylethanolamine(DEEA). Equilibrium cells are generally used for these measurements. In this study, the equilibrium data were measured from the calorimetry. For this purpose a reaction calorimeter...... (model CPA 122 from ChemiSens AB, Sweden) was used. The advantage of this method is being the measurement of both heats of absorption and equilibrium solubility data of CO2 at the same time. The measurements were performed for 30 mass % MEA and 5M DEEA solutions as a function of CO2 loading at three...... different temperatures 40, 80 and 120 ºC. The measured 30 mass % MEA and 5M DEEA data were compared with the literature data obtained from different equilibrium cells which validated the use of calorimeters for equilibrium solubility measurements....

  17. 人民币均衡汇率估计:粘性价格目标区模型方法%Estimating Equilibrium Exchange Rate of Renminbi-A Method of Target Scope of Sticky Price Model

    Institute of Scientific and Technical Information of China (English)

    窦祥胜; 杨炘

    2004-01-01

    The managedfloating exchange rate system is one of special manifestations of target zone system,and actually it is a quasi-target zone system. Hence RMB equilibrium exchange rate may be estimated by use of the method of exchange rate target zone model. At present, the sticky-price model is one of best models, and it is a extension of flex-price model. The model is based on assumptions of price inertia and output decided by demand. Under those assumptions and the condition of the commodity and the currency market equilibrium, a stochastic differential equation may be established, and in the light of theequation,we may get a exchange rate function. Our research indicates a good outcome may be made,applying the sticky-price model to estimate RMB equilibrium exchange rate.

  18. A novel method for collection of soil-emitted nitric oxide (NO) for natural abundance stable N isotope analysis

    Science.gov (United States)

    Yu, Z.; Elliott, E. M.

    2016-12-01

    The global inventory of NO emissions is poorly constrained with a large portion of the uncertainty attributed to soil NO emissions that result from soil abiotic and microbial processes. While natural abundance stable N isotopes (δ15N) in various soil N-containing compounds have proven to be a robust tracer of soil N cycling, soil δ15N-NO is rarely quantified mainly due to the diffuse nature, low concentrations, and high reactivity of soil-emitted NO. Here, we present the development and application of a dynamic flux chamber system capable of simultaneously measuring soil NO fluxes and collecting NO for δ15N-NO measurements. The system couples a widely used flow-through soil chamber with a NO collection train, in which NO can be converted to NO2 through O3 titration in a Teflon reaction coil, followed by NO2 collection in a 20% triethanolamine (TEA) solution as nitrite and nitrate for δ15N analysis using the denitrifier method. The efficiency of NO-NO2 conversion in the reaction coil and the recovery of NO in the TEA solution were determined experimentally and found to be quantitative (>99%) over a 10 to 749 ppbv NO mixing ratio range. An analytical NO tank (δ15N-NO=71.0±0.4‰) was used to calibrate the method for δ15N-NO analysis. The resulting accuracy and precision (1σ) of the method across various environmental conditions were 1.6‰ and 1.2‰, respectively. Using this new method, controlled laboratory incubations have been conducted to characterize NO emissions induced by rewetting of air-dried surface soil sampled from an urban forest. Pulsed NO emissions, up to 30 times higher than maximum soil NO emissions under steady state, were triggered upon the rewetting and lasted for next 36 hours. While the measured δ15N-NO over the course of the NO pulsing ranged from -52.0‰ and -34.6‰, reinforcing the notion that soil δ15N-NO is lower than those of fossil-fuel combustion sources, a transient δ15N-NO shift was captured immediately after the

  19. A novel method of carbon dioxide clumped isotope analysis with tunable infra-red laser direct absorption spectroscopy

    Science.gov (United States)

    Prokhorov, Ivan; Kluge, Tobias; Janssen, Christof

    2016-04-01

    Precise clumped isotopes analysis of carbon dioxide opens up new horizons of atmospheric and biogeochemical research. Recent advances in laser and spectroscopic techniques provides us necessary instrumentation to access extremely low sub-permill variations of multiply-substituted isotopologues. We present an advanced analysis method of carbon dioxide clumped isotopes using direct absorption spectroscopy. Our assessments predict the ultimate precision of the new method on the sub-permill level comparable to state of the art mass spectrometry. Among the most auspicious intrinsic properties of this method we highlight genuine Δ16O13C18O and Δ16O13C18O measurements without isobaric interference, measurement cycle duration of several minutes versus hours for mass spectrometric analysis, reduced sample size of ˜ 10 μmol and high flexibility, allowing us to perform in-situ measurements. The pilot version of the instrument is being developed in an international collaboration framework between Heidelberg University, Germany and Pierre and Marie Curie University, Paris, France. It employs two continuous interband quantum cascade lasers tuned at 4.439 μm and 4.329 μm to measure doubly ( 16O13C18O, 16O13C17O) and singly ( 16O12C16O, 16O13C16O, 16O12C17O, 16O12C18O) substituted isotopologues, respectively. Two identical Herriot cells are filled with dry pure CO2 sample and reference gas at working pressure of 1 - 10 mbar. Cells provide optical path lengths of ˜ 17 m for the laser tuned at doubly substituted isotopologues lines and use a single pass for the laser tuned at the stronger lines of singly substituted isotopologues. Light outside of the gas cells is coupled into optical fiber to avoid absorption by ambient air CO2. Simulations predict sub-permill precision at working pressure of 1 mbar and room temperature stabilised at the ±10 mK level. Our prime target is to apply the proposed method for continuous in-situ analysis of CO2. We are foreseeing potential

  20. Online determination of copper in aluminum alloy by microchip solvent extraction using isotope dilution ICP-MS method.

    Science.gov (United States)

    Kagawa, Tsuyoshi; Ohno, Masashi; Seki, Tatsuya; Chikama, Katsumi

    2009-09-15

    Isotope dilution mass spectroscopy (IDMS)/ICP-MS combined with microchip solvent extraction was successfully applied for the online determination of copper in an aluminum alloy. The microchip solvent extraction was developed for the separation of Cu from major element, and optimal pH range was wider than that of the batchwise extraction method. The dimensions of the microchip were 30 mm x 70 mm and that of micro-channel on the microchip was 180 microm wide and 40 microm deep. The copper complex with 8-hydroxyquinoline was extracted into o-xylene at pH 5.5 and back extracted with 0.1 mol l(-1) nitric acid at flow rate of 20 microl min(-1). The total extraction efficiency (water/organic solvent/nitric acid) was around 40%. IDMS/ICP-MS was coupled with solvent extraction for precise determination of Cu. The extraction and back-extraction on the microchip took about 1s and the total measurement time for the IDMS/ICP-MS was about 40s/sample. The blank value of this method was 0.1 ng g(-1). The proposed method was used for the determination of Cu in Al standard materials (JSAC 0121-C, The Japan Society for Analytical Chemistry and 7074 Al alloy, Nippon Light Metal Co. Ltd.). The obtained analytical results are in good agreement with the certified values.

  1. Iron isotope fractionation between aqueous ferrous iron and goethite

    Science.gov (United States)

    Beard, Brian L.; Handler, Robert M.; Scherer, Michelle M.; Wu, Lingling; Czaja, Andrew D.; Heimann, Adriana; Johnson, Clark M.

    2010-06-01

    The equilibrium Fe isotope fractionation factor between aqueous Fe(II) and goethite has been experimentally measured to be - 1.05 ± 0.08‰ in 56Fe/54Fe (2σ) at 22 °C, using the three-isotope method. Experiments were done using two sizes of goethite (81 × 11 nm and 590 × 42 nm), and the experimental products were subjected to serial extraction using acid partial dissolution techniques to determine if surface Fe(III) atoms have different isotopic properties than the bulk goethite. These experiments indicate that the interaction of Fe(II)aq and goethite is dynamic and results in complete or near-complete Fe isotope exchange over 30 days, involving at least four components: Fe(II)aq, goethite, sorbed Fe(II), and Fe(III)surface. The equilibrium fractionation factor between Fe(II)aq and Fe(II)sorb is the same for both sizes of goethite, at Δ56FeFe(II)aq-Fe(II)sorb = - 1.24 ± 0.14‰; this fractionation factor is significantly different than the results of previous studies on Fe(II) sorption to goethite. The proportion of the Fe(III)surface component is greatest in the experiments that used the smallest goethite, and the Fe(III)surface-Fe(II)aq fractionation is estimated to be at least + 2.1‰. The high Fe(III)surface-Fe(II)aq fractionation may exert a significant influence on the Fe isotope compositions of aqueous Fe(II) in natural systems that contain nanoparticulate goethite, including those involving bacterial iron reduction. These results demonstrate that the isotopic properties of nano-scale minerals may be distinct from micron-scale or larger minerals, as is the case for other thermodynamic properties of nanoparticles.

  2. A method for the routine determination of methylmercury in marine tissue by GC isotope dilution-ICP-MS.

    Science.gov (United States)

    Valdersnes, Stig; Maage, Amund; Fliegel, Daniel; Julshamn, Kåre

    2012-01-01

    Currently, there is no legal limit for methyl mercury (MeHg) in food; thus, no standardized method for the determination of MeHg in seafood exists within the European jurisdiction. In anticipation of a future legislative limit an inductively coupled plasma isotope dilution mass spectrometry (GC-ICP-ID-MS) method was developed in collaboration with the European Standardization Organization (CEN). The method comprises spiking the tissue sample with Me201Hg, followed by decomposition with tetramethylammonium hydroxide, pH adjustment and derivatization with sodium tetraethylborate, and finally organic extraction of the derivatized MeHg in a hexane phase. Subsequently, the sample is analyzed via GC-ICP-MS and the result calculated using the ID equation. The working range of the method was 0.0005-1.321 mg/kg MeHg in marine tissue, with an internal reproducibility (RSD) of 12-1%. The method was validated based on statistical measures, such as the z-scores, using the commercially available reference materials from National Institute of Standards and Technology Standard Reference Material (NIST SRM) 1566b, NIST SRM 2977 and National Research Council of Canada (NRCC) TORT 2, NRCC, DORM 3, NRCC DOLT 4, and European Reference Material (ERM) CE 464. Z-scores for all standard reference materials, except for NIST SRM 1566b, were better than 11.51. The wide range of marine tissues used during the validation ensures that the method will be applicable for measuring of MeHg in seafood matrixes of all kinds.

  3. Technical considerations for the use of passive samplers to quantify the isotopic composition of NOx and NO2 using the denitrifier method

    Science.gov (United States)

    Dahal, Bigyan; Hastings, Meredith G.

    2016-10-01

    The isotopic composition of nitrogen oxides (NOx = NO + NO2) hold potential to trace emissions sources, as well as chemistry in the atmosphere. Passive samplers that collect NOx and NO2 as nitrite could provide a simple and inexpensive means by which to collect samples in a variety of environments, and we report here on several methodological considerations when using Ogawa passive collectors of NOx and NO2 for concentration analysis via colorimetric methods and isotopic analysis via the denitrifier method. Using Ogawa samplers, NOx and NO2 were collected in Providence, RI, USA (41.8°N, 71.4°W) with exposure times of seven, fourteen, twenty-one, and twenty-eight days during summer and winter in an area dominated by vehicle emissions, particularly diesel delivery trucks. Average values were -9.7 ± 0.7‰ for δ15N-NOx and -8.3 ± 0.9‰ for δ15N-NO2 based on duplicate seven, fourteen, twenty-one, and twenty-eight day exposures (n = 8) in summertime, and -11.9 ± 0.7‰ for δ15N-NOx and -6.4 ± 1.4‰ for δ15N-NO2 based on seven, fourteen, twenty-one, and twenty-eight day exposures (n = 7) in wintertime. The oxygen isotopic composition (δ18O, Δ17O) was also determined with averages of: 36.3 ± 2.4‰ for δ18O-NOx (n = 8), 50.5 ± 3.2‰ for δ18O-NO2 (n = 8), 6.2 ± 0.8‰ for Δ17O-NOx and 10.8 ± 0.6‰ for Δ17O-NO2 (n = 4) in summer; and 38.7 ± 2.9‰ for δ18O-NOx and 47.4 ± 1.2‰ for δ18O-NO2 (n = 7), 7.7 ± 1.5‰ for Δ17O-NO2 (n = 4) and 5.3 ± 1.2‰ for Δ17O-NOx (n = 5), in winter. Our isotopic results differ from previous studies that utilized passive samplers and suggest specific nitrogen and oxygen isotopic signatures associated with vehicular emissions. To collect sufficient sample for multiple isotopic analyses (e.g., 10 nmol N for δ15N and δ18O; 50 nmol N for Δ17O) the exposure time for the samplers, even in urban areas, is at least days. This necessarily results in collection of a mixture of local emissions sources, as well as

  4. Application of isotope dilution method for measuring bioavailability of organic contaminants sorbed to dissolved organic matter (DOM)

    Energy Technology Data Exchange (ETDEWEB)

    Delgado-Moreno, Laura, E-mail: laura.delgado@eez.csic.es; Wu, Laosheng; Gan, Jay

    2015-08-15

    Natural waters such as surface water and sediment porewater invariably contain dissolved organic matter (DOM). Association of strongly hydrophobic contaminants (HOCs) with DOM leads to decreased toxicity and bioavailability, but bioavailability of DOM-sorbed HOCs is difficult to measure. Current methods to estimate bioavailability of HOCs in water are based on only the freely dissolved concentration (C{sub free}). The ignorance of the exchangeable fraction of HOCs sorbed on DOM may result in an underestimation of the toxicity potential of HOCs to aquatic organisms. Here we explore the applicability of an isotope dilution method (IDM) to measuring the desorption fraction of DOM-sorbed pyrene and bifenthrin and determining their exchangeable pool (E) as an approximation of bioavailability. E values, expressed as percentage of the total concentration, ranged between 0.80 and 0.92% for pyrene and 0.74 and 0.85% for bifenthrin, depending primarily on the amount of chemical in the freely dissolved form. However, between 34 and 78% of the DOM-sorbed pyrene was exchangeable. This fraction ranged between 23% and 82% for bifenthrin. The ability of IDM to predict bioavailability was further shown from a significant relationship (r{sup 2} > 0.72, P < 0.0001) between E and bioaccumulation into Daphnia magna. Therefore, IDM may be used to improve the bioavailability measurement and risk assessment of HOCs in aquatic systems.

  5. Determination of weathering rate of the Morro do Ferro Th-REEs deposit, Brazil using U-isotope method

    Energy Technology Data Exchange (ETDEWEB)

    Bonotto, D.M. [Departamento de Petrologia e Metalogenia, Universidade Estadual Paulista (UNESP), Campus de Rio Claro, Avnue 24-A No.1515, C.P. 178, CEP 13506-900, Rio Claro, Sao Paulo (Brazil)]. E-mail: dbonotto@rc.unesp.br; Fujimori, K. [In Memoriam, Departamento de Geofisica, Instituto de Astronomia, Geofisica e Ciencias Atmosfericas (IAG-USP), Rua do Matao No. 1226, CEP 05508-900, Sao Paulo (Brazil); Moreira-Nordemann, L.M. [Instituto de Pesquisas Espaciais (INPE-MCT-CNPq), Av. dos Astronautas No. 1758, CEP 12227-010, Sao Jose dos Campos, Sao Paulo (Brazil)

    2007-05-15

    The weathering rate was estimated by changes in {sup 234}U/{sup 238}U activity ratio (AR) and U content of rocks, borehole spoil and surface water samples at the Morro do Ferro Th-REEs deposit. The deposit is situated in the Pocos de Caldas alkaline massif, Brazil. The south stream basin investigated in this paper has not been significantly affected by anthropogenic inputs of pollutants as compared to the Corumbatai River basin in Sao Paulo State, where the method was previously applied. The weathering rate derived utilizing the U-isotopes modeling corresponded to 0.015 mm/yr (67,000 years to weather 1 m of rock under the actual climatic conditions). The estimated rate is very reasonable in comparison with the range of 0.015-0.05 mm/yr of land surface lowering within the entire caldera. It is also compatible with a rate of 0.013 mm/yr determined for the Salgado River basin in a semi-arid region in Bahia State, Brazil. The value generated is reliable and increases the potential use of the method for other different areas in Brazil and elsewhere, because it may be used in regions with different climatic conditions and (un)polluted basins.

  6. Detection of adulteration in honey samples added various sugar syrups with 13C/12C isotope ratio analysis method.

    Science.gov (United States)

    Tosun, Murat

    2013-06-01

    Honey can be adulterated in various ways. One of the adulteration methods is the addition of different sugar syrups during or after honey production. Starch-based sugar syrups, high fructose corn syrup (HFCS), glucose syrup (GS) and saccharose syrups (SS), which are produced from beet or canes, can be used for adulterating honey. In this study, adulterated honey samples were prepared with the addition of HFCS, GS and SS (beet sugar) at a ratio of 0%, 10%, 20%, 40% and 50% by weight. (13)C/(12)C analysis was conducted on these adulterated honey samples using an isotope ratio mass spectrometer in combination with an elemental analyser (EA-IRMS). As a result, adulteration using C(4) sugar syrups (HFCS and GS) could be detected to a certain extent while adulteration of honey using C(3) sugar syrups (beet sugar) could not be detected. Adulteration by using SS (beet sugar) still has a serious detection problem, especially in countries in which beet is used in manufacturing sugar. For this reason, practice and analysis methods are needed to meet this deficit and to detect the adulterations precisely in the studies that will be conducted. Copyright © 2012 Elsevier Ltd. All rights reserved.

  7. Copper isotope signatures in modern marine sediments

    Science.gov (United States)

    Little, Susan H.; Vance, Derek; McManus, James; Severmann, Silke; Lyons, Timothy W.

