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Sample records for equilibrium fe isotope

  1. 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......-type fractionation during precipitation, this experiment yielded an isotope fractionation factor of a56Fesolution-solid=1.00027. Calculations based on these results indicate that isotopic re-equilibration is unlikely to significantly affect our determined equilibrium Fe isotope fractionation between inorganically...... and organically complexed Fe. To determine the equilibrium Fe isotope fractionation between inorganically and organically bound Fe(III), experiments with variable proportions of inorganic Fe were carried out at 25 °C. Irrespective of the proportion of inorganic Fe, equilibrium fractionation factors were within...

  2. 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...... 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...... 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...

  3. Pre-equilibrium emission and nuclear level densities in neutron induced reactions on Fe, Cr and Ni isotopes

    International Nuclear Information System (INIS)

    Ivascu, M.; Avrigeanu, M.; Ivascu, I.; Avrigeanu, V.

    1989-01-01

    The experimentally well known (n,p), (n,α) and (n,2n) reaction excitation functions, from threshold to 20 MeV incident energy, and neutron, proton and alpha-particle emission spectra at 14.8 MeV from Fe, Cr and Ni isotopes are calculated in the frame of a generalized Geometry-Dependent-Hybrid pre-equilibrium emission model, including angular momentum and parity conservation and alpha-particle emission, and the Hauser-Feshbach statistical model. Use of a consistent statistical model parameter set enables the validation of the pre-equilibrium emission model. Moreover, an enhanced pre-equilibrium emission from higher spin composite system states, associated with higher incident orbital momenta, has been evidenced. Higher orbital momenta involved also in the emergent channels of this process are suggested by calculations of the residual nuclei level populations. Finally, the unitary account of the (n, p) and (n, 2n) reaction excitation functions for Fe, Cr and Ni isotopes has allowed the proper establishment of the limits of the transition excitation range between the two different nuclear level density models used at medium and higher excitation energies, respectively. (author). 83 refs, 15 figs

  4. Variability of Fe isotope compositions of hydrothermal sulfides and oxidation products at mid-ocean ridges

    Science.gov (United States)

    Li, Xiaohu; Wang, Jianqiang; Chu, Fengyou; Wang, Hao; Li, Zhenggang; Yu, Xing; Bi, Dongwei; He, Yongsheng

    2018-04-01

    Fe isotopes compositions of the sulfides from the SMAR may suggest the equilibrium fractionation process under high temperature conditions. The red Fe oxides are enriched in heavy Fe isotopes, indicating that the oxidative weathering processes result in the occurrence of significant Fe-isotope fractionation and the preferential enrichment of heavy Fe isotopes in the oxidation product.

  5. Equilibrium Iron Isotope Fractionation at Ultra-High Pressures: Focus on Mantle-Core Differentiation. (Invited)

    Science.gov (United States)

    Polyakov, V. B.

    2009-12-01

    Iron isotope fractionation studies provide an insight into chemical and phase transformations accompanying high-pressure core-mantle differentiation processes in planetary interiors. A method for determination of equilibrium iron isotope fractionation factors (β-factors) at wide range of pressures (up to ~ 150 GPa) was recently established (Polyakov et al., 2005, 2007; Polyakov 2009). The method consists in obtaining 57Fe partial vibration densities of states (PVDOS) at different pressures from synchrotron inelastic nuclear resonance x-ray scattering (INRXS) experiments followed by calculations of iron β-factors from the 57Fe PVDOS. Using INRXS-derived 57Fe PVDOS of Fe-metal (Mao et al., 2001), ferropericlase (FeP) (Lin et al., 2006), and postperovskite (PPV) (Mao et al., 2006), it was shown (Polyakov, 2009) that at high pressures FeP and PPV are enriched in heavy iron isotopes relative to Fe-metal contrary to the low-pressure iron isotope fractionation regularity. Earth's core may contain also Ni, Si, S, H, C, etc. along with iron. I estimated effect of these elements on iron β-factors using INRXS-derived 57Fe PVDOS for Fe0.92Ni0.08 and Fe0.85Si0.15 (Lin et al., 2003), FeS (Kobayashi et al., 2004), Fe3S (Lin et al., 2004), FeHx (Mao et al., 2004), Fe3C (Gao et al., 2008). Additions of Ni and Si to Fe-metal do not affect the iron β-factor contrary to additions of S, H, and C (see figure), which reduce the iron β-factors and aid in heavy iron isotope enrichment of silicate fraction during metal-silicate differentiation. This consits with the explanation of the observed enrichment (~ 0.1‰ for 57Fe/54Fe) of Earth's basalts in heavy isotopes with respect to those from Vesta and Mars (Poitrasson et al., 2004; Weyer et al., 2005; Shoenberg and von Blanckenburg, 2006) in terms of the equilibrium iron isotope fractionation during core-mantle differentiation processes as proposed in Polyakov (2009). Figure. Pressure dependence of 57Fe/54Fe β-factors. Open circles

  6. Identifying apparent local stable isotope equilibrium in a complex non-equilibrium system.

    Science.gov (United States)

    He, Yuyang; Cao, Xiaobin; Wang, Jianwei; Bao, Huiming

    2018-02-28

    Although being out of equilibrium, biomolecules in organisms have the potential to approach isotope equilibrium locally because enzymatic reactions are intrinsically reversible. A rigorous approach that can describe isotope distribution among biomolecules and their apparent deviation from equilibrium state is lacking, however. Applying the concept of distance matrix in graph theory, we propose that apparent local isotope equilibrium among a subset of biomolecules can be assessed using an apparent fractionation difference (|Δα|) matrix, in which the differences between the observed isotope composition (δ') and the calculated equilibrium fractionation factor (1000lnβ) can be more rigorously evaluated than by using a previous approach for multiple biomolecules. We tested our |Δα| matrix approach by re-analyzing published data of different amino acids (AAs) in potato and in green alga. Our re-analysis shows that biosynthesis pathways could be the reason for an apparently close-to-equilibrium relationship inside AA families in potato leaves. Different biosynthesis/degradation pathways in tubers may have led to the observed isotope distribution difference between potato leaves and tubers. The analysis of data from green algae does not support the conclusion that AAs are further from equilibrium in glucose-cultured green algae than in the autotrophic ones. Application of the |Δα| matrix can help us to locate potential reversible reactions or reaction networks in a complex system such as a metabolic system. The same approach can be broadly applied to all complex systems that have multiple components, e.g. geochemical or atmospheric systems of early Earth or other planets. Copyright © 2017 John Wiley & Sons, Ltd.

  7. Solvent Isotope-induced Equilibrium Perturbation for Isocitrate Lyase

    Science.gov (United States)

    Quartararo, Christine E.; Hadi, Timin; Cahill, Sean M.; Blanchard, John S.

    2014-01-01

    Isocitrate lyase (ICL) catalyzes the reversible retro-aldol cleavage of isocitrate to generate glyoxylate and succinate. ICL is the first enzyme of the glyoxylate shunt, which allows for the anaplerosis of citric acid cycle intermediates under nutrient limiting conditions. In Mycobacterium tuberculosis, the source of ICL for these studies, ICL is vital for the persistence phase of the bacteria’s life cycle. Solvent kinetic isotope effects (KIEs) in the direction of isocitrate cleavage of D2OV = 2.0 ± 0.1 and D2O[V/Kisocitrate] = 2.2 ± 0.3 arise from the initial deprotonation of the C2 hydroxyl group of isocitrate or the protonation of the aci-acid of succinate product of the isocitrate aldol cleavage by a solvent-derived proton. This KIE suggested that an equilibrium mixture of all protiated isocitrate, glyoxylate and succinate prepared in D2O, would undergo transient changes in equilibrium concentrations as a result of the solvent KIE and solvent-derived deuterium incorporation into both succinate and isocitrate. No change in the isotopic composition of glyoxylate was expected or observed. We have directly monitored the changing concentrations of all isotopic species of all reactants and products using a combination of NMR spectroscopy and mass spectrometry. Continuous monitoring of glyoxylate by 1H NMR spectroscopy shows a clear equilibrium perturbation in D2O. The final equilibrium isotopic composition of reactants in D2O revealed di-deuterated succinate, protiated glyoxylate, and mono-deuterated isocitrate, with the transient appearance and disappearance of mono-deuterated succinate. A model for the equilibrium perturbation of substrate species, and their time-dependent isotopic composition is presented. PMID:24261638

  8. Effect of Ca content on equilibrium Ca isotope fractionation between orthopyroxene and clinopyroxene

    Science.gov (United States)

    Wang, Wenzhong; Zhou, Chen; Qin, Tian; Kang, Jin-Ting; Huang, Shichun; Wu, Zhongqing; Huang, Fang

    2017-12-01

    Concentration effect on equilibrium inter-mineral isotope fractionation is ubiquitous in solid solution systems, but it is not clear in which concentration range such effect is prominent. Using first-principles calculations, we examine the effect of Ca and Fe contents in orthopyroxene (opx) on its average Casbnd O bond length and the equilibrium Ca isotope fractionation factor (103lnα) between opx and clinopyroxene (cpx). Our results reveal that the average Casbnd O bond length in opx is much smaller than that in cpx and it does not change with variable Ca content x (x and y are mole ratios in CaxFeyMg1-x-ySiO3 thereafter here) when x ≤ 1/48. Incorporation of Fe (y ≥ 1/32) into opx with a fixed Ca content can only slightly increase the average Casbnd O bond length. 103lnαopx-cpx of 44Ca/40Ca is linearly correlated with the average Casbnd O bond length in opx, suggesting that 103lnαopx-cpx of 44Ca/40Ca is controlled by opx Casbnd O bond strength. Our calculations indicate that the Ca concentration effect on 103lnαopx-cpx is significant when x in opx ranges from 2/16 to 1/48, while Fe in natural opx only causes a slight decrease in 103lnαopx-cpx. Our results provide insights into Ca isotope fractionation in high-temperature geochemical processes. Given that Ca content x in opx from natural peridotites is usually lower than 1/32 and Fe content y is generally ∼10 mol%, Ca and Fe concentration effects on 103lnαopx-cpx in natural samples are negligible. Rather, 103lnαopx-cpx is mainly controlled by temperature. 103lnαopx-cpx of 44Ca/40Ca decreases from 0.50‰ to 0.26‰ when temperature increases from 1000 K to 1400 K if the Fe effect is taken into account. Therefore, if Ca isotope fractionation between opx and cpx (Δ44/40Caopx-cpx) in natural peridotites is greater than 0.50‰ or lower than 0.26‰, it may indicate disequilibrium of Ca isotopes. Finally, the large 103lnαopx-cpx relative to our current analytical precision suggests that Δ44/40Caopx

  9. Can Biomass Burning Explain Isotopically Light Fe in Marine Aerosols?

    Science.gov (United States)

    Sherry, A. M.; Anbar, A. D.; Herckes, P.; Romaniello, S. J.

    2016-02-01

    Iron (Fe) is an important micronutrient that limits primary productivity in large parts of the ocean. In these regions, atmospheric aerosol deposition is an important source of Fe to the surface ocean and thus has a critical impact on ocean biogeochemistry. Fe-bearing aerosols originate from many sources with potentially distinct Fe isotopic compositions. Consequently, Fe isotopes may provide a new tool to trace the sources of aerosol Fe to the oceans. Mead et al. (2013) first discovered that Fe in the fine fraction of Bermuda aerosols is often isotopically lighter than Fe from known anthropogenic and crustal sources. 1 These authors suggested that this light isotopic signature was likely the result of biomass burning, since Fe in plants is the only known source of isotopically light Fe. More recently, Conway et al. found that Fe in the soluble fraction of aerosols collected during 2010-2011 North Atlantic GEOTRACES cruises also showed light isotope values, which they likewise attributed to biomass burning.2 These studies are further supported by new modeling work which suggests that biomass burning aerosols should contribute significant amounts of soluble Fe to tropical and southern oceans.3To test if biomass burning releases aerosols with a light Fe isotope composition, we are conducting lab-scale biomass burning experiments using natural samples of vegetation and leaf litter. Burn aerosols were collected on cellulose filters, then digested and analyzed for trace metal concentrations using inductively-coupled mass spectrometry (ICP-MS). Fe isotopes were determined by using multiple collector ICP-MS following separation and purification of Fe using anion exchange chromatography. We will discuss metal concentration and isotope data from these experiments with implications for the interpretation of Fe isotope signals in aerosol samples. 1Mead, C et al. GRL, 2013, 40, 5722-5727. 2 Conway, T et al. Goldschmidt Abs 2015 593. 3Ito, A. ES&T Lett, 2015, 2, 70-75.

  10. Evaluating Volatility-controlled Isotope Fractionation During Planet Formation: Kinetics versus Equilibrium

    Science.gov (United States)

    Young, E. D.

    2017-12-01

    Recent advances in our ability to measure stable isotope ratios of light, rock-forming elements, including those for Zn, K, Fe, Si, and Mg, among others, has resulted in an emerging hypothesis that collisions among rocky planetesimals, planetary embryos, and/or proto-planets caused losses of moderately volatile elements (e.g., K) and "common" or moderately refractory elements (e.g., Mg and Si). The primary evidence is in the form of heavy isotope enrichments in rock-forming elements relative to the chondrite groups that are thought to be representative of planetary precursors. Equilibrium volatility-controlled isotope fractionation for planetesimal magma oceans might have occurred for bodies larger than 0.1% of an Earth mass (½ the mass of Pluto) as these bodies had sufficient gravity to overpower the escape velocities of hot gas at 2000K. Both Jean's escape and viscous drag hydrodynamic escape can obviate the escape velocity limit but will fractionate by mass, not by volatility. Equilibrium vapor/melt fractionation is qualitatively consistent with the greater disparity in 29Si/28Si between Earth and chondrites than in 25Mg/24Mg. However, losses of large masses of vapor are required to record the fractionation in the melts. We consider that if Earth was derived from E chondrite-like materials, the bulk composition of the Earth, assuming refractory Ca was retained, requires > 60% loss of Mg. This is a lot of vapor loss for a process relying on at least intermittent equilibrium, although it comports with the isotopic lever-rule requirements. Paradoxically, the alternative of evaporative loss of rock-forming elements requires less total mass loss. For example, the calculated Mg and Si isotopic compositions of residues resulting from evaporation of chondritic melts can fit the Mg and Si isotopic compositions of Earth, Mars, and angrites with varying background pressures and with total mass losses of near 5% or less. These mass losses are closer to, and even lower than

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

    Science.gov (United States)

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

    2014-06-01

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

  12. Direct determination of equilibrium deuterium isotope effects at natural abundance

    International Nuclear Information System (INIS)

    Zhang, B.; Martin, M.L.

    1992-01-01

    A great variety of techniques has been used to study deuterium-protium partitioning in exchanging systems at equilibrium. In this context it is shown that the determination of site-specific isotope contents by 2 H-NMR at natural abundance provides simple and direct access to thermodynamic isotope fractionation factors. This method avoids the recourse to deuterated species and therefore the approximations inherent in the analysis of complex isotopomeric mixtures. A number of slowly exchanging systems involving OH, NH, or SH groups and water offer suitable conditions (large chemical shift differences, moderate line widths,hor-ellipsis) for the relatively accurate determination of thermodynamic fractionation factors. Moreover multiple fractionations can be observed and compared in ternary mixtures. 25 refs., 2 tabs

  13. Modes of planetary-scale Fe isotope fractionation

    Science.gov (United States)

    Schoenberg, Ronny; von Blanckenburg, Friedhelm

    2006-12-01

    A comprehensive set of high-precision Fe isotope data for the principle meteorite types and silicate reservoirs of the Earth is used to investigate iron isotope fractionation at inter- and intra-planetary scales. 14 chondrite analyses yield a homogeneous Fe isotope composition with an average δ56Fe/ 54Fe value of - 0.015 ± 0.020‰ (2 SE) relative to the international iron standard IRMM-014. Eight non-cumulate and polymict eucrite meteorites that sample the silicate portion of the HED (howardite-eucrite-diogenite) parent body yield an average δ56Fe/ 54Fe value of - 0.001 ± 0.017‰, indistinguishable to the chondritic Fe isotope composition. Fe isotope ratios that are indistinguishable to the chondritic value have also been published for SNC meteorites. This inner-solar system homogeneity in Fe isotopes suggests that planetary accretion itself did not significantly fractionate iron. Nine mantle xenoliths yield a 2 σ envelope of - 0.13‰ to + 0.09‰ in δ56Fe/ 54Fe. Using this range as proxy for the bulk silicate Earth in a mass balance model places the Fe isotope composition of the outer liquid core that contains ca. 83% of Earth's total iron to within ± 0.020‰ of the chondritic δ56Fe/ 54Fe value. These calculations allow to interprete magmatic iron meteorites ( δ56Fe/ 54Fe = + 0.047 ± 0.016‰; N = 8) to be representative for the Earth's inner metallic core. Eight terrestrial basalt samples yield a homogeneous Fe isotope composition with an average δ56Fe/ 54Fe value of + 0.072 ± 0.016‰. The observation that terrestrial basalts appear to be slightly heavier than mantle xenoliths and that thus partial mantle melting preferentially transfers heavy iron into the melt [S. Weyer, A.D. Anbar, G.P. Brey, C. Munker, K. Mezger and A.B. Woodland, Iron isotope fractionation during planetary differentiation, Earth and Planetary Science Letters 240(2), 251-264, 2005.] is intriguing, but also raises some important questions: first it is questionable whether the

  14. Isotopic Evidence of Unaccounted for Fe and Cu Erythropoietic Pathways

    Science.gov (United States)

    Albarede, F.; Telouk, P.; Lamboux, A.; Jaouen, K.; Balter, V.

    2011-12-01

    Despite its potential importance for understanding perturbations in the Fe-Cu homeostatic pathways, the natural isotopic variability of these metals in the human body remains unexplored. We measured the Fe, Cu, and Zn isotope compositions of total blood, serum, and red blood cells of ~50 young blood donors by multiple-collector ICP-MS after separation and purification by anion exchange chromatography. Zn is on average 0.2 permil heavier in erythrocytes (δ 66Zn=0.44±0.33 permil) with respect to serum but shows much less overall isotopic variability than Fe and Cu, which indicates that isotope fractionation depends more on redox conditions than on ligand coordination. On average, Fe in erythrocytes (δ 56Fe=-2.59±0.47 permil) is isotopically light by 1-2 permil with respect to serum, whereas Cu in erythrocytes (δ 65Cu=0.56±0.50 permil) is 0.8 percent heavier. Fe and Cu isotope compositions clearly separate erythrocytes of men and women. Fe and Cu from B-type men erythrocytes are visibly more fractionated than all the other blood types. Isotope compositions provide an original method for evaluating metal mass balance and homeostasis. Natural isotope variability shows that the current models of Fe and Cu erythropoiesis, which assume that erythropoiesis is restricted to bone marrow, violate mass balance requirements. It unveils unsuspected major pathways for Fe, with erythropoietic production of isotopically heavy ferritin and hemosiderin, and for Cu, with isotopically light Cu being largely channeled into blood and lymphatic circulation rather than into superoxide dismutase-laden erythrocytes. Iron isotopes provide an intrinsic measuring rod of the erythropoietic yield, while Cu isotopes seem to gauge the relative activity of erythropoiesis and lymphatics.

  15. Fe and Cu isotope mass balances in the human body

    Science.gov (United States)

    Balter, V.; Albarede, F.; Jaouen, K.

    2011-12-01

    The ranges of the Fe and Cu isotope compositions in the human body are large, i.e. ~3% and ~2%, respectively. Both isotopic fractionations appear to be mainly controlled by redox conditions. The Fe and Cu isotope compositions of the tissues analyzed so far plot on a mixing hyperbolae between a reduced and an oxidized metals pools. The reduced metals pool is composed by erythrocytes, where Fe is bounded to hemoglobin as Fe(II) and Cu to superoxide-dismutase as Cu(I). The oxidized metals pool is composed by hepatocytes, where Fe and Cu are stored as Fe(III) ferritin and as Cu(II) ceruloplasmine, respectively. The position of each biological component in the δ56Fe-δ65Cu diagram therefore reflects the oxidation state of Fe and Cu of the predominant metal carrier protein and allows to quantify Fe and Cu fluxes between organs using mass balance calculations. For instance, serum and clot Fe and Cu isotope compositions show that current biological models of erythropoiesis violates mass conservation requirements, and suggest hidden Fe and Cu pathways during red blood cells synthesis. The results also show that a coupled Fe-Cu strong gender isotopic effect is observed in various organs. The isotopic difference between men and women is unlikely to be due to differential dietary uptake or endometrium loss, but rather reflects the effect of menstrual losses and a correlative solicitation of hepatic stores. We speculate that thorough studies of the metabolism of stable isotopes in normal conditions is a prerequisite for the understanding of the pathological dysregulations.

  16. 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

  17. Menopause effect on blood Fe and Cu isotope compositions.

    Science.gov (United States)

    Jaouen, Klervia; Balter, Vincent

    2014-02-01

    Iron (δ(56) Fe) and copper (δ(65) Cu) stable isotope compositions in blood of adult human include a sex effect, which still awaits a biological explanation. Here, we investigate the effect of menopause by measuring blood δ(56) Fe and δ(65) Cu values of aging men and women. The results show that, while the Fe and Cu isotope compositions of blood of men are steady throughout their lifetime, postmenopausal women exhibit blood δ(65) Cu values similar to men, and δ(56) Fe values intermediate between men and premenopausal women. The residence time of Cu and Fe in the body likely explains why the blood δ(65) Cu values, but not the δ(56) Fe values, of postmenopausal women resemble that of men. We suggest that the Cu and Fe isotopic fractionation between blood and liver resides in the redox reaction occurring during hepatic solicitation of Fe stores. This reaction affects the Cu speciation, which explains why blood Cu isotope composition is impacted by the cessation of menstruations. Considering that Fe and Cu sex differences are recorded in bones, we believe this work has important implications for their use as a proxy of sex or age at menopause in past populations. Copyright © 2013 Wiley Periodicals, Inc.

  18. Thermal equilibration of iron meteorite and pallasite parent bodies recorded at the mineral scale by Fe and Ni isotope systematics

    Science.gov (United States)

    Chernonozhkin, Stepan M.; Weyrauch, Mona; Goderis, Steven; Oeser, Martin; McKibbin, Seann J.; Horn, Ingo; Hecht, Lutz; Weyer, Stefan; Claeys, Philippe; Vanhaecke, Frank

    2017-11-01

    In this work, a femtosecond laser ablation (LA) system coupled to a multi-collector inductively coupled plasma-mass spectrometer (fs-LA-MC-ICP-MS) was used to obtain laterally resolved (30-80 μm), high-precision combined Ni and Fe stable isotope ratio data for a variety of mineral phases (olivine, kamacite, taenite, schreibersite and troilite) composing main group pallasites (PMG) and iron meteorites. The stable isotopic signatures of Fe and Ni at the mineral scale, in combination with the factors governing the kinetic or equilibrium isotope fractionation processes, are used to interpret the thermal histories of small differentiated asteroidal bodies. As Fe isotopic zoning is only barely resolvable within the internal precision level of the isotope ratio measurements within a single olivine in Esquel PMG, the isotopically lighter olivine core relative to the rim (Δ56/54Ferim-core = 0.059‰) suggests that the olivines were largely thermally equilibrated. The observed hint of an isotopic and concentration gradient for Fe of crudely similar width is interpreted here to reflect Fe loss from olivine in the process of partial reduction of the olivine rim. The ranges of the determined Fe and Ni isotopic signatures of troilite (δ56/54Fe of -0.66 to -0.09‰) and schreibersite (δ56/54Fe of -0.48 to -0.09‰, and δ62/60Ni of -0.64 to +0.29‰) may result from thermal equilibration. Schreibersite and troilite likely remained in equilibrium with their enclosing metal to temperatures significantly below their point of crystallization. The Ni isotopic signatures of bulk metal and schreibersite correlate negatively, with isotopically lighter Ni in the metal of PMGs and isotopically heavier Ni in the metal of the iron meteorites analyzed. As such, the light Ni isotopic signatures previously observed in PMG metal relative to chondrites may not result from heterogeneity in the Solar Nebula, but rather reflect fractionation in the metal-schreibersite system. Comparison between

  19. Contrasting Effects of Carbon and Sulfur on Fe-Isotope Fractionation between Metal and Silicate Melt during Planetary Core Formation

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    Elardo, S. M.; Shahar, A.

    2015-12-01

    There are numerous studies that show well-resolved Fe isotope fractionations in igneous materials from different planetary bodies. Potential explanations for these fractionations include a non-chondritic bulk planetary Fe isotopic composition, and equilibrium fractionation between Fe-alloys or minerals and silicate melts during planetary differentiation, mantle melting, or fractional crystallization. This is further complicated by the fact that these processes are not mutually exclusive, making the interpretation of Fe isotope data a complex task. Here we present new experimental results investigating the effect of C on Fe isotope fractionation between molten peridotite and an Fe-alloy. Experiments were conducted at 1 GPa and 1850° C for 0.5 - 3 hours on a mixture of an 54Fe-spiked peridotite and Fe-metal with and without Ni metal in an end-loaded piston cylinder at the Geophysical Laboratory. Carbon saturation was achieved with a graphite capsule, and resulted in C contents of the Fe-alloy in our experiments ranging from 3.8 - 4.9 wt. %. The metal and silicate phases from half of each experiment were separated manually and dissolved in concentrated acids. Iron was separated from matrix elements by anion exchange chromatagraphy. Iron-isotopic compositions were determined with the Nu Plasma II MC-ICP-MS at GL. The other half of each experiment was used for quantitative microbeam analysis. Equilibrium was assessed with a time series and the three-isotope exchange method. The Ni-free experiments resulted in no resolvable Fe isotope fractionation between the Fe-C-alloy and molten silicate. This is in contrast to the results of Shahar et al. (2015) which showed a fractionation for Δ57Fe of ~0.18 ‰ between a peridotite and an Fe-alloy with a similar S abundance to C in these experiments. The one experiment thus far that contained Ni (~4 wt. % in the alloy) showed a resolvable fractionation between the Fe-Ni-C alloy and silicate of ~0.10 ‰. Shahar et al. found a

  20. Variation of Fe3+/Fe2+ and Cu2+/Cu+ equilibrium with basicity of oxide melts

    Science.gov (United States)

    Nakasaki, M.; Hasegawa, M.; Iwase, M.

    2006-12-01

    Oxidation-reduction equilibrium experiments were conducted with Li2O-CaO-Al2O3-ZnO-SiO2-B2O3 melts containing small concentrations of either copper oxide or iron oxide. The results indicated that, for oxide melts containing relatively large proportions of amphoteric oxides, i.e., Al2O3 and ZnO, the ratios lcub;(Cu2+)/(Cu+) P O 2 1/4rcub; and lcub;(Fe3+)/(Fe2+) P O 2 1/4rcub; decreased with an increase in basicity. With further increase in basicity, however, these ratios became independent of basicity. For very basic melts, the ratios increased with an increase in basicity. These variations of lcub;(Cu2+)/(Cu+) P O 2 1/4rcub; and lcub;(Fe3+)/(Fe2+) P O 2 1/4rcub; can be interpreted in terms of the optical basicity of the oxide melts and are consistent with the following general expressions for the red-ox equilibria within acidic and relatively basic melts, respectively: M n++(1/4)O2=M( n+1)++(1/2)O2- M n++(1/4)O2+(3/2)O2-=MO2 (3- n) and M n++(1/4)O2=(3/4)M( n+1)++(1/4)MO2 (3- n)

  1. Equilibrium mercury isotope fractionation between dissolved Hg(II) species and thiol-bound Hg

    NARCIS (Netherlands)

    Wiederhold, Jan G.; Cramer, Christopher J.; Daniel, Kelly; Infante, Ivan; Bourdon, Bernard; Kretzschmar, Ruben

    2010-01-01

    Stable Hg isotope ratios provide a new tool to trace environmental Hg cycling. Thiols (-SH) are the dominant Hg-binding groups in natural organic matter. Here, we report experimental and computational results on equilibrium Hg isotope fractionation between dissolved Hg(II) species and thiol-bound

  2. The solubility and isotopic exchange equilibrium for hydrogen isotopes in lithium

    International Nuclear Information System (INIS)

    Smith, F.J.; Land, J.F.; Begun, G.M.; La Gamma de Batistoni, A.M.

    1979-01-01

    The individual solubilities of hydrogen, deuterium and tritium in lithium have been measured as a function of temperature (700 to 1000 0 C) and pressure (0.1 to 760 torr). An expression is derived for the temperature dependence of the individual solubilities when the mole fraction of LiH, LiD or LiT is less than about 0.1. The mutual solubilities and isotopic exchange equilibria of hydrogen and deuterium in lithium have been measured at temperatures between 700 and 900 0 C. Both of the total pressure and individual partial pressures of H 2 , HD, and D 2 have been determined as a function of the mole fraction of LiH and LiD in the lithium solution with varying hydrogen-to-deuterium ratios. In the plateau region, the hydrogen and deuterium could be treated as a single chemical species. However, in the Sieverts region the hydrogen and deuterium dissolved independently of each other. The equilibrium isotope exchange constant varied from 1.28 at 700 0 C to 1.17 to 850 0 C. (U.K.)

  3. What can Fe stable isotopes tell us about magmas?

    DEFF Research Database (Denmark)

    Stausberg, Niklas

    The majority of the Earth’s crust is formed by magmas, and understanding their production and differentiation is important to interpret the geologic rock record. A powerful tool to investigate magmatic processes is the distribution of the stable isotopes of the major redox-sensitive element...... the differentiation of magmas from the perspective of Fe stable isotopes, integrated with petrology, by studying igneous rocks and their constituent phases (minerals and glasses) from the Bushveld Complex, South Africa, Thingmuli, Iceland, Pantelleria, Italy, and the Bishop Tuff, USA. The findings are interpreted...... and for more quantitative model of the magmatic processes producing enigmatic stable isotope compositions of rhyolitic and granite magmas....

  4. Equilibrium and kinetic studies of Cu (II), Cd (II), Pb (II) and Fe (II ...

    African Journals Online (AJOL)

    Langmuir isotherm and pseudo-second order models were used to analyse the equilibrium and kinetic experimental data respectively. Equilibrium experimental data of Cu (II), Cd (II), Pb (II) and Fe (II) adsorption onto cocoa pod fitted well to Langmuir model and the kinetic data also fitted well to the pseudo-second order ...

  5. Strontium isotope fractionation during strontianite (SrCO3) dissolution, precipitation and at equilibrium

    Science.gov (United States)

    Mavromatis, Vasileios; Harrison, Anna L.; Eisenhauer, Anton; Dietzel, Martin

    2017-12-01

    In this study we examine the behavior of stable Sr isotopes between strontianite [SrCO3] and reactive fluid during mineral dissolution, precipitation, and at chemical equilibrium. Experiments were performed in batch reactors at 25 °C in 0.01 M NaCl solutions wherein the pH was adjusted by bubbling of a water saturated gas phase of pure CO2 or atmospheric air. The equilibrium Sr isotope fractionation between strontianite and fluid after dissolution of the solid under 1 atm CO2 atmosphere was estimated as Δ88/86SrSrCO3-fluid = δ88/86Sr SrCO3 - δ88/86Srfluid = -0.05 ± 0.01‰. On the other hand, during strontianite precipitation, an enrichment of the fluid phase in 88Sr, the heavy isotopomer, was observed. The evolution of the δ88/86Srfluid during strontianite precipitation can be modeled using a Rayleigh distillation approach and the estimated, kinetically driven, fractionation factor αSrCO3-fluid between solid and fluid is calculated to be 0.99985 ± 0.00003 corresponding to Δ88/86SrSrCO3-fluid = -0.15‰. The obtained results further support that under chemical equilibrium conditions between solid and fluid a continuous exchange of isotopes occurs until the system approaches isotopic equilibrium. This isotopic exchange is not limited to the outer surface layer of the strontianite crystal, but extends to ∼7-8 unit cells below the crystal surface. The behavior of Sr isotopes in this study is in excellent agreement with the concept of dynamic equilibrium and it suggests that the time needed for achievement of chemical equilibrium is generally shorter compared to that for isotopic equilibrium. Thus it is suggested that in natural Sr-bearing carbonates an isotopic change may still occur close to thermodynamic equilibrium, despite no observable change in aqueous elemental concentrations. As such, a secondary and ongoing change of Sr isotope signals in carbonate minerals caused by isotopic re-equilibration with fluids has to be considered in order to use Sr

  6. Fe Isotopic Composition of Presolar SiC Mainstream Grains

    Science.gov (United States)

    Tripa, C. E.; Pellin, M. J.; Savina, M. R.; Davis, A. M.; Lewis, R. S.; Clayton, R. N.

    2002-01-01

    Iron isotopic distribution was measured in SiC mainstream grains from the Murchison meteorite by time-of-flight resonance ionization mass spectrometry. All grains exhibit 54Fe depletions of 50 to 200, lower than what are predicted by calculations of s-process nucleosynthesis in AGB stars. Additional information is contained in the original extended abstract.

  7. Geochronology and Hf–Fe isotopic geochemistry of the Phanerozoic ...

    Indian Academy of Sciences (India)

    contributed to their magma generation. As the first magmatic phase, the ∼395 Ma intrusions were ..... traditional stable isotope, Fe is an effective tracer for identifying the input of enriched lithospheric mantle from ..... Ore Geol. Rev., doi: 10.1016/j.oregeorev.2013.03.002. Ling M X, Li Y, Ding X, Teng F Z, Yang X Y, Fan W M,.

  8. Experimental Liquidus Studies of the Pb-Fe-Si-O System in Equilibrium with Metallic Pb

    Science.gov (United States)

    Shevchenko, M.; Jak, E.

    2018-02-01

    Phase equilibria of the Pb-Fe-Si-O system have been investigated at 943 K to 1773 K (670 °C to 1500 °C) for oxide liquid in equilibrium with liquid Pb metal and solid oxide phases: (a) quartz, tridymite, or cristobalite; (b) (fayalite + tridymite) or (fayalite + spinel); (c) spinel (Fe3O4); (d) complex lead-iron silicates (melanotekite PbO·FeO1.5·SiO2, barysilite 8PbO·FeO·6SiO2, 5PbO·FeO1.5·SiO2, and 6PbO·FeO1.5·SiO2); (e) lead silicates (Pb2SiO4, Pb11Si3O17); (f) lead ferrites (magnetoplumbite Pb1+ x Fe12- x O19- x solid solution range); and (g) lead oxide (PbO, massicot). High-temperature equilibration on primary phase or iridium substrates, followed by quenching and direct measurement of Pb, Fe, and Si concentrations in the phases with the electron probe X-ray microanalysis, has been used to accurately characterize the system in equilibrium with Pb metal. All results are projected onto the PbO-"FeO"-SiO2 plane for presentation purposes. The present study is the first systematic characterization of liquidus over a wide range of compositions in this system in equilibrium with metallic Pb.

  9. The temporal evolution of magnesium isotope fractionation during hydromagnesite dissolution, precipitation, and at equilibrium

    Science.gov (United States)

    Oelkers, Eric H.; Berninger, Ulf-Niklas; Pérez-Fernàndez, Andrea; Chmeleff, Jérôme; Mavromatis, Vasileios

    2018-04-01

    This study provides experimental evidence of the resetting of the magnesium (Mg) isotope signatures of hydromagnesite in the presence of an aqueous fluid during its congruent dissolution, precipitation, and at equilibrium at ambient temperatures over month-long timescales. All experiments were performed in batch reactors in aqueous sodium carbonate buffer solutions having a pH from 7.8 to 9.2. The fluid phase in all experiments attained bulk chemical equilibrium within analytical uncertainty with hydromagnesite within several days, but the experiments were allowed to continue for up to 575 days. During congruent hydromagnesite dissolution, the fluid first became enriched in isotopically light Mg compared to the dissolving hydromagnesite, but this Mg isotope composition became heavier after the fluid attained chemical equilibrium with the mineral. The δ26Mg composition of the fluid was up to ∼0.35‰ heavier than the initial dissolving hydromagnesite at the end of the dissolution experiments. Hydromagnesite precipitation was provoked during one experiment by increasing the reaction temperature from 4 to 50 °C. The δ26Mg composition of the fluid increased as hydromagnesite precipitated and continued to increase after the fluid attained bulk equilibrium with this phase. These observations are consistent with the hypothesis that mineral-fluid equilibrium is dynamic (i.e. dissolution and precipitation occur at equal, non-zero rates at equilibrium). Moreover the results presented in this study confirm (1) that the transfer of material from the solid to the fluid phase may not be conservative during stoichiometric dissolution, and (2) that the isotopic compositions of carbonate minerals can evolve even when the mineral is in bulk chemical equilibrium with its coexisting fluid. This latter observation suggests that the preservation of isotopic signatures of carbonate minerals in the geological record may require a combination of the isolation of fluid-mineral system

  10. High-Temperature Equilibrium Isotope Fractionation of Non-Traditional Stable Isotopes: Experiments, Theory, and Applications (Invited)

    Science.gov (United States)

    Young, E. D.; Lazar, G. C.; Macris, C. A.; Manning, C. E.; Schauble, E. A.; Shahar, A.

    2013-12-01

    Experiments are crucial for validating our understanding of stable isotope fractionation at high temperatures. The three-isotope method has been applied with success in the Si, Mg, Fe, and Ni isotope systems to date. The results of these experiments can be compared with expectations from theory and measurements of natural samples. Qualitative insights into the partitioning of heavy and light isotopes between mineral phases are gained by treating the force constant for relevant bonds, Kf j, as electrostatic in origin. The ionic model, based on the mean bond strength as defined by Pauling, has obvious limitations but is useful for rationalizing structures and site occupancies in silicates and oxide minerals and is equally useful in formulating expectations for isotope fractionation between phases. In some cases, as in Fe isotopes in spinels, the expectations are contrary to predictions based on modeling but similar to observations in natural samples. Experimental verification is required. The force constant for a bond between cation i (Mg, Fe, etc.) and anion j (e.g., O) can be written in terms of mean bond strengths si and sj (as defined by Pauling) as Kf,ij = sisj e2 (1-n)/(4 π ɛο r3ij ) where ɛo is the electric constant (vacuum permittivity for simplicity), e is the charge of an electron, n is the exponent in the Born-Mayer formulation for ion repulsion (Born and Mayer 1932), and rij is the interatomic spacing. This equation shows explicitly that larger values for the force constant Kf correspond to smaller coordination numbers (via si and sj). We therefore expect an inverse relationship between isotope ratios (heavy/light) and coordination of its oxygen bond partners in silicate and oxides minerals and this is verified in mantle minerals. Our work with Fe isotope partitioning in mantle spinels suggests that coordination may be equally important as oxidation state, recognizing that these distinctions are not orthogonal. Recent work on the Mg isotopic

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

    Indian Academy of Sciences (India)

    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 ...

  12. Investigations of the photochemical isotope equilibrium between O2, CO2 and O3

    Directory of Open Access Journals (Sweden)

    R. Shaheen

    2007-01-01

    Full Text Available Contrary to tropospheric CO2 whose oxygen isotopic composition follows a standard mass dependent relationship, i.e. δ17O~0.5δ18O, stratospheric CO2 is preferentially enriched in 17O, leading to a strikingly different relation: δ17O~1.7δ18O. It has been shown repeatedly that the isotope anomaly is inherited from O3 via photolytically produced O(1D that undergoes isotope exchange with CO2 and the anomaly may well serve as a tracer of stratospheric chemistry if details of the exchange mechanism are understood. We have studied the photochemical isotope equilibrium in UV-irradiated O2-CO2 and O3-CO2 mixtures to quantify the transfer of the anomaly from O3 to CO2 at room temperature. By following the time evolution of the oxygen isotopic compositions of CO2 and O2 under varying initial isotopic compositions of both, O2/O3 and CO2, the isotope equilibria between the two reservoirs were determined. A very strong dependence of the isotope equilibrium on the O2/CO2-ratio was established. Equilibrium enrichments of 17O and 18O in CO2 relative to O2 diminish with increasing CO2 content, and this reduction in the equilibrium enrichments does not follow a standard mass dependent relation. When molecular oxygen exceeds the amount of CO2 by a factor of about 20, 17O and 18O in equilibrated CO2 are enriched by (142±4‰ and (146±4‰, respectively, at room temperature and at a pressure of 225 hPa, independent of the initial isotopic compositions of CO2 and O2 or O3. From these findings we derive a simple and general relation between the starting isotopic compositions and amounts of O2 and CO2 and the observed slope in a three oxygen isotope diagram. Predictions from this relation are compared with published laboratory and atmospheric data.

  13. Iron Isotopic Compositions of Troilite (FeS) Inclusions from Iron Meteorites

    Energy Technology Data Exchange (ETDEWEB)

    Cook, David L.; Schönbächler, Maria, E-mail: david.cook@erdw.ethz.ch [Institut für Geochemie und Petrologie, ETH Zürich, Clausiusstrasse 25, 8092 Zürich (Switzerland)

    2017-10-01

    We report non-mass-dependent Fe isotopic data for troilite (FeS) inclusions from 10 iron meteorites, representing both non-magmatic (IAB) and magmatic groups (IIAB, IIIAB, IVA). No resolvable variations are present in the most neutron-rich isotope ({sup 58}Fe), but small deficits (≈−0.1 ε ) in {sup 56}Fe were observed in several inclusions. With the exception of several Ca–Al-rich inclusions in primitive meteorites, these are the first reported non-mass-dependent variations in Fe isotopes for material formed in the early solar system. Nucleosynthetic variations in Ni isotopes were previously reported in these same samples. The effects in Fe isotopes are not correlated with those in Ni, which suggests that the origins of the isotopic variations are decoupled from one another. The {sup 56}Fe deficits may represent incomplete mixing of the precursor dust in the protoplanetary disk. Alternatively, a parent body process (e.g., irradiation by galactic cosmic rays) may have modified the Fe isotopic compositions of some inclusions, which initially had homogeneous Fe isotopic compositions.

  14. 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...... in cold regions. With recent instrumental developments it is now possible to test the accuracy of the earlier results as well as extend the temperature range. METHODS: Novel measurements were made of the ice-vapor equilibrium fractionation factor between 0 degrees C and -40 degrees C, from a unique...... experimental setup using both a Picarro cavity ringdown spectrometer and a TC/EA IRMS system. Using both systems allows for continuous monitoring of the equilibrium state of the system as well as testing for reproducibility. RESULTS: The results of the experiments show fractionation factors for H-2 and O-18...

  15. Determination of the equilibrium constant of FeZrCl6 formation from FeCl3 and ZrCl4

    International Nuclear Information System (INIS)

    Berdonosov, S.S.; Kharisov, B.I.; Nikitin, M.I.

    1992-01-01

    Equilibrium pressures of chlorine formed in the course of reaction FeCl 3 +ZrCl 4 ↔ FeZrCl 6 +0.5 Cl 2 were determined at the temperatures of 250-325 deg C. The values of equilibrium constant K p of the reaction mentioned at the temperatures of 250, 275, 300 and 325 deg were calculated, taking into consideration the determined values of p Cl2 and literature data on equilibrium pressures of ZrCl 4 and FeCl 3 vapours

  16. 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

  17. Origin of heavy Fe isotope compositions in high-silica igneous rocks: A rhyolite perspective

    Science.gov (United States)

    Du, De-Hong; Wang, Xiao-Lei; Yang, Tao; Chen, Xin; Li, Jun-Yong; Li, Weiqiang

    2017-12-01

    The origin of heavy Fe isotope compositions in high-silica (>70 wt% SiO2) igneous rocks remains a highly controversial topic. Considering that fluid exsolution in eruptive rocks is more straight-forward to constrain than in plutonic rocks, this study addresses the problem of Fe isotope fractionation in high-silica igneous rocks by measuring Fe isotope compositions of representative rhyolitic samples from the Neoproterozoic volcanic-sedimentary basins in southern China and the Triassic Tu Le Basin in northern Vietnam. The samples show remarkably varied δ56FeIRMM014 values ranging from 0.05 ± 0.05‰ to 0.55 ± 0.05‰, which is among the highest values reported from felsic rocks. The extensional tectonic setting and short melt residence time in magma chambers for the studied rhyolites rule out Soret diffusion and thermal migration processes as causes of the high δ56Fe values. Effects of volcanic degassing and fluid exsolution on bulk rock δ56Fe values for the rhyolites are also assessed using bulk rock geochemical indicators and Rayleigh fractionation models, and these processes are found to be insufficient to produce resolvable changes in Fe isotope compositions of the residual melt. The most probable mechanism accounting for heavy Fe isotope compositions in the high-silica rhyolites is narrowed down to fractional crystallization processes in the magma before rhyolite eruption. Removal of isotopically light Fe-bearing minerals (i.e. ulvöspinel-rich titanomagnetite, ilmenite and biotite) is proposed as the main cause of Fe isotope variation in silicic melts during magmatic evolution. This study implies that crystal fractionation is the dominant mechanism that controls Fe isotope fractionation in eruptive rocks and Fe isotopes could be used to study magmatic differentiation of high-silica magmas.

  18. Site-specific equilibrium isotopic fractionation of oxygen, carbon and calcium in apatite

    Science.gov (United States)

    Aufort, Julie; Ségalen, Loïc; Gervais, Christel; Paulatto, Lorenzo; Blanchard, Marc; Balan, Etienne

    2017-12-01

    The stable isotope composition of biogenic apatite is an important geochemical marker that can record environmental parameters and is widely used to infer past climates, biomineralization processes, dietary preferences and habitat of vertebrates. In this study, theoretical equilibrium isotopic fractionation of oxygen, carbon and calcium in hydroxyapatite and carbonate-bearing hydroxyapatite is investigated using first-principles methods based on density-functional theory and compared to the theoretical isotopic fractionation properties of calcite, CO2 and H2O. Considering the variability of apatite crystal-chemistry, special attention is given to specific contributions of crystal sites to isotopic fractionation. Significant internal fractionation is calculated for oxygen and carbon isotopes in CO3 between the different structural sites occupied by carbonate groups in apatite (typically 7‰ for both 18O/16O and 13C/12C fractionation at 37 °C). Compared with calcite-water oxygen isotope fractionation, occurrence of A-type substitution in apatite structure, in addition to the main B-type substitution, could explain the larger temperature dependence of oxygen isotope fractionation measured at low temperature between carbonate in apatite and water. Theoretical internal fractionation of oxygen isotopes between carbonate and phosphate in B-type carbonated apatite (∼8‰ at 37 °C) is consistent with experimental values obtained from modern and well-preserved fossil bio-apatites. Concerning calcium, theoretical results suggest a small fractionation between apatite and calcite (-0.17‰ at 37 °C). Internal fractionation reaching 0.8‰ at 37 °C occurs between the two Ca sites in hydroxyapatite. Furthermore, the Ca isotopic fractionation properties of apatite are affected by the occurrence of carbonate groups, which could contribute to the variability observed on natural samples. Owing to the complexity of apatite crystal-chemistry and in light of the theoretical

  19. Application of Fe Isotopes to the Search for Life and Habitable Planets

    Science.gov (United States)

    Johnson, Clark M.; Beard, Brian L.; Nealson, Kenneth L.

    2001-01-01

    The relatively new field of Fe isotope geochemistry can make important contributions to tracing the geochemical cycling of Fe, which bears on issues such as metabolic processing of Fe, surface redox conditions, and development of planetary atmospheres and biospheres. It appears that Fe isotope fractionation in nature and the lab spans about 4 per mil (%) in Fe-56/Fe-54, and although this range is small, our new analytical methods produce a precision of +/- 0.05% on sample sizes as small as 100 ng (10(exp -7) g); this now provides us with a sufficient "signal-to-noise" ratio to make this isotope system useful. We review our work in three areas: 1) the terrestrial and lunar rock record, 2) experiments on inorganic fractionation, and 3) experiments involving biological processing of Fe. Additional information is contained in the original extended abstract.

  20. Iron Isotope Fractionation during Fe(II) Oxidation Mediated by the Oxygen-Producing Marine Cyanobacterium Synechococcus PCC 7002

    Energy Technology Data Exchange (ETDEWEB)

    Swanner, E. D.; Bayer, T.; Wu, W.; Hao, L.; Obst, M.; Sundman, A.; Byrne, J. M.; Michel, F. M.; Kleinhanns, I. C.; Kappler, A.; Schoenberg, R.

    2017-04-11

    In this study, we couple iron isotope analysis to microscopic and mineralogical investigation of iron speciation during circumneutral Fe(II) oxidation and Fe(III) precipitation with photosynthetically produced oxygen. In the presence of the cyanobacterium Synechococcus PCC 7002, aqueous Fe(II) (Fe(II)aq) is oxidized and precipitated as amorphous Fe(III) oxyhydroxide minerals (iron precipitates, Feppt), with distinct isotopic fractionation (ε56Fe) values determined from fitting the δ56Fe(II)aq (1.79‰ and 2.15‰) and the δ56Feppt (2.44‰ and 2.98‰) data trends from two replicate experiments. Additional Fe(II) and Fe(III) phases were detected using microscopy and chemical extractions and likely represent Fe(II) and Fe(III) sorbed to minerals and cells. The iron desorbed with sodium acetate (FeNaAc) yielded heavier δ56Fe compositions than Fe(II)aq. Modeling of the fractionation during Fe(III) sorption to cells and Fe(II) sorption to Feppt, combined with equilibration of sorbed iron and with Fe(II)aq using published fractionation factors, is consistent with our resulting δ56FeNaAc. The δ56Feppt data trend is inconsistent with complete equilibrium exchange with Fe(II)aq. Because of this and our detection of microbially excreted organics (e.g., exopolysaccharides) coating Feppt in our microscopic analysis, we suggest that electron and atom exchange is partially suppressed in this system by biologically produced organics. These results indicate that cyanobacteria influence the fate and composition of iron in sunlit environments via their role in Fe(II) oxidation through O2 production, the capacity of their cell surfaces to sorb iron, and the interaction of secreted organics with Fe(III) minerals.

  1. 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

  2. Oxygenation of a Cryogenian ocean (Nanhua Basin, South China) revealed by pyrite Fe isotope compositions

    Science.gov (United States)

    Zhang, Feifei; Zhu, Xiangkun; Yan, Bin; Kendall, Brian; Peng, Xi; Li, Jin; Algeo, Thomas J.; Romaniello, Stephen

    2015-11-01

    The nature of ocean redox chemistry between the Cryogenian Sturtian and Marinoan glaciations (ca. 663-654 Ma) is important for understanding the relationship between environmental conditions and the subsequent emergence and expansion of early animals. The Cryogenian-to-Ediacaran stratigraphic succession of the Nanhua Basin in South China provides a nearly complete sedimentary record of the Cryogenian, including a continuous record of interglacial sedimentation. Here, we present a high-resolution pyrite Fe isotope record for a ∼120-m-long drill-core (ZK105) through Sturtian glacial diamictites and the overlying interglacial sediments in the Nanhua Basin to explore changes in marine chemistry during the late Cryogenian. Our pyrite Fe isotope profile exhibits significant stratigraphic variation: Interval I, comprising middle to upper Tiesi'ao diamictites (correlative with the Sturtian glaciation), is characterized by light, modern seawater-like Fe isotope compositions; Interval II, comprising uppermost Tiesi'ao diamictites and the basal organic-rich Datangpo Formation, is characterized by an abrupt shift to heavier Fe isotope compositions; and Interval III, comprising organic-poor grey shales in the middle Datangpo Formation, is characterized by the return of lighter, seawater-like Fe isotope compositions. We infer that Interval I pyrite was deposited in a predominantly anoxic glacial Nanhua Basin through reaction of dissolved Fe2+ and H2S mediated by microbial sulfate reduction (MSR). The shift to heavier pyrite Fe isotope values in Interval II is interpreted as partial oxidation of ferrous iron to ferric iron and subsequent near-quantitative reduction and transformation of Fe-oxyhydroxides to pyrite through coupling with oxidation of organic matter in the local diagenetic environment. In Interval III, near-quantitative oxidation of ferrous iron to Fe-oxyhydroxides followed by near-quantitative reduction and conversion to pyrite in the local diagenetic environment

  3. Inverse iron isotope effect on the transition temperature of the (Ba,K)Fe2As2 superconductor.

    Science.gov (United States)

    Shirage, Parasharam M; Kihou, Kunihiro; Miyazawa, Kiichi; Lee, Chul-Ho; Kito, Hijiri; Eisaki, Hiroshi; Yanagisawa, Takashi; Tanaka, Yasumoto; Iyo, Akira

    2009-12-18

    We report that the (Ba,K)Fe(2)As(2) superconductor (transition temperature, T(c) approximately 38 K) has an inverse iron isotope coefficient alpha(Fe) = -0.18(3) (where T(c) approximately M(-alphaFe) and M is the iron isotope mass); i.e., the sample containing the large iron isotope mass depicts a higher T(c). Systematic inverse shifts in T(c) were clearly observed between the samples using three types of Fe isotopes ((54)Fe, natural Fe, and (57)Fe). This indicates the first evidence of the inverse isotope effect in high-T(c) superconductors. This anomalous mass dependence on T(c) implies an exotic coupling mechanism in Fe-based superconductors.

  4. 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. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Fe and Cu stable isotopes in archeological human bones and their relationship to sex.

    Science.gov (United States)

    Jaouen, Klervia; Balter, Vincent; Herrscher, Estelle; Lamboux, Aline; Telouk, Philippe; Albarède, Francis

    2012-07-01

    Accurate sex assignment of ancient human remains usually relies on the availability of coxal bones or well-preserved DNA. Iron (Fe) and copper (Cu) stable isotope compositions ((56)Fe/(54)Fe and (65)Cu/(63)Cu, respectively) were recently measured in modern human blood, and an unexpected result was the discovery of a (56)Fe-depletion and a (65)Cu-enrichment in men's blood compared to women's blood. Bones, being pervasively irrigated by blood, are expected to retain the (56)Fe/(54)Fe and (65)Cu/(63)Cu signature of blood, which in turn is useful for determining the sex of ancient bones. Here, we report the (56)Fe/(54)Fe, (65)Cu/(63)Cu, and (66)Zn/(64)Zn ratios from a suite of well-preserved phalanxes (n = 43) belonging to individuals buried in the 17th and 18th centuries at the necropolis of Saint-Laurent de Grenoble, France, and for which the sex was independently estimated from pelvic bone morphology. The metals were purified from the bone matrix by liquid chromatography on ion exchange resin and the isotope compositions were measured by multiple-collector inductively coupled plasma mass spectrometry. The results show that, as expected from literature data on blood, male bone iron is depleted in (56)Fe and enriched in (65)Cu relative to female. No sex difference is found in the (66)Zn/(64)Zn ratios of bone. The concentration and isotopic data show no evidence of soil contamination. Four samples of five (77%) can be assigned their correct sex, a result comparable to sex assignment using Fe and Cu isotopes in blood (81%). Isotopic analysis of metals may therefore represent a valid method of sex assignment applicable to incomplete human remains. Copyright © 2012 Wiley Periodicals, Inc.

  6. Fine print in isotope effects: the glucose anomeric equilibrium and binding of glucose to human brain hexokinase

    International Nuclear Information System (INIS)

    Lewis, B.E; Schramm, V.L.

    2002-01-01

    Binding isotope effects are a sensitive measure of changes in molecular vibrational character that occur during ligand-receptor binding. In this study, we have measured isotope effects on the binding of glucose to human brain hexokinase using the ultrafiltration method, with the following results: 0.991±0.001, 0.908±0.003, 1.010±0.001, 0.974±0.002, 1.022±0.002 for [ 14 C]-glucose mixed with [1- 3 H]-, [2- 3 H]-, [3- 3 H]-, [5- 3 H]-, [6,6- 3 H]-glucose, respectively. Comparing the observed data with isotope effects on the anomeric equilibrium in glucose reported previously proves the existence of binding isotope effects in this system. Preliminary computational results are presented to explain the observed binding isotope effects in terms of hydrogen bond patterns and molecular crowding found in the binary complex of sugar and enzyme. (author)

  7. Fe and S isotope variations in cyanobacterial mats: modern analogues of ancient stromatolites

    Science.gov (United States)

    Severmann, S.; Johnson, C. M.; Beard, B. L.; Yevenes, M.; Huerta-Diaz, M. A.; Thamdrup, B.; Hoehler, T.; Welch, S.

    2004-12-01

    Iron and sulfur isotope variations in modern microbial mats from the hypersaline ponds of the Guerrero Negro salt works, Baja California Sur, Mexico have been investigated. Cyanobacteria are the primary producers of this mat ecosystem. The oxygen concentrations in the surface 2 mm of the mats alternate between oxygen-rich and oxygen-free over a diel cycle. Previous work indicates that heterotrophic metabolism is dominated by sulfate reducing bacteria whereas direct metabolic processing of Fe, such as dissimilatory Fe(III) reduction or photoautotrophic Fe(II) oxidation, is negligible. Extremely high rates of sulfate reduction are observed near the mat surface, which coincides with the highest δ 34S values of sedimentary sulfides (total inorganic sulfide, TRIS). The overall δ 34S values of TRIS are -19 to -46 ‰ decreased relative to seawater sulfate. The absence of significant S isotope variations in sedimentary sulfide below the surface 1 cm indicates that sulfate does not become limiting within the microbial mats. Iron isotope compositions of pyrite, expressed as δ 56Fe and normalized to average igneous rocks, varies between -1.9 and -0.2 ‰ . These values are in the range of previously reported Fe isotope compositions of sedimentary pyrites from Archean shales, Banded Iron Formations and modern continental margin sediments (-2.5 to -0.5 ‰ ). Similar to S isotopes, the highest values in δ 56Fe are observed in the surface 1 cm of the mat. The dominant processes that control S isotope compositions are microbial processing of S, including bacterial sulfate reduction and S disproportionation; inorganic fractionations, e.g. during conversion of H2S, are negligible. In contrast, Fe isotope variations are the cumulative expression of multiple microbial and inorganic reactions, including reductive dissolution, inter-mineral fractionations, ligand-promoted dissolution and redox reactions. In this study we examine how these fundamentally different controls on S and

  8. Calculation of equilibrium stable isotope partition function ratios for aqueous zinc complexes and metallic zinc

    Science.gov (United States)

    Black, Jay R.; Kavner, Abby; Schauble, Edwin A.

    2011-02-01

    The goal of this study is to determine reduced partition function ratios for a variety of species of zinc, both as a metal and in aqueous solutions in order to calculate equilibrium stable isotope partitioning. We present calculations of the magnitude of Zn stable-isotope fractionation ( 66,67,68Zn/ 64Zn) between aqueous species and metallic zinc using measured vibrational spectra (fit from neutron scattering studies of metallic zinc) and a variety of electronic structure models. The results show that the reduced metal, Zn(0), will be light in equilibrium with oxidized Zn(II) aqueous species, with the best estimates for the Zn(II)-Zn(0) fractionation between hexaquo species and metallic zinc being Δ 66/64Zn aq-metal ˜ 1.6‰ at 25 °C, and Δ 66/64Zn aq-metal ˜ 0.8‰ between the tetrachloro zinc complex and metallic zinc at 25 °C using B3LYP/aug-cc-pVDZ level of theory and basis set. To examine the behavior of zinc in various aqueous solution chemistries, models for Zn(II) complex speciation were used to determine which species are thermodynamically favorable and abundant under a variety of different conditions relevant to natural waters, experimental and industrial solutions. The optimal molecular geometries for [Zn(H 2O) 6] 2+, [Zn(H 2O) 6]·SO 4, [ZnCl 4] 2- and [Zn(H 2O) 3(C 3H 5O(COO) 3)] - complexes in various states of solvation, protonation and coordination were calculated at various levels of electronic structure theory and basis set size. Isotopic reduced partition function ratios were calculated from frequency analyses of these optimized structures. Increasing the basis set size typically led to a decrease in the calculated reduced partition function ratios of ˜0.5‰ with values approaching a plateau using the aug-cc-pVDZ basis set or larger. The widest range of species were studied at the B3LYP/LAN2DZ/6-31G ∗ level of theory and basis-set size for comparison. Aqueous zinc complexes where oxygen is bound to the metal center tended to have the

  9. Accurate analysis of stable isotopes 68Zn, 70Zn, and 58Fe in human feces with neutron activation analysis

    International Nuclear Information System (INIS)

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

    1980-01-01

    Accurate isotopic analysis of human fecal samples is discussed in relation to mineral bioavailability studies of human subjects. It is shown that for bioavailability investigations of Zn and Fe, the method of neutron activation analysis is suitable for routine application to clinical experiments; and the human fecal samples resulting from diet suitably enriched in isotopes 70 Zn and 58 Fe can be routinely analyzed with relative precisions of about 1% for the isotopes 68 Zn, 70 Zn and 58 Fe. (Auth.)

  10. Searching for signatures of life on Mars: an Fe-isotope perspective.

    Science.gov (United States)

    Anand, M; Russell, S S; Blackhurst, R L; Grady, M M

    2006-10-29

    Recent spacecraft and lander missions to Mars have reinforced previous interpretations that Mars was a wet and warm planet in the geological past. The role of liquid water in shaping many of the surface features on Mars has long been recognized. Since the presence of liquid water is essential for survival of life, conditions on early Mars might have been more favourable for the emergence and evolution of life. Until a sample return mission to Mars, one of the ways of studying the past environmental conditions on Mars is through chemical and isotopic studies of Martian meteorites. Over 35 individual meteorite samples, believed to have originated on Mars, are now available for lab-based studies. Fe is a key element that is present in both primary and secondary minerals in the Martian meteorites. Fe-isotope ratios can be fractionated by low-temperature processes which includes biological activity. Experimental investigations of Fe reduction and oxidation by bacteria have produced large fractionation in Fe-isotope ratios. Hence, it is considered likely that if there is/were any form of life present on Mars then it might be possible to detect its signature by Fe-isotope studies of Martian meteorites. In the present study, we have analysed a number of Martian meteorites for their bulk-Fe-isotope composition. In addition, a set of terrestrial analogue material has also been analysed to compare the results and draw inferences. So far, our studies have not found any measurable Fe-isotopic fractionation in bulk Martian meteorites that can be ascribed to any low-temperature process operative on Mars.

  11. Iron assimilation by the clam Laternula elliptica: Do stable isotopes (δ⁵⁶Fe) help to decipher the sources?

    Science.gov (United States)

    Poigner, Harald; Wilhelms-Dick, Dorothee; Abele, Doris; Staubwasser, Michael; Henkel, Susann

    2015-09-01

    Iron stable isotope signatures (δ(56)Fe) in hemolymph (bivalve blood) of the Antarctic bivalve Laternula elliptica were analyzed by Multiple Collector-Inductively Coupled Plasma-Mass Spectrometry (MC-ICP-MS) to test whether the isotopic fingerprint can be tracked back to the predominant sources of the assimilated Fe. An earlier investigation of Fe concentrations in L. elliptica hemolymph suggested that an assimilation of reactive and bioavailable Fe (oxyhydr)oxide particles (i.e. ferrihydrite), precipitated from pore water Fe around the benthic boundary, is responsible for the high Fe concentration in L. elliptica (Poigner et al., 2013 b). At two stations in Potter Cove (King George Island, Antarctica) bivalve hemolymph showed mean δ(56)Fe values of -1.19 ± 0.34‰ and -1.04 ± 0.39 ‰, respectively, which is between 0.5‰ and 0.85‰ lighter than the pool of easily reducible Fe (oxyhydr)oxides of the surface sediments (-0.3‰ to -0.6‰). This is in agreement with the enrichment of lighter Fe isotopes at higher trophic levels, resulting from the preferential assimilation of light isotopes from nutrition. Nevertheless, δ(56)Fe hemolymph values from both stations showed a high variability, ranging between -0.21‰ (value close to unaltered/primary Fe(oxyhydr)oxide minerals) and -1.91‰ (typical for pore water Fe or diagenetic Fe precipitates), which we interpret as a "mixed" δ(56)Fe signature caused by Fe assimilation from different sources with varying Fe contents and δ(56)Fe values. Furthermore, mass dependent Fe fractionation related to physiological processes within the bivalve cannot be ruled out. This is the first study addressing the potential of Fe isotopes for tracing back food sources of bivalves. Copyright © 2015 Elsevier Ltd. All rights reserved.

  12. Accelerator mass spectrometry of 59Ni and Fe isotopes at the Argonne superconducting linac

    International Nuclear Information System (INIS)

    Henning, W.; Kutschera, W.; Myslek-Laurikainen, B.; Pardo, R.C.; Smither, R.K.; Yntema, J.L.

    1981-01-01

    We have obtained initial results in an attempt to use the Argonne tandem-linac system for accelerator mass spectrometry of medium-heavy nuclei. Nuclei of the radioisotope 59 Ni (T/sub 1/2 = 7.5 x 10 5 y) and of the stable isotope 58 Fe at low concentrations have been accelerated and clearly identified. The latter experiment is in preparation of a measurement of the half-life of 60 Fe

  13. Hot rotating fp shell Fe isotopes near proton drip line

    International Nuclear Information System (INIS)

    Aggarwal, Mamta

    2003-01-01

    F p shell 44-58 Fe nuclei have been investigated in highly excited state using the statistical theory of hot rotating nucleus. Effects of thermal and rotational excitation at drip line nuclei are studied

  14. Effects of deviations from local thermodynamic equilibrium in the atmospheres of F supergiants. I. Overionization of Fe I atoms

    International Nuclear Information System (INIS)

    Boyarchuk, A.A.; Lyubimkov, L.S.; Sakhibullin, N.A.

    1985-01-01

    For a number of class F supergiants and dwarfs, non-LTE calculations have been made of the Fe I-Fe II ionization balance. It is shown that deviations from local thermodynamic equilibrium lead to a strong overionization of the Fe I atoms in the upper layers of the atmosphere. This confirms the conclusion obtained by Lyubimkov and Boyarchuk on the basis of an investigation of microturbulence in F supergiants. The reason for the overionization (compared with LTE) is the nonequality of the recombination and photoionization temperatures: To recombination processes there corresponds a local temperature T(/tau/), whereas the photoionization takes place under the influence of ultraviolet radiation from deeper and hotter layers of the atmosphere. The equivalent widths of some Fe I lines have been calculated. It is shown that neglect of the overionization in the analysis of sufficiently strong lines may lead to an underestimation of the iron abundance by an order of magnitude

  15. 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.