    2017-09-01

    The development of metal stable isotopes as tools in paleoceanography requires a thorough understanding of their modern marine cycling. To date, no Cu isotope data has been published for modern sediments deposited under low oxygen conditions. We present data encompassing a broad spectrum of hydrographic and redox regimes, including continental margin and euxinic (sulphide-containing) settings. Taken together with previously published data from oxic settings, these data indicate that the modern oceanic sink for Cu has a surprisingly homogeneous isotopic composition of about +0.3‰ (δ65Cu, relative to NIST SRM976). We suggest that this signature reflects one of two specific water-column processes: (1) an equilibrium isotope fractionation between soluble, isotopically heavy, Cu complexed to strong organic ligands and an isotopically light pool sorbed to particles that deliver Cu to the sediment, or (2) an equilibrium isotope fractionation between the same isotopically heavy ligand-bound pool and the particle reactive free Cu2+ species, with the latter being scavenged by particulates and thereby delivered to the sediment. An output flux of about +0.3‰ into sediments is isotopically light relative to the known inputs to the ocean (at around +0.6‰) and the seawater value of +0.6 to +0.9‰, suggesting the presence of an as yet unidentified isotopically light source of Cu to the oceans. We hypothesize that this source may be hydrothermal, or may result from the partial dissolution of continentally derived particles.

  8. Determination of niobium in rocks by an isotope dilution spectrophotometric method

    Science.gov (United States)

    Greenland, L.P.; Campbell, E.Y.

    1970-01-01

    Rocks and minerals are fused with sodium peroxide in the presence of carrierfree 95Nb. The fusion cake is leached with water and the precipitate dissolved in hydrofluoric-sulfuric acid mixture. Niobium is extracted into methyl isobutyl ketone and further purified by ion exchange. The amount of niobium is determined spectrophotometrically with 4-(2-pyridylazo)-resorcinol, and the chemical yield of the separations determined by counting 95Nb. This procedure is faster and less sensitive to interferences than previously proposed methods for determining niobium in rocks.The high purity of the separated niobium makes the method applicable to nearly all matrices. ?? 1970.

  9. Mass spectrometric methods for the direct elemental and isotopic analysis of solid material

    Science.gov (United States)

    Ganeev, A. A.; Gubal, A. R.; Potapov, S. V.; Agafonova, N. N.; Nemets, V. M.

    2016-04-01

    Methods for the direct analysis of solids have a number of undeniable advantages over the methods that require preliminary dissolution of samples. High sensitivity and selectivity make the direct mass spectrometric techniques the most in-demand. The review concerns spark source mass spectrometry, laser ionization mass spectrometry, laser ablation inductively coupled plasma mass spectrometry, secondary ion mass spectrometry, secondary neutral mass spectrometry and glow discharge mass spectrometry. Basic principles, analytical characteristics and trends in the development of these techniques are discussed. Particular attention is given to applications of the techniques as well as to their competitive advantages and drawbacks. The bibliography includes 123 references.

  10. Heavy atom isotope effects on enzymatic reactions

    Science.gov (United States)

    Paneth, Piotr

    1994-05-01

    The theory of isotope effects, which has proved to be extremely useful in providing geometrical details of transition states in a variety of chemical reactions, has recently found an application in studies of enzyme-catalyzed reactions. These reactions are multistep in nature with few steps being partially rate-limiting, thus interpretation of these isotope effects is more complex. The theoretical framework of heavy-atom isotope effects on enzymatic reactions is critically analyzed on the basis of recent results of: carbon kinetic isotope effects on carbonic anhydrase and catalytic antibodies; multiple carbon, deuterium isotope effects on reactions catalyzed by formate decarboxylase; oxygen isotope effects on binding processes in reactions catalyzed by pyruvate kinase; and equilibrium oxygen isotope effect on binding an inhibitor to lactate dehydrogenase. The advantages and disadvantages of reaction complexity in learning details of formal and molecular mechanisms are discussed in the examples of reactions catalyzed by phosphoenolpyruvate carboxylase, orotidine decarboxylase and glutamine synthetase.

  11. Beat the equilibrium

    Energy Technology Data Exchange (ETDEWEB)

    Berty, J.M.; Krishnan, C.; Elliott, J.R. Jr. (Berty Reaction Engineers, Ltd. (USA))

    1990-10-01

    Methanol is synthesised catalytically from H{sub 2}, CO and CO{sub 2}. Equilibrium considerations dictated the use of high pressures until the advent of copper-based catalysts. But equilibrium problems still exist; single pass conversions of CO and H{sub 2} are low, typically 30-40%. A solvent methanol process (SMP) is proposed to overcome existing problems. A high-boiling inert solvent is introduced with the synthesis gas. The solvent selectively absorbs CH{sub 3}OH, thus shifting the equilibrium towards the product. The strongest solvent identified and tested is tetraethyleneglycol dimethyl ether (tetraglyme). 24 refs., 4 figs., 2 tabs.

  12. Neutron multiplication method for measuring the amount of fissile isotopes in the spent fuel

    Energy Technology Data Exchange (ETDEWEB)

    Chwaszczewski, S.; Pytel, K. [Institute of Atomic Energy, 05-400 Otwock-Swierk (Poland); Abou-Zaid, A.A. [Atomic Energy Authority, 13759 Cairo (Egypt)

    2001-07-01

    A nondestructive assay method for determination the amount of fissile materials content along the vertical axis of irradiated fuel is presented. The method, called neutron multiplication method, can be realized as passive measurement technique and the active one. The Monte Carlo code has been used for the neutron transport simulation and optimization of the measuring equipment geometry. On the basis of these results, a preliminary experimental stand for MARIA reactor fuel investigation has been designed and the measurements have been performed for the fresh fuel and the fuel mock-up. Based upon both numerical and experimental simulations, an ultimate measuring stand has been designed and the measurements for MARIA spent fuel assemblies as well as for the fresh fuel and mock-up of the fuel have been carried out. The results showed that the active neutron technique does not provide sufficient resolution of the distribution of the amount of fissile materials. But rather can be applied for measurement of the absolute value. The passive one can be used to restore the distribution of the bum-up and the amount of fissile materials along the axial length of the spent fuel assembly. (author)

  13. Chemical Principles Revisited: Chemical Equilibrium.

    Science.gov (United States)

    Mickey, Charles D.

    1980-01-01

    Describes: (1) Law of Mass Action; (2) equilibrium constant and ideal behavior; (3) general form of the equilibrium constant; (4) forward and reverse reactions; (5) factors influencing equilibrium; (6) Le Chatelier's principle; (7) effects of temperature, changing concentration, and pressure on equilibrium; and (8) catalysts and equilibrium. (JN)

  14. Quantifying mixing using equilibrium reactions

    Science.gov (United States)

    Wheat, Philip M.; Posner, Jonathan D.

    2009-03-01

    A method of quantifying equilibrium reactions in a microchannel using a fluorometric reaction of Fluo-4 and Ca2+ ions is presented. Under the proper conditions, equilibrium reactions can be used to quantify fluid mixing without the challenges associated with constituent mixing measures such as limited imaging spatial resolution and viewing angle coupled with three-dimensional structure. Quantitative measurements of CaCl and calcium-indicating fluorescent dye Fluo-4 mixing are measured in Y-shaped microchannels. Reactant and product concentration distributions are modeled using Green's function solutions and a numerical solution to the advection-diffusion equation. Equilibrium reactions provide for an unambiguous, quantitative measure of mixing when the reactant concentrations are greater than 100 times their dissociation constant and the diffusivities are equal. At lower concentrations and for dissimilar diffusivities, the area averaged fluorescence signal reaches a maximum before the species have interdiffused, suggesting that reactant concentrations and diffusivities must be carefully selected to provide unambiguous, quantitative mixing measures. Fluorometric equilibrium reactions work over a wide range of pH and background concentrations such that they can be used for a wide variety of fluid mixing measures including industrial or microscale flows.

  15. An isotopic exchange method applied to the study of surface mobility in catalysis; Methode d`echange isotopique appliquee a l`etude de la mobilite de surface en catalyse

    Energy Technology Data Exchange (ETDEWEB)

    Martin, D.; Duprez, D. [LACCO, 86 - Poitiers (France)

    1994-12-31

    A method for isotopic exchange of oxygen and hydrogen on the surface of supported metal catalysts (Rh, Pt), is presented. This method allows to determine various properties of oxides used as supports (rate of exchange, quantity of exchanges species, surface and bulk diffusion coefficients) which can be correlated to some specific properties of the oxides (dehydroxylation, acidity and basicity). 5 figs., 9 refs.

  16. An isotope approach based on C-13 pulse-chase labelling vs. the root trenching method to separate heterotrophic and autotrophic respiration in cultivated peatlands

    Energy Technology Data Exchange (ETDEWEB)

    Biasi, C.; Pitkamaki, A. S.; Tavi, N. M.; Koponen, H. T.; Martikainen, P. J. [Univ.of Eastern Finland, Kuopio (Finland). Dept. of Environmental Science], e-mail: christina.biasi@uef.fi

    2012-11-01

    We tested an isotope method based on C-13 pulse-chase labelling for determining the fractional contribution of soil microbial respiration to overall soil respiration in an organic soil (cutaway peatland, eastern Finland), cultivated with the bioenergy crop, reed canary grass. The plants were exposed to CO{sub 2}-13 for five hours and the label was thereafter determined in CO{sub 2} derived from the soil-root system. A two-pool isotope mixing model was used to separate sources of respiration. The isotopic approach showed that a minimum of 50% of the total CO{sub 2} originated from soil-microbial respiration. Even though the method uses undisturbed soil-plant systems, it has limitations concerning the experimental determination of the true isotopic signal of all components contributing to autotrophic respiration. A trenching experiment which was comparatively conducted resulted in a 71% fractional contribution of soil-microbial respiration. This value was likely overestimated. Further studies are needed to evaluate critically the output from these two partitioning approaches. (orig.)

  17. Cerenkov Radiation Energy Transfer (CRET) Imaging: A Novel Method for Optical Imaging of PET Isotopes in Biological Systems: e13300

    National Research Council Canada - National Science Library

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

    2010-01-01

    .... Principal Findings To improve optical imaging of Cerenkov radiation in biological systems, we demonstrate that Cerenkov radiation from decay of the PET isotopes 64Cu and 18F can be spectrally coupled...

  18. The cycle of stable isotopes and tritium in water

    Energy Technology Data Exchange (ETDEWEB)

    Hunziker, J.C. [Inst. de Mineralogie, Lausanne (Switzerland)

    1998-12-31

    In hydrology, meteorology, climatology and environmental research natural hydrogen and oxygen isotopes of water increasingly replace radioactive or chemical tracers used in the past to track fluid paths through nature. This evolution has made possible through the network of precipitation data established since 1961 by the International Atomic Energy Agency (IAEA) in Vienna, that provides the necessary data base for the stable isotope interpretations. Evaporation and condensation and, at higher temperatures, water-rock interaction are the main mechanisms responsible for changing the isotopic ratio of water. These data provide insight into mean residence time of a water body and/or mean altitude of a catchment area. They also yield climatological information and allow the mass transfer quantification because of the temperature dependence of equilibrium fractionation. As the acquired isotopic ratio of a water is generally conserved during flow and percolation through geologic bodies, admixing of water showing different histories can easily be monitored, and when the end members are known or can be measured, mixtures can be calculated. Including isotopic measurements of certain anions, often dissolved in remarkable quantities in groundwaters e.g. nitrates, sulfates or phosphates, increases the reliability and the possibility to trace fluid paths through geologic bodies. In addition in environmental studies, oxygen, nitrogen and sulfur isotopes allow for source determination studies, again providing a possibility of quantification, which can not be obtained by any other method. Recent advances in the specific determination of organic molecules by means of GC-IRMS (gas-chromatography-isotope ratio mass spectrometry) has considerably enlarged our possibilities in detection and quantification of organic water pollution. These organic compounds (debris of macromolecules) increasingly deteriorate the quality of our drinking water; unfortunately they are normally not

  19. Thermodynamics "beyond" local equilibrium

    Science.gov (United States)

    Vilar, Jose; Rubi, Miguel

    2002-03-01

    Nonequilibrium thermodynamics has shown its applicability in a wide variety of different situations pertaining to fields such as physics, chemistry, biology, and engineering. As successful as it is, however, its current formulation considers only systems close to equilibrium, those satisfying the so-called local equilibrium hypothesis. Here we show that diffusion processes that occur far away from equilibrium can be viewed as at local equilibrium in a space that includes all the relevant variables in addition to the spatial coordinate. In this way, nonequilibrium thermodynamics can be used and the difficulties and ambiguities associated with the lack of a thermodynamic description disappear. We analyze explicitly the inertial effects in diffusion and outline how the main ideas can be applied to other situations. [J.M.G. Vilar and J.M. Rubi, Proc. Natl. Acad. Sci. USA 98, 11081-11084 (2001)].

  20. Non-equilibrium Economics

    Directory of Open Access Journals (Sweden)

    Katalin Martinás

    2007-02-01

    Full Text Available A microeconomic, agent based framework to dynamic economics is formulated in a materialist approach. An axiomatic foundation of a non-equilibrium microeconomics is outlined. Economic activity is modelled as transformation and transport of commodities (materials owned by the agents. Rate of transformations (production intensity, and the rate of transport (trade are defined by the agents. Economic decision rules are derived from the observed economic behaviour. The non-linear equations are solved numerically for a model economy. Numerical solutions for simple model economies suggest that the some of the results of general equilibrium economics are consequences only of the equilibrium hypothesis. We show that perfect competition of selfish agents does not guarantee the stability of economic equilibrium, but cooperativity is needed, too.

  1. Response reactions: equilibrium coupling.

    Science.gov (United States)

    Hoffmann, Eufrozina A; Nagypal, Istvan

    2006-06-01

    It is pointed out and illustrated in the present paper that if a homogeneous multiple equilibrium system containing k components and q species is composed of the reactants actually taken and their reactions contain only k + 1 species, then we have a unique representation with (q - k) stoichiometrically independent reactions (SIRs). We define these as coupling reactions. All the other possible combinations with k + 1 species are the coupled reactions that are in equilibrium when the (q - k) SIRs are in equilibrium. The response of the equilibrium state for perturbation is determined by the coupling and coupled equilibria. Depending on the circumstances and the actual thermodynamic data, the effect of coupled equilibria may overtake the effect of the coupling ones, leading to phenomena that are in apparent contradiction with Le Chatelier's principle.

  2. Fractional Absorption of Active Absorbable Algal Calcium (AAACa and Calcium Carbonate Measured by a Dual Stable-Isotope Method

    Directory of Open Access Journals (Sweden)

    Steven A. Abrams

    2010-07-01

    Full Text Available With the use of stable isotopes, this study aimed to compare the bioavailability of active absorbable algal calcium (AAACa, obtained from oyster shell powder heated to a high temperature, with an additional heated seaweed component (Heated Algal Ingredient, HAI, with that of calcium carbonate. In 10 postmenopausal women volunteers aged 59 to 77 years (mean ± S.D., 67 ± 5.3, the fractional calcium absorption of AAACa and CaCO3 was measured by a dual stable isotope method. 44Ca-enriched CaCO3 and AAACa were administered in all subjects one month apart. After a fixed-menu breakfast and pre-test urine collection (Urine 0, 42Ca-enriched CaCl2 was intravenously injected, followed by oral administration of 44Ca-enriched CaCO3 without carrier 15 minutes later, and complete urine collection for the next 24 hours (Urine 24. The fractional calcium absorption was calculated as the ratio of Augmentation of 44Ca from Urine 0 to Urine 24/ augmentation of 42Ca from Urine 0 to Urine 24. Differences and changes of 44Ca and 42Ca were corrected by comparing each with 43Ca. Fractional absorption of AAACa (mean ± S.D., 23.1 ± 6.4, was distinctly and significantly higher than that of CaCO3 (14.7 ± 6.4; p = 0.0060 by paired t-test. The mean fractional absorption was approximately 1.57-times higher for AAACa than for CaCO3. The serum 25(OH vitamin D level was low (mean ± S.D., 14.2 ± 4.95 ng/ml, as is common in this age group in Japan. Among the parameters of the bone and mineral metabolism measured, none displayed a significant correlation with the fractional absorption of CaCO3 and AAACa. Higher fractional absorption of AAACa compared with CaCO3 supports previous reports on the more beneficial effect of AAACa than CaCO3 for osteoporosis.

  3. Automated method for simultaneous lead and strontium isotopic analysis applied to rainwater samples and airborne particulate filters (PM10).

    Science.gov (United States)

    Beltrán, Blanca; Avivar, Jessica; Mola, Montserrat; Ferrer, Laura; Cerdà, Víctor; Leal, Luz O

    2013-09-03

    A new automated, sensitive, and fast system for the simultaneous online isolation and preconcentration of lead and strontium by sorption on a microcolumn packed with Sr-resin using an inductively coupled plasma mass spectrometry (ICP-MS) detector was developed, hyphenating lab-on-valve (LOV) and multisyringe flow injection analysis (MSFIA). Pb and Sr are directly retained on the sorbent column and eluted with a solution of 0.05 mol L(-1) ammonium oxalate. The detection limits achieved were 0.04 ng for lead and 0.03 ng for strontium. Mass calibration curves were used since the proposed system allows the use of different sample volumes for preconcentration. Mass linear working ranges were between 0.13 and 50 ng and 0.1 and 50 ng for lead and strontium, respectively. The repeatability of the method, expressed as RSD, was 2.1% and 2.7% for Pb and Sr, respectively. Environmental samples such as rainwater and airborne particulate (PM10) filters as well as a certified reference material SLRS-4 (river water) were satisfactorily analyzed obtaining recoveries between 90 and 110% for both elements. The main features of the LOV-MSFIA-ICP-MS system proposed are the capability to renew solid phase extraction at will in a fully automated way, the remarkable stability of the column which can be reused up to 160 times, and the potential to perform isotopic analysis.

  4. Equilibrium statistical mechanics

    CERN Document Server

    Mayer, J E

    1968-01-01

    The International Encyclopedia of Physical Chemistry and Chemical Physics, Volume 1: Equilibrium Statistical Mechanics covers the fundamental principles and the development of theoretical aspects of equilibrium statistical mechanics. Statistical mechanical is the study of the connection between the macroscopic behavior of bulk matter and the microscopic properties of its constituent atoms and molecules. This book contains eight chapters, and begins with a presentation of the master equation used for the calculation of the fundamental thermodynamic functions. The succeeding chapters highlight t

  5. Testing of an automated online EA-IRMS method for fast and simultaneous carbon content and stable isotope measurement of aerosol samples

    Science.gov (United States)

    Major, István; Gyökös, Brigitta; Túri, Marianna; Futó, István; Filep, Ágnes; Hoffer, András; Molnár, Mihály

    2016-04-01

    Comprehensive atmospheric studies have demonstrated that carbonaceous aerosol is one of the main components of atmospheric particulate matter over Europe. Various methods, considering optical or thermal properties, have been developed for quantification of the accurate amount of both organic and elemental carbon constituents of atmospheric aerosol. The aim of our work was to develop an alternative fast and easy method for determination of the total carbon content of individual aerosol samples collected on prebaked quartz filters whereby the mass and surface concentration becomes simply computable. We applied the conventional "elemental analyzer (EA) coupled online with an isotope ratio mass spectrometer (IRMS)" technique which is ubiquitously used in mass spectrometry. Using this technique we are able to measure simultaneously the carbon stable isotope ratio of the samples, as well. During the developing process, we compared the EA-IRMS technique with an off-line catalytic combustion method worked out previously at Hertelendi Laboratory of Environmental Studies (HEKAL). We tested the combined online total carbon content and stable isotope ratio measurement both on standard materials and real aerosol samples. Regarding the test results the novel method assures, on the one hand, at least 95% of carbon recovery yield in a broad total carbon mass range (between 100 and 3000 ug) and, on the other hand, a good reproducibility of stable isotope measurements with an uncertainty of ± 0.2 per mill. Comparing the total carbon results obtained by the EA-IRMS and the off-line catalytic combustion method we found a very good correlation (R2=0.94) that proves the applicability of both preparation method. Advantages of the novel method are the fast and simplified sample preparation steps and the fully automated, simultaneous carbon stable isotope ratio measurement processes. Furthermore stable isotope ratio results can effectively be applied in the source apportionment

  6. Copper isotope fractionation between aqueous compounds relevant to low temperature geochemistry and biology

    Science.gov (United States)

    Fujii, Toshiyuki; Moynier, Frédéric; Abe, Minori; Nemoto, Keisuke; Albarède, Francis

    2013-06-01

    Isotope fractionation between the common Cu species present in solution (Cu+, Cu2+, hydroxide, chloride, sulfide, carbonate, oxalate, and ascorbate) has been investigated using both ab initio methods and experimental solvent extraction techniques. In order to establish unambiguously the existence of equilibrium isotope fractionation (as opposed to kinetic isotope fractionation), we first performed laboratory-scale liquid-liquid distribution experiments. Upon exchange between HCl medium and a macrocyclic complex, the 65Cu/63Cu ratio fractionated by -1.06‰ to -0.39‰. The acidity dependence of the fractionation was appropriately explained by ligand exchange reactions between hydrated H2O and Cl- via intramolecular vibrations. The magnitude of the Cu isotope fractionation among important Cu ligands was also estimated by ab initio methods. The magnitude of the nuclear field shift effect to the Cu isotope fractionation represents only ˜3% of the mass-dependent fractionation. The theoretical estimation was expanded to chlorides, hydroxides, sulfides, sulfates, and carbonates under different conditions of pH. Copper isotope fractionation of up to 2‰ is expected for different forms of Cu present in seawater and for different sediments (carbonates, hydroxides, and sulfides). We found that Cu in dissolved carbonates and sulfates is isotopically much heavier (+0.6‰) than free Cu. Isotope fractionation of Cu in hydroxide is minimal. The relevance of these new results to the understanding of metabolic processes was also discussed. Copper is an essential element used by a large number of proteins for electron transfer. Further theoretical estimates of δ65Cu in hydrated Cu(I) and Cu(II) ions, Cu(II) ascorbates, and Cu(II) oxalate predict Cu isotope fractionation during the breakdown of ascorbate into oxalate and account for the isotopically heavy Cu found in animal kidneys.

  7. Experimental thermodynamic study of the equilibrium phase AgBi{sub 3}S{sub 5} by an improved EMF method

    Energy Technology Data Exchange (ETDEWEB)

    Tesfaye, Fiseha, E-mail: fiseha.tesfaye@aalto.fi; Taskinen, Pekka, E-mail: pekka.taskinen@aalto.fi

    2013-06-20

    Highlights: • A new method for constructing and measuring on galvanic cells has been employed. • Galvanic cells including AgI and RbAg{sub 4}I{sub 5} solid electrolytes were measured accurately. • Thermodynamics of the phase assemblages AgBi{sub 3}S{sub 5}–Bi{sub 2}S{sub 3}–S/Bi have been investigated. • Δ{sub f}G° values for sulfur- and bismuth-saturated pavonite (AgBi{sub 3}S{sub 5}) have been determined. • New experimental thermodynamic data for bismuth-saturated pavonite were generated. - Abstract: A thermodynamic study of the equilibrium phase assemblages AgBi{sub 3}S{sub 5}–Bi{sub 2}S{sub 3}–S/Bi was made by an EMF-technique. The ternary phase was synthesized from the pure Ag{sub 2}S and Bi{sub 2}S{sub 3} in an evacuated silica ampoule, and ground into powder before mixing with appropriate compositions of Bi{sub 2}S{sub 3} and S or Bi. The phase mixtures were pressed into different pellets, in a series of experiments. Together with pieces of pure Ag-foil and the electrolytic pellets of superionic conductor RbAg{sub 4}I{sub 5} or AgI, the pellets were assembled to form the galvanic cells Pt(−) | Ag | RbAg{sub 4}I{sub 5} | AgBi{sub 3}S{sub 5} + Bi{sub 2}S{sub 3} + S + (C) | Pt(+) and Pt(−) | Ag | AgI | AgBi{sub 3}S{sub 5} + Bi{sub 2}S{sub 3} + Bi | C | Pt(+). The EMF-measurements were made in a temperature range 299.15–594.15 K. In this paper, the thermodynamic functions for the formation of pavonite (AgBi{sub 3}S{sub 5}) at sulfur and bismuth saturation have been determined. The obtained results are in agreement with some of the available literature values. Furthermore, new experimental thermodynamic data of bismuth-saturated pavonite (AgBi{sub 3+x}S{sub 5}; 0 < x < 0.14), in the temperature range 299.15–594.15 K, were determined.

  8. Validation of the method for determination of plutonium isotopes in urine samples and its application in a nuclear facility at Otwock

    Directory of Open Access Journals (Sweden)

    Rzemek Katarzyna

    2015-03-01

    Full Text Available The studies aimed at determining low activities of alpha radioactive elements are widely recognized as essential for the human health, because of their high radiotoxicity in case of internal contamination. Some groups of workers of nuclear facility at Otwock are potentially exposed to contamination with plutonium isotopes. For this reason, the method for determination of plutonium isotopes has been introduced and validated in Radiation Protection Measurements Laboratory (LPD of the National Centre for Nuclear Research (NCBJ. In this method the plutonium is isolated from a sample by coprecipitation with phosphates and separated on a AG 1-X2 Resin. After electrodeposition, the sample is measured by alpha spectrometry. Validation was performed in order to assess parameters such as: selectivity, accuracy (trueness and precision and linearity of the method. The results of plutonium determination in urine samples of persons potentially exposed to internal contamination are presented in this work.

  9. Sequential Assessment of Cell Cycle S Phase in Flow Cytometry: A Non-Isotopic Method to Measure Lymphocyte Activation In Vitro

    Directory of Open Access Journals (Sweden)

    Ch. Kohler

    1997-01-01

    Full Text Available Lymphocyte multiplication can be induced in vitro by mitogens or specific antigens, and is usually measured using isotopic methods involving tritiated thymidine. Cellular proliferation can also be analyzed by flow cytometry techniques based on cell cycle analysis through the measurement of DNA content. We applied this method to lymphocytes from 113 individuals, to evaluate lymphocyte proliferation after stimulation in vitro by a mitogen (phytohaemagglutinin, PHA or a recall antigen (tetanus toxoid, using a kinetic approach with four points sequential measurements of the S and G2 phases over six days of culture. The proportion of cells in S phase after PHA stimulation was significantly higher than in controls overall and as early as on day three of the culture. Activation with a recall antigen significantly induced increasing S phase cell proportions up to day six. These data suggest that flow cytometric assessment of the S phase could be a useful alternative to isotopic methods measuring lymphocyte reactivity in vitro.

  10. Easy Extraction Method To Evaluate δ13C Vanillin by Liquid Chromatography-Isotopic Ratio Mass Spectrometry in Chocolate Bars and Chocolate Snack Foods.

    Science.gov (United States)

    Bononi, Monica; Quaglia, Giancarlo; Tateo, Fernando

    2015-05-20

    An easy extraction method that permits the use of a liquid chromatography-isotopic ratio mass spectrometry (LC-IRMS) system to evaluate δ(13)C of vanillin in chocolate products and industrial flavorings is presented. The method applies the determination of stable isotopes of carbon to discriminate between natural vanillin from vanilla beans and vanillin from other sources (mixtures from beans, synthesis, or biotechnology). A series of 13 chocolate bars and chocolate snack foods available on the Italian market and 8 vanilla flavorings derived from industrial quality control processes were analyzed. Only 30% of products considered in this work that declared "vanilla" on the label showed data that permitted the declaration "vanilla" according to European Union (EU) Regulation 1334/2008. All samples not citing "vanilla" or "natural flavoring" on the label gave the correct declaration. The extraction method is presented with data useful for statistical evaluation.

  11. Method for determination of uranium isotopes in environmental samples by liquid-liquid extraction with triisooctylamine/xylene in hydrochloric media and alpha spectrometry.

    Science.gov (United States)

    Popov, L

    2012-10-01

    Alternative method for determination of uranium isotopes in various environmental samples is presented. The method is based on total decomposition of the solid materials and preconcentration of liquid samples. The separation of uranium from interfering radionuclides and stable matrix elements is attained by liquid-liquid extraction with triisooctylamine/xylene in hydrochloric media. After the additional removal of stable iron by extraction with diisopropyl ether, purified uranium is electrodeposited on stainless steel disks and measured by alpha spectrometry. The analytical method has been successfully applied to the determination of uranium isotopes in water and bottom sediments from the rivers Danube, Ogosta and Tzibritza in Northwestern Bulgaria. The analytical quality was checked by analyzing reference materials with different matrices.

  12. Evaluation of sample pretreatment methods for analysis of polonium isotopes in herbal medicines.

    Science.gov (United States)

    Sreejith, Sathyapriya R; Nair, Madhu G; Rao, D D

    2014-12-01

    Herbal infusions like ayurvedic aristas are widely consumed by Indian population for good health. With increasing awareness about radiological assessment, an effort was made to assess the radioactivity concentration of naturally occurring radionuclides in herbal medicines. (210)Po is an important alpha particle emitter contributing to internal dose to man from ingestion. Though (210)Po can be spontaneously deposited on silver disk for alpha spectrometric measurements with less radiochemical step, great care has to be taken during the sample pretreatment step owing to the high volatility of polonium even at low temperatures. Aim of the study was to evaluate an appropriate sample pretreatment method for estimation of polonium in herbal medicines. (209)Po was used for radiochemical yield calculation. Conventional open vessel wet ashing, physical evaporation, freeze-drying and microwave digestion in a Teflon vessel were examined. The recovery ranged between 9 and 79%. The lowest recovery was obtained for the samples that were processed by open vessel digestion without any volume reduction. The recoveries were comparable for those samples that were freeze dried and subjected to HNO3 + HClO4 + H2O2 + HF acid digestion and microwave digested samples. (210)Po concentration in the samples ranged from 11.3 to 39.6 mBq/L.

  13. New on-line method for water isotope analysis of fluid inclusions in speleothems using laser absorption spectroscopy: Application to stalagmites from Borneo and Switzerland

    Science.gov (United States)

    Affolter, Stéphane; Fleitmann, Dominik; Nele Meckler, Anna; Leuenberger, Markus

    2014-05-01

    Speleothems are recognised as key continental archives for paleoclimate reconstructions. They contain fluid inclusions representing past drip water trapped in the calcite structure. Speleothem can be precisely dated and therefore the oxygen (δ18O) and hydrogen (δD) isotopes of fluid inclusions constitute powerful proxies for paleotemperature or to investigate changes in the moisture source over several interglacial-glacial cycles. To liberate fluid inclusion water and to analyse its isotopic composition, a new online extraction method developed at Bern is used. The principle can be summarised as follows: Prior to crushing, the sample is placed into a copper tube, fixed to the line previously heated to 140° C and flushed with a nitrogen and standard water mixture. Thereafter, the speleothem sample is crushed using a simple hydraulic crushing device and the released water from fluid inclusions is transferred by the nitrogen-standard water mixture flow to a Picarro L1102-i isotopic liquid water and water vapor analyser. The measuring principle is based on wavelength-scanned cavity ring-down spectroscopy (WS-CRDS) technology that allows us to simultaneously monitor hydrogen and oxygen isotopes. Reproducibility of standard water measurements is typically better than 1.5 o for δD and 0.4 o for δ18O. With this method, we successfully analysed δD and δ18O isotopic composition of a stalagmite from Northern Borneo (tropical West Pacific) covering almost two glacial-interglacial cycles from MIS 12 to early MIS 9 (460-330 ka) as well as recent samples from Switzerland and Borneo. These results are used in combination with calcite δ18O to reconstruct paleotemperature. Currently, we are measuring a stalagmite from Milandre cave (Jura, Switzerland) covering the Bølling-Allerød, Younger Dryas cold phase and the Holocene.

  14. Method development for the redox speciation analysis of iron by ion chromatography-inductively coupled plasma mass spectrometry and carryover assessment using isotopically labeled analyte analogues.

    Science.gov (United States)

    Wolle, Mesay Mulugeta; Fahrenholz, Timothy; Rahman, G M Mizanur; Pamuku, Matt; Kingston, H M 'Skip'; Browne, Damien

    2014-06-20

    An ion chromatography-inductively coupled plasma mass spectrometry (IC-ICP-MS) method was developed for the redox speciation analysis of iron (Fe) based on in-column complexation of Fe(2+) and Fe(3+) by dipicolinic acid (DPA). The effects of column type, mobile phase composition and molecular ion interference were studied in the method optimization. The carryover of the target species in the IC-ICP-MS method was uniquely and effectively evaluated using isotopically enriched analogues of the analytes ((54)Fe(2+) and (57)Fe(3+)). Standard solutions of the enriched standards were injected into the system following analysis of a sample, and the ratios of the isotopes of iron in the enriched standards were calculated based on the chromatographic peak areas. The concentrations of the analytes carried over from the sample to the enriched standards were determined using the quantitative relationship in isotope dilution mass spectrometry (IDMS). In contrast to the routine way of evaluating carryover effect by injecting a blank solution after sample analysis, the use of isotopically enriched standards identified significant analyte carryover in the present method. Extensive experiments were carried out to systematically identify the source of the carryover and to eliminate the problem; the separation column was found to be the exclusive source. More than 95% of the analyte carryover was eliminated by reducing the length of the column. The detection limit of the IC-ICP-MS method (MDL) for the iron species was 2ngg(-1). The method was used to determine Fe(2+) and Fe(3+) in synthetic aqueous standard solutions and a beverage sample.

  15. Abiologic silicon isotope fractionation between aqueous Si and Fe(III)-Si gel in simulated Archean seawater: Implications for Si isotope records in Precambrian sedimentary rocks

    Science.gov (United States)

    Zheng, Xin-Yuan; Beard, Brian L.; Reddy, Thiruchelvi R.; Roden, Eric E.; Johnson, Clark M.

    2016-08-01

    Precambrian Si-rich sedimentary rocks, including cherts and banded iron formations (BIFs), record a >7‰ spread in 30Si/28Si ratios (δ30Si values), yet interpretation of this large variability has been hindered by the paucity of data on Si isotope exchange kinetics and equilibrium fractionation factors in systems that are pertinent to Precambrian marine conditions. Using the three-isotope method and an enriched 29Si tracer, a series of experiments were conducted to constrain Si isotope exchange kinetics and fractionation factors between amorphous Fe(III)-Si gel, a likely precursor to Precambrian jaspers and BIFs, and aqueous Si in artificial Archean seawater under anoxic conditions. Experiments were conducted at room temperature, and in the presence and absence of aqueous Fe(II) (Fe(II)aq). Results of this study demonstrate that Si solubility is significantly lower for Fe-Si gel than that of amorphous Si, indicating that seawater Si concentrations in the Precambrian may have been lower than previous estimates. The experiments reached ˜70-90% Si isotope exchange after a period of 53-126 days, and the highest extents of exchange were obtained where Fe(II)aq was present, suggesting that Fe(II)-Fe(III) electron-transfer and atom-exchange reactions catalyze Si isotope exchange through breakage of Fe-Si bonds. All experiments except one showed little change in the instantaneous solid-aqueous Si isotope fractionation factor with time, allowing extraction of equilibrium Si isotope fractionation factors through extrapolation to 100% isotope exchange. The equilibrium 30Si/28Si fractionation between Fe(III)-Si gel and aqueous Si (Δ30Sigel-aqueous) is -2.30 ± 0.25‰ (2σ) in the absence of Fe(II)aq. In the case where Fe(II)aq was present, which resulted in addition of ˜10% Fe(II) in the final solid, creating a mixed Fe(II)-Fe(III) Si gel, the equilibrium fractionation between Fe(II)-Fe(III)-Si gel and aqueous Si (Δ30Sigel-aqueous) is -3.23 ± 0.37‰ (2σ). Equilibrium

  16. Improvement in Thermal-Ionization Mass Spectrometry (TIMS) using Total Flash Evaporation (TFE) method for lanthanides isotope ratio measurements in transmutation targets

    Energy Technology Data Exchange (ETDEWEB)

    Mialle, S.; Gourgiotis, A.; Aubert, M.; Stadelmann, G.; Gautier, C.; Isnard, H. [Commissariat a l' Energie Atomique, CEA Saclay, DEN/DPC/SECR/LANIE, 91191 Gif sur Yvette (France); Chartier, F. [Commissariat a l' Energie Atomique, CEA Saclay, DEN/DPC, 91191 Gif sur Yvette (France)

    2011-07-01

    The experiments involved in the PHENIX french nuclear reactor to obtain precise and accurate data on the total capture cross sections of the heavy isotopes and fission products require isotopic ratios measurements with uncertainty of a few per mil. These accurate isotopic ratio measurements are performed with mass spectrometer equipped with multi-collector system. The major difficulty for the analyses of these actinides and fission products is the low quantity of the initial powder enclosed in steel container (3 to 5 mg) and the very low quantities of products formed (several {mu}g) after irradiation. Specific analytical developments are performed by Thermal Ionization Mass Spectrometry (TIMS) to be able to analyse several nanograms of elements with this technique. A specific method of acquisition named Total Flash Evaporation was adapted in this study in the case of lanthanide measurements for quantity deposited on the filament in the order of 2 ng and applied on irradiated fuel. To validate the analytical approach and discuss about the accuracy of the data, the isotopic ratios obtained by TIMS are compared with other mass spectrometric techniques such as Multiple-Collector Inductively Coupled Plasma Mass Spectrometer (MC-ICPMS). (authors)

  17. Quantifying Na(I)-insulin and K(I)-insulin non-covalent complexes by ESI-MS method and calculation of their equilibrium constants.