  16. Equilibrium isotope effects on noncovalent interactions in a supramolecular host-guest system.

    Science.gov (United States)

    Mugridge, Jeffrey S; Bergman, Robert G; Raymond, Kenneth N

    2012-02-01

    The self-assembled supramolecular complex [Ga(4)L(6)](12-) (1; L = 1,5-bis[2,3-dihydroxybenzamido]naphthalene) can act as a molecular host in aqueous solution and bind cationic guest molecules to its highly charged exterior surface or within its hydrophobic interior cavity. The distinct internal cavity of host 1 modifies the physical properties and reactivity of bound guest molecules and can be used to catalyze a variety of chemical transformations. Noncovalent host-guest interactions in large part control guest binding, molecular recognition and the chemical reactivity of bound guests. Herein we examine equilibrium isotope effects (EIEs) on both exterior and interior guest binding to host 1 and use these effects to probe the details of noncovalent host-guest interactions. For both interior and exterior binding of a benzylphosphonium guest in aqueous solution, protiated guests are found to bind more strongly to host 1 (K(H)/K(D) > 1) and the preferred association of protiated guests is driven by enthalpy and opposed by entropy. Deuteration of guest methyl and benzyl C-H bonds results in a larger EIE than deuteration of guest aromatic C-H bonds. The observed EIEs can be well explained by considering changes in guest vibrational force constants and zero-point energies. DFT calculations further confirm the origins of these EIEs and suggest that changes in low-frequency guest C-H/D vibrational motions (bends, wags, etc.) are primarily responsible for the observed EIEs. © 2011 American Chemical Society

  17. Carbon isotope fractionation of chlorinated ethenes during oxidation by Fe{sup 2+} activated persulfate

    Energy Technology Data Exchange (ETDEWEB)

    Marchesi, Massimo, E-mail: m2marche@uwaterloo.ca [Departament de Cristallografia, Mineralogia i Diposits Minerals, Universitat de Barcelona, Barcelona, Catalunya 08028 (Spain); Earth and Environmental Department, University of Waterloo, Waterloo, Ontario, Canada N2L 3G1 (Canada); Aravena, Ramon [Earth and Environmental Department, University of Waterloo, Waterloo, Ontario, Canada N2L 3G1 (Canada); Sra, Kanwartej S. [Department of Civil and Environmental Engineering, University of Waterloo, Waterloo, Ontario, Canada N2L 3G1 (Canada); Golder Associates Inc, Toronto, Ontario, Canada L5N 5Z7 (Canada); Thomson, Neil R. [Department of Civil and Environmental Engineering, University of Waterloo, Waterloo, Ontario, Canada N2L 3G1 (Canada); Otero, Neus; Soler, Albert [Departament de Cristallografia, Mineralogia i Diposits Minerals, Universitat de Barcelona, Barcelona, Catalunya 08028 (Spain); Mancini, Silvia [Golder Associates Inc, Toronto, Ontario, Canada L5N 5Z7 (Canada)

    2012-09-01

    The increased use of persulfate (S{sub 2}O{sub 8}{sup 2-}) for in situ chemical oxidation to treat groundwater and soils contaminated by chlorinated hydrocarbon compounds (CHCs) requires unbiased methods to assess treatment performance. Stable carbon isotope analysis offers a potential tool for assessing the in situ treatment performance of persulfate at sites contaminated with CHCs. This study investigated the extent of C isotope fractionation during oxidation of tetrachloroethene (PCE), trichloroethene (TCE) and cis-dichloroethene (cis-DCE) by persulfate activated by ferrous ion (Fe{sup 2+}). An average carbon isotope enrichment factor {epsilon}{sub bulk} of - 4.9 Per-Mille-Sign for PCE, - 3.6 Per-Mille-Sign for TCE and - 7.6 Per-Mille-Sign for cis-DCE were obtained in batch experiments. Variations in the initial S{sub 2}O{sub 8}{sup 2-}/Fe{sup 2+}/CHC molar ratios did not result in any significant differences in carbon isotope fractionation. The occurrence of carbon isotope fractionation during oxidation and the lack of dependence of enrichment factors upon the S{sub 2}O{sub 8}{sup 2-}/Fe{sup 2+}/CHC molar ratio demonstrate that carbon isotope analysis can potentially be used at contaminated sites as an additional technique to estimate treatment efficacy during oxidation of CHCs by Fe{sup 2+} activated persulfate. Highlights: Black-Right-Pointing-Pointer The performance of in situ chemical oxidation (ISCO) is still difficult to assess. Black-Right-Pointing-Pointer We investigated the potential of carbon isotope analysis as a new assessing tool. Black-Right-Pointing-Pointer C isotope of PCE, TCE and DCE oxidized by persulfate activated by Fe{sup 2+} was measured. Black-Right-Pointing-Pointer Enrichment factors of - 4.9 Per-Mille-Sign for PCE, - 3.6 Per-Mille-Sign for TCE and - 7.6 Per-Mille-Sign for cisDCE were obtained. Black-Right-Pointing-Pointer Carbon isotope can potentially be used to estimate the ISCO treatment efficacy.

  18. Stochastic Simulation of Isotopic Exchange Mechanisms for Fe(II)-Catalyzed Recrystallization of Goethite

    Energy Technology Data Exchange (ETDEWEB)

    Zarzycki, Piotr [Energy; Institute; Rosso, Kevin M. [Pacific Northwest

    2017-06-15

    Understanding Fe(II)-catalyzed transformations of Fe(III)- (oxyhydr)oxides is critical for correctly interpreting stable isotopic distributions and for predicting the fate of metal ions in the environment. Recent Fe isotopic tracer experiments have shown that goethite undergoes rapid recrystallization without phase change when exposed to aqueous Fe(II). The proposed explanation is oxidation of sorbed Fe(II) and reductive Fe(II) release coupled 1:1 by electron conduction through crystallites. Given the availability of two tracer exchange data sets that explore pH and particle size effects (e.g., Handler et al. Environ. Sci. Technol. 2014, 48, 11302-11311; Joshi and Gorski Environ. Sci. Technol. 2016, 50, 7315-7324), we developed a stochastic simulation that exactly mimics these experiments, while imposing the 1:1 constraint. We find that all data can be represented by this model, and unifying mechanistic information emerges. At pH 7.5 a rapid initial exchange is followed by slower exchange, consistent with mixed surface- and diffusion-limited kinetics arising from prominent particle aggregation. At pH 5.0 where aggregation and net Fe(II) sorption are minimal, that exchange is quantitatively proportional to available particle surface area and the density of sorbed Fe(II) is more readily evident. Our analysis reveals a fundamental atom exchange rate of ~10-5 Fe nm-2 s-1, commensurate with some of the reported reductive dissolution rates of goethite, suggesting Fe(II) release is the rate-limiting step in the conduction mechanism during recrystallization.

  19. Stochastic Simulation of Isotopic Exchange Mechanisms for Fe(II)-Catalyzed Recrystallization of Goethite.

    Science.gov (United States)

    Zarzycki, Piotr; Rosso, Kevin M

    2017-07-05

    Understanding Fe(II)-catalyzed transformations of Fe(III)-(oxyhydr)oxides is critical for correctly interpreting stable isotopic distributions and for predicting the fate of metal ions in the environment. Recent Fe isotopic tracer experiments have shown that goethite undergoes rapid recrystallization without phase change when exposed to aqueous Fe(II). The proposed explanation is oxidation of sorbed Fe(II) and reductive Fe(II) release coupled 1:1 by electron conduction through crystallites. Given the availability of two tracer exchange data sets that explore pH and particle size effects (e.g., Handler et al. Environ. Sci. Technol. 2014 , 48 , 11302 - 11311 ; Joshi and Gorski Environ. Sci. Technol. 2016 , 50 , 7315 - 7324 ), we developed a stochastic simulation that exactly mimics these experiments, while imposing the 1:1 constraint. We find that all data can be represented by this model, and unifying mechanistic information emerges. At pH 7.5 a rapid initial exchange is followed by slower exchange, consistent with mixed surface- and diffusion-limited kinetics arising from prominent particle aggregation. At pH 5.0 where aggregation and net Fe(II) sorption are minimal, that exchange is quantitatively proportional to available particle surface area and the density of sorbed Fe(II) is more readily evident. Our analysis reveals a fundamental atom exchange rate of ∼10 -5 Fe nm -2 s -1 , commensurate with some of the reported reductive dissolution rates of goethite, suggesting Fe(II) release is the rate-limiting step in the conduction mechanism during recrystallization.

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

    Indian Academy of Sciences (India)

    The neutron skin effect has been investigated for even isotopes of molybdenum at 25.6. MeV 94−100Mo(p,xn) ... exciton numbers from different radii of even Mo isotopes were used to obtain the corresponding neutron ..... nical applications such as the isotope production alternatives (for producing medical ra- dioisotopes ...

  1. Constraining Thermal Histories by Monte Carlo Simulation of Mg-Fe Isotopic Profiles in Olivine

    Science.gov (United States)

    Sio, C. K. I.; Dauphas, N.

    2016-12-01

    In thermochronology, random time-temperature (t-T) paths are generated and used as inputs to model fission track data. This random search method is used to identify a range of acceptable thermal histories that can describe the data. We have extended this modeling approach to magmatic systems. This approach utilizes both the chemical and stable isotope profiles measured in crystals as model constraints. Specifically, the isotopic profiles are used to determine the relative contribution of crystal growth vs. diffusion in generating chemical profiles, and to detect changes in melt composition. With this information, tighter constraints can be placed on the thermal evolution of magmatic bodies. We use an olivine phenocryst from the Kilauea Iki lava lake, HI, to demonstrate proof of concept. We treat this sample as one with little geologic context, then compare our modeling results to the known thermal history experienced by that sample. To complete forward modeling, we use MELTS to estimate the boundary condition, initial and quench temperatures. We also assume a simple relationship between crystal growth and cooling rate. Another important parameter is the isotopic effect for diffusion (i.e., the relative diffusivity of the light vs. heavy isotope of an element). The isotopic effects for Mg and Fe diffusion in olivine have been estimated based on natural samples; experiments to better constrain these parameters are underway. We find that 40% of the random t-T paths can be used to fit the Mg-Fe chemical profiles. However, only a few can be used to simultaneously fit the Mg-Fe isotopic profiles. These few t-T paths are close to the independently determined t-T history of the sample. This modeling approach can be further extended other igneous and metamorphic systems where data exist for diffusion rates, crystal growth rates, and isotopic effects for diffusion.

  2. Isotope-periodic multilayer method for short self-diffusion paths - a comparative neutron and synchrotron Moessbauer reflectometric study of FePd alloys

    Energy Technology Data Exchange (ETDEWEB)

    Merkel, D G; Sajti, S; Fetzer, C; Tancziko, F; Bottyan, L [KFKI Research Institute for Particle and Nuclear Physics, P.O.B 49, H-1525, Budapest (Hungary); Major, J; Major, M; Ruehm, A [Max-Planck-Institut fuer Metallforschung, Heisenbergstr. 3, D-70569 Stuttgart (Germany); Rueffer, R; Stankov, S, E-mail: merkel@rmki.kfki.h [European Synchrotron Radiation Facility, BP 220, 38043 Grenoble CEDEX 9 (France)

    2010-02-01

    FePt, FePd, CoPt, and CoPd in equilibrium exhibit the L1{sub 0} structure with high perpendicular magnetic anisotropy making them attractive candidates for high-density magnetic recording. Magnetic properties of these films depend on the distribution and orientation of the L1{sub 0} fraction controlled by diffusion on atomic scale. Epitaxial isotope-periodic {sup nat}FePd/{sup 57}FePd alloy films were prepared by molecular beam epitaxy and heat treated at 500{sup 0}C for various retention times. Isotope-sensitive non-destructive methods, neutron reflectometry and synchrotron Moessbauer reflectometry were applied to follow very short diffusion paths normal to the film plane. Squared diffusion lengths and diffusion profiles were obtained from the fitting of experimental reflectivity curves for each annealing treatment steps. The somewhat different diffusion lengths obtained for the neutron and synchrotronMoessbauer reflectograms of the same samples are explained by the larger footprint of the sample in the neutron experiment for which interface inhomogeneities are to be averaged. Diffusion in the microscopically different local environments were modelled by piecewise constant diffusion coefficients in the regions identified as different species by conversion electron Moessbauer spectroscopy.

  3. 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

    of Cr(III)-species (Cr3+, CrCl2+ and CrCl2 +) with equilibrium mass-dependent isotope fractionation spanning a range of ∼1‰/amu and consistent with theory. The heaviest isotopes partition into Cr3+, intermediates in CrCl2+ and the lightest in CrCl2 +/CrCl3°. Thus, for a typical reported loss of ∼25% Cr...... in the mass-bias corrected 53Cr/52Cr (μ53Cr* of 5.2ppm) and 54Cr/52Cr (μ54Cr* of 13.5ppm) 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...

  4. Investigations of the Photochemical Isotope Equilibrium between O2, CO2 and O3

    NARCIS (Netherlands)

    Shaheen, R.; Janssen, C.; Röckmann, T.

    2006-01-01

    Contrary to tropospheric CO2 whose oxygen isotopic composition follows a standard mass dependent relationship, i.e. 17O 0.5 18O, stratospheric CO2 is preferentially enriched in 17O, leading to a strikingly different relation with 17O 1.7 18O. The isotope anomaly is likely inherited from O3 via

  5. Investigations of the Photochemical Isotope Equilibrium between O2, CO2 and O3

    NARCIS (Netherlands)

    Shaheen, R.; Janssen, C.; Röckmann, T.

    2007-01-01

    Contrary to tropospheric CO2 whose oxygen isotopic composition follows a standard mass dependent relationship, i.e. 17O 0.5 18O, stratospheric CO2 is preferentially enriched in 17O, leading to a strikingly different relation: 17O 1.7 18O. It has been shown repeatedly that the isotope anomaly is

  6. Phase equilibrium of the system Ag-Fe-Nd, and Nd extraction from magnet scraps using molten silver

    International Nuclear Information System (INIS)

    Takeda, O.; Okabe, T.H.; Umetsu, Y.

    2004-01-01

    To develop a new recycling process, we examined the direct extraction of neodymium (Nd) metal from Nd-Fe-B magnet scraps using molten silver (Ag) as an extraction medium. Prior to the extraction experiment, the phase equilibrium of the system Ag-Fe-Nd was investigated to estimate the theoretical extraction limit. It was observed that the Fe/Nd 2 Fe 17 mixture equilibrates with the molten Ag-Nd alloy containing 50-52 mol% Nd (57-59 mass% Nd) at 1363 K. The experimental results were in good agreement with the thermodynamic calculation based on literature values. By reacting Nd-Fe-B magnet scraps with molten silver at 1273 K, more than 90% of the neodymium in the scrap was extracted, and an Ag-Nd alloy containing 40-50 mass% Nd was obtained. The neodymium in the Ag-Nd alloy was separated from silver as Nd 2 O 3 by oxidizing the obtained alloy in air. Although the wettability of Nd 2 O 3 with molten silver caused some difficulties in the separation of neodymium from silver, molten silver is shown to be an effective medium for neodymium extraction from magnet scrap

  7. Fe (hydro) oxide controls Mo isotope fractionation during the weathering of granite

    Science.gov (United States)

    Wang, Zhibing; Ma, Jinlong; Li, Jie; Wei, Gangjian; Zeng, Ti; Li, Lei; Zhang, Le; Deng, Wenfeng; Xie, Luhua; Liu, Zhifeng

    2018-04-01

    Understanding the fractionation mechanisms of Mo isotopes and seeking the main hosts of light δ98/95Mo during chemical weathering of continental rocks is a prerequisite for constraining heavy δ98/95Mo input into rivers. This study investigates the Mo concentrations and δ98/95Mo values of bulk samples, chemical extractions, and clay fractions of weathering products in a granite weathering profile in Guangdong province, South China, as well as in surrounding stream water. Results from bulk samples show that the τ MoTiO2 values systematically decrease from 59.1% to -77.0%, and δ98/95Mo values systematically increase from -1.46‰ to -0.17‰, upwards in the profile (from 30 to 0 m depth). Atmospheric input has a limited effect on δ98/95Mo variations in the weathering profile. Adsorption and desorption processes of Fe (hydro) oxide are the dominant factors controlling the variations in δ98/95Mo, with light Mo isotopes preferentially adsorbed by Fe (hydro) oxide, and released during desorption process, whereas the incongruent dissolution of primary minerals has little effect. Organic materials and the clay fraction are not the main hosts of light δ98/95Mo, as indicated by the results of chemical extractions, which show that a large proportion (41.5-86.2%) of total Mo with light δ98/95Mo (-1.57‰ to -0.59‰) is associated with Fe (hydro) oxide. Moreover, a significant positive correlation exists between Mo concentrations and δ98/95Mo in the Fe (hydro) oxide extractions from bulk samples. Finally, δ98/95Mo in stream water indicates the release of heavier δ98/95Mo into river water during the chemical weathering of granite rock. The results advance our understanding the mechanisms of Mo isotope fractionation during chemical weathering and its isotopic mass balance in Earth's surface system.

  8. Measurement of beta decay periods for Fe-Ni neutrons rich isotopes

    International Nuclear Information System (INIS)

    Czajkowski, S.

    1992-01-01

    Thermal fission of 239 Pu was used to produce 68,69 Co and 68 Fe isotopes, the lightest ones ever observed in thermal fission, at the ILL high-flux reactor, in Grenoble. Separated with the Lohengrin recoil spectrometer, then identified by means of a Δ E-E ionization chamber, fragments were implanted in a set of Si-detectors, where β-particles were detected too. The fission yields were determined, and the beta-decay half-lives were extracted from delayed coincidence analysis between ion implantation and the subsequent beta detection: They were found to be 0.27±0.05s, 0.18±0.10s, and 0.10±0.06s respectively for 69 Co, 68 Co, and 68 Fe. This method was adapted to a new experimental configuration: 65 Fe isotopes were produced from 86 Kr projectile fragmentation at 500 MeV/u on a Be target. Selected ions were separated with the fragment separator FRS at GSI (Darmstadt), tuned in the monoenergetic mode. Fragments were identified by ΔE-ToF, slowed down, and then implanted in two rows of PIN-diodes that provided an additional range selection. The half-life were determined from the analysis of the decay chain Fe-Co-Ni: it was found 0.4±0.2s. Production rates obtained with the two methods are compared at the end of this work

  9. Status of FeCrAl ODS Irradiations in the High Flux Isotope Reactor

    Energy Technology Data Exchange (ETDEWEB)

    Field, Kevin G. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Fuel Cycle Research and Development (FCRD); Howard, Richard H. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Fuel Cycle Research and Development (FCRD)

    2016-08-19

    FeCrAl oxide-dispersion strengthened (ODS) alloys are an attractive sub-set alloy class of the more global FeCrAl material class for nuclear applications due to their high-temperature steam oxidation resistance and hypothesized enhanced radiation tolerance. A need currently exists to determine the radiation tolerance of these newly developed alloys. To address this need, a preliminary study was conducted using the High Flux Isotope Reactor (HFIR) to irradiate an early generation FeCrAl ODS alloy, 125YF. Preliminary post-irradiation examination (PIE) on these irradiated specimens have shown good radiation tolerance at elevated temperatures (≥330°C) but possible radiation-induced hardening and embrittlement at irradiations of 200°C to a damage level of 1.9 displacement per atom (dpa). Building on this experience, a new series of irradiations are currently being conceptualized. This irradiation series called the FCAD irradiation program will irradiate the latest generation FeCrAl ODS and FeCr ODS alloys to significantly higher doses. These experiments will provide the necessary information to determine the mechanical performance of irradiated FeCrAl ODS alloys at light water reactor and fast reactor conditions.

  10. Recycling of Oceanic Lithosphere: Water, fO2 and Fe-isotope Constraints

    Science.gov (United States)

    Bizmis, M.; Peslier, A. H.; McCammon, C. A.; Keshav, S.; Williams, H. M.

    2014-01-01

    Spinel peridotite and garnet pyroxenite xenoliths from Hawaii provide important clues about the composition of the oceanic lithosphere, and can be used to assess its contribution to mantle heterogeneity upon recycling. The peridotites have lower bulk H2O (approximately 70-114 ppm) than the MORB source, qualitatively consistent with melt depletion. The garnet pyroxenites (high pressure cumulates) have higher H2O (200-460 ppm, up to 550 ppm accounting for phlogopite) and low H2O/Ce ratios (less than 100). The peridotites have relatively light Fe-isotopes (delta Fe -57 = -0.34 to 0.13) that decrease with increasing depletion, while the pyroxenites are significantly heavier (delta Fe-57 up to 0.3). The observed xenolith, as well as MORB and OIB total Fe-isotope variability is larger that can be explained by existing melting models. The high H2O and low H2O/Ce ratios of pyroxenites are similar to estimates of EM-type OIB sources, while their heavy delta Fe-57 are similar to some Society and Cook-Austral basalts. Therefore, recycling of mineralogically enriched oceanic lithosphere (i.e. pyroxenites) may contribute to OIB sources and mantle heterogeneity. The Fe(3+)/Sigma? systematics of these xenoliths also suggest that there might be lateral redox gradients within the lithosphere, between juxtaposed oxidized spinel peridotites (deltaFMQ = -0.7 to 1.6, at 15 kb) and more reduced pyroxenites (deltaFMQ = -2 to -0.4, at 20-25kb). Such mineralogically and compositionally imposed fO2 gradients may generate local redox melting due to changes in fluid speciation (e.g. reduced fluids from pyroxenite encountering more oxidized peridotite). Formation of such incipient, small degree melts could further contribute to metasomatic features seen in peridotites, mantle heterogeneity, as well as the low velocity and high electrical conductivity structures near the base of the lithosphere and upper mantle.

  11. Equilibrium and kinetics studies for the adsorption of Ni2+ and Fe3+ ions from aqueous solution by graphene oxide

    Directory of Open Access Journals (Sweden)

    Konicki Wojciech

    2017-09-01

    Full Text Available In this study, the adsorption of Ni2+ and Fe3+ metal ions from aqueous solutions onto graphene oxide (GO have been explored. The effects of various experimental factors such as pH of the solution, initial metal ion concentration and temperature were evaluated. The kinetic, equilibrium and thermodynamic studies were also investigated. The adsorption rate data were analyzed using the pseudo-first-order kinetic model, the pseudo-second-order kinetic model and the intraparticle diffusion model. Kinetic studies indicate that the adsorption of both ions follows the pseudo-second-order kinetics. The isotherms of adsorption data were analyzed by adsorption isotherm models such as Langmuir and Freundlich. Equilibrium data fitted well with the Langmuir model. The maximum adsorption capacities of Ni2+ and Fe3+ onto GO were 35.6 and 27.3 mg g−1, respectively. In addition, various thermodynamic parameters, such as enthalpy (ΔHO, entropy (ΔSO and Gibbs free energy (ΔGO, were calculated.

  12. Combined Fe-Mg Isotope and Elemental Zoning in Olivines for Better Time Constraints of Magma Assembly and the Timing Prior to Eruption

    Science.gov (United States)

    Ruprecht, P.; Oeser-Rabe, M.; Weyer, S.

    2016-12-01

    Intermediate arc magmas frequently contain diverse crystal populations, many of which are not in equilibrium with the host melt. As a result many crystals are reacting to obtain a new equilibrium, either through diffusive equilibration or through crystallization and dissolution. Snapshots of these transient processes are frozen in at the time of eruption when the magma cools. With known rates of diffusion for specific phases and elements one can extract timescale information from these transient snapshots. However, as crystal growth and elemental diffusion often show similar zoning patterns it remains in question whether calculated diffusion timescales represent the timing of a specific magmatic process. Combined high-precision in situ Fe-Mg isotope analyses by femtosecond-LA-MC-ICP-MS [1] and Fe-Mg elemental zoning may provide a means to distinguish between growths from diffusion processes in olivine and therefore, provide more accurate constraints on the timing of mixing and ascent in magmatic systems. Here we investigate the magmatic events recorded in complex olivines prior to the 1963-65 eruption of Irazú volcano, Costa Rica. The complexly zoned olivines share the normal zoning history of the rims of the magnesian olivines ( Fo87-88 to Fo80-84), with the latter being studied previously to estimate mantle-to-surface magma transit times beneath Irazú of less than 2 years [2]. In contrast to the primitive magnesian olivines, the complex olivines have high Ni and reversely zoned ferrous cores (Fo80) indicating two episodes of crystal growth and represent parts of the plumbing system in the middle to lower crust that was sampled during ascent of the primitive magnesian olivines and jointly erupted. Results of our in situ Fe-Mg isotope analyses reveal strongly-coupled chemical and isotopic zoning in the crystals' interior indicating that the zoning was generated by intra-mineral Fe-Mg inter-diffusion due to Mg-rich rim formation. Combining chemical and isotopic

  13. Fe-isotope fractionation in magmatic-hydrothermal mineral deposits: A case study from the Renison Sn-W deposit, Tasmania

    Science.gov (United States)

    Wawryk, Christine M.; Foden, John D.

    2015-02-01

    We present 50 new iron isotopic analyses of source granite and mineral separates from the Renison tin deposit in western Tasmania. The aim of the study is to characterise the composition of minerals within a tin deposit associated with a reduced, S-type magma. We have analysed bulk samples of granite, and separates of pyrrhotite, pyrite, arsenopyrite, magnetite, chalcopyrite and siderite by multi-collector inductively coupled mass spectrometry. The isotopic compositions of mineral separates are consistent with theoretical predictions of equilibrium fractionation based on Mössbauer spectroscopy and other parametric calculations. Mineral-mineral pairs yield temperatures of formation that are in agreement with prior detailed fluid inclusion studies, but are spatially inconsistent with declining fluid temperatures with distance from the causative intrusion, limiting the use of Fe isotopes as a potential geothermometer, at least in this case. Comparison of our data with published data from other deposits clearly demonstrates that pyrite, magnetite and chalcopyrite from the hottest ore fluids (>300-400 °C) at Renison are isotopically heavier than minerals sampled from a deposit formed at similar temperatures, but associated with a more oxidised and less differentiated intrusion.

  14. Sorption separation of Eu and As from single-component systems by Fe-modified biochar. Kinetic and equilibrium study

    International Nuclear Information System (INIS)

    Fristak, Vladimir; Soja, Gerhard; Michalekova-Richveisova, Barbora; Pipiska, Martin; Viglasova, Eva; Galambos, Michal; Duriska, Libor; Moreno-Jimenez, Eduardo

    2017-01-01

    The utilization of carbonaceous materials in separation processes of radionuclides, heavy metals and metalloids represents a burning issue in environmental and waste management. The main objective of this study was to characterize the effect of chemical modification of corncob-derived biochar by Fe-impregnations on sorption efficiency of Eu and As as a model compounds of cationic lanthanides and anionic metalloids. The biochar sample produced in slow pyrolysis process at 500 C before (BC) and after (IBC) impregnation process was characterized by elemental, FTIR, SEM-EDX analysis to confirm the effectiveness of Fe-impregnation process. The basic physico-chemical properties showed differences in surface area and pH values of BC- and IBC-derived sorbents. Sorption processes of Eu and As by BC and IBC were characterized as a time- and initial concentration of sorbate-dependent processes. The sorption equilibrium was reached for both sorbates in 24 h of contact time. Batch equilibrium experiments revealed the increased maximum sorption capacities (Q max ) of IBC for As about more than 20 times (Q max BC 0.11 and Q max IBC 2.26 mg g -1 ). Our study confirmed negligible effect of Fe-impregnation on sorption capacity of biochar for Eu (Q max BC 0.89 and Q max IBC 0.98 mg g -1 ). The iron-impregnation of biochar-derived sorbents can be utilized as a valuable treatment method to produce stable and more effective sorption materials for various xenobiotics separation from liquid wastes and aqueous solutions.

  15. Sorption separation of Eu and As from single-component systems by Fe-modified biochar. Kinetic and equilibrium study

    Energy Technology Data Exchange (ETDEWEB)

    Fristak, Vladimir; Soja, Gerhard [Austrian Institute of Technology GmbH, Tulln (Austria). Energy Dept. Environmental Resources and Technologies; Michalekova-Richveisova, Barbora; Pipiska, Martin [Trnava Univ. (Slovakia). Dept. of Chemistry; Viglasova, Eva; Galambos, Michal [Comenius Univ., Bratislava (Slovakia). Dept. of Inorganic Chemistry; Duriska, Libor [Slovak Univ. of Technology in Bratislava, Trnava (Slovakia). Faculty of Materials Science and Technology; Moreno-Jimenez, Eduardo [Univ. Autonoma de Madrid (Spain). Dept. de Quimica Agricola y Bromatologia

    2017-03-15

    The utilization of carbonaceous materials in separation processes of radionuclides, heavy metals and metalloids represents a burning issue in environmental and waste management. The main objective of this study was to characterize the effect of chemical modification of corncob-derived biochar by Fe-impregnations on sorption efficiency of Eu and As as a model compounds of cationic lanthanides and anionic metalloids. The biochar sample produced in slow pyrolysis process at 500 C before (BC) and after (IBC) impregnation process was characterized by elemental, FTIR, SEM-EDX analysis to confirm the effectiveness of Fe-impregnation process. The basic physico-chemical properties showed differences in surface area and pH values of BC- and IBC-derived sorbents. Sorption processes of Eu and As by BC and IBC were characterized as a time- and initial concentration of sorbate-dependent processes. The sorption equilibrium was reached for both sorbates in 24 h of contact time. Batch equilibrium experiments revealed the increased maximum sorption capacities (Q{sub max}) of IBC for As about more than 20 times (Q{sub max} BC 0.11 and Q{sub max} IBC 2.26 mg g{sup -1}). Our study confirmed negligible effect of Fe-impregnation on sorption capacity of biochar for Eu (Q{sub max} BC 0.89 and Q{sub max} IBC 0.98 mg g{sup -1}). The iron-impregnation of biochar-derived sorbents can be utilized as a valuable treatment method to produce stable and more effective sorption materials for various xenobiotics separation from liquid wastes and aqueous solutions.

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

    Indian Academy of Sciences (India)

    important structural materials for fusion reactors, accelerator-driven systems, and in many other fields. .... The ALICE/ASH code is an advanced and modified version of the ALICE codes for. PEQ calculations [23]. ..... nical applications such as the isotope production alternatives (for producing medical ra- dioisotopes using ...

  17. Specific equilibrium behavior of hydrogen isotopes adsorbed onto synthetic zeolite A-type governed by lithium cations

    Energy Technology Data Exchange (ETDEWEB)

    Takashima, Shoji [Graduate School of Engineering, Kyushu University, Moto-oka 744, Nishi-ku, Fukuoka 819-0395 (Japan); Kotoh, Kenji, E-mail: kotoh@nucl.kyushu-u.ac.jp [Graduate School of Engineering, Kyushu University, Moto-oka 744, Nishi-ku, Fukuoka 819-0395 (Japan); Faculty of Engineering, Kyushu University, Moto-oka 744, Nishi-ku, Fukuoka 819-0395 (Japan)

    2013-10-15

    Highlights: • Isotherms for H{sub 2} and D{sub 2} adsorbed onto SZ-LiA at 77.4 K are shown. • The adsorption isotherms exhibit specific deviation in the range lower than 10 Pa. • SZ-LiA indicates the power of several 100-times at 0.1 Pa, compared with SZ-NaA. • Experimental isotherms are described empirically by a dual-site Langmuir equation. • The isotope effect on adsorption isotherms appears in the Langmuir constants. -- Abstract: Since synthetic zeolites (SZs) are powerfully adsorptive for hydrogen isotopes at cryogenic temperatures such as liquefied nitrogen, adsorption processes using these have been considered applicable to such as recovery of tritium from the lithium blanket of DT fusion reactor system. Onto these zeolites the adsorptions isotherms for hydrogen isotopes onto SZ-NaA, SZ-CaA and SZ-NaX at 77.4 K were already clarified experimentally and analytically. These isotherms exhibit similar profiles of Langmuir type. In this work, adsorption isotherms were examined for H{sub 2} and D{sub 2} on SZ-LiA at 77.4 K. SZ-LiA was made from SZ-NaA by exchanging its sodium ions for lithium ones, provided by TOSOH Corp. The experimental results demonstrate the specific equilibrium behavior of hydrogen isotopes adsorbed on SZ-LiA, deviating from isothermal profiles on SZ-CaA and SZ-NaX. SZ-LiA show the isothermal profiles of adsorption for H{sub 2} and D{sub 2} similar to on the conventional zeolites in the range from around 1 kPa to the atmospheric pressure, but exhibit a plateau around 1 mol/kg between 0.1 Pa and 100 Pa, while other zeolites show linearly profiling isotherms. This deviation indicates the adsorptive power of SZ-LiA remarkably greater than that of the others.

  18. Specific equilibrium behavior of hydrogen isotopes adsorbed onto synthetic zeolite A-type governed by lithium cations

    International Nuclear Information System (INIS)

    Takashima, Shoji; Kotoh, Kenji

    2013-01-01

    Highlights: • Isotherms for H 2 and D 2 adsorbed onto SZ-LiA at 77.4 K are shown. • The adsorption isotherms exhibit specific deviation in the range lower than 10 Pa. • SZ-LiA indicates the power of several 100-times at 0.1 Pa, compared with SZ-NaA. • Experimental isotherms are described empirically by a dual-site Langmuir equation. • The isotope effect on adsorption isotherms appears in the Langmuir constants. -- Abstract: Since synthetic zeolites (SZs) are powerfully adsorptive for hydrogen isotopes at cryogenic temperatures such as liquefied nitrogen, adsorption processes using these have been considered applicable to such as recovery of tritium from the lithium blanket of DT fusion reactor system. Onto these zeolites the adsorptions isotherms for hydrogen isotopes onto SZ-NaA, SZ-CaA and SZ-NaX at 77.4 K were already clarified experimentally and analytically. These isotherms exhibit similar profiles of Langmuir type. In this work, adsorption isotherms were examined for H 2 and D 2 on SZ-LiA at 77.4 K. SZ-LiA was made from SZ-NaA by exchanging its sodium ions for lithium ones, provided by TOSOH Corp. The experimental results demonstrate the specific equilibrium behavior of hydrogen isotopes adsorbed on SZ-LiA, deviating from isothermal profiles on SZ-CaA and SZ-NaX. SZ-LiA show the isothermal profiles of adsorption for H 2 and D 2 similar to on the conventional zeolites in the range from around 1 kPa to the atmospheric pressure, but exhibit a plateau around 1 mol/kg between 0.1 Pa and 100 Pa, while other zeolites show linearly profiling isotherms. This deviation indicates the adsorptive power of SZ-LiA remarkably greater than that of the others

  19. Fe-O stable isotope pairs elucidate a high-temperature origin of Chilean iron oxide-apatite deposits

    Science.gov (United States)

    Bilenker, Laura D.; Simon, Adam C.; Reich, Martin; Lundstrom, Craig C.; Gajos, Norbert; Bindeman, Ilya; Barra, Fernando; Munizaga, Rodrigo

    2016-03-01

    Iron oxide-apatite (IOA) ore deposits occur globally and can host millions to billions of tons of Fe in addition to economic reserves of other metals such as rare earth elements, which are critical for the expected growth of technology and renewable energy resources. In this study, we pair the stable Fe and O isotope compositions of magnetite samples from several IOA deposits to constrain the source reservoir of these elements in IOAs. Since magnetite constitutes up to 90 modal% of many IOAs, identifying the source of Fe and O within the magnetite may elucidate high-temperature and/or lower-temperature processes responsible for their formation. Here, we focus on the world-class Los Colorados IOA in the Chilean iron belt (CIB), and present data for magnetite from other Fe oxide deposits in the CIB (El Laco, Mariela). We also report Fe and O isotopic values for other IOA deposits, including Mineville, New York (USA) and the type locale, Kiruna (Sweden). The ranges of Fe isotopic composition (δ56Fe, 56Fe/54Fe relative to IRMM-14) of magnetite from the Chilean deposits are: Los Colorados, δ56Fe (±2σ) = 0.08 ± 0.03‰ to 0.24 ± 0.08‰; El Laco, δ56Fe = 0.20 ± 0.03‰ to 0.53 ± 0.03‰; Mariela, δ56Fe = 0.13 ± 0.03‰. The O isotopic composition (δ18O, 18O/16O relative to VSMOW) of the same Chilean magnetite samples are: Los Colorados, δ18O (±2σ) = 1.92 ± 0.08‰ to 3.17 ± 0.03‰; El Laco, δ18O = 4.00 ± 0.10‰ to 4.34 ± 0.10‰; Mariela, δ18O = (1.48 ± 0.04‰). The δ18O and δ56Fe values for Kiruna magnetite yield an average of 1.76 ± 0.25‰ and 0.16 ± 0.07‰, respectively. The Fe and O isotope data from the Chilean IOAs fit unequivocally within the range of magnetite formed by high-temperature magmatic or magmatic-hydrothermal processes (i.e., δ56Fe 0.06-0.49‰ and δ18O = 1.0-4.5‰), consistent with a high-temperature origin for Chilean IOA deposits. Additionally, minimum formation temperatures calculated by using the measured Δ18O

  20. Equilibrium Sorption studies of Fe, Cu and Co ions in aqueous ...

    African Journals Online (AJOL)

    Recinius Communis Linn a commonly found herbal plant was used to prepare activated carbon by physicochemical activation method. The sorption capacity of this bio-resource material to remove Fe(III), Cu(II) and Co(II) from aqueous solutions was determined by batch tests. The influences of important parameters such as ...

  1. Site-Specific Hydrogen Isotope Composition of Propane: Mass spectrometric methods, equilibrium temperature dependence, and kinetics of exchange

    Science.gov (United States)

    Xie, H.; Ponton, C.; Kitchen, N.; Lloyd, M. K.; Lawson, M.; Formolo, M. J.; Eiler, J. M.

    2016-12-01

    Intramolecular isotope ordering can constrain temperatures of synthesis, mechanisms of formation, and/or source substrates of organic compounds. Here we explore site-specific hydrogen isotope variations of propane. Statistical thermodynamic models predict that at equilibrium methylene hydrogen (-CH2-) in propane will be 10's of per mil higher in D/H ratio than methyl hydrogen (-CH3) at geologically relevant temperatures, and that this difference is highly temperature dependent ( 0.5-1 ‰/°C). Chemical-kinetic controls on site-specific D/H in propane could constrain the mechanisms, conditions and extents of propane synthesis or destruction. We have developed a method for measuring the difference in D/H ratio between methylene and methyl hydrogen in propane by gas source mass spectrometry. The data were measured using the Thermo Fisher Double Focusing Sector high resolution mass spectrometer (DFS), and involve comparison of the D/H ratios of molecular ion (C3H8+) and the ethyl fragmental ion (C2H5+). We demonstrate the accuracy and precision of this method through analysis of D-labeled and independently analyzed propanes. In the exchange experiments, propane was heated (100-200 oC) either alone or in the presence of D-enriched water (δD=1,1419 ‰ SMOW), with or without one of several potentially catalytic substrates for hours to weeks. Propane was found to exchange hydrogen with water vigorously at 200 °C in the presence of metal catalysts. In the presence of Ni catalyst, methylene hydrogen exchanges 2.5 times faster than methyl hydrogen. Hydrogen exchange in the presence of Pd catalyst is more effective and can equilibrate hydrogen isotope distribution on propane on the order of 7 days. Isotopic exchange in the presence of natural materials have also been tested, but is only measurable in the methylene group at 200 °C. High catalytic activity of Pd permits attainment of a bracketed, time-invariant equilibrium state that we use to calibrate the site

  2. The importance of a Ni correction with ion counter in the double spike analysis of Fe isotope compositions using a 57Fe/58Fe double spike

    Science.gov (United States)

    Finlayson, V. A.; Konter, J. G.; Ma, L.

    2015-12-01

    We present a new method capable of measuring iron isotope ratios of igneous materials to high precision by multicollector inductively coupled plasma mass spectrometry (MC-ICP-MS) using a 57Fe-58Fe double spike. After sample purification, near-baseline signal levels of nickel are still present in the sample solution, acting as an isobaric interference on 58 amu. To correct for the interference, the minor 60Ni isotope is monitored and used to subtract a proportional 58Ni signal from the total 58 amu beam. The 60Ni signal is difficult to precisely measure on the Faraday detector due to Johnson noise occurring at similar magnitude. This noise-dominated signal is subtracted from the total 58 amu beam, and its error amplified during the double spike correction. Placing the 60Ni beam on an ion counter produces a more precise measurement, resulting in a near-threefold improvement in δ56Fe reproducibility, from ±0.145‰ when measured on Faraday to 0.052‰. Faraday detectors quantify the 60Ni signal poorly, and fail to discern the transient 20Ne40Ar interference visible on the ion counter, which is likely responsible for poor reproducibility. Another consideration is instrumental stability (defined herein as drift in peak center mass), which affects high-resolution analyses. Analyses experiencing large drift relative to bracketing standards often yield nonreplicating data. Based on this, we present a quantitative outlier detection method capable of detecting drift-affected data. After outlier rejection, long-term precision on individual runs of our secondary standard improves to ±0.046‰. Averaging 3-4 analyses further improves precision to 0.019‰, allowing distinction between ultramafic minerals.

  3. Hydrogen isotope exchange between fluoroform and water. 5. Equilibrium deuterium distribution. The temperature dependence of α1

    International Nuclear Information System (INIS)

    Symons, E.A.; Bonnett, J.D.

    1984-01-01

    A knowledge of the equilibrium deuterium distribution between water and fluoroform is useful for design of the redeuteration stage of a heavy water production process based on IR laser-activated decomposition of CF 3 D in excess CF 3 H. The first measured fractionation factor data are presented for the temperature range 70-130 0 C. The deuterium is favored in the fluoroform (α = 1.139 at 130 0 C, 1.215 at 70 0 C, and 1.287 at 25 0 C (extrapolated)). These values are approximately 10-20% higher than various reported theoretical estimates calculated by using isotopic reduced partition function ratios based on molecular vibrational frequencies (with harmonic oscillator approximation). ΔH 0 = -1.23 kJ/mol was calculated from the temperature dependence of ln α

  4. FeO-rich silicates in the Sahara 97159 (EH3) enstatite chondrite: Mineralogy, oxygen isotopic compositions, and origin

    Science.gov (United States)

    Kimura, M.; Hiyagon, H.; Lin, Y.; Weisberg, M. K.

    2003-03-01

    We report the mineralogy and oxygen isotopic compositions of FeO-rich silicates in the Sahara 97159 EH3 chondrite. This component is referred to as FeO-rich because it contains substantially more FeO than the characteristic FeO-poor silicates in the highly reduced enstatite meteorites. These FeO-rich silicates are mostly low-Ca pyroxene (Fs5­35) and their compositions suggest an origin under more oxidizing conditions, like those for the ordinary chondrites. However, the mafic silicates in ordinary and carbonaceous chondrites are dominantly olivine, and the FeO-rich silicates in the E chondrites are less commonly olivine. The oxygen isotopic compositions of the FeO- rich silicates are indistinguishable from those of FeO-poor silicates in Sahara 97159. These observations suggest that both the FeO-rich silicates and the FeO-poor silicates in EH chondrites formed from the same oxygen reservoir where redox conditions varied widely.

  5. Irradiation of Wrought FeCrAl Tubes in the High Flux Isotope Reactor

    Energy Technology Data Exchange (ETDEWEB)

    Linton, Kory D. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Field, Kevin G. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Petrie, Christian M. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2017-09-01

    The Advanced Fuels Campaign within the Nuclear Technology Research and Development program of the Department of Energy Office of Nuclear Energy is seeking to improve the accident tolerance of light water reactors. Alumina-forming ferritic alloys (e.g., FeCrAl) are one of the leading candidate materials for fuel cladding to replace traditional zirconium alloys because of the superior oxidation resistance of FeCrAl. However, there are still some unresolved questions regarding irradiation effects on the microstructure and mechanical properties of FeCrAl at end-of-life dose levels. In particular, there are concerns related to irradiation-induced embrittlement of FeCrAl alloys due to secondary phase formation. To address this issue, Oak Ridge National Laboratory has developed a new experimental design to irradiate shortened cladding tube specimens with representative 17×17 array pressurized water reactor diameter and thickness in the High Flux Isotope Reactor (HFIR) under relevant temperatures (300–350°C). Post-irradiation examination will include studies of dimensional change, microstructural changes, and mechanical performance. This report briefly summarizes the capsule design concept and the irradiation test matrix for six rabbit capsules. Each rabbit contains two FeCrAl alloy tube specimens. The specimens include Generation I and Generation II FeCrAl alloys with varying processing conditions, Cr concentrations, and minor alloying elements. The rabbits were successfully assembled, welded, evaluated, and delivered to the HFIR along with a complete quality assurance fabrication package. Pictures of the rabbit assembly process and detailed dimensional inspection of select specimens are included in this report. The rabbits were inserted into HFIR starting in cycle 472 (May 2017).

  6. Equilibrium isotope exchange kinetics of native and site-specific mutant forms of E. coli aspartate transcarbamoylase

    International Nuclear Information System (INIS)

    Wedler, F.C.; Hsuanyu, Y.; Kantrowitz, E.R.

    1987-01-01

    Isotope exchange kinetics at equilibrium (EIEK) have been used to probe the kinetic and regulatory mechanisms of native aspartate transcarbamoylase (ATCase) from E. coli at pH 7.0, 30 0 . Substrate saturation patterns were most consistent with a preferred order random kinetic mechanism: C-P prior to L-Asp, C-Asp released before Pi, with the Asp ↔ C-Asp exchange rate 5X faster than C-P ↔ Pi. Computer simulations allow one to fit the EIEK experimental data and to arrive at the best set of kinetic constants for a given enzyme state. These approaches have been applied to modified ATCase. Bound CTP and ATP were observed, respectively, to inhibit and activate differentially Asp ↔ C-Asp, but not C-P ↔ Pi, indicating that these modifiers alter the association-dissociation rates of L-Asp and C-Asp but not of C-P or Pi. Low levels of PALA activated both exchange rates (due to shifting the T-R equilibrium), but higher [PALA] completely blocked both exchanges. The effects of a site-specific mutation of Tyr240 Phe have been similarly probed by EIEK methods. The Phe240 mutant enzyme exhibited kinetic properties markedly different from native ATCase: the data indicate that Phe240 ATCase is much closer to an R-state enzyme than is native enzyme

  7. Equilibrium phases in the multiferroic BiFeO3-PbTiO3 system – a revisit

    Directory of Open Access Journals (Sweden)

    Kothai V.

    2014-07-01

    Full Text Available The(1-x BiFeO3-(x PbTiO3 solid solution exhibiting a Morphotropic Phase Boundary (MPB has attracted considerable attention recently because of its unique features such as multiferroic, high Curie point (TC ~ 700°C and giant tetragonality (c/a -1 ~ 0.19. Different research groups have reported different composition range of MPB for this system. In this work we have conclusively proved that the wide composition range of MPB reported in the literature is due to kinetic arrest of the metastable rhombohedral phase and that if sufficient temperature and time is allowed the metastable phase disappears. The genuine MPB was found to be x=0.27 for which the tetragonal and the rhombohedral phases are in thermodynamic equilibrium. In-situ high temperature structural study of x=0.27 revealed the sluggish kinetics associated with the temperature induced structural transformation. Neutron powder diffraction study revealed that themagnetic ordering at room temperature occurs in the rhombohedral phase. The magnetic structure was found to be commensurate G-type antiferromagnetic with magnetic moments parallel to the c-direction (of the hexagonal cell. The present study suggests that the equilibrium properties in this solid solution series should be sought for x=0.27.

  8. Does a Heavy Fe-Isotope Composition of Akilia Quartz-Amphibole-Pyroxene Rocks Necessitate a BIF Origin?

    Science.gov (United States)

    Whitehouse, M J; Schoenberg, R; Fedo, C M; Kamber, B S

    2015-10-01

    The age and origin of the quartz-amphibole-pyroxene (qap) gneiss from the island of Akilia, southern West Greenland, have been the subject of intense debate since the light C-isotope composition of graphite inclusions in apatite was interpreted to indicate the presence of Earth's earliest biological activity. Although this claim for biogenic relicts has been vigorously challenged, the possibility that the rocks might represent some of Earth's earliest water-lain sediments and, hence, a suitable repository for life remains an open question. While some workers have suggested that the entire sequence represents an originally mafic-ultramafic igneous precursor subsequently modified by metasomatism, quartz injection, high-grade metamorphism, and extreme ductile deformation, others maintain that at least a small part of the sequence retains geochemical characteristics indicative of a chemical sedimentary origin. Fractionated Fe isotopes with δ(56)Fe values similar to those observed in Isua BIF have been reported from high-SiO2 units of qap and used to support a chemical sedimentary protolith for the qap unit. Here, we present new Fe isotope data from all lithologic variants in the qap gneiss on Akilia, including layers of undisputed ultramafic igneous origin. Since the latter require introduction of fractionated Fe into at least part of the qap unit, we argue that Fe isotopes must therefore be treated with considerable caution when used to infer BIF for part or all of the qap protolith.

  9. Geochemical and stable isotopic constraints on the generation and passive treatment of acidic, Fe-SO4 rich waters.

    Science.gov (United States)

    Matthies, Romy; Aplin, Andrew C; Boyce, Adrian J; Jarvis, Adam P

    2012-03-15

    Reducing and Alkalinity Producing Systems (RAPS) remediate net-acidic metalliferous mine drainage by creating anoxic conditions in which bacterial sulfate reduction (BSR) raises alkalinity and drives the precipitation of iron and other chalcophilic elements as sulfides. We report chemical and stable isotopic data from a study monitoring the biogeochemical processes involved in the generation of mine waters and their remediation by two RAPS. Sulfur isotopes show that sulfate in all mine waters has a common source (pyrite oxidation), whilst oxygen isotopes show that oxidation of pyritic sulfur is mediated by Fe(III)(aq). The isotopic composition of dissolved sulfide, combined with the sulfur and oxygen isotopic composition of sulfate in RAPS effluents, proves BSR and details its dual isotope systematics. The occurrence and isotopic composition of solid phase iron sulfides indicate the removal of reduced sulfur within the RAPS, with significant amounts of elemental sulfur indicating reoxidation steps. However, only 0 to 9% of solid phase iron occurs as Fe sulfides, with approximately 70% of the removed iron occurs as Fe(III) (hydr)oxides. Some of the (hydr)oxide is supplied to the wetland as solids and is simply filtered by the wetland substrate, playing no role in alkalinity generation or proton removal. However, the majority of iron is supplied as dissolved Fe(II), indicating that acid generating oxidation and hydrolysis reactions dominate iron removal. The overall contribution of BSR to the sulfur geochemistry in the RAPS is limited and sulfate retention is dominated by sulfate precipitation, comparable to aerobic treatment systems, and show that the proton acidity resulting from iron oxidation and hydrolysis must be subsequently neutralised by calcite dissolution and/or BSR deeper in the RAPS sediments. BSR is not as important as previously thought for metal removal in RAPS. The results have practical consequences for the design, treatment performance and long

  10. Composition and thermochemistry of the equilibrium vapour of the systems NaI-FeI2 and NaI-PbI2

    International Nuclear Information System (INIS)

    Hilpert, K.; Gerads, H.; Koberts, D.; Miller, M.

    1987-01-01

    The vaporization of NaI/FeI 2 and NaI/PbI 2 samples of equimolar composition was investigated was investigated in the temperature ranges between 574 to 683 K and 562 to 669 K, respectively, by using the mass spectrometric Knudsen effusion method. The gaseous species I, I 2 , NaI, (NaI) 2 , FeI 2 , (FeI 2 ) 2 , FeI 3 , NaFeI 3 , and Na 2 FeI 4 (NaI-FeI 2 system) as well as NaI, (NaI) 2 , PbI 2 , (PbI 2 ) 2 , and NaPbI 3 (NaI-PbI 2 system) are present in the equilibrium vapours. The equilibrium partial pressures of these species were determined with the exception of I, I 2 , and FeI 3 . Enthalpies and entropies of dissociation resulted for the reactions NaFeI 3 (g) ↔ NaI(g)+FeI 2 (g) (1), Na 2 FeI 4 (g) ↔ 2NaI(g)+FeI 2 (g) and (2) NaPbI 3 (g) ↔ NaI(g)+PbI 2 (g) (3) as Δ d H 298 0 (Eq. (1)) = 184±5 kJ mol -1 , Δ d S 298 0 (Eq. (1)) = 143±8 J mol -1 K -1 ; Δ d H 298 0 (Eq. (2)) = 333±9 kJ mol -1 , Δ d S 298 0 (Eq. (2)) = 274±14 J mol -1 K -1 ; and Δ d H 298 0 (Eq. (3)) = 168±5 kJ mol -1 , Δ d S 298 0 (Eq. (3)) = 151±9 J mol -1 K -1 . Equilibrium constants for these reactions are additionally given. The pressures of NaFeI 3 (g) and NaPbI 3 (g) as all as their enthalpies of dissociation are discussed with respect to their significance of semi empirical rules. (orig.)

  11. Initial rate and equilibrium isotope exchange studies on the ATP-dependent activity of polyphosphate Glucokinase from Propionibacterium shermanii.

    Science.gov (United States)

    Kowalczyk, T H; Horn, P J; Pan, W H; Phillips, N F

    1996-05-28

    Polyphosphate glucokinase [EC 2.7.1.63] catalyzes the phosphorylation of glucose using either inorganic polyphosphate [poly(P)] or ATP as the phosphoryl donor. Both activities purified from Propionibacterium shermanii are the functional properties of a single enzyme with separate binding sites for the two phosphoryl donor substrates. The enzyme was found to utilize poly(P) much more efficiently than it does ATP, with a kcat/Kpoly(P) to kcat/KATP ratio of 2800. The catalytic constant for poly(P) is about 2-fold higher than for ATP. Other nucleotides like GTP and dATP also served as substrates with good efficiencies. The ATP-dependent reaction was analyzed using steady-state kinetics and isotopic exchange kinetics at chemical equilibrium. Intersecting initial velocity patterns for both glucose and ATP indicate sequential addition of substrates. Product inhibition studies resulted in two competitive and two noncompetitive patterns, which is characteristic of a Theorell-Chance mechanism or a random mechanism with two dead-end complexes. Results of isotope exchange experiments, however, rule out a Theorell-Chance mechanism, as well as a truly random mechanism. They are not consistent with a partially random mechanism (although a kinetically compulsory order of substrate binding is not excluded), where glucose is preferentially bound to free enzyme before ATP, and ADP is preferentially released as the first product, followed by glucose 6-phosphate. Dead-end inhibition analysis confirms this order of substrate binding. Competitive inhibition of ADP vs ATP is explained as resulting primarily from binding as a dead-end inhibitor (E.Glc.ADP) and not as a product. Another weaker abortive complex, E.ATP.G6P, is also formed. The chemical transformation or the release of ADP is the rate-limiting step in ATP utilization.

  12. Mass measurement and structure studies of neutron-rich isotopes of Zn, Ni, Fe

    International Nuclear Information System (INIS)

    Dessagne, P.

    1982-01-01

    With the Orsay MP Tandem, the reaction ( 14 C, 16 O) on 58 - 60 - 62 - 64 Ni, 64 - 66 - 68 - 70 Zn, 74 - 76 Ge and 82 Se targets, and the reaction ( 14 C, 15 O) on 60 - 62 - 64 Ni, 68 - 70 Zn, 76 Ge targets, have been investigated at 72 MeV bombarding energy. The mass excess of neutron rich nuclei: 63 Fe (-55.19+-.06MeV), 69 Ni(-60.14+-.06 MeV), 75 Zn(.62.7+-08 MeV) have been measured for the first time, and those of 62 Fe, 68 Ni, 74 Zn, 80 Ge have been remeasured. A new equipment has been designed in order to perform measurements at zero degree. From the angular distribution around 0 0 for the 70 Zn( 14 C, 16 O) reaction, the first state of 68 Ni observed for the first time (1.77 MeV +- .04 MeV) has been shown to be a 0 + . This result establishes a new case of 2 1+ - 0 2+ inversion. The systematics of the ( 14 C, 16 O) measurements on the even Ni and Zn isotopes have shown a different behaviour with two series. For the Ni → Fe (g.s.) transitions, the ratio σsub(exp)/σsub(DWBA) increases by a factor of four when the neutron number varies from 30 to 36. Whereas for the Zn → Ni (gs) transitions this ratio remains constant for the first three isotopes and decrease by a factor of two when N=40. For the Ni → Fe transitions, axial and spherical symmetries have been used. In agreement with the shell model no change are found with the spherical symmetry. For the axial symmetry a variation is observed but strongly dapendant of the sub-shell. Hence no clear conclusion can be deduced for the cross section estimate. For the Zn → Ni transitions, the spherical symmetry has been used. One configuration prevails, leading to a qualitative agreement with the experimental results [fr

  13. Preservation of REE and Fe isotopes in altered stromatolites and the paleo-environmental record

    Science.gov (United States)

    Nies, S. M.; Shapiro, R. S.; Lalonde, S.

    2015-12-01

    Geochemical proxies are increasingly being used to unravel ancient ecosystems and environmental perturbations back to the earliest rock record on Earth. Along with more traditional fossils (stromatolites) and other biosignatures (e.g., lipids), the geochemical record is used specifically to evaluate biogenecity and to understand oxygenation of the atmosphere and ocean in the Archean and Paleoproterozoic. However, the effects of diagenesis, metamorphism, and other modes of secondary alteration are still poorly constrained, particularly as technological advances allow us to expand farther across the periodic table. Our study focused on the robustness and preservation of rare earth element (REE) and Fe isotope compositions of two stromatolitic units that have undergone contact and regional metamorphism. 18 samples were collected from cores, open pit mines, and field locations in Minnesota and Ontario from silicified iron formation (Biwabik-Gunflint formations). The samples were carefully constrained to one of two meter-scale stromatolitic units. Metamorphic grade ranged from essentially unmetamorphosed through prehnite-pumpellyite up to amphibolite (fayalite+hypersthene). Samples were also collected that represented deep secondary weathering, likely related to Cretaceous climatic extremes. Polished samples were first analyzed by electron microprobe and selected samples were further analyzed via laser ablation HR-ICP-MS to constrain trace element (n=13) and Fe isotopic variations (n=8). Preliminary results indicate that transition metal concentrations are surprisingly resilient to high-temperature metamorphic recrystallization. REE concentrations were analyzed in individual iron oxide grains, with full resolution (La to Lu) achieved for some samples and partial resolution (La to Nd) achieved for all samples. Core samples exhibited a relatively stable positive Ce anomaly occurring from low to extremely high alteration. Outcrop and mine samples indicate a shift from a

  14. Redox history of the Three Gorges region during the Ediacaran and Early Cambrian as indicated by the Fe isotope

    Directory of Open Access Journals (Sweden)

    Yusuke Sawaki

    2018-01-01

    To circumvent this deficiency, we drilled a fossiliferous Ediacaran to Early Cambrian sedimentary succession in the Three Gorges region, South China. We analyzed the iron isotope ratios (δ56/54Fe of pyrite grains in the drill cores using laser ablation multi collector inductively coupled plasma mass spectrometry. The results demonstrate large variations in δ56/54Fe, from −1.6 to 1.6‰, and positive iron isotope ratios are observed in many successions. The presence of positive δ56/54Fe in pyrite indicates that the ferrous iron in the seawater was partially oxidized, suggesting that seawater at Three Gorges was ferruginous during the Ediacaran and Early Cambrian periods. However, aggregated pyrite grains in organic carbon-rich black shales at Member 4 of the Doushantuo Formation and the base of the Shuijingtuo Formation yield near-zero δ56/54Fe values; this suggests that the ocean was transiently dominated by sulfidic conditions during these periods. Notably negative δ56/54Fe values, lower than −1‰, can be interpreted as a signature of DIR. The DIR also might contribute in part to the re-mineralization of organic matter during the largest negative carbon isotope anomaly in the Ediacaran.

  15. The groundwater nitrate isotope quandary: Is the dual isotopic composition of groundwater nitrate a recorder of interactions between N and Fe in the subsurface?

    Science.gov (United States)

    Wankel, S. D.; Hansel, C. M.; Tang, Y.; Johnston, D. T.

    2012-12-01

    Recent work continues to reveal the existence of new metabolic processes, novel elemental interactions and unique microbial groups that play potentially central roles in governing the global N cycle. These findings emphasize large gaps in our comprehensive understanding including which processes control ecosystem N loss and emission, how interactions among functional N cycling communities and other elemental cycles are structured, and how these processes and communities are affected by both natural and anthropogenic change. Among these recent advances, evidence for an intimate coupling of microbial N and Fe cycling is mounting. Here we explore N - Fe interactions in the terrestrial subsurface, by examining reactions between NO3- and Fe(II) and their influence on the dual isotopic composition (δ15N and δ18O) of NO3-. Specifically, there is a fundamental discrepancy of coupled O and N isotope effects (18ɛ:15ɛ) between culture-based isotopic studies of denitrifying bacteria and field-based isotopic measurements of groundwater NO3- loss under anaerobic conditions (having been interpreted as denitrification). We suggest this discrepancy may be the result of a ubiquitous, yet largely unrecognized, coupling of abiotic and/or biotic Fe cycling with both reductive and anaerobic oxidative N cycling pathways and present preliminary data in support of this hypothesis. Experimental data show substantial abiotic reduction of NO3- by Fe(II). Though kinetically slow, the presence of metals such as Cu greatly increased rates, although were not required for abiotic NO3- reduction by Fe(II). Kinetic isotope effects for N (15ɛ) and O (18ɛ) during NO3- reduction (with and without catalyst) varied widely across experimental conditions and was influenced by the interaction of Fe(II) with mineral surfaces. The magnitude of 15ɛ, 18ɛ and 18ɛ:15ɛ did not appear to be related to reduction rate. Values of 15ɛ always exceeded 18ɛ (18ɛ:15ɛ = 0.48 to 0.71), which are consistent with

  16. Experimental Phase Equilibria Studies of the Pb-Fe-O System in Air, in Equilibrium with Metallic Lead and at Intermediate Oxygen Potentials

    Science.gov (United States)

    Shevchenko, M.; Jak, E.

    2017-12-01

    The phase equilibria information on the Pb-Fe-O system is of practical importance for the improvement of the existing thermodynamic database of lead-containing slag systems (Pb-Zn-Fe-Cu-Si-Ca-Al-Mg-O). Phase equilibria of the Pb-Fe-O system have been investigated: (a) in air at temperatures between 1053 K and 1373 K (780 °C and 1100 °C); (b) in equilibrium with metallic lead at temperatures between 1053 K and 1373 K (780 °C and 1100 °C); and (c) at intermediate oxidation conditions for the liquid slag in equilibrium with two solids (spinel + magnetoplumbite), at temperatures between 1093 K and 1373 K (820 °C and 1100 °C). The high-temperature equilibration/quenching/electron probe X-ray microanalysis technique has been used to accurately determine the compositions of the phases in equilibrium in the system. The Pb and Fe concentrations in the phases were determined directly; preliminary thermodynamic modeling with FactSage was used to estimate the ferrous-to-ferric ratios and to present the results in the ternary diagram.

  17. An experimental study on the effect of carbonic anhydrase on the oxygen isotope exchange kinetics and equilibrium in the carbonic acid system

    Science.gov (United States)

    Uchikawa, J.; Zeebe, R. E.

    2011-12-01

    Stable oxygen isotopes of marine biogenic carbonates are often depleted in 18O relative to the values expected for thermodynamic equilibrium with ambient seawater. One possibility is that 18O-depletion in carbonates is kinetically controlled. The kinetic isotope effect associated with the hydration of CO2 results in 18O-depleted HCO3-. If the HCO3- is utilized before re-establishing equilibrium with ambient water under rapid calcification, the 18O-depletion will be recorded in carbonates. But one caveat in this kinetic model is the fact that many marine calcifiers posses carbonic anhydrase, a zinc-bearing enzyme that catalyzes the CO2 hydration reaction. It is expected that this enzyme accelerates 18O-equilibration in the carbonic acid system by facilitating direct oxygen isotope exchange between HCO3- and H2O via CO2 hydration. Clearly this argues against the conceptual framework of the kinetic model. Yet the critical variable here is the effectiveness of the carbonic anhydrase, which is likely to depend on its concentration and the carbonate chemistry of the aqueous medium. It is also hitherto unknown whether the presence of carbonic anhydrase alters the equilibrium oxygen isotope fractionations between dissolved carbonate species and water. We performed a series of quantitative inorganic carbonate precipitation experiments to examine the changes in the oxygen isotope equilibration time as a function of carbonic anhydrase concentrations. We conducted experiments at pH 8.3 and 8.9. These pH values are similar to the average surface ocean pH and the elevated pH levels observed within calcification microenvironments of certain corals and planktonic foraminifera. A summary of our new experimental results will be presented.

  18. Study of oxalic acid effect on equilibrium and kinetics of isotopic exchange between penta- and hexavalent neptunium in nitric acid solutions

    International Nuclear Information System (INIS)

    Nikitenko, S.I.; Ionnikova, N.I.

    1989-01-01

    Spectrophotometry at 25 deg C and ionic force μ=1.0 mol/l (KNO 3 +HNO 3 ) was used to show that at HNO 3 concentration 0.1-1.0 mol/l H 2 C 2 O 4 introduction to nitric acid solutions of Np 5+ in the presence of nitrite-ion resulted in the shift of equilibrium between Np 5+ and Np 6+ to the side of Np 6+ accumulation. The presence of H 2 C 2 O 4 at HNO 3 concentration > 1.0 mol/l doesn't affect the equilibrium position. The values of nominal equilibrium constant at different HNO 3 and H 2 C 2 O 4 concentrations were calculated. It was found that isotope exchange ( 239 Np/ 237 Np) between Np 5+ and Np 6+ in oxalate solutions proceeded more slowly than in oxalate absence. Rate constants of isotope exchange calculated at 9 deg C, μ=1.0 mol/l (KNO 3 ), H 2 C 2 O 4 concentration 0.01 mol/l and pH=2.2 and 3.5 are equal to 0.49x10 3 and 0.67x10 2 l/mol·min respectively. Mechanism of isotope exchange including electron transport between Np 5+ and Np 6+ oxalate complexes is suggested

  19. How did Marine Isotope Stage 3 and Last Glacial Maximum climates differ? – Perspectives from equilibrium simulations

    Directory of Open Access Journals (Sweden)

    C. J. Van Meerbeeck

    2009-03-01

    Full Text Available Dansgaard-Oeschger events occurred frequently during Marine Isotope Stage 3 (MIS3, as opposed to the following MIS2 period, which included the Last Glacial Maximum (LGM. Transient climate model simulations suggest that these abrupt warming events in Greenland and the North Atlantic region are associated with a resumption of the Thermohaline Circulation (THC from a weak state during stadials to a relatively strong state during interstadials. However, those models were run with LGM, rather than MIS3 boundary conditions. To quantify the influence of different boundary conditions on the climates of MIS3 and LGM, we perform two equilibrium climate simulations with the three-dimensional earth system model LOVECLIM, one for stadial, the other for interstadial conditions. We compare them to the LGM state simulated with the same model. Both climate states are globally 2°C warmer than LGM. A striking feature of our MIS3 simulations is the enhanced Northern Hemisphere seasonality, July surface air temperatures being 4°C warmer than in LGM. Also, despite some modification in the location of North Atlantic deep water formation, deep water export to the South Atlantic remains unaffected. To study specifically the effect of orbital forcing, we perform two additional sensitivity experiments spun up from our stadial simulation. The insolation difference between MIS3 and LGM causes half of the 30–60° N July temperature anomaly (+6°C. In a third simulation additional freshwater forcing halts the Atlantic THC, yielding a much colder North Atlantic region (−7°C. Comparing our simulation with proxy data, we find that the MIS3 climate with collapsed THC mimics stadials over the North Atlantic better than both control experiments, which might crudely estimate interstadial climate. These results suggest that freshwater forcing is necessary to return climate from warm interstadials to cold stadials during MIS3. This changes our perspective, making the stadial

  20. 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.

  1. Kinetics, Equilibrium, and Thermodynamics of the Sorption of Bisphenol A onto N-CNTs-β-Cyclodextrin and Fe/N-CNTs-β-Cyclodextrin Nanocomposites

    Directory of Open Access Journals (Sweden)

    Keletso Mphahlele

    2015-01-01

    Full Text Available We analysed the adsorptive behaviour of Fe/N-CNTs-β-CD nanocomposite in the removal of bisphenol A (BPA from aqueous solution and identified the key influencing parameters. The Fe/N-CNTs-β-CD nanocomposite adsorbent was prepared by dispersing Fe uniformly on N-CNTs-β-CD using a microwave polyol method and characterized using Fourier transform infrared spectroscopy (FTIR, focused ion beam scanning electron microscopy (FIB-SEM, and energy-dispersive X-ray spectroscopy (EDS. The solution pH and temperature had minimal effect on sorption of BPA while the initial concentration and adsorbent mass affected the adsorption of BPA. No leaching of Fe into the water was observed; thus the nanocomposites were found suitable for use in water purification. From equilibrium isotherm studies, the Langmuir isotherm model gave the best description of the experimental data. The Langmuir monolayer adsorption capacities of BPA onto N-CNTs-β-CD and Fe/N-CNTs-β-CD are 38.20 mg·g−1 and 80.65 mg·g−1 at 298 K, respectively. Evidently, these adsorption capacity values gave an indication that uniform dispersion of Fe N-CNTs-β-CD prepared by the microwave polyol method enhances the adsorption of BPA. Meanwhile, the sorption kinetics of BPA onto Fe/N-CNTs-β-CD were best described by the pseudo-second-order model.

  2. Assimilation of carbonate country rock by the parent magma of the Panzhihua Fe-Ti-V deposit (SW China: Evidence from stable isotopes

    Directory of Open Access Journals (Sweden)

    Clément Ganino

    2013-09-01

    Full Text Available The Panzhihua intrusion in southwest China is part of the Emeishan Large Igneous Province and host of a large Fe-Ti-V ore deposit. During emplacement of the main intrusion, multiple generations of mafic dykes invaded carbonate wall rocks, producing a large contact aureole. We measured the oxygen-isotope composition of the intrusions, their constituent minerals, and samples of the country rock. Magnetite and plagioclase from Panzhihua intrusion have δ18O values that are consistent with magmatic equilibrium, and formed from magmas with δ18O values that were 1–2‰ higher than expected in a mantle-derived magma. The unmetamorphosed country rock has high δ18O values, ranging from 13.2‰ (sandstone to 24.6–28.6‰ (dolomite. The skarns and marbles from the aureole have lower δ18O and δ13C values than their protolith suggesting interaction with fluids that were in exchange equilibrium with the adjacent mafic magmas and especially the numerous mafic dykes that intruded the aureole. This would explain the alteration of δ18O of the dykes which have significantly higher values than expected for a mantle-derived magma. Depending on the exact δ18O values assumed for the magma and contaminant, the amount of assimilation required to produce the elevated δ18O value of the Panzhihua intrusion was between 8 and 13.7 wt.%, assuming simple mixing. The exact mechanism of contamination is unclear but may involve a combination of assimilation of bulk country rock, mixing with a melt of the country rock and exchange with CO2-rich fluid derived from decarbonation of the marls and dolomites. These mechanisms, particularly the latter, were probably involved in the formation of the Fe-Ti-V ores.

  3. Effects of different water storage procedures on the dissolved Fe concentration and isotopic composition of chemically contrasted waters from the Amazon River Basin.

    Science.gov (United States)

    Mulholland, Daniel S; Poitrasson, Franck; Boaventura, Geraldo R

    2015-11-15

    Although recent studies have investigated the Fe isotopic composition of dissolved, colloidal and particulate phases from continental and oceanic natural waters, few efforts have been made to evaluate whether water sample storage and the separation of different pore-size fractions through filtration can cause any change to the Fe isotopic compositions. The present study investigates the possible biases introduced by different water storage conditions on the dissolved Fe concentration and isotopic composition of chemically different waters. Water samples were collected from an organic-rich river and from mineral particulate-rich rivers. Filtered and unfiltered water samples were stored either at room temperature or frozen at -18°C in order to assess possible biases due to (i) different water storage temperature, and (ii) storage of bulk (unfiltered) vs filtered water. Iron isotope measurements were performed by Multicollector Inductively Coupled Plasma Mass Spectrometry with a Thermo Electron Neptune instrument, after Fe purification using anion-exchange resins. Our data reveal that bulk water storage at room temperature without filtration produces minor changes in the dissolved Fe isotopic composition of mineral particulate-rich waters, but significant isotopic composition changes in organic-rich waters. In both cases, however, the impact of the different procedures on the Fe concentrations was strong. On the other hand, the bulk water stored frozen without filtration produced more limited changes in the dissolved Fe concentrations, and also on isotopic compositions, relative to the samples filtered in the field. The largest effect was again observed for the organic-rich waters. These findings suggest that a time lag between water collection and filtration may cause isotopic exchanges between the dissolved and particulate Fe fractions. When it is not possible to filter the samples in the field immediately after collection, the less detrimental approach is to

  4. Decay properties of 68,69,70Mn: Probing collectivity up to N=44 in Fe isotopic chain

    Directory of Open Access Journals (Sweden)

    G. Benzoni

    2015-12-01

    Full Text Available The β decays Mn68→Fe68, Mn69→Fe69 and Mn70→Fe70 have been measured at the RIBF facility at RIKEN using the EURICA γ spectrometer combined with an active stopper consisting of a stack of Si detectors. The nuclei were produced as fission fragments from a beam of 238U at a bombarding energy of 345 MeV/nucleon impinging on a Be target and selected using the BigRIPS separator. Half-lives and β-delayed neutron emission probabilities have been extracted for these decays, together with first experimental information on excited states populated in 69,70Fe. The data indicate a continuously increasing deformation for Fe isotopes up to A=70. This is interpreted, as for Cr isotopes, in terms of the interplay between the quadrupole correlations of the ν1d5/2 and ν0g9/2 orbitals and the monopole component of the π0f7/2–ν0f5/2 interaction.

  5. Equilibrium and generators

    International Nuclear Information System (INIS)

    Balter, H.S.

    1994-01-01

    This work studies the behaviour of radionuclides when it produce a desintegration activity,decay and the isotopes stable creation. It gives definitions about the equilibrium between activity of parent and activity of the daughter, radioactive decay,isotope stable and transient equilibrium and maxim activity time. Some considerations had been given to generators that permit a disgregation of two radioisotopes in equilibrium and its good performance. Tabs

  6. Investigation of very neutron-rich Fe, Co and Ni isotopes encountered along the r-process path

    International Nuclear Information System (INIS)

    Czajkowski, S.; Bernas, M.; Sida, J.L.; Dessagne, P.; Miehe, C.; Pujol, C.

    1992-01-01

    Very neutron-rich nuclei beyond Fe must be investigated in order to understand the r-process. New Ni, Co and Fe isotopes, with ten to twelve neutrons more than the heaviest stable isotopes, were discovered in the thermal fission of 235 U and 239 Pu, and their half-lives were deduced from the analysis of time delayed coincidences between the fragment implantation and the detection of consecutive β-particles in the same Si-pin diode detector. In a pilot experiment, high energy projectile fragmentation was exploited to produce neutron rich species. The fragments of interest were separated and energy bunched with the FRS. After being slowed down, they were selectively implanted in a similar detecting system. The β decay half-life were obtained as in the previous case

  7. Abiotic oxidation of pyrite by Fe(III) in acidic media and its implications for sulfur isotope measurements of lattice-bound sulfate in sediments

    Digital Repository Service at National Institute of Oceanography (India)

    Mazumdar, A.; Goldberg, T.; Strauss, H.

    We have evaluated the relative importance of Fe sup(3+) to dissolved oxygen in pyrite oxidation, and its implications for measuring an accurate sulfur isotope composition (delta Sup(34) S) in trace sulfates extracted from sedimentary rocks. Results...

  8. Equilibrium isotopic fractionation in the kaolinite, quartz, water system : Prediction from first-principles density-functional theory

    OpenAIRE

    Meheut, M.; Lazzeri, M.; Balan, Etienne; Mauri, F.

    2007-01-01

    Isotopic fractionation factors for oxygen, hydrogen and silicon have been calculated using first-principles methods for the kaolinite, quartz, water (ice and gas water) system. Good agreement between theory and experiment is obtained for mineral-water oxygen isotope fractionation. This approach gives reliable results on isotopic fractionation factors as a function of temperature, within a relative precision of typically 5%. These calculations provide independent quantitative constraints on th...

  9. Microbial production of isotopically light iron(II) in a modern chemically precipitated sediment and implications for isotopic variations in ancient rocks

    Science.gov (United States)

    Tangalos, G.E.; Beard, B.L.; Johnson, C.M.; Alpers, Charles N.; Shelobolina, E.S.; Xu, H.; Konishi, H.; Roden, E.E.

    2012-01-01

    The inventories and Fe isotope composition of aqueous Fe(II) and solid-phase Fe compounds were quantified in neutral-pH, chemically precipitated sediments downstream of the Iron Mountain acid mine drainage site in northern California, USA. The sediments contain high concentrations of amorphous Fe(III) oxyhydroxides [Fe(III)am] that allow dissimilatory iron reduction (DIR) to predominate over Fe–S interactions in Fe redox transformation, as indicated by the very low abundance of Cr(II)-extractable reduced inorganic sulfur compared with dilute HCl-extractable Fe. δ56Fe values for bulk HCl- and HF-extractable Fe were ≈ 0. These near-zero bulk δ56Fe values, together with the very low abundance of dissolved Fe in the overlying water column, suggest that the pyrite Fe source had near-zero δ56Fe values, and that complete oxidation of Fe(II) took place prior to deposition of the Fe(III) oxide-rich sediment. Sediment core analyses and incubation experiments demonstrated the production of millimolar quantities of isotopically light (δ56Fe ≈ -1.5 to -0.5‰) aqueous Fe(II) coupled to partial reduction of Fe(III)am by DIR. Trends in the Fe isotope composition of solid-associated Fe(II) and residual Fe(III)am are consistent with experiments with synthetic Fe(III) oxides, and collectively suggest an equilibrium Fe isotope fractionation between aqueous Fe(II) and Fe(III)am of approximately -2‰. These Fe(III) oxide-rich sediments provide a model for early diagenetic processes that are likely to have taken place in Archean and Paleoproterozoic marine sediments that served as precursors for banded iron formations. Our results suggest pathways whereby DIR could have led to the formation of large quantities of low-δ56Fe minerals during BIF genesis.

  10. Fe isotope composition of bulk chondrules from Murchison (CM2): Constraints for parent body alteration, nebula processes and chondrule-matrix complementarity

    Science.gov (United States)

    Hezel, Dominik C.; Wilden, Johanna S.; Becker, Daniel; Steinbach, Sonja; Wombacher, Frank; Harak, Markus

    2018-05-01

    Chondrules are a major constituent of primitive meteorites. The formation of chondrules is one of the most elusive problems in cosmochemistry. We use Fe isotope compositions of chondrules and bulk chondrites to constrain the conditions of chondrule formation. Iron isotope compositions of bulk chondrules are so far only known from few studies on CV and some ordinary chondrites. We studied 37 chondrules from the CM chondrite Murchison. This is particularly challenging, as CM chondrites contain the smallest chondrules of all chondrite groups, except for CH chondrites. Bulk chondrules have δ56Fe between -0.62 and +0.24‰ relative to the IRMM-014 standard. Bulk Murchison has as all chondrites a δ56Fe of 0.00‰ within error. The δ56Fe distribution of the Murchison chondrule population is continuous and close to normal. The width of the δ56Fe distribution is narrower than that of the Allende chondrule population. Opaque modal abundances in Murchison chondrules is in about 67% of the chondrules close to 0 vol.%, and in 33% typically up to 6.5 vol.%. Chondrule Al/Mg and Fe/Mg ratios are sub-chondritic, while bulk Murchison has chondritic ratios. We suggest that the variable bulk chondrule Fe isotope compositions were established during evaporation and recondensation prior to accretion in the Murchison parent body. This range in isotope composition was likely reduced during aqueous alteration on the parent body. Murchison has a chondritic Fe isotope composition and a number of chondritic element ratios. Chondrules, however, have variable Fe isotope compositions and chondrules and matrix have complementary Al/Mg and Fe/Mg ratios. In combination, this supports the idea that chondrules and matrix formed from a single reservoir and were then accreted in the parent body. The formation in a single region also explains the compositional distribution of the chondrule population in Murchison.

  11. Enrichment of57Fe isotope in neutron flux of nuclear reactors observed by Mössbauer spectroscopy.

    Science.gov (United States)

    Sawicki, Jerzy A

    2018-02-01

    The abundance of 57 Fe isotope in nuclear reactor core materials can be considerably enriched by neutron-capture 56 Fe(n,γ) reactions. This is demonstrated using the sections of Zr-2.5 wt.%Nb pressure tubes removed from two CANDU* reactors. The tubes contained 0.11 and 0.04wt% Fe and were irradiated for about 10 effective full power years (EFPY) up to ~10 26 n/m 2 fast neutron (E > 1MeV) fluencies. The Mössbauer spectra of 57 Fe in irradiated samples indicated up to 10 times larger areas than unirradiated off-cuts from the same pressure tubes. The observed effect is in accord with the values calculated for known thermal neutron-capture cross-sections and resonance capture integrals, neutron flux profiles and spectra, and times of irradiation. The build-up of 57 Fe facilitated recording Mössbauer absorption spectra of alloys with minor amount of Fe down to ~ 400ppm, despite intense background radiation emitted by samples. These findings can open new possibilities in post-irradiation studies of alloys used in nuclear reactors and in other objects subjected to large neutron fluencies. Copyright © 2017 Elsevier Ltd. All rights reserved.

  12. Spatial evolution of Zn-Fe-Pb isotopes of sphalerite within a single ore body: A case study from the Dongshengmiao ore deposit, Inner Mongolia, China

    Science.gov (United States)

    Gao, Zhaofu; Zhu, Xiangkun; Sun, Jian; Luo, Zhaohua; Bao, Chuang; Tang, Chao; Ma, Jianxiong

    2018-01-01

    Analyses of sphalerite minerals from the characteristic brecciated Zn-Pb ores of the main ore body in the giant Dongshengmiao deposit have revealed variations in δ66Zn from 0.17 to 0.40‰ and in δ56Fe from -1.78 to -0.35‰. Further, the investigated pyrrhotite samples have iron that is isotopically similar to that of associated sphalerite minerals. The most distinctive pattern revealed by the zinc and iron isotope data is the lateral trend of increasing δ66Zn and δ56Fe values from southwest to northeast within the main ore body. The lead isotopic homogeneity of ore sulfides from the main ore body suggests that there is only one significant source for metal, thus precluding the mixing of multiple metal sources as the key factor controlling spatial variations of zinc and iron isotopes. The most likely control on spatial variations is Rayleigh fractionation during hydrothermal fluid flow, with lighter Zn and Fe isotopes preferentially incorporated into the earliest sulfides to precipitate from fluids. Precipitations of sphalerite and pyrrhotite have played vital roles in the Zn and Fe isotopic variations, respectively, of the ore-forming system. Accordingly, the larger isotopic variability for Fe than Zn within the same hydrothermal system perhaps resulted from a larger proportion of precipitation for pyrrhotite than for sphalerite. The lateral trend pattern revealed by the zinc and iron isotope data is consistent with the occurrence of a cystic-shaped breccia zone, which is characterized by marked elevation in Cu. The results further confirm that Zn and Fe isotopes can be used as a vectoring tool for mineral prospecting.

  13. The Effect of Contact Non-equilibrium Plasma on Structural and Magnetic Properties of MnХFe3 - XО4Spinels.

    Science.gov (United States)

    Frolova, L A; Derhachov, M P

    2017-08-23

    Nano-sized manganese ferrites Mn х Fe 3 - х О 4 (х = 0-1.3) were prepared using contact non-equilibrium plasma (CNP) in two different pH (11.5 and 12.5). The influence of synthesis conditions (e.g., cation ratio and initial pH) on phase composition, crystallite size, and magnetic properties were investigated employing X-ray diffraction (XRD), differential thermal analysis (DTA), Fourier transform infrared (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and magnetic measurement techniques. The formation of monodispersed faceted ferrite particles at х = 0-0.8 was shown. The FTIR spectra revealed reflection in region 1200-1700 cm -1 caused by the presence of water adsorbed on the surface of Fe 3 - x Mn x O 4 micro-granules or embedded into their crystal lattice. The most sensitivity of reflection spectra to the composition changes takes place within a 400-1200 cm -1 range, typical to the stretching vibrations of Fe(Mn)-O (up to 700 cm -1 ), Fe(Mn)-OH, and Fe(Mn)-OH 2 bonds (over 700 cm -1 ). The XRD results showed that the nanocrystalline Mn х Fe 3 - х О 4 (0 spinel crystal structure with average crystallite size 48-49 A. The decrease of crystalline size with the x increase was also observed.

  14. Equilibrium and kinetic studies on acid dye Acid Red 88 adsorption by magnetic ZnFe2O4 spinel ferrite nanoparticles.

    Science.gov (United States)

    Konicki, Wojciech; Sibera, Daniel; Mijowska, Ewa; Lendzion-Bieluń, Zofia; Narkiewicz, Urszula

    2013-05-15

    A magnetic ZnFe2O4 (MNZnFe) was synthesized by microwave assisted hydrothermal method and was used as an adsorbent for the removal of acid dye Acid Red 88 (AR88) from aqueous solution. The effects of various parameters such as initial AR88 concentration (10-56 mg L(-1)), pH solution (3.2-10.7), and temperature (20-60°C) were investigated. Prepared magnetic ZnFe2O4 was characterized by XRD, SEM, HRTEM, ICP-AES, BET, FTIR, and measurements of the magnetic susceptibility. The experimental data were analyzed by the Langmuir and Freundlich models of adsorption. Equilibrium data fitted well with the Langmuir model. Pseudo-first-order and pseudo-second-order kinetic models and intraparticle diffusion model were used to examine the adsorption kinetic data. The adsorption kinetics was found to follow the pseudo-second-order kinetic model. Thermodynamics parameters, ΔG°, ΔH° and ΔS°, indicate that the adsorption of AR88 onto MNZnFe was spontaneous and exothermic in nature. Copyright © 2013 Elsevier Inc. All rights reserved.

  15. Non-equilibrium Modeling of the Fe XVII 3C/3D Line Ratio in an Intense X-Ray Free-Electron Laser Excited Plasma

    Science.gov (United States)

    Loch, S. D.; Ballance, C. P.; Li, Y.; Fogle, M.; Fontes, C. J.

    2015-03-01

    Recent measurements using an X-ray Free Electron Laser (XFEL) and an Electron Beam Ion Trap at the Linac Coherent Light Source facility highlighted large discrepancies between the observed and theoretical values for the Fe xvii 3C/3D line intensity ratio. This result raised the question of whether the theoretical oscillator strengths may be significantly in error, due to insufficiencies in the atomic structure calculations. We present time-dependent spectral modeling of this experiment and show that non-equilibrium effects can dramatically reduce the predicted 3C/3D line intensity ratio, compared with that obtained by simply taking the ratio of oscillator strengths. Once these non-equilibrium effects are accounted for, the measured line intensity ratio can be used to determine a revised value for the 3C/3D oscillator strength ratio, giving a range from 3.0 to 3.5. We also provide a framework to narrow this range further, if more precise information about the pulse parameters can be determined. We discuss the implications of the new results for the use of Fe xvii spectral features as astrophysical diagnostics and investigate the importance of time-dependent effects in interpreting XFEL-excited plasmas.

  16. The Prestudy for Studying Inorganic Nutrient Metabolism in Humans : the Aplication of ICP-MS for Determination of Stable Isotope Ratio of Fe and Zn

    International Nuclear Information System (INIS)

    Rukihati; Sumadjo

    2001-01-01

    A method is described for the determination of isotope ratio of Fe and Zn by means of inductively coupled plasma-mass spectrometry (ICP-MS). The mass spectrometer was operated in low resolution mode to provide maximal sensitivity. Typical conditions for operations were: plasma power 0.85 k W, reflected power 56 Fe/ 54 Fe, 57 Fe/ 54 Fe, 58 Fe/ 54 Fe, dan 64 Zn/ 67 Zn, 66 Zn/ 67 Zn, 68 Zn/ 67 Zn, 70 Zn/ 67 Zn measured by ICP-MS showed a good level of agreement with TIMS (thermal ionization mass spectrometry). This method was prepared for studying the absorption and/or metabolism of inorganic nutrients in humans. (author)

  17. Synthesis and Properties of Fe3O4-Activated Carbon Magnetic Nanoparticles for Removal of Aniline from Aqueous Solution: Equilibrium, Kinetic and Thermodynamic Studies

    Directory of Open Access Journals (Sweden)

    Babak Kakavandi

    2013-02-01

    Full Text Available In this study, powder activated carbon (PAC and magnetic nanoparticles of iron (III oxide were used for synthesis of Fe3O4-activated carbon magnetic nanoparticles (AC-Fe3O4 MNPs as an adsorbent for the removal of aniline. The characteristics of adsorbent were evaluated by SEM, TEM, XRD and BET. Also, the impact of different parameters such as pH, contact time, adsorbent dosage, aniline initials concentration and solution temperature were studied. The experimental data investigated by Langmuir and Freundlich adsorption isotherms and two models kinetically of pseudo first-order and pseudo second-order. The results indicated that the adsorption followed Langmuir and pseudo second-order models with correlation r2 > 0.98 and r2 > 0.99, respectively. The equilibrium time was obtained after 5 h. According to Langmuir model, the maximum adsorption capacity was 90.91 mg/g at pH = 6, and 20°C. The thermodynamic parameters indicated that adsorption of aniline on magnetic activated carbon was exothermic and spontaneous. This synthesized AC-Fe3O4 MNPs due to have advantages such as easy and rapid separation from solution could be applied as an adsorbent effective for removal of pollutants such as aniline from water and wastewater

  18. Determination of 58Fe, and 65Cu enriched stable isotopic tracers in studies of mineral metabolism of babies

    International Nuclear Information System (INIS)

    Whitley, J.E.; Stack, T.; Miller, C.; Aggett, P.J.; Lloyd, D.J.

    1986-01-01

    Neutron activation analysis is an appropriate method for the determination of the excretion by infants if enriched stable isotopes which have been added to synthetic milks for assessment of elemental bioavailability. Similar studies with radioactive tracers are not appropriate for children and total element balances do not provide information on bodily secretion. 58 Fe enrichment in diet and faeces is determined by instrumental neutron activation analysis. 65 Cu is determined by radiochemical neutron activation analysis since matrix activation precludes the instrumental approach. In view of the 5 minute half-life of 66 Cu samples are dissolved before irradiation. Activated Cu is extracted from irradiated solutions with neocuproine and both 64 Cu and 66 Cu are observed in resulting gamma-ray spectra. Accuracy of the methods is confirmed by results for NBS Bovine Liver. Appearence of added stable isotopes in samples collected between carmine red markers has been confirmed, and the method applied to studies of Fe and Cu absorption in relation to the clinical condition of premature babies and to investigate the uptake of these elements from diets prepared from cows milk and milk derived from soya protein. (author)

  19. Experiments on Lunar Core Composition: Phase Equilibrium Analysis of A Multi-Element (Fe-Ni-S-C) System

    Science.gov (United States)

    Go, B. M.; Righter, K.; Danielson, L.; Pando, K.

    2015-01-01

    Previous geochemical and geophysical experiments have proposed the presence of a small, metallic lunar core, but its composition is still being investigated. Knowledge of core composition can have a significant effect on understanding the thermal history of the Moon, the conditions surrounding the liquid-solid or liquid-liquid field, and siderophile element partitioning between mantle and core. However, experiments on complex bulk core compositions are very limited. One limitation comes from numerous studies that have only considered two or three element systems such as Fe-S or Fe-C, which do not supply a comprehensive understanding for complex systems such as Fe-Ni-S-Si-C. Recent geophysical data suggests the presence of up to 6% lighter elements. Reassessments of Apollo seismological analyses and samples have also shown the need to acquire more data for a broader range of pressures, temperatures, and compositions. This study considers a complex multi-element system (Fe-Ni-S-C) for a relevant pressure and temperature range to the Moon's core conditions.

  20. Adsorption properties of kaolinite-based nanocomposites for Fe and Mn pollutants from aqueous solutions and raw ground water: kinetics and equilibrium studies.

    Science.gov (United States)

    Shaban, Mohamed; Hassouna, Mohamed E M; Nasief, Fadya M; AbuKhadra, Mostafa R

    2017-10-01

    Raw kaolinite was used in the synthesis of metakaolinite/carbon nanotubes (K/CNTs) and kaolinite/starch (K/starch) nanocomposites. Raw kaolinite and the synthetic composites were characterized using XRD, SEM, and TEM techniques. The synthetic composites were used as adsorbents for Fe and Mn ions from aqueous solutions and natural underground water. The adsorption by the both composites is highly pH dependent and achieves high efficiency within the neutral pH range. The experimental adsorption data for the uptake of Fe and Mn ions by K/CNTs were found to be well represented by the pseudo-second-order kinetic model rather than the intra-particle diffusion model or Elovich model. For the adsorption using K/starch, the uptake results of Fe ions was well fitted by the second-order model, whereas the uptake of Mn ions fitted well to the Elovich model rather than pseudo-second-order and intra-particle diffusion models The equilibrium studies revealed the excellent fitting of the removal of Fe and Mn ions by K/CNTs and Fe using K/starch with the Langmuir isotherm model rather than with Freundlich and Temkin models. But the adsorption of Mn ions by K/starch is well fitted with Freundlich rather than Temkin and Langmuir isotherm models. The thermodynamic studies reflected the endothermic nature and the exothermic nature for the adsorption by K/CNTs and K/starch nanocomposites, respectively. Natural ground water contaminated by 0.4 mg/L Fe and 0.5 mg/L Mn was treated at the optimum conditions of pH 6 and 120 min contact time. Under these conditions, 92.5 and 72.5% Fe removal efficiencies were achieved using 20 mg of K/CNTs and K/starch nanocomposites, respectively. Also, K/CNTs nanocomposite shows higher efficiency in the removal of Mn ions as compared to K/starch nanocomposite.

  1. Rotational spectra of rare isotopic species of fluoroiodomethane: determination of the equilibrium structure from rotational spectroscopy and quantum-chemical calculations.

    Science.gov (United States)

    Puzzarini, Cristina; Cazzoli, Gabriele; López, Juan Carlos; Alonso, José Luis; Baldacci, Agostino; Baldan, Alessandro; Stopkowicz, Stella; Cheng, Lan; Gauss, Jürgen

    2012-07-14

    Supported by accurate quantum-chemical calculations, the rotational spectra of the mono- and bi-deuterated species of fluoroiodomethane, CHDFI and CD(2)FI, as well as of the (13)C-containing species, (13)CH(2)FI, were recorded for the first time. Three different spectrometers were employed, a Fourier-transform microwave spectrometer, a millimeter/submillimter-wave spectrometer, and a THz spectrometer, thus allowing to record a huge portion of the rotational spectrum, from 5 GHz up to 1.05 THz, and to accurately determine the ground-state rotational and centrifugal-distortion constants. Sub-Doppler measurements allowed to resolve the hyperfine structure of the rotational spectrum and to determine the complete iodine quadrupole-coupling tensor as well as the diagonal elements of the iodine spin-rotation tensor. The present investigation of rare isotopic species of CH(2)FI together with the results previously obtained for the main isotopologue [C. Puzzarini, G. Cazzoli, J. C. López, J. L. Alonso, A. Baldacci, A. Baldan, S. Stopkowicz, L. Cheng, and J. Gauss, J. Chem. Phys. 134, 174312 (2011); G. Cazzoli, A. Baldacci, A. Baldan, and C. Puzzarini, Mol. Phys. 109, 2245 (2011)] enabled us to derive a semi-experimental equilibrium structure for fluoroiodomethane by means of a least-squares fit procedure using the available experimental ground-state rotational constants together with computed vibrational corrections. Problems related to the missing isotopic substitution of fluorine and iodine were overcome thanks to the availability of an accurate theoretical equilibrium geometry (computed at the coupled-cluster singles and doubles level augmented by a perturbative treatment of triple excitations).

  2. 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.

  3. Oxygen isotopic fractionation in the condensation of refractory smokes

    Science.gov (United States)

    Nelson, R.; Thiemens, M.; Nuth, J.; Donn, B.

    1989-01-01

    This paper reports preliminary measurements of the oxygen isotopic fractionation that occurs during the condensation of refractory metal oxide smokes. Fractionation occurred at temperatures in excess of 500 K during and/or subsequent to reaction of SiH4, Fe(CO)5, Al(CH3)3, and O2 in a H2 carrier gas. Observed isotopic fractionation was as high as -15 per mil/amu. The magnitude of the isotopic fractionation suggests that the process is kinetically controlled since the effect is greatly in excess of that expected for equilibrium isotopic exchange.

  4. Experimental Study of Liquidus of the "FeO"-SiO2-PbO Slags in Equilibrium with Air and with Metallic Lead

    Science.gov (United States)

    Shevchenko, Maksym; Hidayat, Taufiq; Hayes, Peter C.; Jak, Evgueni

    Limited data are available on phase equilibria of the "FeO"-SiO2-PbO slag system at conditions used in the lead smelting due to difficulties from lead vaporization and interactions with metal and ceramic crucibles. Recently experimental procedures have been developed and successfully applied to complex industrial slag-metal-matte systems involving high temperature equilibration on a primary phase substrate and rapid quenching followed by the electron probe X-ray microanalysis. The liquidus isotherms and invariant lines in the "FeO"-SiO2-PbO slag system in equilibrium with air and with metallic lead have been constructed. Preliminary data compared to the FactSage package predictions demonstrate differences in some aspects, indicating the possibility for further improvement of the thermodynamic database. The present work is a part of the integrated experimental and thermodynamic modelling research program on multi-phase lead systems in support of the optimization and development of complex lead smelting, refining and recycling technologies.

  5. Iron Isotope Constraints on Planetesimal Core Formation

    Science.gov (United States)

    Jordan, M.; Young, E. D.

    2016-12-01

    The prevalence of iron in both planetary cores and silicate mantles renders the element a valuable tool for understanding core formation. Magmatic iron meteorites exhibit an enrichment in 57Fe/54Fe relative to chondrites and HED meteorites. This is suggestive of heavy Fe partitioning into the cores of differentiated bodies. If iron isotope fractionation accompanies core formation, we can elucidate details about the history of accretion for planetary bodies as well as their compositions and relative core sizes. The equilibrium 57Fe/54Fe between metal and silicate is necessary for understanding observed iron isotope compositions and placing constraints on core formation. We measure this fractionation in two Aubrite meteorites, Norton County and Mount Egerton, which have known temperatures of equilibration and equilibrated silicon isotopes. Iron was purified using ion-exchange chromatography. Data were collected on a ThermoFinnigan NeptuneTM multiple-collector inductively coupled plasma-source mass spectrometer (MC-ICP-MS) run in wet plasma mode. The measured fractionation Δ57Femetal-silicate is 0.08‰ ± 0.039 (2 SE) for Norton County and 0.09‰ ± 0.019 (2 SE) for Mount Egerton, indicating that the heavy isotopes of Fe partition into the metallic phase. These rocks are in isotopic equilibrium at a temperature of 1130 K and 1200 K ± 80 K, respectively. The concentration of the heavy isotopes of iron in the metallic phase is consistent with recent experimental studies. Using our measured metal-silicate Fe isotope fractionation and the resulting temperature calibration, while taking into account impurities in the metallic phase and temperatures of equilibration, determine that core formation could explain the observed difference between magmatic iron meteorites and chondrites if parent bodies have small cores. In order to verify that Rayleigh distillation during fractional crystallization was not a cause of iron isotope fractionation in iron meteorites, we measured

  6. Thermodynamics Behavior of Germanium During Equilibrium Reactions between FeOx-CaO-SiO2-MgO Slag and Molten Copper

    Science.gov (United States)

    Shuva, M. A. H.; Rhamdhani, M. A.; Brooks, G. A.; Masood, S.; Reuter, M. A.

    2016-10-01

    The distribution ratio of germanium (Ge), L_{{Ge}}^{s/m} during equilibrium reactions between magnesia-saturated FeOx-CaO-SiO2 (FCS) slag and molten copper has been measured under oxygen partial pressures from 10-10 to 10-7 atm and at temperatures 1473 to 1623 K (1200 to 1350 °C). It was observed that the Ge distribution ratio increases with increasing oxygen partial pressure, and with decreasing temperature. It was also observed that the distribution ratio is strongly dependent on slag basicity. The distribution ratio was observed to increase with increasing optical basicity. At fixed CaO concentration in the slag, the distribution ratio was found to increase with increasing Fe/SiO2 ratio, tending to a plateau at L_{{Ge}}^{s/m} = 0.8. This behavior is consistent with the assessment of ionic bond fraction carried out in this study, and suggested the acidic nature of germanium oxide (GeO2) in the slag system studied. The characterisation results of the quenched slag suggested that Ge is present in the FeOx-CaO-SiO2-MgO slag predominantly as GeO2. At 1573 K (1300 °C) and p_{{{{O}}2 }} = 10-8 atm, the activity coefficient of GeO2 in the slag was calculated to be in the range of 0.24 to 1.50. The results from the current study suggested that less-basic slag, high operating temperature, and low oxygen partial pressure promote a low Ge distribution ratio. These conditions are desired for maximizing Ge recovery, for example, during pyrometallurgical processing of Ge-containing e-waste through secondary copper smelting. Overall, the thermodynamics data generated from this study can be used for process modeling purposes for improving recovery of Ge in primary and secondary copper smelting processes.

  7. Neutron-proton ratios of collective quadrupole matrix elements in even Fe and Cr isotopes

    International Nuclear Information System (INIS)

    Antalik, R.

    1989-01-01

    M n /M p ratios are investigated within the QRPA framework for the low-lying quadrupole states and for isoscalar giant quadrupole resonances in 54,56,58 Fe and 50,52,54 Cr. Theoretical results for 2 l ? + states are in good agreement with empirical ones obtained from recent proton and pion inelastic scattering studies. 16 refs.; 3 tabs

  8. Reconstructing the evolution of the submarine Monterey Canyon System from Os, Nd, and Pb isotopes in hydrogenetic Fe-Mn crusts

    Science.gov (United States)

    Conrad, T.A.; Nielsen, S.G.; Peucker-Ehrenbrink, Bernhard; Blusztajn, J.; Winslow, D.; Hein, James; Paytan, A.

    2017-01-01

    The sources of terrestrial material delivered to the California margin over the past 7 Myr were assessed using 187Os/188Os, Nd, and Pb isotopes in hydrogenetic ferromanganese crusts from three seamounts along the central and southern California margin. From 6.8 to 4.5 (± 0.5) Ma, all three isotope systems show more radiogenic values at Davidson Seamount, located near the base of the Monterey Canyon System, than in Fe-Mn crusts from the more remote Taney and Hoss seamounts. At the Taney seamounts, approximately 225 km farther offshore from Davidson Seamount, 187Os/188Os values, but not Pb and Nd isotope ratios, also deviate from the Cenozoic seawater curve towards more radiogenic values from 6.8 to 4.5 (± 0.5) Ma. However, none of the isotope systems in Fe-Mn crusts deviate from seawater at Hoss Seamount located approximately 450 km to the south. The regional gradients in isotope ratios indicate that substantial input of dissolved and particulate terrestrial material into the Monterey Canyon System is responsible for the local deviations in the seawater Nd, Pb, and Os isotope compositions from 6.8 to 4.5 (± 0.5) Ma. The isotope ratios recorded in Fe-Mn crusts are consistent with a southern Sierra Nevada or western Basin and Range provenance of the terrestrial material which was delivered by rivers to the canyon. The exhumation of the modern Monterey Canyon must have begun between 10 and 6.8 ± 0.5 Ma, as indicated by our data, the age of incised strata, and paleo-location of the Monterey Canyon relative to the paleo-coastline.

  9. Reconstructing the Evolution of the Submarine Monterey Canyon System From Os, Nd, and Pb Isotopes in Hydrogenetic Fe-Mn Crusts

    Science.gov (United States)

    Conrad, T. A.; Nielsen, S. G.; Peucker-Ehrenbrink, B.; Blusztajn, J.; Winslow, D.; Hein, J. R.; Paytan, A.

    2017-11-01

    The sources of terrestrial material delivered to the California margin over the past 7 Myr were assessed using 187Os/188Os, Nd, and Pb isotopes in hydrogenetic ferromanganese crusts from three seamounts along the central and southern California margin. From 6.8 to 4.5 (±0.5) Ma, all three isotope systems show more radiogenic values at Davidson Seamount, located near the base of the Monterey Canyon System, than in Fe-Mn crusts from the more remote Taney and Hoss Seamounts. At the Taney Seamounts, approximately 225 km farther offshore from Davidson Seamount, 187Os/188Os values, but not Pb and Nd isotope ratios, also deviate from the Cenozoic seawater curve toward more radiogenic values from 6.8 to 4.5 (±0.5) Ma. However, none of the isotope systems in Fe-Mn crusts deviate from seawater at Hoss Seamount located approximately 450 km to the south. The regional gradients in isotope ratios indicate that substantial input of dissolved and particulate terrestrial material into the Monterey Canyon System is responsible for the local deviations in the seawater Nd, Pb, and Os isotope compositions from 6.8 to 4.5 (±0.5) Ma. The isotope ratios recorded in Fe-Mn crusts are consistent with a southern Sierra Nevada or western Basin and Range provenance of the terrestrial material which was delivered by rivers to the canyon. The exhumation of the modern Monterey Canyon must have begun between 10 and 6.8 ± 0.5 Ma, as indicated by our data, the age of incised strata, and paleo-location of the Monterey Canyon relative to the paleo-coastline.

  10. Neutron Capture Reactions on Fe and Ni Isotopes for the Astrophysical s-process

    CERN Document Server

    Lederer, C; Massimi, C; Žugec, P; Barbagallo, M; Colonna, N; Domingo-Pardo, C; Guerrero, C; Gunsing, F; Käppeler, F; Tain, J L; Altstadt, S; Andrzejewski, J; Audouin, L; Bécares, V; Bečvář, F; Belloni, F; Berthoumieux, E; Billowes, J; Boccone, V; Bosnar, D; Brugger, M; Calviani, M; Calviño, F; Cano-Ott, D; Carrapiço, C; Cerutti, F; Chiaveri, E; Chin, M; Cortés, G; Cortés-Giraldo, M A; Diakaki, M; Duran, I; Dressler, R; Dzysiuk, N; Eleftheriadis, C; Ferrari, A; Fraval, K; Ganesan, S; García, A R; Gómez-Hornillos, M B; Gonçalves, I F; González-Romero, E; Griesmayer, E; Gurusamy, P; Jenkins, D G; Jericha, E; Kadi, Y; Karadimos, D; Kivel, N; Koehler, P; Kokkoris, M; Korschinek, G; Krtička, M; Kroll, J; Langer, C; Leeb, H; Leong, L S; Losito, R; Manousos, A; Marganiec, J; Martínez, T; Mastinu, P F; Mastromarco, M; Meaze, M; Mendoza, E; Mengoni, A; Milazzo, P M; Mingrone, F; Mirea, M; Mondelaers, W; Paradela, C; Pavlik, A; Perkowski, J; Pignatari, M; Plompen, A; Praena, J; Quesada, J M; Rauscher, T; Reifarth, R; Riego, A; Roman, F; Rubbia, C; Sarmento, R; Schillebeeckx, P; Schmidt, S; Schumann, D; Tagliente, G; Tarrío, D; Tassan-Got, L; Tsinganis, A; Valenta, S; Vannini, G; Variale, V; Vaz, P; Ventura, A; Versaci, R; Vermeulen, M J; Vlachoudis, V; Vlastou, R; Wallner, A; Ware, T; Weigand, M; Weiß, C; Wright, T J

    2014-01-01

    Neutron capture cross sections in the keV neutron energy region are the key nuclear physics input to study the astrophysical slow neutron capture process. In the past years, a series of neutron capture cross section measurements has been performed at the neutron time-of-flight facility n\\_TOF at CERN focussing on the Fe/Ni mass region. Recent results and future developments in the neutron time-of-flight technique are discussed.

  11. Visualization of 57Fe-Labeled Heme Isotopic Fine Structure and Localization of Regions of Erythroblast Maturation in Mouse Spleen by MALDI FTICR-MS Imaging

    Science.gov (United States)

    Kihara, Makoto; Matsuo-Tezuka, Yukari; Noguchi-Sasaki, Mariko; Yorozu, Keigo; Kurasawa, Mitsue; Shimonaka, Yasushi; Hirata, Michinori

    2017-08-01

    Epoetin beta pegol (continuous erythropoiesis receptor activator; C.E.R.A.), or methoxy-polyethylene glycol-modified epoetin beta, is a long-acting erythropoiesis stimulating agent (ESA) that effectively maintains hemoglobin levels. It promotes proliferation of erythroid progenitor cells in hematopoietic organs and leads to increased reticulocyte and hemoglobin levels. However, the detailed erythropoietic effects of various ESAs on their target organs have yet to be clarified, and new approaches are needed to analyze tissue iron localization with structural information. Matrix-assisted laser desorption/ionization (MALDI) mass spectrometry imaging (MSI) techniques are widely used in basic pharmaceutical research. High-resolution Fourier transform ion cyclotron resonance (FTICR) mass spectrometry (MS) imaging enables the spatial mapping and identification of biomolecules. In this study, mice administered with C.E.R.A. were fed a diet containing the stable iron isotope 57Fe. The 57Fe-heme+ isotopic fine structure peak (m/z 617.1772) was separated from the non-labeled heme+ isotopic peak (Δ0.0029) by FTICR-MS with a resolving power of more than 500,000. We optimized the platform to analyze the distribution of 57Fe-heme in the spleen using MALDI FTICR-MS imaging. The combination of the ultrahigh resolution power of FTICR-MS and a stable isotope labeling technique has the potential to be very effective in basic pharmaceutical research. [Figure not available: see fulltext.

  12. Coupled Fe and multiple-S isotope systematics of pyrite and evidence of increasing atmospheric oxygen in 2.5 Ga sediments of the Kaapvaal Craton

    Science.gov (United States)

    Bauer, A.; Ono, S.; Romaniello, S. J.; Anbar, A. D.

    2017-12-01

    Using combined iron and sulfur isotopic data from black shale-hosted pyrite grains of 2.5 Ga samples from the GKP-01 drill core of the Griqualand West Basin, South Africa, we untangle the pathways of pyrite formation for distinct morphologies of pyrite and evaluate the role of these pyrites as recorders of atmospheric S-MIF signals. The analysis of subsamples at stratigraphic intervals allows us to document the characteristic time scale of change in S-MIF signatures resulting from atmospheric photochemical reactions with respect to residence time of the seawater sulfate reservoir. Disseminated pyrite grains are characterized by a range of Δ33S (-1 to +8‰) and 56Fe (-2.5 to 0‰) values. Pyrite laminae are predominantly characterized by relatively homogeneous and negative Δ33S (-2 to 0 ‰) and 56Fe (-2 to -1‰) isotope signatures. These correlated Fe-S systematics suggest distinct pathways of pyrite formation: 1) pyrite laminae formed below the sediment-water interface via diffusion of dissolved oceanic Fe2+ and sulfate; and 2) disseminated pyrite formed at the chemocline by reaction of reduced and elemental sulfur with a reservoir of Fe2+ affected by removal of Fe oxides. Recognition of distinct mechanisms of pyrite formation for these morphologies is a critical step in deconstructing the pathways for S-MIF production, transfer, and preservation in the Archean sedimentary record. Our results have implications for mass balance and atmospheric modeling studies that rely on the Δ33S record as well as for studies attempting to document larger-scale, lithofacies-specific trends in sulfur isotopic signals. Finally, our results are consistent with locally increasing sulfate concentrations along this Archean continental shelf and may correspond to an increase in low-level O2 production prior to the Great Oxygenation Event.

  13. Rapid Adsorption of Copper(II) and Lead(II) by Rice Straw/Fe3O4 Nanocomposite: Optimization, Equilibrium Isotherms, and Adsorption Kinetics Study

    Science.gov (United States)

    Khandanlou, Roshanak; Ahmad, Mansor B.; Fard Masoumi, Hamid Reza; Shameli, Kamyar; Basri, Mahiran; Kalantari, Katayoon

    2015-01-01

    Rice straw/magnetic nanocomposites (RS/Fe3O4-NCs) were prepared via co-precipitation method for removal of Pb(II) and Cu(II) from aqueous solutions. Response surface methodology (RSM) was utilized to find the optimum conditions for removal of ions. The effects of three independent variables including initial ion concentration, removal time, and adsorbent dosage were investigated on the maximum adsorption of Pb (II) and Cu (II). The optimum conditions for the adsorption of Pb(II) and Cu(II) were obtained (100 and 60 mg/L) of initial ion concentration, (41.96 and 59.35 s) of removal time and 0.13 g of adsorbent for both ions, respectively. The maximum removal efficiencies of Pb(II) and Cu(II) were obtained 96.25% and 75.54%, respectively. In the equilibrium isotherm study, the adsorption data fitted well with the Langmuir isotherm model. The adsorption kinetics was best depicted by the pseudo-second order model. Desorption experiments showed adsorbent can be reused successfully for three adsorption-desorption cycles. PMID:25815470

  14. Isotopically exchangeable phosphorus

    International Nuclear Information System (INIS)

    Barbaro, N.O.

    1984-01-01

    A critique revision of isotope dilution is presented. The concepts and use of exchangeable phosphorus, the phosphate adsorption, the kinetics of isotopic exchange and the equilibrium time in soils are discussed. (M.A.C.) [pt

  15. 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.

  16. Global distribution of beryllium isotopes in deep ocean water as derived from Fe-Mn crusts

    Science.gov (United States)

    Von Blanckenburg, F.; O'Nions, R. K.; Belshaw, N.S.; Gibb, A.; Hein, J.R.

    1996-01-01

    The direct measurement of the ratio of cosmogenic 10Be (T1/2 = 1.5 Ma) to stable terrigenously sourced 9Be in deep seawater or marine deposits can be used to trace water mass movements and to quantify the incorporation of trace metals into the deep sea. In this study a SIMS-based technique has been used to determine the 10Be/9Be ratios of the outermost millimetre of hydrogenetic ferromanganese crusts from the worlds oceans. 10Be/9Be ratios, time-corrected for radioactive decay of cosmogenic 10Be using 234U/ 238U, are in good agreement with AMS measurements of modern deep seawater. Ratios are relatively low in the North and equatorial Atlantic samples (0.4-0.5 ?? 10-7). In the Southwest Atlantic ratios increase up to 1 ?? 10-7, they vary between 0.7 and 1.0 ?? 10-7 in Indian Ocean samples, and have a near constant value of 1.1 ?? 0.2 ?? 10-7 for all Pacific samples. If the residence time of 10Be (??10Be) in deep water is constant globally, then the observed variations in 10Be/9Be ratios could be caused by accumulation of 10Be in deep water as it flows and ages along the conveyor, following a transient depletion upon its formation in the Northern Atlantic. In this view both 10Be and 9Be reach local steady-state concentration in Pacific deep water and the global ??10Be ??? 600 a. An alternative possibility is that the Be isotope abundances are controlled by local scavenging. For this scenario ??10Be would vary according to local particle concentration and would ??? 600 a in the central Pacific, but ??10Be ??? 230 a in the Atlantic. Mass balance considerations indicate that hydrothermal additions of 9Be to the oceans are negligible and that the dissolved riverine source is also small. Furthermore, aeolian dust input of 9Be appears insufficient to provide the dissolved Be inventory. The dissolution of only a small proportion (2%) of river-derived particulates could in principle supply the observed seawater Be content. If true, ocean margins would be the sites for 9Be

  17. A universal fluorogenic switch for Fe(ii) ion based on N-oxide chemistry permits the visualization of intracellular redox equilibrium shift towards labile iron in hypoxic tumor cells.

    Science.gov (United States)

    Hirayama, Tasuku; Tsuboi, Hitomi; Niwa, Masato; Miki, Ayaji; Kadota, Satoki; Ikeshita, Yukie; Okuda, Kensuke; Nagasawa, Hideko

    2017-07-01

    Iron (Fe) species play a number of biologically and pathologically important roles. In particular, iron is a key element in oxygen sensing in living tissue where its metabolism is intimately linked with oxygen metabolism. Regulation of redox balance of labile iron species to prevent the generation of iron-catalyzed reactive oxygen species (ROS) is critical to survival. However, studies on the redox homeostasis of iron species are challenging because of a lack of a redox-state-specific detection method for iron, in particular, labile Fe 2+ . In this study, a universal fluorogenic switching system is established, which is responsive to Fe 2+ ion based on a unique N-oxide chemistry in which dialkylarylamine N-oxide is selectively deoxygenized by Fe 2+ to generate various fluorescent probes of Fe 2+ -CoNox-1 (blue), FluNox-1 (green), and SiRhoNox-1 (red). All the probes exhibited fluorescence enhancement against Fe 2+ with high selectivity both in cuvette and in living cells. Among the probes, SiRhoNox-1 showed an excellent fluorescence response with respect to both reaction rate and off/on signal contrast. Imaging studies were performed showing the intracellular redox equilibrium shift towards labile iron in response to reduced oxygen tension in living cells and 3D tumor spheroids using SiRhoNox-1, and it was found that the hypoxia induction of labile Fe 2+ is independent of iron uptake, hypoxia-induced signaling, and hypoxia-activated enzymes. The present studies demonstrate the feasibility of developing sensitive and specific fluorescent probes for Fe 2+ with refined photophysical characteristics that enable their broad application in the study of iron in various physiological and pathological conditions.

  18. Evaluation of Fe3O4@MnO2 core-shell magnetic nanoparticles as an adsorbent for decolorization of methylene blue dye in contaminated water: Synthesis and characterization, kinetic, equilibrium, and thermodynamic studies

    Science.gov (United States)

    Shayesteh, Hadi; Ashrafi, Amir; Rahbar-Kelishami, Ahmad

    2017-12-01

    In this study, Fe3O4@MnO2 core-shell nanoparticles were synthesis by a simple one-pot method. These nanoparticles were applied for removal of methylene blue (MB) ions from aqueous solution by a batch technique and characterized by TEM, XRD, EDS, FTI), FE-SE, VSM and BET surface area measurement. The influence of different adsorption parameters, such as contact time, adsorbent dosage, initial concentration of MB ions, pH value of solution and temperature have been investigated. Three isotherm equations, Langmuir, Freundlich, and Tempkin, have been tested in order to describe the equilibrium characteristics of adsorption. The equilibrium data for adsorption of MB were fitted well by Freundlich isotherm and the maximum adsorption capacity of Langmuir was 434.78 mg/g at 298 K approximately. The experimental results were fitted better with pseudo-second-order model compared to the other two models. In addition, thermodynamic calculations revealed that the adsorption process was spontaneous, exothermic and feasible. The result of experimental shows that Fe3O4@MnO2 nanoparticles is suitable adsorbent for removal of MB from aqueous solutions.

  19. Phosphorus Equilibrium Between Liquid Iron and CaO-SiO2-MgO-Al2O3-FeO-P2O5 Slag Part 1: Literature Review, Methodology, and BOF Slags

    Science.gov (United States)

    Assis, Andre N.; Tayeb, Mohammed A.; Sridhar, Seetharaman; Fruehan, Richard J.

    2015-10-01

    Although the phosphorus reaction in steelmaking has been extensively studied, it continues to be a relevant topic as low phosphorus iron sources become less available and more expensive, necessitating the need for more accurate predictions of the partitioning of phosphorous as function of slag composition and temperature. The current study revisits some of the relevant literature on the topic and details the methodology and experimental setup used in recent studies on phosphorus equilibrium between liquid iron and slags. New data for BOF-type slags are presented, where equilibrium was approached from both metal and slag sides i.e., phosphorus was transferred from metal to slag and vice versa. It was found that slags with basicities higher than 2.5 and FeO contents around 20 to 25 wt pct can promote extensive dephosphorization, and high L P, ((pct P)/[pct P]), values were observed i.e., greater than 500.

  20. A new model and gas sensitivity of non-equilibrium xSnO2-(1-x)alpha-Fe2O3 nanopowders prepared by mechanical alloying

    DEFF Research Database (Denmark)

    Zhu, W.; Tan, O.K.; Jiang, Jianzhong

    1998-01-01

    Nano-sized xSnO2-(1-x)alpha-Fe2O3 materials have been prepared using the high energy ball milling technique and their structural and gas sensing properties have been characterized. Based on experimental results, we propose a new structure model, xxx, forthese non-equilibrium, nano-sized xSnO2-(1-x......)alpha-Fe2O3 materials. This model can explain non only the lattice expansion of the milled samples, but also takes into account the charge balance by adding oxygen dangling bonds at the particle surfaces, which can be visualized in the nano-sized powders. The thich film gas sensors made by such mechanically...

  1. Evaluation of Kinetic and Equilibrium Parameters of NiFe2O4 Nanoparticles on Adsorption of Reactive Orange Dye from Water

    Directory of Open Access Journals (Sweden)

    Raziyeh Zandipak

    2016-02-01

    Full Text Available Background: Among different pollutants released into the environment, dyes are considered as one of the most dangerous contaminants. In recent years, magnetic nanomaterials have attracted much attention for their dye removal capacity. The aim of this study was to explore the adsorption kinetics of an anionic dye (Reactive Orange 13 (RO by NiFe2O4 nanoparticles (NiFe2O4 NPs under various conditions. Methods: NiFe2O4 nanoparticles (NiFe2O4 NPs were prepared and characterized by X-ray diffraction (XRD, transmission electronic microscopy (TEM, pHpzc and BET methods. The adsorption characteristics of the NiFe2O4 NPs adsorbent were examined using Reactive Orange 13 as an adsorbate. The influences of parameters including pH, dose of adsorbent and contact time were investigated to find the optimum adsorption conditions. Results: Decreasing solution pH and increasing contact time were favorable for improving adsorption efficiency. The kinetic and isotherm data of RO adsorption on NiFe2O4 NPs were well fitted by pseudo-second-order and Langmuir models, respectively. Conclusion: The maximal adsorption capacity of RO was 243.9 mg g-1 at 25◦C and pH 3.0 and the adsorption of RO on the NiFe2O4 NPs follows a monolayer coverage model. NiFe2O4 NPs might be an effective and potential adsorbent for removing anionic dyes from aqueous solutions.

  2. Determination of the cation distribution in Fe2Ni(PO4)2 using isotopic substitution and powder neutron diffraction

    International Nuclear Information System (INIS)

    Henry, P.F.; Weller, M.T.; Wilson, C.C.

    2003-01-01

    The distribution of divalent iron and nickel over the two metal sites with differing coordination geometry in Fe 2 Ni(PO 4 ) 2 , sarcopside, has been investigated using time-of-flight powder neutron diffraction of nickel isotopically substituted materials. Data from four separate samples were collected using HRPD at ISIS, containing nat Ni, 58 Ni, 60 Ni and 62 Ni, under identical conditions. The occupancy of iron on the M(1) site was found to be 0.290 (1) from a combined-data-set Rietveld refinement of the three isotopically substituted samples, compared with 0.26 (4) and 0.26 (15) respectively from this and a previous time-of-flight powder neutron diffraction study using natural-abundance nickel, and 0.366 (6) and 0.376 (3) using anomalous X-ray scattering techniques. A critical comparison of isotope substitution neutron diffraction and anomalous X-ray scattering methods for distinguishing nickel and iron from powder data is presented. (orig.)

  3. A rapid and precise procedure for Pb isotopes in whole blood by Fe co-precipitation and MC-ICPMS analysis

    International Nuclear Information System (INIS)

    Chillrud, Steven N.; Hemming, N. Gary; Ross, James M.; Wallace, Sean; LoIacono, Nancy

    2005-01-01

    Elevated Pb levels in humans through environmental exposure are a significant health concern requiring scientific study of the sources of, and physiological response to this toxin. This requires a simple and precise method for measuring radiogenic Pb isotopes and Pb levels in blood. Presented here is a combination of methods for separation and analysis of Pb previously used predominantly for geologic samples. This includes separation of Pb from the complex matrix of blood samples using an Fe co-precipitation method, followed by isotopic analysis by multi-collector inductively coupled plasma mass spectrometry. Evaluation of the efficacy of this procedure shows that the precision of sample preparations as measured by % difference between the 207 Pb/ 206 Pb of duplicate analyses averages 0.064% (n = 48). Using the same preparation and analysis techniques to measure Pb concentrations by isotope dilution resulted in a reproducibility of better than 6%. The method was successfully used to measure uptake of ingested soil Pb in a study of the bioavailability of Pb in contaminated soils

  4. Application of nano-magnesso ferrite (n-MgFe{sub 2}O{sub 4}) for the removal of Co{sup 2+} ions from synthetic wastewater: Kinetic, equilibrium and thermodynamic studies

    Energy Technology Data Exchange (ETDEWEB)

    Srivastava, Varsha, E-mail: varsha06bhu@gmail.com [Laboratory of Green Chemistry, Faculty of Technology, Lappeenranta University of Technology, Sammonkatu 12, FI-50130 Mikkeli (Finland); Sharma, Y.C. [Department of Chemistry, Indian Institute of Technology, Banaras Hindu University, Varanasi 221005 (India); Sillanpää, Mika [Laboratory of Green Chemistry, Faculty of Technology, Lappeenranta University of Technology, Sammonkatu 12, FI-50130 Mikkeli (Finland)

    2015-05-30

    Graphical abstract: - Highlights: • The removal efficiency of n-MgFe{sub 2}O{sub 4} for Co(II) ions was investigated. • Rapid removal efficiency was observed within 60 min of contact time. • The kinetic data of Co(II) followed the pseudo-second-order model. • Thermodynamic studies revealed that the adsorption reaction was spontaneous. • Desorption study demonstrated its reusability upto three adsorption–desorption cycles. - Abstract: The aim of this research is to investigate the adsorption characteristics of nano-magnesso ferrite (n-MgFe{sub 2}O{sub 4}) for the removal of Co(II) ions from aqueous solution. n-MgFe{sub 2}O{sub 4} was synthesized by precipitation method. XRD of synthesized particles reveals the formation of single-phase n-MgFe{sub 2}O{sub 4} nanoparticles. TEM confirms the formation of particle size in the range of 25–35 nm. AFM and SEM analysis also support the TEM result. BET surface area of nanoparticles was determined to be 53.83 m{sup 2}/g. The adsorption of Co(II) onto n-MgFe{sub 2}O{sub 4} was found to be dependent on pH and the removal increased in alkaline medium. Co(II) adsorption followed pseudo-second-order model. Thermodynamic study showed that the adsorption process was endothermic and spontaneous. The equilibrium adsorption data was analyzed by two parameters and three parameters isotherm. Langmuir adsorption capacity was determined to be 67.41 mg/g. Chi-square test, standard deviations and the sum of squares of the errors (SSE) were evaluated to find out the better isotherm model. Desorption and reusability test suggested that n-MgFe{sub 2}O{sub 4} can be efficiently used up to three adsorption–desorption cycles. The findings of the present study suggest that n-MgFe{sub 2}O{sub 4} is very efficient for the adsorption of Co(II) ions. Adsorption efficiency of n-MgFe{sub 2}O{sub 4} for Co(II) has not yet been studied, so this study can be helpful for the treatment of Co(II) rich wastewater in near future.

  5. Origin of the volcanic-hosted Yamansu Fe deposit, Eastern Tianshan, NW China: constraints from pyrite Re-Os isotopes, stable isotopes, and in situ magnetite trace elements

    Science.gov (United States)

    Huang, Xiao-Wen; Zhou, Mei-Fu; Beaudoin, Georges; Gao, Jian-Feng; Qi, Liang; Lyu, Chuan

    2018-01-01

    The Yamansu Fe deposit (32 Mt at 51% Fe) in the Eastern Tianshan Orogenic Belt of NW China is hosted in early Carboniferous volcano-sedimentary rocks and spatially associated with skarn. The paragenetic sequence includes garnet-diopside (I), magnetite (II), hydrous silicate-sulfide (III), and calcite-quartz (IV) stages. Pyrite associated with magnetite has a Re-Os isochron age of 322 ± 7 Ma, which represents the timing of pyrite and, by inference, magnetite mineralization. Pyrite has δ 34SVCDT values of - 2.2 to + 2.9‰, yielding δ 34SH2S values of - 3.1 to 2‰, indicating the derivation of sulfur from a magmatic source. Calcite from stages II and IV has δ 13CVPDB values from - 2.5 to - 1.2‰, and - 1.1 to 1.1‰, and δ 18OVSMOW values from 11.8 to 12.0‰ and - 7.7 to - 5.2‰, respectively. Calculated δ 13C values of fluid CO2 and water δ 18O values indicate that stage II hydrothermal fluids were derived from magmatic rocks and that meteoric water mixed with the hydrothermal fluids in stage IV. Some ores contain magnetite with obvious chemical zoning composed of dark and light domains in BSE images. Dark domains have higher Mg, Al, Ca, Mn, and Ti but lower Fe and Cr contents than light domains. The chemical zoning resulted from a fluctuating fluid composition and/or physicochemical conditions (oscillatory zoning), or dissolution-precipitation (irregular zoning) via infiltration of magmatic-hydrothermal fluids diluted by late meteoric water. Iron was mainly derived from fluids similar to that in skarn deposits.

  6. Adsorption of C.I. Reactive Red 228 and Congo Red dye from aqueous solution by amino-functionalized Fe3O4 particles: kinetics, equilibrium, and thermodynamics.

    Science.gov (United States)

    Yan, Ting-guo; Wang, Li-Juan

    2014-01-01

    A magnetic adsorbent was synthesized by γ-aminopropyltriethoxysilane (APTES) modification of Fe(3)O(4) particles using a two-step process. Scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), and vibration sample magnetometry were used to characterize the obtained magnetic adsorbent. EDS and XPS showed that APTES polymer was successfully introduced onto the as-prepared Fe(3)O(4)/APTES particle surfaces. The saturation magnetization of the magnetic adsorbent was around 65 emu g(-1), which indicated that the dye can be removed fast and efficiently from aqueous solution with an external magnetic field. The maximum adsorption capacities of Fe(3)O(4)/APTES for C.I. Reactive Red 228 (RR 228) and Congo Red (CR) were 51.4 and 118.8 mg g(-1), respectively. The adsorption of C.I. Reactive Red 228 (RR 228) and Congo Red (CR) on Fe(3)O(4)/APTES particles corresponded well to the Langmuir model and the Freundlich model, respectively. The adsorption processes for RR 228 and CR followed the pseudo-second-order model. The Boyd's film-diffusion model showed that film diffusion also played a major role in the studied adsorption processes for both dyes. Thermodynamic study indicated that both of the adsorption processes of the two dyes are spontaneous exothermic.

  7. Iron isotopic fractionation between silicate mantle and metallic core at high pressure

    Science.gov (United States)

    Liu, Jin; Dauphas, Nicolas; Roskosz, Mathieu; Hu, Michael Y.; Yang, Hong; Bi, Wenli; Zhao, Jiyong; Alp, Esen E.; Hu, Justin Y.; Lin, Jung-Fu

    2017-02-01

    The +0.1‰ elevated 56Fe/54Fe ratio of terrestrial basalts relative to chondrites was proposed to be a fingerprint of core-mantle segregation. However, the extent of iron isotopic fractionation between molten metal and silicate under high pressure-temperature conditions is poorly known. Here we show that iron forms chemical bonds of similar strengths in basaltic glasses and iron-rich alloys, even at high pressure. From the measured mean force constants of iron bonds, we calculate an equilibrium iron isotope fractionation between silicate and iron under core formation conditions in Earth of ~0-0.02‰, which is small relative to the +0.1‰ shift of terrestrial basalts. This result is unaffected by small amounts of nickel and candidate core-forming light elements, as the isotopic shifts associated with such alloying are small. This study suggests that the variability in iron isotopic composition in planetary objects cannot be due to core formation.

  8. Calculation of (n,xγ) cross sections between threshold and 100 MeV for Fe and Pb isotopes: Comparisons with experimental data

    International Nuclear Information System (INIS)

    Young, P.G.; Haight, R.C.; Nelson, R.O.

    1991-01-01

    An experimental program is in progress at the Los Alamos National Laboratory WNR/LAMPF facility to perform high-resolution measurements of (n,xγ) cross sections for individual lines up to incident neutron energies in the medium-energy range for a variety of target materials. Part of the purpose of these measurements is to provide a data base for testing the details of nuclear models in this energy range, with the goal of facilitating model improvements. In this paper initial calculations using the GNASH nuclear theory code and the level density models of Gilbert-Cameron and Ignatyuk are described. The results are compared to the existing experimental data base for 204,206,207,208 Pb isotopes at lower energies and to preliminary data from the WNR/LAMPF measurements on nat Fe and 208 Pb up to E n = 100 MeV. (author). 27 refs, 14 figs

  9. Constraining the role of iron in environmental nitrogen transformations. Dual stable isotope systematics of abiotic NO2- reduction by Fe(II) and its production of N2O

    Energy Technology Data Exchange (ETDEWEB)

    Johnston, David [Harvard Univ., Cambridge, MA (United States); Wankel, Scott David [Woods Hole Oceanographic Inst., MA (United States); Buchwald, Carolyn [Woods Hole Oceanographic Inst., MA (United States); Hansel, Colleen [Woods Hole Oceanographic Inst., MA (United States)

    2015-09-16

    Redox reactions involving nitrogen and iron have been shown to have important implications for mobilization of priority contaminants. Thus, an understanding of the linkages between their biogeochemical cycling is critical for predicting subsurface mobilization of radionuclides such as uranium. Despite mounting evidence for biogeochemical interactions between iron and nitrogen, our understanding of their environmental importance remains limited. Here we present an investigation of abiotic nitrite (NO2-) reduction by Fe(II) or ‘chemodenitrification,’ and its relevance to the production of nitrous oxide (N2O), specifically focusing on dual (N and O) isotope systematics under a variety of environmentally relevant conditions. We observe a range of kinetic isotope effects that are regulated by reaction rates, with faster rates at higher pH (~8), higher concentrations of Fe(II) and in the presence of mineral surfaces. A clear non-linear relationship between rate constant and kinetic isotope effects of NO2- reduction was evident (with larger isotope effects at slower rates) and is interpreted as reflecting the dynamics of Fe(II)-N reaction intermediates. N and O isotopic composition of product N2O also suggests a complex network of parallel and/or competing pathways. Our findings suggest that NO2- reduction by Fe(II) may represent an important abiotic source of environmental N2O, especially in iron-rich environments experiencing dynamic redox variations. This study provides a multi-compound, multi-isotope framework for evaluating the environmental occurrence of abiotic NO2- reduction and N2O formation, helping future studies constrain the relative roles of abiotic and biological N2O production pathways.

  10. Analysis of trace metals (Cu, Cd, Pb, and Fe) in seawater using single batch nitrilotriacetate resin extraction and isotope dilution inductively coupled plasma mass spectrometry

    International Nuclear Information System (INIS)

    Lee, Jong-Mi; Boyle, Edward A.; Echegoyen-Sanz, Yolanda; Fitzsimmons, Jessica N.; Zhang Ruifeng; Kayser, Richard A.

    2011-01-01

    A simple and accurate low-blank method has been developed for the analysis of total dissolved copper, cadmium, lead, and iron in a small volume (1.3-1.5 mL per element) of seawater. Pre-concentration and salt-separation of a stable isotope spiked sample are achieved by single batch extraction onto nitrilotriacetate (NTA)-type Superflow chelating resin beads (100-2400 beads depending on the element). Metals are released into 0.1-0.5 M HNO 3 , and trace metal isotope ratios are determined by ICPMS. The benefit of this method compared to our previous Mg(OH) 2 coprecipitation method is that the final matrix is very dilute so cone-clogging and matrix sensitivity suppression are minimal, while still retaining the high accuracy of the isotope dilution technique. Recovery efficiencies are sensitive to sample pH, number of resin beads added, and the length of time allowed for sample-resin binding and elution; these factors are optimized for each element to yield the highest recovery. The method has a low procedural blank and high sensitivity sufficient for the analysis of pM-nM open-ocean trace metal concentrations. Application of this method to samples from the Bermuda Atlantic Time-Series Study station provides oceanographically consistent Cu, Cd, Pb, and Fe profiles that are in good agreement with other reliable data for this site. In addition, the method can potentially be modified for the simultaneous analysis of multiple elements, which will be beneficial for the analysis of large number of samples.

  11. Analysis of trace metals (Cu, Cd, Pb, and Fe) in seawater using single batch nitrilotriacetate resin extraction and isotope dilution inductively coupled plasma mass spectrometry

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Jong-Mi [Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States); Boyle, Edward A., E-mail: eaboyle@mit.edu [Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States); Echegoyen-Sanz, Yolanda; Fitzsimmons, Jessica N. [Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States); Zhang Ruifeng [State Key Laboratory of Estuarine and Coastal Research, East China Normal University, Shanghai 200062 (China); Kayser, Richard A. [Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States)

    2011-02-07

    A simple and accurate low-blank method has been developed for the analysis of total dissolved copper, cadmium, lead, and iron in a small volume (1.3-1.5 mL per element) of seawater. Pre-concentration and salt-separation of a stable isotope spiked sample are achieved by single batch extraction onto nitrilotriacetate (NTA)-type Superflow chelating resin beads (100-2400 beads depending on the element). Metals are released into 0.1-0.5 M HNO{sub 3}, and trace metal isotope ratios are determined by ICPMS. The benefit of this method compared to our previous Mg(OH){sub 2} coprecipitation method is that the final matrix is very dilute so cone-clogging and matrix sensitivity suppression are minimal, while still retaining the high accuracy of the isotope dilution technique. Recovery efficiencies are sensitive to sample pH, number of resin beads added, and the length of time allowed for sample-resin binding and elution; these factors are optimized for each element to yield the highest recovery. The method has a low procedural blank and high sensitivity sufficient for the analysis of pM-nM open-ocean trace metal concentrations. Application of this method to samples from the Bermuda Atlantic Time-Series Study station provides oceanographically consistent Cu, Cd, Pb, and Fe profiles that are in good agreement with other reliable data for this site. In addition, the method can potentially be modified for the simultaneous analysis of multiple elements, which will be beneficial for the analysis of large number of samples.