    Science.gov (United States)

    Gülfen, Mustafa; Özdemir, Abdil; Lin, Jung-Lee; Chen, Chung-Hsuan

    2017-10-01

    In this study, the dissociation and formation equilibrium constants of Na(I)-insulin and K(I)-insulin complexes have been calculated after the quantifying them on ESI mass spectrometer. The ESI-MS spectra of the complexes were measured by using the solvents as 50% MeOH in water and 100% water. The effect of pH on the Na(I)-insulin and K(I)-insulin complex formation were examined. Serial binding of Na(I) and K(I) ions to the insulin molecule were observed in the ESI-MS measurements. The first formation equilibrium constants were calculated as Kf1: 5.48×10(3) 1/M for Na(I)-insulin complex and Kf1: 4.87×10(3) 1/M for K(I)-insulin in water. The binding capability of Na(I) ions to insulin molecule is higher than the capability of K(I) ions. In case of a comparison together with Ca(II)-insulin and Mg(II)-insulin, the formation equilibrium constants (Kf1) are in order of Ca(II)-insulin>Mg(II)-insulin>Na(I)-insulin>K(I)-insulin in water. The results showed that Na(I) and K(I) ions are involved in the formation of the non-covalent complexes with insulin molecule, since high extracellular and intracellular concentrations of them in the body. Copyright © 2017 Elsevier B.V. All rights reserved.

  18. Oxygen Isotope Fractionation in TiO2 Polymorphs and Application to Geothermometry of Eclogites

    Institute of Scientific and Technical Information of China (English)

    郑永飞

    1995-01-01

    Oxygen isotope fractionation in TiO2 polymorphs has been calculated by the modi-fied increment method .The results that rutile is enriched in 18O relative to brookite but depleted in 18O relative to anatase.Due to the same crystal structure ,oxygen isotope partitioning in the TiO2 polymorphs is determined by the cation-oxygen inter-atomic distances.The theoretical calibrations involving rutile are in fair agreement with known experimental measurements and empirical estimates.Application of the theoretic-cal quartz-rutile calibration to geothermometry of natural eclogite assemblages indicates the preservation of isotopic equilibrium at high temperatures.The isotopic temperatures calculated are only slightly lower than the non-isotopic temperatures,indicating the slow rates of exchange for oxygen diffusion in rutile.The kinetics of exchange for oxygen diffu-sion in rutile is accordingly estimated by reconciling the differences between the isotopic and the non-isotopic temperatures.The rates of exchange for oxygen diffusion in rutile should be smaller than those for hornblende,but may be equal to or greater than those for diopside.

  19. Position-specific and clumped stable isotope studies: comparison of the Urey and path-integral approaches for carbon dioxide, nitrous oxide, methane, and propane.

    Science.gov (United States)

    Webb, Michael A; Miller, Thomas F

    2014-01-16

    We combine path-integral Monte Carlo methods with high-quality potential energy surfaces to compute equilibrium isotope effects in a variety of systems relevant to 'clumped' isotope analysis and isotope geochemistry, including CO2, N2O, methane, and propane. Through a systematic study of heavy-atom isotope-exchange reactions, we quantify and analyze errors that arise in the widely used Urey model for predicting equilibrium constants of isotope-exchange reactions using reduced partition function ratios. These results illustrate that the Urey model relies on a nontrivial cancellation of errors that can shift the apparent equilibrium temperature by as much as 35 K for a given distribution of isotopologues. The calculations reported here provide the same level of precision as the best existing analytical instrumentation, resolving the relative enrichment of certain isotopologues to as little as 0.01‰. These findings demonstrate path-integral methods to be a rigorous and viable alternative to more approximate methods for heavy-atom geochemical applications.

  20. Overview of Uranium Isotopic Reference Materials at IRMM

    Science.gov (United States)

    Alonso-Munoz, A.; Richter, S.; Eykens, R.; Aregbe, Y.; Kuehn, H.; Verbruggen, A.

    2007-12-01

    For many applications in the geological sciences, in particular in geochemistry research, isotope ratio measurements play a significant role. For instance, in geochronology isotope abundances of uranium and its daughter products thorium and lead have been used since more than five decades to determine the age of various samples of geological interest. However, in order to validate mass spectrometric measurement procedures and to calibrate detector systems, suitable isotope reference materials are needed. IRMM is a well recognized provider for nuclear isotope reference materials to the nuclear industry and nuclear safeguards authorities, which can also be used for geological applications. This paper gives an overview of isotope reference materials for uranium prepared and certified at IRMM. These materials are synthetic isotope reference materials prepared based on proven methods of purifying and mixing highly enriched oxides. Firstly, a set of 10 mixtures of 233U, 235U and 238U was made in which the 235U/238U ratios were kept at 1:1 and the 233U/235U ratios varied from 1.0 to 10-6 (IRMM-072). This set is ideal for checking the linearity response of detectors used in isotope mass spectrometry. Recently, after the IRMM-072 series was exhausted, it has been replaced by the IRMM-073 and IRMM-074 series. Secondly the double spike IRMM-3636 with a 233U/236U ratio of 1:1 was prepared which allows internal mass fractionation correction for high precision 235U/238U ratio measurements. The 234U abundance of this double spike material is low enough to allow an accurate and precise correction of 234U/238U ratios, even for measurements of close to equilibrium uranium samples.

  1. Equilibrium games in networks

    Science.gov (United States)

    Li, Angsheng; Zhang, Xiaohui; Pan, Yicheng; Peng, Pan

    2014-12-01

    It seems a universal phenomenon of networks that the attacks on a small number of nodes by an adversary player Alice may generate a global cascading failure of the networks. It has been shown (Li et al., 2013) that classic scale-free networks (Barabási and Albert, 1999, Barabási, 2009) are insecure against attacks of as small as O(logn) many nodes. This poses a natural and fundamental question: Can we introduce a second player Bob to prevent Alice from global cascading failure of the networks? We proposed a game in networks. We say that a network has an equilibrium game if the second player Bob has a strategy to balance the cascading influence of attacks by the adversary player Alice. It was shown that networks of the preferential attachment model (Barabási and Albert, 1999) fail to have equilibrium games, that random graphs of the Erdös-Rényi model (Erdös and Rényi, 1959, Erdös and Rényi, 1960) have, for which randomness is the mechanism, and that homophyly networks (Li et al., 2013) have equilibrium games, for which homophyly and preferential attachment are the underlying mechanisms. We found that some real networks have equilibrium games, but most real networks fail to have. We anticipate that our results lead to an interesting new direction of network theory, that is, equilibrium games in networks.

  2. On equilibrium structures of the water molecule

    Science.gov (United States)

    Császár, Attila G.; Czakó, Gábor; Furtenbacher, Tibor; Tennyson, Jonathan; Szalay, Viktor; Shirin, Sergei V.; Zobov, Nikolai F.; Polyansky, Oleg L.

    2005-06-01

    Equilibrium structures are fundamental entities in molecular sciences. They can be inferred from experimental data by complicated inverse procedures which often rely on several assumptions, including the Born-Oppenheimer approximation. Theory provides a direct route to equilibrium geometries. A recent high-quality ab initio semiglobal adiabatic potential-energy surface (PES) of the electronic ground state of water, reported by Polyansky et al. [Polyansky et al.Science 299, 539 (2003)] and called CVRQD here, is analyzed in this respect. The equilibrium geometries resulting from this direct route are deemed to be of higher accuracy than those that can be determined by analyzing experimental data. Detailed investigation of the effect of the breakdown of the Born-Oppenheimer approximation suggests that the concept of an isotope-independent equilibrium structure holds to about 3×10-5Å and 0.02° for water. The mass-independent [Born-Oppenheimer (BO)] equilibrium bond length and bond angle on the ground electronic state PES of water is reBO=0.95782Å and θeBO=104.485°, respectively. The related mass-dependent (adiabatic) equilibrium bond length and bond angle of H2O16 is read=0.95785Å and θead=104.500°, respectively, while those of D2O16 are read=0.95783Å and θead=104.490°. Pure ab initio prediction of J =1 and 2 rotational levels on the vibrational ground state by the CVRQD PESs is accurate to better than 0.002cm-1 for all isotopologs of water considered. Elaborate adjustment of the CVRQD PESs to reproduce all observed rovibrational transitions to better than 0.05cm-1 (or the lower ones to better than 0.0035cm-1) does not result in noticeable changes in the adiabatic equilibrium structure parameters. The expectation values of the ground vibrational state rotational constants of the water isotopologs, computed in the Eckart frame using the CVRQD PESs and atomic masses, deviate from the experimentally measured ones only marginally, especially for A0 and B0. The

  3. An assessment of geochemical preparation methods prior to organic carbon concentration and carbon isotope ratio analyses of fine-grained sedimentary rocks

    Science.gov (United States)

    KöNitzer, Sven F.; Leng, Melanie J.; Davies, Sarah J.; Stephenson, Michael H.

    2012-09-01

    This study summarizes organic carbon isotope (δ13C) and total organic carbon (TOC) data from a series of tests undertaken to provide an appropriate methodology for pre-analysis treatment of mudstones from an Upper Carboniferous sedimentary succession, in order to develop a consistent preparation procedure. The main treatments involved removing both inorganic carbonate and hydrocarbons (which might be extraneous) before δ13C and TOC analysis. The results show that decarbonating using hydrochloric acid causes significant reduction in δ13C and total carbon (TC) of the bulk material due to the removal of inorganic carbonate. These changes are most pronounced where soluble calcium carbonate (rather than Ca-Mg-Fe carbonate) is present. Deoiled samples show only slightly higher mean δ13C where visible bitumen was extracted from the bulk sample. Moreover, the isotopic signatures of the extracts are closely correlated to those of their respective bulk samples, suggesting that small yields of hydrocarbons were generated in situ with no isotopic fractionation. In addition, further δ13C and TC analyses were performed on samples where mixing of oil-based drilling mud with brecciated core material had been undertaken. Brecciated mudstone material did not display distinct isotopic signals compared to the surrounding fine-grained material. Overall we show that the most accurate assessment of bulk organic carbon isotopes and concentration in these samples can be achieved through decarbonating the material prior to measurement via the `rinse method'. However, our results support recent findings that pre-analysis acid treatments can cause variable and unpredictable errors in δ13C and TOC values. We believe that, despite these uncertainties, the findings presented here can be applied to paleoenvironmental studies on organic matter contained within sedimentary rocks over a range of geological ages and compositions.

  4. New Method for Determining Isotopic Values of Glutamic Acid and Phenylalanine for Estimation of Precise Trophic Position in Food Web Studies

    Science.gov (United States)

    Kamath, T.; Broek, T.; McCarthy, M.

    2012-12-01

    Compound Specific Isotope Analysis of Amino Acids (CSI-AA) has emerged as a highly precise new method of determining trophic levels of both aquatic and terrestrial organisms. Multiple studies have now shown that δ15N values for glutamic acid (Glu) and phenylalanine (Phe) can be coupled to provide extremely precise estimates of trophic position in diverse food web studies. The standard gas chromatography—isotope ratio mass spectrometer (GC-IRMS) approach is presently limited to a select number of labs since necessary equipment is both expensive and not widely accessible. Furthermore, typical GC-IRMS δ15N precision (±1‰) is significantly lower than usual bulk δ15N values (±0.1‰), thus presenting a considerable setback for precise trophic level calculations. In this study, we develop a new dual-column method to purify Glu and Phe using high performance liquid chromatography (HPLC). Phe is purified using an analytical scale reverse phase column embedded with anionic ion-pairing reagents and collected using automated fraction collection. Glu is separated from the non-polar amino acids using the same column and further purified using a hydrophilic interaction liquid chromatography (HILIC) cation and anion-exchange column and collected via automated fraction collection. Isotopic analysis of the purified AAs is then conducted on an elemental analyzer—isotope ratio mass spectrometer (EA-IRMS). As a test of this method, we present and compare the trophic position of five marine organisms—cyanobacteria, deep-sea bamboo coral, juvenile and adult white sea bass, and harbor seal, calculated using Glu and Phe δ15N values produced by both GC-IRMS and our HPLC-EA-IRMS approach. The preliminary results of this study suggest that the HPLC-EA-IRMS method is a viable alternative to GC-IRMS, which should allow accurate trophic position estimates to be made by more researchers using more readily available instrumentation.

  5. Immunity by equilibrium.

    Science.gov (United States)

    Eberl, Gérard

    2016-08-01

    The classical model of immunity posits that the immune system reacts to pathogens and injury and restores homeostasis. Indeed, a century of research has uncovered the means and mechanisms by which the immune system recognizes danger and regulates its own activity. However, this classical model does not fully explain complex phenomena, such as tolerance, allergy, the increased prevalence of inflammatory pathologies in industrialized nations and immunity to multiple infections. In this Essay, I propose a model of immunity that is based on equilibrium, in which the healthy immune system is always active and in a state of dynamic equilibrium between antagonistic types of response. This equilibrium is regulated both by the internal milieu and by the microbial environment. As a result, alteration of the internal milieu or microbial environment leads to immune disequilibrium, which determines tolerance, protective immunity and inflammatory pathology.

  6. Stable iron isotope fractionation between aqueous Fe(II) and model Archean ocean Fe-Si coprecipitates and implications for iron isotope variations in the ancient rock record

    Science.gov (United States)

    Wu, Lingling; Percak-Dennett, Elizabeth M.; Beard, Brian L.; Roden, Eric E.; Johnson, Clark M.

    2012-05-01

    Iron isotope fractionation between aqueous Fe(II) (Fe(II)aq) and two amorphous Fe(III) oxide-Si coprecipitates was investigated in an aqueous medium that simulated Archean marine conditions, including saturated amorphous silica, low sulfate, and zero dissolved oxygen. The equilibrium isotope fractionation (in 56Fe/54Fe) between Fe(II)aq and Fe(III)-Si coprecipitates at circum-neutral pH, as inferred by the three-isotope method, was -3.51 ± 0.20 (2σ)‰ and -3.99 ± 0.17 (2σ)‰ for coprecipitates that had Fe:Si molar ratios of 1:2 and 1:3, respectively. These results, when combined with earlier work, indicate that the equilibrium isotope fractionation factor between Fe(II)aq and Fe(III)-Si coprecipitates changes as a function of Fe:Si ratio of the solid. Isotopic fractionation was least negative when Fe:Si = 1:1 and most negative when Fe:Si = 1:3. This change corresponds with changes in the local structure of iron, as revealed by prior spectroscopic studies. The kinetics of isotopic exchange was controlled by movement of Fe(II) and Si, where sorption of Fe(II) from aqueous to solid phase facilitated atom exchange, but sorption of Si hindered isotopic exchange through blockage of reactive surface sites. Although Fe(II)-Fe(III) isotopic exchange rates were a function of solid and solution compositions in the current study, in all cases they were much higher than that determined in previous studies of aqueous Fe(III) and ferrihydrite interaction, highlighting the importance of electron exchange in promoting Fe atom exchange. When compared to analogous microbial reduction experiments of overlapping Fe(II) to Fe(III) ratios, isotopic exchange rates were faster in the biological experiments, likely due to promotion of atom exchange by the solid-phase Fe(II) produced in the biological experiments. These results provide constraints for interpreting the relatively large range of Fe isotope compositions in Precambrian marine sedimentary rocks, and highlight important

  7. A practical method for the determination of total selenium in environmental samples using isotope dilution-hydride generation-inductively coupled plasma-mass spectrometry

    Science.gov (United States)

    Kleckner, Amy E.; Kakouros, Evangelos; Stewart, A. Robin

    2017-01-01

    A safe, practical, and accurate method for the determination of selenium (Se) in range of environmental samples was developed. Small sample masses, 5–20 mg, were amended with 82Se enriched isotope for the isotope dilution (ID), preceding a multi-step wet digestion with nitric acid (HNO3) and hydrogen peroxide (H2O2). Samples were incubated in an autoclave for 3 h at 20 psi and 126°C. Digestates were subsequently reduced with concentrated hydrochloric acid to Se(IV) the most favorable valence for hydride generation (HG). The solutions were then analyzed on an ICP-MS equipped with Flow Injection system (FIAS-400). Polyatomic, isobaric, and background interferences were removed through the use of HG and ID with an 82Se enriched isotope spike. Recoveries for certified reference materials were determined and averaged 96% for biological tissues (NRCC DOLT3, DOLT4, DORM2, TORT2, and TORT3, and NIST 2976) and 108% for estuarine sediment (NRCC PACS2) with an average coefficient of variation for replicate measurements of ∼ 3.5%. Limit of detection was 0.13 ng Se g−1 dry weight or 0.19 ng Se L−1. This method can be broadly applied to biological tissues, sediments, suspended particulates, and water samples with minimal modifications making this method highly useful for assessing the ecotoxicology of total Se in aquatic ecosystems.