  12. Magnesium isotopic evidence for chemical disequilibrium among cumulus minerals in layered mafic intrusion

    Science.gov (United States)

    Chen, Lie-Meng; Teng, Fang-Zhen; Song, Xie-Yan; Hu, Rui-Zhong; Yu, Song-Yue; Zhu, Dan; Kang, Jian

    2018-04-01

    Magnesium isotopic compositions of olivine, clinopyroxene, and ilmenite from the Baima intrusion, SW China, for the first time, are investigated to constrain the magnitude and mechanisms of Mg isotope fractionation among cumulus minerals in layered mafic intrusions and to evaluate their geological implications. Olivine and clinopyroxene have limited Mg isotope variations, with δ26Mg ranging from -0.33 to +0.05‰ and from -0.29 to -0.13‰, respectively, similar to those of mantle xenolithic peridotites. By contrast, ilmenites display extremely large Mg isotopic variation, with δ26Mg ranging from -0.50 to +1.90‰. The large inter-mineral fractionations of Mg isotopes between ilmenite and silicates may reflect both equilibrium and kinetic processes. A few ilmenites have lighter Mg isotopic compositions than coexisting silicates and contain high MgO contents without compositional zoning, indicating equilibrium fractionation. The implication is that the light Mg isotopic compositions of lunar high-Ti basalts may result from an isotopically light source enriched in cumulate ilmenites. On the other hand, most ilmenites have heavy Mg isotopic compositions, coupled with high MgO concentration and chemical zoning, which can be quantitatively modeled by kinetic Mg isotope fractionations induced by subsolidus Mg-Fe exchange between ilmenite and ferromagnesian silicates during the cooling of the Baima intrusion. The extensive occurrence of kinetic Mg isotope fractionation in ilmenites implies the possibility of widespread compositional disequilibrium among igneous minerals in magma chambers. Consequently, disequilibrium effects need to be considered in studies of basaltic magma evolution, magma chamber processes, and magmatic Fe-Ti oxide ore genesis.

  13. 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. Copyright © 2015, American Association for the Advancement of Science.

  14. Equilibrium Dialysis

    African Journals Online (AJOL)

    context of antimicrobial therapy in malnutrition. Dialysis has in the past presented technical problems, being complicated and time-consuming. A new dialysis system based on the equilibrium technique has now become available, and it is the principles and practical application of this apparatus (Kontron Diapack; Kontron.

  15. Maximin equilibrium

    NARCIS (Netherlands)

    Ismail, M.S.

    2014-01-01

    We introduce a new concept which extends von Neumann and Morgenstern's maximin strategy solution by incorporating `individual rationality' of the players. Maximin equilibrium, extending Nash's value approach, is based on the evaluation of the strategic uncertainty of the whole game. We show that

  16. Strategic Equilibrium

    NARCIS (Netherlands)

    van Damme, E.E.C.

    2000-01-01

    An outcome in a noncooperative game is said to be self-enforcing, or a strategic equilibrium, if, whenever it is recommended to the players, no player has an incentive to deviate from it.This paper gives an overview of the concepts that have been proposed as formalizations of this requirement and of

  17. Minimal Influence of [NiFe] Hydrogenase on Hydrogen Isotope Fractionation in H2-Oxidizing Cupriavidus necator

    Directory of Open Access Journals (Sweden)

    Brian J. Campbell

    2017-10-01

    Full Text Available Fatty acids produced by H2-metabolizing bacteria are sometimes observed to be more D-depleted than those of photoautotrophic organisms, a trait that has been suggested as diagnostic for chemoautotrophic bacteria. The biochemical reasons for such a depletion are not known, but are often assumed to involve the strong D-depletion of H2. Here, we cultivated the bacterium Cupriavidus necator H16 (formerly Ralstonia eutropha H16 under aerobic, H2-consuming, chemoautotrophic conditions and measured the isotopic compositions of its fatty acids. In parallel with the wild type, two mutants of this strain, each lacking one of two key hydrogenase enzymes, were also grown and measured. In all three strains, fractionations between fatty acids and water ranged from -173‰ to -235‰, and averaged -217‰, -196‰, and -226‰, respectively, for the wild type, SH- mutant, and MBH- mutant. There was a modest increase in δD as a result of loss of the soluble hydrogenase enzyme. Fractionation curves for all three strains were constructed by growing parallel cultures in waters with δDwater values of approximately -25‰, 520‰, and 1100‰. These curves indicate that at least 90% of the hydrogen in fatty acids is derived from water, not H2. Published details of the biochemistry of the soluble and membrane-bound hydrogenases confirm that these enzymes transfer electrons rather than intact hydride (H- ions, providing no direct mechanism to connect the isotopic composition of H2 to that of lipids. Multiple lines of evidence thus agree that in this organism, and presumably others like it, environmental H2 plays little or no direct role in controlling lipid δD values. The observed fractionations must instead result from isotope effects in the reduction of NAD(PH by reductases with flavin prosthetic groups, which transfer two electrons and acquire H+ (or D+ from solution. Parallels to NADPH reduction in photosynthesis may explain why D/H fractionations in C. necator

  18. Minimal Influence of [NiFe] Hydrogenase on Hydrogen Isotope Fractionation in H2-OxidizingCupriavidus necator.

    Science.gov (United States)

    Campbell, Brian J; Sessions, Alex L; Fox, Daniel N; Paul, Blair G; Qin, Qianhui; Kellermann, Matthias Y; Valentine, David L

    2017-01-01

    Fatty acids produced by H 2 -metabolizing bacteria are sometimes observed to be more D-depleted than those of photoautotrophic organisms, a trait that has been suggested as diagnostic for chemoautotrophic bacteria. The biochemical reasons for such a depletion are not known, but are often assumed to involve the strong D-depletion of H 2 . Here, we cultivated the bacterium Cupriavidus necator H16 (formerly Ralstonia eutropha H16) under aerobic, H 2 -consuming, chemoautotrophic conditions and measured the isotopic compositions of its fatty acids. In parallel with the wild type, two mutants of this strain, each lacking one of two key hydrogenase enzymes, were also grown and measured. In all three strains, fractionations between fatty acids and water ranged from -173‰ to -235‰, and averaged -217‰, -196‰, and -226‰, respectively, for the wild type, SH - mutant, and MBH - mutant. There was a modest increase in δD as a result of loss of the soluble hydrogenase enzyme. Fractionation curves for all three strains were constructed by growing parallel cultures in waters with δD water values of approximately -25‰, 520‰, and 1100‰. These curves indicate that at least 90% of the hydrogen in fatty acids is derived from water, not H 2 . Published details of the biochemistry of the soluble and membrane-bound hydrogenases confirm that these enzymes transfer electrons rather than intact hydride (H - ) ions, providing no direct mechanism to connect the isotopic composition of H 2 to that of lipids. Multiple lines of evidence thus agree that in this organism, and presumably others like it, environmental H 2 plays little or no direct role in controlling lipid δD values. The observed fractionations must instead result from isotope effects in the reduction of NAD(P)H by reductases with flavin prosthetic groups, which transfer two electrons and acquire H + (or D + ) from solution. Parallels to NADPH reduction in photosynthesis may explain why D/H fractionations in C

  19. The effect of carbonic anhydrase on the kinetics and equilibrium of the oxygen isotope exchange in the CO2-H2O system: Implications for δ18O vital effects in biogenic carbonates

    Science.gov (United States)

    Uchikawa, Joji; Zeebe, Richard E.

    2012-10-01

    Interpretations of the primary paleoceanographic information recorded in stable oxygen isotope values (δ18O) of biogenic CaCO3 can be obscured by disequilibrium effects. CaCO3 is often depleted in 18O relative to the δ18O values expected for precipitation in thermodynamic equilibrium with ambient seawater as a result of vital effects. Vital effects in δ18O have been explained in terms of the influence of fluid pH on the overall δ18O of the sum of dissolved inorganic carbon (DIC) species (often referred to as "pH model") and in terms of 18O depletion as a result of the kinetic effects associated with CO2 hydration (CO2 + H2O ↔ H2CO3 ↔ HCO3- + H+) and CO2 hydroxylation (CO2 + OH- ↔ HCO3-) in the calcification sites (so-called "kinetic model"). This study addresses the potential role of an enzyme, carbonic anhydrase (CA), that catalyzes inter-conversion of CO2 and HCO3- in relation to the underlying mechanism of vital effects. We performed quantitative inorganic carbonate precipitation experiments in order to examine the changes in 18O equilibration rate as a function of CA concentration. Experiments were performed at pH 8.3 and 8.9. These pH values are comparable to the average surface ocean pH and elevated pH levels observed in the calcification sites of some coral and foraminiferal species, respectively. The rate of uncatalyzed 18O exchange in the CO2-H2O system is governed by the pH-dependent DIC speciation and the kinetic rate constant for CO2 hydration and hydroxylation, which can be summarized by a simple mathematical expression. The results from control experiments (no CA addition) are in agreement with this expression. The results from control experiments also suggest that the most recently published kinetic rate constant for CO2 hydroxylation has been overestimated. When CA is present, the 18O equilibration process is greatly enhanced at both pH levels due to the catalysis of CO2 hydration by the enzyme. For example, the time required for 18O

  20. Sweatshop Equilibrium

    OpenAIRE

    Chau, Nancy

    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...

  1. Phase Equilibrium Experiments on Potential Lunar Core Compositions: Extension of Current Knowledge to Multi-Component (Fe-Ni-Si-S-C) Systems

    Science.gov (United States)

    Righter, K.; Pando, K.; Danielson, L.

    2014-01-01

    Numerous geophysical and geochemical studies have suggested the existence of a small metallic lunar core, but the composition of that core is not known. Knowledge of the composition can have a large impact on the thermal evolution of the core, its possible early dynamo creation, and its overall size and fraction of solid and liquid. Thermal models predict that the current temperature at the core-mantle boundary of the Moon is near 1650 K. Re-evaluation of Apollo seismic data has highlighted the need for new data in a broader range of bulk core compositions in the PT range of the lunar core. Geochemical measurements have suggested a more volatile-rich Moon than previously thought. And GRAIL mission data may allow much better constraints on the physical nature of the lunar core. All of these factors have led us to determine new phase equilibria experimental studies in the Fe-Ni-S-C-Si system in the relevant PT range of the lunar core that will help constrain the composition of Moon's core.

  2. Thallium isotope variations in seawater and hydrogenetic, diagenetic, and hydrothermal ferromanganese deposits

    Science.gov (United States)

    Rehkamper, M.; Frank, M.; Hein, J.R.; Porcelli, D.; Halliday, A.; Ingri, J.; Liebetrau, V.

    2002-01-01

    Results are presented for the first in-depth investigation of TI isotope variations in marine materials. The TI isotopic measurements were conducted by multiple collector-inductively coupled plasma mass spectrometry for a comprehensive suite of hydrogenetic ferromanganese crusts, diagenetic Fe-Mn nodules, hydrothermal manganese deposits and seawater samples. The natural variability of TI isotope compositions in these samples exceeds the analytical reproducibility (?? 0.05???) by more than a factor of 40. Hydrogenetic Fe-Mn crusts have ??205TI of + 10 to + 14, whereas seawater is characterized by values as low as -8 (??205TI represents the deviation of the 205TI/203TI ratio of a sample from the NIST SRM 997 TI isotope standard in parts per 104). This ~ 2??? difference in isotope composition is thought to result from the isotope fractionation that accompanies the adsorption of TI onto ferromanganese particles. An equilibrium fractionation factor of ?? ~ 1.0021 is calculated for this process. Ferromanganese nodules and hydrothermal manganese deposits have variable TI isotope compositions that range between the values obtained for seawater and hydrogenetic Fe-Mn crusts. The variability in ??205TI in diagenetic nodules appears to be caused by the adsorption of TI from pore fluids, which act as a closed-system reservoir with a TI isotope composition that is inferred to be similar to seawater. Nodules with ??205TI values similar to seawater are found if the scavenging of TI is nearly quantitative. Hydrothermal manganese deposits display a positive correlation between ??205TI and Mn/Fe. This trend is thought to be due to the derivation of TI from distinct hydrothermal sources. Deposits with low Mn/Fe ratios and low ??205TI are produced by the adsorption of TI from fluids that are sampled close to hydrothermal sources. Such fluids have low Mn/Fe ratios and relatively high temperatures, such that only minor isotope fractionation occurs during adsorption. Hydrothermal

  3. Mass measurements of neutron rich isotopes in the Fe region and electron capture processes in neutron star crusts

    International Nuclear Information System (INIS)

    Estrade, Alfredo; Matos, M.; Schatz, Hendrik; Amthor, A.M.; Beard, Mary; Brown, Edward; Bazin, D.; Becerril, A.; Elliot, T.; Gade, A.; Galaviz, D.; Gupta, Sanjib; Hix, William Raphael; Lau, Rita; Moeller, Peter; Pereira, J.; Portillo, M.; Rogers, A.M.; Shapira, Dan; Smith, E.; Stolz, A.; Wallace, M.; Wiescher, Michael

    2011-01-01

    Experimental knowledge of nuclear masses of exotic nuclei is important for understanding nuclear structure far from the valley of stability, and as a direct input into astrophysical models. Electron capture processes in the crust of accreting neutron stars have been proposed as a heat source that can affect the thermal structure of the star. Nuclear masses of very neutron-rich nuclides are necessary inputs to model the electron capture process. The time-of-flight (TOF) mass measurement technique allows measurements on very short-lived nuclei. It has been effectively applied using the fast fragment beams produced at the National Superconducting Cyclotron Lab (NSCL) to reach masses very far from stability. Measurements were performed for neutron-rich isotopes in the region of the N=32 and N=40 subshells, which coincides with the mass range of carbon superburst ashes. We discuss reaction network calculations performed to investigate the impact of our new measurements and to compare the effect of using different global mass models in the calculations. It is observed that the process is sensitive to the differences in the odd-even mass staggering predicted by the mass models, and our new result for 66Mn has a significant impact on the distribution of heat sources in the crust.

  4. Binary and tertiary reaction cross-sections of V, Cr, Mn, Fe, Ni, Cu, Zr, Nb, Mo, Ta, W, Pt and their isotopes

    International Nuclear Information System (INIS)

    Garg, S.B.

    1982-01-01

    Neutron induced binary and tertiary reaction cross-sections have been evaluated for V, Cr, Mn, Fe, Ni, Cu, Zr, Nb, Mo, Ta, W, Pt and their isotopes in the 'energy range 0.5 MeV to 20 MeV using the nuclear statistical empirical model. The reactions considered are (n,n'), (n,2n), (n,3n), (n,p), (n,d), (n,t), (n, 3 He), (n,α), (n,np), (n,nd), (n,nt), (n,n 3 He), (n,nα), (n,pn), (n,2p), (n,ν), (n,αp), (n,dn) and (n,pα). Most of the above mentioned elements are used as structural materials in nuclear reactors and the measured cross-section data for the above listed reactions are seldom available for the radiation damage and safety analysis. With a view to providing these data, this nuclear model based evaluation has been undertaken. The associated uncertainties in the cross-sections and their fission averages have also been evaluated. (author)

  5. Zn isotopic fractionation caused by sorption on goethite and 2-Lines ferrihydrite

    Science.gov (United States)

    Juillot, F.; Maréchal, C.; Ponthieu, M.; Cacaly, S.; Morin, G.; Benedetti, M.; Hazemann, J. L.; Proux, O.; Guyot, F.

    2008-10-01

    Zn isotopic fractionation caused by sorption on 2-Lines ferrihydrite (Fh2L) and goethite was investigated to assess the role of reactions at the Fe-oxyhydroxide/water interface in changes of the isotopic distribution of Zn. Since sorption reactions are ubiquitous in Earth's surface environments, it is important to evaluate their influence on the isotopic distribution of Zn before it can be used to track and quantify contributions of various sources and/or biogeochemical processes involving this element. Our results show that Zn isotopes are fractionated upon sorption on Fe-oxyhydroxides with an enrichment of the heavy isotopes present on the solid's surface. This fractionation appears to proceed through an equilibrium mechanism and yields different (Δ 66/64Zn) sorbed-aqueous values for Zn sorption on goethite [(Δ 66/64Zn) sorbed-aqueous around +0.29‰] and Fh2L [(Δ 66/64Zn) sorbed-aqueous around +0.53‰]. These different magnitudes of Zn fractionation are related to structural differences between Zn complexes existing on the surface of goethite (octahedrally coordinated Zn by oxygen atoms) and Fh2L (tetrahedrally coordinated Zn by oxygen atoms), as evidenced by Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy and CD-MUSIC modeling. These results show the importance of accounting for reactions at the Fe-oxyhydroxide/water interface when dealing with the isotopic distribution of Zn at the Earth's surface. Considering the large range of other possible sorbents (Mn or Al oxides, phyllosilicates, carbonates, biologic surfaces, etc.) and the importance of reactions at sorbent/water interfaces for other non-traditional stable isotopes (i.e. Cr, Fe, Ni and Cu) that are increasingly used in environmental studies, these results emphasize the need for further experimental studies that are needed to quantify the isotopic fractionation of these elements possibly accompanying their sorption.

  6. 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...

  7. Iron sources and dissolved-particulate interactions in the seawater of the Western Equatorial Pacific, iron isotope perspectives

    Science.gov (United States)

    Labatut, M.; Lacan, F.; Pradoux, C.; Chmeleff, J.; Radic, A.; Murray, J. W.; Poitrasson, F.; Johansen, A. M.; Thil, F.

    2014-10-01

    This work presents iron isotope data in the western equatorial Pacific. Marine aerosols and top core margin sediments display a slightly heavy Fe isotopic composition (δ56Fe) of 0.33 ± 0.11‰ (2SD) and 0.14 ± 0.07‰, respectively. Samples reflecting the influence of Papua New Guinea runoff (Sepik River and Rabaul volcano water) are characterized by crustal values. In seawater, Fe is mainly supplied in the particulate form and is found with a δ56Fe between -0.49 and 0.34 ± 0.07‰. The particulate Fe seems to be brought mainly by runoff and transported across continental shelves and slopes. Aerosols are suspected to enrich the surface Vitiaz Strait waters, while hydrothermal activity likely enriched New Ireland waters. Dissolved Fe isotopic ratios are found between -0.03 and 0.53 ± 0.07‰. They are almost systematically heavier than the corresponding particulate Fe, and the difference between the signature of both phases is similar for most samples with Δ56FeDFe - PFe = +0.27 ± 0.25‰ (2SD). This is interpreted as an equilibrium isotopic fractionation revealing exchange fluxes between both phases. The dissolved phase being heavier than the particles suggests that the exchanges result in a net nonreductive release of dissolved Fe. This process seems to be locally significantly more intense than Fe reductive dissolution documented along reducing margins. It may therefore constitute a very significant iron source to the ocean, thereby influencing the actual estimation of the iron residence time and sinks. The underlying processes could also apply to other elements.

  8. Iron isotopic fractionation during continental weathering

    Energy Technology Data Exchange (ETDEWEB)

    Fantle, Matthew S.; DePaolo, Donald J.

    2003-10-01

    The biological activity on continents and the oxygen content of the atmosphere determine the chemical pathways through which Fe is processed at the Earth's surface. Experiments have shown that the relevant chemical pathways fractionate Fe isotopes. Measurements of soils, streams, and deep-sea clay indicate that the {sup 56}Fe/{sup 54}Fe ratio ({delta}{sup 56}Fe relative to igneous rocks) varies from +1{per_thousand} for weathering residues like soils and clays, to -3{per_thousand} for dissolved Fe in streams. These measurements confirm that weathering processes produce substantial fractionation of Fe isotopes in the modern oxidizing Earth surface environment. The results imply that biologically-mediated processes, which preferentially mobilize light Fe isotopes, are critical to Fe chemistry in weathering environments, and that the {delta}{sup 56}Fe of marine dissolved Fe should be variable and negative. Diagenetic reduction of Fe in marine sediments may also be a significant component of the global Fe isotope cycle. Iron isotopes provide a tracer for the influence of biological activity and oxygen in weathering processes through Earth history. Iron isotopic fractionation during weathering may have been smaller or absent in an oxygen-poor environment such as that of the early Precambrian Earth.

  9. Thermodynamical properties of 56Fe

    International Nuclear Information System (INIS)

    Tavukcu, E.; Becker, J. A.; Bernstein, L. A.; Garrett, P. E.; Younes, W.; Guttormsen, M.; Rekstad, J.; Siem, S.; Mitchell, G. E.; Schiller, A.; Voinov, A.

    2003-01-01

    Average nuclear level densities close to the nuclear binding energy in 56Fe and 57Fe are extracted from primary γ-ray spectra. A step structure is observed in the level density for both isotopes, and is interpreted as breaking of Cooper pairs. Thermal properties of 56Fe are studied within the statistical canonical ensemble. The experimental heat capacity in 56Fe is compared with the theoretical heat capacity calculated within the shell model Monte Carlo approach

  10. Isotope effects on nuclear shielding

    International Nuclear Information System (INIS)

    Hansen, P.E.

    1983-01-01

    This review concentrates upon empirical trends and practical uses of mostly secondary isotope effects, both of the intrinsic and equilibrium types. The text and the tables are arranged in the following fashion. The most 'popular' isotope effect is treated first, deuterium isotope effects on 13 C nuclear shielding, followed by deuterium on 1 H nuclear shieldings, etc. Focus is thus on the isotopes producing the effect rather than on the nuclei suffering the effect. After a brief treatment of each type of isotope effect, general trends are dealt with. Basic trends of intrinsic isotope effects such as additivity, solvent effects, temperature effects, steric effects, substituent effects and hyperconjugation are discussed. Uses of isotope effects for assignment purposes, in stereochemical studies, in hydrogen bonding and in isotopic tracer studies are dealt with. Kinetic studies, especially of phosphates, are frequently performed by utilizing isotope effects. In addition, equilibrium isotope effects are treated in great detail as these are felt to be new and very important and may lead to new uses of isotope effects. Techniques used to obtain isotope effects are briefly surveyed at the end of the chapter. (author)

  11. Isotope effects on chemical equilibria

    International Nuclear Information System (INIS)

    Golding, P.D.

    1974-01-01

    The thermodynamic equilibrium constants of three deuterated substituted acetic acids are reported. The calculation of secondary isotope effects of the second kind for the three isotopic acid pairs has been accomplished by the appropriate comparison of thermodynamic equilibrium constants, and by the comparison of isotopic slopes. The effect of substituent variation on the isotope effects reported here disqualifies the simple inductive model as a legitimate description of secondary isotope effects of the second kind. The correlation of diminishing isotope effect per deuterium atom with increasing acidity is also invalidated by the present results. The syntheses of 9-thia-9,10-dihydrophenanthrene-9-oxide and thioxanthene-10-oxide are described. These compounds have been partially deuterated at their respective methylene positions. Spectral evidence indicates stereoselectivity of the methylene protons in the exchange reactions of both compounds. (author)

  12. A universal fluorogenic switch for Fe(ii) ion based on N-oxide chemistry permits the visualization of intracellular redox equilibrium shift towards labile iron in hypoxic tumor cells† †Electronic supplementary information (ESI) available. See DOI: 10.1039/c6sc05457a Click here for additional data file.

    Science.gov (United States)

    Tsuboi, Hitomi; Niwa, Masato; Miki, Ayaji; Kadota, Satoki; Ikeshita, Yukie; Okuda, Kensuke

    2017-01-01

    Iron (Fe) species play a number of biologically and pathologically important roles. In particular, iron is a key element in oxygen sensing in living tissue where its metabolism is intimately linked with oxygen metabolism. Regulation of redox balance of labile iron species to prevent the generation of iron-catalyzed reactive oxygen species (ROS) is critical to survival. However, studies on the redox homeostasis of iron species are challenging because of a lack of a redox-state-specific detection method for iron, in particular, labile Fe2+. In this study, a universal fluorogenic switching system is established, which is responsive to Fe2+ ion based on a unique N-oxide chemistry in which dialkylarylamine N-oxide is selectively deoxygenized by Fe2+ to generate various fluorescent probes of Fe2+–CoNox-1 (blue), FluNox-1 (green), and SiRhoNox-1 (red). All the probes exhibited fluorescence enhancement against Fe2+ with high selectivity both in cuvette and in living cells. Among the probes, SiRhoNox-1 showed an excellent fluorescence response with respect to both reaction rate and off/on signal contrast. Imaging studies were performed showing the intracellular redox equilibrium shift towards labile iron in response to reduced oxygen tension in living cells and 3D tumor spheroids using SiRhoNox-1, and it was found that the hypoxia induction of labile Fe2+ is independent of iron uptake, hypoxia-induced signaling, and hypoxia-activated enzymes. The present studies demonstrate the feasibility of developing sensitive and specific fluorescent probes for Fe2+ with refined photophysical characteristics that enable their broad application in the study of iron in various physiological and pathological conditions. PMID:28959409

  13. Gallium isotope fractionation during Ga adsorption on calcite and goethite

    Science.gov (United States)

    Yuan, Wei; Saldi, Giuseppe D.; Chen, JiuBin; Vetuschi Zuccolini, Marino; Birck, Jean-Louis; Liu, Yujie; Schott, Jacques

    2018-02-01

    Gallium (Ga) isotopic fractionation during its adsorption on calcite and goethite was investigated at 20 °C as a function of the solution pH, Ga aqueous concentration and speciation, and the solid to solution ratio. In all experiments Ga was found to be enriched in light isotopes at the solid surface with isotope fractionation △71Gasolid-solution up to -1.27‰ and -0.89‰ for calcite and goethite, respectively. Comparison of Ga isotopic data of this study with predictions for 'closed system' equilibrium and 'Rayleigh fractionation' models indicates that the experimental data are consistent with a 'closed system' equilibrium exchange between the fluid and the solid. The results of this study can be interpreted based on Ga aqueous speciation and the structure of Ga complexes formed at the solid surfaces. For calcite, Ga isotope fractionation is mainly triggered by increased Ga coordination and Ga-O bond length, which vary respectively from 4 and 1.84 Å in Ga(OH)4- to 6 and 1.94 Å in the >Ca-O-GaOH(OH2)4+ surface complex. For goethite, despite the formation of Ga hexa-coordinated >FeOGa(OH)20 surface complexes (Ga-O distances of 1.96-1.98 Å) both at acid and alkaline pH, a similar extent of isotope fractionation was found at acid and alkaline pH, suggesting that Ga(OH)4- is preferentially adsorbed on goethite for all investigated pH conditions. In addition, the observed decrease of Ga isotope fractionation magnitude observed with increasing Ga surface coverage for both calcite and goethite is likely related to the formation of Ga surface polymers and/or hydroxides with reduced Ga-O distances. This first study of Ga isotope fractionation during solid-fluid interactions suggests that the adsorption of Ga by oxides, carbonates or clay minerals could yield significant Ga isotope fractionation between secondary minerals and surficial fluids including seawater. Ga isotopes thus should help to better characterize the surficial biogeochemical cycles of gallium and its

  14. Oxygen-isotopic Compositions of Low-FeO relicts in High-FeO Host Chondrules in Acfer 094, a Type 3.0 Carbonaceous Chondrite Closely Related to CM

    Science.gov (United States)

    Rubin, Alan E.; Kunihiro, Tak; Wasson, John T.

    2006-01-01

    With one exception, the low-FeO relict olivine grains within high-FeO porphyritic chondrules in the type 3.0 Acfer 094 carbonaceous chondrite have DELTA O-17 ( = delta O-17 - 0.52 X delta O-18) values that are substantially more negative than those of the high-FeO olivine host materials. These results are similar to observations made earlier on chondrules in C03.0 chondrites and are consistent with two independent models: (1) Nebular solids evolved from low-FeO, low-DELTA O-17 compositions towards high-FeO, more positive DELTA O-17 compositions; and (2) the range of compositions resulted from the mixing of two independently formed components. The two models predict different trajectories on a DELTA O-17 vs. log Fe/Mg (olivine) diagram, but our sample set has too few values at intermediate Fe/Mg ratios to yield a definitive answer. Published data showing that Acfer 094 has higher volatile contents than CO chondrites suggest a closer link to CM chondrites. This is consistent with the high modal matrix abundance in Acfer 094 (49 vol.%). Acfer 094 may be an unaltered CM chondrite or an exceptionally matrix-rich CO chondrite. Chondrules in Acfer 094 and in CO and CM carbonaceous chondrites appear to sample the same population. Textural differences between Acfer 094 and CM chondrites are largely attributable to the high degree of hydrothermal alteration that the CM chondrites experienced in an asteroidal setting.

  15. Fe-oxide fracture fillings as a palæo-redox indicator

    DEFF Research Database (Denmark)

    Dideriksen, Knud; Christiansen, Bo C.; Baker, J.A.

    2007-01-01

    ) Intermediate grain-size crystalline Fe-oxides, that are interpreted to have formed naturally at low-temperatures (~ 10 °C). Fe isotope composition of the Fe-oxides was determined by multiple-collector inductively coupled plasma mass spectrometry using a 58Fe-54Fe double-spike. d56Fe of the Fe-oxides ranges...

  16. Isotope effect and isotope separation. A chemist's view

    International Nuclear Information System (INIS)

    Ishida, Takanobu

    2002-01-01

    What causes the isotope effects (IE)? This presentation will be centered around the equilibrium isotope effects due to the differences in the nuclear masses. The occurrence of the equilibrium constant, K, of isotope exchange reactions which differ from the values predicted by the classical theory of statistical mechanics, K cl , is explored. The non-classical K corresponds to the unit-stage separation factor, α, that is different from unity and forms a basis of an isotope separation process involving the chemical exchange reaction. Here, the word 'chemical exchange' includes not only the isotope exchange chemical reactions between two or more chemical species but also the isotope exchanges involving the equilibria between liquid and vapor phases and liquid-gas, liquid solution-gas, liquid-liquid, and solid-liquid phases. In Section I, origins of the isotope effect phenomena will be explored and, in the process, various quantities used in discussions of isotope effect that have often caused confusions will be unambiguously defined. This Section will also correlate equilibrium constant with separation factor. In Section II, various forms of temperature-dependence of IE and separation factor will be discussed. (author)

  17. Association equilibrium constants and populations of clusters (H2O)n(g) and (D2O)n(g): differences between isotopomers and a possible relation to isotope enrichment

    International Nuclear Information System (INIS)

    Slanina, Z.

    1986-01-01

    Equilibrium constants of H 2 O(g) and D 2 O(g) associations to clusters (H 2 O) n (g) and (D 2 O) n (g) were calculated on the basis of the ab initio SCF CI MCY-B water-water pair potential. Populations of the components of equilibrium cluster mixtures were evaluated at various temperatures and pressures for both isotopomeric series. Differences between the H and D steam are pointed out and possible consequences are discussed. (author)

  18. Stable isotope research pool inventory

    International Nuclear Information System (INIS)

    1984-03-01

    This report contains a listing of electromagnetically separated stable isotopes which are available at the Oak Ridge National Laboratory for distribution for nondestructive research use on a loan basis. This inventory includes all samples of stable isotopes in the Research Materials Collection and does not designate whether a sample is out on loan or is in reprocessing. For some of the high abundance naturally occurring isotopes, larger amounts can be made available; for example, Ca-40 and Fe-56

  19. Methane clumped isotopes: Progress and potential for a new isotopic tracer

    Energy Technology Data Exchange (ETDEWEB)

    Douglas, Peter M. J.; Stolper, Daniel A.; Eiler, John M.; Sessions, Alex L.; Lawson, Michael; Shuai, Yanhua; Bishop, Andrew; Podlaha, Olaf G.; Ferreira, Alexandre A.; Santos Neto, Eugenio V.; Niemann, Martin; Steen, Arne S.; Huang, Ling; Chimiak, Laura; Valentine, David L.; Fiebig, Jens; Luhmann, Andrew J.; Seyfried, William E.; Etiope, Giuseppe; Schoell, Martin; Inskeep, William P.; Moran, James J.; Kitchen, Nami

    2017-11-01

    The isotopic composition of methane is of longstanding geochemical interest, with important implications for understanding hydrocarbon systems, atmospheric greenhouse gas concentrations, the global carbon cycle, and life in extreme environments. Recent analytical developments focusing on multiply substituted isotopologues (‘clumped isotopes’) are opening a potentially valuable new window into methane geochemistry. When methane forms in internal isotopic equilibrium, clumped isotopes can provide a direct record of formation temperature, making this property particularly valuable for identifying different methane origins. However, it has also become clear that in certain settings methane clumped isotope measurements record kinetic rather than equilibrium isotope effects. Here we present a substantially expanded dataset of methane clumped isotope analyses, and provide a synthesis of the current interpretive framework for this parameter. We review different processes affecting methane clumped isotope compositions, describe the relationships between conventional isotope and clumped isotope data, and summarize the types of information that this measurement can provide in different Earth and planetary environments.

  20. Komatiites constrain molybdenum isotope composition of the Earth's mantle

    Science.gov (United States)

    Greber, Nicolas D.; Puchtel, Igor S.; Nägler, Thomas F.; Mezger, Klaus

    2015-07-01

    In order to estimate the Mo isotope composition and Mo abundance in the Bulk Silicate Earth (BSE), a total of thirty komatiite samples from five localities on three continents were analyzed using an isotope dilution double spike technique. Calculated Mo concentrations of the emplaced komatiite lavas range from 25 ± 3 to 66 ± 22 ng /g, and the inferred Mo concentrations in the deep mantle sources of the komatiites range between 17 ± 4 and 30 ± 12 ng /g, with an average value of 23 ± 7 ng /g (2SE). This average value represents our best estimate for the Mo concentration in the BSE; it is identical, within the uncertainty, to published previous estimates of 39 ± 16 ng /g, but is at least a factor of 2 more precise. The Mo isotope compositions of the komatiite mantle sources overlap within uncertainty and range from δ98Mo = - 0.04 ± 0.28 to 0.11 ± 0.10 ‰, with an average of 0.04 ± 0.06 ‰ (2SE). This value is analytically indistinguishable from published Mo isotope compositions of ordinary and enstatite chondrites and represents the best estimate for the Mo isotope composition of the BSE. The inferred δ98Mo for the BSE is therefore lighter than the suggested average of the upper continental crust (0.3 to 0.4‰). Thus, from the mass balance standpoint, a reservoir with lighter Mo isotope composition should exist in the Earth's mantle; this reservoir can potentially be found in subducted oceanic crust. The similarity of δ98Mo between chondritic meteorites and estimates for the BSE from this study indicates that during the last major equilibration between Earth's core and mantle, i.e., the one that occurred during the giant impact that produced the Moon, chemical and isotopic equilibrium of Mo between Fe metal of the core and the silicate mantle was largely achieved.

  1. Fe atom exchange between aqueous Fe2+ and magnetite.

    Science.gov (United States)

    Gorski, Christopher A; Handler, Robert M; Beard, Brian L; Pasakarnis, Timothy; Johnson, Clark M; Scherer, Michelle M

    2012-11-20

    The reaction between magnetite and aqueous Fe(2+) has been extensively studied due to its role in contaminant reduction, trace-metal sequestration, and microbial respiration. Previous work has demonstrated that the reaction of Fe(2+) with magnetite (Fe(3)O(4)) results in the structural incorporation of Fe(2+) and an increase in the bulk Fe(2+) content of magnetite. It is unclear, however, whether significant Fe atom exchange occurs between magnetite and aqueous Fe(2+), as has been observed for other Fe oxides. Here, we measured the extent of Fe atom exchange between aqueous Fe(2+) and magnetite by reacting isotopically "normal" magnetite with (57)Fe-enriched aqueous Fe(2+). The extent of Fe atom exchange between magnetite and aqueous Fe(2+) was significant (54-71%), and went well beyond the amount of Fe atoms found at the near surface. Mössbauer spectroscopy of magnetite reacted with (56)Fe(2+) indicate that no preferential exchange of octahedral or tetrahedral sites occurred. Exchange experiments conducted with Co-ferrite (Co(2+)Fe(2)(3+)O(4)) showed little impact of Co substitution on the rate or extent of atom exchange. Bulk electron conduction, as previously invoked to explain Fe atom exchange in goethite, is a possible mechanism, but if it is occurring, conduction does not appear to be the rate-limiting step. The lack of significant impact of Co substitution on the kinetics of Fe atom exchange, and the relatively high diffusion coefficients reported for magnetite suggest that for magnetite, unlike goethite, Fe atom diffusion is a plausible mechanism to explain the rapid rates of Fe atom exchange in magnetite.

  2. Chemical separation of boron isotopes

    International Nuclear Information System (INIS)

    Palko, A.A.

    1978-06-01

    This is the final report of the research performed at ORNL on the chemical fractionation of boron isotopes between BF 3 gas and the liquid molecular addition compounds of BF 3 . Thirty compounds were studied, ten of them in detail. Graphs and equations are given for variation of isotopic equilibrium constant, vapor pressure, and BF 3 solubility as a function of temperature. Rate of isotopic exchange and melting points were determined. Several of the compounds are likely candidates for use in a gas-liquid countercurrent exchange system for large-scale separation of boron isotopes. 23 figs, 53 tables, 39 references

  3. Chemical separation of boron isotopes

    Energy Technology Data Exchange (ETDEWEB)

    Palko, A.A.

    1978-06-01

    This is the final report of the research performed at ORNL on the chemical fractionation of boron isotopes between BF/sub 3/ gas and the liquid molecular addition compounds of BF/sub 3/. Thirty compounds were studied, ten of them in detail. Graphs and equations are given for variation of isotopic equilibrium constant, vapor pressure, and BF/sub 3/ solubility as a function of temperature. Rate of isotopic exchange and melting points were determined. Several of the compounds are likely candidates for use in a gas-liquid countercurrent exchange system for large-scale separation of boron isotopes. 23 figs, 53 tables, 39 references.

  4. 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

  5. C, Cl and H compound-specific isotope analysis to assess natural versus Fe(0) barrier-induced degradation of chlorinated ethenes at a contaminated site

    Energy Technology Data Exchange (ETDEWEB)

    Audí-Miró, Carme, E-mail: carmeaudi@ub.edu [Grup de Mineralogia Aplicada i Medi Ambient, Departament de Cristal.lografia, Mineralogia i Dipòsits Minerals, Facultat de Geologia, Universitat de Barcelona (UB), Martí Franquès s/n, 08028, Barcelona (Spain); Cretnik, Stefan [Institute of Groundwater Ecology, Helmholtz Zentrum München-National Research Center for Environmental Health, Ingolstädter Landstrasse 1, D-85764 Neuherberg (Germany); Torrentó, Clara; Rosell, Mònica [Grup de Mineralogia Aplicada i Medi Ambient, Departament de Cristal.lografia, Mineralogia i Dipòsits Minerals, Facultat de Geologia, Universitat de Barcelona (UB), Martí Franquès s/n, 08028, Barcelona (Spain); Shouakar-Stash, Orfan [Department of Earth & Environmental Sciences, 200 University Ave. W, N2L 3G1 Waterloo, Ontario (Canada); Otero, Neus [Grup de Mineralogia Aplicada i Medi Ambient, Departament de Cristal.lografia, Mineralogia i Dipòsits Minerals, Facultat de Geologia, Universitat de Barcelona (UB), Martí Franquès s/n, 08028, Barcelona (Spain); Palau, Jordi [Université de Neuchâtel, CHYN - Centre d' Hydrogéologie, Rue Emile-Argand 11, CH-2000 Neuchâtel (Switzerland); and others

    2015-12-15

    Highlights: • {sup 13}C to evaluate natural chlorinated ethenes biodegradation. • {sup 13}C to evaluate the efficiency of a zero-valent iron-permeable reactive barrier. • {sup 13}C-{sup 37}Cl to discriminate biotic from abiotic degradation of cis-dichloroethene. • {sup 13}C-{sup 37}Cl-{sup 2}H of cis-DCE and TCE to elucidate different contaminant sources. - Abstract: Compound-specific isotopic analysis of multiple elements (C, Cl, H) was tested to better assess the effect of a zero-valent iron-permeable reactive barrier (ZVI-PRB) installation at a site contaminated with tetrachloroethene (PCE) and trichloroethene (TCE). The focus was on (1) using {sup 13}C to evaluate natural chlorinated ethene biodegradation and the ZVI-PRB efficiency; (2) using dual element {sup 13}C-{sup 37}Cl isotopic analysis to distinguish biotic from abiotic degradation of cis-dichloroethene (cis-DCE); and (3) using {sup 13}C-{sup 37}Cl-{sup 2}H isotopic analysis of cis-DCE and TCE to elucidate different contaminant sources. Both biodegradation and degradation by ZVI-PRB were indicated by the metabolites that were detected and the {sup 13}C data, with a quantitative estimate of the ZVI-PRB efficiency of less than 10% for PCE. Dual element {sup 13}C-{sup 37}Cl isotopic plots confirmed that biodegradation was the main process at the site including the ZVI-PRB area. Based on the carbon isotope data, approximately 45% and 71% of PCE and TCE, respectively, were estimated to be removed by biodegradation. {sup 2}H combined with {sup 13}C and {sup 37}Cl seems to have identified two discrete sources contributing to the contaminant plume, indicating the potential of δ{sup 2}H to discriminate whether a compound is of industrial origin, or whether a compound is formed as a daughter product during degradation.

  6. C, Cl and H compound-specific isotope analysis to assess natural versus Fe(0) barrier-induced degradation of chlorinated ethenes at a contaminated site

    International Nuclear Information System (INIS)

    Audí-Miró, Carme; Cretnik, Stefan; Torrentó, Clara; Rosell, Mònica; Shouakar-Stash, Orfan; Otero, Neus; Palau, Jordi

    2015-01-01

    Highlights: • 13 C to evaluate natural chlorinated ethenes biodegradation. • 13 C to evaluate the efficiency of a zero-valent iron-permeable reactive barrier. • 13 C- 37 Cl to discriminate biotic from abiotic degradation of cis-dichloroethene. • 13 C- 37 Cl- 2 H of cis-DCE and TCE to elucidate different contaminant sources. - Abstract: Compound-specific isotopic analysis of multiple elements (C, Cl, H) was tested to better assess the effect of a zero-valent iron-permeable reactive barrier (ZVI-PRB) installation at a site contaminated with tetrachloroethene (PCE) and trichloroethene (TCE). The focus was on (1) using 13 C to evaluate natural chlorinated ethene biodegradation and the ZVI-PRB efficiency; (2) using dual element 13 C- 37 Cl isotopic analysis to distinguish biotic from abiotic degradation of cis-dichloroethene (cis-DCE); and (3) using 13 C- 37 Cl- 2 H isotopic analysis of cis-DCE and TCE to elucidate different contaminant sources. Both biodegradation and degradation by ZVI-PRB were indicated by the metabolites that were detected and the 13 C data, with a quantitative estimate of the ZVI-PRB efficiency of less than 10% for PCE. Dual element 13 C- 37 Cl isotopic plots confirmed that biodegradation was the main process at the site including the ZVI-PRB area. Based on the carbon isotope data, approximately 45% and 71% of PCE and TCE, respectively, were estimated to be removed by biodegradation. 2 H combined with 13 C and 37 Cl seems to have identified two discrete sources contributing to the contaminant plume, indicating the potential of δ 2 H to discriminate whether a compound is of industrial origin, or whether a compound is formed as a daughter product during degradation.

  7. Quantity Constrained General Equilibrium

    NARCIS (Netherlands)

    Babenko, R.; Talman, A.J.J.

    2006-01-01

    In a standard general equilibrium model it is assumed that there are no price restrictions and that prices adjust infinitely fast to their equilibrium values.In case of price restrictions a general equilibrium may not exist and rationing on net demands or supplies is needed to clear the markets.In

  8. Importance of reduced sulfur for the equilibrium chemistry and kinetics of Fe(II), Co(II) and Ni(II) supplemented to semi-continuous stirred tank biogas reactors fed with stillage.

    Science.gov (United States)

    Shakeri Yekta, Sepehr; Lindmark, Amanda; Skyllberg, Ulf; Danielsson, Asa; Svensson, Bo H

    2014-03-30

    The objective of the present study was to assess major chemical reactions and chemical forms contributing to solubility and speciation of Fe(II), Co(II), and Ni(II) during anaerobic digestion of sulfur (S)-rich stillage in semi-continuous stirred tank biogas reactors (SCSTR). These metals are essential supplements for efficient and stable performance of stillage-fed SCSTR. In particular, the influence of reduced inorganic and organic S species on kinetics and thermodynamics of the metals and their partitioning between aqueous and solid phases were investigated. Solid phase S speciation was determined by use of S K-edge X-ray absorption near-edge spectroscopy. Results demonstrated that the solubility and speciation of supplemented Fe were controlled by precipitation of FeS(s) and formation of the aqueous complexes of Fe-sulfide and Fe-thiol. The relatively high solubility of Co (∼ 20% of total Co content) was attributed to the formation of compounds other than Co-sulfide and Co-thiol, presumably of microbial origin. Nickel had lower solubility than Co and its speciation was regulated by interactions with FeS(s) (e.g. co-precipitation, adsorption, and ion substitution) in addition to precipitation/dissolution of discrete NiS(s) phase and formation of aqueous Ni-sulfide complexes. Copyright © 2014 Elsevier B.V. All rights reserved.

  9. The empirical equilibrium structure of diacetylene

    OpenAIRE

    Thorwirth, S.; Harding, M. E.; Muders, D.; Gauss, J.

    2008-01-01

    High-level quantum-chemical calculations are reported at the MP2 and CCSD(T) levels of theory for the equilibrium structure and the harmonic and anharmonic force fields of diacetylene, HCCCCH. The calculations were performed employing Dunning's hierarchy of correlation-consistent basis sets cc-pVXZ, cc-pCVXZ, and cc-pwCVXZ, as well as the ANO2 basis set of Almloef and Taylor. An empirical equilibrium structure based on experimental rotational constants for thirteen isotopic species of diacety...

  10. Modeling of Reactive Blue 19 azo dye removal from colored textile wastewater using L-arginine-functionalized Fe{sub 3}O{sub 4} nanoparticles: Optimization, reusability, kinetic and equilibrium studies

    Energy Technology Data Exchange (ETDEWEB)

    Dalvand, Arash; Nabizadeh, Ramin [Department of Environmental Health Engineering, School of Public Health, Tehran University of Medical Sciences, Tehran (Iran, Islamic Republic of); Reza Ganjali, Mohammad [Center of Excellence in Electrochemistry, Faculty of Chemistry, University of Tehran, Tehran (Iran, Islamic Republic of); Biosensor Research Center, Endocrinology and Metabolism Molecular-Cellular Sciences Institute, Tehran University of Medical Sciences, Tehran (Iran, Islamic Republic of); Khoobi, Mehdi [Medical Biomaterials Research Center, Tehran University of Medical Sciences, Tehran (Iran, Islamic Republic of); Department of Medicinal Chemistry, Faculty of Pharmacy and Pharmaceutical Sciences Research Center, Tehran University of Medical Sciences, Tehran 14176 (Iran, Islamic Republic of); Nazmara, Shahrokh [Department of Environmental Health Engineering, School of Public Health, Tehran University of Medical Sciences, Tehran (Iran, Islamic Republic of); Hossein Mahvi, Amir, E-mail: ahmahvi@yahoo.com [Department of Environmental Health Engineering, School of Public Health, Tehran University of Medical Sciences, Tehran (Iran, Islamic Republic of); Center for Solid Waste Research, Institute for Environmental Research, Tehran University of Medical Sciences, Tehran (Iran, Islamic Republic of); National Institute of Health Research, Tehran University of Medical Sciences, Tehran (Iran, Islamic Republic of)

    2016-04-15

    This study aimed to investigate the removal of Reactive Blue 19 from colored wastewater using Fe{sub 3}O{sub 4} magnetic nanoparticles modified with L-arginine (Fe{sub 3}O{sub 4}@L-arginine). In order to investigate the effect of independent variables on dye removal and determining the optimum condition, the Box–Behnken Design (BBD) under Response Surface Methodology (RSM) was employed. Fe{sub 3}O{sub 4}@L-arginine nanoparticles were synthesized and characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, and vibrating sample magnetometer. Applying Fe{sub 3}O{sub 4}@L-arginine nanoparticles for dye removal showed that; by increasing adsorbent dose and decreasing pH, dye concentration, and ionic strength dye removal has been increased. In the optimum condition, Fe{sub 3}O{sub 4}@L-arginine nanoparticles were able to remove dye as high as 96.34% at an initial dye concentration of 50 mg/L, adsorbent dose of 0.74 g/L, and pH 3. The findings indicated that dye removal followed pseudo-second-order kinetic (R{sup 2}=0.999) and Freundlich isotherm (R{sup 2}=0.989). Based on the obtained results, as an efficient and reusable adsorbent, Fe{sub 3}O{sub 4}@L-arginine nanoparticles can be successfully applied for dye removal from colored wastewater. - Highlights: • The Fe{sub 3}O{sub 4}@L-arginine removed RB 19 azo dye from wastewater efficiently. • BBD under RSM was used to analyze and optimize the adsorption process. • pH was the most influential parameter in dye removal.

  11. Isotopic echange of .sup.18./sup.O as a tool in studies of N2O decomposition over Fe-zeolites

    Czech Academy of Sciences Publication Activity Database

    Nováková, Jana; Sobalík, Zdeněk

    2007-01-01

    Roč. 6, - (2007), s. 55-68 ISSN 0972-4508 R&D Projects: GA AV ČR 1ET400400413 Institutional research plan: CEZ:AV0Z40400503 Keywords : N2O decomposition * 18O2 * Fe-zeolites Subject RIV: CF - Physical ; Theoretical Chemistry

  12. Intracellular Cadmium Isotope Fractionation

    Science.gov (United States)

    Horner, T. J.; Lee, R. B.; Henderson, G. M.; Rickaby, R. E.

    2011-12-01

    Recent stable isotope studies into the biological utilization of transition metals (e.g. Cu, Fe, Zn, Cd) suggest several stepwise cellular processes can fractionate isotopes in both culture and nature. However, the determination of fractionation factors is often unsatisfactory, as significant variability can exist - even between different organisms with the same cellular functions. Thus, it has not been possible to adequately understand the source and mechanisms of metal isotopic fractionation. In order to address this problem, we investigated the biological fractionation of Cd isotopes within genetically-modified bacteria (E. coli). There is currently only one known biological use or requirement of Cd, a Cd/Zn carbonic anhydrase (CdCA, from the marine diatom T. weissfloggii), which we introduce into the E. coli genome. We have also developed a cleaning procedure that allows for the treating of bacteria so as to study the isotopic composition of different cellular components. We find that whole cells always exhibit a preference for uptake of the lighter isotopes of Cd. Notably, whole cells appear to have a similar Cd isotopic composition regardless of the expression of CdCA within the E. coli. However, isotopic fractionation can occur within the genetically modified E. coli during Cd use, such that Cd bound in CdCA can display a distinct isotopic composition compared to the cell as a whole. Thus, the externally observed fractionation is independent of the internal uses of Cd, with the largest Cd isotope fractionation occurring during cross-membrane transport. A general implication of these experiments is that trace metal isotopic fractionation most likely reflects metal transport into biological cells (either actively or passively), rather than relating to expression of specific physiological function and genetic expression of different metalloenzymes.

  13. The equilibrium structure of hydrogen peroxide

    Science.gov (United States)

    Baraban, Joshua H.; Changala, P. Bryan; Stanton, John F.

    2018-01-01

    The equilibrium structure of hydrogen peroxide is completely determined for the first time. Recent isotopically substituted data is combined with the results of rovibrational variational calculations to yield a complete semi-experimental structure, which is in excellent agreement with high level ab initio calculated structures. In addition to numerically exact variational calculations, we also investigate the accuracy of approximate rovibrational predictions based on second order vibrational Møller-Plesset perturbation theory with curvilinear coordinates.

  14. The oxygen isotopic composition of water extracted from carbonaceous chondrites

    OpenAIRE

    Baker, L.; Franchi, Ian; Wright, Ian; Pillinger, Colin

    2001-01-01

    The oxygen isotopic composition of water from carbonaceous chondrites suggests that close to isotopic equilibrium was attained on CI and CM parent bodies. This is more consistent with a closed system than one with fluid flow. Tagish Lake does not display such equilibrium.

  15. 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

  16. Thermal equilibrium in strongly damped collisions

    International Nuclear Information System (INIS)

    Samaddar, S.K.; De, J.N.; Krishan, K.

    1985-01-01

    Energy division between colliding nuclei in damped collisions is studied in the statistical nucleon exchange model. The reactions 56 Fe+ 165 Ho and 56 Fe+ 238 U at incident energy of 465 MeV are considered for this purpose. It is found that the excitation energy is approximately equally shared between the nuclei for the peripheral collisions and the systems slowly approach equilibrium for more central collisions. This is in conformity with the recent experimental observations. The calculated variances of the charge distributions are found to depend appreciably on the temperature and are in very good agreement with the experimental data

  17. Studies on the separation of hydrogen isotopes and spin isomers by gas chromatography

    International Nuclear Information System (INIS)

    Pushpa, K.K.; Annaji Rao, K.

    2000-08-01

    Separation and analysis of mixture of hydrogen isotopes has gained considerable importance because of various applications needing different isotopes in lasers, nuclear reactions and tracer or labelled compounds. In the literature gas chromatographic methods are reported using columns packed with partly dehydrated or thoroughly dehydrated alumina/molecular sieve stationary phase at 77 deg K with helium, neon and even hydrogen or deuterium as carrier gas. In the present study an attempt is made to compare the chromatographic behaviour of these two stationary phases using virgin and Fe doped form in partly dehydrated and thoroughly dehydrated state, using helium, neon, hydrogen and deuterium as carrier gas. The results of this study show that helium or neon carrier gas behave similarly broad peaks with some tailing. Sharp symmetric peaks are obtained with hydrogen or deuterium carrier gas. This is attributed to large hold up capacity for H 2 or D 2 at 77 deg K in these materials as compared to helium or neon. Spin isomers of H 2 or D 2 are separated on Fe free stationary phases, though ortho H 2 and HD are not resolved. Using a combination of Fe doped short column and plain alumina column, both maintained in dehydrated form, the effect of Fe doping on thermal equilibrium of ortho/para forms at 77 deg K is clearly demonstrated. (author)

  18. What is the Role of the Transition State in Soret and Chemical Diffusion Induced Isotopic Fractionation?

    Science.gov (United States)

    Dominguez, G.

    2013-12-01

    For over six decades, Urey's (1) statistical mechanical model of isotopic fractionation based on partition functions with quantized energy levels have enjoyed enormous success in quantitatively explaining equilibrium isotopic fractionation in a wide variety of geochemical systems For example, the interpretation of oxygen isotopic variations in carbonate systems (e.g. foraminiferas), in terms of partition functions with quantized energy levels, forms the basis for paleothermometry (2). Recent observations of isotopic fractionation from chemical and thermal (Soret) diffusion (3-7) appear to challenge our theoretical understanding of mass-transport and isotopic fractionation (8, 9). For example, a recently proposed quantum mechanical model of Soret diffusion, which correctly predicts the isotopic fractionation in thermal gradients for isotopes of Mg, Ca, Fe, Si, and possibly oxygen, was critiqued as being unphysical. First, it was argued that the zero point energies needed to explain the magnitude of isotopic fractionation in basalt melts were unrealistically high based on infrared spectra of these melts. Second, it was argued that the chemical diffusion isotopic fractionation (beta) factors expected from these zero-point energies were also unphysical (10). A recently proposed collision-momentum transfer model partially explains observed fractionation factors, although it fails miserably (by a factor of 3) to account for the isotopic fractionation of Mg isotopes (11). In this presentation, I will review recent observations and models of isotopic fractionation in geochemical melts with thermal gradients and expand upon previous work (8, 12) to show how transition state theory can simultaneously explain mass-transport induced isotopic fractionation, including kinetic, equilibrium, and Soret isotopic fractionation. I show this by providing a few example calculations of the kinetic fractionation factors (a.k.a. beta factors) expected in chemical diffusion as well as

  19. 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

  20. Atom exchange between aqueous Fe(II) and structural Fe in clay minerals.

    Science.gov (United States)

    Neumann, Anke; Wu, Lingling; Li, Weiqiang; Beard, Brian L; Johnson, Clark M; Rosso, Kevin M; Frierdich, Andrew J; Scherer, Michelle M

    2015-03-03

    Due to their stability toward reductive dissolution, Fe-bearing clay minerals are viewed as a renewable source of Fe redox activity in diverse environments. Recent findings of interfacial electron transfer between aqueous Fe(II) and structural Fe in clay minerals and electron conduction in octahedral sheets of nontronite, however, raise the question whether Fe interaction with clay minerals is more dynamic than previously thought. Here, we use an enriched isotope tracer approach to simultaneously trace Fe atom movement from the aqueous phase to the solid ((57)Fe) and from the solid into the aqueous phase ((56)Fe). Over 6 months, we observed a significant decrease in aqueous (57)Fe isotope fraction, with a fast initial decrease which slowed after 3 days and stabilized after about 50 days. For the aqueous (56)Fe isotope fraction, we observed a similar but opposite trend, indicating that Fe atom movement had occurred in both directions: from the aqueous phase into the solid and from the solid into aqueous phase. We calculated that 5-20% of structural Fe in clay minerals NAu-1, NAu-2, and SWa-1 exchanged with aqueous Fe(II), which significantly exceeds the Fe atom layer exposed directly to solution. Calculations based on electron-hopping rates in nontronite suggest that the bulk conduction mechanism previously demonstrated for hematite1 and suggested as an explanation for the significant Fe atom exchange observed in goethite2 may be a plausible mechanism for Fe atom exchange in Fe-bearing clay minerals. Our finding of 5-20% Fe atom exchange in clay minerals indicates that we need to rethink how Fe mobility affects the macroscopic properties of Fe-bearing phyllosilicates and its role in Fe biogeochemical cycling, as well as its use in a variety of engineered applications, such as landfill liners and nuclear repositories.

  1. PLASMA EQUILIBRIUM IN TOKAMAKS

    NARCIS (Netherlands)

    de Blank, H. J.

    2010-01-01

    This lecture treats the magnetohydrodynamic (MHD) equilibrium of axisymmetric plasmas, as given by the Grad-Shafranov equation. In a brief introduction, equilibrium parameters such as the q-profile, the internal inductance, and the poloidal beta are introduced. The properties of these quantities

  2. Plasma equilibrium in tokamaks

    NARCIS (Netherlands)

    de Blank, H. J.

    2008-01-01

    This lecture treats the magnetohydrodynamic (MHD) equilibrium of axisymmetric plasmas, as given by the Grad-Shafranov equation. In a brief introduction, equilibrium parameters such as the q-profile, the internal inductance, and the poloidal beta are introduced. The properties of these quantities

  3. Plasma equilibrium in tokamaks

    NARCIS (Netherlands)

    de Blank, H. J.

    2012-01-01

    This lecture treats the magnetohydrodynamic (MHD) equilibrium of axisymmetric plasmas, as given by the Grad-Shafranov equation. In a brief introduction, equilibrium parameters such as the q-profile, the internal inductance, and the poloidal beta are introduced. The properties of these quantities

  4. Fall Back Equilibrium

    NARCIS (Netherlands)

    Kleppe, J.; Borm, P.E.M.; Hendrickx, R.L.P.

    2008-01-01

    Fall back equilibrium is a refinement of the Nash equilibrium concept. In the underly- ing thought experiment each player faces the possibility that, after all players decided on their action, his chosen action turns out to be blocked. Therefore, each player has to decide beforehand on a back-up

  5. ISOTOPE METHODS IN HOMOGENEOUS CATALYSIS.

    Energy Technology Data Exchange (ETDEWEB)

    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.

  6. Use of Isotopes for Studying Reaction Mechanisms

    Indian Academy of Sciences (India)

    In the previous articles of this series, we discussed the use of isotopes to trace the nature of reactive intermediates and also to obtain information about minima and transition states through quantitative measurements of equilibrium and kinetic isotope effects. In this part, we describe an ingenious way of studying dynamic ...

  7. Use of Isotopes for Studying Reaction Mechanisms

    Indian Academy of Sciences (India)

    In the previous articles of this series, we discussed the use of isotopes to trace the nature of reactive intermediates and also to obtain information about minima and transition states through quan- titative measurements of equilibrium and kinetic isotope effects. In this part, we describe an ingenious way of studying dynamic ...

  8. Distribution of iron isotopes in dissolved and particulate iron from the anoxic Gotland Basin in the the Baltic Sea

    OpenAIRE

    M. Staubwasser; R. Schönberg; Friedhelm von Blanckenburg; C. Pohl; Sandra Krüger

    2008-01-01

    Fe isotope ratios are a potentially useful tool to determine the sources of marine dissolved and particulate Fe in the present day ocean and the ocean's redox state of the past. However, to date there are only a few measurements of Fe isotope ratios available from the marine environment. Almost no data exists for dissolved Fe, yet knowledge of the mechanisms and magnitude of Fe isotope fractionation in the marine Fe cycle are essential, if Fe isotope ratios are to be applied to adress either ...

  9. Isotopic separation

    International Nuclear Information System (INIS)

    Chen, C.

    1981-01-01

    Method and apparatus for separating isotopes in an isotopic mixture of atoms or molecules by increasing the mass differential among isotopic species. The mixture containing a particular isotope is selectively irradiated so as to selectively excite the isotope. This preferentially excited species is then reacted rapidly with an additional preselected radiation, an electron or another chemical species so as to form a product containing the specific isotope, but having a mass different than the original species initially containing the particular isotope. The product and the remaining balance of the mixture is then caused to flow through a device which separates the product from the mixture based upon the increased mass differential

  10. Equilibrium and non equilibrium in fragmentation

    International Nuclear Information System (INIS)

    Dorso, C.O.; Chernomoretz, A.; Lopez, J.A.

    2001-01-01

    Full text: In this communication we present recent results regarding the interplay of equilibrium and non equilibrium in the process of fragmentation of excited finite Lennard Jones drops. Because the general features of such a potential resemble the ones of the nuclear interaction (fact that is reinforced by the similarity between the EOS of both systems) these studies are not only relevant from a fundamental point of view but also shed light on the problem of nuclear multifragmentation. We focus on the microscopic analysis of the state of the fragmenting system at fragmentation time. We show that the Caloric Curve (i e. the functional relationship between the temperature of the system and the excitation energy) is of the type rise plateau with no vapor branch. The usual rise plateau rise pattern is only recovered when equilibrium is artificially imposed. This result puts a serious question on the validity of the freeze out hypothesis. This feature is independent of the dimensionality or excitation mechanism. Moreover we explore the behavior of magnitudes which can help us determine the degree of the assumed phase transition. It is found that no clear cut criteria is presently available. (Author)

  11. 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)

  12. Equilibrium coexistence of three amphiboles

    Science.gov (United States)

    Robinson, P.; Jaffe, H.W.; Klein, C.; Ross, M.

    1969-01-01

    Electron probe and wet chemical analyses of amphibole pairs from the sillimanite zone of central Massachusetts and adjacent New Hampshire indicated that for a particular metamorphic grade there should be a restricted composition range in which three amphiboles can coexist stably. An unequivocal example of such an equilibrium three amphibole rock has been found in the sillimanite-orthoclase zone. It contains a colorless primitive clinoamphibole, space group P21/m, optically and chemically like cummingtonite with blue-green hornblende exsolution lamellae on (100) and (-101) of the host; blue-green hornblende, space group C2/m, with primitive cummingtonite exsolution lamellae on (100) and (-101) of the host; and pale pinkish tan anthophyllite, space group Pnma, that is free of visible exsolution lamellae but is a submicroscopic intergrowth of two orthorhombic amphiboles. Mutual contacts and coarse, oriented intergrowths of two and three host amphiboles indicate the three grew as an equilibrium assemblage prior to exsolution. Electron probe analyses at mutual three-amphibole contacts showed little variation in the composition of each amphibole. Analyses believed to represent most closely the primary amphibole compositions gave atomic proportions on the basis of 23 oxygens per formula unit as follows: for primitive cummingtonite (Na0.02Ca0.21- Mn0.06Fe2+2.28Mg4.12Al0.28) (Al0.17Si7.83), for hornblende (Na0.35Ca1.56Mn0.02Fe1.71Mg2.85Al0.92) (Al1.37Si6.63), and for anthophyllite (Na0.10Ca0.06Mn0.06Fe2.25Mg4.11Al0.47) (Al0.47Si7.53). The reflections violating C-symmetry, on X-ray single crystal photographs of the primitive cummingtonite, are weak and diffuse, and suggest a partial inversion from a C-centered to a primitive clinoamphibole. Single crystal photographs of the anthophyllite show split reflections indicating it is an intergrowth of about 80% anthophyllite and about 20% gedrite which differ in their b crystallographic dimensions. Split reflections are

  13. Thermodynamic model for solution behavior and solid-liquid equilibrium in Na-Al(III)-Fe(III)-Cr(III)-Cl-H2O system at 25°C

    Science.gov (United States)

    André, Laurent; Christov, Christomir; Lassin, Arnault; Azaroual, Mohamed

    2018-03-01

    The knowledge of the thermodynamic behavior of multicomponent aqueous electrolyte systems is of main interest in geo-, and environmental-sciences. The main objective of this study is the development of a high accuracy thermodynamic model for solution behavior, and highly soluble M(III)Cl3(s) (M= Al, Fe, Cr) minerals solubility in Na-Al(III)-Cr(III)-Fe(III)-Cl-H2O system at 25°C. Comprehensive thermodynamic models that accurately predict aluminium, chromium and iron aqueous chemistry and M(III) mineral solubilities as a function of pH, solution composition and concentration are critical for understanding many important geochemical and environmental processes involving these metals (e.g., mineral dissolution/alteration, rock formation, changes in rock permeability and fluid flow, soil formation, mass transport, toxic M(III) remediation). Such a model would also have many industrial applications (e.g., aluminium, chromium and iron production, and their corrosion, solve scaling problems in geothermal energy and oil production). Comparisons of solubility and activity calculations with the experimental data in binary and ternary systems indicate that model predictions are within the uncertainty of the data. Limitations of the model due to data insufficiencies are discussed. The solubility modeling approach, implemented to the Pitzer specific interaction equations is employed. The resulting parameterization was developed for the geochemical Pitzer formalism based PHREEQC database.

  14. Thermodynamic model for solution behavior and solid-liquid equilibrium in Na-Al(III-Fe(III-Cr(III-Cl-H2O system at 25°C

    Directory of Open Access Journals (Sweden)

    André Laurent

    2018-03-01

    Full Text Available The knowledge of the thermodynamic behavior of multicomponent aqueous electrolyte systems is of main interest in geo-, and environmental-sciences. The main objective of this study is the development of a high accuracy thermodynamic model for solution behavior, and highly soluble M(IIICl3(s (M= Al, Fe, Cr minerals solubility in Na-Al(III-Cr(III-Fe(III-Cl-H2O system at 25°C. Comprehensive thermodynamic models that accurately predict aluminium, chromium and iron aqueous chemistry and M(III mineral solubilities as a function of pH, solution composition and concentration are critical for understanding many important geochemical and environmental processes involving these metals (e.g., mineral dissolution/alteration, rock formation, changes in rock permeability and fluid flow, soil formation, mass transport, toxic M(III remediation. Such a model would also have many industrial applications (e.g., aluminium, chromium and iron production, and their corrosion, solve scaling problems in geothermal energy and oil production. Comparisons of solubility and activity calculations with the experimental data in binary and ternary systems indicate that model predictions are within the uncertainty of the data. Limitations of the model due to data insufficiencies are discussed. The solubility modeling approach, implemented to the Pitzer specific interaction equations is employed. The resulting parameterization was developed for the geochemical Pitzer formalism based PHREEQC database.

  15. 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.

  16. Computing Equilibrium Chemical Compositions

    Science.gov (United States)

    Mcbride, Bonnie J.; Gordon, Sanford

    1995-01-01

    Chemical Equilibrium With Transport Properties, 1993 (CET93) computer program provides data on chemical-equilibrium compositions. Aids calculation of thermodynamic properties of chemical systems. Information essential in design and analysis of such equipment as compressors, turbines, nozzles, engines, shock tubes, heat exchangers, and chemical-processing equipment. CET93/PC is version of CET93 specifically designed to run within 640K memory limit of MS-DOS operating system. CET93/PC written in FORTRAN.

  17. 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

  18. 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.

  19. Geochemical and iron isotopic insights into hydrothermal iron oxyhydroxide deposit formation at Loihi Seamount

    Science.gov (United States)

    Rouxel, Olivier; Toner, Brandy; Germain, Yoan; Glazer, Brian

    2018-01-01

    Low-temperature hydrothermal vents, such as those encountered at Loihi Seamount, harbor abundant microbial communities and provide ideal systems to test hypotheses on biotic versus abiotic formation of hydrous ferric oxide (FeOx) deposits at the seafloor. Hydrothermal activity at Loihi Seamount produces abundant microbial mats associated with rust-colored FeOx deposits and variably encrusted with Mn-oxyhydroxides. Here, we applied Fe isotope systematics together with major and trace element geochemistry to study the formation mechanisms and preservation of such mineralized microbial mats. Iron isotope composition of warm (<60 °C), Fe-rich and H2S-depleted hydrothermal fluids yielded δ56Fe values near +0.1‰, indistinguishable from basalt values. Suspended particles in the vent fluids and FeOx deposits recovered nearby active vents yielded systematically positive δ56Fe values. The enrichment in heavy Fe isotopes between +1.05‰ and +1.43‰ relative to Fe(II) in vent fluids suggest partial oxidation of Fe(II) during mixing of the hydrothermal fluid with seawater. By comparing the results with experimentally determined Fe isotope fractionation factors, we determined that less than 20% of Fe(II) is oxidized within active microbial mats, although this number may reach 80% in aged or less active deposits. These results are consistent with Fe(II) oxidation mediated by microbial processes considering the expected slow kinetics of abiotic Fe oxidation in low oxygen bottom water at Loihi Seamount. In contrast, FeOx deposits recovered at extinct sites have distinctly negative Fe-isotope values down to -1.77‰ together with significant enrichment in Mn and occurrence of negative Ce anomalies. These results are best explained by the near-complete oxidation of an isotopically light Fe(II) source produced during the waning stage of hydrothermal activity under more oxidizing conditions. Light Fe isotope values of FeOx are therefore generated by subsurface precipitation of

  20. Theory of chemical equilibrium in a lattice

    International Nuclear Information System (INIS)

    Dietrich, K.; Dufour, M.; Balazs, N.L.

    1989-01-01

    The chemical equilibrium is studied for the reaction A+B↔C, assuming that, initially, the particles B form a lattice and the particles A are statistically distributed on interstices. A mass action law is derived which defines the numbers n A , n B , n C of particles A, B, C in the chemical equilibrium assuming the initial distribution to be known. It predicts a considerably larger number n C of fused particles C compared to the mass action law for the gaseous phase. The result holds for an ordinary as well as for a nuclear lattice. Its possible relevance for the production of proton-rich isotopes in the universe is discussed. (orig.)

  1. Iron and oxygen isotope fractionation during iron UV photo-oxidation: Implications for early Earth and Mars

    Science.gov (United States)

    Nie, Nicole X.; Dauphas, Nicolas; Greenwood, Richard C.

    2017-01-01

    Banded iron formations (BIFs) contain appreciable amounts of ferric iron (Fe3+). The mechanism by which ferrous iron (Fe2+) was oxidized into Fe3+ in an atmosphere that was globally anoxic is highly debated. Of the three scenarios that have been proposed to explain BIF formation, photo-oxidation by UV photons is the only one that does not involve life (the other two are oxidation by O2 produced by photosynthesis, and anoxygenic photosynthesis whereby Fe2+ is directly used as electron donor in place of water). We experimentally investigated iron and oxygen isotope fractionation imparted by iron photo-oxidation at a pH of 7.3. The iron isotope fractionation between precipitated Fe3+-bearing lepidocrocite and dissolved Fe2+ follows a Rayleigh distillation with an instantaneous 56Fe/54Fe fractionation factor of + 1.2 ‰. Such enrichment in the heavy isotopes of iron is consistent with the values measured in BIFs. We also investigated the nature of the mass-fractionation law that governs iron isotope fractionation in the photo-oxidation experiments (i.e., the slope of the δ56Fe-δ57Fe relationship). The experimental run products follow a mass-dependent law corresponding to the high-T equilibrium limit. The fact that a ∼3.8 Gyr old BIF sample (IF-G) from Isua (Greenland) falls on the same fractionation line confirms that iron photo-oxidation in the surface layers of the oceans was a viable pathway to BIF formation in the Archean, when the atmosphere was largely transparent to UV photons. Our experiments allow us to estimate the quantum yield of the photo-oxidation process (∼0.07 iron atom oxidized per photon absorbed). This yield is used to model iron oxidation on early Mars. As the photo-oxidation proceeds, the aqueous medium becomes more acidic, which slows down the reaction by changing the speciation of iron to species that are less efficient at absorbing UV-photons. Iron photo-oxidation in centimeter to meter-deep water ponds would take months to years to

  2. Stable isotopes

    International Nuclear Information System (INIS)

    Evans, D.K.

    1986-01-01

    Seventy-five percent of the world's stable isotope supply comes from one producer, Oak Ridge Nuclear Laboratory (ORNL) in the US. Canadian concern is that foreign needs will be met only after domestic needs, thus creating a shortage of stable isotopes in Canada. This article describes the present situation in Canada (availability and cost) of stable isotopes, the isotope enrichment techniques, and related research programs at Chalk River Nuclear Laboratories (CRNL)

  3. Isotope separation

    International Nuclear Information System (INIS)

    Ravoire, Jean

    1978-11-01

    Separation of isotopes is treated in a general way, with special reference to the production of enriched uranium. Uses of separated isotopes are presented quickly. Then basic definitions and theoretical concepts are explained: isotopic effects, non statistical and statistical processes, reversible and irreversible processes, separation factor, enrichment, cascades, isotopic separative work, thermodynamics. Afterwards the main processes and productions are reviewed. Finally the economical and industrial aspects of uranium enrichment are resumed [fr

  4. 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.

  5. Equilibrium shoreface profiles

    DEFF Research Database (Denmark)

    Aagaard, Troels; Hughes, Michael G

    2017-01-01

    Large-scale coastal behaviour models use the shoreface profile of equilibrium as a fundamental morphological unit that is translated in space to simulate coastal response to, for example, sea level oscillations and variability in sediment supply. Despite a longstanding focus on the shoreface...... profile and its relevance to predicting coastal response to changing environmental conditions, the processes and dynamics involved in shoreface equilibrium are still not fully understood. Here, we apply a process-based empirical sediment transport model, combined with morphodynamic principles to provide...... new insight into equilibrium shoreface profile development and shape. The quantitative model is based on field measurements and shows that a balance between onshore sediment transport due to oscillatory wave motion, and offshore sediment transport due to gravity, produces profile shapes...

  6. Isotope separation

    International Nuclear Information System (INIS)

    Eerkens, J.W.

    1979-01-01

    A method of isotope separation is described which involves the use of a laser photon beam to selectively induce energy level transitions of an isotope molecule containing the isotope to be separated. The use of the technique for 235 U enrichment is demonstrated. (UK)

  7. MHD equilibrium and stability

    International Nuclear Information System (INIS)

    Pfirsch, D.

    1978-01-01

    The first part of this lecture discusses the influence of current profiles and noncircular cross-sections on the maximum β obtainable in a Tokamak from the MHD equilibrium point of view. The second part treats limitations on such MHD equilibria resulting from various MHD instabilities like external and internal kinks, localized and nonlocalized modes- and axisymmetric instabilities

  8. Microeconomics : Equilibrium and Efficiency

    NARCIS (Netherlands)

    Ten Raa, T.

    2013-01-01

    Microeconomics: Equilibrium and Efficiency teaches how to apply microeconomic theory in an innovative, intuitive and concise way. Using real-world, empirical examples, this book not only covers the building blocks of the subject, but helps gain a broad understanding of microeconomic theory and

  9. Differential Equation of Equilibrium

    African Journals Online (AJOL)

    user

    differential equation of equilibrium, comparable to that of beam on elastic foundation, was derived from static principles on the ... tedious and more time saving than the classical method in the solution of the aforementioned differential equation. ... silos, pipelines, bridge arches or wind turbine towers [3]. The objective of this ...

  10. Differential Equation of Equilibrium

    African Journals Online (AJOL)

    user

    Department of Civil Engineering. University of Nigeria Nsukka. ABSTRACT. Analysis of underground circular cylindrical shell is carried out in this work. The forth order differential equation of equilibrium, comparable to that of beam on elastic foundation, was derived from static principles on the assumptions of P. L Pasternak.

  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...

  12. Comments on equilibrium, transient equilibrium, and secular equilibrium in serial radioactive decay

    International Nuclear Information System (INIS)

    Prince, J.R.

    1979-01-01

    Equations describing serial radioactive decay are reviewed along with published descriptions or transient and secular equilibrium. It is shown that terms describing equilibrium are not used in the same way by various authors. Specific definitions are proposed; they suggest that secular equilibrium is a subset of transient equilibrium

  13. Combined iron and magnesium isotope geochemistry of pyroxenite xenoliths from Hannuoba, North China Craton: implications for mantle metasomatism

    Science.gov (United States)

    Zhao, Xin Miao; Cao, Hui Hui; Mi, Xue; Evans, Noreen J.; Qi, Yu Han; Huang, Fang; Zhang, Hong Fu

    2017-06-01

    We present high-precision iron and magnesium isotopic data for diverse mantle pyroxenite xenoliths collected from Hannuoba, North China Craton and provide the first combined iron and magnesium isotopic study of such rocks. Compositionally, these xenoliths range from Cr-diopside pyroxenites and Al-augite pyroxenites to garnet-bearing pyroxenites and are taken as physical evidence for different episodes of melt injection. Our results show that both Cr-diopside pyroxenites and Al-augite pyroxenites of cumulate origin display narrow ranges in iron and magnesium isotopic compositions (δ57Fe = -0.01 to 0.09 with an average of 0.03 ± 0.08 (2SD, n = 6); δ26Mg = - 0.28 to -0.25 with an average of -0.26 ± 0.03 (2SD, n = 3), respectively). These values are identical to those in the normal upper mantle and show equilibrium inter-mineral iron and magnesium isotope fractionation between coexisting mantle minerals. In contrast, the garnet-bearing pyroxenites, which are products of reactions between peridotites and silicate melts from an ancient subducted oceanic slab, exhibit larger iron isotopic variations, with δ57Fe ranging from 0.12 to 0.30. The δ57Fe values of minerals in these garnet-bearing pyroxenites also vary widely (-0.25 to 0.08 in olivines, -0.04 to 0.25 in orthopyroxenes, -0.07 to 0.31 in clinopyroxenes, 0.07 to 0.48 in spinels and 0.31-0.42 in garnets). In addition, the garnet-bearing pyroxenite shows light δ26Mg (-0.43) relative to the mantle. The δ26Mg of minerals in the garnet-bearing pyroxenite range from -0.35 for olivine and orthopyroxene, to -0.34 for clinopyroxene, 0.04 for spinel and -0.68 for garnet. These measured values stand in marked contrast to calculated equilibrium iron and magnesium isotope fractionation between coexisting mantle minerals at mantle temperatures derived from theory, indicating disequilibrium isotope fractionation. Notably, one phlogopite clinopyroxenite with an apparent later metasomatic overprint has the heaviest δ57Fe

  14. Decontamination of radioactive isotopes

    International Nuclear Information System (INIS)

    Despotovic, R.; Music, S.; Subotic, B.; Wolf, R.H.H.

    1979-01-01

    Removal of radioactive isotopes under controlled conditions is determined by a number of physical and chemical properties considered radiocontaminating and by the characteristics of the contaminated object. Determination of quantitative and qualitative factors for equilibrium in a contamination-decontamination system provides the basis for rational and successful decontamination. The decontamination of various ''solid/liquid'' systems is interesting from the scientific and technological point of view. These systems are of great importance in radiation protection (decontamination of various surfaces, liquids, drinking water, fixation or collection of radiocontaminants). Different types of decontamination systems are discussed. The dependence of rate and efficiency of the preparation conditions and on the ageing of the scavenger is described. The influence of coagulating electrolyte on radioactive isotope fixation efficiency was also determined. The fixation of fission radionuclide on oxide scavengers has been studied. The connection between fundamental investigations and practical decontamination of the ''solid/liquid'' systems is discussed. (author)

  15. Chromatographic hydrogen isotope separation

    International Nuclear Information System (INIS)

    Aldridge, F.T.

    1983-01-01

    Intermetallic compounds with the CaCu5 type of crystal structure, particularly LaNiCo and CaNi5, exhibit high separation factors and fast equilibrium times and therefore are useful for packing a chromatographic hydrogen isotope separation column. The addition of an inert metal to dilute the hydride improves performance of the column. A large scale multi-stage chromatographic separation process run as a secondary process off a hydrogen feedstream from an industrial plant which uses large volumes of hydrogen can produce large quantities of heavy water at an effective cost for use in heavy water reactors

  16. Chromatographic hydrogen isotope separation

    Science.gov (United States)

    Aldridge, F.T.

    Intermetallic compounds with the CaCu/sub 5/ type of crystal structure, particularly LaNiCo/sub 4/ and CaNi/sub 5/, exhibit high separation factors and fast equilibrium times and therefore are useful for packing a chromatographic hydrogen isotope separation column. The addition of an inert metal to dilute the hydride improves performance of the column. A large scale multi-stage chromatographic separation process run as a secondary process off a hydrogen feedstream from an industrial plant which uses large volumes of hydrogen cn produce large quantities of heavy water at an effective cost for use in heavy water reactors.

  17. Physical conditions in CaFe interstellar clouds

    OpenAIRE

    Gnacinski, P.; Krogulec, M.

    2007-01-01

    Interstellar clouds that exhibit strong Ca I and Fe I lines were called CaFe clouds. The ionisation equilibrium equations were used to model the column densities of Ca II, Ca I, K I, Na I, Fe I and Ti II in CaFe clouds. The chemical composition of CaFe clouds is that of the Solar System and no depletion of elements onto dust grains is seen. The CaFe clouds have high electron densities n=1 cm^-3 that leads to high column densities of neutral Ca and Fe.

  18. The Marine Geochemistry of Iron and Iron Isotopes

    National Research Council Canada - National Science Library

    Bergquist, Bridget A

    2004-01-01

    .... Most of the variation in dissolved Fe is due to variations in colloidal Fe (0.02 to 0.4 micrometer). Trace metal clean plankton tows, river samples, aerosol leachates, and porewater samples were measured for their Fe isotopic composition...

  19. Isotope enrichment

    International Nuclear Information System (INIS)

    Garbuny, M.

    1979-01-01

    The invention discloses a method for deriving, from a starting material including an element having a plurality of isotopes, derived material enriched in one isotope of the element. The starting material is deposited on a substrate at less than a critical submonatomic surface density, typically less than 10 16 atoms per square centimeter. The deposit is then selectively irradiated by a laser (maser or electronic oscillator) beam with monochromatic coherent radiation resonant with the one isotope causing the material including the one istope to escape from the substrate. The escaping enriched material is then collected. Where the element has two isotopes, one of which is to be collected, the deposit may be irradiated with radiation resonant with the other isotope and the residual material enriched in the one isotope may be evaporated from the substrate and collected

  20. Gated equilibrium bloodpool scintigraphy

    International Nuclear Information System (INIS)

    Reinders Folmer, S.C.C.

    1981-01-01

    This thesis deals with the clinical applications of gated equilibrium bloodpool scintigraphy, performed with either a gamma camera or a portable detector system, the nuclear stethoscope. The main goal has been to define the value and limitations of noninvasive measurements of left ventricular ejection fraction as a parameter of cardiac performance in various disease states, both for diagnostic purposes as well as during follow-up after medical or surgical intervention. Secondly, it was attempted to extend the use of the equilibrium bloodpool techniques beyond the calculation of ejection fraction alone by considering the feasibility to determine ventricular volumes and by including the possibility of quantifying valvular regurgitation. In both cases, it has been tried to broaden the perspective of the observations by comparing them with results of other, invasive and non-invasive, procedures, in particular cardiac catheterization, M-mode echocardiography and myocardial perfusion scintigraphy. (Auth.)

  1. 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.

  2. 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

  3. Predictive Framework and Experimental Tests of the Kinetic Isotope Effect at Redox-Active Interfaces

    Science.gov (United States)

    Kavner, A.; John, S.; Black, J. R.

    2013-12-01

    Electrochemical reactions provide a compelling framework to study kinetic isotope effects because redox-related processes are important for a wide variety of geological and environmental processes. In the laboratory, electrochemical reaction rates can be electronically controlled and measured in the laboratory using a potentiostat. This enables variation of redox reactions rates independent of changes in chemistry and, and the resulting isotope compositions of reactants and products can be separated and analyzed. In the past years, a series of experimental studies have demonstrated a large, light, and tunable kinetic isotope effect during electrodeposition of metal Fe, Zn, Li, Cu, and Mo from a variety of solutions (e.g. Black et al., 2009, 2010, 2011). A theoretical framework based on Marcus kinetic theory predicts a voltage-dependent kinetic isotope effect (Kavner et al., 2005, 2008), however while this framework was able to predict the tunable nature of the effect, it was not able to simultaneously predict absolute reaction rates and relative isotope rates. Here we present a more complete development of a statistical mechanical framework for simple interfacial redox reactions, which includes isotopic behavior. The framework is able to predict a kinetic isotope effect as a function of temperature and reaction rate, starting with three input parameters: a single reorganization energy which describes the overall kinetics of the electron transfer reaction, and the equilibrium reduced partition function ratios for heavy and light isotopes in the product and reactant phases. We show the framework, elucidate some of the predictions, and show direct comparisons against isotope fractionation data obtained during laboratory and natural environment redox processes. A. Kavner, A. Shahar, F. Bonet, J. Simon and E. Young (2005) Geochim. Cosmochim. Acta, 69(12), 2971-2979. A. Kavner, S. G. John, S. Sass, and E. A. Boyle (2008), Geochim. Cosmochim. Acta, vol 72, pp. 1731

  4. Iron and oxygen isotope signatures of the Pea Ridge and Pilot Knob magnetite-apatite deposits, southeast Missouri, USA

    Science.gov (United States)

    Childress, Tristan; Simon, Adam C.; Day, Warren C.; Lundstrom, Craig C.; Bindeman, Ilya N.

    2016-01-01

    New O and Fe stable isotope ratios are reported for magnetite samples from high-grade massive magnetite of the Mesoproterozoic Pea Ridge and Pilot Knob magnetite-apatite ore deposits and these results are compared with data for other iron oxide-apatite deposits to shed light on the origin of the southeast Missouri deposits. The δ18O values of magnetite from Pea Ridge (n = 12) and Pilot Knob (n = 3) range from 1.0 to 7.0 and 3.3 to 6.7‰, respectively. The δ56Fe values of magnetite from Pea Ridge (n = 10) and Pilot Knob (n = 6) are 0.03 to 0.35 and 0.06 to 0.27‰, respectively. These δ18O and the δ56Fe values suggest that magnetite crystallized from a silicate melt (typical igneous δ56Fe ranges 0.06–0.49‰) and grew in equilibrium with a magmatic-hydrothermal aqueous fluid. We propose that the δ18O and δ56Fe data for the Pea Ridge and Pilot Knob magnetite-apatite deposits are consistent with the flotation model recently proposed by Knipping et al. (2015a), which invokes flotation of a magmatic magnetite-fluid suspension and offers a plausible explanation for the igneous (i.e., up to ~15.9 wt % TiO2 in magnetite) and hydrothermal features of the deposits.

  5. Isotope separation

    International Nuclear Information System (INIS)

    Bartlett, R.J.; Morrey, J.R.

    1978-01-01

    A method and apparatus is described for separating gas molecules containing one isotope of an element from gas molecules containing other isotopes of the same element in which all of the molecules of the gas are at the same electronic state in their ground state. Gas molecules in a gas stream containing one of the isotopes are selectively excited to a different electronic state while leaving the other gas molecules in their original ground state. Gas molecules containing one of the isotopes are then deflected from the other gas molecules in the stream and thus physically separated

  6. Equilibrium thermodynamics - Callen's postulational approach

    NARCIS (Netherlands)

    Jongschaap, R.J.J.; Öttinger, Hans Christian

    2001-01-01

    In order to provide the background for nonequilibrium thermodynamics, we outline the fundamentals of equilibrium thermodynamics. Equilibrium thermodynamics must not only be obtained as a special case of any acceptable nonequilibrium generalization but, through its shining example, it also elucidates

  7. Equilibrium Arrival Times to Queues

    DEFF Research Database (Denmark)

    Breinbjerg, Jesper; Østerdal, Lars Peter

    a symmetric (mixed) Nash equilibrium, and show that there is at most one symmetric equilibrium. We provide a numerical method to compute this equilibrium and demonstrate by a numerical example that the social effciency can be lower than the effciency induced by a similar queueing system that serves customers...

  8. Isotope effects in gas-phase chemical reactions and photodissociation processes: Overview

    International Nuclear Information System (INIS)

    Kaye, J.A.

    1992-01-01

    The origins of isotope effects in equilibrium and non-equilibrium chemical processes are reviewed. In non-equilibrium processes, attention is given to isotope effects in simple bimolecular reactions, symmetry-related reactions, and photodissociation processes. Recent examples of isotope effects in these areas are reviewed. Some indication of other scientific areas for which measurements and/or calculations of isotope effects are used is also given. Examples presented focus on neutral molecule chemistry and in many cases complement examples considered in greater detail in the other chapters of this volume

  9. Isotopic separation

    International Nuclear Information System (INIS)

    Chen, C.L.

    1979-01-01

    Isotopic species in an isotopic mixture including a first species having a first isotope and a second species having a second isotope are separated by selectively exciting the first species in preference to the second species and then reacting the selectively excited first species with an additional preselected radiation, an electron or another chemical species so as to form a product having a mass different from the original species and separating the product from the balance of the mixture in a centrifugal separating device such as centrifuge or aerodynamic nozzle. In the centrifuge the isotopic mixture is passed into a rotor where it is irradiated through a window. Heavier and lighter components can be withdrawn. The irradiated mixture experiences a large centrifugal force and is separated in a deflection area into lighter and heavier components. (UK)

  10. Isotopic separation

    International Nuclear Information System (INIS)

    Castle, P.M.

    1979-01-01

    This invention relates to molecular and atomic isotope separation and is particularly applicable to the separation of 235 U from other uranium isotopes including 238 U. In the method described a desired isotope is separated mechanically from an atomic or molecular beam formed from an isotope mixture utilising the isotropic recoil momenta resulting from selective excitation of the desired isotope species by radiation, followed by ionization or dissociation by radiation or electron attachment. By forming a matrix of UF 6 molecules in HBr molecules so as to collapse the V 3 vibrational mode of the UF 6 molecule the 235 UF 6 molecules are selectively excited to promote reduction of UF 6 molecules containing 235 U and facilitate separation. (UK)

  11. 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

  12. Hydrogen and chlorine isotope exchange in n-methylimidazolium chloride

    International Nuclear Information System (INIS)

    Szydlowski, J.; Kimizuka, W.

    1993-01-01

    Isotope exchange of deuterium and 36 Cl between N-methylimidazolium chloride and gaseous hydrogen chloride has been studied over the temperature range of 249-322 K. A mechanism of exchange for both atoms is proposed and the equilibrium isotope effect of deuterium accompanying this reaction is discussed. (author) 10 refs.; 1 tab

  13. 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. Copyright © 2016 Elsevier Ltd. All rights reserved.

  14. Assessing kinetic fractionation in brachiopod calcite using clumped isotopes

    OpenAIRE

    Bajnai, David; Fiebig, Jens; Tomašových, Adam; Milner Garcia, Sara; Rollion-Bard, Claire; Raddatz, Jacek; Löffler, Niklas; Primo-Ramos, Cristina; Brand, Uwe

    2018-01-01

    Brachiopod shells are the most widely used geological archive for the reconstruction of the temperature and the oxygen isotope composition of Phanerozoic seawater. However, it is not conclusive whether brachiopods precipitate their shells in thermodynamic equilibrium. In this study, we investigated the potential impact of kinetic controls on the isotope composition of modern brachiopods by measuring the oxygen and clumped isotope compositions of their shells. Our results show that clumped and...

  15. Isotope separation

    International Nuclear Information System (INIS)

    Coleman, J.H.; Marks, T.J.

    1981-01-01

    A process for separating uranium isotopes is described which includes: preparing a volatile compound U-T, in which U is a mixture of uranium isotopes and T is a chemical moiety containing at least one organic or deuterated borohydride group, and which exhibits for at least one isotopic species thereof a fundamental, overtone or combination vibrational absorption excitation energy level at a frequency between 900 and 1100 cm -1 ; and irradiating the compound in the vapour phase with energy emitted by a radiation source at a frequency between 900 and 1100 cm -1 (e.g. a CO 2 laser). (author)

  16. Pathways of coupled arsenic and iron cycling in high arsenic groundwater of the Hetao basin, Inner Mongolia, China: an iron isotope approach

    Science.gov (United States)

    Guo, Huaming; Liu, Chen; Lu, Hai; Wanty, Richard B.; Wang, Jun; Zhou, Yinzhu

    2013-01-01

    High As groundwater is widely distributed all over the world, which has posed a significant health impact on millions of people. Iron isotopes have recently been used to characterize Fe cycling in aqueous environments, but there is no information on Fe isotope characteristics in the groundwater. Since groundwater As behavior is closely associated with Fe cycling in the aquifers, Fe isotope signatures may help to characterize geochemical processes controlling As concentrations of shallow groundwaters. This study provides the first observation of Fe isotope fractionation in high As groundwater and evaluation of Fe cycling and As behaviors in shallow aquifers in terms of Fe isotope signatures. Thirty groundwater samples were taken for chemical and isotopic analysis in the Hetao basin, Inner Mongolia. Thirty-two sediments were sampled as well from shallow aquifers for Fe isotope analysis. Results showed that groundwater was normally enriched in isotopically light Fe with δ56Fe values between −3.40‰ and 0.58‰ and median of −1.14‰, while heavier δ56Fe values were observed in the sediments (between −1.10‰ and 0.75‰, median +0.36‰). In reducing conditions, groundwaters generally had higher δ56Fe values, in comparison with oxic conditions. High As groundwaters, generally occurring in reducing conditions, had high δ56Fe values, while low As groundwaters normally had low δ56Fe values. Although sediment δ56Fe values were generally independent of lithological conditions, a large variation in sediment δ56Fe values was observed in the oxidation–reduction transition zone. Three pathways were identified for Fe cycling in shallow groundwater, including dissimilatory reduction of Fe(III) oxides, re-adsorption of Fe(II), and precipitation of pyrite and siderite. Dissimilatory reduction of Fe(III) oxides resulted in light δ56Fe values (around −1.0‰) and high As concentration (>50 μg/L) in groundwater in anoxic conditions. Re-adsorption of isotopically

  17. 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 increasingly involve competing interactions, geometric frustration, spatial and temporal intrinsic inhomogeneity, nanoscale structures, and interactions spanning many scales. We will focus on a broad class of emerging problems that will require new tools in non-equilibrium statistical physics and that will find application in new material functionality, in predicting complex spatial dynamics, and in understanding novel states of matter. Our work will encompass materials under extreme conditions involving elastic/plastic deformation, competing interactions, intrinsic inhomogeneity, frustration in condensed matter systems, scaling phenomena in disordered materials from glasses to granular matter, quantum chemistry applied to nano-scale materials, soft-matter materials, and spatio-temporal properties of both ordinary and complex fluids.

  18. 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...

  19. Isotope laboratories

    International Nuclear Information System (INIS)

    1978-01-01

    This report from the Dutch Ministry of Health is an advisory document concerned with isotope laboratories in hospitals, in connection with the Dutch laws for hospitals. It discusses which hospitals should have isotope laboratories and concludes that as many hospitals as possible should have small laboratories so that emergency cases can be dealt with. It divides the Netherlands into regions and suggests which hospitals should have these facilities. The questions of how big each lab. is to be, what equipment each has, how each lab. is organised, what therapeutic and diagnostic work should be carried out by each, etc. are discussed. The answers are provided by reports from working groups for in vivo diagnostics, in vitro diagnostics, therapy, and safety and their results form the criteria for the licences of isotope labs. The results of a questionnaire for isotope labs. already in the Netherlands are presented, and their activities outlined. (C.F.)

  20. Isotope Identification

    Energy Technology Data Exchange (ETDEWEB)

    Karpius, Peter Joseph [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2017-09-18

    The objective of this training modules is to examine the process of using gamma spectroscopy for radionuclide identification; apply pattern recognition to gamma spectra; identify methods of verifying energy calibration; and discuss potential causes of isotope misidentification.

  1. Multiple stable isotope fronts during non-isothermal fluid flow

    Science.gov (United States)

    Fekete, Szandra; Weis, Philipp; Scott, Samuel; Driesner, Thomas

    2018-02-01

    Stable isotope signatures of oxygen, hydrogen and other elements in minerals from hydrothermal veins and metasomatized host rocks are widely used to investigate fluid sources and paths. Previous theoretical studies mostly focused on analyzing stable isotope fronts developing during single-phase, isothermal fluid flow. In this study, numerical simulations were performed to assess how temperature changes, transport phenomena, kinetic vs. equilibrium isotope exchange, and isotopic source signals determine mineral oxygen isotopic compositions during fluid-rock interaction. The simulations focus on one-dimensional scenarios, with non-isothermal single- and two-phase fluid flow, and include the effects of quartz precipitation and dissolution. If isotope exchange between fluid and mineral is fast, a previously unrecognized, significant enrichment in heavy oxygen isotopes of fluids and minerals occurs at the thermal front. The maximum enrichment depends on the initial isotopic composition of fluid and mineral, the fluid-rock ratio and the maximum change in temperature, but is independent of the isotopic composition of the incoming fluid. This thermally induced isotope front propagates faster than the signal related to the initial isotopic composition of the incoming fluid, which forms a trailing front behind the zone of transient heavy oxygen isotope enrichment. Temperature-dependent kinetic rates of isotope exchange between fluid and rock strongly influence the degree of enrichment at the thermal front. In systems where initial isotope values of fluids and rocks are far from equilibrium and isotope fractionation is controlled by kinetics, the temperature increase accelerates the approach of the fluid to equilibrium conditions with the host rock. Consequently, the increase at the thermal front can be less dominant and can even generate fluid values below the initial isotopic composition of the input fluid. As kinetics limit the degree of isotope exchange, a third front may

  2. Elemental and isotopic (C, O, Sr, Nd) compositions of Late Paleozoic carbonated eclogite and marble from the SW Tianshan UHP belt, NW China: Implications for deep carbon cycle

    Science.gov (United States)

    Zhu, Jianjiang; Zhang, Lifei; Lü, Zeng; Bader, Thomas

    2018-03-01

    Subduction zones are important for understanding of the global carbon cycle from the surface to deep part of the mantle. The processes involved the metamorphism of carbonate-bearing rocks largely control the fate of carbon and contribute to local carbon isotopic heterogeneities of the mantle. In this study, we present petrological and geochemical results for marbles and carbonated eclogites in the Southwestern Tianshan UHP belt, NW China. Marbles are interlayered with coesite-bearing pelitic schists, and have Sr-Nd isotopic values (εNd (T=320Ma) = -3.7 to -8.9, 87Sr/86Sr (i) = 0.7084-0.7089), typical of marine carbonates. The marbles have dispersed low δ18OVSMOW values (ranging from 14 to 29‰) and unaffected carbon isotope (δ13CVPDB = -0.2-3.6‰), possibly due to infiltration of external H2O-rich fluids. Recycling of these marbles into mantle may play a key role in the carbon budget and contributed to the mantle carbon isotope heterogeneity. The carbonated eclogites have high Sr isotopic compositions (87Sr/86Sr (i) = 0.7077-0.7082) and positive εNd (T = 320 Ma) values (from 7.6 to 8.2), indicative of strong seafloor alteration of their protolith. The carbonates in the carbonated eclogites are mainly dolomite (Fe# = 12-43, Fe# = Fe2+/(Fe2+ + Mg)) that were added into oceanic basalts during seafloor alteration and experienced calcite - dolomite - magnesite transformation during the subduction metamorphic process. The uniformly low δ18O values (∼11.44‰) of carbonates in the carbontaed eclogites can be explained by closed-system equilibrium between carbonate and silicate minerals. The low δ13C values (from -3.3 to -7.7‰) of the carbonated eclogites most likely reflect contribution from organic carbon. Recycling of these carbonated eclogites with C isotope similar to typical mantle reservoirs into mantle may have little effect on the mantle carbon isotope heterogeneity.

  3. 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...

  4. Adsorption characteristics of Fe(III) and Fe(III)-NTA complex on granular activated carbon.

    Science.gov (United States)

    Kim, D S

    2004-01-02

    The adsorption of Fe(3+) ion on granular activated carbon has been studied in kinetic and equilibrium conditions taking into account the adsorbate concentration, temperature and solution pH as major influential factors. In addition, the effect of nitrilotriacetic acid on adsorption reaction as a complexing agent has been examined. Kinetic studies showed that the adsorption rate was increased as the initial Fe(3+) concentration was raised. The adsorption reaction was estimated to be first-order at room temperature. The adsorption rate and equilibrium adsorption of Fe(3+) increased as the temperature rose. The activation energy for adsorption was approximately 2.23 kJ mol(-1), which implied that Fe(3+) mainly physically adsorbed on activated carbon. Coexistence of nitrilotriacetic acid with Fe(3+) resulted in a decrease of equilibrium adsorption and the extent of decrease was proportional to the concentration of nitrilotriacetic acid. In the presence of nitrilotriacetic acid, the adsorbability of Fe(3+) decreased with pH. However, the trend was reversed in the absence of nitrilotriacetic acid. When activated carbon was swelled by acetic acid, the specific surface area was increased and maximum swelling was achieved at approximately 48 h of swelling time. Thermodynamic parameters such as DeltaG(o), DeltaH(o) and DeltaS(o) for adsorption reaction were estimated based on equilibrium data and in connection with these results the thermodynamic aspects of adsorption reaction were discussed.

  5. Iron isotope biogeochemistry of Neoproterozoic marine shales

    Science.gov (United States)

    Kunzmann, Marcus; Gibson, Timothy M.; Halverson, Galen P.; Hodgskiss, Malcolm S. W.; Bui, Thi Hao; Carozza, David A.; Sperling, Erik A.; Poirier, André; Cox, Grant M.; Wing, Boswell A.

    2017-07-01

    Iron isotopes have been widely applied to investigate the redox evolution of Earth's surface environments. However, it is still unclear whether iron cycling in the water column or during diagenesis represents the major control on the iron isotope composition of sediments and sedimentary rocks. Interpretation of isotopic data in terms of oceanic redox conditions is only possible if water column processes dominate the isotopic composition, whereas redox interpretations are less straightforward if diagenetic iron cycling controls the isotopic composition. In the latter scenario, iron isotope data is more directly related to microbial processes such as dissimilatory iron reduction. Here we present bulk rock iron isotope data from late Proterozoic marine shales from Svalbard, northwestern Canada, and Siberia, to better understand the controls on iron isotope fractionation in late Proterozoic marine environments. Bulk shales span a δ 56Fe range from -0.45 ‰ to +1.04 ‰ . Although δ 56Fe values show significant variation within individual stratigraphic units, their mean value is closer to that of bulk crust and hydrothermal iron in samples post-dating the ca. 717-660 Ma Sturtian glaciation compared to older samples. After correcting for the highly reactive iron content in our samples based on iron speciation data, more than 90% of the calculated δ 56Fe compositions of highly reactive iron falls in the range from ca. -0.8 ‰ to +3 ‰ . An isotope mass-balance model indicates that diagenetic iron cycling can only change the isotopic composition of highly reactive iron by seawater iron reservoir, control the isotopic composition of highly reactive iron. Considering a long-term decrease in the isotopic composition of the iron source to the dissolved seawater Fe(II) reservoir to be unlikely, we offer two possible explanations for the Neoproterozoic δ 56Fe trend. First, a decreasing supply of Fe(II) to the ferrous seawater iron reservoir could have caused the reservoir

  6. General equilibrium without utility functions

    DEFF Research Database (Denmark)

    Balasko, Yves; Tvede, Mich

    2010-01-01

    How far can we go in weakening the assumptions of the general equilibrium model? Existence of equilibrium, structural stability and finiteness of equilibria of regular economies, genericity of regular economies and an index formula for the equilibria of regular economies have been known...... and the diffeomorphism of the equilibrium manifold with a Euclidean space; (2) the diffeomorphism of the set of no-trade equilibria with a Euclidean space; (3) the openness and genericity of the set of regular equilibria as a subset of the equilibrium manifold; (4) for small trade vectors, the uniqueness, regularity...

  7. Titanates of the lindsleyite–mathiasite (LIMA) group reveal isotope disequilibrium associated with metasomatism in the mantle beneath Kimberley (South Africa)

    NARCIS (Netherlands)

    Giuliani, Andrea; Woodhead, Jon D.; Phillips, David; Maas, Roland; Davies, Gareth R.; Griffin, William L.

    2018-01-01

    Radiogenic isotope variations unrelated to radiogenic ingrowth are common between minerals found in metasomatised mantle xenoliths entrained in kimberlite, basalts and related magmas. As the metasomatic minerals are assumed to have been in isotopic equilibrium originally, such variations are

  8. The empirical equilibrium structure of diacetylene

    Science.gov (United States)

    Thorwirth, Sven; Harding, Michael E.; Muders, Dirk; Gauss, Jürgen

    2008-09-01

    High-level quantum-chemical calculations are reported at the MP2 and CCSD(T) levels of theory for the equilibrium structure and the harmonic and anharmonic force fields of diacetylene, H sbnd C tbnd C sbnd C tbnd C sbnd H. The calculations were performed employing Dunning's hierarchy of correlation-consistent basis sets cc-pV XZ, cc-pCV XZ, and cc-pwCV XZ, as well as the ANO2 basis set of Almlöf and Taylor. An empirical equilibrium structure based on experimental rotational constants for 13 isotopic species of diacetylene and computed zero-point vibrational corrections is determined (reemp:r=1.0615 Å,r=1.2085 Å,r=1.3727 Å) and in good agreement with the best theoretical structure (CCSD(T)/cc-pCV5Z: r=1.0617 Å, r=1.2083 Å, r=1.3737 Å). In addition, the computed fundamental vibrational frequencies are compared with the available experimental data and found in satisfactory agreement.

  9. Napoleon Is in Equilibrium

    Science.gov (United States)

    Phillips, Rob

    2015-03-01

    It has been said that the cell is the test tube of the twenty-first century. If so, the theoretical tools needed to quantitatively and predictively describe what goes on in such test tubes lag sorely behind the stunning experimental advances in biology seen in the decades since the molecular biology revolution began. Perhaps surprisingly, one of the theoretical tools that has been used with great success on problems ranging from how cells communicate with their environment and each other to the nature of the organization of proteins and lipids within the cell membrane is statistical mechanics. A knee-jerk reaction to the use of statistical mechanics in the description of cellular processes is that living organisms are so far from equilibrium that one has no business even thinking about it. But such reactions are probably too hasty given that there are many regimes in which, because of a separation of timescales, for example, such an approach can be a useful first step. In this article, we explore the power of statistical mechanical thinking in the biological setting, with special emphasis on cell signaling and regulation. We show how such models are used to make predictions and describe some recent experiments designed to test them. We also consider the limits of such models based on the relative timescales of the processes of interest.

  10. Thermodynamic chemical energy transfer mechanisms of non-equilibrium, quasi-equilibrium, and equilibrium chemical reactions

    International Nuclear Information System (INIS)

    Roh, Heui-Seol

    2015-01-01

    Chemical energy transfer mechanisms at finite temperature are explored by a chemical energy transfer theory which is capable of investigating various chemical mechanisms of non-equilibrium, quasi-equilibrium, and equilibrium. Gibbs energy fluxes are obtained as a function of chemical potential, time, and displacement. Diffusion, convection, internal convection, and internal equilibrium chemical energy fluxes are demonstrated. The theory reveals that there are chemical energy flux gaps and broken discrete symmetries at the activation chemical potential, time, and displacement. The statistical, thermodynamic theory is the unification of diffusion and internal convection chemical reactions which reduces to the non-equilibrium generalization beyond the quasi-equilibrium theories of migration and diffusion processes. The relationship between kinetic theories of chemical and electrochemical reactions is also explored. The theory is applied to explore non-equilibrium chemical reactions as an illustration. Three variable separation constants indicate particle number constants and play key roles in describing the distinct chemical reaction mechanisms. The kinetics of chemical energy transfer accounts for the four control mechanisms of chemical reactions such as activation, concentration, transition, and film chemical reactions. - Highlights: • Chemical energy transfer theory is proposed for non-, quasi-, and equilibrium. • Gibbs energy fluxes are expressed by chemical potential, time, and displacement. • Relationship between chemical and electrochemical reactions is discussed. • Theory is applied to explore nonequilibrium energy transfer in chemical reactions. • Kinetics of non-equilibrium chemical reactions shows the four control mechanisms

  11. Stable isotope fractionation in response to variable fluid residence time distributions

    Science.gov (United States)

    Druhan, J. L.; Maher, K.

    2013-12-01

    Hydrogeochemical processes governing groundwater quantity and quality are often inferred from fluid samples that are the flux-weighted average of a heterogeneous system. This connection has been demonstrated for solutes subject to transport and equilibrium constraints, in which the steady state concentration - discharge relationship is cast in terms of the choice of expression for residence time distribution (Maher, 2011). Here, we examine the extent to which the spatial correlation of the permeability field, which governs the fluid residence time distribution, exerts a principle control on the partitioning of stable isotopes between reactant and product species during heterogeneous reactions in groundwater systems. We demonstrate this relationship using numerical simulations of δ53Cr fractionation due to abiotic CrO42- reduction by Fe2+, implemented in the reactive transport code CrunchFlow. The chemically homogeneous redox reaction generates Cr3+ with an isotope ratio distinct from the reactant pool, and in turn this product species precipitates as a mineral phase Cr(OH)3(s) through a non-fractionating reaction. The corresponding chromate δ53Cr enrichment across a homogeneous domain varies from a maximum value set by the kinetic fractionation factor (αk) at high mean fluid residence times, to a value reaction-limited to transport-limited regimes. For physically heterogeneous flow fields, the transition in isotopic fractionation from a reaction-limited to a transport-limited regime becomes variable, and falls between the upper and lower bounds set by the homogeneous simulations at slow and fast precipitation rates, respectively. Our results show that while minimal variation occurs in the steady-state isotopic profile of the reactant species (δ53Cr of CrO42-), the combined effects of the precipitation rate and the heterogeneous structure of the porous media lead to a wide range in the steady state isotopic composition of the product species (δ53Cr of Cr3

  12. Carbon isotope heterogeneities in deep Earth: Recycling of surface carbon or from core?

    Science.gov (United States)

    Satish-Kumar, Madhusoodhan

    2017-04-01

    Subduction of crustal materials, mantle melting and upwelling of deep mantle, in addition to a potential source from the core, largely controls the Earth's deep carbon cycle. Large variations in carbon isotopic composition between different reservoirs have been used widely to differentiate the source of carbon and to understand the carbon inventories and its recycling processes. However, how far high-temperature and hign-pressure conditions can affect the carbon isotope distribution, is a question still unanswered to clearly address the deep carbon cycle. I present here a review on carbon isotope fractionation processes in deep Earth and critically evaluate whether we can easily differentiate between surface carbon and deep carbon based on isotope characteristics. Recent experimental carbon isotope fractionation studies in the Fe-C system suggests that light carbon is selectively partition into metallic core during early magma ocean environment (Satish-Kumar et al., 2011). Furthermore, carbonate melts can be a medium for efficient crystallisation of diamonds in Earth's mantle (Palyanov et al., 2013). Rayleigh fractionation modelling based on fractionation suggests that core can be a reservoir of 12C enriched carbon and can itself form a reservoir which can cause heterogeneity in mantle carbon (Wood et al., 2013). In addition, high pressure experiments in the carbon-saturated model harzburgite system (Enstatite-Magnesite-Olivine-Graphite), carbonated silicate melting resulted in 13C enrichment in the carbon dissolved in the silicate melt relative to elemental graphite (Mizutani et al., 2014). 13C enrichment in carbonate melt were further confirmed in experiments where redox melting between olivine and graphite produced a carbonate melt as well as carbonate reduction experiments to form graphite. A third factor, still unconquered is the effect of pressure on isotope fractionation process. Theoretical studies as well as preliminary experimental studies have suggested

  13. Equilibrium and non-equilibrium controls on the abundances of clumped isotopologues of methane during thermogenic formation in laboratory experiments: Implications for the chemistry of pyrolysis and the origins of natural gases

    Science.gov (United States)

    Shuai, Yanhua; Douglas, Peter M. J.; Zhang, Shuichang; Stolper, Daniel A.; Ellis, Geoffrey S.; Lawson, Michael; Lewan, Michael D.; Formolo, Michael; Mi, Jingkui; He, Kun; Hu, Guoyi; Eiler, John M.

    2018-02-01

    Multiply isotopically substituted molecules ('clumped' isotopologues) can be used as geothermometers because their proportions at isotopic equilibrium relative to a random distribution of isotopes amongst all isotopologues are functions of temperature. This has allowed measurements of clumped-isotope abundances to be used to constrain formation temperatures of several natural materials. However, kinetic processes during generation, modification, or transport of natural materials can also affect their clumped-isotope compositions. Herein, we show that methane generated experimentally by closed-system hydrous pyrolysis of shale or nonhydrous pyrolysis of coal yields clumped-isotope compositions consistent with an equilibrium distribution of isotopologues under some experimental conditions (temperature-time conditions corresponding to 'low,' 'mature,' and 'over-mature' stages of catagenesis), but can have non-equilibrium (i.e., kinetically controlled) distributions under other experimental conditions ('high' to 'over-mature' stages), particularly for pyrolysis of coal. Non-equilibrium compositions, when present, lead the measured proportions of clumped species to be lower than expected for equilibrium at the experimental temperature, and in some cases to be lower than a random distribution of isotopes (i.e., negative Δ18 values). We propose that the consistency with equilibrium for methane formed by relatively low temperature pyrolysis reflects local reversibility of isotope exchange reactions involving a reactant or transition state species during demethylation of one or more components of kerogen. Non-equilibrium clumped-isotope compositions occur under conditions where 'secondary' cracking of retained oil in shale or wet gas hydrocarbons (C2-5, especially ethane) in coal is prominent. We suggest these non-equilibrium isotopic compositions are the result of the expression of kinetic isotope effects during the irreversible generation of methane from an alkyl

  14. Equilibrium and non-equilibrium controls on the abundances of clumped isotopologues of methane during thermogenic formation in laboratory experiments: Implications for the chemistry of pyrolysis and the origins of natural gases

    Science.gov (United States)

    Shuai, Yanhua; Douglas, Peter M.J.; Zhang, Shuichang; Stolper, Daniel A.; Ellis, Geoffrey S.; Lawson, Michael; Lewan, Michael; Formolo, Michael; Mi, Jingkui; He, Kun; Hu, Guoyi; Eiler, John M.

    2018-01-01

    Multiply isotopically substituted molecules (‘clumped’ isotopologues) can be used as geothermometers because their proportions at isotopic equilibrium relative to a random distribution of isotopes amongst all isotopologues are functions of temperature. This has allowed measurements of clumped-isotope abundances to be used to constrain formation temperatures of several natural materials. However, kinetic processes during generation, modification, or transport of natural materials can also affect their clumped-isotope compositions. Herein, we show that methane generated experimentally by closed-system hydrous pyrolysis of shale or nonhydrous pyrolysis of coal yields clumped-isotope compositions consistent with an equilibrium distribution of isotopologues under some experimental conditions (temperature–time conditions corresponding to ‘low,’ ‘mature,’ and ‘over-mature’ stages of catagenesis), but can have non-equilibrium (i.e., kinetically controlled) distributions under other experimental conditions (‘high’ to ‘over-mature’ stages), particularly for pyrolysis of coal. Non-equilibrium compositions, when present, lead the measured proportions of clumped species to be lower than expected for equilibrium at the experimental temperature, and in some cases to be lower than a random distribution of isotopes (i.e., negative Δ18 values). We propose that the consistency with equilibrium for methane formed by relatively low temperature pyrolysis reflects local reversibility of isotope exchange reactions involving a reactant or transition state species during demethylation of one or more components of kerogen. Non-equilibrium clumped-isotope compositions occur under conditions where ‘secondary’ cracking of retained oil in shale or wet gas hydrocarbons (C2-5, especially ethane) in coal is prominent. We suggest these non-equilibrium isotopic compositions are the result of the expression of kinetic isotope effects during the irreversible generation

  15. Random Hamiltonian in thermal equilibrium

    OpenAIRE

    Brody, Dorje C.; Ellis, David C. P.; Holm, Darryl D.

    2009-01-01

    A framework for the investigation of disordered quantum systems in thermal equilibrium is proposed. The approach is based on a dynamical model--which consists of a combination of a double-bracket gradient flow and a uniform Brownian fluctuation--that `equilibrates' the Hamiltonian into a canonical distribution. The resulting equilibrium state is used to calculate quenched and annealed averages of quantum observables.

  16. 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.

  17. A Multiperiod Equilibrium Pricing Model

    Directory of Open Access Journals (Sweden)

    Minsuk Kwak

    2014-01-01

    Full Text Available We propose an equilibrium pricing model in a dynamic multiperiod stochastic framework with uncertain income. There are one tradable risky asset (stock/commodity, one nontradable underlying (temperature, and also a contingent claim (weather derivative written on the tradable risky asset and the nontradable underlying in the market. The price of the contingent claim is priced in equilibrium by optimal strategies of representative agent and market clearing condition. The risk preferences are of exponential type with a stochastic coefficient of risk aversion. Both subgame perfect strategy and naive strategy are considered and the corresponding equilibrium prices are derived. From the numerical result we examine how the equilibrium prices vary in response to changes in model parameters and highlight the importance of our equilibrium pricing principle.

  18. Experimental and thermodynamic assessments of substitutions in the AlFeSi, FeMnSi, FeSiZr and AlCaFeSi systems (65 wt % Si) - solidification simulation

    Energy Technology Data Exchange (ETDEWEB)

    Gueneau, C. [CEA Centre d`Etudes de Saclay, 91 - Gif-sur-Yvette (France). Dept. des Procedes d`Enrichissement]|[Paris-11 Univ., 91 - Orsay (France)]|[Compagnie de Produits Chimiques et Electrometallurgiques Pechiney, 74 - Passy-Chedde (France). Lab. Graphitation; Servant, C. [Paris-11 Univ., 91 - Orsay (France); Ansara, I. [Ecole Nationale Superieure d`Electrochimie et d`Electrometallurgie, 38 - Grenoble (France)

    1994-12-31

    The substitutions of Al <-> Si, Fe <-> Mn and Fe <-> Zr in some intermetallic compounds of the Al-Fe-Si, Fe-Mn-Si and Fe-Si-Zr systems are modelled in the Si-rich corner using a two sublattice model. The solidification paths of the studied alloys are determined at equilibrium. The ascalculated phase volume fractions of the alloys are compared to the experimental ones. Finally, a solidification simulation using the Gulliver-Scheil`s model is performed in order to explain the formation of some precipitates experimentally observed. (authors). 14 figs., 19 refs.

  19. Isotope production

    International Nuclear Information System (INIS)

    Lewis, Dewi M.

    1995-01-01

    Some 2 0% of patients using radiopharmaceuticals receive injections of materials produced by cyclotrons. There are over 200 cyclotrons worldwide; around 35 are operated by commercial companies solely for the production of radio-pharmaceuticals with another 25 accelerators producing medically useful isotopes. These neutron-deficient isotopes are usually produced by proton bombardment. All commonly used medical isotopes can be generated by 'compact' cyclotrons with energies up to 40 MeV and beam intensities in the range 50 to 400 microamps. Specially designed target systems contain gram-quantities of highly enriched stable isotopes as starting materials. The targets can accommodate the high power densities of the proton beams and are designed for automated remote handling. The complete manufacturing cycle includes large-scale target production, isotope generation by cyclotron beam bombardment, radio-chemical extraction, pharmaceutical dispensing, raw material recovery, and labelling/packaging prior to the rapid delivery of these short-lived products. All these manufacturing steps adhere to the pharmaceutical industry standards of Good Manufacturing Practice (GMP). Unlike research accelerators, commercial cyclotrons are customized 'compact' machines usually supplied by specialist companies such as IBA (Belgium), EBCO (Canada) or Scanditronix (Sweden). The design criteria for these commercial cyclotrons are - small magnet dimensions, power-efficient operation of magnet and radiofrequency systems, high intensity extracted proton beams, well defined beam size and automated computer control. Performance requirements include rapid startup and shutdown, high reliability to support the daily production of short-lived isotopes and low maintenance to minimize the radiation dose to personnel. In 1987 a major step forward in meeting these exacting industrial requirements came when IBA, together with the University of Louvain-La-Neuve in Belgium, developed the

  20. Moessbauer-spectroscopic study of structure and magnetism of the exchange-coupled layer systems Fe/FeSn{sub 2}, and Fe/FeSi/Si and the ion-implanted diluted magnetic semiconductor SiC(Fe); Moessbauerspektroskopische Untersuchung von Struktur und Magnetismus der austauschgekoppelten Schichtsysteme Fe/FeSn{sub 2} und Fe/FeSi/Si und des ionenimplantierten verduennten magnetischen Halbleiters SiC(Fe)

    Energy Technology Data Exchange (ETDEWEB)

    Stromberg, Frank

    2009-07-07

    In line with this work the structural and magnetic properties of the exchange coupled layered systems Fe/FeSn{sub 2} and Fe/FeSi/Si and of the Fe ion implanted diluted magnetic semiconductor (DMS) SiC(Fe) were investigated. The main measuring method was the isotope selective {sup 57}Fe conversion electron Moessbauer spectroscopy (CEMS), mostly in connection with the {sup 57}Fe tracer layer technique, in a temperature range from 4.2 K to 340 K. Further measurement techniques were X-ray diffraction (XRD), electron diffraction (LEED, RHEED), SQUID magnetometry and FMR (Ferromagnetic Resonance). In the first part of this work the properties of thin AF FeSn{sub 2}(001) films and of the exchange-bias system Fe/FeSn{sub 2}(001) on InSb(001) were investigated. With the application of {sup 57}Fe-tracer layers and CEMS both the Fe-spin structure and the temperature dependence of the magnetic hyperfine field (B{sub hf}) of FeSn{sub 2} could be examined. The evaporation of Fe films on the FeSn{sub 2} films produced in the latter ones a high perpendicular spin component at the Fe/FeSn{sub 2} interface. In some distance from the interface the Fe spins rotate back into the sample plane. Furthermore {sup 57}Fe-CEMS provided a correlation between the absolute value of the exchange field vertical stroke He vertical stroke and the amount of magnetic defects within the FeSn{sub 2}. Temperature dependent CEMS-measurements yielded informations about the spin dynamics within the AF. The transition temperatures T{sub B}{sup *}, which were interpreted as superparamagnetic blocking temperatures, obtain higher values compared to the temperatures T{sub B} of the exchange-bias effect, obtained with magnetometry measurements. The second part of this work deals with the indirect exchange coupling within Fe/FeSi/Si/FeSi/Fe multilayers and FeSi diffusion barriers. The goal was to achieve Fe free Si interlayers. The CEMS results show that starting from a thickness of t{sub FeSi}=10-12 A of the

  1. Non-equilibrium supramolecular polymerization.

    Science.gov (United States)

    Sorrenti, Alessandro; Leira-Iglesias, Jorge; Markvoort, Albert J; de Greef, Tom F A; Hermans, Thomas M

    2017-09-18

    Supramolecular polymerization has been traditionally focused on the thermodynamic equilibrium state, where one-dimensional assemblies reside at the global minimum of the Gibbs free energy. The pathway and rate to reach the equilibrium state are irrelevant, and the resulting assemblies remain unchanged over time. In the past decade, the focus has shifted to kinetically trapped (non-dissipative non-equilibrium) structures that heavily depend on the method of preparation (i.e., pathway complexity), and where the assembly rates are of key importance. Kinetic models have greatly improved our understanding of competing pathways, and shown how to steer supramolecular polymerization in the desired direction (i.e., pathway selection). The most recent innovation in the field relies on energy or mass input that is dissipated to keep the system away from the thermodynamic equilibrium (or from other non-dissipative states). This tutorial review aims to provide the reader with a set of tools to identify different types of self-assembled states that have been explored so far. In particular, we aim to clarify the often unclear use of the term "non-equilibrium self-assembly" by subdividing systems into dissipative, and non-dissipative non-equilibrium states. Examples are given for each of the states, with a focus on non-dissipative non-equilibrium states found in one-dimensional supramolecular polymerization.

  2. Iron isotope fractionation and the oxygen fugacity of the mantle.

    Science.gov (United States)

    Williams, Helen M; McCammon, Catherine A; Peslier, Anne H; Halliday, Alex N; Teutsch, Nadya; Levasseur, Sylvain; Burg, Jean-Pierre

    2004-06-11

    The oxygen fugacity of the mantle exerts a fundamental influence on mantle melting, volatile speciation, and the development of the atmosphere. However, its evolution through time is poorly understood. Changes in mantle oxidation state should be reflected in the Fe3+/Fe2+ of mantle minerals, and hence in stable iron isotope fractionation. Here it is shown that there are substantial (1.7 per mil) systematic variations in the iron isotope compositions (delta57/54Fe) of mantle spinels. Spinel delta57/54Fe values correlate with relative oxygen fugacity, Fe3+/sigmaFe, and chromium number, and provide a proxy of changes in mantle oxidation state, melting, and volatile recycling.

  3. Spontaneity and Equilibrium: Why "?G Equilibrium" Are Incorrect

    Science.gov (United States)

    Raff, Lionel M.

    2014-01-01

    The fundamental criteria for chemical reactions to be spontaneous in a given direction are generally incorrectly stated as ?G equilibrium are also misstated as being ?G = 0 or ?A = 0. Following a brief review of the…

  4. Isotope generator

    International Nuclear Information System (INIS)

    1979-01-01

    The patent describes an isotope generator incorporating the possibility of stopping elution before the elution vessel is completely full. Sterile ventilation of the whole system can then occur, including of both generator reservoir and elution vessel. A sterile, and therefore pharmaceutically acceptable, elution fluid is thus obtained and the interior of the generator is not polluted with non-sterile air. (T.P.)

  5. Equilibrium with arbitrary market structure

    DEFF Research Database (Denmark)

    Grodal, Birgit; Vind, Karl

    2005-01-01

    Fifty years ago Arrow [1] introduced contingent commodities and Debreu [4] observed that this reinterpretation of a commodity was enough to apply the existing general equilibrium theory to uncertainty and time. This interpretation of general equilibrium theory is the Arrow-Debreu model....... The complete market predicted by this theory is clearly unrealistic, and Radner [10] formulated and proved existence of equilibrium in a multiperiod model with incomplete markets. In this paper the Radner result is extended. Radner assumed a specific structure of markets, independence of preferences...

  6. Phenomenon of Life: Between Equilibrium and Non-Linearity

    Science.gov (United States)

    Galimov, E. M.

    2004-12-01

    A model of ordering applicable to biological evolution is presented. It is shown that a steady state (more precisely approaching to a steady state) system of irreversible processes, under conditions of disproportionation of entropy, produces a lower-entropy product, that is, ordering. The ordering is defined as restricting of degrees of freedom: freedom of motion, interactions etc. The model differs from previous ones in that it relates the ordering to processes running not far from equilibrium, described in the linear field of non-equilibrium thermodynamics. It is shown that a system, which includes adenosine triphosphate (ATP) to adenosine diphosphate (ADP) conversion meets the demands of the physical model: it provides energy maintaining steady state conditions, and hydrolysis of ATP proceeding with consumption of water can be tightly conjugated with the most important reactions of synthesis of organic polymers (peptides, nucleotide chains etc.), which proceed with release of water. For these and other reasons ATP seems to be a key molecule of prebiotic evolution. It is argued that the elementary chemical reaction proceeding under control of an enzyme is not necessarily far from equilibrium. The experimental evidence supporting this idea, is presented. It is based on isotope data. Carbon isotope distribution in biochemical systems reveals regularity, which is inherent to steady state systems of chemical reactions, proceeding not far from equilibrium. In living organisms this feature appears at the statistical level, as many completely irreversible and non-linear processes occur in organisms. However not-far-from-equilibrium reactions are inherent to biochemical systems as a matter of principle. They are reconcilable with biochemical behavior. Extant organisms are highly evolved entities which, however, show in their basis the same features, as the simplest chemical systems must have had been involved in the origin of life. Some consequences following from the

  7. Phase relations in the Fe-Fe3C-Fe3N system at 7.8 GPa and 1350 °C: Implications for carbon and nitrogen hosts in Fe0-saturated upper mantle

    Science.gov (United States)

    Sokol, Alexander G.; Kruk, Alexey N.; Seryotkin, Yurii V.; Korablin, Alexander A.; Palyanov, Yury N.

    2017-04-01

    Phase relations in the Fe-Fe3C-Fe3N system are studied in high-pressure experiments at 7.8 GPa and 1350 °C using a split-sphere multi-anvil apparatus. The starting mixtures consisting of Fe, Fe3C and Fe3N are loaded into ceramic or graphite capsules. Contamination with trace amounts of oxygen leads to the appearance of wüstite in the system retaining oxygen fugacity (fO2) near the iron-wüstite (IW) buffer. The metal melt rich in carbon and nitrogen has a large stability field in the central part of the phase diagram, and this field at 1350 °C is tangent to the Fe-Fe3C side of the Fe-Fe3C-Fe3N triangle at the point of the Fe-Fe3C eutectics. Iron nitride ε-Fe3N (space group P6322 or P63/mmc) contains variable amounts of C and N: up to 2.0-2.5 wt% C and 6.0-7.3 wt% N in equilibrium with a C- and N-rich melt and as little as 1.0 wt% C and 3.2 wt% N in equilibrium with γ- Fe. The limit C and N contents in γ-Fe equilibrated with the C- and N-rich melt is about 1.0 wt%, while the N solubility in cementite (Fe3C) does not exceed 0.5 wt%. The obtained data make basis for the isothermal section of the Fe-Fe3C-Fe3N system. The metal melt phase is inferred to be the main host of carbon and nitrogen in the Fe0-saturated (0.1 wt%) mantle at a depth of ∼250 km. In particular, C- and N-bearing austenite (γ-Fe) and metal melts host carbon and nitrogen in the mantle depleted in volatiles (20 ppm C and 1 ppm N), whereas carbon and nitrogen in the mantle with high concentrations of volatiles (250 ppm C and 100 ppm N) reside in C- and N-rich melts with a minor amount of iron carbide (Fe3C). The presence of nickel and sulphur in metal are expected to inhibit the formation of iron carbide and increases the melt phase stability. Redox freezing of N-rich carbonate melts from subduction slabs in Fe0-saturated mantle may produce iron melts supersaturated with nitrogen and stable ε-Fe3N.

  8. Trapped ion system for sympathetic cooling and non-equilibrium dynamics

    Science.gov (United States)

    Doret, Charlie; Jubin, Sierra; Stevenson, Sarah

    2017-04-01

    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. We present progress towards trapping chains of multiple co-trapped calcium isotopes geared towards measuring thermal equilibration and sympathetic cooling rates. We also discuss plans for future experiments in non-equilibrium statistical mechanics, including exploration of the quantum-to-classical crossover between ballistic transport and diffusive, Fourier's Law conduction. This work is supported by Cottrell College Science Award from the Research Corporation for Science Advancement and by Williams College.

  9. Tungsten Stable Isotope Compositions of Ferromanganese Crusts

    Science.gov (United States)

    Abraham, K.; Barling, J.; Hein, J. R.; Schauble, E. A.; Halliday, A. N.

    2014-12-01

    We report the first accurate and precise data for mass-dependent fractionation of tungsten (W) stable isotopes, using a double spike technique and MC-ICPMS. Results are expressed relative to the NIST 3136 W isotope standard as per mil deviations in 186W/184W (δ186W). Although heavy element mass-dependent fractionations are expected to be small, Tl and U both display significant low temperature isotopic fractionations. Theoretical calculations indicate that W nuclear volume isotopic effects should be smaller than mass-dependent fractionations at low temperatures. Hydrogenetic ferromanganese (Fe-Mn) crusts precipitate directly from seawater and have been used as paleoceanographic recorders of temporal changes in seawater chemistry. Crusts are strongly enriched in W and other metals, and are a promising medium for exploring W isotopic variability. Tungsten has a relatively long residence time in seawater of ~61,000 years, mainly as the tungstate ion (WO42-). Water depth profiles show conservative behaviour. During adsorption on Fe-Mn crusts, W species form inner-sphere complexes in the hexavalent (W6+) state. The major host phase is thought to be Mn oxides and the lighter W isotope is expected to be absorbed preferentially. Surface scrapings of 13 globally distributed hydrogenetic Fe-Mn crusts display δ186W from -0.08 to -0.22‰ (±0.03‰, 2sd). A trend toward lighter W isotope composition exists with increasing water depth (~1500 to ~5200m) and W concentration. One hydrothermal Mn-oxide sample is anomalously light and Mn nodules are both heavy and light relative to Fe-Mn crusts. Tungsten speciation depends on concentration, pH, and time in solution and is not well understood because of the extremely slow kinetics of the reactions. In addition, speciation of aqueous and/or adsorbed species might be sensitive to pressure, showing similar thermodynamic stability but different effective volumes. Thus, W stable isotopes might be used as a water-depth barometer in

  10. Iron Isotope Fractionation in Microbial and Non-Biological Precipitates, and the Human Body

    Science.gov (United States)

    von Blanckenburg, F.; Boettcher, M. E.; Hofmann, B.; Walczyk, T.

    2001-12-01

    We have investigated biotic and abiotic stable iron isotope fractionation pathways in experiments, the low-T natural environment, and the human body. Fe samples were analysed using a Nu Plasma Multicollector ICP-MS. All measured samples plot on the theoretically predicted exponential fractionation line in the Delta57Fe versus Delta56Fe space, demonstrating absence of ArN or ArO interferences. An experimental calibration of Fe isotope fractionation during abiotic formation of iron (III) oxyhydroxide and iron(II) minerals from aqueous solution resulted in significant differences: (a) During fast precipitation of FeOOH during alkalization of a Fe(III)Cl3 solution at room temperature the solid is only slightly enriched by about 0.1permil in 57Fe compared to the solution. (b) Slow precipitation of akaganeite (beta-FeOOH) from aqueous Fe(III)Cl3 solution leads to a depletion of 57Fe by about -2.2permil in the solid phase without a significant influence of temperature. (c) Precipitation of FeOOH during oxidation of aqueous Fe(II) solutions by oxygen yields an enrichment of up to 4.8permil in 57Fe in the solid phase. (d) Iron(II) carbonate precipitation between 20 and 60C leads to an almost negligible depletion in 57Fe compared to aqueous ferrous ions. Interpretation: Large enrichment of the heavy isotope is observed where Fe is oxidised, whereas small to interme-diate depletions of heavy Fe isotopes occur upon forma-tion of Fe-minerals without change in redox state. Addi-tionally, kinetic effects, the speciation of the aqueous solution, or the effect of crystal structures may have to be considered. Biotic isotope fractionation by microorganisms was investigated at two field sites. In a Fe mine (Gonzen, Switzerland), Fe-precipitating microbes (Gallionella ferrugina and Leptohrix ochtraceae) have formed Fe(III)-oxyhydroxides that are ca. 0.6permil heavier in Delta57Fe than the Fe-rich parent solutions. At Cady Mts, California, filamentous fabrics of goethite, thought to

  11. Thermal Field Theory in Equilibrium

    OpenAIRE

    Andersen, Jens O.