  8. Microbial perchlorate reduction: A precise laboratory determination of the chlorine isotope fractionation and its possible biochemical basis

    Science.gov (United States)

    Ader, Magali; Chaudhuri, Swades; Coates, John D.; Coleman, Max

    2008-05-01

    Perchlorate-reducing bacteria fractionate chlorine stable isotopes giving a powerful approach to monitor the extent of microbial consumption of perchlorate in contaminated sites undergoing remediation or natural perchlorate containing sites. This study reports the full experimental data and methodology used to re-evaluate the chlorine isotope fractionation of perchlorate reduction in duplicate culture experiments of Azospira suillum strain PS at 37 °C (Δ 37Cl Cl --ClO 4-) previously reported, without a supporting data set by Coleman et al. [Coleman, M.L., Ader, M., Chaudhuri, S., Coates, J.D., 2003. Microbial Isotopic Fractionation of Perchlorate Chlorine. Appl. Environ. Microbiol. 69, 4997-5000] in a reconnaissance study, with the goal of increasing the accuracy and precision of the isotopic fractionation determination. The method fully described here for the first time, allows the determination of a higher precision Δ 37Cl Cl --ClO 4- value, either from accumulated chloride content and isotopic composition or from the residual perchlorate content and isotopic composition. The result sets agree perfectly, within error, giving average Δ 37Cl Cl --ClO 4- = - 14.94 ± 0.15‰. Complementary use of chloride and perchlorate data allowed the identification and rejection of poor quality data by applying mass and isotopic balance checks. This precise Δ 37Cl Cl --ClO 4- value can serve as a reference point for comparison with future in situ or microcosm studies but we also note its similarity to the theoretical equilibrium isotopic fractionation between a hypothetical chlorine species of redox state + 6 and perchlorate at 37 °C and suggest that the first electron transfer during perchlorate reduction may occur at isotopic equilibrium between an enzyme-bound chlorine and perchlorate.

  9. Determination of thyroid hormones in mouse tissues by isotope-dilution microflow liquid chromatography-mass spectrometry method.

    Science.gov (United States)

    De Angelis, Meri; Giesert, Florian; Finan, Brian; Clemmensen, Christoffer; Müller, Timo D; Vogt-Weisenhorn, Daniela; Tschöp, Matthias H; Schramm, Karl-Werner

    2016-10-15

    Thyroid hormones (THs) play a critical role in the regulation of many biological processes such as growth, metabolism and development both in humans and wildlife. In general, TH levels are measured by immunoassay (IA) methods but the specificity of the antibodies used in these assays limits selectivity. In the last decade, several analytical methods using liquid chromatography-mass spectrometry (LC-MS) and tandem mass spectrometry (LC-MS/MS) have been developed to measure THs. These new techniques proved to be more accurate than the IA analysis and they were widely used for the determination of TH level in different human and animal tissues. A large part of LC-MS/MS methods described in literature employed between 200 and 500mg of sample, however this quantity can be considered too high especially when preclinical studies are conducted using mice as test subjects. Thus an analytical method that reduces the amount of tissue is essential. In this study, we developed a procedure for the analysis of six THs; L-thyroxine (T4), 3,3',5-triiodo-l-thyronine (T3), 3,3',5'-triiodo-l-thyronine (rT3), 3,5-diiodo-l-thyronine (rT2), 3,3'-diiodo-l-thyronine (T2), 3-iodo-l-thyronine (T1) using isotope ((13)C6-T4, (13)C6-T3, (13)C6-rT3, (13)C6-T2) dilution liquid chromatography-mass spectrometry. The major difference with previously described methods lies in the utilization of a nano-UPLC (Ultra Performance Liquid Chromatography) system in micro configuration. This approach leads to a reduction compared to the published methods, of column internal diameter, flow rate, and injected volume. The result of all these improvements is a decrease in the amount of sample necessary for the analysis. The method was tested on six different mouse tissues: liver, heart, kidney, muscle, lung and brown adipose tissue (BAT). The nano-UPLC system was interfaced with a quadrupole time-of-flight mass spectrometer (Q-TOF2-MS) using the positive ion mode electrospray ionization. In our analytical method

  10. Blood: bone equilibrium

    Energy Technology Data Exchange (ETDEWEB)

    Neuman, M.W.

    1982-01-01

    The conundrum of blood undersaturation with respect to bone mineralization and its supersaturation with respect to bone's homeostatic function has acquired a new equation. On the supply side, Ca/sup 2 +/ is pumped in across bone cells to provide the needed Ca/sup 2 +/ x P/sub i/ for brushite precipitation. On the demand side, blood is in equilibrium with bone fluid, which is in equilibrium with a mineral more soluble than apatite. The function of potassium in this equation is yet to be found.

  11. A simple isotopic labeling method to study cysteine oxidation in Alzheimer's disease: oxidized cysteine-selective dimethylation (OxcysDML).

    Science.gov (United States)

    Gu, Liqing; Robinson, Renã A S

    2016-04-01

    Cysteine is widely involved in redox signaling pathways through a number of reversible and irreversible modifications. Reversible modifications (e.g., S-glutathionylation, S-nitrosylation, disulfide bonds, and sulfenic acid) are used to protect proteins from oxidative attack and maintain cellular homeostasis, while irreversible oxidations (e.g., sulfinic acid and sulfonic acid) serve as hallmarks of oxidative stress. Proteomic analysis of cysteine-enriched peptides coupled with reduction of oxidized thiols can be used to measure the oxidation states of cysteine, which is helpful for elucidating the role that oxidative stress plays in biology and disease. As an extension of our previously reported cysDML method, we have developed oxidized cysteine-selective dimethylation (OxcysDML), to investigate the site-specific total oxidation of cysteine residues in biologically relevant samples. OxcysDML employs (1) blocking of free thiols by a cysteine-reactive reagent, (2) enrichment of peptides containing reversibly oxidized cysteine by a solid phase resin, and (3) isotopic labeling of peptide amino groups to quantify cysteine modifications arising from different biological conditions. On-resin enrichment and labeling minimizes sample handing time and improves efficiency in comparison with other redox proteomic methods. OxcysDML is also inexpensive and flexible, as it can accommodate the exploration of various cysteine modifications. Here, we applied the method to liver tissues from a late-stage Alzheimer's disease (AD) mouse model and wild-type (WT) controls. Because we have previously characterized this proteome using the cysDML approach, we are able here to probe deeper into the redox status of cysteine in AD. OxcysDML identified 1129 cysteine sites (from 527 proteins), among which 828 cysteine sites underwent oxidative modifications. Nineteen oxidized cysteine sites had significant alteration levels in AD and represent proteins involved in metabolic processes. Overall

  12. Towards breaking temperature equilibrium in multi-component Eulerian schemes

    Energy Technology Data Exchange (ETDEWEB)

    Grove, John W [Los Alamos National Laboratory; Masser, Thomas [Los Alamos National Laboratory

    2009-01-01

    We investigate the effects ofthermal equilibrium on hydrodynamic flows and describe models for breaking the assumption ofa single temperature for a mixture of components in a cell. A computational study comparing pressure-temperature equilibrium simulations of two dimensional implosions with explicit front tracking is described as well as implementation and J-D calculations for non-equilibrium temperature methods.

  13. 3D quantification of dynamic fluid-fluid interfaces in porous media with fast x-ray microtomography: A comparison with quasi-equilibrium methods

    Science.gov (United States)

    Meisenheimer, D.; Brueck, C. L.; Wildenschild, D.

    2015-12-01

    X-ray microtomography imaging of fluid-fluid interfaces in three-dimensional porous media allows for the testing of thermodynamically derived predictions that seek a unique relationship between capillary pressure, fluid saturation, and specific interfacial area (Pc-Sw-Anw). Previous experimental studies sought to test this functional dependence under quasi-equilibrium conditions (assumed static on the imaging time-scale); however, applying predictive models developed under static conditions for dynamic scenarios can lead to substantial flaws in predicted outcomes. Theory and models developed using dynamic data can be verified using fast x-ray microtomography which allows for the unprecedented measurement of developing interfacial areas, curvatures, and trapping behaviors of fluid phases in three-dimensional systems. We will present results of drainage and imbibition experiments of air and water within a mixture of glass beads. The experiments were performed under both quasi-equilibrium and dynamic conditions at the Advanced Photon Source (APS) at Argonne National Laboratory. Fast x-ray microtomography was achieved by utilizing the high brilliance of the x-ray beam at the APS under pink-beam conditions where the white beam is modified with a 4 mm Al absorber and a 0.8 mrad Pt-coated mirror to eliminate low and high-energy photons, respectively. We present a comparison of the results from the quasi-equilibrium and dynamic experiments in an effort to determine if the Pc-Sw-Anw relationship is comparable under either experimental condition and to add to the discussion on whether the Pc-Sw-Anw relationship is unique as hypothesized by existing theory.

  14. Nondispersive isotope-selective infrared spectroscopy: A new analytical method for {sup 13}C-urea breath tests

    Energy Technology Data Exchange (ETDEWEB)

    Braden, B.; Schaefer, F.; Caspary, W.F.; Lembcke, B. [Johann Wolfgang Goethe Univ., Frankfurt am Main (Germany)

    1996-05-01

    Currently, stable isotope techniques in breath tests using {sup 13}C-labeled substrates are limited to a few centers equipped with expensive and complex isotope spectrometry (IRMS). Although breath samples can be mailed to these centers, widespread application of {sup 13}C-breath tests would be more feasible with a cheaper and more practicable analysis system at hand. The authors therefore tested the newly developed nondispersive isotope-selective infrared spectrometer (NDIRS) with reference to IRMS in a clinical setting, comparing the results of both techniques in 538 consecutive {sup 13}C-urea breath tests performed for the detection of helicobacter pylori infection. With NDIRS five false-positive and three false-negative results were observed; that is, the sensitivity of NDIRS was 98.3%, and the specificity was 98.6%. When running this large number of breath tests in 3 days, the NDIRS proved to be a reliable, stable, and easy-to-operate analytical tool, which is well qualified for gastroenterologic application in the diagnostic routine. Both the price and the easy handling of NDIRS will facilitate the widespread use of the noninvasive stable isotope technique for {sup 13}C breath test. 22 refs., 3 figs., 1 tab.

  15. Mesoscopic non-equilibrium thermodynamics

    Directory of Open Access Journals (Sweden)

    Rubi, Jose' Miguel

    2008-02-01

    Full Text Available Basic concepts like energy, heat, and temperature have acquired a precise meaning after the development of thermodynamics. Thermodynamics provides the basis for understanding how heat and work are related and with the general rules that the macroscopic properties of systems at equilibrium follow. Outside equilibrium and away from macroscopic regimes most of those rules cannot be applied directly. In this paper we present recent developments that extend the applicability of thermodynamic concepts deep into mesoscopic and irreversible regimes. We show how the probabilistic interpretation of thermodynamics together with probability conservation laws can be used to obtain kinetic equations describing the evolution of the relevant degrees of freedom. This approach provides a systematic method to obtain the stochastic dynamics of a system directly from the knowledge of its equilibrium properties. A wide variety of situations can be studied in this way, including many that were thought to be out of reach of thermodynamic theories, such as non-linear transport in the presence of potential barriers, activated processes, slow relaxation phenomena, and basic processes in biomolecules, like translocation and stretching.

  16. Local equilibrium in bird flocks

    Science.gov (United States)

    Mora, Thierry; Walczak, Aleksandra M.; Del Castello, Lorenzo; Ginelli, Francesco; Melillo, Stefania; Parisi, Leonardo; Viale, Massimiliano; Cavagna, Andrea; Giardina, Irene

    2016-12-01

    The correlated motion of flocks is an example of global order emerging from local interactions. An essential difference with respect to analogous ferromagnetic systems is that flocks are active: animals move relative to each other, dynamically rearranging their interaction network. This non-equilibrium characteristic has been studied theoretically, but its impact on actual animal groups remains to be fully explored experimentally. Here, we introduce a novel dynamical inference technique, based on the principle of maximum entropy, which accommodates network rearrangements and overcomes the problem of slow experimental sampling rates. We use this method to infer the strength and range of alignment forces from data of starling flocks. We find that local bird alignment occurs on a much faster timescale than neighbour rearrangement. Accordingly, equilibrium inference, which assumes a fixed interaction network, gives results consistent with dynamical inference. We conclude that bird orientations are in a state of local quasi-equilibrium over the interaction length scale, providing firm ground for the applicability of statistical physics in certain active systems.

  17. 利用GIS水化学和同位素方法判断灵水来源%Source identification of Lingshui Spring using GIS-based hydrochemistry and environmental isotopic methods

    Institute of Scientific and Technical Information of China (English)

    姜光辉; 郭芳

    2012-01-01

    Multiple methods were used in this study in an attempt to identify the boundary and source of the Lingshui Spring, a karst spring in Wuming County of Nanning City. Hydro chemical data from the karst springs, boreholes, and epikarst springs possibly distributed in the Lingshui drainage area were collected in dry and rainy seasons. The hydro-chemical causes for different karst water were distinguished in the CaCC3-CC2-H2O equilibrium system. It was discovered that the chemical equilibrium system was influenced by CO2 partial pressures, pollution, and the existing conditions of groundwater. The analysis of the environmental isotope indicates that the isotopes o H and S 0 in the rainwater of the study area were affected by season and altitude. The variation of isotopes in groundwater was weakened by the mixed process in the aquifer. The average contents of ^H and S180 were almost equal to those of rainfall in summer, indicating that the rainfall infiltration recharge mostly occurred in summer. The GIS technique was used to divide the watersheds of the surface water system, based on which the groundwater drainage area was identified. The drainage area of the Lingshui Spring was found to be 697 km , of which 126 km were buried karst and the rest were covered karst.%尝试利用多种方法确定南宁市武鸣县灵水岩溶泉的补给来源和汇水范围.获取了可能在其汇水范围内的岩溶泉、钻孔、表层岩溶泉枯季及雨季水化学资料,在CaCO3-CO2-H2O平衡体系中区分不同出露形式的岩溶水的水化学成因,发现CO分压、地下水赋存条件和污染等因素影响此化学平衡体系.灵水的钙离子浓度和CO2分压在岩溶泉中较高,体现了灵水为区域地下水流系统的排泄点.环境同位素分析表明,当地雨水的δ2H和δ18O同位素存在季节效应和高程效应,地下水中同位素的变化被混合作用削弱,其平均值接近于夏季雨水的同位素组成,表明该地区的降雨入渗补

  18. Clumped-isotope thermometry of magnesium carbonates in ultramafic rocks

    Science.gov (United States)

    García del Real, Pablo; Maher, Kate; Kluge, Tobias; Bird, Dennis K.; Brown, Gordon E.; John, Cédric M.

    2016-11-01

    Magnesium carbonate minerals produced by reaction of H2O-CO2 with ultramafic rocks occur in a wide range of paragenetic and tectonic settings and can thus provide insights into a variety of geologic processes, including (1) deposition of ore-grade, massive-vein cryptocrystalline magnesite; (2) formation of hydrous magnesium carbonates in weathering environments; and (3) metamorphic carbonate alteration of ultramafic rocks. However, the application of traditional geochemical and isotopic methods to infer temperatures of mineralization, the nature of mineralizing fluids, and the mechanisms controlling the transformation of dissolved CO2 into magnesium carbonates in these settings is difficult because the fluids are usually not preserved. Clumped-isotope compositions of magnesium carbonates provide a means to determine primary mineralization or (re)equilibration temperature, which permits the reconstruction of geologic processes that govern magnesium carbonate formation. We first provide an evaluation of the acid fractionation correction for magnesium carbonates using synthetic magnesite and hydromagnesite, along with natural metamorphic magnesite and low-temperature hydromagnesite precipitated within a mine adit. We show that the acid fractionation correction for magnesium carbonates is virtually indistinguishable from other carbonate acid fractionation corrections given current mass spectrometer resolution and error. In addition, we employ carbonate clumped-isotope thermometry on natural magnesium carbonates from various geologic environments and tectonic settings. Cryptocrystalline magnesite vein deposits from California (Red Mountain magnesite mine), Austria (Kraubath locality), Turkey (Tutluca mine, Eskişehir district) and Iran (Derakht-Senjed deposit) exhibit broadly uniform Δ47 compositions that yield apparent clumped-isotope temperatures that average 23.7 ± 5.0 °C. Based on oxygen isotope thermometry, these clumped-isotope temperatures suggest

  19. Perchlorate isotope forensics

    Science.gov (United States)

    Böhlke, J.K.; Sturchio, N.C.; Gu, B.; Horita, J.; Brown, G.M.; Jackson, W.A.; Batista, J.; Hatzinger, P.B.

    2005-01-01

    Perchlorate has been detected recently in a variety of soils, waters, plants, and food products at levels that may be detrimental to human health. These discoveries have generated considerable interest in perchlorate source identification. In this study, comprehensive stable isotope analyses ( 37Cl/35Cl and 18O/17O/ 16O) of perchlorate from known synthetic and natural sources reveal systematic differences in isotopic characteristics that are related to the formation mechanisms. In addition, isotopic analyses of perchlorate extracted from groundwater and surface water demonstrate the feasibility of identifying perchlorate sources in contaminated environments on the basis of this technique. Both natural and synthetic sources of perchlorate have been identified in water samples from some perchlorate occurrences in the United States by the isotopic method. ?? 2005 American Chemical Society.

  20. The Theory of Variances in Equilibrium Reconstruction

    Energy Technology Data Exchange (ETDEWEB)

    Zakharov, Leonid E.; Lewandowski, Jerome; Foley, Elizabeth L.; Levinton, Fred M.; Yuh, Howard Y.; Drozdov, Vladimir; McDonald, Darren

    2008-01-14

    The theory of variances of equilibrium reconstruction is presented. It complements existing practices with information regarding what kind of plasma profiles can be reconstructed, how accurately, and what remains beyond the abilities of diagnostic systems. The σ-curves, introduced by the present theory, give a quantitative assessment of quality of effectiveness of diagnostic systems in constraining equilibrium reconstructions. The theory also suggests a method for aligning the accuracy of measurements of different physical nature.