    2000-01-01

    In this talk, I review recent developments in equilibrium thermal field theory. Screened perturbation theory and hard-thermal-loop perturbation theory are discussed. A self-consistent $\\Phi$-derivable approach is also briefly reviewed.

  12. On the local equilibrium condition

    International Nuclear Information System (INIS)

    Hessling, H.

    1994-11-01

    A physical system is in local equilibrium if it cannot be distinguished from a global equilibrium by ''infinitesimally localized measurements''. This should be a natural characterization of local equilibrium, but the problem is to give a precise meaning to the qualitative phrase ''infinitesimally localized measurements''. A solution is suggested in form of a Local Equilibrium Condition (LEC), which can be applied to linear relativistic quantum field theories but not directly to selfinteracting quantum fields. The concept of local temperature resulting from LEC is compared to an old approach to local temperature based on the principle of maximal entropy. It is shown that the principle of maximal entropy does not always lead to physical states if it is applied to relativistic quantum field theories. (orig.)

  13. Numerical Verification Of Equilibrium Chemistry

    International Nuclear Information System (INIS)

    Piro, Markus; Lewis, Brent; Thompson, William T.; Simunovic, Srdjan; Besmann, Theodore M.

    2010-01-01

    A numerical tool is in an advanced state of development to compute the equilibrium compositions of phases and their proportions in multi-component systems of importance to the nuclear industry. The resulting software is being conceived for direct integration into large multi-physics fuel performance codes, particularly for providing boundary conditions in heat and mass transport modules. However, any numerical errors produced in equilibrium chemistry computations will be propagated in subsequent heat and mass transport calculations, thus falsely predicting nuclear fuel behaviour. The necessity for a reliable method to numerically verify chemical equilibrium computations is emphasized by the requirement to handle the very large number of elements necessary to capture the entire fission product inventory. A simple, reliable and comprehensive numerical verification method is presented which can be invoked by any equilibrium chemistry solver for quality assurance purposes.

  14. Structural transformation in mechanosynthesized bcc Fe-Al-Si(Ge) solid solutions during heating

    International Nuclear Information System (INIS)

    Kubalova, L.M.; Sviridov, I.A.; Vasilyeva, O.Ya.; Fadeeva, V.I.

    2007-01-01

    X-ray diffractometry and Moessbauer spectroscopy study of Fe 50 Al 25 Si 25 and Fe 50 Al 25 Ge 25 alloys obtained by mechanical alloying (MA) of elementary powders was carried out. Phase transformation during heating of synthesized products was studied using differential scanning calorimetry (DSC). After 2.5 h of MA monophase alloys containing bcc Fe(Al, Ge) solid solutions Fe(Al, Si) are formed. Fe(Al, Si) is partially ordered B2 type and Fe(Al, Ge) is completely disordered. DSC curves of synthesized alloys displayed the presence of exothermal peaks caused by phase transformation. The metastable Fe(Al, Si) solid solution transformed into FeAl 1-x Si x (B2) and FeSi 1-x Al x (B20) equilibrium phases. The Fe(Al, Ge) solid solution transformed into equilibrium phases through intermediate stage of Fe 6 Ge 3 Al 2 metastable phase formation. The Fe 6 Ge 3 Al 2 phase dissociated into three equilibrium phases: FeAl 1-x Ge x (B2), χ-Fe 6 Ge 5 and η-Fe 13 (Ge, Al) 8 (B8 2 ). The structure of Fe 6 Ge 3 Al 2 was calculated by Rietveld method, the distribution of Al and Ge in the elementary cell and its parameters were calculated. Moessbauer study showed that Fe(Al, Si) and Fe(Al, Ge) solid solutions are paramagnetic. In the equilibrium state the alloy containing Si is also paramagnetic while the alloy with Ge showed ferromagnetic properties

  15. Edge equilibrium code for tokamaks

    Energy Technology Data Exchange (ETDEWEB)

    Li, Xujing [Institute of Computational Mathematics and Scientific/Engineering Computing, Academy of Mathematics and Systems Science, Chinese Academy of Sciences, P.O. Box 2719, Beijing 100190 (China); Zakharov, Leonid E. [Princeton Plasma Physics Laboratory Princeton, MS-27 P.O. Box 451, New Jersey (United States); Drozdov, Vladimir V. [Euratom/CCFE Fusion Association, Culham Science Centre, Abingdon OX14 3DB (United Kingdom)

    2014-01-15

    The edge equilibrium code (EEC) described in this paper is developed for simulations of the near edge plasma using the finite element method. It solves the Grad-Shafranov equation in toroidal coordinate and uses adaptive grids aligned with magnetic field lines. Hermite finite elements are chosen for the numerical scheme. A fast Newton scheme which is the same as implemented in the equilibrium and stability code (ESC) is applied here to adjust the grids.

  16. Stable isotopes and heavy metal distribution in Dreissena polymorpha (Zebra Mussels) from western basin of Lake Erie, Canada

    Energy Technology Data Exchange (ETDEWEB)

    Al-Aasm, I.S.; Clarke, J.D.; Fryer, B.J. [Windsor Univ., ON (Canada). Dept. of Earth Sciences

    1998-02-01

    Dreissena polymorpha is an exotic freshwater bivalve species which was introduced into the Great Lakes system in the fall of 1985 through the release of ballast water from European freighters. Utilizing individual growth rings of the shells, the stable isotope distribution ({delta}{sup 18}O and {delta}{sup 13}C) was determined for the life history of selected samples which were collected from the western basin of Lake Erie. These bivalves deposit their shell in near equilibrium with the ambient water and thus reflect any annual variation of the system in the isotopic records held within their shells. Observed values for {delta}{sup 18}O range from -6.64 to -9.46 permille with an average value of -7.69 permille PDB, while carbon values ranged from -0.80 to -4.67 permille with an average value of -1.76 permille PDB. Dreissena polymorpha shells incorporate metals into their shells during growth. Individual shell growth increments were analyzed for Pb, Fe, Mg, Mn, Cd, Cu, and V concentrations. The shells show increased uptake of certain metals during periods of isotopic enrichment which correspond with warmer water temperatures. Since metals are incorporated into the shells, the organism may be useful as a biomonitor of metal pollution within aquatic environments. (orig.)

  17. Mechanical alloying of the FeNi-Ag system

    International Nuclear Information System (INIS)

    Gonzalez, G.; Ibarra, D.; Ochoa, J.; Villalba, R.; Sagarzazu, A.

    2007-01-01

    The Fe-Ni-Ag system is of particular interest for its potential applications as soft magnetic granular material with small magnetic grains embedded in a non-magnetic metal matrix. Under equilibrium conditions: Fe-Ag and Ni-Ag are immiscible and Fe-Ni shows complete solubility. These materials are particularly important for magnetoresistivity properties. The properties of these alloys are closely related to their microstructure; therefore, a detailed study of the transformations occurring during milling was undertaken using pre-alloyed Fe x Ni 100-x (x = 30, 50 and 70) further milled with different Ag content to give the following alloys compositions (Fe x -Ni 100-x ) 100-y Ag y (y = 5, 20, 60). Consolidation of the mechanically alloyed powders by sintering at 950 o C was performed. Morphological and structural characterization of the sintered powders was carried out by scanning and transmission electron microscopy and X-ray diffraction. Fe 30 Ni 70 and Fe 50 Ni 50 formed ordered FeNi 3 compound. Fe 70 Ni 30 showed the formation of a mixture of γ-(Fe,Ni) and α-Fe(Ni) solid solutions. The mixture of these systems with Ag showed the metal solid solutions surrounded by Ag islands of Fe x Ni y -Ag, There was also evidence of Ag diffusing into the γ-(Fe,Ni). High Ag content (60%) shows formation of islands of FeNi surrounded by Ag. Sintering is always improved with the Ag content

  18. Shape characteristics of equilibrium and non-equilibrium fractal clusters.

    Science.gov (United States)

    Mansfield, Marc L; Douglas, Jack F

    2013-07-28

    It is often difficult in practice to discriminate between equilibrium and non-equilibrium nanoparticle or colloidal-particle clusters that form through aggregation in gas or solution phases. Scattering studies often permit the determination of an apparent fractal dimension, but both equilibrium and non-equilibrium clusters in three dimensions frequently have fractal dimensions near 2, so that it is often not possible to discriminate on the basis of this geometrical property. A survey of the anisotropy of a wide variety of polymeric structures (linear and ring random and self-avoiding random walks, percolation clusters, lattice animals, diffusion-limited aggregates, and Eden clusters) based on the principal components of both the radius of gyration and electric polarizability tensor indicates, perhaps counter-intuitively, that self-similar equilibrium clusters tend to be intrinsically anisotropic at all sizes, while non-equilibrium processes such as diffusion-limited aggregation or Eden growth tend to be isotropic in the large-mass limit, providing a potential means of discriminating these clusters experimentally if anisotropy could be determined along with the fractal dimension. Equilibrium polymer structures, such as flexible polymer chains, are normally self-similar due to the existence of only a single relevant length scale, and are thus anisotropic at all length scales, while non-equilibrium polymer structures that grow irreversibly in time eventually become isotropic if there is no difference in the average growth rates in different directions. There is apparently no proof of these general trends and little theoretical insight into what controls the universal anisotropy in equilibrium polymer structures of various kinds. This is an obvious topic of theoretical investigation, as well as a matter of practical interest. To address this general problem, we consider two experimentally accessible ratios, one between the hydrodynamic and gyration radii, the other

  19. Isotope hydrology

    International Nuclear Information System (INIS)

    Drost, W.

    1978-01-01

    The International Symposium on Isotope Hydrology was jointly organized by the IAEA and UNESCO, in co-operation with the National Committee of the Federal Republic of Germany for the International Hydrological Programme (IHP) and the Gesellschaft fuer Strahlen- und Umweltforschung mbH (GSF). Upon the invitation of the Federal Republic of Germany the Symposium was held from 19-23 June 1978 in Neuherberg on the GSF campus. The Symposium was officially opened by Mr. S. Eklund, Director General of the IAEA. The symposium - the fifth meeting held on isotope hydrology - was attended by over 160 participants from 44 countries and four international organizations and by about 30 observers from the Federal Republic of Germany. Due to the absence of scientists from the USSR five papers were cancelled and therefore only 46 papers of the original programme were presented in ten sessions

  20. Isotope separation

    International Nuclear Information System (INIS)

    Coleman, G.H.; Bett, R.; Cuninghame, J.G.; Sims, H.

    1982-01-01

    In the separation of short-lived isotopes for medical usage, a solution containing sup(195m)Hg is contacted with vicinal dithiol cellulose which adsorbs and retains the sup(195m)Hg. sup(195m)Au is eluted from the vicinal dithiol cellulose by using a suitable elutant. The sup(195m)Au arises from the radioactive decay of the sup(195m)Hg. The preferred elutant is a solution containing CN - ion. (author)

  1. Stable isotope deltas: tiny, yet robust signatures in nature.

    Science.gov (United States)

    Brand, Willi A; Coplen, Tyler B

    2012-09-01

    Although most of them are relatively small, stable isotope deltas of naturally occurring substances are robust and enable workers in anthropology, atmospheric sciences, biology, chemistry, environmental sciences, food and drug authentication, forensic science, geochemistry, geology, oceanography, and paleoclimatology to study a variety of topics. Two fundamental processes explain the stable isotope deltas measured in most terrestrial systems: isotopic fractionation and isotope mixing. Isotopic fractionation is the result of equilibrium or kinetic physicochemical processes that fractionate isotopes because of small differences in physical or chemical properties of molecular species having different isotopes. It is shown that the mixing of radioactive and stable isotope end members can be modelled to provide information on many natural processes, including (14)C abundances in the modern atmosphere and the stable hydrogen and oxygen isotopic compositions of the oceans during glacial and interglacial times. The calculation of mixing fractions using isotope balance equations with isotope deltas can be substantially in error when substances with high concentrations of heavy isotopes (e.g. (13)C, (2)H, and (18)O ) are mixed. In such cases, calculations using mole fractions are preferred as they produce accurate mixing fractions. Isotope deltas are dimensionless quantities. In the International System of Units (SI), these quantities have the unit 1 and the usual list of prefixes is not applicable. To overcome traditional limitations with expressing orders of magnitude differences in isotope deltas, we propose the term urey (symbol Ur), after Harold C. Urey, for the unit 1. In such a manner, an isotope delta value expressed traditionally as-25 per mil can be written as-25 mUr (or-2.5 cUr or-0.25 dUr; the use of any SI prefix is possible). Likewise, very small isotopic differences often expressed in per meg 'units' are easily included (e.g. either+0.015 ‰ or+15 per meg

  2. Stable isotope deltas: Tiny, yet robust signatures in nature

    Science.gov (United States)

    Brand, Willi A.; Coplen, Tyler B.

    2012-01-01

    Although most of them are relatively small, stable isotope deltas of naturally occurring substances are robust and enable workers in anthropology, atmospheric sciences, biology, chemistry, environmental sciences, food and drug authentication, forensic science, geochemistry, geology, oceanography, and paleoclimatology to study a variety of topics. Two fundamental processes explain the stable isotope deltas measured in most terrestrial systems: isotopic fractionation and isotope mixing. Isotopic fractionation is the result of equilibrium or kinetic physicochemical processes that fractionate isotopes because of small differences in physical or chemical properties of molecular species having different isotopes. It is shown that the mixing of radioactive and stable isotope end members can be modelled to provide information on many natural processes, including 14C abundances in the modern atmosphere and the stable hydrogen and oxygen isotopic compositions of the oceans during glacial and interglacial times. The calculation of mixing fractions using isotope balance equations with isotope deltas can be substantially in error when substances with high concentrations of heavy isotopes (e.g. 13C, 2H, and 18O ) are mixed. In such cases, calculations using mole fractions are preferred as they produce accurate mixing fractions. Isotope deltas are dimensionless quantities. In the International System of Units (SI), these quantities have the unit 1 and the usual list of prefixes is not applicable. To overcome traditional limitations with expressing orders of magnitude differences in isotope deltas, we propose the term urey (symbol Ur), after Harold C. Urey, for the unit 1. In such a manner, an isotope delta value expressed traditionally as−25 per mil can be written as−25 mUr (or−2.5 cUr or−0.25 dUr; the use of any SI prefix is possible). Likewise, very small isotopic differences often expressed in per meg ‘units’ are easily included (e.g. either+0.015 ‰ or+15 per meg

  3. Opposing authigenic controls on the isotopic signature of dissolved iron in hydrothermal plumes

    Science.gov (United States)

    Lough, A. J. M.; Klar, J. K.; Homoky, W. B.; Comer-Warner, S. A.; Milton, J. A.; Connelly, D. P.; James, R. H.; Mills, R. A.

    2017-04-01

    Iron is a scarce but essential micronutrient in the oceans that limits primary productivity in many regions of the surface ocean. The mechanisms and rates of Fe supply to the ocean interior are still poorly understood and quantified. Iron isotope ratios of different Fe pools can potentially be used to trace sources and sinks of the global Fe biogeochemical cycle if these boundary fluxes have distinct signatures. Seafloor hydrothermal vents emit metal rich fluids from mid-ocean ridges into the deep ocean. Iron isotope ratios have the potential to be used to trace the input of hydrothermal dissolved iron to the oceans if the local controls on the fractionation of Fe isotopes during plume dispersal in the deep ocean are understood. In this study we assess the behaviour of Fe isotopes in a Southern Ocean hydrothermal plume using a sampling program of Total Dissolvable Fe (TDFe), and dissolved Fe (dFe). We demonstrate that δ56Fe values of dFe (δ56dFe) within the hydrothermal plume change dramatically during early plume dispersal, ranging from -2.39 ± 0.05‰ to -0.13 ± 0.06‰ (2 SD). The isotopic composition of TDFe (δ56TDFe) was consistently heavier than dFe values, ranging from -0.31 ± 0.03‰ to 0.78 ± 0.05‰, consistent with Fe oxyhydroxide precipitation as the plume samples age. The dFe present in the hydrothermal plume includes stabilised dFe species with potential to be transported to the deep ocean. We estimate that stable dFe exported from the plume will have a δ56Fe of -0.28 ± 0.17‰. Further, we show that the proportion of authigenic iron-sulfide and iron-oxyhydroxide minerals precipitating in the buoyant plume exert opposing controls on the resultant isotope composition of dissolved Fe passed into the neutrally buoyant plume. We show that such controls yield variable dissolved Fe isotope signatures under the authigenic conditions reported from modern vent sites elsewhere, and so ought to be considered during iron isotope reconstructions of past

  4. Donnan membrane speciation of Al, Fe, trace metals and REEs in coastal lowland acid sulfate soil-impacted drainage waters

    Energy Technology Data Exchange (ETDEWEB)

    Jones, Adele M.; Xue, Youjia [School of Civil and Environmental Engineering, University of New South Wales, Sydney, NSW 2052 (Australia); Kinsela, Andrew S. [School of Civil and Environmental Engineering, University of New South Wales, Sydney, NSW 2052 (Australia); Institute for Environmental Research (IER), Australian Nuclear Science and Technology Organisation (ANSTO), Lucas Heights, NSW 2234 (Australia); Wilcken, Klaus M. [Institute for Environmental Research (IER), Australian Nuclear Science and Technology Organisation (ANSTO), Lucas Heights, NSW 2234 (Australia); Collins, Richard N., E-mail: richard.collins@unsw.edu.au [School of Civil and Environmental Engineering, University of New South Wales, Sydney, NSW 2052 (Australia)

    2016-03-15

    Donnan dialysis has been applied to forty filtered drainage waters collected from five coastal lowland acid sulfate soil (CLASS) catchments across north-eastern NSW, Australia. Despite having average pH values < 3.9, 78 and 58% of Al and total Fe, respectively, were present as neutral or negatively-charged species. Complementary isotope dilution experiments with {sup 55}Fe and {sup 26}Al demonstrated that only soluble (i.e. no colloidal) species were present. Trivalent rare earth elements (REEs) were also mainly present (> 70%) as negatively-charged complexes. In contrast, the speciation of the divalent trace metals Co, Mn, Ni and Zn was dominated by positively-charged complexes and was strongly correlated with the alkaline earth metals Ca and Mg. Thermodynamic equilibrium speciation calculations indicated that natural organic matter (NOM) complexes dominated Fe(III) speciation in agreement with that obtained by Donnan dialysis. In the case of Fe(II), however, the free cation was predicted to dominate under thermodynamic equilibrium, whilst our results indicated that Fe(II) was mainly present as neutral or negatively-charged complexes (most likely with sulfate). For all other divalent metals thermodynamic equilibrium speciation calculations agreed well with the Donnan dialysis results. The proportion of Al and REEs predicted to be negatively-charged was also grossly underestimated, relative to the experimental results, highlighting possible inaccuracies in the stability constants developed for these trivalent Me(SO{sub 4}){sub 2}{sup −} and/or Me–NOM complexes and difficulties in modeling complex environmental samples. These results will help improve metal mobility and toxicity models developed for CLASS-affected environments, and also demonstrate that Australian CLASS environments can discharge REEs at concentrations an order of magnitude greater than previously reported. - Highlights: • CLASS discharge large amounts of metals and their speciation is poorly

  5. Clumped isotope thermometry of cryogenic cave carbonates

    Science.gov (United States)

    Kluge, Tobias; Affek, Hagit P.; Zhang, Yi Ge; Dublyansky, Yuri; Spötl, Christoph; Immenhauser, Adrian; Richter, Detlev K.

    2014-02-01

    Freezing of cave pool water that is increasingly oversaturated with dissolved carbonate leads to precipitation of a very specific type of speleothems known as cryogenic cave carbonates (CCC). At present, two different environments for their formation have been proposed, based on their characteristic carbon and oxygen isotope ratios. Rapidly freezing thin water films result in the fast precipitation of fine-grained carbonate powder (CCCfine). This leads to rapid physicochemical changes including CO2 degassing and CaCO3 precipitation, resulting in significantly 13C-enriched carbonates. Alternatively, slow carbonate precipitation in ice-covered cave pools results in coarse crystalline CCC (CCCcoarse) yielding strongly 18O-depleted carbonate. This is due to the formation of relatively 18O-enriched ice causing the gradual depletion of 18O in the water from which the CCC precipitates. Cryogenic carbonates from Central European caves were found to have been formed primarily during the last glacial period, specifically during times of permafrost thawing, based on the oxygen isotope ratios and U-Th dating. Information about the precise conditions of CCCcoarse formation, i.e. whether these crystals formed under equilibrium or disequilibrium conditions with the parent fluid, however, is lacking. An improved understanding of CCCcoarse formation will increase the predictive value of this paleo-permafrost archive. Here we apply clumped isotopes to investigate the formation conditions of cryogenic carbonates using well-studied CCCcoarse from five different cave systems in western Germany. Carbonate clumped isotope measurements yielded apparent temperatures between 3 and 18 °C and thus exhibit clear evidence of isotopic disequilibrium. Although the very negative carbonate δ18O values can only be explained by gradual freezing of pool water accompanied by preferential incorporation of 18O into the ice, clumped isotope-derived temperatures significantly above expected freezing

  6. Local Equilibrium and Retardation Revisited.

    Science.gov (United States)

    Hansen, Scott K; Vesselinov, Velimir V

    2018-01-01

    In modeling solute transport with mobile-immobile mass transfer (MIMT), it is common to use an advection-dispersion equation (ADE) with a retardation factor, or retarded ADE. This is commonly referred to as making the local equilibrium assumption (LEA). Assuming local equilibrium, Eulerian textbook treatments derive the retarded ADE, ostensibly exactly. However, other authors have presented rigorous mathematical derivations of the dispersive effect of MIMT, applicable even in the case of arbitrarily fast mass transfer. We resolve the apparent contradiction between these seemingly exact derivations by adopting a Lagrangian point of view. We show that local equilibrium constrains the expected time immobile, whereas the retarded ADE actually embeds a stronger, nonphysical, constraint: that all particles spend the same amount of every time increment immobile. Eulerian derivations of the retarded ADE thus silently commit the gambler's fallacy, leading them to ignore dispersion due to mass transfer that is correctly modeled by other approaches. We then present a particle tracking simulation illustrating how poor an approximation the retarded ADE may be, even when mobile and immobile plumes are continually near local equilibrium. We note that classic "LEA" (actually, retarded ADE validity) criteria test for insignificance of MIMT-driven dispersion relative to hydrodynamic dispersion, rather than for local equilibrium. Published 2017. This article is a U.S. Government work and is in the public domain in the USA.

  7. Reduction of hexavalent chromium by ferrous iron: A process of chromium isotope fractionation and its relevance to natural environments

    DEFF Research Database (Denmark)

    Døssing, Lasse Nørbye; Dideriksen, Knud; Stipp, Susan Louise Svane

    2011-01-01

    Stable chromium (Cr) isotopes can be used as a tracer for changing redox conditions in modern marine systems and in the geological record. We have investigated isotope fractionation during reduction of Cr(VI)aq by Fe(II)aq. Reduction of Cr(VI)aq by Fe(II)aq in batch experiments leads to significant...

  8. Investigation of the mechanism of formation of a thiolate-ligated Fe(III)-OOH.

    Science.gov (United States)

    Nam, Elaine; Alokolaro, Pauline E; Swartz, Rodney D; Gleaves, Morgan C; Pikul, Jessica; Kovacs, Julie A

    2011-03-07

    Kinetic studies aimed at determining the most probable mechanism for the proton-dependent [Fe(II)(S(Me2)N(4)(tren))](+) (1) promoted reduction of superoxide via a thiolate-ligated hydroperoxo intermediate [Fe(III)(S(Me2)N(4)(tren))(OOH)](+) (2) are described. Rate laws are derived for three proposed mechanisms, and it is shown that they should conceivably be distinguishable by kinetics. For weak proton donors with pK(a(HA)) > pK(a(HO(2))) rates are shown to correlate with proton donor pK(a), and display first-order dependence on iron, and half-order dependence on superoxide and proton donor HA. Proton donors acidic enough to convert O(2)(-) to HO(2) (in tetrahydrofuran, THF), that is, those with pK(a(HA)) rates which are independent of proton donor concentration. Relative pK(a) values were determined in THF by measuring equilibrium ion pair acidity constants using established methods. Rates of hydroperoxo 2 formation displays no apparent deuterium isotope effect, and bases, such as methoxide, are shown to inhibit the formation of 2. Rate constants for p-substituted phenols are shown to correlate linearly with the Hammett substituent constants σ(-). Activation parameters ((ΔH(++) = 2.8 kcal/mol, ΔS(++) = -31 eu) are shown to be consistent with a low-barrier associative mechanism that does not involve extensive bond cleavage. Together, these data are shown to be most consistent with a mechanism involving the addition of HO(2) to 1 with concomitant oxidation of the metal ion, and reduction of superoxide (an "oxidative addition" of sorts), in the rate-determining step. Activation parameters for MeOH- (ΔH(++) = 13.2 kcal/mol and ΔS(++) = -24.3 eu), and acetic acid- (ΔH(++) = 8.3 kcal/mol and ΔS(++) = -34 eu) promoted release of H(2)O(2) to afford solvent-bound [Fe(III)(S(Me2)N(4)(tren))(OMe)](+) (3) and [Fe(III)(S(Me2)N(4)(tren))(O(H)Me)](+) (4), respectively, are shown to be more consistent with a reaction involving rate-limiting protonation of an Fe

  9. Prediction of isotope effects for anticipated intermediate structures in the course of bacterial denitrification

    International Nuclear Information System (INIS)

    Morgenstern, M.A.; Schowen, R.L.

    1989-01-01

    Vibrational-analysis methods have been used to estimate the equilibrium 14 N/ 15 N isotope effects to be expected for conversion of nitrite anion to thirteen possible intermediate-state and product-state structures [HONO, NO + , NO, NO - , FeNO, ON * NO 2 , O * NNO 2 , O 2 NNO 2 , ONO * N, O * NON, ONNO, * NNO, N * NO] in the reduction of nitrite ion to nitrous oxide denitrifying bacteria. The results, taken in combination with previous experimental isotope-effect and tracer studies of the Pseudomonas stutzeri and related systems, are consistent with a suggestion that a second nitrite anion enters the enzyme-catalytic cycle at the stage of a nitrosyl-ion intermediate but re-emerges after entry of the reducing electrons; the product nitrous oxide is then formed by disproportionation of enzymically generated hyponitrous acid. The calculations are consistent with contributions, under different experimental conditions, of several different transition states to limiting the rate of the enzymic reaction. These transition states (and the corresponding experimental conditions) are the transition states for N-O fission in the generation of a mononitrogen electrophilic species from nitrite anion (high reductant, high nitrite concentrations), for attack of nitrite on this electrophile (high reductant, low nitrite concentrations) and for electron transfer to a dinitrogen-trioxide-like species (low reductant concentration). (orig.)

  10. Isotopic enrichment of 15N by ionic exchange cromatography

    International Nuclear Information System (INIS)

    Trivelin, P.C.O.; Matsui, E.; Salati, E.

    1979-01-01

    The ionic exchange chromatographic method in columns of resin which is employed in the study of isotopic enrichment of 15 N is presented. Determinations are made of the isotopic separation constant for the exchange of isotopes 15 N and 14 N in the equilibrium involving ammonium hidroxide in the solution phase and ions NH 4 + adsorbed in cationic resins: Dowex 50W-X8 and X12, 100-200 mesh. Experiments are also conducted for determination of height of theoretical plates for situations of equilibrium of the NH 4 + band in two systems of resin's columns aimed at estimating the experimental conditions used. The isotopic analyses of nitrogen are carried out by mass spectrometry [pt

  11. Imaging the equilibrium state and magnetization dynamics of partially built hard disk write heads

    Energy Technology Data Exchange (ETDEWEB)

    Valkass, R. A. J., E-mail: rajv202@ex.ac.uk; Yu, W.; Shelford, L. R.; Keatley, P. S.; Loughran, T. H. J.; Hicken, R. J. [School of Physics, University of Exeter, Stocker Road, Exeter EX4 4QL (United Kingdom); Cavill, S. A. [Diamond Light Source, Harwell Science and Innovation Campus, Didcot OX11 0DE (United Kingdom); Department of Physics, University of York, Heslington, York YO10 5DD (United Kingdom); Laan, G. van der; Dhesi, S. S. [Diamond Light Source, Harwell Science and Innovation Campus, Didcot OX11 0DE (United Kingdom); Bashir, M. A.; Gubbins, M. A. [Research and Development, Seagate Technology, 1 Disc Drive, Springtown Industrial Estate, Derry BT48 0BF (United Kingdom); Czoschke, P. J.; Lopusnik, R. [Recording Heads Operation, Seagate Technology, 7801 Computer Avenue South, Bloomington, Minnesota 55435 (United States)

    2015-06-08

    Four different designs of partially built hard disk write heads with a yoke comprising four repeats of NiFe (1 nm)/CoFe (50 nm) were studied by both x-ray photoemission electron microscopy (XPEEM) and time-resolved scanning Kerr microscopy (TRSKM). These techniques were used to investigate the static equilibrium domain configuration and the magnetodynamic response across the entire structure, respectively. Simulations and previous TRSKM studies have made proposals for the equilibrium domain configuration of similar structures, but no direct observation of the equilibrium state of the writers has yet been made. In this study, static XPEEM images of the equilibrium state of writer structures were acquired using x-ray magnetic circular dichroism as the contrast mechanism. These images suggest that the crystalline anisotropy dominates the equilibrium state domain configuration, but competition with shape anisotropy ultimately determines the stability of the equilibrium state. Dynamic TRSKM images were acquired from nominally identical devices. These images suggest that a longer confluence region may hinder flux conduction from the yoke into the pole tip: the shorter confluence region exhibits clear flux beaming along the symmetry axis, whereas the longer confluence region causes flux to conduct along one edge of the writer. The observed variations in dynamic response agree well with the differences in the equilibrium magnetization configuration visible in the XPEEM images, confirming that minor variations in the geometric design of the writer structure can have significant effects on the process of flux beaming.

  12. Equilibrium Temperature Profiles within Fission Product Waste Forms

    Energy Technology Data Exchange (ETDEWEB)

    Kaminski, Michael D. [Argonne National Lab. (ANL), Argonne, IL (United States)

    2016-10-01

    We studied waste form strategies for advanced fuel cycle schemes. Several options were considered for three waste streams with the following fission products: cesium and strontium, transition metals, and lanthanides. These three waste streams may be combined or disposed separately. The decay of several isotopes will generate heat that must be accommodated by the waste form, and this heat will affect the waste loadings. To help make an informed decision on the best option, we present computational data on the equilibrium temperature of glass waste forms containing a combination of these three streams.

  13. Equilibrium chemistry of boron deposition

    International Nuclear Information System (INIS)

    Walsh, P.N.

    1973-01-01

    Machine calculations of the equilibrium chemistry of the H 2 / BCl 3 /Ar system were used to calculate the degree of conversion of BCl 3 to solid B, at several temperatures and one atmosphere total pressure, for constant BCl 3 partial pressure and for constant H 2 /BCl 3 ratio. Combined equilibrium and mass transport calculations were used to deduce diffusion-limited reaction rates for experimental conditions employed in the kinetics study of Carlton, et al. (Second International Vapor Deposition Conference); this analysis confirms that the previous work did measure surface kinetics. Equilibrium calculations for the H 2 /BCl 3 /Cr system indicate that CrCl 2 volatility may be too high for this to be a practical method of forming chromium boride coatings. (U.S.)

  14. The isotopic cycle of oceanic phosphate. I

    International Nuclear Information System (INIS)

    Longinelli, A.; Bartelloni, M.; Cortecci, G.

    1976-01-01

    Steady-state conditions seem to exist in the Atlantic and Pacific Oceans in the case of the 18 O content of dissolved phosphate. The measured delta 18 O(PO 4 3- ) values are fairly constant at all latitudes and depths. A constant difference of about 1% exists between average Atlantic and Pacific results. Oxygen isotope measurements carried out on phosphate in the organic matter of fish, showed an average difference of about 3% when compared with dissolved oceanic phosphate. Such a difference can be attributed to biological fractionation effects in the metabolism of phosphate. However, the equilibrium fractionation factors in the phosphate-water system are poorly known and consequently it is not known whether this difference represents an approach to, or a deviation from, isotopic equilibrium conditions. (Auth.)

  15. The Equilibrium Rule--A Personal Discovery

    Science.gov (United States)

    Hewitt, Paul G.

    2016-01-01

    Examples of equilibrium are evident everywhere and the equilibrium rule provides a reasoned way to view all things, whether in static (balancing rocks, steel beams in building construction) or dynamic (airplanes, bowling balls) equilibrium. Interestingly, the equilibrium rule applies not just to objects at rest but whenever any object or system of…

  16. Spontaneity and Equilibrium: Why "?G Equilibrium" Are Incorrect

    Science.gov (United States)

    Raff, Lionel M.

    2014-01-01

    The fundamental criteria for chemical reactions to be spontaneous in a given direction are generally incorrectly stated as ?G chemistry textbooks and even in some more advanced texts. Similarly, the criteria for equilibrium are also misstated as being ?G = 0 or ?A = 0. Following a brief review of the…

  17. Phosphorus release from anaerobic peat soil during convective discharge – effect of soil Fe:P molar ratio and preferential flow

    DEFF Research Database (Denmark)

    Forsmann, Ditte M.; Kjærgaard, Charlotte

    2014-01-01

    soils (TOC from 5 to 39%) with a gradient in Fe:P molar ratio (molar ratio between bicarbonate dithionite extractable Fe and P (FeBD:PBD) from 3 to 112) and degree of non-equilibrium (preferential) flow. Short-term batch incubation experiments (21 days) indicated that concurrent Fe and P release...

  18. Equilibrium in a Production Economy

    Energy Technology Data Exchange (ETDEWEB)

    Chiarolla, Maria B., E-mail: maria.chiarolla@uniroma1.it [Universita di Roma ' La Sapienza' , Dipartimento di Metodi e Modelli per l' Economia, il Territorio e la Finanza, Facolta di Economia (Italy); Haussmann, Ulrich G., E-mail: uhaus@math.ubc.ca [University of British Columbia, Department of Mathematics (Canada)

    2011-06-15

    Consider a closed production-consumption economy with multiple agents and multiple resources. The resources are used to produce the consumption good. The agents derive utility from holding resources as well as consuming the good produced. They aim to maximize their utility while the manager of the production facility aims to maximize profits. With the aid of a representative agent (who has a multivariable utility function) it is shown that an Arrow-Debreu equilibrium exists. In so doing we establish technical results that will be used to solve the stochastic dynamic problem (a case with infinite dimensional commodity space so the General Equilibrium Theory does not apply) elsewhere.

  19. Stellar atmosphere in statistical equilibrium

    International Nuclear Information System (INIS)

    Kalkofen, W.; Klein, R.I.

    1979-01-01

    A static atmosphere with only Lyman continuum radiation in radiative equilibrium is studied for the effectsof radiative and collisional ionization on deviations from local thermodynamic equilibrium (LTE). Large increases and decreases of the kinetic temperature (range in Tapprox. factor 2) and, correspondingly, very large over- and underpopulation of the bound state (range in bapprox. factor 10 6 ) are found, depending on the frequency dependence of the photoionization cross section. Despite these large deviations from LTE, which strongly modify the emergent spectrum, there is almost no effect on the particle densities, the degree of ionization, and the basic structure of the atmosphere

  20. Equilibrium in a Production Economy

    International Nuclear Information System (INIS)

    Chiarolla, Maria B.; Haussmann, Ulrich G.

    2011-01-01

    Consider a closed production-consumption economy with multiple agents and multiple resources. The resources are used to produce the consumption good. The agents derive utility from holding resources as well as consuming the good produced. They aim to maximize their utility while the manager of the production facility aims to maximize profits. With the aid of a representative agent (who has a multivariable utility function) it is shown that an Arrow-Debreu equilibrium exists. In so doing we establish technical results that will be used to solve the stochastic dynamic problem (a case with infinite dimensional commodity space so the General Equilibrium Theory does not apply) elsewhere.

  1. Nash equilibrium with lower probabilities

    DEFF Research Database (Denmark)

    Groes, Ebbe; Jacobsen, Hans Jørgen; Sloth, Birgitte

    1998-01-01

    We generalize the concept of Nash equilibrium in mixed strategies for strategic form games to allow for ambiguity in the players' expectations. In contrast to other contributions, we model ambiguity by means of so-called lower probability measures or belief functions, which makes it possible...... to distinguish between a player's assessment of ambiguity and his attitude towards ambiguity. We also generalize the concept of trembling hand perfect equilibrium. Finally, we demonstrate that for certain attitudes towards ambiguity it is possible to explain cooperation in the one-shot Prisoner's Dilemma...

  2. Solvent isotope effects in the complex formation of beryllium sulphate

    International Nuclear Information System (INIS)

    Boojj, M.

    1978-01-01

    The kinetics of complex formation and dissociation of BeSO 4 in D 2 O has been studied. The association constant and the inner sphere/outer sphere equilibrium constant were obtained. By comparing with the corresponding results in H 2 O(1) the solvent isotope effect could be evaluated for some of the involved thermodynamic and kinetic constants. The isotope effects can be understood in terms of Swain and Bader's statistical thermodynamical calculations (2). (orig.) [de

  3. Separation of the isotopes of boron by chemical exchange reactions

    Science.gov (United States)

    McCandless, F.P.; Herbst, R.S.

    1995-05-30

    The isotopes of boron, {sup 10}B and {sup 11}B, are separated by means of a gas-liquid chemical exchange reaction involving the isotopic equilibrium between gaseous BF{sub 3} and a liquid BF{sub 3} donor molecular addition complex formed between BF{sub 3} gas and a donor chosen from the group consisting of: nitromethane, acetone, methyl isobutyl ketone, or diisobutyl ketone. 1 Fig.

  4. Separation of the isotopes of boron by chemical exchange reactions

    Science.gov (United States)

    McCandless, Frank P.; Herbst, Ronald S.

    1995-01-01

    The isotopes of boron, .sup.10 B and .sup.11 B, are separated by means of a gas-liquid chemical exchange reaction involving the isotopic equilibrium between gaseous BF.sub.3 and a liquid BF.sub.3 . donor molecular addition complex formed between BF.sub.3 gas and a donor chosen from the group consisting of: nitromethane, acetone, methyl isobutyl ketone, or diisobutyl ketone.

  5. Concentration and excretion of 137Cs, 95Zr-95Nb and 59Fe by marine fishes

    International Nuclear Information System (INIS)

    Koyanagi, Taku; Suzuki, Hamaji; Hirano, Shigeki; Nakahara, Motokazu; Ishii, Toshiaki

    1976-01-01

    Uptake and loss of 137 Cs, 95 Zr- 95 Nb and 59 Fe by several kinds of marine fishes were observed by the radio-isotope tracer experiments with aquariums in laboratory in order to estimate concentration factors and biological half-lives for these radionuclides by the fishes. Concentration of 137 Cs by gill and liver of the fishes reached equilibrium within a month and radioactivities were lost with relatively short half-lives from these parts, whereas accumulation in fish muscles increased even after 200 days. Concentration factors of 137 Cs by fish muscles calculated at 200th day as 17.5-27.5 were lower than the values obtained by the field survey for stable or radioactive Cs suggesting slow turnover in fish muscles and contribution of food for the accumulation of nuclide. An important role of surface absorption of radioactivities was supposed for the accumulation of 95 Zr- 95 Nb and 59 Fe in gill or scale of the fishes but biological concentration through metabolic processes was also suggested from higher concentration factors by bisceral organs of the fishes for these radionuclides. (auth.)

  6. Chromium isotope fractionation in ferruginous sediments

    Science.gov (United States)

    Bauer, Kohen W.; Gueguen, Bleuenn; Cole, Devon B.; Francois, Roger; Kallmeyer, Jens; Planavsky, Noah; Crowe, Sean A.

    2018-02-01

    Ferrous Fe is a potent reductant of Cr(VI), and while a number of laboratory studies have characterized Cr isotope fractionation associated with Cr(VI) reduction by ferrous iron, the expression of this fractionation in real-world ferrous Fe-rich environments remains unconstrained. Here we determine the isotope fractionation associated with Cr(VI) reduction in modern ferrous Fe-rich sediments obtained from the previously well studied Lake Matano, Indonesia. Whole core incubations demonstrate that reduction of Cr(VI) within ferruginous sediments provides a sink for Cr(VI) leading to Cr(VI) concentration gradients and diffusive Cr(VI) fluxes across the sediment water interface. As reduction proceeded, Cr(VI) remaining in the overlying lake water became progressively enriched in the heavy isotope (53Cr), increasing δ53Cr by 2.0 ± 0.1‰ at the end of the incubation. Rayleigh distillation modelling of the evolution of Cr isotope ratios and Cr(VI) concentrations in the overlying water yields an effective isotope fractionation of εeff = 1.1 ± 0.2‰ (53Cr/52Cr), whereas more detailed diagenetic modelling implies an intrinsic isotope fractionation of εint = 1.80 ± 0.04‰. Parallel slurry experiments performed using anoxic ferruginous sediment yield an intrinsic isotope fractionation of εint = 2.2 ± 0.1‰. These modelled isotope fractionations are corroborated by direct measurement of the δ53Cr composition on the upper 0.5 cm of Lake Matano sediment, revealing an isotopic offset from the lake water of Δ53Cr = 0.21-1.81‰. The data and models reveal that effective isotope fractionations depend on the depth at which Cr(VI) reduction takes place below the sediment water interface-the deeper the oxic non-reactive zone, the smaller the effective fractionation relative to the intrinsic fractionation. Based on the geochemistry of the sediment we suggest the electron donors responsible for reduction are a combination of dissolved Fe(II) and 0.5 M HCl extractable (solid

  7. Equilibrium and pre-equilibrium emissions in proton-induced ...

    Indian Academy of Sciences (India)

    ... of medical radioisotopes using cyclotrons [2–5]. Nuclear data evaluation is generally carried out on the basis of experimental data and theoretical model calculations. It is both practically and economically impossible to measure necessary cross-sections for all the isotopes in the periodic table for a wide range of energies.

  8. Isotopic evidence for oxygenated Mesoarchaean shallow oceans

    Science.gov (United States)

    Eickmann, Benjamin; Hofmann, Axel; Wille, Martin; Bui, Thi Hao; Wing, Boswell A.; Schoenberg, Ronny

    2018-02-01

    Mass-independent fractionation of sulfur isotopes (MIF-S) in Archaean sediments results from photochemical processing of atmospheric sulfur species in an oxygen-depleted atmosphere. Geological preservation of MIF-S provides evidence for microbial sulfate reduction (MSR) in low-sulfate Paleoarchaean (3.8-3.2 billion years ago (Ga)) and Neoarchaean (2.8-2.5 Ga) oceans, but the significance of MSR in Mesoarchaean (3.2-2.8 Ga) oceans is less clear. Here we present multiple sulfur and iron isotope data of early diagenetic pyrites from 2.97-Gyr-old stromatolitic dolomites deposited in a tidal flat environment of the Nsuze Group, Pongola Supergroup, South Africa. We identified consistently negative Δ33S values in pyrite, which indicates photochemical reactions under anoxic atmospheric conditions, but large mass-dependent sulfur isotope fractionations of 30‰ in δ34S, identifying active MSR. Negative pyrite δ56Fe values (-1.31 to -0.88‰) record Fe oxidation in oxygen-bearing shallow oceans coupled with biogenic Fe reduction during diagenesis, consistent with the onset of local Fe cycling in oxygen oases 3.0 Ga. We therefore suggest the presence of oxygenated near-shore shallow-marine environments with ≥5 μM sulfate at this time, in spite of the clear presence of an overall reduced Mesoarchaean atmosphere.

  9. Lattice sites of implanted Fe in Si

    CERN Document Server

    Wahl, Ulrich; Rita, E; Araújo, João Pedro; Carvalho-Soares, José

    2005-01-01

    The angular distribution of $\\beta^{-}$-particles emitted by the radioactive isotope $^{59}$Fe was monitored following implantation into Si single crystals at fluences from $1.4 \\times 10^{12}$ cm$^{-2}$ to $1 \\times 10^{14}$ cm$^{-2}$. We identified Fe on three distinct sites: ideal substitutional, displaced substitutional and displaced tetrahedral interstitial. Whereas displaced substitutional Fe was dominating for annealing temperatures below 500 °C, annealing between 500-700 °C caused the majority of Fe to occupy displaced tetrahedral interstitial sites. Ideal substitutional positions were increasingly populated following annealing at 800 °C and above. A comparison of the emission channeling results to Mössbauer and electron paramagnetic resonance experiments is given.

  10. 58Fe AND 54Cr IN EARLY SOLAR SYSTEM MATERIALS

    International Nuclear Information System (INIS)

    Wang, Kun; Moynier, Frederic; Podosek, Frank; Foriel, Julien

    2011-01-01

    Stepwise dissolution of primitive meteorites exhibits large 54 Cr anomalies but no collateral effects on 58 Fe and 48 Ca, two other neutron-rich nuclides from the iron peak. These results suggest that 54 Cr must have been produced in particular zones of the rare Type Ia supernovae or that 48 Ca and/or 58 Fe were produced together in Type II supernovae and were chemically separated into some mineral phase that favors Cr over Ca and Fe, and it is the dissolution properties of that phase that is driving the isotopic effect in leaching. The recent findings of nanometer-size oxide grains with very large 54 Cr excesses favored the latter scenario for the origin of the mono-isotopic Cr isotopic effect. In addition, the absence of isotopic variations in the 58 Fe/ 54 Fe ratio at the mineral scale confirms that the short-lived nuclide 60 Fe (T 1/2 = 2.62 Myr) was homogeneously distributed to a less than 15% dispersion in the early solar nebula.

  11. 58Fe and 54Cr in Early Solar System Materials

    Science.gov (United States)

    Wang, Kun; Moynier, Frederic; Podosek, Frank; Foriel, Julien

    2011-10-01

    Stepwise dissolution of primitive meteorites exhibits large 54Cr anomalies but no collateral effects on 58Fe and 48Ca, two other neutron-rich nuclides from the iron peak. These results suggest that 54Cr must have been produced in particular zones of the rare Type Ia supernovae or that 48Ca and/or 58Fe were produced together in Type II supernovae and were chemically separated into some mineral phase that favors Cr over Ca and Fe, and it is the dissolution properties of that phase that is driving the isotopic effect in leaching. The recent findings of nanometer-size oxide grains with very large 54Cr excesses favored the latter scenario for the origin of the mono-isotopic Cr isotopic effect. In addition, the absence of isotopic variations in the 58Fe/54Fe ratio at the mineral scale confirms that the short-lived nuclide 60Fe (T 1/2 = 2.62 Myr) was homogeneously distributed to a less than 15% dispersion in the early solar nebula.

  12. Isotopic Fingerprint for Phosphorus in Drinking Water Supplies.

    Science.gov (United States)

    Gooddy, Daren C; Lapworth, Dan J; Ascott, Matthew J; Bennett, Sarah A; Heaton, Timothy H E; Surridge, Ben W J

    2015-08-04

    Phosphate dosing of drinking water supplies, coupled with leakage from distribution networks, represents a significant input of phosphorus to the environment. The oxygen isotope composition of phosphate (δ(18)OPO4), a novel stable isotope tracer for phosphorus, offers new opportunities to understand the importance of phosphorus derived from sources such as drinking water. We report the first assessment of δ(18)OPO4 within drinking water supplies. A total of 40 samples from phosphate-dosed distribution networks were analyzed from across England and Wales. In addition, samples of the source orthophosphoric acid used for dosing were also analyzed. Two distinct isotopic signatures for drinking water were identified (average = +13.2 or +19.7‰), primarily determined by δ(18)OPO4 of the source acid (average = +12.4 or +19.7‰). Dependent upon the source acid used, drinking water δ(18)OPO4 appears isotopically distinct from a number of other phosphorus sources. Isotopic offsets from the source acid ranging from -0.9 to +2.8‰ were observed. There was little evidence that equilibrium isotope fractionation dominated within the networks, with offsets from temperature-dependent equilibrium ranging from -4.8 to +4.2‰. While partial equilibrium fractionation may have occurred, kinetic effects associated with microbial uptake of phosphorus or abiotic sorption and dissolution reactions may also contribute to δ(18)OPO4 within drinking water supplies.

  13. Incentives in Supply Function Equilibrium

    DEFF Research Database (Denmark)

    Vetter, Henrik

    2014-01-01

    The author analyses delegation in homogenous duopoly under the assumption that the firm-managers compete in supply functions. In supply function equilibrium, managers’ decisions are strategic complements. This reverses earlier findings in that the author finds that owners give managers incentives...

  14. Essays in general equilibrium theory

    NARCIS (Netherlands)

    Konovalov, A.

    2001-01-01

    The thesis focuses on various issues of general equilibrium theory and can approximately be divided into three parts. The first part of the thesis studies generalized equilibria in the Arrow-Debreu model in the situation where the strong survival assumption is not satisfied. Chapter four deals with

  15. An equilibrium and kinetic modeling

    African Journals Online (AJOL)

    SERVER

    2007-06-18

    Jun 18, 2007 ... The Langmuir and Freundlich adsorption models fitted well with the equilibrium data of the process studied. .... dosages. For the determination of adsorption isotherms, 4 g of bio- sorbent was used at five different .... The basic assumption of the Langmuir theory is that ad- sorption takes place at specific sites ...

  16. Game Theory-Nash Equilibrium

    Indian Academy of Sciences (India)

    Home; Journals; Resonance – Journal of Science Education; Volume 3; Issue 7. Game Theory - Nash Equilibrium. P G Babu. General Article Volume 3 Issue 7 July 1998 pp 53- ... Author Affiliations. P G Babu1. Indira Gandhi Institute of Development Research Gen. A K Vaidya Marg Goregaon(East) Mumbai 400 065, India.

  17. Understanding Thermal Equilibrium through Activities

    Science.gov (United States)

    Pathare, Shirish; Huli, Saurabhee; Nachane, Madhura; Ladage, Savita; Pradhan, Hemachandra

    2015-01-01

    Thermal equilibrium is a basic concept in thermodynamics. In India, this concept is generally introduced at the first year of undergraduate education in physics and chemistry. In our earlier studies (Pathare and Pradhan 2011 "Proc. episteme-4 Int. Conf. to Review Research on Science Technology and Mathematics Education" pp 169-72) we…

  18. Isotopic composition of precipitations in Brazil: isothermic models and the influence of evapotranspiration in the Amazonic Basin

    International Nuclear Information System (INIS)

    Dall'Olio, Attilio.

    1976-11-01

    The simplest theoretical models of the isotopic fractionation of water during equilibrium isothermical processes are analized in detail. The theoretical results are applied to the interpretation of the stable isotope concentrations in the precipitations of 11 Brazilian cities that belong to the international network of IAEA/WMO. The analysis shows that the experimental data are fairly consistent with such equilibrium models; no non-equilibrium processes need to be assumed. The study of the stable isotope content of precipitations in the Amazonic Basin suggests some modifications to the models in order that the evapotranspiration contribution to the vapour balance be taken into account [pt

  19. Stable iron isotopes and microbial mediation in red pigmentation of the Rosso Ammonitico (mid-late Jurassic, Verona area, Italy).

    Science.gov (United States)

    Préat, Alain R; de Jong, Jeroen T M; Mamet, Bernard L; Mattielli, Nadine

    2008-08-01

    The iron (Fe) isotopic composition of 17 Jurassic limestones from the Rosso Ammonitico of Verona (Italy) have been analyzed by Multiple-Collector Inductively Coupled Plasma Mass Spectrometry (MC-ICP-MS). Such analysis allowed for the recognition of a clear iron isotopic fractionation (mean -0.8 per thousand, ranging between -1.52 to -0.06 per thousand) on a millimeter-centimeter scale between the red and grey facies of the studied formation. After gentle acid leaching, measurements of the Fe isotopic compositions gave delta(56)Fe values that were systematically lower in the red facies residues (median: -0.84 per thousand, range: -1.46 to +0.26 per thousand) compared to the grey facies residues (median: -0.08 per thousand, range: -0.34 to +0.23 per thousand). In addition, the red facies residues were characterized by a lighter delta(56)Fe signal relative to their corresponding leachates. These Fe isotopic fractionations could be a sensitive fingerprint of a biotic process; systematic isotopic differences between the red and grey facies residues, which consist of hematite and X-ray amorphous iron hydroxides, respectively, are hypothesized to have resulted from the oxidizing activity of iron bacteria and fungi in the red facies. The grey Fe isotopic data match the Fe isotopic signature of the terrestrial baseline established for igneous rocks and low-C(org) clastic sedimentary rocks. The Fe isotopic compositions of the grey laminations are consistent with the influx of detrital iron minerals and lack of microbial redox processes at the water-interface during deposition. Total Fe concentration measurements were performed by Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES) (confirmed by concentration estimations obtained by MC-ICP-MS analyses of microdrilled samples) on five samples, and resultant values range between 0.30% (mean) in the grey facies and 1.31% (mean) in the red facies. No correlation was observed between bulk Fe content and pigmentation

  20. Gluconeogenesis from labeled carbon: estimating isotope dilution

    International Nuclear Information System (INIS)

    Kelleher, J.K.

    1986-01-01

    To estimate the rate of gluconeogenesis from steady-state incorporation of labeled 3-carbon precursors into glucose, isotope dilution must be considered so that the rate of labeling of glucose can be quantitatively converted to the rate of gluconeogenesis. An expression for the value of this isotope dilution can be derived using mathematical techniques and a model of the tricarboxylic acid (TCA) cycle. The present investigation employs a more complex model than that used in previous studies. This model includes the following pathways that may affect the correction for isotope dilution: 1) flux of 3-carbon precursor to the oxaloacetate pool via acetyl-CoA and the TCA cycle; 2) flux of 4- or 5-carbon compounds into the TCA cycle; 3) reversible flux between oxaloacetate (OAA) and pyruvate and between OAA and fumarate; 4) incomplete equilibrium between OAA pools; and 5) isotope dilution of 3-carbon tracers between the experimentally measured pool and the precursor for the TCA-cycle OAA pool. Experimental tests are outlined which investigators can use to determine whether these pathways are significant in a specific steady-state system. The study indicated that flux through these five pathways can significantly affect the correction for isotope dilution. To correct for the effects of these pathways an alternative method for calculating isotope dilution is proposed using citrate to relate the specific activities of acetyl-CoA and OAA

  1. On generalized operator quasi-equilibrium problems

    Science.gov (United States)

    Kum, Sangho; Kim, Won Kyu

    2008-09-01

    In this paper, we will introduce the generalized operator equilibrium problem and generalized operator quasi-equilibrium problem which generalize the operator equilibrium problem due to Kazmi and Raouf [K.R. Kazmi, A. Raouf, A class of operator equilibrium problems, J. Math. Anal. Appl. 308 (2005) 554-564] into multi-valued and quasi-equilibrium problems. Using a Fan-Browder type fixed point theorem in [S. Park, Foundations of the KKM theory via coincidences of composites of upper semicontinuous maps, J. Korean Math. Soc. 31 (1994) 493-519] and an existence theorem of equilibrium for 1-person game in [X.-P. Ding, W.K. Kim, K.-K. Tan, Equilibria of non-compact generalized games with L*-majorized preferences, J. Math. Anal. Appl. 164 (1992) 508-517] as basic tools, we prove new existence theorems on generalized operator equilibrium problem and generalized operator quasi-equilibrium problem which includes operator equilibrium problems.

  2. Evolutionary analysis of iron (Fe) acquisition system in Marchantia polymorpha.

    Science.gov (United States)

    Lo, Jing-Chi; Tsednee, Munkhtsetseg; Lo, Ying-Chu; Yang, Shun-Chung; Hu, Jer-Ming; Ishizaki, Kimitsune; Kohchi, Takayuki; Lee, Der-Chuen; Yeh, Kuo-Chen

    2016-07-01

    To acquire appropriate iron (Fe), vascular plants have developed two unique strategies, the reduction-based strategy I of nongraminaceous plants for Fe(2+) and the chelation-based strategy II of graminaceous plants for Fe(3+) . However, the mechanism of Fe uptake in bryophytes, the earliest diverging branch of land plants and dominant in gametophyte generation is less clear. Fe isotope fractionation analysis demonstrated that the liverwort Marchantia polymorpha uses reduction-based Fe acquisition. Enhanced activities of ferric chelate reductase and proton ATPase were detected under Fe-deficient conditions. However, M. polymorpha did not show mugineic acid family phytosiderophores, the key components of strategy II, or the precursor nicotianamine. Five ZIP (ZRT/IRT-like protein) homologs were identified and speculated to be involved in Fe uptake in M. polymorpha. MpZIP3 knockdown conferred reduced growth under Fe-deficient conditions, and MpZIP3 overexpression increased Fe content under excess Fe. Thus, a nonvascular liverwort, M. polymorpha, uses strategy I for Fe acquisition. This system may have been acquired in the common ancestor of land plants and coopted from the gametophyte to sporophyte generation in the evolution of land plants. © 2016 The Authors. New Phytologist © 2016 New Phytologist Trust.

  3. Isotope separation

    International Nuclear Information System (INIS)

    Bett, R.; Sims, H.E.; Cuninghame, J.G.

    1983-01-01

    sup(195m)Au is separated from sup(195m)Hg in a solution containing ions of sup(195m)Hg, wherein sup(195m)Au is generated by radioactive decay of the sup(195m)Hg, by contacting the solution with an adsorbing agent to adsorb the sup(195m)Hg as Hg ++ ions followed by elution of sup(195m)Au arising from said radioactive decay. The adsorbing agent is 3-thio-2-hydroxypropyl-ether-Sepharose (R.T.M.); sup(195m)Au may be prepared in this way in a medical isotope generator and is suitable for use in gamma-scan studies of heart action. (author)

  4. Magnetic Properties and Microstructure of FeOx/Fe/FePt and FeOx/FePt Films

    Directory of Open Access Journals (Sweden)

    Jai-Lin Tsai

    2013-01-01

    Full Text Available The Fe(6 nm/FePt film with perpendicular magnetization was deposited on the glass substrate. To study the oxygen diffusion effect on the coupling of Fe/FePt bilayer, the plasma oxidation with 0.5~7% oxygen flow ratio was performed during sputtered part of Fe layer and formed the FeOx(3 nm/Fe(3 nm/FePt trilayer. Two-step magnetic hysteresis loops were found in trilayer with oxygen flow ratio above 1%. The magnetization in FeOx and Fe/FePt layers was decoupled. The moments in FeOx layer were first reversed and followed by coupled Fe/FePt bilayer. The trilayer was annealed again at 500°C and 800°C for 3 minutes. When the FeOx(3 nm/Fe(3 nm/FePt trilayer was annealed at 500°C, the layers structure was changed to FeOx(6 nm/FePt bilayer due to oxygen diffusion. The hard-magnetic FeOx(6 nm/FePt film was coupled with single switching field. The FeOx/(disordered FePt layer structure was observed with further annealing at 800°C and presented soft-magnetic loop. In summary, the coupling between soft-magnetic Fe, FeOx layer, and hard-magnetic L10 FePt layer can be controlled by the oxygen diffusion behavior, and the oxidation of Fe layer was tuned by the annealing temperature. The ordered L10 FePt layer was deteriorated by oxygen and became disordered FePt when the annealed temperature was up to 800°C.

  5. Anisotropic Morphological Changes in Goethite during Fe(2+)-Catalyzed Recrystallization.

    Science.gov (United States)

    Joshi, Prachi; Gorski, Christopher A

    2016-07-19

    When goethite is exposed to aqueous Fe(2+), rapid and extensive Fe atom exchange can occur between solid-phase Fe(3+) and aqueous Fe(2+) in a process referred to as Fe(2+)-catalyzed recrystallization. This process can lead to the structural incorporation or release of trace elements, which has important implications for contaminant remediation and nutrient biogeochemical cycling. Prior work found that the process did not cause major changes to the goethite structure or morphology. Here, we further investigated if and how goethite morphology and aggregation behavior changed temporally during Fe(2+)-catalyzed recrystallization. On the basis of existing literature, we hypothesized that Fe(2+)-catalyzed recrystallization of goethite would not result in changes to individual particle morphology or interparticle interactions. To test this, we reacted nanoparticulate goethite with aqueous Fe(2+) at pH 7.5 over 30 days and used transmission electron microscopy (TEM), cryogenic TEM, and (55)Fe as an isotope tracer to observe changes in particle dimensions, aggregation, and isotopic composition over time. Over the course of 30 days, the goethite particles substantially recrystallized, and the particle dimensions changed anisotropically, resulting in a preferential increase in the mean particle width. The temporal changes in goethite morphology could not be completely explained by a single mineral-transformation mechanism but rather indicated that multiple transformation mechanisms occurred concurrently. Collectively, these results demonstrate that the morphology of goethite nanoparticles does change during recrystallization, which is an important step toward identifying the driving force(s) of recrystallization.

  6. Non-Equilibrium Properties from Equilibrium Free Energy Calculations

    Science.gov (United States)

    Pohorille, Andrew; Wilson, Michael A.

    2012-01-01

    Calculating free energy in computer simulations is of central importance in statistical mechanics of condensed media and its applications to chemistry and biology not only because it is the most comprehensive and informative quantity that characterizes the eqUilibrium state, but also because it often provides an efficient route to access dynamic and kinetic properties of a system. Most of applications of equilibrium free energy calculations to non-equilibrium processes rely on a description in which a molecule or an ion diffuses in the potential of mean force. In general case this description is a simplification, but it might be satisfactorily accurate in many instances of practical interest. This hypothesis has been tested in the example of the electrodiffusion equation . Conductance of model ion channels has been calculated directly through counting the number of ion crossing events observed during long molecular dynamics simulations and has been compared with the conductance obtained from solving the generalized Nernst-Plank equation. It has been shown that under relatively modest conditions the agreement between these two approaches is excellent, thus demonstrating the assumptions underlying the diffusion equation are fulfilled. Under these conditions the electrodiffusion equation provides an efficient approach to calculating the full voltage-current dependence routinely measured in electrophysiological experiments.

  7. Kinetics of FeII-polyaminocarboxylate oxidation by molecular oxygen

    Science.gov (United States)

    Wilson, Jessica M.; Farley, Kevin J.; Carbonaro, Richard F.

    2018-03-01

    Complexation of iron by naturally-occurring and synthetic organic ligands has a large effect on iron oxidation and reduction rates which in turn affect the aqueous geochemistry of many other chemical constituents. In this study, the kinetics of FeII oxidation in the presence of the polyaminocarboxylate synthetic chelating agents ethylene glycol tetraacetic acid (EGTA) and trimethylenediamine-N,N,N‧,N‧-tetraacetic acid (TMDTA) was investigated over the pH range 5.50-8.53. Batch oxidation experiments in the presence of molecular oxygen were conducted using a 2:1 M concentration ratio of polyaminocarboxylate (ligand, L) to FeII. The experimental data resembled first order kinetics for the oxidation of FeII-L to FeIII-L and observed rate constants at pH 6.0 were comparable to rate constants for the oxidation of inorganic FeII. Similar to other structurally-similar FeII-polyaminocarboxylate complexes, oxidation rates of FeII-EGTA and FeII-TMDTA decrease with increasing pH, which is the opposite trend for the oxidation of FeII complexed with inorganic ligands. However, the oxidation rates of FeII complexed with EGTA and TMDTA were considerably lower (4-5 orders of magnitude) than FeII complexed to ethylenediaminetetraacetic acid (EDTA). The distinguishing feature of the slower-reacting complexes is that they have a longer backbone between diamine functional groups. An analytical equilibrium model was developed to determine the contributions of the species FeIIL2- and FeII(H)L- to the overall oxidation rate of FeII-L. Application of this model indicated that the protonated FeII(H)L species are more than three orders of magnitude more reactive than FeIIL2-. These rate constants were used in a coupled kinetic equilibrium numerical model where the ligand to iron ratio (TOTL:TOTFe) and pH were varied to evaluate the effect on the FeII oxidation rate. Overall, increasing TOTL:TOTFe for EGTA and TMDTA enhances FeII oxidation rates at lower pH and inhibits FeII oxidation

  8. Natural isotopes

    International Nuclear Information System (INIS)

    Vogel, J.C.

    1986-01-01

    14 C dates between 600 and 900 AD were obtained for early Iron Age sites in Natal, and from 1300 to 1450 AD for rock engraving sites in Bushmanland. Palaeoenvironmental data derived from the dating of samples related to sedimentary and geomorphic features in the central and northern Namib Desert enabled the production of a tentative graph for the changes in humidity in the region over the past 40000 years. These results suggest that relatively humid conditions came to an end in the Namib at ±25000 BP (before present). The increased precision of the SIRA mass spectrometer enabled the remeasurement of 13 C and 18 O in the Cango stalagmite. This data confirmed that the environmental temperatures in the Southern Cape remained constant to within ±1 o C during the past 5500 years. Techniques and applications for environmental isotopes in hydrology were developed to determine the origin and movement of ground water. Isotopic fractionation effects in light elements in nature were investigated. The 15 N/ 14 N ratio in bones of animals and humans increases in proportion to the aridity of the environment. This suggests that 15 N in bone from dated archaeological sites could be used to detect changes in past climatic conditions as naturally formed nitrate minerals are higly soluble and are only preserved in special, very dry environments. The sources and sinks of CO 2 on the South African subcontinent were also determined. The 13 C/ 12 C ratios of air CO 2 obtained suggest that the vegetation provides the major proportion of respired CO 2 . 9 refs., 1 fig

  9. Electronic and magnetic properties of AlFe3 and AlFe3N nitride

    International Nuclear Information System (INIS)

    Kuhnen, C.A.; Santos, A.V. dos

    2004-01-01

    Self-consistent band structure calculations were performed for the metal aluminide AlFe 3 (in the fcc structure) and the nitride AlFe 3 N (perovskite-like nitride) at several lattice parameters in order to obtain the electronic structure and magnetic properties of these compounds. In this study we have employed the full potential linear augmented plane wave (FPLAPW) and the linear muffin-tin orbital (LMTO-ASA) methods. Our results show that the modeled AlFe 3 is ferromagnetic (FM) with 2.07μ B as the magnetic moment at Fe sites. On the other hand, AlFe 3 N is non-magnetic (NM) contrary to other perovskite nitrides that show magnetic order. Hence as the stable phase of AlFe 3 is magnetic with DO 3 structure a crystallographic transformation occurs accompanied by a magnetic transition from a non-magnetic perovskite structure to a magnetic DO 3 structure as AlFe 3 N lose nitrogen atoms. The LMTO and FPLAPW total energy calculations give the equilibrium volume for both compounds. For AlFe 3 N, the FPLAPW calculations give the equilibrium volume that agrees well with the experimental lattice spacing, which is not achieved by LMTO calculations within the same accuracy. The calculated magnetic moment as function of the lattice parameter for the AlFe 3 shows a collapse of the magnetism at certain critical lattice parameter whose FPLAPW value (2.962 A) differs only slightly from the LMTO value (3.041 A)

  10. Low temperature isotope effects of hydrogen diffusion in metallic glasses

    International Nuclear Information System (INIS)

    Hofmann, A.; Kronmueller, H.

    1989-01-01

    Snoek-like relaxation peaks of Hydrogen and Deuterium in amorphous Fe 80 B 20 , Fe 40 Ni 40 P 14 B 6 and Fe 91 Zr 9 are detected. At low H, D concentrations the peaks are near 200 K and show small isotope effects of the average activation energies (anti Q H ≅ 0.6 eV, anti Q D - anti Q H ≤ 10 meV). For higher H, D-contents the peaks shift to lower temperatures around to 120 K and show distinct isotope effects in the activation energies (anti Q H ≅ 0.3 eV, anti Q D - anti Q H ≅ 30 meV) and in the amplitude of the low temperature tails of the relaxation peaks. This points to isotope mass dependent deviations from the Arrhenius law due to nonthermal tunneling processes. (orig.)

  11. Stable isotope studies

    International Nuclear Information System (INIS)

    Ishida, T.

    1992-01-01

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

  12. Equilibrium and Non-Equilibrium Condensation Phenomena in Tuneable 3D and 2D Bose Gases

    Science.gov (United States)

    2016-04-01

    AFRL-AFOSR-UK-TR-2016-0009 Equilibrium and non- equilibrium condensation phenomena in tuneable 3D and 2D Bose gases Zoran Hadzibabic THE CHANCELLOR...31-Aug-2015 4. TITLE AND SUBTITLE Equilibrium and non- equilibrium condensation phenomena in tuneable 3D and 2D Bose gases 5a. CONTRACT NUMBER... equilibrium and non- equilibrium many-body phenomena, trapping ultracold atomic gases in different geometries including both 3 and 2 spatial dimensions

  13. Effect of Nutrient-limitation on the Microbial S-isotope Fractionation

    Science.gov (United States)

    Sim, M.; Bosak, T.; Ono, S.

    2011-12-01

    Microbial sulfate reduction (MSR) utilizes sulfate as an electron acceptor and produces sulfide that is depleted in heavy isotopes of sulfur relative to sulfate. This process controls much of the distribution of sulfur isotopes in sedimentary sulfides and sulfates, but the magnitude of S-isotope fractionations in natural environments often exceeds those in laboratory cultures. This difference may be due to many factors and environmental stresses, including the limitation by essential nutrients. However, none of the studies to date investigated the effect of nutrients such as nitrogen, iron, or phosphate, on sulfur isotope fractionation by sulfate reducing microbes. Here, we examine the influence of N and Fe limitation on multiple-S isotope fractionation by a marine sulfate reducing bacterium by reducing the concentrations of N and Fe in a defined medium by 10 to 1000 times. Nitrogen limitation reduces the growth rate and the cellular yield, but increases the respiration rate without altering the magnitude of isotope fractionation. In contrast, S-isotope fractionation was up to 40% larger in iron-limited than in iron-replete cultures. This increase in sulfur isotope fractionation is accompanied by a decrease in the growth rate, the cellular yield, the respiration rate, and the cytochrome c content. Thus, iron limitation increases the reversibility of microbial sulfate reduction pathway, possibly by affecting iron-containing respiratory complexes such as cytochromes and iron-sulfur proteins. The apparent influence of iron limitation on S-isotope fractionation is relevant to the interpretations of sulfur isotope data in modern and ancient environments. Some areas where iron limitation may lead to large observed S-isotope effects include iron-limited deep open ocean sediments, whereas smaller S-isotope effects would be expected where Fe is more bioavailable (e.g., in anoxic basins, where Fe enrichment occurs due to Fe shuttling).

  14. Protonation Equilibrium of Linear Homopolyacids

    Directory of Open Access Journals (Sweden)

    Požar J.

    2015-07-01

    Full Text Available The paper presents a short summary of investigations dealing with protonation equilibrium of linear homopolyacids, in particularly those of high charge density. Apart from the review of experimental results which can be found in the literature, a brief description of theoretical models used in processing the dependence of protonation constants on monomer dissociation degree and ionic strength is given (cylindrical model based on Poisson-Boltzmann equation, cylindrical Stern model, the models according to Ising, Högfeldt, Mandel and Katchalsky. The applicability of these models regarding the polyion charge density, electrolyte concentration and counterion type is discussed. The results of Monte Carlo simulations of protonation equilibrium are also briefly mentioned. In addition, frequently encountered errors connected with calibration of of glass electrode and the related unreliability of determined protonation constants are pointed out.

  15. The isotopic contamination in electromagnetic isotope separators

    International Nuclear Information System (INIS)

    Cassignol, Ch.

    1959-01-01

    In the early years of isotope separation, and in particular electromagnetic isotope separation, needs for rapid results have conducted to empiric research. This paper describes fundamental research on the electromagnetic isotope separation to a better understanding of isotope separators as well as improving the performances. Focus has been made on the study of the principle of isotope contamination and the remedial action on the separator to improve the isotope separation ratio. In a first part, the author come back to the functioning of an electromagnetic separator and generalities on isotope contamination. Secondly, it describes the two stages separation method with two dispersive apparatus, an electromagnetic separation stage followed by an electrostatic separation stage, both separated by a diaphragm. The specifications of the electrostatic stage are given and its different settings and their consequences on isotope separation are investigated. In a third part, mechanisms and contamination factors in the isotope separation are discussed: natural isotope contamination, contamination by rebounding on the collector, contamination because of a low resolution, contamination by chromatism and diffusion effect, breakdown of condenser voltage. Analysis of experimental results shows the diffusion as the most important contamination factor in electromagnetic isotope separation. As contamination factors are dependent on geometric parameters, sector angle, radius of curvature in the magnetic field and clearance height are discussed in a fourth part. The better understanding of the mechanism of the different contamination factors and the study of influential parameters as pressure and geometric parameters lead to define a global scheme of isotope contamination and determinate optima separator design and experimental parameters. Finally, the global scheme of isotope contamination and hypothesis on optima specifications and experimental parameters has been checked during a

  16. An introduction to equilibrium thermodynamics

    CERN Document Server

    Morrill, Bernard; Hartnett, James P; Hughes, William F

    1973-01-01

    An Introduction to Equilibrium Thermodynamics discusses classical thermodynamics and irreversible thermodynamics. It introduces the laws of thermodynamics and the connection between statistical concepts and observable macroscopic properties of a thermodynamic system. Chapter 1 discusses the first law of thermodynamics while Chapters 2 through 4 deal with statistical concepts. The succeeding chapters describe the link between entropy and the reversible heat process concept of entropy; the second law of thermodynamics; Legendre transformations and Jacobian algebra. Finally, Chapter 10 provides a

  17. Incentives in Supply Function Equilibrium

    DEFF Research Database (Denmark)

    Vetter, Henrik

    2015-01-01

    The author analyses delegation in homogenous duopoly under the assumption that firm-managers compete in supply functions. He reverses earlier findings in that owners give managers incentives to act in an accommodating way. That is, optimal delegation reduces per-firm output and increases profits ...... to above-Cournot profits. Moreover, in supply function equilibrium, the mode of competition is endogenous. This means that the author avoids results that are sensitive with respect to assuming either Cournot or Bertrand competition....

  18. Fractionation of Boron Isotopes in Icelandic Hydrothermal Systems

    Energy Technology Data Exchange (ETDEWEB)

    Aggarwal, J.K.; Palmer, M.R.

    1995-01-01

    Boron isotope ratios have been determined in a variety of different geothermal waters from hydrothermal systems across Iceland. Isotope ratios from the high temperature meteoric water recharged systems reflect the isotope ratio of the host rocks without any apparent fractionation. Seawater recharged geothermal systems exhibit more positive {delta}{sup 11}B values than the meteoric water recharged geothermal systems. Water/rock ratios can be assessed from boron isotope ratios in the saline hydrothermal systems. Low temperature hydrothermal systems also exhibit more positive {delta}{sup 11}B than the high temperature systems, indicating fractionation of boron due to adsorption of the lighter isotope onto secondary minerals. Fractionation of boron in carbonate deposits may indicate the level of equilibrium attained within the systems.

  19. 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.

  20. Study of the ZrO2-FeO-Fe2O3 system by thermogravimetry in partial pressure of oxygen and temperatures up to 15000C

    International Nuclear Information System (INIS)

    Goldschmidt, R.H.; Kiminami, A.

    1987-01-01

    The dissociation of iron oxide in the ZrO 2 -FeO-Fe 2 O 3 system was investigated in function of the temperature and the constant partial pressure of oxygen by thermal gravimetric analysis. The equilibrium diagram was constructed where the equilibrium relation between the solid phase of zirconium oxide, hematite and magnetite in 1437 0 C and PO 2 = 0.21 atm/m, as well as the equilibrium relation between the solid phase of zirconium oxide and hematite in lower temperatures than 1437 0 C were determined [pt

  1. Diffusion-driven magnesium and iron isotope fractionation in Hawaiian olivine

    Science.gov (United States)

    Teng, F.-Z.; Dauphas, N.; Helz, R.T.; Gao, S.; Huang, S.

    2011-01-01

    Diffusion plays an important role in Earth sciences to estimate the timescales of geological processes such as erosion, sediment burial, and magma cooling. In igneous systems, these diffusive processes are recorded in the form of crystal zoning. However, meaningful interpretation of these signatures is often hampered by the fact that they cannot be unambiguously ascribed to a single process (e.g., magmatic fractionation, diffusion limited transport in the crystal or in the liquid). Here we show that Mg and Fe isotope fractionations in olivine crystals can be used to trace diffusive processes in magmatic systems. Over sixty olivine fragments from Hawaiian basalts show isotopically fractionated Mg and Fe relative to basalts worldwide, with up to 0.4??? variation in 26Mg/24Mg ratios and 1.6??? variation in 56Fe/54Fe ratios. The linearly and negatively correlated Mg and Fe isotopic compositions [i.e., ??56Fe=(??3.3??0.3)????26Mg], co-variations of Mg and Fe isotopic compositions with Fe/Mg ratios of olivine fragments, and modeling results based on Mg and Fe elemental profiles demonstrate the coupled Mg and Fe isotope fractionation to be a manifestation of Mg-Fe inter-diffusion in zoned olivines during magmatic differentiation. This characteristic can be used to constrain the nature of mineral zoning in igneous and metamorphic rocks, and hence determine the residence times of crystals in magmas, the composition of primary melts, and the duration of metamorphic events. With improvements in methodology, in situ isotope mapping will become an essential tool of petrology to identify diffusion in crystals. ?? 2011 Elsevier B.V.

  2. Use of Isotopes for Studying Reaction Mechanisms -RE ...

    Indian Academy of Sciences (India)

    location and distribution of the label in the product(s). There is a more subtle effect ofisotopes which when studied quantitatively can give even greater details of chemical processes. Isotopic substitution can influence an equilibrium, sometimes dramatically. For example, the equilibria are shifted significantly to the right for ...

  3. 3D equilibrium reconstruction with islands

    Science.gov (United States)

    Cianciosa, M.; Hirshman, S. P.; Seal, S. K.; Shafer, M. W.

    2018-04-01

    This paper presents the development of a 3D equilibrium reconstruction tool and the results of the first-ever reconstruction of an island equilibrium. The SIESTA non-nested equilibrium solver has been coupled to the V3FIT 3D equilibrium reconstruction code. Computed from a coupled VMEC and SIESTA model, synthetic signals are matched to measured signals by finding an optimal set of equilibrium parameters. By using the normalized pressure in place of normalized flux, non-equilibrium quantities needed by diagnostic signals can be efficiently mapped to the equilibrium. The effectiveness of this tool is demonstrated by reconstructing an island equilibrium of a DIII-D inner wall limited L-mode case with an n = 1 error field applied. Flat spots in Thomson and ECE temperature diagnostics show the reconstructed islands have the correct size and phase. ).

  4. The Geometry of Finite Equilibrium Datasets

    DEFF Research Database (Denmark)

    Balasko, Yves; Tvede, Mich

    We investigate the geometry of finite datasets defined by equilibrium prices, income distributions, and total resources. We show that the equilibrium condition imposes no restrictions if total resources are collinear, a property that is robust to small perturbations. We also show that the set...... of equilibrium datasets is pathconnected when the equilibrium condition does impose restrictions on datasets, as for example when total resources are widely non collinear....

  5. Accelerating Multiagent Reinforcement Learning by Equilibrium Transfer.

    Science.gov (United States)

    Hu, Yujing; Gao, Yang; An, Bo

    2015-07-01

    An important approach in multiagent reinforcement learning (MARL) is equilibrium-based MARL, which adopts equilibrium solution concepts in game theory and requires agents to play equilibrium strategies at each state. However, most existing equilibrium-based MARL algorithms cannot scale due to a large number of computationally expensive equilibrium computations (e.g., computing Nash equilibria is PPAD-hard) during learning. For the first time, this paper finds that during the learning process of equilibrium-based MARL, the one-shot games corresponding to each state's successive visits often have the same or similar equilibria (for some states more than 90% of games corresponding to successive visits have similar equilibria). Inspired by this observation, this paper proposes to use equilibrium transfer to accelerate equilibrium-based MARL. The key idea of equilibrium transfer is to reuse previously computed equilibria when each agent has a small incentive to deviate. By introducing transfer loss and transfer condition, a novel framework called equilibrium transfer-based MARL is proposed. We prove that although equilibrium transfer brings transfer loss, equilibrium-based MARL algorithms can still converge to an equilibrium policy under certain assumptions. Experimental results in widely used benchmarks (e.g., grid world game, soccer game, and wall game) show that the proposed framework: 1) not only significantly accelerates equilibrium-based MARL (up to 96.7% reduction in learning time), but also achieves higher average rewards than algorithms without equilibrium transfer and 2) scales significantly better than algorithms without equilibrium transfer when the state/action space grows and the number of agents increases.

  6. Phase Equilibrium Modeling for Shale Production Simulation

    DEFF Research Database (Denmark)

    Sandoval Lemus, Diego Rolando

    calculation tools for phase equilibrium in porous media with capillary pressure and adsorption effects. Analysis using these tools have shown that capillary pressure and adsorption have non-negligible effects on phase equilibrium in shale. As general tools, they can be used to calculate phase equilibrium...... in other porous media as well. The compositional simulator with added capillary pressure effects on phase equilibrium can be used for evaluating the effects in dynamic and more complex scenarios....

  7. On the existence of the Fe sub 2 Nb sub 3 phase in the Fe-Nb system

    Energy Technology Data Exchange (ETDEWEB)

    Zelaya Bejarano, J.M. (Centro de Tecnologia, Universidade Estadual de Campinas, SP (Brazil)); Gama, S.; Ribeiro, C.A. (Instituto de Fisica Gleb Wataghin, Universidade Estadual de Campinas, SP (Brazil)); Effenberg, G. (Max-Planck-Inst. fuer Metallforschung, Inst. fuer Werkstoffwissenschaften, PML, Stuttgart (Germany)); Santos, C.

    1991-08-01

    The niobium-rich part of the Fe-Nb system has been investigated using metallography, electron microprobe, differential thermal analysis and the examination of diffusion couples. The phase relations are partially presented in the niobium-rich composition range of the phase diagram. It is concluded that the Fe{sub 2}Nb{sub 3} phase is not an equilibrium phase of the system, but appears metastable during slow cooling processes. (orig.).

  8. Estimation of the solubility limit of Cr in Fe at 300 oC from small-angle neutron scattering in neutron-irradiated Fe-Cr alloys

    International Nuclear Information System (INIS)

    Bergner, F.; Ulbricht, A.; Heintze, C.

    2009-01-01

    The solubility limit of Cr in Fe (α-Fe-Cr) at low temperatures is a matter of debate. We report a direct estimation of the solubility limit at 300 o C from small-angle neutron scattering (SANS) data obtained for neutron-irradiated Fe-Cr alloys. The SANS results indicate that the equilibrium concentration of α' was reached via irradiation-enhanced diffusion. The solubility limit was estimated using an iterative approach based on the SANS invariant and the lever rule of phase equilibrium.

  9. Investigation of equilibrium core by recycling MA and LLFP in fast reactor cycle. 2. Investigation of LLFP confined in Equilibrium Core with element separation

    International Nuclear Information System (INIS)

    Mizutani, Akihiko; Shono, Akira; Ishikawa, Makoto

    2000-02-01

    A feasibility study has been performed on a self-consistent fuel cycle system in the nuclear fuel recycle system with fast reactors. In this system, the self-generated MAs (Minor Actinides) and LLFPs (Long-Lived Fission Products) are confined and incinerated in the fast reactor, which is called the 'Equilibrium Core' concept. However, as the isotope separations for selected LLFPs have been assumed in this cycle system, it seems that this assumption is far from realistic one from the viewpoint of economy with respect to the fuel cycle system. In this study, the possibility for realization of the 'Equilibrium Core' concept is evaluated for three fuel types such as oxide, nitride and metallic fuels, provided that the isotopic separation of LLFPs is changed to the element one. This study provides, that is to say, how many LLFP elements can be confined in the 'Equilibrium Core' with element separation. This report examines the nuclear properties of the Equilibrium Core' for various combinations of LLFP incineration schemes from the viewpoints of the risk of geological disposal and the limit in confinable quantity of LLFPs. From the viewpoint of the risk of geological disposal estimated by the retardation factor, it is possible to confine with element separation for Tc, I and Se even in the oxide fueled core. From the standpoint of the limit of confinable amounts of LLFPs, on the other hand, Tc, I, Se, Sn and Cs can be confined with element separate only in case that the nitride fuel is chosen. (author)

  10. The concept of equilibrium in organization theory

    NARCIS (Netherlands)

    Gazendam, H.W.M.

    1998-01-01

    Many organization theories consist of an interpretation frame and an idea about the ideal equilibrium state. This article explains how the equilibrium concept is used in four organization theories: the theories of Fayol, Mintzberg, Morgan, and Volberda. Equilibrium can be defined as balance, fit or

  11. The concept of equilibrium in organization theory

    NARCIS (Netherlands)

    Gazendam, Henk W.M.

    1997-01-01

    Many organization theories consist of an interpretation frame and an idea about the ideal equilibrium state. This article explains how the equilibrium concept is used in four organization theories: the theories of Fayol, Mintzberg, Morgan, and Volberda. Equilibrium can be defined as balance, fit or

  12. Open problems in non-equilibrium physics

    Energy Technology Data Exchange (ETDEWEB)

    Kusnezov, D.

    1997-09-22

    The report contains viewgraphs on the following: approaches to non-equilibrium statistical mechanics; classical and quantum processes in chaotic environments; classical fields in non-equilibrium situations: real time dynamics at finite temperature; and phase transitions in non-equilibrium conditions.

  13. Stable isotope compositions (O-C) of reef fish otoliths from the Taiaro lagoon (Tuamotu, French Polynesia): isotopic and biologic implications

    International Nuclear Information System (INIS)

    Blamart, D.; Juillet-Leclerc, A.; Ouahdi, R.; Escoubeyrou, K.; Lecomte-Finiger, R.

    2002-01-01

    Nuclei (larval stage) and outer parts (adult stage) of fish otoliths from the Taiaro closed lagoon (French Polynesia) and adjacent ocean have been analysed for the C-O isotopic compositions. δ 18 O values of the nuclei of both populations indicate that isotopic equilibrium is reached. This implies that the lagoonal fish population has done its complete biological cycle in the lagoon and represents an adaptation in a closed system. δ 18 O values of the outer parts show a slight isotopic disequilibrium ( 13 C values exhibit a strong isotopic disequilibrium related to metabolic activity. (authors)

  14. Iron isotope systematics of the Skaergaard intrusion

    DEFF Research Database (Denmark)

    Lesher, Charles; Lundstrom, C.C.; Barfod, Gry

    crystallization on non-traditional stable isotope systems, particularly iron. FeTi oxide minerals (titanomagnetite and ilmenite) appear after ~60% of the magma had solidified. This was a significant event affecting the liquid line of descent and potentially accompanied by iron isotope fractionation. Here we...... report the results of a broad study of the iron isotope compositions of gabbros within the layered and upper border series of the Skaergaard intrusion, pegmatite and granophyre associated with these gabbroic rocks, and the sandwich horizon thought to represent the product of extreme differentiation and....../or liquid immiscibility. Forty-eight whole rock samples from well-constrained stratigraphic levels in the intrusion were crushed, powdered and dissolved, followed by iron separation by ion chromatography. Purified solutions were analyzed by MC- ICPMS in high-resolution mode using the sample-std bracket...

  15. Non-traditional Stable Isotope Systematics of Seafloor Hydrothermal Systems

    Science.gov (United States)

    Rouxel, O. J.

    2009-05-01

    Seafloor hydrothermal activity at mid-ocean ridges is one of the fundamental processes controlling the chemistry of the oceans and the altered oceanic crust. Past studies have demonstrated the complexity and diversity of seafloor hydrothermal systems and have highlighted the importance of subsurface environments in controlling the composition of hydrothermal fluids and mineralization types. Traditionally, the behavior of metals in seafloor hydrothermal systems have been investigated by integrating results from laboratory studies, theoretical models, mineralogy and fluid and mineral chemistry. Isotope ratios of various metals and metalloids, such as Fe, Cu, Zn, Se, Cd and Sb have recently provided new approaches for the study of seafloor hydrothermal systems. Despite these initial investigations, the cause of the isotopic variability of these elements remains poorly constrained. We have little understanding of the isotope variations between vent types (black or white smokers) as well as the influence of source rock composition (basalt, felsic or ultrabasic rocks) and alteration types. Here, I will review and present new results of metal isotope systematics of seafloor hydrothermal systems, in particular: (1) determination of empirical isotope fractionation factors for Zn, Fe and Cu-isotopes through isotopic analysis of mono-mineralic sulfide grains lining the internal chimney wall in contact with hydrothermal fluid; (2) comparison of Fe- and Cu-isotope signatures of vent fluids from mid- oceanic and back-arc hydrothermal fields, spanning wide ranges of pH, temperature, metal concentrations and contributions of magmatic fluids enriched in SO2. Ultimately, the use of complementary non-traditional stable isotope systems may help identify and constrain the complex interactions between fluids,minerals, and organisms in seafloor hydrothermal systems.

  16. Colorimetric Determination of the Iron(III)-Thiocyanate Reaction Equilibrium Constant with Calibration and Equilibrium Solutions Prepared in a Cuvette by Sequential Additions of One Reagent to the Other

    Science.gov (United States)

    Nyasulu, Frazier; Barlag, Rebecca

    2011-01-01

    The well-known colorimetric determination of the equilibrium constant of the iron(III-thiocyanate complex is simplified by preparing solutions in a cuvette. For the calibration plot, 0.10 mL increments of 0.00100 M KSCN are added to 4.00 mL of 0.200 M Fe(NO[subscript 3])[subscript 3], and for the equilibrium solutions, 0.50 mL increments of…

  17. Measurement of Isotopic Distribution in the Evaluation of Oil Fields

    International Nuclear Information System (INIS)

    Blaga, L.

    1969-01-01

    The isotopic concentrations in newly opened hydrocarbon deposits show certain regularities of distribution. The existing isotopic distributions in the fluids present in natural porous media are the cumulative result of certain steady-state processes of physical, chemical and other types which take place in layers of rock. These distributions are reflected in: - the isotopic distribution obtaining between the various components of the fluids in oil-bearing formations; - the gradients of isotopic concentrations appearing over extended distances. The isotopic distribution existing between the different components of the fluids in oil-bearing deposits is the result of isotopic equilibrium or of a process tending towards such equilibrium. Agreement can be obtained between the calculated values and those obtained, for example, in the methane-deposit water system The isotopic concentration gradients, recorded over considerable distances within one phase, are primarily the result of a geothermal gradient. Two characteristic phases are noteworthy from the point of view of the distribution of isotopic concentration gradients in hydrocarbon deposits: (a) The starting phase of isotopic distribution, pre-existing in the deposit, which is a result of the temperature gradients. This distribution can be incorporated in a system of isotopic isoconcentrates (lines of equal isotopic concentration), which can be correlated with the structure of the deposit and also with the various physical, chemical and mechanical factors characteristic of porous media (b) The secondary phase of isotopic distribution, corresponding to the period of operation. The exploitation process results in imbalances due to pressure and water flooding and in large-scale movements of oil from one zone to another. If one considers the isotopic distribution of the starting phase as an initial, natural isotopic labelling, it would appear possible to follow the changes in initial distribution as the exploration

  18. Double differential cross sections for (p,n) reactions of 18 and 25 MeV protons with isotopes of Cr, Fe, Co, Ni, Cu, Y, Zr, Mo, Pd and Tb

    International Nuclear Information System (INIS)

    Scobel, W.; Blann, M.; Komoto, T.; Trabandt, M.; Grimes, S.M.; Hansen, L.F.; Pohl, B.A.; Wong, C.

    1984-06-01

    Cross sections for the inclusive production of neutrons from reactions of 25 MeV protons with 50 52 53 Cr, 54 56 58 Fe, 59 Co, 60 Ni, 63 Cu, 89 Y, 90 91 92 94 Zr, 92 94 95 96 97 98 100 Mo, 110 Pd and 159 Tb and of 18 MeV protons with 90 91 92 94 Zr have been measured with time-of-flight techniques for 16 angles between 3.5 0 less than or equal to theta/sub lab/ less than or equal to 159.0 0 . After a short presentation of the motivations for these measurements, the experimental set up is discussed with emphasis on the systematic and statistical error sources pertinent to this work, in particular the question of background correction in the continuous parts of the spectra. The main purpose of this report is to make the experimental results of this work (angle integrated spectra, angular distributions) available for distribution, reducing thereby the data required in publication of the results of these experiments. 20 references

  19. Controls of Ca/Mg/Fe activity ratios in pore water chemistry models of the Callovian-Oxfordian clay formation

    International Nuclear Information System (INIS)

    Lerouge, C.; Grangeon, S.; Wille, G.; Flehoc, C.; Gailhanou, H.; Gaucher, E.C.; Tournassat, C.; Vinsot, A.; Made, B.; Altmann, S.

    2013-01-01

    In the pore water chemistry model of the Callovian-Oxfordian clay formation, the divalent cations Ca, Mg, and Fe are controlled by equilibrium reactions with pure carbonates: calcite for Ca, dolomite for Mg, and siderite for Fe. Results of a petrological study and computing of the Ca/Mg and Ca/Fe activity ratios based on natural pore water chemistry provide evidence that equilibrium with pure calcite and pure dolomite is a reasonable assumption for undisturbed pore waters; on the other hand, siderite cannot be considered at equilibrium with pore waters at the formation scale. (authors)

  20. Iron isotopic composition of blood serum in anemia of chronic kidney disease.

    Science.gov (United States)

    Anoshkina, Yulia; Costas-Rodríguez, Marta; Speeckaert, Marijn; Van Biesen, Wim; Delanghe, Joris; Vanhaecke, Frank

    2017-05-24

    Chronic kidney disease (CKD) is a general term for disorders that affect the structure and function of the kidneys. Iron deficiency (ID) and anemia occur in the vast majority of CKD patients, most of whom are elderly. However, establishing the cause of anemia in CKD, and therefore making an informed decision concerning the corresponding therapeutic treatment, is still a challenge. High-precision Fe isotopic analysis of blood serum samples of CKD patients with and without ID/anemia was performed via multi-collector inductively coupled plasma-mass spectrometry (MC-ICP-MS) for such a purpose. Patients with CKD and/or iron disorders showed a heavier serum Fe isotopic composition than controls. Many clinical parameters used for the diagnosis and follow-up of anemia correlated significantly with the serum Fe isotopic composition. In contrast, no relation was observed between the serum Fe isotopic composition and the estimated glomerular filtration rate as a measure of kidney function. Among the CKD patients, the serum Fe isotopic composition was substantially heavier in the occurrence of ID anemia, while erythropoietin-related anemia did not exert this effect. The Fe isotopic composition can thus be useful for distinguishing these different types of anemias in CKD patients, i.e. ID anemia vs. erythropoietin-related anemia.

  1. Thermal equilibrium in Einstein's elevator.

    Science.gov (United States)

    Sánchez-Rey, Bernardo; Chacón-Acosta, Guillermo; Dagdug, Leonardo; Cubero, David

    2013-05-01

    We report fully relativistic molecular-dynamics simulations that verify the appearance of thermal equilibrium of a classical gas inside a uniformly accelerated container. The numerical experiments confirm that the local momentum distribution in this system is very well approximated by the Jüttner function-originally derived for a flat spacetime-via the Tolman-Ehrenfest effect. Moreover, it is shown that when the acceleration or the container size is large enough, the global momentum distribution can be described by the so-called modified Jüttner function, which was initially proposed as an alternative to the Jüttner function.

  2. Risk premia in general equilibrium

    DEFF Research Database (Denmark)

    Posch, Olaf

    solutions of dynamic stochastic general equilibrium models, including a novel solution with endogenous labor supply, to obtain closed-form expressions for the risk premium in production economies. We find that the curvature of the policy functions affects the risk premium through controlling the individual......This paper shows that non-linearities can generate time-varying and asymmetric risk premia over the business cycle. These (empirical) key features become relevant and asset market implications improve substantially when we allow for non-normalities in the form of rare disasters. We employ explicit......'s effective risk aversion....

  3. Skill Mismatch in Equilibrium Unemployment

    OpenAIRE

    Bachmann, Ronald

    2005-01-01

    We analyse the effect of skill mismatch in a search model of equilibrium unemployment with risk-neutral agents, endogenous job destruction, and two-sided ex-ante heterogeneity. First, we examine the interaction of labour market institu- tions and skill mismatch. We find that skill mismatch changes the results obtained in a model with ex ante homogeneity. Second, we analyse the interaction of skill mismatch and labour market institutions for the di®erence in the labour market experience of con...

  4. Are the Concepts of Dynamic Equilibrium and the Thermodynamic Criteria for Spontaneity, Nonspontaneity, and Equilibrium Compatible?

    Science.gov (United States)

    Silverberg, Lee J.; Raff, Lionel M.

    2015-01-01

    Thermodynamic spontaneity-equilibrium criteria require that in a single-reaction system, reactions in either the forward or reverse direction at equilibrium be nonspontaneous. Conversely, the concept of dynamic equilibrium holds that forward and reverse reactions both occur at equal rates at equilibrium to the extent allowed by kinetic…

  5. Modeling nuclear volume isotope effects in crystals

    Science.gov (United States)

    Schauble, Edwin A.

    2013-01-01

    Mass-independent isotope fractionations driven by differences in volumes and shapes of nuclei (the field shift effect) are known in several elements and are likely to be found in more. All-electron relativistic electronic structure calculations can predict this effect but at present are computationally intensive and limited to modeling small gas phase molecules and clusters. Density functional theory, using the projector augmented wave method (DFT-PAW), has advantages in greater speed and compatibility with a three-dimensional periodic boundary condition while preserving information about the effects of chemistry on electron densities within nuclei. These electron density variations determine the volume component of the field shift effect. In this study, DFT-PAW calculations are calibrated against all-electron, relativistic Dirac–Hartree–Fock, and coupled-cluster with single, double (triple) excitation methods for estimating nuclear volume isotope effects. DFT-PAW calculations accurately reproduce changes in electron densities within nuclei in typical molecules, when PAW datasets constructed with finite nuclei are used. Nuclear volume contributions to vapor–crystal isotope fractionation are calculated for elemental cadmium and mercury, showing good agreement with experiments. The nuclear-volume component of mercury and cadmium isotope fractionations between atomic vapor and montroydite (HgO), cinnabar (HgS), calomel (Hg2Cl2), monteponite (CdO), and the CdS polymorphs hawleyite and greenockite are calculated, indicating preferential incorporation of neutron-rich isotopes in more oxidized, ionically bonded phases. Finally, field shift energies are related to Mössbauer isomer shifts, and equilibrium mass-independent fractionations for several tin-bearing crystals are calculated from 119Sn spectra. Isomer shift data should simplify calculations of mass-independent isotope fractionations in other elements with Mössbauer isotopes, such as platinum and uranium

  6. Calcium isotopic composition of mantle peridotites

    Science.gov (United States)

    Huang, F.; Kang, J.; Zhang, Z.

    2015-12-01

    Ca isotopes are useful to decipher mantle evolution and the genetic relationship between the Earth and chondrites. It has been observed that Ca isotopes can be fractionated at high temperature [1-2]. However, Ca isotopic composition of the mantle peridotites and fractionation mechanism are still poorly constrained. Here, we report Ca isotope composition of 12 co-existing pyroxene pairs in 10 lherzolites, 1 harzburgite, and 1 wehrlite xenoliths collected from Hainan Island (South Eastern China). Ca isotope data were measured on a Triton-TIMS using the double spike method at the Guangzhou Institute of Geochemistry, CAS. The long-term external error is 0.12‰ (2SD) based on repeated analyses of NIST SRM 915a and geostandards. δ44Ca of clinopyroxenes except that from the wehrlite ranges from 0.85‰ to 1.14‰, while opx yields a wide range from 0.98‰ up to 2.16‰. Co-existing pyroxene pairs show large Δ44Caopx-cpx (defined as δ44Caopx-δ44Cacpx) ranging from 0 to 1.23‰, reflecting equilibrium fractionation controlled by variable Ca contents in the opx. Notably, clinopyroxene of wehrlite shows extremely high δ44Ca (3.22‰). δ44Ca of the bulk lherzolites and harzburgites range from 0.86‰ to 1.14‰. This can be explained by extracting melts with slightly light Ca isotopic compositions. Finally, the high δ44Ca of the wehrlite (3.22‰) may reflect metasomatism by melt which has preferentially lost light Ca isotopes due to chemical diffusion during upwelling through the melt channel. [1] Amini et al (2009) GGR 33; [2] Huang et al (2010) EPSL 292.

  7. The equilibrium of overpressurized polytropes

    Science.gov (United States)

    Huré, J.-M.; Hersant, F.; Nasello, G.

    2018-03-01

    We investigate the impact of an external pressure on the structure of self-gravitating polytropes for axially symmetric ellipsoids and rings. The confinement of the fluid by photons is accounted for through a boundary condition on the enthalpy H. Equilibrium configurations are determined numerically from a generalized `self-consistent-field' method. The new algorithm incorporates an intraloop re-scaling operator R(H), which is essential for both convergence and getting self-normalized solutions. The main control parameter is the external-to-core enthalpy ratio. In the case of uniform rotation rate and uniform surrounding pressure, we compute the mass, the volume, the rotation rate and the maximum enthalpy. This is repeated for a few polytropic indices, n. For a given axial ratio, overpressurization globally increases all output quantities, and this is more pronounced for large n. Density profiles are flatter than in the absence of an external pressure. When the control parameter asymptotically tends to unity, the fluid converges towards the incompressible solution, whatever the index, but becomes geometrically singular. Equilibrium sequences, obtained by varying the axial ratio, are built. States of critical rotation are greatly exceeded or even disappear. The same trends are observed with differential rotation. Finally, the typical response to a photon point source is presented. Strong irradiation favours sharp edges. Applications concern star-forming regions and matter orbiting young stars and black holes.

  8. Departures from Local Thermodynamic Equilibrium

    International Nuclear Information System (INIS)

    McWhirter, R.W.P.

    1968-01-01

    This paper starts with a definition of local thermodynamic equilibrium and points out the relationship between local and complete thermodynamic equilibrium. It is shown that electron collisions are essential for the establishment of LTE and a relationship is derived for the minimum electron density at which collision processes are just sufficiently frequent to cause the plasma to be in LTE in face of the competing radiative processes. This relationship is derived for an optically thin plasma. The effect of radiation trapping is considered and some figures given by which the effect of this can be taken into account in assessing the validity of LTE in such cases. Account is now taken of the finite time required for the atomic collision processes to establish the plasma in LTE. A numerical example is worked out which shows that these considerations can be very important for plasmas of rapidly varying temperature. Mention is also made of departures from LTE caused by inhomogeneities in the plasma and by the positive ions having a different kinetic temperature from the electrons. Finally, it is remarked that even if the criteria for LTE to be valid are not met then the Saha and Boltzmann equations may still be applied to describe the population densities of the upper levels of individual species of atoms or ions. (author)

  9. Electron transfer and atom exchange between aqueous Fe(II) and structural Fe(III) in clays. Role in U and Hg(II) transformations

    Energy Technology Data Exchange (ETDEWEB)

    Scherer, Michelle [Univ. of Iowa, Iowa City, IA (United States)

    2016-08-31

    During this project, we investigated Fe electron transfer and atom exchange between aqueous Fe(II) and structural Fe(III) in clay minerals. We used selective chemical extractions, enriched Fe isotope tracer experiments, computational molecular modeling, and Mössbauer spectroscopy. Our findings indicate that structural Fe(III) in clay minerals is reduced by aqueous Fe(II) and that electron transfer occurs when Fe(II) is sorbed to either basal planes and edge OH-groups of clay mineral. Findings from highly enriched isotope experiments suggest that up to 30 % of the Fe atoms in the structure of some clay minerals exhanges with aqueous Fe(II). First principles calculations using a small polaron hopping approach suggest surprisingly fast electron mobility at room temperature in a nontronite clay mineral and are consistent with temperature dependent Mössbauer data Fast electron mobility suggests that electrons may be able to conduct through the mineral fast enough to enable exchange of Fe between the aqueous phase and clay mineral structure. over the time periods we observed. Our findings suggest that Fe in clay minerals is not as stable as previously thought.

  10. Application of iron and zinc isotopes to track the sources and mechanisms of metal loading in a mountain watershed

    Energy Technology Data Exchange (ETDEWEB)

    Borrok, David M., E-mail: dborrok@utep.edu [Department of Geological Sciences, University of Texas, El Paso, TX 79968 (United States); Wanty, Richard B.; Ian Ridley, W.; Lamothe, Paul J. [US Geological Survey, Denver Federal Center, Denver, CO 80225 (United States); Kimball, Briant A. [US Geological Survey, 2329 W. Orton Cir., Salt Lake City, UT 84119 (United States); Verplanck, Philip L.; Runkel, Robert L. [US Geological Survey, Denver Federal Center, Denver, CO 80225 (United States)

    2009-07-15

    Here the hydrogeochemical constraints of a tracer dilution study are combined with Fe and Zn isotopic measurements to pinpoint metal loading sources and attenuation mechanisms in an alpine watershed impacted by acid mine drainage. In the tested mountain catchment, {delta}{sup 56}Fe and {delta}{sup 66}Zn isotopic signatures of filtered stream water samples varied by {approx}3.5 per mille and 0.4 per mille, respectively. The inherent differences in the aqueous geochemistry of Fe and Zn provided complimentary isotopic information. For example, variations in {delta}{sup 56}Fe were linked to redox and precipitation reactions occurring in the stream, while changes in {delta}{sup 66}Zn were indicative of conservative mixing of different Zn sources. Fen environments contributed distinctively light dissolved Fe (<-2.0 per mille) and isotopically heavy suspended Fe precipitates to the watershed, while Zn from the fen was isotopically heavy (>+0.4 per mille). Acidic drainage from mine wastes contributed heavier dissolved Fe ({approx}+0.5 per mille) and lighter Zn ({approx}+0.2 per mille) isotopes relative to the fen. Upwelling of Fe-rich groundwater near the mouth of the catchment was the major source of Fe ({delta}{sup 56}Fe {approx} 0 per mille) leaving the watershed in surface flow, while runoff from mining wastes was the major source of Zn. The results suggest that given a strong framework for interpretation, Fe and Zn isotopes are useful tools for identifying and tracking metal sources and attenuation mechanisms in mountain watersheds.

  11. SHELL ISOTOPE GEOCHEMISTRY

    African Journals Online (AJOL)

    THE LAND SNAIL LIMICOLARIA KAMBEUL CHUDEAUI GERMAIN. IN THE ETHIOPIAN RIFT VALLEY: HABITAT, ECOLOGY AND. SHELL ISOTOPE GEOCHEMISTRY. Melanie J. Lengl, Henry F. Lamb',. Mohammed Umer Mohammed''* and Elias Dadebo4. 'NERC Isotope Geosciences Laboratory, Keyworth, Nottingham, ...

  12. Optical isotope shifts for unstable samarium isotopes

    International Nuclear Information System (INIS)

    Eastham, D.A.; Walker, P.M.; Griffith, J.A.R.; Evans, D.E.; Grant, I.S.; England, J.G.; Fawcett, M.J.

    1984-01-01

    Using a tunable dye laser beam intersecting a thermal atomic beam, optical isotope shifts and hyperfine splittings have been measured for the four unstable samarium isotopes between 144 Sm and 154 Sm, covering the well known transition region from spherical to deformed shapes. (orig.)

  13. Iron Transformation Pathways and Redox Micro-Environments in Seafloor Sulfide-Mineral Deposits: Spatially Resolved Fe XAS and δ(57/54)Fe Observations.

    Science.gov (United States)

    Toner, Brandy M; Rouxel, Olivier J; Santelli, Cara M; Bach, Wolfgang; Edwards, Katrina J

    2016-01-01

    Hydrothermal sulfide chimneys located along the global system of oceanic spreading centers are habitats for microbial life during active venting. Hydrothermally extinct, or inactive, sulfide deposits also host microbial communities at globally distributed sites. The main goal of this study is to describe Fe transformation pathways, through precipitation and oxidation-reduction (redox) reactions, and examine transformation products for signatures of biological activity using Fe mineralogy and stable isotope approaches. The study includes active and inactive sulfides from the East Pacific Rise 9°50'N vent field. First, the mineralogy of Fe(III)-bearing precipitates is investigated using microprobe X-ray absorption spectroscopy (μXAS) and X-ray diffraction (μXRD). Second, laser-ablation (LA) and micro-drilling (MD) are used to obtain spatially-resolved Fe stable isotope analysis by multicollector-inductively coupled plasma-mass spectrometry (MC-ICP-MS). Eight Fe-bearing minerals representing three mineralogical classes are present in the samples: oxyhydroxides, secondary phyllosilicates, and sulfides. For Fe oxyhydroxides within chimney walls and layers of Si-rich material, enrichments in both heavy and light Fe isotopes relative to pyrite are observed, yielding a range of δ(57)Fe values up to 6‰. Overall, several pathways for Fe transformation are observed. Pathway 1 is characterized by precipitation of primary sulfide minerals from Fe(II)aq-rich fluids in zones of mixing between vent fluids and seawater. Pathway 2 is also consistent with zones of mixing but involves precipitation of sulfide minerals from Fe(II)aq generated by Fe(III) reduction. Pathway 3 is direct oxidation of Fe(II) aq from hydrothermal fluids to form Fe(III) precipitates. Finally, Pathway 4 involves oxidative alteration of pre-existing sulfide minerals to form Fe(III). The Fe mineralogy and isotope data do not support or refute a unique biological role in sulfide alteration. The findings

  14. Microstructure and thermal stability of Fe, Ti and Ag implanted Yttria-stabilized zirconia

    NARCIS (Netherlands)

    van Hassel, B.A.; van Hassel, B.A.; Burggraaf, Anthonie; Burggraaf, A.J.

    1991-01-01

    Yttria-stabilized zirconia (YSZ) was implanted with 15 keV Fe or Ti ions up to a dose of 8×1016 at cm−2. The resulting “dopant” concentrations exceeded the concentrations corresponding to the equilibrium solid solubility of Fe2O3 or TiO2 in YSZ. During oxidation in air at 400° C, the Fe and Ti

  15. Preparation and biodistribution of {sup 59}Fe-radiolabelled iron oxide nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Pospisilova, Martina, E-mail: martinapospisilova@gmail.com; Zapotocky, Vojtech; Nesporova, Kristina [Contipro a.s (Czech Republic); Laznicek, Milan; Laznickova, Alice [Charles University, Faculty of Pharmacy in Hradec Králové (Czech Republic); Zidek, Ondrej; Cepa, Martin; Vagnerova, Hana; Velebny, Vladimir [Contipro a.s (Czech Republic)

    2017-02-15

    We report on the {sup 59}Fe radiolabelling of iron oxide nanoparticle cores through post-synthetic isotope exchange ({sup 59}Fe-IONP{sub ex}) and precursor labelling ({sup 59}Fe-IONP{sub pre}). Scanning electron microscopy and dynamic light scattering measurements showed no impact of radiolabelling on nanoparticle size or morphology. While incorporation efficiencies of these methods are comparable—83 and 90% for precursor labelling and post-synthetic isotope exchange, respectively—{sup 59}Fe-IONP{sub pre} exhibited much higher radiochemical stability in citrated human plasma. Quantitative ex vivo biodistribution study of {sup 59}Fe-IONP{sub pre} coated with triethylene glycol was performed in Wistar rats. Following the intravenous administration, high {sup 59}Fe concentration was observed in the lung and the organs of the reticuloendothelial system such as the liver, the spleen and the femur.

  16. Statistical clumped isotope signatures

    NARCIS (Netherlands)

    Röckmann, T.; Popa, M.E.; Krol, M.C.; Hofmann, M.E.G.

    2016-01-01

    High precision measurements of molecules containing more than one heavy isotope may provide novel constraints on element cycles in nature. These so-called clumped isotope signatures are reported relative to the random (stochastic) distribution of heavy isotopes over all available isotopocules of

  17. Statistical clumped isotope signatures

    Science.gov (United States)

    Röckmann, T.; Popa, M. E.; Krol, M. C.; Hofmann, M. E. G.

    2016-01-01

    High precision measurements of molecules containing more than one heavy isotope may provide novel constraints on element cycles in nature. These so-called clumped isotope signatures are reported relative to the random (stochastic) distribution of heavy isotopes over all available isotopocules of a molecule, which is the conventional reference. When multiple indistinguishable atoms of the same element are present in a molecule, this reference is calculated from the bulk (≈average) isotopic composition of the involved atoms. We show here that this referencing convention leads to apparent negative clumped isotope anomalies (anti-clumping) when the indistinguishable atoms originate from isotopically different populations. Such statistical clumped isotope anomalies must occur in any system where two or more indistinguishable atoms of the same element, but with different isotopic composition, combine in a molecule. The size of the anti-clumping signal is closely related to the difference of the initial isotope ratios of the indistinguishable atoms that have combined. Therefore, a measured statistical clumped isotope anomaly, relative to an expected (e.g. thermodynamical) clumped isotope composition, may allow assessment of the heterogeneity of the isotopic pools of atoms that are the substrate for formation of molecules. PMID:27535168

  18. Chromium isotope variations

    DEFF Research Database (Denmark)

    D'Arcy, Joan Mary

    Chromium (Cr) stable isotopes are a useful tracer of changes in redox conditions because changes in its oxidation state are accompanied by an isotopic fractionation. For this reason the Cr isotope system is being developed as a potential tool for paleo-redox reconstruction. Dissolved Cr in seawater...

  19. Fractionation of oxygen isotopes between mammalian bone-phosphate and environmental drinking water

    International Nuclear Information System (INIS)

    Luz, B.; Kolodny, V.; Horowitz, M.

    1984-01-01

    The delta 18 O of mammalian bone-phosphate varies linearly with delta 18 O of environmental water, but is not in isotopic equilibrium with that water. This situation is explained by a model of delta 18 O in body water in which the important fluxes of exchangeable oxygen through the body are taken into account. Fractionation of oxygen isotopes between body and environmental drinking water is dependent on the rates of drinking and respiration. Isotopic fractionation can be estimated from physiological data and the estimates correlate very well with observed fractionation. Species whose water consumption is large relative to its energy expenditure is sensitive to isotopic ratio changes in environmental water. (author)

  20. Theorical and experimental analysis of nitrogen-15 isotope enrichment by nitrogen monoxide and nitric acid system

    International Nuclear Information System (INIS)

    Ducatti, C.

    1985-01-01

    Nitrogen-15 isotope enrichment by chemical exchange in NO/HNO 3 system was studied using two different theories. The isotope fractionation factors obtained by the countercurrent theory was compared to those estimated by the isotope equipartition theory were confronted through a model. A column in countercurrent was built at laboratory scale and parameters such as: number of theoretical plates, height equivalent to a theoretical plate, type of packing, total height of column, production of H 15 NO 3 /week, obtained under isotope dynamic equilibrium conditions, were studied in comparison to those in the literature. (Author) [pt

  1. Stellar Equilibrium in Semiclassical Gravity

    Science.gov (United States)

    Carballo-Rubio, Raúl

    2018-02-01

    The phenomenon of quantum vacuum polarization in the presence of a gravitational field is well understood and is expected to have a physical reality, but studies of its backreaction on the dynamics of spacetime are practically nonexistent outside of the specific context of homogeneous cosmologies. Building on previous results of quantum field theory in curved spacetimes, in this Letter we first derive the semiclassical equations of stellar equilibrium in the s -wave Polyakov approximation. It is highlighted that incorporating the polarization of the quantum vacuum leads to a generalization of the classical Tolman-Oppenheimer-Volkoff equation. Despite the complexity of the resulting field equations, it is possible to find exact solutions. Aside from being the first known exact solutions that describe relativistic stars including the nonperturbative backreaction of semiclassical effects, these are identified as a nontrivial combination of the black star and gravastar proposals.

  2. Equilibrium calculations and mode analysis

    International Nuclear Information System (INIS)

    Herrnegger, F.

    1987-01-01

    The STEP asymptotic stellarator expansion procedure was used to study the MHD equilibrium and stability properties of stellarator configurations without longitudinal net-current, which also apply to advanced stellarators. The effects of toroidal curvature and magnetic well, and the Shafranov shift were investigated. A classification of unstable modes in toroidal stellarators is given. For WVII-A coil-field configurations having a β value of 1% and a parabolic pressure profile, no free-boundary modes are found. This agrees with the experimental fact that unstable behavior of the plasma column is not observed for this parameter range. So a theoretical β-limit for stability against ideal MHD modes can be estimated by mode analysis for the WVII-A device

  3. 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.

  4. 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.

  5. Secondary hydrogen isotope effects

    International Nuclear Information System (INIS)

    Melander, L.; Sonders, U.

    1983-01-01

    Secondary isotope effects can be produced by isotopes of elements heavier than hydrogen, but secondary isotope effects of hydrogen are of greater interest, because they are larger and can be measured easier. Such aspects of the problem as solvolytic reactions (in the case of α-position and β-position in organic compounds), reactions of compounds with deuterium remoted from reaction centre, with deuterium in nonsaturated compounds, participation of neighbouring groups in the reaction, are considered. Besides, steric isotope effects and inductive isotope effects are considered

  6. Applications of stable isotopes

    International Nuclear Information System (INIS)

    Letolle, R.; Mariotti, A.; Bariac, T.

    1991-06-01

    This report reviews the historical background and the properties of stable isotopes, the methods used for their measurement (mass spectrometry and others), the present technics for isotope enrichment and separation, and at last the various present and foreseeable application (in nuclear energy, physical and chemical research, materials industry and research; tracing in industrial, medical and agronomical tests; the use of natural isotope variations for environmental studies, agronomy, natural resources appraising: water, minerals, energy). Some new possibilities in the use of stable isotope are offered. A last chapter gives the present state and forecast development of stable isotope uses in France and Europe

  7. THE STABILITY OF VAPOR CONDENSATION EQUILIBRIUM

    OpenAIRE

    SHIMIN ZHANG

    2005-01-01

    The system must get across an energy peak of unstable equilibrium during the condensation of pure vapor; as the supersaturated extent of vapor increases and the temperature decreases, the energy peak shortens and vapor condensation becomes easier. The system must get across an energy peak of unstable equilibrium first, and then get into an energy valley of stable equilibrium during the condensation of impure vapor; as the partial pressure of vapor decreases, the energy peak becomes taller, th...

  8. 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.

  9. Study on bioavailability of dietary iron of women by using activable isotopic tracer and neutron activation analysis techniques

    International Nuclear Information System (INIS)

    Zhang Yangmei; Ni Bangfa; Tian Weizhi; Wang Pingsheng; Cao Lei

    2002-01-01

    The bioavailability of diet iron of 10 healthy young women in Beijing area is studied by using two enriched isotopes 54 Fe and 58 Fe, and neutron activation analysis techniques. The abundance of 54 Fe and 58 Fe is 61.4% and 23.4%, respectively. In additional, the atomic absorption spectrometry is employed to measure total iron in fecal samples. Dysprosium, rarely absorbed by human body, is used to monitor the residence time of tracer isotopes in order to collect the fecal samples completely. The results show that the bioavailability of dietary iron in young women is (14.9 +- 3.9)%

  10. Protonation/reduction dynamics at the [4Fe-4S] cluster of the hydrogen-forming cofactor in [FeFe]-hydrogenases.

    Science.gov (United States)

    Senger, Moritz; Mebs, Stefan; Duan, Jifu; Shulenina, Olga; Laun, Konstantin; Kertess, Leonie; Wittkamp, Florian; Apfel, Ulf-Peter; Happe, Thomas; Winkler, Martin; Haumann, Michael; Stripp, Sven T

    2018-01-31

    The [FeFe]-hydrogenases of bacteria and algae are the most efficient hydrogen conversion catalysts in nature. Their active-site cofactor (H-cluster) comprises a [4Fe-4S] cluster linked to a unique diiron site that binds three carbon monoxide (CO) and two cyanide (CN - ) ligands. Understanding microbial hydrogen conversion requires elucidation of the interplay of proton and electron transfer events at the H-cluster. We performed real-time spectroscopy on [FeFe]-hydrogenase protein films under controlled variation of atmospheric gas composition, sample pH, and reductant concentration. Attenuated total reflection Fourier-transform infrared spectroscopy was used to monitor shifts of the CO/CN - vibrational bands in response to redox and protonation changes. Three different [FeFe]-hydrogenases and several protein and cofactor variants were compared, including element and isotopic exchange studies. A protonated equivalent (HoxH) of the oxidized state (Hox) was found, which preferentially accumulated at acidic pH and under reducing conditions. We show that the one-electron reduced state Hred' represents an intrinsically protonated species. Interestingly, the formation of HoxH and Hred' was independent of the established proton pathway to the diiron site. Quantum chemical calculations of the respective CO/CN - infrared band patterns favored a cysteine ligand of the [4Fe-4S] cluster as the protonation site in HoxH and Hred'. We propose that proton-coupled electron transfer facilitates reduction of the [4Fe-4S] cluster and prevents premature formation of a hydride at the catalytic diiron site. Our findings imply that protonation events both at the [4Fe-4S] cluster and at the diiron site of the H-cluster are important in the hydrogen conversion reaction of [FeFe]-hydrogenases.

  11. Collapse and equilibrium of rotating, adiabatic clouds

    International Nuclear Information System (INIS)

    Boss, A.P.

    1980-01-01

    A numerical hydrodynamics computer code has been used to follow the collapse and establishment of equilibrium of adiabatic gas clouds restricted to axial symmetry. The clouds are initially uniform in density and rotation, with adiabatic exponents γ=5/3 and 7/5. The numerical technique allows, for the first time, a direct comparison to be made between the dynamic collapse and approach to equilibrium of unconstrained clouds on the one hand, and the results for incompressible, uniformly rotating equilibrium clouds, and the equilibrium structures of differentially rotating polytropes, on the other hand

  12. Equilibrium sampling by reweighting nonequilibrium simulation trajectories.

    Science.gov (United States)

    Yang, Cheng; Wan, Biao; Xu, Shun; Wang, Yanting; Zhou, Xin

    2016-03-01

    Based on equilibrium molecular simulations, it is usually difficult to efficiently visit the whole conformational space of complex systems, which are separated into some metastable regions by high free energy barriers. Nonequilibrium simulations could enhance transitions among these metastable regions and then be applied to sample equilibrium distributions in complex systems, since the associated nonequilibrium effects can be removed by employing the Jarzynski equality (JE). Here we present such a systematical method, named reweighted nonequilibrium ensemble dynamics (RNED), to efficiently sample equilibrium conformations. The RNED is a combination of the JE and our previous reweighted ensemble dynamics (RED) method. The original JE reproduces equilibrium from lots of nonequilibrium trajectories but requires that the initial distribution of these trajectories is equilibrium. The RED reweights many equilibrium trajectories from an arbitrary initial distribution to get the equilibrium distribution, whereas the RNED has both advantages of the two methods, reproducing equilibrium from lots of nonequilibrium simulation trajectories with an arbitrary initial conformational distribution. We illustrated the application of the RNED in a toy model and in a Lennard-Jones fluid to detect its liquid-solid phase coexistence. The results indicate that the RNED sufficiently extends the application of both the original JE and the RED in equilibrium sampling of complex systems.

  13. Interface spins in polycrystalline FeMn/Fe bilayers with small exchange bias

    Science.gov (United States)

    Pires, M. J. M.

    2018-04-01

    The magnetic moments at the interface between ferromagnetic and antiferromagnetic layers play a central role in exchange biased systems, but their behavior is still not completely understood. In this work, the FeMn/Fe interface in polycrystalline thin films has been studied using conversion electron Mössbauer spectroscopy (CEMS), magneto-optic Kerr effect (MOKE) and micromagnetic simulations. Samples were prepared with 57Fe layers at two distinct depths in order to probe the interface and bulk behaviors. At the equilibrium, the interface moments are randomly oriented while the bulk of the Fe layer has an in-plane magnetic anisotropy. Several models for the interface and anisotropies of the layers were used in the simulations of spin configurations and hysteresis loops. From the whole set of simulations, one can conclude the direct analysis of hysteresis curves is not enough to infer whether the interface has a configuration with spins tilted out of the film plane at equilibrium since different choices of parameters provide similar curves. The simulations have also shown the occurrence of spin clusters at the interface is compatible with CEMS and MOKE measurements.

  14. Interstellar ^{60}Fe on the Surface of the Moon.

    Science.gov (United States)

    Fimiani, L; Cook, D L; Faestermann, T; Gómez-Guzmán, J M; Hain, K; Herzog, G; Knie, K; Korschinek, G; Ludwig, P; Park, J; Reedy, R C; Rugel, G

    2016-04-15

    A dying massive star ends in a supernova explosion ejecting a large fraction of its mass into the interstellar medium. If this happens nearby, part of the ejecta might end on Solar System bodies and, in fact, radioactive ^{60}Fe has been detected on the Pacific ocean floor in about 2 Ma old layers. Here, we report on the detection of this isotope also in lunar samples, originating presumably from the same event. The concentration of the cosmic ray produced isotope ^{53}Mn, measured in the same samples, proves the supernova origin of the ^{60}Fe. From the ^{60}Fe concentrations found we deduce a reliable value for the local interstellar fluence in the range of 1×10^{8}  at/cm^{2}. Thus, we obtain constraints on the recent and nearby supernova(e).

  15. Accumulating the hydride state in the catalytic cycle of [FeFe]-hydrogenases

    Science.gov (United States)

    Winkler, Martin; Senger, Moritz; Duan, Jifu; Esselborn, Julian; Wittkamp, Florian; Hofmann, Eckhard; Apfel, Ulf-Peter; Stripp, Sven Timo; Happe, Thomas

    2017-07-01

    H2 turnover at the [FeFe]-hydrogenase cofactor (H-cluster) is assumed to follow a reversible heterolytic mechanism, first yielding a proton and a hydrido-species which again is double-oxidized to release another proton. Three of the four presumed catalytic intermediates (Hox, Hred/Hred and Hsred) were characterized, using various spectroscopic techniques. However, in catalytically active enzyme, the state containing the hydrido-species, which is eponymous for the proposed heterolytic mechanism, has yet only been speculated about. We use different strategies to trap and spectroscopically characterize this transient hydride state (Hhyd) for three wild-type [FeFe]-hydrogenases. Applying a novel set-up for real-time attenuated total-reflection Fourier-transform infrared spectroscopy, we monitor compositional changes in the state-specific infrared signatures of [FeFe]-hydrogenases, varying buffer pH and gas composition. We selectively enrich the equilibrium concentration of Hhyd, applying Le Chatelier's principle by simultaneously increasing substrate and product concentrations (H2/H+). Site-directed manipulation, targeting either the proton-transfer pathway or the adt ligand, significantly enhances Hhyd accumulation independent of pH.

  16. MOX - equilibrium core design and trial irradiation in KAPS - 1

    International Nuclear Information System (INIS)

    Pradhan, A.S.; Ray, Sherly; Kumar, A.N.; Parikh, M.V.

    2006-01-01

    Option of usage of MOX fuel bundles in the equilibrium core of Indian 220 MWe PHWRs on a regular basis has been studied. The design of the MOX bundle considered is MOX -7 with inner 7 elements with uranium and plutonium oxide MOX fuel and outer 12 elements with natural uranium fuel. The composition of the plutonium isotopes corresponds to that at about 6500 MWD/TeU burnup. Burnup optimization has been done such that operation at design rated power is possible while achieving the maximum average discharge burnup. Operation with the optimized burnup pattern will result in substantial saving of natural uranium bundles. To obtain feedback on the performance of MOX bundles prior to its large scale use about 50 MOX-7 bundles have been loaded in KAPS - 1 equilibrium core. Locations have been selected such that reactor should be operating at rated power without violating any constraints on channel bundle powers and also meeting the safety requirements. Burnup of interest also should be achieved in minimum period of time. The fissile plutonium content in the 50 MOX fuel bundles loaded is about 75.6 wt % . About 38 bundles out of the 50 bundles loaded have been already discharged and remaining bundles are still in the core. The maximum discharge burnup of the MOX bundles is about 12000 MWD/TeU. The performance of the MOX bundles were excellent and as per prediction. No MOX bundle is reported to be failed. (author)

  17. Flux analysis of central metabolic pathways in Geobactermetallireducens during reduction of solubleFe(III)-NTA

    Energy Technology Data Exchange (ETDEWEB)

    Tang, Yinjie J.; Chakraborty, Romy; Garcia-Martin, Hector; Chu,Jeannie; Hazen, Terry C.; Keasling, Jay D.

    2007-01-01

    We analyzed the carbon fluxes in the central metabolism ofGeobacter metallireducens strain GS-15 using 13C isotopomer modeling.Acetate labeled in the 1st or 2nd position was the sole carbon source,and Fe-NTA was the sole terminal electron acceptor. The measured labeledacetate uptake rate was 21 mmol/gdw/h in the exponential growth phase.The resulting isotope labeling pattern of amino acids allowed an accuratedetermination of the in vivo global metabolic reaction rates (fluxes)through the central metabolic pathways using a computational isotopomermodel. The tracer experiments showed that G. metallireducens containedcomplete biosynthesis pathways for essential metabolism, and this strainmight also have an unusual isoleucine biosynthesis route (usingacetyl-CoA and pyruvate as the precursors). The model indicated that over90 percent of the acetate was completely oxidized to CO2 via a completetricarboxylic acid (TCA) cycle while reducing iron. Pyruvate carboxylaseand phosphoenolpyruvate carboxykinase were present under theseconditions, but enzymes in the glyoxylate shunt and malic enzyme wereabsent. Gluconeogenesis and the pentose phosphate pathway were mainlyemployed for biosynthesis and accounted for less than 3 percent of totalcarbon consumption. The model also indicated surprisingly highreversibility in the reaction between oxoglutarate and succinate. Thisstep operates close to the thermodynamic equilibrium possibly becausesuccinate is synthesized via a transferase reaction, and the conversionof oxoglutarate to succinate is a rate limiting step for carbonmetabolism. These findings enable a better understanding of therelationship between genome annotation and extant metabolic pathways inG. metallireducens.

  18. Non-local thermodynamic equilibrium stellar spectroscopy with 1D and 3D models - II. Chemical properties of the Galactic metal-poor disk and the halo

    DEFF Research Database (Denmark)

    Bergemann, Maria; Collet, Remo; Schönrich, Ralph

    2016-01-01

    We have analysed high-resolution spectra of 328 stars and derived Mg abundances using non-local thermodynamic equilibrium (NLTE) spectral line formation calculations and plane-parallel model stellar atmospheres derived from the mean stratification of 3D hydrodynamical surface convection simulations...... of late-type stars. The distribution of Mg abundances in the Galactic disk is analysed from the perspective of Galactic chemical evolution. We find that the trend of [Mg/Fe] shows a mild decline with decreasing metallicity below [Fe/H]~-1.2 and that a significant fraction of low-metallicity stars have [Mg....../Fe] ratios close to solar even at [Fe/H] ~ -2. This is at variance with results of classical abundance analyses based on local thermodynamic equilibrium (LTE) and 1D model stellar atmospheres, which argue for a constant elevated [Mg/Fe] in metal-poor stars of the Galactic thick disk and halo....

  19. Initially Approximated Quasi Equilibrium Manifold

    International Nuclear Information System (INIS)

    Shahzad, M.; Arif, H.; Gulistan, M.; Sajid, M.

    2015-01-01

    Most commonly, kinetics model reduction techniques are based on exploiting time scale separation into fast and slow reaction processes. Then, a researcher approximates the system dynamically with dimension reduction for slow ones eliminating the fast modes. The main idea behind the construction of the lower dimension manifold is based on finding its initial approximation using Quasi Equilibrium Manifold (QEM). Here, we provide an efficient numerical method, which allow us to calculate low dimensional manifolds of chemical reaction systems. This computation technique is not restricted to our specific complex problem, but it can also be applied to other reacting flows or dynamic systems provided with the condition that a large number of extra (decaying) components can be eliminated from the system. Through computational approach, we approximate low dimensional manifold for a mechanism of six chemical species to simplify complex chemical kinetics. A reduced descriptive form of slow invariant manifold is obtained from dissipative system. This method is applicable for higher dimensions and is applied over an oxidation of CO/Pt. (author)

  20. Colin Rowe and ' Dynamic Equilibrium'

    Directory of Open Access Journals (Sweden)

    Pablo López Marín

    2015-05-01

    Full Text Available AbstractIn 1944 Gyorgy Kepes published what undoubtless will be his most influential text, "The language of vision". What Kepes tried to do was a guide of grammar and syntax of vision, which allows to face art as purely sensory experience or just visual, devisted of any literary , semantic or sentimental meaning.Among all the concepts that Kepes developes in his essay perhaps the most decisive one is the so called dynamic equilibrium, which is introduced in this work for fi rst time, verbalizing something that was in the air, orbiting around the entire modern plastic but far only explained in an empirical way.Colin Rowe reverberates the recent readed kepesian ideas on his own writings Transparency: Literal and Phenomenal and Neo-'Classicism' and Modern Architecture I and II, when the author tries to highlight the founding principles of the modern movement refusing the plastic  dimension of the discipline . The article will try to expose and explain this influence.

  1. Iron isotope fractionation during pyrite formation in a sulfidic Precambrian ocean analogue

    Science.gov (United States)

    Rolison, John M.; Stirling, Claudine H.; Middag, Rob; Gault-Ringold, Melanie; George, Ejin; Rijkenberg, Micha J. A.

    2018-04-01

    The chemical response of the Precambrian oceans to rising atmospheric O2 levels remains controversial. The iron isotope signature of sedimentary pyrite is widely used to trace the microbial and redox states of the ocean, yet the iron isotope fractionation accompanying pyrite formation in nature is difficult to constrain due to the complexity of the pyrite formation process, difficulties in translating the iron isotope systematics of experimental studies to natural settings, and insufficient iron isotope datasets for natural euxinic (i.e. anoxic and sulfidic) marine basins where pyrite formation occurs. Herein we demonstrate, that a large, permil-level shift in the isotope composition of dissolved iron occurs in the Black Sea euxinic water column during syngenetic pyrite formation. Specifically, iron removal to syngenetic pyrite gives rise to an iron isotope fractionation factor between Fe(II) and FeS2 of 2.75 permil (‰), the largest yet reported for reactions under natural conditions that do not involve iron redox chemistry. These iron isotope systematics offer the potential to generate permil-level shifts in the sedimentary pyrite iron isotope record due to partial drawdown of the oceanic iron inventory. The implication is that the iron stable isotope signatures of sedimentary pyrites may record fundamental regime shifts between pyrite formation under sulfur-limited conditions and pyrite formation under iron-limited conditions. To this end, the iron isotope signatures of sedimentary pyrite may best represent the extent of euxinia in the past global ocean, rather than its oxygenation state. On this basis, the reinterpreted sedimentary pyrite Fe isotope record suggests a fundamental shift towards more sulfidic oceanic conditions coincident with the 'Great Oxidation Event' around 2.3 billion years ago. Importantly, this does not require the chemical state of the ocean to shift from mainly de-oxygenated to predominantly oxygenated in parallel with the permanent rise

  2. New method for simultaneous determination of 55Fe and 59Fe in blood serum samples

    International Nuclear Information System (INIS)

    Saukkonen, H.; Uhlenius, R.

    1978-01-01

    Routine methods for the measurement of 55 Fe and 59 Fe activities in biological samples are frequently required in metabolic studies of iron. A new simple method for the simultaneous determination of 59 Fe and 55 Fe concentration in 5 cm 3 samples of blood is described and carefully evaluated. Before the measurement of the activity, organic matter was eliminated by HNO 3 -HClO 4 wet ashing and iron was electroplated onto a copper plate. The accuracy of results was studied by assessing samples, which contained known amounts of radioactivity and determining the counts per nanocurie in each case. The accuracy of the results of 59 Fe and 55 Fe determinations was found to be about 5%. The method has been routinely used to determine iron resorption in patients using the double isotope method. The determination proved to be satisfactory and not too laborious. When performing the yield determination there is a way of detecting and correcting mistakes or incompleteness in different stages of the measurement, thus leading to a high degree of reliability. (T.G.)