  1. GC/MS method for determining carbon isotope enrichment and concentration of underivatized short-chain fatty acids by direct aqueous solution injection of biogas digester samples.

    Science.gov (United States)

    Mulat, Daniel Girma; Feilberg, Anders

    2015-10-01

    In anaerobic digestion of organic matter, several metabolic pathways are involved during the simultaneous production and consumption of short-chain fatty acids (SCFA) in general and acetate in particular. Understanding the role of each pathway requires both the determination of the concentration and isotope enrichment of intermediates in conjunction with isotope labeled substrates. The objective of this study was to establish a rapid and simple GC/MS method for determining the isotope enrichment of acetate and concentration of underivatized short-chain fatty acids (SCFA) in biogas digester samples by direct liquid injection of acidified aqueous samples. Sample preparation involves only acidification, centrifugation and filtration of the aqueous solution followed by direct injection of the aqueous supernatant solution onto a polar column. With the sample preparation and GC/MS conditions employed, well-resolved and sharp peaks of underivatized SCFA were obtained in a reasonably short time. Good recovery (96.6-102.3%) as well as low detection (4-7 µmol/L) and quantification limits (14-22 µmol/L) were obtained for all the 6 SCFA studied. Good linearity was achieved for both concentration and isotope enrichment measurement with regression coefficients higher than 0.9978 and 0.9996, respectively. The method has a good intra- and inter-day precision with a relative standard deviation (RSD) below 6% for determining the tracer-to-tracee ratio (TTR) of both [2-(13)C]acetate and [U-(13)C]acetate. It has also a good intra- and inter-day precision with a RSD below 6% and 5% for determining the concentration of standard solution and biogas digester samples, respectively. Acidification of biogas digester samples with oxalic acid provided the low pH required for the protonation of SCFA and thus, allows the extraction of SCFA from the complex sample matrix. Moreover, oxalic acid was the source of formic acid which was produced in the injector set at high temperature. The produced

  2. Toward a universal carbonate clumped isotope calibration: Diverse synthesis and preparatory methods suggest a single temperature relationship

    Science.gov (United States)

    Kelson, Julia R.; Huntington, Katharine W.; Schauer, Andrew J.; Saenger, Casey; Lechler, Alex R.

    2017-01-01

    Carbonate clumped isotope (Δ47) thermometry has been applied to a wide range of problems in earth, ocean and biological sciences over the last decade, but is still plagued by discrepancies among empirical calibrations that show a range of Δ47-temperature sensitivities. The most commonly suggested causes of these discrepancies are the method of mineral precipitation and analytical differences, including the temperature of phosphoric acid used to digest carbonates. However, these mechanisms have yet to be tested in a consistent analytical setting, which makes it difficult to isolate the cause(s) of discrepancies and to evaluate which synthetic calibration is most appropriate for natural samples. Here, we systematically explore the impact of synthetic carbonate precipitation by replicating precipitation experiments of previous workers under a constant analytical setting. We (1) precipitate 56 synthetic carbonates at temperatures of 4-85 °C using different procedures to degas CO2, with and without the use of the enzyme carbonic anhydrase (CA) to promote rapid dissolved inorganic carbon (DIC) equilibration; (2) digest samples in phosphoric acid at both 90 °C and 25 °C; and (3) hold constant all analytical methods including acid preparation, CO2 purification, and mass spectrometry; and (4) reduce our data with 17O corrections that are appropriate for our samples. We find that the CO2 degassing method does not influence Δ47 values of these synthetic carbonates, and therefore probably only influences natural samples with very rapid degassing rates, like speleothems that precipitate out of drip solution with high pCO2. CA in solution does not influence Δ47 values in this work, suggesting that disequilibrium in the DIC pool is negligible. We also find the Δ47 values of samples reacted in 25 and 90 °C acid are within error of each other (once corrected with a constant acid fractionation factor). Taken together, our results show that the Δ47-temperature relationship

  3. Accelerator mass spectrometry in pharmaceutical research and development--a new ultrasensitive analytical method for isotope measurement.

    Science.gov (United States)

    Garner, R C

    2000-09-01

    Accelerator mass spectrometry (AMS) permits the measurement of elemental isotopes at the individual atom level. The main application of AMS in drug discovery and development will be in the analysis of 14-carbon (14C). The principle behind AMS is the separation of individual positively charged atoms through mass, charge and momentum differences. In order to obtain the high-energy charge state required for separation, negative atoms are accelerated through a high voltage field (up to 10 million volts) generated by a tandem Van de Graaff accelerator. In the middle of the accelerator, the outer valency electrons are stripped from the atom and the resulting charged species are separated and counted. For 14C, AMS counts the number of individual atoms rather than measuring radioactive decays. The result is that AMS is up to one million times more sensitive than decay counting. Radioactivity levels as low 0.0001 dpm can be detected using AMS. The exquisite sensitivity of AMS analysis means that much lower amounts of 14C can be used than for conventional counting methods. This makes it easier to use 14C for in vitro, preclinical and clinical research programmes. As 14C poses both a biological and environmental hazard, AMS permits much lower doses to be used. Human drug mass balance studies have been conducted with doses of 50 nanoCuries and below. Radioactive HPLC metabolite profiles of plasma extracts from subjects given nanoCurie doses of 14C-labelled drug have been obtained by injecting as little as 0.25 dpm onto an HPLC column. In studies of biologics, biosynthetically 14C-labelled recombinant protein has been produced with a specific radioactivity sufficient to conduct human clinical studies with AMS analysis. For one human recombinant protein an increase in sensitivity of 2,000-fold over ELISA was obtained with AMS measurement. AMS is an enabling technology that should prove of value in increasing human and environmental safety as well as allowing new research

  4. Lithium isotope separation by laser

    Energy Technology Data Exchange (ETDEWEB)

    Arisawa, T.; Maruyama, Y.; Suzuki, Y.; Shiba, K.

    1982-01-01

    A lithium isotope separation was performed using a laser isotope separation method. It was found that the lithium atoms with a natural isotopic abundance enhanced its /sup 6/Li concentration up to over 90% by tuning the laser wavelength to the /sup 2/Psub(1/2) of /sup 6/Li. Too high power, however, leads to a loss of enrichment due to the power broadening effect which was analysed by the equation of motion of density matrices.

  5. Removal of Reactive Red 198 from aqueous solution by combined method multi-walled carbon nanotubes and zero-valent iron:Equilibrium, kinetics, and thermodynamic

    Institute of Scientific and Technical Information of China (English)

    Sudabeh Pourfadakari; Nader Yousefi; Amir Hossein Mahvi

    2016-01-01

    Dyes often include toxic, carcinogenic compounds and are harmful to humans' health. Therefore, removal of dyes from textile industry wastewater is essential. The present study aimed to evaluate the efficiency of the combina-tion of zero valent iron (ZVI) powder and multi-walled carbon nanotubes (MWCNTs) in the removal of Reactive Red 198 (RR198) dye from aqueous solution. This applied research was performed in a batch system in the lab-oratory scale. This study investigated the effect of various factors influencing dye removal, including contact time, pH, adsorbent dose, iron powder dose, initial dye concentration, and temperature. The equilibrium adsorption data were analyzed using three common adsorption models:Langmuir, Freundlich and Temkin. Besides, kinetic and thermodynamic parameters were used to establish the adsorption mechanism. The results showed, in pH=3, contact time=100 min, ZVI dose=5000 mg·L−1, and MWCNTs dose=600 mg·L−1 in 100 mg·L−1 dye con-centration, the adsorption efficiency increased to 99.16%. Also, adsorption kinetics was best described by the pseudo-second-order model. Equilibrium data fitted well with the Freundlich isotherm (R2=0.99). The negative values ofΔG0 and the positive value ofΔH0 (91.76) indicate that the RR198 adsorption process is spontaneous and endothermic. According to the results, the combination of MWCNTs and ZVI was highly efficient in the re-moval of azo dyes.

  6. Towards Non-Equilibrium Dynamics with Trapped Ions

    Science.gov (United States)

    Silbert, Ariel; Jubin, Sierra; Doret, Charlie

    2016-05-01

    Atomic systems are superbly suited to the study of non-equilibrium dynamics. These systems' exquisite isolation from environmental perturbations leads to long relaxation times that enable exploration of far-from-equilibrium phenomena. One example of particular relevance to experiments in trapped ion quantum information processing, metrology, and precision spectroscopy is the approach to thermal equilibrium of sympathetically cooled linear ion chains. Suitable manipulation of experimental parameters permits exploration of the quantum-to-classical crossover between ballistic transport and diffusive, Fourier's Law conduction, a topic of interest not only to the trapped ion community but also for the development of microelectronic devices and other nanoscale structures. We present progress towards trapping chains of multiple co-trapped calcium isotopes geared towards measuring thermal equilibration and discuss plans for future experiments in non-equilibrium statistical mechanics. This work is supported by Cottrell College Science Award from the Research Corporation for Science Advancement and by Williams College.

  7. Bounded Computational Capacity Equilibrium

    CERN Document Server

    Hernandez, Penelope

    2010-01-01

    We study repeated games played by players with bounded computational power, where, in contrast to Abreu and Rubisntein (1988), the memory is costly. We prove a folk theorem: the limit set of equilibrium payoffs in mixed strategies, as the cost of memory goes to 0, includes the set of feasible and individually rational payoffs. This result stands in sharp contrast to Abreu and Rubisntein (1988), who proved that when memory is free, the set of equilibrium payoffs in repeated games played by players with bounded computational power is a strict subset of the set of feasible and individually rational payoffs. Our result emphasizes the role of memory cost and of mixing when players have bounded computational power.

  8. Quasi-rigorous and non-rigorous 3D limit equilibrium methods for generalized-shaped slopes%一般形状边坡下准严格与非严格三维极限平衡法

    Institute of Scientific and Technical Information of China (English)

    邓东平; 李亮

    2013-01-01

    Adopting the limit equilibrium theory to obtain the solutions of 3D limit equilibrium is an effective way to solve the stability analysis of 3D slopes. After analyzing the stress of columns under general conditions, three parameters are chosen: inter-force parameter λ1 of column's front and back side faces, scaling parameter A between column's left and right side faces and their front and back ones, angle p between directions of shear force on bottom of columns and the sliding plane, and a quasi-rigorous 3D limit equilibrium formula that can meet three-force equilibrium equation and three-moment equilibrium equation is established. When the relative 2D inter-force assumptions are used, 3D Spencer method, 3D M-P method and 3D Sarma method are obtained. By making some of the above-mentioned three parameters equal to zero, the proposed quasi-rigorous method can be transformed into three kinds of non-rigorous methods that only meet part of the mechanical equilibrium conditions. Compared with the classical examples and by comparing the difference of the calculated results between the quasi-rigorous method and the non-rigorous method in two asymmetric cases of width and curve surface of left and right sliding surface's, some conclusions can be drawn as follows: (1) the results calculated by 3D Spencer method, 3D M-P method and 3D Sarma method are quite close to those by other methods, indicating the feasibility of the proposed method; (2) for the case of asymmetric sliding surfaces, except that those by the non rigorous method that gets the limit equilibrium equation by ignoring vertical shear force of front and back side faces of columns are smaller, the calculated results by the quasi-rigorous method and two kinds of non-rigorous methods are the same, showing that the non-rigorous methods are also applicable to cases of 3D asymmetric sliding surface; and (3) the established three-dimensional limit equilibrium solutions are all applicable to the quasi-rigorous method

  9. General Search Market Equilibrium

    OpenAIRE

    Albrecht, James W.; Axell, Bo

    1982-01-01

    In this paper we extend models of “search market equilibrium” to incorporate general equilibrium considerations. The model we treat is one with a single product market and a single labor market. Imperfectly informed individuals follow optimal strategies in searching for a suitably low price and high wage. For any distribution of price and wage offers across firms these optimal strategies generate product demand and labor supply schedules. Firms then choose prices and wages to maximize expecte...

  10. Equilibrium statistical mechanics

    CERN Document Server

    Jackson, E Atlee

    2000-01-01

    Ideal as an elementary introduction to equilibrium statistical mechanics, this volume covers both classical and quantum methodology for open and closed systems. Introductory chapters familiarize readers with probability and microscopic models of systems, while additional chapters describe the general derivation of the fundamental statistical mechanics relationships. The final chapter contains 16 sections, each dealing with a different application, ordered according to complexity, from classical through degenerate quantum statistical mechanics. Key features include an elementary introduction t

  11. Volatility in Equilibrium

    DEFF Research Database (Denmark)

    Bollerslev, Tim; Sizova, Natalia; Tauchen, George

    Stock market volatility clusters in time, carries a risk premium, is fractionally inte- grated, and exhibits asymmetric leverage effects relative to returns. This paper develops a first internally consistent equilibrium based explanation for these longstanding empirical facts. The model is cast......, and the dynamic cross-correlations of the volatility measures with the returns calculated from actual high-frequency intra-day data on the S&P 500 aggregate market and VIX volatility indexes....

  12. 求解一类广义均衡问题的交替方向法%Alternating Direction Method of Multipliers for Solving a Class of General Equilibrium Problem

    Institute of Scientific and Technical Information of China (English)

    徐洁; 张俊容; 刘佳

    2016-01-01

    The alternating direction method is one of the classic methods for solving optimization problems with a separable structure .Its essence is lies in that applying the original problem 'solution equivalent to the saddle point of the augmented Lagrangian function to iterative the parameters ,and then finding out the solution of the original problem .This paper corrects Lagrangian multipliers to construct a new alternating direction method for solving a class of general equilibrium problem ,and then analyzes the properties of the alternating direction method and derives the convergence of the alternating direction method .%通过修正拉格朗日乘子构造了一种新的交替方向法求解一类广义均衡问题,分析了该算法的收敛性及其所产生序列的特性。

  13. Tourism Equilibrium Price Trends

    Directory of Open Access Journals (Sweden)

    Mohammad Mohebi

    2012-01-01

    Full Text Available Problem statement: A review of the tourism history shows that tourism as an industry was virtually unknown in Malaysia until the late 1960s. Since then, it has developed and grown into a major industry, making an important contribution to the country's economy. By allocating substantial funds to the promotion of tourism and the provision of the necessary infrastructure, the government has played an important role in the impressive progress of the Malaysian tourism industry. One of the important factors which can attract tourists to Malaysia is the tourism price. Has the price of tourism decreased? To answer this question, it is necessary to obtain the equilibrium prices as well as the yearly trend for Malaysia during the sample period as it will be useful for analysis of the infrastructure situation of the tourism industry in this country. The purpose of the study is to identify equilibrium tourism price trends in Malaysian tourism market. Approach: We use hotel room as representative of tourism market. Quarterly data from 1995-2009 are used and a dynamic model of simultaneous equation is employed. Results: Based on the result during the period of 1995 until 2000, the growth rate of the equilibrium price was greater than consumer price index and producer price index. Conclusion: In the Malaysian tourism market, new infrastructure during this period had not been developed to keep pace with tourist arrivals.

  14. Standard test method for analysis of isotopic composition of uranium in nuclear-grade fuel material by quadrupole inductively coupled plasma-mass spectrometry

    CERN Document Server

    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...

  15. Leatherback Isotopes

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — SWFSC is currently working on a project identifying global marine isotopes using leatherback turtles (Dermochelys coriacea) as the indicator species. We currently...

  16. Isotopic chirality

    Energy Technology Data Exchange (ETDEWEB)

    Floss, H.G. [Univ. of Washington, Seattle, WA (United States)

    1994-12-01

    This paper deals with compounds that are chiral-at least in part, due to isotope substitution-and their use in tracing the steric course of enzyme reaction in vitro and in vivo. There are other applications of isotopically chiral compounds (for example, in analyzing the steric course of nonenzymatic reactions and in probing the conformation of biomolecules) that are important but they will not be discussed in this context.

  17. Isotopic Paleoclimatology

    Science.gov (United States)

    Bowen, R.

    Paleotemperature scales were calculated by H. C. Urey and others in the 1950s to assess past temperatures, and later work using the stable isotopes of oxygen, hydrogen, and carbon employed standards such as Peedee belemnite (PDB) and Standard Mean Ocean Water (SMOW). Subsequently, subjects as diverse as ice volume and paleotemperatures, oceanic ice and sediment cores, Pleistocene/Holocene climatic changes, and isotope chronostratigraphy extending back to the Precambrian were investigated.

  18. Simulations of an isotopic fractionation by freezing in an open system

    Institute of Scientific and Technical Information of China (English)

    Yoshinori Iizuka

    2003-01-01

    This paper presents a model of isotopic fractionation by freezing under near-equilibrium conditions in an open system and uses the model to predict the fractionation curve and slope gradient of δ18O versus δD.The simulation results show that 1) the fractionation curve and slope gradient are determined by the ratio of freezing rate to input rate, 2) the isotopic value in the initial stage of freezing is determined by the isotopic value of initial water; 3) in the latter half of freezing in an open system, the isotopic value converges to a certain value determined by that of input water.These results suggest that the shape of the fractionation curve is the method to distinguish whether freezing occurred in a closed or open system.This analysis is applied to an isotopic curve observed in basal ice of Hamna Glacier, Sya drainage, East Antarctica.The isotopic curve indicates formation by regelation in an open system with a ratio of freezing/input rates of about 10/4.

  19. The transformation dynamics towards equilibrium in non-equilibrium w/w/o double emulsions

    Science.gov (United States)

    Chao, Youchuang; Mak, Sze Yi; Shum, Ho Cheung

    2016-10-01

    We use a glass-based microfluidic device to generate non-equilibrium water-in-water-in-oil (w/w/o) double emulsions and study how they transform into equilibrium configurations. The method relies on using three immiscible liquids, with two of them from the phase-separated aqueous two-phase systems. We find that the transformation is accompanied by an expansion rim, while the characteristic transformation speed of the rim mainly depends on the interfacial tension between the innermost and middle phases, as well as the viscosity of the innermost phase when the middle phase is non-viscous. Remarkably, the viscosity of the outermost phase has little effect on the transformation speed. Our results account for the dynamics of non-equilibrium double emulsions towards their equilibrium structure and suggest a possibility to utilize the non-equilibrium drops to synthesize functional particles.