  3. Carbon and chlorine isotope analysis to identify abiotic degradation pathways of 1,1,1-trichloroethane.

    Science.gov (United States)

    Palau, Jordi; Shouakar-Stash, Orfan; Hunkeler, Daniel

    2014-12-16

    This study investigates dual C-Cl isotope fractionation during 1,1,1-TCA transformation by heat-activated persulfate (PS), hydrolysis/dehydrohalogenation (HY/DH) and Fe(0). Compound-specific chlorine isotope analysis of 1,1,1-TCA was performed for the first time, and transformation-associated isotope fractionation ε bulk C and ε bulk Cl values were -4.0 ± 0.2‰ and no chlorine isotope fractionation with PS, -1.6 ± 0.2‰ and -4.7 ± 0.1‰ for HY/DH, -7.8 ± 0.4‰ and -5.2 ± 0.2‰ with Fe(0). Distinctly different dual isotope slopes (Δδ13C/Δδ37Cl): ∞ with PS, 0.33 ± 0.04 for HY/DH and 1.5 ± 0.1 with Fe(0) highlight the potential of this approach to identify abiotic degradation pathways of 1,1,1-TCA in the field. The trend observed with PS agreed with a C-H bond oxidation mechanism in the first reaction step. For HY/DH and Fe(0) pathways, different slopes were obtained although both pathways involve cleavage of a C-Cl bond in their initial reaction step. In contrast to the expected larger primary carbon isotope effects relative to chlorine for C-Cl bond cleavage, ε bulk C isotope effects. Therefore, different magnitude of secondary chlorine isotope effects could at least be partly responsible for the distinct slopes between HY/DH and Fe(0) pathways. Following this dual isotope approach, abiotic transformation processes can unambiguously be identified and quantified.

  4. On the interpretation of structures obtained when an alloy is quickly cooled at a temperature at which its equilibrium structure is either a one-phase or two-phase one. Application to δ-ferrite

    International Nuclear Information System (INIS)

    Arzalier, M.

    1971-01-01

    As the equilibrium diagram of an alloy does not allow to predict how its structure will evolve during a quick temperature change (for example during a thermal treatment like a quench), and as this prediction is however possible in the case of Fe-Cr and Fe-Mo alloys, this research aimed at studying whether these alloys are an exception or whether the same prediction could be possible for alloys exhibiting the same shape of equilibrium diagram (with a double austenitic loop). Ternary alloys (Fe-Cr-Ni, Fe-Cr-Co, Fe-Mo-Ni, Fe-Mo-Mn, Fe-Si-Ni) have been systematically studied. More precisely, the author experimentally studied the quench behaviour of the delta ferrite and of any phase. He discusses the specific structures obtained by quenching the delta ferrite

  5. Do intertidal flats ever reach equilibrium?

    NARCIS (Netherlands)

    Maan, D.C.; van Prooijen, B.C.; Wang, Z.B.; de Vriend, H.J.

    2015-01-01

    Various studies have identified a strong relation between the hydrodynamic forces and the equilibrium profile for intertidal flats. A thorough understanding of the interplay between the hydrodynamic forces and the morphology, however, concerns more than the equilibrium state alone. We study the

  6. The geometry of finite equilibrium sets

    DEFF Research Database (Denmark)

    Balasko, Yves; Tvede, Mich

    2009-01-01

    We investigate the geometry of finite datasets defined by equilibrium prices, income distributions, and total resources. We show that the equilibrium condition imposes no restrictions if total resources are collinear, a property that is robust to small perturbations. We also show that the set...

  7. Non-equilibrium modelling of distillation

    NARCIS (Netherlands)

    Wesselingh, JA; Darton, R

    1997-01-01

    There are nasty conceptual problems in the classical way of describing distillation columns via equilibrium stages, and efficiencies or HETP's. We can nowadays avoid these problems by simulating the behaviour of a complete column in one go using a non-equilibrium model. Such a model has phase

  8. Equilibrium and pre-equilibrium calculations of cross-sections of (p ...

    Indian Academy of Sciences (India)

    In this study, the pre-equilibrium and equilibrium calculations of cross-sections of 89Y(, ), 90Zr ( p , x n ) and 94Mo(, ) reactions, which were used for the production of 89Zr, 90Nb and 94Tc positron-emitting radioisotopes, have been investigated. Pre-equilibrium calculations have been performed at different proton ...

  9. On the definition of equilibrium and non-equilibrium states in dynamical systems

    OpenAIRE

    Akimoto, Takuma

    2008-01-01

    We propose a definition of equilibrium and non-equilibrium states in dynamical systems on the basis of the time average. We show numerically that there exists a non-equilibrium non-stationary state in the coupled modified Bernoulli map lattice.

  10. Implementing an Equilibrium Law Teaching Sequence for Secondary School Students to Learn Chemical Equilibrium

    Science.gov (United States)

    Ghirardi, Marco; Marchetti, Fabio; Pettinari, Claudio; Regis, Alberto; Roletto, Ezio

    2015-01-01

    A didactic sequence is proposed for the teaching of chemical equilibrium law. In this approach, we have avoided the kinetic derivation and the thermodynamic justification of the equilibrium constant. The equilibrium constant expression is established empirically by a trial-and-error approach. Additionally, students learn to use the criterion of…

  11. Simulation of startup period of hydrogen isotope separation distillation column

    International Nuclear Information System (INIS)

    Sazonov, A.B.; Kagramanov, Z.G.; Magomedbekov, Eh.P.

    2003-01-01

    Kinetic procedure for the mathematical simulation of start-up regime of rectification columns for molecular hydrogen isotope separation was developed. Nonstationary state (start-up period) of separating column for rectification of multi-component mixture was calculated. Full information on equilibrium and kinetic physicochemical properties of components in separating mixtures was used for the calculations. Profile of concentration of components by height of column in task moment of time was calculated by means of differential equilibriums of nonstationary mass transfer. Calculated results of nonstationary state of column by the 2 m height, 30 mm diameter during separation of the mixture: 5 % protium, 70 % deuterium, 25 % tritium were illustrated [ru

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

    International Nuclear Information System (INIS)

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

    1994-01-01

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

  13. Copper adsorption on magnetite-loaded chitosan microspheres: A kinetic and equilibrium study

    Energy Technology Data Exchange (ETDEWEB)

    Podzus, P.E., E-mail: ppodzus@gmail.com [Grupo de Aplicaciones de Materiales Biocompatibles, Departamento de Quimica, Facultad de Ingenieria, Universidad de Buenos Aires, Paseo Colon 850, C1063ACV Buenos Aires (Argentina); Debandi, M.V. [Grupo de Aplicaciones de Materiales Biocompatibles, Departamento de Quimica, Facultad de Ingenieria, Universidad de Buenos Aires, Paseo Colon 850, C1063ACV Buenos Aires (Argentina); Daraio, M.E., E-mail: medit@fi.uba.ar [Grupo de Aplicaciones de Materiales Biocompatibles, Departamento de Quimica, Facultad de Ingenieria, Universidad de Buenos Aires, Paseo Colon 850, C1063ACV Buenos Aires (Argentina)

    2012-08-15

    A composite of Fe{sub 3}O{sub 4} nanoparticles and the biopolymer chitosan, chemically crosslinked, was prepared as microspheres and used to adsorb copper ions, which were chosen as a model of contaminant metal in water. The adsorption of copper on the magnetic microspheres was studied in a batch process, with different aqueous solutions of Cu (II) at concentrations ranging from 40 to 1100 ppm. Kinetic and equilibrium aspects of the adsorption process were studied. The time-dependent Cu (II) adsorption data were well described by a pseudo-second-order kinetic model. It was found that the equilibrium data follow the Langmuir isotherm, with a maximum adsorption capacity of around 500 mg Cu/g chitosan. The used microspheres were removed and after desorption the material was able to be reused as an adsorbent. The prepared microspheres proved efficient in the removal of copper ions through an adsorption process whose kinetic and equilibrium characteristics were analyzed.

  14. Modelling asphaltene precipitation equilibrium : influence of the experimental contact time and temperature

    Energy Technology Data Exchange (ETDEWEB)

    Dufour, J.; Marugan, J.; Calles, J.A.; Gimenez-Aguirre, R. [Rey Juan Carlos Univ., Madrid (Spain). Dept. of Chemical and Environmental Technology, Repsol-YPF Flow Assurance Laboratory; Pena, J.L. [Rey Juan Carlos Univ., Madrid (Spain). Dept. of Chemical and Environmental Technology, Repsol-YPF Flow Assurance Laboratory; Centro Tecnologico Repsol-YPF, Madrid (Spain); Merino-Garcia, D. [Centro Tecnologico Repsol-YPF, Madrid (Spain)

    2008-07-01

    Asphaltene deposition creates flow assurance problems and economic losses for petroleum companies. Predictive models are therefore needed to prevent these problems. Most models found in the literature are based on equilibrium calculations and must be checked against experimental data of both onset and amount of asphaltenes separated. However, the samples must be equilibrated for a long time since the kinetics of asphaltene aggregation and precipitation are slow. This paper discussed the kinetics of asphaltene precipitation, based on results obtained from a problematic South American crude and its residue. The influence of temperature, chain length of the n-alkane solvent and n-alkane/oil mass ratio was evaluated. The solids were characterized by 1H NMR, elemental analysis and Fourier transform infrared (FTIR) spectroscopy to determine their chemical structure. Metal contents (mainly Fe, V and Ni) have been measured by atomic emission spectroscopy. The true equilibrium data will be used to validate equilibrium models from the literature.

  15. Information-theoretic equilibrium and observable thermalization.

    Science.gov (United States)

    Anzà, F; Vedral, V

    2017-03-07

    A crucial point in statistical mechanics is the definition of the notion of thermal equilibrium, which can be given as the state that maximises the von Neumann entropy, under the validity of some constraints. Arguing that such a notion can never be experimentally probed, in this paper we propose a new notion of thermal equilibrium, focused on observables rather than on the full state of the quantum system. We characterise such notion of thermal equilibrium for an arbitrary observable via the maximisation of its Shannon entropy and we bring to light the thermal properties that it heralds. The relation with Gibbs ensembles is studied and understood. We apply such a notion of equilibrium to a closed quantum system and show that there is always a class of observables which exhibits thermal equilibrium properties and we give a recipe to explicitly construct them. Eventually, an intimate connection with the Eigenstate Thermalisation Hypothesis is brought to light.

  16. Oxygen-isotopic Compositions of Relict and Host Grains in Chondrules in the Yamato 81020 CO3.0 Chondrite

    Science.gov (United States)

    Kunihiro, Takuya; Rubin, Alan E.; McKeegan, Kevin D.; Wasson, John T.

    2006-01-01

    We report the oxygen-isotope compositions of relict and host olivine grains in six high-FeO porphyritic olivine chondrules in one of the most primitive carbonaceous chondrites, CO3.0 Yamato 81020. Because the relict grains predate the host phenocrysts, microscale in situ analyses of O-isotope compositions can help assess the degree of heterogeneity among chondrule precursors and constrain the nebular processes that caused these isotopic differences. In five of six chondrules studied, the DELTA O-17 (=delta O-17 - 0.52 (raised dot) delta O-18) compositions of host phenocrysts are higher than those in low-FeO relict grains; the one exception is for a chondrule with a moderately high-FeO relict. Both the fayalite compositions as well as the O-isotope data support the view that the low-FeO relict grains formed in a previous generation of low-FeO porphyritic chondrules that were subsequently fragmented. It appears that most low-FeO porphyritic chondrules formed earlier than most high-FeO porphyritic chondrules, although there were probably some low-FeO chondrules that formed during the period when most high-FeO chondrules were forming.

  17. Isotope ratio analysis on water: A critical look at developments

    International Nuclear Information System (INIS)

    Meijer, H.A.J.

    2001-01-01

    In this opinion paper a short overview is given of the methods by which the stable isotope ratios of water are determined, ranging from the classical equilibrium technique for δ 18 O and the Uranium-reduction technique for δ 2 H to the recent innovative continuous flow work. Then the extensive IAEA 'GNIP' database is used to show that the overall intercomparison quality of water isotope measurements 'in the field' is still not satisfactory at all, and has not really improved in the last decade. Some suggestions are made as to what are the main causes for this situation, and what can be done to improve the situation. (author)

  18. Isotope Fractionation of Water During Evaporation Without Condensation

    International Nuclear Information System (INIS)

    Cappa, Christopher D.; Drisdell, Walter S.; Smith, Jared D.; Saykally, Richard J.; Cohen, Ronald C.

    2005-01-01

    The microscopic events engendering liquid water evaporation have received much attention over the last century, but remain incompletely understood. We present measurements of isotope fractionation occurring during free molecular evaporation from liquid microjets and show that the isotope ratios of evaporating molecules exhibit dramatic differences from equilibrium vapor values, strong variations with the solution deuterium mole fraction, and a clear temperature dependence. These results indicate the existence of an energetic barrier to evaporation and that the evaporation coefficient of water is less than unity. These new insights into water evaporation promise to advance our understanding of the processes that control the formation and lifetime of clouds in the atmosphere.

  19. The reactions of neutral iron clusters with D2O: Deconvolution of equilibrium constants from multiphoton processes

    International Nuclear Information System (INIS)

    Weiller, B.H.; Bechthold, P.S.; Parks, E.K.; Pobo, L.G.; Riley, S.J.

    1989-01-01

    The chemical reactions of neutral iron clusters with D 2 O are studied in a continuous flow tube reactor by molecular beam sampling and time-of-flight mass spectrometry with laser photoionization. Product distributions are invariant to a four-fold change in reaction time demonstrating that equilibrium is attained between free and adsorbed D 2 O. The observed negative temperature dependence is consistent with an exothermic, molecular addition reaction at equilibrium. Under our experimental conditions, there is significant photodesorption of D 2 O (Fe/sub n/(D 2 O)/sub m/ + hν → Fe/sub n/ + m D 2 O) along with ionization due to absorption of multiple photons from the ionizing laser. Using a simple model based on a rate equation analysis, we are able to quantitatively deconvolute this desorption process from the equilibrium constants. 8 refs., 1 fig

  20. Isotope enrichment systems

    International Nuclear Information System (INIS)

    Spevak, J.S.

    1983-01-01

    This invention provides a system in which both phases of the countercurrent contact isotope exchange concentration process are recycled continuously and an isotope depleted liquid phase substance thereof has its prior content of the desired isotope of hydrogen and/or oxygen replenished in an isotope regenerator by direct contact isotope exchange with a flow of steam from a source external to the concentrating process, whereby such replenished liquid serves as the feed liquid for the concentration process. As the supply of steam is gaseous, all problems incident to mineral solids in solution in liquid water are eliminated. As the elevated temperature corresponds to that of the steam, the isotope replenishment of the process feed liquid may be conducted without materially altering the characteristics of the steam for use as an energy source in any system

  1. Process for isotope separation

    International Nuclear Information System (INIS)

    Emile, B.F.M.

    1983-11-01

    A process is claimed for isotopic separation applied to isotopes of elements that can be placed in at least a physicochemical form in which the isotopic atoms or the molecules containing these atoms can be easily displaced and for which there are selective radiations preferentially absorbed by the isotopes of a certain type or by the molecules containing them, said absorption substantially increasing the probability of ionization of said atoms or molecules relative to the atoms or molecules that did not absorb the radiation. The process consists of placing the isotopic mixture in such a form, subjecting it in a separation zone to selective radiations and to an electrical field that produces migration of positive ions toward the negative electrodes and negative ions toward the positive electrodes, and withdrawing from certain such zones the fractions thus enriched in certain isotopes

  2. Thermal transport across solid-solid interfaces enhanced by pre-interface isotope-phonon scattering

    Science.gov (United States)

    Lee, Eungkyu; Luo, Tengfei

    2018-01-01

    Thermal transport across solid interfaces can play critical roles in the thermal management of electronics. In this letter, we use non-equilibrium molecular dynamics simulations to investigate the isotope effect on the thermal transport across SiC/GaN interfaces. It is found that engineered isotopes (e.g., 10% 15N or 71Ga) in the GaN layer can increase the interfacial thermal conductance compared to the isotopically pure case by as much as 23%. Different isotope doping features, such as the isotope concentration, skin depth of the isotope region, and its distance from the interface, are investigated, and all of them lead to increases in thermal conductance. Studies of spectral temperatures of phonon modes indicate that interfacial thermal transport due to low-frequency phonons (transport. This work may provide insights into interfacial thermal transport and useful guidance to practical material design.

  3. Isotope separation process

    International Nuclear Information System (INIS)

    Lyon, R.K.

    1976-01-01

    The instant invention relates to a process for separating a material into two or more parts in each of which the abundances of the isotopes of a given element differ from the abundances of the isotopes of the same material in said material. In one embodiment, the invention relates to a method for the isotopically selective excitation of gas phase molecules by multiple infrared photon absorption followed by selective dissociation of said excited molecules by the absorption of a single photon of visible or ultraviolet light. This invention is useful for, but not limited to, the separation of the principal isotopes of uranium. 11 Claims, 2 Drawing Figures

  4. Measurement of heavy particle and isotope

    International Nuclear Information System (INIS)

    Matsuoka, Masaru; Kohno, Takeshi; Imai, Takashi; Munakata, Kazuoki

    1987-01-01

    The report describes some achievements made so far in developing heavy particle and isotope measuring equipment that is planned to be mounted on the No.6 technical test satelite of the National Space Development Agency, ETS VI. Some ideas are proposed for such heavy particle and isotope measuring equipment that uses Astromag. The structure of SSD is shown which is planned to be incorporated in the sensor for the equipment. The planned charged particle detector consists of position sensitive detectors, PIN diodes and Si(Li) plates. Tests are made for the basic characteristics of such a detector. The characteristics of a PSD are also investigated. The PSD has a resolution of about 1 mm for 14 MeV He. Tests of a 0.3 mm PIN diode and 1.2 mm Si(Li) is carried out with 234 MeV-nucl Fe beams to determine their pulse height distribution. The PIN diode and Si(Li) are found to have a resolution of 6.79 and 17.6 MeV for energy loss of 158 and 710 MeV, respectively. If developed, a stripe-type Si PIN diode will serve for analysis of isotopes. A conceptual diagram of such a stripe device is proposed. The mechanism of measurement by a heavy particle and isotope detecting system incorporating Astromag is also illustrated. (Nogami, K.)

  5. Solvent isotope effects on the rates of alkylation of thiolamine models of papain

    International Nuclear Information System (INIS)

    Wandinger, A.; Creighton, D.J.

    1980-01-01

    As a test of whether it is chemically reasonable to attribute any or all of the observed kinetic solvent deuterium isotope effects reported on papain to the fundamental properties of the tautomerization equilibrium, the magnitudes of the solvent deuterium isotope effects on the rates of alkylation of the tautomeric forms of cysteine and β-mercaptoethylamine were determined for bromo- and chloroacetate, bromo- and chloroacetamide, as well as for methylbromoacetate. These thiolamines are viewed as elementary chemical models of the sulfhydryl group tautomerization equilibrium envisioned in the active site of papain. (Auth.)

  6. Local Nash equilibrium in social networks.

    Science.gov (United States)

    Zhang, Yichao; Aziz-Alaoui, M A; Bertelle, Cyrille; Guan, Jihong

    2014-08-29

    Nash equilibrium is widely present in various social disputes. As of now, in structured static populations, such as social networks, regular, and random graphs, the discussions on Nash equilibrium are quite limited. In a relatively stable static gaming network, a rational individual has to comprehensively consider all his/her opponents' strategies before they adopt a unified strategy. In this scenario, a new strategy equilibrium emerges in the system. We define this equilibrium as a local Nash equilibrium. In this paper, we present an explicit definition of the local Nash equilibrium for the two-strategy games in structured populations. Based on the definition, we investigate the condition that a system reaches the evolutionary stable state when the individuals play the Prisoner's dilemma and snow-drift game. The local Nash equilibrium provides a way to judge whether a gaming structured population reaches the evolutionary stable state on one hand. On the other hand, it can be used to predict whether cooperators can survive in a system long before the system reaches its evolutionary stable state for the Prisoner's dilemma game. Our work therefore provides a theoretical framework for understanding the evolutionary stable state in the gaming populations with static structures.

  7. Predictions and Verification of an Isotope Marine Boundary Layer Model

    Science.gov (United States)

    Feng, X.; Posmentier, E. S.; Sonder, L. J.; Fan, N.

    2017-12-01

    A one-dimensional (1D), steady state isotope marine boundary layer (IMBL) model is constructed. The model includes meteorologically important features absent in Craig and Gordon type models, namely height-dependent diffusion/mixing and convergence of subsiding external air. Kinetic isotopic fractionation results from this height-dependent diffusion which starts as pure molecular diffusion at the air-water interface and increases linearly with height due to turbulent mixing. The convergence permits dry, isotopically depleted air subsiding adjacent to the model column to mix into ambient air. In δD-δ18O space, the model results fill a quadrilateral, of which three sides represent 1) vapor in equilibrium with various sea surface temperatures (SSTs) (high d18O boundary of quadrilateral); 2) mixture of vapor in equilibrium with seawater and vapor in the subsiding air (lower boundary depleted in both D and 18O); and 3) vapor that has experienced the maximum possible kinetic fractionation (high δD upper boundary). The results can be plotted in d-excess vs. δ18O space, indicating that these processes all cause variations in d-excess of MBL vapor. In particular, due to relatively high d-excess in the descending air, mixing of this air into the MBL causes an increase in d-excess, even without kinetic isotope fractionation. The model is tested by comparison with seven datasets of marine vapor isotopic ratios, with excellent correspondence; >95% of observational data fall within the quadrilateral area predicted by the model. The distribution of observations also highlights the significant influence of vapor from the nearby converging descending air on isotopic variations in the MBL. At least three factors may explain the affect the isotopic composition of precipitation. The model can be applied to modern as well as paleo- climate conditions.

  8. Fast-timing studies of nuclei below $^{68}$Ni populated in the $\\beta$-decay of Mn isotopes

    CERN Multimedia

    Jokinen, A; Simpson, G S; Garcia borge, M J; Koester, U H; Georgiev, G P; Fraile prieto, L M; Aprahamian, A

    2008-01-01

    We intend to investigate structure of nuclei populated in the $\\beta$-decay of Mn isotopes via the ATD $\\beta\\gamma\\gamma$(t) technique. With this method we will measure dynamic moments in Fe isotopes and their daughters in order to characterize the role of particle-hole excitation across the ${N}$=40 sub-shell closure and the development of collectivity.

  9. A Tale of Two Gases: Isotope Effects Associated with the Enzymatic Production of H2 and N2O

    Science.gov (United States)

    Yang, H.; Gandhi, H.; Kreuzer, H. W.; Moran, J.; Hill, E. A.; McQuarters, A.; Lehnert, N.; Ostrom, N. E.; Hegg, E. L.

    2014-12-01

    Stable isotopes can provide considerable insight into enzymatic mechanisms and fluxes in various biological processes. In our studies, we used stable isotopes to characterize both enzyme-catalyzed H2 and N2O production. H2 is a potential alternative clean energy source and also a key metabolite in many microbial communities. Biological H2 production is generally catalyzed by hydrogenases, enzymes that combine protons and electrons to produce H2 under anaerobic conditions. In our study, H isotopes and fractionation factors (α) were used to characterize two types of hydrogenases: [FeFe]- and [NiFe]-hydrogenases. Due to differences in the active site, the α associated with H2 production for [FeFe]- and [NiFe]-hydrogenases separated into two distinct clusters (αFeFe > αNiFe). The calculated kinetic isotope effects indicate that hydrogenase-catalyzed H2 production has a preference for light isotopes, consistent with the relative bond strengths of O-H and H-H bonds. Interestingly, the isotope effects associated with H2 consumption and H2-H2O exchange reactions were also characterized, but in this case no specific difference was observed between the different enzymes. N2O is a potent greenhouse gas with a global warming potential 300 times that of CO2, and the concentration of N2O is currently increasing at a rate of ~0.25% per year. Thus far, bacterial and fungal denitrification processes have been identified as two of the major sources of biologically generated N2O. In this study, we measured the δ15N, δ18O, δ15Nα (central N atom in N2O), and δ15Nβ (terminal N atom in N2O) of N2O generated by purified fungal P450 nitric oxide reductase (P450nor) from Histoplasma capsulatum. We observed normal isotope effects for δ18O and δ15Nα, and inverse isotope effects for bulk δ15N (the average of Nα and Nβ) and δ15Nβ. The observed isotope effects have been used in conjunction with DFT calculations to provide important insight into the mechanism of P450nor. Similar

  10. Discovery of the cadmium isotopes

    International Nuclear Information System (INIS)

    Amos, S.; Thoennessen, M.

    2010-01-01

    Thirty-seven cadmium isotopes have been observed so far and the discovery of these isotopes is discussed here. For each isotope a brief summary of the first refereed publication, including the production and identification method, is presented.

  11. The Conceptual Change Approach to Teaching Chemical Equilibrium

    Science.gov (United States)

    Canpolat, Nurtac; Pinarbasi, Tacettin; Bayrakceken, Samih; Geban, Omer

    2006-01-01

    This study investigates the effect of a conceptual change approach over traditional instruction on students' understanding of chemical equilibrium concepts (e.g. dynamic nature of equilibrium, definition of equilibrium constant, heterogeneous equilibrium, qualitative interpreting of equilibrium constant, changing the reaction conditions). This…

  12. Isotope effects associated with the anaerobic oxidation of sulfide by the purple photosynthetic bacterium, Chromatium vinosum

    International Nuclear Information System (INIS)

    Fry, B.; Gest, H.; Hayes, J.M.

    1984-01-01

    Small inverse isotope effects of 1-3 per thousand were consistently observed for the oxidation of sulfide to elemental sulfur during anaerobic photometabolism by Chromatium vinosum. The inverse fractionation can be accounted for by an equilibrium isotope effect between H 2 S and HS - , and may indicate that C. vinosum (and other photosynthetic bacteria) utilizes H 2 S rather than HS - as the substrate during sulfide oxidation. (Auth.)

  13. Nonideal plasmas as non-equilibrium media

    International Nuclear Information System (INIS)

    Morozov, I V; Norman, G E; Valuev, A A; Valuev, I A

    2003-01-01

    Various aspects of the collective behaviour of non-equilibrium nonideal plasmas are studied. The relaxation of kinetic energy to the equilibrium state is simulated by the molecular dynamics (MD) method for two-component non-degenerate strongly non-equilibrium plasmas. The initial non-exponential stage, its duration and the subsequent exponential stage of the relaxation process are studied for a wide range of ion charge, nonideality parameter and ion mass. A simulation model of the nonideal plasma excited by an electron beam is proposed. An approach is developed to calculate the dynamic structure factor in non-stationary conditions. Instability increment is obtained from MD simulations

  14. Measurement of the isotopic composition of dissolved iron in the open ocean

    Science.gov (United States)

    Lacan, F.; Radic, A.; Jeandel, C.; Poitrasson, F.; Sarthou, G.; Pradoux, C.; Freydier, R.

    2008-12-01

    This work demonstrates for the first time the feasibility of the measurement of the isotopic composition of dissolved iron in seawater for a typical open ocean Fe concentration range (0.1-1 nM). It also presents the first data of this kind. Iron is preconcentrated using a Nitriloacetic Acid Superflow resin and purified using an AG1x4 anion exchange resin. The isotopic ratios are measured with a MC-ICPMS Neptune, coupled with a desolvator (Aridus II), using a 57Fe-58Fe double spike mass bias correction. Measurement precision (0.13‰, 2SD) allows resolving small iron isotopic composition variations within the water column, in the Atlantic sector of the Southern Ocean (from δ 57Fe = -0.19 to +0.32‰). Isotopically light iron found in the Upper Circumpolar Deep Water is hypothesized to result from organic matter remineralization. Shallow samples suggest that, if occurring, an iron isotopic fractionation during iron uptake by phytoplankton is characterized by a fractionation factor, such as: |Δ57Fe(plankton-seawater)| < 0.48‰.

  15. Cenozoic marine geochemistry of thallium deduced from isotopic studies of ferromanganese crusts and pelagic sediments

    Science.gov (United States)

    Rehkamper, M.; Frank, M.; Hein, J.R.; Halliday, A.

    2004-01-01

    Cenozoic records of Tl isotope compositions recorded by ferromanganese (Fe-Mn) crusts have been obtained. Such records are of interest because recent growth surfaces of Fe-Mn crusts display a nearly constant Tl isotope fractionation relative to seawater. The time-series data are complemented by results for bulk samples and leachates of various marine sediments. Oxic pelagic sediments and anoxic marine deposits can be distinguished by their Tl isotope compositions. Both pelagic clays and biogenic oozes are typically characterized by ??205Tl greater than +2.5, whereas anoxic sediments have ??205Tl of less than -1.5 (??205Tl is the deviation of the 205Tl/203Tl isotope ratio of a sample from NIST SRM 997 Tl in parts per 104). Leaching experiments indicate that the high ??205Tl values of oxic sediments probably reflect authigenic Fe-Mn oxyhydroxides. Time-resolved Tl isotope compositions were obtained from six Fe-Mn crusts from the Atlantic, Indian, and Pacific oceans and a number of observations indicate that these records were not biased by diagenetic alteration. Over the last 25 Myr, the data do not show isotopic variations that significantly exceed the range of Tl isotope compositions observed for surface layers of Fe-Mn crusts distributed globally (??205 Tl=+12.8??1.2). This indicates that variations in deep-ocean temperature were not recorded by Tl isotopes. The results most likely reflect a constant Tl isotope composition for seawater. The growth layers of three Fe-Mn crusts that are older than 25 Ma show a systematic increase of ??205Tl with decreasing age, from about +6 at 60-50 Ma to about +12 at 25 Ma. These trends are thought to be due to variations in the Tl isotope composition of seawater, which requires that the oceans of the early Cenozoic either had smaller output fluxes or received larger input fluxes of Tl with low ??205Tl. Larger inputs of isotopically light Tl may have been supplied by benthic fluxes from reducing sediments, rivers, and/or volcanic

  16. Theoretical isotopic fractionation between structural boron in carbonates and aqueous boric acid and borate ion

    Science.gov (United States)

    Balan, Etienne; Noireaux, Johanna; Mavromatis, Vasileios; Saldi, Giuseppe D.; Montouillout, Valérie; Blanchard, Marc; Pietrucci, Fabio; Gervais, Christel; Rustad, James R.; Schott, Jacques; Gaillardet, Jérôme

    2018-02-01

    The 11B/10B ratio in calcite and aragonite is an important proxy of oceanic water pH. However, the physico-chemical mechanisms underpinning this approach are still poorly known. In the present study, we theoretically determine the equilibrium isotopic fractionation properties of structural boron species in calcium carbonates, BO33-, BO2(OH)2- and B(OH)4- anions substituted for carbonate groups, as well as those of B(OH)4- and B(OH)3 species in vacuum. Significant variability of equilibrium isotopic fractionation properties is observed among these structural species which is related to their contrasted coordination state, Bsbnd O bond lengths and atomic-scale environment. The isotopic composition of structural boron does not only depend on its coordination number but also on its medium range environment, i.e. farther than its first coordination shell. The isotopic fractionation between aqueous species and their counterparts in vacuum are assessed using previous investigations based on similar quantum-mechanical modeling approaches. At 300 K, the equilibrium isotope composition of structural trigonal species is 7-15‰ lighter than that of aqueous boric acid molecules, whereas substituted tetrahedral borate ions are heavier than their aqueous counterparts by 10-13‰. Although significant uncertainties are known to affect the theoretical prediction of fractionation factors between solids and solutions, the usually assumed lack of isotopic fractionation during borate incorporation in carbonates is challenged by these theoretical results. The present theoretical equilibrium fractionation factors between structural boron and aqueous species differ from those inferred from experiments which may indicate that isotopic equilibrium, unlike chemical equilibrium, was not reached in most experiments. Further research into the isotopic fractionation processes at the interface between calcium carbonates and aqueous solution as well as long duration experiments aimed at

  17. Metal stable isotope signatures as tracers in environmental geochemistry.

    Science.gov (United States)

    Wiederhold, Jan G

    2015-03-03

    The biogeochemical cycling of metals in natural systems is often accompanied by stable isotope fractionation which can now be measured due to recent analytical advances. In consequence, a new research field has emerged over the last two decades, complementing the traditional stable isotope systems (H, C, O, N, S) with many more elements across the periodic table (Li, B, Mg, Si, Cl, Ca, Ti, V, Cr, Fe, Ni, Cu, Zn, Ge, Se, Br, Sr, Mo, Ag, Cd, Sn, Sb, Te, Ba, W, Pt, Hg, Tl, U) which are being explored and potentially applicable as novel geochemical tracers. This review presents the application of metal stable isotopes as source and process tracers in environmental studies, in particular by using mixing and Rayleigh model approaches. The most important concepts of mass-dependent and mass-independent metal stable isotope fractionation are introduced, and the extent of natural isotopic variations for different elements is compared. A particular focus lies on a discussion of processes (redox transformations, complexation, sorption, precipitation, dissolution, evaporation, diffusion, biological cycling) which are able to induce metal stable isotope fractionation in environmental systems. Additionally, the usefulness and limitations of metal stable isotope signatures as tracers in environmental geochemistry are discussed and future perspectives presented.

  18. A stochastic modeling of isotope exchange reactions in glutamine synthetase

    Science.gov (United States)

    Kazmiruk, N. V.; Boronovskiy, S. E.; Nartsissov, Ya R.

    2017-11-01

    The model presented in this work allows simulation of isotopic exchange reactions at chemical equilibrium catalyzed by a glutamine synthetase. To simulate the functioning of the enzyme the algorithm based on the stochastic approach was applied. The dependence of exchange rates for 14C and 32P on metabolite concentration was estimated. The simulation results confirmed the hypothesis of the ascertained validity for preferred order random binding mechanism. Corresponding values of K0.5 were also obtained.

  19. Practical aspects of the environmental behavior of strontium isotopes

    International Nuclear Information System (INIS)

    Madelmont, Claude; Bittel, Robert; Daburon, Francois.

    1977-03-01

    The practical aspects of contamination patterns of the food chain by strontium isotopes are reviewed - plants with special emphasis on the consequences of irrigation (contamination level at equilibrium); dairy products and the adjustement of a general model to regional conditions (a table of quantitative parameters for some French regions is included); marine and freshwater products. One should keep in mind that transfer parameters may change with time and cannot be assessed definitively [fr

  20. Low energy deuteron-induced reactions on Fe isotopes

    Czech Academy of Sciences Publication Activity Database

    Avrigeanu, M.; Avrigeanu, V.; Bém, Pavel; Fischer, U.; Honusek, Milan; Katovsky, K.; Manailescu, C.; Mrázek, Jaromír; Šimečková, Eva; Závorka, Lukáš

    2014-01-01

    Roč. 89, č. 4 (2014), 044613 ISSN 0556-2813 R&D Projects: GA MŠk LG14004 Institutional support: RVO:61389005 Keywords : cross sections * proton spectra * polarized deuterons Subject RIV: BG - Nuclear, Atomic and Molecular Physics, Colliders Impact factor: 3.733, year: 2014

  1. Geochronology and Hf–Fe isotopic geochemistry of the Phanerozoic ...

    Indian Academy of Sciences (India)

    the Late Mesozoic, when the thin lithosphere enabled enhanced heat transfer from the asthenosphere. In summary, these distinct mantle sources .... observe internal textures, cathodolumi- nescence (CL) imaging was conducted for the ... laser-ablation system at the State Key Laboratory of Continental Dynamics, Northwest ...

  2. Influence of roughness at interfaces on tunneling magnetoresistance in Fe/MgO/Fe

    Energy Technology Data Exchange (ETDEWEB)

    Edalati Boostan, Saeideh [I. Physikalisches Institut, Justus Liebig University Giessen, D-35392 (Germany); Department of Physics, Faculty of Sciences, Ferdowsi University of Mashhad, Mashhad (Iran, Islamic Republic of); Moradi, Hosein [Department of Physics, Faculty of Sciences, Ferdowsi University of Mashhad, Mashhad (Iran, Islamic Republic of); Heiliger, Christian [I. Physikalisches Institut, Justus Liebig University Giessen, D-35392 (Germany)

    2010-07-01

    We propose a theoretical model for magnetic tunnel junction devices with rough interfaces based on a single-band tight-binding approximation. The high tunneling magnetoresistance (TMR) for crystalline MgO barrier was observed at room temperature which is desirable for magnetic random access memory (MRAM) applications. In real junctions the Fe and MgO atoms are interdiffused at interfaces and the numbers of diffused Fe and MgO atoms are not the same. The interface disorder is modeled by considering replacement of MgO sites by Fe atoms with a probability of n>0.5. The non-equilibrium Green's function formalism is used to calculate transport in Fe/MgO/Fe junctions. We investigate the voltage dependencies of TMR and current densities for parallel and anti-parallel configurations for majority and minority spins. The results show that the roughness decreases the TMR. The current density for the parallel (antiparallel) orientations of magnetizations decreases (increases) by including roughness at the interface.

  3. Laser assisted aerodynamic isotope separation

    International Nuclear Information System (INIS)

    Berg, H. van den

    1985-01-01

    It is shown that the efficiency of conventional aerodynamic isotope seperation can be improved by two orders of magnitude with the aid of a relatively weak cw infrared laser which is used to induce isotopically selective condensation. Overall isotope enrichment factors in excess of 2 are obtained as compared to about 1.02 in the conventional seperation. Sulphur isotopes in SF 6 as well as Silicon isotopes in SiF 4 and Bromine isotopes in CF 3 Br are seperated on a laboratory scale. Infrared vibrational predissociation by itself and in combination with isotopically selective condensation are also shown to be effective new ways of isotope separation. (orig.) [de

  4. Isotope separation process

    International Nuclear Information System (INIS)

    Lyon, R.K.

    1979-01-01

    A method is described for the isotopically selective excitation of gas phase molecules by multiple infrared photon absorption after which more of the excited molecules than nonexcited molecules are converted to a chemically different form which may be separated by means known in the art. This invention is useful for, but not limited to, the separation of the principal isotopes of uranium

  5. Stable isotopes labelled compounds

    International Nuclear Information System (INIS)

    1982-09-01

    The catalogue on stable isotopes labelled compounds offers deuterium, nitrogen-15, and multiply labelled compounds. It includes: (1) conditions of sale and delivery, (2) the application of stable isotopes, (3) technical information, (4) product specifications, and (5) the complete delivery programme

  6. Isotopic research in Antarctica

    International Nuclear Information System (INIS)

    Schuetze, H.

    1983-01-01

    Since 1978 scientists of the Central Institute of Isotope- and Radiation Research of the Academy of Sciences of the GDR have participated in antarctic research. Substantial results have been achieved in research on isotope ratios, on the dynamics of water resources, on concentration of deuterium in lichens, and on age determination of a mummified seal and a penguin colony

  7. Isotope research materials

    International Nuclear Information System (INIS)

    Anon.

    1977-01-01

    Preparation of research isotope materials is described. Topics covered include: separation of tritium from aqueous effluents by bipolar electrolysis; stable isotope targets and research materials; radioisotope targets and research materials; preparation of an 241 Am metallurgical specimen; reactor dosimeters; ceramic and cermet development; fission-fragment-generating targets of 235 UO 2 ; and wire dosimeters for Westinghouse--Bettis

  8. MAGNESIUM ISOTOPE RATIOS IN ω CENTAURI RED GIANTS

    International Nuclear Information System (INIS)

    Da Costa, G. S.; Norris, John E.; Yong, David

    2013-01-01

    We have used the high-resolution observations obtained at the Anglo-Australian Telescope with Ultra-High Resolution Facility (R ∼ 100,000) and at Gemini-S with b-HROS (R ∼ 150,000) to determine magnesium isotope ratios for seven ω Cen red giants that cover a range in iron abundance from [Fe/H] = –1.78 to –0.78 dex, and for two red giants in M4 (NGC 6121). The ω Cen stars sample both the ''primordial'' (i.e., O-rich, Na- and Al-poor) and the ''extreme'' (O-depleted, Na- and Al-rich) populations in the cluster. The primordial population stars in both ω Cen and M4 show ( 25 Mg, 26 Mg)/ 24 Mg isotopic ratios that are consistent with those found for the primordial population in other globular clusters with similar [Fe/H] values. The isotopic ratios for the ω Cen extreme stars are also consistent with those for extreme population stars in other clusters. The results for the extreme population stars studied indicate that the 26 Mg/ 24 Mg ratio is highest at intermediate metallicities ([Fe/H] 26 Mg in the extreme population stars is notably higher than that of 25 Mg, in contrast to model predictions. The 25 Mg/ 24 Mg isotopic ratio in fact does not show any obvious dependence on either [Fe/H] or [Al/Fe] nor, intriguingly, any obvious difference between the primordial and extreme population stars.

  9. NOx cycle and tropospheric ozone isotope anomaly: an experimental investigation

    Science.gov (United States)

    Michalski, G.; Bhattacharya, S. K.; Girsch, G.

    2013-04-01

    The oxygen isotope composition of nitrogen oxides (NOx) in the atmosphere may be a useful tool for understanding the oxidation of NOx into nitric acid/nitrate in the atmosphere. A set of experiments were conducted to examine changes in isotopic composition of NOx due to O3-NOx photochemical cycling. At low NO2/O2 mixing ratios, NO2 becomes progressively and nearly equally enriched in 17O and 18O over time until it reaches a steady state with Δ17O values of 40.6 ± 1.9‰ and δ18O values of 84.2 ± 4‰, relative to the isotopic composition of the O2 gas. As the mixing ratio increases, isotopic exchange between O atoms and O2 and NOx suppresses the isotopic enrichments. A kinetic model simulating the observed data shows that the isotope effects during ozone formation play a more dominant role compared to kinetic isotope effects during NO oxidation or exchange of NO2. The model results are consistent with the data when the NO + O3 reaction occurs mainly via the transfer of the terminal atom of O3. The model predicts that under tropospheric concentrations of the three reactants, the timescale of NOx isotopic equilibrium ranges from hours (ppbv mixing ratios) to days/weeks (pptv) and yields steady state Δ17O and δ18O values of 46‰ and 115‰ respectively with respect to Vienna Standard Mean Ocean Water. Interpretation of tropospheric nitrate isotope data can now be done with the derived rate coefficients of the major isotopologue reactions at various pressures.

  10. The iron stable isotope fingerprint of the human diet.

    Science.gov (United States)

    von Blanckenburg, Friedhelm; Noordmann, Janine; Guelke-Stelling, Monika

    2013-12-11

    The stable isotopes of iron disclose the metabolic pathways of iron within the human food chain. We have measured with precise multicollector ICP-MS the iron concentrations and stable isotope composition of 60 food products that are representative of the average German diet. We find that vegetables fall within the range typical of strategy I plants (-0.1 to -1.4‰ in δ(56)Fe), crop products and processed crop foods into the range typical of strategy II plants (-0.6 to +0.4‰), and animal products into the (54)Fe-enriched range known for animal tissue and blood (-1.1 to -2.7‰). Weighting these isotope compositions by the average iron dietary sources, we find a representative composition of European vegetarian diet of -0.45‰, whereas that of omnivores is -0.82‰. For human blood, known to be enriched in light iron isotopes, we find fractionation factors for iron absorption of -2.0 and -2.3‰ for vegetarians (female and male, respectively) and -1.3 and -1.5‰ for omnivores (female and male, respectively). Knowing these fractionation factors is a prerequisite for using stable iron isotope ratios in blood as monitors of intestinal iron uptake regulation.

  11. Level densities of iron isotopes and lower-energy enhancement of y-strength function

    International Nuclear Information System (INIS)

    Voinov, A V; Grimes, S M; Agvaanluvsan, U; Algin, E; Belgya, T; Brune, C R; Guttormsen, M; Hornish, M J; Massey, T N; Mitchell, G; Rekstad, J; Schiller, A; Siem, S

    2005-01-01

    The neutron spectrum from the 55 Mn(d,n) 56 Fe reaction has been measured at E d = 7 MeV. The level density of 56 Fe obtained from neutron evaporation spectrum has been compared to the level density from Oslo-type 57 Fe( 3 He, aγ) 56 Fe experiment [1]. The good agreement supports the recent results [1, 8] including an availability of a low-energy enhancement in the γ-strength function for iron isotopes. The new level density function allowed us to investigate an excitation energy dependence of this enhancement, which is shown to increase with increasing excitation energy

  12. Referesher Course on Contemporary Non-Equilibrium ...

    Indian Academy of Sciences (India)

    Home; Journals; Resonance – Journal of Science Education; Volume 15; Issue 7. Referesher Course on Contemporary Non-Equilibrium Thermodynamics and Statistical Mechanics. Information and Announcements Volume 15 Issue 7 July 2010 pp 678-678 ...

  13. Quantum mechanical evolution towards thermal equilibrium.

    Science.gov (United States)

    Linden, Noah; Popescu, Sandu; Short, Anthony J; Winter, Andreas

    2009-06-01

    The circumstances under which a system reaches thermal equilibrium, and how to derive this from basic dynamical laws, has been a major question from the very beginning of thermodynamics and statistical mechanics. Despite considerable progress, it remains an open problem. Motivated by this issue, we address the more general question of equilibration. We prove, with virtually full generality, that reaching equilibrium is a universal property of quantum systems: almost any subsystem in interaction with a large enough bath will reach an equilibrium state and remain close to it for almost all times. We also prove several general results about other aspects of thermalization besides equilibration, for example, that the equilibrium state does not depend on the detailed microstate of the bath.

  14. Intermittent many-body dynamics at equilibrium

    Science.gov (United States)

    Danieli, C.; Campbell, D. K.; Flach, S.

    2017-06-01

    The equilibrium value of an observable defines a manifold in the phase space of an ergodic and equipartitioned many-body system. A typical trajectory pierces that manifold infinitely often as time goes to infinity. We use these piercings to measure both the relaxation time of the lowest frequency eigenmode of the Fermi-Pasta-Ulam chain, as well as the fluctuations of the subsequent dynamics in equilibrium. The dynamics in equilibrium is characterized by a power-law distribution of excursion times far off equilibrium, with diverging variance. Long excursions arise from sticky dynamics close to q -breathers localized in normal mode space. Measuring the exponent allows one to predict the transition into nonergodic dynamics. We generalize our method to Klein-Gordon lattices where the sticky dynamics is due to discrete breathers localized in real space.

  15. Equilibrium Molecular Interactions in Pure Gases

    Directory of Open Access Journals (Sweden)

    Boris I. Sedunov

    2012-01-01

    Full Text Available The equilibrium molecular interactions in pure real gases are investigated based on the chemical thermodynamics principles. The parallels between clusters in real gases and chemical compounds in equilibrium media have been used to improve understanding of the real gas structure. A new approach to the equilibrium constants for the cluster fractions and new methods to compute them and their significant parameters from the experimental thermophysical data are developed. These methods have been applied to some real gases, such as Argon and Water vapors and gaseous Alkanes. It is shown that the four-particle clusters make a noticeable contribution in the thermophysical properties of the equilibrium Water vapor. It is shown also that the effective bond energy for dimers in Alkanes linearly grows with the number of carbon atoms in the molecule.

  16. Equilibrium Crystal Shapes by Virtual Work

    Science.gov (United States)

    Reivinen, M.; Salonen, E.-M.; Todoshchenko, I.; Vaskelainen, V. P.

    2013-01-01

    A formulation on equilibrium crystal shape determination based on the principle of virtual work is presented. The treatment is restricted to two dimensions. A corresponding discrete solution method is given. Some example cases are presented.

  17. "Secrets" of High Pressure Phase Equilibrium Experiment.

    Czech Academy of Sciences Publication Activity Database

    Wichterle, Ivan

    2005-01-01

    Roč. 54, č. 11 (2005), s. 477-479 ISSN 0022-9830 Institutional research plan: CEZ:AV0Z40720504 Keywords : vapour-liquid equilibrium * experimental work Subject RIV: CF - Physical ; Theoretical Chemistry

  18. Plasma equilibrium and instabilities in tokamaks

    International Nuclear Information System (INIS)

    Caldas, I.L.; Vannucci, A.

    1985-01-01

    A phenomenological introduction of some of the main theoretical and experimental features on equilibrium and instabilities in tokamaks is presented. In general only macroscopic effects are considered, being the plasma described as a fluid. (L.C.) [pt

  19. Computation of Phase Equilibrium and Phase Envelopes

    DEFF Research Database (Denmark)

    Ritschel, Tobias Kasper Skovborg; Jørgensen, John Bagterp

    In this technical report, we describe the computation of phase equilibrium and phase envelopes based on expressions for the fugacity coefficients. We derive those expressions from the residual Gibbs energy. We consider 1) ideal gases and liquids modeled with correlations from the DIPPR database...... and 2) nonideal gases and liquids modeled with cubic equations of state. Next, we derive the equilibrium conditions for an isothermal-isobaric (constant temperature, constant pressure) vapor-liquid equilibrium process (PT flash), and we present a method for the computation of phase envelopes. We...... formulate the involved equations in terms of the fugacity coefficients. We present expressions for the first-order derivatives. Such derivatives are necessary in computationally efficient gradient-based methods for solving the vapor-liquid equilibrium equations and for computing phase envelopes. Finally, we...

  20. Normal variations in the isotopic composition of metabolically relevant transition metals in human blood

    Science.gov (United States)

    Van Heghe, L.; Cloquet, C.; Vanhaecke, F.

    2012-04-01

    Cu, Fe and Zn are transition metals with great catalytic, structural and regulating importance in the human body. Hence, an aberrant metabolism of these elements can have serious implications on the health of a person. It is assumed that, due to differences in isotope fractionation, the isotopic composition of these elements in whole blood of patients can be different from that in blood of healthy subjects. Therefore, isotopic analysis of the element affected by the disease can be a promising approach for early diagnosis. A method for isotopic analysis of Cu, Fe and Zn in human whole blood was developed. The simultaneous chromatographic isolation of these elements and the conditions for isotope ratio measurement via multi-collector ICP - mass spectrometry (MC-ICP-MS) were optimized. So far, only whole blood of supposedly healthy volunteers (reference population) was analyzed. Results for Fe confirmed the known differences in isotopic composition between male and female blood. It is also shown that other parameters can have influence as well, e.g., the isotopic composition of Zn seems to be governed by the diet.

  1. M = Mn, Fe, Co

    Indian Academy of Sciences (India)

    ment as a result of incomplete combustion of fossil fuels can lead to harmful health effects by reducing oxygen delivery to ... fuel cells, and oxygen sensors. The oxygen storage and release in ceria is favoured by its ...... tion of Fe2O3 → Fe3O4, the consumption of surface. CeO2 and overlapping of the reduction of Fe3O4 →.

  2. Non-equilibrium dog-flea model

    Science.gov (United States)

    Ackerson, Bruce J.

    2017-11-01

    We develop the open dog-flea model to serve as a check of proposed non-equilibrium theories of statistical mechanics. The model is developed in detail. Then it is applied to four recent models for non-equilibrium statistical mechanics. Comparison of the dog-flea solution with these different models allows checking claims and giving a concrete example of the theoretical models.

  3. On financial equilibrium with intermediation costs

    DEFF Research Database (Denmark)

    Markeprand, Tobias Ejnar

    2008-01-01

    This paper studies the set of competitive equilibria in financial economies with intermediation costs. We consider an arbitrary dividend structure, which includes options and equity with limited liabilities.We show a general existence result and upper-hemi continuity of the equilibrium...... correspondence. Finally, we prove that when intermediation costs approach zero, unbounded volume of asset trades is a necessary and sufficient condition, provided that, there is no financial equilibrium without intermediation costs....

  4. Edge Equilibrium Code (EEC) For Tokamaks

    Energy Technology Data Exchange (ETDEWEB)

    Li, Xujling

    2014-02-24

    The edge equilibrium code (EEC) described in this paper is developed for simulations of the near edge plasma using the finite element method. It solves the Grad-Shafranov equation in toroidal coordinate and uses adaptive grids aligned with magnetic field lines. Hermite finite elements are chosen for the numerical scheme. A fast Newton scheme which is the same as implemented in the equilibrium and stability code (ESC) is applied here to adjust the grids

  5. Quasi-equilibrium interpretation of aging dynamics

    International Nuclear Information System (INIS)

    Franz, S.; Virasoro, M.A.

    2000-04-01

    We develop an interpretation of the off-equilibrium dynamical solution of mean-field glassy models in terms of quasi-equilibrium concepts. We show that the relaxation of the 'thermoremanent magnetization' follows a generalized version of the Onsager regression postulate of induced fluctuations. We then find the rationale for the equality between the fluctuation-dissipation ratio and the rate of growth of the configurational entropy close to the asymptotic state, found empirically in mean-field solutions. (author)

  6. Equilibrium and nonequilibrium behaviour of surfactant systems

    OpenAIRE

    Reissig, Louisa

    2010-01-01

    In binary systems, surfactant molecules can self-assemble into a large variety of structures depending on their chemical structure, concentration and temperature. The properties and stability of the phases, their coexistence regions and the formation of metastable structures is of great importance not only for fundamental understanding, but also for applications in many fields including industry and medicine. This thesis presents studies of the equilibrium and non-equilibrium b...

  7. Internal equilibrium layer growth over forest

    DEFF Research Database (Denmark)

    Dellwik, E.; Jensen, N.O.

    2000-01-01

    the magnitude of the scatter. Different theoretical friction velocity profiles for the Internal Boundary Layer (IBL) are tested against the forest data. The results yield information on the Internal Equilibrium Layer (IEL) growth and an equation for the IEL height fur neutral conditions is derived. For stable...... conditions the results indicate that very long fetches are required in order to measure parameters in equilibrium with the actual surface....

  8. Reductive dechlorination of DNAPL mixtures with Fe(II/III)-L and Fe(II)-C: Evaluation using a kinetic model for the competitions.

    Science.gov (United States)

    Do, Si-Hyun; Jo, Se-Hee; Roh, Ji Soo; Im, Hye Jin; Park, Ho Bum; Batchelor, Bill

    2018-05-15

    A kinetic model for the competitions was applied to understand the reductive dechlorination of tertiary DNAPL mixtures containing PCE, TCE, and 1,1,1-TCA. The model assumed that the mass transfer rates were sufficiently rapid that the target compounds in the solution and the DNAPL mixture were in phase equilibrium. Dechlorination was achieved using either a mixture of Fe(II), Fe(III), and Ca(OH) 2 (Fe(II/III)-L) or a mixture of Fe(II) and Portland cement (Fe(II)-C). PCE in the DNAPL mixtures was gradually reduced and it was reduced more rapidly using Fe(II)-C than Fe(II/III)-L. A constant total TCE concentration in the DNAPL mixtures was observed, which implied that the rate of loss of TCE by dechlorination and possibly other processes was equal to the rate of production of TCE by PCE dechlorination. On the other hand, 1,1,1-TCA in the DNAPL mixtures was removed rapidly and its degradation rate by Fe(II/III)-L was faster than by Fe(II)-C. The coefficients in the kinetic model (k i , K i ) were observed to decrease in the order 1,1,1-TCA>PCE>TCE, for both Fe(II/III)-L and Fe(II)-C. The concentrations of target compounds in solution were the effective solubilities, because of the assumption of phase equilibrium and were calculated with Rault's Law. The concentration changes observed were an increase and then a decrease for PCE, a sharp and then gradual increase for TCE, and a dramatic decrease for 1,1,1-TCA. The fraction of initial and theoretical reductive capacity revealed that Fe(II)-C had ability to degrade target compounds. Copyright © 2017 Elsevier B.V. All rights reserved.

  9. Investigation of Equilibrium Core by recycling MA and LLFP in fast reactor cycle (I)

    International Nuclear Information System (INIS)

    Mizutani, Akihiko; Shono, Akira; Ishikawa, Makoto

    1999-05-01

    Feasibility study on a self-consistent fuel cycle system is performed in the nuclear fuel recycle system with fast reactors. In this system, the self-generated MAs (Minor Actinides) and LLFPs (Long Lived Fission Products) are confined and incinerated in the fast reactor. Analyses of the nuclear properties for an 'Equilibrium Core', in which the self-generated MAs and LLFPs are confined, are investigated. A conventional sodium cooled oxide fuel fast reactor is selected as the core specifications for the 'Equilibrium Core'. This 600 MWe fast reactor does not have a radial blanket. In this study, the nuclear characteristics of the 'Equilibrium Core' are compared with those of a 'Standard Core' and '5 w/oMA Core'. The 'Standard Core' does not confine MAs and LLFPs in the core, and a 5 w/o-MA Rom LWR is loaded in the '5 w/oMA Core'. Through this comparison between 'Equilibrium Core' and the others, the specific characters of the 'Equilibrium Core' are investigated. In order to realize the 'Equilibrium Core' in the viewpoint of nuclear properties, whether the conventional design concept of fast reactors must be changed or not is also evaluated. The analyses for the nitride and metallic fuel cores are also performed because of their different nuclear characteristics compared with the oxide fuel core. Assuming the separation of REs (Rare Earth elements) from MAs and the isotope separation of LLFPs, most of the nuclear properties for the 'Equilibrium Core' are not beyond those for the '5 w/oMA Core'. It is, therefore, possible to bring the 'Equilibrium Core' into existence without any drastic modification for the design concept of the typical oxide fuel fast reactors. Although the 15.1[w/o] LLFPs are loading in the core of the oxide fuel 'Equilibrium Core', a breeding ratio is more than 1.0 and the difference in a amount of plutonium between a charging and discharging is only 0.04 [ton/year]. Without any drastic change for the design concept of the conventional oxide fuel

  10. Non-equilibrium and band tailing in organic conductors

    Indian Academy of Sciences (India)

    . Non-equilibrium due to coupling between applied energy and free electrons can be responsible for the exponential relaxation from non-equilibrium to equilibrium. Keywords. Band tailing; organic conductors; IR spectra; electrical resistivity.

  11. Uranium Isotopic Fractionation in Soil Extractions

    Science.gov (United States)

    Wang, R.; You, C.; Li, S.

    2008-12-01

    Acid leachable and residual fractions in soils were separated and used for precise U isotopic measurements, as well as other major and trace elements. Two soil profiles (HS and GS) located in a river terrace in central Taiwan were selected to examine the effect of α-recoil, as well as U mobilization during weathering and soil formation. The major and trace elements in leachable and residual fraction were determined by HR- ICP-MS and the U isotopic compositions of 234U/238U and 238U/235U were measured by MC-ICPMS. Prior to isotopic analyses, dissolved U was purified using TRU-spec resin. The external reproducibility of 234U/238U for IAPSO and in-house U standard (sample size of 2-5 ng U) is 1.1 ‰ (2σm, n=10) and 0.6 ‰ (2σm, n=36), respectively compared with that of 0.2 ‰ for 238U/235U (2σm, n=36). The U concentration shows no distinguishable difference at soil horizon in both profiles. The average (234U/238U)AR ratio in the leachable fraction, 1.40, deviates largely from the equilibrium value and appears to be affected by soil maturation and degree of weathering. On the other hand, the average (234U/238U)AR in the residual fraction (0.93) is also much lower than the equilibrium ratio. Further study will focus to examine if these ratios provide information on soil formation rate and/or chemical weathering rate.

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

    Science.gov (United States)

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

    2004-01-01

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

  13. Oxygen-isotope fractionation between marine biogenic silica and seawater

    Science.gov (United States)

    Matheney, Ronald K.; Knauth, L. Paul

    1989-12-01

    A stepwise fluorination technique has been used to selectively react away the water component of hydrous silica in order to better investigate the oxygen-isotope fractionation between biogenic opal and seawater, and to determine whether all taxa produce opal which is suitable for oxygen isotope paleothermometry. δ 18O of the tetrahedrally coordinated silicate oxygen of siliceous sponge spicules grown at a wide variety of temperatures varies independently of temperature. δ 18O from an Eocene radiolarian ooze sample is much more enriched than would be expected from any reasonable isotopic temperature curve, given the probable growing temperature of the sample. δ 18O of diatom samples seems to vary systematically with temperature and to conform approximately to the isotopic temperature curve for diatom frustules obtained by Labeyrie and coworkers using an entirely different analytical technique. Sponges appear to precipitate silica in isotopic disequilibrium with seawater oxygen, and old radiolarian silica may exchange readily with cold oceanic bottom water. Neither will apparently be useful for paleo-climate reconstructions. Diatoms may be useful in deducing ancient surface-water temperatures, but the systematic variation of α with temperature for diatoms may not be related to the quartz-H 2O equilibrium isotope fractionation.

  14. Modeling of hydrogen isotopes separation in a metal hydride bed

    International Nuclear Information System (INIS)

    Charton, S.; Corriou, J.P.; Schweich, D.

    1999-01-01

    A predictive model for hydrogen isotopes separation in a non-isothermal bed of unsupported palladium hydride particles is derived. It accounts for the non-linear adsorption-dissociation equilibrium, hydrodynamic dispersion, pressure drop, mass transfer kinetics, heat of sorption and heat losses at the bed wall. Using parameters from the literature or estimated with classical correlations, the model gives simulated curves in agreement with previously published experiments without any parameter fit. The non-isothermal behavior is shown to be responsible for drastic changes of the mass transfer rate which is controlled by diffusion in the solid-phase lattice. For a feed at 300 K and atmospheric pressure, the endothermic hydride-to-deuteride exchange is kinetically controlled, whereas the reverse exothermic exchange is nearly at equilibrium. Finally, a simple and efficient thermodynamic model for the dissociative equilibrium between a metal and a diatomic gas is proposed. (Copyright (c) 1999 Elsevier Science B.V., Amsterdam. All rights reserved.)

  15. LP Well-Posedness for Bilevel Vector Equilibrium and Optimization Problems with Equilibrium Constraints

    OpenAIRE

    Khanh, Phan Quoc; Plubtieng, Somyot; Sombut, Kamonrat

    2014-01-01

    The purpose of this paper is introduce several types of Levitin-Polyak well-posedness for bilevel vector equilibrium and optimization problems with equilibrium constraints. Base on criterion and characterizations for these types of Levitin-Polyak well-posedness we argue on diameters and Kuratowski’s, Hausdorff’s, or Istrǎtescus measures of noncompactness of approximate solution sets under suitable conditions, and we prove the Levitin-Polyak well-posedness for bilevel vector equilibrium and op...

  16. Fractionation of Stable Isotopes in Atmospheric Aerosol Reactions

    DEFF Research Database (Denmark)

    Meusinger, Carl

    reactions and undergo complex chemical and physical changes during their lifetimes. In order to assess processes that form and alter aerosols, information provided by stable isotopes can be used to help constrain estimates on the strength of aerosol sources and sinks. This thesis studies (mass......-independent) fractionation processes of stable isotopes of C, N, O and S in order to investigate three different systems related to aerosols: 1. Post-depositional processes of nitrate in snow that obscure nitrate ice core records 2. Formation and aging of secondary organic aerosol generated by ozonolysis of X...... as required. The kndings provide important results for the studies' respective felds, including a description of the isotopic fractionation and quantum yield of nitrate photolysis in snow, equilibrium fractionation in secondary organic aerosol and fractionation constants of different oxidation pathways of SO2....

  17. Isotopes in Shangri-la

    International Nuclear Information System (INIS)

    1965-01-01

    In a remote valley of the Andes, snow-bound for half the year, a small community of Pewenche Indians lives in almost complete isolation. Among these people there is a high degree of consanguinity, and most of them suffer from endemic goitre. These conditions offered an opportunity of studying the part played by congenital defects in the prevalence of the disease. With the support of IAEA, an expedition was sent to the place in November 1963 to study goitre with the help of radioisotopes.With these subjects we used - in accordance with various clearly defined research methods - radioactive tracers in the form of inorganic or organic iodine molecules, like thyroxine, tri-iodothyronine or di-iodotyrosine, labelled with iodine-131 or iodine-125. Repeated measurements were made either in vivo or on plasma or urine samples. The latter, combined with micro-measurements of stable iodine (iodine-127), made it possible to calculate various metabolic aspects of the iodine cycle and of thyroid hormone pre duct ion in these patients. A quantitative study of iodine metabolism was carried out on 77 subjects by observing the evolution of specific activities of circulating organic iodine before and after isotopic equilibrium or after stimulation by exogenous thyrotropic hormone. In some cases the thyroid seemed to function in a homogeneous manner while other patients showed a clear functional heterogeneity of the thyroid. While the adaptation of the thyroid gland seemed satisfactory in the cases of diffused goitre, it seemed incomplete in multinodular goitres

  18. Stable isotope characterization of pan-derived and directly sampled atmospheric water vapour

    International Nuclear Information System (INIS)

    Maric, R.; St. Amour, N.A.; Gibson, J.J.; Edwards, T.W.D.

    2002-01-01

    Isotopic characterization of atmospheric water vapour, δ A , and its temporal variability are important prerequisites for quantifying water balance of surface reservoirs and partitioning of evaporation and transpiration fluxes using isotope techniques. Here we present results from a detailed comparison of several methods for determining δ A in field situations, (i) by back-calculation from isotopic and micrometeorological monitoring of a steady-state terminal reservoir (standard Class-A evaporation pan) using boundary-layer mass transfer models [1], (ii) through direct (cryogenic) sampling of ambient atmospheric moisture, and (iii) using the precipitation-equilibrium approximation (i.e., δ A =δ P - ε*)

  19. Iron isotope constraints on arsenic release from Mekong Delta sediments, Cambodia

    Science.gov (United States)

    Matsumoto, T.; Yamaguchi, K. E.; Hirata, T.; Yamagata, Y.; Yamaguchi, A.; Abe, G.

    2017-12-01

    Arsenic-contaminated groundwater is a world-wide environmental problem and threatens more than 100 million people living in delta areas of South, SE and East Asia. It is typically associated with reducing aquifers with organic-rich alluvial sediments, little thermal gradients, low sulfate concentrations, and slow flushing rates. Such conditions are typical for low-lying countries in Asian deltas; however, compared to Bangladesh, Cambodia has received far less attention. Upon reductive dissolution of Fe-(oxyhydr)oxides that adsorbed As, Fe and As are released into solution as dissolved Fe2+ and arsenate, respectively. Following the oxidation of dissolved Fe2+, newly-formed Fe-(oxyhydr)oxides adsorb As again. Thus, in anoxic waters, concentrations of As correlate with those of dissolved Fe2+. Fluctuating redox conditions in the aquifer are control As release, although inhibition of adsorption of arsenate and arsenite onto the Fe-(oxyhydr)oxides occurs when the concentrations of phosphate, bicarbonate, silicate, and/or organic matter become sufficiently high. Biogeochemical redox reactions of Fe result in significant isotope fractionation (e.g., Johnson et al., 2008). We hypothesized that magnitude of isotope fractionation of Fe in the aquifer sediments, reflecting repeated (incomplete) redox reactions of Fe, may be proportional to the amount of total As release. We aim to calibrate the As release from aquifer sediment by Fe isotope analysis. As a preliminary study, series of sediment samples were collected from the Mekong Delta, Cambodia, in September 2016. Based on measurements by XRF, ICP-AES and ICP-MS, concentrations of As varied significantly covering the range from 4.5 to 15.5 µg/g with a median value of 11 µg/g (higher than the average crustal value of 5 µg/g), and those of Fe is from 2.6 to 9.7 wt.% with a median value of 7.1 wt.%. Concentrations of As and Fe show positive correlation (R2 = 0.72), indicating an effective redox cycling of Fe and As as

  20. Average Nuclear Level Densities and Radiative Strength Functions in 56,57FE from Primary (Gamma)-Ray Spectra

    International Nuclear Information System (INIS)

    Tavukcu, E.; Becker, J.A.; Bernstein, L.A.; Garrett, P.E.; Guttormsen, M.; Mitchell, G.E.; Rekstad, J.; Schiller, A.; Siem, S.; Voinov, A.; Younes, W.

    2002-01-01

    An experimental primary γ-ray spectrum vs. excitation-energy bin (P(E x , E γ ) matrix) in a light-ion reaction is obtained for 56,57 Fe isotopes using a subtraction method. By factorizing the P(E x , E γ ) matrix according to the Axel-Brink hypothesis the nuclear level density and the radiative strength function (RSF) in 56,57 Fe are extracted simultaneously. A step structure is observed in the level density for both isotopes, and is interpreted as the breaking of Cooper pairs. The RSFs for 56,57 Fe reveal an anomalous enhancement at low γ-ray energies