  20. Potential application of radiogenic isotopes and geophysical methods to understand the hydrothermal dystem of the Upper Geyser Basin, Yellowstone National Park

    Science.gov (United States)

    Paces, James B.; Long, Andrew J.; Koth, Karl R.

    2015-01-01

    rocks. Details of how the shallow and deep components interact and mechanisms causing these interactions remain unknown, but the data demonstrate the usefulness of obtaining Sr-isotope data from future sample campaigns. Geophysical methods that would be useful for characterization of the UGB subsurface properties and geothermal system include electromagnetic (EM), gravity, and ambient seismic. A suite of ground-based EM methods could be used in a synergistic combination together with airborne EM surveys to provide data for a range of spatial scales and resolutions. Existing thermal data for the shallow subsurface could be used to relate ground and airborne EM survey data to locations of geothermal fluids near the surface. Gravity surveys would be useful for mapping subsurface density anomalies and possibly monitoring changes in degree of saturation with groundwater. Ambient seismic surveys would be useful for estimating the thickness of unconsolidated deposits that contain the shallow groundwater system. A study that combines radiogenic isotope tracers with geophysical methods has the potential to better characterize the geothermal workings in the UGB. Insights gained could lead to a better understanding of the geothermal system and how Park infrastructure may cause perturbations. Measurements of radiogenic isotopes from multiple geysers and pools in localized areas within the UGB that are coupled with data from geophysical surveys would help refine conceptual models of mixing between deep- and shallow-derived subsurface fluids.

  1. Quantification of Labile Soil Mercury by Stable Isotope Dilution Techniques

    Science.gov (United States)

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

    2016-04-01

    Mercury (Hg) is a toxic element that can cause severe health problems to humans. Mercury is emitted to the atmosphere from both natural and anthropogenic sources and can be transported over long distances before it is deposited to aquatic and terrestrial environments. Aside from accumulation in soil solid phases, Hg deposited in soils may migrate to surface- and ground-water or enter the food chain, depending on its lability. There are many operationally-defined extraction methods proposed to quantify soil labile metals. However, these methods are by definition prone to inaccuracies such as non-selectivity, underestimation or overestimation of the labile metal pool. The isotopic dilution technique (ID) is currently the most promising method for discrimination between labile and non-labile metal fractions in soil with a minimum disturbance to soil-solid phases. ID assesses the reactive metal pool in soil by defining the fraction of metal both in solid and solution phases that is isotopically-exchangeable known as the 'E-value'. The 'E-value' represents the metal fraction in a dynamic equilibrium with the solution phase and is potentially accessible to plants. This is carried out by addition of an enriched metal isotope to soil suspensions and quantifying the fraction of metal that is able to freely exchange with the added isotope by measuring the equilibrium isotopic ratio by ICP-MS. E-value (mg kg-1) is then calculated as follows: E-Value = (Msoil/ W) (CspikeVspike/ Mspike) (Iso1IAspike -Iso2IAspikeRss / Iso2IAsoil Rss - Iso1IAsoil) where M is the average atomic mass of the metal in the soil or the spike, W is the mass of soil (kg), Cspike is the concentration of the metal in the spike (mg L-1), Vspike is the volume of spike (L), IA is isotopic abundance, and Rss is the equilibrium ratio of isotopic abundances (Iso1:Iso2). Isotopic dilution has been successfully applied to determine E-values for several elements. However, to our knowledge, this method has not yet

  2. Cryogenic separation of an oxygen-argon mixture in natural air samples for the determination of isotope and molecular ratios.

    Science.gov (United States)

    Keedakkadan, Habeeb Rahman; Abe, Osamu

    2015-04-30

    The separation and purification of oxygen-argon mixtures are critical in the high-precision analysis of Δ(17) O and δ(O2 /Ar) for geochemical applications. At present, chromatographic methods are used for the separation and purification of oxygen-argon mixtures or pure oxygen, but these methods require the use of high-purity helium as a carrier gas. Considerable interest has been expressed in the development of a helium-free cryogenic separation of oxygen-argon mixtures in natural air samples. The precise and simplified cryogenic separation of oxygen-argon mixtures from natural air samples presented here was made possible using a single 5A (30/60 mesh) molecular sieve column. The method involves the trapping of eluted gases using molecular sieves at liquid nitrogen temperature, which is associated with isotopic fractionation. We tested the proposed method for the determination of isotopic fractionations during the gas exchange between water and atmospheric air at equilibrium. The dependency of fractionation was studied at different water temperatures and for different methods of equilibration (bubbling and stirring). Isotopic and molecular fractionations during gas desorption from molecular sieves were studied for different amounts and types of molecular sieves. Repeated measurements of atmospheric air yielded a reproducibility (±SD) of 0.021 ‰, 0.044 ‰, 15 per meg and 1.9 ‰ for δ(17) O, δ(18) O, Δ(17) O and δ(O2 /Ar) values, respectively. We applied the method to determine equilibrium isotope fractionation during gas exchange between air and water. Consistent δ(18) O and Δ(17) O results were obtained with the latest two studies, whereas there was a significant difference in δ(18) O values between seawater and deionized water. We have revised a helium-free, cryogenic separation of oxygen-argon mixtures in natural air samples for isotopic and molecular ratio analysis. The use of a single 13X (1/8" pellet) molecular sieve yielded the smallest isotopic

  3. Noncompact Equilibrium Points and Applications

    Directory of Open Access Journals (Sweden)

    Zahra Al-Rumaih

    2012-01-01

    Full Text Available We prove an equilibrium existence result for vector functions defined on noncompact domain and we give some applications in optimization and Nash equilibrium in noncooperative game.

  4. Extended Mixed Vector Equilibrium Problems

    Directory of Open Access Journals (Sweden)

    Mijanur Rahaman

    2014-01-01

    Full Text Available We study extended mixed vector equilibrium problems, namely, extended weak mixed vector equilibrium problem and extended strong mixed vector equilibrium problem in Hausdorff topological vector spaces. Using generalized KKM-Fan theorem (Ben-El-Mechaiekh et al.; 2005, some existence results for both problems are proved in noncompact domain.

  5. Cerenkov radiation energy transfer (CRET imaging: a novel method for optical imaging of PET isotopes in biological systems.

    Directory of Open Access Journals (Sweden)

    Robin S Dothager

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

  6. Analysis of isotope element by electrolytic enrichment method for ground water and surface water in Saurashtra region, Gujarat, India

    Directory of Open Access Journals (Sweden)

    Sajal Singh

    2016-12-01

    Full Text Available The present study has been aimed for the assessment of isotope element Tritium (3H. It is a great threat to human health and environment for lengthy duration. The tritium exists in earth in diverse forms such as (1 small amounts of natural tritium are produced by alpha decay of lithium-7, (2 natural atmospheric tritium is also generated by secondary neutron cosmic ray bombardment of nitrogen, (3 atmospheric nuclear bomb testing in the 1950s, although the contribution from nuclear power plants is small. Tritium or 3H is a radioactive isotope of hydrogen with a half-life of 12.32 ± 0.02 years. Water samples from ground water, surface water, and precipitation were collected from different locations in Gujarat area and were analyzed for the same. Distillation of samples was done to reduce the conductivity. Deuterium and Hydrogen were removed by the process of physico-chemical fractionation in the tritium enrichment unit. The basis of physico-chemical fractionation is the difference in the strength of bonds formed by the light vs. the heavier isotope of a given element. A total of 10 cycles (runs were executed using Quintals process. Tritium concentration files were created with help of WinQ and Quick start software in Quintals process (Liquid Scintillation Spectrometer. The concentration of tritium in terms of tritium units (TU of various samples has been determined. The TU values of the samples vary in the range of 0.90–6.62 TU.

  7. Isotope methods as a tool to characterize nitrate origin and transport in Kocinka catchment (central Poland): preliminary results

    Science.gov (United States)

    Zurek, Anna; Wachniew, Przemyslaw; Witczak, Stanislaw; Rozanski, Kazimierz; Kania, Jaroslaw

    2014-05-01

    Kocinka catchment with 258 km2 of surface area is one of the Soils2Sea project (BONUS programme) case studies. One of the main scientific objectives of this project is to analyze how changes in land use and climate may affect the nutrient load to the Baltic Sea. Hydrogeological conditions in the Kocinka catchment are determined by Quaternary glacial till and glacifluvial sands and gravels underlain by karstic-fractured limestones which compose the Upper Jurassic Major Groundwater Basin (MGWB 326), one of four most important groundwater reservoirs in Poland. Pollution with nitrates is the most important threat to groundwater quality in this groundwater body. The concentration of nitrate in some wells, in the southern part of Kocinka catchment where outcrops of Jurassic limestones occur, exceeds the maximum permissible level of 50 mgNO3/L and constantly increases. A prerequisite for measures to reduce NO3 loads to the groundwater body is identification of sources of nitrate pollution. The working hypothesis links the high nitrate concentrations with the leaking sewage system in Czestochowa city and its surroundings but agricultural sources cannot be excluded as 66% of Kocinka catchment area is used agriculturally. A dedicated study employing environmental tracers was launched with the main aim of quantifying the pathways and dynamic of groundwater flow in the aquifer. Tritium was found throughout the system but its concentrations vary considerably. Decrease of tritium contents with depth in the aquifer was observed in one of wells. This points to active recharge and characteristic time scales of groundwater flow in order of years to several decades. To identify the origin of nitrate pollution nitrogen and oxygen isotope ratios of dissolved nitrate was analyzed in a number of wells with high nitrate concentrations. The isotopic composition of dissolved nitrates does not confirm the hypothesis on the decisive role of urban sewage in nitrate pollution. The isotope date

  8. Isotope Method for Confined Groundwater Recharge of the Lower Reaches of the Heihe River, Inner Mongolia, China

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Environmental isotopes have been applied to analyze confined groundwater recharge in the lower reaches of the Heihe River, Inner Mongolia. CFC is regarded as a tracer that determines the date of groundwater, the date being less than 45 a. The confined groundwater within the Gurinai area and Ejin Basin other than the surface water of Heihe River might have originated from precipitation from Qilian Mountain or/and the Tibetan Plateau. The deep confined groundwater overflows into an upper aquifer and emerges into the ground, forming springs and lakes within the low-lying area. The recharge volume is estimated to be around 400 million-cubic meters.

  9. An isotopic neutron source method for measuring the thermal neutron absorption cross section of rocks using small samples

    Energy Technology Data Exchange (ETDEWEB)

    Kreft, A.; Bolewski, A. Jr.; Ciechanowski, M. (Institute of Physics and Nuclear Techniques, Cracow (Poland))

    1989-01-01

    An improved isotopic neutron source technique for measuring {Sigma}{sub a} of rocks is presented. A {sup 252}Cf source emitting roughly 4.10{sup 6} n/s and a miniature BF{sub 3}-filled detector are inserted in an annular sample placed in a large polyethylene block. Only one calibration sample is needed. No sample preparation, except grinding, is required. The attainable relative standard deviation on the measured value is about 10% for 25 cm{sup 3} samples and about 3% for 300 cm{sup 3} samples, respectively, both for 1 h counting times. (author).

  10. Non-equilibrium thermodynamics

    CERN Document Server

    De Groot, Sybren Ruurds

    1984-01-01

    The study of thermodynamics is especially timely today, as its concepts are being applied to problems in biology, biochemistry, electrochemistry, and engineering. This book treats irreversible processes and phenomena - non-equilibrium thermodynamics.S. R. de Groot and P. Mazur, Professors of Theoretical Physics, present a comprehensive and insightful survey of the foundations of the field, providing the only complete discussion of the fluctuating linear theory of irreversible thermodynamics. The application covers a wide range of topics: the theory of diffusion and heat conduction, fluid dyn

  11. Calcium Isotope Analysis by Mass Spectrometry

    Science.gov (United States)

    Boulyga, S.; Richter, S.

    2010-12-01

    The variations in the isotopic composition of calcium caused by fractionation in heterogeneous systems and by nuclear reactions can provide insight into numerous biological, geological, and cosmic processes, and therefore isotopic analysis finds a wide spectrum of applications in cosmo- and geochemistry, paleoclimatic, nutritional, and biomedical studies. The measurement of calcium isotopic abundances in natural samples has challenged the analysts for more than three decades. Practically all Ca isotopes suffer from significant isobaric interferences, whereas low-abundant isotopes can be particularly affected by neighboring major isotopes. The extent of natural variations of stable isotopes appears to be relatively limited, and highly precise techniques are required to resolve isotopic effects. Isotope fractionation during sample preparation and measurements and instrumental mass bias can significantly exceed small isotope abundance variations in samples, which have to be investigated. Not surprisingly, a TIMS procedure developed by Russell et al. (Russell et al., 1978. Geochim Cosmochim Acta 42: 1075-1090) for Ca isotope measurements was considered as revolutionary for isotopic measurements in general, and that approach is used nowadays (with small modifications) for practically all isotopic systems and with different mass spectrometric techniques. Nevertheless, despite several decades of calcium research and corresponding development of mass spectrometers, the available precision and accuracy is still not always sufficient to achieve the challenging goals. This presentation discusses figures of merits of presently used analytical methods and instrumentation, and attempts to critically assess their limitations. Additionally, the availability of Ca isotope reference materials will be discussed.

  12. Cyclic causal discovery from continuous equilibrium data

    NARCIS (Netherlands)

    Mooij, J.M.; Heskes, T.; Nicholson, A.; Smyth, P.

    2013-01-01

    We propose a method for learning cycliccausal models from a combination of observational and interventional equilibrium data. Novel aspects of the proposed method are its ability to work with continuous data (without assuming linearity) and to deal with feedback loops. Within the context of biochemi

  13. Distinguishing phosphate from fertilizers and wastewater treatment plant effluents in Western Canada using oxygen isotope measurements

    Science.gov (United States)

    Fau, Veronique; Nightingale, Michael; Tamburini, Frederica; Mayer, Bernhard

    2014-05-01

    The successful application of oxygen isotope ratios as a tracer for phosphate in aquatic ecosystems requires that different sources of phosphate are isotopically distinct. The objective of this study was to determine whether the oxygen isotope ratios of phosphate from fertilizers and effluents from wastewater treatment plants in Western Canada are isotopically distinct. Therefore, we carried out oxygen isotope analyses on phosphate in effluent from five different wastewater treatment plants (WWTP) in the Bow River watershed of Alberta, Canada. Samples were collected directly from the final effluent (post-UV) in Banff and Canmore upstream of Calgary, and from effluents of Calgary's WWTPs at Bonnybrook, Fish Creek and Pine Creek. We also carried out oxygen isotope analyses on a variety of phosphate-containing fertilizers that are widely used in Western Canada. Historically, most of the phosphate contained in manufactured fertilizers sold in Alberta came from two distinct deposits: 1) a weathered Pliocene igneous carbonatite located in eastern Canada, and 2) the Permian Phosphoria Formation in the western USA. Phosphate (PO43-) contained in the water or the fertilizer was concentrated and quantitatively converted to pure silver phosphate (Ag3PO4). The silver phosphate was then reduced with carbon in an oxygen free environment using a TC/EA pyrolysis reactor linked to a mass spectrometer where 18O/16O ratios of CO were measured in continuous flow mode. Preparation of samples for δ18OPO4 analyses was conducted using the Magnesium Induced Coprecipitation (MAGIC) method. Expected oxygen isotope ratios for phosphate in equilibrium with water (δ18Oeq) were calculated using the Longinelli and Nuti equation: T (° C) = 111.4 - 4.3 (δ18Oeq - δ18Owater). Measured δ18O values of phosphate for fertilizer samples varied from 8 to 25 oÈ®n average, fertilizer samples of sedimentary origin had higher δ18O values (15.8) than those of igneous origin (11.5). Phosphate isotopic

  14. Conjugate Acid-Base Pairs, Free Energy, and the Equilibrium Constant

    Science.gov (United States)

    Beach, Darrell H.

    1969-01-01

    Describes a method of calculating the equilibrium constant from free energy data. Values of the equilibrium constants of six Bronsted-Lowry reactions calculated by the author's method and by a conventional textbook method are compared. (LC)

  15. Isotopic Seawater Analysis Using Cavity Ring-Down Spectroscopy: Method for Reducing the Effect of Salts on the Measurements

    Science.gov (United States)

    Kim-Hak, D.; Normandeau, C.; Winkler, R.; Huang, K.; Kerrigan, L.

    2015-12-01

    High-salinity waters such as Seawater poses an operational and maintenance challenge to the measurements of water stable isotopes via Cavity Ring-Down Spectroscopy. As liquid samples are evaporated in the vaporizer peripheral before being sent to the CRDS analyzer, salt precipitates accumulate in the vaporizer chamber. As a result, the sample-to-sample memory performance degrades over time and frequent cleaning is required to maintain the peripheral performance and integrity. To address this issue, earlier work showed that adding a metallic mesh liner into the injection port of the vaporizer could capture salt solids and protect the vaporizer chamber without affecting the sample's isotopic composition and the measurement performance. Additional long-term tests have been recently conducted with the new commercially available Salt Liner accessory to assess its efficacy. We demonstrated the longer stability of the sample-to-sample memory performance on various brine water measurements when compared to a system without the Salt Liner. We also established the guidelines in using, replacing, and cleaning the Salt Liner.

  16. Thermal equilibrium of goats.

    Science.gov (United States)

    Maia, Alex S C; Nascimento, Sheila T; Nascimento, Carolina C N; Gebremedhin, Kifle G

    2016-05-01

    The effects of air temperature and relative humidity on thermal equilibrium of goats in a tropical region was evaluated. Nine non-pregnant Anglo Nubian nanny goats were used in the study. An indirect calorimeter was designed and developed to measure oxygen consumption, carbon dioxide production, methane production and water vapour pressure of the air exhaled from goats. Physiological parameters: rectal temperature, skin temperature, hair-coat temperature, expired air temperature and respiratory rate and volume as well as environmental parameters: air temperature, relative humidity and mean radiant temperature were measured. The results show that respiratory and volume rates and latent heat loss did not change significantly for air temperature between 22 and 26°C. In this temperature range, metabolic heat was lost mainly by convection and long-wave radiation. For temperature greater than 30°C, the goats maintained thermal equilibrium mainly by evaporative heat loss. At the higher air temperature, the respiratory and ventilation rates as well as body temperatures were significantly elevated. It can be concluded that for Anglo Nubian goats, the upper limit of air temperature for comfort is around 26°C when the goats are protected from direct solar radiation.

  17. Equilibrium molecular thermodynamics from Kirkwood sampling.

    Science.gov (United States)

    Somani, Sandeep; Okamoto, Yuko; Ballard, Andrew J; Wales, David J

    2015-05-21

    We present two methods for barrierless equilibrium sampling of molecular systems based on the recently proposed Kirkwood method (J. Chem. Phys. 2009, 130, 134102). Kirkwood sampling employs low-order correlations among internal coordinates of a molecule for random (or non-Markovian) sampling of the high dimensional conformational space. This is a geometrical sampling method independent of the potential energy surface. The first method is a variant of biased Monte Carlo, where Kirkwood sampling is used for generating trial Monte Carlo moves. Using this method, equilibrium distributions corresponding to different temperatures and potential energy functions can be generated from a given set of low-order correlations. Since Kirkwood samples are generated independently, this method is ideally suited for massively parallel distributed computing. The second approach is a variant of reservoir replica exchange, where Kirkwood sampling is used to construct a reservoir of conformations, which exchanges conformations with the replicas performing equilibrium sampling corresponding to different thermodynamic states. Coupling with the Kirkwood reservoir enhances sampling by facilitating global jumps in the conformational space. The efficiency of both methods depends on the overlap of the Kirkwood distribution with the target equilibrium distribution. We present proof-of-concept results for a model nine-atom linear molecule and alanine dipeptide.

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

    Science.gov (United States)

    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 μg 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. Copyright © 2014 Elsevier Ltd. All rights reserved.

  19. Improved methods for Feynman path integral calculations of vibrational-rotational free energies and application to isotopic fractionation of hydrated chloride ions.

    Science.gov (United States)

    Mielke, Steven L; Truhlar, Donald G

    2009-04-23

    We present two enhancements to our methods for calculating vibrational-rotational free energies by Feynman path integrals, namely, a sequential sectioning scheme for efficiently generating random free-particle paths and a stratified sampling scheme that uses the energy of the path centroids. These improved methods are used with three interaction potentials to calculate equilibrium constants for the fractionation behavior of Cl(-) hydration in the presence of a gas-phase mixture of H(2)O, D(2)O, and HDO. Ion cyclotron resonance experiments indicate that the equilibrium constant, K(eq), for the reaction Cl(H(2)O)(-) + D(2)O right harpoon over left harpoon Cl(D(2)O)(-) + H(2)O is 0.76, whereas the three theoretical predictions are 0.946, 0.979, and 1.20. Similarly, the experimental K(eq) for the Cl(H(2)O)(-) + HDO right harpoon over left harpoon Cl(HDO)(-) + H(2)O reaction is 0.64 as compared to theoretical values of 0.972, 0.998, and 1.10. Although Cl(H(2)O)(-) has a large degree of anharmonicity, K(eq) values calculated with the harmonic oscillator rigid rotator (HORR) approximation agree with the accurate treatment to within better than 2% in all cases. Results of a variety of electronic structure calculations, including coupled cluster and multireference configuration interaction calculations, with either the HORR approximation or with anharmonicity estimated via second-order vibrational perturbation theory, all agree well with the equilibrium constants obtained from the analytical surfaces.

  20. Isotope and chemical geothermometry and its applications

    Institute of Scientific and Technical Information of China (English)

    庞忠和

    2001-01-01

    The Na-K-Mg Geoindicator created by Giggenbach (1988) is convenient to use but it is still based on the empirical geothermometry equations and discrepancy for different cation geo-thermometers is observed. In fact, the location of the curve of "full equilibrium" is different if a different Na-K geothermometry equation is used. The difference is pronounced for temperatures lower than about 220℃. A case study on the Zhangzhou geothermal field of SE China resulted in a reliable estimate of reservoir temperature of 150℃ by the SO4-H2O pair Oxygen-18 isotope geothermometer. This has provided an example of attained equilibrium of the marine sulphate in the geothermal system in the low-medium temperature range (<150℃). A recent refinement of the theoretical geothermometry was achieved by the FixAl method, which provides the possibility to identify and solve problems such as an erroneous analytical value of Aluminium, and influence of processes such as mixing and degassing, and therefore makes it possible to

  1. Standard test method for isotopic abundance analysis of uranium hexafluoride and uranyl nitrate solutions by multi-collector, inductively coupled plasma-mass spectrometry

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2014-01-01

    1.1 This test method covers the isotopic abundance analysis of 234U, 235U, 236U and 238U in samples of hydrolysed uranium hexafluoride (UF6) by inductively coupled plasma source, multicollector, mass spectrometry (ICP-MC-MS). The method applies to material with 235U abundance in the range of 0.2 to 6 % mass. This test method is also described in ASTM STP 1344. 1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard. 1.3 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 appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

  2. Accelerator Mass Spectrometry of Actinides in Ground- and Seawater: An Innovative Method Allowing for the Simultaneous Analysis of U, Np, Pu, Am, and Cm Isotopes below ppq Levels.

    Science.gov (United States)

    Quinto, Francesca; Golser, Robin; Lagos, Markus; Plaschke, Markus; Schäfer, Thorsten; Steier, Peter; Geckeis, Horst

    2015-06-02

    (236)U, (237)Np, and Pu isotopes and (243)Am were determined in ground- and seawater samples at levels below ppq (fg/g) with a maximum sample size of 250 g. Such high sensitivity was possible by using accelerator mass spectrometry (AMS) at the Vienna Environmental Research Accelerator (VERA) with extreme selectivity and recently improved efficiency and a significantly simplified separation chemistry. The use of nonisotopic tracers was investigated in order to allow for the determination of (237)Np and (243)Am, for which isotopic tracers either are rarely available or suffer from various isobaric mass interferences. In the present study, actinides were concentrated from the sample matrix via iron hydroxide coprecipitation and measured sequentially without previous chemical separation from each other. The analytical method was validated by the analysis of the Reference Material IAEA 443 and was applied to groundwater samples from the Colloid Formation and Migration (CFM) project at the deep underground rock laboratory of the Grimsel Test Site (GTS) and to natural water samples affected solely by global fallout. While the precision of the presented analytical method is somewhat limited by the use of nonisotopic spikes, the sensitivity allows for the determination of ∼10(5) atoms in a sample. This provides, e.g., the capability to study the long-term release and retention of actinide tracers in field experiments as well as the transport of actinides in a variety of environmental systems by tracing contamination from global fallout.

  3. MaXIC-Q Web: a fully automated web service using statistical and computational methods for protein quantitation based on stable isotope labeling and LC-MS.

    Science.gov (United States)

    Tsou, Chih-Chiang; Tsui, Yin-Hao; Yian, Yi-Hwa; Chen, Yi-Ju; Yang, Han-Yin; Yu, Chuan-Yih; Lynn, Ke-Shiuan; Chen, Yu-Ju; Sung, Ting-Yi; Hsu, Wen-Lian

    2009-07-01

    Isotope labeling combined with liquid chromatography-mass spectrometry (LC-MS) provides a robust platform for analyzing differential protein expression in proteomics research. We present a web service, called MaXIC-Q Web (http://ms.iis.sinica.edu.tw/MaXIC-Q_Web/), for quantitation analysis of large-scale datasets generated from proteomics experiments using various stable isotope-labeling techniques, e.g. SILAC, ICAT and user-developed labeling methods. It accepts spectral files in the standard mzXML format and search results from SEQUEST, Mascot and ProteinProphet as input. Furthermore, MaXIC-Q Web uses statistical and computational methods to construct two kinds of elution profiles for each ion, namely, PIMS (projected ion mass spectrum) and XIC (extracted ion chromatogram) from MS data. Toward accurate quantitation, a stringent validation procedure is performed on PIMSs to filter out peptide ions interfered with co-eluting peptides or noise. The areas of XICs determine ion abundances, which are used to calculate peptide and protein ratios. Since MaXIC-Q Web adopts stringent validation on spectral data, it achieves high accuracy so that manual validation effort can be substantially reduced. Furthermore, it provides various visualization diagrams and comprehensive quantitation reports so that users can conveniently inspect quantitation results. In summary, MaXIC-Q Web is a user-friendly, interactive, robust, generic web service for quantitation based on ICAT and SILAC labeling techniques.

  4. [On-line method for measurement of the carbon isotope ratio of atmospheric methane and its application to atmosphere of Yakela condensed gas field].

    Science.gov (United States)

    Tang, Jun-Hong; Bao, Zheng-Yu; Xiang, Wu; Qiao, Sheng-Ying; Li, Bing

    2006-01-01

    An on-line method for measurement of the 13C/12C ratio of methane by a gas chromatography/high-temperature conversion/ isotope ratio mass spectrometry (GC/C/MS) technique was developed. This method is less laborious, more rapid (45 min), of high precision (+/- 0.4 x 10(-3)) and by using a small amount of sample (about 200 mL of atmosphere). Its application to isotopic characterization, and hence methane source identification, was demonstrated by examination of atmosphere sample collected in Yakela condensed gas field, China. The average 13C/12C ratio of atmospheric methane in Yakela field was -45.0 x 10(-3) heavier by 1.2 x 10(-3) -2.0 x 10(-3) than the global average. This is caused by seepage and diffusing of methane from Yakela condensed gas reservoir. The concentrations of atmospheric methane in daytimes are found to be lower than those in nighttimes, and the corresponding 13C/12C ratios in daytimes are lighter compared to those in nighttimes, a phenomena probably caused by the fact that a small part of methane from Yakela condensate reservoir is consumed in soil's surface under sunlight.

  5. A new serial pooling method of shifted tree ring blocks to construct millennia long tree ring isotope chronologies with annual resolution.

    Science.gov (United States)

    Boettger, Tatjana; Friedrich, Michael

    2009-03-01

    The study presents a new serial pooling method of shifted tree ring blocks for the building of isotope chronologies. This method combines the advantages of traditional 'serial' and 'intertree' pooling, and can be recommended for the construction of sub-regional long isotope chronologies with sufficient replication, and on annual resolution, especially for the case of extremely narrow tree rings. For Scots pines (Pinus sylvestris L., Khibiny Low Mountains, NW Russia) and Silver firs (Abies alba Mill., Franconia, Southern Germany), serial pooling of five consecutive tree rings seems appropriate because the species- and site-specific particularities lead to blurs of climate linkages in their tree rings for the period up to ca. five years back. An equivalent to a five-year running means that curve gained on the base annual data sets of single trees can be derived from the analysis of yearly shifted five-year blocks of consecutive tree rings, and therefore, with approximately 20% of the expense. Good coherence of delta(13)C- and delta(18)O-values between calculated means of annual total rings or late wood data and means of five-year blocks of consecutive total tree rings analysed experimentally on most similar material confirms this assumption.

  6. Module description of TOKAMAK equilibrium code MEUDAS

    Energy Technology Data Exchange (ETDEWEB)

    Suzuki, Masaei; Hayashi, Nobuhiko; Matsumoto, Taro; Ozeki, Takahisa [Japan Atomic Energy Research Inst., Naka, Ibaraki (Japan). Naka Fusion Research Establishment

    2002-01-01

    The analysis of an axisymmetric MHD equilibrium serves as a foundation of TOKAMAK researches, such as a design of devices and theoretical research, the analysis of experiment result. For this reason, also in JAERI, an efficient MHD analysis code has been developed from start of TOKAMAK research. The free boundary equilibrium code ''MEUDAS'' which uses both the DCR method (Double-Cyclic-Reduction Method) and a Green's function can specify the pressure and the current distribution arbitrarily, and has been applied to the analysis of a broad physical subject as a code having rapidity and high precision. Also the MHD convergence calculation technique in ''MEUDAS'' has been built into various newly developed codes. This report explains in detail each module in ''MEUDAS'' for performing convergence calculation in solving the MHD equilibrium. (author)

  7. Deformation of C isotopes

    CERN Document Server

    Kanada-Enyo, Y

    2004-01-01

    Systematic analysis of the deformations of proton and neutron densities in even-even C isotopes was done based on the method of antisymmetrized molecular dynamics. The $E2$ transition strength was discussed in relation to the deformation. We analyze the $B(E2;2^+_1\\to 0^+_1)$ in $^{16}$C, which has been recently measured to be abnormally small. The results suggest the difference of the deformations between proton and neutron densities in the neutron-rich C isotopes. It was found that stable proton structure in C isotopes plays an important role in the enhancement the neutron skin structure as well as in the systematics of $B(E2)$ in the neutron-rich C.

  8. Studies of carbon--isotope fractionation. Annual progress report, December 1, 1974--November 30, 1975

    Energy Technology Data Exchange (ETDEWEB)

    Ishida, T.

    1975-12-01

    The vapor pressure isotope effect of /sup 13/C//sup 12/C-substitution in CClF/sub 3/ was measured at temperatures between 169/sup 0/ and 206/sup 0/K by means of cryogenic distillation. The /sup 13/C//sup 12/C-vapor pressure isotope effect in CHF/sub 3/ was also studied at temperatures between 161/sup 0/ and 205/sup 0/K by a similar method. The construction of a cryostat has progressed as scheduled. The investigation of carbon isotope exchange equilibria between carbon dioxide and various carbamates dissolved in various organic solvents has continued. The five-stage system of Taylor-Ghate design was improved to shorten the transient time. A single stage apparatus was designed, built, and tested. These systems are used to measure the equilibrium constants and various phase equilibria involved in the carbon dioxide--carbamate system. The investigation of the explicit method of total isotope effect has made progress. A satisfactory approximation was found for the classical partition function of a Morse oscillator. The method gives a reasonable result at rho identical with /sup 1///sub 2/..sqrt..(u/sub e//x/sub e/) greater than 1.5. The medium cluster approach was applied to isotopic methanes to investigate the effects of intermolecular distance and mutual orientations of molecules in the liquid upon vapor pressure isotope effect. It was found that all geometrical effects studied tend to vanish as the size of clusters is increased. Isotope effect in the zero-point energy shifts on condensation was calculated on the basis of London dispersion forces in liquid and a semi-empirical molecular orbital theory, and was favorably compared with experimental results. (auth)

  9. A New Modified Hybrid Steepest-Descent by Using a Viscosity Approximation Method with a Weakly Contractive Mapping for a System of Equilibrium Problems and Fixed Point Problems with Minimization Problems

    Directory of Open Access Journals (Sweden)

    Uamporn Witthayarat

    2012-01-01

    Full Text Available The purpose of this paper is to consider a modified hybrid steepest-descent method by using a viscosity approximation method with a weakly contractive mapping for finding the common element of the set of a common fixed point for an infinite family of nonexpansive mappings and the set of solutions of a system of an equilibrium problem. The sequence is generated from an arbitrary initial point which converges in norm to the unique solution of the variational inequality under some suitable conditions in a real Hilbert space. The results presented in this paper generalize and improve the results of Moudafi (2000, Marino and Xu (2006, Tian (2010, Saeidi (2010, and some others. Finally, we give an application to minimization problems and a numerical example which support our main theorem in the last part.

  10. Uranium-lead dating method at the Pará-Iso isotope geology laboratory, UFPA, Belém - Brazil

    Directory of Open Access Journals (Sweden)

    Robert S. Krymsky

    2007-03-01

    Full Text Available Analytical procedures for U-Pb isotope dilution analyses at the Pará-Iso isotope geology laboratory of the Federal University of Pará (UFPA are described in detail. The procedures are applied to zircon, titanite, rutile, apatite, columbite-tantalite and whole rock. Reagent preparation and chemical processing are done in clean-room conditions. Samples are dissolved using TeflonTM microcapsules in steel jacket TeflonTM Parr InstrumentTM bomb or TeflonTM screw cap containers. U and Pb are separated using anion exchange AG 1x8 resin columns. Typical blanks for mineral sample amounts of 0.01 to 1.0 mg are less than 1 pg U and 20-30 pg Pb. Isotope analysis of the U and Pb from the same filament are carried out using a Finnigan MAT 262 mass-spectrometer in static and dynamic modes. The current analytical level is demonstrated on analyses of international standard zircon 91500 with three different 235U-205Pb and 235U-208Pb isotope tracers and whole rock standards. Results of analyses of two zircon samples are also presented.Os procedimentos analíticos para análises U-Pb por diluição isotópica no Laboratório de Geologia Isotópica (Pará-Iso da Universidade Federal do Pará (UFPA são descritos detalhadamente. Esses procedimentos são aplicados para análises de zircão, titanita, rutilo, apatita, columbita-tantalita e rocha total. A purificação dos reagentes e os procedimentos químicos são feitos em salas limpas. As amostras são dissolvidas em microcápsulas de Teflon em bombas do tipo Parr InstrumentTM. U e Pb são separados em colunas com resina de troca iônica AG 1x8. Os brancos de procedimento para amostra típica(0,01-1 mg são menores que 1 pg de U e 20-30 pg de Pb. As análises isotópicas de Pb e de U são feitas em um único filamento de Re em um espectrômetro de massa Finnigan MAT 262 nos modos estático e dinâmico. O nível analítico atual é comprovado pelas análises do padrão internacional de zircão 91500, usando tr

  11. Statistical physics ""Beyond equilibrium

    Energy Technology Data Exchange (ETDEWEB)

    Ecke, Robert E [Los Alamos National Laboratory

    2009-01-01

    The scientific challenges of the 21st century will incr